Abstract:
The invention relates to η 5 :η 1 -cyclopentadienylidene-phosphorane constrained geometry complexes of rare earth metals, abbreviated to η 5 :η 1 -CpPC-CGC, method for production and use of same. The η 5 :η 1 -CpPC-CGCs correspond to the general formula (1), wherein SE=Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu; X=independently of one another, a mono-anionic diorganoamido-, bistrimethylsilylamido-, halogenido-, alkyl-, aryl-, alkoxo-, aryloxo- or alkylaluminate (AlR 4   − ) substituent; L=neutral ligand (PR 3 , NR 3 , pyridine), solvent molecule (THF, ether, DMF, DMSO, HMPT, tetrahydropyran THP, tetrahydrothiofuran THT); R=alkyl with up to 1-10 C atoms or mono- or polycyclical aryl with 6 to 20 C atoms; R 1 , R 4 =independently of one another H or methyl; R 2 , R 3 =independently of one another, H or methyl or tertiary butyl or together a substituted cycloalkyl group; R 5 , R 6 =methyl, n-butyl, tertiary butyl or phenyl; R 7 , R 8 =independently of one another H, trimethylsilyl, alkyl with 1-10 C atoms or mono- or polycyclical aryl with 6 to 20 C atoms, and m=0, 1, 2 or 3.

Description:
This application is a §371 of International Application No. PCT/EP2012/003292 filed Aug. 2, 2012, and claims priority from German Patent Application No. 10 2011 080 283.5 filed Aug. 2, 2011. 
     FIELD OF THE INVENTION 
     The invention relates to η 5 :η 1 -cyclopentadienylidene-phosphorane constrained geometry complexes of rare earth metals, abbreviated η 5 :η 1 -CpPC,-CGC, a method for their production and use. 
     BACKGROUND OF THE INVENTION 
     With the discovery of ferrocene in 1951, the cyclopentadienyl ligand (Cp) gained prominent renown in the field of organometallic chemistry of transition metals and advanced rapidly to dominate in form of bis(cyclopentadienyl) or metallocene complexes the metals of the d-block and p-block. With the development of tris-(cyclopentadienide) of the lanthanoids and of group 3 by W ILKINSON  and B IRMINGHAM , this ligand ultimately also achieved a successful breakthrough in the field of organometallic chemistry of rare earth metals (RE) that is highly sensitive to hydrolysis; syntheses of different bis-(cyclopentadienyl) derivatives followed thereafter. 
     The term metallocene, as it became known due to ferrocene, is used not only for pure bis-(cyclopentadienyl) complexes but also for complexes with metals that carry further anionic ligands (X) or neutral ligands (L) in form of Cp R   2 RE(X) n (L) m  ( FIG. 1 ). Cp R   2 RE(+II) and Cp R   2 RE(+III) halogenides are excellent starting compounds for alkyl, hydrido or amido species. These in turn possess, ultimately, a reactive function for catalytic applications, primarily in hydrometalation reactions, cyclization reactions and polymerization reactions of olefins. Electronic or steric parameters can be varied by organyl substituents R on the cyclopentadienyl unit. Especially prominent variants of C 5 H 5  are pentamethylcyclopentadienyl C 5 Me 4 , indenyl and fluorenyl units (in general, Cp R ). 
     A bridging Y (in most cases, SiR 2 , —C n H 2n —) of both Cp R  units results in ansa-metallocenes. The conformation of the complex becomes fixed, whereby the L EWIS  acidity of the metal center is successfully increased, because the catalyst center is rendered more accessible for larger substrate molecules in the catalysis. Correspondingly, the activity of the ansa-lanthanocene catalyst {Me 2 Si(C 5 Me 4 ) 2 RE(H)} 2  is ten times higher in comparison to the unbridged lanthanocene {Cp 2 RE(H)} 2  in the ethylene polymerization as well as in the copolymerization of ethane with 1-hexene. 
     Achiral ansa-metallocenes of the Me 2 Si(C 5 Me 4 ) 2 LnR and Me 2 Si(C 5 Me 4 )(C 5 H 4 )LnR types and chiral ansa-metallocenes were prepared in a broad variety. Chiral ansa-lanthanocenes play are crucially important in asymmetrical hydroamination, as described for the first time by MARKS shortly after the development of the highly efficient intramolecular hydroamination by achiral lanthanocenes. 
     The successful use of ansa-metallocenes in polymerization catalysis has intensified the interest in further reducing the steric requirements and in studying pure half-sandwich complexes with one or two reactive functions CpRE II (X) or CpRE III (X) 2 , respectively. Since the literature contains relatively little information regarding mono-Cp- as opposed to bis-Cp-systems, it is already obvious that the synthesis of such species is associated with difficulties. In particular, when a sterically undemanding Cp-moiety is to be inserted, in the ligand substitution, there ensues time and time again the formation of thermodynamically favored metallocene or tris-Cp complexes. 
     In addition, the more electropositive nature of the RE central atom results in a stronger ionic bond, which means the compound tends to undergo ligand substitution reactions (ligand scrambling). Although most neutral half-sandwich complexes do not show any activity in the polymerization of olefins, a transfer, however, by way of, for example, MAO or boranes, such as [B(C 6 F 5 ) 3 ], or borates, such as [Ph 3 C][B(C 6 F 5 ) 4 ] or [Ph 2 MeNH][B(C 6 Fs) 4 ], respectively, to a cationic active species resulted multiple times in the successful use in the context of regio- and stereospecific polymerizations of olefins, or also in copolymerization reactions with cyclic and aromatic monomers. 
     A more successful improvement resulted from the substitution of a cyclopentadienyl moiety in an ansa-metallocene with another anionic or neutral donor D obtaining the so-called constrained geometry complexes. Contrary to Cp-rings, which, by way of being inert, strongly protective ligands (spectator ligands), serve for the complex formation of a reactive metal center, the donor D has a more faceted function: it can be hemilabile during catalysis and be subject to temporary decomplexation without degradation of the catalyst system, or it can flexibly contribute 2, 4 or 6 electrons in α- and π-bonds to the central atom. 
     B ERCAW  presented the first constrained geometry complex with the Cp-Y-D-ligand motif in 1990 (P. J. Shapiro, E. Bunel, W. Schaefer, J. E. Bercaw,  Organometallics  1990, 9, 867-869) in form of a dimeric Sc-hydrido complex with the chelate unit CpSiN ( FIG. 2 ). 
     Aside from the many prominent group 4 compounds, ansa-cyclopentadienyl complexes with rare earth metals form a class of interesting homogeneous catalysts that are also used on an industrial scale (EP 0416815A2). 
     Some novel structural motifs for constrained geometry complexes have been developed previously by Sundermeyer et al. They contain a chelating iminophosphorane unit with a strongly basic nitrogen atom ( FIG. 3 ). Initially, based on the isoelectronic relationship of the dianionic unit CpSiN of the classic CGC relative to the monoanionic unit CpPN, a new series of ligands of different steric requirements and electronic donor nature was prepared. The first lutetium complex of the new system was published in 2005. I was possible to study a series of CpPN complexes of further rare earth metals and metals of the groups 3 and 4, where the CpPN unit functions as a chelate ligand, as well as the activity thereof in intramolecular hydroamination and in olefin polymerization (WO2009068000). Moreover, experiments were conducted regarding the synthesis of group 4, aluminum, chromium, vanadium and further rare earth metal CG complexes. Independently but simultaneously in relation to the above, B OURISSOU  et al. published DFT calculations and experimental works regarding fluorenyl-based FluPN ligand systems and the complex formation thereof on group 4 metals. 
     As mentioned previously, in CpPN complexes, the phosphacene unit is bonded directly to the C5-ring via the phosphor atom and is therefore a component of the structurally verifiable chelate unit. The monoanionic CpSiNP ligand is a hybrid of the novel monoanionic CpPN and the classic dianionic CpSiN ligands, where the phosphacene unit is exocyclically arranged relative to C5-Si—N chelate ring that is the identified target. Also related to the ligand system that was described for the first time in 2010 are such compounds with Me 2 Si-bridged cyclopentadienyl-imidazolin-2-imine ligands the N-atoms of which are also a component of an extremely basic, ampholyte-ionically constructed neutral ligand, namely of an imidazole ring. The work group  TAMM  published constrained geometry complexes with this ligand system for chromium (S. Randoll, P. G. Jones, M. Tamm,  Organometallics  2008, 27, 3232-3239), for rare earth metals and alkaline earth metals (T. K. Panda, C. G. Hrib, P. G. Jones, J. Jenter, P. W. Roesky, M. Tamm,  Eur. J. Inorg. Chem.  2008, 4270-4279). Also to be noted in the present context is a further, however, dianionic, CpPN ligand system of the general nomenclature (Cp R PRNR) 2−  with a phosphor(III) atom in the bridge by the work group  SUNDERMEYER , because the corresponding titanium complexes produce linear, highly molecular polyethylene of high activity (J. Sundermeyer et al.  Eur. J. Inorg. Chem.  2002, 678-691;  J. Organomet. Chem.  2001, 640, 21-28). 
     Further to be noted as known in the art are monoanionic, bidendate phosphoniumdiylide ligands (“CPC,” Type A,  FIG. 4 ). Complexes of this flexible chelate-ligand system with metals of the total periodic table have been researched (H. Schmidbaur,  Angew. Chem. Int. Ed.  1983, 22, 907-927). To be mentioned in this field of interest is primarily the first homoleptic, dissolvent-free organyl complexes of lanthanoids by S CHUMANN . This compound class [(CPC) 3 RE] with KZ=6 is sufficiently stabilized by ligands with two α-donors of Type A ( FIG. 4 ) for lutetium and, ranging to the largest of the lanthanoids, lanthanum (H. Schumann, F.-W. Reier,  J. Organomet. Chem.  1982, 235, 287-294). This is why their characterization and their reactivity were studied. Aside from homoleptic complexes, there are also heteroleptic complexes of rare earths of Type A, which are in most cases stabilized by Cp-co-ligands, and the reactivities of which were studied. 
     However, not only the classic phosphonium diylides have awakened scientific interest, calling for attention are also a number of phosphor-bridged ansa-metallocene ligands of Type C (CpPCp) with two π-donors in the chelate unit. Complexes of alkali and alkaline earth metals, group 4 metals and iron were prepared with such bis-cyclopentadienyl-phosphonium diylide ligands of Type C. However, not much is known regarding their reactivity. In one example, a CpPCp-iron complex itself serves as catalyst in the polymerization catalysis (H. Schumann, S. Hohmann,  Chemiker - Zeitung  1976, 100 (7-8), 336). 
     Although cyclopentadienylidene phosphorane of type R 3 P═C 5 R 4 , the structural motif of which is underlying the new ligand class of type B, has been known for a long time as an ampholyte-ionic ligand in the literature, reporting on the advantageous use of complexes containing deprotonated forms of this ligand has been lacking to date (F. Ramirez, S. Levy,  J. Org. Chem.  1956, 29, 1333). 
     OBJECTS OF THE INVENTION 
     Therefore, it is the object of the present invention to provide RE complexes that possess a C 5 R 4  donor and a C donor, which are bonded via a P-bridge atom in a chelate-like manner to a RE central atom. 
     SUMMARY OF THE INVENTION 
     According to the invention, this object is achieved with η 5 :η 1 -CpPC-CGCs of the general formula 1 
                                
