SYNTHESIS AND STRUCTURAL AND REACTIVITY STUDIES OF THIATITANACYCLOPROPANE COMPLEXES [CP-DAGGER-TI(SCHCH2CH2S)](2) (CP-DAGGER=CP,MECP)

The complexes [Cp(+)Ti(SCHCH2CH2S)](2) (Cp(+) = Cp (3), MeCp (4)) are readily prepared from reaction of Cp(+)Ti(SCH2CH2CH2S)Cl (Cp(+) = Cp ( 1), MeCp (2)) with MeLi, AlMe(3), or t-BuLi. Both compounds are centro symmetric dimers in the solid state containing strained thiatitanacycl opropane rings. PMe(3) cleaves these dimers, establishing equilibria b etween 3 and 4 and Cp(+)Ti(SCHCH2CH2S)(PMe(3)) (Cp(+) = Cp (5), MeCp ( 6)), while compound 3 undergoes facile acidolysis with HCl, acetic aci d, PhSH, and propanedithiol affording CpTiCl(3), CpTi(O-2-CMe)(3) (7), CpTi(SCH2CH2CH2S)(SPh), and H+[CpTi(SCH2CH2CH2S)(2)](-). THF (8), res pectively. The thiametallacycles react with benzophenone to give Cp(+) Ti(SCH(CPh(2)O)CH2CH2S) (Cp(+) = Cp (9); MeCp (10)) while reaction wit h cyclohexanone gives the dimeric species [Cp(+)Ti-(SCH(C6H10O)CH2CH2S )](2) (Cp(+) = Cp (11); MeCp (12)). Analogous reactions with 2-methylc yclohexanone, menthone, and nopinone give related addition products wi th varying degrees of diastereoselectivity. The complex 3 also reacts with a series of imines to give complexes of the form CpTi(SCH(CHRNR)C H2CH2S), where the diastereoselectivity observed is a function of the steric demands of the substrate substituents. Reaction of 3 with nitri les, methyl isocyanate, dicyclohexylcarbodiimide, and phenyl thioisocy anate re suits in insertion of the substrate and subsequent enolizatio n to give species of the form CpTi(SC=(C(R)NH)-CH2CH2S). The analogous reaction with phenyl isocyanate yields the bimetallic complex CpTi(SC (PhNCO)CH2CH2S)TiCp(SCH2CH2CH2S) (27). Crystallographic characterizati on of a number of these reaction products is reported. Kinetic studies of the formation of 10 and 12 are consistent with initial formation o f ketone complex adducts and subsequent intra- and intermolecular C-C bond formation reactions. The nature of the products, reaction mechani sms, and reactivity of strained thiatitanacyclopropane rings are discu ssed in the light of EHMO calculations.