Supporting Information

© Wiley-VCH 2008

69451 Weinheim, Germany

Supporting Information for:

An Inverted and More Oxidizing Isomer of [FeIV(O)(TMC)(NCCH3)]2+

Kallol Ray, Jason England, Adam, T. Fiedler, Marlène Martinho, Eckard Münck,* Lawrence Que Jr.*

Materials and physical measurements

Materials: All reagents and dry solvents were purchased from Aldrich and used as

received unless noted otherwise. Iodosobenzene,[1] (PhIOIPh)(BF4)2 [2] and the salt [FeII

(TMC)(OTf)](OTf),[3] were prepared according to published procedures. 1H NMR spectra were recorded on a Bruker AC250 Varian Unity 500 MHz

spectrometer at ambient temperature. Chemical shifts (ppm) were referenced to the

residual protic solvent peaks. UV-Visible studies were performed using a HP8453A

diode array spectrometer equipped with a cryostat from Unisoku Scientific Instruments

(Osaka, Japan). Electrospray ionization mass spectrometry experiments were carried out

on a Bruker BioTOF II mass spectrometer using a spray chamber voltage of 4000 V and a

gas carrier temperature of 60ºC. Mössbauer spectra were recorded with two

spectrometers, using Janis Research Super-Varitemp dewars that allowed studies in

applied magnetic fields up to 8.0 T in the temperature range from 1.5 to 200 K.

Mössbauer spectral simulations were performed using the WMOSS software package

(WEB Research, Edina, MN). Isomer shifts are quoted relative to Fe metal at 298 K. The

mössbauer spectra of 2 and 2-NCS were simulated using the S = 1 spin Hamiltonian of eq

1. The parameters obtained are listed in Table S1 and compared with those reported for 1-

NCCH3 and 1-NCS.

H = D(S z

2 – 2/3) + E(Sx2-Sy

2) + 2βB S + S ⋅A ⋅I – gnβn B ⋅I + HQ (1)

HQ = (eQVzz/12)[3Iz2 -15/4 + η(Ix

2-Iy2)

∆EQ = (eQVzz/2){1 + η2/3}1/2

Electrical conductivity measurements for the complexes were performed in CH3CN

at 25 oC using a Fischer Scientific Accumet portable AP65 model conductivity bridge

with a cell constant of 1.0 cm-1. The equivalent conductance, Λe , was calculated from the

conductance measurements and plotted against the square root of the concentration of

each sample. Extrapolation of the linear portion to zero concentration resulted in the

determination of the equivalent conductance at infinite dilution, Λ0. A plot of (Λ0- Λe)

vs. the square root of the concentration gave the Onsager plots shown in Figure S2.

X-ray absorption spectroscopy (XAS) data for 2 (20 mM in MeCN) were

collected at beamline 9-3 of the Stanford Synchrotron Radiation Laboratory (SSRL),

Stanford Linear Accelerator Center. X-ray absorption spectra at the iron K-edge were

collected between 6.9 and 8.0 eV at a constant temperature of ~15 K. EXAFS data

analysis was performed with the program EXAFSPAK.[4] Refinement was carried out on

k3χ(k) data, using phase and amplitude functions obtained from FEFF.[5] For each fit, the

parameters R and σ2 were optimized, while n was kept fixed. n was then systematically

varied in integer steps. The goodness of fit (GOF) was determined using the formula:

GOF = Σ (χ calc – χ exp)2 / N, where N is the number of data points. The threshold energy

(E0) was also varied, although it was maintained at a common value for all shells.

The SSRL Structural Molecular Biology Program is supported by the Department

of Energy, Office of Biological and Environmental Research, and by the National

Institutes of Health, National Center for Research Resources, Biomedical Technology

Program.

