Oxidation chemistry of uranium(III) complexes of Tpa: synthesis and structural studies of oxo,hydroxo, and alkoxo complexes of uranium(IV)

The crystal structure of the complex [U(tpa)(2)]I(3), 1 (tpa = tris[(2-pyridyl)methyl]amine), has been elucidated. The complex exists as only one enantiomer in the crystal leading to the chiral space group P2(1)2(1)2(1). The coordination geometry of the metal can be described as a distorted cube. Accidental oxidation of [U(tpa)(2)]I(3) led to the isolation of the unusual mononuclear bishydroxo complex of uranium(IV) [U(tpa)(2)(OH)(2)]I(2).3CH(3)CN, 2, which was structurally characterized. The controlled reaction of [U(tpa)(2)]I(3) with water resulted in the oxidation of the metal center and led to the formation of protonated tpa and of the trinuclear U(IV) oxo complex ([U(tpa)(mu-O)I](3)(mu(3)-I))I(2), 3. The solid state and solution structures of this trimer are reported. The pathway suggested for the formation of this complex is the oxidation of the [U(tpa)(2)]I(3) complex by H(2)O to form a U(IV) hydroxo complex which then decomposes, eliminating mono-protonated tpa. The comparison with the reported reaction with water of cyclopentadienyl derivatives points to a higher reactivity toward water reduction of the bis(tpa) complex with respect to the cyclopentadienyl derivatives. The reaction of U(III) with methanol in the presence of the supporting ligand tpa leads to formation of alkoxo complexes similarly to what is found for amide or cyclopentadienyl derivatives. The monomethoxide complex [U(tpa)I(3)(OMe)], 4, has been prepared in good yield by alcoholysis of the U(III) mono(tpa) complex. The crystal structure of this complex has been determined. The reaction of [U(tpa)(2)]I(3) with 2 equiv of methanol in acetonitrile allows the isolation of the bismethoxo complex of U(IV) [U(tpa)I(2)(OMe)(2)], 5, in 35-47% yield, which has been fully characterized. To account for the oxidation of U(III) to U(IV) the suggested mechanism assumes that hydrogen is evolved in both reactions.     

Oxidative addition of Ph2TeCl2 to a dimethylplatinum(II) complex: effects of secondary bonding in the platinum-tellurium products

In the first example of oxidative addition of tellurium-halide bonds to a transition-metal complex, Ph(2)TeCl(2) reacts with [PtMe(2)(bu(2)bpy)], 1, bu(2)bpy = 4,4'-di-tert-butyl-2,2'-bipyridine, to give an organoplatinum(IV) complex that can be formulated as an ionic diphenyl telluride complex [PtClMe(2)(TePh(2))(bu(2)bpy)]Cl or as a neutral chlorodiphenyltelluryl complex [PtClMe(2)(TePh(2)Cl)(bu(2)bpy)]; the complex contains an unusually long Te...Cl bond length of 3.43 A. The weakly bound chloride ligand is easily removed by reaction with AgO(3)SCF(3) to give the cationic complex [PtClMe(2)(TePh(2))(bu(2)bpy)](CF(3)SO(3)) in which the triflate anion is not coordinated to tellurium. This complex reacts with a second 1 equiv of AgO(3)SCF(3) to give the aqua complex [PtMe(2)(OH(2))(TePh(2)..O(3)SCF(3))(bu(2)bpy)](CF(3)SO(3)), in which a triflate anion forms secondary bonds with both the aqua and TePh(2) ligands. In these platinum(IV) complexes, the magnitude of the coupling constant (1)J(PtTe) is strongly influenced by the presence of the weakly bonded Te...X groups.     

