Experimental and quantum chemical studies of structure and vibrational spectra of platinum(II) and palladium(II) thiourea chlorides

Equilibrium geometries of platinum(II) and palladium(II) tetrathiourea dichlorides have been determined by the X-Ray diffraction studies as well as calculated by the Density Functional Theory using the MPW1PW/LanL2DZ functional/basis set. Infrared spectra of the species have also been studied in the 4000–400 cm⁻¹ frequency range both experimentally and theoretically. The experimental and theoretical data remain in satisfactory agreement.     

Electronic structure and vibrational spectra of cis-diammine(orotato)platinum(II), a potential cisplatin analogue: DFT and experimental study

Orotic acid (vitamin B₁₃) is a key intermediate in biosynthesis of the pyrimidine nucleotides in living organisms, moreover, it may serve as the biological carrier for some metal ions. cis-Diammine(orotato)platinum(II), cis-[Pt(C₅H₂N₂O₄)(NH₃)₂] can be considered as a new potential cisplatin analogue. The FT-Raman and FT-IR spectra of the title complex are reported, for the first time. The molecular structure, vibrational frequencies, and the theoretical infrared and Raman intensities have been calculated by the density functional mPW1PW91 method. The detailed vibrational assignment has been made on the basis of the calculated potential energy distribution. The theoretically predicted IR and Raman spectra show very good agreement with experiment. Natural bond orbital (NBO) analyses were performed for cisplatin, carboplatin and the title complex. The results provided new data on the nature of platinum–ligand bonding in these compounds. Strong intramolecular hydrogen bond between the orotate ligand and the coordinated ammonia group stabilizes the structure of the platinum(II) complex. Thus, it is suggested that the orotate ligand in the title complex is more inert to the substitution reactions than the chloride ligands in cisplatin.     

Synthesis and vibrational study of platinum(II) and palladium(II) complexes of glyoxilic acid oxime

New platinum(II) and palladium(II) complexes of glyoxilic acid oxime (gao) have been prepared and characterised by infrared (4000–150 cm⁻¹) and Raman (4000–200 cm⁻¹) spectra. The gao acts as bidentate ligand bonding through the oxime nitrogen and carboxyl oxygen atoms to form neutral bis-chelate square-planar complexes. The lowest energy conformer of the gao ligand (ectt) was selected among 16 theoretically possible conformers on the basis of ab initio calculations at HF/3-21G*, HF/6-31G* and HF/6-311** levels of the theory from which structural parameters and conformational stabilities have been obtained. A complete vibrational assignment of the gao was performed for the lowest energy ectt conformer on the basis of ab initio optimised parameters and normal coordinate analysis calculations (PED). NCA calculations of the complexes studied were also performed.     

Theoretical studies on vibrational spectra of mixed cyanide-halide complexes of platinum(IV) and palladium(IV)

The vibrational spectra of mixed cyanide-halide complexes, M(CN)4X 2 2- and M(CN)5X2- (M=Pt and Pd; X=F, Cl, Br and I), have been systematically investigated by ab initio RHF, B3LYP and MP2 methods with LanL2DZ and SDD basis sets. The calculated vibrational frequencies of platinum complexes are evaluated via comparison with the experimental values. In the infrared frequency region, the C--N stretching vibrational frequencies calculated at B3LYP level with two basis sets are in good agreement with the observed values with deviations, -16-4 cm(-1) for Pt(CN)4X 2 2- and -18 to -2 cm(-1) for Pt(CN)5X2-. However, in far-infrared region, the results obtained at RHF level are better than those calculated at B3LYP and MP2 levels. For RHF/SDD method, the deviations for Ptz.sbnd;X and Ptz.sbnd;C stretching vibrational frequencies are -14-1 and -12 to -2 cm(-1) in the complex Pt(CN)4X2 2-, -19 to -11 and -15-14 cm(-1) in the Pt(CN)5X2- complex, respectively. The vibrational frequencies of palladium(IV) and some platinum(IV) complexes that have not been experimentally reported are predicted.     

