•Highly interesting species with peculiar behavior and reactivity.•These species are found as intermediates in fluorination processes.•A summary of the structural behavior of bifluoride compounds is described.•A summary of the reactivity of bifluoride compounds is described.•Preparation methods and characterization techniques of bifluorides are also described.Since its initial discovery, four decades ago, transition metal bifluoride chemistry has exhibited a slow growth, mainly due to problems associated with synthesis and characterization. Until recently, reports on this chemistry almost always presented these complexes as a fluke discovery. However, with the recent increase in reports and applications involving such species, a renewed interest in these complexes has been observed. Most of the work done in this area, so far, has been directed toward the synthesis and quite challenging characterization of these complexes, yet mostly neglecting the behavior of such species and their influence on catalytic processes. The aim of this work is to present a summary of the various preparation methods, characterization techniques and applications of reported transition metal bifluoride complexes. It is our hope that by centralizing all information available on such species, future efforts aimed at exploiting the full potential of transition metal bifluoride species can be facilitated.A summary of the various preparation methods, characterization techniques and applications of transition metal bifluorides is presented in this review. The classification of the reported systems is also attempted in order to ensure a better understanding and to help guide future efforts toward fully exploiting their potential.

Homo- and heteroleptic bis-NHC copper(I) complexes have been efficiently used as carbene transfer reagents to Au and Pd. The simple and straightforward procedure allows for the synthesis of well-known gold complexes as well as novel cationic bis-NHC Pd(II) species.

•The use of Cu–NHC complexes in catalysis is reviewed.•Mechanistic studies and catalytic cycles are depicted.•Asymmetric systems are described.Although the chemistry of copper has a long history [1a-d], the relatively recent discovery of N-heterocyclic carbene (NHC) as transition-metal supporting ligands has permitted novel vistas to be explored in copper reactivity and catalysis [1e,f]. Shortly after the seminal discovery of Arduengo, Raubenheimer reported a neutral copper carbene complex 0635 and 0640. However, the field remained dormant for almost ten years. In the early 2000s, new breakthroughs were achieved: first, the synthesis of NHC–copper using Cu2O was reported by Danopoulos and followed by the first application in catalysis by Woodward 0645 and 0650. The work by Buchwald and Sadighi appeared next, where the first catalysis using a well-defined complex was described [5].The first reports in this field were based on systems used to mimic their phosphine relatives. NHCs have become ligands of significant interest due to their steric and electronic properties 0660, 0665 and 0670. Combining the NHC ligand family and copper became, for some, an obvious and productive area [6]. Over the last decade alone, numerous systems have been developed. Copper–NHC complexes can be divided into two major classes: neutral mono-NHC and cationic bis-NHC derivatives: [Cu(X)(NHC)] [9] (X = halide, acetate, hydroxide, hydride, etc.) and [Cu(NHC)(L)][Y] (L = NHC or PR3; Y = PF6, BF4) [10].The neutral-halide-bearing complexes have been widely used in catalysis, mainly due to their ease of synthesis [9]. In addition to halide-bearing complexes, notable important related compounds have been reported: Nolan and co-workers disclosed the first hydroxide derivative [Cu(OH)(IPr)] (IPr = N,N’-bis(2,6-di-isopropylphenyl)imidazol-2-ylidene) and Sadighi published alkoxides, hydrides and borate species, which permitted novel reactivity to be explored [9g-i]. With respect to cationic derivatives, homoleptic and heteroleptic bis-NHC complexes have been reported and have been efficiently used in catalysis allowing important improvements [10]. In this review, an overview of the two classes and their respective catalytic performance will be presented.

We report the first examples of highly luminescent di-coordinated Pd(0) complexes. Five complexes of the form [Pd(L)(L′)] were synthesized, where L = IPr, SIPr or IPr* NHC ligands and L′ = PCy3, or IPr and SIPr NHC ligands. The photophysical properties of these complexes were determined in degassed toluene solution and in the solid state and contrasted to the poorly luminescent reference complex [Pd(IPr)(PPh3)]. Organic light-emitting diodes were successfully fabricated but attained external quantum efficiencies of between 0.3 and 0.7%.

A base-catalysed procedure for the synthesis of 2-substituted thiazolines from nitriles and cysteamine hydrochloride under solvent-free conditions is presented. This straightforward approach allows high conversion for a broad range of nitriles and an easy isolation of the desired products.

