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.     

A comparative study of neighbouring group effects on the isomerization of imines in platinum-imine complexes by 1H, 13C, 31P and 195Pt NMR spectroscopy

¹⁹⁵Pt-, ³¹P-, ¹³C- and ¹H-chemical shifts are reported for the first time for complexes of the type trans-[PtCl₂ (η²-C₂H₄) (imine)], I, trans-[PtCl₂ (η²-C₂H₄) (amine)] II, and trans-[PtCl₂(PR′₃) (imine)] III (the imine ligand being derived from cyclopropyl-2-thienylketone and primary amines; PR′₃ = PBuⁿ₃ and PPh₃; amine; the amine ligand obtained by the reduction of the appropriate imine). The use of multinuclear spectroscopy provides strong evidence for E-Z isomerization of imine ligands coordinated to platinum (II) of the type trans-[PtCl₂ (η²-C₂H₄)(imine)]. Tertiary phosphine ligands trans to imine ligand (III) are not strongly labilizing groups, in contrast to η²-C₂H₄, which shows a strong labilizing effect. The effect of neighbouring groups on E-Z isomerization indicates that increase of the bulky substituents close to the imino group tends to increase the rate of isomerization, and increasing the degree of substitution on the imine carbon atoms slows the rate of isomerization. Furthermore, addition of a trace of amine will catalyze the E-Z isomerization. Also, isomerization takes place in the liquid state to give one isomer during the coordination with platinum.     

Synthesis and 31P NMR spectra of some platinum(II) complexes of the phospha-alkene, (mesityl)P=CPh2: Crystal and molecular structure of cis-[PtCl2(PEt3)(C6H2Me3P=CPh2)]·CHCl3

Syntheses of the phospha-alkene complexes cis- and trans-[PtCl₂(PEt₃)(mesityl)P=CPh₂], and cis- [PtX₂{(Mesityl)P=CPh₂}₂](X=Cl, I, Me) complexes are reported. ³¹P NMR spectra indicate that bonding of the phospha-alkene to the metal is via the phosphorus lone pair and this is confirmed by a single crystal X-ray diffraction study of cis-[PtCl₂(PEt₃){(mesityl)P=CPh₂}]CHCl₃.     

Etude du comportement photochimique de complexes {PtCl2(oléfine)(amine)}, influence de la nature de l'olefine et de la configuration du complexe

Irradiation of complexes {PtCl₂(olefine)(amine)} leads to the departure of the olefinic ligand forming a dimeric compound {PtCl₂(amine)}₂ which has a trans configuration. The same behaviour is observed at different irradiation wavelengths, with variation of the nature of the coordinated olefin and with a cis or trans configuration of the starting compound. Experimental results show that the primary photochemical reaction pathway arises probably via a (d → π^★ C₂H₄) charge transfer existed state. A simultaneous cis → trans photoisomerization is observed in the case of the cis complexes.     

Kinetic characterization of the interactions of trans-dichloro-platinum(IV) anticancer prodrugs and a model compound with thiosulfate

Sodium thiosulfate has been utilized as a rescuing agent for relief of the toxic effects of cisplatin and carboplatin. In this work, we characterized the kinetics of reactions of the trans-dichloro-platinum(IV) complexes cis-[Pt(NH₃)₂Cl₄], ormaplatin [Pt(dach)Cl₄] and trans-[PtCl₂(CN)₄]^2? (anticancer prodrugs and a model compound) with thiosulfate at biologically important pH. An overall second-order rate law was established for the reduction of trans-[PtCl₂(CN)₄]^2? by thiosulfate, and varying the pH from 4.45 to 7.90 had virtually no influence on the reaction rate. In the reactions of thiosulfate with cis-[Pt(NH₃)₂Cl₄] and with [Pt(dach)Cl₄], the kinetic traces displayed a fast reduction step followed by a slow substitution involving the intermediate Pt(II) complexes. The reduction step also followed second-order kinetics. Reductions of cis-[Pt(NH₃)₂Cl₄] and [Pt(dach)Cl₄] by thiosulfate proceeded with similar rates, presumably due to their similar configurations, whereas the reduction of trans-[PtCl₂(CN)₄]^2? was about 1,000 times faster. A common reduction mechanism is suggested, and the transition state for the rate-determining step has been delineated. The activation parameters are consistent with transfer of Cl⁺ from the platinum(IV) center to the attacking thiosulfate in the rate-determining step.     

Studies of the reactions of platinum halo complexes with tin(II) halides

The reaction of a dichloromethane solution of a mixture of cis,trans-[PtCl₂(SMe₂)₂] with a tetrahydrofuran solution of SnBr₂ resulted in oxidation of platinum(II) with halogen exchange producing cis,trans-[PtBr₄(SMe₂)₂]. Reaction of a mixture of cis,trans-[PtCl₂(SEt₂)₂], potassium tetrachloroplatinate(II) or potassium hexachloroplatinate(IV) with SnBr₂ in hydrochloric acid solution resulted in formation of predominantly anionic five-coordinate trichlorostannyl platinum(II) complexes. Reaction of potassium tetrabromoplatinate(II) with SnCl₂ in hydrobromic acid in the presence of tetraphenylphosphonium bromide affords cis-[PPh₄]₂[PtBr₂(SnBr₃)₂]. The insertion of SnCl₂ into Pt–Cl bond of platinum(II) complexes cis-[PtCl₂(L₂)] {L₂ = (PPh₃)₂; (PMe₃)₂; {P(OMe)₃}₂; dppm (bis(diphenylphosphino)methane); dppa (bis(diphenylphosphino)amine); and dppe (1,2-bis(diphenylphosphino)ethane)} is described.     

The interaction of vinyl acetate and allyl acetate with chloro-bridged platinum(II) complexes [Pt2Cl4(PR3)2]: Crystal structure of cis-[PtCl2(PMe2Ph2)(CH2=CHOCOCH3)]

Five complexes of type cis-[PtCl₂(PR₃)Q] (PR₃ =PMe₃, PMe₂Ph, PEt₃; Q = CH₂ CHOCOCH₃ or CH₂=CHCH₂OCOCH₃) have been prepared. The crystal structure of cis-[PtCl₂[PME₂Ph)(CH₂=CHOCOCH₃)] is described. Crystals of cis-[PtCl₂(PME₂Ph)(CH₂-CHOCOCH₃)] are triclinic, with a 8.441(4), b 13.660(5), c 7.697(3) Å, a 101.61(3)°, β 111.85(3)° γ 95.22(3)°, pP1, Z = 2. The structure was determined from 2011 reflections I σ 3σ (I) and refined to R = 0.037. The CH₃COO grouping is syn to the cis-PMe₂Ph ligand, with bond lengths of PtCl (trans to P) 2.367(3), PtCl (trans to olefin) 2.314(3), PtP 2.264(2), and PtC of 2.147(12) and 2.168(11) Å. The complexes cis-[PtCl₂- (PR₃)Q] were studied by variable temperature ¹H and ³¹P NMR spectroscopy. Spectra of the vinyl acetate complexes were temperature dependent as a result of rotation about the platinum—olefin bond. The rotation was “frozen out” at ca. 240 K; for cis-[PtCl₂(PME₂Ph)(CH₂=CHOCOCH₃] ΔG≠ (rotation) 15.0 ± 0.2 kcal mol^-1. NMR parameters for the rotamers are reported. NMR studies of the interaction between chloro-bridged complexes of type [Pt₂Cl₂(PR₃)₂] (PR₃ = P-N-Pr₃ or PMe₂Ph) and vinyl acetate shows that even at low temperatures (213 K) equilibrium favours the bridged complex and the proportion of trans-[PtCl₂(PR₃)CH₂=CHOCOCH₃)] is very small e.g. 2%. The allyl acetate complexes cis-[PtCl₂(PR₃)(CH₂₌CHCH₂OCOCH₃)] showed only one rotamer over the range 333–213 K. Reversible dissociation of cis-[PtCl₂(PMe₂Ph)- (CH₂=CHCH₂OCOCH₃)] to [Pt₂Cl₄(PMe₂Ph)₂] + allyl acetate was studied at ambient temperature. At low temperatures e.g. 213–190 K addition of allyl acetate to a CDCl₃ solution of [Pt₂Cl₂(P-n-Pr₃)₂] reversibly gave some olefin complex trans-[PtCl₂(P-n-Pr₃)(CH₂=CHCH₂OCOCH₃)] and some O-bonded complex trans-[PtCl₂(P-n-Pr₃)(CH₂=CHCH₂OCOCH₃)].     

