- Investigation of the catalytic properties of the thermally activated dichloro-tetracarbonyl-tungsten in olefin metathesis reaction
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Combined catalytic, preparative and spectroscopic studies revealed that the ring-opening metathesis polymerisation of norbornene initiated by thermally activated W (CO)4Cl2 (I) proceeds mainly on the surface of a solid decomposition product formed in situ.
- Bencze, Lajos,Szalai, Gabor,Overton, Tina L.
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- REACTIONS OF BIMETALLIC GROUP VI COMPLEXES II. PHOSPHINE AND PHOSPHITE DERIVATIVES; LIGAND TRANSFER AND OXIDATIVE DECARBONYLATION; THE CRYSTAL STRUCTURE OF
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Triphenylphosphine and trimethylphosphite react with (M, M'=Mo, W) (II) to give which on heating revert to II.On prolonged heating is formed. reacts with I2 to give fo
- Quere, J. L. Le,Petillon, F. Y.,Guerchais, J. E.
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- Crystal structure of trans- [W(CO)4(n2-C2H4)2] and IR 1H NMR studies of the reactions of this and related ethene carbonyl complexes of tungsten(0), [W(CO)(n)(n2-C2H4)6-(n)] (n = 3-5)
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The structure of trans-[W(CO)4 (η2-C2H4)2] 1 has been determined by X-ray crystallography at 293 K [orthorhombic, space group Aba2, a = 12.458(3), b = 6.370(2), c = 12.557(3)A, Z = 4, R = 0.022] to confirm that the C=C bonds of the two ethene ligands are mutually staggered while eclipsing the central W(CO)4 unit. Reversible isomerisation of trans- to cis-[W(CO)4(η2-C2H4)2] 2 under the action of selective irradiation has been shown to occur in solid argon matrices at 14-16 K. 1H NMR measurements have also been applied to the identification of not only 1 and 2 but also the labile 1Be complexes [W(CO)5(η2-C2H4)] 3, mer-[W(CO)3(η2C2H4)3] 4, and fac-[W(CO)3(η2-C2H4)3] 5 formed by broad-band UV-visible photolysis of ethene-saturated hydrocarbon solutions of 1 or [W(CO)6] in the temperature range 200-293 K. In these circumstances the mixed ethene carbonyl complexes 2-5 decay thermally with dissociation of an ethene ligand and substitution by CO in reactions which have been monitored by reference to the relevant 1H NMR signals. Pseudo-first-order decay constants in the range 0.6-12 x 10-4 s-1 have thus been estimated with temperature-dependences implying activation energies, E(a), that decrease in the order 3 > 2 > 4 > 5.
- Szymanska-Buzar, Teresa,Kern, Krystyna,Downs, Anthony J.,Greene, Timothy M.,Morris, Leigh J.,Parsons, Simon
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- Reactivity of cyano- And isothiocyanatoborylenes: metal coordination, one-electron oxidation and boron-centred Br?nsted basicity
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Doubly base-stabilised cyano- and isothiocyanatoborylenes of the form LL′BY (L = CAAC = cyclic alkyl(amino)carbene; L′ = NHC = N-heterocyclic carbene; Y = CN, NCS) coordinate to group 6 carbonyl complexesviathe terminal donor of the pseudohalide substituent and undergo facile and fully reversible one-electron oxidation to the corresponding boryl radical cations [LL′BY]˙+. Furthermore, calculations show that the borylenes have very similar proton affinities, both to each other and to NHC superbases. However, while the protonation of LL′B(CN) with PhSH yielding [LL′BH(CN)+][PhS?] is fully reversible, that of LL′B(NCS) is rendered irreversible by a subsequent B-to-CCAAChydrogen shift and nucleophilic attack of PhS?at boron.
- Arrowsmith, Merle,Braunschweig, Holger,Elezi, Dren,Fantuzzi, Felipe,H?rterich, Marcel,Hagspiel, Stephan,Krummenacher, Ivo,Rempel, Anna,Vargas, Alfredo
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- As a source of semi-interstitial phosphorus ligands in cobalt carbonyl clusters
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The PH3-containing complex [(CO)4W(PH 3)2] (1) is synthesized in good yields by the one-pot reaction of [(CO)4W(nbd)] (nbd = norbonadiene) with P(SiMe3)3 and subsequent methanolysis of the reaction mixture. The further reaction of [(CO)4W(PH3) 2] with [Co2(CO)8] results in three novel cobalt clusters, [Co8(CO)18(μ6-P) 2(μ-CO)] (2), [Co10(CO)18(μ7- P)2(μ-CO)6] (3), and [[Co3(CO) 8{μ4-PW(CO)5}][(μ4-P)Co 3(CO)9]] (4). All products have been comprehensively characterized including X-ray diffraction.
- Dreher, Cornelia,Zabel, Manfred,Bodensteiner, Michael,Scheer, Manfred
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- Carbonyltungsten(0) complexes of acryloylferrocene: Synthesis and characterization
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Photolysis of hexacarbonyltungsten(0) in the presence of acryloylferrocene in n-hexane solution at 10 °C yields pentacarbonyl(η2-acryloylferrocene)tungsten(0) (1) as the only photo-substitution product, different from the general reaction patte
- Bo?a, Dilek Ay?e,?zkar, Saim
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- Synthesis and characterisation of novel complexes containing group 15 elements and their potential use as molecular precursors for the formation of transition metal pnictides
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The reaction of [{W(CO)5}2PCl] with K[Co(CO) 4] yields the novel compounds [{W(CO)4Co 2(CO)6}{μ3-PW(CO)5}2] (3) and [{(CO)4WCo3(CO)su
- Scheer, Manfred,Vogel, Ulf,Becker, Uta,Balazs, Gabor,Scheer, Petra,Hoenle, Wolfgang,Becker, Michael,Jansen, Martin
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- Silicon-containing carbene complexes. 6. Stable 16-electron carbonyl carbene complexes of tungsten(0), molybdenum(0), and chromium(0)
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On warming (CO)5W=C(NR2)SiPh3 (NR2 = NMe2, 1a, NC5H10, 1b) under vacuum, a CO ligand is eliminated and 16-electron carbene complexes (CO)4W= C(NR2)SiPh3 (2a,b) are formed as stable compounds. Analogous chromium and molybdenum complexes (CO)4M=C(NC5H10)SiPh3 (M = Mo, 2c, Cr, 2d) are already formed during the preparation of (CO)5M=C-(NC5H10)SiPh3 (1c,d). The reaction is readily reversed on bubbling CO through solutions of 2. X-ray structure determination of (CO)4W=C(NC5H10)SiPh3 (2b) shows that the vacant coordination site at the metal is capped by a phenyl group of the SiPh3 substituent. However, the long W-C(phenyl) distances exclude strong bonding interaction. The driving force for the conversion of 1 to give 2 seems to be relaxation of the steric strain within the carbene ligand.
- Schubert, Ulrich,Hepp, Wolfgang,Müller, Johannes
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- Photochemische Reaktion von Pentacarbonyl(1-ethoxy-2-methyl-2-propenyliden)wolfram und Dekacarbonyldirhenium
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Upon UV irradiation at 223 K pentacarbonyl (1-ethoxy-2-methyl-2-propenylidene)tungsten (1) and decacarbonyl-dirhenium (2) yield enneacarbonyl(μ-η1:3-1-ethoxy-2-methyl-2-propenylidene)ditungsten (3), octacarbonyl(μ-η1:3-1-ethoxy-2-methyl-2-propenylidene)dirhenium (4) and tridecacarbonyl-μ-η1:3-1-ethoxy-2-methyl-2-propenylidene)dirhenium-tungsten (5).The molecular structure of the hetero-trinuclear compound 5 was determined by X-ray structure analysis.The three metal centers form a bent Re-W-Re spine.One of the Re-W bonds is bridged by a carbonyl and the η1:3-1-ethoxy-2-methyl-2-propenylidene ligand.
- Kreiter, Cornelius G.,Schufft, Sabine,Heckmann, Gert
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- Organic synthesis via transition metal complexes. 112. Reactivity enhancement of group VI Fischer carbene complexes by copper and rhodium catalysts: Experimental proof of a carbene rhodium complex as an intermediate
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Rhodium(I) compounds were found to efficiently catalyze reactions of Fischer carbene complexes. It was shown that the thermally quite unreactive tungstaoctatetraenes 14a-d were readily transformed into spiro-fused vinylcyclopentadienes 15a-d in the presence of catalytic amounts of RhCl3·3H2O in MeOH or [(COD)RhCl]2. A reactivity enhancement was observed also for the transformation of the tungsten complex 8a into vinylcyclopentadiene 10a. Experimental proof for the intermediacy of carbene rhodium complexes in these reactions was provided by preparation of the rhodaoctatetraene 16c from the reaction of the tungsten compound 14c with a stoichiometric amount of [(COD)RhCl]2. The carbene rhodium compound 16c was transformed into the vinylcyclopentadiene 15c thermally in a smooth reaction and showed a catalytic activity similar to [(COD)RhCl]2. Not only rhodium but also copper compounds were found to be good catalysts for the π-cyclization of tungstaoctatetraenes.