The reaction of the ruthenium complex cis-Caz-1 with silver fluoride affords the first example of an active olefin metathesis precatalyst containing fluoride ligands. The cis geometry of the precursor complex is key to the successful fluoride exchange reaction. Computational studies highlight the stability of the new Ru–F species, due to push–pull interactions between fluoride and L-type ligands (L: N-heterocyclic carbene, phosphite). Insights into the isomerization process from trans-Caz-1 to cis-Caz-1 are given. Fluoride exchange reactions were performed involving cis- and trans-Caz-1 complexes. Catalytic tests showcase the excellent activity of the Ru–F containing complexes.Keywords: fluoride; halide exchange; homogeneous catalysis; olefin metathesis; ruthenium

The first study of low catalyst loading olefin metathesis reactions in air is reported. TON values of up to 7000 were obtained using nondegassed solvents with commercially available precatalysts Caz-1, Hov-II, and Ind-II. The simple experimental conditions allow olefin metathesis reactions to be carried out on the benchtop using technical grade solvents in air.Keywords: air; homogeneous catalysis; olefin metathesis; phosphite; ruthenium

We report the first example of BAC–Cu complex (BAC = bis(diisopropylamino)cyclopropenylidene) and its use as a carbene-transfer reagent, allowing access to Au–, Pd–, Ir– and Rh–BAC compounds. Catalytic experiments show the high activity of the [CuCl(BAC)] complex in Click chemistry.

The selective synthesis of aromatic and heteroaromatic amides through base-catalysed hydration of nitriles was achieved using inexpensive and commercially available NaOH as the only catalyst. A wide range of nitriles was selectively converted to their corresponding amides. Kinetic studies show that the double hydration of nitriles towards undesirable carboxylic acids is negligible under our reaction conditions.

The N-methylation of amines using CO2 and PhSiH3 as source of CH3 was efficiently performed using a N-heterocyclic carbene copper(I) complex. The methodology was found compatible with aromatic and aliphatic primary and secondary amines. Synthetic and computational studies have been carried out to support the proposed reaction mechanism for this transformation.

A straightforward synthetic route has been developed permitting the formation of homoleptic and heteroleptic bis-N-heterocyclic carbene metal complexes. The methodology has proven efficient for all group 11 members. These complexes are easily synthesized using [M(Cl)(NHC)] with different NHC salts in the presence of inexpensive bases such as sodium hydroxide. These systems were fully characterized and displayed high stability even in the presence of light.

In this short review, we focus on the synthesis and applications of new phosphite-bearing ruthenium complexes in olefin metathesis. These complexes were designed to take advantage of a known synergistic effect between strong σ-donating NHC ligands and π-acidic phosphites. The resulting catalysts display higher stability compared to their phosphine-containing congeners. A comparative summary of their use in ring-closing metathesis, cross metathesis, and ring-opening metathesis polymerization, as well as DFT calculations describing our mechanistic understanding, are presented.

The reaction between nitriles and aminoalcohols to access 2-substituted oxazolines was investigated. Using copper–NHC complexes, various nitriles were successfully converted into the corresponding oxazolines, under milder and less wasteful conditions than those of previously reported methods.

The first “in air” copper-catalyzed method for the selective synthesis of tri- and tetrasubstituted vinylboronate derivatives is presented. Three different variants of the borylation of internal alkynes (α-hydroboration, β-hydroboration, and carboboration) are described using a single catalyst: [Cu(Cl)(IMes)] (IMes = N,N′-bis-[2,4,6-(trimethyl)phenyl]imidazol-2-ylidene) without taking any precaution to avoid the presence of air. Bis(pinacolato)diboron was used to afford β-hydroborated products in the presence of methanol. Adding instead another electrophile allowed the formation of tetrasubstituted vinylboronate species. Finally, the α-products were obtained using pinacolborane as the boron source. All compounds were obtained in high yield with excellent regioselectivity at low catalyst loading (0.04–2 mol %). The protocol constitutes a very convenient route to access these highly valuable molecules.Keywords: alkynes; carboboration; copper; hydroboration; N-heterocyclic carbenes

A novel and efficient method for C–H arylation using well-defined Pd– and Cu–NHC systems has been developed. This process promotes the challenging construction of C–C bonds from arenes or heteroarenes using aryl bromides and chlorides. Mechanistic studies show that [Cu(OH)(NHC)] plays a key role in the C–H activation and is involved in the transmetallation with the Pd–NHC co-catalyst.

