Synthesis and characterization of {[Cu^I₃Sn₂(OBu^t)₆]⁺[Cu^II(hfac)₃]^-} - A heterometallic cluster with unique triangular copper(I) core

New heterometallic Sn-Cu compound that contains copper atoms in two different oxidation states was obtained by the solid state reaction between Sn(OBu^t)₂ (OBu^t = tert-butoxide) and Cu(hfac)₂ (hfac = hexafluoroacetylacetonate). Single crystal X-ray diffraction study revealed the ionic structure of a compound that can be formulated as {[Cu^I₃Sn₂(OBu^t)₆]⁺[Cu^II(hfac)₃]^-} (1) with no significant interactions between complex cation and anion. The anion is comprised of an octahedrally coordinated by three chelating β-diketonate ligands Cu^II atom that shows a typical tetragonal Jahn-Teller distortion of the polyhedron. The heterometallic [Cu₃Sn₂(OBu^t)₆]⁺ cation features a Cu^I triangle capped by two Sn(OBu^t)₃ units. All alkoxide ligands are μ²-bridging between Sn and Cu atoms providing a trigonal pyramidal geometry around tin that is consistent with lone pair Sn^II centers. An almost perfect triangular copper core is stabilized by cuprophilic interactions, similar to those in other polynuclear Cu^I compounds. The cation represents the first example of a Cu^I triangular arrangement that is not supported by μ³-centering atoms or by μ²-all-side bridging. Multinuclear NMR studies unambiguously confirm the retention of heterometallic cluster in solution as well as the absence of ligand redistribution between the anion and cation. The use of a mixed-ligand approach creates broad opportunities for designing new heterometallic complexes with unusual architectures that are not observed in homoleptic counterparts.