An unprecedented tetranuclear Cu(II) cluster, exclusively bridged by two μ3,η3-hydrogenphosphate anions: synthesis, structure, and magnetic properties

A novel tetranuclear HPO42- Cu(II) complex with a new coordination mode of a hydrogenphosphato bridge, [Cu4(di-2-pyridylamine)4(μ3,η3-HPO4)2(H2O)2(NO3)2](NO3)2(H2O)2, has been synthesised and characterised structurally, spectroscopically and magnetically. The geometry around the Cu(II) ions is distorted square pyramidal for Cu1 and an intermediate between square pyramidal and trigonal pyramidal. The magnetic susceptibility measurements have been fit for a weak antiferromagnetic interaction of J = −10.3(1) cm−1 between outer Cu ions and J = −5.3(2) cm−1 between inner Cu atoms.