Divergent Reactivity of CO2 and CO and Related Substrates at the Nickel Carbon Double Bond of (PCcarbeneP)Ni(II) Pincer Complexes

The addition of carbon monoxide (CO), carbon dioxide (CO₂) and isoelectronic isocyanide and isocyanates to the nickel carbene bond in PC_carbeneP pincer complexes is reported. For CO and CNR, irreversible group transfer reactions are observed, while for CO₂, a reversible 2+2 addition to the carbene moiety occurs. The course of the CO and CO₂ reactions are strongly affected by the nature of the PC_carbeneP pincer ligand framework and a new more rigid ligand based on a 10,10-dimethyl-9,10-dihydroanthracene core was designed in order to study these reactions, illustrating the profound effect of small changes in ligand structure on reaction outcomes

Tandem Deoxygenative Hydrosilation of Carbon Dioxide with a Cationic Scandium Hydridoborate and B(C6F5)3

A scandium hydridoborate complex supported by the dianionic pentadentate ligand B2Pz4Py is prepared via hydride abstraction from the previously reported scandium hydride complex with tris-pentafluorophenyl borane. Exposure of [(B2Pz4Py)Sc][HB(C6F5)3] to CO2 immediately forms [(B2Pz4Py)Sc][HCOOB(C6F5)3] at room temperature. The formatoborate complex can also be synthesized directly from the starting material (B2Pz4Py)ScCl with Et3SiH and B(C6F5)3 while in the presence of an atmosphere of CO2 in 81% yield. This compound was evaluated as the transition metal component of a tandem deoxgenative CO2 hydrosilation catalyst. At 5% loadings, complete consumption of Et3SiH was observed along with CO2 reduction products, but conversion to an inactive scandium complex identified as (B2Pz4Py)ScOSiEt3 was observe

Tuning Iridium(I) PCcarbenePFrameworks for Facile Cooperative N2O Reduction

A semiquantitative kinetic study correlates the rate of oxygen atom transfer from N₂O to an iridium carbon double bond with the donor properties of six PC_carbeneP pincer ligand frameworks. Two new rigid, electron rich ligands are described and shown to be the most effective for rapid, selective reaction with N₂O.<br

Electrocatalytic CO2 reduction at low overpotentials using iron(III) tetra(meso-thienyl)porphyrins

The optical and electrochemical properties, as well as the CO2 reduction capability of two different iron(III) thienyl-porphyrins, iron(III) tetra(meso-thien-2-yl)porphyrin (FeTThP) and iron(III) tetra(meso-5-methylthien-2-yl)porphyrin (FeTThMeP), are directly compared to those of iron(III) tetra(meso-phenyl)porphyrin (FeTPP). Through exploitation of mesomeric stabilization effects, FeTThP and FeTThMeP both reduced CO2 to CO with comparable faradaic efficiencies and TONCO relative to FeTPP, with an overpotential 150 mV lower than the benchmark catalyst. </p

Grafting of a Molecular Rhenium CO2 Reduction Catalyst onto Colloid-Imprinted Carbon

An aminophenethyl-substituted [Re(2,2’-bipyridine)(CO)3Cl] catalyst ([Re(NH2-bpy)]) was tethered to nanoporous colloid-imprinted carbon (CIC) electrode surfaces via an electrochemical oxidative grafting method. Hybrid CIC|[Re(NH2-bpy)] electrodes showed an improved stability and an increased loading per geometrical area in comparison to modified smooth glassy carbon electrodes. The catalyst also remained active upon immobilization and CO2 was selectively reduced to CO by the CIC|[Re(NH2-bpy)] electrodes in acetonitrile with a Faradaic efficiency of 92 ± 6% and a Re-based TON of approximately 900

Boron-Nitrogen Doped Dihydroindeno[1,2-b]fluorene Derivatives as Acceptors in Organic Solar Cells

The electrophilic borylation of 2,5-diarylpyrazines results in the formation of boron-nitrogen doped dihydroindeno[1,2-b]fluorene which can be synthesized via mildly air-sensitive techniques and the end products handled readily under atmosphereic conditions. Through transmetallation via diarylzinc reagents a series of derivatives were sythesized which show broad absorption profiles that highlight the versatility of this backbone to be used in organic solar cell devices. These compounds can be synthesized in large yields, in alow number of steps and functionalized at many stages along the way providing a large depth of possibilities. Exploratory device paramaters were studied and show PCE of 2%

Ligand-Centered Electrochemical Processes Enable CO2 Reduction with a Nickel Bis(triazapentadienyl) Complex

We report the synthesis of Ni(TAPPy)2 (TAPPy = 1,3,5-triazapentadienyl-2,4-bis(2-pyridyl)) and its reactivity with CO2 under reducing conditions. Electrochemical reduction of Ni(TAPPy)2 under inert gas reveals that the complex accommodates up to two additional electrons, with DFT calculations indicating that electron density is delocalized almost exclusively onto the TAPPy ligand framework. The singly reduced product [K(crypt)][Ni(TAPPy)2] (crypt = 2.2.2-cryptand) has been synthesized, and its EPR data is consistent with having ligand-based radical anion character. Controlled potential electrolysis experiments reveal that reduced Ni(TAPPy)2 converts CO2 to form CO; however, spectroscopic and computational data indicate that deactivation readily occurs to form Ni(L)(CO)n compounds, CO32-, and carboxylated (RCOO-) ligand decomposition products. This study highlights that redox activity at the ligand can play an important role during the reduction of CO2 using transition metal complexes