Biodegradation of Eu(III)-citrate complexes by Pseudomonas fluorescens

Summary We have investigated the structure of Eu(III)-citrate complexes in aqueous solution and their degradability by Pseudomonas fluorescens. Analysis of 1:1, 1:2, and 1:5 Eu(III):citrate solutions at pH 7 by electrospray ionization mass spectrometry (ESI-MS) showed that the 2:2 Eu(III)-citrate complex is the predominant complex species at a low citrate/Eu(III) ratio, while at a high ratio, a 1:2 Eu(III)-citrate complex is formed preferably. Studies on the biodegradation of Eu(III)-citrate complex by P. fluorescens have shown that a 2:2 Eu(III)-citrate complex is resistent to degradation while a 1:2 complex transforms to a 2:2 complex with the degradation of excess citric acid.     

Reaction of [2-(SiH3)C6H4]2SiH2 with Ni(Et2PCH2CH2PEt2)(PEt3)2: characterization of eta2-(Si-H)Ni and NiIV-H complexes

The reaction of (2-SiH3C6H4)2SiH2 with Ni(Et2PCH2CH2PEt2)(PEt3)2 afforded a new silylnickel complex, which, in the solid state, was determined to be a bis(silyl)eta2-(Si-H)nickel complex, the first example of eta2-(Si-H)nickel complex by single-crystal X-ray analysis. Variable-temperature NMR spectroscopy revealed fluxional behavior of the complex in solution; at room temperature, exchange of five hydrogens (two SiH2 and one hydrogen bound to nickel) was observed, while at -80 degrees C the exchange of hydrogens appeared frozen to adopt a tris(silyl)(hydrido)nickel(IV) structure, which was confirmed by theoretical calculation. The latter complex is the first example of hydridonickel(IV) complex.     

Structures and redox reactivities of copper complexes of (2-pyridyl)alkylamine ligands. Effects of the alkyl linker chain length

Ligand effects on the structures and redox reactivities of copper complexes have been examined using (2-pyridyl)alkylamine derivatives as the supporting ligands, where particular attention has been focused on the effects of the alkyl linker chain length connecting the tertiary amine nitrogen atom and the pyridine nucleus: N[bond]CH(2)[bond]Py (Pym) vs N[bond]CH(2)CH(2)[bond]Py (Pye). X-ray crystallographic analysis of the copper(I) complex of tridentate ligand (Phe)L(Pym2) [N,N-di(2-pyridylmethyl)-2-phenylethylamine] (complex 1) has demonstrated that it possesses a trigonal pyramidal geometry in which a d[bond]pi interaction with an eta(1)-binding mode exists between the metal ion and one of the ortho carbons of the phenyl ring of the ligand side arm (phenethyl). The result shows sharp contrast to the d[bond]pi interaction with an eta(2)-binding mode existing in the copper(I) complex of (Phe)L(Pye2) [N,N-di[2-(2-pyridyl)ethyl]-2-phenethylamine] (complex 2). Such a d-pi interaction has been shown to affect the stability of the copper(I) complex in CH(2)Cl(2). Oxygenation of copper(I) complex 1 supported by (Phe)L(Pym2) produces a bis(mu-oxo)dicopper(III) complex, also being in sharp contrast to the case of the copper(I) complex 2 with ligand (Phe)L(Pye2), which preferentially affords a (micro-eta(2):eta(2)-peroxo)dicopper(II) complex in the reaction with O(2). Such an effect of the alkyl linker chain length of the metal binding site has also been found to operate in the RSSR (disulfide)/2RS(-) (thiolate) redox system. Namely, ligand (S2,R)L(Pym1) (di[2-[(alkyl)(2-pyridinylmethyl)amino]ethyl] disulfide) with the methylene linker group (Pym) induced the reductive disulfide bond cleavage in the reaction with copper(I) ion to give a bis(micro-thiolato)dicopper(II) complex, while the ligand with the ethylene linker group (Pye), (S2,Bn)L(Pye1) (di[2-[(benzyl)(2-(2-pyridinyl)ethyl)amino]ethyl] disulfide), gave a disulfide-dicopper(I) complex. These ligand effects in the Cu(2)[bond]O(2) and Cu(2)[bond]S(2) systems have been discussed by taking into account the difference in electron-donor ability of the pyridine nucleus between the Pym and Pye ligand systems.     

