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1.
Xiao-Yan Jin Rong-Bao Liao Zheng-Jie Huang Hai Wu Ying Zou Hong Zhang 《Journal of Coordination Chemistry》2016,69(19):2864-2871
The fluorine substitution reactions of Keggin polymeric aluminum species K-MAl12 (M = Al, Ga, Ge) were investigated using density functional theory. Two substitution pathways (associative and dissociative) were simulated. The results show that the replacement of charged tetrahedral center metals causes the change in energy barrier either for associative mechanism or dissociative mechanism. The preferred activation mechanisms are proposed by comparing associative and dissociative barriers for fluorine substitution reactions of three Keggin Al species. The fluorine substitution reactions of Al13 and GaAl12 are inclined to dissociative mechanism and GeAl12 follows an associative mode, indicating a mechanistic variation induced by the alteration of tetrahedral metals. 相似文献
2.
Jay A. Labinger 《Journal of organometallic chemistry》1980,187(2):287-296
Comlexes of type LnMCH2O2CCMe3 exhibit relatively large values of 1JCH for the α-carbon; however, unexpectedly large values are also found for the methyl analogs, LnMCH3. Thus technique does not provide evidence for any unusual interactions in the former. Cleavage of the ester linkage by MeLi proceeded cleanly only for LnM = CpMo(Co)3, leading to CpMo(CO)3?; with LnM = Mn(CO)5 or CpFe(CO)2 electron transfer processes predominate. Such reactions are also observed for simple metal alkyls such as CpFe(CO)2CH3. 相似文献
3.
The metal carbonyl derivatives LM(CO)n of manganese, rhenium, molybdenum and tungsten undergo facile ligand substitution by an electrode-mediated process. Phosphine, pyridine and isocyanaide substitutions are shown to be chain reactions by coulometric analysis and by cyclic voltammetry of the metal carbonyl solutions containing the added nucleophiles L. Reversible electrochemical parameters can be obtained for both LM(CO)n and the substitution product LM(CO)n. These allow the digital simulation of the cyclic voltammograms by Feldberg's method, which provides a detailed analysis of the kinetics of the electrocatalytic mechanism for ligand substitution. Generally, the radical cation LM(CO)n+ produced initially at the anode undergoes rapid exchange with L to afford the cationic substituted species LM(CO)n+. This step is followed by electron transfer with the reactant LM(CO)n to yield the substitution product LM(CO)n and regenerate the radical cation LM(CO)n+, which completes the chain propagation sequence. Multiple repetition of this cycle is indicated by the high current efficiencies which are obtainable. The second order rate constants for the ligand exchange of the 17-electron radical cations LM(CO)n+ with added L are evaluated, and found to be more than 106 times larger than that for the neutral, diamagnetic precursor LM(CO)n. The radical cations LM(CO)n+ also react readily with phosphine and alkyl isocyanide nucleophiles, leading to a characteristic distortion of the CV waves. Digital simulation of such cyclic voltammograms allows the kinetics of these processes, particularly the redox catalysis in the oxidation of phosphines by LM(CO)n+, to be evaluated quantitatively. The enhanced reactivity of the 17-electron radical cations LM(CO)n+ is discussed in relationship to recent reports of the substitution lability in other 17- and 19-electron metal carbonyls. 相似文献
4.
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
5.
Intensively coloured stibinidene complexes (LnM)2SbR (LnM = (CO)5Cr; R = tBu, Cl, I, EtS. LnM = C5H5(CO)2Mn; R = Cl. LnM = CH3C5H4(CO)2Mn; R = Br) which contain trigonally planar coordinated Sb(+1) with the stibanediyl ligand stabilized by M Sb(R) M-π-bonding have been obtained. Their synthesis and properties as well as an X-ray structure determination of [CH3C5H4(CO)2Mn]2SbBr are described. 相似文献
6.
