Photolysis and Thermolysis of Platinum(IV) 2,2′‐Bipyridine Complexes Lead to Identical Platinum(II)–DNA Adducts

Two Pt^IV and two Pt^II complexes containing a 2,2′‐bipyridine ligand were treated with a short DNA oligonucleotide under light irradiation at 37 °C or in the dark at 37 and 50 °C. Photolysis and thermolysis of the Pt^IV complexes led to spontaneous reduction of the Pt^IV to the corresponding Pt^II complexes and to binding of Pt^II 2,2′‐bipyridine complexes to N7 of guanine. When the reduction product was [Pt(bpy)Cl₂], formation of bis‐oligonucleotide adducts was observed, whereas [Pt(bpy)(MeNH₂)Cl]⁺ gave monoadducts, with chloride ligands substituted in both cases. Neither in the dark nor under light irradiation was the reductive elimination process of these Pt^IV complexes accompanied by oxidative DNA damage. This work raises the question of the stability of photoactivatable Pt^IV complexes toward moderate heating conditions.     

Extracoordination sensitivity of tetraphenylporphyrin complexes to gaseous ammonia

The sensitivity of metal tetraphenylporphyrin complexes MTPP (M = Pt^II, Pt^IVCl₂, Re^IVO; TPP is tetraphenylporphyrin) to gaseous ammonia was studied. The gas sensitivity of MTPP is due to the heterogeneous catalytic oxidation of ammonia with the dioxygen ligands in the composition of MTPP. The influence of water vapor on the electrophysical properties of the surface layer of the complexes during adsorption of water and its participation in reactions of the coordinated ammonia and dioxygen were found. Empirical equations relating the conductivity of the MTPP surface layer to the content of water vapor and the concentration of gaseous ammonia were found.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2069–2074, October, 2004.     

Cesium dimethyltetrachloroplatinate,a complex of dimethylplatinum(IV). Synthesis and some reductive elimination reactions involving the monomethylplatinum(II) complex as an intermediate

The reduction of Pt(IV) complexes followed by the oxidative addition of dimethyl sulfate to Pt(II) affords Cs₂PtMe₂Cl₄, a complex of dimethylplatinum(IV). On treatment with such nucleophiles as Cl^–, Br^–, I^–, and PtCl₄ ^2– in aqueous solutions at 368 K this complex undergoes reductive elimination to give MeX and Pt^IIMe as a transient species. The latter is further converted to methane upon protolysis, whereas in the presence of an oxidant (Na₂PtCl₆) it gives rise to the Pt^IVMe species. The kinetics of decomposition of Cs₂PtMe₂Cl₄ in aqueous HCl-KCl systems (2M or 3M in Cl^–; [Pt^IVMe₂][Cl^–]) were studied. The reaction takes place as anS _N 2 attack of X^– on the carbon atom of a methyl group located with thetrans position with respect to the aqua-ligand of the [PtMe₂Cl₃(H₂O)]^– complex.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 389–395, February, 1993.     

A one‐dimensional chloride‐bridged PtII/PtIV mixed‐valence complex with a 4‐[(4‐hydroxyphenyl)diazenyl]benzenesulfonate counter‐ion

The title compound, catena‐poly[[[bis(ethylenediamine‐κ²N,N′)platinum(II)]‐ μ‐chlorido‐[bis(ethylenediamine)platinum(IV)]‐μ‐chlorido] tetrakis{4‐[(4‐hydroxyphenyl)diazenyl]benzenesulfonate} dihydrate], {[Pt^IIPt^IVCl₂(C₂H₈N₂)₄](HOC₆H₄N=NC₆H₄SO₃)₄·2H₂O}_n, has a linear chain structure composed of square‐planar [Pt(en)₂]²⁺ (en is ethylenediamine) and elongated octahedral trans‐[PtCl₂(en)₂]²⁺ cations stacked alternately, bridged by Cl atoms, along the b axis. The Pt atoms are located on an inversion centre, while the Cl atoms are disordered over two sites and form a zigzag ...Cl—Pt^IV—Cl...Pt^II... chain, with a Pt^IV—Cl bond length of 2.3140 (14) Å, an interatomic Pt^II...Cl distance of 3.5969 (15) Å and a Pt^IV—Cl...Pt^II angle of 170.66 (6)°. The structural parameter indicating the mixed‐valence state of the Pt atom, expressed by δ = (Pt^IV—Cl)/(Pt^II...Cl), is 0.643.     

