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1.
《Journal of Coordination Chemistry》2012,65(1-2):141-150
Abstract Ring displacement from η2-PDOW(CO)4 (PDO = 2,2,4,7,7-pentamethyl-3.6-dithiaoctane) by L (L = P(0-i-Pr)3 and P(OEt)3) produces a mixture of cis- and trans- (L)2W(CO)4. Results from kinetics experiments are consistent with the results observed for the structurally-related η2-DTOW(CO)4 complex (DTO = 2,2,7,7-tetramethyl-3,6-dithiaoc-tane). A smaller value for the rate constant (k1) for the ring-opening step of η2-PDOW(CO)4 reflects the shorter W-S bond distances observed in η2-PDOW(CO)4. This observation is consistent with the trend observed for a series of η2-DTAW(CO)4 complexes (DTA = Dithiaalkanes) in which the value of k1 increases with the size of the chelate ring. Since the species η2-PDOW(CO)4 and η2-DTOW(CO)4 are five-membered chelate complexes, differences in their molecular and kinetic parameters are being ascribed to the methyl group in the chelate backbone of η2-PDOW(CO)4. Our observations confirm earlier findings that small differences in the structure of DTA greatly affect the rates of ring-opening in η2-DTAW(CO)4 complexes. 相似文献
2.
Ann M. English Keith R. Plowman Ione M. Baibich James P. Hickey Ian S. Butler Gérard Jaouen Paul Lemaux 《Journal of organometallic chemistry》1981,205(2):177-183
The arene complexes, (η6-C6H6)Cr(CO)2(CX) (X = S, Se), react with excess CO gas under pressure in tetrahydrofuran at about 60° C to produce the Cr(CO)5(CX) complexes in high yield. The IR and NMR (13C and 17O) spectra of these complexes are in complete accord with the expected C4v molecular symmetry. Like the analogous W(CO)5(CS) complex, both compounds react with cyclohexylamine to give Cr(CO)5(CNC6H11). However, while W(CO)5(CS) undergoes stereospecific CO substitution with halide ions (Y? to form trans-[W(CO)4(CS)Y]?, the two chromium chalcocarbonyl complexes apparently undergo both CO and CX substitution to afford mixtures of [Cr(CO)5Y]? and trans-[Cr(CO)4(CX)Y]?. 相似文献
3.
Fatma Alper 《Journal of organometallic chemistry》2006,691(12):2734-2738
Pentacarbonylpyrazinetungsten(0), (CO)5W(pyz), is not stable in solution in polar solvents such as acetone or dichloromethane and undergoes conversion to a bimetallic complex, (CO)5W(pyz)W(CO)5 plus free pyrazine. These three species exist at equilibrium. Using the quantitative 1H NMR spectroscopy, the equilibrium constant could be determined to be Keq = (5.9 ± 0.8) × 10−2 at 25 °C. Introducing a second pyrazine ligand into the molecule does not stabilize the complex, as cis-W(CO)4(pyz)2 was found to be less stable than W(CO)5(pyz) and, therefore, could not be isolated. However, introducing trimethylphosphite as a donor ligand into the complex leads to the stabilization of the carbonyl-pyrazine-metal(0) complexes, as shown by the synthesis of cis-W(CO)4[P(OCH3)3](pyz). This complex could be isolated from the reaction of the photogenerated W(CO)4[P(OCH3)3](tetrahydrofuran) with trimethylphosphite upon mixing for 2 h at 10 °C in tetrahydrofuran and characterized by elemental analysis, IR, MS, 1H, 13C, and 31P NMR spectroscopy. 相似文献
4.
M(CO)5X (M = Mn, Re; X = Cl, Br, I) reacts with DAB (1,4-diazabutadiene = R1N=C(R2)C(R2)′=NR′1) to give M(CO)3X(DAB). The 1H, 13C NMR and IR spectra indicate that the facial isomer is formed exclusively. A comparison of the 13C NMR spectra of M(CO)3X(DAB) (M = Mn, Re; X = Cl, Br, I; DAB = glyoxalbis-t-butylimine, glyoxyalbisisopropylimine) and the related M(CO)4DAB complexes (M = Cr, Mo, W) with Fe(CO)3DAB complexes shows that the charge density on the ligands is comparable in both types of d6 metal complexes but is slightly different in the Fe-d8 complexes. The effect of the DAB substituents on the carbonyl stretching frequencies is in agreement with the A′(cis) > A″ (cis) > A′(trans) band ordering.Mn(CO)3Cl(t-BuNCHCHNt-Bu) reacts with AgBF4 under a CO atmosphere yielding [Mn(CO)4(t-BuNCHCHN-t-Bu)]BF4. The cationic complex is isoelectronic with M(CO)4(t-BuNCHCHNt-Bu) (M = Cr, Mo, W). 相似文献
5.
