Ruthenium Tris(pyrazolyl)borate Complexes, 12 Cross Coupling of Acetylenes with Olefins - Formation of (eta)3Butadienyl and (eta)2-Butadiene Complexes via a Metallacyclobutane Intermediate

Cationic rhodium complexes catalyze the amination of 2- and 4-vinylpyridine with secondary amines. Depending on the substrate and the reaction conditions either oxidative amination to yield the corresponding enamines 1a-8a or hydroamination to give 2-aminoethylpyridines 1b-8b occurs. In all cases products with anti-Markovnikov regioselectivity are obtained. For mechanistic studies novel cationic complexes of rhodium(I)-containing cyclooctadiene and vinylpyridine 12 as well as complexes containing cyclooctadiene, vinylpyridine, and morpholine 13 were prepared and characterized by NMR spectroscopy and X-ray diffraction analysis.