bluuebunny/crossref_metadata_2025 huggingface dataset:
Reaktive EC(p‐p)n‐Systeme, XXXVIII. Molekül‐ und Elektronenstruktur des 2‐(Diisopropylamino)‐1λ3‐phosphaethins iPr2NCP
Authors: Becker Gerd , Böhringer Matthias , Gleiter Rolf , Pfeifer Karl‐Heinz , Grobe Joseph , Van Duc Le , Hegemann Marianne
Published: July 2007

Reactive EC(p‐p)π‐Systems, XXXVIII. — Molecular and Electronic Structure of 2‐(Diisopropylamino)‐1λ3‐phosphaethyne iPr2NCP

The molecular structure of 2‐(diisopropylamino)‐1λ3‐phosphaethyne iPr2NCP (3) has been investigated by X‐ray diffraction using a single crystal grown from the melt at −50.2°C. Bond distances and angles indicative for the electronic structure are: P°C 155.2(2), NC(sp) 131.2(3) pm, PCN 179.2(2)°; with a sum of angles 359‐8° the nitrogen atom has a trigonal‐planar coordination. The reported geometrical parameters of 3 have been reproduced by ab initio calculations (3‐21G and DZP basis), showing that the lengthening of the P°C and the shortening of the CN bond can be rationalized by the interaction of the π system of the triple bond with the 2p orbital at N. The He(I) photoelectron spectrum of 3 confirms the strong interaction.
Synthese und Struktur von 5,6,11,12‐Tetrakis(diisopropylamino)‐5,6,11,12‐tetra‐hydrodibenzo[c,g][1,2,5,6]tetraborocin
Authors: Krämer Albrecht , Pritzkow Hans , Siebert Walter
Published: July 2007

Synthesis and Structure of 5,6,11,12‐tetrakis(diisopropylamino)‐5,6,11,12‐tetrahydrodibenzo[c,g][1,2,5,6]tetraborocine

Herrn Prof. Dr. Gottfried Märkl zum 65. Geburtstag gewidmet.

Catalytic dimerization of 1,2‐bis(diisopropylamino)‐1,2‐dihydro‐1,2‐benzodiborete (1) with (phthalocyanine)palladium [Pd(pc)] leads to the eight‐membered title compound 2 in 95% yield. An X‐ray structure analysis of 2 exhibits a chair conformation for the central C4B4 ring (folding angle along B1B2/B1′B2′ 55.5°).
New Cyclopropyl Building Blocks for Organic Synthesis, 21. Diels‐Alder Reactions of Methyl 2‐Chloro‐2‐cyclopropylideneacetate with Electron‐Rich Dienes: Synthesis of Potential Intermediates for Illudin M
Authors: Primke Hartmut , Sarin Gurdeep S. , Kohlstruk Stephan , Adiwidjaja Gunadi , Meijere Armin De
Published: July 2007

1‐Ethoxy‐ (8a) and 1‐(trimethylsilyloxy)‐1,3‐pentadiene (8b) cycloadded to 2‐chloro‐2‐cyclopropylideneacetate 6 to give low yields of endo/exo‐9a and ‐9b, respectively. On the other hand, furans 5a‐d added 6 (5b and 5d reacted regioselectively) to afford mixtures of the corresponding [4 + 2] cycloadducts endo‐11a‐d and exo‐11a‐d in good to high yields. 2‐Methyl‐5‐(trimethylsilyloxy)furan (5e) yielded a mixture of the four cycloadducts endo/exo‐11e and endo/exo‐12e, which upon attempted purification on silica gel underwent facile hydrolysis to give bicyclic hemiacetals endo/exo‐13 and 4‐hydroxycyclo‐2‐hexen‐1‐ones endo/exo‐14, respectively. Similarly endo/exo‐11f, and endo/exo‐12f, obtained from 2‐methoxy‐5‐methylfuran (5f) and 6, upon hydrolysis in the presence of silica gel gave endo/exo‐13 and endo/exo‐14 respectively. The structures of endo‐14 and exo‐12f were established by X‐ray crystallography. In the presence of florisil, the epoxides endo‐and exo‐16 were formed from trimethylsilyloxy‐substituted cycloadducts endo/exo‐11e. Selective reduction of the α‐chlorocarboxylate functionality in the cycloadducts endo‐11a‐d,f with LiBH4, followed by base‐catalyzed cyclization of the resulting chlorohydrins endo‐21a‐d, f yielded the corresponding epoxides endo‐22a‐d,f in 22–73% overall yield. Under identical conditions, the cycloadducts exo‐11a‐f could not be reduced to the corresponding chlorohydrins exo‐21a‐f. Regioselective reduction of the acetal epoxide endo‐22f to the tertiary alcohol endo‐23f was achieved with sodium dihydrobis(2‐methoxyethoxy)aluminate (Red‐Al®). On stirring with moist silica gel, the bicyclic acetals endo‐22d,f and endo‐23f cleanly hydrolysed to the highly substituted spiro[2.5]oct‐6‐en‐5‐ones endo‐24d,f (26 and 24% overall yields, respectively, in four steps from 5d,f and 6) and endo‐25f, respectively (23% overall yield in five steps from 5f and 6).
Liquid‐Crystalline D‐Glucose Dialkyl Acetals and Dodecyl D‐Glucofuranosides
Authors: Tietze Lutz F. , Böge Kai , Vill Volkmar
Published: July 2007

Two new systems of liquid crystalline glucose derivatives 5a‐d, 6a, b are prepared, studied and compared with reference compounds. The α‐ and β‐D‐dodecyl glucofuranosides 6a, b show smectic A phases. The clearing points of the furanosides are of the same magnitude as those of the pyranosides. The alkyl glucose acetals 5a‐d show columnar discotic phases. The clearing points are about 30°C lower than those of the corresponding thioacetals.
syn‐ar,ar′‐Difluorometacyclophanes: Strong 19F,19F Spin—Spin Interactions Transmitted through Space
Authors: Ernst Ludger , Ibrom Kerstin , Marat Kirk , Mitchell Reginald H. , Bodwell Graham J. , Bushnell Gordon W.
Published: July 2007

The close approach of the fluorine nuclei in the difluorinated syn‐[3.3]metacyclophanes 1, 2 and their [2.2] analogues 3, 4 leads to strong 19F,19F spin‐spin interactions which obey a through‐space mechanism. The geometries of 1–4 were estimated by MM2 molecular mechanics computations, those of 1 and 3 were also determined by X‐ray structural analyses. The decrease of the F,F internuclear distance in the series 1, 2, 3, 4 (2.78–2.48 Å) correlates with an increase of J(FF) from +42.1 to +99.2 Hz. It follows that, for a given distance d(FF), J(FF) is up to twice as large as a previous empirical correlation has assumed and even larger with respect to earlier theoretical calculations. Only weak F,F spin interaction occurs in 8, the anti isomer of 4.
Synthese von 6,6‐Dimethylfulven‐2‐carbonsäure‐methylester und ‐2,3‐dicarbonsäure‐dimethylester sowie deren Umsetzung zu 2,3,5,6‐substituierten Nordbornadienen
Authors: Herges Rainer , Reif Wolfgang
Published: July 2007

