The platinum–ethylene binding energy in Pt(PL 3 ) 2 (C 2 H 4 )

New platinum-oxicam complexes as anti-cancer drugs. Synthesis, characterization, release studies from smart hydrogels, evaluation of reactivity with selected proteins and cytotoxic activity in vitro

The reaction of aqueous cis-[Pt(NH(3))(2)(H(2)O)(2)](NO(3))(2) with Na(+)HMEL(-) (H(2)MEL, meloxicam, 4-hydroxy-2-methyl-N-(5-methyl-1,3-thiazol-2-yl)-2H-1,2-benzothiazine-3-carboxamide-1,1-dioxide), and Na(+)HISO(-) (H(2)ISO, isoxicam, 4-hydroxy-2-methyl-N-(5-methylisoxazol-3-yl)-2H-1,2-benzothiazine-3-carboxamide-1,1-dioxide) at pH 7 produced micro-crystalline cis-[Pt(NH(3))(2)(N(1')-HMEL)(2)], 5 and cis-[Pt(NH(3))(2)(N(1')-HISO)(2)], 6. The X-ray diffraction structure of 5 shows two HMEL(-) anions donating through the thiazole nitrogen atoms and adopting a head-to-tail (HT) conformation. The (1)H NMR spectrum for 5 from DMSO-d(6) shows inertness of the complex up to at least 24h. Delivery studies for 5 and 6 from vinyl hydrogel based on L-phenylalanine (pH 6.5, 25 degrees C) show that concentrations of complexes ranging between 2.5 and 5 microM can be reached after a day. Compounds 5 and 6 show strong anti-proliferative effects on CH1 cells (ovarian carcinoma, human) in vitro, IC(50) values being 0.60 and 0.37 microM, respectively (0.16 microM for reference, cis-diamminodichloridoplatinum(II), cisplatin). ESI-MS measurements clearly documented that both 5 and 6 form adducts with the three model proteins ubiquitin (UBI), cytochrome c (CYT C) and superoxide dismutase (SOD), the HISO(-) complex being significantly more effective than the HMEL(-) one. Density functional methods help in finding rationale for the easiest dissociation of Pt-H(2)ISO/HISO bonds when compared to the Pt-N(1)(')-H(2)MEL/N(1)(')-HMEL linkages.

The platinum-olefin binding energy in series of (PH3)2Pt(olefin) complexes - a theoretical study

Theoretical investigation of Pt(0)-olefin organometallic complexes containing tertiary phosphine ligands was focused on the strength of platinum-olefin electronic interaction. DFT theoretical study of electronic effects in a substantial number of ethylene derivatives was evaluated in terms of the Pt-olefin binding energy using MP2 correlation theory. Organometallics bearing coordinated olefins with general formula (R1R2C = CR3R4)Pt(PH3)2 [R = various substituents] had been selected, including olefins containing both electron-donor substituents as well as electron-withdrawing groups. The stability of the corresponding complexes increases with a strengthening electron-withdrawal ability of the olefin substituents.

Theoretical Study of M(PH3)2 Complexes of C60, Corannulene (C20H10), and Sumanene (C21H12) (M = Pd or Pt). Unexpectedly Large Binding Energy of M(PH3)2(C60)

