Carbyne Complexes Research Articles

The First Highly Active, Halide-Free Ruthenium Catalyst for Olefin Metathesis

New ruthenium alkylidyne and alkylidene complexes are prepared, in which aryloxide groups function as pseudohalide ligands. The selectivity for alkylidene or alkylidyne products is controlled by st...

Vibrational spectroscopic data of metallocarbyne complexes

Vibrational spectroscopic data together with electron deformation density results on Fischer's carbyne complexes are briefly reviewed in this article. The nature of the metalcarbyne bonds and modifications in the molecular structures of some carbynes as a function of temperature are presented.

Synthesis, protonation, and electrophilic reactions of Tp′(CO) 2WCOMe, a tungsten methoxycarbyne complex

The synthesis and characterization of the terminal methoxycarbyne complex Tp′(CO) 2WCOMe is described. Nucleophiles attack Tp′(CO) 2WCOMe at the methyl group of the methoxide substituent. The carbyne complex undergoes reversible protonation at the carbyne carbon in the presence of [H(Et 2O) 2][BAr′ 4] to generate the α-agostic carbene complex [Tp′(CO) 2WC(H)OMe][BAr′ 4].

Study towards bioactive pyrone derivatives from the marine red alga Phacelocarpus labillardieri

Red algae of the genus Phacelocarpus labillardieri produce a structurally rather unique class of macrocyclic pyrone derivatives with phospholipase A 2 inhibiting properties and potential neuromuscular blocking activity. They were also shown to be potent feeding inhibitors for various marine herbivorous gastropods. Described herein is the first preparative study towards these conspicuous secondary metabolites. Their carbon skeleton has been assembled in a few straightforward steps using ring closing alkyne metathesis (RCAM) catalyzed by the Schrock alkylidyne complex ( tBuO) 3WCCMe 3 to forge the meta-cyclophane core with high efficiency.

Sequential Chemical Transformations of a Tungsten Carbyne Ligand: Protonation, Alkyne Insertion, Vinylcarbene Formation, and Metallacyclopropene/Metallafuran Isomerization

Proton addition and phenylacetylene insertion convert carbyne complexes of the type Tp‘(CO)2W⋮C−OAr (Ar = Ph, p-C6H4Me, p-C6H4OMe; Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate) into tungsten η3-vinylcarbene complexes of the form [Tp‘(CO)2W(η3-(Cα,Cβ,Cγ)CPh−CHCH(O(p-C6H4R)))][X] (R = H, X = BF4, 6a; R = Me, X = BF4, 6b; R = OMe, X = BF4, 6c; R = H, X = BAr‘4, 6a‘). The intermediate agostic carbene complex [Tp‘(CO)2WC(H)O(p-C6H4OMe)][BAr‘4] (7‘) was characterized by IR, 1H NMR, and 13C NMR spectroscopy. Addition of base to the cationic vinylcarbene complex 6 forms the metallafuran complex Tp‘(CO)2W(κ2-(Cα,O)CPh−CHCH−O) (9) as the major product. Although the net reaction corresponds to loss of C6H5+, mechanistically it is attractive to postulate addition of OH- to the electron-deficient Cγ site followed by proton removal by base coupled with loss of OPh- to generate the metallafuran stoichiometry. Isolation of an intermediate metallacyclopropene complex (10), possessing an aldehyde substituent on the three...

Ligand influences on hydrogen migration in transition metal hydrido–carbyne complexes

Density Functional BP86 calculations are reported for the interconversion reactions of WH(CH)(CO)(PH 3) 3 and WH(CH)(CO) 2(PH 3) 2 to the corresponding five-coordinated carbene complexes W(CH 2)(CO)(PH 3) 3 and W(CH 2)(CO) 2(PH 3) 2, respectively. Transition states have been calculated to be 9.9 and 0.7 kcal mol −1 higher in energy than the carbynes. A comparison with the isoelectronic osmium system OsHCl 2(CMe)(PH 3) 2 with a transition state for interconversion 27.2 kcal mol −1 above the carbyne leads to the conclusion that additional π-acceptors competing with the carbyne or carbene ligand for back donation facilitate the interconversion reaction, whereas additional π-donors undergoing synergic push–pull interactions impede the interconversion reaction.

