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)-κ
3
N,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)-κ
3
N,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)-κ
3
N,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.
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