- Relative hemilabilities of H2B(az)2 (az = pyrazolyl, dimethylpyrazolyl, methimazolyl) chelates in the complexes [M(η-C3H5)(CO)2{H2B(az)2}] (M = Mo, W)
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The reactions of [M(η3-C3H5)Br(CO)2(NCMe)2] (M = Mo, W) or [Mo(η3-C3H5)Br(CO)2(PMe2Ph)2] with Na[H2B(mt)2] (mt = methimazolyl) affords the complexes [M(η3-C3H5)(CO)2{κ3-H,S,S′-H2B(mt)2}], the 3-centre, 2-electron B-H-M interaction of which was found to be inert with respect to opening under mild conditions, while more forcing conditions (heating with PMe2Ph) resulted in cleavage of the entire allyl and borate ligands to form [Mo(CO)3(PMe2Ph)3]. In contrast, the reaction of [Mo(η3-C3H5)Br(CO)2(NCMe)2] with Na[H2B(pz)2] affords either [Mo(η3-C3H5)(CO)2{κ3-H,N,N′-H2B(pz)2}] or (more likely) [Mo(η3-C3H5)(CO)2(NCMe){κ2-N,N′-H2B(pz)2}] which in turn reacts with phosphines to provide [[Mo(η3-C3H5)(CO)2(PPhR2){κ2-N,N′-H2B(pz)2}] (R = Me, Ph). The reactions discussed indicate the propensity for 3-centre, 2-electron B-H-Mo interactions increases in the order H2B(pz)2 2B(pz?)2 2B(mt)2 (pz? = 3,5-dimethypyrazolyl).
- Abernethy, Robyn J.,Foreman, Mark R. St.-J.,Hill, Anthony F.,Smith, Matthew K.,Willis, Anthony C.
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- Photochemistry of bis[cyclopentadienyltricarbonyltungsten] with diphenyl diselenide to produce (benzeneselenato)cyclopentadienyltricarbonyltungsten
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Visible- light photolysis of [CpW(CO)3]2 with diphenyl diselenide in THF or toluene produces good yields of CpW(CO)3SePh. Nonempirical Fenske-Hall MO calculations are used to compare the bonding in the CpW(CO)3S
- Abrahamson, Harmon B.,Marxen, Heather
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Read Online
- Aryl Oligogermanes as Ligands for Transition Metal Complexes
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The ligand properties of a series of aryl oligogermanes R3Ge-GeAr3, 3–7 [Me3Ge-GePh3 (3), Me3Ge-Ge(pTol)3 (4), Ph3Ge-GePh3 (5), (C6F5)3Ge-GePh3 (6), Ph3Ge-GeMe2GePh3 (7)] for the synthesis of transition metal carbonyl complexes such as R3Ge-GeAr2(R′C6H4-η6)M(CO)3 (M = Cr, 3a–7a; M = Mo, 3b; M = W, 3c) were investigated. The target complexes were obtained in moderate yields using several different synthetic approaches. The physicochemical properties of these new derivatives were investigated by IR, UV/Vis, NMR spectroscopy, electrochemistry, and DFT calculations. The molecular structures of 3c, 4a, and 5a were studied by single-crystal X-ray diffraction analysis. A comparative analysis of donor and acceptor properties of aryl oligogermanes as ligands for transition metal carbonyl complexes is reported.
- Zaitsev, Kirill V.,Lam, Kevin,Tafeenko, Viktor A.,Korlyukov, Alexander A.,Poleshchuk, Oleg Kh.
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p. 4911 - 4924
(2018/12/11)
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- On the coordination chemistry of corannulene, the smallest "buckybowl"
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A variety of methods, conventional and non-conventional, are used in attempts to prepare the compounds (η6-corannulene)M(CO) 3 (M = Cr, Mo, W), all unsuccessful. Conventional methods are also utilized in attempts to prepare the compound [CpFe(η6- corannulene)]PF6, but these result in mixtures of cationic CpFe(arene) complexes containing partially hydrogenated corannulene; similar results have been reported for other polyaromatic hydrocarbons. DFT calculations on the compound (η6-corannulene)Cr(CO)3 suggest that the (η6-corannulene)-Cr linkage is only a few kcal/mol weaker than the corresponding bond in (η6-benzene)Cr(CO)3, implying that failures in syntheses arise from kinetic, not thermodynamic problems.
- Stoddart, Michael W.,Brownie, John H.,Baird, Michael C.,Schmider, Hartmut L.
