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“GaOTf” is a simple, convenient source of low‐valent gallium for synthetic chemistry and catalysis. However, little is currently known about its composition or reactivity. In this work, 71Ga NMR spectroscopy shows the presence of [Ga(arene)n]+ salts on oxidation of Ga metal with AgOTf in arene solvents. However, a more complex picture of speciation is uncovered by X‐ray diffraction studies. In all cases, mixed‐valence compounds containing Ga‐arene and Ga‐OTf coordination motifs, in addition to an unusual “naked” [Ga]+ ion, are found. Addition of 18‐crown‐6 allows for the isolation of a discrete GaI crown complex. Evidence of a potential intermediate in the formation of “GaOTf” has been isolated in the form of the bimetallic silver(I)/gallium(I) cluster anion [Ag4{Ga(OTf)3}4(μ‐Ga)6(OTf)4]2−., Gallium(I) triflate is a promising new source of low‐valent gallium for synthesis and catalysis. However, little is known about its composition and structural chemistry. Here it is demonstrated that speciation is quite complex in this system, with compounds containing Ga in multiple oxidation states being isolated from arene solutions. more...

The speciation, conformation, and reactivity of transition metal complexes at the gas–liquid interface are poorly understood, yet the potential is high for observing chemistry unique to this anisot... more...

Palladium catalysed cross-couplings reactions have been a dominant method in synthetic chemistry for decades. Despite this, the role of the solvent is often taken for granted and poorly understood. Regulations affecting some the most frequently used solvents for cross-coupling reactions are accelerating current trends towards using new types of solvents. In this review, the fundamental interactions between solvent and catalyst are explained so that it may inform the rational selection of high performance and safe solvents. The popular cross-coupling methodologies are addressed (Suzuki, Stille, Kumada, Negishi, Hiyama, Heck, Sonogashira, and Buchwald–Hartwig reactions) and novel solvents introduced. more...

A novel scaffold for the construction of self-organised ionic liquids and ionic liquid crystals bearing both perfluorocarbon and hydrocarbon moieties has been developed. The phase behaviour and physical properties of these materials can be tuned as a function of chain length and fluorine content and significant structural elaboration is possible, giving a highly flexible system. more...

The chemistry of phosphorus(III) ligands, which are of key importance in coordination chemistry, organometallic chemistry and catalysis, is dominated by relatively electron-rich species. Many of the electron-poor P(III) ligands that are readily available have relatively small steric profiles. As such, there is a significant gap in “ligand space” where more sterically bulky, electron-poor P(III) ligands are needed. This contribution discusses the coordination chemistry, steric and electronic properties of P(III) ligands bearing highly fluorinated alkoxide groups of the general form PRn(ORF)3-n, where R = Ph, RF = C(H)(CF3)2 and C(CF3)3; n = 1-3. These ligands are simple to synthesize and a range of experimental and theoretical methods suggest that their steric and electronic properties can be “tuned” by modification of their substituents, making them excellent candidates for large, electron-poor ligands. more...

The scope of the univalent gallium salts [Ga(C6H5F)2]+[Al(ORF)4]− and the new completely characterized [Ga(1,3,5-Me3C6H3)2]+[Al(ORF)4]− (RF = C(CF3)3) was investigated in terms of initiating or catalyzing the synthesis of highly reactive poly(2-methylpropylene)—highly reactive polyisobutylene (HR-PIB)—in several solvents. A series of polymerization reactions proved the high efficiency and quality of the univalent gallium salts for the polymerization of isobutylene. The best results were obtained using very low concentrations of [Ga(C6H5F)2]+[Al(ORF)4]− (down to 0.007 mol%) while working at reaction temperatures of up to ±0 °C and in the noncarcinogenic and non-water hazardous solvent toluene. Under these conditions, HR-PIB with an α-content of terminal olefinic double bonds up to 91 mol% and a molecular weight of 1000–2000 was obtained in good yields. Upon changing [Ga(C6H5F)2]+[Al(ORF)4]− for the electron richer [Ga(1,3,5-Me3C6H3)2]+[Al(ORF)4]−, polymerization temperatures could be increased to +10 °C. T... more...

