Carborane reductive-elimination reaction from a six-coordinate hydridocarboranyliridium(III) complex: Kinetic and mechanistic study

A kinetic and mechanistic study of the reductive-elimination reaction of the carborane 1-H-T-C6H5-1,7-C2B10H10 (H-carb) from the six-coordinate iridium(III) complex Ir(H)(Cl)(\u3c3-carb)(CO)(PPh3)2 has been carried out in 1,2-dichloroethane by IR spectroscopy between 20 and 50\ub0C. The mechanism of the carborane-elimination reaction implies a preliminary PPh3 dissociation to give the five-coordinate Ir(H)(Cl)(\u3c3-carb)(CO)(PPh3) complex. This intermediate then undergoes a reductive elimination of the carborane molecule through two pathways: (i) direct elimination to give the three-coordinate iridium(I) complex, IrCl(CO)(PPh3); (ii) a phosphine-induced elimination via trans \u2192 cis isomerization of the H and carb ligands. The kinetic and thermodynamic parameters are also reported and discussed. \ua9 1984 American Chemical Society

Kinetic and mechanistic study of the succinic anhydride reductive-elimination reaction from the six-coordinate Ir(H)[\u3c3-CHCH2C(O)OC(O)](\u3c3-carb)(CO)(PhCN)(PPh 3) complex

The hydridoalkyliridium(III) complex Ir(H)[\u3c3-CHCH2C(O)OC(O)](\u3c3-carb)(CO)(PhCN)(PPh 3), where carb = 7-C6H5-1,7-C2B10H10, undergoes reductive-elimination reaction of succinic anhydride under mild conditions. This reaction, which represents a crucial step in the homogeneous hydrogenation of maleic anhydride catalyzed by the four-coordinate iridium(I) complex Ir(\u3c3-carb)(CO)(PhCN)(PPh3) at T = 50\ub0C (PH2 = 1 atm), has been kinetically investigated in 1,2-dichloroethane solution by IR spectroscopy between 35 and 45\ub0C. The elimination reaction implies preliminary PhCN dissociation to give a five-coordinate intermediate that then undergoes intramolecular reductive elimination of succinic anhydride. The obtained activation parameters indicate that the reductive elimination of succinic anhydride from the five-coordinate hydridoalkyliridium(III) intermediate is a highly concerted process whose drawing force is the incipient formation of the strong C-H bond of the product. \ua9 1984 American Chemical Society

A florous chiral dirhodium(II) complex as a recyclable asymmetric catalyst

The chiral fluorous complex tetrakis-dirhodium(II)-(S)-N-(n-perfluorooctylsulfonyl)prolinate has been prepared and used as a catalyst in homogeneous or fluorous biphasic fashion. The catalyst displays good chemo- and enantioselectivity in intermolecular cyclopropanation and C-H bond activation reactions. The catalyst can be simply and thoroughly separated from the reaction mixture and is recyclable

Chloro and acetato complexes of platinum(II) with functionalized thioethers

The chloro complexes [PtCl2(RSR')(2)] (1-10) (RSR' = MeSCH2C(O)OMe, 1; MeSCH2C(O)OEt, 2; MeSCH2C(O)Omenthyl(-), 3: MeSCH2CH2C(O)OMe, 4; S(CH2)(3)CHC(O)OEt, 5; EtSCH2C(O)Me; 6; MeSCH C(O)Me, 7; MeSPh, 8; MeS-o-C6H4Me, 9; and MeS-o-C6H4Et, 10) are obtained in high yield (63-90%) by reaction of [PtCl2(PhCN)(2)] with the proper thioether in 1/2 molar ratio. in anhydrous chloroform. at reflux under argon for ca. 10 h. The X-ray crystal structure of [PtCl2(MeS-o-C6H4Me)(2)] (9) shows an almost regular trans square planar geometry (triclinic, space group P (1) over bar, a 6.806(1), b 7.789(2), c 10.085(3) Angstrom, alpha 101.80(2)degrees, beta 69.55(2)degrees, gamma 115.27(2)degrees, R(F-o) 0.023, R-w(F-o(2)) 0.065). The dichloro complexes react with silver acetate in a complex manner, which depends on the nature of the thioether, and only with RSR' = MeSPh the simple diacetato complex [Pt(OAc)(2)(RSR')(2)] is obtained as the major product

Reaction mechanisms of metal-metal bonded carbonyls. Part VII. Reaction of alkynes with \u3bc-carbonyl-\u3bc-diphenylgermanio-bis(tricarbonylcobalt)(Co-Co)

Alkynes [C2Ph2, MeC2Ph, PhC2H, and C2(CO2Et)2] displace the bridging GePh2 group from [(OC)3Co(\u3bc-GePh2)(\u3bc-CO)Co(CO)3], (I), to form the well known complexes [(OC)3(Co(\u3bc-alkyne)Co(CO)3] together with (GePh2)n (n = 4-7). The kinetics of reaction of complex (I) with diphenylacetylene in decalin have been studied over a range of temperature. The rate of reaction is first order in [Complex] and [C2Ph2] and the reaction is greatly retarded by carbon monoxide. The results are consistent with a reaction mechanism that involves initial reversible ring opening to form [(OC)3Co(\u3bc-GePh2)Co(CO)4], a process that is also involved in a reactions of complex (I) with carbon monoxide and triphenyl- and tributyl-phosphine. A mechanism involving intermediates with terminally co-ordinated GePh2 groups cannot be conclusively ruled out but is considered to be less probable