DFT and MP2 to MP4(SDQ) methods were applied to M(PH3)2(C60), Pt(PH3)2(C20H10), and Pt(PH3)2(C21H12) (M = Pd or Pt, C20H10 = corannulene, and C21H12 = sumanene). The binding energy considerably fluctuates around MP2 and MP3 levels but much less upon going from MP3 to MP4(SDQ) in Pt(PH3)2(C2H4), Pt(PH3)2(C20H10), and Pt(PH3)2(C21H12). Also, the MP4(SDQ) method presents a binding energy similar to that of the CCSD(T) method in Pt(PH3)2(C2H4). Thus, it is likely that the MP4(SDQ) method is useful to evaluate binding energies of these complexes. The binding energies of Pt(PH3)2(C20H10) and Pt(PH3)2(C21H12) are evaluated to be 24.9 and 26.1 kcal/mol, respectively, by the MP4(SDQ) method and only +5.8 and -2.6 kcal/mol, respectively, by the DFT(B3LYP) method. These MP4(SDQ)-calculated binding energies of Pt(PH3)2(C20H10) and Pt(PH3)2(C21H12) are similar to that of Pt(PH3)2(C2H4), which strongly suggests that these complexes can be successfully synthesized. The binding energy of Pt(PH3)2(C60) is evaluated to be 44.8 and 45.5 kcal/mol with the ONIOM(MP4(SDQ):UFF) and ONIOM(MP4(SDQ):B3LYP) methods, respectively, and that of the Pd analogue is evaluated to be 39.9 kcal/mol with the ONIOM(MP4(SDQ):UFF) method, whereas the DFT(B3LYP), DFT(BVP86), and DFT(BPW91) methods provide much smaller binding energies. It is noted that these binding energies are much larger than those of the ethylene, corannulene, and sumanene analogues. This difference is reasonably interpreted in terms that the LUMO of C60 is at much lower energy than those of ethylene, corannulene, and sumanene. We investigated also how to separate the high level and the low level regions in the ONIOM calculation of M(PH3)2(C60) and proposed here the reasonable way to evaluate the binding energy of transition-metal complexes of C60.

Oxidative addition of the imidazolium cation to zerovalent Ni, Pd, and Pt: a combined density functional and experimental study

Oxidative addition of different imidazolium cations to zerovalent group 10 metals, to afford heterocyclic carbene complexes, has been investigated by both density functional theory (DFT) and experimental studies. The theoretical analysis shows that addition of imidazoliums to Pt(0) and Ni(0) is more exothermic than to Pd(0), and Ni(0) is predicted to react with a much lower barrier than either Pt(0) or Pd(0). Strongly basic supporting ligands on the metal, as well as cis-chelating ligands, increase the exothermicity of the reaction and also lower the activation barrier. The addition of 2-H imidazoliums is easier and more exothermic than addition of 2-alkylimidazoliums, and a halo-imidazolium is expected to further lower the barrier to oxidative addition and increase the exothermicity. The DFT results show that all three of the metals should be able to oxidatively add imidazolium cations under appropriate conditions. Experimental studies confirmed that oxidative addition is possible, and a number of Pt- and Pd-carbene complexes were prepared via oxidative addition of imidazolium salts to M(0) precursors. Most significantly, oxidative addition of 2-H azolium salts was found to readily occur, and the reaction of 1,3-dimethylimidazolium tetrafluoroborate with Pt(PPh(3))(2) and Pt(PCy(3))(2) affords [PtH(dmiy)(PPh(3))(2)]BF(4) (10) and [PtH(dmiy)(PCy(3))(2)]BF(4) (11), while reaction between 3,4-dimethylthiazolium tetrafluoroborate and Pt(PCy(3))(2) yields [PtH(dmty)(PCy(3))(2)]BF(4) (12) (dmiy = 1,3-dimethylimidazolin-2-ylidene, dmty = 3,4-dimethylthiazolin-2-ylidene). Addition of 2-iodo-1,3,4,5-tetramethylimidazolium tetrafluoroborate to Pt(PPh(3))(4) or Pd(dcype)(dba) yields [PtI(tmiy)(PPh(3))(2)]BF(4) (9) and [PdI(tmiy)(dcype)]BF(4) (14), respectively (tmiy = 1,3,4,5-tetramethylimidazolin-2-ylidene, dcype = 1,3-bis(dicyclohexylphosphino)ethane)). X-ray crystal structures are reported for complexes 9 and 11 (cis and trans). These studies clearly show for the first time that oxidative addition of imidazolium and thiazolium cations is possible, and the results are discussed in terms of the ramifications for catalysis in imidazolium-based ionic liquids with both carbene-based and non-carbene-based complexes.