EPR studies of heterocyclic boron compounds

Abstract

EPR STUDIES OF HETEROCYCLIC BORON COMPOUNDS G. R. Eaton* Massachusetts Institute of Technology Cambridge~l Massachusetts 02139 (Received ~ A ~ i l 1972) In spite of their potential utility in elucidating electronic properties, epr measurements involving boron-containing radicals have been limited to triaryl boron anion radicals (i), bipyridine (2), and pyridine (3) stabilized boron radicals, and boron hydride anion radicals (4). The latter are the only radicals for which clear evidence for interaction of more than one boron with the electron spin was reported. In liB NMR studies the liB chemical shift is indicative of the number and type of groups bound to the boron atom (5). It is of interest to determine whether the coupling of boron to the odd electron in radical species is as useful a probe of the electronic environment of the boron atom. If so, the range of studies possible in this area will be greatly expanded. This paper reports an epr study of a heterocyclic boron radical which is a member of a series of considerable potential generality. Preparation of Compounds. The 2,5-dihydroxy-p-benzoquinone ester of diphenylborinic acid (I) was made by published methods (6).