Synthesis of Methyl 6,6‐Dimethylfulvene‐2‐carboxylate and Dimethyl 6,6‐Dimethylfulvene‐2,3‐dicarboxylate as well as their Reaction to 2,3,5,6‐Substituted Norbornadienes

Fulvenes 5 and 6 were synthesized by Diels‐Alder reaction of 6,6‐dimethylfulvene with methyl prop‐2‐ynoate and dimethyl but‐2‐ynedioate, catalytic reduction of the unsubstituted norbornadiene double bond, and a subsequent retro Diels‐Alder reaction under flash vacuum pyrolysis conditions, 5 and 6 are used as the diene component in synthesizing 2,5‐, 2,3,5‐, and 2,3,5,6‐substituted norbornadienes 7–9 by Diels‐Alder reaction with electron‐deficient alkynes.
Dibenzo[18]annulenes Incorporating Two Diphenylhexatriene Units
Authors: Michels Heinz‐Peter , Nieger Martin , Vögtle Fritz
Published: July 2007

The [6.6]cyclophanehexaene hydrocarbon 6a and the dimethoxy[6.6]cyclophanehexaene 6b are prepared starting with the unsaturated diacid 1. An X‐ray analysis of 6a exhibits a planar molecular skeleton. NMR and optical data prove a not fully conjugated macrocyclic π system and its division into two largely separate chromophores.
α‐Mercurio‐Substituted Phosphorus Ylides: A Simple Route to Vinylmercury Compounds
Authors: Steiner Matthias , Pritzkow Hans , Grützmacher HansjöRg
Published: July 2007

The synthesis of novel α‐mercurio‐substituted phosphorus ylides, Ph3PCR[HgN(SiMe3)2] 3a–d (R = Me, Et, iPr, Ph) is easily accomplished by mixing equivalent amounts of a phosphorus ylide 1a–d with Hg[N(SiMe3)2]2 in an inert solvent. These organometallic compound are completely characterized including an X‐ray analysis of 3a. Their reaction with benzaldehyde yields vinylmercury amides (E)/(Z)‐PhHCCR[HgN(SiMe3)2] 4a–d. In reactions involving 3a–c the stereochemistry [favored formation of (E)‐4a (≈︁;72—83%) and (Z)‐4b, c (≈︁60—73%)] in the absence of a lithium salt is contrary to the stereochemistry of the established Wittig olefination reaction with non‐stabilized phosphorus ylides like 1a–d. From the reported results, the preliminary conclusion is drawn that the stereochemistry is mainly controlled by steric interactions. Only in one case a remarkable salt effect is observed. When 3c reacts with benzaldehyde in the presence of LiBr and THF as solvent up to 95% of (E)‐4c is formed. The semistabilized ylide 3d gives under all conditions studied a 50:50 mixture of (E)/(Z)‐4d. The vinylmercury amides 4a, c are cleaved by hydrous NaOH to yield divinyl‐mercury compounds (E,E)‐(PhHCCR)2Hg and (Z,Z)‐(PhHCCR)2Hg (R = Me: 7a; R = iPr: 7c). The compound 4d is cleanly cleaved by NaBH4 in hydrous 3 M NaOH to yield a 50:50 mixture of cis‐ and trans‐stilbene (8).
Sulfur Compounds, 174. Preparation of Long‐Chain Polysulfanes from Dialkoxysulfanes: Synthesis of Bis(2,3,4,6‐tetra‐O‐acetyl‐1‐deoxy‐β‐D‐glucopyranosyl)tetrasulfane and ‐undecasulfane
Authors: Steudel Ralf , Schmidt Heinar
Published: July 2007

Dialkoxysulfanes (RO)2Sn (n ≥ 2) react with thiols R′SH as sulfur transfer reagents to form long‐chain diorganylpoly‐sulfanes R′2Sn+2 under mild conditions. Condensation of tetra‐O‐acetyl‐1‐thio‐β‐D‐glucopyranose (acGlcSH) with diisopropoxydisulfane (iPrO)2S2 and diisopropoxynonasulfane (iPrO)2S9 at 40°C yields bis(2,3,4,6‐tetra‐O‐acetyl‐1‐deoxy‐β‐D‐glucopyranosyl)tetrasulfane (1) (acGlc)2S4 and bis(2,3,4,6‐tetra‐O‐acetyl‐1‐deoxy‐β‐D ‐glucopyranosyl)undecasulfane (2) (acGlc)2S11, respectively. The analogous reaction using diisopropoxymonosulfane does not yield the corresponding trisulfane.
Acid‐Induced Stereoselective Formation of 3,5‐Cycloheptadien‐1‐ones from Ketenes and Dienes
Authors: Seggern Heinke Von , Schmittel Michael
Published: July 2007

The reaction of ketenes 1a or 1b with diene 2 in the presence of trifluoromethanesulfonic acid providing the cycloheptadienones 5a and 5b constitutes the first example of an acid‐induced ketene/diene «cycloaddition». The thermal [2 + 2] cycloadducts, bicyclo[3.2.0]hept‐2‐en‐6‐ones 9, are not intermediates in the acid‐catalyzed reaction since they rearrange under acidic conditions to the tetralinone derivatives 10. The acid‐catalyzed «cycloaddition» was mechanistically investigated and the scope of the reaction explored.
Coordination Polymers, VI. Neutral 1D‐Coordination Polymers from Ethyl (Aminomethylene)cyanoacetate Derivatives and Copper(II) Acetate by Spontaneous Self‐Organization
Authors: Saalfrank Rolf W. , Danion Daniel , Hampel Frank , Hassa Jürgen , Struck Oliver , Toupet Loic
Published: July 2007

Reaction of a solution of copper(II) acetate in methanol with ethyl (aminomethylene)cyanoacetate derivatives 10 (H2L4) or 13 (H2L5) yields the corresponding 1D‐coordination polymers 11 ([CuL4]∞ and 14 ([CuL5]∞, respectively. The products are insoluble in non‐coordinating solvents and thermally highly stable. The structures of 11 and 14 have been established by X‐ray diffraction. The one‐dimensional coordination polymers 11 and 14 have different geometries, depending on the lateral group of the ligands.
(5aS,10aS)‐Octahydro‐1H,5H‐dipyrrolo[1,2‐a:1′,2Prime;‐d]pyrazin «DPP» als Hilfsreagenz bei der enantioselektiven 1,2‐Addition von Grignard‐Reagenzien an prochirale Carbonylverbindungen
Authors: Zadel Guido , Breitmaier Eberhard
Published: July 2007

(5aS,10aS)‐Octahydro‐1H,5H‐dipyrrolo[1,2‐a:1′,2′‐d]pyrazine «DPP» as Auxiliary Reagent for Enantioselective Alkylations of Prochiral Carbonyl Compounds

In the presence of one equivalent of the title compound «DPP» (1) prochiral carbonyl compounds 2 react with Grignard reagents 3 in THF to form enantioselectively alcohols 4 with up to 98% ee, whereas the addition of one equivalent of triethylamine yields the opposite enantiomers with up to 97% ee. The optimal molar ratio of 1 and magnesium reagent 3 was determined by cryoscopic measurements. Asymmetric induction is supposed to arise from transition states involving monomeric octahedral complexes of Grignard reagent, chiral solvent, and carbonyl compound. DPP (1) also catalyses Grignard alkylations, because a tenth of its stochiometric amount gives an enantiomeric eccess four times more than as expected. Prepared from (S)‐proline, only the boat conformation of 1 induces the observed selectivity as detected by 13C‐NMR spectroscopy.
Wismutverbindungen mit voluminösen, mehrfach alkylierten Cyclopentadienyl‐Liganden
Authors: Sitzmann Helmut , Wolmershäuser Gotthelf
Published: July 2007

Bismuth Compounds with Crowded Multiply Alkylated Cyclopentadienyl Ligands

Herrn Professor Helmut Werner zum 60. Geburtstag gewidmet.

