Pnictogen-based vanadacyclobutadiene complexes.

The reactivity of the V[triple bond, length as m-dash]C Bu multiple bonds in the complex (dBDI)V[triple bond, length as m-dash]C Bu(OEt) (C) (dBDI = ArNC(CH)CHC(CH)NAr, Ar = 2,6- PrCH) with unsaturated substrates such as N[triple bond, length as m-dash]CR (R = Ad or Ph) and P[triple bond, length as m-dash]CAd leads to the formation of rare 3d transition metal compounds featuring α-aza-vanadacyclobutadiene, (dBDI)V(κ- , - BuC(R)N) (R = Ad, 1; R = Ph, 2) and β-phospha-vanadacyclobutadiene moieties, (dBDI)V(κ- , - BuPAd) (3). Complexes 1-3 are characterized using multinuclear and multidimensional NMR spectroscopy, including the preparation of the 50% N-enriched isotopologue (dBDI)V(κ- , - BuCC(Ad)N) (1-N). Solid-state structural analysis is used to determine the dominant resonance structures of these unique pnictogen-based vanadacyclobutadienes.

Cationic Bis(hydrosilane)-Coinage-Metal Complexes: Synthesis, Characterization, and Use as Catalysts for Outer-Sphere C=O Hydrosilylation Not Involving Metal Hydrides.

The preparation of cationic bis(hydrosilane)-coinage-metal complexes by chloride abstraction from the neutral metal chloride precursors with Na[BAr ] is described. Unlike previously reported hydrosilane-stabilized copper and silver complexes, the presented complexes are cationic and feature two bidentate (ortho-silylphenyl)phosphine ligands. These complexes were fully characterized by NMR spectroscopy and X-ray diffraction analysis, revealing that both Si-H bonds are activated by the Lewis acidic cationic metal center.

Tellurolate: an effective Te-atom transfer reagent to prepare the triad of group 5 metal bis(tellurides).

We show in this work how lithium tellurolate Li(X)TeCHSiMe (X = THF, = 1, 1; X = 12--4, = 2, 2), can serve as an effective Te-atom transfer reagent to all group 5 transition metal halide precursors irrespective of the oxidation state. Mononuclear and bis(telluride) complexes, namely (PNP)M(Te) (M = V; Nb, 3; Ta, 4; PNP = N[2-PPr-4-methylphenyl]), are reported herein including structural and spectroscopic data. Whereas the known complex (PNP)V(Te) can be readily prepared from the trivalent precursor (PNP)VCl, two equiv.

Controlling π-π Interactions of Highly Soluble Naphthalene Diimide Derivatives for Neutral pH Aqueous Redox Flow Batteries.

Organic redox-active molecules are a promising platform for designing sustainable, cheap, and safe charge carriers for redox flow batteries. However, radical formation during the electron-transfer process causes severe side reactions and reduces cyclability. This problem is mitigated by using naphthalene diimide (NDI) molecules and regulating their π-π interactions.

Metal-Ligand Cooperativity to Assemble a Neutral and Terminal Niobium Phosphorus Triple Bond (Nb≡P).

Decarbonylation along with P-atom transfer from the phosphaethynolate anion, PCO , to the Nb complex [(PNP)NbCl (N BuAr)] (1) (PNP=N[2-P Pr -4-methylphenyl] ; Ar=3,5-Me C H ) results in its coupling with one of the phosphine arms of the pincer ligand to produce a phosphanylidene phosphorane complex [(PNPP)NbCl(N BuAr)] (2). Reduction of 2 with CoCp* cleaves the P-P bond to form the first neutral and terminal phosphido complex of a group 5 transition metal, namely, [(PNP)Nb≡P(N BuAr)] (3). Theoretical studies have been used to understand both the coupling of the P-atom and the reductive cleavage of the P-P bond.

Ligand non-innocence allows isolation of a neutral and terminal niobium nitride.

