220767-38-4Relevant articles and documents
Amido-imido niobium complexes with chloro-silyl-and amino-silyl-functionalized cyclopentadienyl ligands
Alcalde, M. Isabel,Gómez-Sal, M. Pilar,Royo, Pascual
, p. 546 - 554 (1999)
The chloro-imido complex [Nb(η5-C5H4-SiMe2Cl)(CH 2Ph)Cl(NtBu)] undergoes selective substitution of the Nb-Cl bond when it is reacted with LiNHtBu, giving [Nb(η5-C5H4-SiMe2-Cl)(CH 2Ph)(NHtBu)(NtBu)], whereas preferential reaction at the Si-Cl bond occurs with NH2tBu, giving [Nb(η5-C5H4-SiMe2(NH tBu)}(CH2Ph)Cl(NtBu)], which is then transformed into [Nb{η5-C5H4-SiMe2(NH tBu)}(CH2Ph)(NHtBu)(NtBu)] on further reaction with NH2tBu. Chemical reactivity studies demonstrate that a spontaneous transformation of [Nb(η5-C5H4-SiMe2Cl)(CH 2Ph)(NHtBu)(NtBu)] into [Nb{η5-C5H4-SiMe2(NH tBu)}(CH2Ph)Cl(NtBu)] takes place, via an intermolecular reaction, by attack of the silicon-bonded chlorine at the unsaturated niobium center. Benzylation of [Nb{η5-C5H4-SiMe2(NH tBu)}(CH2Ph)Cl(NtBu)] with Mg(CH2Ph)2·2THF gives [Nb{η5-C5H4-SiMe2(NH tBu)}(CH2Ph)2(NtBu)], which also results from reaction of the chloro-silyl derivative [Nb(η5-C5H4-SiMe2Cl)(CH 2Ph)2(NtBu)] with NH2tBu. The dichloro-imido complex [Nb(η5-C5H4-SiMe2Cl)Cl 2(NtBu)], readily obtained from [Nb(η5-C5H4-SiMe2Cl)Cl 4], also reacts preferentially at the Si-Cl bond when treated with NH2tBu to give [Nb{η5-C5H4-SiMe2(NH tBu)}Cl2(NtBu)], which is further transformed into [Nb{η5-C5H4-SiMe2(NH tBu)}Cl(NHtBu)(NtBu)]; the latter is alternatively prepared by reaction of [Nb(η5-C5H4-SiMe2Cl)Cl 4] with a large excess of NH2tBu. The tetrachloro compound reacts with excess LiNHtBu to give the constrained-geometry complex [Nb{η5-C5H4-SiMe2(η 1-NtBu)}(NHtBu)(NtBu)], which is converted into the chloro-niobium derivative by reaction with SiMe3Cl. These constrained-geometry complexes may also be obtained from the dichloro derivative [Nb(η5-C5H4-SiMe2Cl)Cl 2(NtBu)], by reaction with 3 or 2 equiv of LiNHtBu, respectively. Thermal treatment of the benzyl compounds [Nb{η5-C5H4-SiMe2(NH tBu)}(CH2-Ph)X(NtBu)] (X = Cl, CH2Ph) at 160°C results in formation of the silyl-amido complexes [Nb{η5-C5H4-SiMe2(η 1-NtBu)}X(NtBu)] (X = Cl, CH2Ph) with elimination of toluene, whereas a similar transformation of the related iminoacyl complex [Nb{η5-C5H4-SiMe2(NH tBu)}{η2-[C(CH2Ph){N(2,6-Me 2C6H3)}](CH2Ph)(NtBu)] produces a simultaneous isomerization to give the vinylamido compound [Nb{η5-C5H4-SiMe2(η 1-NtBu)}{N(CH=CHPh)(2,6-Me2C6H 3)}(Nt-Bu)]. Insertion of CN(2,6-Me2C6H3) into the niobium-benzyl bonds of complexes [Nb{η5-C5H4-SiMe2(NH tBu)}(CH2Ph)X(NtBu)] (X = Cl, CH2Ph) and [Nb{η5-C5H4-SiMe2(η 1-NtBu)}-(CH2Ph)(NtBu)] leads to the iminoacyl compounds [Nb{η5-C5H4-SiMe2(NH tBu)}{η2-[C(CH2Ph)-{N(2,6-Me 2C6H3)}]}X(NtBu)] (X = Cl, CH2Ph) and [Nb{η5-C5H4-SiMe2(η 1-NtBu)}{η2-[C(CH 2-Ph){N(2,6-Me2C6H3)}]}(N tBu)], respectively. All of the reported new compounds were characterized by elemental analyses and 1H and 13C NMR spectroscopy, and the X-ray molecular structure of [Nb{η5-C5H4-SiMe2(NH tBu)}Cl2(NtBu)] was studied by diffraction methods.
