Synthesis, characterization and cytotoxicity of some palladium(II), platinum(II), rhodium(I) and iridium(I) complexes of ferrocenylpyridine and related ligands. Crystal and molecular structure of trans-dichlorobis(3-ferrocenylpyridine)palladium(II)

The preparation of a series of ferrocenyl nitrogen donor ligands including ferrocenylpyridines, ferrocenylphenylpyridines and 1,1^′-di(2-pyridyl)ferrocene is described. Coordination studies of the substituted pyridines (L) were carried out with platinum, palladium, rhodium and iridium. This resulted in the preparation of the following types of complexes: [MCl(CO)₂(L)] and [M(cod)(L)₂]ClO₄ where M=Rh or Ir, cod=1,5-cyclooctadiene; [M^′Cl₂(L)₂] where M^′=Pt or Pd. The X-ray crystal structure of trans-dichlorobis(3-ferrocenylpyridine)palladium was obtained. The complexes were screened for activity against two human cancer cell lines. At least two of the complexes displayed growth inhibition similar to that of the widely used chemotherapeutic agent, cisplatin.     

Palladium(II)/allylpalladium(II) complexes with xanthate ligands: Single-source precursors for the generation of palladium sulfide nanocrystals

In an effort to find simple and common single-source precursors for palladium sulfide nanostructures, palladium(II) complexes, [Pd(S₂X)₂] (X = COMe (1), COⁱPr (2)) and η³-allylpalladium complexes with xanthate ligands, [(η³-CH₂C(CH₃)CR₂)Pd(S₂X)] (R = H, X = COMe (3); R = H, X = COEt (4); R = H, X = COⁱPr (5); R = CH₃, X = COMe (6)), have been investigated. The crystal structures of [Pd(S₂X)₂] (X = COMe (1), CoⁱPr (2)) and [(η³-CH₂C(CH₃)CH₂)Pd(S₂COMe)] (3) have been established by single crystal X-ray diffraction analysis. The complexes, 1, 2 and 3 all contain a square planar palladium(II) centre. In the allyl complex 3, this is defined by the two sulfurs of the xanthate and the outer carbons of the 2-methylallyl ligand, while in the complexes, 1 and 2 it is defined by the four sulfur atoms of the xanthate ligand. Thermogravimetric studies have been carried out to evaluate the thermal stability of η³-allylpalladium(II) analogues. The complexes are useful precursors for the growth of nanocrystals of PdS either by furnace decomposition or solvothermolysis in dioctyl ether. The solvothermal decomposition of complexes in dioctyl ether gives a new metastable phase of PdS which can be transformed to the more stable tetragonal phase at 320 °C. The nanocrystals obtained have been characterized by PXRD, SEM, TEM and EDX.     

Synthesis and characterization of cyclometallated palladium(II) and platinum(II) complexes with amide-thiolate ligands

The redox reaction of bis(2-benzamidophenyl) disulfide (H₂L-LH₂) with [Pd(PPh₃)₄] in a 1:1 ratio gave mononuclear and dinuclear palladium(II) complexes with 2-benzamidobenzenethiolate (H₂L⁻), [Pd(H₂L-S)₂(PPh₃)₂] (1) and [Pd₂(H₂L-S)₂ (μ-H₂L-S)₂(PPh₃)₂] (2). A similar reaction with [Pt(PPh₃)₄] produced only the corresponding mononuclear platinum(II) complex, [Pt(H₂L-S)₂(PPh₃)₂] (3). Treatment of these complexes with KOH led to the formation of cyclometallated palladium(II) and platinum(II) complexes, [Pd(L-C,N,S)(PPh₃)]⁻ ([4]⁻) and [Pt(L-C,N,S) (PPh₃)]⁻ ([5]⁻). The molecular structures of 2, 3 and [4]⁻ were determined by X-ray crystallography.     

