Reactions of 2-Mercaptobenzoic Acid with Divalent Alkaline Earth Metal Ions: Synthesis, Spectral Studies, and Single-Crystal X-ray Strontium, and Barium Complexes of 2,2'-Dithiobis(benzoic acid)

摘要

The treatment of MCl_2centre dotnH_2O (M=Ca, Sr, or Ba) with 2-mercaptobenzoic acid (H-2-MBA) in a 1:2 ratio in an EtOH/H_2O/NH_3 mixture leads ot the formaiton of extended polymeric solids [{Ca(OOCC_6H_4SSC_6H_4COO)(H_2O)_2}centre dot0.5(C_2H_5OH)]_n (1), [{Sr(OOCC_6H_4SSC_6H_4COO)(H_2O)_2}centre dot0.5(C_2H_5OH)]_n (2), and [{Ba_2(OOCC_6H_4SSC_6H_4COO)_2(H_2O)_2}centre dot0.5H_2O]_n (3), respectively. In all of the cases, under the reaction conditions employed, the H-2-MBA ligand undergoes thiol oxidation to form 2,2'-diethiobis(benzoic acid) (H_2-DTBB). While the DTBB forms a 1:1complex with heavier alkaline earth metals (1-3), only an ammonium slat, [(HOOCC_6H_4SSC_4H_4COOH)(HOOCC_6H_4SSC_6H_4COONH_4)] (4), was otianed as the final product in the reaction of H-2-HBA with MgCl_2centre dot6H_2O. Compounds 1-4 have ben characterized with the aid of elemental analysis, thermal analysis, and infrared spectroscopic studies. All of the products are found to be thermally stable and do not melt on heating to 250deg C. Thermogravimetry on complexes 1-3 indicates the loss of coordianted and latice water/solvent molecules below 200deg C (for compelx 2) or 350deg C (for complexes 1 and 3). The solid-state structures of al of the derivatives 1-4 have been established by single-crystal X-ray diffraction studies. The calcium and strontium coordiantion polymers 1 and 2 are isomorphous. The DTBB ligands in 1 and 2 are hexadentate, and the compounds have a channel structure in which solvent ethanolmoleules are included. In comound 3, barium ion forms a compelx 3-dimensional coordination polymer whee both the carboxylate and the sulfur centers of the DTBB ligands (which are hepta-and octadentate) coordinate to the metal.