sj-pdf-1-ems-10.1177_14690667221149498 - Supplemental material for Synthesis, characterization, and liquid injection field desorption ionization mass spectrometry analysis of pincer ligated group 6 (Cr, Mo, W) carbonyl complexes

Supplemental material, sj-pdf-1-ems-10.1177_14690667221149498 for Synthesis, characterization, and liquid injection field desorption ionization mass spectrometry analysis of pincer ligated group 6 (Cr, Mo, W) carbonyl complexes by Olivia L. Duletski, Navamoney Arulsamy and Michael T. Mock in European Journal of Mass Spectrometry</p

sj-cif-3-ems-10.1177_14690667221149498 - Supplemental material for Synthesis, characterization, and liquid injection field desorption ionization mass spectrometry analysis of pincer ligated group 6 (Cr, Mo, W) carbonyl complexes

Supplemental material, sj-cif-3-ems-10.1177_14690667221149498 for Synthesis, characterization, and liquid injection field desorption ionization mass spectrometry analysis of pincer ligated group 6 (Cr, Mo, W) carbonyl complexes by Olivia L. Duletski, Navamoney Arulsamy and Michael T. Mock in European Journal of Mass Spectrometry</p

sj-cif-4-ems-10.1177_14690667221149498 - Supplemental material for Synthesis, characterization, and liquid injection field desorption ionization mass spectrometry analysis of pincer ligated group 6 (Cr, Mo, W) carbonyl complexes

Supplemental material, sj-cif-4-ems-10.1177_14690667221149498 for Synthesis, characterization, and liquid injection field desorption ionization mass spectrometry analysis of pincer ligated group 6 (Cr, Mo, W) carbonyl complexes by Olivia L. Duletski, Navamoney Arulsamy and Michael T. Mock in European Journal of Mass Spectrometry</p

sj-cif-2-ems-10.1177_14690667221149498 - Supplemental material for Synthesis, characterization, and liquid injection field desorption ionization mass spectrometry analysis of pincer ligated group 6 (Cr, Mo, W) carbonyl complexes

Supplemental material, sj-cif-2-ems-10.1177_14690667221149498 for Synthesis, characterization, and liquid injection field desorption ionization mass spectrometry analysis of pincer ligated group 6 (Cr, Mo, W) carbonyl complexes by Olivia L. Duletski, Navamoney Arulsamy and Michael T. Mock in European Journal of Mass Spectrometry</p

Electronic and Steric Influences of Pendant Amine Groups on the Protonation of Molybdenum Bis(dinitrogen) Complexes

The synthesis of a series of P^EtP^{NRR^′} (P^EtP^{NRR^′} = Et₂PCH₂CH₂P­(CH₂NRR′)₂, R = H, R′ = Ph or 2,4-difluorophenyl; R = R′ = Ph or ^<i>i</i>Pr) diphosphine ligands containing mono- and disubstituted pendant amine groups and the preparation of their corresponding molybdenum bis­(dinitrogen) complexes <i>trans</i>-Mo­(N₂)₂­(PMePh₂)₂­(P^EtP^{NRR^′}) is described. In situ IR and multinuclear NMR spectroscopic studies monitoring the stepwise addition of triflic acid (HOTf) to <i>trans</i>-Mo­(N₂)₂­(PMePh₂)₂­(P^EtP^{NRR^′}) complexes in tetrahydrofuran at −40 °C show that the electronic and steric properties of the R and R′ groups of the pendant amines influence whether the complexes are protonated at Mo, a pendant amine, a coordinated N₂ ligand, or a combination of these sites. For example, complexes containing monoaryl-substituted pendant amines are protonated at Mo and the pendant amine site to generate mono- and dicationic Mo–H species. Protonation of the complex containing less basic diphenyl-substituted pendant amines exclusively generates a monocationic hydrazido (Mo­(NNH₂)) product, indicating preferential protonation of an N₂ ligand. Addition of HOTf to the complex featuring more basic diisopropyl amines primarily produces a monocationic product protonated at a pendant amine site, as well as a trace amount of dicationic Mo­(NNH₂) product that is additionally protonated at a pendant amine site. In addition, <i>trans</i>-Mo­(N₂)₂­(PMePh₂)₂­(depe) (depe = Et₂PCH₂CH₂PEt₂) was synthesized to serve as a counterpart lacking pendant amines. Treatment of this complex with HOTf generated a monocationic Mo­(NNH₂) product. Protonolysis experiments conducted on several complexes in this study afforded trace amounts of NH₄⁺. Computational analysis of <i>trans</i>-Mo­(N₂)₂­(PMePh₂)₂­(P^EtP^{NRR^′}) complexes provides further insight into the proton affinity values of the metal center, N₂ ligand, and pendant amine sites to rationalize differences in their reactivity profiles

