RESUMEN
Bimetallic Ru-Ir/Rh complexes with the Ru-based metalloligand cis-(bpy)2Ru(PPh2)2 (RuP2) serve as catalysts for the selective reduction of allyl alcohol to propylene, employing H2 gas or an electrochemical setup. Metal-metal bonded key π-allyl intermediates [(RuP2)M(η3-C3H5)]2+ (M = Ir, Rh) are identified, advancing the understanding of the catalytic processes.
RESUMEN
The formation of linear hydrocarbon chains by sequential coupling of C1 units on the metal surface is the central part of the Fischer-Tropsch (F-T) synthesis. Organometallic complexes have provided numerous models of relevant individual C-C coupling events but have failed to reproduce the complete chain lengthening sequence that transforms a linear Cn hydrocarbon chain into its Cn+1 homologue in an iterative fashion. In this work, we demonstrate stepwise growth of linear Cn hydrocarbon chains and their conversion to their Cn+1 homologues via consecutive addition of CH2 units on a molecular diruthenium carbide platform. The chain growth sequence is initiated by the formation of a µ-η1:η1-CâCH2 ligand from a C + CH2 coupling between the µ-carbido complex [(Cp*Ru)2(η-NPh)(µ-C)] (1; Cp* = η5-C5Me5) and Ph2SCH2. Then, the chain propagates via a general CâCHR + CH2 coupling and subsequent hydrogen-assisted isomerization of the resulting allene ligand µ-η1:η3-H2CâCâCHR to a higher vinylidene homologue µ-η1:η1-CâCH(CH2)R. By repeating this reaction sequence, up to C6 chains have been synthesized in a stepwise fashion. The key step of this chain homologation sequence is the selective hydrogenation of the µ-η1:η3-allene unit to the corresponding µ-alkylidene ligand. Isotope labeling and computational studies indicate that this transformation proceeds via the hydrogenation of the allene ligand to a terminal alkene form and its isomerization to the µ-alkylidene ligand facilitated by the coordinatively unsaturated diruthenium platform.
RESUMEN
The reaction of [Cp*Ru(µ-NHPh)]2 (Cp* = η5-C5Me5) with Lewis acids of the type MX2 (M = Zn, Sn, Pb; X = Cl, OTf) affords Ru2 â M donor-acceptor adducts characterized as π complexes of a Ru[double bond, length as m-dash]Ru double bond with M(ii) Lewis acids. The results illustrate for the first time the ability of σ-acceptor Lewis acid ligands to induce the formation of a metal-metal multiple bond via stabilizing dative interactions.
RESUMEN
The first phosphido derivative of the bis(bipyridine) ruthenium(ii) fragment, cis-[(bpy)2Ru(PPh2)2] ([RuP2]), has been developed and applied as a P-donor metalloligand to form new Ru-Rh, Ru-Ir and Ru2Cu2 heterometallic complexes. The Ru-Ir hydride complex [([RuP2])IrH(NCMe)3][BF4]2 exhibits significant catalytic activity for (E)-selective semi-hydrogenation of alkynes.
RESUMEN
The first catalytic dehydrative condensation of the benzylic C-H bonds of toluene and p-xylene with aromatic aldehydes is reported herein. This protocol provides highly atom-economical access to stilbene and p-distyrylbenzene derivatives, whereby water is the sole byproduct. The reaction is based on the deprotonation-functionalization of benzylic C-H bonds through η6-complexation of the arenes, which is realized for the first time using a catalytic amount of a transition metal activator. The key to the success of this method is the use of a sulfonamide anion as a catalyst component, which appears to facilitate not only the deprotonation of the benzylic C-H bonds but also the formation of a C-C bonds via an electrophilic tosylimine intermediate.
RESUMEN
Low-temperature deprotonation of the cationic µ-methylidyne complex [(Cp*Ru)2(µ-NPh)(µ-CH)][BF4] (Cp* = η(5)-C5Me5) with KN(SiMe3)2 affords a thermally unstable µ-carbido complex [(Cp*Ru)2(µ-NPh)(µ-C)] (2), as evidenced by trapping experiments with elemental S or Se and (13)C NMR spectroscopic observation. The reactivity of 2 toward CO2, Ph2S(+)CH2(-), EtOH, and an intramolecular C-H bond indicates that the µ-carbido carbon in 2 has an ambiphilic (nucleophilic and electrophilic) nature consistent with the formulation of 2 as the first example of a transition-metal-substituted singlet carbene. DFT study suggests that the Ru substituents in 2 are stronger σ-donor and weaker π-donor to the carbene center than amino substituents in N-heterocyclic carbenes.
RESUMEN
Exceedingly facile (23 °C) and chemoselective H-CF3 activation with [(dppp)Pd(Ph)(OH)] in the presence of a Lewis base promoter such as n-Bu3P leads to Pd-CF3 bond formation in nearly quantitative yield. A combined experimental and computational study points to a new mechanism that involves H-bonding Pd-O(H)···H-CF3 and nucleophilic attack of the promoter on the metal, followed by a push-pull-type collapse of the resultant five-coordinate Pd(II) intermediate via a polar transition state.
