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The dinitrogen (N2) chemistry of lanthanides remains less developed compared to the d‐block metals and lanthanide‐promoted N2 functionalization chemistry in well‐defined lanthanide complexes remains elusive. Here we report the synthesis and characterization (SQUID, EPR, DFT, X‐Ray) of the siloxide supported heterobimetallic (Tm/K) complexes [{KTm(OSi(OtBu)3)3}2(μ‐η2 : η2‐N2)] (1) and [K3{Tm(OSi(OtBu)3)3}2(μ‐η2 : η2‐N2)] (2). Complex 2 provides a rare example of a metal complex of the triply reduced N23− radical. The structure of 2 differs from the few previously reported N23− complexes as it presents two Tm and three K cations binding the N23− radical, facilitating N2 functionalization. Notably, the K3Tm2‐bound N23− moiety reacts with excess H+ to form NH4Cl in 18 % yield, and with MeOTf at room temperature to yield the dimethyl hydrazido complex [K2{Tm(OSi(OtBu)3)3}2(μ‐(CH3)NN(CH3))] (3). Protonolysis of 3 yields MeHN−NMeH ⋅ 2HCl in 18 % yield. [ABSTRACT FROM AUTHOR]

Clathrochelate complexes of cobalt are known in the oxidation states I, II, and III. Low‐valent Co(I) complexes are highly reactive compounds, and there is only limited knowledge about their structures in the solid state. Herein, we describe the crystallographic analyses of three low‐valent clathrochelate complexes, along with analyses of the corresponding Co(II) precursors. Two different ligand environments were studied: a) ligands with alkyl substituents, which render the complexes highly reducing, and b) potentially redox non‐innocent ligands. Our analyses show that the ligands have a large effect on the redox potentials, but only a small effect on the geometry and the electronic state of the central Co ion. [ABSTRACT FROM AUTHOR]

A synthetic route towards polycyclic heteroaryl triazenes has been developed. Alkynyl triazenes were coupled to phenyl‐substituted indoles, imidazoles and sydnones via rhodium‐catalyzed double C−H or C−H/N−H activation reactions. The oxidative annulations gave triazenes connected to imidazo[1,2‐a]quinoline, indolo[2,1‐a]isoquinoline and sydnone‐quinoline scaffolds in moderate to excellent yields. The triazene‐bearing fused sydnone‐quinolines were used for subsequent orthogonal transformations. The sydnone moiety allowed for post‐functionalization via 1,3‐dipolar cycloadditions in excellent yields, and the triazene group can be substituted by a range of functional groups. [ABSTRACT FROM AUTHOR]

Vinyl triazenes are potentially interesting compounds for synthetic organic and medicinal chemistry, but synthetic routes to make olefins with triazene groups are still scarce. In this work, we show that vinyl triazenes are accessible by Pd‐catalyzed addition reactions to alkynyl triazenes. Hydrogenation, hydroarylation, and haloallylation reactions allow preparing mono‐, di‐ and trisubstituted vinyl triazenes in high yields, and with good regio‐ and stereoselectivities. [ABSTRACT FROM AUTHOR]

Abstract: Covalent adducts of imidazole‐based mesoionic carbenes and nitrous oxide (N2O, “laughing gas”) can be converted into azo dyes by reaction with arenes in the presence of AlCl3 or HCl. The azo coupling can be achieved with electron‐rich aromatic compounds such as mesitylene, trimethoxybenzene, azulene, or dibenzo‐18‐crown‐6. The latter coupling reaction allows for the easy preparation of a colorimetric sensor for potassium or sodium ions. As a putative intermediate of the reaction with acid, we were able to isolate and structurally characterize a rare diazohydroxide. Using imidazolium compounds with two N2O groups, it was possible to prepare amine‐substituted azo dyes or dyes with two azoarene groups attached to the heterocycle. A triazole‐based mesoionic carbene was also found to form a stable covalent adduct with N2O. The adduct could be used to prepare novel azo triazolium dyes in good yields. [ABSTRACT FROM AUTHOR]

A simple and versatile method for the preparation of linear, trisubstituted triazenes is reported. The procedure is based on the reaction of Grignard reagents with 1-azido-4-iodobutane or 4-azidobutyl-4-methylbenzenesulfonate. These organic azides enable the regioselective formation of triazenes via an intramolecular cyclization step. The new method can be used for the preparation of aryl, heteroaryl, vinyl, and alkyl triazenes. The synthetic utility of vinyl triazenes is demonstrated by acid-induced C–N, C–O, C–F, C–P, and C–S bond-forming reactions. [ABSTRACT FROM AUTHOR]