Platinum(II) and platinum(IV) chloro complexes with (<Emphasis Type="Italic">RS</Emphasis>)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1Н-1,2,4-triazol-1-ylmethyl)pentan-3-ol

Platinum(II) and platinum(IV) chloro complexes with (RS)-1-(4-chlorophenyl)-4,4-dimethyl-3-(1Н-1,2,4-triazol-1-ylmethyl)pentan-3-ol (L), namely, cis-[PtCl₂L₂], trans-[PtCl₂L₂], and trans-[PtCl₄L₂], were synthesized. The structures of their coordination cores and the coordination mode of the reagent to the metal ions via the N(4) atom of the triazole ring were determined by electronic, IR, and NMR ¹H and ¹³C spectroscopy. The ratio between treo and erythro diastereomers and the conformation of reagent L in the complexes were established from the complete assignment of signals in their NMR spectra.     

Alkyl- and aryl-platinum(II) complexes from K2[PtCl4] and tetraorganotin compounds in dimethylsulphoxide. Preparation and reactions of complexes [PtR2(DMSO)2] and [PtR(C) (DMSO)2]

The reaction between K₂[PtCl₄] and a variety of tetraorganotin compounds SnMe₃R (R = Me, aryl) in DMSO gives the complexes cis-[PtR₂(DMSO)₂] and trans-[PtR(Cl)(DMSO)₂] in which the DMSO ligands are bound to Pt through S in the solid state. The DMSO ligands are easily displaced by a variety of N, P, As and Sb donors.     

Chromatographic study of thermal reactions of cis- and trans-[Coen2 (OCOC6H4X)2]NO3 complexes in the solid phase

Thermal reactions of some cis- and trans-[Coen₂(OCOC₆H₄X)₂]NO₃ complexes mixed with ammonium or sodium chloride, nitrate and sulphate are reported. Reflectance spectra have shown a cis to trans thermal isomerization and, in the presence of NH₄Cl, the formation of trans-[Coen₂Cl₂]Y as final product. For the cis-isomers, the most interesting result is the chromatographic evidence of a stepwise reaction, resulting in the replacement of one carboxylato ligand by chloride and the formation of an intermediate species, characterized as trans-[Coen₂(OCOC₆H₄X)Cl]Y. These intermediate species, are hardly detectable in the corresponding reactions of the trans-isomers. These results may mean that in the trans-carboxylato compounds the reaction rate of the second step is higher than that of the first, while the reverse can be supposed in the corresponding reaction of the cis-isomers.     

Etude du mecanisme de photolyse des complexes cis- et trans-[PtCl2(C2H4)(4-CH3C5H4N)]. Influence de la concentration et de la longueur d'onde

Photodimerization, photoisomerization and photosubstitution quantum yields are measured for cis- and trans-[PtCl₂(C₂H₄)(4-CH₃C₅H₄N)], at various concentrations and wavelengths. Dissociation of the platinumethylene bond o?curs with a quantum yield nearly unity when the cis-compléx is irradiated in the charge transfer bands 5d → π^*(C₂H₄). Dissociation is also observed, but with a lower efficiency, at longer wavelengths. A cis → trans-photoisomerization reaction, probably via a low energy dd excited state is observed at 313,366 and 405 nm, with a constant quantum yield.     

