Versatility of Thiosemicarbazones in the Construction of Monomers, Dimers and Hydrogen-Bonded Networks of Silver(I) Complexes

Reactions of thiosemicarbazones {R 1 R 2 C 2 ═N 3 -N 2 (H)-C 1 (═S)-N 1 H 2 }, a multidonor class of ligands, with silver(I) halides in the presence of PPh 3 have yielded a variety of compounds, viz.: (i) halogen-bridged dimers, [Ag 2 (μ-X) 2 (η 1 -S-Haptsc) 2 (PPh 3 ) 2 ] (R 1 = Ph, R 2 = Me, Haptsc, X = Cl ( 1 ); Br ( 2 )), [Ag 2 (μ-Br) 2 (η 1 -S-Hbtsc) 2 (PPh 3 ) 2 ] (R 1 = Ph, R 2 = H, Hbtsc ( 3 )), [Ag 2 (μ-Br) 2 (η 1 -S-Hactsc) 2 (PPh 3 ) 2 ] (R 1 = R 2 = Me, Hactsc ( 4 )); (ii) sulfur-bridged dimers, [Ag 2 Br 2 (μ-S-Hptsc) 2 (PPh 3 ) 2 ]·2H 2 O (R 1 = pyrrole, R 2 = H, Hptsc ( 5 )), and [Ag 2 Cl 2 (μ-S-Httsc) 2 (PPh 3 ) 2 ]·2CH 3 CN (R 1 = thiophene, R 2 = H, Httsc ( 6 )), and (iii) monomers, [AgX(η 1 -S-Hpytsc)(PPh 3 ) 2 ]·CH 3 CN (R 1 = pyridine, R 2 = H, Hpytsc, X = Br ( 7 ); Cl ( 8 )). In contrast, silver(I) nitrate has formed only sulfur-bridged dimers, [Ag 2 (η 1 -N-μ-S-Hftsc) 2 (Ph 3 P) 2 ](NO 3 ) 2 ( 9 ) (R 1 = furan, R 2 = H, Hftsc), and [Ag 2 (η 1 -S-Hptsc) 2 (μ-S-Hptsc) 2 (Ph 3 P) 2 ](NO 3 ) 2 ·2CHCl 3 ( 10 ) (R 1 = pyrrole, R 2 = H, Hptsc) (Hpytsc = pyridine-2-carbaldehyde thiosemicarbazone, Hptsc = pyrrole-2-carbaldehyde thiosemicarbazone, Httsc = thiophene-2-carbaldehyde thiosemicarbazone, Hftsc = furan-2-carbaldehyde thiosemicarbazone, Hbtsc = benzaldehyde thiosemicarbazone, Hactsc = acetone thiosemicarbazone, and Haptsc = acetophenone thiosemicarbazone). Complexes 1 − 10 are the first examples exhibiting new bonding modes (η 1 -S, μ-S, and μ-S-η 1 -N 3 ) in silver(I)-thiosemicarbazone chemistry. The substituents at C 2 carbon appear to have significant influence on the nature of bonding in the complexes. The intermolecular interactions such as, NH···X (X = S, Br, Cl, O), CH···π and CH···X (X = S, Cl) have led to the formation of one- and two-dimensional (1D and 2D) networks. Interestingly, a novel feature is that some of the 2D networks encapsulate organic molecules in the voids.