Voltammetric, EPR and UV-VIS-NIR spectroscopic studies associated with the characterisation of electrochemically generated tris(dithiocarbamato)cobalt(iv) complexes in dichloromethaneElectronic supplementary information (ESI) available: figures containing additional voltammetric, UV-VIS-NIR and EPR spectroscopic data. See http://www.rsc.org/suppdata/dt/b1/b104636p/

Abstract

Co III (S 2 CNR 2 ) 3 (R = Et, cyclohexyl) complexes were electrochemically oxidised by one-electron in CH 2 Cl 2 containing Bu 4 NPF 6 as the supporting electrolyte. Voltammetric, EPR and UV-VIS-NIR spectroscopic data indicated that the cation complexes, [Co IV (S 2 CNR 2 ) 3 ] ϩ , formed by oxidation of the parent Co III compounds were stable for at least several hours at low temperatures (T = 233 K), although instability was evident at higher temperatures and/or longer times. EPR spectroscopic data obtained by in situ electrogeneration of the oxidised species at low temperatures indicated that the unpaired electron largely resided on the metal centre, thereby confirming a formally Co IV state. The UV-VIS-NIR spectra of the [Co IV (S 2 CNR 2 ) 3 ] ϩ complexes showed a new set of low energy and moderate intensity series of bands at ν = 9600, 13300 and 15500 cm Ϫ1 (ε = 700-1500 L cm Ϫ1 mol Ϫ1 ) which were interpreted as ligand-tometal charge transfer excitations to the unfilled t 2g orbital. The EPR spectra of [Co IV (S 2 CNR 2 ) 3 ] ϩ (g // ≈ 2.65 and g ⊥ ≈ 1.90) required low temperatures to be detected (T < ca. 50 K) and displayed a high degree of anisotropy consistent with a distorted octahedral structure. III (S 2 CNR 2 ) 5 ] ϩ (R = Et and cyclohexyl) having been established, 14a,17 a later study by Barbier et al. 19 unexpectedly claimed to have isolated the Co IV monomers by oxidising Co(S 2 CNR 2 ) 3 with Fe(ClO 4 ) 3 in acetone. While the DALTON FULL PAPER

Stabilization of High‐Valent FeIVS6‐Cores by Dithiocarbamate(1−) and 1,2‐Dithiolate(2−) Ligands in Octahedral [FeIV(Et2dtc)3−n(mnt)n](n−1)− Complexes (n=0, 1, 2, 3): A Spectroscopic and Density Functional Theory Computational Study

“…It has convincingly been shown that the one-electron oxidation of diamagnetic [Co III A C H T U N G T R E N N U N G (S 2 CNEt 2 ) 3 ] to the corresponding monocation is metal-centered affording low-spin Co IV (S = 1 / 2 ). [4,5] EPR spectroscopy proved that the unpaired electron of [Co IV A C H T U N G T R E N N U N G (S 2 CNEt 2 ) 3 ] + resides largely on the metal center confirming the unusual Co IV oxidation state. [4] In no instance has an S,S'-coordinated dithiocarbamato(1À) ligand been shown to behave as a redox noninnocent ligand.…”

“…[4,5] EPR spectroscopy proved that the unpaired electron of [Co IV A C H T U N G T R E N N U N G (S 2 CNEt 2 ) 3 ] + resides largely on the metal center confirming the unusual Co IV oxidation state. [4] In no instance has an S,S'-coordinated dithiocarbamato(1À) ligand been shown to behave as a redox noninnocent ligand. The coordination chemistry of the hypothetical neutral radical [S 2 CNR 2 ]C has not been described to date.…”

“…Dithiocarbamato(1À) ligands are known to stabilize unusually high oxidation states (> + III) in their first-row transition metal-ion complexes. Thus, the monocations [M IV -A C H T U N G T R E N N U N G (S 2 CNEt 2 ) 3 ] + (M = Mn, [1][2][3] Fe, [2] Co, [3][4][5] Ni [6] ) have been reported. In general, the MS 6 polyhedron is distorted octahedral and the observed electronic ground states are d 3 (S = 3 / 2 ) for the Mn IV complex, low-spin d 4 (S = 1) for the Fe IV , low-spin d 5 (S = 1 / 2 ) for the Co IV , and low-spin d 6 (S = 0) for the Ni IV analogue.…”

The Effect of the Buffering Capacity of the Supporting Electrolyte on the Electrochemical Oxidation of Dopamine and 4‐Methylcatechol in Aqueous and Nonaqueous Solvents

“…A Perkin-Elmer Lambda 750 spectrophotometer was used in conjunction with an OSTLE cell (pathlength = 0.05 cm) using a Pt mesh working electrode. [63,64] The cavity of the spectrometer was purged from the atmosphere with a high volume flow of nitrogen gas.…”

In Situ EPR Characterization of a Cobalt Oxide Water Oxidation Catalyst at Neutral pH

“…There is general consensus that Co(IV) species are key reaction intermediates in the water oxidation. Co(IV), a d 7 ion, is an EPR-active species in both its high-spin ( 4 T 1 ) and low-spin ( 2 E) forms, and this method has been previously applied to a series of Co(IV) containing model complexes and minerals [19][20][21][22][23][24][25][26][27][28][29][30] including the Nocera catalyst. Ex situ EPR spectroscopy confirms that the net oxidation state of the Co ions of the film increases at potentials required for water oxidation catalysis.…”