[Low temperature FTIR study of the structure of ruthenium polyhydrides]

A novel compound of Ru2H4 (CO) (PPh3)4 (A) is synthesized under hydrogen atmosphere. An in situ infrared apparatus which can be operated at liquid nitrogen temperarure is established. The structural conversion of RuH4 (PPh3)3 between dihydrogen and dihydride is observed firstly at room temperature. It is suggested that a fluxional molecule between terminal and bridged hydrogen appears in (A) with temperature changes. H2 molecule coordinated in ruthenium complex is rather easy to be substituted by CO, N2 and small organic molecule, this property is very important for activing molecular hydrogen and using in hydrogenation of unsaturated compounds.