Structures and energies of coadsorbed CO and H2 on Fe5C2(001), Fe5C2(110), and Fe5C2(100)

Density functional theory calculations have been carried out on the CO/H2 coadsorption on the (001), (110), and (100) surfaces of Fe5C2 for the understanding of the Fischer-Tropsch synthesis (FTS) mechanism. The stable surface species changes with the variation of the H2 and CO coverage. Along with dissociated hydrogen and adsorbed CO in 2-, 3-, and 4-fold configurations, methylidyne (C(s)H) (C(s), surface carbon), ketenylidene (C(s)CO), ketenyl (C(s)HCO), ketene (C(s)H2CO), and carbon suboxide (C(s)C2O2) are computed as thermodynamically stable surface species on Fe5C2(001) and Fe5C2(110) containing both surface iron and carbon atoms. These surface carbon species can be considered as the preliminary stages for FTS. On Fe5C2(100) with only iron atoms on the surface layer, the stable surface species is dissociated hydrogen and CO with top and 2-fold configurations. The bonding nature of these adsorbed carbon species has been analyzed.     

Synthesis and Crystal Structure of Cluster 〔C_6H_4-1,2-(CO_2CH_2C_2H-μ)_2〕〔Co_2(CO)_6〕_2

１ＩＮＴＲＯＤＵＣＴＩＯＮＯｃｔａｃａｒｂｏｎｙｌｄｉｃｏｂａｌｔｉｓａｖｅｒｙｃｏｎｖｅｎｉｅｎｔｓｔａｒｔｉｎｇｍａｔｅｒｉａｌｆｏｒｔｈｅｐｒｅｐａｒａｔｉｏｎｏｆａｌｍｏｓｔａｎｙｃｏｂａｌｔｃｏｍｐｏｕｎｄ〔１〕．Ｔｈｅｒｅａｃｔｉｏｎｓｏ...     

乙烷与CO2制乙烯反应的热力学和动力学研究

乙烷与ＣＯ２的主要反应及其热力学研究表明，乙烷与ＣＯ２反应很复杂，提高ＣＯ２氧化乙烷脱氢生成乙烯的选择，关键在一催化剂的开发；ＣＯ２不但可提高乙灶脱氢制乙烯的热力学平衡转化率，而且可与催化剂表面的积碳发生反应，延长催化剂的使用寿命。研究了催化剂上乙烷与ＣＯ２制乙烯反应的动力学，确定了ＣＯ２氧化乙烷脱氢反应的动力学方程及参数，表明乙烷与ＣＯ２制乙烯的反应速度比乙烷热裂解制乙烯的反应速度要大得多。     

Isolation, observation, and computational modeling of proposed intermediates in catalytic proton reductions with the hydrogenase mimic Fe2(CO)6S2C6H4

Proposed electrocatalytic proton reduction intermediates of hydrogenase mimics were synthesized, observed, and studied computationally. A new mechanism for H(2) generation appears to involve Fe(2)(CO)(6)(1,2-S(2)C(6)H(4)) (3), the dianions {[1,2-S(2)C(6)H(4)][Fe(CO)(3)(μ-CO)Fe(CO)(2)](2-) (3(2-)), the bridging hydride {[1,2-S(2)C(6)H(4)][Fe(CO)(3)(μ-CO)(μ-H)Fe(CO)(2)]}(-), 3H(-)(bridging), and the terminal hydride 3H(-)(term-stag), {[1,2-S(2)C(6)H(4)][HFe(CO)(3)Fe(CO)(3)]}(-), as intermediates. The dimeric sodium derivative of 3(2-), {[Na(2)(THF)(OEt(2))(3)][3(2-)]}(2) (4) was isolated from reaction of Fe(2)(CO)(6)(1,2-S(2)C(6)H(4)) (3) with excess sodium and was characterized by X-ray crystallography. It possesses a bridging CO and an unsymmetrically bridging dithiolate ligand. Complex 4 reacts with 4 equiv. of triflic or benzoic acid (2 equiv. per Fe center) to generate H(2) and 3 in 75% and 60% yields, respectively. Reaction of 4 with 2 equiv. of benzoic acid generated two hydrides in a 1.7 : 1 ratio (by (1)H NMR spectroscopy). Chemical shift calculations on geometry optimized structures of possible hydride isomers strongly suggest that the main product, 3H(-)(bridging), possesses a bridging hydride ligand, while the minor product is a terminal hydride, 3H(-)(term-stag). Computational studies support a catalytic proton reduction mechanism involving a two-electron reduction of 3 that severs an Fe-S bond to generate a dangling thiolate and an electron rich Fe center. The latter iron center is the initial site of protonation, and this event is followed by protonation at the dangling thiolate to give the thiol thiolate [Fe(2)H(CO)(6)(1,2-SHSC(6)H(4))]. This species then undergoes an intramolecular acid-base reaction to form a dihydrogen complex that loses H(2) and regenerates 3.     