Bismuth complexes of alkylated cyclopentadienyl ligands are obtained in good yield on treating bismuth(III) halides with tetraisopropylcyclopentadienylsodium or 1,2,4‐tri‐tert‐butyl‐cyclopentadienyllithium. A 1:1 stoichiometric ratio gives the complexes [Cp4iBiCl2] (1), [Cp3tBiCl2] (2), and [Cp4iBiI2] (3) (Cp4i = C5iPr4H, Cp3t = C5H2tBu3‐1,2,4). According to X‐ray crystal structure analyses, 1 and 3 display dimeric structures with two bridging and two terminal halogeno ligands and η3‐coordination of the cyclopentadienyl rings. With half an equivalent of tetraisopropylcyclopentadienylsodium BiCl3 forms [Cp4iBi2Cl5] (4). An X‐ray crystal structure analysis of 3 reveals a central Bi2Cl10 core of two edge‐sharing BiCl6 octahedra coordinated to two Bi(η5‐Cp4i) fragments generating a framework of two face‐sharing cubes. Reaction of two equivalents of 1,2,4‐tri‐tert‐butylcyclopentadienyllithium with BiCl3 yields deep purple [Cp3t2BiCl] (5), a bent sandwich complex with an η3,η2‐bonding mode of the cyclopentadienyl ligands. Attempted formation of the octaisopropyl analogue of 5 from BiCl3 and two equivalents of tetraisopropylcyclo‐pentadienylsodium with elimination of propene gives [Cp4iCp3iBiCl] (6) (Cp3i = C5H2iPr3). Use of monodeuterated tetraisopropylcyclopentadienylsodium in the second substitution step gave pure [Cp4i([D1]Cp3i)BiCl] ([D1]6) proving the absence of ring exchange reactions under the reaction conditions employed and elimination of propene from the second incoming sterically crowded tetraisopropylcyclopentadienyl ring system. The importance of proper choice of solvent and reaction conditions on the formation of alkylated cyclopentadienyl bismuth derivatives is demonstrated by extensive formation of 1,1′,3,3′,5,5′‐hexa‐tert‐butyldihydrofulvalene (7) from 1,2,4‐tri‐tert‐butylcyclopentadienylsodium and BiCl3.
Übergangsmetallsubstituierte Acylphosphane und Phosphaalkene, XXI. Isophosphaalkine als μ3‐Liganden in Übergangsmetallkomplexen
Authors: Weber Lothar , Schumann Iris , Stammler Hans‐Georg , Neumann Beate
Published: July 2007

Transition‐Metal‐Substituted Acylphosphanes and Phosphaalkenes, XXI. — Isophosphaalkynes as μ3‐Ligands in Transition Metal Complexes

Reaction of the μ‐isophosphaalkyne complex (η5‐C5H5)2 (CO)2(μ‐CO)Fe2(μ‐CPMes) (Mes = 2,4,6‐Me3C6H2) (2a) with [(Z)‐Cyclooctene]Cr(CO)5 or Fe2(CO)9 gives rise to the μ3‐isophosphaalkyne complexes (η5‐C5H5)2(CO)2(μ‐CO)Fe2{μ‐CP[M(CO)n]Mes} 3a [M(CO)n = Cr(CO)5] and 4a [M(CO)n = Fe(CO)4]. Similarly (η5‐C5H5)2(CO)2(μ‐CO)Fe2{μ‐CP[Cr (CO)5]C6H2(CF3)3‐2,4,6} (3d) is obtained. The metal carbonyl fragments are attached to 2 in a η1‐fashion by the lone‐pair at the phosphorus. In contrast to this the treatment of 2a with (Ph3P)2Pt(η2‐C2H4) affords complex 5a in which 2a serves as an η3‐3e ligand towards the PtPPh3 moiety. The molecular structures of 3a and 5a are determined by single‐crystal X‐ray analysis.
2,6‐Disubstituted 4‐Aminopyridines from 1,3‐Dialkoxy‐2‐azapropenylium Salts and N‐Methyl‐4‐piperidone Enamines
Authors: Schleimer Richard , Würthwein Ernst‐Ulrich
Published: July 2007

1,3‐Dialkoxy‐2‐azapropenylium salts 1 react with enamines 2 of N‐methyl‐4‐piperidone at room temperature to give 2,6‐disubstituted 4‐aminopyridines 4, 5 in low to moderate yield after hydrolysis. Intermediates of the reaction of 1a with 2 are the bicyclic iminium salts 6 and 7, which may be detected 1H‐NMR spectroscopically prior to hydrolysis. Hydrolysis of the mixture obtained from the reaction of 1a with 2a under basic conditions furnishes the bicyclic ketone 3 as the major product. A “retro‐Mannich”‐type reaction is suggested to explain the degradation of the bicyclic intermediates 6, 7 with the formation of the pyridines 4, 5.
Kumulierte Ylide, 22. Umsetzungen von (Triphenylphosphoranyliden)ethenon mit Halogenverbindungen und ihre präparative Anwendung
Authors: Bestmann Hans Jürgen , Geismann Christian , Zimmermann Reiner
Published: July 2007

Cumulated Ylides, 22. — Reactions of (Triphenylphosphoranylidene)ethenone with Halogen Compounds and their Preparative Application

(Triphenylphosphoranylidene)ethenone (6) reacts with halogen compounds 7 to yield four‐membered ylide phosphonium salts 9. Ring opening of 9 under different conditions gives rise to the formation of bis‐ylides 13, ylide salts 14, or bis‐phosphonium salts 15. Compounds 13/14 are hydrolysed to mono‐ylides 16, and the Wittig reaction with aldehydes yields unsaturated acylphosphoranes 17, which on thermolysis afford enyne carboxylic esters 18. From the bis‐salts 15 α‐branched divinyl ketones 22 are available by bis‐Wittig reaction.
New Cyclopropyl Building Blocks for Organic Synthesis, 28. Pd(0)‐Catalysed Coupling of Cyclopropenylzinc Chlorides and Cyclopropenylstannanes — A New Efficient Synthesis of 1‐Phenyl‐, 1‐Ethenyl‐, and 1‐Ethynyl‐1‐cyclopropenes
Authors: Untiedt Sven , Meijere Armin De
Published: July 2007

