A. I. Yanovsky

Novel acetylene complexes of titanocene and permethyltitanocene without additional ligands. Synthesis spectral characteristics and X-ray diffraction study

Abstract New acetylene complexes of titanocene and permethyltitanocene Cp 2 Ti(R 1 C 2 R 2 ) and Cp 2 *Ti(R 1 C 2 R 2 ) (R 1 ue5fbR 2 ue5fbSiMe 3 ; R 1 ue5fbPh, R 2 ue5fbSiMe 3 ) without additional ligands have been prepared by the reaction of Cp 2 TiCl 2 and Cp 2 *TiCl 2 with equimolar amounts of Mg and the appropriate acetylene R 1 C 2 R 2 in THF. The complexes have been isolated from the reaction mixture in an analytically pure state and characterized by spectral methods. The structures of complexes Cp 2 Ti(PhC 2 SiMe 3 ), Cp 2 *Ti(PhC 2 SiMe 3 ) and Cp 2 *Ti(Me 3 SiC 2 SiMe 3 ) have been proved by an X-ray diffraction study. Some chemical properties of the synthesized complexes have been investigated.

On the problem of the stabilization of α-metallocenylcarbocation. Synthesis, properties and crystal structure of [C5Me5OsC5Me4CH2+]BPh4−·CH2Cl2

Abstract The compound, [C 5 Me 5 O sC 5 Me 4 C H 2 + ]BPh 4 ·CH 2 Cl 2 , has been prepared by the reaction of C 5 Me 5 OsC 5 Me 4 CH 2 OH with NaBPh 4 in acetic acid. The Os… C + distance of 2.244 A and the inclination angle (β) of 41.8° of the exocyclic C(1)ue5f8C(2) bond to the Cp-plane found by single-crystal X-ray diffraction study (the crystal was grown from a Et 2 O/CH 2 Cl 2 (mixture) suggest that there is a covalent Osue5f8C bond. Thus the C α (2) atom loses its carbenium character, the positive charge being localized mainly around the metal atom which in this case plays a role of the specific onium center. It has been shown that in nonamethylmetallocenylcarbonium ions the role of direct interaction with the metal atom in the stabilization of α-carbenium cationic center increases in the order Fe

Asymmetric reduction of CC and CO bonds: stereochemical approach

Abstract Simple stereochemical rules have been found that establish a relationship between product configuration and catalyst or reactant configuration for the two most effective and extensively studied asymmetric reactions, viz., asymmetric hydrogenation of dehydroacylamino acids in the presence of chiral rhodium-phosphine complexes and asymmetric reduction of ketones with chiral hydrides. As regards the first reaction, an analysis of available X-ray data as well as of molecular models of catalytic complexes made it possible to suggest a stereochemical rule that correlates the configuration of phosphorus atoms in the chelate ring of a complex with the product configuration. This rule is also valid for non-symmetric chelates (in terms of dentate groups), such as the rhodium complex with PheNOP [PhCH2CH(CH3NPPh2)CH2OPPh2] synthesized and investigated by the authors. The observed effect of hydrogen pressure, substrate concentration, temperature and solvents used on the optical yield of acetamidocinnamic acid hydrogenation in the presence of this complex points to the primary formation of the hydride intermediate. In the absence of the substrate, it was detected by NMR and IR spectroscopy under the reaction conditions. For the second reaction, the rule of quadrants was suggested, which links the chiral hydride structure and the product configuration in acetophenone reduction with hydrides obtained by incomplete decomposition of LiAlH4 or NaBH4 with chiral alcohols, amines or acids. In the case of the chiral hydride prepared by the incomplete decomposition of NaBH4 with diisopropylidenefuranose and an organic acid, the use of this rule permitted prediction of a favourable effect of increased acid radical bulk on optical purity, the effect in question being corroborated experimentally.

Crown compounds for anions. Unusual complex of trimetric perfluoro-o-phenylenemercury with the bromide anion having a polydecker sandwich structure

Abstract Here we show that cyclic trimetric perfluoro- o -phenylenemercury ( o -C 6 F 4 Hg) 3 is capable of forming complexes with [PPh 4 ] + Br − , [PPh 3 Me] + I − and [PPh 4 ] + Cl − of the composition [( o -C 6 F 4 Hg) 3 X] − [PR 3 R′] + (X = Br, R = R′ = Ph; X = I, R = Ph, R′ = Me) or {[( o -C 6 F 4 Hg) 3 X 2 } 2− [PR 3 R′] + 2 (X = Cl, R = R′ = Ph). An X-ray study of the complex with [PPh 4 ] + Br − revealed that it has the unusual structure of the polydecker bent sandwich wherein each Br − anion is coordinated with six mercury atoms of two neighbouring molecules of ( o -C 6 F 4 Hg) 3 .

