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 cations {cis-chlorohydridotetrakis-(triethylphosphine)iridium(III) bis(pyrocatecholato-O,O′)borate, [IrClH(C₆H₁₅P)₄](C₁₂H ₈BO₄), (1); transchlorobis[ethylenebis(diphenylphosphine)]hydridorhodium(III) bis(pyrocatecholato-O,O′)borate dichloromethane solvate, [RhClH(C₂₆H₂₄P₂)₂](C ₁₂H₈BO₄)·CH₂-Cl₂, (2); trans-chlorobis[ethylenebis(dicyclohexylphosphine)]hydridorhodium(III) bis(pyrocatecholato-O,O′)-borate tetrakis(dichloromethane) solvate, [RhClH(C₂₆-H₄₈P₂)₂](C ₁₂H₈BO₄)·4CH₂Cl₂, (3); tetrakis(trimethylphosphine)rhodium(I) bis(pyrocatecholato-O,O′)borate, [Rh(C₃H₉P)₄](C₁₂H₈BO ₄), (4); and cis-dihydridotetrakis-(trimethylphosphine)rhodium(III) bis(pyrocatecholato-O,O′)borate, [RhH₂(C₃H₉P)₄](C₁₂H ₈BO₄), (5)}, the bis-(catecholato)borate anion has approximate D_2d (4̄2m) symmetry, with the central spiro-B atom distorted from regular tetrahedral coordination geometry by reduction of the two intra-ring O - B - O bond angles. The two chelate rings show small deviations from planarity by folding about the O⋯O axis. The hydrido and chloro ligands in the cation of compound (1), which has four monodentate phosphine ligands, are cis to each other, but in compounds (2) and (3), each with two chelating diphosphine ligands, they are mutually trans. The cation in compound (4) has only four phosphine ligands, which are arranged in a tetragonally distorted square-planar arrangement to minimise steric crowding. Its reaction product with molecular dihydrogen, compound (5), has a cis arrangement of the two hydrido ligands in a distorted octahedral cation. The strong trans influence of the hydrido ligands is reflected in lengthened bonds to the opposite ligands in each case.