Synthesis of tantalum fluoride complexes supported by bis(trimethylsilyl)benzamidinate ligands. X-ray structures of [PhC(NSiMe3)2]2TaF3 and [PhC(NSiMe3)2]2TaFPh2

The reaction of [PhC(NSiMe3)2]Li(TMEDA) with TaF5 yields complex 1, [PhC(NSiMe3)2]2TaF3, in 40% isolated yield. The solid-state structure of 1 shows a pentagonal, bipyramidal coordination geometry. Variable temperature 19F-NMR experiments reveal one singlet at an ambient temperature; decoalescence to two singlets (1:2 integration) is observed at −20°C. Complex 1 reacts with Me2Mg to produce [PhC(NSiMe3)2]2TaMe3 (2). The reaction of 1 with Ph2Mg yields [PhC(NSiMe3)2]2TaF2Ph (3) and [PhC(NSiMe3)2]2TaFPh2 (4). Characterization of 4 by X-ray crystallography shows a ligand arrangement similar to that of 1.