Organo-rhodium(I) complexes containing mono and bidentate N-heterocycles

Complexes of the type [Rh(diolefin)(mu-X)](2) [X = Cl or Br; diolefin = cod (cycloocta-1,5-diene) or nbd (norbornadiene)] undergo dihalobridge cleavag e with 2-substituted benzimidazoles to produce mononuclear complexes, RhX(d iolefin)(R-BzlH) (R = alpha-Py or Ph), and N-heterocycle bridged dimers, [R hX(diolefin)](2)(mu-N-N) (N-N = beta-PyBzlH or gamma-PyBzlH). Facile replac ement ofone or both diolefins by CO occurs in the products to yield the cor responding di/tetracarbonyl complexes. Probable structures have been propos ed for the complexes on the basis of physical, i.r., far-i.r. and H-1- and C-13-n.m.r. spectral techniques and FAB-MS.