Pt-Cl Bond Research Articles

Crystal Structure of [p-C6H4(CH2ImMe)2][PtCl6

The structure of the title complex consists of a [p-C6H4(CH2ImMe)2]2+ and [PtCl6](2-) pair. The platinum atom is hexacoordinated by six chloride ions in octahedral coordination geometry. The average Pt-Cl bond distance is 2.3199 A. The imidazolium cation and hexachloroplatinate anion are linked via hydrogen bonds, and the crystal packing is governed by the CH...Cl interactions.

Photosensitization of crystalline and amorphous titanium dioxide by platinum(IV) chloride surface complexes.

Anatase, rutile, and amorphous titania powders were surface-modified by grinding with PtCl4 and H2[PtCl6]. Only the anatase modification afforded hybrid photocatalysts capable of degradation of 4-chlorophenol (4-CP) with visible light, with sufficient stability towards decomplexation. Grinding with K2[PtCl4] produced materials of only low photocatalytic activity. Most efficient photocatalysts contained up to 2 wt% of PtIV. At higher surface loading the excess fraction of the complex is desorbed into the aqueous solution. Scavenging experiments with benzoic acid and tetranitromethane revealed that hydroxyl radicals are produced by the primary reduction of oxygen by conduction band electrons generated through electron injection from a postulated surface platinum(III) complex. It is proposed that the latter is formed from a charge-transfer ligand-to-metal (CTLM) excited state through homolysis of the Pt-Cl bond. Accordingly. the primary oxidation of 4-CP may occur by adsorbed chlorine atoms, the intermediary existence of which was demonstrated by scavenging experiments with phenol.

Cis-Dichloro(dimethyl sulfoxide-S)(2-methoxypyridine-N)platinum(II).

The title complex, [PtCl(2)(C(6)H(7)NO)(C(2)H(6)OS)], exhibits square-planar geometry. The plane of the pyridine ring makes a dihedral angle of 67.2 (3) degrees with the square plane of the metal center. The S-O bond is nearly aligned with the adjacent Pt-N bond, leaving the methyl groups of the dimethyl sulfoxide ligand to stagger the Pt-Cl bond.

Structural and reactivity studies on the ternary system guanine/methionine/trans-[PtCl2(NH3)L] (L=NH3, quinoline): implications for the mechanism of action of nonclassical trans-platinum antitumor complexes

The present model study explores the chemistry of methionine complexes and ternary methionine-guanine adducts formed by trans-[PtCl2(NH3)2] (1) and antitumor trans-[PtCl2(NH3)quinoline] (2) using 1D (1H, 195Pt) and 2D NMR spectroscopy. Compound 2 was substitution inert in reactions with N-acetyl-lmethionine [AcMet(H)]. Reactions of trans-[PtCl(NO3)(NH3)quinoline] (5) ("monoactivated" 2) with AcMetH in water and acetone at various stoichiometries point to Pt(II)-S binding that requires prior activation of the Pt-Cl bond by labile oxygen donors. Trans-[PtCl{AcMet(H)-S}(NH3)quinoline](NO3) (6) and trans-[Pt{AcMet(H)-S}2(NH3)quinoline](NO3)2 (7) were isolated from these mixtures. At high [Cl–], AcMet(H) is displaced from 7, giving 6. Frozen stereodynamics in 6 at the thioether-S and slow rotation about the Pt-Nquinoline bond result in four spectroscopically distinguishable diastereomers. 1H NMR spectra of 7 show faster exchange dynamics due to mutual trans-labilization of the sulfur donors. Substitution of chloride in trans-[PtCl(9-EtGua)(NH3)L]NO3 (L=NH3, 3; L=quinoline, 4; 9-EtGua=9-ethylguanine, which mimics the first DNA binding step of 1 and 2) by methionine-sulfur proceeded ca. 2.5 times slower for the quinoline compound. Both reactions, in turn, proved to be ca. 4 times faster than binding of a second nucleobase under analogous conditions. From the resulting mixtures the ternary adducts trans-[Pt(AcMet-S)(9-EtGua-N7)(NH3)L](NO3, Cl) (L=NH3, 8; L=quinoline, 9) were isolated. A species analogous to 9 formed in a rapid reaction between 6 and 5′-guanosine monophosphate (5′-GMP). From NMR data an AMBER-based solution structure of the resulting adduct, trans-[Pt(AcMet-S)(5′-GMP-N7)(NH3)quinoline] (10), was derived. The unusual reactivity along the N7-Pt-S axis in 8–10 resulted in partial release of both 9-EtGua and AcMet at high [Cl–]. Possible consequences of the kinetic and structural effects (e.g., trans effect of sulfur, steric demand of quinoline) observed in these systems with respect to the (trans)formation of potential biological cross-links are discussed.

