Half-Sandwich Iridium Complexes: A Recyclable and Stable Catalyst for Dehydrogenation of Alcohols to Carboxylic Acids.

A series of acylhydrazone-based N,N-chelate half-sandwich iridium complexes have been synthesized through a facile route in good yields. The dehydrogenation of a series of aromatic and aliphatic primary alcohols to corresponding carboxylic acids has been accomplished catalyzed by the prepared air stable iridium complexes under mild reaction conditions. Carboxylic acids were obtained in high yields under open flask condition with broad substrates and good tolerance to sensitive functional groups. Such a half-sandwich iridium catalyst system exhibited high catalytic activity and stability, and a high TOF of 316.7 h-1 could be achieved with a catalyst loading as low as 0.05 mol %. Furthermore, the sustainable catalyst could be reused at least five times without obviously losing its activity, highlighting its potential application in industry. Molecular structure of iridium complex 1 was confirmed by single-crystal X-ray analysis.

Half-Sandwich Ruthenium Complexes with Hydrazone Ligands: Preparation, Structure, and Catalytic Activity in Cyanosilylether Synthesis under an Air Atmosphere.

A new class of N,O-coordinate half-sandwich ruthenium complexes supported by hydrazone ligands with a general formula of [Ru(η6-p-cymene)Cl(L)] have been obtained in moderate to excellent yields conveniently. These air- and moisture-stable ruthenium complexes exhibited excellent catalytic activity in cyanosilylether synthesis under mild reaction conditions. Under the catalysis of ruthenium, various cyanosilylethers with different substituents were obtained through a one-pot reaction of trimethylsilyl cyanide with carbonyl substrates, with good to excellent yields. Excellent catalytic efficiency, a wide substrate range, and mild reaction conditions made this type of ruthenium catalyst have potential for industrial application. All of the half-sandwich ruthenium complexes have been well described by infrared, nuclear magnetic resonance, and EA analysis. Molecular structures of ruthenium complexes 1 and 4 were confirmed by single-crystal X-ray analysis.

Cyclometalated Half-Sandwich Ruthenium Complexes: Preparation, Structure, and Catalytic Synthesis of Phenolic Esters from Aryl Halides without Using External CO under Air.

A series of cyclometalated C,N-chelate half-sandwich ruthenium complexes based on N-heterocyclic ligands were prepared through a simple route with good yields. These air- and moisture-stable cyclometalated ruthenium complexes showed excellent catalytic efficiency in phenoxy carbonylation of aryl halides with phenyl formate derivatives as a CO source and phenol as a coupling partner under air. Ester products were obtained with high yields at room temperature and without the need for an inert atmosphere. The excellent catalytic activity, broad substrate range, and mild reaction conditions made this catalytic system potential for industrial production. In addition, DFT study has been carried out to elaborate the possible mechanism of this Ru-catalyzed reaction.

Half-Sandwich Iridium Complexes with Hydrazone Ligands: Synthesis and Catalytic Activity in N-Alkylation of Anilines or Nitroarenes with Alcohols via Hydrogen Autotransfer.

Here, we synthesize a series of hydrazone-based N,O-chelate half-sandwich iridium complexes through a facile route. All air-stable iridium complexes show high catalytic activity in N-alkylation of a broad scope of aniline derivatives and alcohols with liberating water as the sole byproduct. This reaction provides a smooth route to synthesize diverse monoalkylated amines in good to excellent yields at moderate temperature with a low catalyst loading. Moreover, the challenging N-alkylation process using nitroarene substrates as coupling partners is also carried out in this catalytic system. The mechanistic study shows that the present iridium catalysis process proceeds through a hydrogen borrowing mechanism. All iridium(III) complexes 1-4 are characterized by infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis.

Synthesis and Optoelectronic Properties of Cationic Iridium(III) Complexes with o-Carborane-Based 2-Phenyl Benzothiazole Ligands.

