bluuebunny/crossref_metadata_2025 huggingface dataset:
Thiaaza‐arachno‐pentaboran SNB3H2tBu3R
Authors: Müller Matthias , Englert Ulli , Paetzold Peter
Published: July 2007

Thiaaza‐arachno‐pentaborane SNB3H2tBu3R

The azadiboriridine [‐B(tBu)‐N(tBu)‐B(tBu)‐] (1) gives 1:1 adducts with the mercaptoboranes BH2(SR), which can be generated from their cyclotrimers by the action of THF. The adduct 4a (R = Ph), a nido cluster with an NB3 skeleton, forms an equilibrium with an adduct 5a, an arachno cluster with an SNB3 skeleton, whose S‐bound ligand Ph is found in an endo position by an X‐ray structural analysis. The equilibrium 4a · 5a involves a Lewis acid‐base reaction, which is electronically coupled to a reduction of a three‐center to give a two‐center π bond. The reaction of 1 with BH2(SPr) gives the corresponding arachno cluster 5b only.
[MeO(CH2CH2O)3(CH2)3C5Me4]FeCl: A Halfsandwich Iron (II) Chloride Complex of Remarkable Stability
Authors: Siemeling Ulrich
Published: July 2007

Reaction of iron(II) chloride with one equivalent of [MeO‐(CH2CH2O)3(CH2)3C5Me4]Li in THF yields the title halfsand‐wich complex 1, which is stable in solution up to room temperature. Compound 1 reacts with C5H5Li and CO to give [MeO(CH2CH2O)3(CH2)3C5Me4]Fe(C5H5) (2) and [MeO‐(CH2CH2O)3(CH2)3C5Me4]Fe(CO)2CI (3), respectively, in high yields.
A Novel Approach to Ferrocenes with Planar Chirality
Authors: Ganter Christian , Wagner Trixie
Published: July 2007

The 2‐metalation of enantiomerically pure (S)‐(2‐methoxy‐methylpyrrolidin‐1‐yl)ferrocene FcSMP (1) with BuLi proceeds with high diastereoselectivity (up to 98% de) to yield the Ph2P‐substituted ferrocene (S,Sp)‐2a after quenching with Ph2PCl. The SMP moiety was removed by heating of 2a at reflux in acetic anhydride to give planar chiral (Sp)‐2‐diphenylphosphanylferrocenylmethyl acetate (5). The diastereoisomer (S,Rp)‐2b was synthesized from 1 by intermediately blocking the primary metalation site with a Me3Si group which can be removed afterwards by treatment with KOtBu in DMSO. Compound 2a was treated with [(C3H5)PdCl]2 to give the complex [(C3H5)Pd·2a]PF6 (7·PF6). The structure of 7·PF6 was determined by a single‐crystal X‐ray diffraction study and showed 2a to act as a bidentate P,N‐chelate ligand.
Oligonuclear Organometallic Complexes with Boron‐Nitrogen Bridges
Authors: Jäkle Frieder , Priermeier Thomas , Wagner Matthias
Published: July 2007

The facile formation of boron‐nitrogen bridges allows the one‐step assembly of oligonuclear organometallic complexes. By the reaction of 1‐(dibromoboryl)ferrocene (1a) and 1,1′‐bis(dibromoboryl)ferrocene (1b) with 1‐[(dimethylamino)methyl]ferrocene (2) and (η6‐aniline)tricarbonylchromium derivatives (3, 4) dinuclear to pentanuclear units (5–10) were obtained. The homodimetallic compound FcBBr2‐NMe2CH2Fc (5, Fc: ferrocene) closely resembles a propylene‐bridged complex. Its dative B‐N link is stable at temperatures as high as 100°C. Each of the heterooligonuclear aggregates 7–10 is tied together by covalent B‐N bonds, which are isoelectronic with ethylene bridges. In FcB(Br)‐N(Me)Bct [7, Bct: (η6‐C6H5)Cr(CO3)] and 1,1′‐Fc[B(Br)‐N(Me)Bct]2 (9) B‐N π bonding dominates over the N‐Bct π interaction as indicated by spectroscopical data and an X‐ray analysis of 9. The N‐lithiated compounds BctNRLi (4a, b; R = H, Me) possess a remarkably increased N‐Bct π donation compared to the protonated parent compounds, which results in a further perturbation of the local C3v symmetry of the (C6H5)Cr(CO3) framework.
Halfsandwich‐Type Osmium Complexes Containing Phosphanylmethanide and Phosphanyl Alcoholate Anions as Bidentate Ligands
Authors: Werner Helmut , Henig Gerhard , Wecker Ulrich , Mahr Norbert , Peters Karl , Schnering Hans Georg Von
Published: July 2007

The mononuclear dichloroosmium(II) complexes [(mes)‐Os(L)Cl2] (2‐5) with the phosphanyl ether L = iPr2PCH2‐CH2OMe and phosphanyl esters L = IPr2P(CH2)nCO2R as ligands are obtained from [(mes)OsCl2]n and L in almost quantitative yield. While compound 3 (L = iPr2PCH2CH2CO2Me) reacts with Mg/Hg in THF in the presence of ethanol to give the monohydrido derivative 6, treatment of 4 (L = iPr2PCH2‐CO2Me) or 5 (L = iPr2PCH2CO2Et) with Al2O3/NaH in THF yields the phosphanylmethanide complexes [(mes)‐Os{k2(P,C)‐iPr2PCHCO2R}Cl] (7, 8). In contrast to the reaction of 4 with Mg/Hg in THF/EtOH which yields the dihydrido compound [(mes)OsH2{k(P)‐iPr2PCH2CO2Me}] (10), the corresponding reaction of 4 with excess PhMgBr does not lead to an OsPh2 species but instead gives the new chelate complex [(mes)OsPh{k2(P,O)‐iPr2PCH2CPh2O}] (11). The crystal and molecular structures of 7 and 11 were determined.
The 13C Chemical Shift of the ipso Carbon Atom in Phenyllithium
Authors: Berger Stefan , Fleischer Ulrich , Geletneky Christian , Lohrenz John C. W.
Published: July 2007

Phenyllithium was labeled with 6Li and 13C at the ipso carbon atom, and the tetramer was measured by solid‐state NMR. The chemical shift tensor data were obtained by a moment analysis of the spinning side bands and were compared with the results obtained by calculations with the IGLO method. Although no splitting by dipolar spin coupling to 6Li was found the very good agreement between IGLO predictions and experimental results allowed alignment of the tensor axis to the molecular frame and interpretation of the data. The large deshielding of the isotropic chemical shift is mainly due to a decrease of the ΔE term in s̀.
Contributions to the Chemistry of Boron, 231. Synthesis and Structures of Borylated Hydrazines
Authors: Hommer Herbert , Nöth Heinrich , Sachdev Hermann , Schmidt Martin , Schwenk Holger
Published: July 2007

