Alkaline Earth Catalyzed CO₂ 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 CO₂ is a challenging goal and precedents exist for the generation of HCOOH, CO, CH₃OH, and CH₄ in mild conditions. In this series, CH₂O, a very reactive molecule, remains an elementary C₁ building block to be observed. Herein we report the direct observation of free formaldehyde from the borane reduction of CO₂ 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 CO₂ can be used as a C₁ 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. CO₂ reacts with Cp₂ZrMe­(C₆D₅Cl)⁺ >10⁴ faster than with Cp₂ZrMe₂, yielding monoacetate products in both cases. These reactions proceed by insertion mechanisms in which Zr- - -O interactions activate the CO₂. In contrast, CO₂ reacts readily with [(PO-ⁱPr)­PdMe₂]⁻ (PO-ⁱPr^– = 2-PⁱPr₂-4-Me-C₆H₃SO₃^–) to yield [(PO-ⁱPr)­PdMe­(OAc)]⁻ but not with (PO-ⁱPr)­PdMe­(L) species. Carboxylation of [(PO-ⁱPr)­PdMe₂]⁻ occurs by direct S_E2 attack of CO₂ at the Pd–Me_{<i>trans</i>‑to‑P} group, and the nucleophilicity of the Pd–Me group controls the reactivity. However, the S_E2 process is accelerated by a Li⁺- - -OCO interaction when Li⁺ 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. CO₂ reacts with Cp₂ZrMe­(C₆D₅Cl)⁺ >10⁴ faster than with Cp₂ZrMe₂, yielding monoacetate products in both cases. These reactions proceed by insertion mechanisms in which Zr- - -O interactions activate the CO₂. In contrast, CO₂ reacts readily with [(PO-ⁱPr)­PdMe₂]⁻ (PO-ⁱPr^– = 2-PⁱPr₂-4-Me-C₆H₃SO₃^–) to yield [(PO-ⁱPr)­PdMe­(OAc)]⁻ but not with (PO-ⁱPr)­PdMe­(L) species. Carboxylation of [(PO-ⁱPr)­PdMe₂]⁻ occurs by direct S_E2 attack of CO₂ at the Pd–Me_{<i>trans</i>‑to‑P} group, and the nucleophilicity of the Pd–Me group controls the reactivity. However, the S_E2 process is accelerated by a Li⁺- - -OCO interaction when Li⁺ 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. CO₂ reacts with Cp₂ZrMe­(C₆D₅Cl)⁺ >10⁴ faster than with Cp₂ZrMe₂, yielding monoacetate products in both cases. These reactions proceed by insertion mechanisms in which Zr- - -O interactions activate the CO₂. In contrast, CO₂ reacts readily with [(PO-ⁱPr)­PdMe₂]⁻ (PO-ⁱPr^– = 2-PⁱPr₂-4-Me-C₆H₃SO₃^–) to yield [(PO-ⁱPr)­PdMe­(OAc)]⁻ but not with (PO-ⁱPr)­PdMe­(L) species. Carboxylation of [(PO-ⁱPr)­PdMe₂]⁻ occurs by direct S_E2 attack of CO₂ at the Pd–Me_{<i>trans</i>‑to‑P} group, and the nucleophilicity of the Pd–Me group controls the reactivity. However, the S_E2 process is accelerated by a Li⁺- - -OCO interaction when Li⁺ 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. CO₂ reacts with Cp₂ZrMe­(C₆D₅Cl)⁺ >10⁴ faster than with Cp₂ZrMe₂, yielding monoacetate products in both cases. These reactions proceed by insertion mechanisms in which Zr- - -O interactions activate the CO₂. In contrast, CO₂ reacts readily with [(PO-ⁱPr)­PdMe₂]⁻ (PO-ⁱPr^– = 2-PⁱPr₂-4-Me-C₆H₃SO₃^–) to yield [(PO-ⁱPr)­PdMe­(OAc)]⁻ but not with (PO-ⁱPr)­PdMe­(L) species. Carboxylation of [(PO-ⁱPr)­PdMe₂]⁻ occurs by direct S_E2 attack of CO₂ at the Pd–Me_{<i>trans</i>‑to‑P} group, and the nucleophilicity of the Pd–Me group controls the reactivity. However, the S_E2 process is accelerated by a Li⁺- - -OCO interaction when Li⁺ 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. CO₂ reacts with Cp₂ZrMe­(C₆D₅Cl)⁺ >10⁴ faster than with Cp₂ZrMe₂, yielding monoacetate products in both cases. These reactions proceed by insertion mechanisms in which Zr- - -O interactions activate the CO₂. In contrast, CO₂ reacts readily with [(PO-ⁱPr)­PdMe₂]⁻ (PO-ⁱPr^– = 2-PⁱPr₂-4-Me-C₆H₃SO₃^–) to yield [(PO-ⁱPr)­PdMe­(OAc)]⁻ but not with (PO-ⁱPr)­PdMe­(L) species. Carboxylation of [(PO-ⁱPr)­PdMe₂]⁻ occurs by direct S_E2 attack of CO₂ at the Pd–Me_{<i>trans</i>‑to‑P} group, and the nucleophilicity of the Pd–Me group controls the reactivity. However, the S_E2 process is accelerated by a Li⁺- - -OCO interaction when Li⁺ 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. CO₂ reacts with Cp₂ZrMe­(C₆D₅Cl)⁺ >10⁴ faster than with Cp₂ZrMe₂, yielding monoacetate products in both cases. These reactions proceed by insertion mechanisms in which Zr- - -O interactions activate the CO₂. In contrast, CO₂ reacts readily with [(PO-ⁱPr)­PdMe₂]⁻ (PO-ⁱPr^– = 2-PⁱPr₂-4-Me-C₆H₃SO₃^–) to yield [(PO-ⁱPr)­PdMe­(OAc)]⁻ but not with (PO-ⁱPr)­PdMe­(L) species. Carboxylation of [(PO-ⁱPr)­PdMe₂]⁻ occurs by direct S_E2 attack of CO₂ at the Pd–Me_{<i>trans</i>‑to‑P} group, and the nucleophilicity of the Pd–Me group controls the reactivity. However, the S_E2 process is accelerated by a Li⁺- - -OCO interaction when Li⁺ 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. CO₂ reacts with Cp₂ZrMe­(C₆D₅Cl)⁺ >10⁴ faster than with Cp₂ZrMe₂, yielding monoacetate products in both cases. These reactions proceed by insertion mechanisms in which Zr- - -O interactions activate the CO₂. In contrast, CO₂ reacts readily with [(PO-ⁱPr)­PdMe₂]⁻ (PO-ⁱPr^– = 2-PⁱPr₂-4-Me-C₆H₃SO₃^–) to yield [(PO-ⁱPr)­PdMe­(OAc)]⁻ but not with (PO-ⁱPr)­PdMe­(L) species. Carboxylation of [(PO-ⁱPr)­PdMe₂]⁻ occurs by direct S_E2 attack of CO₂ at the Pd–Me_{<i>trans</i>‑to‑P} group, and the nucleophilicity of the Pd–Me group controls the reactivity. However, the S_E2 process is accelerated by a Li⁺- - -OCO interaction when Li⁺ is present

Phosphino-Boryl-Naphthalenes: Geometrically Enforced, Yet Lewis Acid Responsive P → B Interactions

Three naphthyl-bridged phosphine-borane derivatives <b>2</b>-BCy₂, <b>2</b>-BMes₂, 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