Ab initio calculations on cis-[ PtCl2(PMe3)2] : Search for a model chemistry for platinum(II) complexes

The capacity of Hartree-Fock (HF), Moller-Plesset second order perturbation (MP2), and density functional (DF) calculations to predict the experimental dipole moment and the metal-ligand bond lengths of a planar platinum(II) complex, cis-[ PtCl2 (PMe3 )2 ] , was investigated. Highly erroneous results were obtained from uncorrelated HF calculations and from MP2 and DF calculations which included the 5s and 5p electrons of platinum in a frozen core or in an effective core potential. DF calculations including these (n-1)s and (n-1)p electrons in the valence space are shown to have the ability to correctly reproduce the platinum-ligand bond lengths and the dipole moment, provided that sufficiently large basis sets including polarization functions are used. MP2 calculations yielded dipole moments comparable to those obtained from DF calculations with the same basis set and reproduced better the difference between the Pt-Cl and Pt-P bond lengths, but required 2-6 times more computer time. The best agreement between calculated and experimental dipole moment and bond length values was obtained with DF calculations using the program ADF, provided that the scalar relativistic terms were included in the hamiltonian. Our results indicate that the mutual influence of the platinum-ligand bonds in trans-position (the so-called trans -influence) involves both electron correlation and relativistic effects.

Crystal structure of platinum(II) chloro(1,1,1-trifluoro-4-imino-2-pentanononate(Hydrate)) [PtCl(ktf)H2O

This paper reports on our study of the mixedligand βiminoketonate complex [PtCl(ktf)H2O] including 1,1,1-trifluoro-4-imino-2-pentanone as a ligand. An X-ray diffraction analysis was performed on a CAD-4 diffractometer (MoKα radiation, ω/2θ scan mode). Crystal data ofPtClF3O2NC5H7: a = 26.264(5), b = 4.750(1), c = 15.955(3) A, β = 108.16(3)°, V = 1891.3A3, space group C2/c, Z = 8, dcalc = 2.82 g/cm3. The Pt atom has a distorted square planar environment. The Pt-Cl, Pt-O(H2O), Pt-N, and Pt-O bonds are 2.29, 2.07, 1.97, and 1.98 A in length, respectively. The chelate angle is 93.7°. The environment of Pt is completed to pyramidal due to interactions with the Cγ atom of the neighboring molecule at a distance of 3.57 A. The compound has a molecular structure. The molecules of the complex are stacked along the Y direction.

Trans-Chloromethylbis(tri-p-tolylarsine)platinum(II)

The title compound, trans-[Pt(Cl)(CH3){As(C6H4CH3)3}2], is one of the few bis tertiary arsine complexes of platinum(II). The complex exhibits a square-planar geometry with the two arsine ligands in a non-linear trans orientation with an As1-Pt-As2 bond angle of 175.66 (4)°. The large trans influence of the methyl substituent is manifested in the long Pt-Cl bond distance of 2.397 (3) Å.

Cis-(R,S)-Bis(benzyl methyl sulfoxide)dichloroplatinum(II)

The coordination around the Pt atom in the title compound [PtCl2(C8H10OS)2] is pyramidally distorted from cis square-planar; two chloride ions form Pt-Cl bonds of 2.310 (3) and 2.307 (3) Å and two benzyl methyl sulfoxide groups form Pt-S bonds of 2.241 (2) and 2.233 (2) Å.

