The Crystal and Molecular Structure of trans-Dichloro-mer-tris(dimethylphenyl-phosphine)hydridoiridium(III) by X-Ray and Neutron Diffraction

Abstract

The crystal and molecular structure of mer -(PMe₂Ph)₃H- trans-Cl₂Ir^III (1) has been determined by single-crystal X-ray and neutron diffraction analyses. Crystals are monoclinic, space group P1, with a 8.91 9(4), b 9.895(4), c 12.269(6) Å, α 70.33(4), β 81.75(4), γ 88.26(4)º, Z 2. The structure was solved by conventional heavy atom methods and refined by full-matrix least-squares analyses to final R values of 0.067 (X-ray data, R = ∑// F_o/-/F_c²/∑F_o/, 7516 independent reflections) and 0.086 (neutron data, R = ∑/F_o²- F_c²/∑ F_o² 2290 independent reflections). Weighted mean values for metal-ligand distances are Ir -P(trans to H) 2.365(2) Å, Ir -P(trans to PMe₂Ph) 2.329(2) Å and Ir -Cl(trans to Cl) 2.402(2) and 2.364(2) Å. The iridium-hydrogen bond [1.616(7) Å] is trans-lengthened, vis-a-vis Ir -H trans to Cl, by c. 0.05 Å. The difference in the mutually trans Ir -Cl bond lengths is ascribed to the inequivalence of intramolecular non-bonding interactions. The Ir -P(trans to PMe₂Ph) bond length in (1) is shorter than that in mer -(PMe₂Ph)Cl₃Ir^III. The smaller steric requirement of the hydride ligand in (1) allows the mutually trans phosphines to move away from their cis neighbour. In turn, the phosphines approach the metal more closely to compensate for the decreased phosphine substituent-phosphine substituent non-bonding interactions.