A new procedure for the synthesis of highly substituted 1,3-diaminopyrazoles is described. As substrates, we have employed 1-alkynyltriazenes and imines. The formation of pyrazoles was achieved by two-fold C-N coupling reactions in the presence of (JohnPhos)AuCl and Ag NTf2 as catalyst precursors. The regioselectivity of the reaction was inferred from a crystallographic analysis of one reaction product. [ABSTRACT FROM AUTHOR]

Drugs that allosterically modulate G protein-coupled receptor (GPCR) activity display higher specificity and may improve disease treatment. However, the rational design of compounds that target the allosteric site is difficult, as conformations required for receptor activation are poorly understood. Guided by photopharmacology, a set of prearranged positive allosteric modulators (PAMs) with restricted degrees of freedom was designed and tested against the glucagon-like peptide-1 receptor (GLP-1R), a GPCR involved in glucose homeostasis. Compounds incorporating a trans-stilbene comprehensively outperformed those with a cis-stilbene, as well as the benchmark BETP, as GLP-1R PAMs. We also identified major effects of ligand conformation on GLP-1R binding kinetics and signal bias. Thus, we describe a photopharmacology-directed approach for rational drug design, and introduce a new class of stilbene-containing PAM for the specific regulation of GPCR activity. [ABSTRACT FROM AUTHOR]

A ditopic carbanionic N-heterocyclic carbene was found to react with the inert gas nitrous oxide, resulting in a stable covalent adduct with two intact N2O groups attached to the heterocycle. Mesoionic N-heterocyclic carbenes derived from C2-arylated 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene are also able to form adducts with one or two N2O groups. Crystallographic analyses of all adducts reveal bent N2O groups, which can adopt a cis or trans configuration. [ABSTRACT FROM AUTHOR]

1-Aryl-3,3-dialkyltriazenes have received considerable attention in the context of synthetic and medicinal chemistry. In contrast, the chemistry of other unsaturated triazenes is largely unexplored. The synthesis of 1-allenyltriazenes is described. This new class of compounds can be obtained by base-induced isomerization of 1-alkynyltriazenes. The latter are accessible by reaction of alkynyl Grignard reagents with lithium amides and nitrous oxide. 1-Allenyltriazenes were found to be thermally labile, but they can be stored without degradation at lower temperatures. In the presence of ZnCl2, 1-allenyltriazenes rearrange into N-aminopyrazoles. [ABSTRACT FROM AUTHOR]

The reduction of the nitride-bridged diuranium(IV) complex Cs[{U(OSi(OtBu)3)3}2(μ-N)] affords the first example of a uranium nitride complex containing uranium in the +III oxidation state. Two nitride-bridged complexes containing the heterometallic fragments Cs2[UIII···-N···-UIV] and Cs3[UIII···-N···-UIII] have been crystallographically characterized. The presence of two or three Cs+ cations binding the nitride group is key for the isolation of these complexes. In spite of the fact that the nitride group is multiply bound to two uranium and two or three Cs+ cations, these complexes transfer the nitride group to CS2 to afford SCN- and uranium(IV) disulfide. [ABSTRACT FROM AUTHOR]

Iron-catalyzed hydrogenation has drawn much attention, yet the scope and chemoselectivity of iron catalysis warrant further improvement. Here we report new iron pincer complexes as chemoselective hydrogenation and transfer hydrogenation catalysts. Several Fe(II) complexes supported by a 2,6-bis(phosphinito)pyridine ligand (PONOP) have been synthesized. Fe(II) hydride complexes [(iPrPONOP)Fe(CO)(H)Br] (2) and [(iPrPONOP)Fe(CO)(H)(CH3CN)](OTf) (3) can activate H2 at room temperature. Complexes 2 and 3 are hydrogenation catalysts at room temperature, and the hydrogenation is selective for aldehyde in the presence of ketone and alkene groups. 2 and 3 are also chemoselective transfer hydrogenation catalysts using sodium formate as the hydride source. [ABSTRACT FROM AUTHOR]

Imidazolin-2-imine and imidazolidin-2-imine ligands are versatile N donors in transition metal chemistry. Here, we describe the synthesis and characterization of (arene)Ru complexes with these ligands. Simple adducts of the type [( p-cymene)Ru(L)Cl2] (L = 1,3-diarylimidazolin-2-imine or 1,3-dimesitylimidalzolidin-2-imine) can be converted into complexes in which the imines act as π ligands with tethered imine groups. Furthermore, the high basicity of the N donor group can promote self-activation of the (arene)Ru complexes. [ABSTRACT FROM AUTHOR]

