Trimethylsilyl imide complexes of tantalum: Can the silyl group be eliminated?

We report the synthesis and structure of a series of tantalum(V) complexes having the trimethylsilylimide moiety and using as ancillary support the pincer ligand PNP (PNP − = N[2-P i Pr 2 -4-methylphenyl] 2 ). Via transmetallation of Li(PNP) with Cl 3 (py) 2 Ta N{SiMe 3 } (py = pyridine), the precursor complex (PNP)Ta N{SiMe 3 }Cl 2 ( 1 ) could be prepared in 94% isolated yield. Attempts to promote FSiMe 3 elimination when 1 was treated with FSnMe 3 resulted in mixtures from which the salt-like product [{(PNP)Ta N{SiMe 3 }} 2 (μ 2 -F) 3 ][Me 3 ClSn(μ 2 -X)SnClMe 3 ] ( 2 ) (X − = F or Cl) was structurally identified. However, conducting the reaction with NaOAr (Ar = 2,6- i Pr 2 C 6 H 3 ) resulted in clean formation to (PNP)Ta N{SiMe 3 }(OAr)Cl ( 3 ) in 79% isolated yield, and when 3 was mixed with FSnMe 3 , the fluoride-imide complex (PNP)Ta N{SiMe 3 }(OAr)F ( 4 ) and ClSnMe 3 were formed cleanly. Attempts to promote FSiMe 3 elimination in 4 thermally and photochemically did not yield the desired nitride (PNP)Ta N(OAr). Complexes 1 – 4 were characterized by single-crystal X-ray diffraction studies and in the case of complexes 1 , 3 and 4 a variety of multinuclear NMR studies are presented and discussed. [ABSTRACT FROM AUTHOR]