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

The syntheses and subsequent characterization of the complexes mer-trans-(PPr3i)(2)(PMe(2)Ph)Cl-cis-H2IrIII (1) and mer-trans-(PPr3i)(2)(PMe(2)Ph)H3IrIII (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 P2(1)/c with a 19 . 277(2), b 9 . 020(1), c 17 . 657(2) Angstrom, beta 101 . 40(1)degrees and Z 4. Crystals of (2) are orthorhombic, space group P2(1)2(1)2(1), With a 19 . 373(3), b 18 . 724(2), c 8 . 113(1) Angstrom 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 Angstrom (av.) in the Ir-P bond lengths cf. those in (2). Also, because of increased steric crowding (two PPr3i ligands in place of two PMe(2)Ph), the Ir-PMe(2)Ph bond in (1) is 0 . 019(2) Angstrom longer than the chemically equivalent bond in mer-(PMe(2)Ph)(3)Cl-cis-H2IrIII. In previously reported complexes in this series metrically similar increases in Ir-PMe(2)Ph distances result from the replacement of just one PMe(2)Ph ligand by PPr3i.