Crystal and molecular structure and electron spin resonance spectrum of trichloro-oxobis(triphenylphosphine oxide)molybdenum(V)

Abstract

Monoclinic crystals of the title complex belong to space group P2₁/c, and have unit-cell dimensions of a= 18.977(5), b= 16.860(5), c= 22.099(6)Å, β= 96.50(5), and Z= 8. The crystal structure has been solved by direct methods using 3 286 statistically significant reflections from diffractometer measurements. Atomic parameters have been refined by full-matrix least-squares calculations to R 0.067. One of the two crystallo-graphically independent [MoOCl₃(PPh₃O)₂] molecules in the asymmetric unit is disordered over two orientations. Bond lengths at the octahedrally co-ordinated molybdenum atom in the ordered complex molecule are: MO–O 1.662(13), Mo–O(PPh₃O) 2.136(11)(trans to MO–O), 2.065(10)(trans to Mo–Cl), and Mo–Cl 2.348(5)–2.386(5)Å. Single-crystal e.s.r. spectra at room temperature give the following molecular values: g₁= 1.929 ± 0.002, g₂= 1.935 ±; 0.002, and g₃= 1.950 ± 0.002. The orientations of these values are different to those found for [MoOCl₃{P(NMe₂)₃O}₂] in that g₃ is closest to the Cl–MO–Cl direction in [MoOCl₃(PPh₃O)₂], whereas g₂ is closest to this direction in [MoOCl₃{P(NMe₂)₃O}₂], The molecular g tensors for these two systems are compared qualitatively on the basis of the ligand-field strengths of the various ligands concerned.