RESUMEN
Diruthenium imido dihydride complexes [(Cp*Ru)(2)(µ-NAr)(µ-H)(2)] (Ar = Ph (2a), p-MeOC(6)H(4) (2b), p-ClC(6)H(4) (2c), 2,6-Me(2)C(6)H(3) (2d); Cp* = η(5)-C(5)Me(5)) have been synthesized by hydrogenation of the corresponding bis(amido) complexes [Cp*Ru(µ-NHAr)](2) (1a-d). Reductive elimination of the N-H bond from 2a-c in the presence of arene yields the amido hydride complexes [(Cp*Ru)(2)(µ-NHAr)(µ-H)(µ-η(2):η(2)-arene)] containing a π-bound arene. The rate and kinetic isotope effect for this reaction are consistent with a mechanism involving initial rate-determining reductive elimination of an N-H bond to produce the coordinatively unsaturated amido hydride species {(Cp*Ru)(2)(µ-NHAr)(µ-H)} (A) followed by rapid trapping of this species by an arene. The existence of A is also supported by the reversible interconversion of [(Cp*Ru)(2)(µ-NHPh)(µ-H)(µ-η(2):η(2)-C(7)H(8))] with the tetranuclear complex [(Cp*Ru)(4)(µ(4)-NHPh)(µ-NHPh)(µ-H)(2)] (4), a dimerization product of A through a µ(4)-NHPh bridge. DFT calculations provide structures of A and transition states for the N-H reductive elimination. Two distinct reaction pathways are found for the N-H reductive elimination, one of which involves direct migration of a µ-hydride to the µ-NAr ligand, and the other involves formation of a transient terminal hydride species.
Asunto(s)
Hidrógeno/química , Imidas/química , Compuestos Organometálicos/química , Compuestos Organometálicos/síntesis química , Rutenio/química , Cristalografía por Rayos X , Modelos Moleculares , Conformación Molecular , Oxidación-ReducciónRESUMEN
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.
RESUMEN
One-handed helical oligo(p-benzamide)s were induced via the domino effect based on the planar-axial-helical chirality relay triggered by a planar chiral transition-metal complex at the terminal position as the single chiral source.
Asunto(s)
Benzamidas/química , Dicroismo Circular , Cristalografía por Rayos X , Modelos Moleculares , Estructura Molecular , Espectrofotometría , EstereoisomerismoRESUMEN
Dirhodium amido complexes [(Cp*Rh)2(mu2-NHPh)(mu2-X)] (X = NHPh (2), Cl (3), OMe (4); Cp* = eta5-C5Me5) were prepared by chloride displacement of [Cp*Rh(mu2-Cl)]2 (1) and have been used as precursors to a dirhodium imido species [Cp*Rh(mu2-NPh)RhCp*]. The imido species can be trapped by PMe3 to give the adduct [Cp*Rh(mu2-NPh)Rh(PMe3)Cp*] (5) and undergoes a formal [2 + 2] cycloaddition reaction with unactivated alkynes to give the azametallacycles [Cp*Rh(mu2-eta2:eta3-R1CCR2NPh)RhCp*] (R1 = R2 = Ph (6a), R1 = H, R2 = t-Bu (6b), R1 = H, R2 = p-tol (6c)). Isolation of a relevant unsaturated imido complex [Cp*Rh(mu2-NAr)RhCp*] (7) was achieved by the use of a sterically hindered LiNHAr (Ar = 2,6-diisopropylphenyl) reagent in a metathesis reaction with 1. X-ray structures of 2, 6a, 7 and the terminal isocyanide adduct [Cp*Rh(mu2-NAr)Rh(t-BuNC)Cp*] (8) are reported.
RESUMEN
[5]- and [6]helicenes were synthesized in moderate to good yields from Z,Z-bis(bromostilbene)s by palladium-catalyzed double C-H arylation reaction. This method can be applied to the syntheses of helicenes possessing electron-deficient substituents.
Asunto(s)
Compuestos Policíclicos/síntesis química , Catálisis , Paladio/química , Estilbenos/químicaRESUMEN
N-Aryl indoles with axially chiral N-C bonds were synthesized by stereoselective nucleophilic aromatic substitution reactions of planar chiral tricarbonyl(2,6-disubstituted-1-fluorobenzene)chromium complexes. The stereochemistry of the products is highly dependent on the position of the substituent in the indole. When indoles devoid of a substituent at the 2-position were used, N-aryl indole chromium complexes having anti orientation with respect to the tricarbonylchromium fragment were obtained diastereoselectively. In contrast, 2-substituted indoles gave the N-aryl indoles with syn orientation between the tricarbonylchromium fragment and the benzene ring of the indole. These results demonstrate that we have succeeded in synthesizing both enantiomers of N-aryl indoles utilizing an identical planar chiral arene chromium complex.