The diboration of the diazene PhN = NSiMe3 (15) by diborane(4) derivatives provides a new synthetic route to N,N'‐diborylated hydrazines. The product formed depends on the type of the diborane(4) compound. Thus, addition of dimesityldiboron dichloride to 15 in a 1:1 ratio afforded (mesCIB)PhN‐N(SiMe3)(BClmes) (16) while bis(dimethyl‐amino)diboron dichloride was found to react in a 1:2 ratio to give a triazadiborolidine derivative 17. In addition, it was demonstrated that in the solid state Me2N–N(BPh2)2 (8) is a derivative of a three‐membered dihydroazadiboriridine C while its isomer, (Ph2B)MeN–NMe(BPh2) (7), forms no BN coordinative bond. The new 3,6‐difluoro‐1,2,4,5‐tetraza‐3,6‐diborine 13 shows a twist conformation. The molecular structures of all these compounds were determined by X‐ray crystal structure analysis, and the influence of the B substituent on the conformation is discussed.
Auf‐ und Abbau von Azadecaboranen; Aza‐nido‐nonaborat
Authors: Roth Martin , Paetzold Peter
Published: July 2007

Synthesis and Degradation of Azadecaboranes; Aza‐nido‐nonaborate

The boranes arachno‐B9H13(NRH2 (1a‐c: R = p‐ClC6H4, p‐MeC6H4, PhCH2) are dehydrogenated at 140°C to give nido‐RNB9H11 (2a‐c), from which the azaboranes closo‐RNB9H9 (3a‐c) are formed on further dehydrogenation at 460°C. These azaboranes are deboronated either by the attack of the amine iPrNH2 or by one of the fluorides [NBu4]F or [S(NMe2)3][Me3SiF2] in THF. One of the four boron atoms adjacent to nitrogen in the closo species is removed and then detected in the borazine (HNBiPr)3 or the borate BF4, respectively, whereas the novel anions nido‐RNB8H9 (4a‐c) remain. The structure of 4a‐c corresponds to that of nido‐SB8‐H9‐, according to NMR spectra. Primary amines R'NH2 deboronate the closo‐boranes 3a, b in a solvent less polar than THF to give the amine – azanonaboranes arachno‐RNB8H10‐(NR'H2) (5a‐c: R' = iPr, Pr, Bu). The nido product [iPrNH3][(p‐ClC6H4)NB8H9 is converted into a mixture of the arachno products 5a and (p‐ClC6H4)NB8H10(NPrH2) (5d) by the action of PrNH2, making plausible that anions of type 4 are intermediates during the transformation of 3 into 5.
Synthese und Reaktivität von Silicium‐Übergangsmetall‐Komplexen, 35. Metallo‐silanole und Metallo‐siloxane, 9. Synthese des diastereomerenreinen Ferrio‐silanols (RS,SR)‐Cp(OC)(Ph3P)Fe‐Si(Me)(Ph)(OH) und Struktur von (RR,SS)‐Cp(OC)(Ph3P)Fe‐Si(Me)(Ph)Cl
Authors: Malisch Wolfgang , Neumayer Michael , Fey Oliver , Adam Waldemar , Schuhmann Rosemarie
Published: July 2007

Synthesis and Reactivity of Silicon Transition Metal Complexes, 35

34. Mitteilung: W. Malisch, R. Lankat, W. Seelbach, J. Reising, M. Noltemeyer, R. Pikl, U. Posset, W. Kiefer, Chem. Ber., 1995, 128, 1109.

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— Metallo Silanols and Metallo Siloxanes, 9

8. Mitteilung: W. Malisch, S. Schmitzer, R. Lankat, M. Neumayer, F. Prechtl, W. Adam, Chem. Ber., 1995, 128, 1251, voranstehend.

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— Synthesis of the Diastereomerically Pure Ferrio Silanol (RS,SR)‐Cp(OC)(Ph3P)Fe‐Si(Me)(Ph)(OH) and Structure of (RR,SS)‐Cp(OC)(Ph3P)Fe‐Si(Me)(Ph)Cl

Herrn Professor Max Schmidt zum 70. Geburtstag gewidmet.

Irradiation of the ferrio chlorosilane Cp(OC)2Fe‐Si(Me)‐(Ph)Cl (1) in the presence of Ph3P leads to Cp(OC)(Ph3P)‐Fe‐Si(Me)(Ph)Cl (2) which is formed as a mixture of diastereomers separated by crystallization. Pure (RR,SS)‐2 is converted highly stereoselectively into (RR,SS)‐Cp(OC)(Ph3P)‐Fe‐Si(Me)(Ph)H (3) with LiAlH4, and further with dimethyldioxirane into (RS,SR)‐Cp(OC)(Ph3P)Fe‐Si(Me)(Ph)(OH) (4). This ferrio silanol diasteromer is alternatively obtained by Cl/OH exchange with KOH from 2. Diastereomerically pure (RR,SS)‐2 is characterized by a single‐crystal structure analysis.
An Efficient Catalyst for the Conversion of Hydrosilanes to Alkoxysilanes
Authors: Lorenz Catrin , Schubert Ulrich
Published: July 2007

The copper(I) hydride [Ph3PCuH]6 is an efficient catalyst for the alcoholysis of primary and secondary silanes. The reactions proceed at room temperature within a few hours and give the alkoxysilanes in high yields. Only with bulky alcohols or silanes are longer reaction times and/or increased temperatures required. The presence of air accelerates the reactions and gives rise to higher yields of alkoxysilanes, particularly with bulky alcohols. Diols react with PhRSiH2 (R = Me, Ph) to afford 1,3‐dioxo‐2‐silacycloalkanes and with tertiary silanes to furnish the bissilylated diols. When unsaturated alcohols (2‐propen‐1‐ol or 2‐propyn‐1‐ol) are employed, the double or triple bond is retained.
Reaction of Alkylzirconocene Cation Complexes with (R–CC–)2SiR2 Reagents: Preparation of Heterodimetallic Compounds Containing a μ‐Alkynyl Ligand Bridge Between Zirconium and Silicon
Authors: Röttger Dirk , Erker Gerhard , Fröhlich Roland , Kotila Sirpa
Published: July 2007

The methylzirconocene cation, employed as the [Cp2ZrCH3(THF)]+BPh4− reagent 1a reacts with (R′CC)2SiR2 substrates (6a–d) by means of carbometallation of an alkynyl group to yield the mixed metal ring systems 8a–d, containing both a 1,1‐disubstituted μ‐alkenyl and an alkynyl bridge between zirconium and silicon (e.g. shown by X‐ray crystal structure analyses of complexes 8a and 8c). A similar addition reaction takes place upon treatment of the (butadiene)zirconocene/tris(pentafluorophenyl)‐borane 1:1 addition product 9 with (CH3–CC)2Si(CH3)2 (6c) to give 10. Here the incipient alkyl zirconocene cation character of the metallocene/borate betaine complex 9 shows up in the alkynyl silane carbometallation reaction.
The Reduction of Oxalic Amidines with Metallic Lithium: Preparation of Lithiated Bisamides [R″N(RR′N)C=C(NRR′)NR″]Li2 and Their Use as Intermediates in a Novel Synthesis of Tetraaminoethenes
Authors: Wenzel Matthias , Lindauer Dirk , Beckert Rainer , Boese Roland , Anders Ernst
Published: July 2007

