Oxidatively induced reactions of a diimine platinum(IV) tetramethyl complex

The oxidation of the Pt(IV) tetramethyl complex [ArNCHCHNAr]PtMe₄ (Ar = 2,6-Me₂C₆H₃) has been investigated in acetonitrile and dichloromethane. Cyclic voltammetry demonstrates that the irreversible oxidation of [ArNCHCHNAr]PtMe₄ occurs at a slightly less positive oxidation potential than the irreversible oxidation of the analogous Pt(II) species [ArNCHCHNAr]PtMe₂. The product distribution arising from the oxidation depends strongly on the reaction conditions and includes cationic Pt(IV) species (acetonitrile, dichloromethane solvents) and Pt(II) species (dichloromethane only). Evidence is presented that suggests that homolytic cleavage of a weakened PtC bond in is involved in the oxidatively induced reactions.     

Further reactions of some bis(vinylidene)diruthenium complexes

Whereas {Ru(dppm)Cp*}₂(μ-CCCC) (2) is the only product formed by deprotonation of [{Ru(dppm)Cp*}₂{μ(CCHCHC)}]⁺ with dbu, a mixture of 2 with Ru{CCCHCH(PPh₂)₂[RuCp*]}(dppm)Cp* (3) and {Cp*Ru(PPh₂CHCCH-)}₂ (4) is obtained with KOBu^t. A similar reaction with [{Ru(dppm)Cp*}₂{μ(CCMeCMeC)}]⁺ (5) gave Ru{CCCMeCH(PPh₂)₂[RuCp*]}(dppm)Cp* (6). X-ray structures of 4, 5 and 6 confirm the presence of the 1-ruthena-2,4-diphosphabicyclo[1.1.1]pentane moiety, which is likely formed by an intramolecular attack of the deprotonated dppm ligand on C(1) of the vinylidene ligand. Protonation of {Ru(dppe)Cp*}₂(μ-CCCC) (8-Ru) regenerates its precursor [{Ru(dppe)Cp*}₂{μ(CCHCHC)}]²⁺ (7-Ru). Ready oxidation of the bis(vinylidene) complex affords the cationic carbonyl [Ru(CO)(dppe)Cp*]PF₆ (9) (X-ray structure).     

Further chemistry of ruthenium butatrienylidene complexes

Several complexes have been obtained from reactions carried out in early attempts to prepare the diynyl complexes Ru(CCCCR)(dppe)Cp* (R = H, SiMe₃). These have been identified crystallographically as the acyl complex Ru{CCC(O)Me}(dppe)Cp* (3), the cationic imido complex [Ru{CCC(NH₂)Me}(dppe)Cp*]PF₆ (4), the binuclear butenynylallenylidene [{Ru(dppe)Cp*}₂{μ-CCC(OMe)CHCMeCC}]PF₆ (5), and the bis(ethynyl)cyclobutenylidene [{Ru(dppe)Cp*}₂{μ-CCC₄H₂(SiMe₃)CC}]PF₆ (6). NMR studies of 5 have revealed the existence of two isomers. Plausible routes for their formation from the putative butatrienylidene intermediate [Ru(CCCCH₂)(dppe)Cp*]⁺ (A) are discussed.     

Nickel alkynyl and allenylidene complexes: Synthesis and properties

Copper-catalyzed reaction of [Cp(PPh₃)NiCl] with the terminal alkynes H-CC-C(O)R (R = O-Menthyl, NMe₂, Ph) yields the alkynyl complexes [Cp(PPh₃)Ni-CC-C(O)R]. Subsequent O-methylation with either [Me₃O]BF₄ or MeSO₃CF₃ affords cationic allenylidene complexes, [Cp(PPh₃)NiCCC(OMe)R]⁺X¯ (X = BF₄, SO₃CF₃). N-Alkylation of Cp(PPh₃)Ni-pyridylethynyl complexes likewise gives cationic allenylidene complexes. [Cp(PPh₃)Ni-CC-C(CH)₄N] adds BF₃ at nitrogen. Modification of the ligand sphere in these nickel allenylidene complexes is possible by replacing PPh₃ by PMe₃ in the alkynyl complex precursors. The first allenylidene(carbene)nickel cation, [Cp(SIMes)NCCC(OMe)NMe₂]⁺, is accessible by successive reaction of [Cp(SIMes)NiCl] with H-CC-C(O)NMe₂ and [Me₃O]BF₄. By the analogous sequence an allenylidene complex containing the chelating (diphenylphosphanyl)ethylcyclopentadienyl ligand can be prepared. DFT Calculations were carried out on the allenylidene complex cation [Cp(PPh₃)NiCCC(OMe)NMe₂]⁺ and on its precursor, the alkynyl complex [Cp(PPh₃)Ni-CC-C(O)NMe₂]. Based on the spectroscopic data and a X-ray structure analysis the bonding in the new nickel allenylidene complexes is best represented by several resonance forms, an alkynyl resonance form considerably contributing to the overall bond.     

