Synthesis of palladium(II) complexes with 3-amino-5-methyl-5-(4-pyridyl)-hydantoin: cytotoxic and antimicrobial investigations and comparison with their platinum analogues

Two new Pd(II) complexes with 3-amino-5-methyl-5-(4-pyridyl)-hydantoin (AMPH) were synthesized: cis-[Pd(AMPH)₂Cl₂]·2H₂O and cis-[Pd(AMPH)₂Br₂]·H₂O. The complexes were characterized by physico-chemical and spectroscopic methods. The determination of crystal water content in the complexes was defined by Karl Fisher titration. The cytotoxic effects of these complexes were examined on a panel of human tumor cell lines. Qualitative antimicrobial assays on three pathogenic microorganisms of the new complexes, their analogues with 5-methyl-5-(4-pyridyl)-hydantoin(MPH) and their platinum analogues were made. Cis-[Pd(mpyh)₂Br₂]·H₂O showed significant activity against C. albicans.     

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.     

A quantum chemical consideration of ligand exchange in palladium(ii) aqueous and chloride complexes

The behavior of potassium tetrachloropalladate(II) in media simulating biological fluids has been studied. In aqueous solutions of NaCl, the aquation rate is higher than the rate of chloro ligand introduction into the internal coordination sphere of palladium. In HCl solutions, on the contrary, the process of palladium chloro complex formation predominates. The latter is apparently due to protonation of water molecules composing aqua complexes. By means of the ZINDO/1 method, the substitution of ligands – water molecules and hydronium ion – in planar complexes of palladium(II) by chloride ion has been investigated. All complexes containing H₂O and H₃O⁺ ligands, other than [Pd(H₂O)₄]²⁺, have intramolecular hydrogen bonds. In [Pd(H₂O)₃(H₃O)]³⁺ and trans-[Pd(H₂O)₂(H₃O)Cl]²⁺, a “non-classic” symmetric hydrogen bond O ··· H ··· O is established (ZINDO/1, RHF/STO-6G*). By the first three steps the substitution of hydronium ion in the internal sphere of palladium atom is more favorable thermodynamically, compared to water molecules. Logarithms of stepwise stability constants of palladium(II) chloride complexes correlate linearly to enthalpies (ZINDO/1, PM3) of water substitution by chloride ion.     

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.     

Molecular modeling,spectral, and biological studies of 4-formylpyridine-4 N-(2-pyridyl) thiosemicarbazone (HFPTS) and its Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Cd(II), Hg(II), and UO2(II) complexes

The present work describes the preparation and characterization of some metal ion complexes derived from 4-formylpyridine-⁴ N-(2-pyridyl)thiosemicarbazone (HFPTS). The complexes have the formula; [Cd(HFPTS)₂H₂O]Cl₂, [CoCl₂(HPTS)]·H₂O, [Cu₂Cl₄(HPTS)]·H₂O, [Fe (HPTS)₂Cl₂]Cl·3H₂O, [Hg(HPTS)Cl₂]·4H₂O, [Mn(HPTS)Cl₂]·5H₂O, [Ni(HPTS)Cl₂]·2H₂O, [UO₂(FPTS)₂(H₂O)]·3H₂O. The complexes were characterized by elemental analysis, spectral (IR, ¹H-NMR and UV–Vis), thermal and magnetic moment measurements. The neutral bidentate coordination mode is major for the most investigated complexes. A mononegative bidentate for UO₂(II), and neutral tridentate for Cu(II). The tetrahedral arrangement is proposed for most investigated complexes. The biological investigation displays the toxic activity of Hg(II) and UO₂(II) complexes, whereas the ligand displays the lowest inhibition activity toward the most investigated microorganisms.     

Structural and Coordinative Variability in Zinc(II), Cadmium(II), and Mercury(II) Complexes of 2‐Pyridineformamide 3‐Hexamethyleneiminylthiosemicarbazone