Novel Reactions of Cyclooctatetraene (COT)-Coordinated Diiron Cationic Bridging Carbyne Complexes with Nucleophiles

The COT-coordinated diiron cationic bridging carbyne complexes [Fe2(μ-CAr)(CO)4(η8-C8H8)][BF4] (1, Ar = C6H5; 2, Ar = p-CH3C6H4; 3, Ar = p-CF3C6H4) were prepared by the reactions of the diiron bridging alkoxycarbene complexes [Fe2{μ-C(OC2H5)Ar}(CO)4(η8-C8H8)] with HBF4·Et2O at low temperature. Cationic 3 reacts with NaSR (R = C2H5, p-CH3C6H4) in THF at low temperature to afford diiron bridging sulfonylcarbene complexes [Fe2{μ-C(SO2R)C6H4CF3-p}(CO)4(η8-C8H8)] (7, R = C2H5; 8, R = p-CH3C6H4), while the reactions of 1−3 with NaBH4 under similar conditions gave diiron bridging arylcarbene complexes [Fe2{μ-C(H)Ar}(CO)4(η8-C8H8)] (9, Ar = C6H5; 10, Ar = p-CH3C6H4; 11, Ar = p-CF3C6H4). Complexes 1−3 can also react with anionic carbonylmetal compounds Na[M(CO)5(CN)] (4, M = Cr; 5, M = Mo; 6, M = W) to produce diiron bridging aryl(pentacarbonylcyanometal)carbene complexes [Fe2{μ-C(Ar)NCM(CO)5}(CO)4(η8-C8H8)] (12, Ar = C6H5, M = Cr; 13, Ar = p-CH3C6H4, M = Cr; 14, Ar = p-CF3C6H4, M = Cr; 15, Ar = C6H5, M = Mo; 16, Ar = p-CH3C6H4, M = Mo; 17, Ar = p-CF3C6H4, M = Mo; 18, Ar = C6H5, M = W; 19, Ar = p-CH3C6H4, M = W; 20, Ar = p-CF3C6H4, M = W). Unexpectedly, aniline and 2-naphthylamine react with cationic 1 and 3 to give novel COT-coordinated iron carbene complexes [Fe2{C(Ar)NHAr‘}(μ-CO)(CO)3(η8-C8H8)] (21, Ar = C6H5, Ar‘ = C6H5; 22, Ar = p-CF3C6H4, Ar‘ = C6H5; 23, Ar = p-CF3C6H4, Ar‘ = 2-naphthyl). In solution, products 21−23 were transformed into chelated iron carbene complexes [Fe2{C(Ar)NAr‘}(CO)4(η2:η3:η2-C8H9)] (24, Ar = C6H5, Ar‘ = C6H5; 25, Ar = p-CF3C6H4, Ar‘ = C6H5; 26, Ar = p-CF3C6H4, Ar‘ = 2-naphthyl) in high yields. The structures of complexes 7, 8, 11, 14, 15, 20, 22, and 24 have been established by X-ray diffraction studies.

A reductive recycle strategy for the facile synthesis of molybdenum(VI) alkylidyne catalysts for alkyne metathesis.

A convenient synthesis of trisamido molybdenum(VI) alkylidyne complexes has been developed, in which the key step is the addition of a geminal dichloride to a trisamido molybdenum(III) complex in the presence of magnesium to continuously recycle unwanted side product 4, selectively generating the desired alkylidyne complexes in high yield.

Synthesis and structure of novel, air-stable carbyne complexes of tungsten

New Fischer type carbyne complexes of tungsten, L(CO) 2WCR/Ar, 1b– 7b, where R=CH 3, Ar=substituted phenyl, and LH=(2-hydroxyphenyl)-bis(3,5-dimethylpyrazolyl)methane, with L − being a tridentate, uninegative ligand, were synthesized from W(CO) 6 via tetraethylammonium acylmetallate salt, as thermally stable and air-stable solids. In another complex, 8b, the aryl ring is complexed with tricarbonylchromium. Crystal structure of a representative complex was determined to confirm structural assignment.

