Bis(µ-pyridazine)-bis[(2-cyanoguanidine)copper(I)] cation: a molecule containing two co-ordinatively unsaturated copper(I) centres

Abstract

2-Cyanoguanidine [(NH₂)₂CNCN (cnge)] stabilises co-ordinatively unsaturated copper(I) in bis(µ-pyridazine)-bis[(2-cyanoguanidine)copper(I)] tetrafluoroborate 1, which has been structurally characterised by single-crystal X-ray diffraction analysis [triclinic, space group P, a= 754.8(2), b= 971.3(2), c= 937.2(2) pm, α= 118.94(2), β= 94.72(2), γ= 107.44(2)°]. The cation in 1 contains two trigonal-planar copper(I) atoms bridged by two pyridazine (pydz) molecules and terminally co-ordinated by a cnge molecule. It acts as a receptor molecule binding a further pydz to form tris(µ-pyridazine)-bis[(2-cyanoguanidine)copper(I)] tetrafluoroborate 2. The structure of 2 was also determined [monoclinic, space group C2/c, a= 2229.3(7), b= 850.0(3), c= 1568.5(3) pm, β= 99.13(2)°]. It contains two distorted-tetrahedral copper(I) atoms bridged by three pydz molecules and terminally co-ordinated by a cnge molecule. Thermogravimetric analysis of 2 showed that heating removes the third bridging pydz molecule to regenerate 1; this behaviour is ascribed to the unusually high stability of the co-ordinatively unsaturated copper(I) moiety in 1.