Metal- ligand-centered reactivity of a cobalt-phenylenediamide complex with electrophiles.

A new series of [Co-CF] complexes supported by a bidentate redox-active ligand is presented. The cationic [Co-CF] complex was first obtained by reacting [CpCo(opda)] (Cp = cyclopentadienyl, opda = -phenylenediamide) with an electrophilic trifluoromethyl source, for which the redox-active phenylenediamide ligand serves as a 2e reservoir to generate [CpCp(bqdi)(CF)] (bqdi = benzoquinonediimine). Electrochemical studies of [Co-CF] revealed two reversible 1e reductions.

Cage Match: Comparing the Anion Binding Ability of Isostructural Versus Isofunctional Pairs of Metal-Organic Nanocages.

Affinities of six anions (mesylate, acetate, trifluoroacetate, p-toluenecarboxylate, p-toluenesulfonate, and perfluorooctanoate) for three related Pt -linked porphyrin nanocages were measured to probe the influence of different noncovalent recognition motifs (e. g., hydrogen bonding, electrostatics, π bonding) on anion binding.

Metal-Ligand Proton Tautomerism, Electron Transfer, and C(sp)-H Activation by a 4-Pyridinyl-Pincer Iridium Hydride Complex.

The -N-pyridyl-based PCP pincer proligand 3,5-bis(di--butylphosphinomethyl)-2,6-dimethylpyridine (pN-PCP-H) was synthesized and metalated to give the iridium complex (pN-PCP)IrHCl (). In marked contrast with its phenyl-based congeners, e.g.

Controlling Intramolecular and Intermolecular Electronic Coupling of Radical Ligands in a Series of Cobaltoviologen Complexes.

Controlling electronic coupling between multiple redox sites is of interest for tuning the electronic properties of molecules and materials. While classic mixed-valence (MV) systems are highly tunable, e.g.

Two-Electron Redox Tuning of Cyclopentadienyl Cobalt Complexes Enabled by the Phenylenediamide Ligand.

Achieving multielectron activity at first-row transition-metal complexes has important implications for homogeneous catalysis using earth-abundant metals. Here, we report a family of cobalt-phenylenediamide complexes that undergo reversible 2e oxidation regardless of the ligand substituents, enabling unprecedented multielectron redox tuning over 0.5 V and, in each case, affording the dicationic Co(III)-benzoquinonediimine species.

A Bis(imidazole)-based cysteine labeling tool for metalloprotein assembly.

Precise metal-protein coordination by design remains a considerable challenge. Polydentate, high-metal-affinity protein modifications, both chemical and recombinant, can enable metal localization. However, these constructs are often bulky, conformationally and stereochemically ill-defined, or coordinately saturated.

Ruthenium Complexes of a Triphosphorus-Coordinating Pincer Ligand: Ru-P Ligand-Substituent Exchange Reactions Driven by Large Variations of Bond Energies.

The reaction of [(-cymene)RuCl] with the triphosphine ligand bis(2-di--butylphosphinophenyl)phosphine (PPP) results in an unusual exchange reaction in which a chloride ligand and a phosphorus-bound H atom are exchanged ("H-P/Ru-Cl exchange") to give the (chlorophosphine)ruthenium hydride complex (PPP)RuHCl [; PPP = bis(2-di--butylphosphinophenyl)chlorophosphine]. Density functional theory calculations indicate that the presumed initial product of metalation, (PPP)RuCl (), undergoes an H-P/Ru-Cl exchange via sequential P-to-Ru α-H migration to give the intermediate (PPP)RuHCl, followed by Ru-to-P α-Cl migration to give the observed product (crystallographically characterized). Dehydrochlorination of under a H atmosphere gives (PPP)RuH (), which then can undergo a second dehydrochlorination and addition of H to give (PPP)RuH ().

Synthesis of [60]- and [70]Fullerene-Fused Tetrahydroquinoxaline Derivatives by Oxidative [4 + 2] Cycloaddition with Unusual Reactivity and Regioselectivity.

The oxidative [4 + 2] reaction of -phenylenediamine-derived disulfonamides with fullerene C and C is reported, in which electron-deficient reactants showed high reactivity. The reaction of C exhibited unusual regioselectivity, yielding a [5,6]-adduct as the major product, which was characterized by H, C NMR and single-crystal X-ray diffraction. DFT calculations revealed the reaction is an inverse-electron-demand Diels-Alder (IEDDA) reaction, and the [5,6]-adduct of C is a kinetic product.

Reactivity of Iridium Complexes of a Triphosphorus-Pincer Ligand Based on a Secondary Phosphine. Catalytic Alkane Dehydrogenation and the Origin of Extremely High Activity.

