(CO)_5MnSiR_3与R'_3SiH的光化学硅烷基交换反应研究

Study on the Photochemical Silyl Exchange Reactions of (CO)_5MnSiR_3 with R'_3SiH

五羰基锰硅烷基配合物(CO)5MnSiR3(3)[SiR3=SiMe2Ph(3b),SiMePh2(3c),SiPh3(3d),SiHPh2(3e),SiEt3(3f)和SiMe2Et(3h)]与不同氢硅烷R'3SiH在5℃光解1 h,这两个物种间的硅烷基交换达到平衡.适中的产物与反应物自由能变化间隔使得这些反应实质上可逆.光催化经由不饱和物种(CO)4MnSiR3(1)和过渡中间体(CO)4MnH(SiR3)(SiR'3)(4)进行.物种3作为通过光活化前催化剂的可行性得到确认.受电子效应和位阻效应的影响,含有体积较大且推电子基团(如乙基)的硅烷基更容易被含有体积较小且吸纳电子基团(如负氢)的硅烷基从五羰基锰硅烷基配合物中置换出来.

Silyl manganese pentacarbonyls（CO）5MnSiR3 [SiR3=SiMe2Ph（3b）,SiMePh2（3c）,SiPh3（3d）,SiHPh2（3e）,SiEt3（3f）,and SiMe2Et（3h）] were photolyzed with different hydrosilanes R＇3SiH at 5 ℃ for 1 h,and the equilibrium of the silyl exchange between the two species was established.Moderate free energy gap between the products and reactants makes these reactions essentially reversible.The photocatalysis was preceded via an unsaturated species（CO）4MnSiR3（1）,and a transitional intermediate（CO）4MnH（SiR3）-（SiR＇3）（4）.Feasibility of species 3 as a precatalyst activated via photolysis was confirmed.Due to both elec-tronic and steric factors,the silyls bearing bulkier and more electrons repelling groups（like ethyl） were more readily to be replaced by that bearing smaller and electron accommodating groups（like hydride） from silyl manganese pentacarbonyls.