Complex cis-Pt Research Articles

Crystal structures of Pt(II) and Pd(II) complexes with the free radical 4-aminoTEMPO

Pt(II) and Pd(II) compounds containing the free radical 4-aminoTEMPO (4amTEMPO) were synthesized and characterised by X-ray diffraction methods. The disubstituted complexes cis- and trans-Pt(4amTEMPO) 2I 2 were studied. The trans isomer was prepared from the isomerisation of the cis analogue. The two Pd(II) compounds trans-Pd(4amTEMPO) 2X 2 (X = Cl and I) were also characterised by crystallographic methods. A mixed-ligand complex cis-Pt(DMSO)(4amTEMPO)Cl 2 was synthesized from the isomerisation of the trans isomer in hot water. Its crystal structure was also determined. In all the complexes, the 4amTEMPO ligand is bonded to the metal through the –NH 2 group, since the nitroxide O atom is not a good donor atom for the soft Pt(II) and Pd(II) metals. The conformation of the 4-aminoTEMPO ligand was compared to those of the few reported structures in the literature.

Synthesis and Characterization of a Novel Phosph(V)azane-Platinum(II) Complex

The substitution reaction of bis(anilino)phosphine oxide (C 6 H 5 NH) 2 P(O)H (1) with trans-PtCl 2 (SEt 2 ) 2 yields the novel unprecedented phosph(V)azane-platinum complex cis-Pt(SEt 2 ) 2 Cl[HNPhP(O)NPh(HNEt 3 )] (3). In this reaction, the bis(anilino)phosphine oxide undergoes P–H activation and a Pt(II)–P(V) bond instead of Pt–N bond forms. 31 P NMR spectra readily distinguish between the “N” and “P” bonding modes. The reaction requires the presence of triethylamine (TEA) as a base in order to deprotonate the phosphazane ligand and is separated as Et 3 NH+Cl−, whereas HTEA+ exists in the final product 3 and is acting as charge balancing and H-bond structure directing agent. The products have been fully characterized by means of IR; MS; UV-Vis; and 1 H, 13 C, and 31 P NMR spectroscopy.

Multinuclear magnetic resonance studies of the hydrolyzed and aquated species of the antitumor complexes cis-Pt(cyclobutylamine) 2X 2 and cis-Pt(NH 3)(cyclobutylamine)X 2 and antitumor testing of mixed -amine Pt(II) compounds

The aquated and hydrolyzed species formed from the complexes cis-Pt(cba) 2I 2 and cis-Pt(NH 3)(cba)I 2 (cba = cyclobutylamine) were studied by multinuclear ( 195Pt, 15N and 1H) magnetic resonance spectroscopy. The iodo ligands were removed with AgNO 3. In acidic medium, the aqueous product consists of the diaqua and the aqua -nitrato cations, although some monohydroxo -bridged dimers are formed after several hours, especially for the mixed -ligand compound. In basic medium, the main species are the dihydroxo compounds. At neutral pD, several species exist in solution, especially with the mixed -amine system, which contained also a small quantity of the symmetric cis-Pt(cba) 2 complexes. Difficulties were encountered because of the insolubility of several oligomeric species, contrary to the cis-Pt(NH 3) 2 system, probably due to the greater lipophilicity of cba compared to NH 3. Monohydroxo -bridged dimers are formed in large quantities and the stereochemistry of the mixed -amine species was determined by 15N NMR spectroscopy. For the latter system, the cyclic dihydroxo -bridged dimers are the predominant species at neutral pD after a few hours. After an extended period of time, most of the oligomers precipitate, leaving the more soluble monohydroxo -bridged dimers as the major species in solution. The preliminary antitumor testing results on several dichloro mixed -ligand compounds are listed. The results on further testing on the most active compound cis-Pt(NH 3)(cba)Cl 2 are also included.