wherein
         RE=Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu;   X=Independently of each other, a monoanionic diorganoamido, bis(trimethylsilyl)amido, halogenide, alkyl, aryl, alkoxo, aryloxo or alkylaluminate (AlR 4 ″) substituent;   L=Neutral ligand, such as triorganylphosphanes (PR3), tertiary amines (NR 3 ), pyridine and/or dissolvent molecule, such as tetrahydrofuran (THF), ether, N,N-dimethylformamide (DMF), dimethylsulfoxide (DMSO), hexamethylphosphoric acid triamide (HMPT), tetrahydropyrane (THP), tetrahydrothiofurane (THT);   R=Alkyl with up to 1-10 carbon atoms or mono- or polycyclic aryl with 6 to 20 carbon atoms;   R 1 , R 4 =Independently of each other, H or methyl;   R 2 , R 3 : Independently of each other, H or methyl or tertiary butyl, or together a substituted cycloalkyl moiety;   R 5 , R 6 =Methyl, n-butyl, tertiary butyl or phenyl;   R 7 , R 8 =Independently of each other, H, trimethylsilyl, alkyl with up to 1-10 carbon atoms or mono- or polycyclic aryl with 6 to 20 carbon atoms;
 
as well as
   m=0, 1, 2 or 3.       

     Alternately, the object according to the invention is achieved with CpPC-CGC of the general formula 2. 
                                
wherein
         RE=Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu;   X=Independently of each other, a monoanionic diorganoamido, bis(trimethylsilyl)amido, halogenido, alkyl, aryl, alkoxo, aryloxo or alkylaluminate (AlR 4 ″) substituent;   R Alkyl with up to 1-10 carbon atoms or mono or polycyclic aryl with 6-20 carbon atoms;   R 1 ,R 4 =Independently of each other, H or methyl;   R 2 ,R 3 =Independently of each other, H or methyl or tertiary butyl or together a substituted cycloalkyl moiety;   R 5 , R 6 =Methyl, n-butyl, tertiary butyl or phenyl;   R 7 ,R 8 =Independently of each other, H, trimethylsilyl, alkyl with up to 1-10 carbon atoms; or mono- or polycyclic aryl with 6-20 carbon atoms.       

     Preferably, RE=Sc, Y, La, Ce, Nd, Sm or Lu; X=hexamethylene disilazanide, N,N-dimethylbenzylamine (dmba) ortho-metallized, N,N,α-trimethylbenzylamine (tmba) ortho-metallized, a silylmethanide —CH 2 SiMe 3  or —CH(SiMe 3 ) 2 , benzyl, allyl, Cl, Br or I in the η 5 :η 1 -CpPC-CGC. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows monodentate Cp ligands (left); bidentate ansa-Cp ligands (right) in complexes of rare earth metals. 
         FIG. 2  shows the first published CGC complex with a CpSiN ligand motif by B ERCAW.    
         FIG. 3  shows CpY-D complexes of rare earth metals and of the metals M (M=Ti, Zr, Hf, Al, V, Cr; X=alkyl, benzyl, amido, halogenide). 
         FIG. 4  shows analogues of the novel mono-Cp-substituted phosphonium diylide type B in relation to previously known bis-Cp-substituted type A and of the classic type C. 
         FIG. 5  shows novel RE complexes with: a) monoanionic and b) dianionic CpPC ligand. 
         FIG. 6  shows  13 C-NMR spectrum of polycaprolactone, polymerized by η 5 :η 1 -C 5 Me 4 PMe 2 CH 2 )La(N(SiMe 3 ) 2 ) 2 ]. 
     
    
    
     DETAILED DESCRIPTION 
     The (η 5 :η 1 -phosphorylide)-rare earth metalloces are preferably selected from the group consisting of:
         [(η 5 :η 1 -C 5 Me 4 PMe 2 CH 2 )Y(N(SiMe 3 ) 2 ) 2 ], [(η 5 :η 1 -C 5 Me 4 PMe 2 CH 2 )Sm(N(SiMe 3 ) 2 ) 2 ],   [(η 5 :η 1 -C 5 Me 4 PMe 2 CH 2 )Nd(N(SiMe 3 ) 2 ) 2 ], [(η 5 :η 1 -C 5 Me 4 PMe 2 CH 2 )Ce(N(SiMe 3 ) 2 ) 2 ],   [(η 5 :η 1 -C 5 Me 4 PMe 2 CH 2 )La(N(SiMe 3 ) 2 ) 2 ], [(η 5 :η 1 -C 3 H 3 tBuPMe 2 CH 2 )Ce(N(SiMe 3 ) 2 ) 2 ],   [(η 5 :η 1 -C 5 H 3 tBuPMe 2 CH 2 )La(N(SiMe 3 ) 2 ) 2 ], [(η 5 :η 1 -C 5 H 3 tBuPMe 2 CH 2 )Nd(N(SiMe 3 ) 2 ) 2 ],   [(η 5 :η 1 -C 5 Me 4 PMe 2 CH 2 )Nd(N(SiMe 2 H) 2 ) 2 ], [(η 5 :η 1 -C 5 Me 4 PPh 2 CH 2 )Y(CH 2 SiMe 3 ) 2 ],   [(η 5 :η 1 -C 5 Me 4 PPh 2 CH 2 )Sm(CH 2 SiMe 3 ) 2 ], [(η 5 :η 1 -C 5 Me 4 PPh 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ],   [(η 5 :η 1 -C 5 H 3 tBuPPh 2 CH 2 )Y(CH 2 SiMe 3 ) 2 ], [(η 5 :η 1 -C 5 Me 4 PMe 2 CH 2 )Sc(CH 2 SiMe 2 H) 2 ],   [(η 5 :η 1 -C 5 H 3 tBuPMe 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ].
 
In all complexes, the CpPC unit represents a bidentate, anionic ligand. Particularly preferred was the preparation of complexes with R 7 , R 8 ═H, which coordinate with a methylene unit as 6+2 electron donor [R 1-4   4 C 5 —PR 5 R 6 —CH 2 ] −  on the rare earth metal. The trivalent RE metal atom is additionally coordinated by further anionic ligands X and neutral ligands L. In the special case of R 8 ═H, it is possible to further deprotonate the CpPC unit and bond the same as a bidentate, dianionic 6+4 electron ligand [R 1-4   4 C 5 —PR 5 R 6 —CR 7 ] 2−  to the metal atom. However, to be claimed as well shall be such complexes wherein at least one of these ligands bonds in a chelate-like fashion to a bivalent or quadrivalent RE-metal atom ( FIG. 5 ).
       