Fast Analysis of Synthetic Pyrethroid Metabolites in Water Samples Using In-Syringe Derivatization Coupled Hollow Fiber Mediated Liquid Phase Microextraction with GC-ECD

A fast and efficient method has been demonstrated for the trace determination of six important metabolites of synthetic pyrethroids including cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis- and trans-Cl₂CA), cis-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis-Br₂CA), 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA), 3-phenoxybenzoic acid (3-PBA), and 2-phenoxybenzoic acid (2-PBA) in environmental water samples using hollow fiber (HF)-mediated liquid-phase microextraction (LPME) coupled with in-syringe derivatization (ISD) followed by gas chromatography (GC) with electron capture detector (ECD) analysis. This method utilizes a HF membrane segment impregnated with extraction solvent as the LPME sampling probe, which was connected to a microsyringe pre-filled with derivatizing agents, and it was immersed into sample solution for extraction. After extraction, the extracting solution was subjected to derivatization reaction that was performed inside the syringe barrel followed by GC-ECD analysis. Under optimal conditions, the best extraction efficiency was obtained using sampling probe (2.0 cm hollow fiber) impregnated with 1-octanol immersed into water sample (5.0 mL, adjusted pH below 1.0) and stirring (1,250 rpm) for 10 min at 70 °C and diisopropylcarbodiimide (2 μL) and 1,1,1,3,3,3-hexafluoro-2-propanol (1 μL) were the derivatizing agents used. The detection limits of 3 ng mL^?1 for cis- and trans-Cl₂CA, 2 ng mL^?1 for cis-Br₂CA, 6 ng mL^?1 for 4-F-3-PBA, and 0.6 ng mL^?1 for 3-PBA and 2-PBA. The method showed good linearity (R ² = 0.973?0.998), repeatability from 4.0 to 13 % (n = 5), recovery from 79.2 to 95.7 %, and enrichment factors ranged between 109 and 159 for target analytes spiked in water samples. The proposed method and conventional methods were compared. Results suggested that the proposed HF-LPME-ISD/GC-ECD method was a rapid, simple, inexpensive, and eco-friendly technique for the analysis of metabolites of pyrethroids.     

Transition metal complexes with bidentate ligand 2, 11-Bis (diphenylphosphinomethyl)benzo[c]phenanthrene (1). X. Preparation and spectroscopic properties of cis-[PtCl2 (1)] trans- and cis-[PtH (PPh3) (1)] [BF4] and crystal and molecular structure of cis-[PtCl2 (1)] · CHCl3

It is shown that ligand 1 , designed to span trans-positions, under appropriate conditions also gives cis-mononuclear complexes of platinum (II). The structure of cis-[PtCl₂ (1) ] (2) has been determined by single-crystal X-ray diffraction. The major distortion from square planar coordination is the P-Pt-P angle of 104.8°. Values of valence angles within the bidentate ligand indicate that this part of the molecule is very strained. Two phenyl groups, one on each phosphorus, lie almost parallel to each other separated by ca. 3.2–3.3 Å. The ¹H-NMR. data for this compound show that the π-phenyl interactions observed in the solid state occur also in solution. The preparation and NMR.-spectroscopic properties of trans- and cis-[PtH(PPh₃) (1) ] [BF₄] are reported.     

