Solution and matrix photochemistry of the isoelectronic series of a ‘half -sandwich’ carbonyl(η5-cyclopentadienyl)nitrosyl complexes of manganese, chromium, and vanadium, [M(η5-C5H5)(CO)3 –n(NO)n](n= 0, M = Mn; n= 1, M = Cr; n= 2, M = V)

Abstract

Photolysis of the isoelectronic η⁵-cyclopentadienyl (cp) half-sandwich compounds [Mn(cp)(CO)₃](1), [Cr(cp)(CO)₂(NO)](2), and [V(cp)(CO)(NO)₂](3) in either low-temperature matrices (CH₄, Ar, CO, N₂) or ambient-temperature solutions [hexane, tetrahydrofuran (thf), cyclo-octene] generally results in elimination of a CO ligand as the primary photoreaction. The photo-generated complexes were characterised by their i.r. absorptions [ν(CO), ν(NO)] and by their secondary reactions in ‘reactive’ matrices (¹³CO, N₂) or co-ordinating solvents (thf, cyclo-octene), respectively. Matrix-isolated [V(cp)(CO)(NO)₂](3) is transformed by visible light into a species [V(cp)(CO)(NO)(NO*)] where NO* is considered as a one-electron ligand. The photo-induced reactions of (1)–(3) with triethylphosphine were also investigated. In contrast to (1) and (2), [V(cp)(CO)(NO)₂](3) undergoes substitution of the CO ligand in the dark at room temperature.