ÜbergangsmetallCarbin-Komplexe: LXXXVI. Synthese mono-, bis-, und tris-Trimethylphosphan-substituierter Diethylaminocarbin-Komplexe des Wolframs

The reaction of trans-I(CO)₄WCNEt₂ (I) with a slight excess of PMe₃ results in the replacement of one carbonyl group to give mer-I(CO)₃(PMe₃)WCNEt₂ (II). Complex II reacts at room temperature with additional PMe₃ under CO replacement to give a mixture of cis- and trans-dicarbonyl-I(CO)₂(PMe₃)₂WCNEt₂ (III, IV). Complexes III and IV, which can be separated by column chromatography, isomerize slowly at room temperature, the thermodynamic equilibrium favouring the more stable trans complex IV. The cis isomer III can be obtained from I(CO)₂py₂WCNEt₂ (V) and PMe₃. Another CO ligand can be eliminated from III or IV by an excess of PMe₃ in boiling hexane and gives mer-I(CO)(PMe₃)₃WCNEt₂ (VI). Moreover complex VI can be prepared by oxidative decarbonylation from III or IV by iodine and subsequent reduction of the intermediate, an isolable, seven-coordinated carbyne complex formulated as (I)₃(CO)(PMe₃)₂WCNEt₂ (VII), by two equivalents of PMe₃.     

Intramolecular rearrangement of the bridging σ,π-acetylide ligand in the Os3H(CO)9(L)(μ-η2-CCPh) (L = CO,PMe2Ph) clusters and crystal structure of Os3H(CO)9(PMe2Ph)(μ-η2-CCPh)

Clusters Os₃H(Cl)(CO)₉(L) (L= CO, PMe₂Ph) react with lithium phenyl-acetylide to yield Os₃H(CO)₉(L)(μ-η²-CCPh),which has a bridging acetylide ligand. The Os₃H(CO)₁₀(μ-η²-CCPh) complex (II) is fluxional owing to rapid π → σ, σ → π interchange of acetylide ligand between the bridged osmium atoms, whereas the phosphine-substituted derivative, Os₃H(CO)₉(PM₂Ph)(μ-η²-CCPh) (III), is stereochemically rigid and exists at room temperature in two isomeric forms. These isomers have been isolated as solids and have been characterized by ¹H and ³¹P{¹H} NMR spectroscopy. According to the spectroscopic data, in the major (IIIa) and minor (IIIb) isomers the phosphine ligand is coordinated to the metal atom which is σ- or π-bonded to the bridging acetylide group, respectively. The isomerization of IIIb into IIIa occurs only at 80°C. The structure of IIIa has been confirmed by an X-ray diffraction study.     

Studies on nucleophilic additions at bridging vinyl ligands in triosmium clusters

The bridging vinyl clusters [HOs₃(CHCHR)(CO)₁₀] (R = H, Ph, or n-Bu) react with PMe₂Ph to give the zwitterionic adducts [HOs₃(CHCHRPMe₂Ph)(CO)₁₀] which contain μ₂-alkylidene ligands. The adducts are not formed so readily when R = Ph or n-Bu but most readily when polar solvents are used. All three CHCHR complexes add cyanide ion irreversibly to give the anionic clusters which were isolated as [N(PPh₃)₂][HOs₃(CHCHRCN)(CO)₁₀]. There is infrared evidence for the addition of various other anions. Acid reverses the addition of methoxide but HCl reacts with the cyanide adduct [HOs₃(CHCH₂CN)(CO)₁₀]^? to give [HOs₃Cl(CO)₁₀] and EtCN. No evidence for nucleophilic addition at [HOs₃(PhCCHPh)(CO)₁₀] was obtained.     

