STUDIES DEALING WITH TITANIUM COMPLEXES CONTAINING STERICALLY DEMANDING 2,6-DI-ALKYL ARYLOXIDES AS LIGANDS: SYNTHESIS, STRUCTURE AND REACTIVITY (METALLATION, INSERTION, ORGANOMETALLIC, C-H BOND ACTIVATION)
Abstract
The reaction of lithium-2,6-di-t-butylphenoxide (LiOAr') with TiCl(,3)(NMe(,3))(,2) yields the complex Ti(OAr')(,3)(OAr' = 2,6-di-t-butylphenoxide). The spectroscopic (EPR and UV-vis) properties and reactivity of this molecule are discussed. LiOAr' reacts with TiX(,4) (X-Cl, Br) to yield Ti(OAr')(,2)X(,2) (X = Br, Cl). The electrochemical and solution properties of these molecules are discussed. The less sterically demanding phenol 2,6-di-i-propylphenol (HOAr") reacts with Ti(CH(,2)SiMe(,3))(,4) form the complex Ti(OAr")(,4) (OAr" = 2,6-di-i-propylphenoxide), which has been structurally characterized. By oxidation of Ti(OAr')(,3) with CX(,4) (X = Cl, Br) or I(,2), complexes of the type Ti(OAr')(,3)X (X = Cl, Br, I) have been formed in high yields as crystalline solids. The structural aspects of the monoiodide, and the solution fluxionality of all these molecules have been studied in great detail. The reaction of HOAr* (OAr* = 2,6-di-i-propyl- or 2,6-di-t-butylphenoxide) with Ti(Bz)(,4)(Bz = CH(,2)C(,6)H(,5)) leads to the formation of Ti(OAr*)(,2)(Bz)(,2). The thermolysis of Ti(OAr')(,2)(Bz)(,2)(OAr' = 2,6-di-t-butylphenoxide) leads to the formation of Ti(OAr)(OC(,6)H(,3)('t)BuCMe(,2)CH(,2))(Bz). Thermolysis of mixtures of Ti(CH(,2)SiMe(,3))(,4) and HOAr' leads to the formation of Ti(OAr')(OC(,6)H(,3)('t)BuCMe(,2)CH(,2))(CH(,2)SiMe(,3)), analogous to the previous product. The bonding aspects of the six membered cyclometallated ring were ascertained by the determination of the crystal structure of Ti(OAr')(OC(,6)H(,3)('t)BuCMe(,2)CH(,2))(CH(,2)SiMe(,3))(py), (py = pyridine). Addition of another equivalent of the phenolic reagent HOAr' to the cyclometallated complexes from above results in the formation of Ti(OAr)(,2)(OC(,6)H(,3)('t)BuCMe(,2)CH(,2)). The reaction of Ti(OAr'')(,2)(Bz)(,2) with one equivalent of ('t)-butylisocyanide (('t)BuNC) leads to the formation of a monoimino acyl complex, Ti(OAr'')(,2)(C(N('t)Bu)Bz)(Bz). The reaction of TI(OAr'')(,2)(CH(,2)C(,6)H(,5))(,2) with 2 eq. of 2,6-dimethylphenyl isocyanide (xyNC) leads to the formation of Ti(OAr'')(,2)(C(Nxy)CH(,2)C(,6)H(,5))(,2). The reaction of Ti(OAr'')(,2)(C(N('t)Bu)(Bz)(Bz) with 1 eq. of 2,6-dimethylphenylisocyanide (xyCN) leads to the formation of the mixed bisiminoacyl, Ti(OAr'')(,2)(C(N('t)Bu)Bz)(C(Nxy)Bz). Thermolysis of Ti(OAr'')(,2)(C(Nxy)Bz)(,2) leads to the formation of the cis coupled product Ti(OAr'')(,2)(N(xy)C(Bz=C(Bz)N(xy)). The reaction of Ti(OAr')(OC(,6)H(,3)('t)BuCMe(,2)CH(,2))(CH(,2)SiMe(,3)) with 2 eq. of xyNC leads to the formation of the trans coupled product, Ti(OAr') CH(SiMe(,3))C(NHxy)=CN(xy) (OC(,6)H(,3)('t)BuCMe(,2)CH(,2)), which has been structurally characterized.
Degree
Ph.D.
Subject Area
Chemistry
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