Synthesis of [Cu2(Me2[9]aneN2S)2(OH)2](PF6)2, a Hydroxo-Bridged Copper(II) Complex of N,N′-Dimethyl-1-thia-4,7-diazacyclononane (Me2[9]aneN2S). X-Ray Structural Analysis, Magnetic Susceptibility, E.P.R. and Visible Spectroscopy

Abstract

The bis(µ-hydroxo) complex [Cu ₂ (Me ₂ [9]aneN ₂ S) ₂ (OH) ₂ ] (PF ₆ ) ₂ (Me ₂ [9]aneN ₂ S = N,N′-dimethyl-1-thia-4,7- diazacyclononane) results after reaction of [Cu(Me ₂ [9]aneN ₂ S)(MeCN)] (PF ₆ ) with dioxygen at −78°C in acetonitrile. The complex has been characterized by X-ray crystallography: orthorhombic, space group Pnma, with a 18.710(3), b 16.758(2), c 9.593(2) Å, and Z = 4. The structure refined to a final R value of 0.051. The complex contains two copper(II) ions bridged by two hydroxo groups with Cu···Cu 2.866(1) Å. The solid-state magnetic susceptibility study reveals ferromagnetic coupling, the fitting parameters being J = +46±5 cm ⁻¹ , g = 2.01±0.01 and &thetas; = −0.58±0.03 K. The frozen-solution e.p.r. spectrum in dimethyl sulfoxide is characteristic of a monomeric copper(II) ion (g _‖ 2.300, g _⊥ 2.063; A _‖156.2 × 10 ⁻⁴ cm ⁻¹ , A _⊥ 9.0 × 10 ⁻⁴ cm ⁻¹ ) with an N ₂ O ₂ donor set. Thioether coordination to the copper(II) in solution is supported by the presence of an intense absorption assigned to a σ(S)→Cu ^II LMCT transition at c. 34000 cm ⁻¹ . The single-crystal spectrum of [Cu ₂ (Me ₂ [9]aneN ₂ S) ₂ (OH) ₂ ] (PF ₆ ) ₂ (273 K) reveals d→d transitions at 14500 and 18300 cm ⁻¹ and a weak π(S)→Cu ^II charge-transfer band at approximately 25000 cm ⁻¹.