Sodium in dry methanol reduces 2‐cyanopyridine in the presence of 3‐hexamethyleneiminylthiosemicarbazide and produces 2‐pyridineformamide 3‐hexamethyleneiminylthiosemicarbazone, HAmhexim ( 1 ). Complexes with zinc(II ), cadmium(II ) and mercury(II ) have been prepared and characterized by spectroscopic techniques. In addition, the crystal structures of HAmhexim ( 1 ), [Zn(Amhexim)(OAc)]₂μ·μDMSO ( 2 ), [Cd(HAmhexim)Cl₂]μ·μDMSO ( 7 ), [Cd(Amhexim)₂] ( 8 ), [Cd(HAmhexim)Br₂]μ·μDMSO ( 9 ), [Cd(HAmhexim)I₂]μ·μEtOH ( 10 ), [Hg(HAmhexim)Cl₂]μ·μDMSO ( 11 ), [Hg(Amhexim)Br]₂ ( 13 ), [Hg₃(HAmhexim)(Amhexim)Br₅]μ·μH₂O ( 14 ) and [Hg(Amhexim)I]₂ ( 15 ) have been determined. Coordination of the anionic and neutral thiosemicarbazone ligand occurs through the pyridine nitrogen atom, imine nitrogen atom, and thiolato or thione sulfur atom. In [Zn(Amhexim)(OAc)]₂ one of the bridging acetato ligands has monodentate coordination and the other bridges in a bidentate manner. [Cd(Amhexim)₂] is a 6‐coordinate species while the other cadmium complexes are 5‐coordinate. In [Hg(Amhexim)Br]₂ and [Hg(Amhexim)I]₂ the thiolato sulfur atoms act as bridges between the Hg atoms to form dimeric compounds and [Hg₃(HAmhexim)(Amhexim)Br₅]μ·μH₂O is a trinuclear complex with three different centers — two metallic centers have a 5‐coordination and the another one has 4‐coordination. In addition, [Hg(HAmhexim)Cl₂]μ·μDMSO and [Hg₃(HAmhexim)(Amhexim)Br₅]μ·μH₂O shown a supramolecular one‐dimensional hydrogen‐bonded self‐assembling.     

The Cocrystallization of the Cubic [Ta6Br12(H2O)6][CuBr2X2]·10H2O and Triclinic [Ta6Br12(H2O)6]X2·trans‐[Ta6Br12(OH)4(H2O)2]·18H2O (X = Cl,Br, NO3) Phases with the Coexistence of [Ta6Br12]2+ and [Ta6Br12]4+ in the Latter

Cubic [Ta₆Br₁₂(H₂O)₆][CuBr₂X₂]·10H₂O and triclinic [Ta₆Br₁₂(H₂O)₆]X₂·trans‐[Ta₆Br₁₂(OH)₄(H₂O)₂]·18H₂O (X = Cl, Br, NO₃) cocrystallize in aqueous solutions of [Ta₆Br₁₂]²⁺ in the presence of Cu²⁺ ions. The crystal structures of [Ta₆Br₁₂(H₂O)₆]Cl₂·trans‐[Ta₆Br₁₂(OH)₄(H₂O)₂]·18H₂O ( 1 ) and [Ta₆Br₁₂(H₂O)₆]Br₂·trans‐[Ta₆Br₁₂(OH)₄(H₂O)₂]·18H₂O ( 3 )have been solved in the triclinic space group P&1macr; (No. 2). Crystal data: 1 , a = 9.3264(2) Å, b = 9.8272(2) Å, c = 19.0158(4) Å, α = 80.931(1)?, β = 81.772(2)?, γ = 80.691(1)?; 3 , a = 9.3399(2) Å, b = 9.8796(2) Å, c = 19.0494(4) Å; α = 81.037(1)?, β = 81.808(1)?, γ = 80.736(1)?. 1 and 3 consist of two octahedral differently charged cluster entities, [Ta₆Br₁₂]²⁺ in the [Ta₆Br₁₂(H₂O)₆]²⁺ cation and [Ta₆Br₁₂]⁴⁺ in trans‐[Ta₆Br₁₂(OH)₄(H₂O)₂]. Average bond distances in the [Ta₆Br₁₂(H₂O)₆]²⁺ cations: 1 , Ta‐Ta, 2.9243 Å; Ta‐Brⁱ , 2.607 Å; Ta‐O, 2.23 Å; 3 , Ta‐Ta, 2.9162 Å; Ta‐Brⁱ , 2.603 Å; Ta‐O, 2.24 Å. Average bond distances in trans‐[Ta₆‐Br₁₂(OH)₄(H₂O)₂]: 1 , Ta‐Ta, 3.0133 Å; Ta‐Brⁱ, 2.586 Å; Ta‐O(OH), 2.14 Å; Ta‐O(H₂O), 2.258(9) Å; 3 , Ta‐Ta, 3.0113 Å; Ta‐Brⁱ, 2.580 Å; Ta‐O(OH), 2.11 Å; Ta‐O(H₂O), 2.23(1) Å. The crystal packing results in short O···O contacts along the c axes. Under the same experimental conditions, [Ta₆Cl₁₂]²⁺ oxidized to [Ta₆Cl₁₂]⁴⁺ , whereas [Nb₆X₁₂]²⁺ clusters were not affected by the Cu²⁺ ion.     

