The compounds (RCp)2Ti(SH)2 (RCp = η5-C5H4R; 1a, R = H; 1b, R = CH3) react with C7H8M(CO)4 (M = Mo, W) to form the dimers (RCp)2Ti(μ-SH)2M(CO)4 (2a, R = H, M = Mo; 2b, R = CH3, M = Mo; 3, R = H, M = W) which were characterized analytically and spectroscopically. The reactivity of 2a,b differs sharply with that observed for 1a,b. While 1a,b show little nucleophilicity at sulfur, compounds 2a,b react with Ph2E2 (E = S, Se), S8, (RCp)2TiS5, and CH2=CHCO2Me to give (RCp)2Ti(EPh)2, (RCp)2TiS5, 1,4-[(RCp)2Ti]2S4, and (RCp)2Ti(SCH2CH2CO2Me) 2Mo(CO)4, respectively. 1H NMR studies show that the bimetallic compounds prepared in this study exist as a mixture of syn and anti isomers which differ in the relative orientation of the hydrogen substituent on the sulfur. Through DNMR studies it was shown that interconversion of these isomers occurs with ΔG* ≈ 72 kJ/mol which is comparable to the barriers found for other SR-bridged 34-electron dimers. While the facility of the isomerization process is unaffected by acid, catalytic quantities of triethylamine has an accelerating effect. Reaction of 2a,b with strong bases gives the highly reactive dianions which were isolated in pure form using bulky counterions.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry