Unprecedented metal-mediated in situ reactions of heterocyclic disulfide of di[4-(pyridin-2-yl)pyrimidinyl]disulfide

Abstract

By the combination of different metal salts and solvents, four unprecedented in situ reactions have been discovered for heterocyclic disulfide of 2-ppds (2-ppds = di[4-(pyridin-2-yl)pyrimidinyl]disulfide). In the CH3CN-DMF solvent, reaction of 2-ppds with AgNO3 produced a one-dimensional chain structure of {[Ag2(1L)2]·2CH3CN}n (1), wherein 2-ppds was converted into its sulfonate of 1L by means of oxidative cleavage of the S-S bond. In the CH3CN-DCM solvent, reaction between 2-ppds and Cu(ClO4)2 yielded a discrete mononuclear Cu(II) coordination structure of [Cu(2L)2H2O)](ClO4)2 (2), of which 2-ppds was turned into a totally unexpected zwitterion product of 2L via C-S bond scission followed by O substitution. In the MeOH-DCM solvent, reaction of 2-ppds with Co(ClO4)2 resulted in a mononuclear Co(III) coordination structure of [Co(3L)2]ClO4·2CH3OH·H2O (3), in which 2-ppds was transformed into its persulfide of 3L via selective single C-S bond rupture. In the CH3CN-DMF solvent, reaction between 2-ppds and CuI afforded a binuclear mixed-valence Cu(I)Cu(II) coordination structure of [Cu2I(4L)2] (4), wherein 2-ppds was converted into its thiolate of 4L through homolytic S-S bond cleavage. The reaction mechanisms of these reactions have also been discussed on the basis of these in situ generated coordination structures coupled with our previous observations on 2-ppds.

Solvothermal heterocyclic disulfide/CuX2 (X = Cl, ClO4) reactions involving dynamic S–S and C–S bond cleavage

“…As reported in our previous work, the same transformation from 2-ppds to L1 can also take place under ambient conditions but with the formation of a discrete mononuclear coordination complex, [Cu(L 1 ) 2 (H 2 O)](ClO 4 ) 2 [24]. Compared to this latter complex, the crystal structure of complex 1 in the present case is obviously disparate.…”

“…This structural difference can be attributed to the larger steric and electronic repulsion of the ClO 4 anion compared with H 2 O. From the viewpoint of mechanism, conversion from 2-ppds to L1 under solvothermal conditions might follow the same route as under ambient solution conditions [24]. However, it is worth noting that this example emphasizes the important influence of reaction conditions on the ultimate coordination complex structure even with the same in situ generated ligand.…”

“…In our previous work, we have described a variety of metal/ 2-ppds (2-ppds = di[4-(pyridin-2-yl)pyrimidinyl]disulfide) reactions in solution at ambient temperature [22][23][24]. In continuation of these studies, herein we describe three solvothermal CuX 2 (X = Cl, ClO 4 )/2-ppds reactions in which 2-ppds experiences dynamic S-S and C-S bond cleavage under different circumstances (Scheme 1).…”