- G?ttker-Schnetmann, Inigo,Aumann, Rudolf,Bergander, Klaus
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- Excimer Laser Photolysis of Gas-Phase W(CO)6
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Laser-Based time-resolved infrared absorption spectroscopy was performed to investigate the excimer laser, XeF (351 nm), XeCl (308 nm), and KrF (248 nm), photolysis of W(CO)6 in the gas phase.The spectra observed in the wavenumber region between 1700 and 2033 cm-1 show the primary production of coordinatively unsaturated tungsten carbonyls through a single photon mechanism.The extent of the fragmentation depends strongly on the absorbed photon energy.Infrared assignments for W(CO)4 and W(CO)5 are determined unambiguously from the stoichiometry revealed by the kinetics of the reactions with added CO.These assignments suggest that W(CO)5 is the only primary product in the XeF and XeCl laser photolysis while W(CO)4 is the main product from KrF laser photolysis.For W(CO)5 the C-O stretching bands are around 1942 and 1980 cm-1, and those of W(CO)4 are at around 1909 and 1957 cm-1.The infrared absorption spectra lead to low-symmetry structure assignments of C4υ for W(CO)5 and C2υ for W(CO)4.This is consistent with the assignment from low-temperature inert gas matrices.These coordinatively unsaturated tungsten carbonyls react with CO about once in every 10 collisions.
- Ishikawa, Yo-ichi,Hackett, Peter A.,Rayner, David M.
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- Synthesis and spectroscopic characterization of new mixed-metal, mixed-chalcogenide clusters [Fe2W(CO)10(μ3-Se)(μ3-E)] (E = Te or S). Structures of [Fe2M(CO)10(μ3-Se)(μ3
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The room-temperature reaction of [Fe2(CO)6(μ-SeTe)] and [Fe2(CO)6(μ-SSe)] with freshly prepared [W(CO)5(thf)] (thf = tetrahydrofuran) yielded the new mixed-metal, mixed-chalcogenide clusters [Fe2
- Mathur, Pradeep,Sekar, Perumal,Satyanarayana, Chilukuri V. V.,Manon, Mary F.
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- Synthetic routes to transition-metal-substituted pentadiynylidene complexes
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Sequential reaction of the dimethylamino(ethynyl)carbene complex [(CO)5W=C(NMe2)C≡CH] (1) with nBuLi, Cul and BrC≡CSiMes affords the dimethylamino(trimethylsilylbutadiynyl)carbene complex [(CO)5W=C(NMe2)CsC-C≡CS
- Hartbaum, Cornelia,Fischer, Helmut
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- SYNTHESE ET ETUDE STRUCTURALE D'UN COMPLEXE MONONUCLEAIRE DU TUNGSTENE PORTANT A LA FOIS UN GROUPEMENT ALKYLIDENE ET UNE DOUBLE LIAISON
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Reaction of W(CO)6 with 4-penten-1-yllithium and 3-buten-1-yllithium leads after alkylation to the unsaturated alkylidene complexes (CO)5WC(OMe)(CH2)3CHCH2 (6) and (CO)5WC(OEt)(CH2)2CHCH2 (13), respectively.Coordination of the double bonds of complexes 6 and 13 occurs in refluxing benzene and gives the isomerized complex W(CO)4C(OMe)(CH2)2CHCHCH3 (7) and complex W(CO)4C(OEt)(CH2)2CHCH2 (14).An X-ray structure of complex 14 shows that the alkylidene function and the coordinated double bond are perpendicular to each other.
- Toledano, Cecilio Alvarez,Levisalles, Jacques,Rudler, Michele,Rudler, Henri,Daran, Jean-Claude,Jeannin, Yves
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- Siliciumhaltige Carben-Komplexe. XIV. Untersuchungen zur Frage der Aciditaet der Si-H-Gruppe in Silylcarben-Komplexen (CO)5MC(XR)SiHR'2 (M = Cr, W; XR = OEt, NR2)
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The very unstable carbene complexes (CO)5MC(OEt)Si(H)Mes2 (1a: M=W; 1b: M=Cr; Mes=mesityl) were prepared by reaction of M(CO)6 with Li, followed by alkylation with BF4.Corresponding complexes with smaller substituents at the silicon atom were considerably less stable.While 1a yielded the aminocarbene complexes (CO)5WC(NHR)Si(H)Mes2 upon reaction with H2NR (R=Me, Et, CH2CH=CH2, i-Pr), reaction with HNR2 was strongly influenced by steric effects.Dialkylaminocarbene complexes (CO)5WC(NR2)Si(H)Mes2 were only obtained with the sterically less demanding amines HNMe2 or HNC4H8.Complex 1b only reacted with H2NMe.The X-ray structure analysis of (CO)5WC(NC4H8)Si(H)Mes2 (2f) showed that the hydrogen atom at silicon is strongly screened and hardly accessible.Although spectroscopic data of the new complexes indicate a slight enhancement of the acidity of the Si-H group compared with R2SiH2, no deprotonation was possible using several bases.
- Schubert, Ulrich,Wuelfert, Peter,Mock, Stefan
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- Development of five-coordinate zinc Mono- and dithiolates as S-donor metalloligands: Formation of a Zn-W coordination polymer
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The synthesis and isolation of mono- and dithiolate-bridged Zn(μ-SR)nW(CO)m (where n = 1, m = 5; n = 2, m = 4) species from the dimeric N,N′-bis(2-mereaptoethyl)-1,4- diazacycloheptanezinc(II), [Zn-1′]2, and the monomeric
- Almaraz, Elky,Foley, William S.,Denny, Jason A.,Reibenspies, Joseph H.,Golden, Melissa L.,Darensbourg, Marcetta Y.
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- Isomeric olefin tetracarbonyl complexes of tungsten(I): An infrared spectroelectrochemical study at low temperatures
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In situ electrolysis within an optically transparent thin-layer electrochemical (OTTLE) cell was applied at 293-243 K in combination with FTIR spectroscopy to monitor spectral changes in the carbonyl stretching region accompanying oxidation of four tetrac
- Gorski, Marcin,Hartl, Frantisek,Szymanska-Buzar, Teresa
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p. 4066 - 4071
(2008/10/09)
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- Unprecedented allenylidene transfer from chromium to tungsten
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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.
- Szesni, Normen,Drexler, Matthias,Fischer, Helmut
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p. 3989 - 3995
(2008/10/09)
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- Intermetallic Communication through Carbon Wires in Heterobinuclear Cationic Allenylidene Complexes of Chromium
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The reaction of [(CO)5M(THF)] (M = Cr, W) with lithiated 2-ethynylquinoline followed by alkylation of the resulting alkynylpentacarbonylmetalate with [R3O]BF4 (R = Me, Et) gives allenylidene complexes in which the terminal carbon atom of the allenylidene chain is part of an N-alkylated quinoline ring. The reaction of [(CO)5M(THF)] (M = Cr, W) with lithiated 2-ethynylpyridine derivatives, Li[C≡CC5H4BrN], and [Et 3O]BF4 affords allenylidene complexes that contain a terminal six-membered N-heterocycle brominated at the 5- or 6-position. Various alkynyl groups can be introduced into the 5-position of the ring through [PdCl2(PPh3)2] -catalyzed coupling of the 5-bromo-substituted allenylidene complexes with the terminal alkynes HC≡CR′ (R′ = TMS, Ph, C10H21, 4-C 6H4-C≡CPh, 4-C6H4-C≡CH, Fc (Fc = (C5H4,)FeCp), 4-C6H4-C=CFc, 4-C 6H4-C≡CC6H4C≡CFc). The analogous replacement reaction of the 6-bromo-substituted chromium complex with HC≡CFc yields the corresponding 6-ferrocenylalkynyl-substituted complex. Desilylation of [(CO)5Cr=C=C=C(CH)2C(C≡CSiMe 3)CHNEt] (6a) gives [(CO)5Cr=C=C= C(CH) 2C(C=CH)CHNEt] (15a). CuI-catalyzed coupling of 15a with {M}-Br ({M} = Ru(CO)2Cp, Fe-(CO)2Cp*) affords the binuclear complexes [(CO)5Cr=C=C=C(CH)2C(C=C-{M})CHNEt]. The symmetrical binuclear complex is formed by oxidative coupling of 15a with [Cu(OAc) 2]. The attachment of a ferrocenyl group to the chromium center via PPh2 to give cis-[(CO)4(Ph2PFc)Cr=C=C=C(CH) 4NEt] is achieved via displacement of a cis-CO ligand in [(CO) 5Cr=C=C=C(CH)4NEt] by PPh2Fc. On addition of Co2(CO)8 to [(CO)5Cr=C=C=C(CH) 2C(C=CPh)CHNEt] a Co2(CO)6 unit adds to the C≡C bond to form a trinuclear complex. The ferrocenyl unit in [(CO) 5Cr=C=C=C(CH)2C(C≡CR)CHNEt] (R = Fc, C 6H4C≡CFc, C6H4C≡CC 6H4C≡CFc) is readily oxidized. Spectroelectrochemical studies (IR, UV/vis) confirm that in the oxidized form there is strong electronic communication of the ferrocenyl group with the (CO)5Cr unit.
