Catalytic thermal and photo-induced CH and CC activation reactions of alkanes with ansa amido functionalized half-sandwich complexes and methylalumoxane

摘要

In the literature most of the dehydrogenation reactions of alkanes are described as CH activation reactions of cyclooctane.The best results of CH activation reactions have been found for the reaction of MAO activated metallocene complexes and cyclooctane at temperatures over 300 degrees C.The application of ansa amido functionalized half sandwich compounds of the type Ind'Si(Me)2Nt-BuMCl(Ind'=monosubstituted indenyl);M=Ti,Zr,Hf)for CH and CC activation reactions is completely unknown in the literature. In contrast to the dehydrogenation reactions of cyclooctane and the metallocene complexes of the group 4metals,where the zirconocene complexes give higher TONs than the titanocene complexes the ansa amido functionalized titanium complexes give more than two times higher TONs than the corresponding Zr or Hfcomplexes.The ansa amido functionalized ligand increases the TONs for the Ticomplexes and decreases the TONs of the Zr complexes.In contrasttothemetallocene complexes, the ansa amido functionalized dichloride complexes of Ti show also a higher activity than the corresponding Zr complexes.It is known that the photolysis of organometallic titanium,zirconium and hafnium(IV)compounds can give M(III)radicals. The formation of the active Ti metal centre is easier than in the case of the corresponding Zr and Hf metal compounds.