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Synthesis, Characterization, and Reactivity of Niobium and Tantalum Complexes Bearing Metal-Nitrogen Bonds. X-ray Molecular Structure of [Nb(C5H4SiMe3){NH(CH2su
文摘
The reaction of the cyclopentadienyl- silyl-amido titanium compound [Ti{ G SRC="/images/gifchars/eta.gif" BORDER=0 >5-C5H4SiMe2- ges/gifchars/eta.gif" BORDER=0 >-N(CH2)2-ges/gifchars/eta.gif" BORDER=0 >-NH2}Cl2] with group 5 metal monocyclopentadienyl complexes [MCpRCl4] (M = Nb, Ta; CpR = C5H4SiMe3 (Cp'), C5Me5 (Cp*)) afforded the heterobimetallic complexes [TiCl2{ges/gifchars/eta.gif" BORDER=0 >5-C5H4SiMe2-ges/gifchars/eta.gif" BORDER=0 >-N(CH2)2-ges/gifchars/kappa.gif" BORDER=0 >-NH2}MCpRCl4] (M = Nb, CpR = Cp', 2a; Cp*, 2b; M = Ta, CpR = Cp', 3a; Cp = Cp*, 3b). Compounds2 evolve at room temperature to give a three-component mixture, the chlorosilyl-substituted cyclopentadienyl titanium compound [Ti(ges/gifchars/eta.gif" BORDER=0 >5-C5H4SiMe2Cl)Cl3], the corresponding mononuclear amido-amino,[NbCpR{NH(CH2)2-ges/gifchars/eta.gif" BORDER=0 >-NH2}Cl3] (CpR = Cp', 4a; Cp*, 4b), and the dinuclear imido niobium complexes[{NbCpRCl2}2(ges/entities/mgr.gif">-N(CH2)2-ges/gifchars/eta.gif" BORDER=0 >-N)] (CpR = Cp', 5a; Cp*, 5b). In contrast, the analogue tantalum complexesthermally degraded, when CpR = Cp' at normal temperature, whereas when CpR = Cp* at temperatureshigher than 50 ges/entities/deg.gif">C, they gave a unique tantalum complex, the corresponding mononuclear amido-aminoderivative [TaCpR{NH(CH2)2-ges/gifchars/eta.gif" BORDER=0 >-NH2}Cl3] (CpR = Cp', 6a; Cp*, 6b). Alternatively, these group 5complexes were prepared by direct reaction of the monocyclopentadienyl derivatives with the correspondingorganic diamine, in the appropriate proportion and reaction conditions. Tantalum amino adducts wereobserved as intermediate species in the course of such reactions, and even the dinuclear derivative[{TaCp*Cl4}2(ges/entities/mgr.gif">-NH2(CH2)2NH2)] (8) could be isolated. Hydrolysis of the dinuclear imido complex 5ayielded the tricyclic tetranuclear niobium oxo derivative [{NbCp'Cl(ges/entities/mgr.gif">2-O)}4(Cl)2(ges/entities/mgr.gif">3-O)] (9), which displaysan asymmetrical structure as a consequence of the triply connected oxygen site. These compounds werecharacterized by elemental analysis and NMR spectroscopy, and the crystal structures of 4a and 9 weredetermined by X-ray diffraction methods. | |
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