Ruthenium(II) and palladium(II) complexes with 2,6-(bispyrazol-1-yl)pyridines

Ruthenium(II) and palladium(II) complexes [Ru(DMSO)(L)Cl₂] and [Pd(L)Cl]Cl, where L = 2,6-bis(pyrazol-1-yl)pyridine (bpp) or 2,6-bis(3,5-dimethylpyrazol-1-yl)pyridine (bdmpp) have been synthesized. All complexes were characterized by elemental analysis, IR, ¹H NMR, UV-Vis, and cyclic voltammetry measurements.     

Preparation,spectroscopic characterization and X-ray crystal and molecular structures of nickel(II), copper(II) and zinc(II) complexes of the Schiff base formed from isatin and S-methyldithiocarbazate (Hisa-sme)

Complexes of general formula, [M(isa-sme)₂] · n(solvate) [M = Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺; isa-sme = monoanionic form of the Schiff base formed by condensation of isatin with S-methyldithiocarbazate; n = 1 or 1.5; solvate = MeCN, DMSO, MeOH or H₂O] have been synthesized and characterized by a variety of physicochemical techniques. An X-ray crystallographic structure determination of the [Ni(isa-sme)₂] · MeCN complex reveals a six-coordinate, distorted octahedral geometry. The two uninegatively charged, tridentate, Schiff base ligands are coordinated to the nickel(II) ion meridionally via the amide O-atoms, the azomethine N-atoms and the thiolate S-atoms. By contrast, the crystal structure of [Zn(isa-sme)₂] · MeOH shows a four-coordinate distorted tetrahedral geometry. The two dithiocarbazate ligands are coordinated as N, S bidentate chelates with the amide O-atom not coordinated. The structure of the copper(II) complex [Cu(isa-sme)₂] · DMSO is complicated and comprises two different complexes in the asymmetric unit, one four- and the other five-coordinate. The four-coordinate copper(II) has a distorted (flattened) tetrahedral geometry as seen in the Zn(II) analogue whereas the five-coordinate copper(II) has a distorted square-pyramidal geometry with one ligand coordinated to the copper(II) ion as a tridentate (N, S, O) ligand and the other coordinated as a bidentate N, S chelate. EPR spectroscopy indicates that in solution only one form is present, that being a distorted tetrahedral complex.     

A study of the reactions of methionine- and histidine-containing peptides with palladium(II) complexes: The key role of steric crowding on palladium(II) in the selective cleavage of the peptide bond

¹H NMR spectroscopy was applied to study the reactions of palladium(II) complexes, cis-[Pd(dpa)Cl₂] and cis-[Pd(dpa)(H₂O)₂]²⁺ (dpa is 2,2′-dipyridylamine acting as a bidentate ligand) with the dipeptides methionylglycine (Met-Gly) and histidylglycine (His-Gly), and the N-acetylated derivatives of these dipeptides, MeCOMet-Gly and MeCOHis-Gly. All reactions were carried out in the pH range 2.0–2.5 with equimolar amounts of the palladium(II) complex and the peptide at two different temperatures, 25 and 60 °C. In the reactions of cis-[Pd(dpa)Cl₂] and cis-[Pd(dpa)(H₂O)₂]²⁺ with Met-Gly and His-Gly, no hydrolysis of the peptide bond was observed. The final product in these reactions was the [Pd(dpa)₂]²⁺ complex. The square-planar structure of this complex was confirmed by X-ray analysis. The reaction of the cis-[Pd(dpa)(H₂O)₂]²⁺ complex with the MeCOHis-Gly and MeCOMet-Gly peptides under the previously mentioned experimental conditions was remarkably selective in the cleavage of the amide bond involving the carboxylic group of methionine in the side chain. The modes of coordination of cis-[Pd(dpa)Cl₂] and cis-[Pd(dpa)(H₂O)₂]²⁺ in the reactions with the non-acetylated peptides and the total steric inhibition of the hydrolytic reaction between cis-[Pd(dpa)(H₂O)₂]²⁺ and MeCOHis-Gly can be attributed to the steric bulk of the palladium(II) complex. This finding should be taken into consideration in designing new palladium(II) complexes for the regioselective cleavage of peptides and proteins.     

