Intermediates in the oxygenation of a nonheme diiron(II) complex, including the first evidence for a bound superoxo species

Shan and Que, Jr . 10.1073/pnas.0409640102.

Supporting Information

Files in this Data Supplement:

Supporting Text
Supporting Table 3
Supporting Table 4
Supporting Figure 6
Supporting Figure 7
Supporting Table 5
Supporting Figure 8
Supporting Figure 9
Supporting Figure 10
Supporting Figure 11
Supporting Table 6

Table 3. Rate constants for the formation of 2 in CH₂Cl₂ under various conditions

Experiment no.	T, K	[1], mM	[O₂], mM	*k_obs, 10^–4 s^–1**
1	203	0.1	5.76	8.8 ± 0.2
2	198	0.1	5.76	7.7 ± 0.2
3	193	0.1	5.76	4.5 ± 0.1
4	193	0.1	4.61	3.7 ± 0.2
5	193	0.1	3.46	2.8 ± 0.1
6	193	0.1	2.30	1.77 ± 0.06
7	183	0.1	5.76	3.3 ± 0.1
8	193	1.0	^†	7.0 ± 1.2

*Shown are values ± SD.

^†Solution prepared by bubbling O₂ through the solution of 1 at 193 K.

Table 4. Rate constants for the conversion of 2 to 4 in CH₂Cl₂ under various conditions

Experiment no.	T, K	[2], mM	*kb , 10^–2 s^–1**	*ka , 10^–2 s^–1**
1	233	1.0	–	4.5 ± 0.1
2	228	1.0	–	3.4 ± 0.2
3	223	1.0	–	1.45 ± 0.05
4	218	1.0	–	0.90 ± 0.02
5	213	1.0	2.32 ± 0.08	0.365 ± 0.006
6	208	1.0	1.81 ± 0.05	0.083 ± 0.003
7	203	1.0	1.9 ± 0.1	0.093 ± 0.003
8	198	1.0	1.08 ± 0.08	0.027 ± 0.001
9	193	1.0	0.89 ± 0.13	–
10	213	1.0^†	2.0 ± 0.1	0.38 ± 0.05

–, Not determined.

*Shown are values ± SD.

^†[Fe^II₂(OD)₂(6-Me₃-TPA)₂]²⁺ was used in this study.

Supporting Figure 6

Fig. 6. Simulated concentrations of 2-4 against time. The rate constants employed in the simulation are k₁ = 7.0 ´ 10^–4 s^–1 (experimental result), k₂ = 1.11 ´ 10^–4 s^–1 (from the Eyring plot in Fig. 3), and k₃ = 8.9 ´ 10^–3 s^–1 (experimental result).

Supporting Figure 7

Fig. 7. Simulated concentrations of 2, 3, and 4 against time. The rate constants employed in the simulation are k₁ = 7.0 ´ 10^–4 s^–1 (experimental result), k₃ = 8.9 ´ 10^–3 s^–1 (experimental result), and k₂ = 1.11 ´ 10^–4 s^–1 (from the Eyring plot in Fig. 3).

Table 5. Percentage of 2–4 of the total amount of diiron complexes in the procedure of 1–4 in CH₂Cl₂ with different conditions

Condition	t, s	[2], %	[3], %	[4], %
1	3136	71	0.88	17
2	308	6.3	13	0.18
2	3248	0.88	71	18

Conditions were as follows. 1, k₁ = 7.0 ´ 10^–4 s^–1, k₂ = 1.11 ´ 10^–4 s^–1, and k₃ = 8.9 ´ 10^–3 s^–1. 2, k₁ = 7.0 ´ 10^–4 s^–1, k₃ = 8.9 ´ 10^–3 s^–1, and k₂ = 1.11 ´ 10^–4 s^–1. The two sets of values for condition 2 represent the fractions of 2–4 calculated at t = 3,085 (when 2 is maximum) and at t = 32,485 (when 3 is maximum).

Supporting Figure 8

Fig. 8. Resonance Raman spectra of the dark olive-green solution generated from the reaction of 1 with O₂ in CH₂Cl₂. Solvent bands are labeled with "S." (Upper) The original spectrum of the dark olive-green solution. (Lower) The spectrum recorded after raising the temperature of the sample to –70° C and staying for 15 min.

Supporting Figure 9

Fig. 9. The plot of the absorbance change at 640 nm against time of the conversion of 2 to 4 in CH₂Cl₂ at –70° C. The fast decrease finishes in 5 min, whereas the slow increase lasts >1 h.

Supporting Figure 10

Fig. 10. Titration of 2 with DTBP in CH₂Cl₂ at –80° C.

Supporting Figure 11

Fig. 11. Pseudo-first-order rate constants against concentration of normal or deuterated DTBP in the reaction with 2. Both straight lines go through the origin, and the slight difference of slopes of these two lines indicates that there is a small kinetic isotope effect for this reaction.

Table 6. Rate constants for the oxidation of normal or deuterated DTBP by 2 in CH₂Cl₂ at 193 K

Experiment no.	[2], mM	[2,4-DTBP], mM	*k_obs, 10^–1 s^–1**
1	0.2	2.0	0.47 ± 0.01
2	0.2	4.0	1.00 ± 0.01
3	0.2	6.0	1.40 ± 0.02
4	0.2	8.0	1.98 ± 0.02
5	0.2	10.0	2.63 ± 0.03
6	0.2	2.0^†	0.31 ± 0.01
7	0.2	4.0^†	0.64 ± 0.02
8	0.2	6.0^†	1.00 ± 0.02
9	0.2	8.0^†	1.46 ± 0.02