Synthesis and characterization of rhodium complexes with phosphine-stabilized germylenes

The reaction of phosphine-stabilized germylenes (1a,b) with dimer complex [Rh(2)(μ-Cl)(2)(COD)(2)] leads to the corresponding phosphine-germylene-Rh(I) complexes (2a,b). Interestingly, the stability of these complexes depends strongly on the nature of the substituent of the germylene fragment. Indeed, the complex (2a) with the chloro-germylene ligand isomerizes into a metallacycle rhodium complex (3a) via germylene insertion into the Rh-Cl bond, while the complex with the phenyl-substituted germylene (2b) was isolated and represents the first stable Rh(I)-germylene complex with a Rh-Cl bond.     

Ruthenium complexes of substituted hydrazine: new solution- and solid-state binding modes

The methylhydrazine complex [Ru(NH(2)NHMe)(PyP)(2)]Cl(BPh(4)) (PyP=1-[2-(diphenylphosphino)ethyl]pyrazole) was synthesised by addition of methylhydrazine to the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(BPh(4))(2). The methylhydrazine ligand of the ruthenium complex has two different binding modes: side-on (eta(2)-) when the complex is in the solid state and end-on (eta(1)-) when the complex is in solution. The solid-state structure of [Ru(PyP)(2)(NH(2)NHMe)]Cl(BPh(4)) was determined by X-ray crystallography. 2D NMR spectroscopic experiments with (15)N at natural abundance confirmed that in solution the methylhydrazine is bound to the metal centre by only the -NH(2) group and the ruthenium complex retains an octahedral conformation. Hydrazine complexes [RuCl(PyP)(2)(eta(1)-NH(2)NRR')]OSO(2)CF(3) (in which R=H, R'=Ph, R=R'=Me and NRR'=NC(5)H(10)) were formed in situ by the addition of phenylhydrazine, 1,1-dimethylhydrazine and N-aminopiperidine, respectively, to a solution of the bimetallic complex [Ru(mu-Cl)(PyP)(2)](2)(OSO(2)CF(3))(2) in dichloromethane. These substituted hydrazine complexes of ruthenium were shown to exist in an equilibrium mixture with the bimetallic starting material.     

钴的二苯甲酰甲烷配合物：晶体结构及其轴向置换反应

Cobalt(Ⅱ) can form complexes with Hdbm in different environments. Hdbm reacted with cobalt nitrate to give complex 1 [Co(dbm)₂·2H₂O]. When complex 1 reacted with pyridine， α-stilbazole or 4，4′-bipyridine respectively， complex 2 [Co(DBM)₂Py₂] (Py=pyridine)， 3 [Co(DBM)₂Sbz₂] (Sbz=α-stilbazole) or 4 [Co(DBM)₂BPy]_n was obtained in turn through metathetical reaction. The coordination modes are octahedral polyhedrons. In the crystal structures， the two dbms take the plane position and two other donor molecules take the axial position. CCDC： 196070 for complex 2; 186859 for complex 3.     

Bimetallic reactivity. One-site addition two-metal oxidation reaction of dioxygen with a bimetallic dicobalt(II) complex bearing five- and six-coordinate sites

The di-Co(2+) complex, [Co(2+)(mu-OH)(oxapyme)Co(2+)(H(2)O)](+), contains an unsymmetrical binucleating ligand (oxapyme) which provides five- and six-coordinate metal sites when a hydroxide bridge is introduced. This complex absorbs 1 equiv of O(2) irreversibly in solution, producing an unstable di-Co(3+) oxygenated product. The oxygenated product has been studied at low temperatures, where its electronic absorption and (1)H NMR spectra were recorded. It is probable that the oxygenation reaction involves a one-site addition two-metal oxidation reaction to produce an end-on-bonded peroxide ligand at the available coordination site, giving the complex [Co(3+)(mu-OH)(oxapyme)Co(3+)(mu(1)-O(2))](+). Addition of 1 equiv of HClO(4) to this oxygenation product gives a stable peroxide complex, [Co(3+)(mu,eta(1):eta(2)-O(2))(oxapyme)Co(3+)](2+), where one of the oxygen atoms bridges the two metals and is sideways bonded to one of the metals. The formation of this stable complex involves expulsion of the OH(-) bridge. Addition of NO(2)(-) to the sideways-bonded peroxide complex leads to the formation of another stable complex, [Co(3+)(mu,eta(1):eta(1)-O(2))(oxapyme)Co(3+)(NO(2))](+), where the peroxide forms a classic di-end-on bridge to the two metals. Both of these complexes have been fully characterized. Addition of acid to this second stable dioxygen complex leads to the release of HNO(2) and the formation of the mu,eta(1):eta(2) sideways-bonded peroxide complex.     

