Synthesis and structural characterization of two novel heterometallic clusters: [Rh4Pt2(CO)11(dppm)2] and [Ru2Rh2Pt2(CO)12(dppm)2

Two novel heterometallic octahedral clusters [Rh(4)Pt(2)(CO)(11)(dppm)(2)](1) and [Ru(2)Rh(2)Pt(2)(CO)(12)(dppm)(2)](2) were synthesized by the reaction of [Rh(2)Pt(2)(CO)(6)(dppm)(2)] with [Rh(6)(CO)(14)(NCMe)(2)] and Ru(3)(CO)(12), respectively. Solid state structures of 1 and 2 have been established by a single crystal X-ray diffraction study. Two dppm ligands in 1 are bonded to one platinum and three rhodium atoms, which form an equatorial plane of the Rh(4)Pt(2) octahedron. Two rhodium and two platinum atoms bound to the diphosphine ligands in 2 are nonplanar to give an octahedral C2 symmetric Ru(2)Rh(2)Pt(2)(dppm)2 framework. The (31)P NMR investigation of and (1D, (31)P COSY, (31)P-[(103)Rh] HMQC) and simulation of 1D spectral patterns showed that in both clusters the structures of the M(6)(PP)(2) fragments found in the solid state are maintained in solution.     

Bimetallic clusters of iron with palladium and platinum. Synthesis and structures of Fe2(CO)9[M(PBu(t)3)]2 (M = Pd or Pt) and Fe2(CO)8[Pt(PBu(t)3)]2(mu-H)2

The reaction of Fe2(CO)9 with Pd(PBu(t)3)2 and Pt(PBu(t)3)2 yielded the Fe-Pd and Fe-Pt cluster complexes Fe2(CO)9[M(PBu(t)3)]2, M = Pd (8) or Pt (9). The structures of 8 and 9 are analogous and consist of nearly planar butterfly clusters of two palladium/platinum atoms in the wing-tip positions and two mutually bonded iron atoms, Fe-Fe = 2.9582(11) A in 8 and 2.9100 (9) A in 9. Compound 8 decomposes to form the mononuclear iron compound Fe(CO)4(PBu(t)3) (11) when heated at 68 degrees C. The reaction of Pt(PBu(t)3)2 with Fe2(CO)9 in the presence of hydrogen at 127 degrees C yielded the dihydrido complex Fe2(CO)8[Pt(PBu(t)3)]2(mu-H)2 (10). Compound 10 contains a closed Fe2Pt2 tetrahedral cluster with hydrido ligands bridging two of the Fe-Pt bonds. Compounds 8, 9, and 10 were structurally characterized crystallographically.     

Ethylenebis(triphenylphosphine)platinum as a probe for niobium-mediated diphosphorus chemistry

Ethylenebis(triphenylphosphine)platinum is used as a trap for the P2-containing molecule W(CO)5(P2), which is eliminated at room temperature from a niobium-complexed diphosphaazide ligand. The rate of W(CO)5(P2) elimination is unaffected by the presence of the platinum species. Attempts to generate and trap free P2 with the platinum ethylene complex were hindered by the direct reaction between the platinum starting material and the P2 generator, (Mes*NPP)Nb(N[Np]Ar)3. In this case, reductive cleavage of the P-P bond in the diphosphaazide ligand is induced by platinum coordination, resulting in the formation of a trimetallic system with two bridging, three-coordinate phosphorus atoms.     

STRUCTURE OF PLATINUM HYDRIDE WITH BULKY PHOSPHINE LIGANDS trans-PtH (PCy_3)_2 {S_2CN (CH_2C_6H_5)_2}

<正> trans-PtH(PCy3)2[S2CN(CH2C6H5)2] crystallizes in triclinic space group P1 with a=10. 961 (9),b= 13. 247 (6), c= 18. 331(4) A ,α=82. 97(2) ,β= 103. 89(5),γ=103. 79(7)°,Mr=1029. 39,V = 2503(4)A3,Z = 2,Dc = 1. 366g/cm3, μ= 30. 06cm-1,F(000) = 1068,R=0. 033 and Rw = 0. 039 for 6940 unique observed reflections. The platinum atom is coordinated by one hydrogen,one sulfur and two phosphorus atoms to form a distorted square plane.     

