Photo-reversible isomerisation of trans- to cis-[W(CO) 4( η2-alkene) 2] complexes in low-temperature matrices

Abstract

Reversible isomerisation of trans- to cis-[W(CO) 4( η 2-alkene) 2] complexes has been induced in argon matrices at low temperatures under the action of selective irradiation. UV photolysis ( λ ≈ 313 nm) of trans-[W(CO) 4( η 2-alkene) 2] (alkene = cyclopentene or 1-pentene) in an argon matrix at 16 K results in formation of the cis isomer as the primary photoprocess. The isomerisation is reversed under the action of visible light ( λ ≈ 445 nm). Species such as [W(CO) 4(alkene)(Ar)] are also formed in small concentrations. Experiments involving annealing, selective photolysis and the use of CO- or alkene-doped matrices have been performed to investigate the mechanism of the photo-isomerisation process. These studies suggest a dissociative mechanism via expulsion of the alkene ligand.