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Organometallics 2010, 29, 5450–5455 DOI: 10.1021/om100410n
Hydrogenolysis versus Methanolysis of First- and Second-Generation Grubbs Catalysts: Rates, Speciation, and Implications for Tandem Catalysis† Nicholas J. Beach, Kenneth D. Camm,‡ and Deryn E. Fogg* Centre for Catalysis Research and Innovation, Department of Chemistry, University of Ottawa, 10 Marie Curie, Ottawa, Ontario, Canada, K1N 6N5. ‡ Current address: Johnson Matthey Technology Centre, Orchard Road, Royston, Hertfordshire (UK) SG8 5HE. Received May 2, 2010
An unexpected “generation gap” is uncovered between the Grubbs catalysts RuCl2(L)(PCy3)(dCHPh) (1a, L = PCy3; 1b, L = IMes, N,N0 -bis(mesityl)imidazol-2-ylidene) in their reactions with hydrogen versus methanol, in the presence of base. Treatment of the first-generation catalyst 1a with H2 and NEt3 (CH2Cl2, 60 °C, 1000 psi H2) affords RuHCl(H2)(PCy3)2 (2a) in 75% yield within 30 min, as determined by in situ NMR analysis. Complex 2a is in turn efficiently converted (96%; 2 h) into the important hydrogenation catalyst RuHCl(CO)(PCy3)2 (3a) by mild thermolysis with methanol and NEt3 (4:1 CH2Cl2-MeOH, 60 °C), 72% net yield for the 1a-3a transformation. In comparison, subjecting the second-generation catalyst 1b to this two-step process effects