A series of cationic cyclometalated iridium(III) complexes with o-carborane cage on the main ligand of 2-phenylbenzothiazole were synthesized. The prepared iridium complexes (C1-C6) were fully characterized by UV-vis, NMR, and FT-IR spectra. The exact molecular structure of complex C1 was further studied by single crystal X-ray diffraction analysis. The different substitution position of o-carborane on the 2-phenylbenzothiazole ring lead to obvious differences in the emission properties of the synthesized complexes. The o-carboranyl unit results in a bathochromic shift of 10 nm in the fluorescence emission spectrum of C2. In addition, the presence of an o-carborane fragment promoted the strong fluorescence intensity of C1 and C4, which can be used as a tool to effectively boost the intensity of fluorescence properties. The emission fluorescent behavior of iridium(III) complexes can be facilely tuned by structural variations in the main ligands of these materials.

Half-Sandwich Iridium Complexes Based on ß-Ketoamino Ligands: Preparation, Structure, and Catalytic Activity in Amide Synthesis.

A series of ß-ketoamino-based N,O-chelate half-sandwich iridium complexes with the general formula [Cp*IrClL] have been prepared in good yields. These air-insensitive iridium complexes showed desirable catalytic activity in an amide preparation under mild conditions. A number of amides with diverse substituted groups were furnished in a one-pot reaction with good-to-excellent yields through an amidation reaction of NH2OH·HCl with aldehydes in the presence of these iridium(III) precursors. The excellent catalytic activity, mild reaction conditions, and broad substrate scope gave this type of iridium catalyst potential for use in industry. All of the obtained iridium complexes were well characterized by different spectroscopy techniques. The exact molecular structure of complex 3 has been confirmed by single-crystal X-ray analysis.

Synthesis, Structure, and Catalytic Hydrogenation Activity of [NO]-Chelate Half-Sandwich Iridium Complexes with Schiff Base Ligands.

A series of N,O-coordinate iridium(III) complexes with a half-sandwich motif bearing Schiff base ligands for catalytic hydrogenation of nitro and carbonyl substrates have been synthesized. All iridium complexes showed efficient catalytic activity for the hydrogenation of ketones, aldehydes, and nitro-containing compounds using clean H2 as reducing reagent. The iridium catalyst displayed the highest TON values of 960 and 950 in the hydrogenation of carbonyl and nitro substrates, respectively. Various types of substrates with different substituted groups afforded corresponding products in excellent yields. All N,O-coordinate iridium(III) complexes 1-4 were well characterized by IR, NMR, HRMS, and elemental analysis. The molecular structure of complex 1 was further characterized by single-crystal X-ray determination.

Cyclometalated Half-Sandwich Iridium(III) Complexes: Synthesis, Structure, and Diverse Catalytic Activity in Imine Synthesis Using Air as the Oxidant.

Four air-stable cyclometalated half-sandwich iridium complexes 1-4 with C,N-donor Schiff base ligands were prepared through C-H activation in moderate-to-good yields. These complexes have been well characterized, and their exact structure was elaborated on by single-crystal X-ray analysis. The iridium(III) complexes 1-4 showed good catalytic activity in the imine synthesis under open-flask conditions (air as the oxidant) from primary amine oxidative homocoupling, secondary amine dehydrogenation, and the cross-coupling reaction of amine and alcohol. Substituents bonded on the ligands of the iridium complexes displayed little effect on the catalytic efficiency. The stability and good catalytic efficiency of the iridium catalysts, mild reaction conditions, and substrate universality showed their potential application in industrial production.

Half-Sandwich Iridium Complexes for the One-Pot Synthesis of Amides: Preparation, Structure, and Diverse Catalytic Activity.

