Crystal structure of the low-spin five-co-ordinate complex bromo[tris(2-diphenylphosphinoethyl)phosphine]cobalt(II) hexafluorophosphate

Abstract

Crystals of the title compound are triclinic, space group P, with a= 12.267(1), b= 12.903(1), c= 16.532(1)Å, α= 106.30(1), β= 91.59(1), γ= 121.08(1 )°, Z= 2. The structure was solved by Patterson and Fourier methods from diffractometer data and refined by least-squares techniques to R 0.064 for 3 831 independent reflections. The geometry of co-ordination is distorted square-pyramidal, with a phosphorus in the apical position [Co–P 2.281(3)Å], the other three phosphorus atoms [Co–P 2.285, 2.254, and 2.156(3)Å] and the halogen atom [Co–Br 2.380(2)Å] lying approximately in the base of the pyramid. Comparison with the structures of analogous complexes suggests the role played by ligand molecules in determining the co-ordination geometry. Further evidence for the effects of a Jahn–Teller distortion in Co^II low-spin complexes of this class is provided. The reflectance spectra of a set of related complexes are compared.