Mixed halide/phosphine complexes of the dirhenium core. Part 7. Reactions of [Re 2I 8] 2− with monodentate phosphines

Abstract

Reactions of the octaiododirhenate anion [Re 2I 8] 2− with monodentate phosphines (PR 3=PMe 3 ( 1), PMe 2Ph ( 2), PEt 3 ( 3), and PEt 2Ph ( 4)) have been studied in two different solvents, ethanol and benzene, at room temperature. The reactions in ethanol resulted in two-electron reduction products having the Re 2 4+ core, Re 2I 4(PR 3) 4 (R 3=Me 3 ( 1a) and Me 2Ph ( 2a)), for which X-ray diffraction study revealed a 1,3,6,8 isomer type. The reaction of [Re 2I 8] 2− with PMe 3 in benzene led to an intermediate edge-sharing bioctahedral dirhenium(III) complex, Re 2(μ-I) 2I 4(PMe 3) 4 ( 1b), with no metal–metal bond. The interaction of PEt 3 with [Re 2I 8] 2− in benzene again yielded a kinetic product with a different stoichiometry and a Re 2 5+ core, [Bu n 4N][Re 2I 6(PEt 3) 2] ( 3c). The analogous reactions of [Re 2I 8] 2− with PMe 2Ph and PEt 2Ph in benzene involved two-electron reductions and gave complex 2a and Re 2I 4(PEt 2Ph) 4 ( 4a), as products. Reduction of 1b with KC 8 gave 1a as the main product along with a few crystals of 1,3,6-Re 2I 5(PMe 3) 3 ( 1d). Mixed iodide/phosphine complexes of the dirhenium core Re 2 n+ , where n=4 ( 1a, 2a, 4a), 5 ( 1d, 3c), and 6 ( 1b) have for the first time been characterized by X-ray crystallography. In addition, these products have been further identified by a combination of mass spectrometry and cyclic voltammetric measurements.