Mononuclear ruthenium(II) complexes bearing the (S,S)-Pr-pybox ligand

The complexes trans-[RuCl₂(L){(S,S)-ⁱPr-pybox}] ((S,S)-ⁱPr-pybox = 2,6-bis[4′-(S)-isopropyloxazolin-2′-yl]pyridine, L = PMe₃ (1), P(OMe)₃ (2), PPh₂(CH₂CHCH₂) (3), CNBn (5), CNCy (6) and MeCN (7)) have been synthesized by substitution of ethylene on the precursor trans-[RuCl₂(η²-C₂H₄){(S,S)-ⁱPr-pybox}]. This complex also reacts with cyclooctadiene (cod) or norbornadiene (nbd) and NaPF₆, in refluxing methanol, giving the coordination compounds [RuCl(η⁴-cod){(S,S)-ⁱPr-pybox}][PF₆] (8) and [RuCl(η⁴-nbd){(S,S)-ⁱPr-pybox}][PF₆] (9). The structures of complexes [RuCl(CO)(PPh₃)(H-pybox)][BF₄] (H-pybox = 2,6-bis(dihydrooxazolin-2′-yl)pyridine) (4), 6 and 8, have been resolved by X-ray diffraction methods. The catalytic activity of the new complexes in transfer hydrogenation of acetophenone has also been examined.     

Silicon containing new salicylaldimine Pd(II) and Co(II) metal complexes as efficient catalysts in transformation of carbon dioxide (CO2) to cyclic carbonates

A new series of metal complexes of salicyladimine ligands with Pd(II) and Co(II) have been prepared and characterized by different techniques (elemental analysis, UV-vis, FT-IR, ¹H NMR spectra, magnetic susceptibility measurements). Electronic spectra and magnetic susceptibility measurements reveal square planar geometry for Pd(II) metal complex and tetrahedral geometry for Co(II) metal complex. The synthesized Pd(II) and Co(II) complexes were also tested as catalysts for the formation of cyclic organic carbonates from carbon dioxide and liquid epoxides which served as both reactant and solvent. The results showed that the [M(L₃)₂] (M = Pd or Co) complexes bearing 5-methyl substituent on the aryl ring are more efficient than the other Pd(II) and Co(II) metal complexes for the formation of cyclic organic carbonates from carbon dioxide. These catalysts, [Pd(L₃)₂] and [Co(L₃)₂] complexes and location (p-position of phenoxy) of electron donating methyl substituent in particular, effectively promote the of carbon dioxide activation with liquid epoxides under solvent-free homogeneous conditions. Furthermore, [Pd(L₃)₂] can be reused more than eight times with a minimal loss of its original catalytic activities.     

Formation and structures of Pd(II) N,S-heterocyclic carbene-pyridyl mixed-ligand complexes

Mononuclear mixed-ligand complexes of Pd(II) containing a N,S-heterocyclic carbene (NSHC) with a secondary alkyl N-substituent and pyridyl ligand, with the general formula [PdI₂(C₁₀H₁₁NS)L] (C₁₀H₁₁NS = 3-isopropylbenzothiazolin-2-ylidene; L = pyridine, 2-aminopyridine, 3-iodopyridine and 4-tert-butyl-pyridine) have been synthesized and characterized by X-ray single-crystal crystallography. Both solution and solid-state structures, as evident from their ¹H NMR spectra and X-ray structures, show anagostic γ-hydrogen interactions of metal with methine of the substituent on the carbene or pyridyl ligand giving 5-membered-chelate-like structures.     