A synthetic procedure for the synthesis of two molecular borophosphate cages is described. Heating of ethyl phosphate with phenylboronic or 4-formylboronic acid in toluene gives [6+6] condensation products of the general formula [EtOPO3BAr]6. Crystallographic analyses show that the compounds form cages, which can be described as dimers of 12-membered (EtOPO3BAr)3 macrocycles. The successful incorporation of aldehyde functions on the cage exterior demonstrates that these borophosphates can be decorated with reactive groups. [ABSTRACT FROM AUTHOR]

Highlights: [•] Four new alkyl-substituted 1-(2′-pyridyl)-pyrazole ligands. [•] Five new green-phosphorescent cationic cyclometalated iridium(III) complexes. [•] Phosphorescence is quenched by alkyl groups that hinder iridium(III)–ligand bonding. [Copyright &y& Elsevier]

The synthesis of a cylindrical, imine-based cage composed of two trimeric metallamacrocycles is described. The cage acts as a heterotopic receptor for alkali metal cations. The small cations Li+, Na+, and K+ bind to the outside of the cage with good selectivity for Li+, whereas the larger cations Rb+ and Cs+ are bound inside the cage to form unusual π complexes with a good selectivity for Cs+. Negative heterotopic cooperativity between the two binding sites is observed. The complexation of Cs+ is associated with a color change, which enables the cage to be used as a specific sensor for Cs+. [ABSTRACT FROM AUTHOR]

Abstract: We achieve a 20–58nm (610–1890cm−1) blue-shift of the phosphorescence maximum of iridium(III) complexes [(C^N)2Ir(N^N)](PF6) of 1,10-phenanthrolines (N^N) by modifying the cyclometalating 2-phenylpyridine ligand (C^N = ppy) with an electron-withdrawing 4′-fluoro or 4′-trifluoromethyl group or by replacing the pyridine in ppy with a pyrazole. New complexes exhibit green or yellow phosphorescence in argon-saturated 10−5 M dichloromethane solution at room temperature with a maximum at 525–563nm, quantum yield of 54–68%, and excited-state lifetime of 1.1–2.7μs. [Copyright &y& Elsevier]

Abstract: Cationic bis-cyclometalated iridium(III) complexes [(C^N)2Ir(N^N)](PF6) with 2-(2′-pyridyl)-5-R-1,3,4-oxadiazoles (N^N; R=1-adamantyl, mesityl, N-diphenylamino) have a redox gap of 2.58–2.68V and exhibit orange–red phosphorescence in argon-saturated dichloromethane solution with a maximum, quantum yield, and excited-state lifetime of 613–644nm, 2–6%, and 90–280ns. [Copyright &y& Elsevier]

A versatile and experimentally facile procedure for the synthesis of borophosphonate cages of the general formula [ tBuPO3BR′]4 is described. The method involves heating of tert-butylphosphonic acid with a boronic acid in toluene to give borophosphonates in [4+4] condensation reactions. The products display a heterocubane structure with bent P-O-B bridges as evidenced by crystallographic analyses. Scrambling experiments show that the borophosphonate cages are constitutionally dynamic scaffolds with exchange reactions occurring on the hour time scale at room temperature. The cages can be decorated with reactive groups such as aldehydes. Our results demonstrate that borophosphonate cages are interesting building blocks for dynamic covalent chemistry. [ABSTRACT FROM AUTHOR]

Abstract: Two new cationic iridium(III) complexes with cyclometalating 1-phenylindazole or 2-phenyl-1,2,3-triazole ligands, [(C^N)2Ir(4,4′-di-tert-butyl-2,2′-dipyridyl)](PF6), exhibit yellow or green phosphorescence with quantum yields and excited state lifetimes of up to 45% and 840ns in argon-saturated dichloromethane solution at room temperature. [Copyright &y& Elsevier]

Abstract: Bis-cyclometalated cationic Ir(III) diimine complexes [Ir(C^N)2(N^N)](PF6) with 1-phenylpyrazoles (C^N) and 1-(4′-tert-butyl-2′-pyridyl)pyrazole (N^N) are white solids that have absorption onset below 425nm and electrochemical gap of up to 3.5V. [Copyright &y& Elsevier]

The nickel(II) hydride complex [(MeN2N)Ni-H](2) was synthesized by the reaction of [(MeN2N)Ni-OMe] (6) with Ph2SiH2and was characterized by NMR and IR spectroscopy as wellas X-ray crystallography. 2was unstable in solution,and it decomposed via two reaction pathways. The first pathway wasintramolecular N–H reductive elimination to give MeN2NH and nickel particles. The second pathway was intermolecular,with H2, nickel particles, and a five-coordinate Ni(II)complex [(MeN2N)2Ni] (8) as the products. 2reacted with acetone and ethylene,forming [(MeN2N)Ni-OiPr] (9) and [(MeN2N)Ni-Et] (10), respectively. 2also reacted with alkylhalides, yielding nickel halide complexes and alkanes. The reductionof alkyl halides was rendered catalytically, using [(MeN2N)Ni-Cl] (1) as catalyst, NaOiPr or NaOMe as base, and Ph2SiH2or Me(EtO)2SiH as the hydride source. The catalysis appearsto operate via a radical mechanism. [ABSTRACT FROM AUTHOR]

