A novel coordination behaviour of bis-oxamato ligands

Subsequent reaction of [nBu4N]OH with the diethyl ester of N,N′-1,2-ethanediylbis(oxamic acid) (endaH2Et2, 1) and [CuCl2(H2O)2] affords the title compound [nBu4N]4[Cu(endaH)2] (2). The solid state structure of 2 is reported. In 2, two bis-oxamato ligands [endaH]3− with only one oxamato substituent per ligand are coordinated towards copper, leading to a trans-bis(endaH-N,O) arrangement around copper. Complex 2 can be considered as a novel flexidentate system for coordination of up to six further transition metals.