14917-12-5Relevant academic research and scientific papers
31p chemical shift anisotropies of trimethyl- and triphenylphosphine- substituted group 6 metal pentacarbonyl complexes
Wosnick, Jordan H.,Morin, Frederick G.,Gilson, Denis F.R.
, p. 1280 - 1283 (1998)
The 31P chemical shift tensor components and anisotropies of the trimethyl- and triphenylphosphine complexes of the group 6 metal pentacarbonyls, M(CO)5PR3 (M = Cr, Mo, W and R = Me, Ph), have been measured using solid-sta
CONTRASTING PHOTOSUBSTITUTION REACTIONS OF DIAZANORBORNENE-CHROMIUM AND -TUNGSTEN PENTACARBONYLS
Albini, Angelo,Fasani, Elisa
, p. C26 - C28 (1984)
Electronic excitation causes efficient labilization of both the azo and carbonyl ligands in Cr(CO)5 (diazanorbornene) via an excited LF state.On the contrary the corresponding tungsten complex undergoes only inefficient azo labilization via a MLCT state.Azo labilization is also promoted by electron-transfer sensitization.
Photoinduced coupling of CO and vinylidene ligands-formation of cyclobutane-1,3-diones
Abd-Elzaher, Mokhles M.,Weibert, Bernhard,Fischer, Helmut
, p. 1050 - 1052 (2005)
Photolysis of pentacarbonyl vinylidene complexes of chromium and tungsten affords cyclobutane-1,3-dione derivatives, whereas thermolysis yields binuclear vinylidene nonacarbonyl complexes. In contrast to vinylidene complexes, photolysis of the diphenylall
Kinetic studies of group VI metal carbonyl complexes. VI. Substitution reactions of the group VI metal hexacarbonyls
Graham, James R.,Angelici, Robert J.
, p. 2082 - 2085 (1967)
Hexacarbonyl complexes of the group VI transition metals react with phosphine and phosphite ligands, L, in decalin solvent according to the equation: M(CO)6 + L → M(CO)5L + CO. The rate of reaction is governed by the two-term rate law: rate = k1[M(CO)6] + k2[L][M(CO)6]. SN1 and SN2 types of reaction mechanisms are proposed to account for the two terms. Positive ΔS1* values for the k1 paths and negative ΔS2* values for the k2 paths support the proposed mechanisms. The values of ΔH1* for the k1 path decrease in the order: Cr(CO)6 ～ W(CO)6 > Mo(CO)6. The magnitude of the second-order rate constants, k2, was found to be a function of the basicity of the ligand, L, and increases as follows: As(C6H5)3 6H5)3 6H5)3 2)3CC2H5 2H5)3 4H9)3. A comparison of k2/k1 ratios for the reaction of the hexacarbonyl complexes with P(n-C4H9)3 suggests that the SN2 path becomes more preferred as the size of the metal atom increases from Cr to Mo to W.
Kinetic studies of the cleavage of M+- (M+ = Na+, PPN+; M' = Cr, W; M'' = Mn, Re; L = CO, PR3)
Park, Yong K.,Kim, Seon J.,Kim, Jin H.,Han, In S.,Lee, Chang H.,Choi, Hyung S.
, p. 193 - 202 (1991)
Heterobimetallic complexes have a donor-acceptor metal-metal bond in which two electrons from the electron rich metal moiety are donated to the other electron-deficient metal moiety.The heterobimetallic species of interest, M+- (M+ = Na+, PPN+; M' = Cr, W; M'' = Mn, Re; L = CO, PR3) undergoes ligand substitution or metal-metal bond cleavage upon reaction with PR3 (R = C6H5, C2H5) or CO.Unprecedented reactions by the counter ion were observed.Factors affecting these dimeric disruptions will be discussed on the basis of the kinetic studies.
UEBERGANGSMETALL-CARBIN-KOMPLEXE. LXXV. SYNTHESE NEUER HALOGENVERBRUECKTER ZWEIKERNIGER CARBINKOMPLEXE VON CHROM UND WOLFRAM
Fischer, Ernst Otto,Wanner, Juergen Karl Roman
, p. 175 - 180 (1983)
Irradiation of hexacarbonyl chromium in dichloromethane at low temperature yields an intensely yellow solution, in which the presence of "Cr(CO)5(CH2Cl2)" is supposed.After addition of carbyne complexes of chromium or tungsten to these solutions the new h
Hydroxylamines as new decarbonylating reagents in the synthesis of metal carbonyl derivatives
Maksakov, V. A.,Ershova, V. A.
