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1.
The complexes trans-[ReL2(dppe)2]BF4 (I, L = CO, CNR with R = Me,But, C6H4OMe-4, C6H4Me-4, C6H4Cl-4 and C6H3Cl2-2,6) were prepared from the reaction of the parent dinitrogen complex trans-[ReCl(N2)(dppe)2] with the appropriate ligand, in thf and in the presence of TlBF4.Their redox properties were studied by cyclic voltammetry at a Pt electrode in [Bu4N][BF4]/thf or acetonitrile; they undergo a one-electron reversible oxidation and the observed EOX12 values were applied to test the validity of a proposed general expression —derived from the electrochemical ligand (PL) and 16-electron metal site (Es, β) parameters [6]— to estimate EOX12 for 18-electron octahedral complexes of the type [M′sL2] with a square planar 14-electron metal centre {M′s}. Es and β parameters were also estimated for the auxilliary {ReL(dppe)2}+ (L = CO or CNR) centres.  相似文献   

2.
《Inorganica chimica acta》1986,112(2):183-187
The fragmentation pathways of (η3-C3H4X)FeCO)2NO, (σ-C3H4X)Fe(CO)2(NO)L, (η3-C3H4X)Fe(CO)(NO)L, (σ-C3H4X)Fe(CO)2(NO)L′, (η3- C3H4X)Fe(CO)(NO)L′, (σ-C3H5)M(CO)5, (η3-C3H5)M(CO)4, (σ-CH2CHC(Me)2)Mn(CO)5, (η3-CH2 CHC(Me)2)Mn(CO)4, (X=2-Cl; L=PPh3; L′= P(OMe)3; M=Mn, Re) have been investigated by mass spectrometry. In the σ derivatives the molecular ion loses CO or the allylic ligand, while in the η3 derivative loss of a CO group is the only fragmentation mode of the molecular ion. Electron impact as well as methane chemical ionization mass spectra have been reported. Kinetic energy release of selected metastable ions indicates that a σ → η3 rearrangement reaction occurs.  相似文献   

3.
The template alkylation of Li2[Ru(CO)2(S2C6H4)2] (S2C6H42− = 1,2-benzenedithiolate(−2)) by S(C2H4Br)2 yields [Ru(CO)2(dpttd)] (dpttd2− = 3,11,12-dibenzo-1,4,7,10,13-pentathiatridecane(−2)) which is thermally converted into the monocarbonyl complex [Ru(CO)(dpttd)]. The reactions of dpttd-H2 or dpttd2− with [RuCl2(PPh3)3], [RuCl2(DMSO)4], [RuCl3(PhSCH3)3] and RuCl3(NO)·xH2O lead to [Ru(L)(dpttd)] and [Ru(L)(dpttd)]Cl (L = PPh3, DMSO, PhSCH3, NO), respectively, which are practically insoluble in all common solvents. Better soluble complexes are obtained with the new sterically demanding ligand tbu4-dpttd2− = 14,16,18,20-tetra(t-butyl)-2,3,11,12-dibenzo-1,4,7, 10,13-pentathiatridecane(−2); it is obtained in isomerically pure form by the reaction of tetrabuthylammonium-3,5-di (t-butyl)-1,2-benzenethiolthiolate, NBu4[tbu2-C6H2S(SH), with S(C2H4Br)2 and yields on reaction with [RuCl2(PPh3)3] the very soluble [Ru(PPh3)2(tbu4-dpttd)] as well as [Ru(PPh3(tbu4-dpttd)]. The 1H NMR and 31P NMR spectra indicate that in solution [Ru(PPh3)2(tbu4-dpttd)] exists as a mixture of diastereomers, whereas [Ru(PPh3)(tbu4-dpttd)] forms one pair of enantiomers only. This was confirmed by an X-ray structure determination of a single crystal. [Ru(PPh3)(tbu4-dpttd)] crystallizes in space group P21/n with a = 10.496(4), b = 14.888(6), c = 32.382(12) Å, β = 98.04(3)°, Z = 4 and Dcalc. = 1.27 g/cm3, R = 4.84; RW = 5.06%; the ruthenium center is coordinated pseudooctahedrally by one phosphorus, two thiolate and three thiother S atoms.  相似文献   