A series of compounds of general formula [Ru(η6-arene)(pta)(PR3)Cl]BF4 (arene = p-cymene or 4-phenyl-2-butanol; pta = 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane, PR3 = PPh2(p-C6H4C2H4C8F17), PPh(p-C6H4C2H4C8F17)2, P(p-C6H4C2H4C6F13)3, PPh3 or P(p-C6H4F)3) have been prepared and characterized by spectroscopic methods. The structure of [Ru(η6-p-cymene)(pta)Cl(P(p-C6H4F)3)]BF4 has also been established in the solid state by X-ray crystallography. The cytotoxicities of the compounds were determined in the A2780 and A2780 cisplatin-resistant cell lines revealing that the fluorinated phosphines significantly increase antiproliferative activity relative to their bis-chloride precursors. Two of the complexes were found to be thermoresponsive, that is, showing poor water solubility at 37 °C and good solubility at 42 °C, the temperature of a heated tumor, providing a method of tumor targeting. Incubation at 42 °C for 2 h resulted in improved cytotoxicities for two of the complexes. [ABSTRACT FROM AUTHOR]

New heterobinuclear lanthanide complexes with benzoxazole-substituted 8-hydroxyquinolines, [Ln(ligand)2(μ-ligand)2Na] (Ln: Yb, Lu), have been prepared and their structure established X-ray crystallography, 1H NMR spectroscopy, and photophysical studies. The complexes display efficient ligand-sensitized near-infrared luminescence of ytterbium at 925—1075 nm with lifetimes and quantum yields as high as 22μs and 3.7%, in the solid state, and 20 μs and 2.6% in CH2Cl2solution, respectively. These quantum yields are the highest reported to date for ytterbium complexes with organic ligands containing C—Hbonds. A long-wavelength and intense intraligand charge-transfer transition (...max=446—456 nm; ϵ ≈1.2×104 M-1 cm-1) allows for the excitation of infrared luminescence with visible light up to 600 nm. Remarkable features of these complexes include (i) quantitative ligand-to-YbIII energy transfer resulting in high overall efficiency of the ytterbium luminescence, (ii) unusually short radiative lifetime of the YbIII ion, 706—745 μs for solutions in CH2Cl2, calculated from the f—f absorption spectra, and 513—635 μs estimated for solid state samples from quantum yield and lifetime data, and (iii) the unexpected large influence of second-sphere composition on the radiative lifetime of ytterbium. [ABSTRACT FROM AUTHOR]

A facile synthesis of benzothiazole- and benzoxazole-substituted pyridine-2-carboxylic acids has been developed. These ligands form mononuclear nine-coordinate complexes [Ln([subK][sup3]-ligand)[sub2]([subK][sup1]-ligand)(H[sub2]O)[sub2]] with light and heavy trivalent lanthanides, as established from the X-ray analysis of 11 complexes. A crystal structure of a minor product, the anhydrous nine-coordinate complex [Eu([subK][sup3]-L)[sub3]], has also been determined. Photophysical studies of gadolinium chelates indicate that the triplet states of the new ligands are located at 20400-21400 cm[sup-1]. The ligands are good sensitizers of the europium luminescence with ligand-to-metal energy transfer efficiency in the range 60-100%. The overall quantum yields of the europium emission are substantial, 12-14% in the solid state, and increases to 29-39% upon replacement of two metal-coordinated water molecules with dimethylsulfoxide in solution. The luminescence of near-infrared emitting lanthanides is also sentisized, but quantum yields are much smaller, reaching 0.17% for neodymium and 1.25% for ytterbium in DMSO, while energy transfer two efficiencies for these two ions are below 50%. [ABSTRACT FROM AUTHOR]

