RHODIUM COMPLEXES WITH THE NEW ANIONIC DIPHOSPHINE [7,8-(PPH(2))(2)-7,8-C2B9H10](-) LIGAND

New rhodium complexes with the eclipsed anionic diphosphine [7,8-(PPh( 2))(2)-7,8-C2B9H10](-) are described. These were prepared from the neu tral cod complex [Rh{7,8-(PPh(2))(2)-7,8-C2B9H10}(cod)] either directl y or via the complex [Rh{7,8-(PPh(2))(2)-7,8-C2B9H10}(CO)(2)], which w as obtained by bubbling CO through a suspension of [Rh{7,8-(PPh(2))(2) -7,8-C2B9H10}(Cod)] in deoxygenated methanol. The CO ligands may be re adily replaced by monophosphines, chelating diphosphines, monoamines, and chelating diamines. CO substitution by monophosphines depends on t he phosphine cone angle more than the phosphine basicity. Both CO liga nds can be replaced in [Rh{7,8-(PPh(2))(2)-7,8-C2B9H10}(CO)(2)] by mon ophosphines with small cone angles, while monophosphines with large co ne angles are only able to displace one CO ligand. Thus [Rh{7,8-(PPh(2 ))(2)-7,8-C2B9H10}(CO)(phosphine)] and [Rh{7,8-(PPh(2))(2)-7,8-C2B9H10 }(phosphine)(2)] can be obtained. By contrast, with chelating diamines , carbamoyl complexes have been obtained.