J . Am. Chem. SOC.1986,108, 3645-3651
3645
Structure and Thermal Reactions of Dihydrogen Complexes: The IR Characterization of M(CO),(H2) (M = Cr, Mo, and W) and c i ~ - C r ( C 0 ) ~ ( H in ~Liquid ) ~ Xenon Solution and the Formation of HD during Exchange of H2 and D2 Rita K. Upmacis, Martyn Poliakoff,* and James J. Turner* Contribution from the Department of'Chemistry, University of Nottingham, Nottingham NG7 2RD, England. Received December 5, 1985
Abstract: UV photolysis of M(C0)6 (M = Cr, Mo, and W) and Hz in liquid Xe at -70 OC yields M(CO),(H,) and, for Cr and W, c~s-M(CO)~(H,)~. For all three metals, M(CO)5(H2)has been fully characterized from IR spectra, including "CO data, C-O factored force field analysis, and observation of v(H-H) bands. Surprisingly, the u(H-H) band for Mo, 3080 cm-I, is at a higher wavenumber than Cr, 3030 cm-I, or W,271 1 cm-I. The thermal stability of the three compounds is in the order Mo(CO),(H2) (least stable)
