Bonding trends of thiosemicarbazones in mononuclear and dinuclear copper(I) complexes: syntheses, structures, and theoretical aspects

Reactions of copper(I) halides with a series of thiosemicarbazone ligands (Htsc) in the presence of triphenylphosphine (Ph(3)P) in acetonitrile have yielded three types of complexes: (i) monomers, [CuX(eta1-S-Htsc)(Ph3P)2] [X, Htsc = I (1), Br (2), benzaldehyde thiosemicarbazone (Hbtsc); I (5), Br (6), Cl (7), pyridine-2-carbaldehyde thiosemicarbazone (Hpytsc)], (ii) halogen-bridged dimers, [Cu2(mu2-X)2(eta1-S-Htsc)2(Ph3P)2] [X, Htsc = Br (3), Hbtsc; I (8), furan-2-carbaldehyde thiosemicarbazone (Hftsc); I (11), thiophene-2-carbaldehyde thiosemicarbazone (Httsc)], and (iii) sulfur-bridged dimers, [Cu2X2(mu2-S-Htsc)2(Ph3P)2] [X, Htsc = Cl (4), Hbtsc; Br (9), Cl (10), pyrrole-2-carbaldehyde thiosemicarbazone (Hptsc); Br (12), Httsc]. All of these complexes have been characterized with the help of elemental analysis, IR, 1H, 13C, or 31P NMR spectroscopy, and X-ray crystallography (1-12). In all of the complexes, thiosemicarbazones are acting as neutral S-donor ligands in eta()S or mu2-S bonding modes. The Cu...Cu separations in the Cu(mu2-X)2Cu and Cu(mu2-S)2Cu cores lie in the ranges 2.981(1)-3.2247(6) and 2.813(1)-3.2329(8) Angstroms, respectively. The geometry around each Cu center in monomers and dimers may be treated as distorted tetrahedral. Ab initio density functional theory calculations on model monomeric and dimeric complexes of the simplest thiosemicarbazone [H2C=N-NH-C(S)-NH2, Htsc] have revealed that monomers and halogen-bridged dimers have similar stability and that sulfur-bridged dimers are stable only when halogen atoms are engaged in hydrogen bonding with the solvent of crystallization or H2O molecules.     

Chemistry of iron complexes. Part V. Electron spin resonance spectra of some iron(III) complexes and X-Ray diffraction (powder) data of iron(II) complexes employing tertiary phosphine/arsine oxides

Summary Electron spin resonance spectra (X-band, 9.3 GHz) of iron(III) chloride complexes with tri-p-tolylarsine oxide (T₃AO), methylenebis(diphenylphosphine oxide) (mdpo) and 1,4-tetramethylenebis(diphenylphosphine oxide) (tmdpo) support their structures as [Fe(L-L)₂Cl₂][FeCl₄] (L-L=mdpo or tmdpo) and [Fe(T₃AO)₂Cl₂(OH₂)₂][FeCl₄]2H₂O. The x-ray powder diffraction patterns of some iron(II) iodide complexes with mdpo, tmdpo, dmdpo, dmdao and tmdao [dmdpo-1,2-dimethylenebis(diphenylphosphine oxide); dmdao and tmdao are the arsine analogs of dmdpo and tmdpo] show that the complexes are crystalline but not isomorphous.     

The crystal structures of 2-(2′-pyridyl)phenyltellurium(II) bromide and of the inclusion compound bis[2-(2′-pyridyl)phenyltellurium(II) chloride]·p-ethoxyphenyl-mercury(II) chloride

In 2-(2′-pyridyl)phenyltellurium(II) bromide (1) the coordination about tellurium may be described as pseudo-trigonal bipyramidal wth bromine (Te---Br = 2.707(11) Å) and nitrogen (Te---N) = 2.236(11) Å) atoms occupying axial positions. The equatorial plane comprises a carbon atome (Te---C = 2.111(6) Å) and two lone pairs of electrons. There are no significant intermolecular interactions between the six independent molecules in the unit cell. Bis[2-2′-pyridyl)phenyltellurium(II) chloride]·p-ethoxy-phenylmercury(II) chloride (2) may be regarded as an “inclusion compound” obtained by replacement of two RTeX (X = Cl or Br) molecules by two p-ethoxyphenylmercury(II) chloride entities. There is approximately linear coordination about mercury (C---Hg---Cl = 179.2°(4), Hg-C = 2.044(14) and Hg---Cl = 2.328(4) Å) and 2-(2′-pyridyl)phenyltellurium(II) chloride, with a structure similar to that of (1) above (Te---N = 2.2366(6), Te---Cl = 2.558(1), Te---C = 2.080(25) Å). There are no significant intermolecular contacts.     

