Single crystals of compounds 3, 4 and 5 were mounted on top of a cryoloop and transferred into the cold nitrogen stream (100 K) of a Bruker-AXS D8 Venture diffractometer. Data collection and reduction was done using the Bruker software suite APEX3.1 The final unit cell was obtained from the xyz centroids of 9884 (3), 9426 (4) or 9035 (5) reflections after integration. A multiscan absorption correction was applied, based on the intensities of symmetry-related reflections measured at different angular settings (SADABS). The structures were solved by direct methods using SHELXS,2 and refinement of the structure was performed using SHLELXL.3 For compound 3, refinement was frustrated by a disorder problem: from the solution it was clear that the tetrabutyl ammonium cation was disordered over two positions. To account for this disorder, a two-site occupancy model was used for which the s.o.f. was refined to 0.58 for the major fraction. Some atoms in the disordered part refined to non-positive definite displacement parameters when allowed to refine anisotropically, and ultimately RIGU instructions were applied to all atoms in the disordered part.
For all structures, the hydrogen atoms were generated by geometrical considerations, constrained to idealised geometries and allowed to ride on their carrier atoms with an isotropic displacement parameter related to the equivalent displacement parameter of their carrier atoms. Crystal data and details on data collection and refinement are presented in Table S1.
Table S1. Crystallographic data for compounds 3, 4 and 5.
3 4 5chem formula C36H53Br2Fe N5 C36H53Cl2Fe N5 C68H77Br2FeN8O
Figure S7. 1H NMR spectrum of FeBr2(THF)2 (1 eq), Bu4NBr (1 eq) and LK (1 eq) (THF-d8, 400 MHZ, 25 °C): t = 1h at r.t. (red line), t = 1 day at r.t (green line), t = 1 day at r.t. + 4 days at +60 °C (blue line).
S15
In situ NMR reaction of 1 + Bu4NBr in toluene-d8
In a glovebox 1 (1 eq, 10.0 mg, 1.5∙10-2 mmol) and Bu4NBr (2 eq, 9.7 mg, 1.5∙10-2 mmol) were mixed
in toluene-d8 in a Young’s NMR tube.
The 1H NMR spectrum acquired after 1h at r.t. shows 1 as major species. The reaction was warmed
up to +60 °C for 1 day and then to +90 °C for 3 days, during which 1 was completely consumed and
broad peaks for 3 and [Bu4N][L] appeared (the low intensity of the signals is due to the low solubility
of these two compounds in toluene-d8).
-8-6-4-2024681012141618202224262830323436δ(ppm)
3 3 3
11
1
11
[Bu4N]+
tol-d8
tol-d8
3 3
Figure S8. 1H NMR spectrum 1 (1 eq) and Bu4NBr (2 eq) (toluene-d8, 400 MHZ, 25 °C): t = 1h at r.t. (red line), t = 1 day at +60 °C (green line), t = 1 day at +60 °C + 3 days at +90 °C (blue line).
S16
Cyclic voltammetry
Figure S9. Cyclic voltammograms of compound 3 (ca. 1.50 mM solution of complex in THF;
0.1 M [Bu4N][PF6] electrolyte; scan rate = 0.1 V∙s-1).
Figure S10. Cyclic voltammogram of compound 3 (ca. 1.50 mM solution of complex in THF;
0.1 M [Bu4N][PF6] electrolyte, scan rate: a) 0.05 V∙s-1, b) 0.1 V∙s-1, c) 0.5 V∙s-1).
S17
Figure S11. Cyclic voltammograms of compounds 4 (ca. 1.50 mM solution of complex in THF;
0.1 M [Bu4N][PF6] electrolyte; scan rate = 0.1 V∙s-1).
Figure S12. Cyclic voltammogram of compounds 4 (ca. 1.50 mM solution of complex in THF;
0.1 M [Bu4N][PF6] electrolyte, scan rate: a) 0.05 V∙s-1, b) 0.1 V∙s-1, c) 0.3 V∙s-1).
S18
Figure S13. Cyclic voltammogram of compound 5 (ca. 1.50 mM solution of complex in 1,2-
dichloroethane; 0.1 M [Bu4N][PF6] electrolyte; scan rate: a) 0.05 V∙s-1, b) 0.1 V∙s-1, c) 0.5 V∙s-
1).
Figure S14. Cyclic voltammograms of compounds 5 (ca. 1.50 mM solution of complex in THF;
0.1 M [Bu4N][PF6] electrolyte; scan rate = 0.1 V∙s-1).
S19
Figure S15. Cyclic voltammogram of compound 5 (ca. 1.50 mM solution of complex in 1,2-
dichloroethane; 0.1 M [Bu4N][PF6] electrolyte; scan rate: a) 0.05 V∙s-1, b) 0.1 V∙s-1, c) 0.5 V∙s-
1).
Figure S16. Cyclic voltammogram of compound 51 with additional NBu4Br (ca. 1.50 mM
solution of complex in 1,2-dichloroethane; 0.1 M [Bu4N][PF6] electrolyte; scan rate 0.1 V∙s-1).
1 Compound 5 was isolated as a mixture with Bu4NBr: the voltammograms with added Bu4NBr refer to equivalents in addition to that already present in 5
S20
UV-Vis absorption spectroscopy
Figure S17. UV-Vis absorption spectra of compound 3 (pink line) and 4 (violet line) in THF.
Figure S18. UV-Vis absorption spectrum of compound 5 in CH2Cl2.
Figure S19. Physical appearance of compound 3 and 4 in THF and 5 in CH2Cl2.
S21
Infrared spectroscopy
Figure S20. IR spectrum of compound 5 in the solid state.
S22
References
(1) Bruker. APEX3, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. 2016.(2) Sheldrick, G. Acta Cryst. A 2008, 64, 112.(3) Sheldrick, G. Acta Cryst. C 2015, 71, 3.
