Ethylidene Complex Research Articles

A Chromium Ethylidene Complex as a Potent Catalyst for Selective Ethylene Trimerization

Going one, twice… Reaction of the mononuclear complex [{?5-(tBu)2C4H2N}CrCl2(thf)] with AlEt3 afforded the dinuclear species [{[?5-(tBu)2C4H2N]CrEt}2(µ-Cl)2] (see picture; Cr purple, Cl green, C sticks/gray, H white). The complex acts a single-component selective trimerization catalyst; a higher loading of AlEt3 activator afforded isomerization of 1-hexene to cis, trans 2-hexene

A Chromium Ethylidene Complex as a Potent Catalyst for Selective Ethylene Trimerization

Eins, zwei, drei …︁: Der Einkernkomplex [{η5-(tBu)2C4H2N}CrCl2(thf)] reagiert mit AlEt3 zu der zweikernigen Spezies [{[η5-(tBu)2C4H2N]CrEt}2(μ-Cl)2] (siehe Bild: Cr violett, Cl grün, C grau, H weiß). Der Komplex wirkt als Einkomponentenkatalysator für die selektive Trimerisierung von Ethylen; bei Zugabe größerer Mengen an aktivierendem AlEt3 kommt es zur Isomerisierung von 1-Hexen zu cis/trans-2-Hexen. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

A Bimetallic Ru2Pt Complex Containing a Trigonal-Planar μ3-Carbido Ligand: Formation, Structure, and Reactivity Relevant to the Fischer−Tropsch Process

The bimetallic Ru(2)Pt complex [(Cp*Ru)(2)(mu(2)-NHPh)(mu(2)-H)(mu(3)-C)PtMe(PMe(3))(2)][OTf] (3; Cp* = eta(5)-C(5)Me(5)) containing a planar three-coordinate carbido ligand has been prepared in 93% yield by thermal isomerization of the bridging methylene precursor [(Cp*Ru)(2)Me(mu(3)-NPh)(mu(2)-CH(2))Pt(PMe(3))(2)][OTf] (2) via cleavage of the methylene C-H bonds. Exposure of the carbido complex 3 to carbon monoxide (1 atm) induced coupling of the carbido ligand with the nearby methyl and hydride ligands to produce the diruthenium ethylidene complex [(Cp*Ru)(2)(mu(2)-CHMe)(mu(2)-NHPh)(CO)(2)][OTf] (4) and the known triplatinum complex [Pt(CO)(PMe(3))](3). The crystal structures of 2, 3, and 4 (BPh(4) salt) are reported.

Reactions of Actinide Metal Atoms with Ethane: Computation and Observation of New Th and U Ethylidene Dihydride, Metallacyclopropane Dihydride, and Vinyl Metal Trihydride Complexes

A combined computational and experimental investigation provides evidence that excited thorium and uranium atoms activate ethane to form the vinyl metal trihydride, metallacyclopropane dihydride, and ethylidene metal dihydride for thorium and the latter complex and the inserted ethyl metal hydride for uranium. These products are trapped in solid argon and identified through deuterium isotopic substitution and vibrational frequencies calculated by density functional theory. Comparisons are made with group 4 and methane reaction products. Numerous calculations using several methods show that these simple ethylidene complexes are more distorted by the agostic interaction than the corresponding methylidene species. This enhanced agostic interaction probably arises from methyl hydrogen to alpha-H repulsions, which leads to a substantial decrease in the alpha-H to Th agostic interaction distance, and contributes to our understanding of agostic distortion in organometallic complexes.

Synthesis of Ruthenium Olefin Metathesis Catalysts with Linear Alkyl Carbene Complexes

Second-generation ruthenium olefin metathesis catalysts with linear alkyl carbenes were needed to install a linear alkyl end group on ROMP polymers. The ethylidene complexes RuCl2(PCy3)(SIMes)CHMe (PCy3 = tricyclohexylphosphine; SIMes = 1,3-bis(mesityl)imidazolidin-2-ylidene) and RuCl2(3BP)2(SIMes)CHMe (3BP = 3-bromopyridine) were readily accessible by reaction of RuCl2(PCy3)(SIMes)CHPh with 2-butene. Synthesis of higher alkyl analogues, such as propylidene and heptylidene, are complicated by the intervention of olefin isomerization. Although slightly less reactive than the parent complex, these complexes are suitable catalysts for both ADMET and ROMP.

