Letter

Elding, Lars Ivar; Romeo, Raffaello; Schmülling, Michael; Ryabov, Alexander D.; Eldik, Rudi van

doi:10.1039/dt9960001471

Cited by 14 publications

(7 citation statements)

References 12 publications

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“…Previous rationalizations 6-8,22 of the high reactivity of cyclometalated complexes in terms of back-bonding to the in-plane aryl ligands do not seem necessary. As pointed out elsewhere, there is no inherent difference with regard to the trans -labilizing ability between the cyclometalated complexes and other platinum complexes with strong platinum−carbon σ-bonds.…”

Section: Discussionmentioning

confidence: 68%

“…Organomet responsible for the reactivity differences observed between some related cyclometalated and bis(phosphine) complexes. 21,22 Experimental Section General Procedures and Chemicals. Reactions involving lithium or Grignard reagents were carried out in dried glass under nitrogen or argon in solvents dried with activated molecular sieves.…”

Section: Introductionmentioning

confidence: 99%

“…To investigate the effect of exchanging the π-accepting phosphines in [Pt(R)Cl(PEt 3 ) 2 ] for thioethers we have synthesized a number of complexes of the type [Pt(R)Cl(SR‘ 2 ) 2 ], where R = phenyl, mesityl, or p -anisyl and R‘ = methyl or ethyl, and investigated the relation between their ground-state structures as observed in the solid state and their reactivity toward nucleophiles in methanol solution. One aim of the present study was to contribute to a better understanding of the factors responsible for the reactivity differences observed between some related cyclometalated and bis(phosphine) complexes. , …”

Section: Introductionmentioning

confidence: 99%

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Synthesis, Structure, and Reactivity of Arylchlorobis(dialkyl sulfide)platinum(II) Complexes

et al. 1997

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Complexes trans-[PtRCl(SR'(2))(2)], where R = Ph, mesityl, and p-anisyl and R' = Me or Et, have been synthesized and their crystal and molecular structures determined. Crystals of trans-[PtPhCl(SEt(2))(2)] (2) are triclinic (P&onemacr;) with a = 10.112(6) Å, b = 13.158(2) Å, c = 14.714(5) Å, alpha = 102.48(2) degrees, beta = 94.394(4) degrees, gamma = 90.22(3) degrees, and Z = 4. Crystals of trans-[Pt(mesityl)Cl(SMe(2))(2)] (4) are monoclinic (P2(1)/c) with a = 13.158(2) Å, b = 9.170(1) Å, c = 16.013(3) Å, beta = 120.93(2) degrees, and Z = 4, and crystals of [Pt(p-anisyl)Cl(SMe(2))(2)] (5) are monoclinic (P2(1)/n) with a = 9.879(4) Å, b = 8.128(2) Å, c = 19.460(5) Å, beta = 96.56(3) degrees, and Z = 4. All complexes are square-planar, featuring Pt-Cl distances between 2.40 and 2.42 Å, indicating a large ground-state trans influence of the aryl group. The coordination geometry is maintained in methanol and chloroform solution as shown by (1)H-NMR spectra. The kinetics of substitution of the labile chloride trans to aryl by various nucleophiles has been studied in methanol by variable-temperature and -pressure stopped-flow spectrophotometry. A two-term rate law with a well-developed solvolytic pathway is followed. Negative entropies and volumes of activation indicate an associative mode of activation in all cases, independent of steric blocking of the axial sites and a large Pt-Cl ground-state bond-weakening. Comparison of the reaction rates of the present series of complexes with their bis(phosphine) analogues and with related cyclometalated compounds shows that the triethylphosphine complexes are 2-3 orders of magnitude less reactive than the thioether complexes, which in turn are a factor 10-20 less reactive than the cyclometalated ones. This reactivity increase can be rationalized mainly in terms of a decrease in steric hindrance in the series. There seems to be no inherent differences with regard to trans labilizing ability of the aryl ligands in the various types of complexes, including the cyclometalated ones.

