Improved synthesis of the radical source bis[2,2,6,6-tetramethylpiperidyl-(1)]-disulfide and photoinduced reactions with M2(CO)10 (M=Mn, Re)

An improved synthesis of bis[2,2,6,6-tetramethylpiperidyl-(1)]-disulfide ((tmps)2) in moderate yield is reported. Reaction of N-(trimethylsilyl)-imidazole with S2Cl2 gives N,N′-dithiobisimidazole and trimethylsilylchloride. The disulfide undergoes exchange of the heterocycle wth 2,2,6,6-tetramethylpiperidine and yields bis[2,2,6,6-tetramethylpiperidyl-(1)]-disulfide and imidazole. This synthesis offers the advantage that only traces of the bis[2,2,6,6-tetramethylpiperidyl-(1)]-trisulfide are produced. The synthesis and spectroscopic properties of the dimeric compounds [M(CO)4tmps] 2 (M=Mn, Re) obtained by UV irradiation of a mixture of (tmps)2 with M2(CO)10 (M=Mn, Re) is described.