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1.
Helmut Fischer Normen Szesni Gerhard Roth Nicolai Burzlaff Bernhard Weibert 《Journal of organometallic chemistry》2003,683(2):301-312
Displacement of tetrahydrofuran in [(CO)5M(THF)] (M=Cr, W) by the anion [CCC(X)Y]− (X=O; NR; Y=NR′2, Ph) followed by alkylation of the resulting metalate with [R″3O]BF4 (R″=Me, Et) offers a convenient and versatile route to π-donor-substituted allenylidene complexes, [(CO)5MCCC(XR″)Y]. Allenylidene complexes in which the terminal carbon atom of the allenylidene ligand constitutes part of a heterocycle are likewise accessible by this reaction sequence. Reaction of [(CO)5M(THF)] with Li[CCC(NMe)Ph]− and subsequent protonation of the metalate afford [(CO)5MCCC(NMeH)Ph] in high yield. As indicated by the spectroscopic data of the compounds and the X-ray analyses of three representative examples, these allenylidene complexes are best described as hybrids of allenylidene and zwitterionic alkynyl complexes with delocalisation of the electron pair at nitrogen towards the metal center. Dimethylamine reacts with the amino(phenyl)allenylidene complex [(CO)5CrCCC(NMe2)Ph] (7a) by addition of the amine across the CαCβ bond to give selectively the E-alkenyl(amino)carbene complex [(CO)5CrC(NMe2)CHC(NMe2)Ph] (12). In contrast, the reaction of dimethylamine with the amino(methoxy)allenylidene complex [(CO)5CrCCC(NMe2)OMe] (1a) proceeds by addition of the amine to the Cγ atom and subsequent elimination of methanol to give the substitution product [(CO)5CrCCC(NMe2)2] (13). Triphenylphosphane neither adds to the Cα nor the Cγ atom of 7a but upon irradiation displaces a CO ligand to form a cis-allenylidene(tetracarbonyl)phosphane complex 15. 相似文献
2.
The thermal substitution kinetics of norbornadiene (NBD) by bis(diphenylphosphino)alkanes (PP), (C6H5)2P(CH2)nP(C6H5)2 (n=1, 2, 3) in M(CO)4(η2:2-NBD) complexes (M=Cr, Mo, W), were studied by quantitative FT-IR spectroscopy. The reaction rate exhibits first-order dependence on the concentration of the starting complex, and the observed rate constant depends on the concentration of the leaving NBD ligand and on the concentration and the nature of the entering PP ligand. In the proposed mechanism there are two competing initial steps: an associative reaction involving the attachment of the entering PP ligand to the transition metal center and a dissociative reaction involving the stepwise detachment of the diolefin ligand from the transition metal center. A rate law is derived from the proposed mechanism. The activation parameters are obtained from the evaluation of the kinetic data. It is found that at higher concentrations of the entering ligand, the associative path is dominant, while at lower concentrations the contribution of the dissociative path becomes significant. Both the observed rate constant and the activation parameters show noticeable variation with the chain length of the diphosphine ligand. 相似文献
3.
Beth A. Dykerman Erin M. McCarvill Natasha D. Doiron Hillary A. Jenkins Kevin M. Smith 《Journal of organometallic chemistry》2007,692(15):3183-3190
Single-electron oxidation of the known Cr(II) bis(amidinate) Cr[(Me3SiN)2CPh]2 (1) provides synthetic access to neutral Cr(III) complexes. The complexes Cr[(Me3SiN)2CPh]2X were prepared by reaction of 1 with AgO2CPh (X = O2CPh, 2), of 1 with iodine in THF (X = I/THF, 3), or of 1 with iodine in pentane, followed by addition of 2-adamantanone (X = I/2-adamantanone, 4). Treatment of 2 or 3 with C3H5MgCl resulted in the thermally stable allyl complex (X = η3-C3H5, 5). A preliminary kinetics study of the reaction of 1 with excess allyl benzoate and allyl acetate was performed. The molecular structures of 2, 3 and 5 were confirmed by single crystal X-ray diffraction. 相似文献
4.
José G. López-Cortés Luis F. Contreras de la Cruz Ruben A. Toscano Henri Rudler 《Journal of organometallic chemistry》2005,690(9):2229-2237
Ferrocenyllithium reacts with M(CO)6 (M = Cr, W, Mo) in THF to give, after alkylation at oxygen, the corresponding carbene complexes 3a-c in good yield. Complexes 3a,b were characterized by X-ray analysis. These complexes react with pentylamine to give the corresponding aminocarbene complexes 7a-c and with allylamine to give, in the case of chromium and tungsten, the corresponding and expected aminonocarbene complexes 8a,b, and for molybdenum, complex 9c in which the double bond is already coordinated to the metal. 8a,b could be converted in 9a,b in excellent yield. The structure of 9a could be confirmed by an X-ray analysis. Alkylations at nitrogen could be carried on complex 9c as well as on complexes 9a,b. 相似文献
5.
