Acetylide Cluster Research Articles

Porphyrin-silver acetylide cluster catalysts with dual active sites for the electrochemical reduction of CO2.

A one-step synthesis of porphyrin-silver acetylide clusters from tetra alkyne-substituted porphyrin is described. The solid-state properties of three 2D-like compounds were fully characterised using XPS and XRD while their catalytic properties under CO2 electroreduction reaction conditions were assessed and their faradaic efficiency quantified.

Self-assembled infinite silver cluster with atomic precision as a scalable catalyst for CO2-electroreduction under industry-relevant reaction rates

Scalable infinite silver acetylide cluster as a CO2 reduction catalyst with high selectivity for CO at industry-relevant rates.

Luminescent heterobimetallic Au(I)/Ag(I) complex stabilized by a unique acetylide fragment: A spectroscopic and computational study of aurophilic ‒ argentophilic interactions

This paper investigates the luminescence and metallophilic interaction in the heterobimetallic Au(I)-Ag(I) acetylide cluster [Au2Ag2(CCPh)4(PPh3)2]. Analysis using single-crystal X-rays shows short Au∙∙∙Ag separations (2.8806(3)-3.0212(3) Å), showing favorable closed shell (d10⋯d10) aurophilic-argentophilic interactions. DFT calculations and ELF analysis reveal electron localization between Au⋯Ag contacts and electron density dispersion around gold and silver ions. Quantum Theory of Atoms in Molecules (QTAIM) research reveals electron density at bond critical points (bcp) and assesses Au(I)⋯Ag(I) interaction strengths. Natural Bond Orbital (NBO) analysis identifies donor–acceptor characteristics of orbitals involved in aurophilic ‒ argentophilic interactions.

The Self-Assembly of [{Ag3(C≡CtBu)2}n]n+ Building Units into a Template-Free Cuboctahedron and Anion-Encapsulating Silver Cages.

We describe the controlled synthesis of silver acetylide clusters based on a simple polymeric [Ag3L2]+ (L = -C≡CtBu) building block. A linear one-dimensional polymeric structure shows alternating pyramidal motifs and is the basic repeating unit forming discrete molecular cages (pentamers [X⊂Ag15L10]4+ and hexamers [PF6⊂Ag18L12]5+) obtained by incorporating suitable templates. These motifs and a rare template-free cuboctahedral [Ag12L8]4+ cluster (tetramer) were crystallographically characterized.

A merged copper(I/II) cluster isolated from Glaser coupling

Ubiquitous copper-oxygen species are pivotal in enabling multifarious oxidation reactions in biological and chemical transformations. We herein construct a macrocycle-protected mixed-valence cluster [(tBuC≡CCuI3)-(μ2-OH)-CuII] by merging a copper acetylide cluster with a copper-oxygen moiety formed in Glaser coupling. This merged Cu(I/II) cluster shows remarkably strong oxidation capacity, whose reduction potential is among the most positive for Cu(II) and even comparable with some Cu(III) species. Consequently, the cluster exhibits high hydrogen atom transfer (HAT) reactivity with inert hydrocarbons. In contrast, the degraded [CuII-(μ2-OH)-CuII] embedded in a small macrocyclic homologue shows no HAT reactivity. Theoretical calculations indicate that the strong oxidation ability of Cu(II) in [(tBuC≡CCuI3)-(μ2-OH)-CuII] is mainly ascribed to the uneven charge distribution of Cu(I) ions in the tBuC≡CCuI3 unit because of significant [dCu(I) → π*(C≡C)] back donation. The present study on in situ formed metal clusters opens a broad prospect for mechanistic studies of Cu-based catalytic reactions.

Phosphorescent mechanochromism through the contraction of Ag12Cu2 clusters in tetradecanuclear copper–silver acetylide complexes

Tetradecanuclear Ag12Cu2 acetylide cluster complexes show a dramatic phosphorescent change from yellow to orange with a drastic emission spectral red-shift upon mechanical grinding due to increased intermetallic contact within Ag12Cu2 clusters.

A Fluxional Copper Acetylide Cluster in CuAAC Catalysis.