Syntheses and crystal structures of two novel Cu(II) and Co(II) complexes with 3-methyl-4-(p-bromophenyl)-5-(2-pyridyl)-1,2,4-triazole

A new ligand, 3-methyl-4-(p-bromophenyl)-5-(2-pyridyl)-1,2,4-triazole (L) and its complexes, trans-[CuL₂(ClO₄)₂] (1) and cis-[CoL₂(H₂O)₂](ClO₄)₂·H₂O·CH₃OH (2), have been synthesized and characterized by UV, IR, electrospray ionization mass spectrum, elemental analyses, and single-crystal X-ray diffraction methods. In the structure, two L ligands are stabilized by intermolecular π···π interactions between the triazole rings. In the complexes, each L ligand adopts a chelating bidentate mode through N atom of pyridyl group and one N atom of the triazole. Both complexes have a similar distorted octahedral [MN₄O₂] core (M = Cu²⁺ and Co²⁺) with two ClO₄ ⁻ ions in the trans position in 1 but two H₂O molecules in the cis arrangement in 2.     

Complexes of Co(II), Ni(II), and Cu(II) with 4-(3,4-dichlorophenyl)-1,2,4-triazole

Novel oligonuclear complexes of Co(II), Ni(II), and Cu(II) with 4-(3,4-dichlorophenyl)-1,2,4-triazole (L) of the composition [M₃L₁₀(H₂O)₂](NO₃)₆ (M = Co(II), Ni(II)), [Ni₃L₆(H₂O)₆]Hal₆ (Hal = Cl^?, Br^?), and [Cu₅L₁₆(H₂O)₂](NO₃)₁₀ · 2H₂O were synthesized and studied by magnetic susceptibility, electronic and IR spectroscopy, and powder X-ray diffraction methods. All the above complexes are X-ray amorphous. Antifer-romagnetic exchange interactions between the M²⁺ ions were discovered in the [Co₃L₁₀(H₂O)₂](NO₃)₆ and [Ni₃L₁₀(H₂O)₂](NO₃)₆ complexes, whereas ferromagnetic exchange interactions were observed in the complexes [Ni₃L₆(H₂O)₆]Cl₆, [Ni₃L₆(H₂O)₆]Br₆, and [Cu₅L₁₆(H₂O)₂](NO₃)₁₀ · 2H₂O.     

Coordination compounds of palladium(II) and platinum(II) with benzotriazoles

Summary The nitrogen-donor ligands 1-methylbenzotriazole (1Mebta), 5-methylbenzotriazole (5MebtaH), 5-chlorobenzotriazole (5ClbtaH) and 5-nitrobenzotriazole (5NO₂btaH) react with palladium(II) and platinum(II) to give cis-[PdL₂Cl₂], cis-[PtL₂Cl₂] (L = 1Mebta, 5MebtaH, 5ClbtaH or 5NO₂btaH), [Pt(5ClbtaH)₄]Cl₂, [Pd-(5MebtaH)Cl₂]₂, [Pd(5ClbtaH)Cl₂]₂ and [Pd(5NO₂btaH)-Cl₂]₂. The complexes were characterized by physicochemical and spectroscopic methods. The benzotriazoles act as monodentate ligands binding through N(3). Monomeric square planar structures are assigned for the 12 complexes and [Pt(5ClbtaH)₄]Cl₂ in the solid state. Centrosymmetric, chloro-bridged, dinuclear square planar structures of C_2h symmetry are proposed for the 11 palladium(II) compounds.     