4.
Substitution of thf ligands in [Cr(thf)3Cl3] and [Cr(thf)2(OH2)Cl3] was investigated. 2,2′-Bipyridine (bipy) was reacted with [Cr(thf)3Cl3] to form [Cr(bipy)(thf)Cl3] (1), which was subsequently reacted with water to give [Cr(bipy)(OH2)Cl3] (2). Reaction of 1 with acetonitrile (CH3CN), pyridine (py) and pyridine derivatives to form [Cr(bipy)(L)Cl3] (L = CH3CN 3, py 4 and 4-pyR with R = NH25, But6 and Ph 7). In addition, the substitution of bipy in [Cr(thf)3Cl3] was followed by 1H NMR spectroscopy at room temperature, which showed completion of the reaction in ca. 100 min. Complex 2 was characterised by single crystal X-ray diffraction. The theoretical powder diffraction pattern of 2 was compared to the experimentally obtained powder X-ray diffraction pattern, and shows excellent agreement. The dimer [Cr2(bipy)2Cl4(μ-Cl)2] was cleaved asymmetrically to give the anionic complex [Cr(bipy)Cl4] (8) and [Cr(bipy)2Cl2]+ (9). Complexes 8 and 9 were characterised by single crystal X-ray diffraction.  相似文献   

5.
Benzophenone imine [M(η1-NHCPh2)(CO)nP5-n]BPh4 [M = Mn, Re; n = 2, 3; P = P(OEt)3, PPh(OEt)2, PPh2OEt, PPh3] complexes were prepared by allowing triflate M(κ1-OTf)(CO)nP5-n compounds to react with an excess of the imine. Hydride-imine [MH(η1-NHCPh2)P4]BPh4 (M = Ru, Os), triflate-imine [Os(κ1-OTf)(η1-NHCPh2)P4]BPh4 and bis(imine) [Ru(η1-NHCPh2)2P4](BPh4)2 [P = P(OEt)3] derivatives were also prepared. The complexes were characterized spectroscopically (IR, 1H, 31P, 13C NMR) and a geometry in solution was also established. Hydride-benzophenone imine [IrHCl(η1-NHCPh2)L(PPh3)2]BPh4and [IrHCl(η1-NHCPh2)L(AsPh3)2]BPh4 [L = P(OEt)3 and PPh(OEt)2] complexes were prepared by reacting hydride IrHCl2L(PPh3)2 and IrHCl2L(AsPh3)2 precursors with an excess of imine. Dihydride IrH21-NHCPh2)(PPh3)3 complex was also obtained and a geometry in solution was proposed.  相似文献   

6.
The SS bond-activation of diorganyl disulfide by the anionic metal carbonyl fragment [Mn(CO)5] gives rise to an extensive chemistry. Oxidative decarbonylation addition of 2,2′-dithiobis(pyridine-N-oxide) to [Mn(CO)5], followed by chelation and metal-center oxidation, led to the formation of [MnII(SC5H4NO)3] (1). The effective magnetic moment in solid state by SQUID magnetometer was 5.88 μB for complex 1, which is consistent with the MnII having a high-spin d5 electronic configuration in an octahedral ligand field. The average Mn(II)S, SC and NO bond lengths of 2.581(1), 1.692(4) and 1.326(4) Å, respectively, indicate that the negative charge of the bidentate 1-oxo-2-thiopyridinato [SC5H4NO] ligand in complex 1 is mainly localized on the oxygen atom. The results are consistent with thiolate-donor [SC5H4NO] stabilization of the lower oxidation state of manganese (Mn(I)), while the O,S-chelating [SC5H4NO] ligand enhances the stability of manganese in the higher oxidation state (Mn(II)). Activation of SS bond as well as OH bond of 2,2′-dithiosalicylic acid by [Mn(CO)5] yielded [(CO)3Mn(μ-SC6H4C(O)O)2Mn(CO)3]2− (4). Oxidative addition of bis(o-benzamidophenyl) disulfide to [Mn(CO)5] resulted in the formation of cis-[Mn(CO)4(SR)2] (R=C6H4NHCOPh) which was employed as a chelating metallo ligand to synthesize heterotrinuclear [(CO)3Mn(μ-SR)3Co(μ-SR)3Mn(CO)3] (8) possessing a homoleptic hexathiolatocobalt(III) core.  相似文献   