Synthesis and x-ray structure determination of an organometallic titanoxane [Cp2TiC(Ph)CH(Ph)]2O. Evidence for the formation of a titanocene complex with tolane

Abstract The reaction of Cp2TiCl2 with magnesium in THF in the presence of tolane at a Cp2TiCl2 : Mg : Ph2C2 ratio of 1 : 1 : 1 results in formation of a dark red-brown solution which yields cis-stilbene when treated with HCl in ethanol, the titanacyclopentadiene complex Cp2 TiC(Ph)ue5fbC(Ph)C(Ph)ue5fbC (Ph) when treated with tolane, and the organometallic titanoxane [Cp2TiC(Ph)ue5fbCH(Ph)]2O when treated with water. It is suggested that in the solution the titanocene complex with tolane [Cp2Ti(Ph2C2)], postulated previously as an intermediate in the catalytic hydrogenation of tolane to dibenzyl under the action of Cp2Ti(CO)2 is present. The structure of [Cp2TiC(Ph)ue5fbCH(Ph)]2O has been established by an X-ray analysis.

Basicity of transition metal carbonyl complexes : XI. Reactions of C5H5Mn(CO)2L with stannic chloride and structure of reaction products

Abstract Adducts of 1 : 2 composition were obtained by reacting C 5 H 5 Mn(CO) 2 L complexes (L = tertiary phosphines, AsPh 3 and SbPh 3 ) with stannic chloride. The crystal and molecular structure of C 5 H 5 Mn(CO) 2 PPh 3 · 2SnCl 4 was established by X-ray structural analysis. It has an ionic structure that corresponds to formula [C 5 H 5 Mn(CO) 2 (PPh 3 )(SnCl 3 )] + SnCl 5 − . The coordination environment of the manganese atom is a distorted square pyramid with a C 5 H 5 ligand at the apex. Using IR spectroscopy it was established that in certain cases a mixture of two isomers is formed in solution. In C 5 H 5 Mn(CO) 2 L complexes the central manganese atom is the site of attack by aprotic acids and is the most basic site of the molecule.

Reaction of a tolane complex of titanocene with carbonyl compounds. Synthesis of titanadihydrofuran metallacycles

Abstract The reaction of a THF solution of a tolane complex of titanocene [Cp2Ti(C2Ph2)] with benzaldehyde and acetone results in the formation of titanadihydrofuran metallacycles Cp2 TiC(Ph)ue5fbC(Ph)CH(Ph)O and Cp2 TiC(Ph)ue5fbC(Ph)C(CH 3 ) 2 O , respectively. The structure of the latter complex has been determined by X-ray analysis.

Template synthesis of organocobalt chelates with tridentate Schiff bases. Crystal structure of [MeCo(7-Me-salen-N-Me)(N-Me-en)]I

Abstract Series of alkylcobalt(III) chelates with tridentate Schiff bases composed of a ketoenol and a diamine in a 1 1 ratio have been prepared via templated synthesis. Stereochemical features of resulting structures have been studied by X-ray and NMR techniques. Scope of the template reaction as well as its route is considered.

Interaction of carbon dioxide with acetylene complexes of titanocene Cp2Ti(RC2R) (R Ph, SiMe3). Synthesis and structure of binuclear σ-alkenylcarboxylate complexes of titanium (III) Cp2TiC(R)C(R) COOTiCp2 and unexpected transformation of these complexes into titanafuranone metallacycles under the action of air oxygen

Abstract It has been shown that carbon dioxide reacts with acetylene complexes of titanocene Cp2Ti(RC2R) (Rue5fbPh, SiMe3) at room temperature and atmospheric pressure to form binuclear σ-alkenylcarboxylate complexes of trivalent titanium Cp2TiC(R)ue5fbC(R)COOTiCp2 containing two fused chelate cycles and a tricoordinated oxygen atom. The interaction of these binuclear carboxylate complexes with air oxygen at 20°C results in rapid formation of titanafuranone metallacycles Cp 2 Ti(R)=C(R)ue5f8C(O)ue5f8O . X-ray diffraction studies of complexes Cp2TiC(SiMe3)ue5fbC(SiMe3)COOTiCp2 and Cp 2 Ti(Ph)=C(Ph)ue5f8C(O)ue5f8O have been carried out.

Chemistry of vinylidene complexes: IV. Synthesis and the crystal and molecular structure of (η5-C5H5)MnOs3(μ2-CHCHPh)(μ-H)(μ-CO)(CO)11, an unusual heterometallic cluster☆

Abstract By the reaction of Cp(CO) 2 Mnue5fbCue5fbCHPh (I) with H 2 Os 3 (CO) 10 (II) the tetranuclear mixed-metal complex CpMnOs 3 (μ 2 -CHue5fbCHPh)(μ-H)(μ-CO)(CO) 11 (III) was prepared. An X-ray study of the structure of III showed that it is a spiked, tetranuclear cluster with the Mn atom linked to one of the vertices of the osmium triangle; the Mnue5f8Os bond is bridged by CO and CHue5fbCHPh groups, the latter being σ-bonded to Os and η 2 -coordinated by Mn. In the course of the formation of III, hydrogenation and n -π rearrangement of the initial phenylvinylidene ligand take place. In solution, complex III readily eliminates the [CpMn(CO) 2 ] fragment to give triosmium clusters containing unsaturated organic ligands: HOs 3 (μ 2 -CHue5fbCHPh)(CO) 10 , H 2 Os 3 (μ 3 -CHue5fcCPh)(CO) 9 , and H 2 Os 3 (μ 3 -Cue5fbCHPh)(CO) 9 .