Reactivity of Diiron Imido Complexes

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1 One-electron Oxidation Chemistry and Subsequent Reactivity of Diiron Imido Complexes Subramaniam Kuppuswamy, Tamara M. Powers, Bruce M. Johnson, Carl K. Brozek, Jeremy P. Krogman, Mark W. Bezpalko, Louise A. Berben, Jason M. Keith, # Bruce M. Foxman, Christine M. Thomas*, Department of Chemistry, Brandeis University, 415 South Street, MS 015, Waltham, MA 02454, United States. Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA. Department of Chemistry, University of California-Davis, Davis, CA 95616, USA. # Department of Chemistry, Colgate University, 13 Oak Dr., Hamilton, NY Index Page NMR spectra, IR spectra, and cyclic voltammograms (CVs) 31 P and 19 F NMR spectra of the crude reaction mixture of 1 and Fc[PF 6 ] S3 1 H NMR spectrum and CV of 3 S4-S5 1 H NMR spectrum and CV of 4 S6-S7 1 H NMR and IR spectrum of 5 S8-S9 1 H NMR and IR spectrum of 6 S10-S11 UV-Vis-NIR data for 3 and 5 X-ray Crystallography Experimental Details X-ray diffraction experimental data collection and refinement details for 3-6 Fully labelled displacement ellipsoid representation of 3 X-ray data collection, solution, and refinement details for 3 Fully labelled displacement ellipsoid representation of 4 X-ray data collection, solution, and refinement details for 4 Fully labelled displacement ellipsoid representation of 5 X-ray data collection, solution, and refinement details for 5 S1 S11 S12 S13 S14-S15 S16 S17 S18 S19 S20

2 Fully labelled displacement ellipsoid representation of 6 X-ray data collection, solution, and refinement details for 6 Computational Details Pictorial representations of the calculated frontier molecular orbitals of 7 Calculated interatomic distances (Å) in complex 7 using two different spin states S24 XYZ coordinates of the DFT-optimized geometry of 7 Pictorial representations of the calculated frontier molecular orbitals of 3 Calculated interatomic distances (Å) in complex 7 using two different spin states S29 XYZ coordinates of the DFT-optimized geometry of 3 XYZ coordinates of the DFT-optimized structure of the antiferromagnetically coupled S = 2 complex 3. Computed spin density surfaces for the ferromagnetically coupled S = 3 complex 3. XYZ coordinates of the DFT-optimized structure of the ferromagnetically coupled S = 3 complex 3. XYZ coordinates of the DFT-optimized structure of the antiferromagnetically coupled S = 2 complex 5. Computed spin density surfaces for the ferromagnetically coupled S = 3 complex 5 with α spin density in yellow and β spin density in blue. XYZ coordinates of the DFT-optimized structure of the ferromagnetically coupled S = 3 complex 5. References S21 S22-S23 S24 S25-S28 S29 S30-S33 S34-S37 S38 S38-S41 S42-S44 S45 S45-S48 S49 S2

3 Figure S1. 19 F{ 1 H} NMR spectrum (A) and 31 P{ 1 H} NMR spectrum (B) of the volatile PF 5 byproduct from the crude reaction mixture of 1 and Fc[PF 6 ] in THF. A B S3

4 Figure S2. 1 H NMR spectrum of 3 in C 6 D 6. Figure S3. 1 H NMR spectrum of 3 in benzene-d 6 (Synthesized via the oxidation of 1 with ferrocenium tetrafluoroborate). S4

5 Figure S4. Cyclic voltammogram of 3 (2 mm in 0.4 M [ n Bu 4 N][PF 6 ] in THF, scan rate = 100 mv/s). The blue trace represents the full cyclic voltammogram, starting at the open circuit potential and scanning in the negative direction. The green trace is a cyclic voltammogram focusing solely on the reductive events, starting at -1.7 V (vs Fc) and proceeding in the negative direction. The red trace is a cyclic voltammogram focusing solely on the oxidative events, starting at ~0.3 V (vs Fc) and scanning in the negative direction. Potential (V vs Fc) Figure S5. Cyclic voltammogram of 1 (2 mm in THF) using in 0.4 M [ n Bu 4 N][PF 6 ] (red trace) and [ n Bu 4 N][ClO 4 ] (blue trace) as the supporting electrolyte (scan rate = 100 mv/s) Potential (V vs Fc) S5