The selective functionalization of alkanes and alkyl groups is a major goal of chemical catalysis. Toward this end, a bulky triphosphine with a central secondary phosphino group, bis(2-di--butyl-phosphinophenyl)phosphine (PPP), has been synthesized. When complexed to iridium, it adopts a meridional ("pincer") configuration.

Stereoelectronic Features of a Complex Ketene Dimerization Reaction.

The amidation reaction of a tetrahydroisoquinolin-1-one-4-carboxylic acid is a key step in the multi-kilogram-scale preparation of the antimalarial drug SJ733, now in phase 2 clinical trials. In the course of investigating THIQ carboxamidations, we found that propanephosphonic acid anhydride (T3P) is an effective reagent, although the yield and byproducts vary with the nature and quantity of the base. As a control, the T3P reaction of a 3-(2-thienyl) THIQ was performed in the absence of the amine, and the products were characterized: among them are three dimeric allenes and two dimeric lactones.

Isocyanide-Induced Annulation Leading to Cyclopento-, Methano-, and Cyclopentano-[60]Fullerene Derivatives.

The three-component annulation reactions of C, alkyl isocyanide, and dimethyl acetylenedicarboxylate (DMAD) or unsymmetric alkynes are investigated to afford cyclopent-2-en-1-imino- and ketenimine methano-[60]fullerene derivatives, which, upon hydration in the presence of acid, yield the corresponding fullerene amides. Dimethyl 2,3-pentadienedioate, the allene counterpart of DMAD, and ethyl buta-2,3-dienoate undergo four-component annulation with C, alkyl isocyanide, and water under similar conditions to yield cyclopentano-[60]fullerene derivatives with similar amide groups.

Unexpected Formation of Metallofulleroids from Multicomponent Reactions, with Crystallographic and Computational Studies of the Cluster Motion.

New multicomponent reactions involving an isocyanide, terminal or internal alkynes, and endohedral metallofullerene (EMF) Lu N@C yield metallofulleroids which are characterized by mass-spectrometry, HPLC, and multiple 1D and 2D NMR techniques. Single crystal studies revealed one ketenimine metallofulleroid has ordered Lu N cluster which is unusual for EMF monoadducts. Computational analysis, based on crystallographic data, confirm that the endohedral cluster motion is controlled by the position of the exohedral organic appendants.

Insights into Formate Oxidation by a Series of Cobalt Piano-Stool Complexes Supported by Bis(phosphino)amine Ligands.

A series of (cyclopentadienyl)cobalt(III) half-sandwich complexes () supported by bidentate bis(phosphino)amine ligands was synthesized and characterized by NMR spectroscopy, X-ray crystallography, and cyclic voltammetry. The Co-hydride complex bearing the bis(cyclohexylphosphine) ligand derivative was successfully isolated via protonation of the neutral reduced Co complex with a weak acid. Experimental and computational methods were used to determine the thermodynamic hydride accepting ability of these Co centers and to evaluate their reactivity toward the oxidation of formate.

Crystallizing Atomic Xenon in a Flexible MOF to Probe and Understand Its Temperature-Dependent Breathing Behavior and Unusual Gas Adsorption Phenomenon.

Flexible metal-organic frameworks (MOFs) hold great promise as smart materials for specific applications such as gas separation. These materials undergo interesting structural changes in response to guest molecules, which is often associated with unique adsorption behavior not possible for rigid MOFs. Understanding the dynamic behavior of flexible MOFs is crucial yet challenging as it involves weak host-guest interactions and subtle structural transformation not only at the atomic/molecular level but also in a nonsteady state.

Evaluation of 1,1-cyclopropylidene as a thioether isostere in the 4-thio-thienopyrimidine (TTP) series of antimalarials.

The 4-(heteroarylthio)thieno[2,3-d]pyrimidine (TTP) series of antimalarials, represented by 1 and 17, potently inhibit proliferation of the 3D7 strain of P. falciparum (EC 70-100 nM), but suffer from oxidative metabolism. The 1,1-cyclopropylidene isosteres 6 and 16 were designed to obviate this drawback.

Ambient and High Pressure CuNiSb: Metal-Ordered and Metal-Disordered NiAs-Type Derivative Pnictides.

The mineral Zlatogorite, CuNiSb, was synthesized in the laboratory for the first time by annealing elements at ambient pressure (CuNiSb-AP). Rietveld refinement of synchrotron powder X-ray diffraction data indicates that CuNiSb-AP crystallizes in the NiAs-derived structure (31, #164) with Cu and Ni ordering. The structure consists of alternate NiSb and CuSb octahedral layers via face-sharing.

The Influence of Redox-Active Linkers on the Stability and Physical Properties of a Highly Electroactive Porphyrin Nanoprism.

