Discrete dinuclear and polymeric copper(I) cations bridged by 4,4′-bipyridine, trans-1,2-bis(4-pyridyl)ethene or bis(4-pyridyl) disulfide

Article abstract of DOI:10.1039/DT9960001947

Treatment of an acetonitrile solution of copper(I) tetrafluoroborate and 4,4′-bipyridine (4,4′-bipy) with 2-cyanoguanidine (cnge) yielded [{Cu(cnge)₂}₂(μ-4,4′-bipy)][BF₄] ₂·MeCN 1. Structural analysis revealed a planar dinuclear cation containing two, three-co-ordinate T-shaped copper centres bridged by 4,4′-bipy and terminally co-ordinated by two cnge molecules. In the absence of cnge but with an excess of copper(I), the product was [Cu(4,4′-bipy)(MeCN)₂]BF₄ 2, structural analysis of which revealed a one-dimensional polymeric cationic zigzag chain, based on tetrahedral copper(I) atoms bridged by 4,4′-bipy and terminally co-ordinated by two MeCN molecules. The same reaction mixture but with an excess of 4,4′-bipy gave [Cu(4,4′-bipy)₂]BF₄·MeCN 3. The corresponding trans-1,2-bis(4-pyridyl)ethene (bpe) systems yielded the analogous [{Cu(cnge)₂}₂(μ-bpe)][BF₄] ₂·6MeCN 4, [Cu(bpe)(MeCN)₂]BF₄ 5 and [Cu(bpe)₂]BF₄ 6, respectively. Only one product has been isolated from the corresponding bis(4-pyridyl) disulfide (bpds) systems, [Cu(bpds)(MeCN)₂]BF₄ 7. Attempts to produce copper(I) derivatives of 3,6-bis(imidazolyl)pyridazine (bimpydz) were unsuccessful, the copper(II) product, Cu(bimpydz)(MeCN)₂(BF₄)₂ 8, invariably being formed. Whereas the [{Cu(cnge)₂}₂(diimine)]²⁺ and [Cu(diimine)(MeCN)₂]⁺ cations reacted with NOBF₄ and NBu^t₄NO₂ forming copper(II) oxidation products, the [Cu(diimine)₂]⁺ cations were unreactive.