     The η 5 :η 1 -CpPC-CGCes according to the invention are prepared in such a manner that a CH-acidic cyclopentadienylidene phosphorane is reacted with a rare earth metal ligand complex in an aprotic solvent in a temperature range from −20° C. to 120° C. The reaction occurs by way of an elimination of amine, salt or hydrocarbon. Preferably, the reaction is performed in aromatics, hydrocarbons, ethers or in mixtures of these solvents. Particularly preferred is a reaction temperature in the range from −10° C. to 80° C. The CH-acidic cyclopentadienylidene phosphorane is preferably reacted with the rare earth metal ligand complex at a molar ratio between 0.8:1 and 1.2:1. Particularly preferred is the conversion of the CH-acidic cyclopentadienylidene phosphorane with the rare earth metal ligand complex in equimolar quantities. 
     The η 5 :η 1 -CpPC-CGCes according to the invention are used as reagent or catalyst in organic reactions. Further advantageous applications are uses as a catalyst in ring-opening polymerizations for the production of polyesters and as precatalyst in the polymerization of olefins. The use as a precatalyst in the polymerization of conjugated olefins is especially advantageous. 
     Advantages of metallocene and metallocene-analogous compounds that must be emphasized in a comparison with the heterogeneous Z IEGLER -N ATTA  catalyst systems are the good solubility in non-polar organic solvents, the well-defined catalytically active location (active side) inside the molecule (single site catalyst) and the stereoselectivity of the C—C-coupling reaction relative to the polymer that can be achieved by the stereochemistry of the catalyst complex (tacticity). Different tacticities of polyolefins result in completely different properties, such as, for example, with regard to the melting point, tensile strength and stability of the polymer, whereby, due to the design of the molecular single-site catalyst, it is possible to adjust the property profile for highly valuable polymers in a targeted fashion. In terms of activity, the new generation of constrained geometry complexes is superior to the metallocenes, allows for a high level of selectivity in the polymerization catalysis and able to withstand considerably higher thermal stresses. 
     The RE complexes were obtained by reactions of CH-acidic ligand precursors with RE amidene (amine elimination) or with RE alkylene (hydrocarbon elimination). A third method presents the reaction of alkali salts of CpPC ligands with RE halogenides (salt elimination) or an in-situ combination of as RE halogenides with the protonated ligand form [CpPC]H and organolithium compounds or lithium amides as base. 
     The invention will be illustrated in further detail below based on a number of examples, which are not intended to limit the scope of the invention in any way. 
     All reactions with substances that react sensitively to hydrolysis and/or oxygen were carried out in heated S CHLENK  instruments under a protective argon gas atmosphere. A change tab system with a rotary vane vacuum pump ( PFEIFFER , model Duo 010 M, end pressure of ca. 2-10 −2  bar) was used. The substances were weighed, samples were prepared for analytical studies and substances reacting sensitively to hydrolysis and/or oxygen were stored in a glovebox (Type MB 150 BG-1, B RAUN , Lab Master 130,  BRAUN ) under a nitrogen atmosphere. 
     The solvents for reactions that are sensitive to air or moisture were dried according to standard procedures and stored in absorption columns over aluminum oxide/molecular sieve 3 Å/R3-11G catalyst ( BASF ). The dedeuterized solvents for NMR measurements were also dried according to standard methods and stored over molecular sieve 3 Å. 
     nBuLi (in hexane), tBuLi (in hexane), MeLi (in Et 2 O), PhLi (nBu 2 O) and LiCH 2 TMS were provided by C HEMETALL . The concentrations of the used solvents of lithium organylene and G RIGNARD  reagents were determined by titration with secbutanol vs. 1,10-phenanthroline as indicator. 
     The NMR spectra were measured on the following instruments at RT: 
       BRUKER  ARX 250:  1 H (250.1 MHz),  13 C (62.5 MHz) 
       BRUKER  ARX 300:  1 H (300.1 MHz),  13 C (75.5 MHz),  31 P (121.5 MHz) 
       BRUKER  AMX 300:  1 H (300.1 MHz),  13 C (75.5 MHz),  31 P (121.5 MHz) 
       BRUKER  DRX 400:  1 H (400.1 MHz),  13 C (100.6 MHz),  31 P (161.9 MHz),  7 Li (155.44) 
       BRUKER  DRX 500:  1 H (500.10 MHz),  13 C (125.8 MHz),  31 P (202.3 MHz),  27 Al (130.3 MHz) 
     All listed  31 P- and  13 C-NMR spectra are  1 H-decoupled. The NMR spectra were recorded according to the standard at 298 K, with the exception of the VT-NMR measurements. Residual proton and solvent signals of the corresponding dedeuterized solvents are used for calibrating the  1 H- and  13 C-NMR spectra. 
       1 H-NMR: 
     C 6 D 6 : δ=7.16 ppm, CDCl 3 : δ=7.24 ppm, d 8 -THF: δ=3.58 ppm, 1.73 ppm, CD 3 CN: δ=1.94 ppm, CD 2 Cl 2 : δ=5.32 ppm, d 6 -toluene: δ=7.09 ppm, d 5 -pyridine: δ=8.71 ppm, C 6 D 5 Br: δ=7.15 ppm, d 6 -DMSO: δ=2.50 ppm 
       13 C-NMR: 
     C 6 D 6 : δ=128.1 ppm, CDCl 3 : δ=77.0 ppm, d 8 -THF: δ=49.0 ppm, 24.2 ppm, CD 3 CN: δ=1.3 ppm, 118.3 ppm, CD 2 Cl 2 : δ=52.79 ppm, d 6 -toluene: δ=137.5 ppm, d 5 -pyridine: δ=149.9 ppm, C 6 D 5 Br: δ=131.8 ppm, d 6 -DMSO: δ=39.5 ppm 
       31 P-NMR spectra were recorded broadband-decoupled and calibrated externally vs. 85% phosphoric acid or using internal standards (PPh 3  in C 6 D 6 : −5.26 ppm). 
     Couplings between nucleus X and nucleus Y with nuclear spin % via n-bonds are indicated by the coupling constant  n J xy  in Hz. 
     The following abbreviations were used for the multiplicity of the signals: 
     s=singlet, d=doublet, t=triplet, q=quadruplet, quin=quintet, m=multiplet. 
     An exact assignment of the signals was done by 2D NMR spectroscopy (COSY, NOESY, HMQC or HSQC and HMBC NMR spectroscopy). In the NMR analysis, the following numbering was used for the cyclopentadienyl ring: 
     
       
                 
         
             
             
         
      
     
     The infrared spectra were recorded either by a  NICOLET  510 M spectrometer (as Nujol rubbings between KBr plates) or an ATR-FT IR spectrometer, model “Alpha-P” by BRUKER (in highly purified material). The absorption bands are indicated in cm −1 . The characteristics of the absorption bands are captioned by the following abbreviations: w=weak, m=medium, s=strong, {tilde over (v)}=wave number/cm −1 . 
     Elemental analyses (C, H, N) were done by the Department for Analytic Chemistry; instrument: CHN-Rapid by H ERAEUS . Hydrolysis- and/or oxygen-sensitive substances were weighed in the glove box in a zinc crucible. Information is given in weight %. 
     The monocrystal x-ray structure analysis was conducted by the Department for Analytical Chemistry of the Philipps-University of Marburg; instrument: IPDS (IPDS-1. S TOE ). A standard graphite monochromator (Mo-Ka-radiation, (λ=71.073 pm) was used for images. Further information as to crystalline structure analyses can be found in the annex containing crystallographic information. The D IAMOND  3 program was used for the figures containing the molecular structures. 
     The TGA was done with a TGA/SDTA 851 instrument (by  METTLER  T OLEDO ). For the TGA measurements, the sample was weighed in each time by the ultra-micro scale into a 70 μL aluminum crucible integrated in the instrument. DSC measurements of the polymer samples were taken with a DSC 821e instrument by  METTLER  T OLEDO . For the DSC measurements, each time, the substance was weighed in into a 40 μL aluminum crucible. A hole was pieced into the lid of the sealed crucible to allow trapped air to escape. A temperature program with two cycles was employed. The samples were measured in a temperature range of −90 to 60° C. at a heating rate of 10 K/min. 
     The molecular weights could be determined by gel permeation chromatography (GPC) relative to polystryrol as standard in THF at 20° C. 
     First, it must be noted that the GPC measurement of polyisoprene was taken in pure THF, while, for the measurement of polycaprolactone, trifluoroascetic acid in a concentration of 5% was added to THF as eluent. By adding the acid, it was possible to suppress any possible crystallization of catalyst moieties. Measurements of the same polymers on the same column, however without the addition of acid, did not produce any useful results, which was due to the formation of excess pressure on the column and material. The separation columns for polycaprolactone are two PSS SDV linear columns (10μ, 2×8×600 mm) with a flow rate of 0.8 mL/min. The separation column for the measurements of polyisoprene samples was a PSS SDV linear column (5μ, 30 cm) (+precolumn (SDV precolumn 5 μL)) and a flow rate of 1 mL/min. 
     Preparation of [(η 5 :η 1 -C 5 R 2   3 R 1 PR 3   2 CH 2 )RE(hmds) 2 ] 
     
