ABSTRACT
Department of Chemistry, San Diego State University, 5500 Campanile Drive,
San Diego, CA 92182-1030
Abstract In our investigations of ligands capable of donating/accepting hydrogen bonds in important catalytic applications, we have found that heterocyclic phosphine ligands, namely 2-pyridyl and 2-imidazolyl phosphines, greatly influence the reactivity of CpRu+ catalysts. This has led to highly efficient anti-Markovnikov hydration of a variety of terminal alkynes, including aryl alkynes and trimethylsilyl alkynes. Enzyme-like rate enhancements of >109 have facilitated experimental and computational mechanistic studies, supporting multipoint cooperativity involving the metal and the heterocyclic phosphine ligands. Introduction Since Bruce’s pioneering work in the area of ruthenium vinylidene chemistry (1), it has been well known that isomerization of a terminal alkyne to a vinylidene on a metal center is not only favorable but also effects a reversal in the reactivity of the carbon atoms. However, hydration catalysis was not possible, because alkyl migration from a proposed acyl intermediate led to an
inactive carbonyl complex. Recently, Wakatsuki et al. developed two catalytic systems based on traditional organometallic approaches, i.e. electronic manipulation of the metal center (2) and use of chelate ligands (3).
