Four-, five-, and six-coordinate nickel(II) in complexes of pseudohalide ions and piperidine ligands

Abstract

The preparations of the pseudohalide complexes Ni(NCX) 2(piperidine) 4 (X = S, Se), Ni(NCO) 2(piperidine) 3 and Ni(NCX) 2(2,6-dimethylpiperidine) 2 (X = O,S) are reported. Ligand field spectra have been used to assign their coordination geometries. The stereochemistry depends on the nature of the pseudohalide ion as well as on the steric requirements of the piperidine ligands. 2,6-Dimethylpiperidine only forms planar complexes. Piperidine forms solid six coordinate complexes Ni(NCX) 2(piperidine) 4 (X = S, Se), but the shape of this ligand appears to be such as to stabilise also the coordination number five (solid Ni(NCO) 2(piperidine) 3 and complexes in solutions of all three pseudohalide ions) and a four coordinate planar configuration (solutions of isocyanate- and isothiocyanate complexes).