Synthesis and Structural and Reactivity Studies of Thiatitanacyclopropane Complexes [Cp†Ti(SCHCH₂CH₂S)]₂ (Cp† = Cp, MeCp)

The complexes [Cp † Ti(SCHCH 2 CH 2 S)] 2 (Cp † = Cp ( 3 ), MeCp ( 4 )) are readily prepared from reaction of Cp † Ti(SCH 2 CH 2 CH 2 S)Cl (Cp † = Cp ( 1 ), MeCp ( 2 )) with MeLi, AlMe 3, or t -BuLi. Both compounds are centrosymmetric dimers in the solid state containing strained thiatitanacyclopropane rings. PMe 3 cleaves these dimers, establishing equilibria between 3 and 4 and Cp † Ti(SCHCH 2 CH 2 S)(PMe 3 ) (Cp † = Cp ( 5 ), MeCp ( 6 )), while compound 3 undergoes facile acidolysis with HCl, acetic acid, PhSH, and propanedithiol affording CpTiCl 3, CpTi(O 2 CMe) 3 ( 7 ), CpTi(SCH 2 CH 2 CH 2 S)(SPh), and H + [CpTi(SCH 2 CH 2 CH 2 S) 2 ] - ·THF ( 8 ), respectively. The thiametallacycles react with benzophenone to give Cp † Ti(SCH(CPh 2 O)CH 2 CH 2 S) (Cp † = Cp ( 9 ); MeCp ( 10 )) while reaction with cyclohexanone gives the dimeric species [Cp † Ti(SCH(C 6 H 10 O)CH 2 CH 2 S)] 2 (Cp † = Cp ( 11 ); MeCp ( 12 )). Analogous reactions with 2-methylcyclohexanone, menthone, and nopinone give related addition products with varying degrees of diastereoselectivity. The complex 3 also reacts with a series of imines to give complexes of the form CpTi(SCH(CHRNR)CH 2 CH 2 S), where the diastereoselectivity observed is a function of the steric demands of the substrate substituents. Reaction of 3 with nitriles, methyl isocyanate, dicyclohexylcarbodiimide, and phenyl thioisocyanate results in insertion of the substrate and subsequent enolization to give species of the form CpTi(SC=(C(R)NH)CH 2 CH 2 S). The analogous reaction with phenyl isocyanate yields the bimetallic complex CpTi(SC(PhNCO)CH 2 CH 2 S)TiCp(SCH 2 CH 2 CH 2 S) ( 27 ). Crystallographic characterization of a number of these reaction products is reported. Kinetic studies of the formation of 10 and 12 are consistent with initial formation of ketone complex adducts and subsequent intra- and intermolecular C−C bond formation reactions. The nature of the products, reaction mechanisms, and reactivity of strained thiatitanacyclopropane rings are discussed in the light of EHMO calculations.