[3,3‐Dimethyl‐2‐(trimethylsilyl)‐1‐cyclopropen‐1‐yl]zinc chloride (4) reacts with haloarenes and ‐alkenes as well as 1‐bromo‐acetylenes under Pd(0) catalysis to give the corresponding 1‐phenyl‐, 1‐ethenyl‐, and 1‐ethynyl‐1‐cyclopropenes 6 in isolated yields ranging from 47 to 99%. The corresponding 1‐cyclopropen‐1‐ylstannane 5 reacts with haloarenes only at higher temperatures, and the yields range from 10 to 98%, depending on the substrate and reaction conditions.
Umsetzung einiger Dihydrobenzoxazaphosphorinone mit Nucleophilen; ungewöhnliche Oxidations‐, Insertions‐ und Umlagerungsprodukte und deren Charakterisierung durch Einkristall‐Röntgenstrukturanalyse
Authors: Neda Ion , Fischer Axel , Kaukorat Thomas , Jones Peter G. , Schmutzler Reinhard
Published: July 2007

Reaction of some Dihydrobenzoxazaphosphorinones with Nucleophiles; Unusual Oxidation, Insertion, and Rearrangement Products and their Characterisation by Single‐Crystal X‐Ray Analysis

The reaction of 2‐chloro‐1,2‐dihydro‐1‐methyl‐4H‐3,1,2‐oxazaphosphorin‐4‐one (2) and its 2‐diethylamino‐substituted derivative 3 with various nucleophiles yielded novel and sometimes unexpected products. Hydrolysis of 2 furnished the 2‐hydroxybenzoxazaphosphorinone 4. In the presence of small amounts of water, two molecules of 4 were transformed into 5, accompanied by cleavage of one of the heterocyclic rings. The reaction of 2 with sodium chlorodifluoroacetate led, possibly in an Arbuzov‐type reaction, to compound 6. The 1,5‐diaza‐4,8‐cyclooctanedione system 7 was formed by reaction of 2 with 1,2,4,5‐tetrakis(trimethylsilyloxy)benzene with concomitant loss of the phosphorus‐containing group. 2,2′‐Bis(trimethylsiloxy)biphenyl reacted with 2 in the expected fashion to form the diphosphorus compound 8. From 8 the chlorogold(I) complex 9 was obtained. The reaction of 3 with tetrachloro‐ and tetrabromo‐o‐benzoquinone did not lead to the expected spirocyclic products by oxidative addition of the quinone system to λ3P. Instead, cleavage and expansion of the heterocyclic ring system with formation of the tricyclic derivatives 10 and 11 took place. Compounds 5‐10 were subjected to X‐ray structure analysis. Compound 5 exists as two modifications 5a and 5b, which differ mainly in the relative orientation of the phenyl rings; intramolecular N–H…O hydrogen bonds are observed. Bond lengths at the halo‐substituted carbon atom in 6 indicate steric crowding. The central 8‐membered ring of 7 displays a “tub” conformation. Compound 8 undergoes a conformational change on complexation to the two gold(I) centres; one of the torsion angles C‐O(exocyc.)‐P‐N is ‐163° in 8, but 95° in 9. The structure determination of 10 served only to confirm the (unexpected) connectivity; the crystal quality was too poor to allow quantitative conclusions.
Zur Addition von Alkyldichlorboranen an Bis(η5‐cyclopentadienyl)dihydridowolfram
Authors: Braunschweig Holger , Wagner Trixie
Published: July 2007

On the Addition of Alkyldichloroboranes to Bis(η5‐cyclopentadienyl)dihydridotungsten

Reaction of basic [Cp2WH2] (1) with the Lewis acids iPrBCl2 and tBuBCl2 does not lead to adducts of the type [Cp2WH2 (RBCl2)] [R = iPr, tBu]. The zwitterions [CpWH3(η5‐C5H4BRCl2)] (R = iPr, 2a; tBu, 2b) having an exocyclic boron substituent were isolated instead in 60% yield. The molecular structure of 2b crystallizing in the space group P21/n is proved by X‐ray structure determination.
Preparation of [5 + 6]‐, [6 + 6]‐, and [6 + 7]‐Bicyclic Guanidines from C,C'‐Bis(iminophosphoranes)
Authors: Molina Pedro , Obòn Rosario , Conesa Carlota , Arques Antonio , De Velasco M. Los Desamparados , Llamas‐Saiz Antonio L. , Foces‐Foces Concepciòn
Published: July 2007

A one‐pot synthesis of [5 + 6]‐, [6 + 6]‐, and [6 + 7]‐rigid bicyclic guanidines (6, 8, 19, 21, 23) based on a bis(iminophosphorane)‐mediated annulation strategy is reported. The crystal and molecular structure of the parent [5 + 6]‐bicyclic guanidine 8 has been established by X‐ray diffraction. The crystallographically independent molecule forms dimers through a centre of symmetry by N–H–N hydrogen bonds. The molecule, and therefore the dimer, is statistically disordered in a 65/35 ratio. A statistical study of N–H–N hydrogen bonds of this kind of dimers has been carried out by using the Cambridge Structural Database.
[3.3]Isoalloxazinophanes and Arene‐Bridged Bis(isoalloxazines): Syntheses, Characterizations and Properties Related to Intramolecular Interactions
Authors: Staab Heinz A. , Kirsch Peer , Zipplies Matthias F. , Weinges Alexa , Krieger Claus
Published: July 2007

In order to study the orientation and distance dependence of π … π interactions between flavins in various redox states, two approaches to bis(isoalloxazine) model compounds are presented: The [3.3]isoalloxazinophanes 2 and 4 and the rigid single‐bridged 1,8‐naphthalene‐ and 1,8‐anthracene‐linked bis(isoalloxazine) systems 6, 8 and 26 were synthesized, characterized, and studied by spectroscopic methods and cyclic voltammetry. The experimental data are discussed in comparison with “monomeric” isoalloxazines and flexible single‐chain trimethylene‐linked bis(isoalloxazine) reference compounds. X‐Ray structure analyses are reported for the 1,8‐bis(isoalloxazinyl)‐9,10‐dihydroanthracene 26 and for 22 as an example of 1,8‐disubstituted naphthalenes with strongly polar substituents comparable to 6.
Zur Reaktion von Bis(trimethylphosphan)titanocen mit Ketonen
Authors: Gleiter Rolf , Wittwer Wolfgang
Published: July 2007

On the Reaction of Bis(trimethylphosphane)titanocene with Ketones

Fulvenes are the products of the reaction of aliphatic and aromatic ketones with bis(trimethylphosphane)titanocene in nonpolar solvents, but no formation of pinacols is observed. The mechanism is discussed.
Umlagerung und Abbau bicyclischer Amin—Tetraorganodiboroxane[1]
Authors: Köster Roland , Schüßler Wilhelm , Seidel Günter , Bläser Dieter , Boese Roland
Published: July 2007

Rearrangement and Degradation of Bicyclic Amine‐Tetraalkyldiboroxanes[1]

