Group 4 imido complexes stabilized by a tridentate diamido-donor ligand

Reaction of the lithium amides [(2-C5H4N)C(CH3){CH2N(Li)SiMe3}(2)](2) (2a) and [(2-C5H4N)C(CH3){CH2N(Li)-SiMe(2)tBu}(2)](2) (2b) with the imidotransit ion metal complexes [Ti(NtBu)Cl-2(py)(3)], [Ti(N-2,6-C(6)H(3)iPr(2))Cl-2(py )(3)], and [Zr(N-2,6-C(6)H(3)iPr(2))Cl-2(thf)(2)] yielded the five-coordina te imido-titanium and -zirconium complexes [{kappa N-3-(2-C5H4N)C(CH3)(CH2N SiMe2R)(2)}Ti(NR')(py)] (R = Me, R' = tBu: 3a, R = tBu, R' = tBu: 3b, R = M e, R' = 2,6-C(6)H(3)iPr(2): 4a, R = Me, R' = 2,6-C6H3Me2: 4b) and [(kappa N -3-(2-C5H4N)C(CH3)(CH2NSiMe3)(2)}Zr(N-2,6-C(6)H(3)iPr(2))(py)] (5). The tri dentate diamido-pyridine ligand adopts a facial coordination mode in the di storted trigonal bipyramidal complexes with the imido ligand occupying an e quatorial position, as was established by X-ray diffraction for 3a and 5. S ublimation of 3a and 4a yielded the pure four-coordinate imidotitanium comp lexes [{kappa N-3-(2-C5H4N)C(CH3)(CH2NSiMe3)(2)}Ti(NR')] (R' = tBu: 6, 2,6- C(6)H(3)iPr(2): 7) which were structurally characterized by X-ray crystallo graphy. Reaction of 3a with the Lewis acid B(C6F5)(3) also led to abstracti on of the axially bound pyridine ligand and the formation of the adduct [py -B(C6F5)(3)] and 6. Reaction of 6 with thf, PMe3, and pyridine led to the f ormation of pentacoordinate complexes [{kappa N-3-(2-C5H4N)C(CH3)(CH2NSiMe3 )(2)}-Ti(NtBu)(thf)] (8), [{kappa N-3-(2-C5H4N)C(CH3)(CH2NSiMe3)(2)}Ti(NtBu )(PMe3)] (9), and [{kappa N-3-(2-C5H4N)C(CH3)(CH2-NSiMe3)(2)}Ti(NtBu)(py)] (3a) in which the donor ligands occupy axial positions.