A molecularly defined copper acetylide cluster with ancillary N-heterocyclic carbene (NHC) ligands was prepared under acidic reaction conditions. This cluster is the first molecular copper acetylide complex that features high activity in copper-catalyzed azide-alkyne cycloadditions (CuAAC) with added acetic acid even at -5 °C. Ethyl propiolate protonates the acetate ligands of the dinuclear precursor complex to release acetic acid and replaces one out of four ancillary ligands. Two copper(I) ions are thereby liberated to form the core of a yellow dicationic C2-symmetric hexa-NHC octacopper hexaacetylide cluster. Coalescence phenomena in low-temperature NMR experiments reveal fluxionality that leads to the facile interconversion of all of the NHC and acetylide positions. Kinetic investigations provide insight into the influence of copper acetylide coordination modes and the acetic acid on catalytic activity. The interdependence of "click" activity and copper acetylide aggregation beyond dinuclear intermediates adds a new dimension of complexity to our mechanistic understanding of the CuAAC reaction.

Soluble Silver Acetylide for the Construction and Structural Conversion of All-Alkynyl-Stabilized High-Nuclearity Homoleptic Silver Clusters

Silver acetylide complex [Ag(ArC≡C)]n (Ar = 3,5-di-tert-butylphenyl) with unprecedented high solubility in common organic solvents has been designed and synthesized. The high solubility is due to two bulky tert-butyl substituents on the phenyl ring. This feature is significant to construct and isolate single crystals of all-alkynyl-stabilized silver clusters, which are crucial to investigate the intrinsic binding interaction and coordination modes between Ag(I) and ethynide ligands. Crystallization of [Ag(ArC≡C)]n under various conditions resulted in three high-nuclearity homoleptic silver acetylide clusters, namely, [Ag21(ArC≡C)20](OH) (1), [Ag16(ArC≡C)16] (2), and [Ag15(ArC≡C)15] (3). Complex 1 has a [Ag21] cluster protected by twenty 3,5-di-tert-butyl-phenylethynide ligands. Complexes 2 and 3 have neutral [Ag16] and [Ag15] clusters, respectively. In addition to these homoleptic silver clusters, two new silver acetylides [Ag20(ArC≡C)16(CH3COO)4] (4) and [Ag22(ArC≡C)16(NO3)4(CH3CH2OH)4](OH)2 (5) were synthesized. The acetate and nitrate anions in these structures are more like counterions instead of acting as critical building blocks or templates for cluster assembly. These results illustrated the significance of 3,5-di-tert-butyl-phenylethynide ligands in the construction and stabilization of high-nuclearity silver clusters. Analysis of structures of 1–5 revealed several novel coordination modes between Ag(I) and ethynide ligands, which contributed considerably to our knowledge of Ag(I)–ethynide binding interactions.

C[sbnd]H and C[sbnd]C bond activation reactions in silver alkynyl cluster cations, RC[tbnd6]CAg2+

A range of silver alkynyl cations RCCAg2+ (R=H, Me, Et, Pr, Bu, tBu and Ph) can be “synthesized” in the gas phase via two approaches using electrospray ionization (ESI) multistage mass spectrometry experiments. The first involves injecting a solution of AgNO3 and the appropriate acid RCCCO2H in a MeOH/H2O solvent mixture into the ESI source, which yields the cluster cations (RCCAg)nAg+ (n=1–12) via decarboxylation. The second involves direct ESI of solutions of pre-synthesized silver acetylides, which yields a series of silver acetylide cluster cations of the type (RCCAg)nAg+ (n=4–18), which upon CID yield RCCAg2+. The low energy CID reactions of the silver alkynyl cations RCCAg2+ have been studied in a linear ion trap mass spectrometer. The rich fragmentation reactions observed included various combinations of CC and CH bond activation to yield the ionic products: (1) CH3CCAg2+ (R=Pr, Bu); (2) Ag2H+ (R=Et, Pr, Bu, tBu); and (3) HCCAg2+ (R=tBu). Other fragmentation channels observed include; AgC bond cleavage and loss of Ag+. CID of the deuterium labelled cation, CD3CH2CH2CCAg2+ (m/z 284), show that: H/D scrambling is not involved in either the loss of CD2CH2 or the formation of Ag2H+ (m/z 215). Formation of the latter ion involves the regioselective activation of the CH bond β to the triple bond, as revealed by the formation of Ag2D+ (m/z 216) in the CID spectrum of the deuterium labelled cation, CD3CD2CH2CCAg2+ (m/z 286).

