Synthesis, spectral and structural characterization of dinuclear rhodium (II) complexes of the anticonvulsant drug valproate with theophylline and caffeine

The dinuclear complex tetra(μ-valproato) dirhodium(II), Rh2(valp)4 (1), and its bis-adducts with theophylline, Rh2(valp)4(ThH)2 (4), or caffeine, Rh2(valp)4(Caf)2 (5), have been synthesized and characterized by elemental analysis, IR, UV–Vis, magnetic moment, 1H and 13C NMR spectroscopic techniques. Spectral data for the complexes are consistent with a dinuclear structure as found for rhodium (II) tetracarboxylate adducts. Theophylline and caffeine bases in complexes 4 and 5, respectively, are axially coordinated to rhodium (II) atoms through the sterically hindered N(9) site. This is confirmed by X-ray crystal structure analyses of complexes 4 and 5.