Preparation and crystal structure of (2,2 ′-bibenzimidazole)dihalobis(triphenylphospine)rhenium(III) halides

Abstract

The reaction of ReOX 3(PPh 3) 2 (where X=Cl, Br) with 2,2 ′-bibenzimidazole (bibzimH 2) in the presence of excess PPh 3 yields the rhenium(III) cationic complexes [ReX 2(PPh 3) 2(bibzimH 2)]X, in which the phosphines are trans to one another, whereas the plane perpendicular to this direction includes the chelating bidentate bibzimH 2 and two cis halogen ligands. The third halogen is a halide counter-ion, attached to the complex cation via a pair of N–H⋯X − hydrogen bonds involving the two N–H groups of bibzimH 2. Crystallographic work on the chloro compound indicates that the departure from octahedral geometry is controlled by the bite of the bibzimH 2 ligand and that the presence of the phenylene groups does not introduce substantial steric hindrance. Despite the fact that the species is paramagnetic, the 1H NMR spectra were fully assigned.