The new well-defined catalyst [Pd(μ-Cl)Cl(IPr*)]2 enables the efficient Grignard reagent cross-coupling for the synthesis of tetra-ortho-substituted biaryls. The high reactivity of the complex is associated with the important bulkiness of the IPr* ligand. The dimer represents the most efficient catalyst reported to date for this challenging transformation.

The highly cross-linked thermoset poly(dicyclopentadiene) (pDCPD) is produced by ring-opening metathesis polymerization and has become an important material for many high-impact applications. Herein, the utility of two less common, yet commercially available ruthenium-based initiators M2 and M22 is disclosed for the polymerization of dicyclopentadiene and compared with the second generation Grubbs catalyst G2. Both initiators are suited to produce pDCPD pieces in high quality (as revealed from mechanical properties of test specimen) and offer a distinctly longer processing window than the reference initiator G2.

The [Pd(SIPr)(PCy3)] complex efficiently promotes a tandem process involving dehydrogenation of formic acid and hydrogenation of C–C multiple bonds using H2 formed in situ. The isolation of a key catalytic hydridoformatopalladium species, [Pd{OC(O)H}(H)(IPr)(PCy3)], is reported. The complex plays a key role in the Pd(0)-mediated formation of hydrogen from formic acid. Mechanistic and computational studies delineate the operational role of the palladium complex in this efficient tandem sequence.

A one-pot procedure for the synthesis of [Cu(X)(NHC)] (X = Cl, Br, I) is reported. The reaction is applicable to a wide range of saturated and unsaturated NHC ligands, is scalable and proceeds under mild conditions using technical grade solvents in air.

[Pd(NHC)(PR3)] complexes were shown to be active catalysts in the dehydrogenation of ammonia borane and the subsequent hydrogenation of unsaturated compounds at very low catalyst loadings (0.05 mol% for some substrates).

N-Heterocyclic carbene ligated copper complexes act as catalysts in a variety of reactions. A brief overview of this rich chemistry is given here. Of particular note is the ability of Cu(NHC) complexes to functionalize carbonyls, alkenes and alkynes. With growth in the number of Cu(NHC) derived complexes, the catalytic possibilities involving these complexes are ever growing. We feel the full potential of these (for the most part) simply accessed complexes has yet to be fully achieved. The litany of reactions which Cu(NHC) catalyst facilitate are outlined here.

A series of N-heterocyclic carbene (NHC)/PR3 palladium(II) and palladium(0) complexes has been synthesized and fully characterized. X-ray crystallographic data have allowed comparison of ligand steric properties. The NHC ligand was found to vary its steric properties as a function of the phosphine co-ligand. These complexes display interesting catalytic properties in the Suzuki–Miyaura reaction performed in aqueous media. The pre-catalyst [PdCl2(IPr)(XPhos)] (IPr = N,N′-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene; XPhos = 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl) was found to be the most efficient system, promoting the coupling of a wide range of aryl chlorides with boronic acids in aqueous media with a typical catalyst loading of 0.03 mol%.

The synthesis, characterization, and catalytic activity of two new complexes, 2a,b, featuring a sterically demanding NHC and two different phosphites are described. Complexes 2a,b display a mutually trans arrangement of the π-acidic phosphite and the strong σ-donor SIPr ligand (SIPr = N,N′-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene). The synergy between the phosphite and the NHC ligand was revealed in the RCM of challenging substrates leading to tetrasubstituted olefins where, in comparison to their phosphine-containing analogues, 2a,b allowed higher conversions of these challenging substrates.