IR spectroscopic and X-ray structural data of rhodium and palladium complexes of N-heterocyclic carbene (NHC) and 1H-pyridin-(2E)-ylidene (PYE) ligands indicate that both ligand classes exhibit similar electron-donating properties. However, catalytic application of palladium PYE complexes appears to be limited by PYE ligand loss. Density functional theory (DFT) calculations show that the Pd–CNHC σ-bond is very low-lying in energy (HOMO-14 and 15, ca. –11 eV) and a π-backbonding contribution is also present, whereas the Pd-NPYE σ-bond is comparatively high-lying (HOMO-9 and 10, ca. –8 eV) and the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) gap is also significantly less (4.0 vs. 5.6 eV). Essentially, electronegativity differences between Pd, C, and N render the Pd–N bond much more polarized and susceptible to electrophilic and nucleophilic attack and hence ligand substitution. more...

Metal vinylidene complexes are widely encountered, or postulated, as intermediates in a range of important metal-mediated transformations of alkynes. However, fluorovinylidene complexes have rarely been described and their reactivity is largely unexplored. By making use of the novel outer-sphere electrophilic fluorination (OSEF) strategy we have developed a rapid, robust and convenient method for the preparation of fluorovinylidene and trifluoromethylvinylidene ruthenium complexes from non-fluorinated alkynes. Spectroscopic investigations (NMR and UV/Vis), coupled with TD-DFT studies, show that fluorine incorporation results in significant changes to the electronic structure of the vinylidene ligand. The reactivity of fluorovinylidene complexes shows many similarities to non-fluorinated analogues, but also some interesting differences, including a propensity to undergo unexpected C-F bond cleavage reactions. Heating fluorovinylidene complex [Ru(η(5)-C5H5)(PPh3)2(C[double bond, length as m-dash]C{F}R)][BF4] led to C-H activation of a PPh3 ligand to form an orthometallated fluorovinylphosphonium ligand. Reaction with pyridine led to nucleophilic attack at the metal-bound carbon atom of the vinylidene to form a vinyl pyridinium species, which undergoes both C-H and C-F activation to give a novel pyridylidene complex. Addition of water, in the presence of chloride, leads to anti-Markovnikov hydration of a fluorovinylidene complex to form an α-fluoroaldehyde, which slowly rearranges to its acyl fluoride isomer. Therefore, fluorovinylidenes ligands may be viewed as synthetic equivalents of 1-fluoroalkynes providing access to reactivity not possible by other routes. more...

Two rare examples of the crystal structures of large molecular clusters formed from the lithium salts of multianions are reported; the first is the dilithium salt of phenylhydrazine, which forms a tetrameric cage with a core of eight Li and eight N centres; the second is a 32-membered cage which forms from the aggregation of two [B(NNPh)3]6- hexaanions, two [NH-NPh]2- dianions and 16 Li+ cations. more...

A combined computational and experimental study is presented that investigates the mechanism of the anti-Markovnikov hydration of phenylacetylene by [Ru(η(5)-C5H5)(6-DPPAP)(3-DPICon)](+) (where 6-DPPAP = 6-(diphenylphosphino)-N-pivaloyl-2-aminopyridine) and 3-DPICon = 3-diphenylphosphinoisoquinolone). The proposed mechanism, modelled using density functional calculations, involves an initial alkyne-vinylidene tautomerism, which occurs via a ligand-assisted proton shuttle (LAPS) mechanism. Intramolecular ligand assistance from the 6-DPPAP and 3-DPICon ligands, particularly the basic nitrogen of 6-DPPAP, is also involved in subsequent stages of the mechanism and three LAPS processes in total are observed. The self-assembled ligand backbone helps to create a water-binding pocket close to the metal centre, which facilitates nucleophilic attack of water at the vinylidene α-carbon and mediates protonation and deprotonation of subsequent acyl and vinyl intermediates. Experimental evidence is also presented for a novel non-productive catalyst deactivation pathway, which appears to arise from an initial lactam-lactim tautomerism of the 3-DPICon ligand followed by coupling with a vinylidene. more...