Complex (PNP)NbCl(N[Bu]Ar) (1) (PNP = N[2-PPr-4-methylphenyl]; Ar = 3,5-MeCH) reacts with one equiv. of NaN to form a mixture of (PNPN)NbCl(N[Bu]Ar) (2) and (PNP)NbN(N[Bu]Ar) (3), both of which have been spectroscopically and crystallographically characterized, including N isotopic labelling studies. Complex 3 represents the first structurally characterized example of a neutral and mononuclear Nb nitride.

An Isolable Azide Adduct of Titanium(II) Follows Bifurcated Deazotation Pathways to an Imide.

AdN (Ad = 1-adamantyl) reacts with the tetrahedral Ti complex [(Tp)TiCl] (Tp = hydrotris(3--butyl-5-methylpyrazol-1-yl)borate) to generate a mixture of an imide complex, [(Tp)TiCl(NAd)] (), and an unusual and kinetically stable azide adduct of the group 4 metal, namely, [(Tp)TiCl(γ-NAd)] (). In these conversions, the product distribution is determined by the relative concentration of reactants. In contrast, the azide adduct forms selectively when a masked Ti complex (N or AdNC adduct) reacts with AdN.

Optical and Fluorescent Dual Sensing of Aminoalcohols by in Situ Generation of BODIPY-like Chromophore.

A novel multifunctional aminophenylboronic acid connected to a diphenylketone gives both circular dichroism and fluorescence signals by in situ generation of a BODIPY-like chromophore in the presence of aminoalcohols. DFT calculations were used to understand the role of each functional group in the mechanism. This new sensor can distinguish different aminoalcohols and quantitatively indicate the concentration of the substrate, allowing for the convenient determination of the ee of racemic mixtures with a single probe.

Living Metathesis and Metallotropy Polymerization Gives Conjugated Polyenynes from Multialkynes: How to Design Sequence-Specific Cascades for Polymers.

On the basis of a combined experimental and computational study, a novel method for preparing fully conjugated polyenynes via cascade metathesis and metallotropy (M&M) polymerization of various multialkynes is developed. DFT calculations elucidate the detailed mechanism of the metallotropic 1,3-shift, which is a key process of M&M polymerization. An α,β-(C,C,C)-agostic interaction stabilizing the metallacyclobutadiene transition state is found to be critically important for the successful polymerization with excellent specificity.

Understanding the Origin of the Regioselectivity in Cyclopolymerizations of Diynes and How to Completely Switch It.

Grubbs-type olefin metathesis catalysts are known to cyclopolymerize 1,6-heptadiynes to afford conjugated polyenes containing five- or six-membered carbocycles. Although high levels of regioselectivity up to >99:1 were observed previously for the formation of five-membered rings, it was neither possible to deliberately obtain six-membered rings at similar levels of selectivity nor understood why certain catalysts showed this selectively. Combining experimental and computational methods, a novel and general theory for what controls the regiochemistry of these cyclopolymerizations is presented.

Room-Temperature Ring-Opening of Quinoline, Isoquinoline, and Pyridine with Low-Valent Titanium.

The complex (PNP)Ti═CHBu(CHBu) (PNP = N[2-PPr-4-methylphenyl]) dehydrogenates cyclohexane to cyclohexene by forming a transient low-valent titanium-alkyl species, [(PNP)Ti(CHBu)], which reacts with 2 equiv of quinoline (Q) at room temperature to form HCBu and a Ti(IV) species where the less hindered C═N bond of Q is ruptured and coupled to another equivalent of Q. The product isolated from this reaction is an imide with a tethered cycloamide group, (PNP)Ti═N[CHN] (1). Under photolytic conditions, intramolecular C-H bond activation across the imide moiety in 1 occurs to form 2, and thermolysis reverses this process.

Cued and Un-Cued Semantic Category Fluency in Older Adults with Mild Cognitive Impairment.

Background And Purpose: Patients with switching deficits reportedly benefit more from categorical cueing for semantic category fluency than do patients with clustering deficits. We explored the contribution of language ability and executive control on the performance of semantic category fluency in older adults with mild cognitive impairment (MCI) by examining the effects of categorical cueing on the task.

Methods: Order adults with MCI (=10) and normal controls (=25) were compared on two versions of a semantic fluency task: a standard, un-cued version (SF) and a version in which subjects were cued (C-SF) with 4 subordinated categories.