Reactions of P-chloro-1,3,2-diazaphospha[3]ferrocenophanes with ECl3 (E = Al, Ga) under solvent-free conditions and with Na[Mn(CO)(5)] furnished salts featuring a ferrocenophane-based phosphenium cation and neutral phosphenium complexes, respectively. All products were characterized by spectroscopic studies. Single-crystal X-ray diffraction studies confirmed the ionic nature of the phosphenium tetrachloroaluminate and the structural analogy between the phosphenium complexes and Fischer-type carbene complexes. Distinct deviations in the conformation of the ansa bridge suggest electronic stabilization of the electrophilic phosphorus atom by phosphorus-nitrogen pi interactions in the free cation and by phosphorus-metal pi bonding in the complexes. The observation of short intermolecular contacts in the crystalline phosphenium salt and its chemical behavior toward donor solvents attest to the cation having an unusually high degree of Lewis acidity, which was confirmed by DFT studies and related to the presence of a rather large N-P-N angle. Computational studies indicate further that the free phosphenium cation exhibits a closed-shell electronic structure with a formal Fe(II) oxidation state and is thus a true analogue to ferrocenophane-based diaminotetrylenes.

A unique anionic phosphenium complex was prepared from reaction of an N-heterocyclic chlorophosphine with Collman's reagent or K[HFe(CO)(4)]/NaH and characterized by spectral and XRD data. The complex behaves as an ambident nucleophile. Reactions with acetic acid, ClSnPh3, and a further equivalent of an N-heterocyclic chlorophosphine proceed via electrophilic functionalization at the metal site to yield appropriate mono- or bis-phosphenium complexes. Reaction with MeI at -70 degrees C produces a P-alkylation product as the first spectroscopically detectable intermediate, which decays at a higher temperature to give a mixture of free P-methylated N-heterocyclic phosphine and its Fe(CO)(4) complex. The different reaction products were characterized by spectral and XRD data. Computational studies indicate that the NHP units in all complexes display p-acceptor behaviour but show no disposition to adopt phosphide-like character or formally oxidize the metal centre.

A library of 70 000 synthetically accessible azulene-based compounds was virtually screened at the OX2 receptor. Based on the results, a series of azulene derivatives was synthesized and the binding to and activation of both orexin receptor subtypes were assessed. Two most promising binders were determined to have inhibition constants in the 3-9 mu M range and two other compounds showed weak OX2 receptor agonism. Furthermore, three compounds exhibited a concentration-dependent potentiation of the response to orexin-A at the OX1 but not the OX2 receptors. Altogether this data opens new approaches for further development of antagonists, agonists, and potentiators of orexin response based on the azulene scaffold. (C) 2018 Elsevier Masson SAS. All rights reserved.

Two N-heterocyclic phosphines with exocyclic SCN substituents were synthesised via metathesis of chlorophosphine precursors with KSCN and fully characterised. The crystallographic studies reveal that the products exhibit pronounced structural differences. The thiocyanato unit binds in one case via the nitrogen atom to yield a molecular structure with a slightly elongated P-N single bond and, in the other case, via the sulfur atom to form a structure that is best described as an ion pair and forms a one-dimensional coordination polymer in the crystal. DFT calculations suggest that the P-N and P center dot center dot center dot S interactions can be described as covalent and dative bonds, respectively, and that the structural differences correlate with the different cation stabilities of the individual phosphenium cation fragments.

Two iridium [Ir(NC)(2)(NN)](+) complexes with the diimine NN ligand containing a long polymethylene hydrophobic chain were synthesized and characterized by using NMR and ESI mass-spectrometry: NN - 2-(1-hexadecyl-1H-imidazol-2-yl)pyridine, NC - methyl-2-phenylquinoline-4-carboxylate (Ir1) and 2-phenylquinoline-4-carboxylic acid (Ir2). These complexes were used to prepare the luminescent PEGylated DPPC liposomes (DPPC/DSPE-PEG2000/Ir-complex = 95/4.5/1 mol%) using a thin film hydration method. The narrowly dispersed liposomes had diameters of about 110 nm. The photophysics of the complexes and labeled liposomes were carefully studied. Ir1 and Ir2 give red emission (lambda(em) = 667 and 605 nm) with a lifetime in the microsecond domain and quantum yields of 4.8% and 10.0% in degassed solution. Incorporation of the complexes into the liposome lipid bilayer results in shielding of the emitters from interaction with molecular oxygen and partial suppression of excited state nonradiative relaxation due to the effect of the relatively rigid bilayer matrix. Delivery of labeled liposomes to the cultured ARPE-19 cells demonstrated the usefulness of Ir1 and Ir2 in cellular imaging. Labeled liposomes were then injected intravitreally into rat eyes and imaged successfully with optical coherence tomography and funduscopy. In conclusion, iridium complexes enabled the successful labeling and imaging of liposomes in cells and animals.