, p. 69 - 78 (1995)
Mononuclear and cluster carbonyl complexes react with amino functional compounds under mild conditions in the presence of H2O2 to form mixed amino carbonyl derivatives.It was found that a group of reactive species facilitating the process are hydroxylamines which arise in situ as a result of oxidation of amino compounds.On the basis of kinetic data and certain other measurements the mechanism of interaction of M(CO)6 (M = Cr, Mo, W) and NH2OH is proposed.This includes nucleophilic attack by NH2OH on a carbonyl carbon resulting in CO oxidation and CO2 elimination with simultaneous intramolecular movement of the amino group to the metal atom.The above mechanism is compared with that for the analogous reaction facilitated by Me3NO, studied earlier. Keywords: Chromium; Molybdenum; Tungsten; Osmium; Cluster; Hydroxylamine
Synthesis of the sterically hindered complexes . Crystal structure of
Beck, Gerhard,Lappert, Michael F.,Hitchcock, Peter B.
, p. 143 - 148 (1994)
The reaction of the dialkylchloroborane BClR2 with a Group 6 pentacarbonyl(cyano)metallate(0) in CH2Cl2 or PhMe gives the thermally stable complexes .Crystalline 2a has a linear Cr-C-N-B skeleton with long Cr-C and B-N bonds and a short C-N bond, consistent (as are the IR, Raman and NMR spectra) with its formulation as -C-BR2>.Key words: Group 6; Boron; Silicon; Crystal structure; Isocyanide; Carbonyl
Unprecedented allenylidene transfer from chromium to tungsten
Szesni, Normen,Drexler, Matthias,Fischer, Helmut
, p. 3989 - 3995 (2008/10/09)
Pyrimidylallenylidene complexes 1 ([(CO)5M=C=C=C(NC 3H3NEt)]; M = Cr (a), W (b)) were prepared in a one-pot procedure from readily available 2-ethynylpyrimidine, butyllithium, [(CO) 5M-(THF)], and triethyloxonium tetrafluoroborate. In addition to 1a,b, the homobinuclear allenylidene complexes 2a,b ([(CO)5M=C=C= C(NC3H3NEt)M(CO)5]; M = Cr, W) were formed. In 2a,b the second (CO)5M moiety is attached to the nonalkylated nitrogen atom of the pyrimidyl ring. Treatment of the chromium complex la with an excess of [(CO)5W(THF)] afforded the tungsten allenylidene complex 2b by transmetalation of the allenylidene ligand and addition of (CO) 5W. The allenylidene ligands of other chromium allenylidene complexes [(CO)5Cr=C=C=C(R1)R2] could likewise be transferred to tungsten. In contrast, the reverse transmetalation from tungsten to chromium could not be achieved. DFT calculations indicate that the reaction proceeds by an associative rather than a dissociative pathway. The initiating reaction step is coordination of a (CO)5W fragment to the C α-Cβ bond of the allenylidene ligand.
Electrophilic addition of Ph3PAu+ to anionic alkoxy Fischer-type carbene complexes: A novel approach to metal-stabilized bimetallic vinyl ether complexes
Raubenheimer, Helgard G.,Esterhuysen, Matthias W.,Timoshkin, Alexey,Chen, Yu,Frenking, Gernot
, p. 3173 - 3181 (2008/10/08)
The addition of the Ph3PAu+ electrophile to deprotonated Fischer-type alkoxy(methyl)-carbene complexes of pentacarbonyl group 6 metals leads to the formation of novel vinyl ether complexes of gold coordinated to the pentacarbonylmetal moiety. X-ray structures and DFT calculations show that the greatest bonding contribution in the vinyl coordination to the M(CO)5 fragment comes from the terminal, partially negatively charged, CH2 carbon atom via partial end-on η1-bonding rather than the usual η2-bonding of olefins. The corresponding positive charge from the asymmetric vinyl coordination is mainly delocalized onto the Ph3PAu fragment, stabilizing this coordination mode. The use of W instead of Cr in the M(CO)5 fragment, in otherwise isostructural compounds, results in somewhat greater asymmetry in the vinyl coordination, with the difference in the two M(CO)5-η2-vinyl carbon bond lengths increasing from 0.252(11) A? (M = Cr) to 0.307(5) A? (M = W) in the solid state.
