N-SUBSTITUTED IMIDAZOLE DERIVATIVES OF RHODIUM(I) AND IRIDIUM(I) - CRYSTAL-STRUCTURE OF THE HEAD-TO-HEAD DINUCLEAR COMPOUND [IR-2(MU-N-BENZYLIMIDAZOLATO-N-3,C-2)(2)(CO)(4)]

Complexes [M(2)(mu-Cl)(2)(diolefin)(2)] (M = Rh or Ir, diolefin = cycl o-octa-1,5-diene (cod), norborna-2,5-diene (nbd)) react with lithium N -benzyl-2-imidazolate (LiBzim) to yield dinuclear [M(2)(mu-Bzim-N-3,C- 2)(2)(diolefin)(2)] [M = Rh, diolefin = cod (1), nbd (2); M = Ir, diol efin = cod (3)]. Carbon monoxide reacts with diethyl ether suspensions of [M(2)(mu-Bzim-N-3,C-2)(2)(diolefin)(2)] to afford the tetracarbony l complexes [M(2)(mu-Bzim-N-3,C-2)(2)(CO)(4)] [M = Rh (4), Ir (5)]. In the crystal structure of dinuclear [Ir-2(mu-Bzim-N-3,C-2)(2)(CO)(4)], organocarbonyliridium(I), the Ir atoms exhibit different coordination environments: one Ir coordinates two CO groups and two N atoms of the imidazolate rings, and the other Ir coordinates two CO groups and two C atoms of the imidazolate rings.