THE CATALYSIS OF IRON-COBALT BIMETALLIC CLUSTERS——1.THERMAL STABILITY AND DECOMPOSITION REACTION OF[R_4N][FeCo_3(CO)_(12)]IN SOLUTION

Thermal decomposition of[R_4N][FeCo_3(CO)_(12)][I](R=ethyl,butyl,hexadecyl,benzyltrimethyl,benzyltriethyl)in n-heptane,toluene and methanol was investigated bythe in situ high pressure IR spectroscopic method.The results show that underhydroformylation conditions all clusters decompose to Co_2(CO)_8,Fe(CO)_5 and the salt ofCo(CO)_4~-,and Co_2(CO)_8 reacts with H_2 to form HCo(CO)_4.Thermal stability of theclusters decrease with the increase of polarity of solvents.Under the hydroformylation con-ditions,IR spectra of the clusters are compatible with those of Fe(CO)_5+Co_2(CO)_8+[R_4N]Cl system.Because of the stabilizing effect or tetra-alkylammonium cation,when the tem-perature drops below 50℃ after decomposition of the clusters,the characteristic absorptionbands of the clusters appear again,so the decomposition process is reversible.     

金属原子簇LECo3（CO）n的催化作用和机理研究

研究了四面体金属原子簇LECo_3(CO)_n对烯烃氢甲酰化反应的催化作用.比较了E=C.Co、Fe.Ru.Rh金属簇的催化活性,异核金属簇的催化活性高于同核簇,异核金属簇中Rh-(Co 簇活性最高.考察了簇YCCO_3(CO)_9和[R_4 N][FeCo_3(CO)_(1-2)]对各种结构烯烃氢甲酰化反应的催化作用和Y与[R_4N]的影响.采用高温、高压原位红外光谱方法研究了YCCo_3(CO)_9和[R_4N][FeCo_3(CO)_(1-2)]的热稳定性和催化烯烃氢甲酰化反应的机理.     

Nitrosyl Complexes 6.Reactions of Na[Fe(CO)_3NO]with Cp~*M(CO)_3Cl(Cp~*=η~5-CH_3C_5H_4,M=Mo or W):Crystal structures of Cp~*M(CO)_2NO and Cp~*M(μ_3-NH)(μ_2-NO)(μ_2-CO)Fe_2(CO)_6

Sodium nitrosylcarbonyliron reacts with methylcyclopentadienylcarbonylmetal(Mo orW)chloride in CH_3OH/THF at room temperature to give CpMo(CO)_2NO(1a)(Cp=η~5-CH_3C_5H_4)or CpW(CO)_2NO(1b),[CpMo(CO)_3]_2(2a)or[CpW(CO)_3]_2(2b),and CpMo(μ3-NH)(μ2-NO)-(μ2-CO)Fe_2(CO)_6(3a)or CpW(μ3-NH)(μ2-NO)(μ2-CO)Fe_2(CO)_6(3b),respectively.Complexes1a,1b,3a and 3b were analyzed by IR,NMR,MS and elemental analyses,and the crystalstructures of 1b,3a and 3b were determined by X-ray diffraction method.The new clusters 3aand 3b have μ3-NH ligands which were formed by redaction of NO in the synthetic reactions.     

Addition Reaction of Fe（CO）_n （n = 3～5） on Fullerene C_（50）, C_（60）, and C_（70）： A Density Functional Theory Study

The electronic structure and reactivities of Fe(CO)n (n = 3~5) addition to different fullerenes have been investigated through the first-principles calculations, and the results indicate that Fe(CO)3 and Fe(CO)4 can be adsorbed to the outside network of fullerene via hollow and bridge sites, respectively. Both of them have larger binding energy, but when Fe(CO)5 is adsorbed via the top site, the binding energy is relatively smaller. According to the directional curvature theory, the reactivities of Fe(CO)3 addition to the fullerenes are determined by KM of the ring center, and those of Fe(CO)4 addition by KD of the C-C bond curvature; while for Fe(CO)5, it presents weak reactivities in the addition reaction because of the larger volume effect. No matter whether the addition reaction takes place on the hollow or bridge site, the binding energies show a linear relationship with KD. This work further enriched the directional curvature theory and applied the isolobel analogy theory in the fullerene addition reactions.     

