Mixed halide/phosphine complexes of the dirhenium core. Part 7. Reactions of [Re2I8](2-) with monodentate phosphines

Reactions of the octaiododirhenate anion [Re2I8](2-) with monodentate phosp hines (PR3 = PMe3 (1), PMe2Ph (2), PEt3 (3), and PEt2Ph (4)) have been stud ied in two different solvents, ethanol and benzene, at room temperature. Th e reactions in ethanol resulted in two-electron reduction products having t he Re-2(4+) core, Re2I4(PR3)(4) (R-3 = Me-3 (1a) and Me2Ph (2a)), for which X-ray diffraction study revealed a 1,3,6,8 isomer type. The reaction of [R e2I8](2-) with PMe3 in benzene led to an intermediate edge-sharing bioctahe dral dirhenium(III) complex, Re-2(mu -I)(2)I-4(PMe3)(4) (1b), with no metal -metal bond. The interaction of PEt3 with [Re2I8](2-) in benzene again yiel ded a kinetic product with a different stoichiometry and a Re-2(5+) core. [ (Bu4N)-N-n][Re2I6(PEt3)(2)] (3c). The analogous reactions of [Re2I8](2-) wi th PMe2Ph and PEt2Ph in benzene involved two-electron reductions and gave c omplex 2a and Re2I4(PEt2Ph)(4) (4a), as products. Reduction of 1b with KC8 gave 1a as the main product along with a few crystals of 1,3,6-Re2I5(PMe3)( 3) (1d). Mixed iodide/phosphine complexes of the dirhenium core Re-2(n+). w here n = 4 (1a, 2a, 4a), 5 (1d, 3c). and 6 (Ib) have for the first time bee n characterized by X-ray crystallography. In addition, these products have been further identified by a combination of mass spectrometry and cyclic vo ltammetric measurements. (C) 2001 Published by Elsevier Science Ltd.