       
                 
         
             
             
         
      
     
     General operating procedure: x mmol ligand (1.0 eq) and x mmol RE(hmds) 3  (1.0 eq) were first dissolved in x mL toluene. The reaction mixture was stirred for different lengths of time at 80° C., depending on the central atom. A reaction control was done by  31 P-NMR spectroscopy. After the individual reaction time, the solvent and any resulting disilazane [H(hmds)] are removed in vacuo. The residue is suspended in 3-5 mL hexane and made into a paste in an ultrasonic bath, if necessary. The suspension is stored overnight at −30° C. to increase the precipitation yield. 
     EXAMPLE 1 
     Preparation of [(η 5 :η 1 -C 5 Me 4 PPh 2 CH 2 )YCl 2 ] 2   
     
       
                 
         
             
             
         
      
     
     97 mg C 5 Me 4 PPh 2 Me (0.30 mmol, 1.00 eq) and 134 mg [YCl 3 (THF) 2.5 ] (0.357 mmol, 1.18 eq) are provided in 8 mL toluene. The orange-colored solution with light solid was cooled to 0° C., and 0.6 mL of the PhLi solution (0.5 M in nBu 2 0/benzene, 0.30 mmol, and 1.00 eq) were dropped in, then the substance then stirred for 1 h at 0° C. During this step, the coloration of the solution disappeared. After the reaction was complete (reaction control by  31 P-NMR spectroscopy), the reaction mixture was filtered with CELITE and washed twice with 3-4 mL toluene each time. The obtained filtrate was evaporated in a fine vacuum, and the residue was suspended in pentane. 
     The mixture was then centrifuged, the supernatant solution was discarded and the beige-colored solid material dried in a fine vacuum. 
     Yield: 129 mg (0.24 mmol, 79%). 
     The same result is achieved, when the reaction is done in THP as solvent and with the use of [Ycl 3 (thp) 2 ]. 
     EXAMPLE 2 
     Preparation [η 5 :η 1 -C 5 Me 4 Pme 2 CH 2 )La(hmds) 2 ] 
     
       
                 
         
             
             
         
      
     
     70 mg C 5 Me 4 Pme 3  (0.36 mmol, 1.00 eq) and 229 mg [La(hmds) 3 ] (0.37 mmol, 1.03 eq) are first dissolved in 10 mL toluene. The reaction solution is stirred for 2 h at 75° C. A reaction control is done by  31 P-NMR spectroscopy. The solvent and H(hmds) are removed at 40° C. in a fine vacuum. The residue is suspended in 3-5 mL hexane and turned into a paste in an ultrasonic bath. The suspension is stored overnight at −30° C. to increase the yield. 
     Yield: 227 mg (0.35 mmol, 96%); product: colorless solid material. 
     Monocrystals can be obtained from a hexane solution at −30° C. 
     EXAMPLE 3 
     Preparation of [(η 5 :η 1 -C 5 Me 4 PPh 2 CH 2 )Sm(CH 2 SiMe 3 ) 2 ] and [(η 5 :η 1 -C 5 Me 4 PPh 2 CH)Sm(CH 2 SiMe 3 )] 2  on NMR Scale 
     
       
                 
         
             
             
         
      
     
     In a small vessel in the glove box, 11.18 mg C 5 Me 4 PPh 2 Me (0.04 mmol, 1.00 eq) are first dissolved in 0.2 mL C 6 D 6 . [Sm(CH 2 SiMe 3 ) 3 (thf) 3 ] (0.04 mmol, 1.00 eq) is dissolved in 0.2 mL C 6 D 6  in a separate vessel. The ligand solution is slowly dropped in the precursor solution with a syringe, and the reaction vessel is lightly swung back and forth during this step. The reaction mixture is transferred into an NMR tube, rinsed with 0.2 mL C 6 D 6 . The compounds are characterized via NMR spectroscopy. 
     EXAMPLE 4 
     Preparation of [(η 5 :η 1 -C 5 Me 4 Pme 2 CH 2 )Y(hmds) 2 ] 
     
       
                 
         
             
             
         
      
     
     Quantity Information: 
     10 mL toluene, 70 mg Me 3 PC 5 Me 4  (0.36 mmol, 1.0 eq), 205 mg Y(hmds) 3  (0.36 mmol, 1.0 eq); time: 5 h (+3 d); temperature: 50° C. (+3 d, RT) 
     Yield: 163 mg (0.27 mmol, 75%); color: colorless solid material 
     Elemental analysis (C 24 H 56 N 2 Psi 4 Y, 604.94 g/mol): calculated: C, 47.65; H, 9.33; N, 4.63. found: C, 45.20; H, 8.91; N, 3.77. 
       31 P-NMR (121.5 MHz, C 6 D 6 ): δ/ppm=3.17 (d,  2 J P,Y =2.08 Hz) 
       1 H-NMR (400.1 MHz, C 6 D 6 ): δ/ppm=2.04 (s, 6H, C 5   Me 4   , 2.5-Cp), 2.00 (s, 6H, C 5   Me 4   , 3.4-Cp), 1.13 (d,  2 J P,H =12.65 Hz, 6H, P me 2   ). 0.42 (s, 36H, N(Si Me 3   ) 2 ), 0.02 (dd, 2H,  2 J P,H =9.80 Hz,  2 J Y,H =2.08 Hz, PC H 2   Y). 
       13 C-NMR (62.8 MHz, C 6 D 6 ): δ/ppm=125.4 (d,  2,3 J C,P =13.2 Hz), 119.3 (d,  2,3 J C,P =12.1 Hz), 91.2 (d,  1 J C,P =100.13 Hz, P C   Cp ), 17.4 (d,  1 J C,P =48.3 Hz, P me 2   ). 14.9 (s, C 5   Me   4 , 3.4-Cp), 12.3 (d,  3 J C,P =1.44 Hz, C   5 Me 4   , 2.5-Cp), 6.62 (s, N(Si Me 3   ) 2 ). The signal for PC H   2 Y is superimposed by signals 
     EI-MS: m/z (%)=355 (35%), 281 (100%), 254 (48%), 239 (39%), 207 (45%), 123 (100%), 105 (56%), 91 (34%), 77 (27%). 
     IR (highly purified material): {tilde over (v)}/cm −1 =2945.47 (m), 2896.22 (m), 1312.51 (m), 1291.25 (m), 1239.93 (s), 1125.00 (w), 951.37 (s), 929.76 (s), 812.79 (s), 770.03 (s), 751.79 (s), 661.53 (m), 607.43 (m), 450.22 (m) 
     EXAMPLE 5 
     Preparation of [(η 5 :η 1 -C 5 Me 4 Pme 2 CH 2 )La(hmds) 2 ] 
     
       
                 
         
             
             
         
      
     
     Quantity Information: 
     10 mL toluene, 70 mg Me 3 PC 5 Me 4  (0.36 mmol), 229 mg La(hmds) 3  (0.37 mmol, 
     1.03 eq); time: 2 h (5 h); temperature: 75° C. (50° C.) 
     Yield: 227 mg (0.35 mmol, 96%); color: colorless solid material 
     Monocrystals can be obtained from a hexane solution at −30° C. 
     Elemental analysis (C 24 H 56 N 2 Psi 4 La, 654.94 g/mol): calculated: C, 42.29; H, 8.07; N, 4.48. found: C, 38.61; H, 7.73; N, 3.58. 
       1 H-NMR (300.1 MHz, C 6 D 6 ): δ/ppm=2.08 (s, 6H, C 5   Me   4 , 2.5-Cp), 2.04 (s, 6H, C 5   Me   4 ), 1.13 (d,  2 J P,H =12.8 Hz, 6H, P me 2   ), 0.40 (s, 36H, N(Si Me 3   ) 2 ), −0.26 (d, 2H,  2 J P,H =7.74 Hz, PCH 2 —La) 
       13 C-NMR (75.5 MHz, C 6 D 6 ): δ/ppm=127.5 (d,  1 J P,C =57.2 Hz, C q P), 124.28 (s,  C 5   Me 4 ), 120.46 (s,  C 5   Me 4 , 2.5-Cp), 13.19 (s, C   5 Me 4   ), 10.70 (s, C   s Me 4   , 2.5-Cp), 17.18 (d,  1 J P,C =48.0 Hz, P me 2   ), 4.17 (s, N(Si Me 3   ) 2 ), 1.68 (d,  1 J P,C =69.9 Hz, P C H 2 La) 
       31 P-NMR (121.5 MHz, C 6 D 6 ): δ/ppm=4.99 
       31 P-NMR (121.5 MHz, Et 2 O): δ/ppm=6.75 
     EI-MS: m/z (%)=161 [hmds], 146 [Me 3 Si—N—SiMe 2 ] 
     IR (highly purified material): {tilde over (v)}/cm −1 =2994.48 (m), 2888.58 (w), 1248.65 (m), 1235.29 (m), 1099.08 (w), 1045.19 (w), 1007.16 (s), 892.52 (m), 819.00 (s), 750.03 (w), 743.17 (m), 688.25 (w), 658.17 (s), 597.40 (m), 438.40 (s) 
     EXAMPLE 6 
     Preparation of [(η 5 :η 1 -C 3 Me 4 Pme 2 CH 2 )Ce(hmds) 2 ] 
     