Environmental concerns have and will continue to have a significant role in determining how chemistry is carried out. Chemists will be challenged to develop new, efficient synthetic processes that have the fewest possible steps leading to a target molecule, the goal being to decrease the amount of waste generated and reduce energy use. Along this path, chemists will need to develop highly selective reactions with atom-economical pathways producing nontoxic byproduct.In this context, C–H bond activation and functionalization is an extremely attractive method. Indeed, for most organic transformations, the presence of a reactive functionality is required. In Total Synthesis, the “protection and deprotection” approach with such reactive groups limits the overall yield of the synthesis, involves the generation of significant chemical waste, costs energy, and in the end is not as green as one would hope. In turn, if a C–H bond functionalization were possible, instead of the use of a prefunctionalized version of the said C–H bond, the number of steps in a synthesis would obviously be reduced. In this case, the C–H bond can be viewed as a dormant functional group that can be activated when necessary during the synthetic strategy.One issue increasing the challenge of such a desired reaction is selectivity. The cleavage of a C–H bond (bond dissociation requires between 85 and 105 kcal/mol) necessitates a high-energy species, which could quickly become a drawback for the control of chemo-, regio-, and stereoselectivity. Transition metal catalysts are useful reagents for surmounting this problem; they can decrease the kinetic barrier of the reaction yet retain control over selectivity. Transition metal complexes also offer important versatility in having distinct pathways that can lead to activation of the C–H bond. An oxidative addition of the metal in the C–H bond, and a base-assisted metal–carbon bond formation in which the base can be coordinated (or not) to the metal complexes are possible. These different C–H bond activation modes provide chemists with several synthetic options.In this Account, we discuss recent discoveries involving the versatile NHC–gold(I) and NHC–copper(I) hydroxide complexes (where NHC is N-heterocyclic carbene) showing interesting Brønsted basic properties for C–H bond activation or C–H bond functionalization purposes. The simple and easy synthesis of these two complexes involves their halide-bearing relatives reacting with simple alkali metal hydroxides. These complexes can react cleanly with organic compounds bearing protons with compatible pKa values, producing only water as byproduct. It is a very simple protocol indeed and may be sold as a C–H bond activation, although the less flashy “metalation reaction” also accurately describes the process. The synthesis of these complexes has led us to develop new organometallic chemistry and catalysis involving C–H bond activation (metalation) and subsequent C–H bond functionalization. We further highlight applications with these reactions, in areas such as photoluminescence and biological activities of NHC–gold(I) and NHC–copper(I) complexes.

The use of a mixed phosphite/N-heterocyclic carbene bearing ruthenium precursor permits the synthesis and characterisation of unprecedented four-coordinate Ru(II) and Ru(III) cationic complexes adopting an unusual sawhorse structure. The cationic Ru(II) complex performs very effectively on challenging substrates at high temperature in very short reaction times and low catalyst loadings.

A series of [Pd(NHC)(PR3)] complexes quantitatively form [Pd(η2-O2)(NHC)(PR3)] products when submitted to an dioxygen atmosphere. Synthetic details and structural features of these Pd–peroxo complexes are described. The palladium compounds were found to be efficient catalysts in the oxidation of alcohols into corresponding carbonyl compounds using O2 or air as oxidant. Reactions proceed at low catalyst loadings with a wide range of alcohols.

The hydroxylation of aryl iodides was performed using complexes of the type [CuCl(NHC)]. Excellent conversions were obtained at very low catalyst loadings.

The first examples of heteroleptic bis-N-heterocyclic carbene (NHC) copper(I) complexes and a mixed NHC–phosphine Cu complex are reported. These complexes are easily synthesized from the reaction of [Cu(OH)(NHC)] with various imidazol(idin)ium or phosphonium tetrafluoroborate salts. These cationic heteroleptic bis-NHC Cu complexes are highly active systems for the azide–alkyne cycloaddition leading to the formation of 1,2,3-triazoles. The mechanism of this transformation was investigated, and information gathered suggests that only one NHC remains coordinated to the metal center during catalysis.

The synthesis of the four olefin metathesis precatalysts Caz-1a–d, featuring the NHC ligand N,N′-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) and four different phosphites (P(OiPr)3, P(OPh)3, P(OEt)3, and P(OMe)3), is reported. The complexes are readily synthesized from commercially available [RuCl2(3-phenylinden-1-ylidene)(pyridine)(SIMes)] (Ind-III) in yields of up to 88%. These complexes adopt an unusual cis configuration between the phosphite and the NHC ligands. NMR experiments and computational studies confirm that the cis complexes are thermodynamically favored in comparison to their trans counterparts. In addition, the isomerization from trans to cis occurs via a mononuclear and non-dissociative mechanism. Among the four precatalysts, cis-Caz-1a, featuring a P(OiPr)3 ligand, displays the highest activity in ring-closing metathesis and cross-metathesis transformations. Experiments at low catalyst loadings demonstrated the potential of this catalyst, allowing better conversions than with commonly used commercially available precatalysts.

