Mono- and dinuclear metallacyclic complexes of Pt(II) synthesized from some eugenol derivatives

The complexes K[PtCl₃(Meug)] (1; Meug = methyleugenol), K[PtCl₃(Meteug)] (2; Meteug = methyl eugenoxyacetate), and K[PtCl₃(Eteug)] (3; Eteug = ethyl eugenoxyacetate) reacted with AgNO₃, SnCl₂, KOH, or ethanol–water solutions to lose one aryl proton and form dinuclear metallacyclic complexes Pt₂Cl₂(Meug-1H)₂ (4), Pt₂Cl₂(Meteug-1H)₂ (5), and Pt₂Cl₂(Eteug-1H)₂ (6), respectively. Complexes 4–6 reacted with aliphatic, aromatic, and heterocyclic amines to give various mononuclear metallacyclic platinum complexes 7–15. ¹H NMR spectra showed that in 4–15 Meug, Meteug, and Eteug are bound with Pt(II) both at the benzene carbon and at the ethylenic double bond of the side chain. NOESY spectra and single-crystal X-ray diffraction indicated that in 7–15 the amines are in cis-position with respect to the ethylenic double bond.     

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.     

Kinetics of the substitution reactions of some Pt(II) complexes with 5′‐GMP and L‐histidine

The reactions of platinum(II) complexes, [PtCl₂(dach)] (dach = (1R,2R)‐1,2‐diaminocyclohexane) and [PtCl₂(en)] (en = ethylenediamine) with biologically relevant ligands such as 5′‐GMP (guanosine‐5′‐monophosphate) and l ‐His (l ‐histidine) were studied by UV–vis spectrophotometry, ¹H NMR spectroscopy, and high‐performance liquid chromatography (HPLC). Spectrophotometrically, these reactions were investigated under pseudo‐first‐order conditions at 310 K in 25 mM Hepes buffer (pH 7.2) and 10 mM NaCl to prevent the hydrolysis of the complexes. The [PtCl₂(en)] complex reacts faster than [PtCl₂(dach)] in the reaction with studied nucleophiles. This confirms the fact that the reactivity of studied Pt(II) complexes depends on the structure of the inert bidentate ligand. Also, the substitution reactions with l ‐His are always faster than the reactions with nucleotide 5′‐GMP. The reactions of [PtCl₂(dach)] and [PtCl₂(en)] complexes with l ‐histidine are studied by ¹H NMR spectroscopy. The obtained rate constants are in agreement with those obtained by UV–vis. The same reactions were studied by HPLC comparing the obtained chromatograms during the reaction. The changes in intensity of signals of the free and coordinated ligand show that after a few days there is only one dominant product in the system. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 43: 99–106, 2011     

Trichloro(Dinitrogen)Platinate(II)

Zeise's salt, [PtCl₃(H₂C=CH₂)]⁻_, is the oldest known organometallic complex, featuring ethylene strongly bound to a platinum salt. Many derivatives are known, but none involving dinitrogen, and indeed dinitrogen complexes are unknown for both platinum and palladium. Electrospray ionization mass spectrometry of K₂[PtCl₄] solutions generate strong ions corresponding to [PtCl₃(N₂)]⁻, the identity of which was confirmed through ion-mobility spectrometry and MS/MS experiments that proved it to be distinct from its isobaric counterparts [PtCl₃(C₂H₄)]⁻ and [PtCl₃(CO)]⁻. Computational analysis established a gas-phase platinum–dinitrogen bond strength of 116 kJ mol⁻¹, substantially weaker than the ethylene and carbon monoxide analogues but stronger than for polar solvents such as water, methanol and dimethylformamide, and strong enough that the calculated N−N bond length of 1.119 Å represents weakening to a degree typical of isolated dinitrogen complexes.     

