Diverse catalytic activity of the cationic actinide complex [(Et2N)3U][BPh4] in the dimerization and hydrosilylation of terminal alkynes. Characterization of the first f-element alkyne π-complex [(Et2N)2U(CCtBu)(η2-HCCtBu)][BPh4]
作者:Aswini K. Dash、Jia Xi Wang、Jean Claude Berthet、Michel Ephritikhine、Moris S. Eisen
DOI:10.1016/s0022-328x(00)00207-2
日期:2000.6
double hydrosilylated alkene, in which the two silicon moieties are connected at the same carbon atom, is obtained. The catalytic hydrosilylation of (TMS)CCH and PhSiH3 with [(Et2N)3U][BPh4] was found to proceed only at higher temperatures. Mechanistically, the key intermediate seems to be the uranium–hydride complex [(Et2N)2UH][BPh4], as evidenced by the lack of the dehydrogenative coupling of silanes
阳离子act系元素络合物[(Et 2 N)3 U] [BPh 4 ]是用于末端炔烃选择性二聚的活性催化前体。区域选择性主要针对双链二聚体,但是对于大的炔烃取代基,也获得了出乎意料的顺式-二聚体。机制研究表明,在催化循环中的第一步骤是的乙炔化物络合物的形成[(ET 2 N)2 UC CR] [BPH 4 ]用Et的伴随可逆消除2 NH,其次是炔的形成π络合物[(ET 2 N)2 UC CR(RCCH)] [BPh 4 ]。后者的络合物(R =t Bu)已通过光谱表征。动力学速率定律在有机act系中是一阶的,并且表现出作为炔烃浓度的函数的两个域行为。在低炔烃浓度下,反应遵循反序,而在高炔烃浓度下,观察到零序。限制营业额的步骤是将末端炔烃的CC键插入the系元素乙炔键中,得到相应的烯基配合物,其ΔH ‡ = 15.6(3)kcal mol -1和ΔS ‡= -11.4(6)欧盟