Synthesis and characterization of the novel Pt(II) complexes of the types cis- and trans-Pt(Ypy)(pyrazine)Cl 2, K 2[Cl 3Pt(μ-pyrazine)PtCl 3] and trans, trans-(Ypy)Cl 2Pt(μ-pyrazine)Pt(Ypy)Cl 2 (Ypy = pyridine derivative)

New types of Pt(II) mixed-ligand complexes containing a pyridine derivative (Ypy) and pyrazine (pz) were synthesized. The compounds were characterized by infrared spectroscopy and by multinuclear ( 1H, 13C and 195Pt) magnetic resonance. The complexes cis-Pt(Ypy)(pz)Cl 2 were synthesized from the reaction of K[Pt(Ypy)Cl 3] with pyrazine (1:1 proportion) in water. When the reaction was carried on in a 2:1 ratio, a mixture of compounds was obtained, which was refluxed in CH 2Cl 2 for several days. The final product was found to be pure and it was identified as trans, trans-Cl 2(Ypy)Pt(μ-pyrazine)Pt(Ypy)Cl 2. The cis monomers isomerize to the trans isomers in organic solvents. Different methyl derivatives of pyridine were studied in order to determine the influence of substitution in ortho position on the pyridine ligand in the complexes. In IR spectroscopy, the cis monomers showed two ν(Pt–Cl) bands, while the trans monomers and dinuclear species showed only one ν(Pt–Cl) band. The NMR results were interpreted in relation to the solvent effect, which seems important in these complexes. The 195Pt NMR signals of the cis monomers were found at slightly higher fields than those of the corresponding trans isomers. The coupling constants J( 195Pt– 1H) and J( 195Pt– 13C) are larger in the cis geometry. The δ( 195Pt) of the dinuclear species were found close to those of the trans monomers and the coupling constants are similar to those of the trans monomers, strongly suggesting a trans–trans configuration for the dinuclear compounds. The pyrazine-bridged complex K 2[Cl 3Pt(μ-pz)PtCl 3] was also synthesized and spectroscopically studied. The crystal structures of the compounds cis-Pt(3,5-lut)(pz)Cl 2 and trans-Pt(2,4,6-col)(pz)Cl 2 were determined by X-ray diffraction methods.

Syntheses, Structures, and Sensitized Lanthanide Luminescence by Pt → Ln (Ln = Eu, Nd, Yb) Energy Transfer for Heteronuclear PtLn2 and Pt2Ln4 Complexes with a Terpyridyl-Functionalized Alkynyl Ligand

Reaction of Pt(dppm-P,P')Cl2 (dppm = 1,2-bis(diphenylphosphino)methane) with HCCPhtpy (HCCPhtpy = 4'-(4-ethynylphenyl)-2,2':6',2"-terpyridine) in the presence of copper(I) iodide and diisopropylamine induced isolation of mononuclear complex cis-Pt(dppm-P,P')(C[triple bond]CPhtpy)2 (1), which can be converted into face-to-face diplatinum(II) species Pt2(mu-dppm)2(C[triple bond]CPhtpy)4 (5) when equivalent dppm is added. Incorporating 1 or 5 to Ln(hfac)3(H2O)2 (Hhfac = hexafluoroacetylacetone) gave PtLn2 (Ln = Nd (2), Eu (3), Yb (4)) or Pt2Ln4 (Ln = Nd (6), Eu (7), Gd (8), Yb (9)) adducts with the lanthanide centers chelated by terdentate terpyridyl in the bridging C[triple bond]CPhtpy. The structures of 1, 6, 7, and 9 were determined by X-ray crystallography. Upon excitation at lambdaex = 360-450 nm (2-4) or 360-500 nm (6-9), where the PtII alkynyl antenna chromophores absorb strongly but the model complexes Ln(hfac)3(HC[triple bond]CPhtpy) lack obvious absorption in this region, these PtLn2 and Pt2Ln4 (Ln = Nd, Eu, Yb) species exhibit band-like lanthanide luminescence that is typical of the corresponding Ln3+ ions, demonstrating unambiguously that efficient Pt --> Ln energy transfer occurs indeed from the PtII alkynyl antenna chromophores to the lanthanide centers across the bridging CCPhtpy with intramolecular Pt...Ln distances being ca. 14.2 A. The Pt --> Ln energy transfer rate (kET) is 6.07 x 10(7) s(-1) for Pt2Nd4 (6) and 2.12 x 10(5) s(-1) for Pt2Yb4 (9) species.

