New Titanium Complexes Containing an Amidinate−Imide Supporting Ligand Set: Cyclopentadienyl, Alkyl, Borohydride, Aryloxide, and Amide Derivatives

A range of chloride metathesis reactions of the monomeric titanium N,N ‘-bis(trimethylsilyl)benzamidinato−imido complexes [Ti(NBu t ){(4-C 6 H 4 R)C(NSiMe 3 ) 2 }Cl(py) 2 ] (R = H ( 1 ) or OMe ( 2 )) are described. Thus, reaction of 1 or 2 with LiC 5 H 5 gave the half-sandwich compounds [Ti(NBu t ){(4-C 6 H 4 R)C(NSiMe 3 ) 2 }(η-C 5 H 5 )] (R = H ( 3 ) or OMe ( 4 )). Reaction of 1 with LiCH 2 SiMe 3 or LiCH(SiMe 3 ) 2 gave the 14-electron, first fully characterized group 4 imido−alkyl derivatives [Ti(NBu t ){PhC(NSiMe 3 ) 2 }{CH(R)SiMe 3 }(py)] (R = H ( 5 ) or SiMe 3 ( 6 )). For comparative purposes, the 16-electron half-sandwich imido−alkyl complex [Ti(NBu t )(ηC 5 Me 5 )(CH 2 SiMe 3 )(py)] ( 7 ) was prepared from LiCH 2 SiMe 3 and [Ti(NBu t )(η-C 5 Me 5 )Cl(py)]. Reaction of 1 with LiBH 4 gave the η 3 -borohydride derivative [Ti(NBu t ){PhC(NSiMe 3 ) 2 }(η 3 -BH 4 )(py)] ( 8 ), while treatment of 1 with LiN(SiMe 3 ) 2, LiO-2,6-C 6 H 3 R 2 (R = Me or Bu t ), or LiPhC(NSiMe 3 ) 2 gave the corresponding aryloxide, amide, or bis(benzamidinate) titanium imido complexes [Ti(NBu t ){PhC(NSiMe 3 ) 2 }{N(SiMe 3 ) 2 }(py)] ( 9 ), [Ti(NBu t ){PhC(NSiMe 3 ) 2 }(O-2,6-C 6 H 3 R 2 )(py)] (R = Me ( 10 ) or Bu t ( 11 )), or [Ti(NBu t ){PhC(NSiMe 3 ) 2 } 2 (py)] ( 13 ). Activation parameters for the concerted, restricted rotation of the aryloxide and benzamidinate ligands in 11 are reported and point to a dissociatively activated mechanism. The X-ray structures of 5 and 7 have been determined.