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Luminescent Copper(I) Halide Adducts of [Au(im(CH2py)2)2]PF6 Exhibiting Short Au(I)···Cu(I) Separations and Unusual Semibridging NHC Ligands

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posted on 07.11.2011, 00:00 by Christoph E. Strasser, Vincent J. Catalano
The picolyl-substituted NHC complex [Au(im(CH2py)2)2]PF6 (1) reacts with two equivalents of copper(I) halides, affording compounds [Au(im(CH2py)2)2(CuX)2]PF6 (X = Cl, 2; Br, 3; I, 4). Each complex contains a nearly linearly coordinated [Au(NHC)2]+ center where the two picolyl groups on each im(CH2py)2 ligand chelate a single copper atom. The Cu(I) center resides in a distorted tetrahedral environment and is coordinated to two pyridyl groups, a halide ion, and a gold metalloligand. The Au(I)–Cu(I) separations measure 2.7030(5), 2.6688(9), and 2.6786(10) Å for 24, respectively. Additionally, each Cu(I) center is further coordinated by a semibridging NHC ligand with short Cu–C separations of ∼2.3 Å. In solution, these complexes dissociate the Cu(I) ion. In the solid state, 24 are photoluminescent with respective emission maxima of 512, 502, and 507 nm. The reaction of [Au(im(CH2py)2)2]PF6 with four equivalents of CuBr afforded the coordination polymer {[AuCu2Br2(im(CH2py)2)2]Br·3CH3CN}n (5). This polymeric complex contains [Au(NHC)2]+ units interconnected by Cu2Br2 dimers. In 5, the Au–Cu separations are long at 4.23 and 4.79 Å, while the Cu–Cu distance is considerably shorter at 2.9248(14) Å. In the solid state, 5 is photoluminescent with a broad band appearing at 533 nm.