Steric Modification of Metal-Phosphorus Bond Lengths: the Preparation, Characterization and CrystalStructures of mer-trans-(PPrⁱ₃)₂(Pme₂Ph)-Cl-cis-H₂Ir^III(1) and mer-trans-(PPrⁱ₃)₂(PMe₂Ph)H₃Ir^III

Abstract

The syntheses and subsequent characterization of the complexes mer -trans-(PPrⁱ₃)₂(Pme₂Ph)-Cl-cis-H₂Ir^III(1) and mer-trans-(PPrⁱ₃)₂(PMe₂Ph)H₃Ir^III (2) by n.m.r. and by low temperature (153±5 K) X-ray diffraction analyses are reported. Crystals of (1) are monoclinic, space group P2₁/c with a 19.277(2), b 9.020(1), c 17.657(2) Ǻ, β 101.40(1)° and Z 4. Crystals of (2) are orthorhombic, space group P2₁2₁2₁, with a 19.373(3), b 18.724(2), c 8.113(1) Ǻ and Z 4. Full-matrix least-squares analyses converged with R = 0.027 and wR = 0.031 for (1) (3243 reflections), and R = 0.030 and wR = 0.038 for (2) (2892 reflections). Consistent with previous observation, the unit increase in chloride content (in place of hydride) in (1) is accompanied by a global lengthening of 0.036 Ǻ (av.) in the Ir -P bond lengths cf. those in (2). Also, because of increased steric crowding (two PPrⁱ₃ ligands in place of two Pme₂Ph), the Ir-PMe₂Ph bond in (1) is 0.019(2) Ǻ longer than the chemically equivalent bond in mer-(PMe₂Ph)₃Cl-cis-H₂Ir^III. In previously reported complexes in this series metrically similar increases in Ir-PMe₂Ph distances result from the replacement of just one Pme₂Ph ligand by PPrⁱ₃.