Theoretical prediction on a special bridging metal–Xe–metal bond with remarkable stability in Re_2Cp_2(PF_3)_4Xe

The bridging Re–Xe–Re bond with a remarkable stability is firstly predicted. The average binding energies for Re–Xe bond in Re_2Cp_2(PF_3)_4Xe with bridging Xe are calculated to be higher than that in Re Cp(CO)_2Xe, Re Cp(CO)(PF_3)Xe and Re Cp(PF_3)_2Xe with terminal Xe. The interaction between two Re Cp(PF_3)_2 fragments provides an additional contribution for the stability of bridging Re–Xe–Re bond. Besides, the Re_2Cp_2(PF_3)_4Xe isomers with bridging Xe are also stable in energy than the isomers with bridging PF_3. As the terminal Re–Xe bond was found to exist in experiments, the more stable bridging Re–Xe–Re bond might be existent under similar or even milder condition.     

Synthesis of Two Novel Rhenium（I） Bipyridyl Photosensitive Dyes

Two novel rhenium(I) 2, 2′-bipyridyl complexes, [(4,4′-di-COOEt-bipy) Re(CO)3 (NCCH3)PF6] and [(4,4′-di-COOEt-bipy) Re (CO)3 (NCS)], a model complex [(4,4′-di-COOEt-bipy) Re (CO)3 (pyridine)PF6], were synthesized. Their ground state electronic spectra and emission spectra were measured in acetonitrile. The MLCT absorption maximum of the complex exhibited a considerable red shift as the ligand changed from pyridine to CNCH3, or SCN.     

SYTHESE AND REACTIONS OF HETEROBINUCLEAR COMPLEXES [PhCl_2SnM(Cl)(CO)_3(CH_3CN)_2] (M = Mo, W)

Abstract The complexes [M(CO)_3(CH_3CN)_3](M=Mo, W)react with an equimolar quantity ofPhSnCl_3 in dichloromethane at room tempreture to afford new heterobinuclearcomplexes [PhCl_2SnM(Cl)(CO)_3(CH_3CN)_2] [M=Mo(1); W(2)]. The complexes reactwith two equivalents of PR_2R'(R=Ph, R'=Ph, Me; R=Cy, R'=H) to yield stablecomplexes [PhCl_2SnM(Cl)(CO)_3(PR_2R')_2]. Reaction of[PhCl_2SnM(Cl)(CO)_3(CH_3CN)_2]with one equivalent of PPh_2(CH_2)nPPh_2(n=I,2) or bulky phosphine ligands PBu_2~tClin dichloromethane at room tempreture to give [PhCl_2SnMo(Cl)(CO)_3{PPh_2(CH_2)n-PPh_2}] .CH_2Cl_2, [PhCl_2SnMo(Cl)(CO)_3PBu_2~tCl]. CH_2Cl_2, respectively. The complexes1 and 2 react with phosphite donor ligands P(OMe)_3 to give [PhCl_2SnM(Cl)(CO)_2-{P(OMe)_3}_3]. All complexes have been characterized by elemental analysis, IRand ~1HNMR spectroscopies. Here we report the preliminary results of this work.     

A Density Functional Study for the Reaction Mechanism of CO Oxidation on the Copper Cluster

We have studied the reaction mechanism of CO oxidation on the Cu_(13) cluster via density functional theory. There are two main reaction pathways to be considered: Eley-Rideal(ER) and Langmuir-Hinshelwood(LH) mechanisms, respectively. According to these two main reaction mechanisms, we have obtained five reaction pathways for the first CO oxidation(denoted as R_(ER1),R_(ER2), R_(LH1), R_(LH_2) and R_(LH3), respectively): R_(ER1) is CO_(gas) + O_(2(ads)) → O(ads) + CO_(2(gas)); R_(ER2) is CO_(gas) + O_(2(ads)) → CO_(3(ads)) → O(ads) + CO_(2(gas)); R_(LH1) refers to CO(ads) + O_(2(ads)) → O(ads) + CO_(2(gas)); R_(LH_2) refers to CO(ads) + O_(2(ads)) → OOCO(ads) → O(ads) + CO_(2(gas)) and R_(LH3) refers to O_(2(ads)) + CO(ads)→ O(ads) + O(ads) + CO(ads) → O(ads) + CO_(2(gas)). These pathways have low energy barriers and are strongly exothermic, suggesting the Cu_(13) cluster is very favorable catalyst for the first CO oxidation. However, there are higher energy barriers of 99. 8 and 45.4 kJ/mol in the process of producing and decomposing intermediates along the R_(LH_2) and R_(ER2), indicating that R_(ER1), R_(LH1) and R_(LH3) are superior pathways with lower energy barriers, especially the R_(ER1) channel. Thereafter, the second CO is more prone to react with the remaining oxygen atom on Cu_(13) along the ER channel in comparison with the LH pathway, in which the moderate barrier is 70.0 kJ/mol and it is exothermic by 59.6 kJ/mol. Furthermore, the interaction between the absorbate and cluster is analyzed by electronic analysis to gain insights into high activity of the copper cluster.     

