The influence of substitution of CO by PR3 on the photochemistry of Fe(CO)3(i-Pr2Ph-DAB) and Ru(CO)3(i-Pr2CH-DAB) (DAB=1,4-diaza-1,3-butadiene); a flash-photolysis and low-temperature study

Article abstract of DOI:10.1016/0022-328X(89)85290-8

The result are presented of a photochemical study of the complexes Fe(CO)3(i-Pr2Ph-DAB) and Ru(CO)3(i-Pr2CH-DAB) and of some of their PR3-containing derivatives.The reaction were studied by flash-photolysis with 308 nm laser light and by irradiation at various temperatures and exciting wavelengths.Both tricarbonyls show release of CO from the 3LF state but no reaction from 3ML state of the metal R-DAB metallacycle at lower energy.In contrast, Fe(CO)2(i-Pr2Ph-DAB)(P(OPh)3) undergoes breaking of a metal-nitrogen bond from the 3LF state, but this reaction is followed by a fast back-reaction to regenerate the parent compound.As a result on ly a reaction from the 3ML state is observed, in which the i-Pr2Ph-DAB ligand changes its coordination from ?,?-N,N' into η⁴-CN,C'N'.For the complexes Ru(CO)2(i-Pr2CH-DAB)(PR3) breaking of the metal-nitrogen bond from the 3LF state leads to release of the i-Pr2CH-DAB ligand and formation of Ru(CO)2(PR3)3 and Ru(CO)3(PR3)2.Low-energy irradiation into the ML band gives rise to the formation of Ru(CO)2(η⁴-i-Pr2CH-DAB)(PR3) from the 3ML state.These differences in photochemical behaviour between the tricarbonyl complexes and their PR3-derivates are discussed in detail.