Organometallic chemistry and catalysis on gold metal surfaces

As in transition metal complexes, CN-R ligands adsorbed on powdered gold undergo attack by amines to give putative diaminocarbene groups on the gold surface. This reaction forms the basis for the discovery of a gold metal-catalyzed reaction of CN-R, primary amines (R′NH₂) and O₂ to give carbodiimides (R′-NCN-R). An analogous reaction of CO, RNH₂, and O₂ gives isocyanates (R-NCO), which react with additional amine to give urea (RNH)₂CO products. The gold-catalyzed reaction of CN-R with secondary amines (HNR′₂) and O₂ gives mixed ureas RNH(CO)NR′₂. In another type of gold-catalyzed reaction, secondary amines HN(CH₂R)₂ react with O₂ to undergo dehydrogenation to the imine product, RCHN(CH₂R). Of special interest is the high catalytic activity of gold powder, which is otherwise well-known for its poor catalytic properties.     

Reactions of β-alkoxyvinyl trihalogenomethyl ketones with triethyl phosphite

The Perkow reaction of triethyl phosphite and β-alkoxyvinyl trihalogenomethyl ketones, which have common acyclic or cyclic structural fragment: -O-CC-C(O)CX₂Cl, yielded dienyl phosphates: -O-CC-C[OP(O)(OEt)₂]CX₂ where X = F or Cl, whereas γ-bromo-β-methoxy-α,β-unsaturated trifluoromethyl ketone CF₃C(O)CHC(OMe)CH₂Br gave diene CF₃C[OP(O)(OEt)₂]CH-C(OMe)CH₂.     

The first evidence for a transient stibaallene ArSbCCR2

Dechlorofluorination of ArSb(F)-C(Cl)CR₂ (CR₂ = fluorenylidene, Ar = 2,4,6-tri-tert-butylphenyl) by tert-butyllithium afforded a 3,4-bis(fluorenylidene)-1,2-distibacyclobutane. The formation of the latter probably involves the transient stibaallene ArSbCCR₂ followed by a head-to-head dimerization via two SbC double bonds. Molecular orbital calculations at the ab initio and DFT levels support the head-to-head dimerization of ArSbCCR₂ with the formation of a 1,2-distibacyclobutane.     

From alkenylphosphane aminoallenylidene ruthenium(II) complexes to highly unsaturated ruthenaphosphabicycloheptene complexes

The alkenylaminoallenylidene complex [Ru(η⁵-C₉H₇){CCC(NEt₂)[C(Me)CPh₂]}{κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)][PF₆] (2) has been prepared by the reaction of the allenylidene [Ru(η⁵-C₉H₇)(CCCPh₂){κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)][PF₆] (1) with the ynamine MeCCNEt₂. The reaction proceeds regio- and stereoselectively, and the insertion of the ynamine takes place exclusively at the C_βC_γ bond of the unsaturated chain. The secondary allenylidene [Ru(η⁵-C₉H₇){CCC(H)[C(Me)CPh₂]}{κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)][PF₆] (3) is obtained, in a one-pot synthesis, from the reaction of aminoallenylidene 2 with LiBHEt₃ and subsequent treatment with silica. Moreover, the addition of an excess of NaBH₄ to a solution of the complex 2 in THF at room temperature gives exclusively the alkynyl complex [Ru(η⁵-C₉H₇){CCCH₂[C(Me)CPh₂]}{κ(P)-Ph₂PCH₂CHCH₂}(PPh₃)] (5). The heating of a solution of allenylidene derivative 3 in THF at reflux gives regio- and diastereoselectively the cyclobutylidene complex [Ru(η⁵-C₉H₇) (PPh₃)][PF₆](4) through an intramolecular cycloaddition of the CC allyl and the C_αC_β bonds in the allenylidene complex 3. The structure of complex 4 has been determined by single crystal X-ray diffraction analysis.     

A ruthenium(II) allenylidene complex with a 4,5-diazafluorene functional group: A new building-block for organometallic molecular assemblies

The synthesis of the new ruthenium(II) allenylidene complex [ClRu(dppe)₂CCC₁₁H₆N₂][OTf] (4) (dppe = 1,2-bis(diphenylphosphino)ethane) terminated with a 4,5-diazafluorene ligand is reported. Further coordination of that metal allenylidene to ruthenium and rhenium moieties leads to the bimetallic adducts [ClRu(dppe)₂CCC₁₁H₆N₂{Ru(bpy)₂}][B(C₆F₅)₄]₃ (5a), [ClRu(dppe)₂CCC₁₁H₆N₂{Ru(^tBu-bpy)₂}][PF₆]₃ (5b) and [ClRu(dppe)₂CCC₁₁H₆N₂{Re(CO)₃Cl}][OTf] (6). Their optical and electrochemical properties show that the allenylidene moiety is an attractive molecular clip for the access to larger original redox-active homo/heteronuclear multi-component supramolecular assemblies. The X-ray crystal structure of the allenylidene metal building block is also described.     

