Abstract
The synthesis of a series of tungsten(VI) amido alkylidyne complexes containing the chelating ligands Tp (hydridotris(1-pyrazolyl)borate) and Tp′ (hydridotris(3,5-dimethyl-1-pyrazolyl)borate) is described. Complexes of general formula, TpW(CC(CH 3) 3)(Cl)(NHR) [R=C 6H 5, 4-BrC 6H 4, 3,5-(CF 3) 2C 6H 3, H], ( 3– 6), were formed by reaction of TpW(CC(CH 3) 3)(Cl) 2 with the appropriate amide [M][NHR] (M=Li, K). In presence of excess [Li][NHPh], TpW(CC(CH 3) 3)(NHPh) 2 ( 7) was isolated. Sub-stoichiometric quantities of H 2O or HCl were found to catalyze the tautomerization of 3 to the corresponding imido alkylidene. Reaction of excess H 2O with 3 produced significant amounts of TpW(O)(CHC(CH 3) 3)(Cl) ( 10) and TpW(O)(CC(CH 3) 3)(Cl) ( 11) along with tautomerization. Attempted acid catalyzed tautomerizations of 4 and 5 with HCl resulted in loss of the amido ligands and recovery of TpW(CC(CH 3) 3)(Cl) 2. The complex Tp′W(CC(CH 3) 3)(Cl)(NHPh) ( 8), was synthesized by reaction of (CH 3) 3SiN(H)Ph with (DME)W(CC(CH 3) 3)(Cl) 3 followed by addition of KTp′. X-ray crystal structures have been obtained for compounds 7 and 8 and show that the amido groups are syn with respect to the neopentylidyne ligand probably due to the steric demands of the chelating Tp and Tp′ ligands.
Published Version
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