Facile ring opening of iron(III) and iron(II) complexes of meso-amino-octaethylporphyrin by dioxygen

Pyridine solutions of ClFe(III)(meso-NH(2)-OEP) undergo oxidative ring opening when exposed to dioxygen. The high-spin iron(III) complex, ClFe(III)(meso-NH(2)-OEP), has been isolated and characterized by X-ray crystallography. In the solid state, it has a five-coordinate structure typical for high-spin (S = 5/2) iron(III) complex. In chloroform-d solution, ClFe(III)(meso-NH(2)-OEP) displays an (1)H NMR spectrum characteristic of a high-spin, five-coordinate complex and is unreactive toward dioxygen. However, in pyridine-d(5) solution a temperature-dependent equilibrium exists between the high-spin (S = 5/2), six-coordinate complex, [(py)ClFe(III)(meso-NH(2)-OEP)], and the six-coordinate, low spin (S = 1/2 with the less common (d(xz)d(yz))(4)(d(xy))(1) ground state)) complex, [(py)(2)Fe(III)(meso-NH(2)-OEP)](+). Such pyridine solutions are air-sensitive, and the remarkable degradation has been monitored by (1)H NMR spectroscopy. These studies reveal a stepwise conversion of ClFe(III)(meso-NH(2)-OEP) into an open-chain tetrapyrrole complex in which the original amino group and the attached meso carbon atom have been converted into a nitrile group. Additional oxidation at an adjacent meso carbon occurs to produce a ligand that binds iron by three pyrrole nitrogen atoms and the oxygen atom introduced at a meso carbon. This open-chain tetrapyrrole complex itself is sensitive to attack by dioxygen and is converted into a tripyrrole complex that is stable to further oxidation and has been isolated. The process of oxidation of the Fe(III) complex, ClFe(III)(meso-NH(2)-OEP), is compared with that of the iron(II) complex, (py)(2)Fe(II)(meso-NH(2)-OEP); both converge to form identical products.     

Synthesis and structural characterization of beta-diketiminate-lanthanide amides and their catalytic activity for the polymerization of methyl methacrylate and epsilon-caprolactone

The synthesis and catalytic activity of lanthanide monoamido complexes supported by a beta-diketiminate ligand are described. Donor solvents, such as DME, can cleave the chloro bridges of the dinuclear beta-diketiminate ytterbium dichloride {[(DIPPh)2nacnac]YbCl(mu-Cl)3Yb[(DIPPh)2nacnac](THF)} (1) [(DIPPh)2nacnac = N,N-diisopropylphenyl-2,4-pentanediimine anion] to produce the monomeric complex [(DIPPh)2nacnac]YbCl2(DME) (2) in high isolated yield. Complex 2 is a useful precursor for the synthesis of beta-diketiminate-ytterbium monoamido derivatives. Reaction of complex 2 with 1 equiv of LiNPri2 in THF at room temperature, after crystallization in THF/toluene mixed solvent, gave the anionic beta-diketiminate-ytterbium amido complex [(DIPPh)2nacnac]Yb(NPri2)(mu-Cl)2Li(THF)2 (3), while similar reaction of complex 2 with LiNPh2 produced the neutral complex [(DIPPh)2nacnac]Yb(NPh2)Cl(THF) (4). Recrystallization of complex 3 from toluene solution at elevated temperature led to the neutral beta-diketiminate-lanthanide amido complex [{(DIPPh)2nacnac}Yb(NPri2)(mu-Cl)]2 (5). The reaction medium has a significant effect on the outcome of the reaction. Complex 2 reacted with 1 equiv of LiNPri2 and LiNC5H10 in toluene to produce directly the neutral beta-diketiminate-lanthanide amido complexes 5 and [{(DIPPh)2nacnac}Yb(NC5H10)(THF)(mu-Cl)]2 (6), respectively. These complexes were well characterized, and their crystal structures were determined. Complexes 4-6 exhibited good catalytic activity for the polymerization of methyl methacrylate and epsilon-caprolactone.     

