SYNTHESIS, AND F-19 NMR AND X-RAY STRUCTURAL STUDIES OF TRIOSMIUM CLUSTERS (MU-H)OS3(CO)10L[ON(CF3)2](L=PPH3, ASPH3 AND SBPH3)

Bis(trifluoromethyl)nitroxyl radical reacts with H2Os3(CO)10L (L=PPh3, AsPh3, SbPh3) to afford the derivatives (mu-H)Os3(CO)10L[ON(CF3)2] in which the (CF3)2NO moiety is revealed by single crystal X-ray determinations to assume an axial position. Variable-temperature F-19 NMR spectral studies indicate that the two CF3 groups of the (CF3)2N moiety become magnetically different at lower temperature due to restricted rotation about the N-O bond. The activation energies estimated from the coalescence temperatures are 54.4 and 52.3 kJ/mole for (mu-H)Os3(CO)10PPh3[ON(CF3)2] and for (mu-H)Os3(Co)10AsPh2-[ON(CF3)2] respectively.