Reactivity of (Pyridine-Diimine)Fe Alkyl Complexes with Carbon Dioxide

The reaction of CO₂ with (PDI)­FeMe (<b>1</b>), (PDI)­Fe­(Me)­PMe₃ (<b>1-PMe</b>_<b>3</b>) and [(PDI)­FeMe]­[BPh₄] (<b>2</b>, PDI = 2,6-(2,6-^<i>i</i>Pr₂–C₆H₃–NCMe)₂–C₅H₃N) generates (PDI)­Fe­OAc (<b>3</b>), (PDI)­Fe­(OAc)­PMe₃ (<b>3-PMe</b>_<b>3</b>), and [(PDI)­FeOAc]­[BPh₄] (<b>4</b>), respectively. Kinetic data and solvent effects provide evidence that these reactions occur by precoordination of CO₂ to the Fe center regardless of the charge state and thus favor an insertion mechanism for carboxylation. Carboxylation of <b>1-PMe</b>_<b>3</b> requires initial dissociation of PMe₃ to generate <b>1</b>, which reacts with CO₂; <b>1-PMe</b>_<b>3</b> itself does not react directly with CO₂. CO₂ reacts 5 times faster with neutral <b>1</b> than with cationic <b>2</b> (at 0 °C), which is ascribed to the higher nucleophilicity of the Fe–Me group in <b>1</b>

Reactivity of (Pyridine-Diimine)Fe Alkyl Complexes with Carbon Dioxide

The reaction of CO₂ with (PDI)­FeMe (<b>1</b>), (PDI)­Fe­(Me)­PMe₃ (<b>1-PMe</b>_<b>3</b>) and [(PDI)­FeMe]­[BPh₄] (<b>2</b>, PDI = 2,6-(2,6-^<i>i</i>Pr₂–C₆H₃–NCMe)₂–C₅H₃N) generates (PDI)­Fe­OAc (<b>3</b>), (PDI)­Fe­(OAc)­PMe₃ (<b>3-PMe</b>_<b>3</b>), and [(PDI)­FeOAc]­[BPh₄] (<b>4</b>), respectively. Kinetic data and solvent effects provide evidence that these reactions occur by precoordination of CO₂ to the Fe center regardless of the charge state and thus favor an insertion mechanism for carboxylation. Carboxylation of <b>1-PMe</b>_<b>3</b> requires initial dissociation of PMe₃ to generate <b>1</b>, which reacts with CO₂; <b>1-PMe</b>_<b>3</b> itself does not react directly with CO₂. CO₂ reacts 5 times faster with neutral <b>1</b> than with cationic <b>2</b> (at 0 °C), which is ascribed to the higher nucleophilicity of the Fe–Me group in <b>1</b>

<i>cis</i>/<i>trans</i> Isomerization of <i>o</i>‑Phosphino-Arenesulfonate Palladium Methyl Complexes

The <i>cis</i>/<i>trans</i> isomerization of (PO-OMe)­PdMe­(lut) ([PO-OMe]⁻ = 2-{P­(2-OMe-Ph)₂}-4-Me-benzenesulfonate) was studied to model the proposed isomerization in chain propagation in ethylene polymerization by (<i>o</i>-phosphino-arenesulfonate)­PdR­(ethylene) species. Nonequilibrium mixtures of <i>cis-P</i>,<i>C</i>- and <i>trans-P</i>,<i>C</i>-(PO-OMe)­PdMe­(2,6-lutidine) were generated by the reaction of Na­[PO-OMe] and {Pd­(μ-Cl)­Me­(2,6-lutidine)}₂ in CD₂Cl₂ at −25 °C. Kinetic studies revealed lutidine-catalyzed and noncatalyzed isomerization pathways. The lutidine-catalyzed pathway involves five-coordinate (PO-OMe)­PdMe­(lut)₂ intermediates that undergo Berry pseudorotation. Kinetic studies, structure–activity relationships, solvent effects, and density functional theory calculations for the noncatalyzed pathway are most consistent with a mechanism, originally proposed by Nozaki, Morokuma, and co-workers, which proceeds through a five-coordinate transition state with κ³-<i>P</i>,<i>O</i>,<i>O</i> coordination of the [PO]⁻ ligand

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