Coordination,oligomerisation and transfer hydrogenation of acetylenes by some ruthenium and osmium carboxylates: Crystal and molecular structures of bis(trifluoroacetato)carbonyl-(methanol) bis(triphenylphosphine)ruthenium(II) and (1,4-diphenylbut-1-en-3-yn-2-yl)trifluoroacetato-(carbonyl) bis(triphenylphosphine)ruthenium(II)

The hydrides [MH(O₂CCF₃)(CO)(PPh₃)₂] (M = Ru or Os) react with disubstituted acetylenes PhCCPh and PhCCMe to afford vinylic products [M{C(Ph)CHPh}(O₂CCF₃)(CO)(PPh₃)₂] and [M{C(Ph)CHMe}(O₂CCF₃)(CO) (PPh₃)₂]/[M{C(Me)CHPh}(O₂CCF₃)(CO)(PPh₃)₂] respectively. Acidolysis of these products with trifluoroacetic acid in cold ethanol liberates cis-stilbene and cis-PhHCCHMe respectively thus establishing the cis-stereochemistry of the vinylic ligands. The complexes [M(O₂CCF₃)₂(CO)(PPh₃)₂] formed during the acidolysis step undergo facile alcoholysis followed by β-elimination of aldehyde to regenerate the parent hydrides [MH(O₂CCF₃)(CO)(PPh₃)₂] and thereby complete a catalytic cycle for the transfer hydrogenation of acetylenes. The molecular structure of the methanol-adduct intermediate, [Ru(O₂CCF₃)₂(MeOH)(CO)(PPh₃)₂] has been determined by X-ray methods and shows that the coordinated methanol is involved in H-bonding with the monodentate trifluoroacetate ligand [MEO-H---OC(O)CF₃; O...O = 2.54 Å]. The hydrides [MH(O₂CCF₃)(CO) (PPh₃)₂]react with 1,4-diphenylbutadiyne to afford the complexes [M{C(CCPh)CHPh} (O₂CCF₃)(CO)(PPh₃)₂]. The ruthenium product, which has also been obtained by treatment of [RuH(O₂CCF₃)(CO)(PPh₃)₂] with phenylacetylene, has been shown by X-ray diffraction methods to contain a 1,4-diphenylbut-1-en-3-yn-2-yl ligand. The osmium complexes [Os(O₂CCF₃)₂(CO)(PPh₃)₂], [OsH(O₂CCF₃)(CO)(PPh₃)₂] and [Os{C(CCPh)CHPh}(O₂CCF₃)(CO)(PPh₃)₂] all serve as catalysts for the oligomerisation of phenylacetylene. Acetylene reacts with [Ru(O₂CCF₃)₂(CO)(PPh₃)₂] in ethanol to afford the vinyl complex [Ru(CHCH₂)(O₂CCF₃)(CO)(PPh₃)₂].     

Vinylidene complexes of transition metals : III. Derivatives of cyclopentadienyltricarbonyl rhenium with phenylvinylidene ligands. Crystal and molecular structure of Cp(CO)2Re[CC(Ph)C(Ph)CH2]Re(CO)2Cp

The novel complexes CpRe(CCHPh)(CO)₂ and Cp₂Re₂(μ-CCHPh)(CO)₄ containing a terminal and a bridging phenylvinylidene ligand respectively and the binuclear complex Cp(CO)₂Re[CC(Ph)C(Ph)CH₂]Re(CO)₂Cp were obtained in the reaction of CpRe(CO)₃ with PhCCH.According to an X-ray study of the latter complex the unusual bridging ligand is η¹-bonded to one Re atom and η²-bonded to the other.     

Synthesis and Characterization of Rhenabenzyne Complexes

Reactions of [ReH₅(PMe₂Ph)₃] with alkynols HC≡CC(OH)(R)C≡CSiMe₃ (R=tBu, iPr, 1‐adamantyl) in the presence of HCl give the vinylcarbyne complexes [Re{≡CCH?C(R)C≡CSiMe₃}Cl₂(PMe₂Ph)₃], which react with tBuMgCl to give [Re{≡CCH?C(R)C≡CSiMe₃}HCl(PMe₂Ph)₃]. Treatment of [Re{≡CCH?C(R)C≡CSiMe₃}HCl(PMe₂Ph)₃] with nBu₄NF gives [Re{≡CCH?C(R)C≡CH}HCl(PMe₂Ph)₃], which first isomerizes to the bicyclic complexes [Re{CH?CH? C(R)?CCH?}Cl(PMe₂Ph)₃], and then to the rhenabenzynes [Re{≡CCH?C(R)CH?CH}Cl(PMe₂Ph)₃]. The NMR spectroscopic and structural data as well as the aromatic stabilization energy (ASE) and nucleus‐independent chemical‐shift (NICS) values suggest that these rhenabenzynes have aromatic character.     

