X-ray Structures of Two Unexpected Complexes Isolated during CO Substitutions by Phosphine Ligands in Dinuclear Bridged d8 Metal Complexes

Article abstract of DOI:10.1021/ja00375a021

The reaction of in concentrated hexane solution with 2 mol of trimethylphosphine results in the two complexes and , for which the structures have been determined by X-ray crystallography.The first complex crystallizes in space group P4^(*)2₁c with a=15.334 (2) Angstroem, c=26.623 (4) Angstroem, and Z=8.On the basis of 2313 unique reflections, the structure was refined by full-matrix least-squares techniques to conventional indices of R=0.045 and R_w=0.035.The Ir-Ir separation is 2.702 (1) Angstroem, and a CO ligand is in a bridging position whereas a S-t-Bu ligand is in an equatorial position.The complex crystallizes in space group P2₁/c with a=16.521 (3) Angstroem, b=10.060 (3) Angstroem, c=21.295 (4) Angstroem, β=90.23 (1) deg, and Z=4.On the basis of 1746 unique reflections, the structure was refined by full-matrix least-squares techniques to R=0.059 and R_w=0.072.The structure of the trinuclear entity ressembles that of , owing to the Ir-Ir separation of 2.712 (3) Angstroem and the presence of the bridging CO and S-t-Bu ligands.Infrared studies of these two complexes and of their CO loss in solution to form the disubstituted complex allow us to propose a new pathway for this type of dinuclear iridium complexes to the CO substitution by tertiary phosphine ligands.