Functionalization and H/D exchange of alkanes by the action of platinum complexes: Reactions of intermediate organometallic compounds

The reactivity of organoplatinun intermediates in the catalytic functionalization of alkanes in the RH-Pt^II-Pt^IV-H₂O(D₂O) system is examined. The arguments for the two alternative models for the activation of C-H bonds by Pt^II complexes, namely, oxidative addition and electrophilic substitution, are analyzed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 6, pp. 351–360, November–December, 1995.This work was made possible by the partial support from the International Science Fund (Grant No. U9A000).     

Rate and Equilibrium Data for Substitution Reactions of [Pd( dien)Cl] + with L-Cysteine and Glutathione in Aqueous Solution

The kinetics of the complex formation reactions between monofunctional palladium(II) complex, [Pd(dien)Cl]⁺, where dien is diethylene triamine or 1,5-diamino-3-azapentane, with L-cysteine and glutathione were studied in an aqueous 0.10M perchloric acid medium by using variable stopped-flow spectrophotometry. Second-order rate constants, <$>{k_2}^{298}<$>{k_2}^{298}<>, were (3.89±0.02) 10²M^–1s^–1 for L-cysteine and (1.44±0.01) 10³M^–1s^–1 for glutathione. The negative entropies of activation support a strong contribution from bond formation in the transition state of the process. The hydrolysis of Pd^II complex gave the monohydroxo species, [Pd(dien)(OH)]⁺ and the dimer with a single hydroxo-bridge species, [Pd₂(dien)₂OH]³⁺. L-Cysteine and glutathione ligands form complexes of 1:1 stoichiometry and a dimer with a single ligand bridge. The formation constants of the complexes were determined, and their concentration distribution as a function of pH was evaluated.     

A Simple Route to the Synthesis of Pt Nanobars and the Mechanistic Understanding of Symmetry Reduction

Noble-metal nanocrystals with anisotropic shapes have received increasing interest owing to their unique properties. Here, a facile route to the preparation of Pt nanobars with aspect ratios tunable up to 2.1 was reported by simply reducing a Pt^IV precursor in N,N-dimethylformamide (DMF) at 160 °C in the presence of poly(vinyl pyrrolidone) (PVP). In addition to its commonly observed roles as a solvent and a reductant, DMF could also decompose to generate CO, a capping agent capable of selectively passivating Pt{100} facets to promote the formation of nanobars. The size and aspect ratio of the nanobars could be tuned by varying the amount of Pt^IV precursor involved in the synthesis, as well as the concentration of PVP because of its dual roles as a stabilizer and a co-reductant. Our mechanistic study indicated that the anisotropic growth resulted from both particle coalescence and localized oxidative etching followed by preferential growth.     

Square-Planar Nickel(II) O,O′-Dialkyldithiophosphato Complexes with Triphenylphosphine of the Type [NiX(S2P{OR}2)(PPh3)] (X = Cl,Br, I and NCS)

A series of new [NiX(S₂P{O-c-Hex}₂)(PPh₃)](X = Cl^–, Br^–, I^– and NCS^–)(1)–(4) and [Ni(NCS)(S₂P{OR}₂)(PPh₃)][R =n-Pr (5), i-Pr (6)] complexes has been synthesized and characterized by elemental analyses, f.i.r., i.r., u.v.–vis., ¹H-, ¹³C{¹H}- and ³¹P{¹H}-n.m.r. spectra, magnetochemical and conductivity measurements. A single crystal X-ray analysis of [Ni(NCS)(S₂P{O-n-Pr}₂)(PPh₃)](5) reveals the molecular structure of the complex and confirms a square-planar geometry around the central atom of nickel with the NCS anion coordinated via the nitrogen atom.     

