Luminescent <i>nido</i>-Carborane−Diphosphine Anions [(PR₂)₂C₂B₉H₁₀]^- (R = Ph, ⁱPr). Modification of Their Luminescence Properties upon Formation of Three-Coordinate Gold(I) Complexes

The free nido-diphosphine anions [(PR2)2C2B9H10]- (R = Ph, iPr) show luminescence properties whereas the closo-diphosphines [(PR2)2C2B10H10] do not. Four families of three-coordinate complexes of stoichiometry [Au{(PR2)2C2B10H10}L]OTf (L = tertiary phosphine) and [Au{(PR2)2C2B9H10}L] have been studied in order to analyze the influence of the closo- or nido-nature of the diphosphine, the monophosphine coordinated to gold and the substituent at the diphosphine on the luminescence of the complexes. Only the nido-derivatives show luminescence. The maxima of the emissions are shifted to lower energies than those of the corresponding free nido-diphosphines. When the substituent at the diphosphine is phenyl, a new emission appears, which has been assigned as arising from a metal to ligand charge transfer [Au→π*(L)] excited state.