The mesomeric betaine imidazolium-1-ylphenolate forms a borane adduct with tris(pentafluorophenyl) borane by coordination with the phenolate oxygen, whereas its NHC tautomer 1-(2-phenol) imidazol-2-ylidene reacts with (triphenylphosphine) gold(I) chloride to give the cationic NHC complex [Au(NHC)(2)][Cl] by coordination with the carbene carbon atom. The anionic N-heterocyclic carbene 1-(2-phenolate) imidazol-2-ylidene gives the complexes [K][Au(NHC-)(2)], [Rh(NHC-)(3)] and [Ni(NHC-)(2)], respectively. Results of four single crystal analyses are presented.

The homolytic P-P bond fission in a series of sterically congested tetraaminodiphosphanes (R2N)(2)P-P-(NR2)(2) ({4}(2)-{9}(2), two of which were newly synthesized and fully characterized) into diaminophosphanyl radicals (R2N)(2)P-center dot (4-9) was monitored by VT EPR spectroscopy. Determination of the radical concentration from the EPR spectra permitted to calculate free dissociation energies Delta G(Diss)(295) as well as dissociation enthalpies Delta H-Diss and entropies Delta S-Diss, respectively. Large positive values of Delta G(Diss)(295) indicate that the degree of dissociation is in most cases low, and the concentration of persistent radicals - even if they are spectroscopically observable at ambient temperature - remains small. Appreciable dissociation was established only for the sterically highly congested acyclic derivative {9}(2). Analysis of the trends in experimental data in connection with DFT studies indicate that radical formation is favoured by large entropy contributions and the energetic effect of structural relaxation (geometrical distortions and conformational changes in acyclic derivatives) in the radicals, and disfavoured by attractive dispersion forces. Comparison of the energetics of formation for CC-saturated N-heterocyclic diphosphanes and the 7 pi-radical 3c indicates that the effect of energetic stabilization by pi-electron delocalization in the latter is visible, but stands back behind those of steric and entropic contributions. Evaluation of spectroscopic and computational data indicates that diaminophosphanyl radicals exhibit, in contrast to aminophosphenium cations, no strong energetic preference for a planar arrangement of the (R2N)(2)P unit.

In this report, we describe a series of cyclophanyl-derived mono- and binuclear N,C-palladacycles by regioselective ortho-palladation of amine-functionalized [2.2]paracyclophanes. Employing Pd(OAc)(2) followed by LiCl and with the subsequent modular treatment of Ph3P, Cy3P, and (Ph2PCH2)(2), this strategy allows to prepare stable cyclophanyl-derived planar and central chiral N,C-palladacycles in a highly selective manner. The regioselective ortho-palladation mono- and bimetallic product formation was analyzed by detailed spectroscopic techniques, mass spectrometry and unambiguously confirmed by single-crystal X-ray analysis.

Reaction of a phosphane-decorated benzenedithiol (pbdtH(2)) with coinage metal salts furnished polynuclear complexes [M-2(pbdtH)(2)] (M=Au-I) or [cat][M-5(pbdt)(3)] (cat=unipositive cation, M=Ag-I, Cu-I), which were characterized by analytical and spectroscopic techniques and single-crystal X-ray diffraction studies. Furthermore, a double salt with an anion [Ag-5(pbdt)(3)(PPh3)](-) that proved unstable in solution was characterized crystallographically. The spectroscopic and crystallographic data revealed that the Cu(I) and Ag(I) complexes exhibit, despite their like stoichiometric composition, isomeric molecular structures. The observed disparities were reproduced by DFT studies. The dinuclear Au(I) complex was found to undergo air-oxidation to furnish a mixed-valent complex [(Au-III)(2)(Au-I)(2)(pbdt)(4)]. The copper(I) - but not the isomeric silver(I) complexes - showed luminescence in the solid state.

Metathesis of Na[Mn(CO)(5)] with N-tBu and N-Mes substituted, electrophilic N-heterocyclic phosphane derivatives afforded in the first case an ionic N-heterocyclic phosphenium (NHP) metalate and in the second case a covalent phosphenium complex. The products were characterized by analytical and spectroscopic data and the NHP complex as well by a single-crystal X-ray diffraction study. A DFT study allows relating the different outcome of the reactions studied with the energetics of the decarbonylation of the appropriate NHP metalates. Closer evaluation reveals steric factors as the key to explaining the observed behavior, and indicates that their impact displays close parallels to NHC chemistry.