Web Release Date: May 3,
Cyclometalated Tantalum Diphenolate Pincer Complexes:
Intramolecular C-H/M-CH3 
-Bond Metathesis May Be Faster
than O-H/M-CH3 Protonolysis
Arnold and Mabel Beckman Laboratories of Chemical Synthesis, California Institute of Technology, Pasadena, California 91125
Received March 23, 2007
Abstract:
A diphenol linked at the ortho positions to a benzene
ring was metalated with TaCl2(CH3)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-CH3 -bond metathesis,
leading to cyclometalation of the linking ring and finally
protonation of the cyclometalated group by the pendant phenol.
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