. Author manuscript; available in PMC: 2011 Dec 22.

Published in final edited form as: J Am Chem Soc. 2010 Nov 29;132(50):17733–17740. doi: 10.1021/ja103998v

Table 2.

Half-wave Potentials (V) for the [Fe₂(SR)₂]^0/+ and [Fe₂(SR)₂]^+/2+ Couples for Fe₂[(SCH₂)₂X](CO)₃(dppv)(PMe₃). Conditions: 1 mM diiron complex, 100 mM [Bu₄N]PF₆, CH₂Cl₂ Solution, vs Fc^0/+, 0.1 V/s scan rate. Under our experimental conditions, an internal standard of Fc (1 mM) displayed ΔE_p ≈ 100 mV. The i_pa/i_pa values for E₁ were recorded under conditions where the scan range did not extend to E₂

Dithiolate	Electrolyte	E₁ for [Fe₂(SR)₂]^0/+ (ΔE_p, V) [i_pc/i_pa]	E₂ for [Fe₂(SR)₂]^+/2+ (ΔE_p) [i_pc/i_pa]	E₂ – E₁
(SCH₂)₂NBn (2′)	[(C₄H₉)₄N]PF₆	−0.643 0.118) [>0.9]	−0.128 (0.147) [>0.9]	0.515
(SCH₂)₂NBn (2′)	[(C₄H₉)₄N]BAr^F₄	−0.715 (0.111) [0.9]	−0.070 (0.222) [0.7]^b	0.645
(SCH₂)₂NH (2)	[(C₄H₉)₄N]PF₆	−0.561 (0.095) not determined^a	−0.363 (0.101) not determined^a	0.198
(SCH₂)₂NH (2)	[(C₄H₉)₄N]BAr^F₄	−0.624 (0.075) [>0.9]	−0.249 (0.175) [0.1]^b	0.375
(SCH₂)₂CH₂ (1)	[(C₄H₉)₄N]PF₆	−0.609 (0.126) [>0.9]	0.356 (0.160) [0.2]	0.965
(S₂C₂H₄)	[(C₄H₉)₄N]PF₆	−0.469 (0.121) [>0.9]	0.345 (0.143) [0.5]	0.930
(SCH₂)₂O (3)	[(C₄H₉)₄N]PF₆	−0.528 (0.139) [>0.9]	0.353 (0.233) [0.1]	0.840
[(SCH₂)₂NBn(H)]⁺ ([H2′]⁺)	[(C₄H₉)₄N]PF₆	E_p/2 = 0.040 (irrev.)	---	---
[(SCH₂)₂NH₂]⁺ ([H2]⁺)	[(C₄H₉)₄N]PF₆	E_p/2 = 0.050 (irrev.)	---	---

The close separation of the two oxidation steps precludes accurate measurement of this current ratio.

At fast scan rates the cathodic return wave of E₂ becomes broadened making the i_pc/i_pa value an inaccurate representation of reversibility. At slow scan rates E₂ is fully reversible.