Late transition metal .mu.-oxo and .mu.-imido complexes. 4. Preparation and characterization of rhodium .mu.-imido/amido A-frame complexes

Treating Rh{sub 2}(CO){sub 2}Cl{sub 2}({mu}-dxpm){sub 2} (dxpm = bis(diphenylphosphino)methane (dppm) or bis(dimethylphosphino)methane (dmpm)) with 2 equiv of LiNHR (R = Me, Ph, p-MeOPh, p-MePh, o-MePh, o,o{prime}-Me{sub 2}Ph, p-FPh, p-BrPh, p-NO{sub 2}Ph) gives Rh{sub 2}({mu}-NR)(CO){sub 2}({mu}-dxpm){sub 2} (1), its tautomer Rh{sub 2}({mu}-NHR)(CO){sub 2}({mu}-dxpm)({mu}-dxpm-H) (2), or equilibrium mixtures of 1 and 2 (1/2) (dxpm-H = bis(diphenylphosphino)methanide or bis(dimethylphosphino)methanide). Both tautomers have been characterized by x-ray crystal structure determinations. Crystals of tautomer 1 (dppm, R = p-NO{sub 2}Ph) from CH{sub 2}Cl{sub 2}/Et{sub 2}O are monoclinic (C2/c) with a = 11.337 (4) {angstrom}, b = 36.451 (8) {angstrom}, c = 12.821 (3) {angstrom}, {beta} = 90.59 (3){degree}, V = 5297.7 {angstrom}{sup 3}, and Z = 4. The structure of 2 (dppm, R = Me) clearly shows the presence of the dppm-H and the NHMe ligands. Crystals from toluene are triclinic (P{anti 1}) with a = 10.459 (12) {angstrom}, b = 14.348 (3) {angstrom}, c = 20.867 (6) {angstrom}, {alpha} = 104.96 (2){degree}, {beta} = 101.12 (4){degree}, {gamma} = 93.47 (6){degree}, V = 2,948.3 {angstrom}{sup 3}, and Z = 2.