An Experimental and Theoretical (DFT) Investigation of the Coordination Mode of 2,4-Dithiouracil (2,4-dtucH2) in Copper(I) Complexes with1,2-Bis(diphenylphosphanyl)benzene (dppbz): The Crystal Structures of [Cu(μ-Br)(dppbz)]2 and [CuBr(dppbz)(2,4-dtucH2)]
✍ Scribed by Paraskevas Aslanidis; Philip J. Cox; Andreas Kaltzoglou; Athanasios C. Tsipis
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 248 KB
- Volume
- 2006
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
Abstract
Novel copper(I) mixed‐ligand complexes containing 1,2‐bis(diphenylphosphanyl)benzene (dppbz) and 2,4‐dithiouracil (2,4‐dtucH~2~) ligands have been synthesised by addition of the thione ligand to the dinuclear [Cu(μ‐X)(dppbz)]~2~ intermediate in acetonitrile/methanol or acetone solution. The molecular structures of both the precursor [Cu(μ‐Br)(dppbz)]~2~ and the [CuBr(dppbz)(2,4‐dtucH~2~)] complexes were established by single‐crystal X‐ray diffraction. Interestingly, the structure of the thione‐free dimer involves two diphosphane‐chelated Cu^I^ centres bridged by two bromide ligands, thus forming a non‐planar Cu~2~Br~2~ core. The structure of [CuBr(dppbz)(2,4‐dtucH~2~)] corresponds to a four‐coordinate Cu^I^ centre in a tetrahedral coordination environment with the heterocyclic dithione ligand being coordinated to the metal centre in a unidentate fashion through its exocyclic sulfur donor atom. The structural, bonding and electronic properties of the model complexes [Cu(μ‐X)(dppbz)]~2~ and [CuX(dppbz)(2,4‐dtucH~2~)] (X = Cl, Br, or I) are adequately described by DFT/B3LYP computational techniques. All model dinuclear [Cu(μ‐X)(dppbz)]~2~ complexes exhibit π‐type MOs delocalised over the entire four‐membered Cu(μ‐X)~2~Cu ring, thereby accounting for the near equivalency of the Cu–X bonds. Moreover, the [Cu(μ‐X)(dppbz)]~2~ dimers possess a σ‐type MO corresponding to weak Cu···Cu bonding interactions, which further stabilize the Cu(μ‐X)~2~Cu ring. According to our calculations, the interaction energies of the 2,4‐dtucH~2~ ligand with the Cu^I^ centre are predicted to be about 13–16 kcal mol^–1^. The coordination of the 2,4‐dtucH~2~ ligand is further stabilized by an X···H–N hydrogen bond that is perpendicular to the plane of the dppbz ligand. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)