Nicola Poli

Catalytic activation of phenylisocyanate by Ti(bpy)3

Abstract Ti(bpy) 3 activates PhNCO catalytically toward cyclotrimerization and condensation with aliphatic aldehydes. An important step of such catalytic reactions is the head-to-tail reductive coupling of PhNCO.

Intermolecular interaction of tris-bipyridyl metal complexes, M(bpy)3 (M = Al, V, Fe), with tetracyanoethylene

A partir de M(bpy) et TCNE on prepare M(bpy) 3 2+• 2TCNE −• . Etude de la reaction, caracterisation spectrometrique des produits intermediaires. Mecanisme reactionnel faisant intervenir un transfert de charge

Characterization of bis(β-diimino-tetracyanopyrrolizinido)copper(II) complex. X-ray crystal structure of the acetonitrile adduct and structural comparison with the tetrahydrofuran derivative

Abstract The X-ray crystal structure of the bis(1,2,6,7-tetracyano-3,5-diimino-3,5-dihydro-pyrrolizinido)copper(II) complex, as an adduct with acetonitrile, CuL2 · 2CH3CN (1a), is described and compared with that of the analogous tetrahydrofuran derivative Cu L2 · 2THF (1b), previously reported. The molecular structure of both complexes is almost the same (the copper atom is centrosymmetrically surrounded by four chelating imino groups in a square planar configuration), whereas the spatial arrangement is totally different: in 1a the molecular units are slipped stacked, while in 1b they are mutually orthogonal. The results of a number of physical measurements on both 1a and 1b are reported and correlated with the structures. The solution electronic spectrum is also reported and compared with that, extraordinarily similar, of copper-phthalocyanine.

Solution studies of the reaction between the pyrrolenine anion 1,2,-tricyano-2-(3,4-dicyano-5-imino-2,5-dihydro-1H-pyrrol-2-ylidene)ethanide and palladium(II) chlorides. Formation and characterization of the mono β-diimino-tetracyano-pyrrolizinido-palladium(II) complex

Abstract The metal-assisted isomerization of the pyrrolenine anion 1,1,2-tricyano-2-(3,4-dicyano-5-imino-2,5-dihydro-1H-pyrrol-2-ylidene) ethanide (C11N7H2−, L′) to the 1,2,6,7-tetracyano-3,5-diimino-2,5-dihydro-pyrrolizinide anion (L) has been studied in solutions of CH3Cl2 or tetrahydrofuran (THF) with the palladium(II) chlorides, PdCl42− or Pd2Cl62−, respectively. In THF the bis-chelate PdL2 and the mono-chelate PdLCl2− are formed. In CH2Cl2, only mono-chelate species are formed such as PdLCl2− or PdLCl(CN)−. The mono-chelate species how an optical spectrum, due to the ue60bPdL chromophore, qualitatively more similar to that of the corresponding phthalocyanide, PdPc, than that of PdL2.

Reaction products of benzimidazole with tetracyanoethylene. Mechanism of formation and 13C NMR spectroscopy of the anions C16N8H5–, dicyano(3,4-dicyano-5-benzimidazol-1-yl-2H-pyrrol-2-ylideneamino)methanide (1) and C18N9H4–, 1,2,4,5-tetracyano-3,6,7,12,13-penta-aza-5H-indeno[1,2-d]-acenaphthylen-5-ide (2). Crystal and molecular structure of their tetraphenylarsonium salts

The anions (1) and (2) have been synthesized by the reaction of benzimidazole with tetracyano-ethylene. They have been characterized by X-ray crystallography and 13C NMR spectroscopy. The molecular structures of their tetraphenylarsonium salts have been determined. The charge delocalization and mechanism of formation are discussed.

Incorporation of 2-(5-amino-3,4-dicyano-2H-pyrrol-2-ylidene)-1,1, 2-tricyanoethanide in crosslinked polyvinylformal: Formation and properties of the Copper(II) complex in the matrix

The metal(II) coordinating anion 2-(5-amino-3,4-dicyano-2H-pyrrol-2-ylidene)-1,1,2-tricyanoethanide (C11N7H2−, L′, λmax = 570 nm) has been incorporated by impregnation as the sodium salt in a membrane (0.1 mm thick) of crosslinked polyvinylformal (PVF) at a concentration 1.5 × 10−3 M. The L′-doped PVF membrane, soaked in a concentrated aqueous solution of Cu2+ (0.1 M), changes colour from violet to blue on formation of the corresponding pure bis-pyrrolizinato complex CuL2 (λmax = 660 nm). The CuL2-doped PVF membrane reacts in the gas phase on exposure to species (X) that are copper-coordinating ligands stronger than L, generating the reverse colour change to violet. The remarkable stability towards water of CuL2/PVF is a promising indication for prospective use of ML2 complexes, incorporated in polymeric membranes, for the detection of (X) species in the atmosphere even in the presence of moisture, or directly in aqueous solutions.

