Thermochemistry and Molecular Structure of a Remarkable Agostic Interaction in a Heterobifunctional Ruthenium−Boron Complex

摘要

Hydrocarbon functionalization is an important reaction class innorganic synthesis and has a central role in applications ranging fromnutilization of hydrocarbon feedstocks to fine-chemical synthesis.n1nIn this area, our group is developing ligand metal bifunctionalncatalysts that manipulate hydrides. Our general approach to C Hnfunctionalization involves cooperative effects between a transitionnmetal and a ligand-centered coordination-directing element. Thisnis analogous to hydrogen-bond-directed oxidation catalysts suchnas Noyori’s (Ts-DPEN)(cym)RuCl systemsn2nand the cyclopenta-ndienone-ligated systems from Shvo3nand Casey4n(Figure 1A), exceptnthat a Lewis acid directing group such as boron (Figure 1B) doesnnot require a protic functionality in the substrate. In this com-nmunication, we report the synthesis, X-ray structure, and uniquenthermochemistry of an unusually strong C H agostic methyl bridgenbetween boron and ruthenium (Figure 1C). This agostic complexnhas structural homology to a potential transition state for boron-ndirected C H cleavage (Figure 1B).