Unique trapping of paddlewheel copper(ii) carboxylate by ligand-bound {Cu2} fragments for [Cu6] assembly

The bridging nature of in situ generated hydroxide ions and carboxylates (RCOO(-); R = CH3, C2H5, CH2Ph) has been utilized to design a new family of [Cu6] coordination complexes: [Cu6(μ3-OH)2(μ-H2L)2(μ1,1,3-O2CCH3)2(μ1,3-O2CCH3)2(μ-ClO4)2](ClO4)2·H2O (), [Cu6(μ3-OH)2(μ-H2L)2(μ1,1,3-O2CC2H5)4(μ-ClO4)2](ClO4)2·2H2O () and [Cu6(μ3-OH)2(μ-H2L)2(μ1,3-O2CCH2Ph)4(ClO4)2](ClO4)2·2H2O (). Tetracarboxylate bridged {Cu2} core units are trapped between two ligand-bound {Cu2(μ-H2L)(μ-OH)}(2+) subunits forming the [Cu6] complexes. The hexanuclear {Cu6(μ3-OH)2(H2L)2(μ-O2CR)4}(4+) cores having six interconnected Cu(II) ions assume a hitherto unknown dumbbell-shaped topology. Detailed characterizations have been done using X-ray crystallography and variable temperature magnetic measurements. For complexes , the dominant coupling constant (J') values between carboxylate bridged copper centers are -36.2 to -45.2 cm(-1) for short CuCu separations of 2.540-2.578 Å. In MeCN solutions all three complexes showed catalytic oxidation of 3,5-di-tert-butyl catechol (3,5-DTBCH2) in air.