PDF Supplementary Information for Chapter 4

General Considerations: All manipulations were performed using standard Schlenk or glovebox techniques under an N2 or Ar atmosphere. Electrochemistry: Voltammetry experiments were performed with a Biologic VSP-300 or CH Instruments 600B potentiostat using a one-compartment three-electrode cell, and coulometric experiments were performed with a Biologic VSP-300 potentiostat using a one-compartment three-electrode cell with a septum uncovered 14/20 joint for headspace analysis. All redox potentials in this work are reported versus the Fc/Fc+ pair, measured before each experiment to be approx. +0.12 V relative to our Ag/AgOTf reference electrode.

CV measurements were performed using IR compensation that compensated 85% of the resistance measured at one high frequency value (100 kHz). Gas chromatography: Gas chromatography was performed in the Environmental Analysis Center using HP 5890 Series II instruments. Isotope measurements were performed with a separate HP 5890 Series II equipped with a GasPro column with helium as the carrier gas.

Structures were solved using direct methods with SHELXS or SHELXT and refined to F2 on all data by full-matrix least squares with SHELXL. 5 All solutions were performed in the Olex2 program. 6 The crystals were mounted on a glass fiber under Paratone N . oil. XPS measurements were checked for surface charge effects, and the diamond carbon (sp3) 1s peak was verified to be in.

Figure C1. 1 H NMR spectrum of [(TPA)Fe(MeCN) 2 ]OTf 2 in CD 3 CN at 25 °C. Spectrum also shows 1,3,5-trimethoxybenzene used for Evan’s method

Catalytic controlled potential coulometry experiments

For experiments with naturally abundant ammonia, saturated 2 M solutions of 8 in acetonitrile were prepared by bubbling anhydrous ammonia through the acetonitrile in a Schlenk tube under an argon/ammonia atmosphere. For 15NH3-labeled experiments, ammonia was released from 15NH4OTf by addition of 1.1 equivalents of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to 15N-labeled ammonium triflate dissolved in acetonitrile in a Schlenk tube under an argon compartment. for gloves. CPC: Inside the argon glove box was a gas-tight electrochemical cell fitted with a 24/40 cap containing three tungsten rods for electrical contacts and a 14/20 valve joint carefully sealed with a Suba-Seal barrier.

All chemical reagents were then quickly added to the cell to prevent evaporation of ammonia, and then the cell was sealed with the 24/40 cap. Recharge experiments: After a completed CPC experiment, the valve 14/20 joint on the electrochemical cell was sealed, the septum was removed, and a 14/20 joint-to-tube adapter was connected. This joint is connected to a double-manifold Schlenk line and placed under an argon atmosphere.

The cell was then carefully evaporated to dryness under vacuum and placed in an argon glove box. For entries where reloading experiments were performed, the entries are listed as x.1 and x.2 for the initial and subsequent reloading experiment, respectively.

Table B1. Results of catalytic CPC experiments performed at 0.85 V vs Fc/Fc + for 24 h with 0.05 mM [Fe] and 20 mM NH 3 (400 equivalents)

Electrode rinse test after CPC

XPS spectra of BDD plate electrode

Full XPS spectrum of rinsed BDD plate electrode after 24 h CPC with 0.05 mM [(bpyPy2Me)Fe(MeCN)2]OTf2 and 20 mM NH3 solution and higher resolution spectra centered on the regions characteristic of Fe 2p and N 1s. Full XPS spectrum of rinsed BDD plate electrode after 24 h of CPC with 0.05 mM FeOTf2 · 2 MeCN and 20 mM NH3 solution and higher resolution spectra centered on the regions characteristic of Fe 2p and N 1s.

