Photochemical and photocatalytic behaviour of ‘flyover-bridge’ complexes
Abstract
The photochemical behaviour of a number of flyover-bridge complexes [Fe2(CO)6{(RC2R)2CO}] is discussed with regard to their electronic structure. In the case of [Fe2(CO)6{(PhC2Ph)2CO}] the overall photochemical event is the formation of an unsaturated species upon CO loss, which evolves, in the absence of any Lewis bases, to the fragments [Fe(CO)3{(PhC2Ph)2CO}], C4Ph4CO, and [Fe(CO)5]. Photosubstitution of CO by phosphine occurs very rapidly and proceeds stereospecifically in a pseudo-axial position as assessed by 13C n.m.r. studies. The title complexes exhibit photocatalytic activity toward olefin isomerization and, interestingly, this reaction can be activated simply by sunlight exposure. The dienone chain clasps the metal–metal bond, preventing complex decomposition and acts as a good sensitizer for the sunlight.