Initial nucleation of platinum clusters after reduction of K(2)PtCl(4) in aqueous solution: a first principles study

The initial nucleation of platinum clusters after the reduction of K(2)PtCl(4) in aqueous solution is studied by means of first principles molecular dynamics simulations. A reaction mechanism leading to a Pt dimer is revealed both by gas-phase simulations and by simulations which model the solution environment. The key step of the observed reaction process is the formation of a Pt-Pt bond between a Pt(I) complex and an unreduced Pt(II) complex. In light of this result, we discuss the reduction process leading to the formation of platinum nanoparticles. In the generally accepted model, the nucleation of Pt particles starts only when a critical concentration of Pt(0) atoms is reached. Here, we discuss a complementary mechanism where metal-metal bonds form between Pt complexes in higher oxidation states. This is consistent with a number of experimental results which show that a high concentration of zerovalent atoms is not necessary to start the nucleation.     

Organoplatinum(II) complexes containing chelating or bridging bis(N-heterocyclic carbene) ligands: formation of a platinum(II) carbonate complex by aerial CO2 fixation

The preparation of two new bis(N-heterocyclic carbene) platinum(II) complexes, in which NHC rings are joined by a CH(2) linker group, is described. While, the chelate complex [PtMe(2)(bis-NHC1)], 1, was formed with large tert-butyl wingtips, the iso-propyl N-substituent analogue favors formation of the cluster complex [Pt(2)Me(4)(μ-SMe(2))(μ-bis-NHC2)](2)(μ-Ag(2)Br(2)), 2, in which two binuclear platinum(II) complexes are linked together by an Ag(2)Br(2) unit. The chelating platinum complex 1 undergoes aerial CO(2) fixation and forms platinum(II) carbonate complex [Pt(CO(3))(bis-NHC1)], 3.     

Synthesis, characterization, and electronic structures of a series of two-dimensional trimetallic cluster complexes, Ru3(CO)9(mu-SnPh2)3[Pt(PBu(t)3)]x, x = 0-3

The triruthenium-tritin cluster complex, Ru3(CO)9(mu-SnPh2)3, 13 was obtained from the reaction of Ru3(CO)12 with Ph3SnH. Compound 13 reacts with Pt(PBut3)2 to yield three new Pt(PBut3) adducts of 13 Ru3(CO)9(mu-SnPh2)3[Pt(PBut3)]x, 14-16 x = 1 - 3 formed by the addition of Pt(PBut3) groups to the Ru-Sn bonds. The new complexes form a novel series of trimetallic complexes having planar arrangements of the metal atoms. The UV-vis absorptions of the four complexes shift progressively to longer wavelengths as the number of platinum atoms is added to the cluster. The electronic structures of these complexes have been investigated in the ground and excited states by density functional theory and time-dependent density functional theory, and this has provided a detailed understanding of the metal-metal bonding and electronic transitions that are responsible for their UV-vis absorption properties. The predicted absorption maximum for the model structures for 13, 14, 15, and 16 at 465, 508, 556, and 585 nm differ only 4-18 nm from the experimental values of 474, 490, 552, and 576 nm. The shift of principal UV-vis absorption can be explained by a lowering of the HOMO-LUMO energy gap due to interactions of the platinum atoms with the HOMO and LUMO of the Ru3Sn3 core.     

Bis(μ‐pyridine‐2‐thiol­ato)‐κ4S:N;N:S‐bis­[(pyridine‐2‐thiol­ato‐κS)(2‐pyridyl­phen­yl‐κ2N,C2)platinum(III)](Pt—Pt): the non‐solvated and acetonitrile‐solvated forms

The title dinuclear platinum(III) complex, [Pt₂(C₁₁H₈N)₂(C₅H₄NS)₄], forms two crystal structures, viz. the non‐solvated and acetonitrile‐solvated (C₂H₃N) forms. For both forms, two (2‐pyridylphenyl)platinum units are bridged by two pyridine‐2‐thiol­ate (pyt) anions in a head‐to‐tail configuration, and the other two pyridine‐2‐thiol­ate anions occupy the axial position, coordinated through their S atoms. The most remarkable difference between the two forms is the orientation of the axial monodentate ligands. Those for the solvated form are located over the 2‐pyridylphenyl ligands, being related by a twofold axis which lies through the centre of the Pt—Pt bond, while the axial pyt ligands for the non‐solvated form are oriented irregularly, which is attributable to the dimeric arrangement in the crystal.     