Synthesis,crystal structure,Hirshfeld surfaces,and spectral properties of Cu(II) and Co(II) complexes with 3-phenoxymethyl-4-phenyl-5-(2-pyridyl)-1,2,4-triazole

A new asymmetrical substituted triazole, 3-phenoxymethyl-4-phenyl-5-(2-pyridyl)-1,2,4-triazole (L) and its complexes, cis-[Cu₂ L ₂Cl₄]·2CH₃CN (1) and trans-[CoL ₂Cl₂]·2H₂O·2CH₃CN (2), have been synthesized and characterized by IR, single-crystal X-ray diffraction, thermogravimetric analyses and Hirshfeld surfaces. In the structure, two L are mainly stabilized by an intermolecular C–H?N hydrogen bond. In 1 (or 2), each L involves a doubly-bidentate (or chelating bidentate) coordination mode through one pyridine and two nitrogens (or one) of triazole, respectively. Complex 1 has a distorted trigonal bipyramidal [CuN₃Cl₂] core with two cis Cl^? while 2 shows a distorted octahedron [CoN₄Cl₂] with two trans Cl^?. We also prepared molecular Hirshfeld surface and fingerprint plot for L, 1 and 2, which revealed the influence of different metals on coordinate of L.     

Palladium(II) Complexes of 1-vinylimidazole

Two new co-ordination compounds of Pd^II with 1-vinylimidazole of the formulae [PdL₄]Cl₂·3H₂O and trans-[PdL₂Cl₂], where L is a 1-vinylimidazole molecule, have been obtained. The compounds were characterised by spectroscopic, molar conductivity, thermogravimetric and magnetochemical measurements. Single crystal X-ray structure analyses of the complexes were also carried out. The compounds are diamagnetic with square-planar coordinatination around the palladium(II) ions. Other physico-chemical properties of the both complexes are compatible with their structures.     

Synthesis and characterization of CuII and CoII complexes derived from 2,4,6-tri-(2-pyridyl)-1,3,5-triazine (TPT) by chemical and tribochemical reactions

Four Cu^II and Co^II complexes–[Cu(L₁)Cl₂(H₂O)]3/2H₂O · 1/2EtOH, [Cu(L₁)₂Cl₂]6H₂O, [Co(L₁)Cl₂]3H₂O · EtOH, and [Co₂(L₁)(H₂O)Cl₄]1.5H₂O · EtOH (L₁ = 2,4,6-tri(2-pyridyl)-1,3,5-triazine; TPT)–were synthesized by conventional chemical method and used to synthesize another four metal complexes–[Cu(L₁)I₂(H₂O)]6H₂O, [Cu(L₁)₂I₂]6H₂O, [Co(L₁)I(H₂O)₂]I · 2H₂O, and [Co₂(L₁)I₄(H₂O)₃]–using tribochemical reaction, by grinding it with KI. Substitution of chloride by iodide occurred, but no reduction for Cu^II or oxidation of Co^II. Oxidation of Co^II to Co^III complexes was only observed on the dissolution of Co^II complexes in d₆-DMSO in air while warming. The isolated solid complexes (Cu^II and Co^II) have been characterized by elemental analyses, conductivities, spectral (IR, UV-Vis, ¹H-NMR), thermal measurements (TGA), and magnetic measurements. The values of molar conductivities suggest non-electrolytes in DMF. The metal complexes are paramagnetic. IR spectra indicate that TPT is tridentate coordinating via the two pyridyl nitrogens and one triazine nitrogen forming two five-membered rings around the metal in M : L complexes and bidentate via one triazine nitrogen and one pyridyl nitrogen in ML₂ complexes. In binuclear complexes, L is tridentate toward one Co^II and bidentate toward the second Co^II in [Co₂(L₁)Cl₄]2.5H₂O · EtOH and [Co₂(L₁)I₄(H₂O)₃]. Electronic spectra and magnetic measurements suggest a distorted-octahedral around Cu^II and high-spin octahedral and square-pyramidal geometry around Co^II.     

Synthesis and characterization of palladium(II) complexes of thioureas. X-ray structures of [Pd( N , N ′-dimethylthiourea)4]Cl2?·?2H2O and [Pd(tetramethylthiourea)4]Cl2

Palladium(II) complexes of thiones having the general formula [Pd(L)₄]Cl₂, where L = thiourea (Tu), methylthiourea (Metu), N,N′-dimethylthiourea (Dmtu), and tetramethylthiourea (Tmtu) were prepared by reacting K₂[PdCl₄] with the corresponding thiones. The complexes have been characterized by elemental analysis, IR and NMR spectroscopy, and two of these, [Pd(Dmtu)₄]Cl₂ · 2H₂O (1) and [Pd(Tmtu)₄]Cl₂ (2), by X-ray crystallography. An upfield shift in the >C=S resonance of thiones in ¹³C NMR and downfield shift in N–H resonance in ¹H NMR are consistent in showing sulfur coordination with palladium(II). The crystal structures of the complexes show a square-planar coordination environment around the Pd(II) ions with the average cis and trans S–Pd–S bond angles of 89.64° and 173.48°, respectively. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. An erratum to this article can be found at     

