Co-ordination and catalytic chemistry of 1,1'-bis(diphenylphosphino)-ruthenocene (dppr). Synthesis of [MCl2(dppr)] (M=Ni, Pd or Pt) and molecular structures of dppr and [PtCl2(dppr)]center dot O.5CH(2)Cl(2)

Three complexes of 1,1'-bis(diphenylphosphino)ruthenocene (dppr) viz. [MCl2(dppr)] (M = Ni, Pd or Pt) were synthesized and characterized. An improved synthesis of dppr was elaborated. The crystal structures of dppr and [PtCl2(dppr)]. 0.5CH(2)Cl(2) were determined by X-ray crystallography. That of dppr shows a ruthenocene derivatized by a PPh2 group on each C-5 ring. It is centrosymmetric with two PPh2 groups trans disposed and the C-5 rings staggered and anti. The C-5 (centroid)... C-5 (centroid) separation is 3.606 Angstrom. In [PtCl2(dppr)] the planar platinum(II) centre is angularly distorted by the large bite size of dppr to give a large bite angle (P-Pt-P) of 101.0(1)degrees with a compressed Cl-Pt-Cl angle of 85.6(1)degrees and other C, ring deformations. The C, rings in dppr are parallel (theta = 0 degrees) but subtended at 8.8 degrees in the platinum(II) complex. The catalytic efficiency of [PdCl2(dppr)] in the Grignard coupling of MgPhBr with 1,2-dibromobenzene, which results in 93% conversion of the latter and gives 2-bromobiphenyl (79%) and o-terphenyl (15%) under reflux conditions, is superior to that shown by [PdCl2(dppf)] and [Pd(dppf)] [dppf = 1,1'-bis(diphenylphosphino)ferrocene]. This catalytic enhancement by dppr is consistent with a greater C-5 ring separation and larger bite angle subtended by dppr compared to that of dppf.