Ari Lehtonen Hynek Balcar Reijo Sillanpää 《Journal of organometallic chemistry》2008,693(7):1171-1176
Tungsten(VI) and molybdenum(VI) complexes [MO(L1)Cl2] and [M(X)(L2)Cl3] (X = O, NPh) with tridentate aminobis(phenolate) ligand L1 = methylamino-N,N-bis(2-methylene-4,6-dimethylphenolate) and bidentate aminophenolate ligand L2 = 2,4-di-tert-butyl-6-((dimethylamino)methyl)phenolate) were prepared and characterised. These complexes are principally stable in open atmosphere under ambient conditions. When activated with Et2AlCl, they exhibited high activity in ring-opening metathesis polymerisation (ROMP) of 2-norbornene (NBE) and its derivatives. Especially complexes [M(NPh)(L2)Cl3], which are easily available from corresponding metal oxides MO3 by a simple three-step synthesis, were found very efficient ROMP catalysts for NBE (M = Mo, W) and 2-norbornen-5-yl acetate (M = Mo). 相似文献
6.
7.
The reaction of [CpOs(PPh3)2Br] with diphenylpropargylic alcohol HCCCPh2(OH) in the presence of ammonium hexafluorophosphate leads to the formation of cationic osmiumallenylidene complex [CpOs(CCCPh2)(PPh3)2][PF6] (1), but when the dimethylpropargylic alcohol HCCCMe2(OH) was used as a substrate, a dicationic diosmium vinylidene-alkylidene complex of the formula [(CpOs)2(μ-C10H12)(PPh3)4][PF6]2 (2) was obtained. The structures of these complexes have been determined by X-ray diffraction. Complex 1 crystallizes in monoclinic space group P21/c with a=13.4083(6) Å, b=19.5700(9) Å, c=20.3806(9) Å and β=100.3620(10)°. Complex 2 crystallizes in triclinic space group with a=13.0396(11) Å, b=15.2420(13) Å, c=21.6406(19) Å and α=72.5290(10)°, β=75.1960(10)°, γ=85.6360(10)°. 相似文献
8.
Density functional and second-order Moller–Plesset theory were used to model W(0) carbene mediated homogeneous metathesis reaction of propylene. The calculations show that the rate determining step of the metathesis is the initiation. After the initiation has been completed the rate determining step becomes dissociation of olefin–metallocarbene complex. The low stereoselectivity of the olefin metathesis reaction is due to the close matching of activation energies for cis and trans isomer formation and the fast cis–trans isomerization caused by the catalysts. The non-productive olefin metathesis reaction always dominates the reaction mixture owing to its very low activation energy. The electronic structure of metal carbene olefin complexes can be described as a combination of donor–acceptor interactions between HOMO of the olefin and LUMO of metal carbene located at carbene carbon on the one hand, and the Dewar, Chatt and Duncanson back donation scheme on the other. 相似文献
9.
Salah A. Naman Ayad H. Jassim Mahasin F. Alias 《Journal of photochemistry and photobiology. A, Chemistry》2002,150(1-3):41-48
Photodecomposition of 10 different molybdenum and tungsten mixed carbonyl complexes, [M(CO)3(B)(A)]I2 where B=o-phenanthroline or bipyridyl, A=3-(2-propynyl)thio-4,5-diphenyl-4H-1,2,4-triazole (TRZA) or S-propynyl-2-thio benz-imidazole (BIMDA) and 2(2-propynyl-thio(5-phenyl)-1,3,4-oxadiazole (OXA). M(CO)3(TRZA)I2, [M(CO)2(PPh3)X(TRZA)IY]IZ where M=Mo, X, Y and Z=1 and M=W, X and Z=2, Y=0, have been performed at 365 nm in oxygen saturated chloroform at 25 °C. The absorbance spectrum of these complexes have been recorded with the time of irradiation in order to examine the kinetics of photodecay.
The apparent rate constant (Kd) for the first-order reaction have been calculated and found to be (3.32–4.79)×10−5 s−1. The primary quantum yields (Φ) has also been calculated and were in the range (8.33–12.1)×10−4. The mechanism of the photodecomposition has been suggested according to the kinetic, and photoproduct analysis data, and is similar to reaction of photo-oxidative degradation of polluted molecules in the water. 相似文献
10.