7.
The reaction of AgX (X=ClO4, NO3 or SO3CH3) acceptors with excesses of tris(pyrazol-1-yl)methane ligands L (L=CH(pz)3, CH(4-Mepz)3, CH(3,5-Me2pz)3, CH(3,4,5-Me3pz)3 or CH(3-Mepz)2(5-Mepz)) yields 1:1 [AgX(L)], 2:1 [Ag(L)2]X or 3:2 [(AgX)2(L)3] complexes. The ligand to metal ratio in all complexes is dependent on the number and disposition of the Me substituents on the azole ring of the neutral ligand and on the nature of the Ag(I) acceptor. All complexes have been characterized in the solid state as well as in solution (medium- and far-IR, 1H and 13C NMR and conductivity determinations) and the solid-state structures of [Ag(NO3){(pz)3CH}](∞/∞) and [Ag{(3,5-Me2pz)3CH}2]NO3 determined by single crystal X-ray studies.  相似文献   

8.
Mixed-ligand complexes [ReBr(CO)2(CNR)nL3−n] (1-4) [R = 4-CH3OC6H4, 4-CH3C6H4, C(CH3)3; L = P(OEt)3, PPh(OEt)2; n = 1, 2] were prepared by allowing carbonyl compounds [ReBr(CO)4L] and [ReBr(CO)3L2] to react with an excess of isocyanide. Treatment of these bromocomplexes [ReBr(CO)2(CNR)nL3−n] with SnCl2 · 2H2O yielded the trichlorostannyl derivatives [Re(SnCl3)(CO)2(CNR)nL3−n] (5-8). Trihydridestannyl complexes [Re(SnH3)(CO)2(CNR)nL3−n] (9-12) were prepared by allowing trichlorostannyl compounds 5-8 to react with NaBH4 in ethanol. The trimethylstannyl derivative [Re(SnMe3)(CO)2(CNC6H4-4-CH3){PPh(OEt)2}2] (13b) was also prepared by treating [Re(SnCl3)(CO)2(CNC6H4-4-CH3){PPh(OEt)2}2] with an excess of MgBrMe in diethylether. Reaction of the tin trihydride complexes [Re(SnH3)(CO)2(CNR)nL3−n] (9-12) with CO2 (1 atm) led to dinuclear OH-bridging bis(formate) derivatives [Re{Sn(OC(H)O)2(μ-OH)}(CO)2(CNR)nL3−n]2 (14, 15). The complexes were characterised spectroscopically (IR, 1H, 31P, 13C, 119Sn NMR) and by X-ray crystal structure determination of [Re(SnH3)(CO)2{CNC(CH3)3}{PPh(OEt)2}2] (10b).  相似文献   

