Synthetic and structural studies on copper 1 H-[1,10]-phenanthrolin-2-one coordination complexes: isolation of a novel intermediate during 1,10-phenanthroline hydroxylation.

The synthesis and crystal structure elucidation of a novel dinuclear heteroleptic copper(II) complex has led to an alternative mechanism in the formation of covalent hydrates. During further studies on the synthesis and properties of [Cu(2)(ophen)(2)] (1), a dinuclear complex of copper(I) with 1 H-[1,10]-phenanthrolin-2-one (Hophen), two intermediates/alternative products 2 and 3 were isolated. The dinuclear, antiferromagnetic complex [Cu(2)(ophen)(2)(phen)(2)](NO(3))(2)9H(2)O (3, phen=1,10-phenanthroline) contains two five-coordinate copper(II) ions, both with trigonal-bipyramidal coordination, which are bridged together through deprotonated hydroxyl groups with a Cu--Cu non-bonding distance of 3.100 A. Complex [Cu(phen)(2)(H(2)O)](NO(3))(2) (2) is a polymorph of a previously reported material. The occurrence of 2 and 3 has led us to propose a variation to the Gillard mechanism for the formation of covalent hydrates in bidentate N-heterocycles in which the attacking nucleophile may be the deprotonated form of 2, [Cu(phen)(2)(OH)](-), rather than free OH(-).