Gold-rhodium and gold-iridium hydride clusters

The hydrides MH3(tripod) (M = Rh and Ir; tripod = triphos and triars) react with [Au(L)]+ cations to give heterometallic species of the types [(tripod)MH,Au(L)]+, type A, [(tripod)MH,(A~(L))~]~+, type B, and [(trip~d)MH~(Au(L))~]*+, type C. The complexes of type A can be described as containing one M-H-Au unit which, however, is still dynamic at -90 OC. Similar behavior is observed for the complexes of type B where two M-H-Au units are present. The complexes of type C contain only two hydride ligands. The X-ray crystal structure of [(triphos)RhH2(Au(PPh3)),] (CF,S03)2 shows the presence of a RhAu, tetrahedron with the rhodium capped by triphos, while each gold atom is coordinated to one PPh,. The hydride ligands could not be located, but it is proposed that they may occupy two RhAu2 triangular faces. Crystal data: space group R3c, a = 20.343 (3) A, c = 44.937 (7) A, Z = 6, V = 16104.9 A3, p(ca1cd) = 1.486 g cm-,, and R = 0.049.