Structure of Chlorocarbonyl(sulfur dioxide)bis(triphenylphosphine)iridium

The crystal and molecular structure of chlorocarbonyl(sulfur dioxide)bis(triphenylphosphine)iridium, IrCl(CO)(SO₂)(P-(C₈H₅)₅)₂, has been determined from three-dimensional X-ray data. The material crystallizes in space group C₂h⁵-P2₁/c of the monoclinic system, with four molecules in a cell of dimensions a = 12.11, 6 = 16.79, c = 17.09 A, β = 103.0°. The individual monomeric units are well separated, the closest Ir-Ir distance being greater than 8 A. The coordination geometry around the Ir is that of a tetragonal pyramid, with CO, CI, and trans P atoms in the base and the S of the SO₂ group at the apex. The O (of the CO), CI, and two P atoms are coplanar; the Ir lies 0.21 A above this plane toward the S. The basal interatomic distances are normal. However, the Ir-S bond length of 2.49 A is very long and the Ir, S, and two O atoms of the SO₂ group are not coplanar. Rather the Ir-S vector makes an angle of 32° with the normal to the SO₂ plane. The dimensions of the SO₂ group are not significantly different from those found in solid SO₂. The basic geometry of the SO₂ complex differs markedly from that of the analogous O₂ complex, Ir(O₂)Cl(CO)(P(C₆H₅)₃)₂, in which the Ir is in a trigonal bipyramidal configuration with trans P atoms at the apices.