Synthese und Charakterisierung von Aquapentachloroplatinaten(IV) – Struktur von [K(18-Krone-6)][PtCl5(H2O)]

Synthesis and Characterization of Aquapentachloroplatinates(IV) – Structure of [K(18-crown-6)][PtCl₅(H₂O)] The crown ether complex of the aquapentachloroplatinic acid of the composition [H₁₃O₆][PtCl₅(H₄O₂)] · 2(18-cr-6) ( 2 ) reacts with K₂CO₃ and [NⁿBu₄]OH in aqueous solution to give [K(18-cr-6)][PtCl₅(H₂O)] ( 5 a ) and [NⁿBu₄][PtCl₅(H₂O)] · ¹/₂ (18-cr-6) · H₂O ( 5 b ), respectively. Both compounds were characterized by microanalysis, vibrational (IR, Raman) and NMR (¹H, ¹³C, ¹⁹⁵Pt) spectroscopy. The X-ray structure analysis of 5 a (orthorhombic, pnma; a = 16,550(4), b = 18,044(3), c = 7,415(1) Å; Z = 4; R1 = 0,0183; wR2 = 0,0414) reveals that the crystal is threaded by chains built up of [PtCl₅(H₂O)]^? and [K(18-cr-6)]⁺ units. There are tight K …? Cl contacts (d(K? Cl1)) = 3,0881(9) Å and O_W? H? O_cr hydrogen bridges (d(O1 …? O2) = 2,806(3) Å) between these units. The coordination polyhedron [PtCl₅O] has approximately C_4v symmetry.     

Ligand Substitution Reactions on Aquapentachloro‐ and Hexachloroplatinic Acid — Synthesis and Characterization of Tetrachloroplatinum(IV) Complexes with Heterocyclic N,N Donors

Reactions of aquapentachloroplatinic acid, (H₃O)[PtCl₅(H₂O)]·2(18C6)·6H₂O ( 1 ) (18C6 = 18‐crown‐6), and H₂[PtCl₆]·6H₂O ( 2 ) with heterocyclic N, N donors (2, 2′‐bipyridine, bpy; 4, 4′‐di‐tert‐butyl‐2, 2′‐bipyridine, tBu₂bpy; 1, 10‐phenanthroline, phen; 4, 7‐diphenyl‐1, 10‐phenanthroline, Ph₂phen; 2, 2′‐bipyrimidine, bpym) afforded with ligand substitution platinum(IV) complexes [PtCl₄(N∩N)] (N∩N = bpy, 3a ; tBu₂bpy, 3b ; Ph₂phen, 5 ; bpym, 7 ) and/or with protonation of N, N donor yielding (R₂phenH)₂[PtCl₆] (R = H, 4a ; Ph, 4b ) and (bpymH)⁺ ( 8 ). With UV irradiation Ph₂phen and bpym reacted with reduction yielding platinum(II) complexes [PtCl₂(N∩N)] (N∩N = Ph₂phen, 6 ; bpym, 9 ). Identities of all complexes were established by microanalysis as well as by NMR (¹H, ¹³C, ¹⁹⁵Pt) and IR spectroscopic investigations. Molecular structures of [PtCl₄(bpym)]·MeOH ( 7 ) and [PtCl₂(Ph₂phen)] ( 6 ) were determined by X‐ray diffraction analyses. Differences in reactivity of bpy/bpym and phen ligands are discussed in terms of calculated structures of complexes [PtCl₅(N∩N)]^— with monodentately bound N, N ligands (N∩N = bpy, 10a ; phen, 10b ; bpym, 10c ).     

Influence de la nature du solvant sur le comportement photochimique de complexes trans- ET cis-[PtCl2(éthylène)(amine)]

Nature of the solvent plays a major role in the photochemical behaviour of cis- and trans-[PtCl₂(ethylene)(amine)] complexes. Dimeric compounds [Pt₂Cl₄-(amine)₂] are obtained on irradiation of these complexes in chloroform or diethyl ether. A non-stereospecific reaction of photosubstitution is observed in nitrile solvents. When methanol, dimethoxyethane or dimethylformamide are used as solvents, cis and trans complexes have a quite different photochemical behaviour, but in all of the cases, a photodegradation leading to ionic species [PtCl₃(ethylene)]^? H⁺ amine and [PtCl₃(amine)]^? H⁺ amine is the main reaction.     