The density functional theory (DFT) calculations were performed using Becke’s

three parameter hybrid (B3LYP) and basis set 6-311g provided by the Gaussian’03

software package.[9] The SCF procedure and geometry optimization were terminated

upon reaching the default convergence criteria. The model for 1-NCCH3 was constructed

using the crystal structure of 1-NCCH3. The model for 2 was constructed using the

optimized geometry for 1-NCCH3 and exchanging the acetonitrile and terminal oxygen

groups. The optimized geometries of 1-NCCH3 and 2 are shown in Figure S10.

Figure S1. 4.2 K (a and b) and 30 K (c) Mössbauer spectra of 2. The spectra were

recorded in applied parallel fields as indicated. A high-spin Fe3+ contaminant

representing 15 % of total Fe has been removed from the spectra. The red solid lines are

spectral simulations using the S = 1 spin Hamiltonian of eq 1 and the parameters listed in

Table S1.

Figure S2. Onsager conductivity plots for the complexes in CH3CN at 25 oC.

Figure S3. ESI-MS spectra of 1-NCCH3 and 2 in CH3CN. The inset shows the observed

isotope distribution patterns for the peaks at m/z = 184.4 and 476.9.

Figure S4. Fourier transform (R’ space) of the Fe K-edge EXAFS data [k3*χ(k)] of 2.

Fourier transform range k = 2.0-14.0 Å-1. Experimental data (---) and fit 8 (solid line)

with 1 O at 1.64 Å, 5 N at 2.08 Å, 3 C at 2.87 Å, and 2 C at 3.04 Å (Table S2). Inset:

Unfiltered EXAFS data (---) with the corresponding fit (solid).

Figure S5. 4.2 K spectrum of 2-NCS in acetonitrile recorded in an 8.0 T field applied

parallel to the observed γ- radiation. The dotted line is a spectral simulation, using an S =

5/2 spin Hamiltonian, of a high-spin Fe3+ contaminant representing 30% of the iron in the

sample. The red solid line is a spectral simulation for Fe(IV)-oxo complex 2-NCS.

Figure S6. 30 K Mössbauer spectrum of 2-NCS recorded in an 8.0 T field applied

parallel to the observed γ- radiation (Fe3+ contaminant not removed). The red solid line is

a spectral simulation using the S = 1 spin Hamiltonian of eq 1.

Figure S7. 1H NMR spectra of 1-NCS (Top) and 2-NCS (Bottom) at –30 oC in CD3CN in the

range 70 to -60 ppm. The insets show the NMR spectra in the range –170 to –220 ppm. The peaks

are assigned to the TMC ligand as follows: ■ -NCH2CH2CH2N- ; ● –NCH2; ▲-NCH3.

Figure S8. Changes in the absorption spectrum associated with the reaction of 2 with 1

eq [FeII(BnTPEN)(CH3CN)]2+ in CH3CN at 25 oC.

Figure S9. Changes in the absorption spectrum associated with the reaction of 2,

generated by addition of 2 eq PhI(OAc)2 and 0.2 eq NBu4BF4 to [FeII(TMC)(OTf)](OTf),

with 1eq [FeII(TMC)(OTf)](OTf) in CH3CN at 0 oC.

Figure S10. Optimized geometries for 1-NCCH3 and 2.

1-NCCH3 2

Bond distances calculated for 1-NCCH3: Fe=O, 1.641 Å; Fe-NCCH3, 2.100 Å, Fe-

NTMC(ave), 2.133 Å Bond distances calculated for 2: Fe=O, 1.628 Å; Fe-NCCH3,

2.199 Å, Fe-NTMC(ave), 2.118 Å

Table S1. Fine structure parameters and hyperfine parameters for 1-NCCH3, 2, 1-NCS, and 2-

NCS.

Complex D (cm-1)

E/D (Ax,Ay,Az)/gnβn (T)

∆EQ (mm/s)

η δ (mm/s)

Ref.