Helmut Behrens Ralf-Jürgen Lampe Peter Merbach Matthias Moll 《Journal of organometallic chemistry》1978,159(2):201-217
The covalent carbamoyl carbonyl compounds Re(CO)5COHN2, cis-M(CO)4(L)CONH2, M(CO)3(L)2CONH2 and M(CO)3(D)CONH2 (M = Mn, Re; L = PPh3, PEt3; D = bipy, phen) are formed by reactions of the cationic complexes [Re(CO)6]+, [M(CO)5L]+, [M(CO)4L2]+ and [M(CO)4D]+ (M = Mn, Re; L = PPh3, PEt3; D = bipy, phen) with liquid NH3 with concomitant deprotonation: [M(CO)6?nLn]+ + 2 NH3 → M(CO)5?nLnCONH2 + NH4+ (n = 0, 1, 2) and [M(CO)4D]+ + 2 NH3 → M(CO)3(D)CONH2 + NH4+ The stability of the above-mentioned carbamoyl carbonyl complexes increases from the penta- to the tetra- to the tri-carbonyl derivatives. In all cases the rhenium compounds are much more stable than the corresponding manganese complexes. Whereas the carbamoyl compound Re(CO)4(PEt3)CONH2 can be isolated by reaction of [Re(CO)5PEt3]+ with NH3, the corresponding manganese complex undergoes Hofmann degradation of amides even at ?70°C to form HMn(CO)4PEt3 and NH4NCO. The IR and some mass and 1H NMR spectra of the new hexacoordinated carbamoyl carbonyl complexes are discussed and the reactions of these compounds with liquid NH3, HCl and CH3OH are described. 相似文献
7.
Bernhard Walther Harald Albert Alfred Kolbe 《Journal of organometallic chemistry》1978,145(3):285-302
Diorganothallium transition metal complexes of the general formula R2Tl—MLn with MLn = M(CO)2LCp (M = Mo, W; L = CO, PPh3) are obtained by protolytic reactions, redistribution reactions or by methatetic reactions, and are characterized spectroscopically and by chemical reactions. For MLn = Cr(CO)3Cp, Fe(CO)2Cp and Co(CO)4 R3Tl and Tl(MLn)3 can always be isolated. In the case of Me2Tl—M(CO)3Cp (M = Mo, W) variable temperature NMR measurements gave evidence for a symmetrisation—redistribution equilibrium 3 R2Tl—MLn—MLn ? R3Tl + Tl(MLn, which generally determines the stability of the diorganomthallium transition metal complexes. 相似文献
8.
The reactions of the substituted Group VI metal carbonyls of the type M(CO)4(2-Mepy)2 (M = Mo, w) and M(CO)3(L)3 (L = py, M = Mo, W; L = NH3, M = Mo) with mercuric derivatives HgX2 (X = Cl, CN, SCN) have given rise to three series of tricarbonyl complexes: M(CO)3(py)HgCl2 · 1/2HgCl2 (M = Mo, W); 2[M(CO)3(L)]Hg(CN)·nHg(CN)x (L = py, M = Mo, W, n = , × = 2; L = 2- Mepy, × = 1; M = Mo, n = 3; M = W, n = 1); and [M(CO)3(L)Hg(SCN)2 · nHg(SCN)2] (L = py, M = Mo,W, n = 0; L = 2-Mepy, M = Mo, W, n = ; L = NH3, M = Mo, n = 0) depending on which mercuric compound is employed. All the reactions with Hg(SCN)2 give isolable products whereas those with Hg(CN)2 and HgCl2 did so far only the reactions with [M(CO)4(2-Mepy)2] and M(CO)3(py)3. The greater reactivity of Hg(SCN)2 than of Hg(CN)2 and HgCl2 is consistent with the various acceptor capacities of the groups bonded to the mercury atom.The reactions studied always involve displacement of the N-donor ligand of the original complex and partial or total displacement of the halide or pseudohalide groups of the mercury compound to give in all cases compounds containing MHg bonds. In addition, elimination of a CO group in the tetracarbonyl complexes M(CO)4(2-Mepy)2occurs. 相似文献
9.
