H. Adams et al., HETEROLEPTIC TRIPODAL COMPLEXES OF COPPER(II) .2. FORMATION OF AXIAL PHENOLATE-METAL BONDS IN SQUARE-PYRAMIDAL COMPLEXES, Journal of the Chemical Society. Dalton transactions, (11), 1996, pp. 2233-2237
Copper(II) complexes derived from tripodal ligands capable of forming
5,6,6- or 5,5,6-membered chelate ring sequences have been synthesised
and characterised. The crystal structures of two complexes [CuL(O(2)CB
u(t))]. MeCN [HL = 5-nitrophenylmethyl)(pyridin-2-ylethyl)(pyridin-2-
ylmethyl)amine] and [CuL(O(2)CMe)]. H2O [HL = -5-nitrophenylmethyl)bis
(pyridin-2-ylmethyl)amine] have been solved. They are neutral, mononuc
lear copper(II) species in the solid state. In contrast to copper(II)
complexes derived from related tripodal ligands forming 6,6,6-membered
chelate rings, the present complexes have an axial phenolate-copper(I
I) bond in their square-pyramidal structures. The formation of this bo
nd is related to the steric factors arising from the flexibility of th
e ligand pendant arms. The complex [CuL(O(2)CMe)] exhibits structural
features related to the biosite in galactose oxidase; an acetate co-or
dinates to copper equatorially and a phenolate oxygen atom occupies th
e axial position.