6 Figure S6. 1 H NMR spectrum of 4 in C 6 D 6. S6

7 Figure S7. Cyclic voltammogram of 4 (2 mm in 0.4 M [ n Bu 4 N][PF 6 ] in THF, scan rate = 100 mv/s) is shown in blue and the red overlay is complex 3. Potential (V vs Fc) S7

8 Figure S8. 1 H NMR spectrum of 5 in C 6 D 6. S8

9 Figure S9. IR spectrum of 5 (KBr solution cell, benzene). S9

10 Figure S10. 1 H NMR spectrum of 6 in C 6 D 6. S10

11 Figure S11. IR spectrum of 6 (KBr solution cell, benzene). Figure S12. UV-Vis-NIR spectra for complexes 3 and 5 (in benzene solution). S11

12 Table S1. X-ray diffraction experimental data collection and refinement details for pentane 5 2Et 2 O 6 2Et 2 O chemical formula C 49 H 60 F 1 Fe 2 N 4 P 3 C 60 H 78 F 1 Fe 2 N 4 P 3 C 53 H 66 F 1 Fe 2 N 3 O 3.5 P 3 C 61 H 84 F 1 Fe 2 N 5 O 1.5 P 3 fw T (K) λ (Å) a (Å) (10) (10) (6) (3) b (Å) (11) (8) (8) (13) c (Å) (10) (15) (11) (5) α (deg) (3) 90 β (deg) (3) (3) (6) γ (deg) (3) 90 V (Å 3 ) (8) (6) (3) 12028(2) space group Pbca P2 1 /c P-1 C2/c Z, Z 8, 1 4, 1 2, 1 8, 1 D calcd (g/cm 3 ) µ (cm 1 ) R1, wr2 a (I > 2σ) , , , , a R1 = Σ( Fo Fc ) / Σ Fo, wr2 = {Σ[w(Fo 2 - Fc 2 )] 2 /Σ[w(Fo) 2 ]} 1/2 S12

13 Figure S13. Fully labelled displacement ellipsoid representation (50%) of 3. Hydrogen atoms have been omitted for clarity. S13

14 X-ray data collection, solution, and refinement for 3. All operations were performed on a Bruker-Nonius Kappa Apex2 diffractometer, using graphite-monochromated MoKα radiation. All diffractometer manipulations, including data collection, integration, scaling, and absorption corrections were carried out using the Bruker Apex2 software. 1 Preliminary cell constants were obtained from three sets of 12 frames. Data collection was carried out at 120K, using a frame time of 10 sec and a detector distance of 60 mm. The optimized strategy used for data collection consisted of four phi and three omega scan sets, with 0.5 steps in phi or omega; completeness was 99.8 %. A total of 1067 frames were collected. Final cell constants were obtained from the xyz centroids of 9878 reflections after integration. From the systematic absences, the observed metric constants and intensity statistics, space group Pbca was chosen initially; subsequent solution and refinement confirmed the correctness of this choice. The structure was solved using SuperFlip, 2 and refined (full-matrix-least squares) using the Oxford University Crystals for Windows program. 3 All non-hydrogen atoms were refined using anisotropic displacement parameters. After location of H atoms on electrondensity difference maps, the H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C---H in the range Å and U iso (H) in the range times U eq of the parent atom), after which the positions were refined with riding constraints. 4 During the structure solution, electron density difference maps revealed that there were considerable disordered solvent molecules which could not be successfully modeled. From history, the remaining solvate was likely diethyl ether in a volume of Å 3 per unit cell (8.8%). It appeared that the cavity area contained about four ether molecules, located near the centers of symmetry at (0, 0, 0), (0, ½, ½), (½, ½, 0) and (½, 0, ½) as shown in the bc projection below. 5 S14

Modeling with or without restraints was unsuccessful, as was step by step acquisition of peaks using successive electron density difference maps.