       
                 
         
             
             
         
      
     
     Quantity Information: 
     8 mL toluene, 86 mg Me 3 PC 5 Me 4  (0.44 mmol, 1.0 eq), 273 mg Ce(hmds) 3  (0.44 mmol, 1.0 eq); time: 3 h; temperature: 80° C., the compound is highly sensitive to oxidation. 
     Yield: 137.5 mg (0.21 mmol, 47.7%); color: light-brown solid material 
     Monocrystals can be obtained from a hexane solution at −30° C. 
     Elemental analysis (C 24 H 56 N 2 Psi 4 Ce, 656.15 g/mol): calculated: C, 43.93; H, 8.60; N, 4.27. found: C, 28.50; H, 5.26; N, 0.89. 
       1 H-NMR (300.1 MHz, C 6 D 6 ): δ/ppm=4.36 (s, 6H, C   5 Me   4 ), 3.70 (s, 6H, C   5  Me   4 ), 2.38 (bs, 6H, P me 2   ), 0.13 (s, 36H, N(Si Me 3   ) 2 ), −2.71 (bs, PC H 2   Ce). 
       31 P-NMR (121.5 MHz, C 6 D 6 ): δ/ppm=−32.3. 
       13 C-NMR (75.5 MHz, C 6 D 6 ): signals disappear in the background noise due to paramagnetism 
     EI-MS: m/z (%)=161 [hmds]*, 146 [Me 3 Si—N—SiMe 2 ]* 
     IR (highly purified material): {tilde over (v)}/cm −1 =2949.64 (m), 2900.61 (w), 1240.32 (m), 997.91 (m), 967.72 (s), 948.33 (m), 860.47 (m), 825.12 (s), 801.88 (s), 737.84 (s), 660.62 (m), 591.05 (m), 450.45 (w) 
     EXAMPLE 7 
     Preparation of [(η 5 η:η 1 -C 5 Me 4 Pme 2 CH 2 )Nd(hmds) 2 ] 
     
       
                 
         
             
             
         
      
     
     Quantity Information: 
     5 mL toluene, 96 mg Me 3 PC 5 Me 4  (0.49 mmol, 1.00 eq), 320 mg Nd(hmds) 3  (0.51 mmol, 1.04 eq); time: 6 h; temperature: 75° C. (+3 d RT) 
     Yield: 211.3 mg (0.32 mmol, 65.3%); color: blue solid material 
     Dark-blue monocrystals could be obtained from a hexane solution at −20° C. after 2 d 
     Elemental analysis: (C 24 H 56 N 2 Psi 4 Nd; 657.23 g/mol): calculated: C, 43.66; H, 8.55; N, 4.24. found: C, 39.21; H, 8.08; N, 3.48. 
       31 P-NMR (121.5 MHz, C 6 D 6 ): δ/ppm=−200.7 (bs) 
       1 H-NMR (400.1 MHz, C 6 D 6 ): δ/ppm=12.88 (s, 6H, C   5 Me 4   ), 5.16 (s, 6H, C   5  Me 4   ), −0.75 (bs, 6H, P me 2   ), −5.10 (bs, 18H, N(Si Me 3   ) 2 ), −7.58 (bs, 18H, N(Si Me 3   ) 2 ), −69.8 or −16.38 (bs, 2H, PC H 2   Nd) 
       13 C-NMR (100.6 MHz, C 6 D 6 ): δ/ppm=210.2 (s,  C 5   Me 4 ), 180.2 (s,  C 5   Me 4 , 168.6 (d,  1 J P,C =95.6 Hz, PC Cp ), 68.3 (bs, C 5   Me 4   ), 34.0 (d,  1 J P,C =47.3 Hz, Pme 2 ), 24.9 (C 5   Me 4   ), 6.41 (N(Si Me 3   ) 2 ), 1.18, −13.27 (N(Si Me 3   ) 2 ) 
     The signal for P C H 2 Nd could not be identified. 
     IR (highly purified material): {tilde over (v)}/cm −1 =2946.89 (m), 2895.13 (w), 1239.15 (m), 963.29 (s), 945.74 (s), 814.66 (s), 766.15 (s), 747.21 (s), 659.85 (s), 598.84 (s), 438.86 (m) 
     EXAMPLE 8 
     Preparation of [(η 5 :η 1 -C 5 Me 4 Pme 2 CH 2 )Sm(hmds) 2 ] 
     
       
                 
         
             
             
         
      
     
     Quantity Information: 
     10 mL toluene, 49 mg Me 3 PC 5 Me 4  (0.25 mmol, 1.0 eq), 158 mg Sm(hmds) 3  (0.25 mmol, 1.0 eq); time: 3 h; temperature: 80° C. 
     Yield: 98 mg (0.147 mmol, 58.8%); color: beige-colored solid material 
     Elemental analysis: (C 24 H 66 N 2 Psi 4 Sm, 667.25 g/mol): calculated: C, 43.26; H, 8.47; N, 4.20. found: C, 41.73; H, 8.76; N, 3.92. 
       31 P-NMR (121.5 MHz, toluene): δ/ppm=37.9 (bs) 
       1 H-NMR (300.1 MHz, C 6 D 6 ): δ/ppm=3.21 (s, 6H, C   5 Me 4   ), 2.29 (s, 6H, C   5 Me 4   ), −0.05 (bs, 6H, Pme 2 ), −1.57 (s, 36H, N(SiMe 3 ) 2 ), −3.86 (bs, 2H, PC H 2   Sm) 
       13 C-NMR (75.5 MHz, C 6 D 6 ): The signals cannot be identified. 
     EI-MS: m/z (%)=652.2 [M + -Me]. 
     IR (highly purified material): {tilde over (v)}/cm −1 =3067.14 (bm), 2949.59 (w), 1240.45 (m), 998.29 (m), 968.28 (s), 948.34 (m), 860 (m), 825.51 (s), 801.91 (s), 737.98 (s), 660.75 (s), 591.22 (s), 450.30 (m), 405 (m) 
     EXAMPLE 9 
     Preparation of [(η 5 :η 1 -C 5 H 3 tBuPMe 2 CH 2 )La(hmds) 2 ] 
     
       
                 
         
             
             
         
      
     
     Quantity Information: 
     10 mL toluene, 98.0 mg Me 3 PC 5 Me 4  (0.50 mmol, 1.00 eq), 415 mg La(hmds) 3  (0.67 mmol, 1.34 eq); time: 2 h; temperature: 80° C. 
     Yield: 194 mg (0.30 mmol, 60%); color: beige-colored solid material Colorless monocrystals could be obtained from a hexane solution at −30° C. 
     Elemental analysis: (C 24 H 56 PlaN 2 Si 4 , 652.0 g/mol): calculated: C, 44.01; H, 8.62; N, 4.28. found: C, 32.17; H, 6.48; N, 1.41. 
       1 H-NMR (C 6 D 6 , 400.15 MHz): δ/ppm=6.65 (m, 1H, C   5 H 3   ), 6.28 (m, 1H, C   5 H 3   ), 5.91 (m, 1H, C   5 H 3   ), 1.43 (s, 9H, tBu), 1.08 (d,  2 J H,P =13.1 Hz, 3H, P me ), 1.03 (d,  2 J H,P =12.8 Hz, 3H, P me ), 0.45 (bs, 18H, (N(Si Me 3   ) 2 ), 0.33 (s, 18H, (N(SiMe 3 ) 2 ), −0.58 (dd,  2 J H,P =8.2 Hz,  2 J H,H =3.6 Hz, 2H, PC H 2   La) 
       31 P-NMR (C 6 D 6 , 161.90 MHz): δ/ppm=7.21 
       13 C-NMR (75.5 MHz, C 6 D 6 ): δ/ppm=147.1 (d,  2 J CP =11.3 Hz,  C 5   H 3 tBu,  C q   tBu), 113.8 (d,  2 J CP =13.6 Hz,  C 5   H 3 tBu), 112.2 (d,  2 J CP =12.8 Hz,  C 5   H 3 tBu), 109.7 (d,  3 J CP =12.8 Hz, C 5 H 3 tBu), 94.3 (d,  1 J Cp =104.7 Hz, P C CP   ), 33.6 (s, C( C H 3 ) 3 ), 32.4 (d,  C (CH 3 ) 3 ), 15.3 (d,  1 J CP =47.5 Hz, P me ), 12.8 (d,  1 J CP =53.5 Hz, P me ), 7.95 (d,  1 J CP =38.42 Hz, P C H 2 La), 4.4 (bs, (N(Si Me 3   ) 2 , 24.3 (s, (N(SiMe 3 ) 2 . 
     EI-IMS: m/z=196 [Me 3 PC 5 H 3 tBu], 181[Me 2 PC s H 3 tBu], 61 [Me 2 P] 
     IR (highly purified material): {tilde over (v)}/cm −1 =3066.61 (w), 2946.81 (m), 2899.33 (w), 1460.77 (w), 1414.74 (m), 1357.36 (w), 1291.67 (s), 1241.43 (s), 1201.91 (s), 1176.04 (s), 1091.89 (s), 1056.23 (m), 1004.24 (s), 975.35 (vs), 747.93 (vs), 9.8067 (w), 861.32 (s), 824.38 (m), 801.99 (m), 765.70 (s), 744.09 (m), 663.42 (vs), 589.99 (vs), 488.12 (w), 449.73 (w) 
     EXAMPLE 10 
     Preparation of [(η 5 :η 1 -C 5 H 3 tBuPMe 2 CH 2 )Ce(hmds) 2 ] 
     
