Co-ordination of organophosphorus anions. Part III. Spectral studies of some five- and six-co-ordinate cobalt(II) and zinc(II) halides and pseudohalides

Abstract

The anions [P(CHCOCH₂R)O(OEt)₂]^–[R = NEt₂(L²), [graphic omitted]H₂(L³), or [graphic omitted]H₂(L⁴⁾] form five-co-ordinate complexes [MX(L)](M = Co^II, L = L², L³, or L⁴ and X = Br, I, NCS, or NCSe; M = Zn^II, L = L³ of L⁴, and X = Cl, Br, or I). A trigonal-bipyramidal stereochemistry is ascribed to these complexes, essentially on the basis of electronic and vibrational spectra and of X-ray powder and single-crystal results. Such a structure may be attained by polymerization using X, the phosphorus and carbonyl oxygen atoms, and the nitrogen atom of the ligand, but depends on the metal ion and the steric demands of the ligands. Under suitable conditions, six-co-ordination is attained for the complexes [Co(NCY)(L³)(OH₂)](Y = S or Se), the stability of which is attributed to the formation of hydrogen bonds.