Ferromagnetic copper(II)–copper(II) interaction in a single chlorido and dicyanamido bridged mixed–valence copper(I/II) 2-D polymer generated byin situpartial reduction of copper(II)

A mixed-valence 2-D Cu(I/II) complex, [{Cu(II)(dmen)(μ-Cl)(μ 1,5 -dca)}{Cu(I)(μ 1,5 -dca)}] n (1) (dmen = N,N-dimethylethylenediamine, dca = dicyanamide = [N(CN) 2 ] − ), has been synthesized by in situ partial reduction of Cu(II) to Cu(I) using benzoin (2-hydroxy-1,2-di(phenyl)ethanone) as reductant. Complex 1 was characterized by spectroscopic techniques, single crystal X-ray diffrac- tion, and low temperature magnetic measurements. Structural investigation reveals that 1 represents a mixed-valence 2-D coordination polymer formed by parallel 1-D [Cu(II)(dmen)(Cl)Cu(I)(μ 1,5 - dca) 2 ] n chains running along the b axis, where chloride bridges Cu(II) ions of adjacent polymers through long connections (2.8401(1) Å) to form a 2-D network. The metal centers have two differ- ent geometrical environments (distorted square pyramidal and distorted trigonal planar geometries for Cu(II) and Cu(I), respectively). The Cu(II) ions in [Cu(II)(dmen)(μ-Cl)(dca)] n are interconnected through single chloride bridges while within the [Cu(I)(μ 1,5 -dca)] n units, the dca connects adjacent Cu(I) ions through μ 1,5 -dca bridges. Magnetic susceptibility measurements reveal weak ferromag- netic interactions (J = +0.3 cm −1 ) within the chlorido-bridged Cu(II) regular chain present in 1. Simultaneous presence of μ 1,5 -dca and single chlorido bridges with ferromagnetic coupling is believed to be unique in mixed-valence Cu(I)/Cu(II) complexes.