Low temperature photochemistry of (η 5-C 5H 5)M(CO) 2LX, M = V, L = X = P(OMe) 3, P(OEt) 3, CO; M = W, L = P(OMe) 3, P(nBu) 3, PPh 3, X = I: Structure, solvation and interconversion of the CO loss products, (η 5-C 5H 5)M(CO)LX

Abstract

The photochemistry of selected four-legged piano stool molecules, (η 5-C 5H 5)M(CO) 2LX, has been investigated at temperatures as low as 12 K by FTIR spectroscopy. For molecules of the type cis- or trans-(η 5-C 5H 5)V(CO) 2L 2, L = P(OMe) 3, P(OEt) 3, photolysis resulted in the formation of a distinct CO loss product depending on the stereochemistry of the starting complexes. This intermediate reacted thermally with CO to regenerate the substrate in its original isomeric form. In contrast, complexes such as cis- or trans-(η 5-C 5H 5)W(CO) 2IL, L = P(OMe) 3, PPh 3, P(nBu) 3, show temperature-dependent intermediates. At 12 K they behave the same as the vanadium compounds, i.e. isomerically distinct intermediates were produced from photolysis of the cis and trans compounds. However, at 77 K, the intermediates isomerize resulting in the generation of a mixture of both the cis and trans compounds during the thermal back reaction with CO. Analysis of the FTIR spectral data by Timney's method indicates that the intermediates are solvated.