Voltammetric behaviour of cis-diarylbis(triethylphosphine)platinum(II) complexes

The voltammetric behaviour of cis-[Pt(PEt₃)₂(YC₆H₄)₂] complexes in acetonitrile has been investigated by cyclic voltammetry and controlled potential coulometry. The oxidation potential increases linearly with increasing electron-withdrawing ability of the Y substituent in the platinum-bonded aryl ligand. The data are related to studies of electrophilic Pt—C bond cleavage.     

cis,cis,cis,cis-1,2,3,4,5-Pentakis(hydroxymethyl)cyclopentane

All-cis pentamethanolcyclopentane has been obtained in six steps by Diels–Alder condensation of maleic anhydride with (benzyloxymethyl)cyclopenta-2,4-diene, reduction of the anhydride to a diol that was protected as the acetonide. Then, ozonolysis of the double bond, followed by reduction led to a cis-diol. Then successive deprotections of the three other methanol groups gave the cis,cis,cis,cis-1,2,3,4,5-pentakis(hydroxymethyl)cyclopentane.     

N-aminorhodamne complexes of palladium(II), palladium(IV) and platinum(II)

Summary TheN-aminorhodanine (L) complexes: PdLX, (X = Br or I), ML_1.5Cl₂ (M = Pd or Pt), PtL₂X₂ (X = Br, I or ClO₄), PdL₃(ClO₄)₂, PdL_1.5Cl₄ and PdL₃(ClO₄)₄ have been prepared and investigated. The ligand is bonded to the metal ion through the aminic nitrogen atom as monodentate or through this atom and the thiocarbonylic sulphur atom when it acts as chelating or bridging ligand. The carbonylic oxygen atom is never coordinated.     

Ab initio study on far-infrared spectra of dihalodiammine complexes of palladium(II) and platinum(II).

The far-infrared spectra of dihalodiammine complexes of Pd(II) and Pt(II) are calculated using ab initio method at RHF/LANL2DZ level. The calculated vibrational frequencies are in good agreement with the experimental ones except for M-N stretching frequencies in cis-M(NH3)2X2 complexes, and the reason for the deviation is discussed.     

Carbamoyl and alkoxycarbonyl complexes of palladium(II) and platinum(II)

Carbamoyl and alkoxycarbonyl complexes of palladium(II) and platinum(II) of the type M(pnp)(CONHR)Cl (pnp = 2,6-bis(diphenylphosphinomethyl)pyridine; M Pd, R  C₆H₅, p-CH₃C₆H₄, p-CH₃OC₆H₄, C₆H₁₁, t-Bu; M  Pt, R  C₆H₅), Pd(pnp)[CON(Pr)₂]Cl (Pr = propyl), M(pnp)(COOR)Cl (M  Pd, R  C₆H₅, CH₃; M  Pt, R  CH₃), Pd(pnp)(COOCH₃)₂ result from reaction of M(pnp)Cl₂ with carbon monoxide and amines or alkoxides at room temperature and atmospheric pressure.The carbamoyl complexes react with bases to give urethane or diphenylurea depending upon the experimental conditions.     

Some palladium(II) and platinum(II) lead bonded complexes

Complexes of the type M(PPh₃)₂(PbPh₃)₂ [M = Pd, (Ia) and Pt, (Ib)] have been prepared by oxidative addition of hexaphenyldilead to M(PPh₃)₄. The compound Pt(PPh₃)₂(PbPh₃)₂, (Ib), slowly decomposes in dichloromethane to give cis-Pt(PPh₃)₂(PbPh₃)Ph, (II). which can also be obtained by treating (Ib) with the stoichiometric amount of LiPh. Reaction of Pt(PPh₃)₄ with hexamethyldidead gives the complex Pt(PPh₃)₂(PbMe₃)Me directly.The MPb bonds are easily cleaved by bromine, iodine and hydrogen bromide. The X-ray structure of (II) has been determined using three-dimensional counter data and refined by the least-square method (R = 0.07). The crystals are monoclinic a = 22.501, b = 10.502, c = 24.120 Å, β = 113.43°, space group P2₁/c with Z = 4. The complex exhibits a cis configuration, with the coordination around the platinum atom essentially square-planar: the PtPb and PtC(phenyl)bond lengths are 2.698(1) and 2.055(3)Å, respectively.     

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.     

The chemistry of binuclear palladium(II) and platinum(II) complexes

The chemistry of binuclear palladium(II) and platinum(II) complexes has been reviewed. This review deals with complexes derived from various classes of ligands and covers various aspects, viz. synthesis, spectroscopic and structural features and chemical reactivity, of these complexes. Applications of these complexes are briefly described in the respected sections.     