Several types of air-stable N,O-coordinate half-sandwich iridium complexes containing Schiff base ligands with the general formula [Cp*IrClL] were synthesized in good yields. These stable iridium complexes displayed a good catalytic efficiency in amide synthesis. A variety of amides with different substituents were obtained in a one-pot procedure with excellent yields and high selectivities through the amidation of aldehydes with NH2OH·HCl and nitrile hydration under the catalysis of complexes 1-4. The excellent and diverse catalytic activity, mild conditions, broad substance scope, and environmentally friendly solvent make this system potentially applicable in industrial production. Half-sandwich iridium complexes 1-4 were characterized by NMR, elemental analysis, and IR techniques. Molecular structures of complexes 2 and 3 were confirmed by single-crystal X-ray analysis.

Air-Stable Half-Sandwich Iridium Complexes as Aerobic Oxidation Catalysts for Imine Synthesis.

Several N,O-coordinate half-sandwich iridium complexes, 1-5, containing constrained bulky ß-enaminoketonato ligands were prepared and clearly characterized. Single-crystal X-ray diffraction characterization of these complexes indicates that the iridium center adopts a distorted octahedral geometry. Complexes 1-5 showed good catalytic efficiency in the oxidative homocoupling of primary amines, dehydrogenation of secondary amines, and the oxidative cross-coupling of amines and alcohols, which furnished various types of imines in good yields and high selectivities using O2 as an oxidant under mild conditions. No distinctive substituent effects of the iridium catalysts were observed in these reactions. The diverse catalytic activity, broad substrate scope, mild reaction conditions, and high yields of the products made this catalytic system attractive in industrial processes.

Half-Sandwich Ruthenium Complexes for One-Pot Synthesis of Quinolines and Tetrahydroquinolines: Diverse Catalytic Activity in the Coupled Cyclization and Hydrogenation Process.

Four types of half-sandwich ruthenium complexes with an N,O-coordinate mode based on hydroxyindanone-imine ligands have been prepared in good yields. These stable ruthenium complexes exhibited high activity in the catalytic synthesis of quinolines from the reactions of amino alcohols with different types of ketones or secondary alcohols under very mild conditions. Moreover, the methodology for the direct one-pot synthesis of tetrahydroquinoline derivatives from amino alcohols and ketones has been also developed on the basis of the continuous catalytic activity of this ruthenium catalyst in the selective hydrogenation of the obtained quinoline derivatives with a low catalyst loading. The corresponding products, quinolines and tetrahydroquinoline derivatives, were afforded in good to excellent yields. The efficient and diverse catalytic activity of these ruthenium complexes suggested their potential large-scale application. All of the ruthenium complexes were characterized by various spectroscopies to confirm their structures.

Iridium-mediated regioselective B-H/C-H activation of carborane cage: a facile synthetic route to metallacycles with a carborane backbone.

One-pot reactions of carborane carboxylic acids (L), [Cp*IrCl2]2, and silver salt are reported, which lead to regioselective B-H or C-H bond activation at ambient temperature in good yields. This process is demonstrated for three carborane (o-, m-, p-) dicarboxylates, and metal-mediated B-H functionalization of a p-carborane derivative is accomplished for the first time. Two metal-induced self-assembly routes to tetra-nuclear metallacycles 3 and 5 were performed through B(4, 7)/H and B(2, 10)/H activation, respectively, and the two metallacycles were found to be stable and to exist in solution as discrete complexes. Different activation modes in the carborane cage were ascribed to the characteristic structure of the products and the electronic density differences. The analogous reaction of o-carborane monocarboxylate with the same metal precursor gave the C-H activation complex 6, indicating that the B-H bond is more stable than the C-H bond in this carborane cage. The selective activation was confirmed by DFT calculation results. In this study, a facile and efficient synthetic route has been developed through specific B-H bond activation to construct carborane-based metallacycles that are unavailable by conventional methods.

Half-sandwich ruthenium complexes with acylhydrazone ligands: synthesis and catalytic activity in the N-alkylation of hydrazides.