The amine‐tetraalkyldiboroxanes [1a: R1,4,7,7′ = Et; 1b: R1,4,7 = Et, R7′ = Ph; 1b′: R4,7,7′ = Et,R1 = Ph; 1c: R1,7,7′ = Et, R4 = Ph] react on heating by EtBO elimination and allylborane rearrangement to yield the allyl‐aminoboranes Me2NB(Et)CH2C(R4)=C(R7,7′) [2a: R4,7,7′ = Et; 2b/2b′: R4 = Et, R7,7′ = Et, Ph; 2c: R4 = Ph, R7,7′ = Et]: On heating above 60°C the diastereomeric syn/anti‐Id/1d′(Id: R1,7 = C8H14, R4,7′ = Et; 1d′: R1,7′ = C8H14, R4,7 = Et) give the unsaturated rac‐amino‐trialkyldiboroxane (rac‐3) (X‐ray structure analysis) by intramolecular 1,2‐deaminoboration. rac‐3 is characterized by reaction with (Et2BH)2 and (Et2BD)2 with formation of the 1,2,6‐oxadiborinane 5 by evolution of H2 or HD respectively. The intramolecular CH‐borylation of rac‐3 is compared with those of the thujopsen hydrocarbons I–III.
Synthesis and Structure of Organotin(IV) Complexes of Maltol
Authors: Bhattacharya Subrato , Seth Neena , Gupta Vishnu D. , Nöth Heinrich , Polborn Kurt , Thomann Martina , Schwenk Holger
Published: July 2007

A series of organotin(IV) maltol complexes R4 — xSnLx (1–4, 6; x = 1–3) and the dichloro‐compound Cl2SnL2 (5) have been prepared and characterized on the basis of their IR‐, 1H‐, 13C‐ and 119Sn‐NMR data. While an X‐ray crystal structure analysis of Ph2SnL2 (4) and Cl2SnL2 (5) reveals distorted cis‐octahedral structures, the Me2SnL2 molecule (2) adopts a skew‐trapezoidal bipyramidal configuration with a very significant difference in the Sn‐O(keto) bond distances. The tris‐maltol complex BuSnL3 (6) exhibits a distorted pentagonal‐bipyramidal geometry with the butyl carbon and a hy‐droxy oxygen constituting the axial orientations.
(R)‐1,2,2‐Triphenyl‐2‐(trimethylsiloxy)ethyl Propionate: anti‐Selective and Diastereofacially Selective Aldol Addition; Diastereoselective Silylation and Alkylation
Authors: Sacha Hubert , Waldmüller Delia , Braun Manfred
Published: July 2007

The propionates (R)‐5 and (R)‐6 which are derived from the readily available chiral auxiliary reagent (R)‐triphenylglycol (4) have been applied in stereoselective aldol reactions. Whereas the enolate 7 and the silyl ketene acetal 12, both generated from the ester (R)‐6, display only moderate diastereoselectivity when treated with benzaldehyde, ß‐hydroxyesters 8b and 16a, b are formed in diastereomeric ratios up to 95:5 (ratio of the main product to the sum of all other stereoisomers) when the propionate (R)‐5 is subsequently deprotonated, transmetalated into the zirconium enolate and allowed to react with aldehydes. Alkaline hydrolysis or reduction with LiAlH4 enables the conversion of the adducts 8a and 16a
Einfluß der Reaktionsbedingungen auf die enantioselektive Protonierung von Lacton‐Enolaten
Authors: Gerlach Uwe , Haubenreich Thomas , Hünig Siegfried
Published: July 2007

Stereoselective Protonation of Carbanions, 5[1]. — Effects of Reaction Conditions on the Enantioselective Protonation of Lactone Enolates[2]

Protonation of the enolates 1Li and 2Li by using standard conditions yields enantioselectivities up to 54 and 50% ee, respectively, depending on the chiral proton source[1]. These values may change dramatically by the following variations (standard ee's in parenthesis): (i) In Et2O/THF (90:10) (S)‐2 with 72% ee (44%) is formed with (R)‐pantolactone (3) but only 48% ee (39%) with (R,R)‐tartaric ester 4 (Figure 1). (ii) Lewis acids may produce rac‐2 (SnCl2, MgBr2) or definitely increase the enantioselectivity: With lactone 3: 46% ee (44%); with esters 4: 48% ee (39%); with bissulfonamide 7: 67% ee (47%) (Table 1, 2). (iii) Lithium chloride (2–4 equiv.) in THF yields (S)‐1 with 68% ee (47%) and (S)‐2 with 77% ee (39%) but only if ester 4 ist employed as chiral proton source (Figure 2). (iv) Chiral Lewis bases create (S)‐2 with up to 30% ee on protonation with achiral acids (Table 3, 4). (v) Deuteration of 2Li ranges from 16 to 95% depending on the nature of the base as well as the deuteron source. The degrees of deuteration and enantioselectivity are not correlated. All results demonstrate the complexity of enantioselective protonation of enolates which still needs empirical optimization.
Hexakis(alkylthio)‐Substituted Unsymmetrical Phthalocyanines
Authors: Dabak Salih , Gül Ahmet , Bekaroǧlu özer
Published: July 2007

Cyclotrimerization of 4,5‐bis(hexylthio)phthalodinitrile (1) in 1‐chloronaphthalene in the presence of BCl3 leads to the subphthalocyanine 4. Unsymmetrical phthalocyanines (5, 6) with six alkylthio substituents on three of the benzenoid units are synthesized by the reaction of 4 with an diiminoisoindoline derivative (R′ = H or NO2). These extremely soluble compounds are characterized by IR, 1H‐ and 13C‐NMR as well as UV/Vis spectra.
Diastereoselective Synthesis of α‐Hydroxy‐ and α‐Aminoindolizidines and ‐quinolizidines. Evidence for a Novel Cyclization/Hydride Migration Mechanism in the TiCl4‐Induced Reaction of Prolinal Benzylimines by Deuterium Labeling Studies
Authors: Laschat Sabine , Grehl Matthias
Published: July 2007

Lewis acid‐catalyzed cyclization of prolinal and 2‐piperidine‐carbaldehyde benzylimines 11, 12 results in the diastereoselective formation of α‐amino‐β‐alkyl‐substituted indolizidines 15, 17, 19, 21 and ‐quinolizidines 16, 18, 20, respectively. Both diastereoselectivity and constitution depend on the Lewis acid. FeCl3 yields α,β‐trans‐α‐(benzylamino)‐β‐isopropenyl derivatives 15 and 16, probably by a cationic cyclization via carbenium ions 32a, b. In contrast, TiCl4 yields α,β‐cis‐α‐(benzylideneamino)‐β‐isopropyl derivatives 19 and 20 by a novel cyclization/intermolecular hydride transfer mechanism, which was supported by deuterium labeling studies. Compounds 15, 16, 19, and 20 were converted to the diastereomeric acetamides 24, 25 and 28, 29. By an analogous cyclization of the aldehydes 8 and 9 only α,β‐cis‐α‐hydroxy‐β‐isopropenylindolizidines 51 and ‐quinolizidines 52 were obtained irrespective of the Lewis acid used. The structures of 30 and 52 were elucidated by X‐ray analysis.
A Chiral Adamantanophane: Preparation, Enantiomer Separation, Theoretical and Experimental Circular Dichroism and Absolute Configuration
Authors: Grimme Stefan , Lemmerz Ralf , Vögtle Fritz
Published: July 2007