An improved synthesis of 2-(2'-benzothiazole)- and 2-(2'-benzoxazole)-8-hydroxyquinoline ligands that combine a tridentate N,N,O-chelating unit for metal binding and extended chromophore for light harvesting is developed. The 2-(2'-benzoxazole)-8-hydroxyquinoline ligands form mononuclear nine-coordinate complexes with neodymium, [Nd- (κ[sup3]-ligand)[sub3]], and an eight-coordinate complex with ytterbium, [Yb(κ[sup3]-ligand)[sub2] ∙ (κ[sup1]-ligand) ∙ H[sub2]O], as verified by crystallographic characterization of five complexes with four different ligands. The chemical stability of the complexes increases when the ligand contains 5,7-dihalo-8-hydroxyquinoline versus an 8-hydroxyquinoline group. The complexes feature a ligand-centered visible absorption band with a maximum at 508-527 nm and an intensity of (7.5-9.6) x 10[sup3] M[sup-1] ∙ cm[sup-1]. Upon excitation with UV and visible light within ligand absorption transitions, the complexes display characteristic lanthanide luminescence in the near-infrared at 850-1450 nm with quantum yields and lifetimes in the solid state at room temperature as high as 0.33% and 1.88 μs, respectively. The lanthanide luminescence in the complexes is enhanced upon halogenation of the 5,7- positions in the 8-hydroxyquinoline group and upon the addition of electron-donating substituents to the benzoxazole ring. Facile modification of chromophore units in 2-(2'-benzoxazole)-8-hydroxyquinoline ligands provides means for controlling the luminescence properties of their lanthanide complexes. [ABSTRACT FROM AUTHOR]

A new class of benzimidazole-substituted 8-hydroxyquinoline ligands has been prepared that contain a monoanionic tridentate N,N,O-coordinating unit. These ligands form charge-neutral lanthanide complexes of the type [Ln(L-R)3]·nH2O or [Ln2(L2)3]·nH2O (n = 1-3) with early lanthanides from LaIII to GdIII inclusive. Crystallographic characterization was carried out for 11 complexes with 6 different ligands. In all of these structures, the lanthanide ion was found to be nine-coordinated by three ligands arranged in an "up-up-down" fashion around the metal center. The coordination environment can be described as a tricapped trigonal prism, with N atoms of quinoline rings occupying capping positions. Upon deprotonation of the ligand and complex formation, a new absorption band appears in the visible range of the spectrum with a maximum in the range of 466-483 nm and molar absorption coefficient of (7.2 - 18) x 10³ M-1 cm-1. Its origin is likely to be an intraligand phenolate-to-pyridyl charge transfer transition centered on the 8-hydroxyquinolate chromophore. Upon excitation in ligand absorption bands, new NdIII complexes display characteristic metal-centered luminescence in the near-infrared region from 850 to 1450 nm with quantum yields and lifetimes in solid state at room temperature as high as 0.34% and 1.2 μs, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A solvent-dependent silyl migration of lithiated biphenyls is described, involving the intermediate formation of a pentacoordinated silicate complex. Differences in the relative basicities of the aryllithium intermediates are the possible driving force for this migration. [Copyright &y& Elsevier]

A new synthetic strategy for the construction of boron-based macrocycles and dendrimers is described. Condensation of aryl- and alkylboronic acids with 3,4-dihydroxypyridine is shown to give pentameric macrocycles in which five boronate esters are connected by dative B-N bonds. Three macrocycles have been characterized crystallographically. The boron atoms of these assemblies represent chiral centers, and the assembly process is highly diastereoselective. Attachment of amino or aldehyde groups in the meta position of the arylboronic acid building blocks does not interfere with macrocyclization. This allows performing multicomponent assembly reactions between functionalized boronic acids, dihydroxypyridine ligands, and amines or aldehydes, respectively. Reaction of 3,5-diformylphenylboronic acid, 3,4-dihydroxypyridine, and a primary amine R-NH2 (R = Ph, Bn) gives dendritic nanostructures having a pentameric macrocyclic core and 10 amine-derived R groups in their periphery. Combination of 3,5- diformylphenylboronic acid with 2,3-dihydroxypyridine and the dendron 3,5-(benzyloxy)benzylamine, on the other hand, results in formation of a dendrimer with a tetrameric macrocyclic core and eight dendrons in its periphery. [ABSTRACT FROM AUTHOR]

Two unsymmetrical ditopic hexadentate ligands designed for the simultaneous recognition of two different trivalent lanthanide ions have been synthesized, LAB2 and LAB3, where A represents a tridentate benzimidazole-pyridine-benzimidazole coordination unit, B2 a diethylamine-substituted benzimidazole-pyridine-carboxamide one, and B3 a chlorine-substituted benzimidazole-pyridine-carboxamide moiety. Under stoichiometric 2:3 (Ln/L) conditions, these ligands self-assemble with lanthanide ions to yield triple-stranded bimetallic helicates. The crystal structures of four helicates with LAB3 of composition [LnLn′(LAB3)3](ClO4)6•solv (CeCe, PrPr, PrLu, NdLu) show the metal ions embedded into a helical structure with a pitch of about 13.2-13.4 Å. The metal ions lie at a distance of 9.1-9.2 Å and are nine-coordinated by the three ligand strands, which are oriented in a HHH (head-head-head) fashion, where all ligand strands are oriented in the same direction. In the presence of a pair of different lanthanide ions in acetonitrile solution, the ligand LAB3 shows selectivity and gives high yields of heterobimetallic complexes. LAB2 displays less selectivity, and this is shown to be directly related to the tendency of this ligand to form high yields of HHT (head-head-tail) isomer. A fine-tuning of the HHH ⇆ HHT equilibrium and of the selectivity for heteropairs of LnIII ions is therefore at hand. [ABSTRACT FROM AUTHOR]

