Ethylidyne Groups Research Articles

Titanium–Alkaline Earth Molecular Oxides as Supports for Carbanions Derived from μ3‐Ethylidyne Groups (Eur. J. Inorg. Chem. 11/2006)

AbstractThe cover picture shows how the treatment of the oxide molecular model [{TiCp*(μ‐O)}3(μ3‐CMe)] (Cp* = η5‐C5Me5) with alkaline earth metal amide and alkyl compounds produces the deprotonation of the μ3‐ethylidyne fragment to give μ3‐CCH2−, μ3‐CHCH− or μ3‐CCH2− carbanions. Simultaneously, the alkaline earth cation is incorporated through the oxygen atoms to build new cage structures. Details of this chemistry are described by M. Mena et al. on p. 2137 ff.

Titanium–Alkaline Earth Molecular Oxides as Supports for Carbanions Derived from μ3‐Ethylidyne Groups

AbstractTreatment of the μ3‐ethylidyne complex [{TiCp*(μ‐O)}3(μ3‐CMe)] (1) (Cp* = η5‐C5Me5) with the alkaline earth amides [M{N(SiMe3)2}2(thf)2] (M = Mg, Ca, Sr) promotes the deprotonation of the alkylidyne moiety μ3‐CMe and leads to the oxoheterometallocubane derivatives [{(thf)x(Me3Si)2NM}(μ3‐O)3{Ti3Cp*3(μ3‐CCH2)}] [M = Mg, x = 0 (2a); Ca, x = 1 (3); Sr, x = 1 (4)]. In the case of the magnesium amide, complex 2a is obtained together with the isomer [{(Me3Si)2NMg}(μ3‐O)3{Ti3Cp*3(μ3‐η2‐CHCH)}] (2b). The addition of pentamethylcyclopentadiene (C5Me5H) or triphenylmethanol (Ph3COH) to these compounds causes the displacement of the amide fragment to give the heterometallocubanes [RM(μ3‐O)3{Ti3Cp*3(μ3‐C2H2)}] [R = C5Me5, M = Ca (5), Sr (6); R = Ph3CO, M = Mg (7a,b), Ca (8), Sr (9)]. This substitution can also be performed on 3 and 4 by treatment with the starting complex 1, which gives the corner‐shared doublecubanes [M{(μ3‐O)3(Ti3Cp*3)(μ3‐CCH2)}2] [M = Ca (11), Sr (12)]. Complexes 2a,b do not react with 1, and heating of this mixture affords the edge‐linked double cubane [Mg(μ4‐O)(μ3‐O)2{Ti3Cp*3(μ3‐CCH)}]2 (10). The combination of the barium reagents [Ba(CH2Ph)2] or [Ba{N(SiMe3)2}2] with 1 leads to the corner‐shared double cubane [Ba{(μ3‐O)3(Ti3Cp*3)(μ3CCH2)}2] (13). The molecular structures of 3 and 10 have been established by single‐crystal X‐ray analysis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

An infrared spectroscopic study of CC bond-breaking during the thermal decomposition of the chemisorbed species from ethane on a Pt/SiO 2 catalyst

Although many studies have been made on the infrared spectra of unsaturated hydrocarbons (alkenes, alkynes, and benzenes) and of cycloparaffins chemisorbed on metal surfaces, very few such studies have been made on adsorbed alkanes. In the pioneering era of such research, Eischens and Pliskin reported qualitatively that ethane adsorbed on Ni/SiO{sub 2} catalysts gave spectra similar to those from adsorbed ethylene on the hydrogen-free Ni surface, but very weak ones on the hydrogen-covered surfaces. Lee et al. have shown that methane molecules incident with high Kinetic energy chemisorb on Ni(111) to give surface methyl groups below 150 K. McDougall showed that ethane was chemisorbed at room temperature on a finely divided silica-supported platinum catalyst (EUROPT-1) and gave rise to a spectrum characteristic of surface ethylidyne groups CH{sub 3}CPt{sub 3}. Such surface species have previously been identified from the adsorption of ethene (ethylene) on various oxide-supported Pt catalysts and on Pt(111) and Pt(100) (5 x 20) single-crystal surfaces. In the present paper the authors report the effects of heating to 573 K from room temperature (294 K) on the surface species, including ethylidyne, derived from ethane chemisorbed on an impregnated finely divided Pt/SiO{sub 2} catalyst. Direct evidence is found for C-Cmore » bond-breaking processes.« less

