Yuri Lee, Pathorn Teptarakulkarn, Jeffrey K. Klinger, Niyati Patel, Anna L. Poptic, Yunqiao J. Gan, Emily N. Doss, Abigail M. Houser, Chris Nieto, Hannah Shafaat, Shiyu Zhang. “A heterobimetallic MnᴵᴵᴵFeᴵᴵᴵ complex reproduces the enhanced C–O bond formation reactivity of biological MnFe cofactors over FeFe analogs.” ChemRxiv (). https://doi.org/10.26434/chemrxiv.15007667/v1

The supporting information is appended to the main paper

(Ph₃P=O)₂:H₂O₂
¹H NMR analysis 97 % of Ph₃P=O is bound to H₂O₂
SI, p. 5
4-(dimethylamino)phenol
¹H NMR (400 MHz, CD₃OD) δ 6.79 – 6.76 (d, 2H), 6.72 – 6.69 (d, 2H), 2.76 (s, 6H)
¹H NMR (400 MHz, methanol-d₄), solvent assignments Dichloromethane peak at 5.49 ppm is denoted with a green circle; H₂O peak at 4.87 ppm is denoted with a red circle
SI, pp. 7–8
6,6′-dimethoxy-[1,1′-biphenyl]-3,3′-diol
¹H NMR (400 MHz, CDCl₃) δ 6.97 – 6.95 (d, 2H), 6.90 – 6.89 (d, 2H), 6.88 – 6.87 (d, 2H), 6.83 – 6.82 (d, 2H), 5.37 (s, 2H), 3.79 (s, 6H)
SI, p. 9
4-methoxy-2-(4-methoxyphenoxy)phenol
¹H NMR (400 MHz, CDCl₃) δ 7.00 – 6.87 (m, 5H), 6.55 – 6.52 (dd, 1H), 6.37 – 6.36 (d, 1H), 5.26 (s, 1H), 3.81 (s, 3H), 3.67 (s, 3H)
¹H NMR (400 MHz, chloroform-d₁), solvent assignment The residual benzene peak at 7.36 ppm is denoted with a blue circle
SI, pp. 9–10
4-(dimethylamino)-2-(4-(dimethylamino)phenoxy)phenol
¹H NMR (400 MHz, CDCl₃) δ 8.10 (s, 1H), 6.97 – 6.94 (d, 2H), 6.92 – 6.90 (d, 1H), 6.73 – 6.71 (d, 2H), 6.44 – 6.42 (dd, 1H), 6.30 – 6.29 (d, 1H), 2.93 (s, 6H), 2.77 (s, 6H)
SI, p. 10
2,4-di-tert-butyl-6-chlorophenol
¹H NMR (400 MHz, CDCl₃) δ 7.20 (d, 1H), 7.18 (d, 1H), 5.69 (s, 1H), 1.41 (s, 9H), 1.28 (s, 9H)
SI, p. 11
2,4-di-tert-butyl-6-(2,4-di-tert-butylphenoxy)phenol
¹H NMR (400 MHz, CDCl₃) δ 7.42 (d, 1H), 7.11 – 7.06 (td, 2H), 6.75 (d, 1H), 6.64 (d, 1H), 5.71 (s, 1H), 1.48 (s, 9H), 1.45 (s, 9H), 1.32 (s, 9H), 1.23 (s, 9H)
SI, p. 13
3,3′,5,5′-tetra-tert-butyl-[1,1′-biphenyl]-2,2′-diol
¹H NMR peak annotations (400 MHz, chloroform-d₁) δ 7.39, 7.39, 7.11, 7.10, 5.20, 1.45, 1.32
SI, p. 15
MnᴵᴵᴵFeᴵᴵᴵ(O)
UV–vis absorption (CH₂Cl₂, −80 °C) Broad absorption band with λmax = 500 nm (ε = 463 M⁻¹ cm⁻¹)
X-band and pulsed Q-band EPR reporting conditions Main: X-band, 9.4 GHz, frozen CH₂Cl₂, 6 K; pulsed Q-band, 34 GHz, frozen CH₂Cl₂, 5 K, π/2 = 16 ns, τ = 200 ns. SI: both spectra at 6 K and 0.200 mW
