12 research outputs found
Alkaline Earth Catalyzed CO<sub>2</sub> Hydroboration into Acetal Derivatives Leading to C–S Bond Formation
The use of Mg and Ca hydride catalysts for the 4e– reduction of CO2 is reported. Borabicyclo[3.3.1]nonane
(9-BBN) and dicyclohexylborane (HBCy2), as reductants,
led to the generation of the corresponding bis(boryl)acetal (BBA)
which in situ reacted with thiol to afford new borylated hemithioacetal
compounds (R2BOCH2SR) under mild neutral conditions.
These hemithioacetals were then converted into dithioacetal (RSCH2SR) with the addition of a second equivalent of thiol under
acidic activation, or amino-methyl sulfide (RSCH2NR2) upon reaction with secondary amine
Ruthenium-Catalyzed Reduction of Carbon Dioxide to Formaldehyde
Functionalization of CO<sub>2</sub> is a challenging goal and precedents
exist for the generation of HCOOH, CO, CH<sub>3</sub>OH, and CH<sub>4</sub> in mild conditions. In this series, CH<sub>2</sub>O, a very
reactive molecule, remains an elementary C<sub>1</sub> building block
to be observed. Herein we report the direct observation of free formaldehyde
from the borane reduction of CO<sub>2</sub> catalyzed by a polyhydride
ruthenium complex. Guided by mechanistic studies, we disclose the
selective trapping of formaldehyde by in situ condensation with a
primary amine into the corresponding imine in very mild conditions.
Subsequent hydrolysis into amine and a formalin solution demonstrates
for the first time that CO<sub>2</sub> can be used as a C<sub>1</sub> feedstock to produce formaldehyde
Comparative Reactivity of Zr– and Pd–Alkyl Complexes with Carbon Dioxide
Structure/reactivity
trends and DFT studies reveal mechanistic
differences and parallels for the carboxylation of Zr and Pd alkyls.
CO<sub>2</sub> reacts with Cp<sub>2</sub>ZrMe(C<sub>6</sub>D<sub>5</sub>Cl)<sup>+</sup> >10<sup>4</sup> faster than with Cp<sub>2</sub>ZrMe<sub>2</sub>, yielding monoacetate products in both cases. These
reactions
proceed by insertion mechanisms in which Zr- - -O interactions
activate the CO<sub>2</sub>. In contrast, CO<sub>2</sub> reacts readily
with [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> (PO-<sup>i</sup>Pr<sup>–</sup> = 2-P<sup>i</sup>Pr<sub>2</sub>-4-Me-C<sub>6</sub>H<sub>3</sub>SO<sub>3</sub><sup>–</sup>) to yield [(PO-<sup>i</sup>Pr)PdMe(OAc)]<sup>−</sup> but not with (PO-<sup>i</sup>Pr)PdMe(L) species. Carboxylation of [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> occurs by direct S<sub>E</sub>2 attack
of CO<sub>2</sub> at the Pd–Me<sub><i>trans</i>‑to‑P</sub> group, and the nucleophilicity of the Pd–Me group controls
the reactivity. However, the S<sub>E</sub>2 process is accelerated
by a Li<sup>+</sup>- - -OCO interaction when Li<sup>+</sup> is present
Comparative Reactivity of Zr– and Pd–Alkyl Complexes with Carbon Dioxide
Structure/reactivity
trends and DFT studies reveal mechanistic
differences and parallels for the carboxylation of Zr and Pd alkyls.
CO<sub>2</sub> reacts with Cp<sub>2</sub>ZrMe(C<sub>6</sub>D<sub>5</sub>Cl)<sup>+</sup> >10<sup>4</sup> faster than with Cp<sub>2</sub>ZrMe<sub>2</sub>, yielding monoacetate products in both cases. These
reactions
proceed by insertion mechanisms in which Zr- - -O interactions
activate the CO<sub>2</sub>. In contrast, CO<sub>2</sub> reacts readily
with [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> (PO-<sup>i</sup>Pr<sup>–</sup> = 2-P<sup>i</sup>Pr<sub>2</sub>-4-Me-C<sub>6</sub>H<sub>3</sub>SO<sub>3</sub><sup>–</sup>) to yield [(PO-<sup>i</sup>Pr)PdMe(OAc)]<sup>−</sup> but not with (PO-<sup>i</sup>Pr)PdMe(L) species. Carboxylation of [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> occurs by direct S<sub>E</sub>2 attack
of CO<sub>2</sub> at the Pd–Me<sub><i>trans</i>‑to‑P</sub> group, and the nucleophilicity of the Pd–Me group controls
the reactivity. However, the S<sub>E</sub>2 process is accelerated
by a Li<sup>+</sup>- - -OCO interaction when Li<sup>+</sup> is present
Comparative Reactivity of Zr– and Pd–Alkyl Complexes with Carbon Dioxide
Structure/reactivity
trends and DFT studies reveal mechanistic
differences and parallels for the carboxylation of Zr and Pd alkyls.
