Group 4 Imido Complexes Stabilized by a Tridentate Diamido-Donor Ligand

Reaction of the lithium amides [(2-C 5 H 4 N)C(CH 3 ){CH 2 N(Li)SiMe 3 } 2 ] 2 ( 2a ) and [(2-C 5 H 4 N)C(CH 3 ){CH 2 N(Li)SiMe 2 t Bu} 2 ] 2 ( 2b ) with the imidotransition metal complexes [Ti(N t Bu)Cl 2 (py) 3 ], [Ti(N-2,6-C 6 H 3 i Pr 2 )Cl 2 (py) 3 ], and [Zr(N-2,6-C 6 H 3 i Pr 2 )Cl 2 (thf) 2 ] yielded the five-coordinate imido-titanium and -zirconium complexes [{κ 3 N -(2-C 5 H 4 N)C(CH 3 )(CH 2 NSiMe 2 R) 2 }Ti(NR‘)(py)] (R = Me, R‘ = t Bu: 3a, R= t Bu, R‘ = t Bu: 3b, R = Me, R‘ = 2,6-C 6 H 3 i Pr 2: 4a, R = Me, R‘ = 2,6-C 6 H 3 Me 2: 4b ) and [{κ 3 N -(2-C 5 H 4 N)C(CH 3 )(CH 2 NSiMe 3 ) 2 }Zr(N-2,6-C 6 H 3 i Pr 2 )(py)] ( 5 ). The tridentate diamido-pyridine ligand adopts a facial coordination mode in the distorted trigonal bipyramidal complexes with the imido ligand occupying an equatorial position, as was established by X-ray diffraction for 3a and 5 . Sublimation of 3a and 4a yielded the pure four-coordinate imidotitanium complexes [{κ 3 N -(2-C 5 H 4 N)C(CH 3 )(CH 2 NSiMe 3 ) 2 }Ti(NR‘)] (R‘ = t Bu: 6, 2,6-C 6 H 3 i Pr 2: 7 ) which were structurally characterized by X-ray crystallography. Reaction of 3a with the Lewis acid B(C 6 F 5 ) 3 also led to abstraction of the axially bound pyridine ligand and the formation of the adduct [py−B(C 6 F 5 ) 3 ] and 6 . Reaction of 6 with thf, PMe 3, and pyridine led to the formation of pentacoordinate complexes [{κ 3 N -(2-C 5 H 4 N)C(CH 3 )(CH 2 NSiMe 3 ) 2 }Ti(N t Bu)(thf)] ( 8 ), [{κ 3 N -(2-C 5 H 4 N)C(CH 3 )(CH 2 NSiMe 3 ) 2 }Ti(N t Bu)(PMe 3 )] ( 9 ), and [{κ 3 N -(2-C 5 H 4 N)C(CH 3 )(CH 2 NSiMe 3 ) 2 }Ti(N t Bu)(py)] ( 3a ) in which the donor ligands occupy axial positions.