Theoretical Study on Trinuclear Osmium Carbonyls

In order to find the best method of theoretical calculation for the transition metal compounds of the sixth period and predict the structure of the new compounds that can be synthesized experimentally,a series of neutral trinuclear osmium carbonyls Os3(CO)n(n=12,11,10,9) have been studied by three selected density functional theory(DFT) methods with two effective core potential(ECP) basis sets.Eighteen stable isomers were found.Comparison of the theoretical and experimental structural parameters as well as ν(CO) frequencies for Os3(CO)12 suggest that the DFT MPW1PW91 method with a suitable ECP basis set including relativistic effects represent a reliable method for predicting structures and vibrational frequencies of third row transition metal carbonyl derivatives.Using this method,structures of unsaturated trinuclear osmium carbonyl derivatives Os3(CO)n(n=11,10,9) have been investigated for comparison with their iron carbonyl analogues.