C/O/P/S cycles derived from oxidative intramolecular disulfide (-S-S-) coupling of ferrocenyl dithiophosphonates

The symmetrical 2,4-diferrocenyl-1,3-dithiadiphosphetane disulfide dimer, [FcP(mu-S)S](2) (Fc = ferrocenyl), reacts with ethanediol (molar ratio 1:1), trans-1,2-cyclohexanediol (molar ratio 1:1) and pentaerythritol (molar ratio 2:1) at 70 degrees C to form the respective dithiophosphonic acids in high yield. The acids were readily deprotonated by anhydrous ammonia to yield the corresponding ammonium salts (NH4)(2)[S2P(Fc)OCH2CH2O(Fc)PS2] (1), (NH4)(2)[(S(2)PFc)(2)(trans-1,2-O,O'-C6FH10)] (2) and (NH4)(4)[C {CH2OPS2(Fc)}(4)] (3). The salts undergo facile intramolecular oxidation with the mild oxidant iodine in a I-2/MeOH mixture resulting in new ferrocene-based disulfides of the type [{-CH2OP(S)(Fc)S-}(2)] (4), [(S2P-Fc)(2)(trans-1,2-O,O'-C6H10)] (5) and [C{CH2OP(S)(Fc)S}(4)] (6). The compounds 1-6 were characterized by H-1 and P-31 NMR and bulk purity were confirmed by either ESI-MS or elemental analysis. Compounds 4-6 were additionally characterized by single crystal X-ray analyses and 4 and 6 subjected to electrochemical investigations. Compounds 4-6 represent the first examples of structurally characterized intramolecular S S coupled products derived from ferrocene-based dithiophosphonates. (C) 2015 Elsevier BY. All rights reserved.