Chlorosilyl-Substituted Monocyclopentadienyl Niobium Chloro, Imido Chloro, and Benzyl Complexes. X-ray Molecular Structure of [{(NbCl2)2(μ-O)(μ-Cl)2}{(η5-C5H4)2(Me2SiOSiMe2)}

Abstract

We report the synthesis of 1-(chloromethylphenylsilyl)cyclopentadiene. The reaction of a toluene/CH2Cl2 suspension of NbCl5 with 1-(SiClMeX)-1-(SiMe3)C5H4 (X = Me, Ph) leads to the monocyclopentadienyl derivatives [M{η5-C5H4(SiClMeX)}Cl4] (X = Me, Ph) in 90 and 78% yields, respectively. Reaction of 1 equiv of water with [M{η5-C5H4(SiClMe2)}Cl4] in toluene takes place with elimination of HCl, resulting in formation of the dinuclear niobium oxo derivative [{(NbCl2)2(μ-O)(μ-Cl)2}{(η5-C5H4)2(Me2SiOSiMe2)}]. Reaction of the complexes [M{η5-C5H4(SiClMeX)}Cl4] with LiNHtBu and NEt3 in toluene leads to the half-sandwich imido complexes [Nb{η5-C5H4(SiClMeX)}Cl2(NtBu)] (X = Me, Ph), which react at room temperature with 1 equiv of Mg(CH2Ph)2(THF)2 to give the imido dibenzyl complexes [Nb{η5-C5H4(SiClMeX)}(CH2Ph)2(NtBu)] (X = Me, Ph). The reaction of the chloro imido complexes [Nb{η5-C5H4(SiClMeX)}Cl2(NtBu)] with excess Mg(CH2Ph)2(THF)2 on heating for 2−3 days to 80−90 and 50−60 °C, respectively, takes place, affording the totally alkylated complexes [Nb{η5-C5H4[Si(CH2Ph)MeX]}(CH2Ph)2(NtBu)] (X = Me, Ph). The chloro benzyl derivative [Nb{η5-C5H4(SiClMe2)}(CH2Ph)Cl(NtBu)], which could not be prepared by addition of the stoichiometric amount of the alkylating agent, was isolated in quantitative yield by heating a mixture of the dichloro and dibenzyl complexes in toluene at 120 °C for 4 h. The 18-electron imido η2-iminoacyl derivatives [Nb{(η5-C5H4(SiMeXY)}R(NtBu){η2-C(CH2Ph)N(2,6-Me2C6H3)}] (R = CH2Ph, X = Cl, Y = Me, Ph; R = CH2Ph, X = CH2Ph, Y = Me, Ph; R = Cl, X = Cl, Y = Me) are formed when the isocyanide CN(2,6-Me2C6H3) is added to a hexane solution of the benzylimido complexes. The molecular structure of the oxo complex [{(NbCl2)2(μ-O)(μ-Cl)2}{(η5-C5H4)2(Me2SiOSiMe2)}] has been determined by X-ray diffraction methods.