ic300390s_si_001.pdf (1.65 MB)
B–H Bond Activation Using an Electrophilic Metal Complex: Insights into the Reaction Pathway
journal contribution
posted on 2013-01-07, 00:00 authored by Rahul Kumar, Balaji R. JagirdarA highly electrophilic ruthenium center in the [RuCl(dppe)2][OTf] complex brings about the activation of the B–H
bond in ammonia borane (H3N·BH3, AB) and
dimethylamine borane (Me2HN·BH3, DMAB).
At room temperature, the reaction between [RuCl(dppe)2][OTf]
and AB or DMAB results in trans-[RuH(η2-H2)(dppe)2][OTf], trans-[RuCl(η2-H2)(dppe)2][OTf],
and trans-[RuH(Cl)(dppe)2], as noted in
the NMR spectra. Mixing the ruthenium complex and AB or DMAB at low
temperature (198/193 K) followed by NMR spectral measurements as the
reaction mixture was warmed up to room temperature allowed the observation
of various species formed enroute to the final products that were
obtained at room temperature. On the basis of the variable-temperature
multinuclear NMR spectroscopic studies of these two reactions, the
mechanistic insights for B–H bond activation were obtained.
In both cases, the reaction proceeds via an η1-B–H
moiety bound to the metal center. The detailed mechanistic pathways
of these two reactions as studied by NMR spectroscopy are described.