Figure C16. Full XPS spectrum of rinsed BDD plate electrode after 24 h CPC with 0.05 mM [(bpyPy 2 Me)Fe(MeCN) 2 ]OTf 2 and 20 mM NH 3 solution and higher resolution spectra centered on the regions characteristic for Fe 2p and N 1s

DPV data for E 1 analysis

Further analysis of speciation related to E 1

This conclusion is in excellent agreement with our DFT results (Fig. C21), which show identical experimental and predicted potentials. However, two other likely pathways from [(bpyPy2Me)Fe(MeCN)(NH3)]2+ are proton-coupled oxidation without further ammonia substitution (Scheme 4.2a in the main text) or oxidation without proton transfer. Based on our DFT results, oxidation without proton transfer is the second lowest energy process generating [(bpyPy2Me)Fe(MeCN)(NH3)]3+.

When [(bpyPy2Me)Fe(MeCN)(NH3)]2+ is examined by CV at high scan rates under certain concentration regimes, an additional feature appears in the cyclic voltammogram as a shoulder in the catalytic E2 wave at ca. 0.55 V (Fig. C22). Considering that the E1 process, a proton-coupled oxidation associated with an additional ammonia substitution, could be slow due to Interestingly, this shoulder does not move with varying NH3 concentration as would be expected if it was also coupled to proton transfer.

Furthermore, an increase in the current at E1* (Fig. C21, 2000 mV/s) results in an increase in the return current at E1, indicating that they are connected via a square mechanism, that is, E1 and E1* generate the same product upon purchase. All these data points are consistent with our assignment of E1* as oxidation without proton transfer to generate [(bpyPy2Me)Fe(MeCN)(NH3)]3+.

Figure C21. Possible E 1 processes and their calculated E (V) values.

Catalytic rate versus iron and NH 3 concentrations (E 2 )

Rate dependence measured with catalytic current at 1.08 V with different concentrations of NH3 and 0.5 mM [(bpyPy2Me)Fe(MeCN)2]OTf2 in MeCN with 0.05 M NH4OTf with BDD reference electrodes, Pt counter and Ag/AgOTf. The low [NH3] regime is perfectly linear (R2 = 0.99), but at higher concentrations the higher rate likely results in substrate depletion manifested by the slight concave behavior for the overall fit (R2 = 0.95). FOWA calculated kobs for AO using various concentrations of [(bpyPy2Me)Fe(MeCN)2]OTf2 in MeCN with 0.05 M NH4OTf and 0.2 M NH3 with working BDD, Pt counter, and Ag/AgOTf reference electrode.

Figure C25. Rate dependence as measured by catalytic current at 1.08 V with varying concentrations of NH 3 and 0.5 mM [(bpyPy 2 Me)Fe(MeCN) 2 ]OTf 2 in MeCN with 0.05 M NH 4 OTf with BDD working, Pt counter, and Ag/AgOTf reference

Procedure for FOWA

Linear sweep voltammogram with red trace showing the range of data used to perform the FOWA. FOWA for an ECcat mechanism calculated from the above linear sweep voltammogram showing strong concavity.

Figure C27. Linear sweep voltammogram with red trace showing the data range employed for performing the FOWA

Further reactivity considered at E 2

Computational methodology

To determine thermochemical values, oxidations are referred to ferrocene/ferrosenium (Fc/Fc+), and reactions involving net hydrogen atom transfer are calculated using TEMPO as a reference value (BDFE = 66.5 kcal/mol) and the acetonitrile CG value of 54.9 kcal/ to use. mole. 11.

DFT spin-state ordering

Relative energies for multiples of [(bpyPy2Me)Fe(Lax)(Leq)]n+ complexes with formal oxidation states of +4. Lax and Leq represent ligands axial/trans to bipyridine and equatorial/trans to pyridine, respectively, according to the orientation defined in the main text. Relative energies for multiples of [(bpyPy2Me)Fe(Lax)(Leq)]n+ complexes with formal oxidation states of +5.

Figure C32. Relative energies for multiplicities of [(bpyPy 2 Me)Fe(L ax )(L eq )] n+ complexes with formal oxidation states of +4

DFT tabulated energies

DFT structures