Reduction of the 1,4‐diaza‐1,3‐butadiene substructure of hexasubstituted oxalic amidines with lithium metal yields the new lithium diamides 3. Subsequent reaction of 3 with various electrophiles gives the title substances 4, 5, and the acylated derivative 6, respectively. The first SET step in this reaction is the formation of monolithium radical anions 2, which were detected by EPR spectroscopy. The second electron transfer leads to the deeply colored dianions 3. – In the case of compound 3a [cis‐3a · 3 Et2O], the X‐ray crystal structure reveals the cisoid arrangement of the bidental ligand and three molecules of diethyl ether which are located in a 2:1 fashion in the first coordination sphere of the lithium cations. The NMR 2D‐1H,6Li‐HOESY investigations of 3a in [D10]diethyl ether/diethyl ether (8:1) show Li+ contacts to the hydrogen atoms of the ether molecules and to the ortho‐hydrogen atoms of the aryl moieties. Results of semiempirical calculations (PM3) are throughout in acceptable agreement with the experimental data and explain the unusual coordination pattern of the lithium cations of compounds 3.
Synthesis of Novel Tridentate N,O,S and N,N,O Ligands of the Tripod Type in Racemic and Enantiomerically Pure Form
Authors: Berkessel Albrecht , Frauenkron Matthias , Nowak Thorsten , Schwenkreis Thomas , Seidel Lutz , Steinmetz Adrian , Bolte Michael
Published: July 2007

A series of seven chiral, tripodal N,O,S and N,N,O ligands were prepared in which N stands for a secondary amine or imidazole donor, O for a phenol, and S for a thioether or thiol metal‐binding group. Key steps are (1) the construction of ortho‐hydroxyacetophenones bearing the phenolic binding group and either a thioether, a protected thiol or an imidazole substituent in the α‐position, and (2) subsequent reductive amination with a primary amine. The modular synthesis allows a rapid construction of a variety of structurally related ligands. In three cases, the enantiomers of the racemic products could be separated after condensation with (R)‐glyceraldehyde acetonide as chiral auxiliary. The relative configurations of the cyclic N,O‐ and N,N‐acetals thus obtained were established by NOE spectroscopy. X‐ray structural analysis of two crystalline N,O‐ and N,N‐acetals allowed the assignment of absolute configurations. Hydrolysis of the dia‐stereomerically pure acetals afforded the enantiomerically pure ligands in high yield. By comparison of their CD spectra, absolute configuration could also be assigned to the third pair of enantiomerically pure ligands.
Synthesis and Structure of Bis(2,4‐di‐tert‐butyl‐1,3‐cyclopentadien‐1‐yl)‐disulfane, S2(tBu2C5H3)2, and Bis[2,4‐di‐tert‐butyl‐5‐(trimethylsilyl)‐1,3‐cyclopentadien‐1‐yl]disulfane, S2 [tBu2(Me3Si)C5H2]2
Authors: Thaler Georg , Wurst Klaus , Sladky Fritz
Published: July 2007

Reaction of 1,3‐di‐tert‐butylcyclopentadienyllithium and 1,3‐di‐tert‐butyl‐4‐(trimethylsilyl)cyclopentadienyllithium with S2Cl2 gives bis(2,4‐di‐tert‐butyl‐1,3‐cyclopentadien‐1‐yl)di‐sulfane (1) and bis[2,4‐di‐tert‐butyl‐5‐(trimethylsilyl)‐1,3‐cyclopentadien‐1‐yl) disulfane (2), respectively. The structure of 2 was determined by single‐crystal X‐ray diffraction. Compounds 1 and 2 are the first biscyclopentadienylchalcogens with the chalcogen in vinylic position.
Activation of Carbon Dioxide, VI. Ligand Effects in the Catalytic Hydrogenation of Carbon Dioxide to Formic Acid Using in situ Catalysts Formed from [{(cod)Rh(μ‐Cl)}2] and Monodentate and Bidentate Phosphorus Ligands
Authors: Graf Elisabeth , Leitner Walter
Published: July 2007

Highly active catalysts for the hydrogenation of CO2 to formic acid in DMSO/NEt3 are formed in situ from [{(cod)Rh(μ‐Cl)}2] and various monodentate or bidentate ligands with phosphorus as the donor atom. Formic acid concentrations up to 2.3 · 0.2 mol l–1 can be obtained in less than 6 hours at ambient temperature under a total initial pressure of 40 atm by using rhodium concentrations of 5 · 10–3 mol l–1. The changes in catalytic activities observed upon structural changes of monodentate ligands are discussed in terms of classical ligand parameters like basicity and steric demand of the PR3 group, while with bidentate ligands R2P(CH2)nPR2 the chain length n plays a dominant role for the activity of the catalyst. The effects cannot be explained by a direct impact of the ligand on catalytically active intermediates only, but influences on the formation of these species must also be taken into account.
Chirale Tripodliganden mit Phosphor‐ und Schwefeldonoren. Synthese und Komplexchemie
Authors: Reinhard Gunther , Soltek Rainer , Huttner Gottfried , Barth Annette , Walter Olaf , Zsolnai Laszlo
Published: July 2007

Chiral Tripod Ligands with Phosphorus and Sulfur Donors. Synthesis and Complex Chemistry

Neopentane based tripod ligands CH3C(CH2X)(CH2Y)‐(CH2Z) with mixed donor groups X,Y,Z (PR2, SR, SH) are accessible via two different strategies. The functionalized thietane CH3(CH2X)ČH2SCH2 allows stepwise introduction of P or S donors by substitution of the mesylate function and subsequent nucleophilic cleavage of the thietane ring. Tripod ligands 5 [CH3C(CH2X)(CH2Y)(CH2Z)] with up to three different donor groups (X = SH; Y = PPh2; Z = P(4‐Tol)2, SCH2Ph, PPh2) are thus available. As an alternative the neopentane derivatives 8 [CH3C(CH2X)(CH2Y)(CH2Cl)] which are easily assessible from CH3C(CH2OSO2Me)(CH2Br)‐(CH2Cl) (7) by stepwise substitution with phosphides LiPAr2 (Ar = aryl) may be transformed to 9 [CH3C(CH2X)(CH2Y)(CH2SBzl)]. Under controlled conditions the S—benzyl bond of 9 is cleaved reductively without concomitant cleavage of P—Ar bonds. Ligand 5a [CH3C(CH2PPh2)2(CH2SH)] reacts with Ni(BF4)2 · 6 H2O to yield the dinuclear species [(CH3C(CH2PPh2)2‐(CH2S)Ni)2]2+ (10). The two ligands are bonded in an equivalent way with each of the two nickel centers interacting with one of the two phosphane functions of the ligand; the thiolate functions form μ2‐SR bridges between the two nickel atoms. The SCH2 group at the four‐membered S2Ni2 ring are in mutual cis position with the four‐membered ring bent along the sulfur–sulfur axis by 70°. The internal strain in 10 is analyzed by comparing its structure with the ones of [(CH3C(CH2‐PPh2)3NiSPh)2]2+ (11) and [(CH3C(CH2OH)(CH2PPh2)2‐NiOH)2]2+ (12).
Chalcogen Transfer to Bis[2‐(dimethylaminomethyl)phenyl]silanediyl by Isocyanates and Isothiocyanates
Authors: Belzner Johannes , Ihmels Heiko , Kneisel Boris O. , Herbst‐Irmer Regine
Published: July 2007

