Oxidative addition of 1,2,5,6-Tetrathiocins to Co(I): A Re-Examination of Crown Ether Functionalized Benzene Dithiolate Cobalt(III) Complexes

Abstract

Oxidative addition of the 4′,4″,5′,5″-crown-functionalized dibenzo-1,2,5,6-tetrathiocins, [(OCH 2 CH 2 ) n OC 6 H 2 S 2 ] 2 (1, n = 4; 2, n = 5), to the Co(I) complex CpCo(CO) 2 under microwave irradiation in toluene affords 16e − Co(III) dithiolate complexes CpCo{S 2 C 6 H 2 O(CH 2 CH 2 O) n } 3 (n = 4) and 4 (n = 5) in 71−75% recovered yield. Complexes 3 and 4 were characterized by X-ray diffraction. Compound 3 was found to be polymorphic, crystallizing as the 16e − monomer, 3, or the 18e − dimer, (3) 2 , depending upon reaction conditions. In contrast to previous literature which suggested formation of 1:1 complexes between 3 and s-block cations, reaction of 3 with the s-block metal salts M[BPh 4 ] (M = Na, K, Rb, and Cs) formed the 2:1 complexes [{CpCo(S 2 C 6 H 2 O-(CH 2 CH 2 O) 4 )} 2 M][BPh 4 ] (5a−5d, respectively) whose structures were determined by X-ray diffraction and revealed that the alkali metal ion is sandwiched by two crown ether substituents in all cases. UV/vis titration studies of complex 3 with NaBPh 4 were consistent with formation of the 2:1 complex as the dominant species in solution. Mass spectrometry studies on 5a−5d revealed the presence of both [(3) 2 M] + and [(3)M] + ions (M = Na, K, Rb, and Cs). Electrochemical studies on 3 revealed an irreversible 1e − oxidation attributed to a ligand-based process based on DFT calculations. Chemical oxidation of 3 afforded two dimeric structures [{CpCo(S 2 C 6 H 2 O(CH 2 CH 2 O) 4 )} 2 ][X] 2 (6a, X = OTf; 6b, X = BF 4 ) in which dithiolate ligand oxidation leads to complexes containing a disulfide bond, consistent with electrochemical and computational studies.

Cleaner and stronger: how 8-quinolinolate facilitates formation of Co(iii)–thiolate from Co(ii)–disulfide complexes

“…The redox changes involved in the redox-conversion reaction is relatively rare as it requires no external oxidant or reductant. 4–6…”

“…The redox changes involved in the redox-conversion reaction is relatively rare as it requires no external oxidant or reductant. [4][5][6] In recent years, the study of the redox-conversion reaction of disulfide and thiolate compounds has progressed from the copper-based system to other metal ions such as Mn, Fe, and Co. [7][8][9][10][11] The cobalt system in particular is interesting, as redoxconversion of cobalt-based systems is relatively underexplored. Currently, only a handful of reports describe the redox-conversion between cobalt(II)-disulfide and cobalt(III)-thiolate compounds induced chemically by addition or removal of halide ions, or by changing the solvent system.…”

“…4 ( py and pyMe)),8.47-8.50 (dd, 1H, H 6 ( py)), 9.26-9.29 (dd, 1H, ortho-CH-N(quin − )). Elemental analysis (%) for [2 S ]Cl•H 2 O (C 24 H 25 ClCoN 4 OS•H 2 O), calcd C, 54.50; H, 4.95; N, 10.59; found C, 54.26; H, 4.79; N, 10.49.…”