Synthesis and reactivity of new methylallylpalladium(II) complexes with bidentate 2-(methylthio-N-benzylidene)anilines

This work describes the synthesis, characterisation and reactivity of new methylallyl Pd(II) complexes that contain bidentate 2-(methylthio-N-benzylidene)anilines as ligands. The reaction of the binuclear complex [(η³-Me-allyl)Pd(μ-Cl)₂] with AgBF₄ causes the total abstraction of the chloride bridges, with the subsequent formation of an intermediary fragment of Pd(II). This fragment in turn reacts with neutral bidentate 2-(methylthio-N-benzylidene)anilines to give cationic complexes of Pd(II) of general formula [(η³-Me-allyl)Pd(η²-S,N-MeSC₆H₄NCHC₆H₄(X)Y)]BF₄ [X=H, Y=H (1); X=F, Y=H (2); X=Me, Y=H (3); X=H, Y=Cl (4); X=H, Y=Me₂N (5); X=H, Y=NO₂ (6)]. The new complexes were characterised by means of elemental analysis, IR, NMR [¹H, ¹⁹F{¹H}, ¹³C{¹H}, ³¹P{¹H}, Dept, ¹H-¹H-COSY, HSQC, HMBC] and mass spectroscopies. The reaction of the Pd(II) complexes with nucleophiles such as NaI, (EtO)₂PS₂K, KCN, KSCN or NaH lead to the deco-ordination of the bidentate ligands to give dimeric or polymeric complexes of Pd(II). The reactivity pattern observed is discussed by a theoretical analysis based on Fukui functions.     

Bis(saccharinato)palladium(II) and platinum(II) complexes with 2,2′-bipyridine: Syntheses,structures, spectroscopic,fluorescent and thermal properties

New palladium(II) and platinum(II) complexes, cis-[Pd(bpy)(sac)₂] (1) and cis-[Pt(bpy)(sac)₂] (2), where sac = saccharinate, bpy = 2,2′-bipyridine, have been synthesized and characterized by elemental analysis, UV–Vis, IR, ¹H NMR and ¹³C NMR. The structures of the DMSO solvated complexes are determined by X-ray diffraction. Both complexes are isomorphous and the metal ions are coordinated by two N-bonded sac ligands, and two nitrogen atoms of pyridyl groups of bpy in a cis fashion. The mononuclear species interact each other through weak intermolecular C–H?O hydrogen bonds, C–H?π and π?π interactions leading to three-dimensional supramolecular networks. All complexes exhibit a high thermal stability in the solid state, and are fluorescent in the solution.     

Palladium(II) and platinum(II) saccharinate complexes containing pyridine and 3-acetylpyridine: Synthesis, crystal structures, fluorescence and thermal properties

New palladium(II) and platinum(II) complexes of saccharinate (sac), trans-[Pd(py)₂(sac)₂] (1), cis-[Pt(py)₂(sac)₂] (2), trans-[Pd(3-acpy)₂(sac)₂] (3) and cis-[Pt(3-acpy)₂(sac)₂] (4) (py = pyridine and 3-acpy = 3-acetylpyridine) have been synthesized. Elemental analysis, UV-Vis, IR, NMR and TG/DTA characterizations have been carried out. The structures of 1-4 were determined by X-ray diffraction. The palladium(II) and platinum(II) ions are coordinated by two N-bonded sac ligands, and two nitrogen atoms of py or 3-acpy, forming a distorted square-planar geometry. The palladium(II) complexes (1 and 3) are trans isomers, while the platinum(II) complexes (2 and 4) are cis isomers. The mononuclear species in the solid state are connected by weak intermolecular C-H?O hydrogen bonds, C-H?π and π?π stacking interactions. The platinum(II) complexes show significant fluorescence at the room temperature.     