1-NCCH3 26.95 (a) 0 -21.3, -20.3 -2.9 1.24 0.5 0.17 3 2 27.5 0 -22, -22, -5 0.78 0.2 0.14 This

work 1-NCS 30 0 -22, -22, -5 0.61(b) 0.2 0.16 6 2-NCS 31 0 -23, -23, -5 0.60 0 0.14 This

work

(a) Krystek et al. [7] recently determined for 1-NCCH3 by high-frequency EPR the

zero-field splitting parameters and the g-tensor (gx,y=2.10 and gz = 2.04). We

have used their D- value (26.95 cm-1 rather than our previous3 29 ± 3 cm-1) and

g-values (gx,y = 2.1 rather than 2.3) to (slightly) refine the A-tensor of 1-NCCH3.

(b) The values for 1-NCS were reported previously by Sastri et al.[8] to be ∆EQ =

0.55 mm/s and δ= 0.18 mm/s based on a preparation containing a ≈ 50%

diiron(III) contaminant. The parameters of ref 6, based on a preparation

containing a 15% mononuclear Fe3+, are more precise.

Table S2. EXAFS Fitting Results for Complex 2 and 1-NCCH3.a

a Fourier-transform range is 2 – 14 Å-1 (resolution = 0.13 Å). σ2 is in units of 103 Å2. b GOF = goodness of fit. c ref 6 d ref 3

Table S3. Comparative reactivity of the complexes

k2 (M-1s-1) Complex

PPh3a

)

DHAb)

1-NCCH3 0.8 0.13

2 28 22 a)at -20 oC; b) at 0 oC;

Fe-N/O Fe-N/O Fe-N/O Fe···C

Fit no n R (Å) σ2 n R (Å) σ2 n R

(Å) σ2 n R

(Å) σ2 GOF

b 1 6 2.07 3.9 714 2 5 2.07 2.8 1 1.64 0.6 286 3 4 2.08 1.9 2 1.65 4.4 346 4 5 2.07 2.8 1 1.64 0.6 4 2.97 5.4 195 5 5 2.07 2.9 1 1.64 1.0 4 3.01 6.7 152 3 2.85 9.7 6 4 2.09 1.3 1 1.64 1.4 1 1.97 0.9 4 3.00 5.7 151 3 2.83 9.5 7 3 2.08 1.7 1 1.64 1.2 2 2.02 6.0 4 3.01 6.4 153 3 2.84 9.2 8 5 2.08 3.0 1 1.64 1.1 2 3.04 1.9 147 3 2.87 5.5

Results for 1-NCCH3 EXAFSc 5 2.08 5.8 1 1.64 3.8 4 2.97 6.5

XRDd 2.084(3) 1.646(3)

Table S4. X, Y and Z coordinates of the optimized geometry of 1-NCCH3.

Atoms x, y, z coordinates Fe O N N N N C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H N C C H H H

