184171-83-3Relevant academic research and scientific papers
Studies on the insertion reactions of activated alkynes into Nb-H bonds in hydride-niobocene complexes. X-ray crystal structures of Nb(η5-C5H4SiMe3) 2(H)[η2-RO2C(H)=C(H)CO2R] (R = Me or tBu)
Anti?olo, Antonio,Carrillo-Hermosilla, Fernando,Fajardo, Mariano,García-Yuste, Santiago,Lanfranchi, Maurizio,Otero, Antonio,Pellinghelli, Maria Angela,Prashar, Sanjiv,Villase?or, Elena
, p. 5507 - 5513 (1996)
The hydride isocyanide complexes, Nb(η5-C5H4SiMe3) 2(H)(CNR), R = xylyl = 2,6-dimethylphenyl; Cy (cyclohexyl); tBu; as well as the hydride carbonyl complex Nb(η5-C5H4SiMe3) 2-(H)(CO) react with several activated alkynes to afford the corresponding alkenyl isocyanide complexes Nb(η5-C5H4SiMe3) 2(CNR)(C(R′)=CH(R″)), R = Xylyl, R′ = R″ = CO2Me 1; R = Xylyl, R′ = R″ = CO2tBu 2; R = Xylyl, R′ = CO2Me, R″ = H 3; R = Xylyl, R′ = CO2Me, R″ = Me 4; R = Cy, R′ = R″ = CO2Me 5; R = Cy, R′ = R″ = CO2tBu 6; R = Cy, R′ = CO2Me, R″ = Me 7; R = tBu, R′ = R″ = CO2Me 8; tBu, R′ = R″ = CO2tBu 9 and alkenyl-carbonyl complexes, Nb(η5-C5H4SiMe3) 2(CO)(C(R′)=CH(R″)), R′ = R″ = CO2Me 10; R′ = R″ = CO2tBu 11; R′ = CO2Me, R″ = H 12. The reaction of hydride isocyanide complexes with activated alkynes gives cis-insertion resulting in the formation of (E)-alkenyl products. However, the hydride carbonyl derivative undergoes insertion to give, under kinetic control, a mixture of (E)- and (Z)-alkenyl isomers. Finally, the trihydride niobocene complex Nb(η5-C5H4-SiMe3) 2(H)3, reacts with esters RO2CC≡CCO2R′ or MeO2CC≡CH to give the hydride olefin derivatives, Nb(η5-C5H4SiMe3) 2(H)[η2-RO2C(H)=C(H)CO 2R′], R = R′ = Me 13; R = R′ = tBu 14; and Nb(η5-C5H4SiMe3) 2(H)[η2-MeO2C(H)=CH2] 15, probably as the result of a stereospecific trans-insertion. The different complexes have been characterized by spectroscopic methods. In addition, the structure of 13 and 14 were determined by single crystal X-ray diffraction.