CO<sub>2</sub> reacts with Cp<sub>2</sub>ZrMe(C<sub>6</sub>D<sub>5</sub>Cl)<sup>+</sup> >10<sup>4</sup> faster than with Cp<sub>2</sub>ZrMe<sub>2</sub>, yielding monoacetate products in both cases. These
reactions
proceed by insertion mechanisms in which Zr- - -O interactions
activate the CO<sub>2</sub>. In contrast, CO<sub>2</sub> reacts readily
with [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> (PO-<sup>i</sup>Pr<sup>–</sup> = 2-P<sup>i</sup>Pr<sub>2</sub>-4-Me-C<sub>6</sub>H<sub>3</sub>SO<sub>3</sub><sup>–</sup>) to yield [(PO-<sup>i</sup>Pr)PdMe(OAc)]<sup>−</sup> but not with (PO-<sup>i</sup>Pr)PdMe(L) species. Carboxylation of [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> occurs by direct S<sub>E</sub>2 attack
of CO<sub>2</sub> at the Pd–Me<sub><i>trans</i>‑to‑P</sub> group, and the nucleophilicity of the Pd–Me group controls
the reactivity. However, the S<sub>E</sub>2 process is accelerated
by a Li<sup>+</sup>- - -OCO interaction when Li<sup>+</sup> is present
Comparative Reactivity of Zr– and Pd–Alkyl Complexes with Carbon Dioxide
Structure/reactivity
trends and DFT studies reveal mechanistic
differences and parallels for the carboxylation of Zr and Pd alkyls.
CO<sub>2</sub> reacts with Cp<sub>2</sub>ZrMe(C<sub>6</sub>D<sub>5</sub>Cl)<sup>+</sup> >10<sup>4</sup> faster than with Cp<sub>2</sub>ZrMe<sub>2</sub>, yielding monoacetate products in both cases. These
reactions
proceed by insertion mechanisms in which Zr- - -O interactions
activate the CO<sub>2</sub>. In contrast, CO<sub>2</sub> reacts readily
with [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> (PO-<sup>i</sup>Pr<sup>–</sup> = 2-P<sup>i</sup>Pr<sub>2</sub>-4-Me-C<sub>6</sub>H<sub>3</sub>SO<sub>3</sub><sup>–</sup>) to yield [(PO-<sup>i</sup>Pr)PdMe(OAc)]<sup>−</sup> but not with (PO-<sup>i</sup>Pr)PdMe(L) species. Carboxylation of [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> occurs by direct S<sub>E</sub>2 attack
of CO<sub>2</sub> at the Pd–Me<sub><i>trans</i>‑to‑P</sub> group, and the nucleophilicity of the Pd–Me group controls
the reactivity. However, the S<sub>E</sub>2 process is accelerated
by a Li<sup>+</sup>- - -OCO interaction when Li<sup>+</sup> is present
Comparative Reactivity of Zr– and Pd–Alkyl Complexes with Carbon Dioxide
Structure/reactivity
trends and DFT studies reveal mechanistic
differences and parallels for the carboxylation of Zr and Pd alkyls.