       
                 
         
             
             
         
      
     
     Quantity Information: 
     10 mL toluene, 98.0 mg Me 3 PC 5 Me 4  (0.51 mmol, 1.00 eq), 380 mg Ce(hmds) 3  (0.61 mmol, 1.19 eq); time: 2 h; temperature: 80° C. 
     Yield: 144 mg (0.22 mmol, 43%); color: brown solid material 
     Yellow monocrystals could be obtained from a hexane solution at −18° C. 
     Elemental analysis: (C 24 H 56 PceN 2 Si 4 , 653.2 g/mol): calculated: C, 43.93; H, 8.60; N, 4.27. found: C, 39.43; H, 7.97; N, 2.96. 
       1 H-NMR (300.1 MHz, C 6 D 6 ): δ/ppm=46.27 (s, 1H, C 5   H 3   tBu), 18.05 (s, 1H, C   5 H 3   tBu), 15.06 (s, 3H), 5.27 (s, 9H, C 5 H 3   tBu ), −0.81 (very wide signal cannot be integrated N(Si Me 3   ) 2 ), −4.43 (s, 3H), −9.85 (bs, 1H, C   5 H 3   tBu), −11.55 (very wide signal cannot be integrated N(SiMe 3 ) 2 ), −25.80 (s, 1H, C 5 H 3 tBu), −35.82 (bs, 2H, PC H 2   Ce). Even after an extended measurement period, it was not possible to obtain useful results from the 2D-spectra of this compound. 
       31 P-NMR (121.5 MHz, C 6 D 6 ): δ/ppm=−27.8 (bs) 
     EI-MS m/z (%)=181 [Me 2 P-Cp tBu ], 196 [Me 3 P-Cp tBu ], 61 [Me 2 P] 
     IR (highly purified material): {tilde over (v)}/cm −1 =3065.81 (w), 2946.36 (m), 2897.23 (m), 2858.60 (w), 1427.61 (m), 1355.52 (m), 1291.51 (m), 1200.65 (m), 1174.10 (s), 1091.93 (s), 1057.31 (s), 977.72 (m), 946.70 (vs), 860.54 (m), 825.67 (m), 764.56 (vs), 667.43 (vs), 608.64 (w), 488.04 (w), 450.21 (m) 
     EXAMPLE 11 
     Preparation of [(η 5 :η 1 -C 5 H 3 tBuPMe 2 CH 2 )Nd(hmds) 2 ] 
     
       
                 
         
             
             
         
      
     
     Quantity Information: 
     10 mL toluene, 49 mg Me 3 PC 5 Me 4  (0.25 mmol, 1.00 eq), 163 mg Nd(hmds) 3  (0.26 mmol, 1.04 eq); time: 4 h; temperature: 80° C. 
     Yield: 118.3 mg (0.18 mmol, 72%); color: blue, crystalline solid material 
     Elemental analysis (C 24 H 56 N 2 Psi 4 Nd, 657.23 g/mol) 
       31 P-NMR (121.5 MHz, C 6 D 6 ) δ/ppm=−178.5. 
       1 H-NMR (300.0 MHz, C 6 D 6 ) δ/ppm 
     IR (highly purified material): {tilde over (v)}/cm −1 =2945.93 (m), 2895.00 (w), 1239.31 (s), 965.02 (s), 945.84 (s), 823.47 (s), 766.02 (m), 746.05 (m), 659.71 (s), 598.92 (s), 440.34 (w) 
     EXAMPLE 12 
     Preparation of [(η 5 :η 1 -C 6 H 3 tBuPPh 2 CH 2 )La(hmds) 2 ] 
     
       
                 
         
             
             
         
      
     
     Quantity Information: 
     8 mL toluene, 80 mg C 5 H 3 tBuPPh 2 Me (0.25 mmol, 1.00 eq), 155 mg La(hmds) 3  (0.25 mmol, 1.00 eq); time: 3 h; temperature: 80° C. 
     Yield: 115 mg (0.148 mmol, 59.1%); color: beige-colored solid material 
     Elemental analysis (C 34 H 60 LaN 2 PSi 4 , 778.3 g/mol): calculated: C, 52.42; H, 7.76; N, 3.60. 
       1 H-NMR (C 6 D 6 ) 400.1 MHz): δ/ppm=7.82-7.74 (m, 4H, Ph m ), 7.03-7.00 (m, 6H, Ph 0,P ), 6.77 (m, 1H, C   ≡ H 3   ), 6.40 (m, 1H, C   5 H 3   ), 6.04 (m, 1H, C   5 H 3   ), 1.39 (s, 9H, tBu), 0.33 (bs, 18H, (N(Si Me 3   ) 2 ), 0.30 (bs, 2H, PC H 2   La, with superimposed signal for hmds), 0.27 (s, 18H, (N(SiMe 3 ) 2 ) 
       31 P-NMR (C 6 D 6 , 121.90 MHz): δ/ppm=12.6. 
       13 C-NMR (75.5 MHz, C 6 D 6 ): δ/ppm=132.42 (s, Ph p ), 132.41 (s, Ph p ), 131.9 (d,  3 J C,P =2.33 Hz, Ph m ), 131.7 (d,  3 J C,P =2.12 Hz, Ph m ), 129.0 (d,  2 J C,P =5.9 Hz, Ph 0 ), 131.7 (d,  2 J C,P =5.9 Hz, Ph 0 ), 116.3 (d,  2,3 J CP =13.4 Hz,  C 5   H 3 tBu), 114.7 (d,  2,3 J Cp =13.7 Hz,  C 5   H 3 tBu), 113.2 (d,  2,3 J CP =13.1 Hz,  C 5   H 3 tBu), 91.9 (m, P C CP   ), 32.7 (s, C( C H 3 ) 3 ), 4.5 (bs, (N(SiMe 3 ) 2 ) 3.5 (s, (N(SiMe 3 ) 2    
     The signals of the quaternary carbon atom of the tert-butyl group and the methylene bridge cannot be observed. 
     IR (highly purified material): {tilde over (v)}/cm −1 =2949.77 (m), 2900.52 (m), 1240.51 (m), 997.76 (m), 967.78 (s), 948.38 (m), 860.62 (m), 825.20 (s), 801.99 (s), 764.14 (s), 738.03 (m), 660.67 (s), 591.07 (s), 450.52 (m) 
     EXAMPLE 13 
     Preparation of [(η 5 :η 1 -C 5 Me 4 PPh 2 CH 2 )LaBr(hmds)(thf)] 
     
       
                 
         
             
             
         
      
     
     16.0 mg (0.044 mmol, 1.05 eq) of C s Me 4 PPh 2 CH 3  and 25.5 mg (0.042 mmol, 1.00 eq) La(hmds) 2 Br(thf)] 2  were weighed in together into an NMR tube and dissolved in 0.7 mL d 8  toluene. The reaction solution is examined by NMR-spectroscopy. 
     The temperature is then increased by 10° C. and one spectrum each of  31 P-NMR and  1 H-NMR is measured. 
       31 P-NMR (202.3 MHz, d 8 -tol): δ/ppm=14.4 
       1 H-NMR (500.1 MHz, d 8 -tol): δ/ppm=7.89-6.99 (m, 10H, Ph), 3.58 (4H, thf), 2.09 (s, 6H, C   5 Me 4   ), 1.82 (s, 6H, C   5 Me 4   ), 1.52 (4H, thf), 0.44 (d, 2H,  2 J PH =6.0 Hz, PC H 2   La), 0.08 (s, 18H, N(Si Me 3   ) 2 ). 
       13 C-NMR (125.8 MHz, d 8 -tol): δ/ppm=133.1 (Ph), 133.0 (Ph), 131.4 (Ph), 14.1 (C 6   Me 4   ), 11.9 (C 6   Me 4   ), 2.66 (s, N(Si Me 3   ) 2 ), 1.39 (P C H 2 La). The signals for the quaternary carbon atoms of the Cp-ring are not visible. The signal splits of the C atoms of the phenyl ring relative to the phosphor atom cannot be clearly defined due to the width of the signals. 
     EXAMPLE 14 
     Preparation of [(η 5 :η 1 -C 5 Me 4 PMe 2 CH 2 )LaBr(hmds)(thf)] 
     
