Crystal and molecular structure of the low-spin five-co-ordinate complex iodo[tris-(2-diphenylphosp hinoethyl) amino-NP]-nickel(II) iodide

Abstract

The absolute configuration of the complex iodo[tris-(2-diphenylphosphinoethyl) amino-NP]-nickel(II) iodide [Ni(tda)l]l, chromophore, NiNP₃l, has been determined by a three-dimensional X-ray analysis with photographic data. The crystals are trigonal, space group R3, with Z= 3 in a hexagonal unit cell of dimensions: a= 16·363 ± 0·014, c= 12·398 ± 0·023 Å. The structure has been solved by three-dimensional Patterson and Fourier syntheses and refined by least-squares techniques to R 0·064 over 797 independent observed reflections.

The complex consists of discrete [Ni(tda)l]⁺ cations and l- anions. The nickel atoms are five-co-ordinate, with an NP₃l donor set. The cations possess a trigonal symmetry, so that the co-ordination polyhedron is a regular trigonal bipyramid. This is the first example of crystallographic trigonal symmetry found in a low-spin five-co-ordinate nickel(II) complex.