The crystal and molecular structure of the tetrameric methyl-2-mercaptobenzimidazole.AgBr (acetone solvate) complex : Mode of complex formation between silver bromide and thione type photographic stabilizers

The complex formed from the reaction of an important thione based stabilizer in conventional silver halide photography, methyl-2-mercaptobenzimidazole (MBI), and silver bromide has been isolated for the first time as a single crystal and characterized by X-ray structure techniques. The resulting compound is tetrameric and has the formulation [AgBr.MBI] 4 and also contains residual solvent from the crystallization process. The crystal and molecular structure of [AgBr.MBI] 4 consists of intertwined dimers of [AgBr] 2 four-membered rings that connect the foundational silver-mercaptobenzimidazole [AgS] 4 eight-membered rings into a high molecular weight polymeric network superstructure. The complex demonstrates the powerful silver halide solubilization properties of the thiourea type ligand. The bridging sulfur remains in the thione form and N-H…Br-Ag hydrogen bonds suggest the title complex is an intermediate in the formation of the deprotonated AgMBI complex. Normal Ag-Br and Ag-S bond lengths were found: Ag-S=2.5026(8), Ag-Br=2.7423(9) and 2.7956(10) A, C 9.50 H 11 AgBrN 2 O 0.50 S, Cell Data: I4 1 /amd, a = 19.1034(2) A, b = 19.1034(2) A, c = 13.5019(2) A.