Syntheses and structures of [Mo(CO)(3)(TPA)(3)] and [Mo(CO)(3)(ETPB)(3)]. A structural and spectroscopic correlation

Molybdenum tricarbonyl complexes of the type [Mo(CO)(3)L-3] (where L=1,3,5-triaza-7-phosphaadamantane [TPA] or 4-ethyl-2,6,7-trioxa-1-phosphabicyclo-[2.2.2]octane [ETPB] have been synthesized and characterized by IR, H-1; P-31 and Mo-95 NMR spectroscopies and single crystal X-ray diffraction methods. The X-ray structural determinations are correlated with the observed spectroscopic data. The average Mo-P bond distance in [Mo(CO)(3)(TPA)(3)] [2.489(9) Angstrom] is longer than in the corresponding [Mo(CO)(3)(ETPB)(3)] complex [2.428(5) Angstrom] which is consistent with weaker pi-acceptor ability for the cyclic aliphatic TPA ligand compared to the cage phosphite ETPB ligand. (C) 1997 Elsevier Science Ltd.