Electronic structure and chain-length effects in diplatinum polyynediyl complexes trans,trans-[(X)(R3P)2Pt(C triple bond C)(n)Pt(PR3)2(X)]: a computational investigation

Structure and bonding in the title complexes are studied using model compounds trans,trans-[(C6H5)(H3P)2Pt(C triple bond C)(n)Pt(PH3)2(C6H5)] (PtCxPt; x = 2n = 4-26) at the B3LYP/LACVP* level of density functional theory. Conformations in which the platinum square planes are parallel are very slightly more stable than those in which they are perpendicular (DeltaE = 0.12 kcal mol(-1) for PtC8Pt). As the carbon-chain length increases, progressively longer C triple bond C triple bonds and shorter triple bond C-C triple bond single bonds are found. Whereas the triple bonds in HCxH become longer (and the single bonds shorter) as the interior of the chain is approached, the PtC triple bond C triple bonds in PtCxPt are longer than the neighboring triple bond. Also, the Pt-C bonds are shorter at longer chain lengths, but not the H-C bonds. Accordingly, natural bond orbital charge distributions show that the platinum atoms become more positively charged, and the carbon chain more negatively charged, as the chain is lengthened. Furthermore, the negative charge is localized at the two terminal C triple bond C atoms, elongating this triple bond. Charge decomposition analyses show no significant d-pi* backbonding. The HOMOs of PtCxPt can be viewed as antibonding combinations of the highest occupied pi orbital of the sp-carbon chain and filled in-plane platinum d orbitals. The platinum character is roughly proportional to the Pt/Cx/Pt composition (e.g., x = 4, 31 %; x = 20, 6 %). The HOMO and LUMO energies monotonically decrease with chain length, the latter somewhat more rapidly so that the HOMO-LUMO gap also decreases. In contrast, the HOMO energies of HCxH increase with chain length; the origin of this dichotomy is analyzed. The electronic spectra of PtC4Pt to PtC10Pt are simulated. These consist of two pi-pi* bands that redshift with increasing chain length and are closely paralleled by real systems. A finite HOMO-LUMO gap is predicted for PtCinfinityPt. The structures of PtCxPt are not strictly linear (average bond angles 179.7 degrees -178.8 degrees ), and the carbon chains give low-frequency fundamental vibrations (x = 4, 146 cm(-1); x = 26, 4 cm(-1)). When the bond angles in PtC12Pt are constrained to 174 degrees in a bow conformation, similar to a crystal structure, the energy increase is only 2 kcal mol(-1). The above conclusions should extrapolate to (C triple bond C)(n) systems with other metal endgroups.     

配合物Cu_2（C_（21）H_（20）N_2O_3）（CH_3COO）_2的EXAFS研究

用延伸Ｘ射线吸收精细结构（ＥＸＡＦＳ），测定了标题化合物中两个铜原子的配位结构。两个铜原子有相同的配位，确认每个铜原子均与一个氮原子，三个氧原子形成四配位结构。一氧一氮源于ＨＳＢ，而另两个氧由乙酸提供。     

Zum nukleophilen Abbau von Tris(pentasulfido)platinat(IV), [Pt(S5)3]2−, und Bis(pentasulfido)platinat(II),[Pt(S5)2]2−

On the Nucleophilic Degradation of Tris(pentasulfido)platinum(IV), [Pt(S₅)₃]^2?, and Bis(pentasulfido)platinum(II), [Pt(S₅)₂]^2? The behaviour of [Pt(S₅)₃]^2?, ( I ), towards sulfite, arsenite, sulfide, hydroxide, and triphenylphosphine has been studied qualitatively and quantitatively. With stoichiometric amounts of nucleophile one ring is degraded; the reaction product [Pt(S₅)₂]^2?, ( II ), can be isolated. With excess of nucleophile all sulfur atoms are taken off from the platinum; with triphenylphosphine, however, (PPh₃)₂PtS₄, ( III ), is formed. A mechanistic interpretation of the course of the reaction is given and supported by kinetic studies.     

Novel platinum(II) ammine hydroxamate and hydroximate complexes and the platinum-assisted hydrolysis of hydroxamic acids