Reaction of hexakis[2‐(dimethylaminomethyl)phenyl]cyclo‐trisilane (1) with isocyanates results in the clean formation of cyclic di‐ or trisiloxanes 3 and 4a and the corresponding isonitrile. Single‐crystal X‐ray analysis of tetrakis[2‐(dimethylaminomethyl)phenyl]cyclodisiloxane (4a) reveals each silicon center to interact with two amino groups forming Si ⃛N distances, which differ significantly in length. Phenyl isothio‐cyanate reacts with 1 with transfer of sulfur to yield penta‐coordinated bis[2‐(dimethylaminomethyl)phenyl]silanethione (11).
Metal‐Assisted Assembly of Chain and Macrocyclic As–S Ligands from Ethylcycloarsathiane (C2H5AsS)n
Authors: Häusler Thomas , Sheldrick William S.
Published: July 2007

Treatment of cyclo‐(EtAsS)n with [RuCl2(Ph3P)3] and [Re‐Br(CO)5] affords the respective complexes [RuCl2{cyclo‐(EtAsS)4}(Ph3P)] (1) and [{Re(CO)3}2{μ‐(Et4As4S5)}] (2). Whereas 1 contains a η3 As coordinated intact cyclotetramer (EtAsS)4, ring cleavage leads to the chain anion Et4As4S52−, stabilised as a bridging hexadentate ligand in 2. Reaction of MCl3 with cyclo‐(EtAsS)n in toluene in a Carius tube enables the metal‐mediated temperature controlled assembly of the novel 16‐ and 14‐membered macrocyclic hexadentate As–S ligands in (M{cyclo‐(Et6As8S10)}] (3: M = Os; 4: M = Ru) and [Ru{cyclo‐(Et4As6S10)}] (5). The structures of the products were established by X‐ray crystallography.
Synthesis and Structure of Tris(trialkylstannyl)‐ and Tris(dialkylhalostannyl)amines; Stabilization of the Sn3N Skeleton by Intramolecular Sn–X–Sn Bridges
Authors: Appel Andrea , Kober Christian , Neumann Christine , Nöth Heinrich , Schmidt Martin , Storch Wolfgang
Published: July 2007

Tris(triorganylstannyl)amines (R2R'Sn)3N (1, 2) with substituents R = R' = Me, Bu or R = Me and R' =iPr,tBu are obtained by metathesis from R2R'SnX and NaNH2in liquid ammonia or by transamination of R3SnNMe2with NH3. Tris(diorga‐nylhalostannyl)amines (R2XSn)3N (3) are synthesized by stannazane cleavage of (Me3Sn)3N (1) with R2SnX2. Information from multinuclear magnetic resonance spectra ascertain the planarity of the Sn3N skeleton of type2and3, as well as the relationship between the coupling constants1J(119Sn15N) and2J(119Sn117Sn) and the Sn–N bond length as determined by the X‐ray structure analysis of1, 3band3r. Compound3bshows an almost undistorted D3hsymmetry with a planar Br3Sn3N skeleton and SnN bond lengths of 1.99 Å, which beside those of3aare the shortest found so far. According to MNDO approximate andab initiocalculations π interactions between the lone electron pair at the N atom and empty orbitals at the Sn atoms can be excluded. Therefore, the tristan‐nylamines discussed here have a trigonal planar nitrogen center with its lone electron pair in ap‐type orbital. Further characteristic features of the molecular structures of typ3compounds are the intramolecular Sn–X–Sn bridges (X = Cl, Br, I) found in the solid state as well as in solution. The molecular geometries of the tristannylamines are supported by MS fragmentation patterns as well as by infrared and Raman spectra.
Ring‐Enlargement and Ring‐Opening Reactions of Benzoxazole, Thiazoles, and Benzisoxazole by Zirconocene‐Alkyne Complexes
Authors: Arndt Perdita , Lefeber Claudia , Kempe Rhett , Rosenthal Uwe
Published: July 2007

Zirconocene alkyne complexes Cp2Zr(L)(Me3SiC2R) (L = Py, THF; R = SiMe3 tBu) react with heterocyclic compounds like benzoxazole and related thiazoles to yield ring‐expanded adducts (1–3) and (4, 5) by formal C‐X (X = O, S) bond cleavage and coupling with the coordinated alkyne. In the case of benziso‐xazole, the alkyne is not coupled but eliminated, and with ring‐enlargement of the benzisoxazole a N‐bridged dimer (6) is formed. The obtained complexes 1, 3, and 6 were characterized by NMR spectra and crystal structure analysis.
Synthesen und Strukturen von neuen 1,3,5‐Triphospha‐2,4,6‐trisilacyclohexanen und Untersuchung ihrer Ligandeneigenschaften gegenüber [M(CO)3]‐Komplexfragmenten (M = Cr, Mo)
Authors: Drieß Matthias , Pritzkow Hans , Reisgys Michael
Published: July 2007

Syntheses and Structures of New 1,3,5‐Triphospha‐2,4,6‐trisilacyclohexanes and Investigation of Their Ligand Properties Toward [M(CO)3] Complex Fragments (M = Cr, Mo)*

The synthesis of the new P3Si3‐heterocyclohexanes 1b‐1e are reported. They are easily accessible by salt elimination reaction of the corresponding dichloro organosilanes with lithium cyclohexylphosphanide. Their NMR‐spectroscopic properties, structural features and reactivity toward [M(CO)3(NCMe)3] are compared to those of the previous described derivative 1a. The structure of 1b has been established by X‐ray crystallography, showing that the Si3P3six‐membered ring has a slightly distorted chair‐like conformation and the organo substituents at silicon and phosphorus are located in the equatorial positions. The phosphorus atoms are pyramidal surrounded [sum of bond angles 302.1 (P1), 304.8 (P2) and 303.1° (P3)] and the Si‐P distances are identical with those in 1a and in other silacyclophosphanes. The complexation of the triphosphane‐coronands 1b‐e with [M(CO)3(NCMe)3] (M = Cr, Mo) gives the desired triphos‐phane crown‐like complexes 2b‐e and 3e in 38–53% yield. The X‐ray crystal structures of the Cr complexes 2b and 2e exhibit that the organo groups at silicon, surprisingly, being axial oriented and the cyclohexyl groups being in equatorial positions, whereas in case of the Mo analogue of 2e, that is 3e, all organo substituents prefer equatorial sites. The different configuration of the free ligand 1b compared with that in the complex 2b and the different configuration of the ligand 1e in the complexes 2e and 3e is due to the steric congestion (bulky aryl and [M(CO)3] groups) in these molecules. The change of configurations can be achieved by phosphorus inversion during the complexation process; the ease of inversion is rationalized by a intrinsic low inversion barriere at phosphorus (10–20 kcal mol−1) in silacyclophosphanes. Another complex type has been observed for the previous reported unusual Cr complex 2a, in which one Si‐H bond ousts a phosphorus atom in the coordination to the Cr center. The different structures of the Cr complexes 2b‐d compared to the structure of 2a clearly proves that the formation of a Si, H, Cr three‐center two‐electron bond in 2a is determined by the second ortho‐methyl group at the aryl substituent (mesityl) and the tiny metal center (Cr).
Synthesis and Characterization of a Novel Cyclobutadiene‐octatetrayne Polymer
Authors: Altmann Markus , Enkelmann Volker , Bunz Uwe H. F.
Published: July 2007