       
                 
         
             
             
         
      
     
     5.95 mg (0.030 mmol, 1.00 eq) C 5 Me 4 PMe 3  and 20.61 mg (0.034 mmol, 1.13 eq) [La(hmds) 2 Br(thf)] 2  are weighed in together into an NMR tube and dissolved in 10 mL toluene. The reaction solution is examined by  31 P-NMR-NMR spectroscopy. 
       31 P-NMR (121.5 MHz, C 6 D 6 ): δ/ppm=9.15. 
       1 H-NMR (300.1 MHz, C 6 D 6 ): δ/ppm=3.58 (thf), 2.08 (s, 6H, C   5 Me 4   ), 2.04 (s, 6H, C   5 Me 4   ), 1.31 (thf), 0.79 (d, 6H,  2 J P,H =12.0 Hz, P Me 2   ). −0.27 (d, 2H,  2 J P,H =9.0 Hz, PC H 2   La), 0.40 (s, 18H, N(SiMe 3 ) 2 ). 
     EXAMPLE 15 
     Preparation of [(η 5 :η 1 -C 5 Me 4 PPh 2 CH 2 Y(CH 2 SiMe 3 ) 2 ] Via One-Pot Reaction 
     
       
                 
         
             
             
         
      
     
     99 mg LiCH 2 SiMe 3  (1.05 mmol, 3.51 eq) is dissolved in 4 mL toluene, cooled to 0° C. and slowly dropped to a suspension, which has also been cooled to 0° C., of 133 mg [YCl 3 thf 25 ] (0.354 mmol, 1.18 eq) and 96 mg C 5 Me 4 PPh 2 Me (0.300 mmol, 1.00 eq) in 4 mL toluene. A light precipitate fell out of the solution. The mixture is stirred for 1 h at 0° C. A reaction control shows a main product and a secondary product, as well as partially free ligands. The mixture is filtered off in an inverted glass frit, over Celite, and the solvent is removed from the filtrate in vacuo. The residue is then suspended in pentane. After sedimentation of the solid material, the  31 P-NMR spectrum of the supernatant substance shows that both species are now present in the solution in equal ratios. A colorless crystal can be grown from the supernatant solution at −30° C., identifying species 2. 
       31 P-NMR (121.5 MHz, toluene): δ/ppm=12.88 (d,  1 J P,Y =5.36 Hz, 86%, species 1), 7.47 (d,  1 J P,Y =5.36 Hz, 9%, species 2), 1.81 (m, 5%, ligand) 
       31 P-NWIR (121.5 MHz, pentane): δ/ppm=13.84 (d,  1 J P,Y =5.36 Hz, 33%, species 1), 8.40 (m, 33%, species 2), 2.41 (m, 33%. ligand) 
     EXAMPLE 16 
     Ring-Opening Polymerization of ε-Caprolactone with CpPC-bis-hmds Compounds 
     
       
                 
         
             
             
         
      
     
     0.25 mmol of the corresponding ligands were is together in 10 mL toluene with 0.25 mmol of the corresponding RE(hmds) 3  for a time and temperature as indicated below. The completeness of the conversion of the ligands into a complex is checked by  31 P-NMR spectroscopy. Now, 1 mL (ca. 0.025 mmol complex, 1.00 eq) of the reaction solution is injected in 50 mL toluene and 1.14 g (10 mmol, 400 eq) of ε-caprolactone is added. The substance is stirred for 1 h at RT. Afterwards 900 mL MeOH (mixed in with 0.1 mL HCl concentrate ) is added to the solution. A white solid material precipitates immediately, and the solution becomes cloudy. The substance is stirred overnight to ensure the completeness of the precipitation. The next day, the polymer is filtered off using a funnel by B ÜCHNER  and dried for two days at 40° C. in vacuo. 
     The polymer is dissolved in ca. 50-100 mL CHCl 3 , filtered with Celite (to separate. RE 2 O 3 , if necessary); the precipitation is repeated in 500 mL MeOH. The polymer is dissolved two more times and re-precipitated to ensure a high level of purity of the material for analytical purposes. The polymer is analyzed by GPC and NMR spectroscopy. 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
               
               
                 Catalyst 
                 t/min 
                 Yield 
                 Mw/g/mol 
                 PD 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 [(η 5 : η 1 - 
                 60 
                 80% 
                 204.282 
                 2.37 
               
               
                 C 5 Me 4 PMe 2 CH 2 )Y(N(SiMe 3 ) 2 ) 2 ] 
               
               
                 [(η 5 : η 1 - 
                 60 
                 81% 
                 80.408 
                 1.99 
               
               
                 C 5 Me 4 PMe 2 CH 2 )Sm(N(SiMe 3 ) 2 ) 2 ] 
               
               
                 [(η 5 : η 1 - 
                 60 
                 60% 
                 225.549 
                 4.13 
               
               
                 C 5 Me 4 PMe 2 CH 2 )Nd(N(SiMe 3 ) 2 ) 2 ] 
               
               
                 [(η 5 : η 1 - 
                 60 
                 28% 
                 86.171 
                 2.67 
               
               
                 C 5 Me 4 PMe 2 CH 2 )Ce(N(SiMe 3 ) 2 ) 2 ] 
               
               
                 [(η 5 : η 1 - 
                 60 
                 99% 
                 255.060 
                 1.97 
               
               
                 C 5 Me 4 PMe 2 CH 2 )La(N(SiMe 3 ) 2 ) 2 ] 
               
               
                 [(η 5 : η 1 - 
                 60 
                 78% 
                 22.00 
                 1.57 
               
               
                 C 5 H 3 tBuPMe 2 CH 2 )Ce(N(SiMe 3 ) 2 ) 2 ] 
               
               
                 [(η 5 : η 1 - 
                 60 
                 45% 
                 300.380 
                 3.55 
               
               
                 C 5 H 3 tBuPMe 2 CH 2 )La(N(SiMe 3 ) 2 ) 2 ] 
               
               
                 [(η 5 : η 1 - 
                 60 
                 95% 
                 213.040 
                 1.88 
               
               
                 C 5 H 3 tBuPMe 2 CH 2 )Nd(N(SiMe 3 ) 2 ) 2 ] 
               
               
                 [(η 5 : η 1 - 
                 60 
                 75% 
                 189.825 
                 2.31 
               
               
                 C 5 Me 4 PMe 2 CH 2 )Nd(N(SiMe 2 ) 2 ) 2 ] 
               
               
                   
               
               
                 Legend: N(SiMe 3 ) 2  denotes the anion hmds 
               
             
          
         
       
     
     There are no signals in the  31 P-NMR spectrum. The signals of the  13 C-NMR spectrum of polycaprolactone in the experiments correspond to those as noted in the literature ( FIG. 6 ). 
     The detected polydispersities (PD) are in the range of ca. 2. Evidence for a live polymerization is a PD value of 1.0; meaning, all chains are comprised of an equal number of monomer units and therefore evenly grown. However, the initiation rate can naturally be slower than the polymerization rate. This also results in differences as to the chain lengths among chains, which is expressed by a value of PD&gt;1. 
     EXAMPLE 17 
     Isoprene Polymerization 
     
       
                 
         
             
             
         
      
     
     Pre-catalyst synthesis: 0.010 mmol (1.0 eq) of the corresponding ligands in 0.25 mL benzene is dissolved together with 0.011 mmol (1.1 eq) of the corresponding RE(CH 2 SiMe 3 ) 3 thf x  in 0.25 mL benzene and added to an NMR tube. The composition of the pre-catalyst is established by  31 P-NMR spectroscopy. Percentage-type information as to the formation of alkyl or the corresponding alkylidene compound is indicated in the table below. 
     To the solution is now added, inside a schlenk tube, 7.3 mL C 6 H 5 Cl until a quantity of 10 mL is reached after all reagents have been added. 
     1 mL (680 mg) isoprene (10.0 mmol, 1000 eq) is injected, then 1 mL of a (PhNHMe 2 ][B(C 6 F 5 ) 4 ] solution in C 6 H 5 Cl (8.012 mg/1 mL, 0.01 mmol, 1.0 eq) is injected into the solution. Immediately thereafter, 0.2 mL of a triisobutylaluminum solution in toluene (0.1154 g/mL, 0.116 mmol, 11.6 eq) is added. 
     The substance is stirred for 24 h at RT. 
     Afterwards, the viscous solution is added to 100 mL-250 mL HCl-acidic MeOH (0.2 mL HC concentrate ), with a spatula-tip amount of 2,6-di-tert-butyl-4-methylphenol as stabilizer. A while solid material precipitates immediately, and the solution becomes cloudy. The reaction vessels are rinsed with a few mL of CHCl 3 ; in part, the reaction mixtures have such highly viscosity that it is necessary to rinse several times. The quantity of the added precipitation agent is always ten times the volume relative to the polymer solution. The substance is stirred overnight to ensure a complete precipitation. On the following day, polyisoprene is filtered off using a BUCHNER funnel and dried at RT in vacuo for three days. 
     The polymer is dissolved in ca. 10 mL-50 mL CHCl 3 , filtered through a syringe filter (to separate any possible RE 2 O 3  or other contaminations), then precipitated again in 100 mL-250 mL MeOH to ensure a high level of purity for analytical purposes. 
     The polymer is analyzed by GPC, TGA, DSC and NMR spectroscopy. 
     Table: The  31 P-NMR spectroscopic control shows the ratio of the RE alkyl relative to the RE alkylidene compound immediately after adding the reactants in benzene [(C 5 R 1 R 2   3 PR 3   2 CH 2 )RE(CH 2 SiMe 3 ) 2 ] 2  (R′=tBu, Me; R 2 ═H, Me; R 3 =Me, Ph). 
     