Oxidative Addition of the Dithiobis(formamidinium) Cation to Platinum(II) Chloro Am(m)ine Compounds: Studies on Structure, Spectroscopic Properties, Reactivity, and Cytotoxicity of a New Class of Platinum(IV) Complexes Exhibiting S-Thiourea Coordination.

The oxidative addition of the salt [{SC(NMe(2))(2)}(2)]Cl(2).2H(2)O (1), the disulfide-like dimerized form of 1,1,3,3-tetramethylthiourea (tmtu), to Pt(II) chloro am(m)ine compounds is described. Oxidation of the [PtCl(3)(NH(3))](-) anion with 1 in methanol yields cis-[PtCl(4)(NH(3))L] (2; L = tmtu) as the result of the trans addition of one tmtu and one chloro ligand. The same mode of oxidation is found in reactions of 1 with [PtCl(dien)](+) (dien = diethylenetriamine) and trans-[PtCl(2)(NH(3))(2)]. In these cases, however, the oxidation is followed by (light-independent) cis,trans isomerizations, giving trans,mer-[PtCl(2)(dien)L]Cl(2) (4) and fac-[PtCl(3)(NH(3))(2)L]Cl.0.5MeOH (6), respectively. The single-crystal X-ray structures of 2 and trans,mer-[PtCl(2)(dien)L](BF(4))(2) (4a) have been determined. 2: monoclinic, space group P2(1)/n, a = 6.280(1) Å, b = 13.221(3) Å, c = 16.575(2) Å, beta = 96.45(1) degrees, Z = 4. 4a: monoclinic, space group C2/m, a = 21.093(5) Å, b = 8.9411(9) Å, c = 14.208(2) Å, beta = 124.65(2) degrees, Z = 4. The tmtu ligands are S-bound. In 2 a pronounced trans influence of the S-donor ligand on the Pt-Cl bond (2.370(1) Å) trans to sulfur is observed. The unusual acidity of the Pt(IV) complexes exhibiting tmtu coordination trans to chloride is attributed to hydrolysis of the labilized Pt-Cl(trans) bond, which is supported by ion sensitive electrode measurements. An upfield shift of the (195)Pt resonances is found on changing the ligand combination from NCl(4)S (2) to N(3)Cl(2)S (4). This order correlates with the trans influences of the ligands: tmtu > am(m)ine > chloride. The cytotoxicity of 2 and 6 in L1210 cell lines is reported and discussed in terms of a possible mechanism of action of the compounds invivo. It is suggested that tmtu may act as a lipophilic carrier ligand and therefore enhance the cellular uptake of the new potential Pt(IV) drugs.

Synthesis and X-ray crystal structure of cis-dichloro(cyclopentylamine) (dimethyl sulphoxide)platinum(II)

cis-Dichlorocyclopentylamine(dimethyl sulphoxide)-platinum(II) is obtained, in addition to small quantities of the corresponding trans compound, by reaction of K2PtCl4 with cyclopentylamine in DMSO solution, where it is formed as the thermodynamically favoured isomer. An X-ray crystal structure analysis confirms the cis configuration. Coordination around the metal centre is square planar, and the ligand bond angles at the Pt atom are close to the expected values of 90 and 180°. The DMSO ligand is S-coordinated to Pt. The Pt-Cl bond lengths, 2.299(2) and 2.317(2) A, are normal for structures of this type, as are the Pt-N and Pt-S bond distances, 2.059(5) and 2.191(2) A, respectively.