Synthesis and study of Pt(II)-aromatic amines complexes of the types cis- and trans-Pt(amine) 2(NO 3) 2 and cis-Pt(amine) 2(R(COO) 2)

Complexes of the types cis- and trans-Pt(amine) 2(NO 3) 2 with amines containing a phenyl group were synthesized and studied mainly by IR and multinuclear magnetic resonance spectroscopies. The cis complexes could be synthesized pure only with the amines of the type Ph–R–NH 2 (R = alkyl), while pure trans compounds were synthesized with all the studied amines. In 195Pt NMR spectroscopy, the dinitrato complexes of the amines Ph–R–NH 2 were observed around −1700 ppm for the cis isomers and at about −1580 for the trans complexes. For the other amines, where a phenyl ring is directly attached to the amino group, the signals were observed at lower fields, −1528 ppm for cis-Pt(PhNH 2)(NO 3) 2 and around −1450 ppm for all the trans isomers. There is a linear relationship between the δ(Pt) of the Pt(amine) 2(NO 3) 2 complexes and the p K a of the protonated amines. The coupling constants 2 J( 195Pt– 1HN) are larger in the cis compounds (ave. 76 Hz) than in the trans isomers (ave. 63 Hz). The complexes cis-Pt(amine) 2(R(COO) 2) with bidentate dicarboxylato ligands were also synthesized and characterized mainly by IR spectroscopy. The compounds apparently decompose in DMF and are too insoluble in other solvents for solution studies.

Multinuclear magnetic resonance study of Pt(II) compounds with sulfoxide ligands and crystal structures of complexes of the types [Pt(R 2SO)X 3] − and Pt(R 2SO) 2Cl 2

Pt(II) complexes of the types K[Pt(R 2SO)X 3], NR 4[Pt(R 2SO)X 3] and Pt(R 2SO) 2Cl 2 (where X = Cl or Br) were characterized by multinuclear magnetic resonance spectroscopy ( 195Pt, 1H and 13C). In 195Pt NMR, the chloro ionic compounds have shown signals between −2979 and −3106 ppm, while the cis disubstituted complexes were observed at higher fields, between −3450 and −3546 ppm. The signal of the compound trans-Pt(DPrSO) 2Cl 2 was found at higher field (−3666 ppm) than its cis analogue (−3517 ppm), since π-back-donation is considerably less effective in the trans geometry. In 1H NMR, a single signal was observed for the sulfoxide in [Pt(DMSO)Cl 3] −, but for the other more sterically hindered ligands, two series of resonances were observed for the protons in α and β positions. The coupling constant 3 J( 195Pt– 1H) are between 15 and 33 Hz. The 13C NMR results were interpreted in relation to the concept of inversed polarization of the π sulfoxide bond. The 2 J( 195Pt– 13C) values vary between 35 and 66 Hz, while a few 3 J( 195Pt– 13C) couplings were observed (13–26 Hz). The crystal structures of five monosubstituted ionic compounds N( n-Bu) 4[Pt(TMSO)Cl 3], N(Me) 4[Pt(DPrSO)Cl 3], K[Pt(EMSO)Cl 3], K[Pt(TMSO)Br 3] · H 2O and N(Et) 4[Pt(DPrSO)Br 3] and one disubstituted complex cis-Pt(DBuSO) 2Cl 2 were determined. The trans influence of the different ligands is discussed.

Cis-Pt Mediated Assembly of Gold Nanoparticles on DNA

In this work we describe the formation of 1-dimensional (1D) assemblies of cysteamine functionalized gold nanoparticles on DNA using the complex cis-Pt (cis-Pt(NH3)2Cl2) as site specific linker and their immobilization on mica and silicon. The characterization by atomic force microscopy and electron microscopy served as complementary methods. Using atomic force microscopy with additional information of phase images the DNA as well as the Au particles can be visualized independently and be differentiated in the 1-dimensional aggregates. Electron microscopy shows individual particles are arranged as a string of pearls.

Thermal reactivity of cis- and trans-bis(triphenylgermyl)bis(tertiary phosphine)platinum(II)

The complex cis-Pt(Ph 3Ge) 2(PMe 2Ph) 2 underwent smooth isomerization to give the trans-isomer at room temperature via an associative five-coordinated intermediate. Thermodynamic parameters and activation energy for the cis to trans isomerization were obtained, Δ H # = 105 kJ mol −1, Δ S # = 12.5 J mol −1 K −1, and Ea = 107 kJ mol −1, respectively. Heating of trans-Pt(Ph 3Ge) 2(PMe 2Ph) 2 at 50 °C for 36 days produced trans-PtPh(Ph 3Ge)(PMe 2Ph) 2 followed by the formation of trans-PtPh 2(PMe 2Ph) 2, Pt(PMe 2Ph) 4, and Ph 4Ge finally via elimination of the phenyl group from Ph 3Ge ligand with liberation of the Ph 2Ge unit and subsequent reductive elimination of the remaining Ph 3Ge ligand at 80 °C for 1 month.