Synthesis and Characterization of Tetrametal Cluster〔Co_2(CO)_6〕〔μ-HC_2CH_2OCH_2C_2H-μ〕〔Co_2(CO)_6〕

１ＩＮＴＲＯＤＵＣＴＩＯＮＩｎｔｅｎｓｅｉｎｔｅｒｅｓｔｉｎｔｒａｎｓｉｔｉｏｎ ｍｅｔａｌｃｌｕｓｔｅｒｓｃｏｎｔｉｎｕｅｓｂｅｃａｕｓｅｔｈｅｙｒｅｐｒｅｓｅｎｔｐｏｓ ｓｉｂｌｅｃｏｎｃｅｐｔｕａｌｂｒｉｄｇｅｓｂｅｔｗｅｅｎｈｏｍｏｇｅｎｅｏ...     

Reactions of monomeric [1,2,4-(Me3C)3C5H2]2CeH and CO with or without H2: an experimental and computational study

Addition of CO to [1,2,4-(Me3C)3C5H2]2CeH,Cp'2 CeH, in toluene yields the cis-(Cp'2Ce)2(mu-OCHCHO), in which the cis-enediolate group bridges the two metallocene fragments. The cis-enediolate quantitatively isomerizes intramolecularly to the trans-enediolate in C6D6 at 100 degrees C over 7 months. When the solvent is pentane, Cp'2Ce(OCH2)CeCp'2 forms, in which the oxomethylene group or the formaldehyde dianion bridges the two metallocene fragments. The cis-enediolate is suggested to form by insertion of CO into the Ce-C bond of Cp'2Ce(OCH2)CeCp'2, generating Cp'2CeOCH2COCeCp'2. The stereochemistry of the cis-enediolate is determined by a 1,2-hydrogen shift in the OCH2CO fragment that has the OC(H2) bond anti-periplanar relative to the carbene lone pair. The bridging oxomethylene complex reacts with H2, but not with CH4, to give Cp'2CeOMe, which is also the product of the reaction between Cp'2CeH and a mixture of CO and H2. The oxomethylene complex reacts with CO to give the cis-enediolate complex. DFT calculations on C5H5 model metallocenes show that the reaction of Cp2CeH with CO and H2 to give Cp2CeOMe is exoergic by 50 kcal mol-1. The net reaction proceeds by a series of elementary reactions that occur after the formyl complex, Cp2Ce(eta2-CHO), is formed by further reaction with H2. The key point that emerges from the calculated potential energy surface is the bifunctional nature of the metal formyl in which the carbon atom behaves as a donor and acceptor. Replacing H2 by CH4 increases the activation energy by 17 kcal mol-1.     

Chiral organometallic triangles with Rh-Rh bonds. 2. Compounds prepared from enantiopure cis-Rh2(C6H4PPh2)2(OAc)2(HOAc)2 and their catalytic potentials