Synthesis and reactivity of hydridotris(1-pyrazolyl)borate tungsten(VI) amido alkylidyne complexes

The synthesis of a series of tungsten(VI) amido alkylidyne complexes containing the chelating ligands Tp (hydridotris(1-pyrazolyl)borate) and Tp′ (hydridotris(3,5-dimethyl-1-pyrazolyl)borate) is described. Complexes of general formula, TpW(CC(CH 3) 3)(Cl)(NHR) [R=C 6H 5, 4-BrC 6H 4, 3,5-(CF 3) 2C 6H 3, H], ( 3– 6), were formed by reaction of TpW(CC(CH 3) 3)(Cl) 2 with the appropriate amide [M][NHR] (M=Li, K). In presence of excess [Li][NHPh], TpW(CC(CH 3) 3)(NHPh) 2 ( 7) was isolated. Sub-stoichiometric quantities of H 2O or HCl were found to catalyze the tautomerization of 3 to the corresponding imido alkylidene. Reaction of excess H 2O with 3 produced significant amounts of TpW(O)(CHC(CH 3) 3)(Cl) ( 10) and TpW(O)(CC(CH 3) 3)(Cl) ( 11) along with tautomerization. Attempted acid catalyzed tautomerizations of 4 and 5 with HCl resulted in loss of the amido ligands and recovery of TpW(CC(CH 3) 3)(Cl) 2. The complex Tp′W(CC(CH 3) 3)(Cl)(NHPh) ( 8), was synthesized by reaction of (CH 3) 3SiN(H)Ph with (DME)W(CC(CH 3) 3)(Cl) 3 followed by addition of KTp′. X-ray crystal structures have been obtained for compounds 7 and 8 and show that the amido groups are syn with respect to the neopentylidyne ligand probably due to the steric demands of the chelating Tp and Tp′ ligands.

Energy decomposition analysis of the chemical bond in main group and transition metal compounds.

The nature of the chemical bond in the main group diborane(4) compounds X2B-BX2 (X = H,F,Cl,Br,I) and in the Fischer- and Schrock-type transition metal carbene and carbyne complexes and heavier homologues (CO)5W-CH2, (CO)5W-E(OH)2, Cl4W-EH2, Cl(CO)4W-EH and Cl3W-EH (E = C,Si,Ge,Sn,Pb) have been investigated with an energy decomposition analysis (EDA). The results give a deep insight into the nature of the chemical interactions. The EDA results can be used as a bridge between the heuristic models of experimental chemists which have been proven as useful ordering schemes for experimental observations and the physical mechanism which leads to a chemical bond. At the time the data give a well defined qantitative answer to the questions about the strength of the covalent and electrostatic interactions and about the contributions of sigma and pi electrons to the covalent bond.

An investigation into the relative influence of alkoxide and thiolate ligands on the metal–carbon triple bond in X 3MCH compounds, where M=Cr, Mo and W and X=OH, SH, OCH 3, SCH 3, OCF 3 and SCF 3 from electronic structure calculations

Electronic structure calculations using density functional theory with the aid of the gaussian-98 package have been employed on the model Group 6 metal alkylidyne complexes X 3MCH, where M=Cr, Mo and W and X=OH, SH, OCH 3, SCH 3, OCF 3 and SCF 3. Collectively, these calculations reveal that the relative energies of the metal–carbon π-bonding molecular orbitals are greatly influenced by the metal and the ancillary ligand X. In comparing the bonding in related O and S containing molecules, the effect of oxygen is to increase the relative energy of the M–C π bond by approximately 1 eV as a result of M–O π antibonding interactions. In contrast, the ligand-based lone-pair orbitals lie higher in energy for sulfur and for the series where X=SH, SCH 3 and SCF 3, the HOMO is a sulfur lone-pair combination of a 2 symmetry in the C 3 v point group. The relative influence of H, CH 3 and CF 3 within each series is as expected based on their electron releasing properties. A comparison is made with related compounds having metal to metal or metal to nitrogen triple bonds.

Novel N-Nucleophilic Addition to and Ring-Breaking of Coordinated Cyclooctatetraene in Diiron Bridging Carbyne Complexes

The reactions of the diiron cationic carbyne complexes 1−3 with NaN(SiMe3)2 or LiN(SiMe3)2 in THF at low temperature give novel N-nucleophilic addition products, the neutral diiron bridging carbyne complexes 4−6, while the reactions of 1−3 with LiNEt2 lead to breaking of the COT ring to produce the diiron bridging carbene inner salts 7−9, among which the structures of 4 and 7 have been established by X-ray diffraction studies.

