Preparation and spectroscopic properties of electroneutral alkoxy(organo)carbene complexes of platinum(II) and the crystal and molecular structure of cis-[benzyl(ethoxy)carbene]dichloro(dimethylphenylphosphine)platinum(II)

Abstract

A series of electroneutral alkoxy(organo)carbene complexes of platinum(II), cis-[PtX₂L{C(OR′)(CH₂R)}], has been prepared by reaction of the halide-bridged dimer [Pt₂X₄L₂](X = Cl, Br, or l; L = PMe₂Ph or PEt₃) with monosubstituted acetylenes RCCH(R = Ph, Me, or Et) and alcohols R′OH (R′= Me, Et, or Prⁿ). The complexes have been characterised analytically, by ¹H and ³¹P n.m.r. and i.r. spectroscopy, and by X-ray analysis of a typical member of the series. Crystals of the title complex are monoclinic, space group P2₁/n, with a= 15.084(2), b= 8.4,19(3), c= 15.801(3)Å, β= 92.93(2)°, and Z= 4. The structure has been solved by the heavy-atom method and refined by full-matrix least squares to R= 0.036 for 2 166 diffractometric intensity data corrected for absorption. The crystals are built of discrete molecules with cis square-planar geometry. Selected bond lengths are : Pt–P 2.240(3), Pt–Cl(trans to P) 2.355(3), Pt–Cl(trans to C) 2.375(3), and Pt–C 1.920(9)Å. The molecular structure displays a Pt ⋯ H contact of 2.6(1)Å to a hydrogen atom of the ethoxy CH₂ group. The ¹H n.m.r. spectra indicate that this Pt ⋯ H interaction persists in solution, and is a general feature of these neutral complexes.