Co-ordination chemistry of (8-methyl-2-quinolylmethyl)di-t-butyl-phosphine (mqp) with palladium, rhodium, iridium, and manganese: crystal structure of [PdCl2(mqp)]

Abstract

Complexes of the new title ligand (mqp) have been synthesised which contain unidentate, bidentate, or 3-metallated modes of co-ordination as established by ¹H and ¹³C n.m.r. data. The complex [PdCl₂(mqp)₂] contains unidentate mqp while [PdCl₂(mqp)](as a CH₂Cl₂ solvate) contains bidentate mqp as shown by a single-crystal structure determination. Crystals are monoclinic, space group P2₁/c, with a= 12.936(3), b= 13.108(3), c= 15.085(3)Å, β= 100.48(2)°, and Z= 4. The structure has been determined by Patterson and Fourier methods and refined by least squares to R 0.047 for 3 490 diffractometer data. In-plane bidentate co-ordination would require a considerable clash of mqp with one cis Cl, but distortions within the still essentially square-planar complex reduce this clash. A small pyramidal distortion at the co-ordinated nitrogen atom contributes to this reduction. This complex yields 3-metallated [Pd₂Cl₂(mqp-H³)₂] in refluxing alcohols in the presence of lithium acetate, but in the absence of the latter the HCl formed leads to the quinolinium salt of the 3-metallated product. Various chlorocarbonyl derivatives of [Rh₂Cl₂(CO)₄] are described, the most significant being [Rh₂Cl₂(CO)₃(mqp)] which contains bidentate mqp and shows nuclear spin–spin coupling between the nuclei of the 8-Me group and the ¹⁰³Rh and ³¹P nuclei, indicating a significant interaction between the non-metallated Me group and the metal atom. 3-Metallated mqp complexes of iridium(III) and of manganese(I) are also described.