Dinuclear Paddle-Wheel Copper(II) Carboxylates in the Catalytic Oxidation of Carboxylic Acids. Unusual Polymeric Chains Found in the Single-Crystal X-ray Structures of [Tetrakis(μ-1-phenylcyclopropane-1-carboxylato-O,O‘)bis(ethanol-O)dicopper(II)] and catena-Poly[[bis(μ-diphenylacetato-O:O‘)dicopper](μ₃-diphenylacetato-1-O:2-O‘:1‘-O‘)(μ₃-diphenylacetato-1-O:2-O‘:2‘-O‘)]

Abstract

The X-ray structures and spectroscopic and magnetic properties of [tetrakis(&mgr;-1-phenylcyclopropane-1-carboxylato-O,O')bis(ethanol-O)dicopper(II)], 1, and catena-poly[[bis(&mgr;-diphenylacetato-O:O')dicopper](&mgr;(3)-diphenylacetato-1-O:2-O':1'-O')(&mgr;(3)-diphenylacetato-1-O:2-O':2'-O')], 2, two extended-chain copper(II) carboxylates with dinuclear paddle-wheel subunits, are reported. 1 crystallizes in the triclinic space group P&onemacr;, with a = 6.8873(3) Å, b = 11.7367(6) Å, c = 13.7899(7) Å, alpha = 107.076(4) degrees, beta = 93.545(4) degrees, gamma = 103.967(4) degrees, Z = 1. The Cu.Cu distance is 2.6009(4) Å, and the Cu.carboxylate O distances are in the range 1.937(2)-1.962(2) Å. The ethanol at the apex forms an unsymmetrical bifurcated H bond to two carboxylate oxygens of another dinuclear unit with O.O distances 2.980(3) and 3.108(3) Å, thereby extending the structure along the a-axis. The magnetic structure consists of isolated antiferromagnetically coupled dinuclear copper units, with a -2J value of 242 cm(-)(1), in concurrence with the EPR parameters, viz., g(x)() = 2.03(1), g(y)() = 2.07(1), g(z)() = 2.35(1), A( parallel) = 0.064(2) cm(-)(1), D = 0.316(15) cm(-)(1), E = 0.005(1) cm(-)(1). The -2J value is the smallest value measured for dinuclear copper carboxylates with oxygen-donor ligands at the axial position and no electron-withdrawing carboxylate R groups. 2 crystallizes in the monoclinic space group P2(1)/c, with a = 15.953(2) Å, b = 5.385(6) Å, c = 28.322(10) Å, beta = 120.22(3) degrees, Z = 2. The compound contains tetrakis(diphenylacetato)dicopper(II) units, forming a polymeric structure along the b-axis by axial coordination of a carboxylate oxygen to copper of a subsequent dinuclear unit, at 2.323(11) Å. The intradimer Cu.Cu distance is 2.594(4) Å; the interdimer Cu.Cu distance is 3.425(5) Å. The -2J value of 321 cm(-)(1) was interpreted as originated from isolated antiferromagnetically coupled dinuclear copper units. The EPR parameters are g(x)() = 2.07(1), g(y)() = 2.02(1), g(z)() = 2.33(1), D = 0.347(10) cm(-)(1), E = 0.0034(5) cm(-)(1). The dinuclear subunits are likely candidates for the catalytically active Cu species in copper(II)-catalyzed oxidation of carboxylic acids.

Syntheses of two new hybrid metal-organic polymers using flexible aliphatic dicarboxylates and pyrazine: Crystal structures and magnetic studies

“…Hence, the Cu(OCO) 4 Cu paddle-wheel cage plays an important role in the magnetic properties of polymer 1. For this type of structure the antiferromagnetic interaction is strong because unpaired electron density from both Cu(II) ions is transferred to the same orbital of the bridging caboxylate [16,[21][22][23].…”

Reactions Catalysed by a Binuclear Copper Complex: Aerobic Cross Dehydrogenative Coupling of N‐Aryl Tetrahydroisoquinolines

“…Many such dicopper carboxylate complexes have been synthesized, with hundreds crystallographically characterized –. Surprisingly, their potential as catalysts for organic synthesis has rarely been explored thus far, although these dicopper complexes have been extensively studied as superoxide dismutase mimetics in bioinorganic and medicinal chemistry ,,…”

Mono and Dinuclear Cu(II) Carboxylate Complexes with Pyridine and 1‐methylimidazole as Co–Ligands: Synthesis, Structure, Antibacterial Activity and Catalytic Nitroaldol Reactions

“…In most cases, the copper(II) carboxylate complexes general formula is Cu 2 (OOCR) 4 L 2 and Cu(OOCR) 2 L 2 [L=Py (pyridine), MIm (1−methylimidazole), Hdmpz (3,5‐dimethylpyrazole), H 2 O, DMSO (dimethylsulfoxide)]. The binuclear Cu(II) carboxylate complexes exhibit a paddle‐wheel cage structure, but due to the different coordination modes of the carboxylate ligands and the mononuclear copper carboxylate complexes has also confirmed the existence of unidentate coordination modes of the ligands …”