Mixed-carboxylato β-diketonato complexes of chromium (III) (R=C13H27, C15H31 or C17H35 and L=CH3OH) [Cr3O(OOCR)3(dike)3L3]+ have been synthesized by enforced substitution reactions of [Cr3O(OOCCH3)7(H2O)] first with straight chain fatty acids (myristic, palmitic or stearic acid) and then with β-diketones (Hβ-dike) like acetylacetone(Hacac) or benzoylacetone(Hbzac) in toluene under reflux. These are new type of oxo-bridged chromium(III) complexes in which one ligand is a fatty acid while the other one is a β-diketone. The complexes were characterized by elemental analyses, spectral (infrared, electronic, FAB mass and powder XRD) studies, molar conductance and magnetic susceptibility measurements. Bridging coordination modes for both carboxylate and β-diketonate anions were indicated by presence of νasym(Cr3O) vibrations in the infrared spectra. Trinuclear nature of the complexes and their structural features have been discussed on the basis of physicochemical studies. 相似文献
11.
《Journal of organometallic chemistry》2004,689(2):293-301
Lithium derivatives of substituted cyclopentadiene ligands reacted with CrCl3(THF)3 in THF solution to afford homodinuclear complexes of the type [{(η5-RCp)CrCl(μ-Cl) }2] [R=SiMe3 (1), CH2C(Me)CH2 (2)]. Complex 1 reacts with pyrazole (C3H4N2) to yield the mononuclear half-sandwich complex [(η5-Me3SiCp)CrCl2(pyrazole)] (3). The similar complex [Cp*CrCl2(pyrazole)] (4) was synthesised by reaction of [{Cp*CrCl(μ-Cl)}2] with pyrazole. Complex 2 reacts with bidentate ligands to give binuclear complexes of the type [{(η5-CH2C(Me)CH2Cp)CrCl2 }2(μ-L-L)] [L-L=Ph2PCH2CH2PPh2 (5), trans-Ph2P(O)CHCHP(O)Ph2 (6)]. All complexes were structurally characterised by X-ray diffraction. After reaction with methylaluminoxane these complexes are active in the polymerization of ethylene. At 25 °C and 4 bar of ethylene, complex 3 yields polyethylene with a bimodal molecular weight distribution centred at 155,000 and 2000 g/mol. Complex 4 shows similar activity, yielding only the low molecular weight fraction. On the other hand, the binuclear complexes 5 and 6 under the same conditions were three times more active than mononuclear complexes. The melting point of the polymers indicates the formation of linear polyethylene. 相似文献
12.
The reactions of a bulky amino-methoxy bis(phenolate) ligand H2L with Y(CH2SiMe3)3(THF)2 and Y[N(SiHMe2)2]3(THF)2 under mild condition leads to the selective formation of the thermally stable complexes [L]Y(CH2SiMe3)(THF) (1) and [L]Y[N(SiHMe2)2](THF) (2). The X-ray structures revealed very similar binding of the [ONOO] ligand core to the metal for both complexes, which feature an octahedral geometry involving coordination of the methoxy side-arm of the ligand and of a remaining THF molecule. 1H-NMR spectroscopy indicates that the solid state structure of 1 and 2 is retained in hydrocarbon solutions with THF coordinated to yttrium. Alkyl complex 1 showed no activity in ethylene polymerization, presumably due to the presence of coordinated THF. The amido complex 2 catalyzed sluggishly the polymerization of methyl methacrylate to give isotactic-rich PMMA but is very active for the ring-opening polymerization of ε-caprolactone. 相似文献
13.
14.
Eight chromium(III) complexes of tetradentate Schiff bases have been prepared in situ by condensing of a substituted salicylaldehyde compound with ethylenediamine. These were characterized by elemental analysis, m.p., IR, molar conductivity, magnetic moment measurements, and electronic spectra. The free ligands were also characterized by 1H and 13C NMR spectra. The 13C NMR spectra are discussed in terms of possible substituent effects. The IR and electronic spectra of the free ligand and the complexes are compared and discussed. The electrospray ionization (ESI) mass spectra of four free ligands and their complexes were measured. The deconvolution of the visible spectra of the complexes, C2v symmetry, in DMSO yields three peaks at ca. 15 600–17 600, 18 400–20 400 and 20 000–23 100, and are assigned to the three d–d transitions, 4B1g → 4Eg(4T2g); 4B1g → 4B2g(4T2g); 4B1g → 4Eg(4T1g), respectively. The complexes showed magnetic moment in the range of 3.5–4.2 BM which corresponds to three unpaired electrons. 相似文献
15.