The synthesis of 3a starting from compound 1 is described. Copper‐catalyzed oxidative coupling of 3b under Hay conditions gives the novel polymer 9 with octatetrayne‐cyclobutadiene units.
Organometallic Group‐13 Metal Complexes of d‐Block Elements, XIV. Intramolecularly Base‐adduct‐stabilized Transition‐metal‐substituted Indanes: Synthesis and Spectroscopic Characterization, Structure of (η5‐C5H5)(CO)NiInBr2(NC7H13)
Authors: Weiß Jurij , Frank Alissa , Herdtweck Eberhardt , Nlate Sylvain , Mattner Mike , Fischer Roland A.
Published: July 2007

The reaction of InBr/InBr3 or InBr/BrIn[(CH2)3NMe2]2 with the transition metal dimers [L(CO)nM]2 {L = CO, Cp, C5H4[(CH2)2NMe2]; M = Fe, Co, Ni; n = 1–3} in THF or dioxane gives in almost quantitative yield the transition metal indium complexes L(CO)nMInBr2(Do) (Do = THF, NC7H13) and L(CO)nMIn[(CH2)3NMe2](Br) respectively. The new compounds were characterized by elemental analysis, infrared v(CO) spectroscopy, NMR, and mass spectrometry. An X‐ray single crystal structure determination of (η5‐C5H5)(CO)‐Ni–InBr2(NC7H13) (1a) revealed a short Ni–In bond of 246.3(1) pm.
Improved Access to {[ω‐(Phosphanyl)alkyl]cyclopentadienyl}cobalt(I) Complexes: Decomplexation of the Phosphane Arm; Alkyne Complexes; Synthesis of Mononuclear Vinylidenecobalt(I) Complexes
Authors: Foerstner Jan , Kettenbach Ralf , Goddard Richard , Butenschön Holger
Published: July 2007

An improved synthesis of [(2‐phosphanylethyl)cyclopenta‐dienyl]cobalt(I) chelate complexes is presented, in which the paramagnetic chloride 3 is a precursor of the ethene complex 4. The latter readily undergoes ligand exchange reactions which in the case of bidendate reagents (1,5‐cyclooctadiene, 1,2‐bis(diisopropylphosphanyl)ethane, 2,2′‐bipyridine, nor‐bornadiene) cause a decomplexation of the phosphane arm at room temperature with formation of 7, 5, 6, 8. The ethene ligand in 4 can be replaced by alkynes under equally mild reaction conditions (formation of 9, 11 – 16). The reaction with ethyne results in the formation of vinylidene complex 10. The yields of the reactions with nonaromatic alkynes could be improved by treating 3 with the alkyne in the presence of sodium amalgam. The unsubstituted vinylidene complex 10 and its tert‐butyl derivative 17 were obtained by this route in 38 and 40% yield, respectively.
Metal Complexes of Biologically Important Ligands, LXXXVI. Organometallic Complexes of Ruthenium(II), Rhodium(III), Iridium(III), and Gold(I) with Cinchona Alkaloids
Authors: Missling Christopher , Mihan Shahram , Polborn Kurt , Beck Wolfgang
Published: July 2007

The following chiral organometallic complexes of the cinchona alkaloids quinine (L1), cinchonidine (L2), quinidine (L3), cinchonine (L4) were prepared: [(η5‐C5H5)(Ph3P)(OC)‐Ru(L)]BF4 (1: L=L1; 2: L=L2; 3: L=L3), ClAuL1 (4), [(η5‐C5Me5)(Cl2)Ir(L)] (5: L=L1; 6: L=L2; 7: L=L4), [(η5‐C5Me5)(Cl2)Rh(L2)] (8), [(η6‐p‐cymene)(Cl2)Ru(L)] (9: L=L1; 10: L=L2; 11: L=L4). In all complexes the tertiary nitrogen atom of the cinchona alkaloids is bound to the metal. Complexes 5 – 11 are formed as mixtures of isomers. Elimination of HCl from 10 and 11 gives the neutral N,O‐chelate complexes (η6‐p‐cymene)(Cl)Ru(L2 – H+) (13) and (η6‐p‐cymene)‐(Cl)Ru(L4 – H+) (14) which were structurally characterized by X‐ray diffraction.
(Iminoboryl)borate [R3BBNR]−: Durch Elektrophile E induzierte Umlagerung zu (Aminoboryl)boranen R2BBRNRE
Authors: Luckert Stefan , Englert Ulli , Paetzold Peter
Published: July 2007

(Iminoboryl)borates [R3BBNR]−: Rearrangement to (Aminoboryl)boranes R2BBRNRE by the Addition of Electrophiles E

(Iminoboryl)borates [Li(tmeda)2][R2R′B–BNR (2a–c, R′ = Me, Me3SiCH2, Me3CCH2) are formed from the azadiboriridine NB2R3 (1, R = tBu) and LiR′ in the presence of tmeda. Vinyllithium brings about a ring expansion of 1 to give the five‐membered anionic ring [–CHCH–BRNR–BHR–]–, to which [Li(tmeda)]+ is bound (3). The (aminoboryl)boranes R2B–BMeNER (4a–c, EX = HCl, MeI, Me3SiI) are obtained, when the polar compounds EX are added to 2a, accompanied by the elimination of LiX and the migration of Me. The borate 2b reacts with HCl to give a mixture of the isomers R2B–B(CH2SiMe3)=NHR (4d) and R(Me3SiCH2)‐B–BR=NHR (4d′), and 2c reacts with HCl to yield the borane R(Me3CCH2)B–BR=NHR (4e′) exclusively. The transformation of [R2R′B–BNR]‐ to R2B–BR′ = NRE by the attack of electrophiles E corresponds to the known transformation of [R′3B–CR″] to R′2B–CR′=CR″E.
Reaction of the Alkylindium(I) Compound In4[C(SiMe3)3]4 with Octacarbonyldicobalt: Bridging of the CoCo Bond by one or two InC(SiMe3)3 Groups
Authors: Uhl Werner , Keimling Sven Uwe , Hiller Wolfgang , Neumayer Markus
Published: July 2007

tetrahedra‐Tetrakis[tris(trimethylsilyl)methyl]tetraindane(4) (1) reacts with octacarbonyldicobalt to yield two products, depending on the stoichiometric ratio of the starting compounds: By replacement of one bridging carbonyl group a dicobalt monoindium derivative 2 is formed, which contains a CoCo bond [256.81(5) pm] bridged by one carbonyl and one monoalkylindium group. While 2 is a monomer in benzene solutions, it dimerizes in the solid state by an interaction of the oxygen atom of the bridging carbonyl group to the coordinatively unsaturated In atom of a second molecule across a center of symmetry. Another compound (3) is formed by the replacement of both bridging carbonyl ligands, which exhibits a strongly distorted Co2In2 tetrahedron with normal CoIn bond lengths of 253.44(6) pm, but long CoCo [280.14(6) pm] and InIn distances [336.18(6) pm].
8‐quinolylcyclopentadienyl, a ligand with a tailored fit for chelate complexes
Authors: Enders Markus , Rudolph Ralph , Pritzkow Hans
Published: July 2007