Unusual reactions of cationic bridging carbyne complexes of dimethylsilane-bridged bis(η 5-cyclopentadienyl)diiron tricarbonyl with carbonylmetal anions

The reactions of the dimethylsilane-bridged cationic carbyne complexes of diiron, [Fe 2(μ-CO)(μ-CAr)(CO) 2{(η 5-C 5H 4) 2Si(CH 3) 2}]BBr 4 ( 1, Ar=C 6H 5; 2, Ar= p-CF 3C 6H 4), with carbonylmetal anionic compounds Na[M(CO) 5CN] ( 4, M=Cr; 5, M=Mo; 6, M=W) in THF at low temperature afford diiron bridging carbene complexes [Fe 2(μ-CO){μ-C(Ar)NCM(CO) 5}(CO) 2{(η 5-C 5H 4) 2Si(CH 3) 2}] ( 9, M=Cr, Ar=C 6H 5; 10, M=Mo, Ar=C 6H 5; 11, M=W, Ar=C 6H 5; 12, M=Cr, Ar= p-CF 3C 6H 4; 13, M=Mo, Ar= p-CF 3C 6H 4; 14, M=W, Ar= p-CF 3C 6H 4). In contrast to the reaction of 1 and 2, cationic carbyne complex [Fe 2(μ-CO)(μ-CC 6H 4CH 3- p)(CO) 2{(η 5-C 5H 4) 2Si(CH 3) 2}]BBr 4 ( 3) reacts with 4– 6 under the same conditions to produce novel cationic bridging carbyne complexes [Fe 2(μ-CO)(μ-CC 6H 4CH 3- p)(CO) 2{(η 5-C 5H 4) 2Si(CH 3) 2}] +[M(CO) 5CN] − ( 15, M=Cr; 16, M=Mo; 17, M=W). Analogous cationic bridging carbyne complex [Fe 2(μ-CO)(μ-CC 6H 4CH 3- p)(CO) 2{(η 5-C 5H 4) 2Si(CH 3) 2}] +[Fe(CO) 4CN] − ( 18) can also be obtained from the reaction of 3 with Na[Fe(CO) 4CN] ( 7). Complex 15 or 16 reacts with NaSR (R=CH 3, C 6H 5, p-CH 3C 6H 4) to give bridging mercaptocarbene complexes [Fe 2(μ-CO){μ-C(SR)C 6H 4CH 3- p}(CO) 2{(η 5-C 5H 4) 2Si(CH 3) 2}] ( 19, R=CH 3; 20, R=C 6H 5; 21, R= p-CH 3C 6H 4) in high yields. The related reaction of 1 with NaN(SiMe 3) 2 affords a novel benzonitrile-coordinated diiron complex [Fe 2(μ-CO) 2(CO)NCC 6H 5{(η 5-C 5H 4) 2Si(CH 3) 2}] ( 22). Unexpectedly, the reactions of 1 and 2 with 7 yield diiron bridging arylcarbene complexes [Fe 2(μ-CO){μ-C(H)Ar}(CO) 2{(η 5-C 5H 4) 2Si(CH 3) 2}] ( 23, Ar=C 6H 5; 24, Ar= p-CF 3C 6H 4). The products 23 and 24 and bridging p-tolyl-carbene complex [Fe 2(μ-CO){μ-C(H)C 6H 4CH 3- p}(CO) 2{(η 5-C 5H 4) 2Si(CH 3) 2}] ( 25) were also obtained from the reactions of 1– 3 with [(PPh 3) 2N][Cr(CO) 4NO] ( 8). The structures of 14, 15, 22, and 23 have been established by X-ray crystallography.