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p. 3440 - 3450
(2007/10/03)
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- Synthesis and structures of dinuclear iron, molybdenum and tungsten complexes derived from (PhCHCHPh)-coupled bis(cyclopentadiene)
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Reductive coupling of phenylfulvene with amalgamated calcium metal followed by hydrolysis yields CpPhCHCHPhCp (1) in high yield. Refluxing ligand 1 and Fe(CO)5 in xylene produces (PhCHCHPh)-coupled bis(cyclopentadienyl) tetracarbonyl diiron (PhCHCHPh)[(η5-C5H 4)Fe(CO)2]2 (2) as a mixture of meso (2-meso) and racemic isomers (2-rac). The pure racemic isomers of the Mo and W analogues (3-rac and 4-rac) have been synthesized by lithiation of ligand 1 and addition of (MeCN)3M(CO)3 (M = Mo, W) followed by oxidation with 2 equiv. of ferrocenium tetrafluoroborate. All the new complexes have been fully characterized. The molecular structures of 1-meso, 2-meso, 2-rac, 3-rac, and 4-rac have been determined by X-ray diffraction analysis.
- Li, Bin,Wang, Baiquan,Xu, Shansheng,Zhou, Xiuzhong
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p. 5309 - 5317
(2007/10/03)
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- Synthesis and characterization of 6,7 and 8-coordinate monomeric complexes of tungsten obtained from reaction of [W(CO)3(MeCN)3] with pyridine-2-thiol (pySH) and PPh3
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Complexes [W(CO)4(PPh3)2] 1, [W(CO) 4(pySH)(PPh3)] 2, [W(CO)2(pyS) 2(PPh3)] 3 and [W(pyS)4] 4 have been obtained from the reaction of [W(CO)3(MeCN)3] with pyridine-2-thiol (pySH) and PPh3 in refluxing THF. 1 and 2 are normal 6-coordinate complexes but 3 and 4 are unusual 7 and 8-coordinate complexes, respectively. The complexes have been characterized by IR, 1H and 31P{1H}NMR, mass spectra and elemental analysis.
- Anjumanara,Begum, Noorjahan,Camellia, Farzana K.,Kabir, Shariff E.,Kundu, Kalipada
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p. 1123 - 1125
(2007/10/03)
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- Syntheses, characterization and structures of chromium group carbonyl complexes containing a multifunctional Ph2P(o-C6H4)CH=N(CH2) 2(o-C6H4N) ligand
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Reactions of the phosphine-imine-pyridine-containing ligand Ph2P(o-C6H4)CH=N(CH2) 2(o-C6H4N) (PNN) with M(CO)3(NCMe)3 (M=Cr, Mo, W) produce the tridentate complexes fac-M(CO)3(η3-PNN). On the other hand, treating W(CO)4(NCMe)2 with PNN results in the bidentate complex W(CO)4(η2-PNN), which converts to fac-W(CO)3(η3-PNN) upon heating, but no facial→meridional isomerism is evidenced. The new compounds have been characterized by elemental analysis and mass, IR, and NMR spectroscopy. The molecular structures of W(CO)4(η2-PNN), fac-W(CO)3(η3-PNN) and fac-Mo(CO)3(η3-PNN) are determined by an X-ray diffraction study.
- Yang, Ching-Chao,Yeh, Wen-Yann,Lee, Gene-Hsiang,Peng, Shie-Ming
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p. 353 - 358
(2007/10/03)
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- Comparison of a range of rhodium-based catalysts for the hydroformylation of selected alkenes
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To determine whether the activity and selectivity of bimetallic catalysts improve during the hydroformylation of alkenes compared to their monometallic counterparts, the hydroformylation of styrene, 1-hexene, and a variety of amino- and phosphino-alkenes using four Rh-based catalyst systems ((OC)4W(μ-PPh2)2RhH(CO)(PPh3), (OC)2RhMo(CO)3(C5H4PPh2), (OC)2RhW(CO)3(C5H4PPh2), and [Rh(OAc)2]2/PPh3) was investigated. The Rh-catalyzed reactions of unsaturated amines with H2/CO differed in chemo- and regioselectivity depending on the catalyst and the reaction conditions. The reactions of unsaturated amides differed in product ratios with varying catalyst systems.
- Dickson,Gladiali,Bowen,Campi,Jackson,Jonasson,McGrath,Paslow,Polas,Renton
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p. 133 - 146
(2008/10/09)
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- Tris[(alkylthio)methyl]silanes: Syntheses and structures of chromium, molybdenum, and tungsten complexes with a tripodal thioether ligand
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The first member of a new family of tripodal thioether ligands, the methyltris[(alkylthio)methyl]silanes MeSi-(CH2SR)3 (R = Me), has been synthesized and characterized. Reactivity studies lead to the isolation of the complete series of group 6 metal carbonyl derivatives {η3-MeSi(CH2SMe)3}M(CO)3 (M = Cr, Mo, W), whose structures have been determined by single-crystal X-ray diffraction. The three complexes are isomorphous and display distorted octahedral structures with face-capping tridentate thioether ligands. {η3-MeSi(CH2SMe)3}Cr(CO)3 is monoclinic, P21/c, a = 8.1658(2) A?, b = 15.0563(2) A?, c = 26.5791(3) A?, β= 90.3653(6)°, V = 3267.74(8) A?3, Z = 8. {η3-MeSi(CH2SMe)3}Mo(CO)3 is monoclinic, P21/c, a = 8.34630(6) A, b = 15.2747(2) A?, c = 27.1865(4) A?, β = 90.8987(9)°, V= 3465.44(10) A?3, Z = 8. {η3-MeSi(CH2SMe)3}W(CO)3 is monoclinic, P21/c, a = 8.1582(2) A?, b = 14.9903(2) A?, c = 26.7268(4) A?, β = 90.6568(8)°, V = 3268.30(9) A?3, Z = 8.
