烷基对取代锂氟类硅烯R2SiLiF的构型和热稳定性的影响

利用从头计算法研究了二甲基锂氟类硅烯和二乙基锂氟类硅烯的各异构体的构型和能量.烷基的引入增加了Si的σ电子对Li的授与而降低了F对Si空p轨道的电子回授,使类硅烯的p-络合物构型热稳定性下降,而σ-络合物热稳定性增加.在上述两种作用的共同影响下,三元环构型的热稳定性只有很小的变化.

Effect of Alkyl Group on the Structures and Thermal Stability of Substituted Lithofluro-Silylenoids R2SiLiF

Isomeric structures and energies of dimethyllithoflurosilylenoid and diethyl lithoflurosilylenoid were investigated by using ab initio molecular orbital theory. Alkyl groups increase the donor of σ electrons of silicon to lithium atom and it leads to an increase of the thermal stability of σ-complex. But alkyl groups decrease the donor of π electrons of fluorine atom to silicon, leading to a decrease of the thermal stability of p-complex. However, because of the joint action of that two effect, alkyl groups change little the thermal stability of the three-membered ring.