Mechanism for the formation and structure of the iodoplatination product of propargyl acid in the Pt(IV)-I−-H2O system

Propargyl alcohol in aqueous Pt(IV) iodide solutions at 10–15°C gives the product of the addition of Pt^IV and iodide to the triple bond, isolated as Pt^IV(CH=Cl-CH₂OH)₂I₂(CH₃OH). The vinyl ligands in this complex are in cis position. The complex decomposes at 80°C to give E,E-2,5-diiodo-2,4-hexadiene-1,6-diol and PtI₂. The E, E structure of the diene indicates trans addition of Pt^IV and I^– to the alkyne in the iodoplatination steps.L. M. Litvinenko Institute of Physical Organic and Coal Chemistry, National Academy of Sciences of Ukraine, 70 R. Lyuksemburg St., 340114 Donetsk, Ukraine. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 32, No. 4, pp. 234–237, July–August, 1996. Original article submitted October 17, 1995.     

Kinetics of oxidation of hypophosphite ion by platinum(IV) in an alkaline medium

Summary The kinetics of the oxidation of hypophosphite ion by platinum(IV) have been studied spectrophotometrically in alkaline medium at different temperatures. The rate increases as the pH increases and the empirical rate law applicable to the reaction is given by:-d[Pt^IV]/dt = k₃[Pt^IV][H₂PO^2–][OH^–]The rate constant is 2.17×10^–3 (l² mo^–2s^–1) at 40.5°. The energy and entropy of activation for the reaction are 104.2 kJ mol^–1 and 28.5 JK^–1mol^–1 respectively.     

Synthesis and spectroscopic characteristics of σ-vinyl derivatives of platinum(<Emphasis Type="SmallCaps">IV</Emphasis>) chloride complexes

A procedure was developed for the synthesis of previously unknown β-chlorovinyl derivatives of Pt^IV chloride complexes by chloroplatination of terminal alkynes catalyzed by Pt^II chloride complexes. The reaction is highly stereoselective and gives only the products of trans-anti-addition of platinum and chlorine atoms. The regioselectivity of the catalytic reaction formally corresponds to Markovnikov’s rule, e.g., in alkynes containing electron-donating substituents, platinum attacks the terminal carbon atom. The σ-vinyl derivatives of Pt^IV chloride complexes were characterized by IR spectroscopy and ¹H and ¹³C NMR spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2380–2384, October, 2005.     

A Ratiometric Fluorescent Probe for Cisplatin: Investigating the Intracellular Reduction of Platinum(IV) Prodrug Complexes

The Pt^IV prodrug strategy has emerged as an excellent alternative to tackle the problems associated with conventional Pt^II drug therapy. However, there is a lack of tools to study how this new class of Pt^IV drugs are processed at the cellular level. Herein, we report the first ratiometric probe for cisplatin detection and use it to investigate Pt^IV anticancer complexes in biological systems. The probe was able to distinguish between cisplatin and its Pt^IV derivatives, allowing us to probe the intracellular reduction of Pt^IV prodrug complexes. The correlation between the amount of active Pt^II species available after intracellular reduction of Pt^IV complexes and their cytotoxicity and the role glutathione plays in the reduction of Pt^IV complexes were investigated.     

Facile generation of platinum(IV) compounds with mixed labile moieties. Hydrogen peroxide oxidation of platinum(II) to platinum(IV) compounds