Structural Study of Nickel(II), Copper(II), and Palladium(II) Complexes of 2‐Pyridineformamide 3‐Hexamethyleneiminylthiosemicarbazone

Reduction of 2‐cyanopyridine by sodium in the presence of 3‐hexamethyleneiminylthiosemicarbazide produces 2‐pyridineformamide 3‐hexamethyleneiminylthiosemicarbazone, HAmhexim. Complexes with nickel(II), copper(II) and palladium(II) have been prepared and the following complexes structurally characterized: [Ni(Amhexim)OAc], [{Cu(Amhexim)}₂C₄H₄O₄]·2DMSO·H₂O, [Cu(HAmhexim)Cl₂] and [Pd(Amhexim)Cl]. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur atom when coordinating as the anionic or neutral ligand, respectively. [{Cu(Amhexim)}₂C₄H₄O₄] is a binuclear complex with the two copper(II) ions bridged by the succinato group in [Cu‐(HAmhexim)Cl₂] the Cu atom is 5‐coordinate and close to a square pyramid structure and in [Ni(Amhexim)OAc] and [Pd(Amhexim)Cl] the metal atoms are planar, 4‐coordinate.     

Copper(II) and Cadmium(II) Complexes Based on N,N‐Bis(3, 5‐dimethyl‐2‐hydroxybenzyl)‐N‐(2‐pyridylmethyl)amine Ligand: Syntheses,Structures, Magnetic,and Luminescent Properties

The reaction of the aryl‐oxide ligand H₂L [H₂L = N,N‐bis(3, 5‐dimethyl‐2‐hydroxybenzyl)‐N‐(2‐pyridylmethyl)amine] with CuSO₄ · 5H₂O, CuCl₂ · 2H₂O, CuBr₂, CdCl₂ · 2.5H₂O, and Cd(OAc)₂ · 2H₂O, respectively, under hydrothermal conditions gave the complexes [Cu(H₂L¹)₂] · SO₄ · 3CH₃OH ( 1 ), [Cu₂(H₂L²)₂Cl₄] ( 2 ), [Cu₂(H₂L²)₂Br₄] ( 3 ), [Cd₂(HL)₂Cl₂] ( 4 ), and [Cd₂(L)₂(CH₃COOH)₂] · H₂L ( 5 ), where H₂L¹ [H₂L¹ = 2, 4‐dimethyl‐6‐((pyridin‐2‐ylmethylamino)methyl)phenol] and H₂L² [H₂L² = 2‐(2, 4‐dimethyl‐6‐((pyridin‐2‐ylmethylamino)methyl)phenoxy)‐4, 6‐dimethylphenol] were derived from the solvothermal in situ metal/ligand reactions. These complexes were characterized by IR spectroscopy, elementary analysis, and X‐ray diffraction. A low‐temperature magnetic susceptibility measurement for the solid sample of 2 revealed antiferromagnetic interactions between two central copper(II) atoms. The emission property studies for complexes 4 and 5 indicated strong luminescence emission.     

Stereoisomeric Pt(IV) complexes with threonine

Stereoisomeric Pt(IV) complexes with threonine (ThrH = HOCH(CH₃)CH(NH₂)COOH, ??-amino-??-hydroxybutyric acid) were obtained. In the complexes trans-[Pt(S-ThrH)₂Cl₄] and trans-[Pt(R-ThrH)(S-ThrH)Cl₄], the ThrH molecules act as monodentate ligands coordinated through the NH₂ group. In the complexes cis- and trans-[Pt(S-Thr)₂Cl₂] and trans-[Pt(R-Thr)(S-Thr)Cl₂], the deprotonated ligands are coordinated in a bidentate fashion through the NH₂ and COO^?-groups (R,S is the absolute configuration of the asymmetric carbon atom). All the complexes were identified using elemental analysis, IR spectroscopy, and ¹⁹⁵Pt, ¹³C, and ¹H NMR spectroscopy. The complexes trans-[Pt(S-ThrH)₂Cl₄] · 3H₂O and cis-[Pt(S-Thr)₂Cl₂] · 2H₂O were additionally characterized by X-ray diffraction.     