- Szesni, Normen,Drexler, Matthias,Maurer, Joerg,Winter, Rainer F.,De Montigny, Frederic,Lapinte, Claude,Steffens, Stefan,Heck, Juergen,Weibert, Bernhard,Fischer, Helmut
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p. 5774 - 5787
(2008/10/09)
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- Coordinating properties of [M(CO)5(CN)]- [M=Cr; Mo; W] ligands: Formation of ion pairs or dinuclear cyanide-bridged complexes, spectroscopic and X-ray diffraction studies
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The reaction of sodium cyanopentacarbonylmetalates Na[M(CO)5 (CN)] (M=Cr; Mo; W) with cationic Fe(II) complexes [Cp(CO)(L)Fe(thf)] [O3SCF3], [L=PPh3 (1a), CN-Benzyl (1b), CN-2,6-Me2C6H
- Palazzi, Antonio,Sabatino, Piera,Stagni, Stefano,Bordoni, Silvia,Albano, Vincenzo G.,Castellari, Carlo
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p. 2324 - 2337
(2007/10/03)
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- Unexpected formation of a weak metal-metal bond: Synthesis, electronic properties, and second-order NLO responses of push-pull late-early heteronuclear bimetallic complexes with W(CO)3(1,10-phenanthroline) acting as a donor ligand
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In attempts to bridge the complex [W(CO)3(phen)(pyz)] (phen = 1,10-phenanthroline; pyz = pyrazine) to acceptor centers, either soft centers such as cis-M(CO)2CL (M = Rh(I), Ir(I)) and fac-M(CO)3Cl2 (M = Ru(II), Os(II)) or hard centers such as BF3, the pyrazine ligand is lost, while the fragment W(CO)3(phen) behaves as a σ-donor base with the unexpected formation of heteronuclear early-late bimetallic compounds with a weak metal-metal bond, as confirmed by the easy substitution of W(CO)3(phen) by soft ligands (PPh3, CO, pyridine). The X-ray structures of [(CO)3(phen)W-cis-Ir(CO)2Cl] and [(CO)3(phen)W-fac-Os(CO)3Cl2] confirm a single metal-metal bond with an halogen bridging asymmetrically the two metallic moieties and with the tungsten atom achieving a distorted (6 + 1) octahedral coordination. All the heteronuclear bimetallic complexes investigated show in their electronic spectra a new solvatochromic absorption band at around 385-450 nm in addition to the MLCT (W→π*phen) absorption band typical of [W(CO)3(phen)L] complexes (L = CO, pyz, CH3CN) and an increased, in comparison to [W(CO)4(phen)], negative nonlinear (NLO) second-order emission working with the EFISH technique with an incident wavelength of 1.907 μm. The increase is due to an additional negative contribution of the new absorption band at around 385-450 nm, as shown by a solvatochromic investigation.
- Pizzotti, Maddalena,Ugo, Renato,Dragonetti, Claudia,Annoni, Elisabetta,Demartin,Mussini
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p. 4001 - 4011
(2008/10/08)
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- Stabilization of the P(CF3)2- and P(C6F5)2- ions by coordination to pentacarbonyl tungsten: Structures of [18-crown-6-K]P(CF3)2, [18-crown-6-K][W{P(CF3)2}(CO)5], and [18-crown-6-K][{W(CO)5}2{μ-P(C6 F5)2}]·THF
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The stabilization of the P(CF3)2- ion by intermediary coordination to the very weak Lewis acid acetone gives access to single crystals of [18-crown-6-K]P(CF3)2. The X-ray single crystal analysis exhibits nearly isolated P(CF3)2-ions with an unusually short P-C distance of 184(1) pm, which can be explained by negative hyperconjugation and is also found by quantum chemical hybrid DFT calculation. Coordination of the P(CF3)2- ion to pentacarbonyl tungsten has only a minor effect on electronic and geometric properties of the P(CF3)2 moiety, while a strong increase in thermal stability of the dissolved species is achieved. The hitherto unknown P(C6F5)2- ion is stabilized by coordination to pentacarbonyl tungsten and isolated as a stable 18-crown-6 potassium salt, [18-crown-6-K]- [W{P(C6F5)2}(CO)5], which is fully characterized. The tungstate, [W{P(C6F5)2}(CO)5]-, decomposes slowly in solution, while coordination of the phosphorus atom to a second pentacarbonyl tungsten moiety results in an enhanced thermal stability in solution. The single-crystal X-ray analysis of [18-crown-6-K][{W(CO)5}2{μ-P(C5 F5)2}]·THF exhibits a very tight arrangement of the two C6F5 and two W(CO)5 groups around the central phosphorus atom. NMR spectroscopic investigations of the [{W(CO)5}2{μ-P(C6 F5)2}]- ion exhibit a hindered rotation of both the C6F5 and W(CO)5 groups in solution.
- Hoge, Berthold,Thoesen, Christoph,Herrmann, Tobias,Pantenburg, Ingo
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p. 3633 - 3641
(2008/10/08)
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- Organic syntheses via transition metal complexes. 116. Carbocyclic four-, five-, and six-membered rings by condensation of (alkyl,ethoxy)carbene complexes (M = W, Cr) with α,β-unsaturated tertiary acid amides
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4-Amino-1-tungsta-1,3,5-hexatrienes (CO)5W=C(OEt)CH=C(NR2)CH=CHPh (3E)-2 and (cyclohexan-4-on-1-yl)carbene tungsten complexes 6 were obtained by condensation of (ethoxy,methyl)carbene tungsten complex (OC)5W=C(OEt)CH3 1a with α,β-unsaturated tertiary acid amides PhCH=CHC(=O)NR2 7 in the presence of POCl3/Et3N and (COCl)2/Et3N, respectively. Compounds 2 underwent a π-cyclization to zwitterionic η1-cyclopentadiene complexes 3. Condensation of (prim-alkyl,ethoxy)carbene complexes (CO)5M=C(OEt)CH2R1 1 (M = W, Cr; R1 = c-C7H7, n-Pr) with compounds 7 afforded (cyclobutenyl)carbene complexes 9.
- Aumann, Rudolf,Vogt, Dominik,Fu, Xiaolin,Fr?hlich, Roland,Schwab, Pia
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p. 1637 - 1645
(2008/10/08)
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- Spiro-fused cyclopentadienes and novel pyridinium carbonyltungstates from (1-alkynyl)carbene tungsten complexes and exo-methylene n-heterocycles. Competition between 1,4-addition, 1,2-addition, and metathesis
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Reaction of (1-alkynyl)carbene tungsten complexes 1a-c with different exo-methylene N-heterocycles was found to yield 1,4- and 1,2-adducts as well as metathesis products in ratios depending on structural details. 2-Methyleneindoline 2a gave conjugated metallahexatrienes 4a,c and cross-conjugated metallahexatrienes 3a,c by 1,4-addition and metathesis, respectively. Cross-conjugated metallahexatrienes were shown to be thermally transformed in conjugated metallahexatrienes by a skeletal rearrangement. 2-Propenylideneindolines 2b-d afforded cross-conjugated metallaoctatetraenes 8 and 9 resulting from metathesis of the exo-propenylidene moiety at the 1,2- and the 3,4-double bond position, respectively. 2-Methylene-1,2-dihydropyridines 12a,b and 4-methylene-1,4-dihydropyridines 13c-e yielded conjugated metallaoctatetraenes 14 and 15 in each case by 4-addition, which underwent a π-cyclization to spiro compounds 16 and 17, respectively. 4-Methylene-1,4-dihydropyridines 13f,g afforded no 4-addition products but novel pyridinium carbonylmetalates 18 by 2-addition.
- G?ttker-Schnetmann,Aumann, Rudolf,Kataeva, Olga,Holst, Christiane,Fr?hlich, Roland
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p. 2889 - 2904
(2008/10/08)
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- Synthesis of the germanium(I) compounds [Ge2Hal4]2- and their reductive condensation to octahedral [Ge6]2- clusters in an organometallic environment
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GeI2 reacts with [M2(CO)10]2- (M = Cr, W) leading to reductive coupling of two GeI2 units to produce the [Ge2I4]2- ligands of [{(OC)5M}I2Ge-GeI2{M(CO)5}]2- (1a and 2a). The [Ph4P] salts of these anions have been characterised by X-ray structure analyses as have the [Ph4P] salts of [{(OC)5M}Cl2Ge-GeCl2{M(CO)5}]2- (lb and 2b) obtained from the iodo derivatives la and 2a by halide metathesis with [Ph4P]Cl. Treatment of GeI2 with [W2(CO)10]2- in the presence of 2,2'- bipyridine leads to [{(OC)5W}I2GeGe(bipy){W(CO)5}] (3). The digermanium ligands in 1-3 contain germanium in the unconventional formal oxidation state +I. Reductive condensation of [{(OC)5Cr}I2GeGeI2{Cr(CO)5}]2- (1a) by addition of [Cr2(CO)10]2- leads to the octahedral cluster [{(OC)5Cr}6Ge6]2- (4) in a yield of 40%. The sequence of reactions as reported describes the first systematic approach to the synthesis of [E6]2- clusters.