Nickel poly-acetylide carbonyl clusters: structural features, bonding and electrochemical behaviour

The reactions of [NEt(4)](2)[Ni(6)(CO)(12)] with miscellaneous carbon halides (e.g. CCl(4), C(4)Cl(6)) in CH(2)Cl(2) have been extensively investigated particularly focusing on the stoichiometric ratio of the reagents and reaction temperature. This allowed the preparation of the previously known acetylide clusters [Ni(16)(C(2))(2)(CO)(23)](4-), [HNi(25)(C(2))(4)(CO)(32)](3-) and [Ni(22)(C(2))(4)(CO)(28)Cl](3-), as well as isolation and full characterisation of the closely related [Ni(17)(C(2))(2)(CO)(24)](4-) and [Ni(25)(C(2))(4)(CO)(32)](4-) tetraanions. From a structural point of view, all these clusters are based on a Ni(16) square orthobicupola which contain interstitial C(2), Ni(η(2)-C(2))(4) or Ni(2)(μ-η(2)-C(2))(4) moieties, displaying rather short C-C bonds. Electrochemical studies reveal that all these species undergo different redox processes, even if their stability is rather limited. This is corroborated by an extensive analysis of the interaction between interstitial C(2) acetylide units and the metal cluster cage by Extended Huckel Molecular Orbital (EHMO) calculations, which indicates that tightly bonded C-C units are less effective than isolated C-atoms in stabilising the cluster cage.

Synthesis, structures and magnetic properties of carbon-encapsulated nanoparticles via thermal decomposition of metal acetylide

A new low-temperature synthetic method for carbon-encapsulated metal and metal carbide nanoparticles was developed, where the metal cation M 2+ is reduced by C 2 2 - . In this method, metal cations form ( M 2 + C 2 2 - ) n clusters at the beginning, followed by neutralization and segregation. Formations of metallic tin and cobalt, and metastable carbides of cobalt, palladium and nickel are evidenced by powder X-ray diffractions. TEM observation reveals that the nanoparticles are encapsulated in carbon shells despite the low temperature treatment. The formation of the metastable carbides and carbon shells can be explained by the carbon-rich precursor, acetylide clusters. Surplus carbon atoms tend to be excluded from the metal–carbon cores even at low temperature, automatically forming carbon shells.

One-pot self-assembly of trinuclear silver(I) clusters containing propargyl alcohols and bis(diphenylphosphino)methane (dppm) ligands

The reaction of silver(I) nitrate with the propargyl alcohols HC CCRR′OH (R = R′ = H, Me and R = Me, R′ = Et) in the presence of Et 3N and bis(diphenylphosphino)methane (dppm) affords the trinuclear silver clusters [Ag 3(μ 3-η 1-C CCRR′OH)(μ-dppm) 3](NO 3) 2 in high yields. The complexes were fully characterised by spectroscopic techniques, and, in the case of rac-[Ag 3{μ 3-η 1-C CC(Et)(Me)OH}(μ 2- O-NO 3)(μ-dppm) 3]NO 3 · CH 2Cl 2 by single crystal X-ray diffraction. This high-yielding one-pot self-assembly process represents a safe and simple method for the assembly of trinuclear silver(I) acetylide clusters from simple, commercially available reagents.

OXO INCORPORATED METAL ACETYLIDE COMPLEXES

ABSTRACT Studies on organometallic oxo complexes have intensified in recent years due to their implications in catalytic oxidations or as reagents in the oxidation of organic molecules. Synthesis of such complexes containing a hydrocarbon ligand besides the carbonyl and oxo provides an opportunity to obtain complexes with both low oxidation state metal carbonyl fragment and high oxidation state metal oxide fragment in the same molecule. Our attention has been focused on oxo incorporated metal acetylide complexes, in particular, to understand how oxo ligands bond to the metal atoms. Synthetic strategy, structural behavior and reactivity of oxo acetylide metal complexes and clusters are reviewed.