Exploring possible reaction pathways for the o‐atom transfer reactions to unsaturated substrates catalyzed by a [Ni‐NO2] ↔ [Ni‐NO] redox couple using DFT methods

The (nitro)(N‐methyldithiocarbamato)(trimethylphospane)nickel(II), [Ni(NO₂)(S₂CNHMe)(PMe₃)] complex catalyses efficiently the O‐atom transfer reactions to CO and acetylene. Energetically feasible sequence of elementary steps involved in the catalytic cycle of the air oxidation of CO and acetylene are proposed promoted by the Ni(NO₂)(S₂CNHMe)(PMe₃)] ↔ Ni(NO₂)(S₂CNHMe)(PMe₃) redox couple using DFT methods both in vacuum and dichloromethane solutions. The catalytic air oxidation of HC≡CH involves formation of a five‐member metallacycle intermediate, via a [3 + 2] cyclo‐addition reaction of HC≡CH to the Ni‐N = O moiety of the Ni(NO₂)(S₂CNHMe)(PMe₃)] complex, followed by a β H‐atom migration toward the C_α carbon atom of the coordinated acetylene and release of the oxidation product (ketene). The geometric and energetic reaction profile for the reversible [Ni( ‐NO₂)(S₂CNHMe)(PMe₃)] [Ni( ‐ONO)(S₂CNHMe)(PMe₃)] linkage isomerization has also been modeled by DFT calculations. © 2017 Wiley Periodicals, Inc.     

Modification of the acid-base properties of hydroxycarbonyl complexes of iridium(III) by substitution of carbon monoxide by a tertiary phosphine ligand

A dichloromethane solution of the cationic carbonyl complex [IrCl₂(CO)(PMe₂Ph)₃)][ClO₄] reacts with aqueous KOH to give [IrCl₂(CO₂H)(PMe₂Ph)₃] which has been characterised spectroscopically. This CO₂H compound is very much more basic and very much less acidic than [IrCl₂(CO₂H)(CO)(PMe₂Ph)₂). Tertiary amines will not deprotonate [IrCl₂(CO₂H)(PMe₂Ph)₃] while Li[N(SiMe₃)₂] leads to decarboxylation products trans, mer- and cis, mer-[IrHCl₂(PMe₂Ph)₃]. The mechanisms of these reactions are considered and the hydroxycarbonyl complex is compared with its formato isomer which decarboxylates much less readily.     

The protonation and hydrogen transfer processes in alkene and alkyne derivatives of Os3 and H2Os3(CO)10

The complexes H₃O_s3(CO)₉CMe, H₂O_s3(CO)₁₀, H₂O_s3(CO)₉L (L = PEt₃, PPh₃ or AsPh₃), HO_s3(CO)₁₀CHC(H)Ph, and O_s3(CO)₁₀HC₂Me undergo protonation in acid to yield [H₄O_s3(CO)₉CMe]⁺ and [H₄O_s3(CO)₁₀]²⁺, [H₃O_s3(CO)₉L]⁺, [H₂O_s3(CO)₁₀CHC(H)Ph]⁺ and [HO_s3(CO)₁₀HC₂Me]⁺, respectively. The structure of these ions and their hydrido-ligand transfer reactions are described.     

Molecular structure of π-C5H5NiFe(CO)3Ph3PCCH

The mixed metal complex π-C₅H₅NiFe(CO)₃Ph₃PCCH, obtained from the reaction of π-C₅H₅Ni(PPh₃)CCH with Fe₂(CO)₉, is shown by an X-ray diffraction study to contain the ethynyltriphenylphosphonium group as the bridging ligand. Based on this structure, new reactions of [Ph₃PCCPh]Br with some organometallic compounds have been attempted from which π-C₅H₅NiFe(CO)₃(Ph₃PC₂Ph) and CoFe(CO)₆(Ph₃PC₂Ph) can be obtained.     

Announcement

[Ru(2–6-η-bicyclo[5.1.0]octadienyl)(PMe₂Ph)₃][PF₆], formed from the reaction of cyclooctatetraene with [RuH(COD)(PMe₂Ph)₃][PF₆] (COD = cycloocta-1,5-diene), has been characterised spectroscopically from ¹J(CH) coupling constants and an X-ray structural analysis; the bicyclic ligand contains an elongated bridging CC bond (1.63 Å).     

