Metal ion-mediated selective activations of C-H and C-CI bonds. Direct aromatic thiolation reactions via C-S bond cleavage of dithioacids

摘要

The reactions of potassium salt of dithiocarbonate, R'OCS2K, 4 (R' = Me, Et, nPr, nBu, iPr, iBu, -CH2ph) with the low-spin etc-RuII(L)2Cl2, 1, etc-OsII(L)2Br2 2 and mer[CoII(L)3](ClO4),'H2O 3 [L = 2-(arylazo)pyridine, NC5H4-N=N-C6H4(R), R=H, o-Me/CI, m-Me/CI, p-Me/CI; etc cis-trans-cis with respect to halides, pyridine and azo nitrogens respectively) in boiling dimethylformamide solvent resulted in low-spin diamagnetic RuII(L')2, 5, Os II(L')2 6 and [CoIII(L')2]ClO4 7 respectivcly (L' =o-S-C6H3(R)N=NC5H4N). In the complexes 5, 6 and 7 ortho carbon-hydrogen bond of the pendant phenyl ring of the ligands (L') has been selectively and directly thiolated via the carbon-sulphur bond cleavage of 4. The newly formed tridenate thiolated ligands (L') are bound to the metal ion in a meridional fashion. In the case of cobalt complex (7), during the activation process the bivalent cobalt ion in the starting complex 3 has been oxidised to the trivalent Co III state. The reactions are highly sensitive to the nature and the location of the substituents present in the active phenyl ring. The presence of electron donating Me group at the ortho and para positions of the pendant phenyl ring with respect to the activation points can only facilitate the thiolation process. The complexes (1c, 2c and 3c) having chloride group at the ortho position of the active phenyl ring underwent the thiolation reaction selectively via the carbon-chloride bond activation process. The rate of carbon-chloride activation process has been found to be much faster compared to the C-H bond activation. The reactions a