Effect of 5-Me substituent(s) on the catalytic activity of palladium(II) 2,2-bipyridine complexes in CO/4-tert-butylstyrene copolymerization

The coordination of two 5-substituted-2,2^′-bipyridines L (L¹=5-methyl-2,2^′-bipyridine, L²=5,5^′-dimethyl-2,2^′-bipyridine) to palladium was studied. The neutral complexes [Pd(L)Cl₂] and [Pd(L)(Me)Cl], and the cationic complexes obtained after chlorine abstraction [Pd(L)₂][BAr^′₄]₂ and [Pd(L)(Me)(NCMe)][BAr^′₄] (Ar^′=3,5-(CF₃)₂-C₆H₃), respectively, were isolated and characterized by NMR and FAB mass spectroscopy. The complex [Pd(L²)(L³)][BAr^′₄]₂ (L³=2,2^′-bipyridine) bearing different ligands, was prepared for comparison purposes. The activity of the monocationic and dicationic complexes as catalytic precursors in the CO/4-tert-butylstyrene copolymerization was compared with that of related well-known catalysts containing the unsubstituted 2,2^′-bipyridine as nitrogen ligand, to evaluate the influence of the substituents in 5- and 5,5^′-position. The presence of one or two substituents on the nitrogen ligand has a positive effect on productivity using both types of precursors. No influence was observed on the polymer properties in terms of molecular weight and tacticity. Analysis of the reactivity of the methyl-palladium complexes towards carbon monoxide shows further differences depending on the nitrogen ligand.     

Calculations of microconstants and equilibrium formation constants for platinum(II) and palladium(II) halide complexes in solution

Distribution diagrams and formation functions for halide complexes [M(H₂O)_{4 ? n} Cl _n ]^{2 ? n} (M = Pt(II) or Pd(II)) and [PdCl_{4 ? n} Br _n ]^2? (n = 0?C4) in solution are analyzed in terms of the matrix model. Equilibrium constants for binding the first ligand $\left( {\bar K} \right)$ and corrections for the mutual influence between ligands (??) in the course of complex formation in solution are calculated. In examples analyzed, the substitution of chloride ion for water in the coordination sphere of platinum(II) and palladium(II) is an anti-cooperative process. The substitution of bromide ion for chloride ion in the coordination sphere of [PdCl₄]^2? is weakly cooperative. Quantum-chemical calculations show that platinum(II) and palladium(II) cis-bisaquadichloro complexes in the gas phase are thermodynamically less stable than trans-isomers. The cis-trans isomerization constants in the gas phase calculated by the DFT method and those found for solutions using the matrix model have the same order of magnitude.     

Search of structure and ligands exchange for palladium(II) complexes with N-allylimidazole; X-ray and solid-state/solution NMR studies

Two coordination compounds of palladium(II) with N-allylimidazole (l) of the general formula [PdL₄]Cl₂ · 3H₂O (1) and trans-[PdL₂Cl₂] (2) have been synthesized. The crystal and molecular structure of complexes 1 and 2 was established by single-crystal X-ray diffraction analysis. The X-ray structural data were supplemented by solid-state ¹³C NMR measurements (CP MAS and PASS 2D). The 1D and 2D NMR studies in solution reveal that complex 1 is unstable at room temperature and undergoes reversible decomposition to 2. The method for how to preserve a complex with four allyl-imidazole ligands in solution is shown.     

Synthesis,characterization and bioactivity of mixed-ligand Cu(II) complexes containing Schiff bases derived from S-benzyldithiocarbazate and saccharinate ligand and the X-ray crystal structure of the copper-saccharinate complex containing S-benzyl-β-N-(acetylpyrid-2-yl)methylenedithiocarbazate