Voltammetric behaviour of rhenium(I) complexes with phosphine and carbon monoxide ligands in acetonitrile solvent

Summary The anodic and cathodic behaviour of the complexesmer-[ReCl(CO)₃(PMe₂Ph)₂],fac[ReCl(CO)₃(PMe₂Ph)₂],mer-[ReCl(CO)₃(PPh₃)₂], and [ReCl(CO)₂(PMe₂Ph)₃] in acetonitrile solvent were studied using platinum and mercury electrodes. Cyclic voltammetry and controlled potential coulometry were the main electroanalytical techniques employed. The nature of the electrolysis products and of the electrode oxidation and reduction processes were investigated. In particular, [ReCl(CO)(MeCN)₂(PMe₂Ph)₃][ClO₄]₂, [ReCl₃(CO)₂(PMe₂Ph)₂], and a not completely defined rhenium(-I) complex were electrochemically synthesized and characterized by means of i.r. and¹H n.m.r. spectroscopy, and by elemental analysis.     

Electron‐Rich Diferrous–Phosphane–Thiolates Relevant to Fe‐only Hydrogenase: Is Cyanide “Nature's Trimethylphosphane”?

The two‐step one‐pot oxidative decarbonylation of [Fe₂(S₂C₂H₄)(CO)₄(PMe₃)₂] ( 1 ) with [FeCp₂]PF₆, followed by addition of phosphane ligands, led to a series of diferrous dithiolato carbonyls 2 – 6 , containing three or four phosphane ligands. In situ measurements indicate efficient formation of 1 ²⁺ as the initial intermediate of the oxidation of 1 , even when a deficiency of the oxidant was employed. Subsequent addition of PR₃ gave rise to [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₃(PMe₃)₃]²⁺ ( 2 ) and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₂(PMe₃)₂(PR₃)₂]²⁺ (R=Me 3 , OMe 4 ) as principal products. One terminal CO ligand in these complexes was readily substituted by MeCN, and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)₂(PMe₃)₃(MeCN)]²⁺ ( 5 ) and [Fe₂(S₂C₂H₄)(μ‐CO)(CO)(PMe₃)₄(MeCN)]²⁺ ( 6 ) were fully characterized. Relevant to the H_red state of the active site of Fe‐only hydrogenases, the unsymmetrical derivatives 5 and 6 feature a semibridging CO ligand trans to a labile coordination site.     

Coordinatively unsaturated alkyne complexes: synthesis of mono and bis-alkyne complexes of tungsten (II)

[WBr₂(CO₄]_n reacts with alkynes to give complexes [WBr₂CO(RCCR)₂]₂ (1) (R = R′ = Me, Et, Ph; R = Me, R′ = Ph), which react with nucleophiles L{L = CNBu^t, PPh₃, or P(OMe)₃} to give monoalkyne derivatives (WBr₂(CO)(RCCR′)L₂](2). An intermediate bis-alkyne adduct [WBr₂CO(MeCCMe)₂(CNBu^t)] (3) was isolated in the reaction of [WBr₂CO(MeCCMe)₂]₂ with CNBu^t illustrating that cleavage of the dimer (1) is the first stage in these reactions.     

Protonation of Cp(CO)(PPh3) RuCCPh: Formation of cationnic phenylacetylene and phenylvinylidene complexes and subsequent reaction with ethylene oxide to form the net [2 + 3] cycloadduct [Cp(CO)(PPH3)Ru=CCH(Ph)CH2CH2O]+

Protonation of the alkynyl complex Cp(CO)(PPh₃)RuCCPh (1) at low temperature affords quantitatively the vinylidened complex [Cp(CO)(PPh₃)RuCCH(Ph)]⁺ (3), which upon warming to room temperature forms an equilibrium with the η²-phenylacetylene complex [Cp(CO)(PPh₃)Ru(η²-HCCPh)]⁺ (4), with the latter predominating. Subsequent reaction with ethylene oxide yields the cyclic oxacarbene complex [Cp(CO)(PPH₃)Ru=CCH(Ph)CH₂CH₂O]⁺ (5), which can be regarded as the result of a net [3+2] cycloaddition reaction between 3 and ethylene oxide. Depronation of 5 affords teh corresponding neutral cyclic vinyl complex [Cp(CO)(PPH₃)RuC=C(Ph)CH₂CH₂O]⁺ (6), which can in turn be protonated to regenerate 5 in a diastereoselective manner. The structures of complexes 5 and 6 were determined by X-ray crystallography.     