8‐Lithioquinoline reacts with 2,3,4,5‐tetramethylcyclopentenone to give 8‐quinolylcyclopentadiene (1/2) after acidic workup and treatment with ammonia. Two of the possible three isomers are formed; the acidic protons on the Cp rings show unusual downfield shifts in the 1H‐NMR spectra. Treatment with strong bases led to the intensely coloured anionic 4 which was converted into the trimethylsilyl derivative 5. This is a suitable starting compound for the trihalotitanium and ‐zirconium compounds 6 and 7. The two complexes were investigated by crystal structure analyses. In both cases the quinolyl nitrogen atom is coordinated to the metal.
Reactions of diaminophosphenium and 1,3,2‐diazaphospholenium triflates with silver salts
Authors: Gudat Dietrich , Holderberg Andreas W. , Kotila Sirpa , Nieger Martin
Published: July 2007

Reaction of bis(diisopropylamino)phosphenium triflate (1[CF3SO3]) with silver salts AgY [Y– = CF3CO2– (2a), CF3‐SO3– (2b), CH3CO2– (2c)] affords neutral complexes [{(iPr2N)2(Y)P} Ag(OSO2CF3)] (3a–c). While 3a, c are stable up to ambient temperature, 3b is only stable at low temperature and in equilibrium with the cation 1. The constitution of 3a–c was derived from multinuclear (1H, 13C, 31P, 109Ag) NMR spectra. Compound 3a was further studied by X‐ray single‐crystal diff ractommetry which showed the presence of dimeric units with μ2‐bridging triflate ligands and three‐coordinate silver atoms with a planar T‐shaped coordination geometry. Reaction of 4‐chloro‐1,3‐bis(2,6‐dimethylphenyl)‐1,3,2‐diazaphospholenium triflate (4[CF3SO3]) with 2a, c affords equilibrium mixtures whose 31P‐ and 109Ag‐NMR spectra suggested the presence of silver complexes 5a, c with constitutions similar to those of 3a, c besides unreacted cation 4. No reaction was observed between 4[CF3SO3] and 2b. A common mechanism accounting for the different outcome of the individual reactions will be discussed.
Über das Silaethen tBu2SiC(SiMe3)2 und die Struktur sowie Reaktivität seines [4 + 2]‐Cycloaddukts mit Ph2CO
Authors: Wiberg Nils , Hwang‐Park Hae‐Sook , Lerner Hans‐Wolfram , Dick Stefan
Published: July 2007

On the Silaethene tBu2Si=C(SiMe3)2, and the Structure and Reactivity of Its [4 + 2] Cycloadduct with Ph2C=O

From tBu2SiFCLi(SiMe3)2 by LiF elimination only Me2Si= C(SiMe3)(SiMetBu2) (1b) instead of tBu2Si=C(SiMe3)2 (1a) is isolated. With benzophenone, silaethene 1b (from its THF adduct 1b · THF) forms at –78 °C a yellow [4 + 2] cycloadduct (5) and a colorless [2 + 2] cycloadduct (6). With increasing temperature 5 transforms into 6, and 6 transforms –more slowly – into the yellow [4 + 2] cycloadduct (7) of 1a and Ph2CO. It follows from this that the migration equilibrium 1a ⇄ 1b really exists. The structure of 7 shows a planar OCPhC6H5–framework with the cycloadded atoms Si and C from –tBu2SiC(SiMe3)2– located above the plane. The =C6H5C bond (1.62 Å) is exceptionally long. 7 is a source for 1a which is trapped by acetone (formation of an ene product) and by benzaldehyde [formation of a [2 + 2] cycloadduct, unstable against cycloreversion into PhHC=C(SiMe3)2 and tBu2SiO‐containing substances]. Reaction of 7 with trimethylsilyl azide, less reactive than acetone or benzaldehyde, leads – by way of 1a which transforms into 1b – to a trapping product of 1b (formation of a [3 + 2] cycloadduct, unstable against transformation into (RMe2Si)(Me3Si)CN2 with R = (Me3Si)2N, or cycloreversion into (tBu2MeSi)(Me3Si)CN2 and Me2SiNSiMe3‐containing substances). Reaction of 1b or 1b · THF with acetone leads only to an ene reaction product of 1b. This means, that only undetectable amounts of 1a or 1a · THF are in equilibrium with 1b or 1b · THF. A minor substance which is shown by NMR at low temperatures besides 1b or 1b · THF is interpreted as a rotamer of 1b or 1b · THF.
The Synthesis of Stabilized Dimetallated Thioimidate Complexes by the Insertion of Ethoxycarbonylisothiocyanate into a Rhenium–Rhenium Bond
Authors: Adams Richard D. , Huang Mingsheng
Published: July 2007

Molecules containing dimetallated hydrocarbyl groupings are of great chemical interest[1–3]. These groupings often represent intermediates in important catalytic processes[4]. Recently, we have shown that substituted dimetallated olefins can be formed by alkyne insertion into the metal–metal bonds of certain dinuclear complexes[2,5]. Complexes having dimetallated hydrocarbyl groups combined with heteroatoms are quite rare[6]. Herein is described the formation of a dimetallathioimidate grouping by the insertion of an organic isothiocyanates into an unsupported metal–metal bond. Organic isothiocyanates are useful reagents in organic synthesis[7], but the organometallic chemistry of these molecules is not yet well developed[8].
Organophosphorus Compounds, 112. Lewis Acid Mediated Spirocyclotrimerization of Kinetically Stabilized Phosphaalkynes – Key Step for the Selective Generation and Trapping of Triphospha Dewar Benzenes
Authors: Breit Bernhard , Regitz Manfred
Published: July 2007

In the presence of Lewis acidic derivatives of group 13 elements, phosphaalkynes 7 undergo spirocyclotrimerization with incorporation of the corresponding Lewis acids to form 10a–f. Scope and limitations of this novel cyclooligomerization process are examined. Starting from the spirocyclotrimer 10a reaction with the Lewis base dimethyl sulfoxide, we have in hand for the first time a method for the selective generation of two isomeric triphospha Dewar benzene derivatives (18, 19). Both can be trapped efficiently by further reaction with the phosphaalkyne to furnish the two novel phosphaalkyne cyclotetramers 20 and 21, both still possessing a phosphorus–carbon double bond. In the case of 21, further functionalization of the phosphaalkene unit is possible by [3 + 2] cycloaddition with a nitrile oxide (→ 23).
Ethyloboration of Selenium Dioxide and Selenium Bis(tert‐butylimide) – Molecular Structure of an Organo‐Substituted Eight‐Membered [–BOSeO–]2 Heterocycle
Authors: Köster Roland , Schüßler Wilhelm , Boese Roland , Herberhold Max , Gerstmann Silke , Wrackmeyer Bernd
Published: July 2007