X-band and pulsed Q-band EPR Broad S = 1/2 signal with a characteristic six-line splitting pattern due to coupling to the manganese center (⁵⁵Mn, I = 5/2)
X-band EPR comparison (frozen CH₂Cl₂, 6 K) Upon oxidation, the characteristic six-line ⁵⁵Mn (I = 5/2) hyperfine pattern of MnᴵᴵᴵFeᴵᴵᴵ appears, in contrast to the weak, broad signal of MnᴵᴵFeᴵᴵ
EPR electronic-state assignment S = 5/2 Feᴵᴵᴵ center antiferromagnetically coupled to an S = 2 Mnᴵᴵᴵ center
⁵⁷Fe Mössbauer (4.2 K) δ = 0.48 mm s⁻¹; |ΔEQ| = 0.92 mm s⁻¹; assigned to an S = 5/2 Feᴵᴵᴵ center
Resonance Raman (77 K, 457 nm excitation), H₂¹⁶O₂/H₂¹⁸O₂ 503 cm⁻¹ shifted to 496 cm⁻¹; 813 cm⁻¹ shifted to 796 cm⁻¹
Resonance Raman assignment These two isotope-sensitive peaks suggest a bimetallic center with a bridging oxo or hydroxo ligand
Resonance Raman (77 K, 407 nm excitation), 30 equiv. H₂¹⁸O The 503 cm⁻¹ and 813 cm⁻¹ peaks associated with MnᴵᴵᴵFeᴵᴵᴵ did not shift to positions associated with ¹⁸O-labeled MnᴵᴵᴵFeᴵᴵᴵ, suggesting the bridging ligand is not exchangeable, consistent with the behavior of a bridging oxo ligand
Main, pp. 4–5; SI, pp. 18–19, 23–25
⁵⁷Fe-labeled MnᴵᴵᴵFeᴵᴵᴵ(O) solid-state sample
⁵⁷Fe Mössbauer best-fit parameters (150 K, 0 mT) χ² = 0.915, δ = 0.48 mm s⁻¹, |ΔEQ| = 0.92 mm s⁻¹, ΓL = 1.65, ΓR = 1.94
⁵⁷Fe Mössbauer, noise baseline Attributed to the weak irradiation from the ⁵⁷Co source
Main, p. 4; SI, pp. 20–21
FeᴵᴵFeᴵᴵ and FeᴵᴵᴵFeᴵᴵᴵ(O)
UV–vis titration (0.5 mM FeᴵᴵFeᴵᴵ, CH₂Cl₂, −80 °C) Maximum absorbance reached after addition of 4 equiv. (Ph₃P=O)₂:H₂O₂, confirming that FeᴵᴵFeᴵᴵ reacts with (Ph₃P=O)₂:H₂O₂ in a 1:4 ratio
SI, p. 16
⁵⁷Fe-labeled FeᴵᴵᴵFeᴵᴵᴵ(O) solid-state sample
⁵⁷Fe Mössbauer best-fit parameters (150 K, 0 mT) χ² = 9.076, δ = 0.44 mm s⁻¹, |ΔEQ| = 0.91 mm s⁻¹, ΓL = 2.00, ΓR = 2.17; assigned to two S = 5/2 Feᴵᴵᴵ centers
⁵⁷Fe Mössbauer, noise baseline Attributed to the weak irradiation from the ⁵⁷Co source
Main, p. 5; SI, p. 21
FeᴵᴵᴵFeᴵᴵᴵ(O)
Resonance Raman (77 K, 407 nm excitation) Resonantly enhanced peaks at 525 cm⁻¹ and 603 cm⁻¹
Resonance Raman (77 K, 407 nm excitation), 30 equiv. H₂¹⁸O Treatment of FeᴵᴵᴵFeᴵᴵᴵ with 30 equivalents of H₂¹⁸O did not generate the ¹⁸O-isotopologue, suggesting the FeᴵᴵᴵFeᴵᴵᴵ also contains a bridging oxo ligand
Main, p. 5; SI, pp. 22, 25