The reaction of half-sandwich complexes of ruthenium, rhodium, and iridium with amino-substituted 3-hydroxy-2-pyridone ligands in aqueous solution gives monomeric O,O'-chelate complexes. Upon addition of base, the complexes assemble to form trimeric metallamacrocycles, as evidenced by NMR spectroscopy and single-crystal X-ray analyses. The macrocycles are able to act as highly selective receptors for lithium ions. The binding constants depend on the nature of the half-sandwich complex, the ligand, and the pH. With a commercially available (cymene)Ru complex, a receptor with a Li+ binding constant of Ka = 5.8 (±1.0) × 104 M-1 and a Li+--N+ selectivity of 10 000:1 can be obtained. The fact that the assembly process of the receptor is pH-dependent can be used to detect the presence of lithium ions by a pH measurement. Furthermore, it is possible to transduce the binding of Li+ into a change of color by means of a chemical reaction with FeCl3. This allows the detection of Li+ in the pharmacologically relevant concentration range of 0.5-1.5 mM by the "naked eye". [ABSTRACT FROM AUTHOR]

The reaction of [(arene)RuCl2]2 (arene = cymene, 1,3,5-C6H3Me3) and [Cp*RhCl2]2 half-sandwich complexes with tridentate heterocyclic ligands in the presence of base has been investigated. In all cases, the chloro-ligands were substituted to give metallacyclic products with ring sizes between 4 and 18 atoms. The cyclization occurs in a highly diastereoselective fashion with chiral recognition between the different metal fragments. The complexes were comprehensively characterized by elemental analysis, NMR spectroscopy, and single crystal X-ray crystallography. For 2-hydroxy-nicotinic acid and 2-amino-nicotinic acid, dinuclear structures were obtained (1517) whereas for 2,3-dihydroxyquinoline, 2,3-dihydroxyquinoxaline, and 6-methyl-2,3-phenazinediol, trimeric assemblies were found (19-22), and for 4-imidazolecarboxylic acid, a tetrameric assembly (18) was found. [ABSTRACT FROM AUTHOR]

The aminophosphine C[sub 6]H[sub 4](o-CN)NHPPh[sub 2], 1, containing an electron-withdrawing nitrile group, was prepared from the lithiation of 2-aminobenzonitrile followed by addition of Ph[sub 2]PCI. Lithiation of 1 using [sup n]BuLi affords the anion [Ph[sub 2]PN(Li)C[sub 6]H[sub 4](o-CN)(thf)]sub 2], 2. Compound 2 reacts with Ph[sub 2]PCI or MeI to afford C[sub 6]H[sub 4](o-CN)N=PPh[sub 2]—PPh[sub 2], 3, and [C[sub 6]H[sub 4](o-CN)N=PPh[sub 2](CH[sub 3])(LiI)(C[sub 2]H[sub 5]O)]sub 2], 4, respectively. In these products new P-P and P-C bonds have been formed rather than N-P and N-C bonds. The structures of 1-4 have been determined by single-crystal X-ray diffraction analysis, and the synthetic results are discussed in terms of the structural data and NMR spectroscopic studies. [ABSTRACT FROM AUTHOR]

Examines the complexes of molecular LiF and LiFHF using metallamacrocyclic receptors. Characterization of complexes by multinuclear nuclear magnetic resonance spectroscopy; Observation of strong scalar coupling of compounds; Determination on the structure of complexes by single-crystal X-ray analysis.

Investigates the structure and reactivity of aquacarbonylruthenium(II) complexes. Oxygen exchange between the bulk water and the carbonyl oxygens; Water-soluble organometallic compounds; Reactivity of metal complexes; Comparison of different ground-state properties with the observed reactivities.

Examines the structure, thermodynamic, and photophysical properties of the lanthanide helicates both in the solid state and in water. Characterization of lanthanide helicates; Stability of helicates between pH = 4 and 13; Functionalization of the ligands; Structural design of the receptor based on the dimetallic triple-stranded helicates.