The ruthenium naphthalene complex [Ru(η(5)-C5H5)(η(6)-C10H8)](+) is a catalyst precursor for the direct C-H alkenylation of pyridine and related nitrogen heterocycles by terminal alkynes. Stoichiometric studies have demonstrated that the naphthalene ligand may be displaced by either pyridine, 4-methylpyridine or dimethylaminopyridine (DMAP) to give species [Ru(η(5)-C5H5)L3](+) (L = nitrogen-based ligand). Reaction of in situ-generated [Ru(η(5)-C5H5)(py)3](+) (py = pyridine) with PPh3 results in the formation of [Ru(η(5)-C5H5)(PPh3)(py)2](+), the active catalyst for direct alkenylation, some [Ru(η(5)-C5H5)(PPh3)2(py)](+) is also formed in this reaction. A one-pot procedure is reported which has allowed for the nature of the nitrogen heterocycle and phosphine ligand to be evaluated. The sterically demanding phosphine PCy3 inhibits catalysis, and only trace amounts of product are formed when precursors containing a pentamethylcyclopentadienyl group were used. The greatest conversion was observed with PMe3 when used as co-ligand with [Ru(η(5)-C5H5)(η(6)-C10H8)](+). more...

A combined experimental and theoretical study has demonstrated that [Ru(η(5)-C(5)H(5))(py)(2)(PPh(3))](+) is a key intermediate, and active catalyst for, the formation of 2-substituted E-styrylpyridines from pyridine and terminal alkynes HC≡CR (R = Ph, C(6)H(4)-4-CF(3)) in a 100% atom efficient manner under mild conditions. A catalyst deactivation pathway involving formation of the pyridylidene-containing complex [Ru(η(5)-C(5)H(5))(κ(3)-C(3)-C(5)H(4)NCH═CHR)(PPh(3))](+) and subsequently a 1-ruthanaindolizine complex has been identified. Mechanistic studies using (13)C- and D-labeling and DFT calculations suggest that a vinylidene-containing intermediate [Ru(η(5)-C(5)H(5))(py)(═C═CHR)(PPh(3))](+) is formed, which can then proceed to the pyridylidene-containing deactivation product or the desired product depending on the reaction conditions. Nucleophilic attack by free pyridine at the α-carbon in this complex subsequently leads to formation of a C-H agostic complex that is the branching point for the productive and unproductive pathways. The formation of the desired products relies on C-H bond cleavage from this agostic complex in the presence of free pyridine to give the pyridyl complex [Ru(η(5)-C(5)H(5))(C(5)H(4)N)(═C═CHR)(PPh(3))]. Migration of the pyridyl ligand (or its pyridylidene tautomer) to the α-carbon of the vinylidene, followed by protonation, results in the formation of the 2-styrylpyridine. These studies demonstrate that pyridylidene ligands play an important role in both the productive and nonproductive pathways in this catalyst system. more...

Copper and silver form coordination complexes with P4 whereas gold forms a homoleptic [Au(P4)2]+ cation.

Collisions of hyperthermal oxygen atoms, with an average translational energy of 520 kJ mol−1, on continuously refreshed ionic liquids, 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl) imide ([emim][NTf2]) and 1‐dodecyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl) imide ([C12mim][NTf2]), were studied with the use of a beam‐surface scattering technique. Time‐of‐flight and angular distributions of inelastically scattered O and reactively scattered OH and H2O were collected for various angles of incidence with the use of a rotatable mass spectrometer detector. For both O and OH, two distinct scattering processes were identified, which can be empirically categorized as thermal and non‐thermal. Non‐thermal scattering is more probable for both O and OH products. The observation of OH confirms that at least some reactive sites, presumably alkyl groups, must be exposed at the surface. The ionic liquid with the longer alkyl chain, [C12mim][NTf2], is substantially more reactive than the liquid with the ... more...