-0.019983 0.003211 -0.205279 0.007747 0.019954 -1.845446 -1.414649 1.592128 -0.337296 1.457019 1.560914 -0.145963 1.455736 -1.556876 -0.178535 -1.415762 -1.581453 -0.370033 -0.610961 2.660376 -1.055696 0.715957 2.875358 -0.368832 2.406936 1.321923 -1.317560 3.198161 0.012728 -1.260839 2.405491 -1.293976 -1.345167 0.713667 -2.865898 -0.428775 -0.613404 -2.635620 -1.110234 -2.614501 -1.252260 -1.245280 -3.370548 0.011248 -0.855550 -2.614265 1.282419 -1.218743 -1.921140 2.129342 0.974573 2.276064 1.760155 1.105055 2.274792 -1.782488 1.067867 -1.923366 -2.145471 0.930001 -1.181863 3.591922 -1.077436 -0.471789 2.319955 -2.076214 0.577492 3.345207 0.602033 1.343671 3.546637 -0.957268 3.111565 2.157876 -1.333312 1.810371 1.358142 -2.223436 3.856471 0.021590 -2.134506 3.877571 0.003242 -0.407408 1.808619 -1.310455 -2.251396 3.109168 -2.130208 -1.378802 1.340658 -3.524958 -1.031548 0.575466 -3.356096 0.531992 -1.185144 -3.566077 -1.150492 -0.474511 -2.275086 -2.123851 -3.280624 -2.118140 -1.218374 -2.244735 -1.146482 -2.261792 -3.685170 0.000551 0.189547 -4.300124 0.017314 -1.430667 -2.245146 1.198422 -2.237540 -3.280030 2.147820 -1.173073 -2.548725 3.003411 0.793779 -1.098564 2.418193 1.617627 -2.512903 1.373870 1.480061 2.924881 2.628699 0.976557 2.898586 0.902209 1.312283 1.622083 1.938688 1.951020 2.926430 -2.645753 0.919539 1.620668 -1.983530 1.908779 2.894032 -0.927340 1.295470 -2.555987 -3.011806 0.730286 -2.510545 -1.398714 1.453444 -1.101576 -2.453749 1.565119 -0.103655 -0.017950 1.892107 -0.155887 -0.038316 3.052820 -0.218491 -0.062675 4.502335 0.532135 -0.742211 4.909154 -1.200794 -0.396311 4.840359 -0.035907 0.931651 4.913079

Table S5. X, Y and Z coordinates of the optimized geometry of 2.

Atoms x, y, z coordinates Fe N N N N C C C C C C C C C C C C C C H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H H N C C H H

-0.020542 0.000436 -0.425617 1.383894 1.573369 -0.393515 -1.470552 1.551871 -0.318855 -1.470189 -1.551417 -0.321567 1.384164 -1.572259 -0.396190 0.687507 2.667615 0.385469 -0.723269 2.872081 -0.126356 -2.414832 1.317757 0.850176 -3.198232 -0.000883 0.811401 -2.414567 -1.319444 0.847834 -0.722718 -2.871831 -0.131292 0.687997 -2.667961 0.380932 2.705548 -1.277773 0.290624 3.400389 0.000555 -0.168659 2.705397 1.278030 0.292741 1.688465 2.068664 -1.791110 -2.291416 1.731989 -1.579972 -2.290911 -1.729547 -1.583049 1.688813 -2.065094 -1.794629 1.253033 3.598698 0.295389 0.690574 2.382990 1.432240 -0.704647 3.377788 -1.087259 -1.287274 3.511227 0.554613 -3.133542 2.141998 0.857731 -1.830172 1.394073 1.761978 -3.837730 -0.001728 1.699111 -3.897034 -0.000225 -0.024283 -1.829860 -1.397221 1.759502 -3.133115 -2.143838 0.853999 -1.286631 -3.512242 0.548559 -0.703993 -3.375864 -1.093072 1.253715 -3.598776 0.289275 0.690976 -2.385142 1.428187 3.358739 -2.137278 0.120807 2.516490 -1.224203 1.361036 3.574225 0.001456 -1.244569 4.397945 0.000255 0.278626 2.516489 1.222802 1.363079 3.358433 2.137895 0.124151 2.324570 2.953207 -1.728055 0.775954 2.307429 -2.320204 2.194759 1.294765 -2.353939 -2.870039 2.653634 -1.500421 -2.975904 0.910175 -1.721758 -1.630803 1.776621 -2.437202 -2.869589 -2.651288 -1.505001 -1.630185 -1.772923 -2.440266 -2.975291 -0.907462 -1.723713 2.325499 -2.949332 -1.733110 2.194504 -1.289991 -2.356345 0.776354 -2.303618 -2.323914 0.180921 -0.001343 1.763810 0.323313 -0.002903 2.918781 0.492585 -0.005290 4.360542 0.990696 0.907157 4.692500 1.095792 -0.857743 4.677259

H O

-0.474977 -0.067175 4.861520 -0.085743 0.001901 -2.052099

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