Insertion of SnCl2 into Pt–Cl bonds: synthesis and characterization of four- and five-coordinate trichlorostannylplatinum(II) complexes

Reaction of platinum(IV) chloride with SnCl₂?·?2H₂O in the presence of [NHR₃]₃Cl (R?=?Me, Et) in 3M hydrochloric acid affords the anionic five-coordinate platinum(II) complexes [NHR₃]₃[Pt(SnCl₃)₅], R?=?Me (1), Et (2), respectively. Moreover, platinum(IV) chloride reacts with SnCl₂?·?2H₂O in the presence of bis(triphenylphosphoranylidene)ammonium chloride in acetone/dichloromethane to form [N(PPh₃)₂]₃[Pt(SnCl₃)₅] (3). In contrast, reaction of an acetone solution of platinum(IV) chloride with SnCl₂?·?2H₂O in the presence of bis(triphenylphosphoranylidene) ammonium chloride resulted in the formation of cis-[N(PPh₃)₂]₂[PtCl₂(SnCl₃)₂] (4). The same products are obtained by using a platinum(II) salt as starting material. Similarly, cis and trans- dichlorobis(diethyl sulfide)platinum(II) reacts with SnCl₂?·?2H₂O in 5M hydrochloric acid to give [PtCl(SEt₂)₃]₃[Pt(SnCl₃)₅] (5) by facile insertion of SnCl₂ into the Pt–Cl bond. However, treatment of an acetone solution of cis- and trans-[PtCl₂(SEt₂)₂] with SnCl₂?·?2H₂O in the presence of a small amount of HCl resulted in the formation of 5, which dissociates in solution to give [PtCl₂(SEt₂)₂]. The complexes have been fully characterized by elemental analysis and multinuclear NMR (¹H,?¹³C,?¹⁹⁵Pt,?¹¹⁹Sn) spectroscopy. A structure determination of crystals grown from a solution of 2 by X-ray diffraction methods shows that platinum adopts a regular trigonal bipyramidal geometry.     

Synthesis and spectral studies of new N2S2 and N2O2 Mannich base ligands and their metal complexes

New Mannich bases bis(thiosemicarbazide methyl) phosphinic acid H₃L¹ and bis(1-phenylsemicarbazide methyl) phosphinic acid H₃L² were synthesized from condensation of phosphinic acid and formaldehyde with thiosemicarbazide and 1-phenylsemicarbazide, respectively. Monomeric complexes of these ligands, of general formula K₂[Cr^III(L ⁿ )Cl₂], K₃[Fe^II(L¹)Cl₂], K₃[Mn^II(L²)Cl₂], and K[M(L ⁿ )] (M = Co(II), Ni(II), Cu(II), Zn(II) or Cd(II); n = 1, 2) are reported. The mode of bonding and overall geometry of the complexes were determined through IR, UV-Vis, NMR, and mass spectral studies, magnetic moment measurements, elemental analysis, metal content, and conductance. These studies revealed octahedral geometries for the Cr(III), Mn(II), and Fe(II) complexes, square planar for Co(II), Ni(II), and Cu(II) complexes and tetrahedral for the Zn(II) and Cd(II) complexes. Complex formation via molar ratio in DMF solution has been investigated and results were consistent to those found in the solid complexes with a ratio of (M : L) as (1 : 1).     

]Preparation and x-ray crystal structure of biss(diphenylphosphino)methanido platinum(II), [Pt(Ph2PCHPPh2)2]

[Pt(Ph₂PCHPPh₂)₂], the first homoleptic complex containing the chelated bis(diphenylphosphino)methanide ligand, has been synthesised by reaction of K₂[PtCl₄] and Ph₂PCH₂PPh₂ with KOH in ethanol, and characterised by ¹H and ³¹P NMR spectroscopy and X-ray crystallography.     

