REACTIONS OF TITANIUM IMIDO COMPLEXES WITH ALPHA-DIIMINES - COMPLEXATION VERSUS TI=N C=N BOND METATHESIS/

The reactions of the titanium imido complexes [Ti(NR)Cl-2(py)(3)] (R = Bu-t I, C6H3M2-2,6 2 or C6H3Pr2i-2,6 3) with alpha-diimines (1,4-diaz a-1,3-butadienes) of the type ArNC(R')C(R')NAr (Ar = phenyl or substit uted phenyl, R' = H or methyl) are reported. The reaction products and metal complex stability are critically dependent on the nature of bot h the imido N- and diimine N- and backbone C-substituents, Reaction of 3 with PhNC(Me)C(Me)NPh gave the crystallographically characterised a dduct [Ti(NC6H3Pr2i-2,6)Cl-2 {eta(2)-PhNC(Me)C(Me)NPh} (py)] 4 which p osseses mutually trans Cl ligands and has one diimine nitrogen atom ci s and one trans to the arylimido group. The compound 4 is the first cr ystallographically characterised titanium complex to have a formally n eutral(le. non-reduced) alpha-diimine ligand and decomposes fairly qui ckly in solution at room temperature. H-1 NMR evidence only is present ed for the formation of the tert-butyl- and 2,6-dimethylphenyl-imido h omologues of 4, namely [Ti(NR)Cl-2{eta(2)-ArNC(Me)C(Me)NAr}(py)] (R = Bu-t or C6H3Me2-2,6; Ar = Ph or tolyl, Tol): these compounds are consi derably less stable in solution, rapidly decomposing to a number of pr oducts including the corresponding amines RNH2 and [Ti(NR)Cl-2(py)(n)] (n = 2 or 3). Reaction of 1 with alpha-diimines of the type ArNC(H)C( H)NAr (Ar = Tol or 2,6-C6H3Me2), i.e. without methyl substituents in t he backbone, do not give detectable adducts analogous to 4. In these c ases titanium imide/organic imine metathesis occurs to form [Ti(NAr)Cl -2(py)(n)] (n = 2 or 3) and (BuNC)-N-t(H)C(H)NAr and/or (BuNC)-N-t(H)C (H)NBut.