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] †

Abstract

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) Å] and two longer [2.549(2) Å] 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) Å] and two longer Cu–O distances [2.668(3) Å], 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.

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