Synthesis and structural characterization of Ti(III) and Mo(III) complexes supported by PNP pincer ligands

Abstract

New Ti(III) and Mo(III) complexes of formulae [(PNP-Ph)TiCl₃], 1, and [(PNP-ⁱPr)MoCl₃], 2, where PNP-Ph = N,N’-bis(diphenylphosphino)-2,6-diaminopyridine and PNP-ⁱPr = N,N’-bis(diisopropylphosphino)-2,6-diaminopyridine were synthesised, in moderate yields, by reaction of MCl₃·(THF)₃ (M = Ti and Mo) with the suitable ligand precursor. The solid-state molecular structures of complexes 1 and 2 were obtained by single-crystal X-ray diffraction. Crystal data for C₃₇H₄₁Cl₃N₃O₂P₂Ti (1·(C₄H₈O)₂): triclinic, space group P-1 (no. 2), a = 10.0945(4) Å, b = 10.3002(4) Å, c = 18.6233(7) Å, α = 92.412(2)°, β = 91.108(2)°, γ = 101.705(3)°, V = 1893.65(13) ų, Z = 2, µ(MoKα) = 0.559 mm^-1, D_calc = 1.361 g.cm^-3, 20760 reflections measured (2.021 ≤ Θ ≤ 27.130), 8327 unique (R_int = 0.0399, R_sigma = 0.0414) which were used in all calculations. The final R₁ was 0.0316 (I > σ(I)) and wR₂ was 0.0850 (all data). Crystal data for C₁₇H₃₃Cl₃MoN₃P₂ (2): tetragonal, space group I4₁/a (no. 88), a = b = 19.468(4) Å, c = 31.711(6) Å, α = β = γ = 90°, V = 12019(5) ų, Z = 16, µ(MoKα) = 0.816 mm^-1, D_calc = 1.202 g.cm^-3, 42367 reflections measured (2.569 ≤ Θ ≤ 25.347), 5498 unique (R_int = 0.1408, R_sigma = 0.1293) which were used in all calculations. The final R₁ was 0.1005 (I > σ(I)) and wR₂ was 0.3194 (all data). The coordination geometry around the titanium and molybdenum centers is best described as octahedral, with three donor atoms of the PNP ligand and one chlorine atom occupying the equatorial plane. The axial positions of the octahedron are occupied by the other two chlorido ligands in both complexes. The NH spacer groups in the PNP ligands have an important role in the establishment of hydrogen bonds between the complexes and molecules of the solvent or neighbouring species.