BIS-(N1,N1-DIMETHYLBIGUANIDE-N2,N4)-COPPE R(II) BIS(HYDROGEN CARBONATE) [CU(C4H11N5)2]2HCO3

The structure of bis(N1,N1-dimethylbiguanide-N2,N4)copper(II) bis(hydr ogencarbonate) consists of a [Cu(C4H11N5)2]+ cation and two HCO3- anio ns. The Cu atom is at a centre of symmetry and forms a square-planar s tructure with four N atoms belonging to two N,N-dimethylbiguanide (met formin) groups. The metformin ligand is planar, allowing delocalizatio n of the pi electrons in the metal-ligand ring. The hydrogencarbonate anions are hydrogen bonded to N(1), N(2) and N(3).