Enantiomers of the orthometalated dirhodium compound cis-Rh2(C6H4PPh2)2(OAc)2(HOAc)2 (R-1 and S-1) were prepared from carboxylate exchange reactions of the resolved diasteroisomers of cis-Rh2(C6H4PPh2)2(protos)2(H2O)2 (protos = N-4-methylphenylsulfonyl-l-proline anion) and acetic acid. These compounds react with excess Me3OBF4 in CH3CN, producing the enantiomers of [cis-Rh2(C6H4PPh2)2(CH3CN)6](BF4)2 (R-2 and S-2) which have six labile and replaceable CH3CN ligands in equatorial and axial positions. Reactions of R-2 and S-2 with tetraethylammonium salts of the linear dicarboxylic acids, terephthalic acid (HO2CC6H4CO2H), oxalic acid (HO2CCO2H), and 4,4'-diphenyl-dicarboxylic acid (HO2CC6H4C6H4CO2H) afford the enantiopure triangular supramolecules [cis-Rh2(C6H4PPh2)2(O2CC6H4CO2)(py)2]3, RRR-3 and SSS-3, Rh6(cis-C6H4PPh2)6(O2CCO2)3(py)5(CH2Cl2), RRR-4 and SSS-4, and Rh6(cis-C6H4PPh2)6(O2CC6H4C6H4CO2)3(py)4(CH2Cl2)2, RRR-5 and SSS-5, respectively. The absolute structures of each of the enantiomers of 1, 3, 4, and 5 were determined by X-ray diffraction analyses. The enantiomers of 3, 4, and 5 were found to be enantiomorphically isostructural, whereas R-1 and S-1 crystallized in different space groups. In 4 and 5, CH2Cl2 molecules coordinate to rhodium atoms in the axial positions. The 1H and 31P[1H] NMR spectra of all compounds are reported. The triangular compounds are redox-active, and their electrochemistry is also discussed. An assay of the catalytic activity/selectivity performance of the triangles for typical metal carbene transformation, using the model intermolecular cyclopropanation of styrene with ethyl diazoacetate in both homogeneous and heterogeneous phases, show that these chiral triangles are very active and have remarkable selectivity when compared with simple Rh2 paddle-wheel catalysts with chiral amidate ligands.     

Chiral organometallic triangles with Rh-Rh bonds. 1. Compounds prepared from racemic cis-Rh2(C6H4PPh2)2(OAc)2

Reaction of racemic cis-Rh(2)(C(6)H(4)PPh(2))(2)(OAc)(2)(HOAc)(2) with excess Me(3)OBF(4) in CH(3)CN results in the formation of racemic cis-[Rh(2)(C(6)H(4)PPh(2))(2)(CH(3)CN)(6)](BF(4))(2).0.5H(2)O (1.0.5H(2)O), an ionic dirhodium complex which has two cisoid nonlabile orthometalated phosphine bridging anions and six labile CH(3)CN ligands in equatorial and axial positions. Reactions of 1 with tetraethylammonium salts of the linear dicarboxylates, oxalate, terephthalate, and 4,4'-biphenyl-dicarboxylate, in organic solvents, produced racemic crystals of the triangular compounds [Rh(2)(C(6)H(4)PPh(2))(2)](3)(C(2)O(4))(3)(py)(6).6MeOH.H(2)O (2.6MeOH.H(2)O), [Rh(2)(C(6)H(4)PPh(2))(2)](3)(O(2)CC(6)H(4)CO(2))(3)(DMF)(6).6.5DMF.0.5H(2)O (3.6.5DMF.0.5H(2)O), and [Rh(2)(C(6)H(4)PPh(2))(2)](3)(O(2)CC(6)H(4)C(6)H(4)CO(2))(3)(py)(6).4.5CH(3)OH.0.75H(2)O (4.4.5CH(3)OH.0.75H(2)O), respectively. All compounds are electrochemically active. The relative chiralities of the dirhodium units in each triangle have been established using a combination of data from X-ray crystallography and (31)P NMR spectroscopy.     

B(C6F5)3 adducts of transition metal acyl compounds

The transition metal acyl compounds [Co(L)(CO)3(COMe)] (L = PMe3, PPhMe2, P(4-Me-C6H4)3, PPh3 and P(4-F-C6H4)3), [Mn(CO)5(COMe)] and [Mo(PPh3)(eta(5)-C5H5)(CO)2(COMe)] react with B(C6F5)3 to form the adducts [Co(L)(CO)3(C{OB(C6F5)3}Me)] (L = PMe3, 1, PPhMe2, 2, P(4-Me-C6H4)3, 3, PPh3, 4, P(4-F-C6H4)3), 5, [Mn(CO)5(C{OB(C6F5)3}Me)] 6 and [Mo(eta(5)-C5H5)(PPh3)(CO)2(C{OB(C6F5)3}Me)], 7. Addition of B(C6F5)3 to a cooled solution of [Mo(eta(5)-C5H5)(CO)3(Me)], under an atmosphere of CO gave [Mo(eta(5)-C5H5)(CO)3(C{OB(C6F5)3}Me)] 8. In the presence of adventitious water, the compound [Co{HOB(C6F5)3}2{OP(4-F-C6H4)3}2] 9, was formed from [Co(P(4-F-C6H4)3)(CO)3(C{OB(C6F5)3}Me)]. The compounds 4 and 9 have been structurally characterised. The use of B(C6F5)3 as a catalyst for the CO-induced migratory-insertion reaction in the transition metal alkyl compounds [Co(PPh3)(CO)3(Me)], [Mn(CO)5(Me)], [Mo(eta(5)-C5H5)(CO)3(Me)] and [Fe(eta(5)-C5H5)(CO)2(Me)] has been investigated.     