Synthesis, multinuclear magnetic resonance and crystal structures of Pt(II) complexes containing amines and bidentate carboxylate ligands

A novel synthetic method for the synthesis of the complexes cis-Pt(amine) 2R(COO) 2 is compared to two other methods involving the use of either barium dicarboxylate or sodium carboxylate. Pt(II) compounds with monodentate and bidentate amines were studied. The reaction involves the use of a silver dicarboxylato complex, which is the intermediate in the new synthetic procedure. The crystal structure of the silver intermediate with the ligand 1,1-cyclobutanedicarboxylate (1,1-CBDCA) was determined by X-ray diffraction. The crystal Ag 2(1,1-CBDCA) has a very interesting 3-D extended structure. The complexes cis-Pt(amine) 2R(COO) 2 were studied in solution by multinuclear ( 1H, 13C and 195Pt) magnetic resonance spectroscopy, but the solubilities are very low. D 2O was found to be the best solvent. In 195Pt NMR, the complexes containing bidentate amines forming five-membered chelates were observed at higher fields than those containing monodentate amines. The resonances of the NH 3 compounds were also found at lower fields than the primary amine complexes. All the dicarboxylato ligands form six-membered chelates except 1,2-CBDCA, whose Pt(II) compounds were observed at lower fields than the others. The crystal structures of Pt(en)(1,1-CBDCA), Pt(Meen)(1,1-CBDCA) and Pt(en)(benzylmalonato) were confirmed by X-ray diffraction methods. Several compounds are disordered. The crystals are stabilized by intermolecular hydrogen bonds between the –NH 2 groups and the carboxylato O atoms.

Successive Formation of Hydrido(germyl)platinum, Germaplatinacycle, and Germylene-Bridged Dinuclear Platinum Complexes from the Reaction of a Zerovalent Platinum Complex with α,ω-Dihydrodigermanes

The reaction of Pt(η2-C2H4)(PPh3)2 (1) with HPh2Ge(SiMe2)nGePh2H (2; n = 0−3) initially forms the hydrido(germyl)platinum complex cis-Pt(H)[GePh2(SiMe2)nGePh2H](PPh3)2 (3), followed by the generation of the cyclic bis(germyl)platinum complex (4) and finally formation of a dinuclear platinum complex with bridging diphenylgermyl ligands containing a Pt−Pt bond, [Pt(μ-GePh2)(PPh3)]2 (5). The structures of 4 (n = 2) and 5 were determined by X-ray crystallography.

C−Si Reductive Elimination from cis-Vinyl(silyl)platinum(II) Complexes

The complexes cis-Pt(CHCH2)(SiR3)(PMe2Ph)2 (SiR3 = SiPh3 (3a), Si(C6H4Me-p)3 (3b), Si(C6H4OMe-p)3 (3c), SiMePh2 (3d), SiFPh2 (3e)) have been prepared by the reactions of trans-PtCl(SiR3)(PMe2Ph)2 with Mg(CHCH2)2 in THF, followed by trans−cis isomerization of the resulting trans-alkenyl(silyl) complexes in solution promoted by CO. Complexes 3a−e undergo C−Si reductive elimination in toluene-d8 to give platinum(0) complexes coordinated with vinylsilanes. Kinetic data have suggested a direct reaction path without dissociation of the phosphine ligand.

