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Mononuclear and Dinuclear Copper(I) Complexes of Bis(3,5-dimethylpyrazol-1-yl)methane:  Synthesis, Structure, and Reactivity

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journal contribution
posted on 22.08.2005, 00:00 by Chang-Chuan Chou, Chan-Cheng Su, Andrew Yeh
The synthesis and structures of a mononuclear copper(I) carbonyl complex [Cu(OClO3)(CO)(H2CP )] (3) and a dinuclear copper(I) carbonyl complex [{Cu(CO)(H2CP )}2(μ-pyrazine)](ClO4)2 (4), where H2CP = bis(3,5-dimethylpyrazol-1-yl)methane, are described. These two compounds were generated by the carbonylation of the corresponding copper(I)-acetonitrile complexes, [Cu(H2CP )(MeCN)](ClO4) (1) and [{Cu(H2CP )(MeCN)}2(μ-pyrazine)](ClO4)2 (2). Alternatively, treatment of mononuclear 1 and 3, respectively, with pyrazine in a molar ratio of 2:1 produces the pyrazine-bridged dinuclear CuI complexes 2 and 4. Each of the complexes 14 can react with PPh3 to generate a common three-coordinated copper(I) complex [Cu(PPh3)(H2CP )](ClO4) (5). The structures of complexes 15 were all confirmed by X-ray crystallography. Comparison of the CuI−C(CO) bond distances and the CO stretching frequencies of 3 and 4 indicates the back-donating properties of dπ(Cu)−π*(pyrazine) bonds in 4, and accordingly, stabilizes the mixed-valence species generated from 2. Complex 3, stabilized by the strong interaction between copper(I) ion and perchlorate counteranion (CuI−O(ClO4) = 2.240(3) Å), is a potential precursor for polynuclear copper(I) carbonyl complexes.