The synthesis of [FeRu(CO)2(μ-CO)2(η-C5H5)(η-C5Me5)] and convenient entries to its organometallic chemistry

The synthesis, fluxionality and reactivity of the heterobimetallic complex [FeRu(CO)2(mu-CO)2(eta-C5H5)(eta-C5Me5)] are described. Complex exhibits enhanced photolytic reactivity towards alkynes compared to its homometallic analogues, forming the dimetallacyclopentenone complexes [FeRu(CO)(mu-CO){mu-eta]1:eta3-C(O)CR"CR'}eta]-C5H5)(eta-C5Me5)]( R'= R"= H; R'= R"= CO2Me; R'= H, R"= CMe2OH). Prolonged photolysis with diphenylethyne gives the dimetallatetrahedrane complex [FeRu(mu-CO)(mu-eta2:eta2-CPhCPh)(eta-C5H5)(eta-C5Me5)], which contains the first iron-ruthenium double bond. Complexes containing a number of organic fragments can be synthesised using , and . Heating a solution of gave the alkenylidene complex [FeRu(CO)2(mu-CO){mu-eta]1:eta2-C=C(CO2Me)2}(eta-C5H5)(eta-C5Me5)] through an unusual methylcarboxylate migration. Protonation and then addition of hydride to gives the ethylidene complex [FeRu(CO)2(mu-CO)(mu-CHCH3)(eta-C5H5)(eta-C5Me5)] via the ionic vinyl species [FeRu(CO)2(mu-CO)(mu-eta]1:eta2-CH=CH2)(eta-C5H5)(eta-C5Me5)][BF4]. Compound exhibits cis/trans isomerisation at room temperature. Protonation of dimetallacyclopentenone complexes gives the allenyl species [FeRu(CO)2(mu-CO)(mu-eta1:eta2-CH=C=CMe2)(eta-C5H5)(eta-C5Me5)][BF4]. Compound exist as three isomers, two cis and one trans. The two cis isomers are shown to be interconverting by sigma-pi isomerisation. The solid state structures of these compounds were established by X-ray crystallography and are discussed.

Fate of CH2CHE (E = H, OMe) in the Presence of Unsaturated Ru(X)(H)L2q+(X = Cl,q= 0; X = CO,q= 1): Highly Sensitive to X and E

DFT (B3PW91) calculations have been carried out to discuss the role of the ancillary ligand X on the transformations of ethylene and vinyl ether by RuHX(PH3)2q+ (X = Cl, q = 0; X = CO, q = 1). This study follows the experimental results presented in the preceding paper. The energy of isomerization of the vinyl ether adduct into an alkoxy-stabilized carbene complex is insensitive to the nature of X, whereas the energy of isomerization of the ethylene adduct into the ethylidene complex depends significantly on X. This is interpreted as competing donations from both the metal fragment and the alkoxy group into the empty p orbital of carbene. The insertion of an olefin into the Ru−H bond to make an unsaturated 14-electron alkyl complex is calculated to be strongly endothermic for Cl and much less so for CO. This is shown to be associated with the greater stability of the olefin adduct in the presence of Cl. Insertion of methyl vinyl ether follows the same rules as ethylene. This accounts for the direct (vinyl...