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Section: Discussionmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Synthesis, Structure, and Reactivity of Arylchlorobis(dialkyl sulfide)platinum(II) Complexes

et al. 1997

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“…This is what we believe we observe when we use the mild conditions of a CO atmosphere with a room-temperature solution of the chloride-bridged dimers 4 and 6 to form 9t and 11t . (Quite how large this trans effect is in cyclometalated complexes has been the subject of some debate recently, ,− and we do not propose to discuss it further here.) However, it is apparent from our modeling studies (see later) that these isomers (the kinetic products) with the CO cis to the N are unfavorable with respect to those with the chloride cis to the N (the thermodynamic products).…”

Section: Resultsmentioning

confidence: 91%

C−H Activation Induced by Water. Monocyclometalated to Dicyclometalated: C∧N∧C Tridentate Platinum Complexes

et al. 2000

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Metalation of 2,6-diphenylpyridine (1) by potassium tetrachloroplatinate in acetic acid gives a monocyclometalated chloride-bridged dimer 4. This dimer is split with CO to give a kinetic product 9t with the incoming CO trans to the orthometalated carbon. The kinetic product of cleavage is shown to be 16 kJ mol -1 higher in energy than the thermodynamic product 9c, which has the CO trans to the pyridine nitrogen. The isomerization of 9t to 9c is shown not to take place via an associative mechanism and, with analogue 11, is effectively suppressed when excess chloride is added, implying that it takes place via a chloride dissociation. The monocyclometalated 9 undergoes a second cyclometalation to give the C∧N∧C dicyclometalated complex 15 in high yield. This second cyclometalation is brought about by the simple expedient of adding water to the monocyclometalated precursor. The addition of water is rationalized on the basis of needing to ionize the HCl byproduct of the reaction. Using a substituted pyridine (5) analogous chemistry is observed. Single-crystal X-ray structures of one of the intermediates (6) and one of the final products (15) have been solved. Density functional theory calculations are used to rationalize the isomerizations of the monocyclometalated intermediates and the need to ionize HCl in the second cyclometalation.

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“…The binding of ORGANObisPt was considerably faster than that of both 1,1/c,c and cisplatin. The high rate of substitution of chloride (or water) ligands, which are trans to the methyl group in the ORGANObisPt molecules, with the nitrogen donor atoms of the guanine residues in DNA is consistent with high translabilizing eect of a platinum-carbon r-bond [33]. Overall alterations in DNA conformation induced by global modi®cation by ORGANObisPt evaluated in the present work were dierent from those induced by 1, 1/c,c [8] or cisplatin [31,32].…”

Section: Discussionmentioning

confidence: 59%

Biophysical analysis of natural, double-helical DNA modified by a dinuclear platinum(II) organometallic compound in a cell-free medium

et al. 2002

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Modifications of natural DNA by the dinuclear platinum(II) organometallic complex [[Pt(Me)Cl(Me(2)SO)](2)(mu-N-N)] [where N-N=H(2)N(CH(2))(6)NH(2)] (ORGANObisPt) were studied by methods of molecular biophysics. These methods include DNA binding studies using atomic absorption spectrophotometry, HPLC analysis of enzymatically digested DNA, interstrand cross-linking employing gel electrophoresis under denaturing conditions, DNA unwinding studied by gel electrophoresis, mapping of DNA adducts by transcription assay, DNA melting curves measured by absorption spectrophotometry and conformational analysis of platinated DNA by differential pulse polarography. The results indicate that the complex ORGANObisPt binds irreversibly to DNA. Its DNA binding mode is, however, different from that of the formally equivalent [[cis-PtCl(NH(3))(2)](2)(mu-N-N)] (1,1/c,c), which exhibits antitumor activity including that in the tumor cells resistant to cisplatin. Interestingly, ORGANObisPt binds to DNA considerably faster than 1,1/c,c and cisplatin. In addition, when ORGANObisPt binds to DNA it exhibits a strong base sequence specificity to guanine residues. ORGANObisPt forms mainly monofunctional adducts on double-helical DNA. It forms also a small amount of DNA interstrand cross-links (approximately 2%), i.e. a radically smaller amount in comparison with the complex 1,1/c,c. Importantly, these interstrand cross-links of ORGANObisPt are capable of terminating RNA synthesis in vitro, while its major monofunctional adducts are not. In addition, the adducts of ORGANObisPt affect the conformation of DNA, but in a different way than its dinuclear analogue 1,1/c,c or cisplatin. Some structural features of ORGANObisPt, such as the charge or nature of the trans and cis activating groups relative to the labile chloride, might be responsible for the altered DNA binding mode and biological activity in comparison with the 1,1/c,c compound.

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Letter

Cited by 14 publications

References 12 publications

Synthesis, Structure, and Reactivity of Arylchlorobis(dialkyl sulfide)platinum(II) Complexes

Synthesis, Structure, and Reactivity of Arylchlorobis(dialkyl sulfide)platinum(II) Complexes

C−H Activation Induced by Water. Monocyclometalated to Dicyclometalated: C∧N∧C Tridentate Platinum Complexes

Biophysical analysis of natural, double-helical DNA modified by a dinuclear platinum(II) organometallic compound in a cell-free medium

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