Diamine Bis(phenolate) M(III) (Y, Ti) Complexes: Synthesis, Structures, and Reactivity

Reactions of titanium and yttrium trichlorides with 1 equiv of the sodium or potassium salts of the diamine bis(phenolate) (H2O2NN)-O-tBu2' (Me2NCH2CH2-(CH2-2-HO-3,5-(C6H2Bu2)-Bu-t)(2)) led to formation of [TiCl((O2NN)-O-tBu2')(L)] (L = THF, 1; py, 2) and [YCl((O2NN)-O-tBu2')(DME)], 3. Reactions of I or 3 with MCH2-(2-NMe2)C6H4 and with M[2-(CH2NMe2)C6H4] (M = Li, K) led to [Ti((O2NN)-O-tBu2')(kappa(2)-(CH2C6H4NMe2))], 5, [Y((O2NN)-O-tBu2')(kappa(2)-(CH2C6H4NMe2))], 6, and [Y((O2NN)-O-tBu2')(kappa(2)-(C6H4CH2NMe2))], 7. [Y((O2NN)-O-tBu2')N(SiMe3)(2)],4, was obtained from 3 and KN(SiMe3)(2), whereas [(Y((O2NN)-O-tBu2')(CHSiMe3))(2)(mu(4)-O)(mu(3)-Li)(2)], 8, formed from reaction of 3 and LiCH2SiMe3. The reaction of 7 with I equiv of CH3CN gave [Y((O2NN)-O-tBu2')(NC(CH3)C6H4CHNMe2)], 10, which displays a chelating ketimide ligand formed by nitrile insertion in the Y-Ph bond. Further reaction with CH3CN led to [Y((O2NN)-O-tBu2')(kappa(2)- (N(H)C(CH3)C(H)C(C6H4CH2NMe2)N(H)], 9, the formation of which involves an imme-enamme tautomerism followed by a second nitrile insertion and 1,3-hydrogen shift. The reaction of I with CH3CN gave [TiCl((O2NN)-O-tBu2')(NCCH3)], which upon heating converts to a new paramagnetic species that is likely a chloride-bridged Ti(III) dimer. The EPR study performed reveals that bis(phenolate) Ti(III) complexes do not promote nitrile coupling reactions by electron transfer. The solid state molecular structures of 1-9 revealed that in all the complexes the bis(phenolate) ligand is coordinated to the metal center by the two oxygen atoms and the two nitrogen atoms with trans phenolate arrangement.