Infrared absorption spectra of the CO(2)/H(2)O complex in a cryogenic nitrogen matrix--detection of a new bending frequency

Infrared absorption spectra have been measured for the mixture of CO(2) and H(2)O in a cryogenic nitrogen matrix. The 1:1 CO(2)/H(2)O complex has been observed. Each structure of this complex should have two bending frequencies corresponding to the CO(2) fundamental bending mode (ν(2)). In this work, three bending frequencies corresponding to the CO(2) fundamental bending mode (ν(2)) have been detected; one of them at 660.3 cm(-1) is reported here for the first time. This finding helps confirm the existence of two structures for this complex. A new feature attributed to a CO(2) and H(2)O complex is observed at 3604.4 cm(-1) and is tentatively assigned to the CO(2)/H(2)O complex band corresponding to the CO(2) combination mode (ν(3) + 2ν(2)). In addition, a band that belongs to a CO(2) and H(2)O complex is detected at 3623.8 cm(-1) for the first time and is tentatively assigned to the (CO(2))(2)/H(2)O complex band corresponding to the symmetric stretching mode (ν(1)) of H(2)O.     

Formation and characterization of the oxygen-rich scandium oxide/dioxygen complexes ScOn (n = 4, 6, 8) in solid argon

The reactions of scandium atoms and O(2) have been reinvestigated using matrix isolation infrared spectroscopy and density functional theory calculations. A series of new oxygen-rich scandium oxide/dioxygen complexes were prepared and characterized. The ground state scandium atoms react with dioxygen to form OSc(eta(2)-O(3)), a side-on bonded scandium monoxide-ozonide complex. The OSc(eta(2)-O(3)) complex rearranges to a more stable Sc(eta(2)-O(2))(2) isomer under visible light irradiation, which is characterized to be a side-on bonded superoxo scandium peroxide complex. The homoleptic trisuperoxo scandium complex, Sc(eta(2)-O(2))(3), and the superoxo scandium bisozonide complex, (eta(2)-O(2))Sc(eta(2)-O(3))(2), are also formed upon sample annealing. The Sc(eta(2)-O(2))(3) complex is determined to have a D(3h) symmetry with three equivalent side-on bonded superoxo ligands around the scandium atom. The (eta(2)-O(2))Sc(eta(2)-O(3))(2) complex has a C(2) symmetry with two equivalent side-on bonded O3 ligands and one side-on bonded superoxo ligand.     

Exhaustive oxidation of a nickel dithiolate complex: some mechanistic insights en route to sulfate formation

