X-Ray crystal-structure analysis and magnetic and spectral properties of tetrachlorotris[dichloro(methyl)phosphine]molybdenum(IV)–carbon disulphide (3/1)

Abstract

The title complex (1) is one product of the reaction between MoCl₅, PMeCl₂, and Bu^tCl. It can also be prepared by direct reaction between MoCl₅ and the phosphine. Crystals of (1) are trigonal, with unit-cell dimensions a=b= 9.760(2), c= 71.167(16)Å, α=β= 90, γ= 120°, Z= 12, and space group Rc. The structure has been determined from X-ray diffractometer data by Patterson and Fourier syntheses, and refined by full-matrix least-squares calculations to R 0.061 for 726 observed reflections (3σ). The Mo and Cl(1) atoms lie on three-fold special positions and a CS₂ solvent molecule straddles a six-fold site, but with-two thirds occupancy. The Mo atom is seven-co-ordinate having capped-octahedral stereochemistry. Three Cl atoms occupy an uncapped face whilst the fourth caps a face occupied by the three P atoms. The magnetic properties of (1) are consistent with a strong-field, high delocalisation of the metal d electrons, and a low-symmetry ligand-field component. The Mo–Cl bond-stretching frequencies and a spin-forbidden electronic transition have been identified.