Reaction of (eta(5)-Ph5C5)Ru(CO)(2)(Ot-Bu) with 5-hexen-2-ol produces two diastereomers of an alkoxycarbonyl complex having the double bond coordinated to ruthenium. The complexes were characterized by H-1 and C-13 NMR spectroscopy and in situ FT-IR measurements. The C-13 NMR carbonyl. peaks of the complexes appear at 203.48, 203.55, and 204.0 ppm in a ratio of 1:1:2. IR peaks for CO and acyl were detected at 1982 (CO) and 1644 (acyl) cm(-1).