Reactions of the alkylidyne tungsten complexes [W(CR)(CO)2(η-C5H5)] (R = Me or C6H4Me-4) with the dirhodium compound [Rh2(μ-SPh)2(cod)2]; crystal structure of [W2Rh2(μ-CMe)(μ3-CMe)(μ-SPh)2(CO)4(η-C5H5)2

In THF (tetrahydrofuran) the alkylidynetungsten complexes [W(CR)(CO)2(η-C5H5)] (R = Me or C6H4Me-4) react with [Rh2(μ-SPh)2(cod)2] (cod = cyclo-octa-1,5-diene) to give, respectively, the tetranuclear mixed-metal compound [W2Rh2(μ-CMe)(μ3-CMe)(μ-SPh)2(CO)4(η-C5H5)2] and the trinuclear metal species [WRh2(μ-CC6H4Me-4)(μ-SPh)2(CO)3(cod)(η-C5H5)]. The molecular structure of the former has been established by X-ray diffraction. The metal atom core is based on a 'butterfly' arrangement with the two rhodium atoms forming the body of the butterfly (RhRh 2.588(1) Å) and the tungsten atoms occupying the 'wing-tip' positions (WRh mean 2.817 Å). The two WRh2 triangles forming the wings of the butterfly are inclined at 20° to one another. In one triangle the WRh bonds are bridged, respectively, by a μ-CMe group (μ-CW 1.88(1), μ-CRh 2.08(1) Å) and by two μ-SPh ligands (mean μ-SW 2.403, mean μ-SRh 2.416 Å), and the tungsten atom carries a C5H5 ring. The other WRh2 triangle is triply bridged by an ethylidyne group (μ3-CW 2.02(1), mean μ3-CRh 2.09 Å), and one of the WRh bonds is semi-bridged by a CO ligand (WCO 168(1)°, WCO 1.97(1), Rh ··· CO 2.42(1) Å). The tungsten atom is also ligated by a C5H5 ring and another CO group (WCO 171(1)°). Each rhodium atom carries an essentially terminally bound CO ligand. The NMR data (1H and 13C{1H}) for the new compounds are reported and discussed.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 106. Synthesis and reactions of the alkylidyne complexes [M(CR)(CO)2{(C6F5)AuC(pz)3}](M = WorMo, R = alkyloraryl, pz = pyrazol-1-yl); crystal structure of [WPtAU(C6F5)(µ3-CMe)(CO)2(PMe2Ph)2{(C6F5)AuC(pz)3}

Treatment of the salts [M (CR)(CO)2{HC(pz)3}][BF4][M = W or Mo, R = alkyl or aryl, HC(pz)3= tris(pyrazol-1 -yl)methane] in thf (tetrahydrofuran) with NaOEt, followed by [Au(C6F5)(tht)](tht = tetrahydrothiophene), affords the neutral alkylidynemetal compounds [M(CR)(CO)2{(C6F5)AuC(pz)3}](M = W or Mo, R = C6H4Me-4; M = W, R = Me or C6H3Me2-2,6). The complexes (M = W, R = Me or C6H4Me-4) have been used to prepare several compounds containing heteronuclear metal–metal bonds, including [WAuX(µ-CMe)(CO)2{(C6F5)AuC(pz)3}](X = Cl or C6F5), [WCo2(µ3-CR)(CO)8{(C6F5)AuC(pz)3}], [WPt(µ-CR)(CO)2(PMe2Ph)2{(C6F5)AuC(pz)3}], and [W2Pt(µ-CR)2(CO)4{(C6F5)AuC(pz)3}2]. The cluster compound [WPtAu(C6F5)(µ3-CMe)(CO)2(PMe2Ph)2{(C6F5)AuC(pz)3}] has been synthesised by different routes, and its structure established by X-ray diffraction. The core of the molecule consists of a WPtAu triangle [W–Pt 2.798(2), W–Au 2.841(2), and Pt–Au 2.932(2)A] asymmetrically capped by an ethylidyne group [µ-C–W 2.06(3), µ-C–Pt 2.05(3), and µ-C–Au 2.31 (3)A]. The latter lies appreciably further from the Au atom than from the W or Pt atoms. The two carbonyl ligands semi-bridge the W–Pt [W–C–O 160(2)°] and W–Au [W–C–O 165(3)°] bonds. The Pt atom carries the PMe2Ph groups [P–Pt 2.26(1) and 2.32(1)A], and the Au atom is co-ordinated by the C6F5 group [C–Au 2.04(3)A]. The W atom is ligated by the three nitrogens of the (C6F5)AuC(pz)3 moiety (N–W average 2.21 A). The n.m.r. data (1H, 13C-{1H}, 31P-{1H}, and 19F-{1H}) for the new compounds are reported and discussed where appropriate.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 89. Tetra- and penta-nuclear tungsten–rhodium complexes: crystal structures of [W3Rh2(µ-CO)2(µ-CMe){µ-C(Me)C(O)}(µ-PPh2)2(µ3-CMe)(CO)2(η-C5H5)3] and [W3Rh2(µ-CO)3(µ-CMe){µ-C(Me)PPh2}(µ3-CMe)-(CO)2(ηC5H5)3

