Coinage metal derivatives of salicylaldehyde thiosemicarbazones: Synthesis, structures, bond isomerism and H-bonded networks

Reactions of salicylaldehyde thiosemicarbazone {(2-HO–C6H4)(H)C2N3–N2H–C1(S)N1H2, H2stsc} and salicylaldehyde N-methyl thiosemicarbazone {(2-HO–C6H4)(H)C2N3–N2H–C1(S)N1HMe, H2stscNMe} with copper(I)/silver(I) halides in presence of PPh3 have yielded complexes of compositions, mononuclear [CuCl(η1-S–Htsc)(PPh3)2] (Htsc = H2stsc 3; H2stscNMe, 6), [AgX(H2stscNMe)(PPh3)]2 (Br 9, Cl 10), sulfur-bridged dimers, [Cu2(μ-S–H2stscNMe)2X2(PPh3)2] · 2CH3CN (I 4; Br 5), [Ag2Cl2(μ-S–H2stsc)2(PPh3)2] 8 and bond isomers, [M2X2 (H2stsc)2(PPh3)2] (M: Cu I 1, Br 2; Ag 7). Complexes 1, 2 and 7 exist as halogen-bridged [M2(μ-X)2(η1-S–H2stsc)2(PPh3)2] (M: Cu, 1a, 2a; Ag, 7a), and sulfur bridged [M2(μ-S–H2stsc)2X2(PPh3)2] (M: Cu, 1b, 2b; Ag, 7b) isomers in the same lattice. Among the bond isomers, the Cu···Cu contacts were found to be shorter in sulfur-bridged isomers (1b, 3.113; 2b, 3.063 Å) vis-à-vis those in halogen bridged isomers (1a, 3.182; 2a, 3.190 Å). The Ag···Ag contact in sulfur-bridged isomer 7b (3.4223 Å) is longer than in bromo-bridged isomer 7a (3.2021 Å). The complexes form 1D or 2D H-bonded networks, entrapping solvent molecules in some cases.

Graphical abstractSalicylaldehyde thiosemicarbazone (H2stsc) has formed 1D and 2D polymeric networks in complexes with coinage metals. For example, dimer [Ag2Br2(H2stsc)2(PPh3)2] (7) exists as alternate H-bonded linear polymeric chains of halogen bridged [Ag2(μ-Br)2(η1-S–H2stsc)2(PPh3)2] (7a) (green) and sulfur bridged [Ag2Br2(μ-S–H2stsc)2(PPh3)2] (7b) (red) bond isomers in the same lattice, forming 2D network.Figure optionsDownload full-size imageDownload as PowerPoint slide