Synthesis,Structure and Noncovalent Interactions Palladium（Ⅱ）Complexes with N—Benzoyl—β—phenylalaniate Dianion and Aromatic Diimine

Two palladium(II) complexes, [Pd(bipy)(BzPhe‐N,O)] and [Pd(phen)(BzPhe‐N,O)]·4H₂O were synthesized by reactions between Pd(bipy)Cl₂ and BzPheH₂ (N‐benzoyl‐β‐phenylalanine), Pd(phen) Cl₂ and BzPheH₂ in water at pH‐9, with their structures determined by X‐ray diffraction analysis. The Pd atom is coordinated by two nitrogen atoms of bipy (or phen), the deprotonated amido type nitrogen atom and one of the carboxylic oxygens of BzPhe (BzPhe = N‐benzoyl‐β‐phenylalaninate dianion). In the complex [Pd(phen) (BzFne‐N,O)] · 4H₂O, the side chain of phenylalanine is located above and approximately parallels to the coordination plane. Both the aromatic‐aromatic stacking interaction between the phenyl ring of phenylalanine and phen, and the metal ion‐aromatic interaction between the phenyl ring of phenylalanine and Pd(II) were observed. [Pd(bipy)(BzPhe‐N,O)] has the phenylalanyl side chain oriented outwards from the coordination plane, which is mainly due to the interaction between the carbonyl oxygen atom of the amido group and the phenyl ring of phenylalanine. The reason for the different orientation of phenylalanyl side chain in the complexes was suggested.     

Addition of protic molecules to coordinated 2-pyridinecarboxaldehyde in gold(III), palladium(II), and platinum(II) complexes

The reactions of Au^III, Pt^II and Pd^II complexes with 2-pyridinecarboxaldehyde (2CHO-py) have been examined in protic (H₂O, MeOH, EtOH) and aprotic (DMF, CH₂Cl₂) solvents. Compounds in which the pyridine ligand is N-coordinated, either in the original aldehydic form or in a new form derived from addition of one or two protic molecules, have been isolated, namely: [Au(2CHO-py · H₂O)Cl₃], [Au(2CHO-py · MeOH)Cl₃], [Au(2CHO-py · 2EtOH)Cl₃], cis-[Pt(2CHO-py)₂Cl₂], trans-[Pd(2CHO-py)₂Cl₂], trans-[Pt(dmso)(2CHO-py)Cl₂], [Pt{C₅H₄N-(CH₂SMe)}Cl(2CHO-py)](ClO₄), [Pt(terpy)(2CHOpy)](ClO₄)₂, [Pt(terpy)(2CHO-py · H₂O)](ClO₄)₂ (terpy = 2,2′:6′,2′′-terpyridine). ¹H-n.m.r. experiments show that the addition of the protic molecule(s) to the Pt^II and Pd^II complexes is reversible. The effects of the nature of the metal ion and the ancillary ligands as well as of the total charge of the complexes on the relative stability of the addition products are discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Palladium(II) and platinum(II) complexes of rhodanine and 3-methylrhodanine

Summary The following palladium(II) and platinum(ll) complexes of rhodanine (HRd) and 3-methylrhodanine (MRd) have been prepared: Pd(HRd)_1.5Cl₂, Pd(HRd)₂Br₂, Pd(HRd)₂Br₂ · 0.25 EtOH, M(MRd)₂X₂ [M = Pd, X = Cl (0.25 EtOH) or Br; M = Pt, X = Cl or Br], Pd(MRd)₃Br₂, and M(MRd)₄(ClO₄)₂ (M = Pd or Pt). The ligands are coordinated to the metal through the thiocarbonylic sulphur atom. Pd(HRd)_1.5Cl₂ has presumably a structure such as (X = Cl or Br) complexes have a trans-planar coordination. Pd(MRd)₂X₂ (X = Cl or Br) complexes arecis-planar coordinated. Pd(MRd)₃Br₂ has presumably a square coordination with two MRd molecules and two CI ionscis-coordinated in the equatorial plane, and a MRd molecule and a Cl ion weakly bonded in apical position. The M(MRd)₄(ClO₄)₂ complexes have square planar coordination.Author to whom all correspondence should be addressed.