- Yim, Hing W.,Tran, Linh M.,Dobbin, Ebern D.,Rabinovich, Daniel,Liable-Sands, Louise M.,Incarvito, Christopher D.,Lam, Kin-Chung,Rheingold, Arnold L.
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p. 2211 - 2215
(2008/10/08)
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- 1,3,5-Trimethyl-1,3,5-triazacyclohexane tricarbonyl complexes of Mo and W as sources of the fac-M(CO)3 fragment. Mild syntheses of fac-[M(CO)3(CH3CN)3] (M=Mo, W), [W(CO)3(PR3)3], [W(CO)(alkyne)3] and [W(CO)3(π-arene)] complexes
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The 1,3,5-trimethyl-1,3,5-triazacyclohexane (Me3tach) group in [M(CO)3(Me3tach)] complexes (M=Mo, W) is easily displaced by a variety of ligands under mild conditions. The lability of the Me3tach ligand allows the [M(CO)3(Me3tach)] complexes to be used as synthetic intermediates in convenient syntheses of products such as fac-[M(CO)3(CH3CN)3] (M=Mo, W), [W(CO)(alkyne)3], [W(CO)3(PR3)3] and [W(CO)3(η6-arene)] complexes. An improved synthesis of [W(CO)3(Me3tach)] from [W(CO)6] and Me3tach is described.
- Baker, Murray V.,North, Michael R.
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p. 225 - 230
(2007/10/03)
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- Synthesis and Structures of Low-Valent Tungsten Complexes Bearing Chiral Oxazoline-Derived Ligands
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The synthesis of low-valent tungsten (0 and II) complexes bearing chiral bidentate phosphino-oxazoline or bisoxazoline ligands is described.The structures of four of the complexes have been determined by single crystal X-ray analyses.Tungsten(II)-allyl complexes of the type (PN = phosphino-oxazoline) are fluxional in solution, but can be crystallized as single diastereoisomers.The complex , which also crystallizes as a single diastereomer, is readily oxidized in solution and solid state, in stark contrast to analogous compounds bearing four carbonyl ligands or (NN = bisoxazoline) which were found to be stable. functions as a highly enantioselective catalyst in allylic substitution reactions with dimethyl sodiomalonate, whereas complexes of the type (Z = H, Ph; X = Cl, Br) failed to yield allylic alkylation products. - Keywords: Chiral Tungsten Complexes, Phosphino-oxazoline Ligands, Bisoxazoline Ligands, Tungsten Allyl Complexes, Asymmetric Catalysis
- Lloyd-Jones, Guy C.,Pfaltz, Andreas
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p. 361 - 367
(2007/10/02)
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- Reactivity of 17-, 18-, and 19-Electron Cationic Complexes Generated by the Electrochemical Oxidation of Tricarbonyl(mesitylene)tungsten
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The electrochemical oxidation of (mesitylene)W(CO)3 (W) in MeCN produces the 17-electron complex W+, which reacts very rapidly with solvent (S) or tri-n-butyl phosphite (P) to give 19-electron species (WS+, WP+) that undergo spontaneous further oxidation to the 18-electron analogues (WS2+, WP2+). The identities of WS2+ and WP2+ were established by voltammetric, IR spectroelectrochemical, and NMR experiments. Although the 17-electron ? 19-electron transformation is not directly observable, digital simulation techniques allowed selection of a probable mechanism and semiquantitative determination of the rate and equilibrium parameters describing the interconversion of the 17-, 18-, and 19-electron species: W+ + S ? WS+, k ? 105 M-1 s-1, Keq ? 10-1 M-1; W+ + P ? WP+, k ? 107 M-1 s-1, Keq ? 3 × 103 M-1 at 298 K. The related 18-electron complex WS2+ is quite reactive, but orders of magnitude less so than W+ and WS+. Experiments with (mesitylene)Cr(CO)3 (Cr) suggest that associative attack by MeCN at the 17-electron Cr+ is 104 times slower than attack at the W+ analogue. This study illustrates the power of digital simulation techniques for interpreting complex mechanistic schemes and characterizing important but unobservable reaction intermediates. Electrochemical oxidation of (arene)W(CO)3 occurs without loss of arene or CO ligands, suggesting that the electroactivation of these complexes may have useful synthetic applications; this contrasts sharply with (arene)Cr(CO)3 analogues, which decompose with loss of arene and CO ligands upon oxidation in MeCN.