The use of phosphites in second generation, ruthenium-based olefin metathesis pre-catalysts leads to an improvement in catalyst stability and activity at low catalyst loadings.

The efficient preparation of [Pd(Amphos)(cinnamyl)Cl)] and [Pd(Amphos)(TFA)(κ2-N,C-C6H4-CH2NMe2)] (Amphos = 4-(di-tert-butylphosphino)-N,N-dimethylaniline and TFA = trifluoroacetate), two new well-defined palladium precatalysts, is reported. These complexes prove highly active in the Buchwald–Hartwig amination reaction, allowing the coupling of a wide range of (hetero)aryl chlorides, including unactivated, neutral, and sterically hindered substrates, with a wide range of amines, including primary and secondary amines. Finally, the catalytic systems have proven efficient at low catalyst loadings ranging from 0.1 to 0.3 mol %.

A method is described that makes use of easily prepared, inexpensive copper synthons as N-heterocyclic carbene (NHC) transfer agents to generate catalytically relevant gold and palladium complexes.

The synthesis, characterisation and catalytic behaviour of ruthenium indenylidene complexes bearing an N-heterocyclic carbene and triisopropylphosphite are described.

A novel synthetic route leading to N-heterocyclic carbene copper complexes has been developed by using air-stable and commercially available copper(I) oxide and imidazolium salts starting materials.

A series of mixed P(OR)3/NHC Pd complexes was synthesized and fully characterized. The steric properties of both types of ligands were computationally determined using X-ray data. These structural studies clearly show that N-heterocyclic carbenes modulate their bulkiness with respect to the steric requirements of the coligands. Catalytic studies were performed using this new class of complexes for the Suzuki−Miyaura reaction. It was found that alkoxide or hydroxide bases and/or alcohols were necessary to achieve good catalytic activity. Mechanistic studies were undertaken in order to gain insights into the role of alkoxide groups. These studies suggest that alcohols or alkoxide groups play a major role in the activation of the precatalyst to generate the catalytically active species. Catalytic studies proved these systems to be efficient using 0.1 mol % of Pd loading for the coupling of aryl, benzyl, and heterocyclic chlorides with boronic acids.

The hydrodehalogenation of polychlorinated phenyls and biphenyls (PCBs), catalysed by palladium N-heterocyclic carbene complexes, proceeds with excellent yields, at very low catalyst loadings and at room temperature, using isopropanol as the hydrogen source and NaOH as the base.

Cross-coupling reactions of Grignard reagents with functionalized aryl, heteroaryl, and sterically hindered aryl chlorides are reported. A protocol disclosing the coupling of a wide range of substrates using complexes of the type [Pd(μ-Cl)(Cl)(NHC)]2 (NHC = N-heterocyclic carbene) as precatalysts (at low catalyst loading) under mild conditions is presented. The system allows for the synthesis of highly sterically hindered products, including tri- and tetra-ortho-substituted biaryls.

A series of N-heterocyclic carbene (NHC)/PR3 palladium(II) and palladium(0) complexes has been synthesized and fully characterized. X-ray crystallographic data have allowed comparison of ligand steric properties. The NHC ligand was found to vary its steric properties as a function of the phosphine co-ligand. These complexes display interesting catalytic properties in the Suzuki–Miyaura reaction performed in aqueous media. The pre-catalyst [PdCl2(IPr)(XPhos)] (IPr = N,N′-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene; XPhos = 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl) was found to be the most efficient system, promoting the coupling of a wide range of aryl chlorides with boronic acids in aqueous media with a typical catalyst loading of 0.03 mol%.

The selective synthesis of aromatic and heteroaromatic amides through base-catalysed hydration of nitriles was achieved using inexpensive and commercially available NaOH as the only catalyst. A wide range of nitriles was selectively converted to their corresponding amides. Kinetic studies show that the double hydration of nitriles towards undesirable carboxylic acids is negligible under our reaction conditions.

The use of a mixed phosphite/N-heterocyclic carbene bearing ruthenium precursor permits the synthesis and characterisation of unprecedented four-coordinate Ru(II) and Ru(III) cationic complexes adopting an unusual sawhorse structure. The cationic Ru(II) complex performs very effectively on challenging substrates at high temperature in very short reaction times and low catalyst loadings.