       
         
               
               
               
             
           
               
                   
               
               
                                           Reactants 
                                                    
 
                 
                   
                             
                     
                         
                         
                     
                   
                 
               
               
                   
               
             
             
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
                  90% 
                 10% 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
                  38% 
                 62% 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 100% 
                 — 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
                  95% 
                  5% 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 100% 
                 — 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 100% 
                 — 
               
               
                   
               
               
                 
                   
                             
                     
                         
                         
                     
                   
                 
                 100% 
                 — 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 
               
             
             
               
                   
               
               
                 Isomers polyisoprene, identified by  1 H-NMR spectroscopy 
               
             
          
           
               
                 Precatalyst 
                 Yield 
                 cis/% 
                 3.4/% 
                 trans/% 
                 1.2/% 
               
               
                   
               
               
                 [(η 5 : η 1 -C 5 Me 4 PPh 2 CH 2 )Y(CH 2 SiMe 3 ) 2 ] 
                 100% 
                 57.3 
                 20.7 
                 22.0 
                 — 
               
               
                 [(η 5 : η 1 -C 5 Me 4 PPh 2 CH 2 )Sm(CH 2 SiMe 3 ) 2 ] 
                 100% 
                 16.4 
                 83.6 
                 — 
                 — 
               
               
                 [(η 5 : η 1 -C 5 Me 4 PPh 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ] 
                 96.3%  
                 80.5 
                 19.5 
                 — 
                 — 
               
               
                 [(η 5 : η 1 -C 5 H 3 tBuPPh 2 CH 2 )Y(CH 2 SiMe 3 ) 2 ] 
                  5.9% 
                 52.4 
                 25.9 
                 21.7 
                 — 
               
               
                 [(η 5 : η 1 -C 5 H 3 tBuPPh 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ] 
                 13.2%  
                 80.0 
                 12.1 
                  7.9 
                 — 
               
               
                 [(η 5 : η 1 -C 5 H 3 tBuMe 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ] 
                 100% 
                 82.2 
                 17.8 
                   
                 — 
               
               
                 [(η 5 : η 1 -C 5 Me 4 PMe 2 CH 2 )Sc(CH 2 SiMe 2 H) 2 ] 
                  4.1% 
                 28.6 
                 30.9 
                 40.5 
                 — 
               
               
                 [Sc(CH 2 SiMe 3 ) 3 thf 2 ] 
                 100% 
                 60.5 
                 20.7 
                 18.8 
                 — 
               
               
                 [Y(CH 2 SiMe 3 ) 3 thf 2 ] 
                 100% 
                 61.4 
                 19.5 
                 19.1 
                 — 
               
               
                 [Sm(CH 2 SiMe 3 ) 3 thf 2 ] 
                 100% 
                 70.3 
                 16.3 
                 13.4 
                 — 
               
               
                 [(η 5 : η 1 -C 5 Me 4 PPh 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ], without 
                  0% 
               
               
                 borate, without TIBAL 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 
               
             
             
               
                   
               
               
                 Glass transition temperature, established by TLC measurement 
               
             
          
           
               
                   
                 Precatalyst 
                 Glass transition 
               
               
                   
                   
               
               
                   
                 [(η 5 : η 1 -C 5 Me 4 PPh 2 CH 2 )Y(CH 2 SiMe 3 ) 2 ] 
                 −51.1° C. 
               
               
                   
                 [(η 5 : η 1 -C 5 Me 4 PPh 2 CH 2 )Sm(CH 2 SiMe 3 ) 2 ] 
                  6.3° C. 
               
               
                   
                 [(η 5 : η 1 -C 5 Me 4 PPh 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ] 
                 −50.83 
               
               
                   
                 [(η 5 : η 1 -C 5 H 3 tBuPPh 2 CH 2 )Y(CH 2 SiMe 3 ) 2 ] 
                 Not determined 
               
               
                   
                 [(η 5 : η 1 -C 5 H 3 tBuPPh 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ] 
                 −57.6° C. 
               
               
                   
                 [(η 5 : η 1 -C 5 H 3 tBuMe 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ] 
                 −52.7° C. 
               
               
                   
                 [(η 5 : η 1 -C 5 Me 4 PMe 2 CH 2 )Sc(CH 2 SiMe 2 H) 2 ] 
                 Not determined 
               
               
                   
                 [Sc(CH 2 SiMe 3 ) 3 thf 2 ] 
                 −51.3° C. 
               
               
                   
                 |Y(CH 2 SiMe 3 ) 3 thf 2 ] 
                 −53.5° C. 
               
               
                   
                 [Sm(CH 2 SiMe 3 ) 3 thf 2 ] 
                 −56.0° C. 
               
               
                   
                 Natural rubber 
                   −68° C. 
               
               
                   
                   
               
               
                   
                 *not determined since no substance was available any longer. Yield &lt;6% 
               
             
          
         
       
     
     It could be determined by TGA measurements that there is no significant break-down in excess of 5% until the degradation point at ca. 390-450° C. is reached. TLC measurements show that the polymer has, with a glass point of ca. −50° C. and without melting point, ideal properties that are typical for an elastomer until the degradation point is reached. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 
               
             
             
               
                   
               
               
                 Polydispersity and molecular weights, detected by GPC 
               
             
          
           
               
                 Precatalyst 
                 Mw/g/mol 
                 PD 
               
               
                   
               
               
                 [(η 5 : η 1 -C 5 Me 4 PPh 2 CH 2 )Y(CH 2 SiMe 3 ) 2 ]* 
                 &gt;600.000 
                   
               
               
                 [(η 5 : η 1 -C 5 Me 4 PPh 2 CH 2 )Sm(CH 2 SiMe 3 ) 2 ]** 
                 Not detectable 
               
               
                 [(η 5 : η 1 -C 5 Me 4 PPh 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ]* 
                 &gt;600.000 
               
               
                 [(η 5 : η 1 -C 5 H 3 tBuPPh 2 CH 2 )Y(CH 2 SiMe 3 ) 2 ] 
                   70.3970 
                 2.591 
               
               
                 [(η 5 : η 1 -C 5 H 3 tBuPPh 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ]* 
                 &gt;600.000 
               
               
                 [(η 5 : η 1 -C 5 H 3 tBuPMe 2 CH 2 )Sc(CH 2 SiMe 3 ) 2 ]** 
                 Not detectable 
               
               
                 [(η 5 : η 1 -C 5 Me 4 PMe 2 CH 2 )Sc(CH 2 SiMe 2 H) 2 ]** 
                 Not detectable 
               
               
                 [Sc(CH 2 SiMe 3 ) 3 thf 2 ]*** 
                 ca. 60.000 
               
               
                 |Y(CH 2 SiMe 3 ) 3 thf 2 ]*** 
                 ca. 75.000 
               
               
                 [Sm(CH 2 SiMe 3 ) 3 thf 2 ] 
                  367.700 
                 3.099 
               
               
                 Natural rubber 
                 2-4 × 10° 
                 3-10 
               
               
                   
               
               
                 *Molecular weight so great that it ends up as void volume (&gt;10), the molecular weight (Mw) cannot be detected exactly. 
               
               
                 **Samples are poorly soluble in THF, and/or they cannot be completely pressed through the syringe filter. 
               
               
                 ***Curve with more than one maximum, bimodal distribution 
               
             
          
         
       
     
     The detected polydispersities (PD) are also in a range around 2. In this case as well, the catalysts start the polymerization so fast that the polymerization rate is greater than the initiation rate. Moreover, the chains are extraordinarily long, such that any measurement that yields an exact value Mw/g/mol is not possible. Without determining the Mw, it is not possible to detect polydispersities, which are, however, not important in the synthesis of natural rubber (natural rubber: PD 3-10).