A comparison of NH3, PH3, PH2, OH2 and SH as ligands in iridium(III) complexes

Abstract

The aqua complex trans,mer-[IrCl₂(H₂O)(PMe₂Ph)₃][ClO₄] of known crystal structure contains a highly labile H₂O ligand which is readily substituted. The corresponding ammonia and phosphine complexes trans,mer-[IrCl₂(EH₃)(PMe₂Ph)₃][ClO₄](E = N or P), synthesised from the aqua complex, are inert and have been structurally characterised and compared with the aqua species. The cationic complex containing PH₃ is readily deprotonated, but not the one with NH₃, to give the structurally characterised neutral complex trans,mer-[IrCl₂(PH₂)(PMe₂Ph)₃]. The Ir–PH₃ bond is significantly shorter than the Ir–PH₂ bond and there are clear conformational changes resulting from deprotonation. Replacement of H₂O by H₂S leads to spontaneous deprotonation and formation of trans,mer-[IrCl₂(SH)(PMe₂Ph)₃](crystal structure also reported). Analysis of the geometries of trans,mer-[IrCl₂L(PMe₂Ph)₃][ClO₄](L = H₂O, NH₃ or PH₃) and of trans,mer-[IrCl₂X(PMe₂Ph)₃](X = H, Cl, SH or PH₂) has allowed the properties of these ligands, in particular their trans influences, to be assessed.