Mehdi Rashidi

Platinum nanostructures at the liquid–liquid interface: catalytic reduction of p-nitrophenol to p-aminophenol

Platinum nanostructures were synthesized by reduction of the PtCl2(SMe2)2 complex at the interface between water and toluene at room temperature. Platinum nanosheets were obtained by using polyvinylpyrrolidone (PVP) as a stabilizer. Dendritic tree-like nanostructures of platinum were synthesized by using aminoclay. In the absence of stabilizer, the resulting thin film contained connected chains of platinum nanoparticles. Catalytic activities of platinum nanostructures were investigated in the reduction of p-nitrophenol to p-aminophenol and on the basis of comparative kinetic studies, the following trend was obtained for the effect of the related thin film catalyst on the rate of reaction: Pt/aminoclay > Pt/PVP > Pt/no stabilizer.

In Vitro and In Vivo Antitumor Activities and DNA Binding Mode of Five Coordinated Cyclometalated Organoplatinum(II) Complexes Containing Biphosphine Ligands

New complexes [Pt(C(∧)N)Cl(dppa)] (1), and [Pt(C(∧)N)Cl(dppm)] (2), (C(∧)N. deprotonated 2-phenylpyridine; dppa. bis(diphenylphosphino)amine; dppm. bis(diphenylphosphino)methane) were suggested to have pentacoordinated geometry as investigated by NMR and conductometry. Pharmacological effects of 1 and 2 were evaluated for their proteasome-inhibitory and apoptosis-inducing activities under in vitro and in vivo conditions, showing significant proteasome-inhibitory activity against purified 20S proteasome, while 2 demonstrated superior inhibitory activity against cellular 26S proteasome. Consistently, this effect was associated with higher levels of proteasome target proteins and apoptosis induction in breast cancer cells. Importantly, preliminary studies show 1 and 2 were able to exert a similar effect in vivo by inhibiting the growth of breast cancer xenografts in mice, which was associated with proteasome inhibition and apoptosis induction. Interaction of 1 and 2 with herring sperm DNA was investigated by fluorimeteric emission, suggesting that Pt(II)-containing biphosphine complexes with DNA binding capabilities can also target and inhibit the tumor proteasome.

New precursors for chemical vapour deposition of platinum and the hydrogen effect on CVD

Abstract Volatile organoplatinum(II) complexes have been studied as precursors for low temperature chemical vapour deposition (CVD) of platinum films. The temperature of CVD and the carbon contamination of the films can both be decreased by conducting the CVD process in the presence of hydrogen. Good adherence of the films to a silicon semiconductor is obtained.

The synthesis, characterization and reactions of a binuclear tetramethylplatinum(IV) complex

Abstract Reaction of excess MeLi and MeI with [PtCl 2 SMe 2 ) 2 ] gives the first binuclear tetramethylplatinum(IV) complex [Pt 2 Me 8 (μ-SMe 2 ) 2 ]. The characterization of this complex, and its reactions with donor ligands to give cis -[PtMe 4 L 2 ] (L 2 = Ph 2 PCH 2 PPh 2 , Ph 2 PCH 2 CH 2 PPh 2 , 2,2′-bipyridyl, 1,10-phenanthroline or L = PMe 2 Ph, PMePh 2 ) are described.

Cyclometalated Cluster Complex with a Butterfly-Shaped Pt2Ag2 Core

The cyclometalated platinum complex [PtMe(bhq)(dppy)] (1), in which bhq = benzo{h}quinoline and dppy = 2-(diphenylphosphino)pyridine, was prepared by the reaction of [PtMe(SMe(2))(bhq)] with 1 equiv of dppy at room temperature. Complex 1 contains one free pyridyl unit and was readily characterized by multinuclear NMR spectroscopy and elemental microanalysis. The reaction of complex 1 with 1 equiv of [Ag(CH(3)CN)(4)]BF(4) gave the cyclometalated cluster complex [Pt(2)Me(2)(bhq)(2)(mu-dppy)(2)Ag(2)(mu-acetone)](BF(4))(2) (2) in 70% yield. The crystal structure of complex 2 was determined by X-ray crystallography, indicating a rare example of a butterfly cluster with a Pt(2)Ag(2) core in which the Ag atoms occupy the edge-sharing bond. In solution, the bridging acetone dissociates from the cluster complex 2, but as shown by NMR spectroscopy, the Pt(2)Ag(2) core is retained in solution and a dynamic equilibrium is suggested to be established between the planar and butterfly skeletal geometries.

Bis-µ-[bis(diphenylphosphino)methane]-bis(halogenoplatinum)(Pt–Pt); dimeric complexes of platinum(I) containing a platinum–platinum bond

Bis-µ-[bis(diphenylphosphino)methane]-bis(chloroplatinum)(Pt–Pt), [{PtCl(dppm)}2](dppm = Ph2PCH2PPh2), is obtained by treatment of the platinum(II) complex [PtCl2(dppm)] with Na[BH4]–MeOH followed by HCl–C6H6. The corresponding dimeric bromo- and iodo-complexes of PtI are obtained from the chloro-complex by halide exchange. The 1H and 31P n.m.r. and vibrational spectra of these complexes are analysed and strongly support the assigned structure rather than the halogenide-bridged structure proposed earlier. Bands assigned to ν(Pt–Pt) are present in the Raman spectra.