Synthesis and structure of platinum complexes [Ph4P]+[PtCl3(DMSO)]− and [Ph4P]+[PtCl5(DMSO)]−

The reaction of tetraphenylphosphonium chloride with an equimolar amount of potassium tetrachloroplatinate or hexachloroplatinic acid in dimethyl sulfoxide gave the complexes [Ph₄P]⁺[PtCl₃(DMSO)]^? (I) and [Ph₄P]⁺[PtCl₅(DMSO)]^? (II), respectively. The phosphorus atoms in the cations have tetrahedral environment, the CPC angles and P-C distances 105.63(13)°–112.13(14)°, 1.795(3)–1.797(3) Å I) and 105.7(3)°–112.9(3)°, 1.783(7)–1.791(6) Å II). The platinum coordination polyhedra in the anions [PtCl₃(DMSO)]^? and [PtCl₅(DMSO)]^? are distorted square (Pt-S, 2.1937(8); Pt-Cl, 2.2894(10)–2.3024(10) Å; trans-angles: SPtCl, 177.38(4)°; ClPtCl, 175.40(4)°) and octahedron (Pt-S 2.291(2) Å; Pt-Cl, 2.312(2)–2.334(2) Å, trans-angles: SPtCl, 178.28(9)°; ClPtCl, 178.80(9)° and 178.88(8)°).     

Substitution behavior of square-planar and square-pyramidal Cu(II) complexes with bio-relevant nucleophiles

Substitution reactions of [CuCl₂(en)] and [CuCl₂(terpy)] complexes (where en = 1,2-diaminoethane and terpy = 2,2′:6′,2″-terpyridine) with bio-relevant nucleophiles such as inosine-5′-monophosphate (5′-IMP), guanosine-5′-monophosphate (5′-GMP), L-methionine (L-Met), glutathione (GSH) and DL-aspartic acid (DL-Asp) have been investigated at pH 7.4 in the presence of 0.010 M NaCl. Mechanism of substitution was probed via mole-ratio, kinetic, mass spectroscopic and EPR studies at pH 7.4. In the presence of an excess of chloride, the octahedral complex anion [CuCl₄(en)]^2? is formed rapidly while equilibrium reaction was observed for [CuCl₂(terpy)]. Different order of reactivity of bio-molecules toward Cu(II) complexes was observed. Mass spectrum of [CuCl₂(terpy)] in Hepes buffer has shown two new signals at m/z = 477.150 and m/z = 521.00, assigned to [CuCl(terpy)]⁺-Hepes fragments of coordinated Hepes buffer. These signals also appear in the mass spectra of ligand substitution reactions between [CuCl₂(terpy)] and bio-molecules in molar ratio 1:1 and 1:2. According to EPR data, L-Met forms the most stable complex with [CuCl₂(en)] among the ligands considered, while [CuCl₂(terpy)] complex did not show significant changes in its square-pyramidal geometry in the presence of the buffer or bio-ligands.     

Oxidation of coordinated olefins: the reactions of Cl2 with trichloro(ehtylene)platinate(II)

The oxidation of [PtCl₃(C₂H₄)]- by Cl₂ in aqueous solution, to yield CH₂ClCH₂OH and [PtCl₄]^2-, has been shown to proceed through the following sequence of steps: [PtCl₃(C₂H₄)] Cl₂Cl [PtCl₅(CH₂CH₂Cl)]^2-$\text{H}{}_2\text{O}\text{(HCl)}$ [PtCl₅(CH₂CH₂OH)]^2- → [PtCl₄^2- + CH₂ClCH₂OHEach of the steps and intermediates in this mechanistic sequence has been identified and characterized.     

Tin(II) Halide Insertion or Halogen Exchange in the Reactions of Dihaloplatinum(II) Complexes with Tin(II) Halide