Preparation and Crystal Structure of Hetero-metal Clusters [h5-C5H4C(O)CH2CH2C(O)OCH3]FeCoM(m3-S)(CO)8 (M = Mo or W)

The hetero-metal clusters [h5-C5H4C(O)CH2CH2C(O)OCH3]FeCoM(m3-S)(CO)8 (M = Mo 1, M = W 2) were prepared by thermal reactions of FeCo2(CO)9(m3-S) with metal exchange reagent [h5-C5H4C(O)CH2CH2C(O)OCH3]M(CO)3Na (M = Mo or W) in THF. Cluster 1 reacted with 2,4-dinitrophenylhydrazine at room temperature to yield the cluster hydrazone derivative (m3-S)CoFeMo(CO)8[h5-C5H4C(NR)Me] [R = NHC6H3-2,4-(NO2)2] 3. All the compounds were characterized by elemental analyses, IR and NMR spectra. Cluster 1 was determined by single crystal X-ray diffraction. Crystal data: C18H11O11SCoFeMo, Mr = 646.05, triclinic, space group P_1, a = 8.148(2), b = 10.685(3), c = 13.410(4) ?, a = 100.077(5), b = 102.452(5), g = 91.108(6)°, V = 1120.4(5) ?3, Z = 2, Dc = 1.915 g/cm3, F(000) = 636, m = 2.071 mm-1, the final R = 0.0378 and wR = 0.0968 for 5074 observations with (I > 2s(I)).     

Synthesis and Crystal Structure of a Molybdenum Carbonyl Compound with Thiolate and Dithiocarbamate Ligands,[Bu4N][(OC)4Mo(μ-SC6H5)2Mo(C5H10CNS2)(CO)2]

A di-molybdenum carbonyl compound containing thiolate and dithiocarbamate li- gands, [Bu4N][(CO)4Mo(μ-SC6H5)2Mo(C5H10dtc)(CO)2] 1 (C5H10dtc = S2CNC5H10), has been pre- pared by reaction of [Mo2(SC6H5)2(CO)8] with C5H10dtcNa and [NBu4]Br in acetone. It crystallizes in monoclinic, space group P21/n with a = 13.162(3), b = 17.466(2), c = 20.453(4)(A),β = 100.77(1)°, Z = 4, V = 4619(2)(A)3, C40H56Mo2N2O6S4, Mr = 980.95, Dc = 1.389 g/cm3, μ= 7.66 cm-1, F(000) = 1988 and R = 0.0746 for 5161 observed reflections with I > 2σ(I). The complex contains a [Mo2S2]2- planar core in which one Mo atom is chelated by a C5H10dtc ligand, leading to different coordination environments of the two Mo atoms. 95Mo NMR measurement indicates that the two Mo atoms are in different oxidation states.     

Ab initio chemical kinetic study on the reactions of ClO with C2H2 and C2H4

The mechanisms for the reactions of ClO with C(2)H(2) and C(2)H(4) have been investigated at the CCSD(T)/CBS level of theory. The results show that in both systems, the interaction between the Cl atom of the ClO radical and the triple and double bonds of C(2)H(2) and C(2)H(4) forms prereaction van der Waals complexes with the O-Cl bond pointing perpendicularly toward the π-bonds, both with 2.1 kcal/mol binding energies. The mechanism is similar to those of the HO-C(2)H(2)/C(2)H(4) systems. The rate constants for the low energy channels have been predicted by statistical theory. For the reaction of ClO and C(2)H(2), the main channels are the production of CH(2)CO + Cl (k(1a)) and CHCO + HCl (k(1b)), with k(1a) = 1.19 × 10(-15)T(1.18) exp(-5814/T) and k(1b) = 6.94 × 10(-21) × T(2.60) exp(-6587/T) cm(3) molecule(-1) s(-1). For the ClO + C(2)H(4) reaction, the main pathway leads to C(2)H(4)O + Cl (k(2a)) with the predicted rate constant k(2a) = 2.13 × 10(-17)T(1.52) exp(-3849/T) in the temperature range of 300-3000 K. These rate constants are pressure-independent below 100 atm.     

