Preparation and reactivity of benzo-1,2-dichalcogenete derivatives and their bis(triphenylphosphine)platinum complexes

Abstract

The reaction of 4,5-(o-xylylenedichalcogeno)-3,6-dialkylphthalonitrile (1a-d) with aluminum chloride in toluene gave ring-opened products, 3,6-dialkyl-4,5-dicyanobenzene-1,2-dithiols (2a,b), for sulfur derivatives and cyclized products, 3,6-dialkyl-4-,5-dicyanobenzo-1,2-diselenetes (2c,d), for selenium derivatives. Asymmetrically substituted 3,6-diethylbenzo-1,2-diselenete (2e) with a bromo and a nitrile group was prepared by the reaction of 4,5-(o-xylylenediseleno)-3,6-diethyl-2-cyano-1-bromobenzene (1e) with aluminum chloride in toluene. Compound 2e was unstable compared with 2c and produced an equilibrium mixture of 2e and dimerized dibenzotetraselenocin 3e in the chloroform solution. Compound 2c was reacted with methyl iodide in the presence of sodium hydroxide to produce 1,2-bis(methylseleno)-3,6-diethyl-4,5-dicyanobenzene (4) and bis(2-methylseleno-3,6-diethyl-4,5-dicyanophenyl)diselenide (5). Compounds 2a and 2c were reacted with tetrakis(triphenylphosphine)platinum in toluene to give the corresponding platinum complexes 6a and 6c with a dichalcogenaplatinumole ring, respectively. The structures of 6a and 6c were determined by NMR, MS, and X-ray crystallography. To obtain theoretical information, the structures of dichalcogenetes 2a′, 2c, 2e, 2f, 2g and platinum complexes 6a and 6c were optimized by the DFT method using the Gaussian 09 program and their HOMO and LUMO energy levels were calculated by time-dependent density functional theory.