7 research outputs found
Selective reduction of CO<sub>2</sub> to a methanol equivalent by B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>-activated alkaline earth catalysis
Treatment of β-diketiminato Mg and Ca amidoborane compounds with B(C6F5)3 induces hydride elimination and formation of alkaline earth hydrido-tris(pentafluorophenyl)borate derivatives. Both species react with CO2 to provide formate complexes, one of which has been structurally characterised, and may be applied to the highly selective reductive hydroboration of CO2 with pinacolborane (HBpin) to provide the methanol equivalent, CH3OBpin
Activation of N-heterocyclic carbenes by {BeH<sub>2</sub>} and {Be(H)(Me)} fragments
A stable three-coordinate dimethylberyllium
species coordinated
by the 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) ligand
is readily converted to the corresponding methylhydrido derivative
through metathetical reaction with phenylsilane. Attempts to synthesize
the corresponding molecular dihydrides are, however, unsuccessful
and result in ring opening of an IMes ligand through hydride transfer
to the donor carbon atom and the consequent formation of a heterocyclic
beryllium organoamide. In agreement with previous calculations, we
suggest that this process occurs via a Schlenk-type equilibration
process and formation of a four-coordinate bis-NHC beryllium dihydride.
These species are not observed, however, as the steric pressure exerted
by coordination of the two sterically demanding IMes ligands is sufficient
to induce hydride transfer. The latter deduction is supported by the
observation that a similar ring-opened product, but derived from methyl
and hydride transfer, is available through the introduction of a further
equivalent of IMes to the isolated beryllium methyl hydride species.
In the latter case the ring-opening process is more facile, which
we ascribe to the increased steric pressure achieved upon the formation
of four-coordinate beryllium. In a further striking reaction under
more forcing thermal conditions, the carbene carbon center of an IMes
ligand is observed to be completely eliminated with selective formation
of a three-coordinate diamidoberyllium species