SYSTEMATIC STUDIES OF 17-ELECTRON RHENIUM(II) CARBONYL PHOSPHINE COMPLEXES

Oxidative electrochemical properties in dichloromethane have been exam ined for compounds of the types cis- or trans-[Re(CO)(2)(P-P)(2)](+) a nd trans-Re(CO)(P-P)(2)X (P-P = diphosphine ligand, X = Cl, Br) which exhibit a range of charge and ligand types. In all cases 17e Re(II) sp ecies are formed, although the oxidation potentials vary over a reason ably wide range. The Re(II) compounds have been characterized by spect roelectrochemical (IR) and electrospray mass spectrometry (ESMS) studi es. The stabilities of the Re(II) species are dependent upon charge an d ligand types. The trans configuration is strongly preferred in the R e(II) state, so when the starting material is cis, there is rapid isom erization following electron transfer. The major form of reactivity de tected is facile reduction of the trans-[Re(CO)(2)(P-P)(2)](2+) specie s. The particularly high stability of trans-[Re(CO)(dpe)(2)X](+) (dpe = Ph2P(CH2)(2)PPh2) allows solid-state studies to be undertaken for th e trans-[Re(CO)( dpe)(2)X](+/0) couple when the compounds are mechanic ally attached to a graphite electrode immersed in water (electrolyte).