Energy density analysis of cluster size dependence of surface-molecule interactions: H2, C2H2, C2H4, and CO adsorption onto Si(100)-(2x1) surface

Adsorption of H2, C2H2, C2H4, and CO onto a Si(100)-(2x1) surface has been treated theoretically using Si(12n - 3)H(8n + 4) (n = 1-4) clusters. The energy density analysis (EDA) proposed by Nakai has been adopted to examine surface-molecule interactions for different cluster sizes. EDA results for the largest model cluster Si45H36 have shown that the adsorption-induced energy density variation in Si atoms decays with distance from the adsorption site. Analysis of this decay, which can be carried out using the EDA technique, is important because it enables verification of the reliability of the model cluster used. In the cases of H2, C2H2, C2H4, and CO adsorption onto the Si(100)-(2x1) surface, it is found that at least a Si21H20 cluster is necessary to treat the surface-molecule interaction with chemical accuracy.     

Unsaturated Ru(0) species with a constrained bis-phosphine ligand: [Ru(CO)2(tBu2PCH2CH2PtBu2)]2. Comparison to [Ru(CO)2(PtBu2Me)2

The synthesis of Ru(C2H4)(CO)2(dtbpe) (dtbpe = tBu2PC2H4PtBu2), then green [Ru(CO)2(dtbpe)]n is described. In solution, n = 1, while in the solid state, n = 2; the dimer has two carbonyl bridges. DFTPW91, MP2, and CCSD(T) calculations show that the potential energy surface for bending one carbonyl out of the RuP2C(O) plane is essentially flat. Ru(CO)2(dtbpe) reacts rapidly in benzene solution to oxidatively add the H-E bond of H2, HCl, HCCR (R = H, Ph), [HOEt2]BF4, and HSiEt3. The H-C bond of C6HF5 oxidatively adds at 80 degrees C. CO adds, as does the C=C bond of H2C=CHX (X = H, F, Me). The following do not add: N2, THF, acetone, H3COH, and H2O.     

Selective coupling of methylene groups at a Rh/Os core, yielding C2, C3, or C4 fragments: roles of the adjacent metals in carbon-carbon bond formation

The mixed-metal complex, [RhOs(CO)(4)(dppm)(2)][BF(4)] (1; dppm = micro-Ph(2)PCH(2)PPh(2)) reacts with diazomethane to yield a number of products resulting from methylene incorporation into the bimetallic core. At -80 degrees C the reaction between 1 and CH(2)N(2) yields the methylene-bridged [RhOs(CO)(3)(micro-CH(2))(micro-CO)(dppm)(2)][BF(4)] (2), which reacts further at ambient temperature to give the allyl methyl species, [RhOs(eta(1)-C(3)H(5))(CH(3))(CO)(3)(dppm)(2)][BF(4)] (4). At intermediate temperatures compounds 1 and 2 react with diazomethane to yield the butanediyl complex [RhOs(C(4)H(8))(CO)(3)(dppm)(2)][BF(4)] (3) by the incorporation and coupling of four methylene units. Compound 2 is proposed to be an intermediate in the formation of 3 and 4 from 1 and on the basis of labeling studies a mechanism has been proposed in which sequential insertions of diazomethane-generated methylene fragments into the Rh-C bond of bridging hydrocarbyl fragments occur. Reaction of the tricarbonyl species, [RhOs(CO)(3)(micro-CH(2))(dppm)(2)][BF(4)] with diazomethane over a range of temperatures generates the ethylene complex [RhOs(eta(2)-C(2)H(4))(CO)(3)(dppm)(2)][BF(4)] (7a), but no further incorporation of methylene groups is observed. This observation suggests that carbonyl loss in the formation of the above allyl and butanediyl species only occurs after incorporation of the third methylene fragment. Attempts to generate C(2)-bridged species by the reaction of 1 with ethylene gave no reaction, however, in the presence of trimethylamine oxide the ethylene adducts [RhOs(eta(2)-C(2)H(4))(CO)(3)(dppm)(2)][BF(4)] (7b; an isomer of 7a) and [RhOs(eta(2)-C(2)H(4))(2)(CO)(2)(dppm)(2)][BF(4)] (8) were obtained. The relationship of the above products to the selective coupling of methylene groups, and the roles of the different metals are discussed.     

