184172-09-6Relevant articles and documents
Synthesis and characterization of the first Niobocene germyl complexes and reactivity of triphenylsilyl-, triphenylgermyl-, and triphenylstannylniobocene derivatives. X-ray molecular structures of d0 Nb(η5-C5H4SiMe3) 2(H)2(EPh3) (E = Ge, Sn)
Antin?olo,Carrillo-Hermosilla,Castel,Fajardo,Ferna?ndez-Baeza,Lanfranchi,Otero,Pellinghelli,Rima,Satge?,Villasen?or
, p. 1523 - 1529 (2008/10/08)
Thermal treatment of Nb(η5-C5H4SiMe3) 2(H)3 (1) with the appropriate organogermanium hydrides (HGeR3) and HSnPh3 gives the corresponding niobocene germyl hydrides Nb(η5-C5H4SiMe3) 2(H)2(GeR3), GeR3=GePh3 (2), GePh2H (3), GeEt3 (4), Ge(C6H13)3 (5), GeiAm3 (iAm = CH2CH2CH(CH3)2) (6), Ge(C6H13)2Cl (7), GeiAm2Cl (8), Ge(C6H13)2H (9), GeiAm2H (10), and Nb(η5-C5H4SiMe3) 2(H)2(SnPh3) (11) in good yields. Spectroscopic data indicate the presence of only one of the two possible structural isomers in which the germyl or stannyl group is in the equatorial plane with a symmetrical structure. Reactivity studies on the series Nb(η5-C5H4SiMe3) 2(H)2(ER3), E = Si (12), Ge (2), Sn (11), were carried out. 12 reacts with H2 to give 1, but 2 and 11 were unreactive toward this reagent. Furthermore, a similar behavior was observed with CO and CN(2,6-Me2C6H3). Thus, 12 reacts with these reagents to give rise, after elimination of HSiPh3, to Nb(η5-C5H4SiMe3) 2(H)(CO) and Nb(η5-C5H4SiMe3) 2-(H)(CN(2,6-Me2C6H3)), respectively, while 2 and 11 do not react. Reactions of 12 with HGePh3 and HSnPh3 and of 2 with HSnPh3 gave σ-bond metathesis products, but no reactions were observed between 2 and HSiPh3 or between 11 and HSiPh3 or 11 and HGePh3. The kinetics of these processes have been studied by 1H NMR spectroscopy and indicated the following reactivity trends Nb-SiPh3 > Nb-GePh3 > Nb-SnPh3 for the different processes considered. The X-ray molecular structures of 2 and 11 were established by diffraction studies The two isostructural complexes show a bent-sandwich coordination with the two hydrides flanking either side of the Nb-Ge and Nb-Sn bonds (2.710(1), 2.830(1) A? in 2 and 11, respectively).
Synthesis and spectroscopic properties of dihydrogen isocyanide niobocene [Nb(η5-C5H4SiMe3)2(η2-H2)(CNR)]+ complexes. Experimental and theoretical study of the blocked rotation of a coordinated dihydrogen
Anti?olo, Antonio,Carrillo-Hermosilla, Fernando,Fajardo, Mariano,Garcia-Yuste, Santiago,Otero, Antonio,Camanyes, Santiago,Maseras, Feliu,Moreno, Miquel,Lledós, Agustí,Lluch, José M.
, p. 6107 - 6114 (2007/10/03)
Synthesis of stable hydride isocyanide derivatives Nb(η5- C5H4SiMe3)2(H)(CNR) has been achieved through the formation of coordinatively unsaturated 16-electron species Nb(η5-C5H4SiMe3)2H by thermolytic loss of H2 followed by the coordination of an isocyanide ligand. Low-temperature protonation with a slight excess of CF3COOH leads to the η2-dihydrogen complexes [Nb(η5-C5H4SiMe3)2(η2-H2)(CNR)]+. NMR spectra of these H-H complexes and their monodeuterated H-D isotopomers present a single high-field resonance at room temperature. By lowering the temperature to 178 K, decoalescence of the signal was observed for the H-D complexes but not for the H-H ones. By combining DFT electronic structure calculations with a monodimensional rotational tunneling model, it has been shown that the absence of decoalescence of the H-H signal is due to the existence of a very large exchange coupling. Conversely, for the H-D isotopomer, the difference in zero point energy corresponding to two nonequivalent (H-D and D-H) positions leads to a slight asymmetry which dramatically reduces the exchange coupling, allowing decoalescence to be observed. Therefore, the H-D classical rotation and the quantum exchange processes will not be practically observed for this complex, whereas only the classical process for the H-H species is quenched out on the NMR time scale.
