Diphenylboron complexes of the enol tautomers of arylpyruvic acids. Crystal and molecular structure of triethylammonium (2-nitrophenyl)pyruvato-diphenylboron(1-)
Synthesis has been carried out of 15 examples of anionic diphenylboron complexes of arylpyruvic acids, and the structures of the compounds have been determined from spectroscopic data and from X-ray analysis of one of the compounds. Crystals of5j are monoclinic, P21/n,a = 9.5566(10), b = 15.961(3), c = 16.6382(6) Å, beta = 99.3239(10)°, and Z = 4, at 180 K. The structure was solved by direct methods and refined by full-matrix least-squares procedures to R(F2) = 0.056 for 6662 CCD data. 5j contains a triethylammonium cation and an anion containing a planar five-membered OBOCC ring, with cation and anion linked by an N-H···O hydrogen bond. Spectroscopic data and bond distances establish that the pyruvate ligand is the enol-tautomeric state.