Isoprene platinum(II) complexes from cis-dichlorobis(triphenylphosphine) platinum(II) and isopropenylacetylene. Crystal and molecular structures of trans-chloro(1-isopropenylvinyl)bis(triphenylphosphine)-platinum(II)–benzene (1/1) and trans-(isopropenylethynyl)(1-isopropenylvinyl)bis(triphenylphosphine)platinum(II)

Abstract

When cis-[PtCl₂(PPh₃)₂] is warmed in ethanol with hydrazine hydrate in the presence of isopropenylacetylene three main products are obtained: trans-[PtCl(CH₂C–CMeCH₂)(PPh₃)₂](1), trans-[Pt(CH₂C–CMeCH₂)(CC–CMeCH₂)(PPh₃)₂](2), and [Pt(CHC–CMeCH₂)(PPh₃)₂](3). Formation of (1), (2), or (3) is dependent on the reaction time and reagent concentrations. For comparison, the behaviour of phenylacetylene under similar conditions has been examined and trans-[Pt(CCPh)(CH₂CPh)(PPh₃)₂] has also been obtained. The structures of (1) and (2) have been determined by single-crystal X-ray drffractometry: (1), monoclinic, a= 15.521 (3), b= 18.738(8), c= 16.872(5)Å, β= 125.07(2)°, Z= 4, space group Cc, R= 0.056: (2), orthorhombic, a= 18.94(1), b= 19.57(1), c= 10.42(1)Å, Z= 4, space group P2₁2₁2₁, R= 0.050. In both complexes the co-ordination around Pt is trans planar and the organic ligands are σ-bonded to platinum. The metal–ligand distances are: in (1) Pt–C 2.07(1), Pt–P 2.296(9), 2.299(14), and Pt–Cl 2.408(3)Å; in (2), Pt–C(isopropenylvinyl) 2.09(2), Pt–C-(isopropenylethynyl) 1.99(1), and Pt–P 2.287(5), 2.284(4)Å.