Simultaneous formation of both novel bis(µ-sulfur)- and bis(µ-oxo)bridged copper(II) dimers by reaction of N-benzoyl-N′,N′-dimethylthiourea (HL) with CuCl2. Syntheses, crystal structures and magnetic properties of [{CuL(HL)Cl}2] and [{CuL2}2]†

Reaction of N-benzoyl-N′,N′-dimethylthiourea (HL) with copper(II) chloride yielded simultaneously two novel dimers: a pale green bis(µ-sulfur) bridged copper(II) dimer 1, [{CuL(HL)Cl}2], and a dark green bis(µ-oxo) bridged copper(II) dimer 2, [{CuL2}2], instead of the mononuclear copper(II) complexes, [CuL2], usually formed from other dialkyl-substituted benzoylthiourea ligands. The molecular structures of 1 and 2 have been established by single-crystal X-ray analyses. In dimer 1 the central copper(II) ion has a distorted tetrahedral co-ordination environment with one chloride and three sulfur atoms derived from one terminal and two bridging ligands. The two sulfur atoms of both bridging ligands with two copper(II) ions form a strictly planar Cu2S2 bridging core, including two short [2.330(2) A] and two longer [2.549(2) A] Cu–S distances. The dimer 2 may be considered as comprising two mononuclear [CuL2] complexes bridged by one of the acyl oxygen atoms of each to the copper atom of the other, resulting in a distorted tetragonal pyramidal geometry at each copper(II) center, and forming a planar four-membered Cu2O2 bridging unit which consists of two short [1.944(3) A] and two longer Cu–O distances [2.668(3) A], bridging bond angle Cu–O–Cu* [97.9(1)°]. Magnetic measurements for both dimers showed weak antiferromagnetic coupling between the copper(II) centers through bis-sulfur or bis-oxo bridges. The best fitting of the experimental magnetic susceptibility data gave g = 2.110, J = –33 cm–1 for dimer 1 and g = 2.107, J = –4.5 cm–1 for 2.