Reactions of SnCl₂ with the complexes cis‐[PtCl₂(P₂)] (P₂=dppf (1,1′‐bis(diphenylphosphino)ferrocene), dppp (1,3‐bis(diphenylphosphino)propane=1,1′‐(propane‐1,3‐diyl)bis[1,1‐diphenylphosphine]), dppb (1,4‐bis(diphenylphosphino)butane=1,1′‐(butane‐1,4‐diyl)bis[1,1‐diphenylphosphine]), and dpppe (1,5‐bis(diphenylphosphino)pentane=1,1′‐(pentane‐1,5‐diyl)bis[1,1‐diphenylphosphine])) resulted in the insertion of SnCl₂ into the Pt? Cl bond to afford the cis‐[PtCl(SnCl₃)(P₂)] complexes. However, the reaction of the complexes cis‐[PtCl₂(P₂)] (P₂=dppf, dppm (bis(diphenylphosphino)methane=1,1′‐methylenebis[1,1‐diphenylphosphine]), dppe (1,2‐bis(diphenylphosphino)ethane=1,1′‐(ethane‐1,2‐diyl)bis[1,1‐diphenylphosphine]), dppp, dppb, and dpppe; P=Ph₃P and (MeO)₃P) with SnX₂ (X=Br or I) resulted in the halogen exchange to yield the complexes [PtX₂(P₂)]. In contrast, treatment of cis‐[PtBr₂(dppm)] with SnBr₂ resulted in the insertion of SnBr₂ into the Pt? Br bond to form cis‐[Pt(SnBr₃)₂(dppm)], and this product was in equilibrium with the starting complex cis‐[PtBr₂(dppm)]. Moreover, the reaction of cis‐[PtCl₂(dppb)] with a mixture SnCl₂/SnI₂ in a 2 : 1 mol ratio resulted in the formation of cis‐[PtI₂(dppb)] as a consequence of the selective halogen‐exchange reaction. ³¹P‐NMR Data for all complexes are reported, and a correlation between the chemical shifts and the coupling constants was established for mono‐ and bis(trichlorostannyl)platinum complexes. The effect of the alkane chain length of the ligand and Sn^II halide is described.     

Interactions of zinc(II) complexes with 5′-GMP and their cytotoxic activity

The mechanism of substitution from tetrahedral [ZnCl₂(en)] and square-pyramidal [ZnCl₂(terpy)] complexes (where en = 1,2-diaminoethane or ethylenediamine and terpy = 2,2′:6′,2′′-terpyridine) by guanosine-5′-monophosphate (5′-GMP) have been investigated by ¹H NMR spectroscopy. The substitution reaction of [ZnCl₂(terpy)] complex is faster than the reaction of [ZnCl₂(en)], which was finished after 48?h. Information about the structures of the final products in solution were obtained from the DFT calculations (B3LYP/6-31G(d)) and experimental ¹H NMR data acquired during the course of the reaction. The cytotoxic activity of zinc(II) complexes was tested on human breast cancer cell line MDA-MB-231, human colon cancer cell line HCT-116 and normal human lung fibroblast cell line MRC-5. Both complexes reduced cell viabilities, while [ZnCl₂(terpy)] was significantly cytotoxic on MDA-MB-231 after 72?h, and HCT-116 after 24?h without dose dependence. The differences in reactivity toward 5′-GMP and cytotoxic activity of Zn(II) complexes may be attributed to the very stable square-pyramidal geometry of [ZnCl₂(terpy)] in solution, while weak ligand effect of the en compared to the terpy affected slow interaction of tetrahedral [ZnCl₂(en)] complex with the target bio-molecule.     

Synthesis and spectral characterization of platinum(II) complexes containing eugenol,a natural allylphenol

For the first time, eugenol, a natural bioactive allylphenol, was introduced into coordination with platinum(II) by replacement of ethylene from Zeise’s salt with eugenol (Eug). The obtained complex, K[PtCl₃(Eug)] (1), was used as the key compound for preparation of the series of trans-[PtCl₂(Eug)(Amine)] (2–11), [PtCl(Eug)(8-O-quinoline)] (12) and [PtCl(Eug)(2-O₂C-quinoline)] (13). The synthesized complexes were characterized by elemental analyses, IR, ¹H NMR, ¹³C NMR, HSQS, HMBC, NOESY, and MS spectra. In 1–13 eugenol coordinates with Pt(II) at ethylenic double bond of the allyl group, the donor N of the amines is in trans-position in comparison with the double bond. A display of the trans-effect on the chemical shift of ¹H and ¹³C was remarked. Seven complexes were tested for cell in vitro cytotoxicity on human cancer cells. Complexes 3 and 12 exhibit high activities on Hep-G2 with IC₅₀ = 3.12 and 5.29 μM; 12 gives high activity against KB, Lu and MCF-7 with IC₅₀ = 0.43, 2.95 and 1.84 μM, respectively. Most of these IC₅₀ are lower than those of cisplatin.     