The 2-pyridinecarboxylate (2-pyca) platinum(IV) complex [2-pycaH2][PtCl4(2-pyca)].H2O, 1, has been synthesised from K2[PtCl4] following the hydrolysis of 2-pyridinehydroxamic acid (2-pyhaH) in the presence of H2O2, and directly from K2[PtCl6] and picolinic acid. Structural characterisation of 1 reveals octahedral geometry about platinum(IV) consisting of a (N,O)-bidentate pyridinecarboxylate ligand and four chloride ligands. A mechanism for the hydrolysis of 2-pyridinehydroxamic acid to 2-pyridinecarboxylic acid is proposed. Two novel coordination modes of hydroxamic acids to platinum(II) are also reported. The dinuclear platinum ammine hydroximato complex, [{cis-Pt(NH3)2}2(mu-2-pyhaH(-1))](ClO4)2.H2O, 3, has been synthesised where the two platinum(II) centres are bridged via(O,O) and (N,N) coordination. The latter coordination mode is via the hydroximate nitrogen and the pyridine nitrogen. The corresponding mononuclear platinum(II) pyridinehydroxamate complex, [cis-Pt(NH3)2(2-pyha)]ClO4, 4, has been synthesised. Spectroscopic studies indicate that the coordination mode is through the pyridine nitrogen and hydroxamate oxygen atoms (N,O).     

X-ray structures of the first platinum complexes with Z configuration iminoether ligands: trans-dichlorobis(1-imino-1-methoxy-2,2'-dimethylpropane)platinum(II) and trans-tetrachlorobis(1-imino-1-methoxy-2,2'-dimethylpropane)platinum(IV)

Platinum complexes with Z configuration iminoether ligands (trans-[PtCl(2)(HN=C(OMe)Bu(t))(2)], 1, and trans-[PtCl(4)(HN=C(OMe)Bu(t))(2)], 2) have been structurally characterized for the first time. The nearly planar Pt-N-C-O-C chain, all atoms being in gauche conformation, brings the terminal Pt and C atoms very close to one another. The steric clash is released by considerably increasing the Pt-N-C, N-C-O, and C-O-C bond angles (133, 124, and 121 degrees for 1, respectively; 147, 129, and 127 degrees for 2, respectively), which are well above the expected values (120 degrees for Pt-N-C and N-C-O; less than 120 degrees for C-O-C owing to the repulsive effect exerted by the lone pair of electrons on the oxygen atom). In the platinum(II) case the smaller increase of bond angles is accompanied by a greater value of the Pt-N-C-O torsion angle (27.3 and 15.6 degrees for 1 and 2, respectively). The stabilization of the Z configuration, notwithstanding the steric clashes described above, has been achieved by a careful choice of the R substituent in the iminoether moiety (a bulky tert-butyl group). The reactions of the platinum(IV) species (2) in basic and acidic conditions and with triphenylphosphine have been investigated. Bases and acids both interact with the coordinated ligand in such a way to weaken the coordinative bond and promote the release of the iminoether ligands. The phosphine promotes a ready and complete reduction of the platinum(IV) complex to the corresponding platinum(II) species (1). Compound 1 reacts with a stoichiometric amount of phosphine (1:1 molar ratio) to form cis-[PtCl(2)(PPh(3))(Z-HN=C(OMe)Bu(t))] and with excess phosphine to form [PtCl(2)(PPh(3))(2)] and free iminoether. The latter two reactions leading to formation of a mixed phosphine/iminoether platinum species and to free iminoether, which can be used as a synthon for further organic transformations, can be of synthetic utility.     

Effect of amine ligand bulk on the interaction of methionine with platinum(II) diamine complexes

Molecular mechanics and dynamics calculations have been used in conjunction with experimental data to study the effects of amine ligand bulk on the formation of both guanine and methionine complexes with platinum diamine compounds. The AMBER force field has been supplemented with previous modifications [Yao; et al. Inorg. Chem. 1994, 33, 6061-6077. Cerasino; et al. Inorg. Chem. 1997, 36, 6070-6079] and has been further modified to include parameters for platinum bound to the sulfur atom of methionine. Molecular mechanics calculations with this modified AMBER force field have suggested that a platinum complex with two sulfur-bound methionine ligands and a bulky diamine ligand (N,N,N',N'-tetramethylethylenediamine, Me(4)en) would have severe interligand clashes; such interligand clashes are less pronounced in bis(9-ethylguanine) complexes. Consistent with these observations, NMR studies with [Pt(Me(4)en)(D(2)O)(2)](2+) have indicated that guanine 5'-monophosphate reacts in a 2:1 guanine:platinum ratio while both methionine and N-acetylmethionine react with only a 1:1 stoichiometry. Methionine forms a chelate via the sulfur and nitrogen atoms whereas N-acetylmethionine forms a chelate via the sulfur and oxygen atoms. The oxygen of the latter chelate can be displaced by the addition of guanosine 5'-monophosphate, although complete displacement of the N-acetylmethionine was not observed.     

