ELECTRONIC CONTROL OF REGIOSELECTIVITY IN COUPLING REACTIONS OF SIME3-SUBSTITUTED ALKENES WITH CP2ZR(ETA-2(N,C2)-6-PHENYLPYRIDYL)(THF)+

The reaction of [Cp2Zr(η2(N,C2)-6-phenyl-pyridyl)(THF)] [BPh4] (1) with allyltrimethylsilane proceeds via 1,2-insertion to afford [Cp2Zr(η2(C,N)-CH2CH-(CH2SiMe3)(6-phenylpyrid-2-yl))] [BPh4] (2), in which the CH2SiMe3 substituent is placed at the β-carbon. In contrast, the reaction of 1 with vinyltrimethylsilane proceeds via 2,1-insertion to afford [Cp2Zr(η2(C,N)-CH(SiMe3)CH2-(6-phenylpyrid-2-yl))] [BPh4] (4), in which the SiMe3 substituent is located on the α-carbon. These results are rationalized on the basis of electronic effects originating from the SiMe3 group that dominate the steric effects and control the coupling/insertion regiochemistry in these systems. © 1990, American Chemical Society. All rights reserved.