Tandem isomerisation–carbonylation catalysis: highly active palladium(II) catalysts for the selective methoxycarbonylation of internal alkenes to linear esters

Ligand exchange reaction between NiMe2L2 (L = bpy, PEt3) and ditertiary phosphines Ph2P(CH2)nPPH2 (n = 1−4) and effect of ligand on ease of reductive elimination of C2H6 from NiMe2(Ph2P(CH2)nPPh2)

Mononuclear complexes of formula [M(SR)2(dppe)](M = Pd 1 or Pt 2; R = C5H9NMe, dppe = Ph2PCH2CH2PPh2) are formed in reactions of [MCl2(dppe)] with the sodium salt of 4-mercapto-1-methylpiperidine NaSR in acetonitrile–methanol solution. Subsequent reaction of 1 with [PdCl2(dppe)] and of 2 with [PtCl2(dppe)] in acetonitrile solution produces the bridged dinuclear cationic complexes [M2(µ-SR)2(dppe)2]2+, which are obtained as crystalline salts with tetraphenylborate anions (M = Pd 3 or Pt 4). An apparently mixed PtPd product 5 is formed in an analogous reaction from 1 and [PtCl2(dppe)] or from 2 and [PdCl2(dppe)]. The structures of complexes 1–5 have been determined crystallographically. Complexes 1 and 2 are isostructural, with a slightly distorted square-planar cis-MP2S2 co-ordination geometry. The isostructural complexes 3–5 also show square-planar co-ordination; the two aminothiolate ligands act as bridges between the metal atoms, giving a precisely planar central M2S2 ring. In all five structures the MP2C2 chelate rings have a twist conformation. The nitrogen atoms of the aminothiolates are not co-ordinated to the metal atoms. Infrared and 1H, 31P and 195Pt NMR spectra are presented and discussed. The combined evidence suggests that 5 is essentially a simple solid-solution mixture of pure complexes 3 and 4 in variable proportions, with at most a minor component of a genuinely heterobimetallic complex.

Dipalladium and diplatinum bis(µ-alkanethiolato) complexes with a planar M2S2 ring

The reaction ofcis-[PtCl2(CO)(PPh3)] with two equivalents of SnCl2. 2H2O in acetone solution allows isolation ofcis-[PtCl2(PPh3)2] as the acetone solvate, the crystal structure of which has been determined. Crystals ofcis-[PtCl2(PPh3)2]·C3H6O are monoclinic, space groupP21/c (No. 14) with four formula units in a cell of dimensionsa=10.288(3),b=24.372(5),c= 15.367(3) A, /gb=98.07(2)°. The structure was solved by the heavy-atom method and refined by full-matrix least-squares calculations to a finalRof 0.033 for 3761 reflections withI>(I). The crystal structure contains discrete well-resolvedcis-PtCl2(PPh3)2 molecules with acetone of solvation filling cavities in the crystal structure. The Pt coordination is slightly distorted square-planar with Pt-Cl 2.333(2) and 2.356(2), Pt-P 2.251(2) and 2.265(2) A, P-Pt-P 97.8(1), and Cl-Pt-Cl 87.1(1)°.

The structure ofcis-dichloro-bis-(triphenylphosphine)platinum(II); a product in the reaction ofcis-[PtCl2(CO)(PPh3)] with tin (II) chloride

Palladium and Platinum

X-Ray crystal structure analyses of [PtCl2{(t-Bu)2P(CH2)2P(t-Bu)2}] (I) and [PtCl2{(t-Bu)2P(CH2)2P(t-Bu)2}, C6H5C1] (II) have been carried out. Crystals of I belong to monoclinic system: a=20.595(3), b=7.917(3), c=14.885(2) A, β=109.03(1)°, space group P21/c with Z=4. II forms monoclinic crystals, P21/c: a=14.873(2), b=13.193(2), c=15.314(2) A, β=98.75(1)°, Z=4. Both structures, solved by the heavy-atom method, have been refined anisotropically by least-squares procedure to R=0.067 and 0.078 for I and II respectively. There is no essential difference between the structures of [PtCl2{(t-Bu)2P(CH2)2P(t-Bu)2}] molecules in I and II. The coordination around the platinum atom is square-planar; Pt–P=2.262(3) and 2.265(3) A and Pt–Cl=2.374(4) and 2.365(4) A. The molecule has a pseudo-C2 symmetry: the platinum atom and the center of the C–C bond in the P–C–C–P lie on this pseudo-C2 axis.

The Crystal and Molecular Structures of Dichloro-1,2-bis(di-t-butylphosphino)ethaneplatinum(II) and its Chlorobenzene Solvate

X-Ray crystal structure analysis of [PtCl2{(t-Bu)2P(CH2)3P(t-Bu)2}]·0.5C6H5Cl has been carried out. Crystals belong to monoclinic system: a=11.532(2), b=14.984(5), c=16.455(4) A, β=106.96(2)°, space group P21/c with Z=4. The structure, solved by the heavy-atom method, has been refined anisotropically by least-squares procedure to R=0.056 for 5019 non-zero reflections. The coordination around the platinum atom is approximately square-planar, however, it showed a slight deviation toward the tetrahedral geometry; Pt–P=2.281(3) and 2.282(3), Pt–Cl=2.359(3) and 2.362(3) A, P–Pt–P=99.05(9) and Cl–Pt–Cl=83.18(11)°.

Masahiro Harada

Papers

The Crystal and Molecular Structures of Dichloro-1,2-bis(di-t-butylphosphino)ethaneplatinum(II) and its Chlorobenzene Solvate

The Crystal and Molecular Structure of Dichloro[1,3-bis(di-t-butylphosphino)propane]platinum(II) Chlorobenzene Solvate