Both selenium dioxide (1) and selenium bis(tert‐butylimide) (2) react with triethylborane (A) by 1,2‐ethyloboration. In the case of 1, ethane, ethene, diethylselane (4a), tetraethyldiboroxane (Et2B)2O (B), triethylboroxine (EtBO)3 (D) and a cyclic compound [–Et2BOSe(Et)O–]2 (52) are formed after heating to 65°C. Compound 52 is also formed when 1 reacts with B. Treatment of selenous acid (3) with A or, preferentially for synthetic purposes, with B provides further routes to 52. The reaction of the diimide 2 with A starts already below –50°C: a cyclic ethaneselenic acid derivative 6, Et2BN(tBu)‐Se(Et)NtBu, is formed, and 6 starts to decompose at –50°C by elimination of ethene to give finally (tert‐butylamino)diethylborane (8), bis(diethylboryl)‐tert‐butylamine (9), and Et2Se (4a). Transborylation of 52 with (9‐BBN)2O (C) affords [–(9‐BBN)OSe(Et)O–]2 (102), which crystallizes in the monoclinic space group P21/n with the lattice constants (118 K) a = 667.1(1), b = 1282.5(1), c = 1289.1(1) pm and β = 93.06(1)°. All reactions were monitored by 11B‐ and 77Se‐NMR spectroscopy. Furthermore, the reactions of 1 with A and B and the transborylations were studied by 17O‐NMR spectroscopy using the 17O‐enriched compounds 1(17O), B(17O), C(17O), and D(17O).
Transition Metal Complexes with Sulfur Ligands, Part 119. Synthesis of Water Soluble Fe and Ru Complexes with Novel Multidentate Thioether Thiolate Ligands Containing Carboxylate Substituents
Authors: Sellmann Dieter , Becker Thomas , Knoch Falk
Published: July 2007

In search of water soluble transition metal complexes with sulfur dominated coordination spheres that model key reactions of nitrogenases, the benzenedithiol derivatives ‘CO2HS2’‐H2 (1) and ‘CO2Me‐S2’‐H2 (2) were synthesized as precursors for multidentate sulfur ligands. The template alkylation of 2 by C2H4Br2 at [Fe(CO)2] fragments yielded a mixture of two diastereomeric C2 symmetrical [Fe(CO)2(‘CO2Me‐S4’)] complexes (4a and 4b), which were separated by crystallization. The hydrolysis of the mixture of the diastereomers 4a and 4b led to the isomerically pure tetradentate thioether thiol ligand ‘CO2Me‐S4’‐H2 (5) proving the regioselectivity of the template alkylation of the asymmetrical dithiol 2. The C1 symmetrical [Fe(‘CO2Me‐S2’)2]2‐ anion is an intermediate of the template alkylation and was isolated as (AsPh4)2 [Fe(‘CO2Me‐S2’2] (11), 4a, 5 and 11 were characterized by X‐ray structural analysis. Saponification of the methyl ester groups of 5 yielded ‘CO2H‐S4’‐H2 (7). Treatment of 7 with FeCl2 · 4 H2O in the presence of CO and LiOMe gave a mixture of two C2 symmetrical and water soluble diastereomers of Li2[Fe(CO)2(‘CO2‐S4’)] (8). Upon treatment with [RuCl2 (PPh3)3] 7 yielded isomerically pure [Ru(PPh3)2‐(‘CO2H‐S4’)] (9). 9 also exhibits C2 symmetry and could be reversibly deprotonated to form the water soluble complex K2[Ru(PPh3)2 (‘CO2‐S4’)] (10). Treatment of (NBu4)2 (‘CO2MeS2’) with “Ru(NO)Cl3” led to isomerically pure (NBu4)[Ru(NO)(‘CO2Me‐S2’)2] (12).
Contribution to the Chemistry of Boron, 232. Formation, Structure and Reactions of a P,P′‐Bi(1,3,2,4‐diphosphadiboretane)
Authors: Kaufmann Bernhard , Nöth Heinrich , Paine Robert T.
Published: July 2007

Photolysis of the 1,3,2,4‐diphosphadiboretane (tBuPBtmp)2 (1) in dilute toluene solution yields the bicyclic diphosphadiboretane 2. In concentrated toluene solution or in hexane, however, the P,P′‐connected bi(diphosphadiboretane) 4 is also formed implying that the radical [tBuP(Btmp)2P] 3 is the first photolysis product. On further photolysis, 3 and 4 are converted into bicyclic 2 as the final product. Reduction of 4 with sodium‐potassium alloy followed by silylation with Me3‐SiCl leads to the 1,3,2,4‐diphosphadiboretanes (tmpBP‐SiMe3)2 and [HP(Btmp)2PSiMe3]2. In contrast to many 1,3,2,4‐diboretanes, 4 in the absence of photon or thermal promotion does not react with Cr(CO)5 · THF, Fe2(CO)9, or Pd(PPh3)4. However, a mixture of Cr(CO)5 · THF and 4 on photolysis gives the known complex (tmpBP)2 · 2 Cr(CO)5.
Silver(I) Complex of a Crown Thioether Retaining the Transoid S–C–C–S Ligand Conformation
Authors: Gleiter Rolf , Röckel Harald , Nuber Bernhard
Published: July 2007

The crown thioether 3 with the novel diisopropylidene building block was synthesized by an S′N cyclization reaction of 2,7‐dichloro‐2,7‐dimethylocta‐3,5‐diyne (1) with 3‐thia‐pentane‐1,5‐dithiol (2). Ligand 3 shows all the sulfur centers in exodentate positions. Reaction of 3 with Ag1 triflate and triphenylphosphane yielded the tetrahedral complex 4, which shows unique spectroscopic data in solution. Crystallization furnished two different crystal forms (4a and 4b). Both are different conformers which are stable in the solid state. 4a exhibits a crown‐like structure of the thioether ligand with cisoid SCCS chains. To our knowledge 4b is the first silver(1) complex with a crown thioether retaining the tran‐soid SCCS conformation in the metal complex.
Gold(I) and Silver(I) Complexes with Methanide Ligands [C{PPh2(X)}3]– (X = O, S). Crystal Structures of [M{C(PPh2(X))3}(PPh3)] (M  Au, X  O; M  Ag, X  S)
Authors: Gimeno M. Concepción , Jones Peter G. , Laguna Antonio , Villacampa M. Dolores
Published: July 2007

Metal complexes (M(acac)(PPh3)] act as deprotonating agents in the reaction with equimolar amounts of [CH{PPh2(X)}3)] to give the neutral complexes [M{C(PPh2(X))3}(PPh3)] [M = Ag, X = O (1) or S (2); M = Au; X = O (3) or S (4)]. The crystal structures of 2 and 3 have been established by X‐ray crystallography. In the structure of 2 (two independent molecules) the silver(I) atoms display a distorted tetrahedral coordination by phosphorus (of PPh3) and three sulfur atoms. In complex 3 the gold(I) atom exhibits linear coordination by phosphorus of PPh3 and the carbon atom of [C{PPh2 (O)}3]‐. The reaction of [CH{PPh2(X)}3] with [Ag(CF3SO3)] or [Ag(CF3SO3)(PPh3)] (molar ratio 1:1) leads to [Ag(CF3SO3){CH(PPh2(X))3}] [X = O (5), S (6)] or [Ag(CH(PPh2 (S))3}(PPh3)](CF3SO3) (7), respectively.
The Chemistry of Metallacyclic Alkenylcarbene Complexes, 4. Unsaturated Metallacyclic Carbene Complexes as Flexible Tools in Organic Synthesis. Novel Rearrangement and Cascade Pathways to Functionalized Alkadienes, Carbo‐, and Heterocycles
Authors: Schobert Rainer
Published: July 2007