Synthesis and catalytic activity of dinitosylchromium complexes of the type [Cr(NO) 2(CO) 2L 2] 2+, {Cr(NO) 2(OR) 2} n (R=Et, i-Pr) and Cr(NO) 2(O 2CPh) 2

New trans-dinitrosylchromium complexes of the type [Cr(NO) 2(CO) 2L 2](BF) 4 (L=MeNO 2, MeCN, MeOH; L 2=bipy), [Cr(NO) 2L 4](BF 4) 2 (L=MeNO 2, MeOH, L 2=bipy), {Cr(NO) 2(OR) 2} n (R=Et, i-Pr) and Cr(NO) 2(O 2CR) 2 (R=Ph) were obtained. Interactions of these complexes with Lewis acids (TiCl 4, SnCl 4 and EtAlCl 2) were investigated. The effect of those interactions is trans–cis isomerization of nitrosyl ligands and formation of respective adducts, while the adducts with EtAlCl 2, by further transformations, form cis-dinitrosylchromium ethylidene complexes. Catalytic activities of the systems complexes—Lewis acids were tested in the reactions with olefins (pent-1-ene, pent-2-ene, cyclopentene) and phenylacetylene. The adduct [Cr(NO) 2(OEt) 2(EtAlCl 2) 2] and the first dinitrosylalkylidenechromium complex {Cr(NO) 2(CHMe) 2(OEt) 2(AlCl 2) 2} n were synthesized and characterized spectroscopically. Their catalytic activities were studied, too.

Electrophilic Cationic Ethylidene Complexes of Ir(III). Comparative α-Migratory Insertion Processes into Hydride and Ethyl Groups

Electrophilic Cationic Ethylidene Complexes of Ir(III). Comparative α-Migratory Insertion Processes into Hydride and Ethyl Groups

Reaction of alkylidenedinitrosylmolybdenum complexes with vinyl trisubstituted silanes and substituted acetylenes

Reaction of Mo(NO) 2 (CHMe) (OR) 2(AlCl 2) (EtAlCl 2) (R = Et, O-i-Pr) with vinyl silanes (vinyltrimethoxysilane and vinyltrimethylsilane) with substituted acetylenes (phenylacetylene and hex-2-yne) are studied. The ethylidene complex has been found to be an efficient catalyst for metathesis reaction of vinyl silanes. 1,2-Bis (trimethoxysilyl) ethene and ethylene are formed, via metathesis of vinyltrimethoxysilane, with a yield of above 80%. Similarly, the self-metathesis of vinyltrimethylsilane in the presence of this complex occurs, yielding 1,2-bis (trimethylsilyl) ethene and ethylene (yield below 20%). The latter reaction was accompanied by a dimerization leading to 1,4-bis (trimethylsilyl) butene-2 which was the prevailing product (above 30%). Trans-cisoidal poly (phenyl acetylene) with low molecular weight, as well as a polymer of hex-2-yne with high molecular weight are produced using this ethylidenemolybdenum complexes. Degradation of the poly (phenylacetylene) by cross-metathesis with vinyltrimethoxysilane was studied, too.

Organometallic Complexes of Tantalum That Contain the Triamidoamine Ligand, [(Me3SiNCH2CH2)3N]3-, Including an Ethylidene Complex Formed via a Phosphine-Catalyzed Rearrangement of an Ethylene Complex

Organometallic Complexes of Tantalum That Contain the Triamidoamine Ligand, [(Me3SiNCH2CH2)3N]3-, Including an Ethylidene Complex Formed via a Phosphine-Catalyzed Rearrangement of an Ethylene Complex

The reaction of (μ-H) 2Os 3(CO) 9(PPh 3) with ethylene affords the ethylidene complex (μ-H) 2Os 3(CO) 9(PPh 3)(μ-CHCH 3)

The product isolated from the reaction of (μ-H) 2Os 3(CO) 9(PPh 3) with ethylene is shown to be the ethylidene complex (μ-H) 2Os 3(CO) 9(PPh 3)(μ-CHCH 3) ( 1) rather than the ethylene complex (μ-H)(H)Os 3(CO) 9(PPh 3)(C 2H 4), as previously claimed. The characterization of 1 is based on a combination of 1H and 13C NMR results. The 1H NMR data (δ 6.84 (1 H D), 2.53 (3 H C), J(CD) = 7.4 Hz) establish the presence of the ethylidene moiety, whereas detailed analysis of the 1-D and 2-D 13C NMR spectra of 13CO-enriched 1 indicates the relative positions of the ethylidene, hydride, and phosphine ligands on the triosmium framework.