The complexes [MHCl(CO)(PPh3)3] (M = Ru or Os) readily undergo substitution at the site trans to the hydride ligand to afford phosphinite-, phosphonite-, or phosphite-containing products [MHCI(CO)(PPh3)2L] [L = P(OR)Ph2, P(OR)2Ph or P(OR)3 respectively; R = Me or Et]. The ruthenium complexes alone undergo further substitution to afford complex cations [RuH(CO)(PPh3)nL4?n]+ [n = 2, L = P(OMe)3; n = 1, L = P(OR)3; n = 0, L = P(OR)2Ph or P(OR)Ph2] which were isolated and characterised as their tetraphenylborate salts. Synthesis of the cationic complexes [IrHL5][BPh4]2 [L = P(OR)3, R = Me or Et] is also reported. Stereochemical assignments based on NMR data are given, and second order 31P and high field 1H NMR patterns are analysed. 相似文献
10.
Perfluoromethyl-Element-Ligands. XVIII. Preparation and Spectroscopic Investigation of M(CO)5L and M(CO)4L2 Complexes [L = MenP(CF3)3?n; n = 0–3; M = Cr, Mo, W] M(CO)5L and cis-M(CO)4L2 complexes, respectively [M = Cr, Mo, W; L = MenP(CF3)3?n; n = 0–3] are prepared reacting M(CO)5 · THF or M(CO)4norbor with L at room temperature. The cis-compounds isomerize above 50°C yielding the trans-complexes; the rate of isomerization increases with increasing number of CF3 groups. Thermal reaction of M(CO)6 (M = Cr, Mo, W) with P(CF3)3 yields M(CO)5P(CF3)3 and trans-M(CO)4[P(CF3)3]2. Introduction of three P(CF3)3 ligands by reaction with M(CO)3(cycloheptatriene) (M = Cr, Mo) proves unsuccessful; besides little M(CO)5P(CF3)3 trans-M(CO)4[P(CF3)3]2 is formed. The new compounds are characterized by analytical and spectroscopic (n.m.r., i.r., MS) methods. 相似文献
11.
Summary The bisacetonitrile complexes [MI2(CO)3(NCMe)2] react with an equimolar amount of L in CH2Cl2 at room temperature to give [MI2(CO)3(NCMe)L] which when mixedin situ with an equimolar amount of [NBu
4
n
]X affords the anionic seven-coordinate compounds [NBu
4
n
][MI2X(CO)3L][M=Mo or W,X=I, L=PPh3 (for M=W only), AsPh3 or SbPh3 (for M=Mo only); M=Mo and W, X=Br3 or Br2I, L=PPh3, AsPh3 or SbPh3]. These reactions are likely to occurvia the stepwise dissociative displacement of two acetonitrile ligands. Low-temperature (–70° C, CD2Cl2)13C n.m.r. spectra (CO resonances) are reported for several of the complexes in order to infer the likely stereochemistry of these compounds. 相似文献
12.
近期我们报道了M(CO)_2(M=Cr,Mo,W)与Me_2NO反应的动力学研究结果。 本文报道在CH_2Cl_2,-CH_2CN(体积比1:1)混合溶剂中,三甲胺氧化物存在下的二取代反应: Mo(CO)_5L Me_3NO L→顺-Mo(CO)_4L_2 Me_3N CO_3 (1)式中L=P(c-hx)_3,P(n-Bu)_3,NMe_3Pyr,PPh_3,AsPh_3,P(OEt)和P(OMe)_3,在金属原子不变的情况下对配体的电子效应(以Mo(CO)_5L的羰基伸缩振动频率表现出来)和立体效应做探讨。 相似文献
13.
