Five-co-ordination in nickel(II) complexes. The crystal structure of dibromobis-(2-diphenylphosphinoethyl)aminenickel(II)

Abstract

The crystal structure of the diamagnetic complex dibromobis-(2-diphenylphosphinoethyl)aminenickel(II), Ni·[HN[CH₂·CH₂·P(C₆H₅)₂]₂-Br₂, has been determined from three-dimensional X-ray data collected by photographic methods. The structure has been refined by least-squares techniques to a conventional R of 0·049. Crystals of the compound belong to the space group Abm2 with the following cell dimensions : a= 15·01 ± 0·02, b= 24·55 + 0·02, c= 7·30 + 0·02 Å, Z= 4.

The structure consists of discrete molecules, in which the nickel atom shows a distorted square-pyramidal co-ordination. C_s crystallographic symmetry is imposed on the molecule. The apical Ni–Br distance is 0·37 Å longer than the basal one. This lengthening is compared with results available for other low-spin square-pyramidal nickel(II) complexes and may be explained by the stereochemical activity of the 3d electrons of the metal.