Crystal and molecular structure of (η³-allyl)carbonylchlorobis(dimethylphenylphosphine)- iridium(III) hexafluorophosphate, [Ir(η³-C₃H₅)Cl(CO)(P(CH₃)₂(C₆H₅))₂][PF₆

The structure of (η³-allyl)carbonylchlorobis(dimethylphenylphosphine)-iridium(III) hexafluorophosphate, [Ir(η³-C₃H₅)Cl(CO)(P(CH₃)₂(C₆H₅))₂][PF₆], has been determined from three-dimensional X-ray data to add support for a proposed mechanism of the oxidative addition of allyl halides to IrX(CO)(PR₃)₂ (X = halide). The compound crystallizes in space group C⁵_2h-P2₁/c with four formula units in a cell of dimensions a = 11.027(1), b = 12.230(2), c = 19.447(5) Å, and β = 103.16(2)⁰. Least-squares refinement of the structure has led to a value of the conventional R index (on F) of 0.066 for the 3018 independent reflections having F²₀>3-(F²₀). The crystal structure consists of discrete, monomericions. The hexafluorophosphate anion is disordered. The coordination geometry around the iridium atom may be described as octahedral, with the chloro ligand trans to the carbonyl group and each phosphorus atom trans to a terminal carbon of the allyl group. Structural parameters: Ir-P = 2.366(4), 2.347(3);Ir-Cl = 2.389(3); Ir-C(allyl) = 2.28(1), 2.24(1),2.25(1); Ir-C (carbonyl) = 1.85(1) Å; P-Ir-P = 105.7(1); C(terminal)-Ir-C(terminal) = 66.2(8); C-C-C = 125(2)^o. The allyl group makes an angle of 126^o with the P-Ir-P plane. Correlations between geometric structure and number of d electrons are noted among several M-C₃H₅-complexes, and are interpreted in the light of theoretical models of the M-C₃H₅- bond.