2-Benzoylpyridine thiosemicarbazone as a novel reagent for the single pot synthesis of dinuclear CuI–CuII complexes: formation of stable copper(ii)–iodide bonds

Abstract

2-Benzoylpyridine thiosemicarbazone {R(1)R(2)C(2)=N(2)·N(3)H-C(1)(=S)-N(4)H(2), R(1) = py-N(1), R(2) = Ph; Hbpytsc} with copper(I) iodide in acetonitrile-dichloromethane mixture has formed stable Cu(II)-I bonds in a dark green Cu(II) iodo-bridged dimer, [Cu(2)(II)(μ-I)(2)(η(3)-N(1),N(2),S-bpytsc)(2)] 1. Copper(I) bromide also formed similar Cu(II)-Br bonds in a dark green Cu(II) bromo-bridged dimer, [Cu(2)(II)(μ-Br)(2)(η(3)-N(1),N(2),S-bpytsc)(2)] 3. The formation of dimers 1 and 3 appears to be due to a proton coupled electron transfer (PCET) process wherein copper(I) loses an electron to form copper(II), and this is accompanied by a loss of -N(3)H proton of Hbpytsc ligand resulting in the formation of anionic bpytsc(-). When copper(I) iodide was reacted with triphenylphosphine (PPh(3)) in acetonitrile followed by the addition of 2-benzoylpyridine thiosemicarbazone in dichloromethane (Cu : PPh(3) : Hbpytsc in the molar ratio 1:1:1), both Cu(II) dimer 1 and an orange Cu(I) sulfur-bridged dimer, [Cu(2)(I)I(2)(μ-S-Hbpytsc)(2)(PPh(3))(2)] 2 were formed. Copper(I) bromide with PPh(3) and Hbpytsc also formed Cu(II) dimer 3 and an orange Cu(I) sulfur-bridged dimer, [Cu(2)(I)Br(2)(μ-S-Hbpytsc)(2)(PPh(3))(2)] 4. While complexes 2 and 4 exist as sulfur-bridged Cu(I) dimers, 1 and 3 are halogen-bridged. The central Cu(2)S(2) cores of 2 and 4 as well as Cu(2)X(2) of 1 (X = I) and 3 (X = Br) are parallelograms. One set of Cu(II)-I and Cu(II)-Br bonds are short, while the second set is very long {1, Cu-I, 2.565(1), 3.313(1) Å; 3, Cu-Br, 2.391(1), 3.111(1) Å}. The Cu···Cu separations are long in all four complexes {1, 4.126(1); 2, 3.857(1); 3, 3.227(1); 4, 3.285(1) Å}, more than twice the van der Waals radius of a Cu atom, 2.80 Å. The pyridyl group appears to be necessary for stabilizing the Cu(II)-I bond, as this group can accept π-electrons from the metal.

Cu(ii), Ga(iii) and In(iii) complexes of 2-acetylpyridine N(4)-phenylthiosemicarbazone: synthesis, spectral characterization and biological activities

“…The Cu1⋯Cu2 distance inside the dimeric unit is 3.540(24) Å, similar to those in μ 2 -thiolate bridged CuIJII) dimers. [47][48][49][50][51][52][53][54][55][56][57] Noticeably, three deprotonated ligands in the [Cu 2 IJL) 3 ] + cation display two kinds of coordination modes: two ligands coordinate to two Cu atoms in an expected N 2 S tridentate manner, while the last one serves as a tetradentate donor with two N atoms (pyridine N atom, imine N atom) adopting a normal chelating mode and S bridging mode (μ 2 ) linking two metal centers. The C-S distances range between 1.738(13) and 1.767(12) Å, being within the normal range of a C-S single bond, indicating that the ligands are coordinated in their deprotonated thiolate form.…”

“…The C-S distances range between 1.738(13) and 1.767(12) Å, being within the normal range of a C-S single bond, indicating that the ligands are coordinated in their deprotonated thiolate form. 58 Such a structure of the [Cu 2 IJL) 3 ] dimeric unit is unique and more interesting since the stoichiometry of metal : thiosemicarbazone ligand is 2 : 3 and two copperIJII) ions show different chelating modes with bridging S atoms to form a square-planar/octahedral complex (4 : 6-coordination), as compared with those of reported CuIJII)-thiosemicarbazone dimers, [47][48][49][50][51][52][53][54][55][56][57] where the stoichiometry of metal : thiosemicarbazone is 1 : 1 and two Cu centers both have the same 5-coordinated square-pyramidal topology. In addition, the crystal structure is stabilized by the linking of the different components of intermolecular hydrogen bonds of 1 (Fig.…”

Synthesis, characterization and crystal structure of platinum(II) complexes with thiourea derivative ligands

“…For example N-(alkyl/aryl)-N'-acylthiourea and N-di(alkyl/aryl)-N'-acylthiourea derivatives which have oxygen, nitrogen and sulphur donor atoms, exhibit prevalent coordination modes. Organic ligands that have thiourea moiety are able to bind metal ions in several ways, like: (i) acting as monodentate ligands through sulphur atom in mononuclear complexes [1-4] (ii) binding to metal ions forming S-bridges in dinuclear complexes [4][5][6][7][8] or (iii) chelating sulphur and nitrogen atoms [4][5][6][8][9][10][11][12][13][14][15][16] Thiourea derivatives as a ligand have a large dipole moment and these ligands can also form extensive network of hydrogen bonds due to their unique structures. For example in 3-monosubstituted arylthioureas [17][18][19], the carbonyl group and the proton on the nitrogen attach in a strong hydrogen bond interaction which unite into a planar six-membered ring structure forming an "S" shaped conformation of the C=O and C=S groups [20,21].…”

Crystal structures of 3/4-pyridyl-based thiosemicarbazones and related Cu and Ni coordination compounds

“…The coordination chemistry of pyridine-based thiosemicarbazones, [(2-py)R 1 C 2 N 3 -N 2 (H)-C 1 ( S)N 1 R 2 R 3 ], with the pyridin-2-yl group as one substituent at C 2 (I in Scheme 1), has been extensively explored owing to the variable bonding, structural diversity and biochemical implications (Lobana et al, 2006(Lobana et al, , 2008(Lobana et al, , 2009(Lobana et al, , 2010(Lobana et al, , 2012Basuli et al, 1998;Ashfield et al, 2004;Da Silva et al, 2013;Jansson et al, 2010;Kovala-Demertzi et al, 1999;Richardson et al, 2009;Gou et al, 2016). As regards other groups at the C 2 -carbon of thiosemicarbazones, such as pyridin-3-yl or pyridin-4-yl (structures II and III in Scheme 1, as examples), there is limited coordination chemistry reported.…”