Acylthiourea Ligands Research Articles

Chiral (η6-p-Cymene)ruthenium(II) Complexes Containing Monodentate Acylthiourea Ligands for Efficient Asymmetric Transfer Hydrogenation of Ketones

The new chiral ligands (R)-/(S)-N-((1-phenylethyl)carbamothioyl)benzamide (L1/L2), (R)-/(S)-N-((1-phenylethyl)carbamothioyl)thiophene-2-carboxamide (L3/L4), and (R)-/(S)-N-((1-phenylethyl)carbamothioyl)furan-2-carboxamide (L5/L6) were synthesized, characterized, and used to prepare novel chiral Ru(II) complexes. The chiral Ru(II) complexes 1–6 were obtained from reactions between the chiral ligands L1–L6 and [RuCl2(p-cymene)2]2. The complexes were characterized by analytical and spectroscopic (NMR, FT-IR, electronic) techniques. The solid-state structures of the ligands L1 and L3 and complexes 1, 4, and 6 were determined by single-crystal X-ray diffraction methods. In all of the complexes, the ligand is bound to the Ru(II) center only via the sulfur donor atom. This monodentate coordination of the acylthiourea ligands was observed for the first time with ruthenium. The Ru(II) complexes 1–6 all act as efficient catalysts for the asymmetric transfer hydrogenation of aromatic ketones in the presence of 2-propanol and KOH to produce chiral alcohols. All of the catalysts showed excellent conversions of up to 99% and enantiomeric excesses of up to 99%.

Hypodentate coordination of N,N-di(alkyl/aryl)-N′-acylthiourea derivatives in Cu(I) complexes

New four-coordinated tetrahedral Cu(I) complexes of the general formula [CuCl(HL)(PPh3)2] have been synthesized from the reactions between [CuCl2(PPh3)2] and N-(dibenzylcarbamothioyl)benzamide (HL1) or N-(methylpentylcarbamothioyl)benzamide (HL2) in benzene. The complexes have been characterized by elemental analyses, IR, UV–Vis, 1H, 13C and 31P NMR spectroscopy. The molecular structures of [CuCl(HL1)(PPh3)2] (1) and [CuCl(HL2)(PPh3)2] (2) were determined by single crystal X-ray crystallography. Each complex displays a distorted tetrahedral, ClP2S, coordination geometry with hypodentate coordination of acylthiourea ligands which coordinate the Cu(I) centre through sulfur atom exclusively.

Bipodal Acylthiourea Ligands as Building Blocks for Bi-, Tetra-, and Polynuclear Oxorhenium(V) Complexes

Reactions of (NBu4)[ReOCl4] and 3,3,3',3'-tetraalkyl-1,1'-isophthaloylbis(thioureas), H2phth(R2tu)2 where R = Et, i-Bu, in hot MeOH with the addition of Et3N give red products of the composition [ReO(OMe){phth(R2tu)2}]2 (8a, R = Et; 8b, R = i-Bu). X-ray structures of 8 reveal symmetric binuclear complexes containing two almost coplanar organic ligands, each of which coordinates to two rhenium centers via the two bidentate-O,S moieties. The octahedral coordination spheres of the rhenium atoms are completed by each one oxo and one methoxido ligand which are directed perpendicular to the plane defined by the {phth(R2tu)2}(2-) ligands. While in 8a, both methoxido ligands point to the same side of the described plane and form a syn isomer, the MeO(-) ligands in 8b are located at opposite sides and form an anti isomer. Studies in solution show that there exists a reversible equilibrium between the anti and syn isomers. Dimerization/condensation of complexes 8 with the formation of tetranuclear complexes of the composition [{ReO{phth(R2tu)2}}2O]2 (9) and/or polynuclear species is observed in solutions, which do not contain MeOH.

Extraction and transport of gold(III) using some acyl(aroyl)thiourea ligands and a crystal structure of one of the complexes

Abstract A number of acyl(aroyl)thiourea ligands were used for the extraction of gold(III). Extraction was observed with all the ligands under the experimental conditions employed. The same ligands were also employed for transport studies of gold(III) which was observed with only N,N-dibutyl-N′-benzoylthiourea. All other ligands resulted in the metal ion being present in the organic phase, but none in the receiving phase. A crystal structure of the ligand N,N-diethyl-N′-camphanylthiourea as its complex with Au(I) was obtained. The complex crystallizes in the monoclinic space group P21 with an R-factor of 1.5%. The coordination sphere around Au(I) shows a nearly linear arrangement of sulphur and chloride.