Dichloro(ethylenediamine)platinum(II)

The crystal structure of a new polymorph of dichloro(1,2-ethanediamine)platinum(II), [PtCl 2 (C 2 H 8 N 2 )], has been determined and is described. Average Pt-N and Pt-Cl bond lengths are 2.032 and 2.318 A, respectively

XAS and XRD Studies on Graphite Intercalation Compounds of H2ptcl6

Abstract Graphite intercalation compounds (GICs) of H2PtCl6 were studied using X-ray diffraction and X-ray absorption (XAS) methods. Particularly, the results will be interpreted in correlation to charge transfer. For the orthogonal in-plane lattice following parameters are found: a = 2024 pm, b = 1353 pm, and γ = 90°. The analysis of the EXAFS at the Pt LIII edge yields a slightly decreased Pt-Cl bond length and additionally coordinated Cl atoms in comparison to the pure compound. This is in agreement with results evaluated from the Cl K edge. A small energy shift of 0.25 eV of the Pt LIII edge to higher energies excludes a charge transfer to Pt in the intercalate.

Characterization and properties of monoammine nitroimidazole complexes of platinum [PtCl2(NH3)(NO2Im)]. Crystal and molecular structure of cis-amminedichloro(1-{(((2-hydroxyethyl)amino)carbonyl)methyl}-2-nitroimidazole)platinum(II)

The characterization of monoammine(nitroimidazole)platinum(II) complexes of structure (PtCl{sub 2}(NH{sub 3})(NO{sub 2}Im)) (NO{sub 2}Im = 1-((((2-hydroxyethyl)amino)carbonyl)methyl)-2-nitroimidazole, Etanidazole (I), 1-(2-nitro-1-imidazolyl)-3-methoxy2-propanol, Misonidazole (II), and 1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole, Metronidazole (III)) is reported. Both is cis and trans isomers may be isolated for II and III. The crystal structure of cis-amminedichloro(1-((((2-hydroxyethyl)amino)carbonyl)methyl)-2-nitroimidazole)platinum(II) has been determined by X-ray diffraction. The crystals are orthorhombic, space group Pnab with cell dimensions a = 14.867 (7) {angstrom}, b = 9.915 (5) {angstrom}, c = 19.015 (9) {angstrom}, and Z = 8. The structure was refined to R = 0.062 and R{sub w} = 0.052. Platinum has the expected square-planar coordination. The Pt-Cl bond trans to the nitroimidazole ligand is shorter (2.269 (3) {angstrom}) than normal. The dihedral angle between the platinum plane and the imidazole ring is 111{degree}, while the nitro group makes an angle of 31{degree} with the imidazole ring plane. Electrochemistry and {sup 195}Pt NMR data are also reported. The relevance of the chemical properties to their biological properties as radiosensitizers and hypoxic cytotoxins is discussed.

Trans-dichlorobis(di-n-propyl sulfoxide)platinum(II).

[PtCl2(C6H14OS)2], Mr = 534.48, monoclinic, P2(1)/c, a = 9.092 (2), b = 5.696 (2), c = 19.749 (7) A, beta = 110.63 (3) degrees, V = 957.2 (6) A3, Z = 2, D chi = 1.854 Mg m-3, lambda(Mo K alpha) = 0.71069 A, mu(Mo K alpha) = 7.894 mm-1, F(000) = 520, room temperature, R = 0.047 for 1842 unique observed reflections. The Pt atom is located on a center of symmetry. Pt has trans square-planar coordination and the sulfoxide ligands are bonded through their S atoms. The Pt-Cl bond distances are 2.292 (3) A. The Pt-S bond lengths [2.292 (2) A] are significantly longer than the corresponding distances in the cis isomer. The packing consists of layers of molecules parallel to the ab plane.

Structure of cis-Pt(asb)2Cl2, a platinum(II) complex with a styrylbenzothiazole ligand.