Comparison of(η~6-Fluoroarene)tricarbonylchromium Complexes with Their Chloro-analogs in Radical Aromatic Substitutions

Reactions of fluoroarene-Cr(CO)_3 complexes with SmI_2 andcarbonyl compounds in THF/HMPA at-40— -60℃ affordedthe corresponding radical aromatic substitution products in highyield. Compared to the corresponding chloroarene-Cr.(CO)_3complexes, fluoroarene-Cr(CO)_3 complexes showed a higher ef-ficiency and slightly lower regioselectivity.     

SYNTHESIS, STRUCTURE AND ELECTROCHEMICAL STUDIES ON SINGLE MoFe_3S_4 AND WFe_3S_4 CUBANE-TYPE CLUSTER COMPOUNDS*

Single cubane-like clusters, MFe_3S_4(R_2dtc)_5 (M=Mo, R_2=—(CH_2)_4—, Bz_2; M=W, R_2=Me_2, —(CH_2)4—; dtc=dialkyldithiocarbamate) were synthesized by assembly reaction of (NH_4)_2MS_4 (M=Mo, W), FeCl_2 with R_2dtcNa (or NH_4) in DMF. The structure, IR, EPR and cyclic voltammogram are described and discussed. MoFe_3S_4(C_4H_8dtc)_5 was also obtained from the conversion of linear cluster Fe(DMF)_6[(FeCl_2)_2MoS_4] in the presence of C_4H_8dtc NH_4. Both clusters MoFe_3S_4(C_4H_8dtc)_4·2C_2H_5CN and WFe_3S_4(C_4H_8dtc)_5·2DMF crystallize in the monoclinic space group C2/c with a=12.544(2), (Mo-cluster), 12.533(4) (W-cluster); b=20.478(4), 20.121(6); c=19.582(7), 19.659(2);β=102.82(2), 102.96(3)°; and Z=4, 4. Their structures were refined to R=0.057 and 0.064 with use of 2690 and 2179 reflections (ι>3Q(I)), respectively. Many similarities in structure for Mo and W clusters indicate that both Mo and W play a very similar role in the clusters.     

Alpha-hydroxylation at C-15 and C-16 in cholesterol: synthesis of (25R)-5alpha-cholesta-3beta,15alpha,26-triol and (25R)-5alpha-cholesta-3beta,16alpha,26-triol from diosgenin

[reaction: see text] (25R)-5alpha-cholesta-3beta,16alpha,26-triol 7b and (25R)-5alpha-cholesta-3beta,15alpha,26-triol 10b were synthesized, via (25R)-5alpha-cholesta-3beta,16beta,26-triol 5a, from diosgenin 3 in 52% yield over six steps and 47% yield over eight steps, respectively. An efficient method for inversion of a C-16beta hydroxyl to the C-16alpha position and a short method for transposition of a C-16beta hydroxyl to the C-15alpha position via the unexpected beta-reduction of a C-15 ketone in a steroid are reported.     

Emissive chromium(III) complexes with substituted arylethynyl ligands

Arylethynylchromium(III) complexes of the form trans-[Cr(cyclam)(CCC(6)H(4)R)(2)]OTf (where cyclam = 1,4,8,11-tetraazacyclotetradecane, R = H, CH(3), or CF(3) in the para position, and OTf = trifluoromethanesulfonate) have been prepared and characterized by IR spectroscopy and X-ray diffraction. The complexes are emissive with excited-state lifetimes in a deoxygenated fluid solution between 200 and 300 micros.     

