The role of the second coordination sphere of [Ni[([P.sup.cy][N.sub.2.sup.Bz]).sub.2]][(BF4).sub.2] in reversible carbon monoxide binding

The rapid and reversible reaction taking place between [Ni[([P.sup.cy][N.sub.2.sup.Bz]).sub.2]][(BF4).sub.2] complex and carbon monoxide is discussed. The second coordination sphere of the molecule is found to be essential for controlling the reactivity.