Complexation of 3,4-bis(cyanamido)cyclobutane-1,2-dione dianion with copper. Crystal structures and spectroscopic data of copper-(I) and -(II) complexes

Three complexes [Cu-2(PPh3)(4)(MeCN)(2)(cis-(NCN)(2)sq)]. MeCN 1, {[Cu-2(di en)(2)(cis-(NCN)(2)sq)(2)]. 5H(2)O}(n) 2 and [Cu(tren)(cis-(NCN)(2)sq)] 3 w here [cis- (NCN)(2)sq](2-)=3,4-bis(cyanamido)cyclobutane-1,2-dione dianion, have been synthesized and characterized by electronic absorption and IR sp ectroscopies. The structures of the three complexes have been determined by X-ray crystallography. Complex 1 is present as a dinuclear copper(I) compo und. Complex 2 is made of infinite chains with copper(II) atoms bridged by the bis monodentate [cis-(NCN)(2)sq](2-) ion. In the mononuclear complex 3 the co-ordination of the cyanamido group unusually occurs via the amido nit rogen and not by the nitrile group; this is accompanied by an important dis tortion of the co-ordinated cyanamido group. The co-ordination mode of the cyanamido moiety is discussed in regard to IR data and crystallographic res ults.