59Co nuclear magnetic resonance of organo-cobalt compounds

Abstract

The ⁵⁹Co nuclear magnetic resonance spectra of cobalticenium chloride, octacarbonyldicobalt dodecacarbonyl-tetracobalt, octacarbonylmercurydicobalt, dicarbonylcyclopentadienylcobalt, nitrosyltricarbonylcobalt, and the hydrides and sodium salts of the tetracarbonylcobaltate and tetrakis(trifluorophosphine)cobaltate anions have been measured in solution in various solvents. The chemical shift of the cobalticenium ion is in excellent agreement with that predicted by ligand-field theory and the chemical shifts of the two cobaltate ions and the nitrosyl provide good evidence for metal to ligand donor–acceptor π-bonding. The π-bonding abilities of the ligands are in the order nitrosyl > carbonyl > trifluorophosphine. Hyperfine structure was observed from the ¹³C nucleus in the sodium tetracarbonyl cobaltate and from the ³¹P and ¹⁹F nuclei in potassium tetrakis(trifluorophosphine)cobaltate and the magnitudes of the coupling constants suggest a σ-bond order Co–P > Co–C. The sharp lines of the two cobaltates show that the cobalt atom is in the tetrahedral configuration, the remainder have the broad lines expected from a nucleus with spin 7/2 in a non-cubic environment.