Absorption and emission spectral studies of M(CO)4L complexes (M = Cr Mo, W; L = 2,2′-bipyridine, 1,10-phenanthroline, 5-CH3-, 5-Cl-, 5-Br-, 5-NO2-1,10-phenanthroline) have been carried out and reveal that the lowest excited state in every case is charge-transfer (CT) in character, M→ CT in absorption, and in no case do the ligand field (LF) excited states cross below the CT state. Minimum energies of the LF states have been established by the spectroscopic study of cis-bis(pyridine)- and cis-bis(aliphatic amine)-tetracarbonylmetal(0) complexes which all have LF lowest excited states for M = Mo, W. For the M(CO)4L complexes emission is detectable for M = Mo or W and occurs in the range 14.40-15.66 kK with lifetimes of 7.9-13.3 μsec and quantum yields of 0.02–0.09 all in EPA solution at 77 K. For the bis-pyridine and -aliphatic amine complexes emission occurs only from the W complexes and is of the order of 3.0–4.0 kK higher in energy than for the M(CO)4L complexes. Photosubstitution of pyridine is efficient in cis-W(CO)4(py)2 (py = pyridine): Φ436nm = 0.23; Φ405nm = 0.27; and Φ366nm = 0.23. The M(CO)4L complexes have strongly wavelength dependent, but modest, quantum yields for CO substitution and show that the lowest CT state is unreactive. Typical values for CO substitution for M = W and L = 1,10-phenanthroline are: Φ436nm = 1.6 × 10?4; Φ405nm = 1.2 × 10?3; Φ366nm = 9.2 × 10?3; and Φ313nm = 2.2 × 10?2. 相似文献
6.
《Journal of organometallic chemistry》1987,331(3):341-346
The mixed ligand tetracarbonyl derivatives, cis-M(CO)4(PPh2H)(PPh3) (M Cr, Mo, W) and cis-W(CO)4(PPh2H)(L) (L PEt3, PEt2Ph, PEtPh2) have been prepared from the reaction of M(CO)5PPh2H with L in THF in the presence of potassium t-butoxide. These reactions are accompanied in most instances by the formation of [W(CO)5PPh2]−, [(OC)5M(μ-PPh2)M(CO)5]−, [(OC)5M(μ-PPh2)-M(CO)4(PPh2H)]−, [(OC)4M(μ-PPh2)2M(CO)4]2−, (OC)4M(μ-PPh2)2M(CO)4, and cis-M(CO)4(PPh2H)2. 相似文献
7.
The [Et4N][M(CO)5SCOPh] complexes (1a, M = Mo; 2a, M = W) have been prepared at ambient temperatures by reacting the photogenerated M(CO)5 THF intermediate with [Et4N][SCOPh] in THF. Kinetic studies of the reactions of the anions [M(CO)5SCOPh]– with the tri(iso-propyl)phosphite (L) ligand under pseudo-first-order conditions indicate that these reactions are first-order in substrate and are independent of the P(OPr-i)3 concentration. It is thus envisaged that these CO substitutions proceed via a mechanism which involves initial cis-M—CO bond-breaking, followed by fast attack of the incoming nucleophile on the resulting intermediate to give [cis-M(CO)4{P(O-Pri)3}SCOPh]–. This facile displacement of cis-CO indicates the labilizing nature of the thiobenzoate ligand, most probably by virtue of distal oxygen atom participation. Activation parameters for the reactions are: [M(CO)5SCOPh]– + L cis-[M(CO)4(L)SCOPh]– + CO M = Mo, H
= 24.6(2) kcal mol–1, S
= 8.2(6) eu; M = W, H
= 28.4(2) kcal mol–1, S
= 11.3(5) eu. Kinetic data and the mechanism of these ligand-substitutions are discussed. 相似文献
8.
Low voltage mass spectra of cis-M(CO)4(13CO)piperidine (M = Cr,W) show the initial loss of CO to proceed with complete scrabling of the label between axial and equatorial sites. 相似文献
9.