Electrochemical reduction of the bis(1,2,6,7-tetracyano-3,5-dihydro-3,5-diimino-pyrrolizinido) palladium (II) complex: syntheses and properties of its radical monoanion as the tetraethylammonium salt

Abstract The electrochemical reduction of the bis(1,2,67-tetracyano-3,5-dihydro-3,5-diiminopyrrolizinido) palladium(II) complex, Pd(C 11 N 7 H 2 ) 2 , furnishes the corresponding radical anion, isolated as PdL 2 ·NEt 4 ·2CH 3 CN·2H 2 O ( 1 ). 1 is a semiconductor of low conductivity ( σ RT = 1.4 × 10 −10 S cm −1 ), presumably consisting of segregated stacks of radical anions, weakly interacting antiferromagnetically at room temperature ( μ SO = 1.50 μ B , 300 K). Lowering the temperature, the magnetic moment undergoes a gradual reduction ( μ SO = 0.65 μ B , 5 K), due probably to a partial dimerisation of the radical units. Other chemicophysical properties of 1 are in agreement with its proposed solid state structure: (i) the EPR signal is strong and broad ( g = 2.005, linewidth = 19G), indicative of a high spin concentration fast relaxing along the anion stacks; (ii) the reflectance spectrum shows a broad band centred at 1200 nm, due to an interanionic π→π ∗ transition between adjacent radical anions, delocalised along the anion stacks.

Characterization of the bis(β-diimino-tetracyano-pyrrolizinido)-metal(II) complexes incorporated in polymeric matrices

The bis(β-diimino-tetracyano-pyrrolizinido)-Cu(II) complex (CuL2) has been incorporated in polystyrene (0.28% w/w), by evaporating tetrahydrofuran solutions either at room temperature (a) or at 100°C (b). From IR and UV-vis measurements and optical microscopy on the resulting films (a orb, thickness 50 μm) it is concluded that CuL2 is present as a concentrated (C≈10−1 M) THF solution ina and as small solid particles (diameter <1 μm) inb. The difference in colour of the films (dark bluea, light blueb), due to the different physical state of CuL2 in the matrix, is expected, and has been preliminarily shown using similar films based on NiL2, to be useful for sensing organic vapours in the atmosphere.

Preparation, characterization and crystal structure of bis(1,2,6,7-tetracyano-3,5-dihydro-3,5-diiminopyrrolizinido)-palladium(II)–1,2-dimethoxyethane (1/2)

The neutral, planar complex [PdL2](L = 1,2,6,7-tetracyano-3,5-dihydro-3,5-diiminopyrrolizinide) is described along with the crystal structure of its adduct with 1,2-dimethoxyethane; structural and electronic features are discussed and correlated with previously reported data for the analogous [NiL2] complex.

Interaction of bis(1,2,6,7-tetracyano-3,5-dihydro-3,5-diiminopyrrolizinide) metal complexes with phenazine and derivatives. Crystal structures of addition compounds of the nickel(II) complex with phenazine and 5,10-dimethyl-5,10-dihydrophenazine

The charge-transfer compounds of the electron-acceptor moiety [NiL2](L = 1,2,6,7-tetracyano-3,5-dihydro-3,5-diiminopyrrolizinide) and the electron-donating phenazine derivatives [phenazine (phz), 5,10-dimethyl-5,10-dihydrophenazine (dmphz) and N-methylphenazinium cation (mphz+)] have been synthesized and characterized. The X-ray crystal structures of [NiL2]˙2phz˙2MeCN 1a and [NiL2]˙dmphz˙2MeCN 1b have been determined. Both compounds are monoclinic, mixed-stacked compounds, with planar acceptor and donor moieties alternating along the c axis [1a: space group P21/n, a= 14.687(1), b= 21.364(2), c= 7.8208(6)A, β= 110.958(6)°, Z= 2; 1b: space group P21/c, a= 12.975(5), b= 19.838(7), c= 7.651(3)A, β= 106.05(2)°, Z= 2]. While 1a, as expected, does not show any solid-state collective property, 1b is a semiconductor (single crystal ρ= 3.6 × 103Ω cm at room temperature; Ea= 0.28 eV); its degree of ionicity gradually increases, on lowering the temperature, from zero to a small amount corresponding to an effective magnetic moment (µeff)= of 0.28 µB per molecular formula. The cobalt derivative [CoL2]˙dmphz˙2MeCN has also been synthesized and characterized, which is isomorphous and isostructural with the nickel analogue, and qualitatively behaves likewise (single crystal ρ= 4.2 × 105Ω cm at room temperature; Ea= 0.26 eV); its magnetic measurements show a highspin metal configuration (S=, µeff= 4.13 µB). The N-methylphenazinium (mphz+) derivative, isolated as [NiL2]˙–˙mphz+˙2MeOH, is assumed to be a mixed-stacked radical anion salt from magnetic (µeff= 1.72 µB) and electrical (powder ρ= 5.5 × 106Ω cm at room temperature, Ea= 0.43 eV) measurements.