Hydridotetrakis triphenyl phosphite rhodium I

X-ray data suggest that the complexes [CoH P(OPh)3 4], [Ni P(OPh)3 4], [Pt P(OPh)3 4], and [RhH P(OPh)3 4] are iso-morphous. A tetrahedral arrangement of phosphite ligands about the metal atom is to be expected for the nickel(O) and platinum(O) complexes and on the evidence of the x-ray data appears highly probable for the cobalt and rhodium hydride derivatives also. The hydride ligand in the latter complexes is probably located along a C3 axis of the molecule as postulated for the related complex [CoH(CO)4]. 

No uu—u stretching vibrations can be detected in the infrared spectra of the cobalt and rhodium complexes, but the presence of hydride ligands is confirmed by the appearance of a quintet pattern in the high-field n.m.r. spectra of these derivatives. The apparent equivalent coupling of the hydride ligand to the four 31P nuclei has been tentatively explained in terms of a nonrigid structure.2 

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