Jingran Dong Shuying Huo Changying Song Shigang Shen Yanli Ren Tiesheng Shi 《Transition Metal Chemistry》2014,39(2):127-133
Sodium thiosulfate has been utilized as a rescuing agent for relief of the toxic effects of cisplatin and carboplatin. In this work, we characterized the kinetics of reactions of the trans-dichloro-platinum(IV) complexes cis-[Pt(NH3)2Cl4], ormaplatin [Pt(dach)Cl4] and trans-[PtCl2(CN)4]2? (anticancer prodrugs and a model compound) with thiosulfate at biologically important pH. An overall second-order rate law was established for the reduction of trans-[PtCl2(CN)4]2? by thiosulfate, and varying the pH from 4.45 to 7.90 had virtually no influence on the reaction rate. In the reactions of thiosulfate with cis-[Pt(NH3)2Cl4] and with [Pt(dach)Cl4], the kinetic traces displayed a fast reduction step followed by a slow substitution involving the intermediate Pt(II) complexes. The reduction step also followed second-order kinetics. Reductions of cis-[Pt(NH3)2Cl4] and [Pt(dach)Cl4] by thiosulfate proceeded with similar rates, presumably due to their similar configurations, whereas the reduction of trans-[PtCl2(CN)4]2? was about 1,000 times faster. A common reduction mechanism is suggested, and the transition state for the rate-determining step has been delineated. The activation parameters are consistent with transfer of Cl+ from the platinum(IV) center to the attacking thiosulfate in the rate-determining step. 相似文献
10.
The reactions of trans-[MoO(ONOMe)Cl2] 1 (ONOMe = methylamino-N,N-bis(2-methylene-4,6-dimethylphenolate) dianion) and trans-[MoO(ONOtBu)Cl2] 2 (ONOtBu = methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenolate) dianion) with PhNCO afforded new imido molybdenum complexes trans-[Mo(NPh)(ONOMe)Cl2] 3 and trans-[Mo(NPh)(ONOtBu)Cl2] 4, respectively. As analogous oxotungsten starting materials did not show similar reactivity, corresponding imido tungsten complexes were prepared by the reaction between [W(NPh)Cl4] with aminobis(phenol)s. These reactions yielded cis- and trans-isomers of dichloro complexes [W(NPh)(ONOMe)Cl2] 5 and [W(NPh)(ONOtBu)Cl2] 6, respectively. The molecular structures of 4, cis-6 and trans-6 were verified by X-ray crystallography. Organosubstituted imido tungsten(VI) complex cis-[W(NPh)(ONOtBu)Me2] 7 was prepared by the transmetallation reaction of 6 (either cis or trans isomer) with methyl magnesium iodide. 相似文献
11.
Complexes Containing Antimony Ligands: [tBu2(Cl)SbW(CO)5], [tBu2(OH)SbW(CO)5], O[SbPh2W(CO)5]2, E[SbMe2W(CO)5]2 (E = Se, Te), cis‐[(Me2SbSeSbMe2)2Cr(CO)4] Syntheses of [tBu2(Cl)SbW(CO)5] ( 1 ), [tBu2(OH)SbW(CO)5] ( 2 ), O[SbPh2W(CO)5]2 ( 3 ), Se[SbMe2W(CO)5]2 ( 4 ), cis‐[(Me2SbSeSbMe2)2Cr(CO)4] ( 5 ) Te[SbMe2W(CO)5]2 ( 6 ) and crystal structures of 1 – 5 are reported. 相似文献
12.
James A.S. Howell John C. Kola Denis T. Dixon Philip M. Burkinshaw Marion J. Thomas 《Journal of organometallic chemistry》1984,266(1):83-96
Kinetic data for the exchange of 1,3-cyclohexadiene with (η4-benzylideneacetone)Fe(CO)2L complexes (L = CO, PPh3-xMex (x = 0-2) or P(OPh)3) to give (η4-1,3-cyclohexadiene)Fe(CO)2L derivatives indicate a mechanism involving stepwise competing D and Id opening of the ketonic M-CO π-bond. Rates increase in the order CO ? PPh3 ≈ P(OPh)3 > PPh2Me ? PPhMe2, and both steric and electronic factors appear to be important. (η4-1,3-cyclohexadiene)Fe(CO)2L complexes of potential use in enantioselective synthesis (L=(+)-Ph2P(menthyl) or (+)-Ph2PCH2CH(Me)Et) may be prepared via their (η4-benzylideneacetone)Fe(CO)2L complexes. 相似文献
13.
The covalent complex Rh(diphos)(η-BPh4) (I) reacts with CO in polar solvents to afford the cationic dicarbonyl cis-[Rh(diphos)(CO)2](BPh4). I is an effective catalyst for methylacetylene oligomerization and allene polymerization. In the presence of CO2 and methylacetylene, I affords 4,6-dimethyl-2-pyrone. 相似文献
14.