- Renner, Gerd,Kircher, Peter,Huttner, Gottfried,Rutsch, Peter,Heinze, Katja
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p. 879 - 887
(2007/10/03)
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- Catalytic transformations of vinylthiiranes by tungsten carbonyl complexes. A new route to 3,6-dihydro-1,2-dithiins
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W(CO)5(NCMe) (1) has been found to transform vinylthiirane and a series of methyl-substituted vinylthiiranes into a series of 3,6-dihydro-1,2-dithiin compounds. Two equivalents of the vinylthiirane are required, and 1 equiv of a butadiene is formed by the transfer of its sulfur atom to the second vinythiirane, which is then transformed into the dihydrodithiin. The formation of 3,6-dihydro-1,2-dithiin (9) proceeds at 15 turnovers/h at 25°C using vinylthiirane (4) and 1 as the catalyst. The catalyst is long-lived (up to 2000 turnovers have been obtained without loss of activity) and relatively insensitive to air. Methyl substitutents on the vinyl group increase the rate of reaction while methyl substituents on the thiirane ring slow it considerably. The introduction of phosphine ligands to the catalyst also leads to significant increases in the rate of reaction. The dithiin complex W(CO)5(SSCH2CH=CHCH2) (13) was isolated from the catalytic reactions and was structurally characterized. The dihydrodithiin is coordinated to the tungsten atom through one of its two sulfur atoms. Compound 13 was shown to be a species in the catalytic cycle. A mechanism involving a vinylthiirane intermediate that undergoes spontaneous ring opening, followed by addition of a second vinylthiirane to the terminal carbon of the chain, elimination of 1 equiv of butadiene, and formation of a sulfur-sulfur bond leading to 13 is proposed. The vinylthiirane intermediate is regenerated by ligand substitution which releases the dihydrodithiin product. Compound 9 readily polymerizes when its pure form is exposed to visible light. If the polymerization is interrupted at an early stage, 1,2,7,8-tetrathiacyclododeca-4,10-diene (14), a dimer of 9, can be isolated. Compound 14 was obtained in 5.6% yield and was structurally characterized crystallographically.
- Adams, Richard D.,Perrin, Joseph L.
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p. 3984 - 3991
(2007/10/03)
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- Preparation, characterization, and properties of various novel ionic derivatives of pentacarbonyltungsten
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The complexes [Li(DIME)2][W(CO)5L] [L = OCN 2, NCS 3a, PPh2 4, SiMe2Ph 8, N(SiMe3)2 9, CH2Ph 10, Si6Me11 11; DIME = diethylene glycol dimethyl ether] have been prepared by reaction of [Li(DIME)2][W(CO)5I] (1) with KOCN, KSCN, NaPPh2, LiSiMe2Ph, LiN(SiMe3)2, PhCH2MgCl, and KSi6Me11, respectively. Photochemical ligand substitution in W(CO)6 has been used as an alternative method for the preparation of pentacarbonyl tungstates; [K(DIME)2][W(CO)5NCS] (3b), [Na(DIME)2][W(CO)5N3] (5), [Li(DIME)2][W2(CO)10(υ-H)] (6), and [K(DIME)2][W2(CO)10(υ-CN)] (7) were synthesized in this manner. The molecular structure of [Li(DIME)2][W(CO)5Si6Me11] (11) has been determined by X-ray diffraction analysis. The spectral and chemical properties of 2-11 are discussed. Pyrolysis of 11 leads to tungsten silidde and tungsten carbide.
- Palitzsch, Wolfram,Beyer, Christian,B?hme, Uwe,Rittmeister, Ben,Roewer, Gerhard
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p. 1813 - 1820
(2007/10/03)
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- Transition metal complexes of chromium, molybdenum, tungsten, and manganese containing η1(S)-2,5-dimethylthiophene, benzothiophene, and dibenzothiophene ligands
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Ultraviolet photolysis of hexanes solutions containing the complexes M(CO)6 (M = Cr, Mo, W) or CpMn(CO)3 (Cp = η5-C5H5) and excess thiophene (T*) (T* = 2,5-dimethylthiophene (2,5-Me2T), benzothiophene (BT), or dibenzothiophene (DBT)) produces the η1(S)-T* complexes (CO)5M(η1(S)-T*) 1-8 or Cp(CO)2Mn(η1(S)-T*) 9-11, respectively. However, when T* = DBT and M = Mo, a mixture of two products results, which includes (CO)5Mo(η1(S)-DBT), 4a, and the π-complex (CO)3Mo(η6-DBT), 4b, as detected by 1H NMR spectroscopy. Only the complexes (CO)5W(η1(S)-DBT) (1), (CO)5Cr(η1(S)-DBT) (5), and Cp(CO)2Mn(η1(S)-DBT) (9) were sufficiently stable (several days) to be isolated and characterized by elemental analyses. Rates of DBT ligand displacement by CO (1 atm) at room temperature decreased in the order 5 > 1 > 9. Single-crystal, X-ray structural determinations are reported for 1, 5, and 9. The tilt angle (θ) of the DBT ligand in these and related complexes is discussed in terms of π-back-bonding to the DBT ligand.
- Reynolds, Michael A.,Guzei, Ilia A.,Logsdon, Bradley C.,Thomas, Leonard M.,Jacobson, Robert A.,Angelici, Robert J.
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p. 4075 - 4081
(2008/10/08)
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- Metal ion mediated transfer and cleavage of diaminocarbene ligands
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Under mild conditions, reactions of (CO)5M=C[N(R)CH2]2 [M = W, Mo, Cr; R = Et, allyl, benzyl, 4-pentenyl] with (PhCN)2PdCl2, (PhCN)2PtCl2, [(CO)2RhCl]2, (Me2S)AuCl, [(CH3-CN)4Cu]BF4, and AgBF4 provide the corresponding diaminocarbene complexes via carbene ligand transfer. The resulting Pd(II), Pt(II), Rh(I), and Au(I) carbene complexes are stable and were isolated. The Cu(I) and Ag(I) complexes readily undergo acid-induced M=C cleavage to yield the imidazolidin-2-ylidinium salts. The carbene-transfer reactions were studied for two phosphine donors: (CO)m(L)W=C[N(R)CH2]2 {R = Et, benzyl; L = PPh3, m = 4; L = dppe, m = 3}. The X-ray crystal structures of (CO)5W=C[N(CH2C6H5)CH 2]2 (1c), cis-(CO)4-(PPh3)W=C[N(CH2C6H 5)CH2]2 (5b), fac-(CO)3(dppe)W=C[N(CH2C6H5)CH 2]2 (6b), Cl2(CO)-Pt=C[N(CH2C6H5)CH 2]2 (9c), and cis-Cl2Pt{=C[N(CH2C6H5)CH 2]2}2 (11b) are reported.
- Ku, Rong-Zhi,Huang, Jen-Chung,Cho, Jian-Yang,Kiang, Fu-Mei,Reddy, K. Rajender,Chen, Yi-Chun,Lee, Kuo-Jeng,Lee, Jung-Hua,Lee, Gene-Hsiang,Peng, Shie-Ming,Liu, Shiuh-Tzung
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p. 2145 - 2154
(2008/10/08)
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- Coordination compounds of monoborane - Lewis base adducts: Syntheses and structures of [M(CO)5(η1-BH3·L)] (M = Cr, Mo, W; L = NMe3, PMe3, PPh3)
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Photolysis of [M(CO)6] (M = Cr, W) in the presence of BH3·L (L = NMe3, PMe3, PPh3) gave isolable borane complexes [M(CO)5(η1-BH3·L)] (1a, M = Cr, L = PMe3; 1b, M = Cr, L = PPh3; 1c, M = Cr, L = NMe3; 2a, M = W, L = PMe3; 2b, M = W, L = PPh3; 2c, M = W, L = NMe3). In products 1 and 2, the monoborane - Lewis base adduct coordinates to the metal center through a B-H-M three-center two-electron bond, which was confirmed by X-ray structural analyses of 1a, 2a, and 2b at low temperature. The X-ray crystal structural analysis of 1c at ambient temperature also showed the same coordination mode, although the positions of hydrogen atoms on the boron were not determined. The 1H NMR spectra of 1 and 2 exhibit only one BH signal at -2 to -3 ppm with an intensity of 3H in the temperature range of -80 °C to room temperature. This indicates that the coordinated BH and terminal BH's are rapidly exchanging in solution even at low temperature. When [Mo(CO)6] was used as a precursor, the formation of the corresponding molybdenum - borane complexes, [Mo(CO)5(η1-BH3·L)] (3a, L = PMe3; 3b, L = PPh3; 3c, L = NMe3), was observed by NMR spectroscopy, but the complexes could not be isolated because of their thermal instability. Complexes of pyridineborane [M(CO)5(η1-BH3·NC5H 5)] (1d, M = Cr; 2d, M = W) were also observable by NMR spectroscopy. Fenske - Hall MO calculations for the model compound [Cr(CO)5(η1-BH3·PH3)] (1e) demonstrated that the bonding between the borane and metal can be described as donation of the bonding electron pair of BH to the a1 orbital of [Cr(CO)5], and that π back-donation from the metal d orbital to the antibonding σ* orbital of BH is negligible. Compounds 1-3 can be regarded as model compounds of the methane complex [M(CO)5(CH4)], which is observed in the photolyses of [M(CO)6] in methane matrixes. Structural and spectroscopic features of the ligated borane are discussed and compared with those of related compounds.