CO<sub>2</sub> reacts with Cp<sub>2</sub>ZrMe(C<sub>6</sub>D<sub>5</sub>Cl)<sup>+</sup> >10<sup>4</sup> faster than with Cp<sub>2</sub>ZrMe<sub>2</sub>, yielding monoacetate products in both cases. These
reactions
proceed by insertion mechanisms in which Zr- - -O interactions
activate the CO<sub>2</sub>. In contrast, CO<sub>2</sub> reacts readily
with [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> (PO-<sup>i</sup>Pr<sup>–</sup> = 2-P<sup>i</sup>Pr<sub>2</sub>-4-Me-C<sub>6</sub>H<sub>3</sub>SO<sub>3</sub><sup>–</sup>) to yield [(PO-<sup>i</sup>Pr)PdMe(OAc)]<sup>−</sup> but not with (PO-<sup>i</sup>Pr)PdMe(L) species. Carboxylation of [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> occurs by direct S<sub>E</sub>2 attack
of CO<sub>2</sub> at the Pd–Me<sub><i>trans</i>‑to‑P</sub> group, and the nucleophilicity of the Pd–Me group controls
the reactivity. However, the S<sub>E</sub>2 process is accelerated
by a Li<sup>+</sup>- - -OCO interaction when Li<sup>+</sup> is present
Comparative Reactivity of Zr– and Pd–Alkyl Complexes with Carbon Dioxide
Structure/reactivity
trends and DFT studies reveal mechanistic
differences and parallels for the carboxylation of Zr and Pd alkyls.
CO<sub>2</sub> reacts with Cp<sub>2</sub>ZrMe(C<sub>6</sub>D<sub>5</sub>Cl)<sup>+</sup> >10<sup>4</sup> faster than with Cp<sub>2</sub>ZrMe<sub>2</sub>, yielding monoacetate products in both cases. These
reactions
proceed by insertion mechanisms in which Zr- - -O interactions
activate the CO<sub>2</sub>. In contrast, CO<sub>2</sub> reacts readily
with [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> (PO-<sup>i</sup>Pr<sup>–</sup> = 2-P<sup>i</sup>Pr<sub>2</sub>-4-Me-C<sub>6</sub>H<sub>3</sub>SO<sub>3</sub><sup>–</sup>) to yield [(PO-<sup>i</sup>Pr)PdMe(OAc)]<sup>−</sup> but not with (PO-<sup>i</sup>Pr)PdMe(L) species. Carboxylation of [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> occurs by direct S<sub>E</sub>2 attack
of CO<sub>2</sub> at the Pd–Me<sub><i>trans</i>‑to‑P</sub> group, and the nucleophilicity of the Pd–Me group controls
the reactivity. However, the S<sub>E</sub>2 process is accelerated
by a Li<sup>+</sup>- - -OCO interaction when Li<sup>+</sup> is present
Comparative Reactivity of Zr– and Pd–Alkyl Complexes with Carbon Dioxide
Structure/reactivity
trends and DFT studies reveal mechanistic
differences and parallels for the carboxylation of Zr and Pd alkyls.
CO<sub>2</sub> reacts with Cp<sub>2</sub>ZrMe(C<sub>6</sub>D<sub>5</sub>Cl)<sup>+</sup> >10<sup>4</sup> faster than with Cp<sub>2</sub>ZrMe<sub>2</sub>, yielding monoacetate products in both cases. These
reactions
proceed by insertion mechanisms in which Zr- - -O interactions
activate the CO<sub>2</sub>. In contrast, CO<sub>2</sub> reacts readily
with [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> (PO-<sup>i</sup>Pr<sup>–</sup> = 2-P<sup>i</sup>Pr<sub>2</sub>-4-Me-C<sub>6</sub>H<sub>3</sub>SO<sub>3</sub><sup>–</sup>) to yield [(PO-<sup>i</sup>Pr)PdMe(OAc)]<sup>−</sup> but not with (PO-<sup>i</sup>Pr)PdMe(L) species. Carboxylation of [(PO-<sup>i</sup>Pr)PdMe<sub>2</sub>]<sup>−</sup> occurs by direct S<sub>E</sub>2 attack
of CO<sub>2</sub> at the Pd–Me<sub><i>trans</i>‑to‑P</sub> group, and the nucleophilicity of the Pd–Me group controls
the reactivity. However, the S<sub>E</sub>2 process is accelerated
by a Li<sup>+</sup>- - -OCO interaction when Li<sup>+</sup> is present
Phosphino-Boryl-Naphthalenes: Geometrically Enforced, Yet Lewis Acid Responsive P → B Interactions
Three
naphthyl-bridged phosphine-borane derivatives <b>2</b>-BCy<sub>2</sub>, <b>2</b>-BMes<sub>2</sub>, and <b>2</b>-BFlu,
differing in the steric and electronic properties of the boryl moiety,
have been prepared and characterized by spectroscopic and crystallographic
means. The presence and magnitude of the P → B interactions
have been assessed experimentally and theoretically. The naphthyl
linker was found to enforce the P → B interaction despite steric
shielding, while retaining enough flexibility to respond to the Lewis
acidity of boron