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)}]

We report the synthesis of 1-(chloromethylphenylsilyl)cyclopentadie. The reaction of a toluene/CH2Cl2 suspension of NbCl5 with 1-(SiClMeX)-1-(SiMe3)C5H4 (X = Me, Ph) leads to the monocyclopentadienyl derivatives [M{eta(5)-C5H4(SiClMeX)}Cl-4] (X = Me, Ph) in 90 and 78% yields, respectively. Reaction of 1 equiv of water with [M(eta(5)-C5H4(SiClMe2))Cl-4] in toluene takes place with elimination of HCl, resulting in formation of the dinuclear niobium oxo derivative [((NbCl2)(2)(mu-O)(mu-Cl)(2))((eta(5)-C5H4)(2)(Me2SiOSiMe2)}]. Reaction of the complexes [M{eta(5)-C5H4(SiClMeX))Cl-4] with (LiNHBu)-Bu-t and NEt3 in toluene leads to the half-sandwich imido complexes [Nb{eta(5)-C5H4(siClMeX))Cl-2((NBu)-Bu-t)] (X = Me, Ph), which react at room temperature with 1 equiv of Mg(CH2Ph)(2)(THF)(2) to give the imido dibenzyl complexes [Nb{eta(5)-C5H4(siClMeX))(CH2Ph)(2)((NBu)-Bu-t)] (X = Me, Ph). The reaction of the chloro imido complexes [Nb{eta(5)-C5H4(SiClMeX))Cl-2((NBu)-Bu-t)] with excess Mg(CH2Ph)(2)(THF)(2) on heating for 2-3 days to 80-90 and 50-60 degrees C, respectively, takes place, affording the totally alkylated complexes [Nb{eta(5)-C5H4[si(CH2Ph)MeX])(CH2Ph)(2)((NBu)-Bu-t) (X = Me, Ph). The chloro benzyl derivative [Nb{eta(5)-C5H4(SiClMe2))(CH2Ph)Cl((NBu)-Bu-t)], 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 degrees C for 4 h. The 18-electron imido eta(2)-iminoacyl derivatives [Nb{(eta(5)-C5H4(SiMeXY))R((NBu)-Bu-t){eta(2)-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)(mu-O)(mu-Cl)(2)){(eta(5)-C5H4)(2)(Me2SiOSiMe2)}] has been determined by X-ray diffraction methods.