An Attractive Route to Olefin Metathesis Catalysts: Facile Synthesis of a Ruthenium Alkylidene Complex Containing Labile Phosphane Donors

Reaction of RuHCl(PPh3)34 with 3-chloro-3-methyl-1-butyne effects transformation into RuCl2(PPh3)2(CHCHCMe2) 1c. Starting 4 is available commercially, or via quantitative reaction of RuCl2(PPh3)3 with one equivalent of alkali phenoxides or isopropoxides in refluxing benzene-2-propanol. Phosphane exchange between 1c and PCy3 or 1,3-(CH2PCy2)2C6H4 is rapid at RT, affording RuCl2(PCy3)2(CHCHCMe2) 1b or the novel alkylidene complex RuCl2[1,3-(CH2PCy2)2C6H4](CHCHCMe2) 7. Much slower exchange occurred on use of RuCl2(PCy3)2(CHPh) (1a) as precursor. Complex 1c is stable indefinitely (months) in the solid state at RT under N2, but dimerizes slowly in solution to give RuCl(PPh3)2(μ-Cl)3Ru(PPh3)2(CHCHCMe2) 6a. 2,7-Dimethyl-octa-2,4,6-triene, the formal product of carbene coupling, is observed by 1H NMR. Dimerization does not compete with phosphane exchange. A side-product arising from use of excess 3-chloro-3-methyl-1-butyne in the synthesis of 1c was identified as Ru(IV) carbyne complex RuCl3(PPh3)2(≡CCHCMe2) 5, the structure of which was confirmed by X-ray crystallography.

Oxidative dehydrodimerization of manganese vinylidene complexes (η5‐C5R5)(CO)(L)MnCCHPh (R = Me, L = CO; R = H, L = PPh3)

AbstractThe oxidative dehydrodimerization of the phenylvinylidene manganese complexes (η5‐C5R5)(CO)(L)MnCCHPh (5: R=Me, L=CO; 6: R=H, L=PPh3) into the corresponding bis‐vinylidene compounds (η5‐C5R5)(CO)(L)MnCCPhCPhCMn(CO)(L)(η5‐C5R5) (7: R=Me, L=CO; 8: R=H, L=PPh3) was studied by cyclic voltammetry and chemical experiments. It was found that dehydrodimerization of 5 and 6 proceeds via direct C(β)C(β) coupling of the radical cations 5 +· and 6 +· to give dicationic bis‐carbyne complexes [(η5‐C5R5)(CO)(L)Mn≡CCPhHCPhHC≡Mn(CO)(L)(η5‐C5R5)]2+ (10 ++: R=Me, L=CO; 11 ++: R=H, L=PPh3), which can be converted into bis‐vinylidene complexes 7 and 8 respectively by reduction with (η‐C6H6)2Cr. In this process, binuclear 19‐electron bis‐carbyne compounds 10 ·· and 11 ·· undergo further transformation into the dimers 7 and 8 via homolysis of C(β)H bonds of the bis‐carbyne ligand, thus exhibiting rare examples of reductive activation of CH bonds in 19‐electron transition metal carbyne complexes. Copyright © 2002 John Wiley & Sons, Ltd.

Novel Reactions of Cationic Carbyne Complexes of Manganese and Rhenium with Polymetal Carbonyl Anions. An Approach to Trimetal Bridging Carbyne Complexes

The reaction of a cationic carbyne complex of manganese, [(η-C5H5)(CO)2Mn⋮CC6H5]BBr4 (1), with [(Ph3P)2N]2[Ru3(CO)11] (3) in THF at low temperature gave the heteronuclear trimetal bridging carbyne complex [MnRu2(μ-H)(μ-CO)2(μ3-CC6H5)(CO)6(η-C5H5)] (7). A cationic carbyne complex of rhenium, [(η-C5H5)(CO)2Re⋮CC6H5]BBr4 (2), reacts similarly with 3, affording the corresponding bridging carbyne complex [ReRu2(μ-H)(μ-CO)2(μ3-CC6H5)(CO)6(η-C5H5)] (8) and neutral Re−carbyne dimer [Re(CO)2(η-C5H5)(μ-CC6H5)]2 (9). The compound [(Ph3P)2N]2[Os3(CO)11] (4) only reacts with 1 to give the trimetal bridging carbyne complex [MnOs2(μ-H)(μ-CO)2(μ3-CC6H5)(CO)6(η-C5H5)] (10) and neutral Mn−carbyne dimer [Mn(CO)2(η-C5H5)(μ-CC6H5)]2 (11). [(Ph3P)2N]2[Fe4(CO)13] (5) also reacts with cationic carbyne complexes 1 and 2 to give the trimetal bridging carbyne complexes [MnFe2(μ-H)(μ-CO)2(μ3-CC6H5)(CO)6(η-C5H5)] (12) and [ReFe2(μ-H)(μ-CO)2(μ3-CC6H5)(CO)6(η-C5H5)] (13), respectively. Product 13, when treated with an excess of PPh3, g...