Exchange of aromatic units (e.g. benzene) for aliphatic/ali‐cyclic building blocks (e.g. adamantane) in cyclophanes leads to molecules of the “araliphane” type. The synthesis of the highly strained [2.2](1,3)adamantanometacyclophanes 5a–c is described. The cyclophane skeletons of these molecules are conformationally rigid and therefore 5a–c are planar‐chiral. The circular dichroism of 5c has been calculated theoretically with NDDO/MRD‐CI methods and was measured. Agreement of theory and experiment is good, a comparison of both allows the assignment of the absolute configuration of the two enantiomers of 5c with high probability. Furthermore, analysis of the nπ* band in the CD spectrum yields a, simple general rule to determine the conformation of the carboxyl group in phenyl ester substructures. Theoretical calculations of the strain energy (Es) of 5c reveal the distribution of strain within the molecule.
A Convenient Synthesis of Enantiomerically Pure Ethylene‐Bridged Metallocene Complexes Bearing Fluorenyl‐ and Octahydrofluorenyl Ligands[1]
Authors: Rieger Bernhard , Jany Gerhard
Published: July 2007

Ring opening of (R)‐(–)‐epoxystyrene (1) with fluorenyllithium leads to the optically active alcohol 2 in high yield. Derivatization of 2 to the trifluoromethanesulfonate 4 and subsequent reaction with one equivalent of fluorenyllithium gives the ligand precursor (1S)‐1,2‐bis(9‐fluorenyl)‐1‐phenylethane (5), which is used for the synthesis of [(1R)‐1,2‐bis(η5‐9‐fluorenyl)‐1‐phenylethane]ZrCl2 (6).
Regioselective Protonation of Allyllithium Compounds
Authors: Lüning Ulrich , Wangnick Carsten , Kümmerlin Martin
Published: July 2007

By varying the general acid, the regioselectivity of the protonation of (triphenylsilyl)allyllithium (1) in diethyl ether in the presence of HMPT can be changed from 9:1 to 1:9 at room temperature. When other aprotic solvents are used, the nature of the lithium salt changes, and the selectivity decreases. The regioselectivity of the protonation of the dithio‐stabilized allyllithium 4 by water is highly dependent on the age of the allyllithium solution with α/γ ratios varying from 2.7:1 to 1:3.5.
Synthese und Eigenschaften von Makrocyclen aus Resorcinen sowie von entsprechenden Derivaten und Wirt‐Gast‐Komplexen
Authors: Schneider Ulrich , Schneider Hans‐Jörg
Published: July 2007

Synthesis and Properties of Macrocycles from Resorcinol, Corresponding Derivatives and Host‐Guest Complexes

Structural variations of the metacyclophanes obtained from the condensation of resorcinol with aldehydes RCHO are described, mostly based on the stereoisomer with all R in cis configuration. The basic tetraphenolate (with R = CH3, 1a) shows a cone‐conformation as evident e.g. from vicinal 13C–C–C–1H coupling constants. Substituents R′ in the 2‐position of the phenyl rings at the upper rim of the macro‐cycle are either introduced with the resorcinol derivative used (R′ = CH3, COOH), or by Mannich reactions after cyclization (R′ = CH2NR″2), which partially lead to intermediate oxacine formation. Acid‐base properties are evaluated with potentiometric and NMR‐shift titrations. Mannich products from amino acids such as proline, which are formed without racemization, show no pK differences for the groups at the four equivalent phenyl rings, but three distinct pK values for the deprotonation of OH, COOH, and +NH3 substituents; the pK of the latter is two units lower than in proline itself as it is involved in hydrogen bridging. Complexation constants K of such derivatives with Fe3+, Cu2+, and Zn2+ show the expected increase with metal ion acidity; they are increased by a power of 5 in comparison to proline. Complexation constants and complexation‐induced NMR shifts (CIS values) are determined for 51 complexes, with positively charged organic guest molecules for the basic tetraphenolate skeleton as well as for the aminomethylation derivatives. A temperature dependence study shows that the corresponding equilibrium is driven by ΔH with negligible ΔS contributions. No chiral discrimation is observed upon complexation of e.g. carnitine with the optically active amino acid derivatives. This is in line with CIS and K values obtained with several complexes showing an orientation of the NR″2 groups away from the cavity. The COOH substituents R′ form strong hydrogen bonds with the adjacent phenolic groups, leading to alternating pseudo‐eq and ‐ax positions of the phenyl rings. Their interconversion barrier, determined by NMR spectroscopy, is 72 kJ mol‐1; they bind mono‐ and bis‐ammonium ions as function of distance matching. The presence of lipophilic substituents (R = phenyl, benzyl, biphenyl, n‐hexyl, n‐undecyl) at the bottom of the macrocycle furnishes a second binding center which allows to complex e.g. diethyl ether in water. Coordination of zinc to the proline derivative still allows co‐complexation of choline acetate, the hydrolysis of which is not inhibited anymore as it is by the zinc‐free macrocycle.
Coordination Polymers, IX[1] Synthesis and Crystal Structure of a 1D‐Sodium Coordination Polymer: [NaL4(PMDETA)]∞
Authors: Saalfrank Rolf W. , Struck Oliver , Davidson Matthew G. , Snaith Ronald
Published: July 2007

Reaction of sodium hydride with the tridentate tetrazole ligand 10 (HL4) and pentamethyldiethylenetriamine (PMDETA) in toluene yields by self‐assembly in the solid‐state the well‐ordered 1D‐coordination polymer [NaL4(PMDETA)]∞, (11). The structure of 11 was established by single‐crystal X‐ray diffraction. The generation of the 1D‐polymer 11 is understandable if intermediate formation of coordinatively unsaturated, neutral sodium building blocks [NaL4(PMDETA)] (12) is assumed. Such a self‐complementary monomer 12 acts in a monodentate fashion via its CN group, leading to linkage of monomers and to coordinative saturation at the sodium centre of 12. The sodium ions of the resulting polymeric chains of 11 are coordinated in a distorted octahedral manner. These results indicate that sodium derivatives of CN‐containing ligands may be tuned as to their dimensionality, especially so since Na+ can cope with coordination numbers of 4, 5, or 6, such tuning could be probed initially by provision of further available functionalities within the anionic ligand and/or by provision of Lewis base donors of varying denticity.
Face‐Selective and endo‐Selective Cycloadditions with Enantiomerically Pure Cyclopentadienes
Authors: Beckmann Marion , Meyer Thorsten , Schulz Frauke , Winterfeldt Ekkehard
Published: July 2007

A general synthetic route to the enantiopure bicyclic cyclopentadienes (S)‐3 and (R)‐3 of the hydrindane series, starting from the Hajos‐Wiechert ketone 4 or its enantiomer is described. Reasons for the excellent face and endo selectivity of cycloadditions and the resulting consequences for chiral recognition are discussed.
Stereoselective Synthesis of Alcohols, XLVII[1] Application of Chiral Z‐Pentenylboronates to the Synthesis of Erythronolide Building Blocks
Authors: Hoffmann Reinhard W. , Stürmer Rainer
Published: July 2007