Treatment of [Rh2(µ-PPh2)2(cod)2](cod = cyclo-octa-1,5-diene) in thf (tetrahydrofuran) at room temperature with 2 equivalents of [W(CMe)(CO)2(η-C5H5)] rapidly affords the tetranuclear metal complex [W2Rh2(µ-CMe)2(µ-PPh2)2(CO)4(η-C5H5)2](4). If the same reaction is carried out using an excess of the ethylidynetungsten complex two metal cluster compounds are obtained: [W2Rh2(µ-CO){µ-C(Me)C(O)}(µ-PPh2)2(µ3-CMe)(CO)2(η-C5H5)2](5)(formed as a separable mixture of two diastereoisomers) and [W3Rh2(µ-CO)2(µ-CMe){µ-C(Me) C(O)}(µ-PPh2)2(µ3-CMe)(CO)2(η-C5H5)3](6). The structure of the latter was established by X-ray diffraction. The molecule has an essentially planar W(1), Rh(1), W(2), Rh(2), W(3) framework. Carbonyl groups bridge the Rh(1)–W(1) and Rh(2)–W(2) bonds, and PPh2 ligands span the Rh(1)–W(2) and Rh(2)–W(3) linkages. Ethylidyne groups edge-bridge the Rh(1)–W(1) bond and triply bridge the atoms Rh(1)W(2)Rh(2), but the Rh(1)⋯ Rh(2) separation [3.115(4)A] is non-bonding. The Rh(2)–W(3) bond is bridged by a C(Me)C(O) ketenyl group, and the terminal W atoms in the chain each carry a CO ligand and a C5H5 ring. A third C5H5 group ligates W(2). The metal–metal distances fall into two groups [Rh(1)–W(2) 2.791(6), Rh(2)– W(3) 2.813(4); and Rh(1)–W(1) 2.696(5), Rh(2)–W(2) 2.664(5)A], with the shorter separations corresponding to double bonds and the longer to single bonds. Compound (6) is produced by addition of a molecule of [W(CMe)(CO)2(η-C5H5)] to (5), while the latter is formed by isomerisation of (4), a process necessitating migration of µ-CMe and µ-PPh2 between the metal centres. After several hours solutions of (6) in thf afford quantitatively the complex [W3Rh2(µ-CO)3(µ-C(Me){µ-C(Me)PPh2}(µ-PPh2)(µ-CMe)(CO)2(η-C5H5)3](7) an isomer of (6). The structure of (7) was established by X-ray diffraction. An essentially planar metal atom chain W(1), Rh(1), W(2), Rh(2), W(3) forms the spine of the molecule. The various ligands ligate the rhodium and tungsten atoms in a similar manner to those in (6), with the exception of the groups which span the Rh(2)–W(3) bond. This bond is now bridged by a λ5- phospha-alkyne C(Me) PPh2 fragment such that the phosphorus atom ligates W(3) and the carbon atom CMe is bonded to Rh(2) and W(3). The Rh(2)–W(3) bond is also bridged by a CO ligand. Thus the conversion of (6) into (7) involves a novel interchange of CO and PPh2 fragments such that in the former a µ-C(Me)C(O) group is present and in the latter a µ- C(Me)PPh2 moiety. The n.m.r. data (1H, 13C-{1H), and 31P-{1H}) for the new compounds are reported and discussed.