Cationic metallacyclic carbene complexes of iron and cobalt bearing a terminal η3‐allyl ligand are susceptible to nucleophilic attack at different sites depending on the particular set of substituents, the central metal fragment, and the nucleophile. Attack of enolates, cuprates, acetylides, or heteroatom nucleophiles like phosphanes at the metallacyclic perimeter of the iron complexes 18 provides an easy access to unsaturated organic products like 1,2‐ or 1,3‐dienes, δ‐lactones, and functionalized cyclopentenones through novel rearrangement or cascade pathways. Synthetic applications are described; factors governing reactivity/selectivity are discussed; X‐ray analytical structures of novel metallacycles are provided.
Ring Expansion of Spirocyclic Cyclobutenylidene Ligands in Pentacarbonylchromium Complexes to Tetrahydroindene Derivatives
Authors: Fischer Helmut , Karl Christoph C. , Roth Gerhard
Published: July 2007

Pentacarbonyl(pentamethylenevinylidene)chromium, [(CO)5CrCC(CH2)5] (1), reacts with 1‐methylthio‐1‐propyne (2a) and N‐(1‐propynyl)phenothiazine (2b) by regio‐specific addition of the CC bond of the alkyne to the CC bond of the vinylidene ligand of 1. Initially, complexes with a spirocyclic cyclobutenylidene ligand are formed, [(CO)5Cr(CH2)5] (3) and [(CO)5‐Cr(CH2)5] (10). Subsequent thermally initiated ring expansion affords the 2‐methyl‐4,5,6,7‐tetrahydroindenyl(methyl)thioether complex [(CO)5‐Cr–S(Me)(Me‐C9H10)] (4) and the N‐(2‐methyl‐4,5,6,7‐tetrahydroindenyl)phenothiazine complex [(CO)5Cr–S(C6H4)2‐N–(Me‐C9H10)] (11), respectively. In both complexes, 4 and 11 the ligand is coordinated to the metal via the sulfur atom. The constitutions were established by (H,H)‐, (H,C)‐ and NOE‐correlated NMR spectroscopy. In the reaction of 1 with 2a, in addition to 3 and 4, the methyl(propynyl)thioether complex [(CO)5Cr–S(Me)CCMe] (5) was formed. An isolable 3‐methylthio‐substituted cyclobutenylidene complex, [(CO)5CrPh2] (9) was obtained from [(CO)5CrCCPh2] (8) and 2a. The 4,5,6,7‐tetrahydroindenylthioether ligand of 11 was cleaved from the metal by exposure of 11 adsorbed on silica gel to air or by treatment of 11 with [NEt4]Br in dichloromethane.
Reactions of Complex Ligands, LXX. An Intramolecular Alkyne Insertion/Carbonylation/Cyclization Sequence of Chromium Aminocarbene Complexes: A Novel Access to Indole and Indenoindole Skeletons
Authors: Leese Thomas , Dötz Karl Heinz
Published: July 2007

2‐Alkynylanilinocarbene chromium complexes 1–7 bearing a rigid arene C2 spacer between the aminocarbene and alkyne units were prepared from pentacarbonyl(aroyl)chromates(–I), acetyl bromide, and 2‐alkynylanilines. They undergo intramolecular cyclization the course of which depends on the substitution pattern at the alkyne terminus. A tandem alkyne insertion into the metal–carbene bond/carbonylation sequence affords Cr(CO)3‐coordinated 3‐indolylketenes 8, 9, 12–14 by using a bulky substituent; the rate of the reaction increases with N‐alkylation. Less bulky n‐alkynylanilinocarbene complexes 4, 5 exhibit two competing carbene annulation sequences: Benzannulation leads to benzo[a]carbazoles 15, 16, whereas cyclopentannulation without prior carbonylation furnishes indeno[1,2‐b]indoles 17, 18.
The Reaction of As4Sn (n = 3, 4) and As2S3 with (C5Me4R)2Co2(CO)2 (R = Me, Et): Fragmentation and Reassembling of Main‐Group Ligands by Organometallic Complexes
Authors: Brunner Henri , Kauermann Heike , Poll Ludwig , Nuber Bernhard , Wachter Joachim
Published: July 2007

The reaction of Cp2#Co2(CO)2 1 (Cp# = Cp* or Cpx; Cp* = C5Me5: a; Cpx = C5Me4Et: b) with equimolar amounts of As4Sn (n = 3, 4) and As2S3 was investigated at different temperatures. The formation of Cp2#Co2(CO)As2S2 3, Cp2#Co2As2S3 4, Cp3#Co3As2S4 5, and Cp3#Co3As4S2 6 was observed in ratios depending on the reaction conditions. Starting from As4S4 or As4S3 and 1b insertion of a CpxCo(CO) fragment into one of the As–As bonds of the cages was achieved in low yields leading to CpxCo(CO)As4S4 2b and CpxCo(CO)As4S3 8, respectively. Structures were studied by means of IR and 1H‐NMR spectroscopy and X‐ray diffraction analyses. Cp2#Co2(CO)As2S2 3 may be supposed to be the key intermediate in the whole reaction sequence: On heating solutions of 3 complexes 4–6 of higher nuclearity and different connectivity within the inorganic ligand were formed.
Hexacoordinated Group‐14 Elements with Phosphorus Donor Ligands: Syntheses and Structures of Cl2E[C(PMe2)2(SiMe3)]2 (E = Si, Ge, Sn)
Authors: Karsch Hans H. , Deubelly Brigitte , Keller Ursula , Steigelmann Oliver , Lachmann Joachim , Müller Gerhard
Published: July 2007

The group‐14 tetrahalides ECl4 (E = Si, Ge, Sn) react with two equivalents of Li[C(PMe2)2(SiMe3)] to give the trans‐hexacoordinated complexes Cl2E[C(PMe2)2(SiMe3)]2, which were characterized spectroscopically and by structure determinations in the solid state. The complexes were found to crystallize with or without tetrahydrofuran (THF) molecules, depending on the presence or absence of this solvent. In the case of the silicon complex, the structures of both crystal forms were determined, showing slightly different molecular structures of the complexes in the solid state. Without cocrystallized THF, Cl2Si[C(PMe2)2(SiMe3)]2 has no crystallographically imposed molecular symmetry, while in the presence of THF its crystallographic symmetry is C2h (2/m). The tin and germanium complexes were crystallized either with and without THF molecules, respectively, their crystal structures being isotypic with the respective ones of the silicon complex. In all cases, small amounts of the cis‐hexacoordinated isomers were also observed in solution, but only in the case of the silicon complex, it was isolated in pure form. It rearranges to the trans isomer at ambient temperature. trans‐Cl2Si[C(PMe2)3]3, trans‐Cl2Si[C(PPh2)2(SiMe3)]2 and cis‐Me2‐Si[C(PMe2)2(SiMe3)]2 were likewise obtained.