A study of the step-wise oxidation of a Ni(II) diaminodithiolate complex through the formation of sulfate, the ultimate sulfur oxygenate, is reported. Controlled oxygenations or peroxidations of a neutral, planar, tetracoordinate, low-spin Ni(II) complex of a N(2)S(2)-donor ligand, (N,N'-dimethyl-N-N'-bis(2-mecaptoethyl)-1,3-propanediaminato) nickel(ii) (1), led to a series of sulfur oxygenates that have been isolated and characterized by ESI-MS and single-crystal X-ray diffraction. A monosulfenate complex (2) was detected by ESI-MS as a product of oxidation with one equivalent of H(2)O(2). However, this complex proved too unstable to isolate. Reaction of the dithiolate (1) with two equivalents of H(2)O(2) or one O(2) molecule leads to the formation of a monosulfinate complex (3), which was isolated and fully characterized by crystallography. The oxidation product of the monosulfinate (3) produced with either O(2) or H(2)O(2) is an interesting dimeric complex containing both sulfonate and thiolate ligands (4), this complex was fully characterized by crystallography, details of which were reported earlier by us. A disulfonate complex (7) is produced by reaction of 1 in the presence of O(2) or by reaction with exactly six equivalents of H(2)O(2). This complex was isolated and also fully characterized by crystallography. Possible intermediates in the conversion of the monosulfinate complex (3) to the disulfonate complex (7) include complexes with mixed sulfonate/sulfenate (5) or sulfonate/sulfinate (6) ligands. Complex 5, a four-oxygen adduct of 1, was not detected, but the sulfonate/sulfinate complex (6) was isolated and characterized. The oxidation chemistry of 1 is very different from that reported for other planar cis-N(2)S(2) Ni(ii) complexes including N,N'-dimethyl-N-N'-bis(2-mecaptoethyl)-1,3-ethylenediaminato) nickel(II), (8), and N,N'-bis(mercaptoethyl)-1,5-diazacyclooctane nickel(II). To address the structural aspects of the reactivity differences, the crystal structure of 8 was also determined. A comparison of the structures of planar Ni(II) complexes containing cis-dithiolate ligands, strongly suggests that the differences in reactivity are determined in part by the degree of flexibility that is allowed by the NN' chelate ring.     

Dimethylaminoborane (H2BNMe2) coordination to late transition metal centers: snapshots of the B-H oxidative addition process

The reaction of cyclodiborazane [Me(2)N-BH(2)](2) with the chloro(dihydrogen) ruthenium complex RuHCl(η(2)-H(2))(P(i)Pr(3))(2) (1) led to the formation of the unsymmetricaly coordinated dimethylaminoborane complex RuHCl(H(2)BNMe(2))(P(i)Pr(3))(2) (2). The dimethylaminoborane coordination (H(2)BNMe(2)) to the ruthenium center in 2 was carefully studied by combining X-ray, multinuclear NMR, and density functional theory (DFT) techniques, and compared with the recently reported osmium analogue which was originally formulated as a σ-B-H borinium complex [OsH(2)Cl(HBNMe(2))(P(i)Pr(3))(2)] (4). All our data are in favor of a bis(σ-B-H) coordination mode at a very activated stage in the case of the ruthenium complex 2, whereas in the osmium complex 4, full oxidative addition is favored leading to a complex better formulated as an osmium(IV) boryl species with an α-agostic B-H interaction. The synthesis and characterization of the symmetrical dihydride complex RuH(2)(H(2)BNMe(2))(P(i)Pr(3))(2) (3) from addition of the lithium dimethylaminoborohydride to 1 is reported for comparison.     

Facile oxygenation reactions of ruthenium acetylide complex containing substituted olefinic group

Reaction of the ruthenium acetylide complex Cp(dppe)RuC≡CCH(OMe)CPh(2)-CH(2)CH=CMe(2) (5a) with oxygen readily gives acetone and the acyl complex 6 in almost quantitative yield. Protonation of 5a is followed by an elimination of MeOH and a hydroxyl addition at Cα in the presence of water to give the hydroxycarbene complex 7a. The structures of the acyl complex 6 and the hydroxycarbene complex 7c are fully characterized by single crystal X-ray diffraction analysis.     

Synthesis of a base-stabilized silanone-coordinated complex by oxygenation of a (silyl)(silylene)tungsten complex

Base-stabilized silanone complex Cp*(OC)(2)W(SiMe(3)){O═SiMes(2)(DMAP)} (2) was synthesized by the reaction of (silyl)(silylene)tungsten complex Cp*(OC)(2)W(SiMe(3))(═SiMes(2)) (1) with 1 equiv of pyridine-N-oxide (PNO) in the presence of 4-(dimethylamino)pyridine (DMAP). Further oxygenation of 2 with 3 equiv of PNO at 80 °C resulted in the formation of a W-O-Si-O-Si framework to give disiloxanoxy complex Cp*(O)(2)W{OSiMes(2)(OSiMe(3))} (3). Complex 3 was also obtained by the direct reaction of complex 1 with 4 equiv of PNO at 80 °C.     