Electronic and Steric Influences of Pendant Amine Groups on the Protonation of Molybdenum Bis(dinitrogen) Complexes

The synthesis of a series of P^EtP^{NRR^′} (P^EtP^{NRR^′} = Et₂PCH₂CH₂P­(CH₂NRR′)₂, R = H, R′ = Ph or 2,4-difluorophenyl; R = R′ = Ph or ^<i>i</i>Pr) diphosphine ligands containing mono- and disubstituted pendant amine groups and the preparation of their corresponding molybdenum bis­(dinitrogen) complexes <i>trans</i>-Mo­(N₂)₂­(PMePh₂)₂­(P^EtP^{NRR^′}) is described. In situ IR and multinuclear NMR spectroscopic studies monitoring the stepwise addition of triflic acid (HOTf) to <i>trans</i>-Mo­(N₂)₂­(PMePh₂)₂­(P^EtP^{NRR^′}) complexes in tetrahydrofuran at −40 °C show that the electronic and steric properties of the R and R′ groups of the pendant amines influence whether the complexes are protonated at Mo, a pendant amine, a coordinated N₂ ligand, or a combination of these sites. For example, complexes containing monoaryl-substituted pendant amines are protonated at Mo and the pendant amine site to generate mono- and dicationic Mo–H species. Protonation of the complex containing less basic diphenyl-substituted pendant amines exclusively generates a monocationic hydrazido (Mo­(NNH₂)) product, indicating preferential protonation of an N₂ ligand. Addition of HOTf to the complex featuring more basic diisopropyl amines primarily produces a monocationic product protonated at a pendant amine site, as well as a trace amount of dicationic Mo­(NNH₂) product that is additionally protonated at a pendant amine site. In addition, <i>trans</i>-Mo­(N₂)₂­(PMePh₂)₂­(depe) (depe = Et₂PCH₂CH₂PEt₂) was synthesized to serve as a counterpart lacking pendant amines. Treatment of this complex with HOTf generated a monocationic Mo­(NNH₂) product. Protonolysis experiments conducted on several complexes in this study afforded trace amounts of NH₄⁺. Computational analysis of <i>trans</i>-Mo­(N₂)₂­(PMePh₂)₂­(P^EtP^{NRR^′}) complexes provides further insight into the proton affinity values of the metal center, N₂ ligand, and pendant amine sites to rationalize differences in their reactivity profiles

A Cobalt-Based Catalyst for the Hydrogenation of CO₂ under Ambient Conditions

Because of the continually rising levels of CO2 in the atmosphere, research for the conversion of CO2 into fuels using carbon-neutral energy is an important and current topic in catalysis. Recent research on molecular catalysts has led to improved rates for conversion of CO2 to formate, but the catalysts are based on precious metals such as iridium, ruthenium and rhodium and require high temperatures and high pressures. Using established thermodynamic properties of hydricity (ΔGH–) and acidity (pKa), we designed a cobalt-based catalyst system for the production of formate from CO2 and H2. The complex Co­(dmpe)2H (dmpe is 1,2-bis­(dimethylphosphino)­ethane) catalyzes the hydrogenation of CO2, with a turnover frequency of 3400 h–1 at room temperature and 1 atm of 1:1 CO2:H2 (74 000 h–1 at 20 atm) in tetrahydrofuran. These results highlight the value of fundamental thermodynamic properties in the rational design of catalysts