Reaction of (R)-(-)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato)platinum( II) with guanosine

The reaction of a new antitumor platinum complex, (R)-(-)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato++ +)platinum(II) (1) with guanosine at room temperature in an aqueous solution was followed by proton nuclear magnetic resonance (1H-NMR) spectroscopy and high performance liquid chromatography (HPLC) at intervals. Both techniques showed that a new compound was formed by displacement of the 1,1-cyclobutanedicarboxylate moiety of 1 with two guanosines, and its 1H-NMR spectrum and HPLC chromatogram were proved to be identical with those of [(R)-(-)-2-aminomethylpyrrolidine]bis(N7-guanosine)platinum(II) (2), which was obtained upon successive treatment of (R)-(-)-2-aminomethylpyrrolidinedichloroplatinum(II) (3) with AgNO3 and 2 mol eq of guanosine in water. The binding sites of the platinum to the two guanosine moieties in 2 were confirmed by the pH dependence of the two G-H8 signals.     

用X-射线光电子能谱(XPS)研究聚-γ-二苯基膦丙基硅氧烷-铂络合物的结构及其催化活性

本文用X-射线光电子能谱(XPS)研究了聚-γ-二苯基膦丙基硅氧烷-铂络合物,证明了这一催化剂是络合物,提出了它的可能结构,探讨了催化剂制备中不同的P/Pt克分子比及其所催化体系的酸碱度对它的活性的影响。由不同条件下催化剂中两个分离的Cl_(2P)光电子峰强度得出:适当的P/Pt克分子比和HCl加入催化体系所导致的活性提高是由于络合物中反映H_2PtCl_6分子络合特征程度的增加。     

Growth of a Pt film on non-reduced ceria: a density functional theory study

The growth of platinum on non-reduced CeO(2) (111) surface is studied by means of calculations based on the density functional theory. Particles of increasing size are formed on the oxide surface by incorporating the platinum atoms one by one until multilayer films are obtained. The main conclusion is that platinum atoms tend to maximize the number of metallic bonds and to approach the situation of the bulk, hence preferring films to particles, particles to isolated atoms, and a three-dimensional growth to a two-dimensional one. The supported particles and the films exhibit a contraction of the Pt-Pt distances, with respect to those of the Pt bulk, in order to match the ceria lattice. The density of states projected on the film surface platinum atoms shows important differences in shape and energy (lower d-band center) compared to the Pt(111) reference surface, which could be the major reason for the observed changes in catalytic reactivity when deposited particles are compared with single crystal surfaces.     

A CNDO/2 study on bonding mechanism of cis-dichlorodiammine platinum (II) with DNA

Bonding mechanism of cis-Pt (NH₃)Cl₂ with DNA has been studied by CNDO/2 calculation. The computed results of the six models considered indicated that from the point of view of overlap population Q_AB and two atoms energy E_AB, the most favorable bonding form was that between platinum and two N₇ atoms, from guanines (G) to form [(NH₃)₂PtG₂]³⁺. Thus, intrastrand cross-linkage mechanism which had been previously proposed by some authors was confirmed by our calculation. Chelation mechanism could not completely be excluded. Under certain conditions, it was possible for platinum to combine with a guanine through its N₇ and O(C₆) to form a chelate, but it was unstable as compared with [(NH₃)₂PtG₂]²⁺. Although the intrastrand cross-linkage mechanism is favored by our calculation, the question of how such a mode of combination hampers replication of DNA remains to be solved.     

Macromolecular architecture of group 10 metal‐poly(yne)s: dendritic,hyperbranched, and helical macromolecules

Novel two‐ and three‐dimensional organometallic polymers of palladium and platinum have been prepared by choice of some acetylene linkages with characteristic structures. When o‐diethynylbenzene was used for a bridging ligand, a macrocyclic complex was selectively produced. Helical poly(yne) polymers were prepared from the reaction with chiral 1,1′‐bi(6‐ethynyl‐2‐naphthol). Platinum acetylide dendrimers, in which platinum atoms are linked by 1,3,5‐triethynylbenzene derivatives, have been prepared by a convergent method up to the third generation.     

(EnH2)2Ge2S6的合成与结构表征

用溶剂热方法制备了(EnH2)2Ge2S6单晶.单晶X射线衍射分析结果表明,(EnH2)2Ge2S6属单斜晶系,P2(1)/n空间群,晶胞参数a=0.67125(5)nm,b=1.12290(4)nm,c=1.07518(4)nm,β=92.288(2)°,Z=2.利用DSC及TG分析研究了其热稳定性,结果表明,该化合物在200℃以下能够稳定存在.