Discrete dinuclear and polymeric copper(I) cations bridged by 4,4′-bipyridine, trans-1,2-bis(4-pyridyl)ethene or bis(4-pyridyl) disulfide
Abstract
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]BF42, 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]BF45 and [Cu(bpe)2]BF46, respectively. Only one product has been isolated from the corresponding bis(4-pyridyl) disulfide (bpds) systems, [Cu(bpds)(MeCN)2]BF47. Attempts to produce copper(I) derivatives of 3,6-bis(imidazolyl)pyridazine (bimpydz) were unsuccessful, the copper(II) product, Cu(bimpydz)(MeCN)2(BF4)28, invariably being formed. Whereas the [{Cu(cnge)2}2(diimine)]2+ and [Cu(diimine)(MeCN)2]+ cations reacted with NOBF4 and NBut4NO2 forming copper(II) oxidation products, the [Cu(diimine)2]+ cations were unreactive.