The chiral pentenylboronate 3 was the key reagent in the stereoselective construction of two erythronolide building blocks 6 and 7. Addition of 3 to achiral aldehydes furnished homoallylic alcohols 21 and 26 with >98% e.e. Addition of 3 to chiral aldehydes 8 or 11 generated homoallylic alcohols with >95% d.e. In the mismatched case of addition to the aldehyde 29 diastereoselectivity reached merely 80%.
Heterogene Gasphasen‐Eliminierungen mit dem System Magnesiumoxid/Kalium
Authors: Maier Günther , Weber Claudia
Published: July 2007

Heterogeneous Gasphase Eliminations with the System Magnesium Oxide/Potassium

After evaporation of potassium and condensation on a magnesium oxide surface a highly reactive blue reagent is formed which is active in dehydrogenation reactions. 1,4‐Cyclo‐hexadiene (1) and 1,3‐cyclohexadiene (2) can effectively be converted into benzene at room temperature while dehydrogenation of cyclohexene 3 needs temperatures higher than 200°C. The reaction mechanism is discussed. Debrominations with MgO/K can likewise be carried out under rather mild conditions.
Reaktionen von R2AlAlR2 (R  CH(SiMe3)2) mit Trimethylsilylazid — Insertion in die AlAl‐Bindung und Abbau zum trimeren Dialkylaluminiumazid
Authors: Uhl Werner , Gerding Rolf , Pohl Siegfried , Saak Wolfgang
Published: July 2007

Reactions of R2AlAlR2 (R  CH(SiMe3)2) with Trimethylsilyl Azide — Insertion into the AlAl Bond and Formation of a Trimeric Dialkylaluminium Azide

Tetrakis[bis(trimethylsilyl)methyl]dialuminium(4) (1) reacts with trimethylsilyl azide under insertion of one nitrogen atom into the AlAl bond. As shown by NMR spectra and crystal structure the product contains three and four coordinated Al atoms due to the coordination of the α‐nitrogen atom of the azide group to one of the Al atoms. An electronically delocalized N3‐system is formed with a NN bond length of 132.0 pm and a bond order of 1.5 for both NN bonds. With an excess of trimethylsilyl azide further reaction is observed only under mild irradiation conditions with an exchange of the azide group between Si and Al and formation of Me6Si2 and the dialkylaluminium azide 3, which is better synthesized by the reaction of Me3SiN3 with ClAl[CH(SiMe3)2]2. The sterically highly shielded aluminium azide 3 is a trimer in the solid state showing a non‐planar 12‐membered Al3N9 heterocycle with short NN bonds (114 pm).
Darstellung und Charakterisierung der Tetrahedrane [CpM(CO)2]3P (M = Mo, W) sowie der Derivate [CpMo(CO)2]3P‐Mo(CO)5 und [CpW(CO)2]3P–W(CO)5
Authors: Kilthau Thomas , Nuber Bernd , Ziegler Manfred L.
Published: July 2007

Synthesis and Characterization of the Tetrahedranes [CpM(CO)2]3P (M = Mo, W) and Their Derivatives [CpMo(CO)2]3P–Mo(CO)5 and [CpW(CO)2]3P–W(CO)5

The reaction of Na[CpM(CO)3] (M = Mo, W) with PCl3 in diglyme yields the cluster compounds [CpMo(CO)2]3P–Mo(CO)5 (2a) and [CpW(CO)2]3P–W(CO)5 (2b) in good yields as well as the tetrahedranes [CpMo(CO)2]3P (3a) and [CpW(CO)2]3P (3b) as side products. Compounds 3a, b are obtained independently by the reaction of 2a, b with PPh3. The clusters 2a, b and 3a, b were characterized spectroscopically (IR, NMR, MS), and X‐ray structure determinations were carried out on 2a, b.
Pn‐Liganden mit maximaler Elektronendonorfähigkeit, 7. Dreikomponentenreaktion von P4‐Phosphor mit [CpxRh(CO)2] in Gegenwart von [Cr(CO)5THF] oder [CpMn(CO)2THF]. – Eine Methode zum Studium des Transformationsweges vom P4‐Tetraeder zum planaren cyclo‐P4‐Liganden
Authors: Scheer Manfred , Troitzsch Christa , Hilfert Liane , Dargatz Manfred , Kleinpeter Erich , Jones Peter G. , Sieler Joachim
Published: July 2007

Pn Ligands with Maximum Electron‐Donor Capacity, 7. – Three‐Component Reaction of P4‐Phosphorus with [CpxRh(CO)2] in the Presence of [Cr(CO)5THF] or [CpMn(CO)2THF]. – A Method of Studying the Pathway from Tetrahedral P4 to the Planar cyclo‐P4 Ligand

Herrn Professor Gerhard Fritz zum 75. Geburtstag gewidmet.

The reaction of P4 with [CpxRh(CO)2] (Cpx = Cp′, Cp′′; Cp′ = η5‐C5H4tBu, Cp′′ = η5‐C5H3tBu2‐1,3) in the presence of [Cr(CO)5THF] leads to [CpxRh(CO)(η1:1‐P4){Cr(CO)5}4] (1a, b), [Cp′′Rh(η4‐P4){Cr(CO)5}3] (2b), and [Cp′Rh(η4‐P4){Cr‐(CO)5}4] (3a). In the corresponding reaction with [CpMn‐(CO)2THF] no P4 takes part, and [(Cp′′RhCO)(CpMnCO)(μ‐CO)2] (4) is formed. An X‐ray structure determination of [CpxRh(CO)(η1:1‐P4){Cr(CO)5}4] (1) and [Cp′Rh(η4‐P4)‐{Cr(CO)5}4] (3a) indicates a stepwise (PP) bond cleavage as the transformation pathway from the P4 tetrahedron to the cyclo‐P4 ligand by passing a bicyclotetraphosphane. In the cyclo‐P4 ligand complex 3a all P atoms are able to coordinate to [Cr(CO)5] groups. However, in [Cp′′Rh(η4‐P4){Cr(CO)5}3] (2b) the additional tBu group at the Cpx ligand sterically influences the coordination behavior of the P atoms, and only three of them are able to coordinate to [Cr(CO)5] units. In these syntheses the [Cr(CO)5] moieties promote the reaction and stabilise intermediates along the reaction pathway. Variable‐temperature 31P{1H}‐NMR measurements indicate for 2b the freezing of the Cp′′ rotation at low temperature and reveals a ΔG (at the coalescence temperature) of 36 kJ mol−1. Surprisingly, in [(Cp′′RhCO)(CpMnCO)(μ‐CO)2]‐(Rh‐Mn) (4) the Cpx ligands are cis‐oriented whereas in [(Cp*RhCO)(CpMnCO)(μ‐CO)2](Rh‐Mn) a trans arrangement is observed. This indicates the unusual behavior of the Cp′′ ligand as a “rod” and not as an “enlarged disk” like Cp* in the crystal lattice of these compounds.
Darstellung von phosphor‐ und fluorhaltigen Calix[4]aren‐Derivaten. Konformationsanalyse, Trennung der Konformere und Röntgenstrukturanalyse an einem Konuskonformer
Authors: Neda Ion , Plinta Hans‐J. , Sonnenburg Ralf , Fischer Axel , Jones Peter G. , Schmutzler Reinhard
Published: July 2007

Preparation of Phosphorus— and Fluorine‐Containing Calix[4]arene Derivatives. Conformational Analysis, Separation of the Conformers, and X‐Ray Crystal Structure Analysis of a Cone Conformer

Herrn Professor Helmut Werner zum 60. Geburtstag gewidmet.

