An Iron‐Hydrogen Bond Resistant to Protonation and Oxidation

Collett, Joel D.; Ransohoff, Rebecca W.; Krause, Jeanette A.; Guan, Huashi

doi:10.1002/zaac.202100066

Cited by 3 publications

(3 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This was further supported by variable-temperature NMR experiments (in toluene- d 8 ) showing two well-resolved hydride resonances upon cooling to −10 °C (as triplets of doublets of doublets) and a coalescence of the two resonances upon warming to ∼50 °C. Our previous studies of pincer-supported iron(II) hydride complexes indicate that the two resonances could be assigned based on the correlation of the chemical shift value with the trans ligand . We thus attribute the resonance at −9.76 ppm to the hydride trans to CO and the resonance at −14.01 ppm to the hydride trans to the central phosphorus.…”

Section: Resultsmentioning

confidence: 99%

Iron Dihydride Complex Stabilized by an All-Phosphorus-Based Pincer Ligand and Carbon Monoxide

2022

Self Cite

View full text Add to dashboard Cite

PNP-pincer-stabilized iron carbonyl dihydride complexes are key intermediates in catalytic hydrogenation and dehydrogenation reactions; however, decomposition through these intermediates has been observed. This inspires the development of a PPP-pincer system that may show improved catalyst stability. In this work, bis[2-(diisopropylphosphino)phenyl]phosphine (or iPr PP H P) is used to react with FeCl 2 under a carbon monoxide (CO) atmosphere to yield trans-( iPr PP H P)Fe(CO)Cl 2 . A subsequent reaction with NaBH 4 produces syn/ anti-( iPr PP H P)FeH(CO)Cl or cis,anti-( iPr PP H P)Fe(CO)H 2 , depending on the amount of NaBH 4 employed. The cis-dihydride complex shows catalytic activity for the conversion of PhCHO to PhCH 2 OH (under H 2 ) or PhCO 2 CH 2 Ph (under Ar). It also catalyzes the dehydrogenation of PhCH 2 OH to PhCHO and PhCO 2 CH 2 Ph, albeit with limited turnover numbers. A more efficient catalytic process is the dehydrogenation of formic acid to carbon dioxide (CO 2 ), which can operate under additive-free conditions. Mechanistic investigation suggests that the cis-dihydride complex undergoes protonation with formic acid to release H 2 while forming anti-( iPr PP H P)FeH(CO)(OCHO)•HCO 2 H, in which the CO ligand has shifted and the formate is hydrogen-bonded to formic acid. The hydrido formate complex loses CO 2 under ambient conditions, completing the catalytic cycle by reforming the cis-dihydride complex.

show abstract

Section: Resultsmentioning

confidence: 99%

Iron Dihydride Complex Stabilized by an All-Phosphorus-Based Pincer Ligand and Carbon Monoxide

2022

Self Cite

View full text Add to dashboard Cite

show abstract

“…Evidently, acetic acid reacts with 1 rapidly to generate a new hydride complex . We initially predicted that protonation would occur to one of the β-carbons of the coordinated pyrrolyl group, analogous to what we observed in the study of an iron hydride supported by a PNP-pincer ligand, cis -(κ P ,κ N ,κ P - Cy PNP)Fe(CO) 2 H ( Cy PNP = 2,5-bis(dicyclohexylphosphinomethyl)pyrrolyl) . To our surprise, the isolated product from the reaction of 1 with acetic acid (>2 equiv) was characterized as trans -(κ P - Cy PN H ) 2 Ni(OAc)H·HOAc ( 3 ·HOAc, see Scheme ) by both X-ray crystallography (Figure ) and elemental analysis.…”

Section: Resultsmentioning

confidence: 60%

“…31 We initially predicted that protonation would occur to one of the β-carbons of the coordinated pyrrolyl group, analogous to what we observed in the study of an iron hydride supported by a PNP-pincer ligand, cis-(κ P ,κ N ,κ P -Cy PNP)Fe(CO) 2 H ( Cy PNP = 2,5-bis(dicyclohexylphosphinomethyl)pyrrolyl). 32 To our surprise, the isolated While the solid-state structure shows different environments around the two Cy PN H ligands, 3•HOAc dissolved in C 6 D 6 displays NMR spectra indicative of a more symmetrical molecule. In particular, the hydride resonance was located at −27.19 ppm as a triplet (J H−P = 76.8 Hz), and, in a fully 1 H-decoupled spectrum, the phosphorus resonance was found at 27.9 ppm as a singlet.…”

Section: ■ Results and Discussionmentioning

confidence: 85%

Nickel Hydride Complexes Supported by a Pyrrole-Derived Phosphine Ligand

2022

Self Cite

View full text Add to dashboard Cite

The synthesis of two nickel hydride complexes bearing the pyrrolederived phosphine ligand Cy PN H (2-(dicyclohexylphosphino)methyl-1H-pyrrole) was developed, namely, (κ P -Cy PN H )(κ P ,κ N -Cy PN)NiH and the acid-stable trans-(κ P -Cy PN H ) 2 Ni(OAc)H•HOAc. (κ P -Cy PN H )(κ P ,κ N -Cy PN)NiH stoichiometrically reduces benzaldehyde and acetophenone in a metal−ligand cooperative manner and catalytically dimerizes ethylene and cycloisomerizes 1,5-cyclooctadiene and 1,5hexadiene. trans-(κ P -Cy PN H ) 2 Ni(OAc)H•HOAc, available from the protonation of (κ P -Cy PN H )(κ P ,κ N -Cy PN)NiH with acetic acid, catalyzes the cycloisomerization of 1,5-cyclooctadiene more effectively and produces the less thermodynamically favored cycloisomers of 1,5-cyclooctadiene.

show abstract

Methyl Effects on the Stereochemistry and Reactivity of PPP-Ligated Iron Hydride Complexes

2023

Self Cite

View full text Add to dashboard Cite

Iron dihydride complexes are key intermediates in many iron-catalyzed reactions. Previous efforts to study molecules of this type have led to the discovery of a remarkably stable cis-FeH2 complex, which is supported by bis[2-(diisopropylphosphino)phenyl]phosphine ( iPrPPHP) along with CO. In this work, the hydrogen on the central phosphorus has been replaced with a methyl group, and the corresponding iron carbonyl dichloride, hydrido chloride, and dihydride complexes have been synthesized. The addition of the methyl group favors the anti configuration for the Me–P–Fe–H moiety and the trans geometry for the H–Fe–CO motif, which is distinctively different from the iPrPPHP system. Furthermore, it increases the thermal stability of the dihydride complex, cis-( iPrPPMeP)Fe(CO)H2 ( iPrPPMeP = bis[2-(diisopropylphosphino)phenyl]methylphosphine). The variations in stereochemistry and compound stability contribute greatly to the differences between the two PPP systems in reactions with PhCHO, CS2, and HCO2H.

show abstract

An Iron‐Hydrogen Bond Resistant to Protonation and Oxidation

Cited by 3 publications

References 44 publications

Iron Dihydride Complex Stabilized by an All-Phosphorus-Based Pincer Ligand and Carbon Monoxide

Iron Dihydride Complex Stabilized by an All-Phosphorus-Based Pincer Ligand and Carbon Monoxide

Nickel Hydride Complexes Supported by a Pyrrole-Derived Phosphine Ligand

Methyl Effects on the Stereochemistry and Reactivity of PPP-Ligated Iron Hydride Complexes

Contact Info

Product

Resources

About