Bis(amino)allenylidene complexes by displacement of the MeO group in methoxy allenylidene complexes of chromium and tungsten. Synthesis, DFT calculations and solid-state structures of new bis(amino)allenylidene complexes

Pentacarbonyl dimethylamino(methoxy)allenylidene tungsten, [(CO)₅WCCC(OMe)NMe₂] (1b), reacts with one equivalent of primary amines, H₂NR, by selectively replacing the methoxy group to give dimethylamino(amino)allenylidene complexes, [(CO)₅WCCC(NHR)NMe₂]. When the amine is used in excess both terminal groups, OMe as well as NMe₂, are replaced by the primary amino group giving [(CO)₅WCCC(NHR)₂ ]. The NHR substituent in these complexes may be modified by deprotonation with LDA followed by alkylation. The replacement of the methoxy group in 1b by a secondary amino group, NR₂, can be achieved by a stepwise process. Addition of Li[NR₂] to the C_γ atom of 1b affords an alkynyl tungstate. Subsequent OMe⁻ elimination induced by TMS-Cl/SiO₂ yields the allenylidene complexes [(CO)₅WCCC(NR₂)NMe₂]. When bidentate diamines are used instead of monoamines both substituents, OMe and NMe₂, are replaced and allenylidene complexes are formed in which C_γ constitutes part of a 5-, 6-, or 7-membered heterocycle. The reaction of [(CO)₅CrCCC(OMe)NMe₂] (1a) with diethylene triamine affords an allenylidene complex with a heterocyclic endgroup carrying a dangling CH₂CH₂NH₂ substituent. All reactions follow a strict regioselective attack of the nucleophile at C_γ and proceed with good to excellent yields. The addition of N-H to the C_αC_β bond is not observed. By applying either one of these routes nearly any substitution pattern in bis(amino)allenylidene complex can be realized.     

Polyfluoroaromatic compounds with a NCClR group—a reactive type of polyfluoroarene

This review deals with syntheses and reactivity of polyfluoroarenes with a NCClR group (including those with RCl). The most promising and convenient methods of synthesis of these type compounds are based on co-pyrolysis reactions of low-basic polyfluoroaromatic amines with RCCl₃ type derivatives and the interaction of such amines and polyfluoroaromatic hydrazines with RCX₃ (XCl,F) compounds in the presence of AlCl₃ at moderate temperature; they have no analogues in the nonfluorinated series. Reactions with different nucleophilic reagents, the formation of electrophilic intermediates of the nitrilium cation type and reactions of the latter with aromatic and fluoroaromatic hydrocarbons, amines, and compounds with CN, C≡N and CO multiple bonds are described. It is shown that polyfluoroaromatic compounds with a NCClR group are promising precursors for syntheses of a wide range of compounds of various classes, including heterocyclic derivatives.     

Triosmium compounds containing the oxametallacycle [Os(CO)3{C(R)CHC(O)CHC(H)C5H4FeC5H5}] moiety. Synthesis and electrochemical studies

The compounds [Os₃(CO)₁₀{μ,η³-(SCH₂CH₂SCCHC(O)CHCH(C₅H₄)Fe (C₅H₅)}] (2), [Os₃(CO)₉{μ,η³-(SCH₂CH₂SCCHC(O)CHCH(C₅H₄)Fe(C₅H₅)}] (3) and [Os₃(CO)₈{μ₃,η²-{CCHC(O)CHCH(C₅H₄)Fe(C₅H₅)}(SCH₂CH₂S)}] (4) have been obtained by rupture of S-C bonds in the ketene dithioacetal [C₅H₅FeC₅H₄CHCHC(O)CHC(SCH₂CH₂S)], in their reaction with the activated cluster [Os₃(CO)₁₀(NCMe)₂]. The presence of an oxametallacycle in these derivatives has been confirmed by an X-ray diffraction analysis. The electrochemical study has indicated the ability of these compounds to modify the electrode surfaces.     