Competitive bulk liquid membrane transport and solvent extraction of some transition and post-transition metal ions using acylthiourea ligands as ionophores

Competitive transport experiments involving metal ions from an aqueous source phase through a chloroform membrane into an aqueous receiving phase have been carried out using a series of acylthiourea ligands as the ionophore present in the organic phase. The source phase contained equimolar concentrations of cobalt(II), nickel(II), copper(II), zinc(II), silver(I), cadmium(II) and lead(II) with the source and receiving phases being buffered at a number of different pHs. Transport selectivity was observed for silver(I) in all but one case. Selectivity for silver(I) was also observed in a series of parallel solvent extraction experiments carried out under similar source and membrane phase conditions. An X-ray diffraction study of the silver(I) complex of the N,N-dibutyl-N′-benzoylthiourea from this series is reported. There are two crystallographically independent molecules in the asymmetric unit and each molecule consists of four silver(I) ligand complex units, hence giving rise to Z = 8. In each molecule, both chelate and monodentate co-ordination modes of complexation to silver(I) are evident. Hence, each silver is co-ordinated to a sulfur and oxygen atom from one ligand and to a shared (bridging) sulfur from another ligand. Each silver atom is thus co-ordinated to three donor atoms.

Synthesis, Characterization And Antitumor Activity OfCopper(II) Complexes, [CuL2] [HL1-3=N,N‐Diethyl‐N′‐(R‐Benzoyl)Thiourea (R=H, o‐Cl and p‐NO2)

The copper (II) complexes (CuL2) were prepared by reaction of Cu(CH3COO)2 with the corresponding derivatives of acylthioureas in a Cu:HL molar ratio of 1:2. Acylthiourea ligands, N,N-diethyl-N'-(R-benzoyl) thiourea (HL1-3) [R=H, o-Cl and p-NO2] were synthesized in high yield (78-83%) and characterized by elemental analysis, infrared spectroscopy, 1H and 13C NMR spectroscopy. The complexes CuL2 were characterized by elemental analysis, IR, FAB(+)-MS, magnetic susceptibility measurements, EPR and cyclic voltammetry. The crystal structure of the complex Cu(L2)2 shows a nearly square-planar geometry with two deprotonated ligands (L) coordinated to CuII through the oxygen and sulfur atoms in a cis arrangement. The antitumor activity of the copper(II) complexes with acylthiourea ligands was evaluated in vitro against the mouse mammary adenocarcinoma TA3 cell line. These complexes exhibited much higher cytotoxic activity (IC50 values in the range of 3.9-6.9 μM) than their corresponding ligands (40-240 μM), which indicates that the coordination of the chelate ligands around the CuII enhances the antitumor activity and, furthermore, this result confirmed that the participation of the nitro and chloro substituent groups in the complex activities is slightly relevant. The high accumulation of the complexes Cu(L2)2 and Cu(L3)2 in TA3 tumor cells and the much faster binding to cellular DNA than Cu(L1)2 are consistent with the in vitro cytotoxic activities found for these copper complexes.

Synthesis and characterisation of mixed-ligand platinum(II)–sulfoxide complexes, [PtCl(DMSO)(L)], for potential use as chemotherapeutic agents (HL= N, N-dialkyl- N′-(3- R-benzoyl)thiourea)

A novel series of mixed-ligand platinum(II) complexes of the type [PtCl(DMSO)(L)], where HL= N, N-diethyl- N′-(3- R-benzoyl)thiourea, N, N-di(2-hydroxyethyl)- N′-(3- R-benzoyl)thiourea or N-morpholino- N′-(3- R-benzoyl)thiourea (R=H, Cl, NO 2, CH 3O, CH 3), have been synthesised and characterised by elemental analysis, IR spectroscopy and 1H and 195Pt NMR spectroscopy. The spectroscopic data are consistent with the complexes containing an O, S chelated ligand and an S-bonded sulfoxide ligand which is in a cis arrangement to that of the sulfur donor atom of the chelated ligand. Trends in the NMR spectra can be correlated with the electronic effects of the substituents on the phenyl ring of the acylthiourea ligands.

Chiral and achiral platinum(II) complexes for potential use as chemotherapeutic agents: crystal and molecular structures of cis-[Pt(L1)2] and [Pt(L1)Cl(MPSO)] [HL1 = N,N-diethyl-N ′-benzoylthiourea

The synthesis and characterisation of platinum(II) complexes, with the general formula [Pt(acylthioureato)Cl(RR′SO)], is reported. These complexes are readily formed by the reaction of [PtCl2(RR′SO)2] with the acylthiourea ligands, N,N-di(2-hydroxyethyl)-N′-benzoylthiourea (HL), N,N-diethyl-N′-benzoylthiourea (HL1) and N,N-adipoylbis(N′,N′-diethylthiourea) (H2L2) in the presence of sodium acetate. Variation of the sulfoxide ligand (RR′SO) enables preparation of achiral complexes when RR′SO is dimethylsulfoxide (DMSO) or methylphenylsulfoxide (MPSO), and chiral complexes when use is made of the chiral sulfoxides, such as (R)-methyl(p-tolyl)sulfoxide and (S)-methyl(p-tolyl)sulfoxide. The reaction also yields, as a minor product, the corresponding cis-bis(acylthioureato)platinum(II) complexes, which can be removed by chromatography. The molecular structures of the two products, [Pt(L1)Cl(MPSO)] and cis-[Pt(L1)2], were determined by X-ray crystallography. The sulfoxide of [Pt(L1)Cl(MPSO)] is sulfur bound, as expected, and cis to the sulfur atom of the acylthioureato ligand. All bond lengths and bond angles around the square planar platinum are normal, with the Pt–S bond trans to Cl being 2.257(4) A and the Pt–S bond trans to O 2.192(3) A in length. The Pt–O and Pt–Cl bonds are 2.016(9) and 2.334(3) A, respectively, and are within the expected ranges. Similarly, the bond lengths and bond angles around the coordination plane of cis-[Pt(L1)2] compare well with related complexes.

