The first heterometallic Cu(II)/Cr(III) complex with an open-chain Schiff-base ligand self-assembled from copper powder, Reineckes salt, ethylendiamine and acetone

A novel supramolecular assembly [{Cu(enac)}(2)Cr(NCS)(4)(NH3)(2)][Cr(NCS)(4)(NH3)(2)](3) center dot 4(CH3)(2)CO (enac = 4,6,6-trimethyl-3,7-diazanon-3-ene-1,9-diamine), the first example of a Cu/Cr heterometallic compound containing a Schiff-base ligand such as enac, and an anion of Reineckes salt, Cr(NCS)(4)(NH3)(2)(-), as a building block, was obtained by the self-assembly reaction of copper powder and Reineckes salt in an acetone/methanol (1:4) solution of ethylenediamine in the open air. An X-ray study shows that the complex includes a trinuclear Cu2Cr cation, constructed from two Cu(enac)(2+) moieties and a trans[Cr(NCS)(4)(NH3)(2)](-) block as a two-linking bridging ligand. The metal-metal separations within the cation are Cu center dot center dot center dot Cr = 6.393(31) angstrom and Cu center dot center dot center dot Cu = 12.786(63) angstrom. The supramolecular architecture of the complex involves two types of H-bonded chains, the first chain is generated by trinuclear cations [{Cu(enac)}(2)Cr(NCS)(4)(NH3)](2+), [Cr(NCS)(4)(NH3)(2)](-) anions and (CH3)(2)CO molecules, while the second by crystallographically different anions of Reineckes salt and (CH3)(2)CO. Variable-temperature (1.8-300 K) magnetic susceptibilities show a slight change of the mu(B) value at low temperature, indicative of weak anti-ferromagnetic interactions (J(CuCr) = -0.9 cm(-1)) between the paramagnetic centers. (C) 2008 Elsevier Ltd. All rights reserved.