Dinuclear oxidative addition of N-H and S-H bonds at chromium. Reaction of (*)Cr(CO)(3)(C(5)Me(5)) with [o-(HA)C(6)H(4)S-Cr(CO)(3)(C(5)Me(5))] (A = S,NH) yielding [eta(2)-o-(mu-A)C(6)H(4)S-Cr(C(5)Me(5))](2) and H-Cr(CO)(3)(C(5)Me(5))

Reaction of the 17-electron radical (*)Cr(CO)(3)Cp* (Cp* = C(5)Me(5)) with 0.5 equiv of 2-aminophenyl disulfide [(o-H(2)NC(6)H(4))(2)S(2)] results in rapid oxidative addition to form the initial product (o-H(2)N)C(6)H(4)S-Cr(CO)(3)Cp*. Addition of a second equivalent of (*)Cr(CO)(3)Cp* to this solution results in the formation of H-Cr(CO)(3)Cp* as well as (1)/(2)[[eta(2)-o-(mu-NH)C(6)H(4)S]CrCp*](2). Spectroscopic data show that (o-H(2)N)C(6)H(4)S-Cr(CO)(3)Cp* loses CO to form [eta(2)-(o-H(2)N)C(6)H(4)S]Cr(CO)(2)Cp*. Attack on the N-H bond of the coordinated amine by (*)Cr(CO)(3)Cp* provides a reasonable mechanism consistent with the observation that both chelate formation and oxidative addition of the N-H bond are faster under argon than under CO atmosphere. The N-H bonds of uncoordinated aniline do not react with (*)Cr(CO)(3)Cp*. Reaction of the 2 mol of (*)Cr(CO)(3)Cp* with 1,2-benzene dithiol [1,2-C(6)H(4)(SH)(2)] yields the initial product (o-HS)C(6)H(4)S-Cr(CO)(3)Cp and 1 mol of H-Cr(CO)(3)Cp*. Addition of 1 equiv more of (*)Cr(CO)(3)Cp to this solution also results in the formation of 1 equiv of H-Cr(CO)(3)Cp*, as well as the dimeric product (1)/(2)[[eta(2)-o-(mu-S)C(6)H(4)S]CrCp*](2). This reaction also occurs more rapidly under Ar than under CO, consistent with intramolecular coordination of the second thiol group prior to oxidative addition. The crystal structures of [[eta(2)-o-(mu-NH)C(6)H(4)S]CrCp*](2) and [[eta(2)-o-(mu-S)C(6)H(4)S]CrCp*](2) are reported.     

Raman,infrared and force field studies of K2(12)C2O4 x H2O and K2(13)C2O4 x H2O in the solid state and in aqueous solution,and of (NH4)2(12)C2O4 x H2O and (NH4)2(13)C2O4 x H2O in the solid state

The Raman and infrared spectra of solid K2(12)C2O4 x H2O are reported together with, for the first time, the corresponding Raman and infrared spectra of solid K2(13)C2O4 x H2O. Raman spectra of aqueous solutions of both isotopomers are also reported. In the solid state the oxalate anion is planar with D2h symmetry in this salt, whereas in aqueous solution the Raman spectra of the anion are best interpreted on the basis of D2d symmetry. The Raman spectra of solid (NH4)2(12)C2O4 x H2O and (NH4)2(13)C2O4 x H2O, in which the oxalate anion is twisted from planarity by 28 degrees about the CC bond, have also been recorded. Several reassignments have been made. The harmonic force field for the oxalate anion in the D2h, D2 and D2d geometries has been determined in part, and approximate values of key valence force constants determined. All the observed band wavenumbers and 12C/13C isotopic shifts are well reproduced by the force fields. The potential energy distribution of the totally symmetric normal modes of planar oxalate indicates that each mode consists of extensively mixed symmetry corrdinates and that the labels previously used for the bands seen here at 475 and 879 cm(-1) would better be described as v(CC) and deltaS(CO2), respectively, putting them in the same wavenumber order as v(NN) and deltaS(NO2) for the isoelectronic and isostructural molecule N2O4. The stretching force constants of N2O4 and planar C2O4(2-) are established to be in the order f(NN) < f(CC) and f(NO) > f(CO), consistent with the known relative bond lengths.     