Cytotoxic properties of platinum(IV) and dinuclear platinum(II) complexes and their ligand substitution reactions with guanosine-5′-monophosphate

The substitution reaction of the Pt(IV) complex [PtCl₄(bipy)] with guanosine-5??-monophosphate (5??-GMP) was studied by UV?CVis spectrophotometry. This reaction was investigated under pseudo-first-order conditions at 37?°C in 25?mM Hepes buffer (pH?=?7.2) in the presence of 10?mM NaCl to prevent the hydrolysis of the complex. The substitution of chlorides in [{trans-Pt(NH₃)₂Cl}₂(??-1,2-bis(4-pyridyl)ethane)](ClO₄)₂ (Pt3) complex by 5??-GMP was followed by ¹H NMR spectroscopy under second-order conditions. Very similar values for the rate constants of both substitution steps were obtained. The Pt(IV) complexes, [PtCl₄(bipy)] and [PtCl₄(dach)], as well as dinuclaer Pt(II) [{trans-Pt(NH₃)₂Cl}₂(??-pyrazine)](ClO₄)₂ (Pt1), [{trans-Pt(NH₃)₂Cl}₂(??-4,4??-bipyridyl)](ClO₄)₂?·?DMF (Pt2) and [{trans-Pt(NH₃)₂Cl}₂(??-1,2-bis(4-pyridyl)ethane)](ClO₄)₂ (Pt3) complexes, displayed potent cytotoxic activity against human ovarium carcinoma cell line TOV21G and lower activity toward human colon carcinoma HCT116 cell line at the same concentrations. Our data indicate that these platinum complexes could be explored further, as potential therapeutic agents for ovarian cancer.     

Indium(III) complexes containing bithiazole derivatives,chloride, methanol,and dimethyl sulfoxide: X‐ray studies,spectroscopic characterization,and thermal analyses

[In(dm4bt)Cl₃(MeOH)]?·?0.5dm4bt (1) (dm4bt is 2,2′‐dimethyl‐4,4′‐bithiazole) and [In(4bt)Cl₃(MeOH)] (2) (4bt is 4,4′‐bithiazole) were prepared from the reaction of 4,4′‐bithiazole and 2,2′‐dimethyl‐4,4′‐bithiazole with InCl₃?·?4H₂O in methanol, respectively. [In(4bt)Cl₃(DMSO)] (3) was also prepared from recrystallization of 2 in DMSO. These complexes were characterized by IR, UV‐Vis, ¹H NMR, ¹³C{¹H} NMR, and luminescence spectroscopy and their structures were studied by single‐crystal X‐ray crystallography. The thermal stabilities of 1 and 3 were studied by thermogravimetric and differential thermal analyses.     

Kinetics and mechanism of oxidation of the binary and ternary complexes of chromium(III) involving inosine and glycine by N -bromosuccinimide

The kinetics of oxidation of the chromium(III) complexes, [Cr(Ino)(H₂O)₅]³⁺ and [Cr(Ino)(Gly)(H₂O)₃]²⁺ (Ino?=?Inosine and Gly?=?Glycine) involving a ligands of biological significance by N-bromosuccinimide (NBS) in aqueous solution to chromium(VI) have been studied spectrophotometrically over the 25–45°C range. The reaction is first order with respect to both [NBS] and [Cr], and increases with pH over the 6.64–7.73 range in both cases. The experimental rate law is consistent with a mechanism in which the hydroxy complexes [Cr(Ino)(H₂O)₄(OH)]²⁺ and [Cr(Ino)(Gly)(H₂O)₂(OH)]⁺ are significantly more reactive than their conjugate acids. The value of the intramolecular electron transfer rate constant, k ₁, for the oxidation of the [Cr(Ino)(H₂O)₅]³⁺ (6.90?×?10^?4?s^?1) is lower than the value of k ₂ (9.66?×?10^?2?s^?1) for the oxidation of [Cr(Ino)(Gly)(H₂O)₂]²⁺ at 35°C and I?=?0.2?mol?dm^?3. The activation parameters have been calculated. Electron transfer apparently takes place via an inner-sphere mechanism.     

