Crystal and molecular structure of di-iodotris(2-diphenylphosphinoethyl)aminecobalt(II)

Abstract

The crystal structure of the low-spin complex CoLl₂[L = N(CH₂·CH₂·PPh₂)₃] has been determined by X-ray photographic techniques and refined by least-squares methods to R 0·079 for 2103 independent reflections. The cell dimensions are: a= 16·597 ± 0·027, b= 11·137 ± 0·008, c= 21·984 ± 0·017 Å, β= 93° 28′± 9′, Z= 4, space group P2/c.

The structure consists of [CoLl]⁺ cations and I^– anions. In the complex cation the metal atom exists in a distorted square pyramidal co-ordination with one phosphorus atom at the apex of the pyramid, the two others, together with the nitrogen and iodine atoms, forming the base. This is an unusual example of a symmetric ‘tripod’ ligand giving rise to a square pyramidal geometry. The factors responsible for the stability of the complex are discussed.