The intensities of the absorbances of i(C0) at 1975 and 2045cm-' and v(0,CCF;) at 1694and 1644 em-' increase in a c o n ~t a n t ratio. Compared with v(0,CCF;) of 1676cm-' in 2 and 1692cm-' in Bu,N. the hypsochromic shift ofone 0,CCF; group (1694 cm-') corresponds to an ionic 0,CCF; unit and the bathochromic shift of a second 0,CCF; group (1644cm-') is typical for the formation of a bidentate complex. Therefore the absorbances are assigned to Os(CO),(PPh,),(t$ O,CCF,) The other absorbance at 1892 cm-' is identical to that of 1. 1171 IR spectrum of the final product from thermal reation of 2 in CH,CI,: r(C0): 1977(s) and 2046(s) c m -' , v(0,CCF;): 1691 cin-'. For coinparison the known [OsCI,(CO),(PPh,)J. prepared by the method of Collman and Roper [6]. caused these absorptions to increase when added to the same solution. The uncoordinated 0,CCF; group in Bu,N has an absorbance at 1691 cm-' in CH,CI,. r() VCH VeriugsjieseiIscha/t nihH, W-6940 Wch?l?ettn, I992 0570-0833/92~0606-0772 X 3.50 + .25/0 Angev.. Chem. Inr. Ed. Engl. 31 (1992) No. 6 (c) VCH Verlugsgesellschufi