A coumarin derivative was employed for the detection of biogenic amines in buffered aqueous solution by UV-Vis or fluorescence spectroscopy. Incorporated in a polymeric matrix, the dye can also be used for the optical detection of gaseous amines. [ABSTRACT FROM AUTHOR]

Clusters containing nine lanthanide and six sodium ions are crystallized with the help of a tridentate ligand bearing a phosphonic acid group; the structure of the Eulll compound reveals a host-guest assembly Eu⊂Na6Eu8L16 with a substantial quantum yield (32%). A similar Eulll-Yblll structure displays dual luminescence in the visible (Eulll) and NIR (Yblll) ranges. [ABSTRACT FROM AUTHOR]

The reaction of [(Et3P)PdCl2]2 with 2,3-dihydroxypyridine, 5-chloro-2,3,-dihydroxypyridine, or 2-hydroxynicotinic acid in the presence of base gives neutral, metallomacrocyclic compounds in which the heterocycles act as dianionic, bridging ligands. The macrocycles contain four or ten palladium atoms as evidenced by single crystal X-ray analyses. [ABSTRACT FROM AUTHOR]

The oxidative addition of 1 equiv. of Ph3SnH to Pt3(μ-CO)3(PCy3)3 affords the triangular cluster [Pt3(μ-CO)3(PCy3)3(Ph3Sn)H] (1). The same reaction with the isostructural 42-electron cluster [Pt3(μ-CO)3(PtBu3)3] gives the 18-electron monomeric complex [PtH(CO)(PtBu3)(SnPh3) ] (2) instead of the 44-electron product. The structure of both complexes in solution have been established by 1H, 13C, 31P, 195Pt and 119Sn NMR spectroscopic methods and found to be in accordance with the solid state geometry of 1. [Copyright &y& Elsevier]

Thirteen palladium‐ligand assemblies with different structures and topologies were investigated for the ability to bind lithium ions. In one case, the addition of LiBF4 resulted in a profound structural rearrangement, converting a dincluclear [Pd2L4]4+ complex into a low‐symmetry [Pd4L8]8+ assembly with two binding pockets for solvated LiBF4 ion pairs. The rearrangement could only be induced by Li+, indicating highly specific host–guest interactions. A structural analysis of the [Pd4L8]8+ receptor revealed a compact structure with multiple intramolecular interactions, reminiscent of what is seen for natural and synthetic foldamers. [ABSTRACT FROM AUTHOR]

Thirteen palladium‐ligand assemblies with different structures and topologies were investigated for the ability to bind lithium ions. In one case, the addition of LiBF4 resulted in a profound structural rearrangement, converting a dincluclear [Pd2L4]4+ complex into a low‐symmetry [Pd4L8]8+ assembly with two binding pockets for solvated LiBF4 ion pairs. The rearrangement could only be induced by Li+, indicating highly specific host–guest interactions. A structural analysis of the [Pd4L8]8+ receptor revealed a compact structure with multiple intramolecular interactions, reminiscent of what is seen for natural and synthetic foldamers. [ABSTRACT FROM AUTHOR]

Single-atom (group 15 and group 16 anions) bridged dimetallic complexes of low oxidation state uranium provide a convenient route to implement multielectron transfer and promote magnetic communication in uranium chemistry, but remain extremely rare. Here we report the synthesis, redox and magnetic properties of N3−, O2−, and S2− bridged diuranium complexes supported by bulky aryloxide ligands. The U(IV)/U(IV) nitride [Cs(THF)8][(U(OAr)3)2(μ-N)], 1 could be prepared and characterized but could not be reduced. Reduction of the neutral U(IV)/U(IV) complexes [(U(OAr)3)2(μ-X)] A (X = O) and B (X = S) led to the isolation and characterization of the U(IV)/U(III) and U(III)/U(III) analogues. Complexes [(K(THF)4)2(U(OAr)2)2(μ-S)2], 5 and [K(2.2.2-cryptand)]2[(U(OAr)3)2(μ-S)], 6 are the first examples of U(III) sulphide bridged complexes. Computational studies and redox properties allow the reactivity of the dimetallic complexes to be related to their electronic structure. [ABSTRACT FROM AUTHOR]