Synthesis, characterisation and coordination chemistry of novel chiral N,N-dialkyl-N ′-menthyloxycarbonylthioureas. Crystal and molecular structures of N,N-diethyl-N ′-(−)-(3R)-menthyloxycarbonylthiourea and cis-(S,S)-[Pt(L)Cl(DMSO)] [where HL = N-(+)-(3R)-menthyloxycarbonyl-N′-morpholinothiourea or N-benzoyl-N′,N′-diethylthiourea

The novel ligands N,N-diethyl-N′-(−)-(3R)-menthyloxycarbonylthiourea (HL3), N,N-diethyl-N′-(+)-(3R)-menthyloxycarbonylthiourea (HL4), N-(−)-(3R)-menthyloxycarbonyl-N′-morpholinothiourea (HL5) and N-(+)-(3R)-menthyloxycarbonyl-N′-morpholinothiourea (HL6) have been prepared and characterised. The molecular structure of HL3 has been confirmed by X-ray crystallography. The reaction of these N,N-disubstituted-N′-menthyloxycarbonylthiourea ligands with cis-[PtCl2(DMSO)2] in the presence of sodium acetate yields geometric isomers of the resultant [Pt(L)Cl(DMSO)] complexes, that is the DMSO is sulfur bonded to the platinum in either a cis-(S,S) or trans-(S,S) arrangement with respect to the sulfur donor atom of the chelated ligand. This is in contrast to the complexation reaction of cis-[PtCl2(DMSO)2] with N-benzoyl-N′,N′-diethylthiourea (HL1) or N-benzoyl-N′-morpholinothiourea (HL2) which yields only one [Pt(L)Cl(DMSO)] complex in which the DMSO is in a cis-(S,S) arrangement with respect to the sulfur donor atom of the chelated ligand. The molecular structures of cis-(S,S)-[Pt(L)Cl(DMSO)], where L = (L1)− or (L6)−, have been determined by X-ray crystallography. The difference in the coordination chemistry of the acylthiourea and alkoxycarbonylthiourea ligands has been examined further by treating the [Pt(L)Cl(DMSO)] complexes with PPh3 to give the corresponding mono- and bis-(phosphine) complexes, [Pt(L)Cl(PPh3)] and [Pt(L)(PPh3)2]+. The 31P NMR studies of these complexes reveal that the alkoxycarbonylthiourea ligands bind less strongly than the acylthiourea ligands, which is consistent with the crystallographic studies. The weaker binding properties of the alkoxycarbonylthiourea ligands might be a possible explanation for the observed geometric isomerisation of the complexes and that the mechanism could involve a chelate ring opening step.

Synthesis, crystal structure and magnetic properties of a bis-sulfur-bridged copper(II) dimer containing N-ferrocenecarbonyl-N ′,N ′-dimethylthiourea (HL), [{CuL(HL)Cl}2

The bis-sulfur-bridged copper(II) dimer [{CuL(HL)Cl}2] (HL = N-ferrocenecarbonyl-N′,N′-dimethylthiourea) has been synthesized and structurally characterized. The central copper(II) ion has a distorted tetrahedral environment with one chloride and three sulfur atoms derived from one terminal and two bridging acylthiourea ligands. The two sulfur atoms of both bridging ligands with two copper(II) ions form a strictly planar Cu2S2 bridging core including two short [2.3649 Å] and two longer Cu–S distances [2.4496 Å]. Dimers with this type of bridging are very scarce. Magnetic measurements showed antiferromagnetic coupling between the copper(II) centers through the sulfur bridges. The best fitting to the experimental magnetic susceptibilities gave g = 2.06, J = –196.3 cm–1.

Synthesis and crystal structure of trans-bis(N,N-dibutyl-N′-naphthoylthioureato) platinum(II). First example of trans chelation of N,N-dialkyl-N′-acylthiourea ligands

N,N-Dibutyl-N′-naphthoylthiourea (HL1) reacted with [PtCl4]2– to yield a mixture of cis-(85%) and trans-[PtL12](15%); the crystal structure of the latter has been determined and represents the first example of trans chelation of N,N-dialkyl-N′-acylthiourea ligands.