Cyclometalated Tantalum Diphenolate Pincer Complexes: Intramolecular C−H/M−CH_3σ-Bond Metathesis May Be Faster than O−H/M−CH_3 Protonolysis
A diphenol linked at the ortho positions to a benzene ring was metalated with TaCl_2(CH_3)_3. Deuterium labeling of the phenol hydrogens and of the linking 1,3-benzenediyl ring reveals an unexpected mechanism involving protonolysis of a methyl group, followed by C−H/Ta−CH_3 σ-bond metathesis, leading to cyclometalation of the linking ring and finally protonation of the cyclometalated group by the pendant phenol.
Additional Information© 2007 American Chemical Society. Received 23 March 2007. Published online 3 May 2007. Published in print 1 June 2007. We thank Dr. Michael W. Day and Lawrence M. Henling (Caltech) for assistance with single-crystal X-ray crystallographic studies. We are grateful to the USDOE Office of Basic Energy Sciences (Grant No. DE-FG03-85ER13431) for financial support.
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