Platinum Bis(tricyclohexylphosphine) Silyl Hydride Complexes

A series of platinum metal silyl hydride complexes, cis-Pt(PCy3)2(H)(SiR2R‘) (SiR2R‘ = SiPh2H, SiEt2H, SiPh3, SiEt3, SiMe2(OSiHMe2), Si(OSiMe3)2Me, SiMe2(CH2CHCH2), SiMe2Et, SiMe2[OCH2C(Me)CH2], Si(OMe)2(CH2CHCH2), SiPh2(OSiPh2H)), have been prepared in solution by reaction of Pt(PCy3)2 with the appropriate silane, HSiR2R‘. The complex cis-Pt(PCy3)2(H)(HSiPh2) (1-cis) has been characterized by X-ray crystallography at −100 °C. The platinum center exhibits a distorted-square-planar geometry with angles P(1)−Pt−P(2) = 113.55(3)°, P(1)−Pt−Si = 146.83(3)°, and P(2)−Pt−Si = 99.37(3)°. The reaction of Pt(PCy3)2 with chlorinated hydrosilanes at −78 °C yields the analogous complexes cis-Pt(PCy3)2(H)(SiR2R‘) (SiR2R‘ = SiMe2Cl, SiMeCl2, SiCl3), which isomerize to their trans isomers on warming to room temperature. The complex 1-cis and several analogues convert to the trans isomers photochemically at room temperature. Ready silane exchange is demonstrated by the reaction of HSiPh3 with cis-Pt(PCy3)2(D)(SiPh3) and b...

Synthesis and characterization of Ni-, Pd- and Pt-complexes of functionalized, tripodal phosphine ligands

The tripodal ether, ester and cyano functionalized phosphine ligands (tdppcymome) ( a), (tdppcyme) ( b), and (tdppcycn) ( c), respectively, of the cyclohexane backbone type cis,cis-1,3,5-(PPh 2) 3-1,3,5-(R) 3-C 6H 5 (tdppcyR) (with R=–CH 2OCH 3, –COOCH 3, –CN) are each treated with the cyclooctadiene complexes M(COD)Cl 2 ( 1, 2) (M=Pt, Pd) and NiCl 2 ( 3). The potentially tridentate ligands form with these transition metals four-coordinated, bidentate dichloro complexes cis-M II(η 2-tdppcyR)Cl 2 ( 1a– c, 2a– c, 3a– c), in which two diphenylphosphino donor groups are bound to the metal center, and one phosphorus remains uncoordinated. Treatment of the ether functionalized complex 1b with SnCl 2 a bimetallic platinum tin complex cis-Pt(tdppcyme)Cl(SnCl 3) ( 1e) is obtained. Detailed NMR investigations were undertaken to characterize structural properties. The platinum and palladium complexes have square-planar coordination geometries, whereas the nickel compounds show a different behavior with a temperature-dependent change from square-planar to tetrahedral arrangements. For Ni(tdppcyme)Cl 2 ( 3b) a single-crystal X-ray structure determination was performed which established the η 2-coordination of the phosphine ligand and the square-planar geometry of the nickel complex in the solid state. The cyclohexane backbone of the ligand prefers the boat conformation.

N,N-Diethylcarbamato tertiary phosphine complexes as precursors to carbonato and carbamoyl platinum(II) derivatives ‡

The complexes cis-Pt(O2CNEt2)2(PR3)2 (R = Ph, Et) and Pt(O2CNEt2)2(DPPE) [DPPE = 1,2-bis(diphenylphosphino)ethane] were prepared by the reaction of the corresponding phosphino-chloro complexes of platinum with Ag(O2CNEt2). The new N,N-diethylcarbamato complexes are excellent precursors for the high-yielding preparation of the corresponding carbonato derivatives Pt(CO3)(PR3)2 or Pt(CO3)(DPPE) by reaction with a stoichiometric amount of water. The carbamato complex cis-Pt(O2CNEt2)2(PPh3)2 reacts with CO producing the carbamoyl derivative cis-Pt[C(O)NEt2]2(PPh3)2. The chloro-carbamoyl complex, prepared by reacting cis-PtCl2(PPh3)2 with NHEt2 and CO, and recrystallized from toluene as the solvated species trans-PtCl[C(O)NEt2](PPh3)2·2 C6H5Me has been structurally characterized.

