Successive OH and sp3 CH bond activation of ortho-substituted phenols by a ruthenium(0) complex

Ru0 or RuII: A Study on Stabilizing the “Activated” Form of Ru-PNP Complexes with Additional Phosphine Ligands in Alcohol Dehydrogenation and Ester Hydrogenation

“…It is important to note that the alcohol oxidatively adds in a trans disposition to the Ru 0 center of 6 , forming a Ru II complex. − The same 0/2+ oxidation on ruthenium was observed by us with the Ru 0 complex 3 . When 8 and 9 are compared, complex 8 resembles a precursor to 9 , in which the transformation 8 → 9 is only precluded by the tight binding of PMe 3 to the ruthenium center.…”

Carbon−Oxygen and Carbon−Hydrogen Bond Cleavage Reactions of ortho-Substituted Phenols by Ruthenium(II) Complexes

“…Although we have reported facile sp 3 C−H bond cleavage reaction of 2,6-xylenol and 2,6-dimethylbenzenethiol by the 1 /PMe 3 system, , the C−O bond in the methoxy group was cleaved and the methyl group remained as a spectator group to form 2f when 2-methoxy-6-methylphenol was employed as a substrate (Scheme ). The C−O bond in the ester group showed higher reactivity than the methyl or methoxy group (compounds 2g and 2h ).…”

“…We previously reported stoichiometric and catalytic C−H bond cleavage reactions of ortho -substituted phenols, benzenethiols, allylic alcohols, and carboxylic acids assisted by use of chalcogen anchor groups in ruthenium(II) complexes (Scheme ). Herein we report C−O and C−H bond cleavage reactions of ether, ester, or formyl groups in the ortho positions of phenols.…”

Bond activation by low valent ruthenium complexes

“…Treatment of 1/PMe 3 with phenols rapidly resulted in the protonation of the 1,3,5-COT ligand giving a cationic (η 5 -cyclo-octadienyl)ruthenium() complex, 30 (Scheme 15). 54 Chaudret and co-workers also reported protonation of 1 with HBF 4 , 55 where the proton attacks at the ruthenium centre followed by migration of the hydride to the 1,3,5-COT ligand to give (η 5 -cyclo-octadienyl)ruthenium(). Complex 30 would also be formed by a similar mechanism.…”

“…Similar treatment of 1/PMe 3 with 2-allylphenol gave an oxaruthenacycle complex 29, but that with phenol or 2-cresol gave cis-(aryloxo)(hydrido)ruthenium() complex 31. 54 2,6-Disubstitution may provide effective orbital overlap between the C-H bond and the ruthenium centre and the C-H bond in the 2-allyl group may be more susceptible to cleavage in general. Therefore, this system could provide a good probe for discriminating between the competitive sp 3 C-H and sp 2 C-H bond cleavage reactions at ruthenium().…”