Thiam Seong Chong 《Journal of organometallic chemistry》2005,690(18):4132-4138
Three methods of obtaining time-resolved Fourier-Transform infrared (TR-FTIR) absorption spectra of transition metal carbonyl radicals in hexane are reported here. For the first method, CpM(CO)2L and Cp*M(CO)2L (M = Mo, W; L = CO, PR3) radicals have been generated by photodissociation of the corresponding metal-metal bonded dimers. Radicals of formula M(CO)4L (M = Mn, Re; L = CO, PR3, AsPh3, SbPh3) and CpM(CO)n (M = Fe, Mo; n = 2, 3) have been produced via the second method which is halogen abstraction of the transition metal carbonyl halides using CpMo(CO)3 radical. For the third method, fast radical ligand substitution kinetics has been exploited to generate CpMo(CO)2PR3 radicals from CpMo(CO)3 in the presence of free phosphines. An assessment of the three methods with respect to TR-FTIR spectroscopic detection of radicals was also discussed. 相似文献
14.
I. Bartz J. Grobe A. Krummen N. Krummen R. Martin 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract The coordinating properties of dipod and tripod phosphorus ligands LI = R2M′ (OCH2PMe2) n(CH2CH2PMe2) 2-n and LII = RM′ (OCH2PMe2)n(CH2CH2PMe2)3-n (M′ = Si, Ge) with separated donor and acceptor centres have been investigated using electron rich metal complex fragments, e. g. M(CO)m, (M = Cr, MO, W), π-C5H5Co, RhCl(CO) or Ni(CO), as bonding partners. 相似文献
15.
C. G. R. Barrett J. Charalambous R. G. Copperthwaite M. J. Frazer 《Journal of mass spectrometry : JMS》1975,10(2):146-154
The relative intensities of peaks in the mass spectra of the compounds MX4?noxn (oxH = 8-quinolinol; n = 2; M = Ti; X = F, Cl, Br or OEt; M = Sn; X = F, Cl, Br or I; M = Ge; X = Cl or Br; n = 1; M = Ti; X = OEt) depend on the insertion temperature and the residence time of the sample in the mass spectrometer. In most cases ions which cannot arise by fragmentation of the respective molecular ions are observed. These ions arise from the ionisation and fragmentation of species which are due to redistribution reactions in the mass spectrometer. The fragmentation pattern of the compounds MX2ox2 (X = halogen), mainly involving loss of ligand radicals, is related to the common oxidation states of the metals and reflects the metal-halogen bond strength. The molecular ions of the compounds Ti(OEt)4?noxn (n = 0, 1 or 2) fragment by loss of intact ligand radicals. 相似文献
16.
The water gas shift reaction (CO + H2O = CO2+ H2) is catalyzed by aqueous metal carbonyl systems derived from simple mononuclear carbonyls such as Fe(CO)5 and M(CO)6 (M = Cr, Mo, and W) and bases in the 140–200 °C temperature range. The water gas shift reaction in a basic methanol-water solution containing Fe(CO)5 is first order in [Fe(CO)5], zero order in [CO], and essentially independent of base concentration and appears to involve an associative mechanism with a metallocarboxylate intermediate [(CO)4Fe-CO2H]–. The water gas shift reactions using M(CO)6 as catalyst precursors are first order in [M(CO)6], inverse first order in [CO], and first order in [HCO2
–] and appear to involve a dissociative mechanism with formatometallate intermediates [(CO)5M-OCHO]–.The Reppe hydroformylation of ethylene to produce propionaldehyde and 1-propanol in basic solutions containing Fe(CO)5 occurs at 110–140 °C. This reaction is second order in [Fe(CO)5], first order in [C2H4] up to a saturation pressure >1.5 MPa, and inhibited by [CO]. These experimental results suggest a mechanism where the rate-determining step involves a binuclear iron carbonyl intermediate. The substitution of Et3N for NaOH as the base facilitates the reduction of propionaldehyde to 1-propanol but results in a slower rate for the overall reaction.The homogeneous photocatalytic decomposition of the formate ion to H2 and CO2 in the presence of Cr(CO)6 appears to be closely related to the water gas shift reaction. The rate of H2 production from the formate ion exhibits saturation kinetics in the formate ion and is inhibited by added pyridine. The infrared spectra of the catalyst solutions indicate an LCr(CO)5 intermediate. Photolysis of the Cr(CO)6/formate system in aqueous methanol in the presence of an aldehyde RCHO (R =n-heptyl,p-tolyl, andp-anisyl) results in catalytic hydrogenation of the aldehyde to the corresponding alcohol RCH2OH by the formate ion. Detailed kinetic studies onp-tolualdehyde hydrogenation by this method indicates saturation kinetics in formate ion, autoinhibition by thep-tolualdehyde, and a threshold effect for Cr(CO)6 at concentrations >0.004 mol L–1. The presence of an aldehyde can interrupt the water gas shift catalytic cycle by interception of an HCr(CO)5
– intermediate by the aldehyde.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1533–1539, September, 1994. 相似文献
17.