The ruthenium bis-acetate complex Ru(κ(2)-OAc)(2)(PPh(3))(2) reacts with HC≡CPh to afford the vinylidene-containing species Ru(κ(1)-OAc)(κ(2)-OAc)(=C=CHPh)(PPh(3))(2). An experimental study has demonstrated that this reaction occurs under very mild conditions, with significant conversion being observed at 255 K. At lower temperatures, evidence for a transient metallo-enol ester species Ru(κ(1)-OAc)(OC{Me}O-C=CHPh)(PPh(3))(2) was obtained. A comprehensive theoretical study to probe the nature of the alkyne/vinylidene tautomerisation has been undertaken using Density Functional Theory. Calculations based on a number of isomers of the model system Ru(κ(1)-OAc)(κ(2)-OAc)(=C=CHMe)(PH(3))(2) demonstrate that both the η(2)(CC) alkyne complex Ru(κ(1)-OAc)(κ(2)-OAc)(η(2)-HC≡CMe)(PH(3))(2) and the C-H agostic σ-complex Ru(κ(1)-OAc)(κ(2)-OAc)(η(2){CH}-HC≡CMe)(PH(3))(2) are minima on the potential energy surface. The lowest energy pathway for the formation of the vinylidene complex involves the intramolecular deprotonation of the σ-complex by an acetate ligand followed by reprotonation of the subsequently formed alkynyl ligand. This process is thus termed a Ligand-Assisted Proton Shuttle (LAPS). Calculations performed on the full experimental system Ru(κ(1)-OAc)(κ(2)-OAc)(=C=CHPh)(PPh(3))(2) reinforce the notion that lowest energy pathway involves the deprotonation/reprotonation of the alkyne by an acetate ligand. Inclusion of the full ligand substituents in the calculations are necessary to reproduce the experimental observation of Ru(κ(1)-OAc)(κ(2)-OAc)(=C=CHPh)(PPh(3))(2) as the thermodynamic product. more...

The conversion of the alkyne complex RhCl(PPr(i)3)2(eta2-PhC[triple bond]CH) into its vinylidene isomer RhCl(PPr(i)3)2(=C=CPhH) has been monitored via NMR spectroscopy in a range of solvents. In THF and hexane solution the reaction was observed to proceed via the alkynyl hydride complex Rh(H)Cl(PPr(i)3)2(-C[triple bond]CPh). The kinetic profile of the reaction demonstrates that this species is an intermediate in the formation of the vinylidene complex. more...

Recent studies concerning p-block imido anion chemistry have tended to focus on imido compounds where the central atom is from groups 15 or 16. The imido anions of group 13 are less well investigat... more...

Attempted metallation of a triamidoaluminane gives a complex containing the [R′Al(NR) 3 ] 4− anion whose formal tetranegative charge is the highest charge observed crystallographically for a simple mononuclear imido main group anion system. more...

Reaction of equimolar quantities of MX (M = Au, Cu, X = Cl; M = Ag, X = OTf) and GaCl(3) in CH(2)Cl(2) with P(4) leads to phosphorus ligating a cationic coinage metal centre. For Cu and Ag, ion-contacted coordination polymers are formed; for Au, an ion-separated complex is observed that features the [Au(η(2)-P(4))(2)](+) cation, which is the first homoleptic Au-P(4) complex to be characterised in the condensed phase. more...

Stable salts of the first homoleptic Cu-phosphorus and Cu-ethene complexes, [Cu(eta2-P4)2]+ and [Cu(eta2-C2H4)3]+, isolated by the aid of the weakly coordinating anion (WCA) [Al(OC(CF3)3)4]-, were obtained. more...

Reaction of AsCl3 with 3 equivalents of (2-OPh)C6H4NH2 in toluene/NEt3, followed by metallation with 3 equivalents of BunLi produces a bis(imido)organoarsenate dianion as a lithium salt which co-complexes BunLi to form a dimeric cage with a 14 membered core. more...