Kinetic and thermodynamic studies of carbon monoxide insertion in alkylosmium(II) complexes and comparison with iron(II) and ruthenium(II) isoelectronic complexes

Abstract

The equilibrium constants of the reaction of cis,trans-[Os(CO) 2 (PMe 3 ) 2 (Me)I] 1c with carbon monoxide to give cis,trans-[Os(CO) 2 (PMe 3 ) 2 (COMe)I] 2c have been measured and compared with the values obtained for the isoelectronic complexes of iron and ruthenium. The kinetics of the above reaction as well as of the analogous insertion reaction with C 6 H 11 NC, which affords trans-[Os(CO)(PMe 3 ) 2 (C 6 H 11 NC)(COMe)I] 3, has been investigated. The results are interpretable by the methyl migration mechanism. The crystal structure of the new complex 3 has been determined. Furthermore, the isomer trans,trans-[Os(CO) 2 (PMe 3 ) 2 (Me)I] 1t has been synthesized by the photochemical isomerization of 1c in the solid state. The spectroscopic properties of the cis,trans (c) and trans,trans (t) isomers for the triad Fe, Ru and Os are compared.