15 Modeling with or without restraints was unsuccessful, as was step by step acquisition of peaks using successive electron density difference maps. Thus, the structure factors were modified using the PLATON SQUEEZE 6, 7 technique, in order to produce a solvate-free structure factor set. PLATON reported a total electron density of 157 e - per unit cell, likely representing four ether molecules, consistent with our earlier observations. Use of the SQUEEZE technique resulted in a decrease of ca. 1.5 % in R. The final least-squares refinement converged to R 1 = (I > 2σ(I), data) and wr 2 = (F 2, data, 532 parameters). The final CIF is available as supporting material. S15

16 Figure S14. Fully labelled displacement ellipsoid representation (50%) of 4. Hydrogen atoms have been omitted for clarity. S16

17 X-ray data collection, solution, and refinement for 4. All operations were performed on a Bruker-Nonius Kappa Apex2 diffractometer, using graphite-monochromated MoKα radiation. All diffractometer manipulations, including data collection, integration, scaling, and absorption corrections were carried out using the Bruker Apex2 software. 1 Preliminary cell constants were obtained from three sets of 12 frames. Data collection was carried out at 120K, using a frame time of 10 sec and a detector distance of 60 mm. The optimized strategy used for data collection consisted of three phi and five omega scan sets, with 0.5 steps in phi or omega; completeness was 99.1%. A total of 2600 frames were collected. Final cell constants were obtained from the xyz centroids of 9920 reflections after integration. From the systematic absences, the observed metric constants and intensity statistics, space group P2 1 /c was chosen initially; subsequent solution and refinement confirmed the correctness of this choice. The structure was solved using SIR-92, 8 and refined (full-matrix-least squares) using the Oxford University Crystals for Windows program. 3 All non-hydrogen atoms were refined using anisotropic displacement parameters. After location of H atoms on electrondensity difference maps, the H atoms were initially refined with soft restraints on the bond lengths and angles to regularise their geometry (C---H in the range Å and U iso (H) in the range times U eq of the parent atom), after which the positions were refined with riding constraints. 4 The pentane solvate was disordered; this was modeled as a two-component disorder. Major component methylene C atoms C(570) and C(590) were refined by using anisotropic displacement parameters, while minor component atoms C(570) and C(590) were refined by using isotropic displacement parameters. Occupancies of the major and minor components were constrained to sum to 1.0; the major component occupancy refined to a value of 0.762(4). The S17

18 final least-squares refinement converged to R 1 = (I > 2σ(I), data) and wr 2 = (F 2, data, 640 parameters). The final CIF is available as supporting material. S18

19 Figure S15. Fully labelled displacement ellipsoid representation (50%) of 5. Hydrogen atoms have been omitted for clarity. S19

20 X-ray data collection, solution, and refinement for 5. All operations were performed on a Bruker-Nonius Kappa Apex2 diffractometer, using graphite-monochromated MoKα radiation. All diffractometer manipulations, including data collection, integration, scaling, and absorption corrections were carried out using the Bruker Apex2 software. 1 Preliminary cell constants were obtained from three sets of 12 frames. Data collection was carried out at 120K, using a frame time of 30 sec and a detector distance of 60 mm. The optimized strategy used for data collection consisted of three phi and four omega scan sets, with 0.5 steps in phi or omega; completeness was 97.6%. A total of 2815 frames were collected. Final cell constants were obtained from the xyz centroids of 9888 reflections after integration. From the systematic absences, the observed metric constants and intensity statistics, space group P-1 was chosen initially; subsequent solution and refinement confirmed the correctness of this choice. The structure was solved using SIR-92, 8 and refined (full-matrix-least squares) using the Oxford University Crystals for Windows program. 3 One of the two ether solvate molecules was disordered, with atom O(3) occupying a center of symmetry; occupancies of atoms C(53) and C(54) (required to be 0.5) were fixed in the refinement. Atoms C(53) and C(54) were refined by using isotropic displacement parameters, and the C(53) to O(3) bond length was restrained to a normal value (1.42 Å). All other non-hydrogen atoms were refined using anisotropic displacement parameters. After location of H atoms on electron-density difference maps, the H atoms were initially refined with soft restraints on the bond lengths and angles to regularise their geometry (C---H in the range Å and U iso (H) in the range times U eq of the parent atom), after which the positions were refined with riding constraints. 4 The final least-squares refinement converged to R 1 = (I > 2σ(I), data) and wr 2 = (F 2, data, 591 parameters). The final CIF is available as supporting material. S20

