Sándor Vastag

Rhodium phosphine complexes as homogeneous catalysts: 14. Asymmetric hydrogenation of a Schiff base of acetophenone — effect of phosphine and catalyst structure on enantioselectivity

Abstract Using catalysts prepared in situ from [Rh(NBD)Cl] 2 and chiral diphosphines of the type Ph 2 PCHRCH 2 PPh 2 (R = Ph, i-Pr, PhCH 2 ) optical yields above 60% were achieved in the hydrogenation of PhMeCNCH 2 Ph. Although reproducibility of the results was poor, it can be concluded that the chiral diphosphines DIOP and diPAMP are much less effective, and that the halide ligand is necessary for good enantioselectivity.

Preparation and infrared spectra of monosubstituted PR3 and P(OR)3 (R alkyl, aryl) derivatives of (μ2-L)2Co2(CO)6 compounds☆

Abstract (μ 2 -L) 2 Co 2 (CO) 5 PR 3 and (μ 2 -L) 2 Co 2 (CO) 5 P(OR) 3 (R  alkyl, aryl, L 2  P 2 , As 2 , acetylene, L  CO and but-2-en-4-olid-4-ylidene) compounds were prepared. The ν(CO) infrared spectra are in agreement with the expected C s or C 1 symmetry. The results indicate that the PR 3 or P(OR) 3 substituent is in all cases in the axial position.

Rhodium phosphine complexes as homogeneous catalysts. 7. Effect of phosphine structure on catalytic activity in acetone hydrogenation

Abstract The activity of catalysts for acetone hydrogenation formed in situ from [Rh(norbornadiene)Cl]2 and phosphines or phosphinic acid esters is determined by the electronic and steric effects of the ligand. The electronic parameter used was the infrared νco value of Rh(PR3)2(CO)Cl complexes containing the same P(III)-ligands. Catalytic activity increases with decreasing νco (i.e., increasing basicity of the ligand) and reaches its highest level with PEt3. Phosphines with larger, or branched, alkyl groups show still lower νco values but yield catalysts of lower, or even zero, activity because of the steric effects of the bulky ligands.

Rhodium phosphine complexes as homogeneous catalysts. part 3. Homogeneous ssymmetric hydrogenation of schiffs bases

SummaryComplexes formed from [Rh(norbornadiene)Cl]2 and tertiary phosphines under hydrogen are active catalysts for the homogeneous hydrogenation of Schiff bases at 30–80° and 1-70 bars. Using chiral phosphines some optical induction can be achieved, but the optical yields are rather low.

Homogenkatalytische asymmetrische hydrierung von ketonen

Zusammenfassung Complexes formed from [Rh(1,5-hexadiene)Cl] 2 and tertiary phosphines under hydrogen are active catalysts for the homogeneous hydrogenation of ketones. Using chiral phosphines optical yields up to 51% were achieved.

Synthesis and structure of Co3(μ3-S) (C6F5) (CO)8, a cobalt carbonyl cluster with an aryl-metal sigma bond

Dicobalt octacarbonyl and perfluoro diphenyl disulfide react to form Co3(μ3-S) (C6F5)(CO)8 (1), an unusual cobalt carbonyl cluster containing an aryl-metal sigma bond. The structure of complex 1 was determined by X-ray crystallography; it crystallizes in triclinic P-1 space group with a = 8.218(2), b = 13.379(2), c = 18.864(2) A, α = 106.96(2), β = 96.91(2), γ = 97.39(2)°. The final R is 0.0376 for 5286 observed reflections (F0>4.0σF0).