Chemistry of polynuclear metal complexes with bridging carbene or carbyne ligands. Part 59. Reactions of the alkylidyne compounds [M(CR)(CO)2{HB(pz)3}][M = Cr, Mo, or W, R = C6H4Me-4; M = W, R = Me, HB(pz)3= hydrotris(pyrazol-1-yl)borate] with d10complexes; crystal structure of [PtW2(µ-CMe)2(CO)4{HB(pz)3}2

Treatment of the compound [W(CMe)(CO)2{HB(pz)3}][{HB(pz)3}= hydrotris(pyrazol-1-yl)borate] with [Ni(cod)2](cod = cyclo-octa-1,5-diene) or [Pt(C2H4)3] affords the trimetal complexes [M′W2(µ-CMe)2(CO)4{HB(pz)3}2](M′= Ni or Pt). Similarly, reactions between the species [M (CC6H4Me-4)(CO)2{HB(pz)3}](M = Cr, Mo, or W) and [Pt(C2H4)3] yield the related compounds [PtM2(µ-CC6H4Me-4)2(CO)4{HB(pz)3}2]. The molecular structure of [PtW2(µ-CMe)2(CO)4{HB(pz)3}2] has been established by X-ray diffraction. The molecule has a nearly linear W–Pt–W spine [172.8(1)°], with mean Pt–W separations of 2.716 A. Each metal–metal bond is bridged by an ethylidyne group [mean values µ-C–W 1.885, µ-C–Pt 2.040 A] and semi-bridged by a carbonyl ligand [W–C–O 166°]. The dihedral angle between the two dimetallacyclopropene rings is 79°. Each tungsten atom carries a terminally bound CO ligand and a HB(pz)3 group. If the metal–metal bonds are ignored, each tungsten is in a pseudo-octahedral environment defined by the three nitrogen atoms of its associated HB(pz)3 ligand, the two CO groups and a µ-CMe fragment. A gold salt [AuW2(µ-CMe)2(CO)4{HB(pz)3}2][PF6] has been obtained by treating [W(CMe)(CO)2{HB(pz)3}] with [AuCl(tht)](tht = tetrahydrothiophene) in the presence of TIPF6. Reactions between the complexes [M(CR)(CO)2{HB(pz)3}](M = Cr, Mo, or W, R = C6H4Me-4; M = W, R = Me) and [Pt(C2H4){P(OMe)3}2] give dimetal compounds [PtM(µ-CR)(CO)2{P(OMe)3}2{HB(pz)3}], but only the ethylidyne-bridged platinum–tungsten compound is reasonably stable in solution. A molybdenum–platinum salt formulated as [PtMo{µ-σ:η3-CH(C6H4Me-4)}(CO)2{P(OMe)3}2{HB(pz)3}][BF4] has also been prepared. Spectroscopic data for the new compounds are reported.