Hydrogen peroxide oxidation of platinum(II) compounds containing labile groups such as Cl, OH, and alkene moieties has been carried out and the products characterized. The reactions of [Pt^II (X)₂ (N–N)] (X = Cl, OH, X₂ = isopropylidenemalorate (ipm); N–N 2,2-dimethyl-1,3-propanediamine [(dmpda), N-isopropyl-1,3-propanediamine (ippda)] with hydrogen peroxide in an appropriate solvent at room temperature affords [Pt^IV (OH)(Y)(X)₂(N–N)] (Y = OH, OCH₃). The crystal structures of [Pt^IV(OH)(OCH₃)(Cl)₂(dmpda)]·2H₂O (P-1 bar, a = 6.339(2) Å , b = 9.861(1) Å, c = 11.561(1) Å, a = 92.078(9)°, β = 104.78(1)°, γ=100.54(1)°, V = 684.3(2) ų, Z = 2R = 0.0503) and [Pt^IV(OH)₂(ipm)(ippda)]·3H₂O (C 2/c, a = 27.275(6) Å, b=6.954(2) Å, c = 22.331(4) Å, β = 118.30(2)°, V = 3729(2) ų, Z = 8, R = 0.0345) have been solved and refined. The local geometry around the platinum(IV) atom approximates to a typical octahedral arrangement with two added groups (OH and OCH₃; OH and OH) in a transposition. The platinum(IV) compounds with potential labile moieties may be important intermediate species for further reactions.     

Inorganic and organometallic chemistry of PtIII complexes having a delocalized PtIII—PtIII bond

Amidate-bridged dinuclear Pt^III complexes having a Pt^III—Pt^III bond react with ketones and alkenes. In the reaction with alkenes in water, 1,2-diols are obtained. In the reactions with conjugated dienes, stereospecific 1,4-diols are formed selectively. A kinetic study revealed that at each intermediate step of the reaction with alkenes the electronic state of the Pt—Pt bond changes between Pt^III—Pt^III and Pt^II—Pt^IV and stabilizes the reaction intermediates.     

Hydrogen bonds and protonation of carbonyl-containing polynuclear rhodium complexes

According to IR spectroscopy data, the interaction of bi-, tri-, and tetranuclear cyclopentadienylcarbonyl rhodium complexes with rather weak protic acids (phenols, fluoroalcohols) in low-polarity media results in the formation of hydrogen bonds of the OH...O=C type with bridged carbonyl groups. According to¹H NMR data, protonation of these complexes with strong acids (CF₃COOH and HBF₄) occurs at the the Rh-Rh bond to give the symmetrical bridge.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 386–388, February, 1995.This work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 93-03-0461).     

Observation of the Properties of a Single Unit of a Limited CDW Structure in a PtII/PtIV Host–Guest Binary System Based on a Square‐Shaped Complex

A macrocyclic tetranuclear platinum(II) complex [Pt(en)(4,4′‐bpy)]₄(NO₃)₈ ( 1 ?(NO₃)₈; en=ethylenediamine, 4,4′‐bpy=4,4′‐bipyridine) and a mononuclear platinum(IV) complex [Pt(en)₂Br₂]Br₂ ( 2 ?Br₂) formed two kinds of Pt^II/Pt^IV mixed valence assemblies when reacted: a discrete host–guest complex 1 ? 2 ?Br₁₀ ( 3 ) and an extended 1‐D zigzag sheet 1 ?( 2 )₃?Br₈(NO₃)₆ ( 4 ). Single crystal X‐ray analysis showed that the dimensions of the assemblies could be stoichiometrically controlled. Resonance Raman spectra suggested the presence of an intervalence interaction, which is typically observed for quasi‐1‐D halogen‐bridged M^II/M^IV complexes. The intervalence interaction indicates the presence of an isolated {Pt^II???X? Pt^IV? X???Pt^II} moiety in the structure of 4 . On the basis of electronic spectra and polarized reflectance measurements, we conclude that 4 exhibits intervalence charge transfer (IVCT) bands. A Kramers–Kronig transformation was carried out to obtain an optical conductivity spectrum, and two sub‐bands corresponding to slightly different Pt^II–Pt^IV distances were observed.     