Reactions of platinum complexes with 4,7-phenanthroline: crystal structures of mono- and binuclear platinum(II) complexes containing 4,7-phenanthroline

The reaction of a mixture of cis and trans-[PtCl₂(SMe₂)₂] with 4,7-phen (4,7-phen = 4,7-phenanthroline) in a molar ratio of 1 : 1 or 2 : 1 resulted in the formation of mono and binuclear complexes trans-[PtCl₂(SMe₂)(4,7-phen)] (1) and trans-[Pt₂Cl₄(SMe₂)₂(μ-4,7-phen)] (2), respectively. The products have been fully characterized by elemental analysis, ¹H, ¹³C{¹H}, HHCOSY, HSQC, HMBC, and DEPT-135 NMR spectroscopy. The crystal structure of 1 reveals that platinum has a slightly distorted square planar geometry. Both chlorides are trans with a deviation from linearity 177.66(3)°, while the N–Pt–S angle is 175.53(6)°. Similarly, the reaction of a mixture of cis and trans-[PtBr₂(SMe₂)₂] with 4,7-phen in a 1 : 1 or 2 : 1 mole ratio afforded the mono or binuclear complexes trans-[PtBr₂(SMe₂)(4,7-phen)] (3) and trans-[Pt₂Br₄(SMe₂)₂(μ-4,7-phen)] (4), respectively. The crystal structure of trans-[Pt₂Br₄(SMe₂)₂(μ-4,7-phen)].C₆H₆ reveals that 4,7-phen bridges between two platinum centers in a slightly distorted square planar arrangement of the platinum. In this structure, both bromides are trans, while the PtBr₂(SMe₂) moieties are syn to each other. NMR data of mono and binuclear complexes of platinum 1–4 show that the binuclear complexes exist in solution as a minor product, while the mononuclear complexes are major products.     

Mono-, di-, and trinuclear phosphonate oxygen-bridged copper(II) complexes: syntheses,structures, and properties

Reactions of copper salts, zoledronic acid, and 2,2′-bipyridine/1,10-phenanthroline in aqueous ethanolic solutions afforded four phosphonate oxygen-bridged copper complexes, Cu(bipy)(H₄zdn)(HSO₄) (1), [Cu₂(bipy)₂(H₂zdn)(H₂O)(Cl)]·4H₂O (2), [Cu₂(phen)₂(H₂zdn)(H₂O)(Cl)]·2.5H₂O (3), and [Cu₃(bipy)₃(H₄zdn)(H₂zdn)(SO₄)]·5H₂O (4) (H₅zdn = zoledronic acid, bipy = 2,2′-bipyridine, phen = 1,10-phenanthroline). The copper centers of 1–4 have square pyramidal coordination geometries. The Cu(II) ions are coordinated to bipy/phen, zoledronate, and HSO₄^?/Cl^? forming mononuclear units for 1, dinuclear for 2 and 3, and trinuclear for 4. These building units are further extended into 3-D supramolecular networks via multiple hydrogen bond interactions. Temperature-dependent magnetic properties of 2 and 4 suggest weak antiferromagnetic coupling (J = ?4.53(8) cm^?1 for 2, J = ?1.69(4) cm^?1 for 4). The antitumor activity of 2 was evaluated against the human lung cancer cell line and indicates effective time- and dose-dependent cytotoxic effects.     

Pseudo-capsular behaviour of two trans-coordinated calixarenyl phosphines

The square-planar complex trans-[PtCl₂L₂] (L = 5-diphenylphosphinyl-25,26,27,28-tetrabenzyloxy-calix[4]arene) was prepared in two steps from [PtCl₂(cod)] (cod = 1,5-cyclooctadiene) and the corresponding phosphine. In the solid state, the calixarene moieties adopt a typical pinched cone conformation; they are both turned towards the Cl–Pt–Cl rod, thereby forming a capsule that hosts the platinum centre.     

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.