The reactions of tetrakis(triphenylphosphine)platinum and -palladium with selenium: X-Ray crystal structure of [Pt(Se2CH2)(PPh3)2]

Treatment of tetrakis(triphenylphosphine)platinum with elemental selenium (red or vitreous) in toluene solution under reflux yields an insoluble solid. This dissolves in dichloromethane with reaction, eventually to form a 1 : 1 mixture of [PtCl₂(PPh₃)₂] and the new compound [Pt(Se₂CH₂)(PPh₃)₂], which has been characterized by multinuclear NMR spectroscopy and X-ray crystallography. Under the same conditions, tetrakis(triphenylphosphine)-palladium yields only decomposition products. © John Wiley & Sons, Inc.     

A novel PtII–dibenzo‐18‐crown‐6 (DB18C6) complex

The novel Pt^II–dibenzo‐18‐crown‐6 (DB18C6) title complex, μ‐[tetrakis­(thio­cyanato‐S)­platinum(II)]‐N:N′‐bis{[2,5,8,­15,18,21‐hexa­oxa­tri­cyclo­[20.4.0.1^9,14]­hexa­cosa‐1(22),9(14),10,12,23,25‐hexaene‐κ⁶O]­potassium(I)}, [K(C₂₀H₂₄O₆)]₂[Pt(SCN)₄], has been isolated and characterized by X‐ray diffraction analysis. The structure analysis shows that the complex displays a quasi‐one‐dimensional infinite chain of two [K(DB18C6)]⁺ complex cations and a [Pt(SCN)₄]^2? anion, bridged by K⁺?π interactions between adjacent [K(DB18C6)]⁺ units.     

Ring opening in epichlorohydrin and β-methylepichlorohydrin under the action of the [PtCl4]2– anion in aqueous solutions

Oxidative addition of epoxides to [PtCl₄]^2– in aqueous acids affords the platinum(iv) derivatives [PtCl₅(CH₂CR(OH)CH₂Cl)]^2– (R = H (1) and Me (2)). Complex 1 was isolated as a cesium salt and characterized by IR spectroscopy. The complex is stable in acidic media; under basic conditions, the original epoxide and platinum(ii) are recovered. The formation of complex 2 was detected by ¹H NMR spectroscopy.     

Partial molar compressibilities of halogeno complexes of platinum and palladium in aqueous solutions at 25°C

Ultrasonic propagation velocities were measured at 25°C for dilute aqueous solutions of K₂[PtX₄], K₂[PtX₆], K₂[PdX₄], and K₂[PdX₆] (X = Cl, Br, or SCN). The data obtained were combined with our previous density data to calculate the adiabatic compressibilities of each solution. Then, the infinite dilution values of partial molar adiabatic compressibilitiesK _o ^s were evaluated. By subtraction of theK _o ^s (K⁺) from those of the complexes, the values ofK _o ^s for the halogeno complex ions [PtX₄]^2-, [PtX₆]^2-, [PdX₄]^2- and [PdX₆]^2- were determined. The values for the thiocyano complex ions [Pt(SCN)₄]^2- and [Pt(SCN)₆]^2- are positive, showing that the interaction of the ligand SCN^- with the solvent water is very weak. Although the V ₂ ^o behavior of the complex ions [PtCl₆]^2- and [PdCl₆]^2- differed only slightly, compressibility measurement has indicated that the ion [PdCl₆]_2- interacts more strongly than [PtCl₆]^2-.     

