Metal ion biomolecule interactions. PART VII. Synthesis, spectroscopic properties and crystal structure investigations of some bis(theophyllinato)tetraaquocadmium(II) compounds

Abstract

The synthesis, 1H and 13C nmr and infrared spectra of the complex bis(theophyllinato)tetraaquocadmium(II), [CdC14H22N4O5], and its N,N-dimethylformamide solvates are reported. The crystals containing two molecules of N,N-dimethylformamide per complex belong to the monoclinic space group P21/c with a = 10.891(3), b = 13.696(7), c = 10.110(2) Å, β = 109.03(4)°, ρc = 1.595 g cm−3, and Z = 2. Least-squares refinement of the structure has led to a final value of the conventional R factor of 0.044 for 261 variables, using 1299 nonzero MoKα reflections. The complex consists of monomeric [CdTh2(H2O)4] units. The cadmium lies on an inversion center. The geometry of the atoms bonded to cadmium is roughly octahedral with the two theophyllinate ions trans to each other and coordinated through N(7). The Cd—N(7), Cd—O(13), and Cd—O(14) distances of 2.300(5) Å, 2.346(5) Å, and 2.336(5) Å, respectively, are normal. The hydrogen bonding in the crystals is complex, with all the ligand donor and acceptor atoms participating. N,N-Dimethylformamide is not coordinated to cadmium, but participates in the hydrogen bonding system. The nmr spectra are consistent with theophyllinate ion being similarly bonded to cadmium in dimethyl sulfoxide solution.