- Shimoi, Mamoru,Nagai, Shin-Ichiro,Ichikawa, Madoka,Kawano, Yasuro,Katoh, Kinji,Uruichi, Mikio,Ogino, Hiroshi
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p. 11704 - 11712
(2007/10/03)
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- Photochemical behaviour of trans-[W(CO)4(η2-alkene)2] complexes in low temperatures: IR characterization of catalytically important intermediates
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UV irradiation (313 or 367 nm) of trans-[W(CO)4(η2-alkene)2] [alkene = propene (1), 1-butene (2), cyclopentene (3)] complexes in an alkane solution at temperatures ranging from 123 to 263 K leads to two primary photoprocesses, alkene and CO loss. The loss of the alkene is accompanied by the formation of 16-electron coordinatively unsaturated species: trans- and cis-[W(CO)4(η2-alkene)(s)], A (s = solvent molecule). The CO loss leads to the formation of mer- and fac-[W(CO)3(η2-alkene)2(s)]. In the case of propene and 1-butene, the 16-electron complex A transforms into the IR detected cis-[WH(π-allyl)(CO)4], B. Under conditions of excess alkene, the 16-electron tetracarbonyl species A binds alkene and forms cis-[W(CO)4(η2-alkene)2], C, but the 16-electron tricarbonyl species transforms to fac-[W(CO)3(η2-alkene)3], D, and mer-[W(CO)3(η2-alkene)3], E. The relative amounts of the photoproducts A-E were dependent on the temperature, photolysis time, type of alkene ligand, photolysing radiation wavelength and the presence in solution of free alkene.
- Szymanska-Buzar, Teresa,Kern, Krystyna,Stufkens, Derk J.
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p. 1539 - 1544
(2008/10/08)
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- Photochemistry of (η6-arene)Mo(CO)3 and the role of alkane solvents in modifying the reactions of coordinatively unsaturated metal carbonyl fragments
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The reactions of (η6-arene)Mo(CO)2(Sol) and M(CO)5(Sol) with CO have been studied in a range of alkane solvents (Sol), and the kinetic and activation parameters have been determined (M = Cr, Mo, or W). For M = Cr the ΔH? is constant (22 ± 2 kJ mol-1), while the ΔS? term becomes less negative as the alkane chain length increases. For the larger metals the variation in kinetic and activation parameters is less significant. Solvent displacement by CO involves an interchange mechanism for the Cr system, while for Mo or W complexes the mechanism is more associative in character. The photochemistry of (η6-arene)Mo(CO)3 (arene = benzene, mesitylene, p-xylene, or hexamethylbenzene) compounds was investigated by laser flash photolysis, supported by matrix isolation and time-resolved infrared spectroscopy (TRIR). In contrast to the behavior to the analogous (η6-arene)Cr-(CO)3, it is found that the efficiency for photochemical expulsion of CO from (η6-mesitylene)-Mo(CO)3 is markedly wavelength dependent (ΦCO = 0.587, 0.120, and 0.053 at 266, 313, and 334 nm, respectively).
- Breheny, Ciara J.,Kelly, John M.,Long, Conor,O'Keeffe, Siobhan,Pryce, Mary T.,Russell, Graham,Walsh, Margaret M.
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p. 3690 - 3695
(2008/10/08)
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- Four-coordinate group-14 elements in the formal oxidation state of zero - Syntheses, structures, and dynamics of [{(CO)5Cr}2Sn(L2)] and related species
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The sodium salts Na2[{(CO)5M}2EX2] (M = Cr, Mo, W; E = Ge, Sn, Pb; X = Cl, I, OOCCH3) react with 2,2′-bipyridine (bipy) to form neutral compounds [{(CO)5M}2E(bipy)] (E = Sn: 1a-1c; E = Ge: 3a; E = Pb: 4). 1,10-Phenanthroline (phen) analogues of compounds 1a-1c and 3a [{(CO)5M}2E(phen)] (E = Sn: 1d-1f, E = Ge: 3b) are as well accessible. The 2,2′-bipyridine ligand in 1 may be formally replaced by two pyridine (py) ligands resulting in [{(CO)5M}2Sn(py)2] (1g: M = Cr, 1h: M = W). The bis-bidentate ligand 2,2′-bipyrimidine (bpmd) is found to coordinate just one [{(CO)5M}2Sn] entity in [{(CO)5M}2Sn(bpmd)] (2b: M = Cr, 2c: M = W). The biimidazolato (biim) ligand binds two [{(CO)5Cr}2Sn] moieties in [{(CO)5Cr}2Sn(biim)Sn{Cr(CO)5} 2]2-, 2a. It is shown by 1H-NMR that the pyrimidine entities in these compounds (2b, 2c) are able to rotate by a full 180° turnaround with respect to one another. This process must involve complete de-coordination of at least one of the two nitrogen donors in again at least one of the chelate cycles, the activation energy for this process being around 60 kJ/ mol. By 119Sn-NMR spectroscopy of almost all of the tin compounds described it is shown that equilibria between [{(CO)5M}2Sn(L2)] and [{(CO)5M}2Sn(L)] + L exist in all cases. From the temperature dependence of the δ values it is concluded that the activation barriers for this association/ dissociation process is below 10 kJ/mol. The structures of all new compounds are documented by X-ray analyses and all compounds are characterized by the usual analytical and spectroscopical techniques.
- Kircher, Peter,Huttner, Gottfried,Heinze, Katja,Schiemenz, Berthold,Zsolnai, Laszlo,Buechner, Michael,Driess, Alexander
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p. 703 - 720
(2007/10/03)
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- Mesoionic pyrrolium complexes and dihydropyrroles by cycloaddition of (Non-enolizable) imines to an [(1-alkynyl)carbene]tungsten complex
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Reaction of the [(1-alkynyl)carbene]tungsten complex (CO)5W=C(OEt)C≡CPh (1a) with non-enolizable imines, e.g. 9-fluorenone imines 2 [NR = N(iPr), N(c-C6H11)], affords novel mesoionic pyrrolium carbonyltungstates 3 (by [3+2] cycloaddition) together with dihydropyrroles 4 (by dichotomy of the C=N bond and subsequent insertion of the carbene carbon atom into an NC-H bond). Cross-conjugated azametallatrienes 6 and pentacarbonyltungsten complexes 7 of the dihydropyrroles 4 have been identified to be precursors to compound 4. Compounds 3b, 4a, and 6a have been characterized by X-ray crystal structure analyses.
- Aumann, Rudolf,Yu, Zhengkun,Froehlich, Roland,Zippel, Frank
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p. 1623 - 1629
(2008/10/08)
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- Matrix isolation study into the mechanism of photoinduced cyclization reactions of chromium carbenes
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The complex (CO)5Cr[C(OMe)(Me)] is known to react photochemically with N-benzyli-denemethylamine (CH3NC(Ph)H) to form a β-lactam (1,3-dimethyl-3-methoxy-4-phenyl-2-azetidinone), whereas our study shows that (CO)5W[C(OMe)(Me)] does not. Irradiation of the complexes in argon and nitrogen matrices (λ > 390 nm) resulted in a geometrical isomerization and the trapping of the syn isomers. There was no evidence from the matrix isolation experiments for the formation of a metal-ketene complex, a likely intermediate in the solution photochemistry of (CO)5Cr[C(OMe)(Me)] with respect to β-lactam formation. Three differences were observed in the matrix and solution photochemistry of (CO)5Cr-[C(OMe)(Me)] and (CO)5W[C(OMe)(Me)]. (i) (CO)5Cr[C(OMe)(Me)] undergoes CO loss upon irradiation with UV light more readily than its tungsten analogue, (ii) Upon UV irradiation of (CO)5Cr[(C(OMe)(Me)] in a nitrogen matrix bands were observed in the IR spectrum which indicated that two (CO)4(N2)Cr[C(OMe)(Me)] isomers were formed, whereas irradiation of (CO)5W[C(OMe)(Me)] under the same conditions produced only one nitrogen adduct. (iii) Irradiation of (CO)5Cr[C(OMe)(Me)] in solution and in a solid CO matrix showed that this complex underwent loss of the carbene ligand more readily than the tungsten analogue. These findings are consistent with the proposal that, upon irradiation of chromium carbenes, a ketene transient could be formed by a cleavage of the chromium-carbene σ bond and intramolecular nucleophilic attack by the carbene on a metal carbonyl. The photochemistry of the complex (CO)5Cr(OMeXbiphenyl) was studied in both argon and nitrogen matrices. This complex underwent CO loss very readily, and it is likely that this step is involved in at least one pathway of its solution photochemistry.
- Gallagher, M. Louise,Greene, J. Barry,Rooney, A. Denise
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p. 5260 - 5268
(2008/10/08)
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- Mimicking the HDS activity of promoted tungsten catalysts. A homogeneous modeling study using a two-component tungsten/rhodium system
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Reaction of W(CO)5THF with (triphos)Rh[η3-S(C6H4)CH=CH2] (1), obtained by insertion of the 16e- fragment [(triphos)RhH] into the C2-S bond of benzo[b]thiophene (BT), gives the dimer (triphos)Rh[η3-(CO)5WS(C6H 4)CH=CH2] (2; triphos = MeC(CH2PPh2)3). Unlike 1, the heterometal dimer 2 reacts with H2 (30 atm) above 70°C in THF, undergoing the desulfurization of the C-S-inserted BT. As a result, a mixture of the hydrido carbonyl species (triphos)RhH(CO), ethylbenzene, and WSx (xav = 1.5) is obtained. High-pressure NMR spectroscopy in the temperature range from 20 to 70°C shows that the desulfurization step is preceded by the formation by the dimer (triphos)RhH(μ-H)[μ-o-S(C6H4)C2H 5]W(CO)4 (5), in which the Rh and W centers are held together by bridging 2-ethylthiophenolate and hydride ligands. Complex 5 has been characterized in both the solid state (single-crystal X-ray analysis) and solution (multinuclear NMR spectroscopy). The desulfurization of 5 occurs also by thermolysis in THF at 120°C under a nitrogen atmosphere. Reaction of 5 with CO (30 atm, 40°C) gives the complex [(triphos)Rh(CO)2][(CO)5W(o-S(C6H 4)C2H5)] (8), in which the thiolate ligand is η1-S bound to the tungsten atom in the complex anion [(CO)5W-(o-S(C6H4)C2H 5)]-. The hydrogenation of 8 (30 atm of H2, > 70°C) gives exclusively free 2-ethylthiophenol. The carbonylation of 2 (30 atm of CO, room temperature) results in the formation of [(triphos)Rh(CO)2][(CO)5W(o-S(C6H 4)CH=CH2)] (3), in which the 2-vinylthiophenolate ligand is η1-S bound to the tungsten atom. The possible similarity in the C-S bond cleavage mechanism in the desulfurization of 5 to those occurring in the HDS over promoted heterogeneous catalysts is discussed.