Silicon-transition metallic silacyclobutanes CpFe(L2)H2 [L = CO or Ph2MeP; or L2 = (CO)(Ph2MeP)] have been prepared and their reactions (substitution at Si or Fe, Si—Fe cleavage, or ring-opening) studied. 相似文献
18.
《Journal of Coordination Chemistry》2012,65(10):1199-1207
Reactions of M(CO)5THF, which was generated photochemically from M(CO)6 in THF, with (CH3)3CS(CH2)nSC(CH3)3 (=SS; n=5, 6; M=W, Cr) at room temperature afforded exclusively the bimetallic complexes (CO)5MSSM(CO)5. These new complexes with dithiaalkane bridging ligands have been characterized by IR and 1H NMR spectroscopies and elemental analysis. Kinetic studies of ligand-exchange reactions in these complexes in chlorobenzene (=CB) solutions employing tri(iso-propyl)phosphite (=L) as an incoming nucleophile indicated that the bridging ligand SS is replaced by L to afford finally (CO)5MP(O-i-Pr)3 as the sole reaction product. The kinetic data have also confirmed that replacement of SS by L under pseudo-first-order reaction conditions is dissociative and proceeds via a mechanism which involves initial M-S bond breaking followed by other steps. First order rate constants and activation parameters for these reactions have been determined. 相似文献
19.
Complexes of Chromium and Molybdenum with Aminoarsanes as Ligands. III The reaction of the norbornadien complexes (CO)4MC7H8 (M = Cr, Mo) with aminoarsanes MemAs(NMe2)n (m = 2, 1; n = 1, 2) is examined. The substitution reaction results in the formation of complexes of the formula cis-(CO)4M(aminoarsane)2. These complexes rearrange to a mixture of hexacarbonyles M(CO)6 and monosubstituted complexes (CO)5M-aminoarsane. The cleavage of the As? N bond in the coordinated aminoarsane ligand with acid molecules as ethanol, thioethanol, or glycol yields complexes of the type (CO)4M[AsMen)? Xm]2. 相似文献
20.
The ability of H2Os3(CO)10 to undergo addition reactions under mild conditions allows associative CO substitution via isolable intermediates of the type H2Os3(CO)10 (L = CO, PMe2Ph, PPh3 or PhCN) whose spectra and structures are discussed. It is probable that simple addition of alkenes to H2Os3(CO)10 is in part responsible for its facile catalysis of alkene isomerisation. The kinetics of catalytic conversion of terminal to internal alkenes and of allylic alcohols to aldehydes or ketones are reported and discussed. The reactions of H2Os3(CO)10 with allylic halides to give the complexes HOs3X(CO)10 and Os3X2(CO)10 where X = Cl, Br or I are described. Compound H2Os3(CO)10 complies with the 18ρ-rule but nevertheless has a chemistry much like that of coordinatively unsaturated molecules. 相似文献