MnᴵᴵᴵFeᴵᴵᴵ(O) reaction-monitoring series
UV–vis reaction monitoring (0.5 mM MnᴵᴵᴵFeᴵᴵᴵ, 500 equiv. 4-OMe-2,6-di-tert-butylphenol, CH₂Cl₂, −80 °C) Growth of a band at 407 nm; kobs = 0.00161 s⁻¹
UV–vis reaction monitoring with 4-X-2,6-di-tert-butylphenol (X = Me, tBu, H) New absorbance features in the 350–440 nm region
UV–vis kinetic isotope effect, TEMPOH/TEMPOD 1.05
UV–vis reaction monitoring (0.5 mM complex, 500 equiv. 4-OMe-2,6-di-tert-butylphenol, CH₂Cl₂, −80 °C, 407 nm), kobs (s⁻¹) Trials: 0.00185, 0.00101, 0.00198; average: 0.0016; stdev: 0.00053
UV–vis reaction monitoring (0.5 mM complex, 500 equiv. 4-Me-2,6-di-tert-butylphenol, CH₂Cl₂, −80 °C, product absorption band between 400 and 500 nm), kobs (s⁻¹) Trials: 0.00110, 0.00100, 0.00109; average: 0.00106; stdev: 0.00006
UV–vis reaction monitoring (0.5 mM complex, 500 equiv. 4-tBu-2,6-di-tert-butylphenol, CH₂Cl₂, −80 °C, product absorption band between 400 and 500 nm), kobs (s⁻¹) Trials: 0.000784, 0.000865, 0.000635; average: 0.000761; stdev: 0.00012
UV–vis reaction monitoring (0.5 mM complex, 500 equiv. 2,6-di-tert-butylphenol, CH₂Cl₂, −80 °C, product absorption band between 400 and 500 nm), kobs (s⁻¹) Trials: 0.0007, 0.000332, 0.000998; average: 0.000677; stdev: 0.00033
UV–vis reaction monitoring (0.5 mM complex, 20 equiv. TEMPOH, CH₂Cl₂, −80 °C, 400 nm), kobs (s⁻¹) Trials: 0.00268, 0.00286, 0.00246; average: 0.00267; stdev: 0.00020
UV–vis reaction monitoring (0.5 mM complex, 20 equiv. TEMPOD, CH₂Cl₂, −80 °C, 400 nm), kobs (s⁻¹) Trials: 0.00248, 0.00259, 0.00256; average: 0.00254; stdev: 0.00006
Main, p. 6; SI, pp. 38, 40–46
FeᴵᴵᴵFeᴵᴵᴵ(O) reaction-monitoring series
UV–vis kinetic isotope effect, TEMPOH/TEMPOD 2.44
UV–vis reaction monitoring (0.5 mM complex, 500 equiv. 4-OMe-2,6-di-tert-butylphenol, CH₂Cl₂, −80 °C, 407 nm), kobs (s⁻¹) Trials: 0.00371, 0.00409, 0.00273; average: 0.00351; stdev: 0.00069
UV–vis reaction monitoring (0.5 mM complex, 500 equiv. 4-Me-2,6-di-tert-butylphenol, CH₂Cl₂, −80 °C, product absorption band between 400 and 500 nm), kobs (s⁻¹) Trials: 0.003378, 0.003568, 0.00308; average: 0.00334; stdev: 0.00025
UV–vis reaction monitoring (0.5 mM complex, 500 equiv. 4-tBu-2,6-di-tert-butylphenol, CH₂Cl₂, −80 °C, product absorption band between 400 and 500 nm), kobs (s⁻¹) Trials: 0.00217, 0.00209, 0.00203; average: 0.00209; stdev: 0.00007
