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Monocyclopentadienylhydride Derivatives of Ruthenium:  Stereoselective Proton Transfer and Proton-Hydride Exchange in an Extremely Short Dihydrogen Bond

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posted on 09.06.2004, 00:00 by Ester Cayuela, Félix A. Jalón, Blanca R. Manzano, Gustavo Espino, Walter Weissensteiner, Kurt Mereiter
Diastereomerically pure complexes of formula CpRuCl(PP*) and CpRuH(PP*) with chiral ferrocenyl diphosphines were prepared and the selectivity of proton-transfer processes over the monohydride compounds with different acids was studied. With 1 equiv of HBF4 the cis-dihydrogen and trans-dihydride complexes were formed while with 3 equiv of CF3CO2H the trans-dihydride derivative was the only product. However, the use of 1 equiv of CF3CO2H led to a dihydrogen bonded complex with an extremely short RuH···HO2CF3 interaction that exhibits proton-hydride exchange. Using the labeled acid CF3CO2D, a stereoselective transference of the deuteron was demonstrated that implies the previous epimerization of the monohydride and the subsequent attack of the acid in the position previously occupied by the hydride.