Understanding the Formation of N−H Tautomers from α-Substituted Pyridines: Tautomerization of 2-Ethylpyridine Promoted by Osmium

Reaction of [OsH(η2-H2){η2-C,C-κ-N-(CH2CH-o-C5H4N)}(PiPr3)2]BF4 with benzophenone affords [OsH2{κ-C,O−C6H4C(O)Ph}{κ-C-(HNC5H3Et)}(PiPr3)2]BF4 as a result of the orthometalation of the ketone, the hydrogenation of the vinyl substituent of the pyridine, and its subsequent tautomerization. In acetonitrile, the ketone is released and complex [OsH{κ-C-(HNC5H3Et)}(NCCH3)(PiPr3)2]BF4 is formed.