UV–vis reaction monitoring (0.5 mM complex, 500 equiv. 2,6-di-tert-butylphenol, CH₂Cl₂, −80 °C, product absorption band between 400 and 500 nm), kobs (s⁻¹) Trials: 0.00243, 0.00163, 0.00284; average: 0.00230; stdev: 0.00061
UV–vis reaction monitoring (0.5 mM complex, 20 equiv. TEMPOH, CH₂Cl₂, −80 °C, 400 nm), kobs (s⁻¹) Trials: 0.00284, 0.00291, 0.00318; average: 0.00297; stdev: 0.00018
UV–vis reaction monitoring (0.5 mM complex, 20 equiv. TEMPOD, CH₂Cl₂, −80 °C, 400 nm), kobs (s⁻¹) Trials: 0.00114, 0.00130, 0.00122; average: 0.00122; stdev: 0.00008
Main, p. 6; SI, pp. 38, 41–46
MnᴵᴵFeᴵᴵ- and FeᴵᴵFeᴵᴵ-catalyzed reaction mixtures of 4-methoxyphenol and H₂O₂
GC–MS (100 equiv. substrate, 10 equiv. H₂O₂, 0.5 mM catalyst, CH₂Cl₂, −80 °C) Starting material, 4-methoxyphenol: 8.90 min; internal standard, benzophenone: 10.92 min; product, 4-methoxy-2-(4-methoxyphenoxy)phenol: 12.503 min, m/z 246.1
SI, pp. 28–29
MnᴵᴵFeᴵᴵ- and FeᴵᴵFeᴵᴵ-catalyzed reaction mixtures of 2,4-di-tert-butylphenol and H₂O₂
GC–MS (100 equiv. substrate, 10 equiv. H₂O₂, 0.5 mM catalyst, CH₂Cl₂, −80 °C) Starting material, 2,4-di-tert-butylphenol: 10.35 min; internal standard, benzophenone: 10.92 min; product, 3,3′,5,5′-tetra-tert-butyl-[1,1′-biphenyl]-2,2′-diol: 14.13 min, m/z 410.3
SI, pp. 30–31
MnᴵᴵFeᴵᴵ- and FeᴵᴵFeᴵᴵ-catalyzed reaction mixtures of 4-(dimethylamino)phenol and H₂O₂
GC–MS (100 equiv. substrate, 10 equiv. H₂O₂, 0.5 mM catalyst, CH₂Cl₂, −80 °C) Starting material, 4-(dimethylamino)phenol: 9.66 min; internal standard, benzophenone: 10.92 min; product, 4-(dimethylamino)-2-(4-(dimethylamino)phenoxy)phenol: 14.62 min, m/z 272.1
SI, pp. 32–33
MnᴵᴵFeᴵᴵ- and FeᴵᴵFeᴵᴵ-catalyzed reaction mixtures of 4-methoxy-2,6-di-tert-butylphenol and H₂O₂
GC–MS (100 equiv. substrate, 10 equiv. H₂O₂, 0.5 mM catalyst, CH₂Cl₂, −80 °C) Starting material, 4-methoxy-2,6-di-tert-butylphenol: 10.89 min; internal standard, 1,4-dichlorobenzene: 8.7 min; product, 2,6-di-tert-butyl-1,4-benzoquinone: 10.20 min, m/z 220.1
SI, pp. 34–35
MnᴵᴵFeᴵᴵ- and FeᴵᴵFeᴵᴵ-catalyzed reaction mixtures of 4-tert-butylphenol and H₂O₂
GC–MS (100 equiv. substrate, 10 equiv. H₂O₂, 0.5 mM catalyst, CH₂Cl₂, −80 °C) Internal standard, benzophenone: 10.92 min; product, 4-tert-butyl-2-(4-tert-butylphenoxy)phenol: 12.875 min, m/z 298.19