Synthesis and X-ray characterization of mono- and polynuclear thiolatocopper(I) complexes: The effect of steric bulk on coordination number and nuclearity

We have synthesized a number of Cu^I complexes of thiophenolato ligands with different alkyl substituents in the ortho positions in a single-step procedure starting from a readily available copper(I) precursor to evaluate the coordination preferences of the metal atom. In most cases similar reaction conditions led to the formation of two complexes: a mononuclear complex and a polynuclear cluster, as evident from X-ray crystallography. One dinuclear complex formed has the unique geometry of an L₂Cu ₂(μ-L)₂ core that has not previously been observed for related systems. The steric bulk around the metal atom has a clear effect on the coordination sphere of the complex obtained. Ligands with no ortho substituents and those with one substituent with a size varying from methyl to tert-butyl all lead to the formation of three-coordinate complexes for the mononuclear species, and clusters of different sizes where larger substituents lead to larger cages and all copper centers are three-coordinate as well. The introduction of two methyl substituents (one in each ortho position) leads to either a mononuclear two-coordinate copper complex or a polynuclear cluster where two copper centers are three-coordinate and three are two-coordinate.