[Pd(NHC)(PR3)] complexes were shown to be active catalysts in the dehydrogenation of ammonia borane and the subsequent hydrogenation of unsaturated compounds at very low catalyst loadings (0.05 mol% for some substrates).

A method is described that makes use of easily prepared, inexpensive copper synthons as N-heterocyclic carbene (NHC) transfer agents to generate catalytically relevant gold and palladium complexes.

N-Heterocyclic carbene ligated copper complexes act as catalysts in a variety of reactions. A brief overview of this rich chemistry is given here. Of particular note is the ability of Cu(NHC) complexes to functionalize carbonyls, alkenes and alkynes. With growth in the number of Cu(NHC) derived complexes, the catalytic possibilities involving these complexes are ever growing. We feel the full potential of these (for the most part) simply accessed complexes has yet to be fully achieved. The litany of reactions which Cu(NHC) catalyst facilitate are outlined here.

A series of [Pd(NHC)(PR3)] complexes quantitatively form [Pd(η2-O2)(NHC)(PR3)] products when submitted to an dioxygen atmosphere. Synthetic details and structural features of these Pd–peroxo complexes are described. The palladium compounds were found to be efficient catalysts in the oxidation of alcohols into corresponding carbonyl compounds using O2 or air as oxidant. Reactions proceed at low catalyst loadings with a wide range of alcohols.

The synthesis, characterisation and catalytic behaviour of ruthenium indenylidene complexes bearing an N-heterocyclic carbene and triisopropylphosphite are described.

A one-pot procedure for the synthesis of [Cu(X)(NHC)] (X = Cl, Br, I) is reported. The reaction is applicable to a wide range of saturated and unsaturated NHC ligands, is scalable and proceeds under mild conditions using technical grade solvents in air.

The new well-defined catalyst [Pd(μ-Cl)Cl(IPr*)]2 enables the efficient Grignard reagent cross-coupling for the synthesis of tetra-ortho-substituted biaryls. The high reactivity of the complex is associated with the important bulkiness of the IPr* ligand. The dimer represents the most efficient catalyst reported to date for this challenging transformation.

The use of phosphites in second generation, ruthenium-based olefin metathesis pre-catalysts leads to an improvement in catalyst stability and activity at low catalyst loadings.

A novel and efficient method for C–H arylation using well-defined Pd– and Cu–NHC systems has been developed. This process promotes the challenging construction of C–C bonds from arenes or heteroarenes using aryl bromides and chlorides. Mechanistic studies show that [Cu(OH)(NHC)] plays a key role in the C–H activation and is involved in the transmetallation with the Pd–NHC co-catalyst.

We report the first example of BAC–Cu complex (BAC = bis(diisopropylamino)cyclopropenylidene) and its use as a carbene-transfer reagent, allowing access to Au–, Pd–, Ir– and Rh–BAC compounds. Catalytic experiments show the high activity of the [CuCl(BAC)] complex in Click chemistry.

The hydrodehalogenation of polychlorinated phenyls and biphenyls (PCBs), catalysed by palladium N-heterocyclic carbene complexes, proceeds with excellent yields, at very low catalyst loadings and at room temperature, using isopropanol as the hydrogen source and NaOH as the base.

Homo- and heteroleptic bis-NHC copper(I) complexes have been efficiently used as carbene transfer reagents to Au and Pd. The simple and straightforward procedure allows for the synthesis of well-known gold complexes as well as novel cationic bis-NHC Pd(II) species.

A novel synthetic route leading to N-heterocyclic carbene copper complexes has been developed by using air-stable and commercially available copper(I) oxide and imidazolium salts starting materials.

We report the first examples of highly luminescent di-coordinated Pd(0) complexes. Five complexes of the form [Pd(L)(L′)] were synthesized, where L = IPr, SIPr or IPr* NHC ligands and L′ = PCy3, or IPr and SIPr NHC ligands. The photophysical properties of these complexes were determined in degassed toluene solution and in the solid state and contrasted to the poorly luminescent reference complex [Pd(IPr)(PPh3)]. Organic light-emitting diodes were successfully fabricated but attained external quantum efficiencies of between 0.3 and 0.7%.

The N-methylation of amines using CO2 and PhSiH3 as source of CH3 was efficiently performed using a N-heterocyclic carbene copper(I) complex. The methodology was found compatible with aromatic and aliphatic primary and secondary amines. Synthetic and computational studies have been carried out to support the proposed reaction mechanism for this transformation.