H₂ Binding, Splitting, and Net Hydrogen Atom Transfer at a Paramagnetic Iron Complex

While diamagnetic transition metal complexes that bind and split H2 have been extensively studied, paramagnetic complexes that exhibit this behavior remain rare. The square planar S = 1/2 FeI(P4N2)+ cation (FeI+) reversibly binds H2/D2 in solution, exhibiting an inverse equilibrium isotope effect of KH2/KD2 = 0.58(4) at −5.0 °C. In the presence of excess H2, the dihydrogen complex FeI(H2)+ cleaves H2 at 25 °C in a net hydrogen atom transfer reaction, producing the dihydrogen-hydride trans-FeII(H)­(H2)+. The proposed mechanism of H2 splitting involves both intra- and intermolecular steps, resulting in a mixed first- and second-order rate law with respect to initial [FeI+]. The key intermediate is a paramagnetic dihydride complex, trans-FeIII(H)2+, whose weak FeIII–H bond dissociation free energy (calculated BDFE = 44 kcal/mol) leads to bimetallic H–H homolysis, generating trans-FeII(H)­(H2)+. Reaction kinetics, thermodynamics, electrochemistry, EPR spectroscopy, and DFT calculations support the proposed mechanism

Spectroscopic and Computational Studies on [Ni(tmc)CH₃]OTf: Implications for Ni−Methyl Bonding in the A Cluster of Acetyl-CoA Synthase

The five-coordinate high-spin (S = 1) Ni2+ complex [Ni(tmc)CH3]+ (1) (tmc = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) serves as a model for a viable reaction intermediate of the A cluster of acetyl-CoA synthase (ACS) in which the distal nickel center is methylated. Spectroscopic and density functional theory (DFT) computational studies afford a quantitative bonding description for 1 that reveals a highly covalent Ni−CH3 bond. From a normal coordinate analysis of resonance Raman data obtained for 1, a value of kNi-C = 1.44 mdyn/Å is obtained for the Ni−C stretch force constant of this species. This value is smaller than kCo-C = 1.85 mdyn/Å, which is reported for the Co−C stretch in the methylcobinamide cofactor (5) that serves as the methyl donor to the A cluster in the ACS catalytic cycle. Experimentally calibrated DFT computations on viable methylated A cluster models reveal that the methyl group binds to the proximal (Nip) rather than the distal (Nid) nickel center and afford a simple electronic argument for this preference. By correlating the experimental force constants with the computed bond orders of the M−C bonds in 1 and 5, the Nip2+−CH3 bond strength for an A cluster model with a square-planar Nip conformation, which is the most probable structure of the methylated A cluster on the basis of steric and energetic considerations, is predicted to be similar to the Co3+−CH3 bond strength in CH3−CoFeSP. This similarity could be a crucial thermodynamic prerequisite for the reversibility of the enzymatic transmethylation reaction

Monovalent Iron in a Sulfur-Rich Environment

A series of low-coordinate, paramagnetic iron complexes in a tris(thioether) ligand environment have been prepared. Reduction of ferrous {[PhTttBu]FeCl}2 [1; PhTttBu = phenyltris((tert-butylthio)methyl)borate] with KC8 in the presence of PR3 (R = Me or Et) yields the high-spin, monovalent iron phosphine complexes [PhTttBu]Fe(PR3) (2). These complexes provide entry into other low-valent derivatives via ligand substitution. Carbonylation led to smooth formation of the low-spin dicarbonyl [PhTttBu]Fe(CO)2 (3). Alternatively, replacement of PR3 with diphenylacetylene produced the high-spin alkyne complex [PhTttBu]Fe(PhCCPh) (4). Lastly, 2 equiv of adamantyl azide undergoes a 3 + 2 cycloaddition at 2, yielding high-spin dialkyltetraazadiene complex 5