Spherical assemblies of the type [PdnL2n]2n+ can be obtained from PdII salts and curved N‐donor ligands, L. It is well established that the bent angle, α, of the ligand is a decisive factor in the self‐assembly process, with larger angles leading to complexes with a higher nuclearity, n. Herein, we report heteroleptic coordination cages of the type [PdnLnL′n]2n+, for which a similar correlation between the ligand bent angle and the nuclearity is observed. Tetranuclear cages were obtained by combining [Pd(CH3CN)4](BF4)2 with 1,3‐di(pyridin‐3‐yl)benzene and ligands featuring a bent angle of α=120°. The use of a dipyridyl ligand with α=149° led to the formation of a hexanuclear complex with a trigonal prismatic geometry; for linear ligands, octanuclear assemblies of the type [Pd8L8L′8]16+ were obtained. The predictable formation of heteroleptic PdII cages from 1,3‐di(pyridin‐3‐yl)benzene and different dipyridyl ligands is evidence that there are entire classes of heteroleptic cage structures that are privileged from a thermodynamic point of view. [ABSTRACT FROM AUTHOR]

The first metallasilsesquioxane of a divalent lanthanide, [Yb{Cy7Si7O11(OSiMe3)}(THF)]2, 1, was synthesized and structurally characterized. The Cy7Si7O11(OSiMe3)2− ligands in 1 bind two Yb(II) ions in a bridging mode. The dinuclear complex effects the two-electron reduction of azobenzene yielding the Yb(III) complex [{Yb(Cy7Si7O11(OSiMe3))(THF)2}2(PhNNPh)], 2, and the CO2 reduction to CO and carbonate. [ABSTRACT FROM AUTHOR]

The synthesis of vinyl triazenes by metal‐catalyzed processes is attractive, but only few examples have been described so far. Here, we describe Rh‐catalyzed [3+2] annulation reactions of arylboronic acid derivatives and alkynyl triazenes. These reactions provide access to functionalized indenyl triazenes. The regioselectivity of the annulations is mostly high, but strongly dependent on the substituents on the alkyne. The triazene group in the products can be cleaved under acidic condition. In contrast to what has been reported for other vinyl triazenes, rearrangements are observed instead of direct substitution reactions. [ABSTRACT FROM AUTHOR]

The synthesis of lanthanides other than cerium in the oxidation state +IV has remained a desirable but unmet target until recently, when two examples of TbIV with saturated coordination spheres were isolated. Here we report the third example of an isolated molecular complex of terbium(IV), where the supporting siloxide ligands do not saturate the coordination sphere. The fully characterized six‐coordinate complex [TbIV(OSiPh3)4(MeCN)2], 2‐TbPh, shows high stability and the labile MeCN ligands can be replaced by phosphinoxide ligands. Computational studies suggest that the stability is due to a strong π(O−Tb) interaction which is stronger than in the previously reported TbIV complexes. Cyclic‐voltammetry experiments demonstrate that non‐binding counterions contribute to the stability of TbIV in solution by destabilizing the +III oxidation state, while alkali ions promote TbIV/TbIII electron transfer. [ABSTRACT FROM AUTHOR]

The synthesis of lanthanides other than cerium in the oxidation state +IV has remained a desirable but unmet target until recently, when two examples of TbIV with saturated coordination spheres were isolated. Here we report the third example of an isolated molecular complex of terbium(IV), where the supporting siloxide ligands do not saturate the coordination sphere. The fully characterized six‐coordinate complex [TbIV(OSiPh3)4(MeCN)2], 2‐TbPh, shows high stability and the labile MeCN ligands can be replaced by phosphinoxide ligands. Computational studies suggest that the stability is due to a strong π(O−Tb) interaction which is stronger than in the previously reported TbIV complexes. Cyclic‐voltammetry experiments demonstrate that non‐binding counterions contribute to the stability of TbIV in solution by destabilizing the +III oxidation state, while alkali ions promote TbIV/TbIII electron transfer. [ABSTRACT FROM AUTHOR]

The high stability of the + IVoxidation state limits thorium redox reactivity. Here we report the synthesis and the redox reactivity of two Th(IV) complexes supported by the arene‐tethered tris(siloxide) tripodal ligands [(KOSiR2Ar)3‐arene)]. The two‐electron reduction of these Th(IV) complexes generates the doubly reduced [KTh((OSi(OtBu)2Ar)3‐arene)(THF)2] (2OtBu) and [K(2.2.2‐cryptand)][Th((OSiPh2Ar)3‐arene)(THF)2](2Ph‐crypt) where the formal oxidation state of Th is +II. Structural and computational studies indicate that the reduction occurred at the arene anchor of the ligand. The robust tripodal frameworks store in the arene anchor two electrons that become available at the metal center for the two‐electron reduction of a broad range of substrates (N2O, COT, CHT, Ph2N2, Ph3PS and O2) while retaining the ligand framework. This work shows that arene‐tethered tris(siloxide) tripodal ligands allow implementation of two‐electron redox chemistry at the thorium center while retaining the ligand framework unchanged. [ABSTRACT FROM AUTHOR]