Synthesis and structure of complexes formed in the reaction between dicobalt octacarbonyl and tetramethyl-biphosphine disulfide

Co2(CO)8 and Me2P(S)P(S)Me2 react to form the two cluster complexes: Co4(CO)9S(PMe2)2) (1) and Co3(CO)7S(SPMe2) (2). The strucure of1 and of the disubstituted triphenyl phosphine derivative of2. Co3(CO)5(PPh3)2S (SPMe3) (2a) were determined. Compound1 contains a quasi-planar rhomboidal Co4 cluster formed by two Co3 isosceles triangles sharing a Co-Co edge. One triangle is capped by a sulfur atom, the other triangle has two edge-bridging PMe2 moieties. Electron counting gives 64 electrons corresponding to a planar system; the distribution of long Co-Co distances, in particular in the triangle bearing PMe2 bridges, suggests that the excess electrons are located on Co-Co antibonding ortibals. Compound2a contains a Co3S cluster with one side bridged by a SPMe2 unit forming a four-membered Co2SP ring. The substitution of two CO groups with two PPh3 causes a large deformation of the cluster Co-Co bondscis to these two phosphorus atoms. Crystal data for1, space group P1,a = 9.728(2) Å,b = 10.288(2) Å,c = 11.860(3) Å,α = 86.41(2)°,β = 76.20(2)°,γ = 80.37(5)°,Z = 2, 5300 reflections,R = 0.0398; for2a, space group P1,a = 9.78(3) Å,b = 13.05(4) Å,c = 18.28(6) Å,α = 93.23(3)°,β = 99.17(2)°,γ = 97.26(6)°,Z = 2, 2976 reflections,R = 0.0579.

Mononuclear cobalt carbonyls containing monodentate thiolate or xanthate groups. The structures of PhSCo(CO)2(PPh2OMe)2 and MeOCS2CO(CO)2(PPh2iBu)2

Abstract Complexes of the type PhSCo(CO) 2 L 2 ( 1 ; L = phosphine or phosphite) and the complex MeOCS 2 Co(CO) 2 (PPh 2 i Bu) 2 ( 5 ) have been prepared from CoCl 2 · 6H 2 O, CO, the appropriate phosphine or phosphite, and PhSH + NaOMe or MeOCS 2 K, respectively. The crystal structures of 1a (L = PPh 2 OMe) and 5 · MeCN have been determined. These compounds are the first structurally characterized cobalt carbonyl complexes containing a monodentate thiolate or xanthate group.

Reductive carbonylation of cobalt(II) in the presence of diphenylphosphine: synthesis and structure of (PPN)[Co(CO)3(PPh2OMe)] and MeCOCo(CO)2(PPh2H)(PPh2OMe)

Cobalt(II) is reduced to Co(−I) by PPh2H in the presence of CO in MeOH solution containing NaOMe; the complex (PPN)[Co(CO)3(PPh2OMe)] (1) was isolated from the reaction product in 12% yield. Alkylation of the cobaltate anion with MeI gave after addition of PPh2H the disubstituted acylcobalt carbonyl complex MeCOCo(CO)2(PPh2H)(PPh2OMe) (2). The crystal structures of both complexes were determined: 1 monoclinic, P31/n, a 10.748(3), b 13.255(2), c 32.123(8) A, β 93.15(2)°, V 4569(2) A3, Z = 4, R(F) 0.048. 2 monoclinic, P21/n, a 14.440(5), b 16.768(6), c 11.526(3) A, β 102.27(3)°, V 2727(2) A3, Z = 4, R(F) 0.068. The anion of 1 contains a tetrahedral Co coordination geometry and 2 a trigonal bipyramidal geometry with the PPh2OMe and MeCO groups occupying axial positions.

SYNTHESIS AND STRUCTURE OF A DINUCLEAR COBALT CARBONYL DERIVATIVE CONTAINING METHYLDITHIOFORMATE AS A FIVE-ELECTRON DONOR LIGAND

Abstract Dicobalt octacarbonyl reacts with an excess of (MeSCS2)2 to form several sulfur-containing cobalt carbonyl derivatives; on addition of PPh3, the complex Co2(CO)2(PPh3)2(1,3-η-S2CSMe)(μ-1,2-η-SCSMe) (1) could be isolated from the reaction mixture. The structure of complex 1 was determined by X-ray crystallography; it contains a methyl dithioformate ligand in which the ligand donates five electrons to the cluster and the CS group is bound perpendicular to the Co2 core.