9.
A triad of interacting group (TyrOH? His$ \underline\ominus$O2C) in angiotensin II (ANG II) has been postulated to create the tyrosinate anion pharmacophore (tyanophore) responsible for receptor activation/triggering (Biochim. Biophys. Acta 1991, 1065, 21). In the present study we investigated the effects on bioactivity of substituting the Tyr4 residue in [Sar1]ANG II with other anionic or electronegative amino acids, and with a number of aromatic amino acids lacking a hydroxyl group. [Sar1 Nva(δ-OH)4]ANG II, [Sar1 Nva(δ-OCH3)4]ANG II, [Sar1 Met4]ANG II, [Sar1 Gln4]ANG II, [Sar1 Glu4]ANG II and [Sar1 DL -Alg4]ANG II had agonist activities in the rat isolated uterus assay of 4, 3, 19, 10, > 0.1 and > 0.1%, respectively, of that of ANG II. [Sar1 Nal4]ANG II, [Sar1 Pal4]ANG II, [Sar1 DL -Phg(4′-F)4]ANG II, [Sar1 Phe(4′-F)4]ANG II, [Sar1 Phe(F5)4]ANG II and [Sar1 His4]ANG II had agonist activities of 4.5, 7, < 0.1, 0.2, 1 and 0.6%, respectively. All peptides investigated were devoid of measurable antagonist activity except [Sar1] Phe(4′-F)4 ANG II (pA2 = 7.7). These findings illustrate that anionic or electronegative aliphatic side chains replacing tyrosinate at position 4 can partially activate the angiotension receptor. For ANG II analogues containing an aromatic amino acid other than Tyr at position 4, ligand binding and agonist activity are not dependent on the electronegativity or dipole moment of the aromatic ring, or on the ability of the 4′ ring substituent to accept a proton. Modelling based on ab initio calculations of aromatic ring multipoles illustrate that the apparent binding affinity (PA2) of ANG II analogues is associated with a perpendicular electrostatic interaction of the position 4 aromatic ring with a receptor-based group. In addition, intramolecular interactions providing for the conformation of the ligand as it approaches its receptor appear to have a role in determining agonist vs antagonist activity.  相似文献   

10.
The reaction of TiX4(X=Cl or Br) with the tripodal ligands MeC(CH2SMe)3 or MeC(CH2SeMe)3, (L3) in anhydrous n-hexane or CH2Cl2 produced the extremely moisture sensitive complexes [TiX4(L3)]. These were characterised by microanalysis, IR, UV-Vis and variable temperature 1H,13C{1H} and 77Se NMR spectroscopy. The NMR studies showed that in solution in CH2Cl2 the complexes contain L3 bound as bidentates, and that pyramidal inversion and exchange between the free and coordinated chalcogen donors is rapid at room temperature. Ligand dissociation/exchange increases TiCl4<TiBr4 and MeC(CH2SMe)3<MeC(CH2SeMe)3 and attempts to isolate TiI4 analogues were unsuccessful. The reactions of [MCl4(Me2S)2] (M=Zr or Hf) with (L3) in anhydrous CH2Cl2 produces white or cream 7-coordinate [MCl4(L3)], which are insoluble in chlorocarbon solvents. The reactions of TiX4 (X=Cl, Br or I) with the trithia-macrocycles [9]aneS3 and [10]aneS3 produced [TiX3([n]aneS3)]X, whilst reaction of TiCl4, SbCl5 and [9]aneS3 in anhydrous CH2Cl2 gave [TiCl3([9]aneS3)]SbCl6. Spectroscopic studies suggest these macrocyclic compounds contain 6-coordinate cations, [TiX3([n]aneS3)]+ (n=9 or 10) but with Zr and Hf the complexes [MCl4([n]aneS3)] are 7-coordinate and neutral.  相似文献   

11.
From the interaction between azole-type ligands L and AgX (X = NO3 or ClO4) or [AgX(PPh3)n] (X = Cl, n = 3; X = MeSO3, n = 2), new ionic mononuclear [Ag(L)2]X and [Ag(PPh3)3L][X] or neutral mono-([Ag(PPh3)nL(X)]) or di-nuclear ([{Ag(PPh3)(L)(μ-X)}2]) complexes have been obtained which have been characterized through elemental analysis, conductivity measurements, IR, 1H NMR and, in some cases, also by 31P{1H} NMR spectroscopy, and single-crystal X-ray studies. Stoichiometries and molecular structures are dependent on the nature of the azole (steric hindrance and basicity), of the counter ion, and on the number of the P-donor ligands in the starting reactants. Solution data are consistent with partial dissociation of the complexes, occurring through breaking of both Ag-N and Ag-P bonds.  相似文献   