Ligating properties of tertiary phosphine/arsine sulphides or selenides—VI. Addition compounds of zinc(II), cadmium(II) and mercury(II) with sulphides or selenides of triphenyl- and tri- -tolylphosphines and 1,3-trimethylenebis (diphenylphosphine)

Post-transition elements react with ligands, triphenylphosphine sulphide or selenide (Ph₃PS or Ph₃PSe), tri-p-tolylphosphine sulphide or selenide (T₃PS or T₃PSe) and 1,3-trimethylenebis-(diphenylphosphine sulphide or selenide) (PDPS or PDPSe) in suitable organic solvents forming complexes of compositions: MX₂. L(M = Zn, X = I, L = all except Ph₃PS: M = Cd, X = I, L = T₃PS, T₃PSe, M = Hg, L = T₃PSe, X = Cl, Br, I); ZnI₂·2Ph₃PS, Hg(NO₃)₂·2Ph₃PS, CdBr₂·3T₃PSe and 3Hg(NO₃)₂·4Ph₃PSe. All these have been characterized through elemental analyses, ir spectra (4000−200 cm⁻¹) and molar conductance (nitrobenzene). Complexes are essentially nonelectrolytes. Tetrahedral structures have been assigned to all except a 1 : 3 complex which has been assigned a bridged octahedral structure.     

Ligating properties of tertiary phosphine/arsine sulphides or selenides. Part VII. Synthesis and characterisation of palladium(II) complexes with some mono- and ditertiary phosphine sulphides or selenides

Summary Palladium(II) halides react with triphenylphosphine sulphide or selenide, 1,1-methylenebis(diphenylphosphine sulphide or selenide) (MDPS or MDPSe), 1,3-trimethylene-bis-(diphenylphosphine selenide) (PDPSe) or tetramethyldiphosphine disulphide (TMDPS) forming complexes [PdBr₂ · 2L], [2PdBr₂ · 3L] (L=Ph₃PS or Ph₃PSe), [PdX₂ · L] (X=Cl, L =PDPSe; X=Br, L=MDPS or MDPSe; X=Cl or Br, L=TMDPS) and [3PdBr₂ · 2TMDPS]. Characterisation and stereochemical assignments have been made through elemental analyses, i.r., far i.r. and electronic spectra, magnetic susceptibility and molar conductance data and tga studies. Bidentate ligand complexes have higher thermal stability than the monodentate ligand complexes. Chelation or bridging modes of the bidentate ligands have been demonstrated.     

Heterocyclic thioamides of copper(I): Synthesis and crystal structures of copper complexes with 1,3-imidazoline-2-thiones in the presence of triphenyl phosphine

Reaction of copper(I) chloride with 1,3-imidazoline-2-thione (imzSH) in the presence of Ph₃P in 1:2:2 or 1:1:2 (M:L:PPh₃) molar ratios yielded a compound of unusual composition, [Cu₂(imzSH)(PPh₃)₄Cl₂] · CH₃OH (1), whose X-ray crystallography has shown that its crystals consist of four coordinated [CuCl(1κS-imzSH)(PPh₃)₂] (1a), and three coordinated [Cu(PPh₃)₂Cl] (1b) independent molecules in the same unit cell. In contrast, crystals of complexes of copper(I) bromide/iodide are formed by single molecules of [CuBr(1κS-imzSH)(PPh₃)₂] · H₂O (2) and [CuI(1κS-imzSH)(PPh₃)₂] (3), respectively, similar to molecule 1a. The related ligand, 1,3-benzimidazoline-2-thione (bzimSH) formed a complex [CuBr(1κS-bzimSH)(PPh₃)₂] · CH₃COCH₃ (4), similar to 2. The formation of 1a and 1b has been also revealed by NMR spectroscopy. The NMR spectra of 2–4 also showed weak signals indicating formation of compounds similar to 1b. It reveals that the lability of the Cu–S bond varies in the order: Cl ? Br ∼ I. Weak interactions {e.g. C–H?π electrons of ring, –NH?halogens/oxygen, C–H?halogens/oxygen, π?π (between rings)} have played an important role in building 2D chains of complexes 1–4.     

Copper(I) Derivative of Pyridine-3-carbaldehyde-N-ethylthiosemicarbazone and Triphenylphosphine—First Case of Crystal Structure Study

The synthesis and crystal structure of pyridine-3-carbaldehyde-N-ethylthiosemicarbazone (3-pytscH-NHEt) 1, and its Cu^I complex of stoichiometry, [CuCl(3-pytscH-NHEt)(PPh₃)₂] 2, studied using single crystal X-ray crystallography, are reported in this paper. Crystal data: 1, monoclinic, P2₁/n, a?=?6.6322(3), b?=?21.1200(8), c?=?7.2989(3) Å; β?=?91.883(4), T?=?173(2), R factor?=?0.0457; 2: triclinic, P-1, a?=?19.3600(5), b?=?20.6241(6), c?=?23.8015(6) Å,α?=?92.647(2), β?=?104.388(2), γ?=?114.377(3), R factor?=?0.0662. The thio-ligand, as a neutral entity, is coordinating to Cu through its S donor atom in complex 2. It has exhibited an unusual feature of forming four independent molecules (A, B, C, D) in the unit cell, with minor differences in the bond angles / distances / torsion angles. The geometry of each molecule of 2 is distorted tetrahedral. Crystal packing, as well as Infrared, electronic absorption and proton NMR spectroscopic studies, are also reported. Copper compound 2 represents the first example of a structurally studied copper coordination compound of 3-pyridyl based thiosemicarbazones.