C-H activation and C=C double bond formation reactions in iridium ortho-methyl arylphosphane complexes

The Vaska-type iridium(I) complex [IrCl(CO){PPh(2)(2-MeC(6)H(4))}(2)] (1), characterized by an X-ray diffraction study, was obtained from iridium(III) chloride hydrate and PPh(2)(2,6-MeRC(6)H(3)) with R=H in DMF, whereas for R=Me, activation of two ortho-methyl groups resulted in the biscyclometalated iridium(III) compound [IrCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)] (2). Conversely, for R=Me the iridium(I) compound [IrCl(CO){PPh(2)(2,6-Me(2)C(6)H(3))}(2)] (3) can be obtained by treatment of [IrCl(COE)(2)](2) (COE=cyclooctene) with carbon monoxide and the phosphane in acetonitrile. Compound 3 in CH(2)Cl(2) undergoes intramolecular C-H oxidative addition, affording the cyclometalated hydride iridium(III) species [IrHCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}] (4). Treatment of 2 with Na[BAr(f) (4)] (Ar(f)=3,5-C(6)H(3)(CF(3))(2)) gives the fluxional cationic 16-electron complex [Ir(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)][BAr(f) (4)] (5), which reversibly reacts with dihydrogen to afford the delta-agostic complex [IrH(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}][BAr(f)(4)] (6), through cleavage of an Ir-C bond. This species can also be formed by treatment of 4 with Na[BAr(f)(4)] or of 2 with Na[BAr(f)(4)] through C-H oxidative addition of one ortho-methyl group, via a transient 14-electron iridium(I) complex. Heating of the coordinatively unsaturated biscyclometalated species 5 in toluene gives the trans-dihydride iridium(III) complex [IrH(2)(CO){PPh(2)(2,6-MeC(6)H(3)CH=CHC(6)H(3)Me-2,6)PPh(2)}][BAr(f) (4)] (7), containing a trans-stilbene-type terdentate ligand, as result of a dehydrogenative carbon-carbon double bond coupling reaction, possibly through an iridium carbene species.     

Reactions of metalloalkynes. New C2 bonding mode in a trimetallic complex

The reaction of the silver complexes [((Ru(CO)2(eta-C5H4R))2(mu-C identical to C))3Ag3][BF4]3 (R = H or Me) with [RuCl(CO)2(eta-C5H4R)] at room temperature gave the new trimetallic complexes [(Ru(CO)2(eta-C5H4R))3(eta 1:eta 2-C identical to C))][BF4] which contain the C2(2-) ligand surrounded by ruthenium atoms; these complexes do not contain metal-metal bonds and were characterised by single crystal X-ray studies; the solid state structure is not retained in solution, where it is found to be fluxional on the NMR timescale and the dynamic process postulated could be described as 'bearing-like'.     

(Na[Fe(CO)2C5H5]2)n的形成和反应特性的研究

King[1]认为,双环戊二烯基二羰基铁[Fe(CO)2C5H5]2与钠汞齐(Na/Hg)作用可直接得到环戊二烯基二羰基铁钠Na[Fe(CO)2C5H5].但我们在研究合成异核金属配合物过程中,按文献[1]所述方法制得的环戊二烯基二羰基铁钠,分别与主族金属元素锡的配合物L3SnCl (L=C6H11,C6H5)和过渡金属稀土元素的配合物(C5Me5)2 LnCl(Ln=Dy,Gd,Sm,Nd,Pr) 在相同反应条件下作用,却得到了金属间具有完全不同成键形式的两类异核金属配合物.为此,我们对[Fe(CO)2C5H5]2与钠汞齐(Na/Hg)反应产物的结构形式和其在异核金属配合物合成中的反应特性进行了初步研究.