21 Figure S16. Fully labelled displacement ellipsoid representation of 6. Hydrogen atoms have been omitted for clarity. S21

22 X-ray data collection, solution, and refinement for 6. All operations were performed on a Bruker-Nonius Kappa Apex2 diffractometer, using graphite-monochromated MoKα radiation. All diffractometer manipulations, including data collection, integration, scaling, and absorption corrections were carried out using the Bruker Apex2 software. 1 Preliminary cell constants were obtained from three sets of 12 frames. Data collection was carried out at 120K, using a frame time of 40 sec and a detector distance of 65 mm. The optimized strategy used for data collection consisted of three phi and three omega scan sets, with 0.5 steps in phi or omega; completeness was 99.4%. A total of 1761 frames were collected. Final cell constants were obtained from the xyz centroids of 2625 reflections after integration. From the systematic absences, the observed metric constants and intensity statistics, space group C2/c was chosen initially; subsequent solution and refinement confirmed the correctness of this choice. The structure was solved using SIR-92, 8 and refined (full-matrix-least squares) using the Oxford University Crystals for Windows program. 3 All non-hydrogen atoms were refined using anisotropic displacement parameters. After location of H atoms on electron-density difference maps, the H atoms were initially refined with soft restraints on the bond lengths and angles to regularise their geometry (C---H in the range Å and U iso (H) in the range times U eq of the parent atom), after which the positions were refined with riding constraints. 4 The asymmetric unit contains one complex and 1.5 ether solvate molecules. The oxygen atom of the ether solvate at half occupancy occupies a crystallographic twofold axis. The nominally full-occpancy ether molecule was actually disordered and modeled by using twocomponents. All component atoms were refined by using isotropic refinement parameters. Occupancies of the major [C(58) through C(61); O(2)] and minor components [C(580) through C(610); O(20)] were constrained to sum to 1.0; the major component occupancy refined to a S22

23 value of 0.600(11). The final least-squares refinement converged to R 1 = (I > 2σ(I), 6449 data) and wr 2 = (F 2, data, 659 parameters). The final CIF is available as supporting material. S23

Figure S17. Pictorial representations of the frontier molecular orbitals of 7 (and their relative energies) calculated using DFT calculations. Table S2.

24 Figure S17. Pictorial representations of the frontier molecular orbitals of 7 (and their relative energies) calculated using DFT calculations. Table S2. Calculated (DFT geometry optimization) interatomic distances (Å) in complex 7 using two different spin states. S = 2 S = 3 Fe-Fe Fe-P (avg) Fe-N (avg) Fe-N imide Relative energy (kcal/mol) S24

25 Table S3. XYZ coordinates of the DFT-optimized geometry of 7. Symbol X Y Z Fe Fe P P P N N N N C C C C C C C C C C C C C C C C C S25

26 C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C H H H H H H H H H H S26

27 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 H H H H H H H H H H S27

28 H H H H H H H H S28

Figure S18. Pictorial representations of the frontier molecular orbitals of 3 (and their relative energies) calculated using DFT calculations. Table S4.