The Calix[4]arene 1 reacts with hexamethyldisilazane or (diethylamino)trimethylsilane to form the bis‐trimethylsilyl‐ated derivative 2. Treatment of 2 with PF2C1 gives the mono‐and bis‐difluorophosphites 3 and 4, which react with elimination of Me3SiF or PF3 to yield the monofluorophosphite derivative 5. All four OH hydrogen atoms in 1 are replaced by lithium on reaction with nBuLi with formation of the tetrali‐thiated product 6. This has been allowed to react with the Pchlorophosphorinanones 7–9. From 7 the cone conformer 10a is formed, whereas in the case of 8 and 9 a mixture of all four possible conformars 11a‐d and 12a‐d is obtained. The pure conformers 12a‐d are isolated. By refluxing the cone conformer 12a in tetrachloroethane a conformational conversion is effected. In order to evaluate its coordinating ability, 12a was allowed to react with dichloro(cycloocta‐1, 5‐diene)platinum(II) to form the trans‐disubstituted complex 13. In the case of 12a (acetonitrile solvate) a single‐crystal X‐ray structure analysis has been conducted. The molecule displays a cone conformation, whereby two of the opposing phenyl rings are approximately parallel and the other two approximately perpendicular to each other.
Synthese kationischer η2‐Phosphinocarben‐Komplexe des Molybdäns und Wolframs
Authors: Kreißl Fritz R. , Ostermeierx Josef , Ogric Cynthia
Published: July 2007

Synthesis of Cationic η2‐Phosphinocarbene Complexes of Molybdenum and Tungsten

Herrn Professor Hubert Schmidbaur zum 60. Geburtstag gewidmet.

The reaction of chlordimethylphosphane or chlordiphenyl‐phosphane and sodium tetraphenylborate with dicarbonyl(η5‐cyclopentadienyl)carbyne complexes of molybdenum and tungsten enables the direct conversion of a MCR group into a MC(R)PR2 unit providing dicarbonyl substituted η2‐phosphinocarbene complexes in high yields. In the absence of Na[BPh4] a base induced carbonyl carbene coupling reaction affords η3‐phosphinoketene complexes.
Fe(NCMe)‐Komplexe von chiralen Tripodliganden mit drei verschiedenen Donorgruppen: Dynamik und Struktur
Authors: Heidel Horst , Scherer Johannes , Asam Alexander , Huttner Gottfried , Walter Olaf , Zsolnai Laszlo
Published: July 2007

Fe(NCMe) Complexes of Chiral Tripod Ligands Bearing three Different Donor Groups: Dynamics and Structure

Chiral tripod ligands [tripod = CH3C(CH2PR2)(CH2PR′2)(CH2‐PR′′2), 1a–d] with three different donor groups react with Fe(NCMe)6(BF4)2 to yield the complexes tripodFe(NCMe)3(BF4)2 (2a–d). These complexes show an idealized octahedral coordination based on a facial coordination of the tripod ligand. The asymmetry of the chiral tripod ligands a–d induces a differentiation of the remaining coordination sites at iron. The structure and the dynamic behaviour of the compounds 2a, b is elucidated by X‐ray structural analyses and 2D‐NMR techniques.
Transition‐Metal Complexes with the Novel Scorpionate Ligand Dihydrobis‐(tetrazolyl)borate: Synthesis and Characterization of Infinite Two‐Dimensional Metal‐Ligand Frameworks and One‐Dimensional Water Substructures
Authors: Janiak Christoph , Scharmann Tobias G. , Brzezinka Klaus‐Werner , Reich Peter
Published: July 2007

Dihydrobis(tetrazolyl)borate metal compounds of the composition [M(L)2{μ‐H2B(CHN4)2}2]n for M = Mn, Fe, Co, Zn, Cd with L = H2O and for M = Cu with L = NH3 are obtained from metal salts and K[H2B(CHN4)2]. Single‐crystal X‐ray studies reveal the formation of two‐dimensional rhombic grid sheets through the bridging action of the bis(tetrazolyl)borate ligands. Each metal atom is octahedrally coordinated with two trans L ligands and four H2B(CHN4) nitrogen donors. Two additional, hydrogen‐bonded water molecules occupy the rhombic openings in the compounds with M = Mn, Fe, Co, Zn, and Cd. The water of crystallization is held in place through hydrogen bonding from the water ligands and to the nitrogen atoms to give a substructure of parallel kinked water chains. Temperature‐variable magnetic measurements show a Curie‐Weiss behavior for the paramagnetic complexes with M = Mn, Fe, Co, and Cu.
Dilithium Derivatives of Bis(tert‐butyldimethylsilylamino)silanes as Building Units for Inorganic Ring Compounds
Authors: Hemme Ina , Tecklenburg Brigitte , Noltemeyer Mathias , Klingebiel Uwe
Published: July 2007

The bis[(tert‐butyldimethylsilyl)amino]silanes 1–3 are converted into their lithium derivatives 4–7 with BuLi. Depending on the bulkiness of the substituents, the dilithium derivatives 4 and 5 crystallize in cis or trans conformation. Monolithiated 3 (6) forms a four‐membered (SiFLiN) ring system, while its dilithium salt is characterized as a lithium silyldiamide (7), Although 4, 5, and 7 have different structures, they react with PF3 (8, 9), SiF4 (10, 11), and CMe3SiF3 (12) as diamides to give the corresponding four‐membered ring systems 8–12. The crystal structures of 4 and 5 are reported.
Ionenpaarbildung und Cyclisierungsreaktionen an koordinierten Oxalamidinen
Authors: Fehling Peer , Döring Manfred , Knoch Falk , Beckert Rainer , Görls Helmar
Published: July 2007

Ion Pairing and Cyclization on Coordinatively Bound Oxalamidines

The tetraphenyloxalamidine ligand of complex 8a reacts easily in the presence of bases with elementorganic dichlorides (R2MCl2) to form coordinated metalacycles. The cyclization with phosgene gives the (CO)4Mo‐coordinated 1,3‐diphenyl‐4,5‐bis(phenylimino)‐2‐imidazolidinones 10. In contrast to the reaction forming the piperazine derivative 2, the reaction of 8a with oxalyl chloride also proceeds to 10 by decarbonylation. The product of this cyclization, (CO)4Mo(OCTPOA) (10), and two possible intermediates, the dinuclear sodium salts Na2(THF)8[(CO)4Mo(HTPOA)]2 (11a) and Na(THF)4[(CO)4Mo(EtO2COCTTOA)]2 (15) have been characterized by X‐ray analyses. 11a contains the coordinated oxalaminate anion. The structure of the ionic complex 15 shows the simultaneous attack at both sp3‐hybridized nitrogen atoms and the selective formation of the five‐membered 2‐imidazolidinone heterocycle by coordination of the oxalamidine. Both sodium complexes 11a and 15 are dimeric and centrosymmetric ion pairs. Complex 11a contains two CONaOC bridges while compound 15 has a central [Na2O2] four‐membered ring consisting of sodium alcoholate bridges.