Formation of a cyclobutenylidene by cyclo-addition of an alkynyl-ruthenium complex to a cyano(alkynyl)ethene

In contrast to the usual formal [2+2]-cycloaddition reaction, (NC)₂CC{CC(SiPrⁱ₃)}₂, containing bulky alkynyl substituents, reacts with Ru(CCPh)(PPh₃)₂Cp to give the unprecedented cyclobutenylidene complex Ru{C(CN)₂C[CC(SiPrⁱ₃)]CC(SiPrⁱ₃)CPhC}(PPh₃)Cp, formed by addition of one of the CC(SiPrⁱ₃) groups to the Ru-CCPh moiety and subsequent electronic reorganisation.     

Preparation of E-(1,2-difluoro-1,2-ethenediyl)bis(tributylstannane)

Chlorotrifluoroethene is converted in situ to [F₂CCFSiMe₃]. The crude [F₂CCFSiMe₃] solution is reduced with lithium aluminum hydride to (HFCCFSiMe₃), which (without isolation) is converted to (Z)-HFCCFSnBu₃. Subsequent metallation and trapping of the vinyllithium reagent with Bu₃SnCl gives (E)-Bu₃SnCFCFSnBu₃ in 73% overall yield. Only two isolation steps are required and the use of Me₃SiCl and F₂CCFCl provides a cheap, economical route to this useful synthon.     

Iodo-alkynyl- and iodo-butadiynyl-ruthenium complexes

Addition of [I(py)₂]BF₄ to Ru(CCH)(dppe)Cp∗ gave the iodovinylidene [Ru(CCHI)(dppe)Cp∗]BF₄1, which could be deprotonated to Ru(CCI)(dppe)Cp∗ 2. The attempted preparation of Ru(CCCCI)(dppe)Cp∗, followed by derivatisation with tcne, gave the dienynyl Ru{CCC[C(CN)₂]CIC(CN)₂}(dppe)Cp∗ 3. The Pd(0)/Cu(I)-catalysed reaction of 3 with Ru{CCCCAu(PPh₃)}(dppe)Cp∗ afforded Ru{CCCC(CN)₂CC(CN)₂Au(PPh₃)}(dppe)Cp∗ 4 by formal replacement of I⁺ by [Au(PPh₃)]⁺. XRD structures of 1-4 are reported.     

Protonation of manganese phosphonioallenyl complexes

The addition of phosphines to the manganese allenylidene complexes Cp(CO)₂MnCCC(Ph)R (R = H, Ph) proceeds selectively at the C_α atom to result in the α-phosphonioallenyl complexes Cp(CO)₂Mn⁻-C(⁺PR₃¹)CC(Ph)R. The protonation of the latter affords the η²-(1,2)-phosphonioallenes Cp(CO)₂Mn{η²-(1,2)-HC(⁺PR₃¹)CC(Ph)R}, rather than the phosphoniovinylcarbenes Cp(CO)₂MnC(⁺PR₃¹)-HCC(Ph)R. All complexes obtained are stereochemically rigid and do not isomerize into the η²-(2,3)-phosphonioallene isomers.     

Direct addition of supercritical alcohols, acetone or acetonitrile to the alkenes without catalysts

The reactions of the alkenes with supercritical organic compounds under non-catalytic conditions were investigated. The H and CR₂OH, CH₂COCH₃ or CH₂CN of supercritical alcohols (CHR₂OH), acetone (CH₃COCH₃) or acetonitrile (CH₃CN) added to the CC bonds of alkenes form C-C bonds between the α-carbons of the supercritical organic compounds and the sp² carbons of the alkenes.     

Synthesis and properties of conjugated bimetallic ruthenium complexes with σ,σ-bridging azobenzene chains

A versatile synthetic route to conjugated bimetallic ruthenium complexes with σ,σ-bridging azobenzene chains was developed, and new ruthenium complexes with various ligands were synthesized and characterized. These bimetallic complexes showed a remarkable absorption in the visible region (λ_max: 452-483 nm), and undergo trans-to-cis isomerization under UV light irradiation for short time. Electrochemical study showed that the metal centers in bimetallic complexes containing the CHCHC₆H₄NNC₆H₄CHCH bridge interact with each other.     

Synthesis and characterisation of a diphosphaalkene, a diphosphaalkyne and the first diphosphavinyl lithium complex

The preparation and characterisation of a diphosphaalkene, (Me₃Si)PC(OSiMe₃){C(C₂H₄)₃C}C(OSiMe₃)P(SiMe₃), and the second example of a diphosphaalkyne, PC{C(C₂H₄)₃C}CP, are described. In addition, the reaction of another diphosphaalkyne, PC{C(C₆H₄)₃C}CP, with MeLi/LiBr in the presence of tmeda has given the first diphosphavinyl lithium complex, [MePC{Li₂Br(tmeda)₂}{C(C₆H₄)₃C}C{Li₂Br(tmeda)₂}PMe], which is stable at room temperature and has been crystallographically characterised.