Solution Behaviour and Biomolecular Interactions of Two Cytotoxic trans‐Platinum(II) Complexes Bearing Aliphatic Amine Ligands

A novel trans‐platinum(II) complex bearing one dimethylamine (dma) and one methylamine (ma) ligand, namely trans‐[PtCl₂(dma)(ma)], recently synthesised and characterised in our laboratory, displayed relevant antiproliferative properties in vitro, being more active than the parent complex, trans‐[PtCl₂(dma)(ipa)], which has isopropylamine (ipa) in place of methylamine. We have analysed comparatively the solution behaviour of these two complexes under various experimental conditions, and investigated their reactivity with horse heart cytochrome c by mass spectrometry, inductively coupled plasma–optical emission spectroscopy (ICP‐OES), 2D [¹H,¹⁵N],[¹H,¹³C] HSQC and [¹H,¹H] NOESY NMR. Some important changes that occurred in the [¹H,¹³C] HSQC NMR spectrum of cytochrome c treated with trans‐[PtCl₂(dma)(ma)] in water, after two days’ incubation, most probably arose from direct platinum coordination to the protein side chain; this was proved conclusively by [¹H,¹H] NOESY NMR and [¹H,¹⁵N] HSQC NMR measurements. Met65 was identified as the primary Pt binding site on cytochrome c. Electrospray mass spectrometry (ESIMS) results provided evidence for extensive platinum–protein adduct formation. A fragment of the [Pt(amine)(amine′)] type was established to be primarily responsible for protein metalation. ICP‐OES analysis revealed that these trans‐platinum(II) complexes bind preferentially to the serum proteins albumin and transferrin rather than to calf thymus DNA. Pt binding to DNA was found to be far lower than in the case of cisplatin. The implications of the results for the mechanism of action of novel cytotoxic trans‐platinum complexes are discussed.     

Platinum and Palladium Complexes Bearing New (1R,2R)‐(–)‐1,2‐Diaminocyclohexane (DACH)‐Based Nitrogen Ligands: Evaluation of the Complexes Against L1210 Leukemia

The reaction of (1R,2R)‐(–)‐1,2‐diaminocyclohexane ( 1 ) [DACH] with the aldehyde (1R)‐(–)‐myrtenal ( 2 ) in MeOH afforded the bidentate diimine ligand, (1R,2R)‐(–)‐N¹,N²‐bis{(1R)‐(–)myrtenylidene}‐1,2‐diaminocyclohexane ( 3 ) in a high yield. Reduction of 3 using LiAlH₄ led to the formation of the desired ligand ( 4 ) (1R,2R)‐(–)‐N¹,N²‐bis{(1R)‐(–)myrtenyl}‐1,2‐diaminocyclohexane. Treatment of compound 4 with K₂PtCl₄ or K₂PdCl₄ yielded the corresponding platinum(II) and palladium(II) complexes, Pt‐5 and Pd‐6 , respectively. The reaction of compound 3 with K₂PtCl₄ gave the diimine complex Pt‐7 . The cytotoxic activity of the complexes Pt‐5 , Pd‐6 and Pt‐7 was tested and compared to the approved drugs, cisplatin ( Cis ‐Pt ) and oxaliplatin ( Ox‐Pt ). The complexes ( Pt‐5 , Pd‐6 and Pt‐7 ) inhibit L1210 cell line proliferation with an IC₅₀ of 0.6, 4.2, and 0.7 μL, respectively as evidenced by measuring thymidine incorporation.     

Catalytic olefin hydrogenation by platinum(II)/tin(II) systems supported on phosphinated polystyrenes: a solid-state phosphorus-31 NMR study

Polymer-supported platinum(II) phosphine complexes have been prepared by the reaction of phosphinated polystyrenes with [PtCl₂(NCPh)₂] and by the direct terpolymerization of styrene, divinylbenzenes, and cis-[PtCl₂L₂] (L = p-styryldiphenylphosphine). The polymer-supported complexes have been fully characterized by solid-state phosphorus-31 NMR spectroscopy employing cross-polarization, magic angle spinning, and high power proton decoupling techniques and by elemental analysis. Samples of these polymer-supported complexes containing 10, 15, and 30% cross-linking have been employed in the tin(II) chloride co-catalyzed hydrogenation of styrene, using either methylene chloride or acetone as the reaction medium. Following catalysis, the polymer-supported complexes were examined by soild-state phosphorus-31 NMR spectroscopy to determine structural changes. Comparison with spectroscopic data obtained for analogous homogeneous systems allow insight into the catalytic chemistry.     