Novel half-sandwich ruthenium complexes termed [(p-cymene)RuClL] were synthesized by chelating arylhydrazone ligands with [(p-cymene)RuCl2]2 and were then fully characterized using different spectroscopic and analytical techniques. The crystal structure of complex 4 indicated that the hydrazone ligands bonded to the ruthenium ion in a bidentate manner through the imine nitrogen and imidazolate oxygen, exhibiting a pseudo-octahedral geometry centered by the ruthenium atom. The as-fabricated air and moisture stable half-sandwich ruthenium complexes demonstrated excellent catalytic activity towards the N-alkylation of hydrazides under mild conditions. Under the catalysis of ruthenium complexes, acyl hydrazides were reacted with different types of alcohols in a one-pot reaction, resulting in N-alkylation hydrazides with different substituents. This catalyst exhibited characteristics such as high catalytic efficiency, broad substrate scope, and mild reaction conditions, indicating that it has great potential for industrial applications.

Cationic N,S-chelate half-sandwich iridium complexes: synthesis, characterization, anticancer and antiplasmodial activity.

A series of pyrazole-based ligands and their corresponding cationic N,S-chelate half-sandwich iridium complexes were successfully synthesized. All iridium complexes exhibited good anticancer activity against the MCF-7 and MDA-MB-231 human breast cancer cells. The cytotoxic activity of unsubstituted iridium complex 1 is greater than that of cisplatin against MCF-7 cells. In addition, the cationic half-sandwich iridium complexes are also efficient in antiplasmodial study and complex 1 displayed the best activity as its IC50 was observed to be approximately 0.11 µM against the CQS-NF54 strain. These iridium complexes generally exhibited enhanced activity against the CQS-NF54 strain in comparison with that against the CQR-K1 strain. An "IC50 speed assay" investigation against the CQS-NF54 strain indicated complexes 1-3 to be fast-acting complexes that reach their lowest IC50 values within 16 hours. All complexes were fully characterized by IR spectroscopy, NMR spectroscopy, and elemental analysis, and the structure of the iridium complex was confirmed by single-crystal X-ray diffraction.

Half-sandwich iridium complexes with hydrazone ligands: preparation, structure, and catalytic synthesis of cyanosilylethers under air.

A series of hydrazone-based N,O-chelate half-sandwich iridium complexes were synthesized through a facile route with good yields. These air- and moisture-stable iridium complexes exhibited excellent catalytic activity in the cyanosilylether synthesis under mild reaction conditions. Under the catalysis of iridium, various cyanosilylethers with different substituents were obtained through a one-pot reaction of trimethylsilyl cyanide (TMSCN) with carbonyl substrates, with good to excellent yields. The excellent catalytic efficiency, wide substrate range, and mild reaction conditions made this type of iridium catalyst have the potential for industrial applications. All the half-sandwich iridium complexes were well characterized by IR, NMR, and EA analyses. The molecular structure of iridium complex 1 was confirmed by single-crystal X-ray analysis.

Superconductivity and density-wave fluctuations in an extended triangular Hubbard model: an application to SnSe2.

We employ the fluctuation-exchange approximation to study the relation of superconducting pairing symmetries and density-wave fluctuations based on the extended triangular Hubbard model upon electron doping and interactions, with an possible application to the layered metal dichalcogenide SnSe2. For the case where the interactions between electrons contain only the on-site Hubbard term, the superconducting pairings are mainly mediated by spin fluctuations, and the spin-singlet pairing with thed-wave symmetry robustly dominates in the low and moderate doping levels, and ad-wave to extendeds-wave transition is observed as the electron doping reachesn = 1. When the near-neighbor site Coulomb interactions are also included, the charge fluctuations are enhanced, and the spin-triplet pairings with thep-wave andf-wave symmetries can be realized in the high and low doping levels, respectively.

Versatile reactivity of half-sandwich Ir and Rh complexes toward carboranylamidinates and their derivatives: synthesis, structure, and catalytic activity for norbornene polymerization.