Synthesis and characterization of new platinum(II) phosphinate complexes

The syntheses of platinum(II) complexes of bis(dimethylphosphinylmethylene)amine and bis(aminomethyl)phosphinic acid were investigated. In the case of bis(dimethyl-phosphinylmethylene)amine the reaction with K₂[PtCl₄] yields the potassium amino-trichloroplatinate K[PtCl₃L] (L?=?bis(dimethylphosphinylmethylene)amine), which was characterized by multinuclear (¹H, ¹³C, ³¹P, and ¹⁹⁵Pt) NMR spectroscopy in solution. Bis(aminomethyl)phosphinic acid reacts with K₂[PtCl₄] under strictly controlled pH conditions to give colorless crystals of the cisplatin analog K[PtCl₂L′] (L′?=?bis(aminomethyl)phosphinate). This complex was characterized by multinuclear NMR spectroscopy in solution as well as by single-crystal X-ray diffraction in the solid state. The bis(aminomethyl)phosphinate coordinates to platinum via both amino functions, thus acting as a chelating ligand.     

Reactions of diphosphineplatinum(II) oxalate complexes with phenylacetylene. Formation of phenylalkynylplatinum complexes

[Pt(C₂O₄)(dppe)] reacts thermally with PhCCH to produce [Pt(CCPh)₂(dppe)], which has been prepared by alternative routes. Similar treatment of [Pt(C₂O₄)(dppm)] initially produces [Pt(CCPh)₂(dppm)], which rearranges to give cis,cis-[Pt₂(CCPh)₄(μ-dppm)₂]. Reaction of [PtCl₂(dppm)] with PhCCH/KOH/18-crown-6, or with (PhCC)SnMe₃, gives [Pt(CCPh)₂(dppm)], which may be converted to the cis,cis-dimer by addition of oxalic acid. Ultraviolet irradiation or refluxing with a trace amount of dppm converts [Pt(CCPh)₂(dppm)] to trans,trans-[Pt₂(CCPh)₄(μ-dppm)₂], but the cis,cis-dimer is stable under these conditions. [Pt(C₂O₄)L₂] (L = PPh₃, PEt₃) complexes also react thermally with PhCCH to yield [Pt(CCPh)₂L₂] species.     

An efficient method for selective oxidation of (oxime)Pt(II) to (oxime)Pt(IV) species using <Emphasis Type="Italic">N,N</Emphasis>-dichlorotosylamide

The oxidation of (oxime)Pt^II species using the electrophilic chlorine-based oxidant N,N-dichlorotosylamide (4-CH₃C₆H₄SO₂NCl₂) was studied. The reactions of trans-[PtCl₂(oxime)₂] (where oxime = acetoxime, cyclopentanone oxime, or acetaldoxime) with this oxidant led to trans-[PtCl₄(oxime)₂] products. The oxidation of trans-[Pt(o-OC₆H₄CH = NOH)₂] at room temperature gave trans-[PtCl₂(o-OC₆H₄CH = NOH)₂], whereas the same reaction upon heating was accompanied by electrophilic substitution of the benzene rings.     

Ruthenium complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane for atom and group transfer reactions