- Bianchini, Claudio,Jiménez, M. Victoria,Meli, Andrea,Moneti, Simonetta,Patinec, Véronique,Vizza, Francesco
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p. 5696 - 5705
(2008/10/08)
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- Photochemical heterolysis of the metal-metal bond in (Me3P)(OC)4OsW(CO)5
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The photochemistry of (Me3P)(OC)4OsW(CO)5 (1), a molecule with a dative covalent metal-metal bond, was investigated. The results indicate that the photoprocess is heterolytic cleavage of the metal-metal bond, rather than homolytic cleavage as is found in compounds with nondative covalent metal-metal bonds. The principal evidence for heterolysis comes - from the irradiation (λ > 400 nm) of 1 in benzene in the presence of PPh3. The major products were Os(CO)4(PMe3), Os(CO)3(PMe3)(PPh3), and W(CO)5(PPh3). These products are consistent with a pathway that involves initial heterolysis to form Os(CO)4(PMe3) and W(CO)5 followed by trapping of the coordinatively unsaturated W(CO)5 species with PPh3. (Control experiments showed that Os(CO)3(PMe3)(PPh3) forms from Os(CO)4(PMe3) and PPh3 under the reaction conditions.) Primary photoprocesses involving either M-CO bond dissociation or Os-W bond homolysis are incompatible with the results of other experiments. For example, when the irradiation of 1 was carried out under CO, the quantum yield for disappearance of 1 increased to 0.28 ± 0.05 from its value of 0.13 ± 0.01 under N2, a result inconsistent with M-CO dissociation as the primary photoprocess. Likewise, control experiments showed that [W(CO)5.1] was readily trapped under the reaction conditions, but all attempts to trap [W(CO)5.1] (one of the expected homolytic primary photoproducts) with the metal-radical traps benzyl chloride, CCl4, or TMIO (1,1,3,3-tetramethylisoindoline-2-oxyl) during the photolysis of 1 were fruitless. Compound 1 reacted photochemically with CCl4 to form fac-Os(CO)3(PMe3)Cl2 (fac-2) and W(CO)6. The fac-Os(CO)3(PMe3)Cl2 product is likely formed by a secondary photolysis of Os(CO)4(PMe3). Control experiments showed that irradiation of Os(CO)4(PMe3) in CCl4 initially formed a compound believed to be Os(CO)3(PMe3)(CCl3)-Cl, which in the presence of W(CO)5 then reacted to form fac-Os(CO)3(PMe3)Cl2. Small amounts of W(CO)6 (8percent) were also produced in the photochemical reaction of 1 with PPh3. An experiment in a more viscous solvent system indicated that W(CO)6 is not formed in a CO abstraction reaction involving the [(Me3P)(OC)4Os, W(CO)5] solvent cage pair. The formation of W(CO)6 is attributed to a second (minor) heterolytic pathway involving an intermediate with a bridging CO that directly yields W(CO)6 and Os(CO)3(PMe3).
- Male, Jonathan L.,Pomeroy, Roland K.,Tyler, David R.
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p. 3431 - 3438
(2008/10/08)
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- Cyclodimerization of the tropylium ring by reduction of [(η7-C7H7)Mo(CO)3]+ to give [{Mo(CO)3}2(μ-η5:η 5-C7H7-C7H7
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Reductive activation of the tropylium ring in [(η7-C7H7)M(CO)3]BF4 (M = Cr, Mo, W) leads to cyclodimerization and formation of [{M(CO)3}2(μ-η5:η5-C 7/
- Brown, David A.,Burns, John C.,Mock-Knoblauch, Cordula,Glass, William K.
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p. 139 - 141
(2008/10/08)
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- Photo-reversible isomerisation of trans- to cis-[W(CO)4(η2-alkene)2] complexes in low-temperature matrices
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Reversible isomerisation of trans- to cis-[W(CO)4(η2-alkene)2] complexes has been induced in argon matrices at low temperatures under the action of selective irradiation. UV photolysis (λ ≈ 313nm) of trans-[W(CO)4(η2-alkene)2] (alkene = cyclopentene or 1-pentene) in an argon matrix at 16 K results in formation of the cis isomer as the primary photoprocess. The isomerisation is reversed under the action of visible light (λ ≈ 445nm). Species such as [W(CO)4(alkene)(Ar)] are also formed in small concentrations. Experiments involving annealing, selective photolysis and the use of CO- or alkene-doped matrices have been performed to investigate the mechanism of the photo-isomerisation process. These studies suggest a dissociative mechanism via expulsion of the alkene ligand.
- Szymanska-Buzar,Jaroszewski,Downs,Greene,Morris
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p. 207 - 216
(2007/10/03)
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- Heterobimetallic complexes with a propynylidene C3-bridge: General synthetic routes to bimetallic ethynylcarbene complexes
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Sequential reaction of the dimethylamino(trimethylsilylethynyljcarbene complexes [(CO)5M'=C(NMe2)CsCSiMe3] [M' = W (1a), M' = Cr (lb)] with KF/THF/MeOH, nBuLi and transition metal halides, [XMLn], affords heterobimetallic propynylidene complexes of the type [(CO)SM'=C(N-Me2)C=CMLn] [MLn= Ni(PPh3)Cp (4a, b), Ni(PMe2Ph)2-(Mes) (Mes = 2, 4, 6-C6H2Me3) (5a), Rh(CO)(PPh3)2 (6a), Fe(CO)2Cp (7a, b)]. In contrast, reaction of la with MeLi LiBr and [IFe(CO)2Cp] yields the novel N-metallated complex [(CO)2cP=C{N(Me)Fe(CO)2Cp)C=CSiMe3] (8a). The complexes [(CO)5M'=C(NMe2)C=CMLn] [MLn = Fe(CO)2Cp (7a, b), Ru(CO)2Cp (10a, b), Ru(CO)(PPh3)Cp (11a), Mn(CO)5 (12a), Re(CO)5 (13a)] are accessible by Pd-catalyzed coupling of the C-stannylated carbene complexes [(CO)SM'=C-(NMe2)C=CSnBu3] (9a, b) with [XMLn1. The related monomethylaminocarbene complexes [(CO)5M'=C(NHMe)C= CSnBu3] (16a, b), obtained by stannylation of [(CO)5M'=C(NHMe)C=CH] (15a, b) with Bu3SnNEt2, react with [IFe(CO)2Cp] to give the bimetallic complexes [(CO)5M'=C(NHMe)OCFe(CO)2Cp] (17a, b). The complexes 4a, 5a, 7a and 10a were characterized by X-ray structural analyses. The spectroscopic and structural data suggest that the two metal centers in 4-7, 10-13 and 17 interact only weakly. VCH Verlagsgesellschaft mbH.
- Hartbaum, Cornelia,Roth, Gerhard,Fischer, Helmut
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p. 479 - 488
(2007/10/03)
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- The catalytic ring-opening cyclooligoraerization (ROC) of by the complexes M(CO)5L (M = Cr and W; L = CO, and 1,5,9-trithiacyclododecane)
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The following four compounds have been synthesized: M(CO)5L (3 and 4, where M= Cr and W, and L = SCH2CH2CH2), W(CO)5(12S3) (5, where 12S3 = 1,5,9-trithiacyclododecane), and [W(CO)5]2(12S3) (6). The molecular structures of 4 and 5 were established by single-crystal X-ray diffraction analyses. Both compounds contain a W(CO)5 group coordinated to one of the sulfur atoms of the heterocycle. The ability of the compounds M(CO)6, 1 and 2 (M= Cr and W), and 3-5 to catalytically produce ring opening cyclooligomerization JROC) of thietane into 12S3 and 24S6, (2486= 1,5,9,13,17,21-hexathiacyclotetracosane) has been investigated. Compounds 1-3 have relatively low activity. Compounds 4 and 5 have the highest activity and selectivity for 12S3 formation. Crystal Data for 4: space group = P212121, a = 12.906(2) A, b = 13.730(4) A, c = 6.427(1) A, Z = 4, 1306 reflections, R - 0.033; for 5: space group = P1, a = 12.703(1) A, b = 13.510(2) A, c = 5.833(1) A, α = 101.75(1)°, β = 97.54(1)°, γ = 101.70(1)°, Z = 2, 2225 reflections, R = 0.023. VCH Verlagsgesellschaft mbH. 1996.