Binuclear cyclometalated organoplatinum complexes containing 1,1'-bis(diphenylphosphino)ferrocene as spacer ligand: kinetics and mechanism of MeI oxidative addition

The binuclear complex [Pt2Me2(ppy)2(mu-dppf)], 1, in which ppy = deprotonated 2-phenylpyridyl and dppf = 1,1'-bis(diphenylphosphino)ferrocene, was synthesized by the reaction of [PtMe(SMe2)(ppy)] with 0.5 equiv of dppf at room temperature. In this reaction when 1 equiv of dppf was used, the dppf chelating complex 2, [PtMe(dppf)(ppy-kappa1C)], was obtained. The reaction of Pt(II)-Pt(II) complex 1 with excess MeI gave the Pt(IV)-Pt(IV) complex [Pt2I2Me4(ppy)2(mu-dppf)], 3. When the reaction was performed with 1 equiv of MeI, a mixture containing unreacted complex 1, a mixed-valence Pt(II)-Pt(IV) complex [PtMe(ppy)(mu-dppf)PtIMe2(ppy)], 4, and complex 3 was obtained. In a comparative study, the reaction of [PtMe(SMe2)(ppy)] with 1 equiv of monodentate phosphine PPh3 gave [PtMe(ppy)(PPh3)], A. MeI was reacted with A to give the platinum(IV) complex [PtMe2I(ppy)(PPh3)], C. All the complexes were fully characterized using multinuclear (1H, 31P, 13C, and 195Pt) NMR spectroscopy, and complex 2 was further identified by single crystal X-ray structure determination. The reaction of binuclear Pt(II)-Pt(II) complex 1 with excess MeI was monitored by low temperature 31P NMR spectroscopy and further by 1H NMR spectroscopy, and the kinetics of the reaction was studied by UV-vis spectroscopy. On the basis of the data, a mechanism has been suggested for the reaction which overall involved stepwise oxidative addition of MeI to the two Pt(II) centers. In this suggested mechanism, the reaction proceeded through a number of Pt(II)-Pt(IV) and Pt(IV)-Pt(IV) intermediates. Although MeI in each step was trans oxidatively added to one of the Pt(II) centers, further trans to cis isomerizations of Me and I groups were also identified. A comparative kinetic study of the reaction of monomeric platinum(II) complex A with MeI was also performed. The rate of reaction of MeI with complex 1 was some 3.5 times faster than that with complex A, indicating that dppf in the complex 1, as compared with PPh 3 in the complex A, has significantly enhanced the electron richness of the platinum centers.     

有机配合剂稳定高价稀土元素的研究 I.丙二酸水溶液中稳定Pr(IV)的研究

本文通过751G型发光光度计和pHS-2型酸度计, 研究了有机配合剂(Pr(IV)-CH~2(COO)~2^-^2)碱式碳酸盐溶于丙二酸水溶 液中, Pr(IV)在该溶液中的行为和稳定情况。总Pr量用EDTA配位滴定法, 二甲酸橙作指示剂;Pr(IV)分析用碘量法, 并扣除空白。     

Synthesis of a eta 2-2,3-diphosphabutadiene complex of zerovalent platinum from the corresponding eta 2-phosphaalkyne complex

Hydrozirconation of the eta 2-phosphaalkyne complex [Pt(dppe)(eta 2-tBuCP)] with [ZrHCl(eta 5-C5H5)2], followed by treatment with the chlorophosphaalkene ClP=C(SiMe3)2 affords the eta 2-2,3-diphosphabutadiene complex [Pt(dppe)(eta 2-tBuC(H)=PP=C(SiMe3)2]. In the presence of [Pt(PPh3)2] the latter undergoes an addition reaction with water to afford the structurally characterised Pt(II) complex [Pt(dppe)(tBuCH2P(O)HPC(SiMe3)2].