COORDINATION 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 crystal lography. That of dppr shows a ruthenocene derivatized by a PPh2 group on each C-5 ring. It is centrosymmetric with two PPh2 groups trans di sposed 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 d ppr to give a large bite angle (P-Pt-P) of 101.0(1)degrees with a comp ressed 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 o f [PdCl2(dppr)] in the Grignard coupling of MgPhBr with 1,2-dibromoben zene, which results in 93% conversion of the latter and gives 2-bromob iphenyl (79%) and o-terphenyl (15%) under reflux conditions, is superi or to that shown by [PdCl2(dppf)] and [Pd(dppf)] [dppf = 1,1'-bis(diph enylphosphino)ferrocene]. This catalytic enhancement by dppr is consis tent with a greater C-5 ring separation and larger bite angle subtende d by dppr compared to that of dppf.