12.
Base-assisted reduction of [Ru(CO)3Cl2]2 in the presence of NP-Me2 (2,7-dimethyl-1,8-naphthyridine) in thf provides an unsupported diruthenium(I) complex [Ru2(CO)4Cl2(NP-Me2)2] (1). Two NP-Me2 and four carbonyls bind at equatorial positions and two chlorides occupy sites trans to the Ru-Ru single bond. Reaction of [Ru(CO)3Cl2]2, TlOTf, KOH and NP-Me2 in acetonitrile, in a sealed container, affords a bicarbonate bridged diruthenium(I) complex [Ru2(CO)2(μ-CO)2(μ-O2COH)(NP-Me2)2](OTf) (2). The in situ generated CO2 is the source for bicarbonate under basic reaction medium. Isolation of 2 validates the decarboxylation step in the base-assisted reduction of [RuII(CO)3Cl2]2 → [RuI2(CO)4]2+.  相似文献   

13.
The 87.5 MHz 45Sc NMR spectrum of 0.025 M aqueous Sc(NO3)3 exhibits two resonance signals, separated by ca. 25 ppm, attributable to [Sc(H2O)6]3+ and [Sc(H2O)5OH]2+. Acidification leads to a single, comparatively sharp line (W1/2 = 160 Hz) for the hexaqua complex, the temperature dependence (temperature gradient = 0.076 ppm/deg) of which indicates that relaxation is dominated by the quadrupole mechanism. Addition of α-alanine gives rise to an additional broad signal at ca. +70 ppm (relative to [Sc(H2O)6]3+), which is assigned to a carboxylato complex [Sc(H2O)6−n(ala)n]3+ or [Sc(H2O)5−nOH- (ala)n]2+ (1 < n < 2). At ambient temperatures, these species are in slow exchange with the hexaqua and pentaqua-hydroxo complex, progressing through medium towards fast exchange as the temperature increases, and giving rise to an exchange contribution to relaxation. W1/2 becomes a measure for the stability of the complexes, which increases in the order ala < (ala)4 ∼ (ala)2 < ala-val-leu. The pronounced stability of the latter is due to the formation of a chelate-five ring structure (participation of the NH- function of the peptide bond in coordination to Sc3+). 1 M aqueous ScCl3 probably contains the two species [Sc(H2O)6]3+ and [Sc(H2O)5Cl]2+, separated by 33 ppm.  相似文献   

14.
Raman, infra-red and multinuclear NMR spectroscopy were used to establish the structure of several TiX4·2L adducts (X=F, Cl, Br; L=Lewis base) in inert solvents. In contrast to the analogous SnX4·2L adducts where a cis-trans equilibrium prevails, most of the TiX4·2L adducts studied were found to have only the cis configuration. Trans isomers were observed but their formation was dependent on the donor ability of the ligand. In dichloromethane solution, the adducts with L=Me2O, Me2S, (MeOCH2-)2, Et2S, THT, Me2Se, MeCN, Me2CO, Cl(MeO)2PO, Cl2(MeO)PO, Cl3PO and Cl2(Me2N)PO were found to have the cis configuration only. For the adducts with L=THF, Cl(Me2N)2PO and TMPA, a cis-trans equilibrium was observed. The thermodynamic parameters were measured for cis-trans isomerization for TiCl4·2TMPA in CHCl3; these parameters are: Kiso277=[trans] / [cis]=0.36, ΔH°iso=− 1.3 ± 1.3 kJ/mol, ΔS°iso=−13.1 + 7.5 J/mol K, and ΔV°iso= − 1.3+0.8 cm3/mol. A complex equilibrium involving cis and trans isomers and the ionic complex [TiCl3·3HMPA]Cl was found to occur for the TiCl4 adduct with L=HMPA. 1H NMR was used to establish the relative stabilities of the cis adducts and the following sequence was obtained: Me2O ∼ MeCN < Me2CO < Me2S < Me2Se < Cl(MeO)2PO < TMPA < CI(Me2N)2PO.  相似文献   