- Adams, Richard D.,Falloon, Stephen B.,Perrin, Joseph L.,Qoeisser, Joachim A.,Yamamoto, John H.
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p. 313 - 318
(2007/10/02)
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- Complexes with metal-phosphorus triple bonds as possible intermediates in the reactions between chlorophosphinidenes and metalates of various transition metals
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The reaction of [{M′(CO)5}2PCl] (M′ = Cr, W) with various metalates ([Cp′'Mo(CO)3r, [Cp*Ni(CO)]-, [Cr2(CO)10]2-) yields the M2P2 tetrahedral complexes [(MLn)2(,rpP2){M′(CO)5} 2] (MLn= Cp'Ni, M'= Cr (1), W (2); MLn = Cp′Mo(CO)2, M′ = Cr (4); Cp" = r5-C5Mes, Cp′ = ifC5H3tBu2) and the cydo-P4 compound [{Cr(CO)4(TfP4S]Cr(CO)3)4] 6. As side products the distorted prismane [(Cp*Ni;2μ4,]4-(P2-O-P 2)H(CO)5}2] 3 and the diphosphinomethanone complex [{Cp′Mo{CO)22]2{μ 4,η2 [Cr(CO)5}2] 5 are formed. The complexes are characterised by NMR, IR, MS, and X-ray structure analysis (1-5). Studying the reaction pathway provided evidence of phosphide intermediates of the type [LnM=P→M′Ln]. VCH Verlagsgeselischaft mbH, 1996.
- Scheer, Manfred,Schuster, Kay,Krug, Andre,Hartung, Helmut
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p. 973 - 979
(2007/10/03)
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- Synthesis of 5,5'-Diphenyl-2,2'-bifuran, a Biaryl Compound with Remarkable Fluorescence Properties
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The 2-oxacyclic α,β-unsaturated carbene complex 1 reacts with an excess of dimethylamine to give the diphenylbifuran 2.The structure of 2 was established by independent synthesis from 2-phenylfuran (4) via regioselective lithiation and transmetalation to zinc and tin organometallics 6a-c and final oxidative copper coupling reactions. - Key Words: Carbene ligands/ Tungsten complexes/ 2,2'-Bifuran/ Copper coupling reaction
- Christoffers, Jens,Doetz, Karl Heinz
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p. 641 - 644
(2007/10/02)
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- Preparation of α-Diazines and α-2-Pyridylazines containing (1R)-(+)-Camphor or (1R)-(-)-Fenchone Residues and their Complexes with Group 6 Metal Carbonyls
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New 2,3,6,7-tetraaza-1,3,5,7-octatetraene (α-diazine) derivatives camph=N-N=CH-CH=N-N=camph I, where camph is a (1R)-(+)-camphor residue, C10H16, and fench=N-N=CH-CH=N-N=fench II, where fench is a 1R-(-)-fenchone residue, C10H16, have been obtained together with the 2'-pyridyl derivatives camph=N-N=CHC5H4N III and fench=N-N=CHC5H4N IV.The configurations around the four C=N bonds of I or II are E,E,E,E whilst those around the two azine C=N bonds in III and IV are E,E.Complexes of the types (M = Cr, Mo or W; L = I-IV), (L = I, L' = NCMe, PPh3 or AsPh3; L = II-IV, L' = PPh3), (L = III or IV) and 3-CH2CH=CH2)L> (L = I, III or IV) containing these azines as ligands have also been obtained.Complexes of II are the most unstable and these together with tetracarbonyl complexes of IV appear to show restricted rotation around the N-N bond(s) caused by the steric requirements of the methyl groups on the fenchone residue(s).All the complexes have been characterised by multinuclear NMR (1H, 13C and 31P), IR and UV/VIS spectroscopies and mass spectrometry.The crystal structures of camph=N-N=CH-CH=N-N=camph I and fench=N-N=CHC5H4N IV have been determined.
- Shaw, Bernard L.,Thornton-Pett, Mark,Vessey, Jonathan D.
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p. 3597 - 3606
(2007/10/02)
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- Water-soluble organometallic compounds. 3. Kinetic investigations of dissociative phosphine substitution processes involving water-soluble group 6 metal derivatives in miscible aqueous/organic media
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Mechanistic aspects of ligand substitution reactions of group 6 metal carbonyl derivatives containing the trisulfonated phosphine P(m-C6H4SO3Na)3 (hereafter referred to as TPPTS) in pure water and water/THF media have been investigated by examination of the reactions of these derivatives with carbon monoxide as an incoming ligand. The reactions, which were carried out under 500 psi of CO in the temperature range 110-160°C, were monitored in situ by infrared spectroscopy employing a cylindrical internal reflectance reactor. Kinetic measurements show the reactions are first-order in metal complex concentration and independent of CO pressure at high CO pressures, and the rates are retarded by added TPPTS. The activation parameters for TPPTS dissociation from M(CO)5TPPTS derivatives (M = Mo, W), e.g., in 1:1 THF/H2O, ΔH? = 28.8 ± 1.4 kcal/mol and ΔS? = -4.2 ± 3.5 eu and ΔH? = 31.8 ± 1.5 kcal/mol and ΔS? = -0.73 ± 3.6 eu, respectively were shown to be quite similar to those determined for the analogous processes involving the nonsulfonated PPh3 ligand in the same solvent systems. In addition only small solvent effects were noted in going from aqueous to organic solvents for these dissociative processes. For the cis-Mo(CO)4[TPPTS]2 derivative, in which the sodium ions are encapsulated by a cryptand, kryptofix-221, a steric acceleration of TPPTS dissociation is noted relative to its PPh3 analog. The steric requirements of the TPPTS ligand were defined by X-ray structural data obtained on [Na-kryptofix-221]3[W(CO)5P(C6H 4SO3)3] and Fe(CO)4TPPTS. By way of contrast for the cis-Mo(CO)4[TPPTS]2 derivative in which the Na+ ions are free to interact with the sulfonate groups, a stabilizing effect is noted which is attributed to intramolecular interligand interactions via the Na+ cations. In the case of cis-W(CO)4[TPPTS]2 and cis-W(CO)4[PPh3]2 an intramolecular rearrangement to the corresponding trans product was observed.
- Darensbourg, Donald J.,Bischoff, Christopher J.
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- Time-resolved IR study of the photobehavior of W(CO)5(4-acpy) (4-acpy = 4-acetylpyridine)
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Fast time-resolved infrared spectroscopy (TRIR) is used to probe the photochemistry of W(CO)5(4-acetylpyridine) in n-heptane. Visible irradiation (510 nm) populates the lowest MLCT state, which is monitored by TRIR. Subsequent dissociation to W(CO)5?n-heptane, via equilibrium with the 3LF state, is also followed. On UV irradiation (308 nm), the LF state is populated directly and W(CO)5?n-heptane appears immediately. With 510-nm irradiation, the yield of W(CO)5?n-heptane as a function of temperature is measured to give a value for the energy gap between the lowest MLCT state and the 3LF state, ～4000 cm-1.
- Johnson, Frank P. A.,George, Michael W.,Turner, James J.
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p. 4226 - 4229
(2008/10/08)
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- The catalytic decarboxylation of cyanoacetic acid: Anionic tungsten carboxylates as homogeneous catalysts
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Cyanoacetic acid was observed to catalytically decompose to its component parts, CO2 and CH3CN, in the presence of soluble tungsten(0) carboxylates. In the case in which W(CO)5O2CCH2CN- was used as the catalyst, the reaction was inhibited by the substrate via an equilibrium process in which the free acid displaced the carboxylate ligand and bound to the metal through the nitrogen atom. The equilibrium constant for this process was measured and determined to be 0.413 at 50°C, where kf = 6.11 × 10-3 M-1 s-1 and kr = 1.48 × 10-2 M-1 s-1. Activation parameters for the decarboxylation process were determined and yielded ΔH* = 21.0 ± 0.7 kcal·mol-1 and ΔS* = -3.4 ± 1.9 eu. The rate limiting step is proposed to be loss of cis CO from the metal with concomitant formation of cis-W(CO)4(O2CCH2CN)(NCCH2COOH) -, since the free energy of activation is quite similar to that for cis carbonyl loss, 23.0 ± 0.9 kcal·mol-1. Subsequent proton transfer and CO2 loss are fast relative to cis CO displacement. The carboxylate ligand acts as an intramolecular Lewis base, mediating the proton-transfer steps. This was demonstrated by the use of W(CO)PPh2(CH2)nX- (n = 1 or 2, X = base) as catalysts for the same decarboxylation. Detailed kinetic studies and a proposed mechanism are presented.
- Darensbourg, Donald J.,Chojnacki, Jennifer A.,Atnip, Earl V.