Mechanistic Study on the Insertion of Phenylacetylene into cis-Bis(silyl)platinum(II) Complexes

Four bis(silyl)platinum complexes cis-Pt(SiR3)2(PMe2Ph)2 (SiR3 = SiMe2Ph (1a), SiMePh2 (1b), SiPh3 (1c), SiFPh2 (1d)) have been prepared and their reactions with alkynes and alkenes examined. The X-ray structures of 1a−c exhibit significant distortion from the square planar geometry in the order 1b > 1c > 1a. Complexes 1a−d react with phenylacetylene in solution to give the corresponding insertion complexes cis-Pt{C(Ph)CH(SiR3)}(SiR3)(PMe2Ph)2 (2a−d). Complex 1c reacts also with acetylene to afford the insertion complex cis-Pt(CHCHSiPh3)(SiPh3)(PMe2Ph)2 (2e), whose structure has been determined by X-ray diffraction study. Kinetic studies indicate the insertion process involving prior dissociation of PMe2Ph ligand from 1, followed by insertion of phenylacetylene into the Pt−SiR3 bond. The reactivity toward insertion decreases in the order 1c > 1a > 1b ≫ 1d. Factors responsible for the reactivity order are discussed on the basis of kinetic data and X-ray structures.

Reactions of 1,2-diaminoethane-N,N,N′N′-tetra(N-methylacetamide), L, with potassium tetrachloroplatinate(II). Crystal and molecular structures of Pt(LH−2)Cl2·2H2O, a novel platinum(IV) complex containing deprotonated amide ligands, and of (2H+-L) [PtCl4

Abstract Reaction of 1,2-diaminoethane-N,N,N′,N′-tetra(N-methylacetamide), L, with potassium tetrachloroplatinate(II) in aqueous solution afforded the crystalline salt (2H+-L)[PtCl4] and the neutral platinum(IV) complex cis-Pt(LH−2)Cl2·2H2O. The crystal and molecular structure of the latter shows that the chloride ligands are cis, PtCl = 2.308(2) A, and that LH−2 is present as a tetradentate ligand coordinated through its two amino nitrogen atoms, PtN = 2.097(6) A, and two deprotonated amide nitrogens, PtN = 2.032(4) A which are trans to each other. This structure is the first of a platinum(IV) complex containing deprotonated amide ligands and may serve as a model for platinum(IV)-peptide/protein interactions. The fact that this complex is formed without any added oxidant other than air suggests that deprotonated amide groups facilitate the oxidation of platinum(II) to platinum(IV). The CN and CO bond distances in the coordinated, deprotonated amide groups are almost identical to those of the uncoordinated amide groups indicative of similar π electron delocalisation in the NCO groups in both cases. This is in contrast to the situation in a recently reported platinum(II)-amidate complex in which there is considerably greater π electron delocalisation than in the free amide. The crystal structure of (2H+-L)[PtCl4] is also reported, av. PtCl = 2.292 A. Crystal data: cis-Pt(LH−2C2·H2O, monoclinic space group P2/n, 1 = 11.764(4), b = 7.840(1), c = 11.829(3) A , β = 104.09(2)°, Z = 2 ; (2H+-L)[PtCl4], triclinic, space group P1, a = 9035(1), b = 9.316(1), c = 7.308(2) A , α = 100.88(1), β = 106.52(1), γ = 99.96(1)°, Z = 1 .

The new antitumor compound, cis-[Pt(NH 3) 2(4-methylpyridine) Cl]Cl, does not form N7,N7-d(GpG) chelates with DNA. An unexpected preference for platinum binding at the 5′G in d(GpG)

The reaction of the antitumor active agent cis-[Pt(NH 3) 2(4-mepy)Cl]Cl (4-mepy stands for 4-methyl-pyridine) with d(GpG) has been investigated by 1H magnetic resonance spectroscopy. Initially, two mononuclear complexes cis-Pt(NH 3) 2(4-mepy){d(GpG)-N7(1)} 1 and cis-Pt(NH 3) 2(4-mepy){d(GpG)-N7(2)} 2 are formed in an unexpected ratio 65:35, as determined by 1H NMR and enzymatic digestion techniques. Both products react further with a second equivalent of cis-[Pt(NH 3) 2(4-mepy)Cl]Cl forming the dinuclear platinum complex cis-Pt(NH 3) 2(4-mepy)] 2{μ-d(GpG)-N7(1),N7(2)} 3. With [Pt(dien)Cl]Cl and [Pt(NH 3) 3Cl]Cl similar complexes are formed. No evidence was found for the formation of chelates cis-Pt(NH 3)(4-mepy){d(GpG)-N7(1),N7(2)}, which would be formed upon ammonia release from the mononuclear complexes 1 and 2. Even addition of strong nucleophiles, like sodium diethyldithiocarbamate, thiourea, cysteine, or methionine, before or after reaction, do not induce the formation of a chelate. Under all conditions the N-donor ligands remain coordinated to Pt in 1, 2 and 3. In addition, the results of bacterial survival and mutagenesis experiments with E. coli strains show that the in vivo formation of bifunctional adducts in DNA, comparable to those induced by cis-Pt(NH 3) 2Cl 2, by treatment of cells with cis-[Pt(NH 3) 2(4-mepy)Cl]Cl is unlikely. Also, a mechanism of binding and intercalation is not supported by experimental data. All experiments suggest that the mechanism of action of this new class of antitumor agents must be different from that of cis-Pt(NH 3) 2Cl 2.

