Mixed chloride–phosphine complexes of the dirhenium core: 9. The first mixed monodentate phosphine complex, 1,2,7,8-Re2Cl4(PMe2Ph)3(PEt2H)

The reduction of the Re2 5+ core in 1,2,7-Re2Cl5(PR3)3 molecules, followed by addition of 1 equiv. of a different phosphine ligand, PR3′, allows the preparation of the mixed monodentate phosphine compounds of the Re2 4+ type, namely 1,2,7,8-Re2Cl4(PR3)3(PR3′). The stereochemistry of the starting materials dictates the stereochemistry of the final products. The one-electron reduction of the 1,2,7-isomer of Re2Cl5(PMe2Ph)3 with KC8 to the corresponding anion, [1,2,7-Re2Cl5(PMe2Ph)3]− (1), followed by non-redox substitution of one chloride ion by one diethylphosphine, PEt2H, afforded the first mixed monodentate phosphine compound of the dirhenium(II) core, Re2Cl4(PMe2Ph)3(PEt2H) (2), in good yield. Crystal structure determination as well as other physical methods and elemental analysis unambiguously confirmed the formation of 2. The related system 1,2,7-Re2Cl5(PMe3)3Co(C5H5)2PEt2H leads to several products, one of which is 1,2,7,8-Re2Cl4(PMe3)3(PEt2H) (3).