Synthesis and crystal structure of the dicopper(II) complex [Cu 2{Ph2P(=O)(o-C6H4)CO 2}2(THF)2(H2O)2][BF 4]2 by oxidation of [Cu{Ph2P(o-C 6H4)C(=O)H}2(NCMe)][BF4] with aqueous H2O2