Complexes of substituted dipyridylpyridazines with palladium(II) and platinum(II)

Reactions of 3,6-bis(2′-pyridyl)pyridazine derivatives (n-dppn)¶ ¶For the n-dppn ligands, n stands for the size of the cyclic aliphatic ring on positions 4 and 5 of the pyridazine ring, n?=?5, 6, 8, and 12. with MX₂(PhCN)₂ (M?=?Pd, Pt; X?=?Cl,?Br) have been investigated. The new complexes cis-[PdCl₂(n-dppn)] (n?=?5,?6,?8,?12), cis-[PtCl₂(n-dppn)]?·?H₂O (n?=?5,?6), cis-[PtCl₂(8-dppn)] and cis-[PtBr₂(5-dppn)] have been characterized by elemental analyses, conductivity measurements, infrared, electronic and ¹H-NMR spectra.     

Microwave spectra of cis and trans 2-furylisocyanate conformers

The microwave spectrum of 2-furylisocyanate has been obtained in the frequency region from 8 to 40 GHz. This spectrum is attributed to the ground state of the cis and trans configurations. The rotational constants for both ground vibrational states have been determined. Two sets of vibrational satellites are observed and assigned to the modes of C-N torsion and CNC bending. The microwave results show and MINDO/3 calculations confirm that the barrier between the cis and trans conformers is high and that the cis conformer is more stable than the trans by 3 kcal mol^?1.     

Reactivity of cis dichlorodiammineplatinum(II) (cisplatin) toward selected nucleophiles

Results are reported for the reaction of cis-dichlorodiammineplatinum(II) (“cisplatin”) with various nucleophiles in aqueous solution at constant ionic strength (μ = 0.5) and 30°C. The reactivity is described in terms of linear free energy relationships between the logarithm of the second order rate constants and two established indices of nucleophilicity, i.e. electrode potentials, E° and nucleophilic reactivity constants, n_Pt^o (based on reactivity of trans-[Pt(PY)₂Cl₂] in methanol). New nucleophilic reactivity constants, (n_Pt^o)′are reported based on “cisplatin” reactivity in water.     

Synthesis of cis,cis,cis-1-alkylidene-2,3,4,5-tetrakis(diphenylphosphinomethyl)cyclopentanes

A new strategy to prepare tetradentate or pentadentate diphenylphosphine ligands has been explored from Diels-Alder adducts of fulvenes and maleic anhydride. A tetradentate phosphine ligand, bearing a side chain allowing the formation of a bond with polystyrene resin, has been prepared in seven steps from cyclopentadiene. The cis,cis,cis-1-cyclohexylidene-2,3,4,5-tetrakis(diphenylphosphinomethyl)cyclopentane (Cyclo-Tedicyp) in combination with [PdCl(C₃H₅)]₂ led to an efficient catalyst for the Heck, Suzuki and Sonogashira coupling reactions.     

Ab initio and density functional theory studies on vibrational spectra of palladium (II) and platinum (II) complexes of methionine and histidine: effect of theoretical methods and basis sets

The vibrational spectra of methionine and histidine-containing palladium (II) and platinum (II) complexes, cis-M(Met)X2 and cis-M(His)X2 (M = Pd and Pt; X = F, Cl, Br and I; Met = methionine, His = histidine), have been systematically investigated by ab initio Restricted Hartree-Fock (RHF) and density functional B3LYP methods with LanL2DZ and SDD basis sets. The geometries of cis-Pd(Met)Cl2, cis-Pt(Met)Cl2, cis-Pd(His)Cl2 and cis-Pt(His)I2 optimized and vibrational frequencies and IR intensities of cis-M(Met)Cl2 and cis-M(His)Cl2 (M = Pd and Pt) calculated are evaluated via comparison with the experimental values. The vibrational frequencies calculated show that the methods, rather than basis sets, affect the accuracy of the calculation. The best results that can reproduce the experimental ones are obtained at B3LYP level without any scale factor used. The vibrational frequencies of cis-M(Met)X2 and cis-M(His)X2 (M = Pd and Pt; X = F, Br and I) that have not yet been experimentally reported are predicted.