Novel air-stable and volatile bis(pyridylalkenolato)palladium(II) and -platinum(II) derivatives

Six novel homoleptic palladium(II) and platinum(II) complexes of donor-substituted alkenol ligands [PyCHC(R)OH; Py = pyridine, R = CH(3), CF(3), C(2)F(5), C(3)F(7)] of the general formula M[PyCHC(R)O](2) (M = Pd, Pt) were synthesized by reacting the deprotonated ligands with PdCl(2) and K(2)PtCl(4), respectively. Molecular structures, revealed by single-crystal X-ray diffraction analyses, showed a square-planar arrangement of ligands around palladium and platinum centers, with the pyridine-ring nitrogen atoms situated in a mutually trans position. The monomeric nature of the compounds in the solution state was confirmed by multinuclear ((1)H, (13)C, and (19)F) NMR spectroscopy. Thermal decomposition profiles recorded under a nitrogen atmosphere suggested their potential as volatile precursors to palladium and platinum materials. The volatility was increased upon elongation of the perfluoroalkyl chain, which suppressed the intermolecular interactions, as is evident in crystal packings. The volatility of these compounds was attributed to bidentate chelation of the alkenol units and cooperativity among the electron-back-donating nitrogen atom and interplay of electron-withdrawing C(x)F(y) groups, resulting in an effective steric shielding of the metal atoms.     

Solvent effects on the S0(1(1)Ag-) --> S2(1(1)Bu+) transition of beta-carotene, echinenone, canthaxanthin, and astaxanthin in supercritical CO2 and CF3H

Solvent-induced spectral shifts of the four C40 carotenoids, beta-carotene, echinenone, canthaxantin, and astaxanthin, have been studied in supercritical CO2 and CF3H. In situ absorption spectroscopic analysis was used to determine the maximum peak position of the electronic transitions from the ground state (1(1)Ag-) to the S2 state (1(1)Bu+) of the carotenoids. The medium polarizability function, R(n) = (n2 - 1)/(n2 + 2) of the refractive index of the solvent was varied over the range R(n) = 0.08-0.14, by changing the pressure of CO2 or CF3H between 90 and 300 bar at the temperature 308 K. For all the carotenoids studied here, a significant hypsochromic shift of ca. 20-30 nm was observed in supercritical fluids as compared to that in nonpolar liquids. The spectral shifts in supercritical fluids were compared with those in liquids and showed a clear linear dependence on the medium polarizability. The temperature-dependent shift of the absorption maxima was less significant. Interestingly, there was almost no difference in the energetic position of the absorption maxima in supercritical CO2 and CF3H at a given R(n) value. This is in contrast to previous extrapolations from studies in liquids at larger R(n) values, which yielded different slopes of the R(n)-dependent spectral shifts for polar and nonpolar solvents toward the gas-phase limit of R(n) = 0. The current experimental results in the gas-to-liquid range show that the polarity of the solvent has only a minor influence on the 1(1)Ag- --> 1(1)Bu+ transition energy in the region of low R(n). We also obtain more reliable extrapolations of this 0-0 transition energy to the gas-phase limit nu(0-0)(gas-phase) approximately (23,000 +/- 120) cm(-1) for beta-carotene.     

Synthesis of trans-(3S)-amino-(4R)-alkyl- and -(4S)-aryl-piperidines via ring-closing metathesis reaction

[reaction: see text] trans-(3S)-Amino piperidines bearing various alkyl and aryl substituents at the C-4 position were synthesized via a ring-closing metathesis reaction. The absolute stereochemistry was controlled using a protected D-serine as a starting material. Stereoselective hydrogenation of allylamines provided trans-(3S)-amino-(4R)-alkyl- and -(4S)-aryl-piperidines. This procedure presents the first method for the asymmetric synthesis of 4-substituted 3-amino piperidines.     