《Journal of Coordination Chemistry》2012,65(12):2096-2109
Two new complexes, [Ni(HL1)(N3)(μ1,1N3)]2 (1) [HL1: NC5H4CH3C=NNH (C=O) NH2] and [Ni(L2)N3] (2) [HL2: NC5H4HC=N NH(C=S)NH2], have been synthesized by reaction of Ni(OAC)2·4H2O and sodium azide with HL1 and HL2 and characterized by elemental analysis, FT-IR, and UV–vis spectral studies. Single-crystal X-ray diffraction reveals that 1 is dinuclear with nickel(II) in an octahedral environment of NNO donors of HL1, two nitrogens of azide bridges and one nitrogen of terminal azide; 2 is mononuclear containing nickel(II) in a distorted square-planar environment of NNS donors of HL2 and one terminal azide. The structures of 1 and 2 have been optimized by density functional theory. The results of antimicrobial activities of ligands, 1 and 2 demonstrated that HL2 and 2 have good antimicrobial activity in contrast with HL1 and 1, related to the presence of sulfur donor in HL2. 相似文献
16.
Two novel tricarbonyl rhenium complexes based on the bidentate heterocyclic N–N ligands [bis(pyrazol-1-yl)methane(bpzm) and bis(3,5-dimethylpyrazol-1-yl)methane(bdmpzm)] have been synthesized by heating at reflux [Re(CO)5Cl] with the appropriate N–N ligand in toluene. The compounds have been characterized by IR and UV–Vis spectroscopy and X-ray analysis. Density functional theory (DFT) and time-dependent (TD) DFT calculations have been carried out for the [Re(CO)3(bdmpzm)Cl] complex. 相似文献
17.
Summary Three Cr(III) species (dichlorotetraaquachromium (III), [CrCl2(H2O)4]+; monochloropentaaquachromium(III), [CrCl(H2O)5]2+; and hexaaquachromium(III), [Cr(H2O)6]3+) have been separated and determined by capillary electrophoresis. The first two complexes could be detected in direct mode
in phosphate buffer, but because the absorption of complex [Cr(H2O)6]3+ is poor in the UV range, indirect UV detection had to be used. For indirect detection 5 mM imidazole was added to the buffer
solution. The formation and decomposition of the different Cr(III) complexes were monitored in time after the preparation
of solutions of CrCl3.6H2O. The slowest process was the decomposition of [CrCl(H2O)5]2+; 300 h after preparation of a solution of CrCl3.6H2O of pH 1 the solution contained only [Cr(H2O)6]3+. The effects of pH and the content of some matrix ions on the rates of conversion of the complexes were studied. The kinetic
characteristics of this complex system could be investigated adequately by means of capillary electrophoresis.
Presented at Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 1–3, 1999 相似文献
18.
Jiansheng Xu 《Journal of organometallic chemistry》2007,692(7):1505-1510
Two new ligands 1-(2-methoxyphenyl)-3,4-diphenylcyclopentadiene (1) and 1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadiene (2), as well as their corresponding cyclopentadienylchromium complexes η5-1-(2-methoxyphenyl)-3,4-diphenylcyclopentadienyl chromium dichloride (3) and η5-1-(2-methoxyphenyl)-2,3,4,5-tetramethylcyclopentadienyl chromium dichloride (4) were synthesized and characterized. Molecular structures of 3 and 4 were determined by single-crystal X-ray diffraction. Complexes 3 and 4 were tested as catalyst precursors for ethylene polymerization. When activated with Al(iBu)3 and , complex 3 shows reasonable catalytic activity while 4 exhibits high catalytic activity for ethylene polymerization. The effects of temperature and Al/Cr ratio on the catalytic activity were studied. The molecular weight and melting temperature of the produced polyethylenes were determined. 相似文献
19.
Reduction in situ of WCl4(MeCN)2 with zinc in the presence of diazadiene ligands 1b-f is reported and produces a series of diamagnetic complexes (DAD)WCl22b-f. All complexes were characterized by 1H, 13C NMR and IR spectroscopic data. The crystal structures of complexes 2b and 2e were solved by X-ray diffraction methods. 相似文献
20.
《Journal of Coordination Chemistry》2012,65(9):1544-1552
Two new compounds containing the possible Fe(III) spin-crossover cation, [Fe(qsal)2]+ (qsalH = N-(8-quinolyl)salicylaldimine), and nickel bis(dithiolene) anions have been synthesized. Both are 1 : 1 salts [Fe(qsal)2][Ni(dddt)2] · CH3CN · CH3OH (1) and [Fe(qsal)2][Ni(pddt)2] (2) (dddt = 5,6-dihydro-1,4-dithiin-2,3-dithiolate; pddt = 6,7-dihydro-5H-1,4-dithiepin-2,3-dithiolate). They have been characterized by X-ray crystal structure determination, elemental analysis, UV-Vis spectra and magnetic susceptibility measurements. The UV–Vis spectra are dominated by [Ni(L)2]? (1, L = dddt; 2, L = pddt). Magnetic studies show antiferromagnetic interaction in 1 from intermolecular S···S contacts and π–π stacking interactions, while the antiferromagnetic interaction in 2 is very weak. 相似文献