Syntheses, spectroscopic properties and photochemistry of [Re(R)(CO) 3(4,4′-Me 2-bpy)] (R = alkyl) complexes

Abstract

The complexes [Re(R)(CO) 3(dmb)] (dmb = 4,4′-dimethyl-2,2′-bipyridine; R = CH 3, CD 3, Et, Bz, or iPr) were synthesized and their spectroscopic ( 1 H , and 13 C NMR, IR, UV–Vis, resonance Raman) properties were studied. According to the resonance Raman spectra the lowest-energy electronic transition has mainly MLCT character. It is therefore concluded that the 3 σ (Re–R)π*(dmb) state from which these complexes undergo homolysis of the Re–alkyl bond, is occupied by surface crossing from the nonreactive MLCT states. The [Re(CO) 3(dmb)] ⋅ radicals, formed by the homolysis reaction, were trapped by nitrosodurene and PPh 3, and their adducts were identified with EPR spectroscopy. The thermal reactions of the radicals in different media were followed with IR spectroscopy.