Synthesis and carbonylation reactions of alkyl and phenyl complexes of palladium- and platinum-(II) containing β-diketonate type ligands

Abstract

Methyl and phenyl complexes of the formula [MR(β-dik)(PPh₃)](M = Pt or Pd, R = Me or Ph, β-dik =β-diketonate or monothio-β-diketonate ligand) have been prepared and fully characterized. Carbon monoxide readily inserts into the M–C bond to form the corresponding acyl complexes, and several of these complexes were isolated and characterized. Kinetic studies on the carbonylation of the palladium(II) complexes suggests that it is a pseudo-first order reaction with a rate that is sensitive to the nature of the β-diketonate ligand. Factors which influence the insertion process including the important role of the β-diketonate ligand in controlling the insertion step are discussed. The crystal structure of [Pt(COMe)(bzac)(PPh₃)](bzac = 3-mercapto-1-phenylbut-2-en-1-onate) has been determined (R= 0.040 for 6198 observed reflections). Crystals are monoclinic, space group P2₁/c, a= 14.785(3), b= 10.654(8), c= 20.102(8)Å, β= 122.56(2)° and Z= 4. The complex has square planar co-ordination with the acyl group trans to the oxygen atom [Pt–S, –P, –O, –C 2.291(2), 2.267(2), 2.134(5), 1.974(9)Å]. The chelate ring forms an angle of 3.6(1)° with the PtSOPC co-ordination plane.