Coordination chemistry of unsymmetrical tripodal ligands with an NNO2 donor set

The synthesis of two new tripodal ligands N(CH2CH2NH2)(CH2CH2CH2OH)(2) (H-4 -1) and N[2,3,5-C6H2(OH)(SCH3)(CH3)](CH2CH2CH2NH2)(CH2CH2CH2OH) (H4-2) is r eported. Both tetradentate ligands contain a central tertiary nitrogen atom , as well as two OH and one NH2 functionalized ligand arm. The tripods do n ot only exhibit an unsymmetrical N2O2 donor set, but also possess two C-3 a nd one C-2 chains between the central nitrogen atom and the terminal donors . On coordination of the central tertiary nitrogen atom, the ligands are ca pable of forming both six- and five-membered chelate rings in their metal c omplexes. Both ligands react with [Cu(OAc)(2).H2O](2) to give the dinuclear copper(II) complexes [Cu(eta (4)-mu -O-H-3-1)(2)Cu](PF6)(2) (3) and [(eta H-3(3)-2)Cu( mu -OAc)(2)Cu(eta (3)-H-3-2)]. 2CH(3)CN (4 . 2CH(3)CN). The mo lecular structures of 3 and 4.2CH3CN have been determined by X-ray diffract ion. Complex 3 contains two slightly distorted square-pyramidal (tau = 0.18 1) copper atoms, with O-donors in the apical positions. The dinuclear compl ex 4, which was synthesized to model the copper site in galactose oxidase, also shows a distorted square-pyramidal coordination geometry (tau = 0.205 and tau = 0.101) around both copper(II) atoms. Complex 4 contains two uncoo rdinated primary alcohol functionalities of the ligands. In addition, both the ligand H-4-2 and its dinuclear copper complex [(eta (3)-H-3-2)Cu(mu -OA c)(2)(eta (3)-H-3-2)]. 2CH(3)CN can easily be oxidized to yield free or coo rdinated phenoxyl radicals, which are stable on the time scale of cyclic vo ltammetry.