Synthesis and Molecular Structure of [n‐Bu2(F)SnOSn(F)t‐Bu2]2 — an Unsymmetrically Substituted Tetraorganodistannoxane

The dimeric tetraorganodistannoxane [n‐Bu₂(F)SnOSn(F)t‐Bu₂]₂ ( 1 ) was prepared by the reaction of (t‐Bu₂SnO)₃ with n‐Bu₂SnF₂ and characterized in solution by multinuclear NMR spectroscopy and ESI MS spectrometry and in the solid state by ¹¹⁹Sn MAS NMR spectroscopy and single crystal X‐ray diffraction.     

Reactions of Bis(chloromethyl)phosphinic(-Phosphinothioic) Chlorides with Silylated Carbamates and Trimethylsilyl N-Trimethylsilylacetimidoate

Bis(chloromethyl)phosphinic chloride reacts with trimethylsilyl methylcarbamate in benzene in the presence of a base to give trimethylsilyl bis(chloromethyl)phosphinate. The same reaction performed without a solvent and in the absence of a base yields trimethylsilyl bis(chloromethyl)phosphinate and bis(chloromethyl)phosphinic anhydride. Reaction of bis(chloromethyl)phosphinic chloride with trimethylsilyl diethylcarbamate yields N,N-diethylbis(chloromethyl)phosphinic amide. The reaction of bis(chloromethyl)phosphinic (-phosphinothioic) chlorides with trimethylsilyl N-trimethylsilylacetimidoate was studied.     

The preparation and electrochemistry of gold(III), palladium(II) and platinum(II) complexes with 2-(diphenylphosphino)thiobenzene: X-ray crystal structure of [Au(Ph2PC6H4S)(Ph2][BPh4]

Summary Tetrachloroaurate(III) reacts with two equivalents of the bidentate (1-) mixed phosphinothiol ligand 2-(diphenylphosphino)benzenethiol (DPPBTH) in mildly alkaline MeOH to give a cation that can be precipitated from solution as the tetraphenylborate salt, the title complex [Au(DPPBT)₂][BPh₄] (1). The X-ray crystal structure of the complex shows it has a square planar geometry. K₂[PtCl₄] or PtCl₄ react with DPPBTH in mildly alkaline MeOH to give the 16 electron platinum(II) complex [Pt(DPPBT)₂] (2), whilst reaction of Na₂[PdCl₄] with DPPBTH under similar conditions gives the 16 electron palladium complex [Pd(DPPBT)₂] (3). The complexes have been studied by u.v., i.r. and n.m.r. The electrochemical behaviour of complex (1) was also investigated. Bis-[2-(diphenylphosphino)benzenethiolato]aurate(III).     

Nucleophilic addition of bifunctional sulfimidosulfides to platinum(<Emphasis Type="SmallCaps">IV</Emphasis>)-coordinated nitriles

Reactions of the platinum(IV) nitrile complexes [PtCl₄(RCN)₂] (R = Me, CH₂Ph, Ph) with 1,2- and 1,4-PhS(=NH)C₆H₄SPh in CH₂Cl₂ afforded addition products of sulfimides and coordinated nitriles, viz., the [PtCl₄{NH=C(R)N=S(Ph)(C₆H₄SPh)}₂] complexes. The latter were isolated in 75—90% yields and characterized by elemental analysis, positive-ion FAB mass spectrometry, IR spectroscopy, and ¹H and ¹³C¹H NMR spectroscopy. The temperature dependence of the ¹H NMR spectra of the model [PtCl₄{NH=C(R)N=SPh₂}₂] complexes (R = Me, Et) in CD₂Cl₂ studied in a temperature range from +40 to -70 °C demonstrated that E—Z isomerization of the ligands is a dynamic process in a range from +40 to -10 °C. The activation free energy of this process was calculated.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1618–1622, August, 2004.     