- Zhang, Yun,Gosser,Rieger,Sweigart
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p. 4062 - 4068
(2007/10/02)
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- Solution calorimetric, equilibrium, and synthetic studies of oxidative addition/reductive elimination of C5R5H (R = H, Me, indenyl) to/from the complexes M(CO)3(RCN)3/(η5-C5R 5)M(CO)3H (M = Cr, Mo, W)
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Equilibrium data are reported for the reaction CpMo(CO)3H + 3MeCN ? Mo(CO)3(MeCN)3 + CpH. Over the temperature range 43-82°C, ΔH = -11.2 kcal/mol, ΔS = -51.3 cal/(mol°C). Calorimetric data for the enthalpies of displacement of C5R5H by nitriles are reported: Cr, R = Me, -0.7 ± 0.7 kcal/mol, M = W, R = H, -5.6 ± 0.7, R = Me, -5.4 ± 0.7 kcal/mol. The enthalpy of reaction of Na+(indenyl)- with (p-xylene)Mo(CO)3 forming Na+Mo(CO)3(indenyl)- is -17.3 ± 0.2 kcal/mol, approximately 10 kcal/mol less than the corresponding reaction of Na+C5H5-. The heat of reaction of (indenyl) W(CO)3H with EtCN forming W(CO)3(EtCN)3, -20.0 ± 0.8 kcal/mol, is approximately 14 kcal/mol more exothermic than the corresponding reaction of the cyclopentadienyl complex, also in keeping with a reduced M-indenyl ground-state bond energy. Synthetic strategies to the (C5R5)M(CO)3H complexes are summarized.
- Kubas, Gregory J.,Kiss, Gabor,Hoff, Carl D.
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p. 2870 - 2876
(2008/10/08)
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- UEBERGANGSMETALL-FULVEN-KOMPLEXE. XXVIII. REAKTIONEN VON (FULVEN)Cr(CO)3-KOMPLEXEN UND Α-FERROCENYL-CARBENIUMIONEN MIT NUKLEOPHILEN
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Tricarbonyl(fulvene)chromium complexes react with anionic nucleophiles to give functionally substituted cyclopentadienyl derivatives.The nucleophilic attack occurs at the exocyclic carbon atom of the fulvene ligand.Addition of PPh2- to (η6-6,6-dimethylfulvene)Cr(CO)3 (1) yields the novel anion 5-C5H4C(CH3)2PPh2)Cr(CO)3>-, which can be isolated as a K+, (C2H5)4N+, (C6H5)4P+, or Tl+ derivative (2-5).The potassium salt of the uncoordinated C5H4C(CH3)2PPh2- anion (7) is obtained by treatment of 6,6-dimethylfulvene with KPPh2*2C4H8O2.Similarly, NaC5H5 reacts with 1 to give Na5-C5H4C(CH3)2C5H5)Cr(CO)3> (8).The reactions of (6-dimethylaminofulvene)Cr(CO)3 (15) with nucleophiles are accompanied by elimination of dimethylamine.Addition of Ph3P=CH2 to 15 gives an unstable product, but after reaction of 6-dimethylaminofulvene with Ph3P=CH2, the free ligand C5H4=CHCH=PPh3 (17) can be isolated in moderate yields.Deeply colored anions of the type 5:η5-C5H4C(R)=C5H4)Cr2(CO)6>- (R = H, N(CH3)2 are synthesized by reaction of 15 or (6-dimethylamino-6-methylthiofulvene)Cr(CO)3 with NaC5H5 and subsequent complexation of the mononuclear intermediate with (CH3CN)3Cr(CO)3.In addition, the synthesis of the new fulvene complexes M(CO)3 (23,24; M = Cr, Mo) is described.The investigation is extended to α-ferrocenylcarbenium ions, which are isoelectronic with (fulvene)Cr(CO)3 complexes. 5-C5H5)Fe(C5H4CPh2)>+ BF4- (25) adds tertiary phosphines at the exocyclic carbon atom to give phosphonium salts of the type 5-C5H4)Fe(C5H4CPh2PR3)>+ BF4-.A CO-substitution product of a tricarbonyl(fulvene)chromium complex is obtained for the first time by irradiation of (η6-6,6-diphenylfulvene)Cr(CO)3 in the presence of PPh3.In addition, an improved synthesis of the (CH3CN)3M(CO)3 complexes (M = Cr, Mo, W) is reported.
- Edelmann, Frank,Behrens, Peter,Behrens, Sabine,Behrens, Ulrich
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p. 333 - 356
(2007/10/02)
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