Cu(II) complexes with labile apical coordination: Synthesis, crystal structure, H-1 NMR investigation, and oxidation properties of mononuclear [Cu-II(dien)(2-PhIm)(ClO4)](+) (1), [Cu-II(dien)(2-MeBzIM)](2+) (2), complexes

摘要

The compounds [Cu(dien)(2-PhIm)(ClO4)](ClO4) (1); [Cu(dien)(2-MeBZIm)](ClO4)(2) (2); where then = diethylenetriamine, 2-PhIm = 2-phenylimidazole and 2-MeBzIm = 2-methylbenzimidazole, were synthesized and characterized. The complexes possessing [Cu(II)dien] moiety as common, the former containing 2-phenylimidazole, yielded square pyramidal geometry with apical perchlorate coordination [Cu1-O(5) = 2.449 A], while the latter with 2-methylbenzimidazole formed square planar geometry with weak perchlorate contact [Cu1-O(8) = 2.596 A] in its apical position. The effect of solvent and the variable temperature H-1 NMR investigation combinedly explore the geometrical rearrangement towards five coordination around Cu(II) metal center by accommodating the solvent molecule in its fifth coordination. Possessing easily labile perchlorate anion, both these complexes were investigated for their oxidation capability using 3,5-di-tert-butyl catechol (DTBC). The rate constant determined for the oxidation of DTBC to corresponding quinone indicates that they are catalytically quite similar and the k(cat) of 1 approximate to 2. The crystal structure and the NMR investigations are discussed in detail. (c) 2005 Elsevier B.V. All rights reserved.