Synthesis,characterization, DNA interaction studies and anticancer activity of platinum–clotrimazole complexes

New trans-platinum complexes of clotrimazole (CTZ) have been prepared and characterized. Their interaction with DNA and activity against tumour cell lines were evaluated. [Pt (CTZ)₂I₂] (1) was synthesized by the reaction of K₂PtCl₄, KI and CTZ, and [Pt(CTZ)₂Cl₂] (2) by direct reaction of K₂PtCl₄ with CTZ. These complexes were characterized by a combination of elemental analysis, molar conductivity, UV–Vis, IR, and NMR spectroscopy in one and two dimensions. DNA–platinum complex interactions were studied by spectroscopic, thermal denaturation and viscosity titration measurements. Covalent interaction studies were also performed. From these results we suggest that complexes 1 and 2 interact with the minor groove of DNA. Both complexes showed growth inhibitory effects on four out of the six tumour cells lines with GI₅₀ (50% growth inhibition) values in the 5–25 μM range, but there was no indication of cytotoxicity over the range of concentrations tested.     

Platinum(IV) complexes with N-alkylphenothiazines: synthesis,characterization, and antibacterial activity

Two new platinum(IV) complexes (1, trifluoperazinehydrochloride-aquapentachloridoplatinate(IV) and 2, chlorpromazine-chlorpromazinehydrochloridepentachloridoplatinate(IV)) were synthesized in the reaction of K₂[PtCl₆] with trifluoperazine dihydrochloride (TF·2HCl) or chlorpromazine hydrochloride (CP·HCl). The complexes were characterized by elemental analysis, molar conductivity measurement, and spectral (IR, ¹H, ¹³C, 2D ¹H–¹³C heteronuclear correlation spectra, ¹⁹⁵Pt NMR, and MS) methods. Outer-coordination sphere was proposed for 1; while in 2, the ligand was coordinated to the metal. The complexes exhibit antibacterial effect on strains of Bacillus subtilis, Bacillus cereus, Bacillus pumilus, and methicillin-resistant Staphylococci as Gram-positive bacteria and an Escherichia coli as Gram-negative bacteria, as well as the reference strains.     

Synthesis and structural studies of new Mannich base ligands and their metal complexes

The new Mannich bases bis(1,4-diphenylthiosemicarbazide methyl) phosphinic acid H₃L¹ and bis(1,4-diphenylsemicarbazide methyl) phosphinic acid H₃L² were synthesised from the condensation of phosphinic acid, formaldehyde with 1,4-diphenyl thiosemicarbazide and 1,4-diphenylsemicarbazide, respectively. Monomeric complexes of these ligands, of general formulae K₂[Cr^III(L ⁿ )Cl₂], K₃[Mn^II(L ⁿ )Cl₂] and K[M(L ⁿ )] (M = Co(II), Ni(II), Cu(II), Zn(II) or Hg(II); n = 1, 2), are reported. The mode of bonding and overall geometry of the complexes were determined through physico-chemical and spectroscopic methods. These studies revealed octahedral geometries for the Cr(III), Mn(II) complexes, square planar for Co(II), Ni(II) and Cu(II) complexes and tetrahedral for the Zn(II) and Hg(II) complexes.     