Mixed-ligand complexes of general formula, [Cu(NNS)(sac)] (NNS′ = S-benzyl-β-N-(2-acetylpyrid-2-yl)methylenedithiocarbazate, NNS″ = S-benzyl-β-N-(2-benzoylpyrid-2-yl)methylenedithiocarbazate and NNS? = S-benzyl-β-N-(6-methylpyrid-2-yl)methylenedithio-carbazate, sac = the saccharinate anion) have been synthesized by reacting [Cu(sac)₂(H₂O)₄] · 2H₂O with the appropriate ligands in ethanol and characterized by various physico-chemical techniques. Magnetic and spectral evidence indicate that the complexes are four-coordinate in which the Schiff bases coordinate as NNS ligands and the sac- anion coordinates as a unidentate N-donor ligand. An X-ray crystallographic structural analysis of [Cu(NNS′)(sac)] shows that the complex has a distorted square-planar geometry with the Schiff base coordinated to the copper (II) ion as a uninegatively charged tridentate chelating agent via the pyridine nitrogen atom, the azomethine nitrogen atom and the thiolate sulphur atom while the fourth coordination position is occupied by the N-bonded saccharinate anion. The complexes have been evaluated for their biological activities against selected pathogens and cancer cell lines. They display weak activity against the pathogenic bacteria and fungi. The complexes were highly active against the leukemic cell line (HL-60) but only [Cu(NNS′)(sac)] was found to exhibit strong cytotoxicity against the ovarian cancer cell line (Caov-3). All complexes were inactive against the breast cancer cell line (MCF-7).     

Palladium(II) complexes with S-benzyl dithiocarbazate and S-benzyl-N-isopropylidenedithiocarbazate: Synthesis,spectroscopic properties and X-ray crystal structures

Two new palladium(II) bis(NS) chelates, bis(S-benzyl dithiocarbazato)palladium(II) (1) and bis(S-benzyl-N-isopropylidenedithiocarbazato)palladium(II) (2), have been prepared and characterized using single-crystal X-ray diffraction and spectroscopic (electronic, IR and NMR) techniques. Complex 1 has a perfectly square planar trans configuration (point group C_i), while complex 2 has a distorted square planar cis configuration.     

Thermal, spectral, electrochemical and biologic characterization of new Pd(II) complexes with ligands bearing biguanide moieties

New complexes [Pd(HDMBG)₂]Cl₂·H₂O, [PdL¹]Cl₂·0.5H₂O and [PdL²]Cl₂·1.5H₂O (HDMBG: dimethylbiguanide, L¹ and L²: ligands resulted from HDMBG, ammonia/hydrazine and formaldehyde template condensation) were synthesized and characterized. The features of complexes have been assigned from microanalytical, IR, UV–Vis and cyclic voltammetry data. The thermal transformations are complex processes according to TG and DTA curves including water and hydrochloric acid elimination, thermolysis processes leading to paracyanide formation as well as PdO decomposition, final product being palladium. Complexes were screened for their antimicrobial properties against some pathogenic Gram-positive and Gram-negative bacterial as well as fungal Candida albicans strains. The complexes exhibit specific antibacterial and/or antifungal activity, depending on their structure and the tested microbial strains. All complexes inhibit the microbial biofilm development on the inert substratum. It was also observed that PdCl₂ complexation minimized their cytotoxic effect on the eukaryotic cells.     

Synthesis, characterization, antibacterial and cytotoxic activity of new palladium(II) complexes with dithiocarbamate ligands: X-ray structure of bis(dibenzyl-1-S:S′-dithiocarbamato)Pd(II)

Six palladium(II) dithiocarbamates of general formula Pd(AmDTC)₂, where HAmDTC = aminedithiocarbamic acid, [Pd(II) piperidinedithiocarbamate (1), Pd(II) 4-methylpiperidinedithiocarbamate (2), Pd(II) N-methylbenzyldithiocarbamate (3), Pd(II) dibenzyldithiocarbamate (4), Pd(II) dicyclohexyldithiocarbamate (5), Pd(II) N-cyclohexyl-N-methyldithiocarbamate (6)] have been synthesized and characterized by elemental analyses, FT-IR, ¹H and ¹³C NMR. The X-ray structure of Pd(II), compounds 3 and 4, showed that the ligands are chelated by both sulfur atoms with bond angles S1-Pd-S4 = 179.24(2)° and S2-Pd-S3 = 179.09(5)°, with a distorted square planar geometry around Pd. All these complexes were screened for cytotoxic and antibacterial effects and showed significant antibacterial activity and no substantial in vitro cytotoxicity indicating specificity of the compounds.