Synthesis, structure, and reactivity of carboranylamidinate-based half-sandwich iridium and rhodium complexes are reported for the first time. Treatment of dimeric metal complexes [{Cp*M(µ-Cl)Cl}(2)] (M = Ir, Rh; Cp* = η(5)-C(5)Me(5)) with a solution of one equivalent of nBuLi and a carboranylamidine produces 18-electron complexes [Cp*IrCl(Cab(N)-DIC)] (1 a; Cab(N)-DIC = [iPrN=C(closo-1,2-C(2)B(10)H(10))(NHiPr)]), [Cp*RhCl(Cab(N)-DIC)] (1 b), and [Cp*RhCl(Cab(N)-DCC)] (1 c; Cab(N)-DCC = [CyN=C(closo-1,2-C(2)B(10)H(10))(NHCy)]). A series of 16-electron half-sandwich Ir and Rh complexes [Cp*Ir(Cab(N')-DIC)] (2 a; Cab(N')-DIC = [iPrN=C(closo-1,2-C(2)B(10)H(10))(NiPr)]), [Cp*Ir(Cab(N')-DCC)] (2 b, Cab(N')-DCC = [CyN=C(closo-1,2-C(2)B(10)H(10)(NCy)]), and [Cp*Rh(Cab(N')-DIC)] (2 c) is also obtained when an excess of nBuLi is used. The unexpected products [Cp*M(Cab(N,S)-DIC)], [Cp*M(Cab(N,S)-DCC)] (M = Ir 3 a, 3 b; Rh 3 c, 3 d), formed through BH activation, are obtained by reaction of [{Cp*MCl(2)}(2)] with carboranylamidinate sulfides [RN=C(closo-1,2-C(2)B(10)H(10))(NHR)]S(-) (R = iPr, Cy), which can be prepared by inserting sulfur into the C-Li bond of lithium carboranylamidinates. Iridium complex 1 a shows catalytic activities of up to 2.69×10(6)  g(PNB) mol(Ir)(-1) h(-1) for the polymerization of norbornene in the presence of methylaluminoxane (MAO) as cocatalyst. Catalytic activities and the molecular weight of polynorbornene (PNB) were investigated under various reaction conditions. All complexes were fully characterized by elemental analysis and IR and NMR spectroscopy; the structures of 1 a-c, 2 a, b; and 3 a, b, d were further confirmed by single crystal X-ray diffraction.

An Efficient Probe of Cyclometallated Phosphorescent Iridium Complex for Selective Detection of Cyanide.

A cyclometallated phosphorescent iridium-based probe to detect CN- was prepared through a cyanide alcoholize reaction based on the C^N type main ligand and N^N type ancillary ligand (2-phenyl pyridine and 1,10-phenanthroline-5-carboxaldehyde, respectively). The efficient probe exhibited good sensitivity in response to CN- in an CH3CN and H2O (95/5) mixture within a 1.23 µM detection limit. The response of PL is directly in line with the concentration of CN- from 0 to 2.0 equiv. The PL investigation of other reactive anions proved the great selectivity to CN-. Additionally, upon adding 1.0 equiv. of cyanide, the formation of cyanohydrin was correctly elucidated in 1H NMR, FT-IR, and mass spectra studies. The conspicuous results indicate that the iridium complex has the potential possibility of application in other biosystems related to CN-.

Catalytic hydrogenation of carbonyl and nitro compounds using an [N,O]-chelate half-sandwich ruthenium catalyst.

A series of N,O-chelate half-sandwich ruthenium complexes for both carbonyl and nitro compound hydrogenation have been synthesized based on ß-ketoamino ligands. All complexes exhibited high activity for the catalytic hydrogenation of a series of ketones and nitroarenes with molecular H2 as the reducing reagent in aqueous medium. Consequently, the catalytic system showed the catalytic TON values of 950 for 1-phenylethanol in acetophenone hydrogenation and 1960 for 1-chloro-4-nitrobenzene in p-chloroaniline hydrogenation. Good catalytic activity was displayed for various kinds of substrates with either electron-donating or electron-withdrawing groups. The neutral ruthenium complexes 1-4 were fully characterized using NMR, IR, and elemental analysis. Molecular structures of complexes 2 and 4 were further confirmed using single-crystal X-ray diffraction analysis.