Metathesis of functionalized alkenes by dinitrosylmolybdenum catalyst

The dicomponent Mo(NO) 2(OR) 2EtAlCl 2 and tricomponent Mo(NO) 2(OR) 2Et 4SnAlCl 3 catalytic systems as well as ethylidene complexes [(AlCl 2) 2(μ-OR) 2Mo(NO) 2(CHMe)] (R = Et, iPr) show activity for self-metathesis of ethyl but-3-enoate and very limited activity for cometathesis of this ester with trans-hex-3-ene. Blocking of the Lewis basic functional groups of this ester with a Lewis acid (EtAlCl 3, AlCl 3), however, increased the effectiveness of the catalysts used. Metathesis reactions of Zn(oleate) 2 and Al(O-allyl) 3 by both catalytic systems, without excess Lewis acid co-catalysts, demonstrate that coordination of the functional groups to the appropriate metal ions completely eliminated the poisoning effect of these groups.

Alkylidene dinitrosyl molybdenum complexes. Synthesis and characterization of ethylidene complexes of the type [(Et 3Sn · AlCl 3) 2(μ-OR) 2Mo(NO) 2(CHMe)

Reactions of dialkoxy dinitrosyl molybdenum complexes with Et 4Sn (alkylating agent) and AlCl 3 (Lewis acid) yield ethylidene dinitrosyl molybdenum complexes. They were isolated as polymeric species {(Et 3Sn · AlCl 3) 2(μ-OR) 2MO(NO) 2(CHMe)} n n (R = Me, Et, iPr) and 1H NMR, IR and analytically characterized. These are new examples of low-valent nucleophilic alkylidene complexes.

Dinitrosylmolybdenum alkylidene complexes containing n-alkyl alkoxy ligands: synthesis, spectroscopic characterization and metathesis activity

Reactions of {Mo(NO) 2(OR) 2S n } and {Mo(NO) 2(OR) 2} 2 (R = Me, Et) with EtAlCl 2 at room temperature yield the ethylidene [(AlCl 2) 2(η-OR) 2Mo(NO) 2 (CHMe)] complexes. They were characterized by 1H NMR and IR spectroscopy. They are examples of low-valent ethylidene complexes with nucleophili CHMe ligands. These ethylidene complexes are the products of transformation of the adducts [EtAlCl 2) 2 (η-OR) 2Mo(NO) 2] into diethyl-complexes, followed by α-hydrogen elimination. These adducts were also obtained and characterized. Reactions of the ethylidene complexes with hex-3-ene yield are respective propylidene complexes. In this way the complex [(AlCl 2) 2(η-OEt) 2Mo(NO) 2(CHEt)] was obtained. The alkylidene complexes are active catalysts for olefin metathesis. Addition of AlCl 3 to ([EtAlCl 2) 2(η-OR) 2Mo(NO) 2] also converted them into active ctalysts.

The first example of a dinitrosylmolybdenum alkylidene complex: synthesis, spectroscopic characterization and metathesis activity

The first spectrally characterized example of a stable dinitrosylmetal ethylidene complex, [(AlCl 2) 2(μ-O-i-Pr) 2Mo(NO) 2(CHMe)], is reported. This complex is the product of transformation of the adduct [(EtAlCl 2) 2(μ-O-i-Pr) 2Mo(NO) 2] to a dialkyl complex followed by α-hydrogen elimination. The ethylidene complex is an active catalyst for olefin metathesis.

Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 40. Transformation of terminally bound alkylidyne ligands to µ-alkylidene, µ-vinyl, µ-alkyl, and µ-aryl groups at a bimetal centre; X-ray crystal structures of [N(PPh3)2][ReW(µ-CHR)(CO)9], [ReW(µ-CH2R)(µ-Me2PCH2PMe2)(CO)7], and [ReW(µ-OCCH2R)(µ-Ph2PCH2PPh2)(CO)6{P(OMe)3}](R = C6H4Me-4)

