Preparation and characterization of the seven coordinate cadmium(II) complex [Cd(3,4-H(2)dhb)(2)(H2O)3]center dot HCl center dot(3,4-H(3)dhb)center dot 2.5H(2)O; The first structural determination of a complex containing the 3,4-dihydroxybenzoato(-1)(3,4-H(2)dhb(-)) ligand