ChemInform Abstract: Syntheses and Chemical Properties of Platinum Blues

Since the first report in 1908, a class of platinum compounds called “platinum blues” have attracted interests of chemists because of their unusual dark blue color. However, because of the difficulty in isolating and crystallizing the complexes, their formulas and structures have been left unclarified till a decade ago. About ten years ago when it turned out that the famous anti-tumor complex cis-Pt (NH3) 2CL2 effects its activity by binding to DNA and obstructing the DNA duplication, a study regarding the coordination reaction of cis-Pt (NH3) 2Cl2 with pyrimidine bases started and the platinum pyrimidine blues found in the study again aroused interest of chemists. In the course of intensive studies, the first crystal structure determination of platinum blue was carried out for a compound with α-pyridone as a pyrimidine model and the tetranuclear 5+ mixed-valent chain structure of [Pt4 (NH3) 8 (C5H4NO) 4] was revealed.In the present article, syntheses, structures and chemical properties of platinum blues and several other related multinuclear platinum complexes containing hetero metal atoms are surveyed with an emphasis on the specific nature of amidate ligands that stabilize unusually high oxidation state of metals.

Displacement of norbornadiene (NBD) from Pt(CF 3) 2(NBD) by weak donor ligands L, and reactions of cis-Pt(CF 3) 2L 2 with water and acids

The NBD ligand in Pt(CF 3) 2(NBD) has been replaced under mild conditions by a number of neutral S-, N-, and O-donor ligands to form cis-Pt(CF 3) 2L 2 complexes (L 2 = N, N, N′, N′-tetramethylethylenediamine (tmen), bipyridine (bipy), ethylenediamine (en); L = pyridine (py), NH 3, dimethylsulfoxide (DMSO), CH 3CN, C 6H 5CN, N, N-dimethylformamide (DMF)). Reaction with DMSO produces predominantly the isomer cis-Pt(CF 3) 2(DMSO- S)(DMSO- O), with cis-Pt(CF 3) 2(DMSO- S) 2 a minor component, as a result of steric constraints. Water or methanol attacks the CF 3 groups, producing fluoride ion. The fluorine atoms of cis-Pt(CF 3) 2L 2 (L 2 = bipy, tmen; L = py) are susceptible to electrophilic attack by H +. Reaction with aqueous HCl or HClO 4 converts one CF 3 group into a coordinated CO group. With HCl, simultaneous protonation and displacement of the N-donor ligands occurred, yielding cis-Pt(CF 3)(CO)Cl 2 −. With HClO 4, the complexes cis-Pt(CF 3)(CO)L 2 + are initially generated, with subsequent displacement of the tmen and py (but not bipy) ligands to form cis-Pt(CF 3)(CO)(OH 2) 2 +. The remaining CF 3 group is not attacked by H +. Reaction of Pt(CF 3) 2(NBD) with halide ions in acetone initially produced the binuclear complexes [(CF 3) 2Pt(μ-X) 2Pt(CF 3) 2] 2− (X = I, Cl) containing bridging halide. With larger amounts of halide ion the expected cis-Pt(CF 3) 2X 2 2− complexes were not obtained, and instead cis-Pt(CF 3)(CO)X 2 − and fluoride ion were formed. When the complexes [(CF 3) 2Pt(μ-X) 2Pt(CF 3) 2] 2− were kept in the presence of NBD, cis-Pt(CF 3)(CO)X 2 − and Pt(CF 3) 2(NBD) were formed. When X = I, these two complexes then reacted together to yield cis-Pt(CF 3) 2I(CO) − and Pt(CF 3)I(NBD).