Transition metal hydrides as ligands

The characterization of [(PPh3)(3)IrH3AgH3Ir(PPh3)(3)](CF3SO3) is reviewed. The structural and spectroscopic properties of [(tripod)MH3M'H3M(tripod)](CF3SO3) (tripod=CH3C(CH2PPh2)(3), CH3C(CH2AsPh2)(3); M = Rh, Ir; M' = Cu(I), Ag(I), Au(I), Cd(II)) are also reviewed. It is pointed out that (a) in the Cu(I) and Ag(I) species, each trihydride forms one stronger and one weaker M-H-M'-H-M interaction, (b) in the Au(I) species the trimetallic units are held together mainly by M-Au-M bonds and (c) in the Cd(II) species this cation may weakly interact with all six hydrides. Qualitative bonding schemes describing the M-H-M'-H-M interactions are presented. The formation and properties of the hydrido-bridged heterobimetallic complexes of the type [(tripod)MH3M'L-n](CF3SO3) (tripod = as above; M = Rh, Ir; M' = Cu(I), Ag(I), Au(I), L = PR3) are summarized. The structural features of the hexametallic complexes [{(CH3C(CH2PPh2)(3))MH3M'}(3)](CF3SO3)(3) (M = Rh, Ir; M' = Cu(I), Ag(I), Au(I)) are reviewed.