Graphical Abstract

Copper(I) chloride with pyridine-3-carbaldehyde-N-ethylthiosemicarbazone and PPh₃ in CH₃CN yielded a copper compound, 2 (Green-Cl, blue-N; aqua-Cu, orange-S, magneta-P).

     

Pyridine-2-thione (pySH) derivatives of silver(I): Synthesis and crystal structures of dinuclear [Ag2Cl2(μ-S-pySH)2(PPh3)2] and [Ag2Br2(μ-S-pySH)2(PPh3)2] complexes

Reaction of silver(I) halides with PPh₃ in acetonitrile and then with pyridine-2-thione (pySH) chloroform (1:1:1 molar ratio) has yielded sulfur bridged dimers of general formula, [Ag₂X₂(μ-S-pySH)₂(PPh₃)₂] (X = Cl, 1, Br, 2). Both these complexes have been characterized using analytical data, NMR spectroscopy and single crystal X-crystallography. The central Ag₂S₂ cores form parallelograms with unequal Ag–S bond distances (2.5832(8), 2.7208(11) Å) in 1 and (2.6306(4), 2.6950(7) Å) in 2, respectively. The Ag?Ag contacts of compounds 1 and 2 are 3.8425(8) and 3.8211(4) Å, respectively. The angles around Ag (in the range 87.19(2)–121.71(2)° in 1 and 87.81(2)–121.53(2)° in 2) reveal highly distorted tetrahedral geometry. There are inter dimer π–π stacking interactions between pyridyl rings (inter ring distances of 3.498 and 3.510 Å in complexes 1 and 2, respectively). The solution state ³¹P NMR spectroscopy has shown the existence of both monomers and dimers. The studies reveal relatively weaker intramolecular –NH?Cl hydrogen bonding in case of AgCl vis-à-vis that in CuCl which favored both a monomer and a dimer with AgCl, and only a monomer with CuCl.     

The Influence of Substituents at C2 Carbon Atom of Thiosemicarbazones {R(H)C2=N3‐N2(H)‐C1(=S)‐N1H2} on their Dentacy in PtII/PdII Complexes: Synthesis,Spectroscopy, and Crystal Structures

The coordination chemistry of platinum(II) with a series of thiosemicarbazones {R(H)C²=N³‐N²(H)‐C¹(=S)‐N¹H₂, R = 2‐hydroxyphenyl, H₂stsc; pyrrole, H₂ptsc; phenyl, Hbtsc} is described. Reactions of trans‐PtCl₂(PPh₃)₂ precursor with H₂stsc (or H₂ptsc) in 1 : 1 molar ratio in the presence of Et₃N base yielded complexes, [Pt(η³‐ O, N³, S‐stsc)(PPh₃)] ( 1 ) and [Pt(η³‐ N⁴, N³, S‐ptsc)(PPh₃)] ( 2 ), respectively. Further, trans‐PtCl₂(PPh₃)₂ and Hbtsc in 1 : 2 (M : L) molar ratio yielded a different compound, [Pt(η²‐ N³, S‐btsc)(η¹‐S‐btsc)(PPh₃)] ( 3 ). Complex 1 involved deprotonation of hydrazinic (‐N²H‐) and hydroxyl (‐OH) groups, and stsc^2? is coordinating via O, N³, S donor atoms, while complex 2 involved deprotonation of hydrazinic (‐N²H‐) and ‐N⁴H groups and ptsc^2? is probably coordinating via N⁴, N³, S donor atoms. Reaction of PdCl₂(PPh₃)₂ with Hbtsc‐Me {C₆H₅(CH₃)C²=N³‐N²(H)‐C¹(=S)‐N¹H₂} yielded a cyclometallated complex [Pd(η³‐C, N³, S‐btsc‐Me)(PPh₃)] ( 4 ). These complexes have been characterized with the help of analytical data, spectroscopic techniques {IR, NMR (¹H, ³¹P), U.V} and single crystal X‐ray crystallography ( 1 , 3 and 4 ). The effects of substituents at C² carbon of thiosemicarbazones on their dentacy and cyclometallation are emphasized.