Formal Hydrogenation of a Permetalated Ethene, (μ4-CC)Fe2Ru2(η5-C5Me5)2(CO)8(dppm), via Successive Protonation−Hydride Reduction Leading to C2HnCluster Compounds

Formal hydrogenation of the CC moiety in permetalated ethenes, (μ4-CC)Fe2Ru2Cp*2(CO)8L2 (Cp*= η5-C5Me5; L2= (CO)2 (2), dppm (4)), via successive addition of proton and hydride was examined. Treatment of 2 with a carboxylic acid, α-chloropropionic acid, did not result in protonation at the expected CC moiety but addition to the Ru−Ru bond to give the μ-hydrido μ-carboxylato derivative (μ4-CC)(μ-H)(μ-κ1:κ1-CH3CHClCOO)Fe2Ru2Cp*2(CO)8 (3). Irradiation of 2 in the presence of diphosphines, Ph2P(CH2)nPPh2 (n = 1, 2), afforded the substituted products (μ4-CC)Fe2Ru2Cp*2(CO)8[μ-Ph2P(CH2)nPPh2] (n = 1 (4), 2 (5)), and reaction of the dppm derivative 4 with HBF4·OEt2 resulted in protonation at the CC moiety to give the cationic μ4-C2H complex [(μ4-CCH)Fe2Ru2Cp*2(CO)7(dppm)]BF4 (6). Further reduction of 6 with NEt4BH4 caused elimination of one of the iron fragments to afford the trinuclear acetylide cluster compound (μ3-C⋮CH)FeRu2Cp*(CO)5(dppm) (8), whereas treatment of 6 with H2SiPh2 led to H addition to provide the trinuclear μ3-HCCH complex (μ3-HCCH)(μ-H)FeRu2Cp*(CO)5(dppm) (9). Thus, the μ3-HCCH ligand in 9 arises from formal hydrogenation of the μ4-CC ligand in 4 (2) and the ligand transformations described in this paper are realized by the flexible coordination capability of the C2 ligand. Cluster expansion by reaction of 4 with Co2(CO)8 gave the trinuclear acetylide cluster (μ3-C⋮CFp*)FeRu2CoCp*(CO)7(dppm) (10). Complexes 3, 4, 6, and 8−10 have been fully characterized by means of spectroscopic and crystallographic methods.

Higher Nuclearity Fe,Ru Mixed-Metal Dicarbide Cluster Compounds Derived from Ethynediyldiiron Complex (η5-C5Me5)(CO)2Fe−C⋮C−Fe(η5-C5Me5)(CO)2

Reaction of the ethynyliron complexes FP−C⋮C−H [FP = Fp (1), Fp* (1*); Fp = (η5-C5H5)Fe(CO)2; Fp* = (η5-C5Me5)Fe(CO)2] with Ru3(CO)12 in refluxing benzene affords triruthenium μ-η1(Ru1):η2(Ru2):η2(Ru3)-acetylide cluster type compounds Ru3(CO)9[μ3-η1:η2:η2-C⋮C−FP] [FP = Fp (3), Fp* (3*)] in a manner similar to the reaction of 1-alkynes. In contrast to the clean reaction of 1 and 1*, reaction of the ethynediyldiiron complex, Fp*−C⋮C−Fp* (2*), gives a complicated mixture of products, from which Cp*2Fe2Ru2(μ4-C2)(CO)10 (5*) and Cp*2Fe2Ru6(μ6-C2)(CO)17 (6*) are isolated and characterized as permetalated ethene and permetalated ethane, respectively, by X-ray crystallography. It is revealed that the permetalated hydrocarbon structures in 5* and 6* are constructed via formal addition of a dimetallic species to the C−C triple bond in 2*. The octanuclear complexes 6* and 6 (Cp derivative) are also prepared by thermal dimerization of the tetranuclear FeRu3(μ-C2) core in 3* and 3. Higher nuclearity cluster compounds including the heptanuclear dicarbide cluster compound CpFeRu6(μ5-C2)(μ5-C2H)(CO)16 (12) and the heptanuclear bis(dicarbide) cluster compound Cp2Fe2Ru5(μ5-C2)2(CO)17 (15) are obtained not only by thermolysis but also by one-electron oxidation of the deprotonated anionic form of 3 (13).

