Synthesis and Structure of (Triphenylsilyl)imido Complexes of Titanium and Zirconium

Titanium and zirconium (triphenylsilyl)imido complexes are available through transimination from the tert -butylimido complexes with H 2 NSiPh 3 . The useful starting material Ti(NSiPh 3 )Cl 2 (py) 2 ( 1 ) is prepared in 88% yield by treatment of Ti(NBu t )Cl 2 (py) 3 with H 2 NSiPh 3 . Imido 1 is a dimer in the solid state with bridging chlorides; however, solution molecular weight studies indicate that 1 is a monomer in CH 2 Cl 2 . 1 reacts with 4,4‘-di- tert -butyl-2,2‘-bipyridine (bpy) to generate the pseudo-octahedral Ti(NSiPh 3 )(bpy)(py)Cl 2 ( 2 ) in 74% recrystallized yield. Replacement of the chloride ligands of 1 with 2 equiv of Lidap, 1 equiv of Libap, or 1 equiv of Lipap afforded the pyrrolylimido complexes Ti(NSiPh 3 )(dap) 2 ( 3 ), Ti(NSiPh 3 )(bap)Cl ( 4 ), and Ti(NSiPh 3 )(pap)Cl ( 5 ), respectively. The reaction of 2 equiv of neophyl (Nph) magnesium bromide with 1 provided [Ti(μ-NSiPh 3 )(Nph) 2 ] 2 ( 6 ) in 59% yield. The pseudo-octahedral complex Ti(NSiPh 3 )(dpma)(bpy) ( 8 ) was available through addition of Li 2 dpma to 1, forming Ti(NSiPh 3 )(dpma)(py) 2 ( 7 ) followed by treatment with bpy. Alternatively, 8 was prepared by addition of bpy and H 2 NSiPh 3 to Ti(NMe 2 ) 2 (dpma). The zirconium tert -butylimido complex Zr(NBu t )(dpma)(bpy) ( 9 ) was available in 43% yield by treatment of Zr(NMe 2 ) 2 (py)(dpma) with bpy and H 2 NBu t . Transimination on 9 with H 2 NSiPh 3 provided the (triphenylsilyl)imido complex Zr(NSiPh 3 )(dpma)(bpy) ( 10 ) in 34% yield. In an unusual transformation, 10 reacts with excess sodium 2,6-dimethylphenoxide in THF to afford [Na(bpy)][Zr(dpma)(OAr) 3 ] ( 11 ), where the Na coordinates to the bpy and both pyrrole rings of the dpma in an η 5 fashion. Compounds 1, 5, 6, 8, and 11 were structurally characterized.