29 Figure S18. Pictorial representations of the frontier molecular orbitals of 3 (and their relative energies) calculated using DFT calculations. Table S4. Experimental (X-ray) and calculated (DFT geometry optimization) interatomic distances (Å) in complex 3 using two different spin states (the optimized geometry with S = 2 is most consistent with the X-ray derived geometry). Experiment Calculated S = 2 S = 3 Fe-Fe (3) Fe-P (avg) Fe-N (avg) Fe-N imide Fe-F Relative energy (kcal/mol) S29

30 Table S5. XYZ coordinates of the DFT-optimized structure of 3. Symbol X Y Z Fe -4.3E Fe P P P N N N N C C C C C C C C C C C C C C C C C S30

31 C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C H H H H H H H H H H S31

32 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 H H H H H H H H H H S32

33 H H H H H H H H F S33

34 Table S6. XYZ coordinates of the DFT-optimized structure of the antiferromagnetically coupled S = 2 complex 3. Tag Symbol X Y Z 1 Fe Fe P P P N N N N C C C C C C C C C C C C C C C C C S34

35 27 C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C H H H H H H H H H H S35

36 69 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 H H H H H H H H H H S36

37 111 H H H H H H H H F S37

Figure S19. Computed spin density surfaces for the ferromagnetically coupled S = 3 complex 3 with α spin density in yellow and β spin density in blue. Table S7.

38 Figure S19. Computed spin density surfaces for the ferromagnetically coupled S = 3 complex 3 with α spin density in yellow and β spin density in blue. Table S7. XYZ coordinates of the DFT-optimized structure of the ferromagnetically coupled S = 3 complex 3. Tag Symbol X Y Z 1 Fe Fe P P P N S38

39 7 N N N C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C S39

40 49 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 S40

41 91 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 F S41

42 Table S8. XYZ coordinates of the DFT-optimized structure of the antiferromagnetically coupled S = 2 complex 5. Tag Symbol X Y Z 1 Fe Fe P P P F N N N C C C C C C C C C C C C C C C C S42

43 26 C C C C C C C C C C C C C C C C C 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 S43

44 68 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 H H H H H H H H O O S44

Figure S20. Computed spin density surfaces for the ferromagnetically coupled S = 3 complex 5 with α spin density in yellow and β spin density in blue. Table S9.

45 Figure S20. Computed spin density surfaces for the ferromagnetically coupled S = 3 complex 5 with α spin density in yellow and β spin density in blue. Table S9. XYZ coordinates of the DFT-optimized structure of the ferromagnetically coupled S = 3 complex 5. Tag Symbol X Y Z 1 Fe Fe P P P S45

46 6 F N N N C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C S46

47 48 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 H S47

48 90 H H H H H H H H H H H H H H H H H H O O S48

49 References (1) Apex2, Version 2 User Manual, M86-E01078, Bruker Analytical X-ray Systems, Madison, WI, June (2) Palatinus, L.; Chapuis, G.; J. Appl. Cryst. 2007, 40, 786. (3) Betteridge, P. W.; Carruthers, J. R.; Cooper, R. I.; Prout, K.; Watkin, D. J. J. Appl. Cryst. 2003, 36, 1487; Prout, C.K;. Pearce, L.J. CAMERON, Chemical Crystallography Laboratory, Oxford, UK, (4) Cooper, R. I.; Thompson, A. L.; Watkin, D. J. J. Appl. Cryst. 2010, 43, (5) Macrae, C. F; Bruno, I. J.; Chisholm, J. A.; Edgington, P. R.; McCabe, P.; Pidcock, E.; Rodriguez-Monge, L.; Taylor, R.; van de Streek, J.; Wood, P. A. J. Appl. Cryst., 41, , 2008 (6) (a) Spek, A. L. Acta Crystallogr., Sect A 1990, A46, C34. (b) PLATON, A Multipurpose Crystallographic Tool, Utrecht University, Utrecht, The Netherlands, Spek, A. L (7) v. d. Sluis, P.; Spek, A. Acta Crystallogr., Sect. A 1990, A46, (8) Altomare, A; Cascarano, G; Giacovazzo, G.; Guagliardi, A.; Burla, M. C.; Polidori, G.; Camalli, M. J. Appl. Cryst. 1994, 27, 435. S49

Comparison of the Electronic Properties of Diarylamido-Based PNZ Pincer Ligands: Redox Activity at the Ligand and Donor Ability Towards the Metal

Supporting Information Comparison of the Electronic Properties of Diarylamido-Based PNZ Pincer Ligands: Redox Activity at the Ligand and Donor Ability Towards the Metal Jillian J. Davidson 1, Jessica C.