Syntheses and Reactivity Studies of the Carbido-Alkylidyne Cluster Complexes LWRu4(μ5-C)(μ-CPh)(CO)12and LWRu5(μ6-C)(μ-CPh)(CO)14, L = Cp and Cp*, Obtained from Reversible Scission of Acetylide Ligand

Treatment of a 1:1 mixture of Ru3(CO)12 and the acetylide cluster LWRu2(CO)8(C2Ph) (1, L = Cp and Cp*) in hydrocarbon solvents afforded two carbido-alkylidyne cluster complexes, LWRu4(μ5-C)(CO)12(μ-CPh) (2) and LWRu5(μ6-C)(CO)14(μ-CPh) (3). Complexes 2 contain a square pyramidal cluster skeleton with a μ5-carbide and an accompanying bridging alkylidyne ligand, while WRu5 complexes 3 possess a distorted octahedral WRu5(μ6-C) framework. The transformation from 1 to 2 and 3 illustrates a reversible cleavage of an acetylide carbon−carbon bond induced by the cluster-building reaction. Moreover, the hydrogenation of complexes 2 and 3 was found to depend on the ancillary ligand on the W atom, showing selective formation of only two hydride complexes, CpWRu4(μ5-C)(μ-CPh)(μ-H)2(CO)11 (4) and Cp*WRu5(μ6-C)(μ-CPh)(μ-H)2(CO)13 (5), respectively. Single-crystal X-ray analysis on complex 4 indicated that the hydrides resided near the apical Ru atom, while the hydrides in complex 5 were associated with the unique W meta...

A study of the photochemistry and thermal chemistry of Ru3(CO)9(PR3)3{R = Ph, OMe} with two-electron donor ligands

The photochemistry of the tris-substituted clusters Ru3(CO)9(PR3)3 (R = Ph or OMe) with no added ligands, with CO, C2H4, alkynes and H2 is compared and contrasted with results obtained for analogous thermal reactions. Photolysis of a CH2Cl2 solution of Ru3(CO)9(PPh3)3 leads to the metallated complex HRu3(CO)8(PPh3)2(PPh2C6H4). In CCl4, Ru(CO)3(PR3)Cl2 is formed on photolysis of Ru3(CO)9(PR3)3. Photolysis of CO saturated solutions of Ru3(CO)9(PR3)3 leads to Ru(CO)4(PR3). C2H4 saturated solutions of Ru3(CO)9(PR3)3 generate the novel Ru(CO)3(PR3)(η2-C2H4) complexes upon photolysis. With C2H2, photolysis of solutions of Ru3(CO)9(PR3)3 leads to the novel complexes Ru(CO)3(PR3)(η2-C2H2). Substituted alkyne complexes have been prepared. Thermolysis of Ru3(CO)9(PR3)3 with HC≡CPh leads to the novel acetylide clusters HRu3(CO)6(PR3)3(μ3-η2-C2Ph). With PhC≡ CPh, only Ru3(CO)9{P(OMe)3}3 reacts, yielding the novel alkyne cluster Ru3(CO)6{P(OMe)3}3(μ3-η2-C2Ph2). With H2, photolysis of CH2Cl2 solutions of Ru3(CO)9(PR3)3 leads to H2Ru(CO)2(PR3)2. Irradiating a 4:1 CH2Cl2 to EtOAc solution of Ru3(CO)9(PR3)3 under an atmosphere of H2 leads to the novel dihydrido species H2Ru3(CO)7(PR3)3. Thermolysis of H2 saturated solutions of Ru3(CO)9(PR3)3 leads to H4Ru4(CO)8(PR3)4.