Some mono- and binuclear platinacyclopentane complexes: a comparative kinetic study of reaction of ethyl iodide with platina(II)cyclopentane and dimethylplatinum(II) complexes

Abstract The reaction of Li(CH2)4Li with [PtCl2(SEt2)2] yielded an unstable complex, probably [{Pt(CH2CH2CH2CH2)(μ-SEt2)}2], 1. Complex 1 reacts with bis(diphenylphosphino)methane, dppm, and forms [{Pt(CH2CH2CH2CH2)(μ-dppm)}2], 2. Complex 2 has been fully characterized using multinuclear NMR and FAB mass spectroscopies and shown to be fluxional in solution. The bright red platinacyclopentane complex [Pt(CH2CH2CH2CH2)(bpy)], 3, in which bpy=2,2′ bipyridyl, has been prepared by reaction of 1 with bpy. In a comparative kinetic study, it was demonstrated that at different temperatures, EtI reacted 2.2–2.6 times faster with the platina(II)cyclopentane complex 3 than with the dimethyl analogue [PtMe2(bpy)].

Studies of binuclear methyl and phenyl derivatives of platinum(II)

Some reactions of the binuclear organoplatinum complexes [Pt2R4(μ-SMe2)2], where R  Me or Ph are described, and a new synthetic method for the complex with R  Ph is reported. The dimethyl-sulphide ligands are easily displaced by other ligands, L, to give cis-[PtR2L2]. When R  Me, reaction with MeI and Ph2PCH2PPh2, dppm, gives [{PtMe3(μ-I)}2(μ-dppm)], whereas when R  Ph, reaction with MeI gives [(PtPh2MeI)4], which has been characterized as its adduct with 2,2′-bipyridine [PtIMePh2(bipyl)]. The latter complex exists as a mixture of two isomers, though the reaction between [PtPh2(bipyl)] and MeI initially gives only one isomer of [PtIMePh2(bipy)], formed by trans-oxidative addition. The reaction of [Pt2Me4(μ-SMe2)2] with hydrochloric acid yields a 1 : 1 mixture of [PtCl2(SMe2)2] and (PtMe3Cl)4], and it is suggested that this reaction involves an intramolecular methyl group transfer between the platinum atoms of the dimer.

ω-Monobromoalkyl platina(IV)cyclopentane complexes: synthesis, characterization and kinetic studies of the formation

Abstract The complexes [Pt(CH 2 CH 2 CH 2 CH 2 )(NN)], 1a (NN=2,2′-bipyridyl) and 1b (NN=1,10-phenanthroline), react with dibromoalkanes Br(CH 2 ) n Br ( n =3–6) to give new platina(IV)cyclopentane complexes fully characterized as [PtBr(CH 2 CH 2 CH 2 CH 2 ){(CH 2 ) n Br}(NN)]. When n =2, complexes 1 react with Br(CH 2 ) 2 Br to give binuclear complexes [Pt 2 Br 2 (CH 2 CH 2 CH 2 CH 2 ) 2 { μ -(CH 2 ) 2 }(NN) 2 ]. All the reactions proceed by the S N 2 mechanism and rates of reactions follow the sequence n =2⪢6>3>4≅5. The trend of reactivity is discussed in terms of chain lengths of dibromides and 1 J (Pt–C) values of bond between Pt and polymethylene chain in the platina(IV)cyclopentane complexes.

Diorganoplatinum(II) complexes with chelating PN ligand 2-(diphenylphosphinoamino)pyridine; synthesis and kinetics of the reaction with MeI

New organoplatinum(II) complexes [PtR2(PN)] (PN = 2-(diphenylphosphinoamino)pyridine, R = Me, 1a, or p-MeC6H4, 1b) were synthesized by the reaction of [Pt(p-MeC6H4)2(SMe2)2] or [Me2Pt(μ-SMe2)2PtMe2] with 1 and 2 equiv. of PN, respectively. The reaction of Pt(II) complexes 1 with MeI gave the Pt(IV) complexes [PtR2(PN)MeI] (R = Me; 2a, and p-MeC6H4; 2b). All the complexes were fully characterized using multinuclear (1H, 31P, 13C, and 195Pt) NMR spectroscopy. Density functional theory calculations have been performed to find approximate structures for all described complexes. The platinum(II) complexes have a 5dπ(Pt)-π*(PN) metal-to-ligand charge-transfer band, which was used to easily follow the kinetics of their reactions with MeI. The classical SN2 mechanism was suggested. The rates of the reactions at different temperatures were measured and were consistent with the proposed mechanism, large negative ΔS‡ values were found in each reaction. The PN chelating complexes [PtR2(PN)], 1, reacted almost 100 or 300 times slower with MeI as compared to that of the NN chelating complex [PtR2(bpy)] (bpy = 2,2′-bipyridine) in acetone or benzene, respectively. This was attributed to the π-acceptance through the P ligating atom of PN ligand, which decreases the electron density of Pt(II) in PN chelating complexes.