Treatment of the complexes [ReM(CR)(CO)9] in tetrahydrofuran (thf) with K[BH(CHMeEt)3], followed by addition of [N (PPh3)2]Cl affords the salts [N (PPh3)2][ReM (µ-CHR)(CO)9](M = Cr, Mo, or W, R = C6H4Me-4; M = W, R = Me). The structure of one of these species (M = W, R = C6H4Me-4) was determined by X-ray diffraction. In the anion, the Re-W bond [3.033(1)A] is asymmetrically spanned by the µ-CH(C6H4Me-4) group [µ-C-Re 2.155(8), µ-C–W 2.404(6)A]. The rhenium atom is ligated by four CO groups and the tungsten by five of these ligands. On warming in thf solution, the bridged ethylidene complex [N(PPh3)2][ReW(µ-CHMe)(CO)9] releases CO and converts to the hydrido- and vinyl-bridged salt [N(PPh3)2][ReW(µ-H)(µ-CHCH2)(CO)8]. Treatment of the compounds [N (PPh3)2][ReM{µ-CH (C6H4Me-4)}(CO)9] with the bidentate phosphines R′2PCH2PR′2(R′= Ph or Me) affords the complexes [N(PPh3)2][ReM{µ-CH(C6H4Me-4)}(µ-R′2PCH2PR′2)(CO)7](M = W, R′= Ph; M = Cr, Mo, or W, R′= Me). The rhenium–tungsten species on protonation (HBF4·Et2O) afford complexes [ReW(µ-CH2C6H4Me-4)(µ-R′2PCH2PR′2)(CO)7] in which the p-tolylmethyl group asymmetrically bridges the metal-metal vector, being σ-bonded to the rhenium and co-ordinated to the tungsten by a three-centre, two-electron C–H⇀W bond. This result, strongly indicated by 1H and 13C-{1H} n.m.r. data, was confirmed by an X-ray diffraction study on the Me2PCH2PMe2 derivative [µ-C-Re 2.302(7), µ-C-W 2.539(7)A]. The Re–W vector [2.950(2)A] is also spanned by the Me2PCH2PMe2 ligand and a strongly semi-bridging carbonyl attached to the tungsten [W–C–O 153.6(6)°]. The Me2PCH2PMe2 and CH2C6H4Me-4 groups are cisoid in the bridge system. The rhenium and tungsten atoms each carry three terminally bound CO ligands. Several reactions of the bridged p-tolylmethyl rheniumtungsten compounds have been investigated, that between [ReW(µ-CH2C6H4Me-4)(µ-Ph2PCH2PPh2)(CO)7] and P(OMe)3affording the complex [ReW(µ-OCCH2C6H4Me-4)(µ-Ph2PCH2PPh2)(CO)6{P(OMe)3}], the structure of which was established by X-ray diffraction. In this compound the Re–W bond [3.155(1)A] is bridged by the Ph2PCH2PPh2 ligand and by the aryl group [Re–C 2.167(8), W–O 2.206(5)A]. The rhenium atom carries three terminally bound CO groups and the tungsten two. A further CO ligand on tungsten semi-bridges the Re–W bond [W–C–O 157.0(6)A], the tungsten being also ligated by the P(OMe)3 group. The Ph2PCH2PPh2 and aryl groups in the bridge system are cisoid. The n.m.r. spectra (1H, 13C-{1H}, and 31P-{1H}) of the new compounds are reported and discussed.

Multiple metal [sbnd]carbon bonds : XIV. Preparation of alkylidenetantalum complexes by alkylidene transfer from phosphoranes. The first ethylidene complex and how it decomposes

The reaction of TaCp 2(L)Me (L = PMe 3 or PMe 2Ph) with R 3P=CHR′ (R = Me, Et, or Ph; R′ = H, Me, or Ph) gives L, R 3P, and TaCp 2(CHR′)Me in good yield. The ethylidene complex has properties much like other alkylidene complexes in this class, but most importantly, it does not rearrange to the known TaCp 2(C 2H 4)Me complex under conditions where the latter is stable. Instead, it rearranges to TaCp 2(propylene)H, possibly by migration of the alkyl to the alkylidene ligand followed by β-hydride elimination.