Asunto(s)
Química Orgánica/métodos , Indoles/síntesis química , Carbono/química , Compuestos de Cromo/química , Indoles/química , Espectroscopía de Resonancia Magnética , Estructura Molecular , Nitrógeno/química , EstereoisomerismoRESUMEN
Methylenecyclopentanones were synthesized by the nickel-catalyzed [3+1+1] cycloaddition reactions of alkenyl Fischer carbene complexes with methylenecyclopropanes. The methylenecyclopropane was transformed into the C(2)-symmetric bis-cyclopentapyridazine derivative by reacting with p-toluenesulfonyl hydrazine.
RESUMEN
A reaction between [CpFeCl]x and LiNHPh (1 equiv to Fe) produces a new paramagnetic Fe(II)-Fe(III) mu2-amido-mu2-imido complex [(CpFe)2(mu2-NHPh)(mu2-NPh)] (1), which, upon interaction with 2,2'-azobis(2,4-dimethylvaleronitrile), undergoes a net N-H hydrogen atom abstraction reaction to give a diamagnetic Fe(III)-Fe(III) mu2-imido dimer [CpFe(mu2-NPh)]2 (2). The molecular structures of 1 and 2 have been determined by single-crystal X-ray diffraction.
RESUMEN
The diruthenium mu2-imido mu2-methylene complex [(Cp*Ru)2(mu2-NPh)(mu2-CH2)] serves as a bifunctional scaffold for cluster synthesis, producing a mu3-imido Ru2Pt cluster [(Cp*Ru)2(mu3-NPh)(mu2-CH2)Pt(PMe3)2] on treatment with [Pt(eta2-C2H4)(PMe3)2] and a mu3-methylidyne Ru4Pd2 cluster [(Cp*Ru)2(mu2-NPh)(mu3-CH)PdCl]2 with [PdMeCl(cod)].
RESUMEN
Treatment of a dinuclear Ru(II) amido complex [Cp*Ru(mu2-NHPh)]2 (Cp* = eta5-C5Me5) with small organic substrates including CO, tert-butyl isocyanide, a sulfur ylide Ph2S=CH2, and diphenylacetylene resulted in an unexpected disproportionation reaction of the bridging amido ligands to produce a free amine and a series of imido-bridged diruthenium complexes [(Cp*Ru)2(mu2-L)(mu2-NPh)] (L = CO, t-BuNC, CH2). In the case of diphenylacetylene, the bridging imido ligand underwent subsequent coupling reaction with the coordinated alkyne to form an iminoalkenyl complex [(Cp*Ru)2(mu2-PhNCPhCPh)].
RESUMEN
A stepwise reaction of p-tert-butylthiacalix[4]arene (TC4A-(OH)(4)) with [CpTiCl3]-NEt(3) and cis-[Mo(N(2))(2)(PMe(2)Ph)(4)] afforded a new Ti-Mo heterobimetallic complex [TC4A-(O)(4)Ti(micro2-C(5)H(5))MoH(PMe(2)Ph)(2)] which shows an unusual alpha-agostic micro2-eta5:eta2-coordination of a cyclopentadienyl ligand.
RESUMEN
The reaction of [NiCl(2)(PMe(2)Ph)(2)] with fc(SH)(2) (fcS(2) = 1,1'-ferrocenedithiolato) afforded the Ni-Fe heterobimetallic complex containing an Fe-->Ni dative bond [Ni(S(2)fc)(PMe(2)Ph)] (1) with concurrent liberation of one of the PMe(2)Ph ligands. In contrast, similar treatment of [MCl(2)(dppe)] (M = Ni, Pd, Pt; dppe = Ph(2)PCH(2)CH(2)PPh(2)) gave a series of group 10 metal-ferrocenedithiolato complexes [M(S(2)fc)(dppe)] (2) which do not contain such a dative bond. Furthermore, oxidation of complexes 2 with 1 equiv of [(eta(5)-C(5)H(5))(2)Fe][PF(6)] resulted in the formation of 1,1'-ferrocenedithiolato-bridged complexes [{M(dppe)}(2)(&mgr;-S(2)fc)][PF(6)](2) (3) along with poly(1,1'-ferrocenylene disulfide). Complexes 2 were also converted into the Fe-Ru-M heterotrimetallic complexes [(p-cymene)RuCl(&mgr;-S(2)fc)M(dppe)][PF(6)] (4; p-cymene = 4-isopropyltoluene) by the reaction of 2 with [(p-cymene)RuCl(2)](2) and NH(4)PF(6) in acetonitrile. The detailed structures of 1, [Ni(S(2)fc)(dppe)] (2a), [Pd(S(2)fc)(dppe)] (2b), [{Ni(dppe)}(2)(&mgr;-S(2)fc)][PF(6)](2) (3a), and [(p-cymene)RuCl(&mgr;-S(2)fc)Ni(dppe)][PF(6)] (4a) have been determined by X-ray crystallography.