15.
《Inorganica chimica acta》1986,116(2):125-133
Previously discussed topological models of metal cluster bonding are now extended to the treatment of anionic rhodium carbonyl clusters having structures consisting of fused polyhedra. Examples of such rhodium carbonyl clusters built from fused octahedra include the ‘biphenyl analogue’ [Rh12(CO)30]−2, the ‘face-sharing naphthalene analogue’ [Rh9- (CO)19]3−, and the ‘perinaphthene analogue’, [Rh11- (CO)23]3−. More complicated anionic rhodium carbonyl clusters treated in this paper include the [Rh13(CO)24H5−q]q anions (q = 2, 3, 4) having an Rh13 centered cuboctahedron, the [Rh14(CO)25- H4−q]q (q = 3,4) and [Rh14(CO)26]2− anions based on a centered pentacapped cube, the [Rh15- (CO)30]3− anion having an Rh15 centered 14-vertex deltahedron, the [Rh15(CO)27]3− anion having a tricapped centered 11-vertex polyhedron, the [Rh17- (CO)30]3− anion having a tetracapped centered cuboctahedron, and the [Rh22(CO)37]4− anion having a hexacapped centered cuboctahedron fused to an octahedron so that the octahedron and the cuboctahedron share a triangular face. Analyses of the bonding topologies in [Rh9(CO)19]3−, [Rh17- (CO)30]3−, and [Rh22(CO)37]4− indicate that a polyhedral network containing several fused globally delocalized polyhedral chambers will not necessarily have a multicenter core bond in the center of each such polyhedral chamber. This observation is of potential importance in extending topological models of metal cluster bonding to bulk metals.  相似文献   

16.
The versatility of cuboidal Mo3S4Co clusters for the preparation of complexes with different numbers of valence shell electrons (VSE) in the cluster is described. The reaction of the geometrically incomplete cuboidal cluster salt [(η5-Cp′)3Mo3S4][pts] (pts = p-toluenesulfonate) with one molar equivalent of [Co2(CO)8] afforded almost quantitatively the electroneutral 60 VSE cluster [(η5-Cp′)3Mo3S4Co(CO)] (1), which previously has been prepared in low yield by Curtis et al. in autoclave syntheses [M.D. Curtis, U. Riaz, O.J. Curnow, J.W. Kampf, Organometallics 14 (1995) 5337]. Cluster 1 was also obtained in high yield by reaction of [(η5-Cp′)3Mo3S4][pts] with [(η5-Cp)Co(CO)2]. Reaction of [(η5-Cp′)3Mo3S4][pts] with two molar equivalents of [Co(I)(CO)3(PPh3)] led to a complex mixture of products, of which the electron deficient 58 VSE cluster salt [(η5-Cp′)3Mo3S4Co(I)][Co(I)3(thf)] ([2][Co(I)3(thf)]) was isolated as single crystals. In the crystal structures of 1 and [2][Co(I)3(thf)], the Co-Mo bond lengths are almost identical, indicating a delocalization of the electron deficiency in [2]+. The reduced form of [2]+, [(η5-Cp′)3Mo3S4Co(I)] (2), was prepared by oxidative substitution of the carbonyl ligand in 1 by I2. Further reactions of 1 with PPh3 and NO leading to the 60 and 61 VSE cluster complexes [(η5-Cp′)3Mo3S4Co(PPh3)] (3) and [(η5-Cp′)3Mo3S4Co(NO)] (4), respectively, enabled the preparation of Mo3S4Co clusters in altogether four different oxidation states.  相似文献   

17.
《Inorganica chimica acta》1988,148(2):247-250
The seven-coordinate bisacetonitrile complexes [MI2(CO)3(NCMe)2] (M = Mo or W) react with L′ (L′ = PPh3, AsPh3 or SbPh3) in CH2Cl2 at room temperature to give [MI2(CO)3(NCMe)L′] which when reacted in situ with L (L = pyridine or substituted pyridines) affords good yields of 28 mixed seven-coordinate complexes [MI2(CO)3LL′]. It is likely these reactions occur via successive dissociative displacements of two acetonitrile ligands.  相似文献   