Redox-active metal-organic nanocages are of interest for many applications, but the development of cages with extensive redox activity is often hindered by their limited stability and solubility across multiple charge states. This report reveals that these properties can be tuned for cages with redox-active walls by incorporating additional redox activity into the linkers. In particular, new +12 charged triangular nanoprisms , were formed from three electroactive tetrakis(3-pyridyl)porphyrin walls linked by six [(TMEDA)Pt] (for ) or [(2,2'-bipy)Pt] (for ) vertices, the latter of which are also electroactive.

Identification of the local electrical properties of crystalline and amorphous domains in electrochemically doped conjugated polymer thin films.

Doped polymer thin films have several applications in electronic, optoelectronic and thermoelectric devices. Often the electrical properties of doped conjugated polymer thin films are affected by their local physical and mechanical characteristics. However, investigations into the effects of doping on local domain properties have not been carried out.

Evaluation of Exfoliated Graphite to Graphene in Polyamide 66 Using Novel High Shear Elongational Flow.

Graphene has been publicized as the game changing material of this millennium. To this day, scalable production leading to exceptional material properties has been difficult to attain. Most methods require harsh chemicals, which result in destroying the graphene surface.

Molecular Thorium Compounds with Dichalcogenide Ligands: Synthesis, Structure, Se NMR Study, and Thermolysis.

A series of dimeric thorium disulfides and diselenides have been prepared with sterically undemanding ancillary ligands. Five complexes, (py)ThI(μ-S), (py)ThBr(SCF)(μ-S), (py)ThI(μ-Se), (py)ThI(SCF)(μ-Se), and (py)ThBr(SCF)(μ-Se), were isolated in high yields by first reducing mixtures of I, FCSSCF, PhSeSePh, or PhSSPh, and PhSeBr with elemental Th, followed by in situ ligand-based redox reactions with elemental sulfur or selenium. These are the first examples of thorium compounds with bridging dichalcogenide ligands.

Organosoluble tetravalent actinide di- and trifluorides.

Soluble molecular actinide(iv) fluorides can be prepared in high yield via redox or metathesis reactions of silver fluorides with actinide compounds containing ancillary iodide or fluorinated thiolate ligands. Two compounds, (py)4UF2I2·2py and (py)7Th2F5(SC6F5)3·2py were isolated and characterized by conventional methods, powder and low temperature single crystal X-ray diffraction.

Monomeric thorium chalcogenolates with bipyridine and terpyridine ligands.

Thorium chalcogenolates Th(ER)4 react with 2,2'-bipyridine (bipy) to form complexes with the stoichiometry (bipy)2Th(ER)4 (E = S, Se; R = Ph, C6F5). All four compounds have been isolated and characterized by spectroscopic methods and low-temperature single crystal X-ray diffraction. Two of the products, (bipy)2Th(SC6F5)4 and (bipy)2Th(SeC6F5)4, crystallize with lattice solvent, (bipy)2Th(SPh)4 crystallizes with no lattice solvent, and the selenolate (bipy)2Th(SePh)4 crystallizes in two phases, with and without lattice solvent.

Chiral bisoxazoline ligands designed to stabilize bimetallic complexes.

Chiral bisoxazoline ligands containing naphthyridine, pyridazine, pyrazole, and phenol bridging units were prepared and shown to form bimetallic complexes with various metal salts. X-ray crystal structures of bis-nickel naphthyridine-bridged, bis-zinc pyridazine-bridged, and bis-nickel as well as bis-palladium pyrazole-bridged complexes were obtained.

Thorium Cubanes-Synthesis, Solid-State and Solution Structures, Thermolysis, and Chalcogen Exchange Reactions.

Thorium cubanes (py)Th(μ-E')(μ-EPh)(η-EPh) (E, E' = S, Se) were prepared from ligand-based redox reactions of elemental E' with Th(EPh). Products with all four possible E/E' combinations (E,E' = S,S; Se,Se; S,Se; Se,S) were isolated and structurally characterized, ligand exchange reactions were explored, and the heterochalcogen compounds (py)Th(μ-S)(μ-SePh)(η-SePh) and (py)Th(μ-Se)(μ-SPh)(η-SPh) were heated to deliver solid solutions of ThS Se. NMR spectroscopy indicated that the structure of (py)Th(μ-Se)(μ-SePh)(η-SePh) is static in pyridine solution, with no exchange between bridging and terminal PhE ligands on the NMR time scale.

Efficient NIR Emission from Nd, Er, and Tm Complexes with Fluorinated Selenolate Ligands.

(DME)Ln(SeCF) (Ln = Nd, Er, Tm) can be isolated in high yield by reductive cleavage of the Se-Se bond in (SeCF) with elemental Ln in DME. All three Ln compounds are isostructural, with 8 coordinate Ln bound to four O from DME, three terminally bound Se(CF), and a dative bond from an arene fluoride to a fluorine at the ortho position of one selenolate. Emission measurements indicate that these compounds are bright NIR sources.