STRUCTURE OF 5-(N-METHYL-β-NAPHTHYLAMINO)-PENTA-2,4-DIENAL,C_(16)H_(15)NO

<正> M=237.31, orthorhombic, Pbca, a=8.342(2), b=15.675(3), c=19.779 (4)A3, Z=8, Dx=1.21 g/cm3, λ(MoKα)=0.71069A, μ=0.71 cm-1, F(000)=1008, room temperture, R=0.046. The planes of the formyl butadienyl group and the naph-thyl ring are tilted with respect to the plane of the nitrogen frame N by 2.8° and 31.4° , respectively. The O atom and the methyl group are in Z position.     

STRUCTURE OF 3-(N-METHYL- β-NAPHTHYLAMINO)-ACROLEIN,C_(14)H_(13)NO

<正> M=211.28, monoclinic, P21/c, a=10.268(2), b=11.581(2), c=9.605(2)A, β=100.40(2)°, V=1123.5(4)A3, 2=4, Dx=1.25 g/cm3, λ=0.71069A, u=0.73 cm-1, F(000)=448, room temperature, R=0.041. The planes of the formylvinyl groupand the naphthyl ring are tilted with respect to the plane of nitrogen frameN by 8.6 and 33.6 , respectively. The O atom and the methyl group are in Z position.     

Effects of tris(pyrazolyl)borato ligand substituents on dioxygen activation and stabilization by copper compounds

Dinuclear [Cu2(mu-O)2(Tp(R,R')2] complexes, analogues of the active site of oxyhemocyanin, are theoretically studied, and the effect of the substituents of the tris(pyrazolyl)borate ligands, Tp(R,R'), is analyzed. Density functional theory calculations reveal that the type of bridging oxygen, peroxo, or bisoxo is strongly influenced by the nature and position of the R substituents because of variable substituent...bridging oxygen interactions, as well as electronic effects. The electronic effects of ligands at the 5 position are not significant, but peroxo complexes are favored by electron-withdrawing groups at the 3 position while bisoxo ones are strongly sterically disfavored.     

A new efficient route to chiral 1,3-disubstituted ferrocenes: application to the syntheses of (R(p))- and (S(p))-17alpha-[(3'-formylferrocenyl)ethynyl]estradiol

Starting from (2S,4S)-2-ferrocenyl-4-(methoxymethyl)-1,3-dioxane (4), use of the stereogenic ortho-directing menthyl para-tolyl sulfoxide group, which occupies the 2' position in the ferrocenyl ring and redirects subsequent lithiation to the 3' position, allowed the synthesis of optically pure (S(p))-1-formyl-3-iodoferrocene (8), that was characterized by single-crystal X-ray diffraction. Combination of this method with a protection-deprotection strategy, using trimethylsilyl as a temporary blocking group, yielded (R(p))-1-formyl-3-iodoferrocene (13). Separate Sonogashira coupling of each of the enantiomeric iodoformylferrocenes 8 and 13 with 17alpha-ethynyl-estradiol produced (R(p))-17alpha-[(3'-formylferrocenyl)ethynyl]estradiol (14) and (S(p))-17alpha-[(3'-formylferrocenyl)ethynyl]estradiol (15), respectively.     

Preparation and biological activity of 2-[4-(thiazol-2-yl)phenyl]propionic acid derivatives inhibiting cyclooxygenase.

A series of 2-[4-(thiazol-2-yl)phenyl]propionic acids substituted at various positions were prepared by the reaction of diethyl 2-methyl-2-(4-thiocarbamoylphenyl)malonates with alpha-bromoaldehyde diethyl acetals or alpha-haloketones followed by hydrolysis of esters. The inhibition of prostaglandin H synthetase (cyclooxygenase) was assayed by use of an enzyme preparation from guinea pig polymorphonuclear leukocytes. Examination of the structure-activity relationship of these compounds indicated that the substitution pattern with halogens at position 3 (R1) of the benzene ring and a methyl group in position 4 (R2) and/or 5 (R3) of the thiazole ring were favorable for inhibitory activity. The compounds bearing bulky alkyl or polar functional groups at the R2 position were weak inhibitors. The potent inhibitors of cyclooxygenase were tested for their ability to reduce carrageenin-induced inflammation of rat paws. These derivatives had strong anti-inflammatory activity based on their strong inhibition of cyclooxygenase, with some exceptions, including those with a thiomethyl group at R1.