New stereoselective C_{sp^2 } - C_{sp^3 } coupling: Catalytic iodomethylation of acetylene with methyl iodide into E-1-iodopropene

The catalytic addition of methyl iodide to acetylene yielding E-1-iodopropene has been discovered. The reaction competes with the formation of E,E-1,4-diiodobuta-1,3-diene. The key intermediate in these reactions is the methylvinyl derivative of Pt^IV resulting from acetylene iodoplatination by the Pt^IV methyl complex forming in the equilibrium process. The \(C_{sp^2 } - C_{sp^3 }\) coupling product in the reductive elimination of the ligands is E-1-iodopropene. E,E-1,4-diiodobuta-1,3-diene is the product of the iodoplatination of the second acetylene molecule by this intermediate followed by the \(C_{sp^2 } - C_{sp^2 }\) coupling of the vinyl ligands.     

A one‐dimensional iodine‐bridged PtII/PtIV mixed‐valence complex,catena‐poly[[[bis­(ethyl­ene­diamine)­platinum(II)]‐μ‐iodo‐[bis­(ethyl­ene­di­amine)platinum(IV)]‐μ‐iodo] hydrogenphosphate dihydrogenphosphate iodide trihydrate]

The title compound, {[Pt^IIPt^IVI₂(C₂H₈N₂)₄](HPO₄)(H₂PO₄)I·3H₂O}_n, has a chain structure composed of square‐planar [Pt(en)₂]²⁺ and elongated octa­hedral trans‐[PtI₂(en)₂]²⁺ cations (en is ethyl­ene­diamine) stacked alternately along the c axis and bridged by the I atoms; a three‐dimensionally valence‐ordered system exists with respect to the Pt sites. The title compound also has a unique cyclic tetra­mer structure composed of two hydrogenphosphate and two dihydrogenphosphate ions connected by strong hydrogen bonds [O⋯O = 2.522 (10), 2.567 (10) and 2.569 (11) Å]. The Pt and I atoms form a zigzag ⋯I—Pt^IV—I⋯Pt^II⋯ chain, with Pt^IV—I bond distances of 2.6997 (7) and 2.6921 (7) Å, inter­atomic Pt^II⋯I distances of 3.3239 (8) and 3.2902 (7) Å, and Pt^IV—I⋯Pt^II angles of 154.52 (3) and 163.64 (3)°. The structural parameters indicating the mixed‐valence state of platinum, expressed by δ = (Pt^IV—I)/(Pt^II—I), are 0.812 and 0.818 for the two independent I atoms.     

Potentiometric Study of Reactions of Titanium Complexes in Phosphate–Perchlorate Acid Solutions

The potentiometric method is used to measure the equilibrium potential in the Ti(IV)/Ti(III) system and determine that monophosphate Ti(IV) complexes and Ti³⁺hydrated complexes dominate in phosphate–perchlorate acid solutions, 4M(H, Na)ClO₄, at of 5 × 10^–2to 4 × 10^–1M. Equations that describe the total electrode reaction are proposed. Decreasing the concentration of free hydrogen ions from 3 to 0.12 M results in the deprotonation of TiO(H₂PO₄)⁺complexes and the formation of TiO(HPO₄) complexes. Equilibrium constants for reactions of the formation of Ti(IV) monophosphate complexes and the protonation of TiO(HPO₄) complex are calculated.     

Silver(I), palladium(II), platinum(II) and platinum (IV) complexes with isoorotate and 2-thioisoorotate ligands: synthesis,i.r. and n.m.r. spectra,thermal behaviour and antimicrobial activity

Summary From the reaction of isoorotic and 2-thioisoorotic acids with Ag^I, Pd^II, Pt^II and Pt^IV ions, twelve new complexes containing the uracil ligand in either monoor dianionic forms have been isolated and studied by conductivity measurements, i.r. and n.m.r. spectroscopies, and by thermal methods (t.g. and d.s.c.). From the data obtained, tentative molecular structures are suggested for each complex. The most common coordination mode of both acids involves formation of a six-membered chelate ring through the exocyclic O(4) atom and an oxygen of the carboxylate group. The antimicrobial activity of these compounds against several bacteria and yeast has also been assayed. It is noticeable that PdCl(H₂CU)py complex is active againstPseudomonas sp. andMicrococcus sp. at MIC values lower than 50 g cm^–3.