Emerging Trends in the Coordination Chemistry of Thiazolidinone-Containing Polydentate Ligands: Unconventional...

This work presents an efficient and straightforward method for obtaining two previously described thiazolidinone-based ligands, HAm4DHotaz (N'-(4-oxothiazolidin-2-ylidene)picolino-hydrazonamide) and Am4Eotaz (N'-(3-ethyl-4-oxothiazol-idin-2-ylidene)picolinohydrazonamide), with high yield and purity. Moreover, the reactivity of these ligands toward different Ag⁺ salts has been explored, resulting in the isolation of four novel coordination complexes: two mononuclear species, [Ag(HAm4DHotaz)₂](NO₃)·H₂O (1·H₂O) and [Ag(Am4Eotaz)₂](NO₃) (2), and two tetranuclear compounds, [Ag₄(Am4DHotaz)₄]·8H₂O (3·8H₂O) and [Ag₄(Am4Eotaz)₄(NO₃)₂(H₂O)](NO₃)₂·1.18H₂O (4·1.18H₂O). The crystal structures of 1·H₂O, 2, 4·1.18H₂O, and 3·3DMF, the latter obtained by recrystallization of [Ag₄(Am4DHotaz)₄]·8H₂O in dimethylformamide, have been determined. Notably, in 4·1.18H₂O, the thiazolidinone moiety shows the unprecedented bridging mode μ₂-κ¹S:κ¹S. In addition, 3·3DMF represents a rare example of a thiazolidinone-containing complex featuring a μ₂-κ¹N:κ¹S bridge. Moreover, across these complexes, the Am4Rotaz (R = DH or E) ligands display five hitherto unknown coordination modes. These ligands, and the auxiliary donors (present in 4·1.18H₂O), provide different Ag⁺ coordination environments: AgN₄ cores with a seesaw geometry in the mononuclear complexes, and AgN₂, AgN₂S, AgN₄, AgN₂OS, AgN₂S₃ or AgN₂O₂S₃ cores with varied geometries in the tetranuclear ones. Furthermore, structures of the polynuclear species reveal significant argentophilic Ag···Ag interactions, which play a key role in directing the formation of the multinuclear frameworks.