Salts of the bis(catecholato)borate anion with rhodium- and iridium-phosphine complex cations

In a series of five salts with rhodium- or iridium-phosphine complex cation s {cis-chlorohydridotetrakis(triethylphosphine) iridium(III) bis(pyrocatech olato O,O')borate, [IrClH(C6H15P)(4)](C12H8BO4), (1); transchlorobis [ethyl enebis(diphenylphosphine)]hydridorhodium(III) bis(pyrocatecholato-O,O')bora te dichloromethane solvate, [RhClH(C26H24P2)(2)](C12H8BO4) . CH2Cl2, (2); t rans-chlorobis[ethylenebis(dicyclohexylphos phine)]hydridorhodium(III) bis( pyrocatecholato-O,O')borate tetrakis(dichloromethane) solvate, [RhCIH(C26H4 8P2)(2)](C12H8BO4) . CH2Cl2, (3); tetrakis(trimethylphosphine)rhodium(I) bi s(pyrocatecholato -O,O')borate, [Rh(C3H9P)(4)](C12H8BO4), (4); and cis-dihy dridotetrakis(trimethylphosphine)rhodium(III) bis(pyrocatecholato O,O')bora te, [RhH2(C3H9P)(4)](C12H8BO4), (5)}, the bis(catecholato)borate anion has approximate D-2d ((4) over bar 2m) symmetry, with the central spiro-B atom distorted from regular tetrahedral coordination geometry by reduction of th e two intra-ring O-B-O bond angles. The two chelate rings show small deviat ions from planarity by folding about the O...O axis. The hydride and chloro ligands in the cation of compound (1), which has four monodentate phosphin e ligands, are cis to each other, but in compounds (2) and (3), each with t wo chelating diphosphine ligands, they are mutually trans. The cation in co mpound (4) has only four phosphine ligands, which are arranged in a tetrago nally distorted square-planar arrangement to minimise steric crowding. Its reaction product with molecular dihydrogen, compound (5), has a cis arrange ment of the two hydride ligands in a distorted octahedral cation. The stron g trans influence of the hydride ligands is reflected in lengthened bonds t o the opposite ligands in each case.