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p. 4675 - 4682
(2007/10/02)
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- Time-Resolved IR Study of Gas-Phase Reaction of Benzene with Group VIB Metal Pentacarbonyls and Tetracarbonyls
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The gas-phase reactions of benzene and deuterated benzene (benzene-d6) with group VIB metal pentacarbonyls M(CO)5 (M=Cr and W) and tetracarbonyl W(CO)4 were probed with time-resolved infrared spectroscopy.Benzene reacts with M(CO)5 forming presumably (η2-benzene)M(CO)5 in which benzene coordinates to the metal via an isolated double bond.The rate constants for reactions of C6H6 and C6D6 with Cr(CO)5 were found to be (3.0 +/- 0.7) and (3.3 +/- 0.2) x 1013 cm3 mol-1 s-1, respectively.The corresponding values with W(CO)5 are (2.8 +/- 0.4) and (3.5 +/- 0.6) x 1013 cm3 mol-1 s-1.From the temperature dependence of the rate of dissociative loss of benzene from (η2-benzene)Cr(CO)5, a bond dissociation energy of 9.2 +/- 0.8 kcal mol-1 was determined for (η2-benzene)Cr(CO)5.The lower limit for bond dissociation energy for loss of the benzene ligand from (η2-benzene)W(CO)5 was estimated to be 11.7 kcal mol-1.Benzene reacts with W(CO)4 producing a species, presumably (η2-benzene)W(CO)4, which is stable in the milisecond time scale.The rate constants for reactions of C6H6 and C6D6 with W(CO)4 were determined to be (3.5 +/- 0.2) and (4.1 +/- 0.4) x 1013 cm3 mol-1 s-1, respectively.Secondary addition of CO to (η2-benzene)W(CO)4 forms (η2-benzene)W(CO)5, and the rate constants are (9.4 +/- 0.9) and (8.7 +/- 1.0) x 1011 cm3 mol-1 s-1, respectively, for additions of CO to (η2-C6H6)W(CO)4 and (η2-C6D6)W(CO)4.
- Wang, Wenhua,Zheng, Youfeng,Lin, Jingu,She, Yongbo,Fu, Ke-Jian
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p. 11921 - 11928
(2007/10/02)
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- Carbon-carbon coupling of a μ-ethynyl ligand with an isocyanide at a ditungsten center. Preparation and structure of W2(μ-CCCNHXyl)(OSiMe2BUt) 5(CNXyl)4, where Xyl = 2,6-Me2C6H3
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The ethynyl-bridged complex W2(μ-CCH)-(OSiMe2But)5 reacts in hydrocarbon solvents with xylyl isocyanide, 2,6-Me2C6H3NC, to give W2(μ-CCCNHXyl)-(OSiMe2But) 5(CNXyl)4 which has been characterized by NMR spectroscopy and a single-crystal X-ray study. The bridging μ-CCCNHXyl ligand may be viewed as an η2-aminoalkyne to one tungsten and an alkylidyne to the other. One tungsten is in a pseudooctahedral environment being coordinated to four isocyanide ligands, one siloxide, and an η2-alkyne moiety while the other is a five-coordinate pseudo-square-based pyramid having four siloxides in the basal plane and the alkylidyne carbon at the apical site. Crystal data for W2(μ-CCCNHXyl)-(OSiMe2But) 5(CNXyl)4·1/2(toluene) at -158°C: a = 21.354(7) A?, b = 17. 095(6) A?, c = 24.288(9) A?, β = 100.18-(2)°, dcalcd = 1.347 g cm-3, Z = 4, and space group P21/n.
- Chisholm, Malcolm H.,Cook, Cindy M.,Huffman, John C.,Martin, James D.
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p. 2354 - 2359
(2008/10/08)
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- Structural and reactivity studies of a cyanoacetic acid derivative of tungsten pentacarbonyl. X-ray structure of W(CO)5NCCH2COOH
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The new cyanoacetic acid complex W(CO)5NCCH2COOH (1) has been synthesized from the reaction of W(CO)5THF and NCCH2COOH. The molecular structure of 1 has been determined by X-ray diffraction methods. The compound crystallizes in the triclinic space group P1 with two molecules in a cell of dimensions a = 6.7390 (10) ?, b = 9.745 (2) ?, c = 10.241 (2) ?, α = 63.57 (2)°, β = 81.71 (2)°, γ = 76.22 (2)°. Full-matrix least-squares refinement gives final R and Rw on F of 0.026 and 0.037 for 2030 observed [F > 4σ(F)] data. The structure confirms the presence of the nitrile ligand located 2.178 (7) ? from the tungsten center, with the carboxyl groups of two molecules coupled by strong intermolecular hydrogen-bonding (O-H?O = 2.627 (3) ?). This hydrogen-bonding structure was observed as well in solution as indicated by infrared spectroscopy. The displacement of the cyanoacetic acid ligand in 1 by carbon monoxide was shown to proceed via a solvent-assisted Id process in tetrahydrofuran and by a D process in the less-interacting solvent methylene chloride. The activation parameters for these processes are consistent with the proposed mechanism, with ΔH? and ΔS? for the displacement of the NCCH2COOH ligand determined to be 19.4 kcal/mol and -14.7 eu in THF and 29.2 kcal/mol and 11.8 eu in CH2Cl2, respectively. Comparable kinetic data were observed for the tungsten complexes containing the electronically similar ligands NC(CH2)10COOH and CH3CN. The relevance of this study to the catalytic decarboxylation reaction of cyanoacetic acid in the presence of W(CO)5O2CCH2CN- is discussed.
- Darensbourg, Donald J.,Atnip, Earl V.,Reibenspies, Joseph H.
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p. 4475 - 4480
(2008/10/08)
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- Rare gas-metal carbonyl complexes: Bonding of rare gas atoms to the group VI pentacarbonyls
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Transient infrared spectroscopy has been used to study reactions of M(CO)5 generated by 355-nm photolysis of M(CO)6 where M = Cr, Mo, and W. At 298 K, M(CO)5 reacts with CO with bimolecular rate constants of (1.4 ± 0.2) × 10-10, (1.5 ± 0.1) × 10-10, and (1.4 ± 0.1) × 10-10 cm3 molecule-1 s-1 for Cr, Mo, and W, respectively. M(CO)5 also reacts with Xe with bimolecular rate constants of (0.9 ± 0.4) × 10-10, (0.9 ± 0.4) × 10-10, and (2.6 ± 0.2) × 10-10 cm3 molecule-1 s-1 for Cr, Mo, and W, respectively. Infrared absorptions attributed to M(CO)5Xe and W(CO)5Kr were observed. The rate of dissociative loss of the Xe atom from the M(CO)5Xe complexes was determined by the observation of the rate of regeneration of M(CO)6 in a reaction mixture consisting of M(CO)5, CO, and Xe. The bond dissociation energy for the loss of the Xe atom from M(CO)5Xe for all three metals is the same within experimental error and has an average value of 8.5 kcal/mol. A bond dissociation energy was estimated for the loss of Kr from W(CO)5Kr, and an upper limit can be estimated for the bond dissociation energy for loss of Ar from W(CO)5Ar.
- Wells,Weitz, Eric
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p. 2783 - 2787
(2007/10/02)
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- Organic Syntheses via Transition Metal Complexes, 60. - Novel Type of Benzoannelation with Carbene Complexes and Alkynes. - 2-Oxybenzoannelation of Cycloheptatriene via (Cycloheptatrienylmethyl)carbene Complexes of Chromium and Tungsten
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We report on a three-step procedure for the regiospecific 2-oxybenzoannelation to cycloheptatriene by means of Fischer carbene complexes and alkynes.The first step involves the formation of (cycloheptatrienylmethyl)carbene complexes LnM=C(OEt)-CH2-c-C7H7 nM = Cr(CO)5 (a), W(CO)5 (b)> from the corresponding methylcarbene complexes and a tropylium salt. 1 reacts with the alkyne Et2N-CC-Me (2) to give the (E)- and (Z)-1-amino(1-alkenyl)carbene comlexes LnM=C(NEt2)-C(Me)=C(OEt)-CH2-c-C7J7 (3 and 4 resp.).Thermolysis of 3b n = W(CO)5, 100 deg C, 5 h> finally leads to elimination of W(CO)5(Et2NH) (6b) and the regiospecific formation of ethoxybenzocycloheptatrienes 5, 7, and 8 in 92percent total yield.The reaction is kinetically controlled and yields an isomeric ratio of 5:7:8 = 60:12:20percent with the thermodynamically less stable isomer 5 predominating. Key Words: Carbene complexes, cycloaddition reactions of / Carbene complexes, reactions with alkynes / Benzocycloheptatrienes / 2-Oxybenzannelation / (Cycloheptatrienylmethyl)carbene complexes of chromium and tungsten
- Aumann, Rudolf
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p. 1861 - 1864
(2007/10/02)
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- Metal carbonyl complexes with xenon and krypton: IR spectra, CO substitution kinetics, and bond energies
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IR spectra for complexes between Xe and Kr and M(CO)5 (M = Cr, W) have been obtained using laser photolysis of M(CO)6 and rapid-scan FTIR spectroscopy of liquid rare-gas solutions. The Kr complexes have lifetimes of ～0.1 s at 150 K in liquid Kr while W(CO)5Xe has a lifetime of ～1.5 min at 170.0 K in liquid Xe. W(CO)5Xe reacts with CO to form W(CO)6 and the CO substitution kinetics were investigated in liquid Xe over a range of temperatures (173.0-198.0 K) and CO concentrations. The kinetics are consistent with a dissociative substitution mechanism in which W(CO)5Xe is in equilibrium with W(CO)5. From the temperature dependence of the equilibrium constant, the Xe-W bond energy in W(CO)5Xe is obtained, ΔH = 8.4 ± 0.2 kcal/mol in good agreement with a recent gas-phase value.
- Weiller, Bruce H.
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p. 10910 - 10915
(2007/10/02)
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