With support by macrocyclic tertiary amine ligand 1,4,7-trimethyl-1,4,7-triazacyclononane (Me₃tacn), a number of mononuclear metal–ligand multiple bonded complexes have been isolated. Starting with a brief summary of these complexes, the present review focuses on ruthenium-oxo and -imido complexes of Me₃tacn. A family of monooxoruthenium(IV) complexes [Ru^IV(Me₃tacn)O(N–N)]²⁺ (N–N = 2,2′-bipyridines) and a cis-dioxoruthenium(VI) complex cis-[Ru^VI(Me₃tacn)O₂(CF₃CO₂)]⁺ have been isolated, and the structures of [Ru^IV(Me₃tacn)O(bpy)](ClO₄)₂ (bpy = 2,2′-bipyridine) and cis-[Ru^VI(Me₃tacn)O₂(CF₃CO₂)]ClO₄ have been determined by X-ray crystallography. Oxidation of [Ru^III(Me₃tacn)(NHTs)₂(OH)] (Ts = p-toluenesulfonyl) with Ag⁺ and electrochemical oxidation of [Ru^III(Me₃tacn)(H₂L)](ClO₄)₂ (H₃L = α-(1-amino-1-methylethyl)-2-pyridinemethanol) are likely to generate ruthenium-imido complexes supported by Me₃tacn. DFT calculations on cis-[Ru^VI(Me₃tacn)O₂(CF₃CO₂)]⁺ and proposed ruthenium-imido complexes have been performed. Complexes [Ru^IV(Me₃tacn)O(N–N)]²⁺ are reactive toward alkene epoxidation, and cis-[Ru^VI(Me₃tacn)O₂(CF₃CO₂)]⁺ efficiently oxidizes various organic substrates including concerted [3+2] cycloaddition reactions with alkynes and alkenes to selectively afford α,β-diketones, cis-diols, or CC bond cleavage products. Related oxidation reactions catalyzed by ruthenium Me₃tacn complexes include epoxidation of alkenes, cis-dihydroxylation of alkenes, oxidation of alkanes, alcohols, aldehydes, and arenes, and oxidative cleavage of CC, CC, and C–C bonds, all of which exhibit high selectivity. Ruthenium Me₃tacn complexes are also active catalysts for amination of saturated C–H bonds.     

Kinetics of substitution reactions of transition metal complexes in 1,3-dioxolan-2-one + water and 4-methyl-1,3-dioxolan-2-one + water solvent mixtures

Summary Rate constants are reported and discussed for several substitutions of inorganic complexes in ethylene carbonate (1,3-dioxolan-2-one) + water and in propylene carbonate (4-methyl-1,3-dioxolan-2-one) + water solvent mixtures. The reactions include aquation ofcis- and oftrans-[Co(en)₂Cl₂]⁺, aquation oftrans-[Cr(OH₂)₄Cl₂]⁺, bromide substitution at [Pd(Et₄dien)Cl]⁺, thiourea substitution atcis-[Pt(4-NCpy)₂Cl₂], and aquation and cyanide attack at [Fe(X-phen)₃]²⁺ cations.     

Heterobimetallic [Ru(II)/Fe(II)] complexes: On the formation of trans- and cis-[RuCl2(dppf)(diimines)]

The synthesis and characterization of trans/cis-[RuCl₂(dppf)(diimines)], dppf = 1,1′-bis(diphenylphosphino)ferrocene; diimines = 2,2′-bipyridine (trans/cis-(1)), the new complexes with 4,4′-dimethyl-2,2′-bipyridine (trans/cis-(2)) and 1,10-phenanthroline (cis-(3)) are presented. The complexes were synthesized using two routes and the trans/cis-isomer formation is dependent upon conditions and the precursor applied. The trans-isomer (kinetic) readily isomerizes to the cis-isomer (thermodynamic) when exposed to light (fluorescent) and this process was followed by cyclic voltammetry and UV-vis. The electrochemical studies on these complexes reveal that Fe^(III)/Fe^(II) couples are insensitive to the isomer (trans/cis) formed, but the Ru^(III)/Ru^(II) couples are dependent on the isomer. Transfer-hydrogenation reactions for reduction of acetophenone were conducted using complexes cis-(1) and cis-(2) and the results are compared with that obtained for similar complexes. X-ray structure for cis-(3) are presented and discussed.     

Phosphinic complexes of rhenium and tungsten in reactions with stereoindicators

Stereoindicators (cis-4,4′-dimethoxystilbene (DMS) or cis-α,β-dinitrostilbene (DNS)) were used to investigate the donor/acceptor properties of the complexes trans-[ReCl(N₂)(dppe)₂] or trans-[W(CO)₄(dppe)]. The former induced cis/trans conversion of DMS, and the latter cis/trans conversion of DNS, both resulting from charge transfer (in the first case from DMS to the rhenium complex and, in the second case, from the tungsten cofnplex to DNS). The rhenium complex acts as an acceptor, and the tungsten complex as a donor in the framework of the stereoindicator approach.