INFRARED-SPECTRA OF C-2 HYDROCARBON LIGANDS COORDINATED TO A TRIOSMIUM FRAMEWORK - THE EFFECT OF HIGH-PRESSURE AS A TOOL FOR ASSIGNMENT

The effect of high pressure on the vibrational frequencies of a set of triosmium clusters (Os3(CO)10(μ3,η2-C 2H2) (1), HOs3(CO)9(μ3,η2-CCH) (2), H2Os3(CO)9(μ3,η 2-CCH2) (3), H3Os3(CO)9(μ3-CCH3) (4) has been measured in the range 0-96 kbar. The pressure shifts observed for various infrared bands are used to assign previously uncharacterized bands and to confirm other existing assignments. For clusters 2 and 4, the effect of deuteration on the hydrocarbon vibrations is reported in addition. In general, the pressure dependencies of the vibrational bands in terms of dv/dP follow the order C-H stretch > C-C stretch > C-H bend, with all bands typically shifting to higher energy with increasing pressure. For 2, 3, and 4, this order changes to C-C stretch > C-H stretch > C-H bend, if the shifts are formulated in terms of a percent change Δv/v0. For the C-C stretch, the magnitude of its shift to higher energy with increasing pressure is proportional to the initial value at atmospheric pressure. © 1990 American Chemical Society.