Definitive examples of polyhydride complexes which do not eliminate H 2 in the primary photochemical reaction. Photodissociation of PR 3 from [ReH 3(PR 3) 4] and [ReH 5(PR 3) 3] complexes

Abstract

Irradiation of the complexes [ReH 5L 3] (L  PMe 2Ph, PMePh 2, PPh 3)and [ReH 3(PMe 2Ph) 4]gives efficient loss of phosphine in the primary photochemical reaction, in contrast to most monomeric polyhydride complexes which lose H 2 upon photolysis. The 366 nm quantum yields for the [ReH 5L 3] complexes range from 0.13–0.18; the 366 nm quantum yield for PMe 2Ph loss from [ReH 3(PMe 2Ph) 4] is 0.4. Under an H 2 atmosphere, [ReH 3(PMe 2Ph) 4] is converted into [ReH 5(PMe 2Ph) 3] upon photolysis; the pentahydrides in turn lose another equivalent of phosphine to give the corresponding [ReH 7L 2] complexes. The heptahydrides are themselves photosensitive and react to give a mixture of [Re 2H 8L 4] and [Re 2H 6L 5 dimers. Photolysis of degassed solutions of the [ReH 5L 2] complexes leads to a complex mixture of [ReH 7L 2], [ReH 3L 4], [Re 2H 8L 4], and [Re 2H 6L 5]. The efficientphotoelimination of L from the [ReH 3L 4] complexes is discussed in view of the reported photochemistry of [ReH 3(Ph 2PCH 2CH 2PPh 2) 2]which loses H 2 upon irradiation.