cis-Bis[2-(2-acetoxystyryl)benzothiazole]dichloroplatinum(II), [PtCl2(C17H13NO2S)2], Mr = 856.7, triclinic, P1, a = 12.145 (6), b = 12.859 (4), c = 11.021 (5) A, alpha = 105.88 (3), beta = 90.64 (4), gamma = 87.64 (4) degrees, V = 1654 (2) A3, Z = 2, D chi = 1.72 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 46.1 cm-1, F(000) = 840, T = 296 K, final R = 0.029 for 6121 unique observed reflections. The [PtCl2(asb)2] complex has square-planar geometry about the Pt, with the asb coordinated to the Pt through the N of the thiazole ring. The average Pt-N and Pt-Cl bond distances are 2.035 (1) and 2.287 (5) A. The ligand is non-planar with an average dihedral angle of 36 (3) degrees between the benzothiazole and the benzene rings. The dihedral angles between the platinum coordination plane and the benzothiazole and benzene rings are 78 (4) and 69 (7) degrees respectively. The acetoxybenzene rings in the two ligands have different orientations with respect to the olefin C atoms.

THE CRYSTAL STRUCTURE OF D,L-PHENYLALANINE ETHYL ESTER CHLOROPLATINITE [C_6H_5CH_2·CH(NH_3)~+CO_2C_2H_5]_2·[PtCl_4

The space group of the crystal of the title compound is P2/a, with unit cell constants a=12.006, b = 8.398, c= 14.261? ,β= 93.98°. the cell contains two formula units of [phCH2CH(NH3)+CO2C2H5]2? [PtCl4]. The structre was determined from 1759 observed reflections and refined by the block-diagonal least-squares method to R = 0.038. The platinum atoms occupy one set of symmetrical center special positions. The [PtCl4]2- ion is coplanar with Pt-Cl bond, the bond lengths are 2.304(3) and 2.294(3)?, The discreate phenylalanine ethyl ester does not coordinate to the platinum atoms. The [PtCl4]2- ion and [phCH2CH(NH3)+CO2C2H5] ions are connected by ionic fores and hydrogen bonds between the nitrogen and chlorine atoms. Therefore this compound is an adduct of phenylalanine ethylester with anion of chloropladnite.

Mean Palladium and Platinum–Halogen Bond Energies in Complexes of the Divalent and Tetravalent Metals

THE approximate calculations of the mean energies of platinum and palladium-halogen bonds, described in this communication were originally required for comparison with other thermodynamic data for these metals, but are also interesting in their own right. First, they demonstrate that, in common with other metal ions, platinum and palladium are only class “b” or “soft acids” in solution and that in the gas phase they exhibit normal class “a” or “hard acid” character, in that they form stronger bonds with chlorine than with bromine. Second, there are many examples where the properties of the octahedral complexes of tetravalent platinum and palladium can be understood by considering the corresponding square-planar complexes of the divalent metal and adding two “inert” ligands, one above and one below the square plane, which barely alter the original metal-ligand bonds1. For example, consider the following points, (i) The covalent radii of the divalent and tetravalent metals are almost equal2,3, (ii) The Pt-Cl bond lengths in K2PtCl4 (ref. 4) and K2PtCl0 (ref. 5) are equal (2.33 A). (iii) The Pt-Cl and Pt-N bonds in the platinum (II) complex, illustration are very similar6, (iv) The infrared spectra of trans-[Pt(SMe2)2X4], where X is a halide ion, can be interpreted as a superposition of the spectra of square planar [PtX4]2− and linear Me2S-Pt-SMe2 units7, (v) The net charges on the metal atoms in K2MCl6 and K2MC14 determined from the chlorine nuclear quadrupole resonance frequencies, assuming in each case that the halide bonding orbitals have 15% s-character, 85% p-character and 0% d-character, are very similar: (Et4N)2PdCl4, Pd + 0.72 (ref. 8); K2PdCl6, Pd + 0.58 (ref. 9); K2PtCl4, Pt + 0.68 (ref. 10); K2PtCl6, Pt + 0.64 (ref. 11). Open image in new window

The cis-effect in trans-[PtCl2XY] compounds

The cis-influence observed in chlorine NQR data of X, Y affecting the Pt-Cl bonds in compounds of type trans-[PtCl2XY] is interpreted. σ-bonding differences in Pt-Cl bonds are suggested to account for the trends in NQR frequencies. Pt-Cl π-bonding is negligibly small for both d π (Pt)−p π (Cl) and p π −p π (Cl) interactions.