The reaction of the complexes [Ti(η5- C5H3R′SiMe2Cl)Cl3] (R′ = H, SiMe3 ) with the terpenoid preligand C7H6Me3(OH)(NCH2CH2NH2) affords the stereospecific synthesis of the constrained-geometry chiral titanium complexes [Ti{(η5-C5H3R′SiMe2N(CH2)2NC7H6Me3O)- κ3N,N′,O}Cl] (R′ = H, 1; R′ = SiMe3 2), bearing a new cyclopentadienyl-terpenoid ligand derived from α-pinene. The corresponding alkyl derivatives [Ti{(η5-C5H4SiMe2N- (CH2)2NC7H6Me3O)-κ3N,N′,O}R] (R = Me, 4; R = nBu, 5) have been prepared by treatment with suitable alkylating reagents. The reactivity of the methyl complex 4 with different protonic reagents such as alcohols and thiols proceeds via protonation of the amido nitrogen to stereospecifically give the corresponding strain-free alkoxide- and thiolate-methyl compounds [Ti{(η5- C5H4SiMe2NH(CH2)2NC7H6Me3O)-κO}Me(XR)] (X = O, R = iPr, 6; X = S, R = Et, 7; R = p-MeC6H4, 8). The reversibility of this protonation reaction is observed in the case of the thiolate compounds, which are thermically converted, via methane release, into the corresponding constrained-geometry thiolate derivatives [Ti{(η5-C5H4SiMe2N(CH2)2NC7H6Me3O)-κ3N,N′,O}(SR)] (R = Et, 9; R = C6H4-p-Me, 10). However, the analogous alkoxide-methyl compound 6 does not undergo a similar transformation. To gain further insights into the results reached in the reactions of 4 with alcohols and thiols and to understand the different behavior of the strain-free alkoxide- and thiolate-methyl complexes with regard to the thermal decomposition, calculations using DFT methods have been performed.

Ministerio de Ciencia, Innovacion y Universidades (project RTI2018−094840−B-C31) and Universidad de Alcalá (project UAH-AE-2017−2)

11 pags., 6 figs., 6 schs.