Trimolybdenum cluster compounds with two capping ethylidyne groups

Three Compounds containing equilateral-triangular trimolybdenum clusters capped on both sides by ethylidyne (CCH3) groups are described: (I) , [MO~(CCH~)~(~~CCH~)~(H~~)~] (CF3S03)2 (2), and [MO~(CCH~)~(~~CCH~)~(H~~)~](P-CH~C~H~S~~)~~~OH~~ (3). All three are obtained by suitable workup of the reaction mixture after refluxing M o ( C O ) ~ with a 1O:l v/v mixture of acetic acid and acetic anhydride. For the last two permanganate oxidation is used. The crystal structures of the three compounds have been solved and refined. In 1, where there are five electrons for the M o ~ cluster, the Mo-Mo bond orders are 5 / 6 and the mean Mo-Mo distance is 2.814 ( 5 ) A; this is about 0.06 A longer than that in a closely related cluster with Mo-Mo bond orders of 1.0. In 2 and 3, which each contain a bicapped M o ~ cluster with only four electrons, and hence a bond order of 2/3, the mean Mo-Mo distances are 2.883 (1) 8, and 2.892 (1) A, Le., about 0.13 A longer than for the Mo-Mo bonds of order 1.0. The cation in 1 has one unpaired electron showing an essentially constant g factor slightly above 2.0 in the range 4-300 K according to bulk susceptibility measurements. It shows no EPR spectrum but has a sharp 360-MHz IH NMR spectrum in which the resonance of the 02CCH3 protons is shifted to 14 ppm downfield while that of the CCH3 protons is broadened and shifted 85 ppm downfield. The cations in 2 and 3 appear to be paramagnetic, but the temperature dependence is unusual and still under study. The cation gives an 'H NMR spectrum with lines at 15.6 and 27.1 ppm with relative intensities of 3.3 to 1.0.

The unexpected formation of a mixed bis(η 5-pentamethylcyclopentadienyl)tetracarbonyl(μ 3-ethylidene)triangulotricobalt compound and its structural characterization

The title compound was first obtained photolytically from (η 5-Me 5C 5)Co(CO) 2 (by a mechanism not understood) and later by refluxing C 5Me 5H with Co 3(CO) 9CCH 3. It was identified and characterized structurally by X-ray crystallography. The crystals belong to space group P2 1/n with a 9.529(2), b 18.325(4), c 14.801(3) Å, β 95.69(2)° with Z = 4, making one entire molecule the asymmetric unit. Using 2641 reflections with F 0 2 > 3σ (F 0 2 the structure was solved and refined to R 1 = 0.051 and R 2 = 0.067. It consists of a triangular pyramid with two (η 5-C 5Me 5)Co groups and one Co(CO) 3 group in the base and CCH 3 at the apex. The basal edge between the (η 5-C 5Me 5)Co groups has a bridging CO group and a Co—Co distance of 2.405(1) Å, while the other two unbridged Co—Co distances are 2.484(1) and 2.501(1) Å. The distances from the apical C atom to the bridged Co atoms are 1.857(6) and 1.866(6) but 1.932(6) Å to the unique Co atom. The C—C distance in the ethylidyne group is 1.497(9) Å. The structure is closely similar to that of the analogous (η 5-C 5H 5) 2Co 3(CO) 4CCH 3 compound.

LEED analysis of acetylene and ethylene chemisorption on the Pt(111) surface: Evidence for ethylidyne formation

The stable surface species formed from the chemisorption of acetylene (C2H2) or ethylene (C2H4) on the Pt(111) surface (T∼300–350 K) has been studied by a low-energy electron diffraction intensity analysis. High resolution electron energy loss spectra reported by Ibach et al. have been interpreted by comparison to infrared data on relevant model compounds. The surface species most consistent with these studies is ethylidyne ( C–CH3). The species is coordinated to a threefold surface site with the C–C axis normal to the surface within an uncertainty of ∼15°. A saturated C–C bond length of 1.50±0.05 Å and three equivalent Pt–C bond lengths of 2.00±0.05 Å are determined by the LEED analysis and are consistent with the reported structures of ethylidyne in organometallic clusters. The ethylidyne group forms readily upon exposure of C2H4 to the Pt(111) surface at T∼300 K with the loss of one hydrogen atom per ethylene. The complete conversion of C2H2 to ethylidyne requires the presence of hydrogen atoms and proceeds rapidly at T∼350 K. By comparison to reported reaction mechanisms on related transition metal clusters it seems likely that vinylidene ( C=CH2) is an intermediate in both reactions.

Chemistry of methinyltricobalt enneacarbonyls. Part I. Mass spectra

The mass spectra of the methinyltricobalt enneacarbonyls, Co3(CO)9CY (Y = H, F, Cl, Br, CH3, and C6H5), are presented and discussed in terms of the known structures. Parent molecular ions are observed for all derivatives. Initial progressive loss of carbon monoxide with retention of the Co3CY unit is followed by cleavage of cobalt–cobalt rather than cobalt–carbon bonds.The ethylidyne group C–CH3 undergoes a novel type of breakdown to give ethylenic-type fragments.