290357-00-5Relevant academic research and scientific papers
New studies on the reactivity of hydride-containing niobocene complexes towards insertion and protonation processes
Antinolo, Antonio,Carrillo-Hermosilla, Fernando,Fernandez-Baeza, Juan,Garcia-Yuste, Santiago,Otero, Antonio,Sanchez-Prada, Javier,Villasenor, Elena
, p. 1437 - 1443 (2000)
The trihydride complex [Nb(η5-C5H4SiMe3)2(H)3] (1) reacts with diphenylphosphane to afford the monohydride [Nb(η5- C5H4SiMe3)2(H)(PHPh2)] (3). The synthesis of complex 3 has also been achieved from the initial formation of the phosphonium salt [Nb(η5- C5H4SiMe3)2(H)2(PHPh2)]Cl (2) by reaction of the trihydride complex [Nb(η5-C5H4SiMe3)2(H)3] (1) with chlorodiphenylphosphane, followed by deprotonation of this salt in aqueous NaOH. Protonation of complex 3 at low temperature with a slight excess of CF3COOH or CF3COOD leads to the η2- dihydrogen complex [Nb(η5-C5H4SiMe3)2(η2-H2)(PHPh2)]CF3CO2 (4) or its monodeuterated isotopomer [Nb(η5-C5H4SiMe3)2(η2- HD)(PHPh2)]CF3CO2 (5). When the temperature is increased to room temperature, complexes 4 and 5 transform into the transoid dihydrides [Nb(η5-C5H4SiMe3)2(H)2(PHPh2)]CF3CO2 (6) and [Nb(η5- C5H4SiMe3)2(H)2(PDPh2)]CF3CO2 (7), respectively. Complex 3 undergoes an insertion of CS2 into the niobium-hydrogen bond to give the η1- dithioformato complex [Nb(η5-C5H4SiMe3)2(PHPh2)(η1-S-S(S)CH)] (8). This complex could be detected by NMR spectroscopy but could not be isolated due to rapid conversion into the η2-dithioformato complex [Nb(η5- C5H4SiMe3)2(η2-S,S-SSCH)] (9) by loss of the phosphane molecule. Complex 3 also reacts with CO2 to give the η2-formato complex [Nb(η5- C5H4SiMe3)2(η2-O,O-OOCH)](10); in this case the η1-formato complex could not be detected. The reagent ClPPh2 very smoothly inserts into the Nb- H bond of the complexes [Nb(n5-C5H4SiMe3)2(H)(L)] [L = PHPh2, CN(xylyl), CO; xylyl = 2,6-dimethylphenyl], yielding the new ionic complexes [Nb(η5-C5H4SiMe3)2(PHPh2)(L)]C1 [L = PHPh2 (11), CN(xylyl) (12), CO (13)]. All the complexes described have been characterized by analytical and spectroscopic methods.