Reaction of ethynediyl, butadiynediyl and ethynyl iron complexes, ( η5-C 5R 5)(CO) 2Fe–(CC) n–X [X=Fe( η5-C 5R 5)(CO) 2, H; R 5=Me 5, Me 4Et; n=1, 2], with Fe 2(CO) 9 leading to polynuclear C 2 and C 4 complexes

Polynuclear C 2 and C 4 cluster compounds are prepared by treatment of the iron complexes containing μ-C 2 (ethynediyl), μ-C 4 (butadiynediyl) and C 2H (ethynyl) ligands with Fe 2(CO) 9. The ethynediyl complex ( η 5-C 5Me 5)(CO) 2Fe–CC–Fe( η 5-C 5Me 5)(CO) 2 gives the tetrairon dicarbide complex, ( μ 4-C 2)Fe 4( η 5-C 5Me 5) 2(CO) 9, which shows dynamic behavior by way of reversible scission and recombination of the Fe–Fe bonds. Reaction of the butadiynediyl complex, ( η 5-C 5Me 5)(CO) 2Fe–CC–CC–Fe( η 5-C 5Me 5)(CO) 2, affords tetranuclear nona- and decacarbonyl cluster compounds depending on the reaction conditions. The nonacarbonyl cluster compound formed exclusively in benzene adopts a normal acetylide cluster type structure and one of the two CC functional groups remains unreacted, but the decacarbonyl cluster isolated as a minor product from the reaction in THF consists of a μ 3- η 3-propargylidene diiron core and a ketene functional group, which should be formed by addition of an Fe 2 unit followed by migration of CO to the terminal carbon atom of the C 4 bridge. In contrast, reactions of polyynyl complexes are found to be less selective. Reaction of ( η 5-C 5Me 5)(CO) 2Fe–CC–H results in the formation of a low yield mixture of products, of which the p-quinone complex, c-2,5-[Fe( η 5-C 5Me 5)(CO) 2] 2–C 6H 2O 2, has been isolated and characterized by X-ray crystallography, though ( η 5-C 5Me 5)(CO) 2Fe–CC–CC–H merely gives an intractable reaction mixture.

Alkyne−Acetylide Coupling in Cluster Compounds Bearing a Triosmium Carbonyl Os3(CO)8 Fragment and a High Oxidation State (C5Me5)W(O)2 Unit

Treatment of acetylide cluster Cp*WOs3(μ-O)2(μ-CCPh)(CO)9 (1), Cp* = C5Me5, with diphenylacetylene affords two cluster complexes Cp*W(O)Os3(μ-O)(CCPh)(PhC2Ph)(CO)8 (2) and Cp*W(O)Os3(μ-O)(CCPhCPhCPh)(CO)8 (3a) by alkyne coordination and cluster-assisted formation of C−C bonds between acetylide and alkyne, respectively. For the reaction with phenylacetylene, only the coupled product Cp*W(O)Os3(μ-O)(CCPhCHCPh)(CO)8 (3b) is obtained, together with a small amount of Cp*W(O)Os3(μ-O)(CCPhCCHPh)(CO)8 (4). Complex 2 slowly converts to 3a and the complex Cp*W(O)(μ-O)Os3(CCPhCPhCPh)(CO)8 (5a) when heated in toluene, whereas the formation of 4 is believed to pass through a pathway involving an alkyne-to-vinylidene rearrangement. The conversion from complexes 3 to 5 demonstrates a unique skeletal isomerization involving the interchange of a Cp*W(O)2 unit and one Os(CO)3 fragment.

Homogeneous and Solid-Gas Hydrogenation of Alkynes and of 1,4-Cyclohexadiene in the Presence of the Hydrido Acetylide Cluster HRu3(CO)9(⊥-C2But)

The hydridic complex HRu3(CO)9(⊥-C2But) (Complex 1), containing an acetylide coordinated in perpendicular fashion with respect to one edge of the triangular cluster, catalyzes the hydrogenation of alkynes and of 1,4-cyclohexadiene (1,4-CHD) either under homogeneous and under solid–gas conditions. Cluster catalysis is likely to occur; however, under homogeneous conditions, evidence for partial fragmentation of the cluster has also been found. In these conditions, formation of known metallacyclic compounds and of the new dinuclear derivative Ru2(CO)6 (HC2But)(C2Ph2) (Complex 2a) has been observed: they are presumably inactive byproducts.