18.
The reaction with acetone of nickel(II) and copper(II) bis-chelated compounds of 6-methyl-2-pyridylmethylamine gives compounds of the quadridentate [N4] ligand 2,6-diaza-1,7-bis-(6′-methyl-2′-pyridyl)-3,5,5-trimethyl-hept-2-ene(Q). In the nickel series also, a bis-chelated perchlorate of the terdentate ligand 2-aza-1-(6′-methyl-2′-pyridyl)-3-methyl-hex-2-ene-5-one was obtained. In the copper series, five-coordinate species [Cu(Q)X]X (X = Br, I, NCS) and [Cu(QX]ClO4 (X = Cl) were isolated. If left in acetone, these undergo further reaction, with increasing ease in the order Cl < Br < I. An intermediate formation of a transient brown colour suggests the possible involvement of a copper(I) intermediate. The nature of the products was established by an X-ray analysis of the structure of [Ni(Q)NO3]NO3. Crystals are orthorhombic, a = 20.36(2), b = 13.38(1), c = 8.226(5) Å, space group Pna21. Using two-circle diffractometer data (1598 reflections), the structure was solved by Patterson and Fourier methods, and refined by block diagonal least-squares methods to a final R of 0.030. The expected quadridentate ligand was found in the cis-β configuration about the metal, with coordination sphere completed by a bidentate nitrate. Bond-lengths and angles within the molecular cation were unexceptionable considering the small ‘bite’ of the chelated nitrato group of only 59°.  相似文献   

19.
Cyclic voltammograms of cis-diammineplatinum α-pyrrolidone-blue and -tan, [Pt4(NH3)8(C4H6NO)4]n+ (n = 5 and 6, respectively) show for either complex only one redox peak at 0.53 V (average potential of the anodic and cathodic peak potentials). Coulometry and UVVis spectra of bulk- electrolyzed solution indicated that the redox peak corresponds to the reaction [Pt4(NH3)8(C4H6NO)4]8+ + 4e ⇄ 2[Pt2(NH3)4(C4H6NO)2]2+. When cyclic voltammetry is carried out in a solution of [Pt4(NH3)8(C4H6NO)4]6+ or a platinum electrode adsorbed with [Pt4(NH3)8(C4H6NO)4]6+ is used in the presence of oxidizing agent in the solution, O2 gas generates from the electrode surface with large catalytic cathodic current at potentials below ca. 0.8 V. The O2 gas was confirmed to generate from water by GC-MS analysis. This abnormal O2 generation phenomenon is explained with cyclic reactions of chemical surface oxide formation on the electrode by the oxidizing agent and electrochemical reduction of the surface oxide. Oxygen gas generates from the reaction of [Pt4(NH3)8(C4H6NO)4]8+ or [Pt4(NH3)8(C4H6NO)4]6+ with OH produced in the course of the electrochemical reduction of the electrode surface oxide. The ability of [Pt4(NH3)8(C4H6NO)4]8+ and [Pt4(NH3)8(C4H6NO)4]6+ to oxidize OH into O2 has been reported previously.  相似文献   

20.
Reaction of [Rh(CO)2I]2 (1) with MeI in nitrile solvents gives the neutral acetyl complexes, [Rh(CO)(NCR)(COMe)I2]2 (R=Me, 3a; tBu, 3b; vinyl, 3c; allyl, 3d). Dimeric, iodide-bridged structures have been confirmed by X-ray crystallography for 3a and 3b. The complexes are centrosymmetric with approximate octahedral geometry about each Rh centre. The iodide bridges are asymmetric, with Rh-(μ-I) trans to acetyl longer than Rh-(μ-I) trans to terminal iodide. In coordinating solvents, 3a forms mononuclear complexes, [Rh(CO)(sol)2(COMe)I2] (sol=MeCN, MeOH). Complex 3a reacts with pyridine to give [Rh(CO)(py)(COMe)I2]2 and [Rh(CO)(py)2(COMe)I2] and with chelating diphosphines to give [Rh(Ph2P(CH2)nPPh2)(COMe)I2] (n=2, 3, 4). Addition of MeI to [Ir(CO)2(NCMe)I] is two orders of magnitude slower than to [Ir(CO)2I2]. A mechanism for the reaction of 1 with MeI in MeCN is proposed, involving initial bridge cleavage by solvent to give [Rh(CO)2(NCMe)I] and participation of the anion [Rh(CO)2I2] as a reactive intermediate. The possible role of neutral Rh(III) species in the mechanism of Rh-catalysed methanol carbonylation is discussed.  相似文献   

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