Some studies of the reaction of μ-dichlorotetracarbonyldirhodium with dimethylphenylphosphine

The addition of PMe₂Ph to solutions of Rh₂Cl₂(CO)₄ has been studied by infrared and ¹H NMR spectroscopy, by measurement of conductance and of the carbon monoxide evolved. Under an atmosphere of CO the dominant course of the reaction is chloride bridge cleavage followed by CO substitution, whereas in refluxing cyclohexane substitution occurs initially. The formation of RhCl(CO)(PMe₂Ph)₂ on addition of PMe₂Ph (2 mol/mol Rh) is independent of solvent whereas addition of more tertiary phosphine leads to very different behaviour, depending upon the solvent and whether the solution is under CO or N₂. ¹H NMR studies show that all species with no more than one PMe₂Ph coordinated to a rhodium atom are in rapid equilibrium leading to averaged NMR signals.     

η2-dithiomethyliron(II) ionic complexes. Evidence for a strong dependence on the nature of the trans-phosphorus ligands bonded to iron

Cationic η²-dithiomethyliron(II) complexes have been made by alkylation of the uncoordinated sulfur atom of Fe(CO)₂[η²-CS₂](L)₂. Surprisingly, only when the phosphorus ligands L are strong donors (PMe₃, PMe₂Ph) does coordination of iodide take place to give the neutral Fe(η²-CS₂CH₃)(I)(CO)(L)₂ derivatives. The ¹³C NMR spectra of the latter at 215 K indicated the presence of both isomers when L was PMe₂Ph. Reaction with iodine under carbon monoxide regenerated the cationic precursor.     

Synthesis and Reactivity of Molybdenum and Tungsten Alkyne Complexes Containing 6-Methylpyridine-2-thiolate Ligands

A series of M(II) and M(IV) (M=Mo, W) alkyne adducts employing two 6-methylpyridine-2-thiolate (6-MePyS) ligands was synthesized and investigated towards the nucleophilic attack of PMe₃ on the coordinated alkynes. For this approach, 2-butyne (C₂Me₂), phenylacetylene (HC₂Ph), and diphenylacetylene (C₂Ph₂) were used. For the exploration of an intramolecular attack, but-3-yn-1-ol (HCCCH₂CH₂OH) was coordinated to the metal centers. A nucleophilic attack of PMe₃ was observed in [W(CO)(HC₂Ph)(6-MePyS)₂] yielding an η²-vinyl compound. Reaction of [W(CO)(C₂Ph₂)(6-MePyS)₂] with excess PMe₃ resulted in the selective coordination of one molecule of PMe₃ concomitant with decoordination of the nitrogen atom of one 6-MePyS ligand. In contrast, the W(IV) complexes did not react with PMe₃. While no selectivity was observed in the reaction of the Mo(II) compounds with PMe₃, alkynes in the Mo(IV) compounds were replaced by PMe₃. Addition of Et₃N to the but-3-yn-1-ol complexes did not lead to the anticipated formation of 2,3-dihydrofuran.     

Facile synthesis and reactivity of CO-free monocyclopentadienylvanadium(I) alkyne complexes

Reactive CO-free monocyclopentadienylvanadium(I) complexes CpV(η²-RCCR′)(PMe₃)₂ (R,R′ = Ph,Ph; Ph,Me; Et,Et) can be synthesized by Mg reduction of CpVCl₂(PMe₃)₂ in the presence of free alkyne. Reaction with a second alkyne, or use of diynes in the reduction, produces metallacycles with the metallacyclopentatriene structure.     

Reactions of nitrilium triflate salts with trans-[IrCl(CO)(PPh3)2

Low yields of the ionic carbene complexes [Ir(RCNHMe)Cl(CO)(PPh₃)₂-(O₃SCF₃)]O₃SCF₃]O₃SCF₃ (R  Ph or PhCH₂) have been isolated from the reactions of trans-[IrCl(CO)(PPh₃)₂] with the nitrilium triflate salts, [RCNMe]O₃SCF₃. The major products from these, and the similar reactions of the nitrilium salts where R  Me or Bu^t, are amorphous, yellow complexes [Ir(RCNHMe)Cl(CO)(PPh₃)₂O₃SCF₃.