Total synthesis of the turrianes and evaluation of the DNA-cleaving properties.

The first total synthesis of three naturally occurring cyclophane derivatives belonging to the turriane family of natural products is described. Their sterically hindered biaryl entity is formed by reaction of the Grignard reagent derived from aryl bromide 10 with the oxazoline derivative 18, and the macrocyclic tether of the targets is efficiently forged by ring closing metathesis. While conventional RCM catalyzed by the ruthenium-carbene complexes 33 or 34 invariably leads to the formation of mixtures of both stereoisomers with the undesirable (E)-alkene prevailing, ring closing alkyne metathesis (RCAM) followed by Lindlar reduction of the resulting cycloalkynes 37 and 38 opens a convenient and stereoselective entry into this class of compounds. RCAM can either be accomplished by using the tungsten alkylidyne complex [(tBuO)3 [triple bond] WCCMe3] or by means of a catalyst formed in situ from [Mo(CO)6] and para-trifluoromethylphenol. The latter method is significantly accelerated when carried out under microwave heating. Furthermore, the judicious choice of the protecting groups for the phenolic -OH functions turned out to be crucial. PMB-ethers were found to be compatible with the diverse reaction conditions en route to 3-5; their cleavage, however, had to be carried out under carefully optimized conditions to minimize competing O-C PMB migration. Turrianes 3-5 are shown to be potent DNA cleaving agents under oxidative conditions when administered in the presence of copper ions.

Monomeric and Dinuclear Tungsten Carbyne Complexes Containing Benzyl, Allyl, and Alkenyl Carbyne Substituents

The phosphonium carbyne complexes [Tp‘(CO)2W⋮CPMe2Ph]+ (Tp‘ = hydridotris(3,5-dimethylpyrazolyl)borate) add the Grignard reagents PhCH2MgCl and CH2CHCH2MgCl at Cα to generate the zwitterionic carbene complexes Tp‘(CO)2WC(CH2R)(Me2Ph) (R = Ph, CHCH2) as intermediates which lose PMe2Ph to form neutral Tp‘(CO)2W⋮CCH2R (R = Ph, CHCH2) carbyne complexes. Deprotonation of these carbyne complexes with strong base occurs at Cβ to form the reactive vinylidene anions [Tp‘(CO)2WCC(H)(R)]-, which have been characterized by IR and NMR spectroscopy. The phenylvinylidene anion [Tp‘(CO)2WCC(H)(Ph)]- adds electrophiles at Cβ, and the vinylvinylidene anion [Tp‘(CO)2WCCHCHCH2]- reacts with MeI at Cβ to generate Tp‘(CO)2W⋮CCH(CH3)(CHCH2). Treatment of this chiral carbyne complex with nBuLi generated the [Tp‘(CO)2WC C(CH3)CHCH2]- anion, which reacts with MeI primarily at Cβ to form Tp‘(CO)2W⋮CC(CH3)2CHCH2, although some methylation occurs at Cδ to generate the conjugated carbyne Tp‘(CO)2W⋮CC(CH3)C(H)(CH2CH3). Isomerization of...

Chemical bonding in methylidyne complexes: neutron diffraction study on a single crystal of BrWCH(dmpe-d12)2

Carbyne complexes have been extensively studied but only a few of them contain the MC–H moiety (M = transition metal). In order to contribute to the debate about the linearity of this fragment, two neutron diffraction experiments on single crystal have been performed at 100 and 293 K on the trans-W(CH)(dmpe)2Br (dmpe = 1,2-bis(dimethylphosphino)ethane) (1). The results point, without ambiguity, to the linearity of the fragment. The specific behaviour of the dmpe ligand is modelled and interpreted.