ABSTRACT
The coordination chemistry of the bidentate P,N hybrid ligand 2-(2'-pyridyl)-4,6-diphenylphosphinine (1) towards Pd(II) and Pt(II) has been investigated. The molecular structures of the complexes [PdCl(2)(1)] and [PtCl(2)(1)] were determined by X-ray diffraction, representing the first crystallographically characterized λ(3)-phosphinine-Pd(II) and -Pt(II) complexes. Both complexes reacted with methanol at the P=C double bond at an elevated temperature, leading to the corresponding products [MCl(2)(1H·OCH(3))]. The molecular structure of [PdCl(2)(1H·OCH(3))] was determined crystallographically and revealed that the reaction with methanol proceeds selectively by syn addition and exclusively to one of the P=C double bonds. Strikingly, the reaction of [PdCl(2)(1H·OCH(3))] with the chelating diphosphine DPEphos at room temperature in CH(2)Cl(2) led quantitatively to [PdCl(2)(DPEphos)] and phosphinine 1 by elimination of CH(3)OH and rearomatization of the phosphorus heterocycle.
Subject(s)
Palladium/chemistry , Phosphines/chemistry , Phosphines/chemical synthesis , Platinum/chemistry , Pyridines/chemistry , Pyridines/chemical synthesis , Crystallography, X-Ray , Magnetic Resonance Spectroscopy , Molecular Conformation , Molecular Structure , StereoisomerismABSTRACT
High selectivity in acids is obtained in the first example of hydrocarboxylation of 1-octene in supercritical carbon dioxide using a Pd/P(4-C6H4-CF3)3 catalyst system and a perfluorinated surfactant.
ABSTRACT
3-Hydroxy-2-methylpropionamide, an important intermediate in the synthesis of methyl methacrylate, has been obtained with excellent conversion and high selectivity from acrylamide by a tandem hydroformylation-hydrogenation sequence catalysed by Rh/PPh3 and Raney Ni, respectively.
Subject(s)
Acrylamide/chemistry , Acrylamides/chemical synthesis , Acrylamides/chemistry , Catalysis , Hydrogenation , Ligands , Molecular Structure , Nickel/chemistry , Organometallic Compounds/chemistry , Rhodium/chemistry , TemperatureABSTRACT
Modular ligands of C(2) symmetry (13a-e, 14a,b,d, and ent-9), systematically modified at positions 2 and 5, were easily prepared from d-glucosamine, D-glucitol, and tartaric acid, respectively. The application of these ligands in the rhodium-catalyzed hydrogenation of methyl acetamidoacrylate, methyl acetamidocinnamate, and dimethyl itaconate shows that both the configuration and the substituents at positions 2 and 5 of the tetrahydrofuran backbone have a strong influence on the enantioselectivty of the processes.
Subject(s)
Carbohydrates/chemistry , Organometallic Compounds/chemical synthesis , Phosphites/chemical synthesis , Rhodium/chemistry , Catalysis , Glucosamine/chemistry , Hydrogenation , Ligands , Molecular Structure , Organometallic Compounds/chemistry , Sorbitol/chemistry , Stereoisomerism , Structure-Activity RelationshipABSTRACT
Palladium-rhodium and platinum-rhodium heterobimetallic bridged dithiolate complexes of general formula [(P-P)M(&mgr;-S-S)Rh(COD)]ClO(4) (COD = 1,5-cyclooctadiene. For M = Pt: P-P = (PPh(3))(2) and S-S = EDT(2)(-) (1,2-ethanedithiolate) (1), PDT(2)(-) (1,3-propanedithiolate) (2), and BDT(2)(-) (1,4-buthanedithiolate) (3); P-P = dppb (1,4-bis(diphenylphosphino)butane) and S-S = EDT(2)(-) (4), PDT(2)(-) (5), and BDT(2)(-) (6); P-P = dppp (1,3-bis(diphenylphosphino)propane) and S-S = EDT(2)(-) (7), PDT(2)(-) (8), and BDT(2)(-) (9). For M = Pd: P-P = dppb and S-S = EDT(2)(-) (10), PDT(2)(-) (11), and BDT(2)(-) (12); P-P = dppp and S-S = EDT(2)(-) (13), PDT(2)(-) (14), and BDT(2)(-) (15)) have been prepared. The crystal structures for complexes 1-3, 6, 9, and 12 have been determined, and hinged structures were found with angles between local coordination planes MS(2)Rh ranging from 111.27 degrees for complex 1 to 151.34 degrees for complex 3. Metal-metal distances show nonbonding interactions between metals. X-ray data for 1: triclinic, P&onemacr;, a = 11.311(6) Å, b = 12.991(6) Å, c = 16.140(6) Å, alpha = 84.86(6) degrees, beta = 75.73(6) degrees, gamma = 86.43(6) degrees, Z = 2, R = 0.0427 (R(w) = 0.1151). X-ray data for 2: triclinic, P&onemacr;, a = 11.084(5) Å, b = 13.094(6) Å, c = 16.338(6) Å, alpha = 86.06(6) degrees, beta = 75.67(6) degrees, gamma = 88.55(6) degrees, Z = 2, R = 0.0470 (R(w) = 0.1264). X-ray data for 3: orthorhombic, Pbca, a = 14.439(6) Å, b = 19.807(6) Å, c = 38.156(6) Å, Z = 8, R = 0.0864 (R(w) = 0.2457). X-ray data for 6: monoclinic, P2(1)/c, a = 20.338(6) Å, b = 14.227(6) Å, c = 14.570(6) Å, beta = 100.94(6) degrees, Z = 4, R = 0.0536 (R(w) = 0.1449). X-ray data for 9: monoclinic, P2(1)/c, a = 20.326(6) Å, b = 14.109(6) Å, c = 14.368(6) Å, beta = 100.90(6) degrees, Z = 4, R = 0.0380 (R(w) = 0.0990). X-ray data for 12: monoclinic, P2(1)/c, a = 20.365(6) Å, b = 14.186(6) Å, c = 14.592(6) Å, beta = 101.04(6) degrees, Z = 4, R = 0.0507 (R(w) = 0.1500).
