The crystal and molecular structure of triphenylphosphoniodithio-carboxylato-ss'-carbonylbis (trikphenylphosphine) iridium(I) tetrafluoroborate [Ir(S2CPPh3) (CO) (PPh3)2]BF4.

Crystal and molecular structures of the title compound have been determined from a three-dimensional X-ray analysis using diffractometer data. The crystals are monoclinic, space group P2₁/c, with Z = 4 in a unit cell of dimensions a = 10.5876(9), b = 31.518(10), c = 16.2164(5) Å, β = 92.521(1)°. The observed and calculated densities are 1.38 and 1.374 g cm^-1 respectively. The crystals decompose under X-rays, and three crystals were required to complete data collection. The structure was solved and refined by convetional methods to final residuals R and R_w of 0.087 and 0.107 respectively.The crystals contain monomeric cations, and BF₄ anions. The iridium atom is in a distorted trigonal bipyramidal environment consisting of the two sulphur atoms (one axial, one equatorial) of a bidentate triphenylphosphoniodi-thiocarboxylate ligand, two triphenylphosphine groups (equatorial) and the carbonyl ligand (axial). The non-equivalent Ir-s distances are 2.377 and 2.307(5) Å, the Ir-P distances are 2.334, 2.331(5) Å. Within the zwitterion, the C-S distances are 1.66 and 1.70(2) Å, while P-C is 1.78(2) Å. The condensation of PPh₃ and CS₂ to form the PH₃P⁺-CS₂ zwitterion is in contrast to that predicted previously.It is probable that the other complexes of iridium and rhodium prepared in a similar manner 2] should now be reformulated as containing Ph₃P⁺-CS₂^- ligands.