The reactions of cis-Mn(CO)4LBr (L = PPh3, AsPh3, SbPh3) with 96%18O-enriched CO in cyclohexane solution at 35°C have been investigated by IR spectroscopy in the ν(CO) region and the vibrational modes of the parent molecules and the various C18O-substituted species produced have ben assigned with the aid of approximate force field calculations for the energy-factored CO stretching blocks of the (FG) matrices. The IR data for the reaction of the triphenylphosphine complex indicate that, while all four carbonyl groups are eventually replaced by C18O, there is initially a stereochemical preference for axial CO substitution. For the other two complexes, both carbonyl and L substitution take place. 相似文献
15.
Summary Rate constants have been obtained for reactions ofcis-tetracarbonylbis(4-methylpyridine)tungsten(0),cis-[W(CO)4(4Mepy)2], with 1, 10-phenanthroline, 2,2-bipyridyl, and related diimine ligands in toluene solution at 298.2K. Effects of varying the nature and concentration of the entering ligand, and of addition of 4-methylpyridine, indicate the operation of a limiting dissociative (D) mechanism. This is confirmed by the establishment of an activation volume of + 8 cm3 mol–1, in toluene at 298.2K. 相似文献
16.
《Journal of Inorganic and Nuclear Chemistry》1980,42(8):1161-1164
The kinetics of the anation of cis (aquo)(ammine)bis(ethylenediamine)Co(III) by H2C2O4, HC2O4− and C2O42− have been investigated at 50–60°C and I = 1.0 mol dm−3 (ClO4−). Association of the aquo cation with oxalic acid could not be identified. The association constants of the aquo-HC2O4− and aquo-C2O42− ion-pairs are essentially temperature independent and have values 1.5 and 5.8 dm3 mol−1 (50–60°C) respectively. The interchange reactions of the ion-pairs to yield the innersphere complexes, cis[(en)2(NH3)CoC2O4]+ or its acid form, are assigned a dissociative mechanism, Id, involving CoO bond breaking. The mechanism of the anation of the aquo cation by H2C2O4 may be Id but the possibility of rate limiting addition of oxalic acid to the CoO bond can not be completely ruled out. 相似文献
17.
Oxotungsten(VI) complex cis-[WO(LtBu)Me2] (LtBu = methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenolate) dianion) was prepared by the transmetallation reaction of [WO(LtBu)Cl2] (either cis or trans isomer) with methyl magnesium iodide. This unexpectedly stable dialkyl complex can be activated by Et2AlCl to catalyze the ring-opening metathesis polymerization of norbornene. 相似文献
18.
Gianfranco Bellachioma Alceo Macchioni Chiara Venturi Cristiano Zuccaccia 《Journal of organometallic chemistry》2006,691(18):3881-3888
Fe(CO)4X2 complexes [X = I (1), Br(1′)] react with phosphine ligands L (L = PMe3, PEt3, PMe2Ph, PMePh2, PPh3) via a two-step mechanism: in the first step fac-Fe(CO)3LX2 complexes are formed; in the second step two parallel pathways, a and b, are observed; in pathway a, reductive elimination with formation of equimolar amounts of Fe(CO)3L2 (5) and phosphonium salts [LX]+X− is observed; in pathway b, disubstituted dihalide complexes cis,trans,cis-Fe(CO)2L2X2 are formed. The relative weights of pathways a and b depend on the basicity, steric hindrance and concentration of ligand L, on the nature of the halogen and on temperature. A radical mechanism which accounts for most of the experimental results is proposed. 相似文献
19.
《Journal of organometallic chemistry》1986,311(3):C47-C50
Ring-closure via olefin coordination in coordinatively-unsaturated cis-[(η1-pdpp)W(CO)4], (pdpp = CH2CH(CH2)3P(C6H5)2, 4-pentenyldiphenylphosphine) produced via pulsed laser flash photolysis of cis-(pip)(η1-pdpp)W(CO)4 (pip = piperidine) in chlorobenzene has been identified unequivocally. Rates and activation parameters for this pathway and for competitive bimolecular interaction of pip at the solvated coordination site have been measured. 相似文献
20.
Reaction of the complexes Ru(CO)2Cl2L [L = 2,2′-bipyridyl (bpy) or 1,10-phenanthroline (phen)] with trifluoromethanesulphonic acid under carefully controlled conditions yields Ru[cis-(CO)2] [cis-(O3SCF3)2] (bidentate complexes. From reactions of the trifluoromethanesulphonates with the appropriate bidentate ligands, the new complexes [cis-Ru(CO)2-L(L′)]2+ (L as above; L′ = 4,4′-dimethyl-2,2′-bipyridyl or 4,4′-diisopropyl-2,2′-bipyridyl) as well as the known [cis-Ru(CO)2L2]2+ and [cis-Ru(CO)2bpy(phen)]2+ have been prepared. 相似文献