Double C-H activation results in ruthenium complexes of a neutral PCP ligand with a central carbene moiety
Academic Article
Overview
Research
Identity
Additional Document Info
Other
View All
Overview
abstract
Ru complexes of a new neutral PCP pincer ligand containing a central carbene ligand have been prepared (referred to as (P 2C=) for emphasis). The ligand precursor P 2CH 2 can be prepared in good yield in two steps from pyrrole, formaldehyde, and chlorodiisopropylphosphine. The reaction between P 2CH 2 and [(p-cymene)RuCl 2] 2 in the presence of Et 3N cleanly furnishes (P 2C=)RuHCl. The latter possesses a Y-shaped five-coordinate geometry about Ru, as determined in an X-ray diffraction study. Reactions of (P 2C=)RuHCl with a series of potential ligands have been examined. Addition of pyridine, MeCN, or ethylene leads to a simple adduct formation and addition of CO leads to coordination of two CO ligands to Ru with concomitant hydride-to-carbene migration, while addition of PMe 3 gives rise to both types of products. (P 2C=)RuHCl is a moderately active precatalyst for transfer hydrogenation of ketones. Addition of phenylacetylene leads to the insertion of the triple bond into Ru-H to give (P 2C=)Ru(-CPh=CH 2)-Cl. (P 2C=)RuHCl can be converted to (P 2C=)RuCl 2 by action of an iminium chloride reagent. (P 2C=)RuCl 2 adds one molecule of CO with retention of the carbene moiety, even at elevated temperatures. These results demonstrate the potential of (P 2C=) as a robust and electronically distinctive ancillary ligand. 2006 American Chemical Society.