Crystal structure of K[PtCl3(caffeine)] and its interactions with important nitrogen-donor ligands

The crystal structure of K[PtCl₃(caffeine)] was determined. The coordination geometry around platinum is square-planar formed by N9 of the caffeine ligand and three Cl^? ions. The bond lengths and angles of K[PtCl₃(caffeine)] were compared with those reported for [PtCl₃(caffeine)]^? and K[PtCl₃(theobromine)]. At the level of the statistical significance of the data we have compared, no differences in the bond distances and angles for any of these compounds were noticed. Weak interactions between K⁺ and Cl^? are responsible for the formation of 1-D polymeric chains in the crystal structure of the complex. The interactions of K[PtCl₃(caffeine)] with inosine (Ino) and guanosine-5′-monophosphate (5′-GMP) were studied by ¹H NMR spectroscopy at 295 K in D₂O in a molar ratio of 1 : 1. The results indicate formation of the reaction product [PtCl₃(Nu)] (Nu=Ino or 5′-GMP) with the release of caffeine from the coordination sphere of the starting complex. The higher stability of the bond between the Pt(II) ion and Ino or 5′-GMP compared to the stability of the platinum–caffeine bond is confirmed by density functional theory calculations (B3LYP/LANL2DZp) using as models 9-methylhypoxanthine and 9-methylguanine.     

Synthesis and characterizations of N,N′‐bis(diphenylphosphino)‐2‐(aminomethyl)aniline derivatives: application of a palladium(II) complex as pre‐catalyst in Heck and Suzuki cross‐coupling reactions

The reaction of 2‐(aminomethyl)aniline with 2 equivalents of PPh₂Cl in the presence of Et₃N, proceeds in CH₂Cl₂ to give N,N′‐bis(diphenylphosphino)‐2‐(aminomethyl)aniline 1 in good yield. Oxidation of 1 with aqueous H₂O₂, elemental sulfur or gray selenium gave the corresponding oxide, sulfide and selenide dichalcogenides [Ph₂P(E)NHC₆H₄CH₂NHP(E)Ph₂] (E: O, 2a; S, 2b; Se, 2c), respectively. The reaction of [Ph₂PNHC₆H₄CH₂NHPPh₂] with PdCl₂(cod), PtCl₂(cod) and [Cu(MeCN)₄]PF₆ gave the corresponding chelate complexes, PdCl₂1, PtCl₂1 and [Cu(1)₂]PF₆. The new compounds were fully characterized by NMR, IR spectroscopy and elemental analysis. The catalytic activity of the Pd(II) complex was tested in the Suzuki coupling and Heck reactions. The Pd(II) complex catalyzes the Suzuki coupling and Heck reaction, affording biphenyls and stilbenes respectively, in good yields. Copyright © 2009 John Wiley & Sons, Ltd.     

HPLC Method for the Determination of the Purity of K[Pt(NH3)Cl3], a Precursor of the Platinum Complexes with Cytostatic Activity

K[Pt(NH₃)Cl₃], a valuable precursor for the preparation of platinum complexes with cytostatic activity, e.g. satraplatin, picoplatin, LA-12 and cycloplatam, is currently prepared from cis-[Pt(NH₃)₂Cl₂] or K₂[PtCl₄] and these are the usual impurities in the final product. A simple, selective and sensitive HPLC-UV analytical method for the determination of the purity of K[Pt(NH₃)Cl₃] and the quantification of the impurities has been developed and validated. The platinum complexes present in the final product were separated on a strong base ion exchange column by the gradient elution with detection at 213 nm. Intra-assay precisions for the platinum complexes respective to their ions ([PtCl₄]^2?, [Pt(NH₃)Cl₃]^? and cis-[Pt(NH₃)₂Cl₂]) were between 0.1 and 2.0% (relative standard deviation); intermediate precisions were between 1.4 and 2.0% and accuracies were between 98.6 and 101.4%. Limits of detection of [PtCl₄]^2?, [Pt(NH₃)Cl₃]^? and cis-[Pt(NH₃)₂Cl₂] were 6 µg · ml^?1, 13 mg · ml^?1 and 5 µg · ml^?1 respectively, limits of quantification of [PtCl₄]^2?, [Pt(NH₃)Cl₃]^? and cis-[Pt(NH₃)₂Cl₂] were 51 µg · ml^?1, 55 mg · ml^?1 and 20 µg · ml^?1 respectively.