Alkylation and Arylation of Dichloro [N,N'-ethylenebis(salicylideneiminato)]titanium(IV)

The alkylation of [Ti(salen)Cl2] 1 [salen = N,N′-ethylenebis(salicylideneiminate)] using LiMe in toluene gave the first octahedral trans-dimethyltitanium(IV) derivative, [Ti(salen)Me2] 2. Complex 2 is thermally labile and a thermally induced methyl migration to the ligand salen was observed in solution. The isolation of a compound derived from an aryl migration to the ligand was achieved in the reaction of MgBr(mes) (mes = 2,4,6-Me3C6H2) with 1 leading to [Ti(L)(mes)] 3, containing the mesityl group bonded to the metal, and the second one attached to the carbon of the imino group of salen. The alkylation reaction is greatly affected by the solvent. When alkylation or arylation of 1 is carried out in tetrahydrofuran (thf) with MgXR (R = Ph or mes) reductive arylation of 1 occurs with the isolation of the corresponding titanium(III) derivatives [Ti(salen)R(thf)] (R = Ph 4 or mes 5). Crystallographic details: complex 2, orthorhombic, space group P212121, a = 22.795(2), b = 14.734(1), c = 6.849(1) Å, Z = 4, and R = 0.047 for 882 independent observed reflections; 3, monoclinic, space group P21/n, a = 12.804(1), b = 26.566(3), c = 10.014(1) Å, β = 95.27(1)°, Z = 4, and R = 0.057 for 3625 observed reflections; 4, orthorhombic, space group P212121, a = 18.455(2), b = 14.633(2), c = 13.172(2) Å, Z = 4, and R = 0.118 for 1524 observed reflections.