Carlo Floriani
University of Lausanne
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Advances in Organometallic Chemistry | 2001
Carlo Floriani; Rita Floriani‐Moro
Publisher Summary This chapter reviews the potential of calix [4] arenes as ancillary ligands in coordination and organometallic chemistry of transition metals, in the areas of both metal reactivity and catalysis. Therefore, the metalation of calix [4] arenes and their O-alkylated derivatives is focused, only when it produces compounds potentially useful for exploring the chemical reactivity of the metal centers. The chemistry associated with the metal-oxo-surfaces modeled by the metallacalix [4] arene at the molecular is reviewed. In the metalla-derivatives, calix [4] arenes exclusively assume the cone conformation, thus keeping the oxygen set quasi-planar. They usually act as tetra-anionic ligands, though the charge of the O 4 set can be tuned by a different degree of alkylation. The metal-oxo molecular models outlined in the chapter have a potential for studying the metal activity in a quite unusual environment. Some of the possibilities could be the generation and the chemistry of M––C, M=C, M≡C functionalities; the interaction with alkenes, alkynes, hydrocarbons, and hydrogen; the activation of small molecules, such as N 2 6 and CO; the support of metal–metal bonded functionalities; and the generation of highly reactive low-valent metals.
Inorganica Chimica Acta | 1998
Antonio Zanotti-Gerosa; Euro Solari; Luca Giannini; Carlo Floriani; Nazzareno Re; Angiola Chiesi-Villa; Corrado Rizzoli
Abstract Lithiation of [ p -Bu t -calix[4]-(OMe) 2 (OH) 2 ] ( 1 ), followed by reaction with TiCl 3 (thf) 3 or TiCl 4 (thf) 2 , led to the corresponding titanium-calix[4]arene complexes [ p -Bu t -calix[4]-(OMe) 2 (O) 2 ]TiCl] ( 2 ) and [ p -Bu t -calix[4]-(OMe) 2 (O) 2 ]TiCl 2 ] ( 3 ), respectively. Reaction of 1 with TiCl 4 (thf) 2 results in demethylation of the calix[4]arene and the obtention of [ p -Bu t -calix[4]-(OMe) 2 (O) 3 ]TiCl] ( 4 ), whose hydrolysis led to [ p -Bu t -calix[4]-(OMe)(OH) 3 ] ( 6 ). The preparation of 6 can be carried out as a one-pot synthesis. Both 2 and 4 undergo alkylation reactions using conventional procedures, thus forming surprisingly stable organometallic species, namely [ p -Bu t -calix[4]-(OMe) 2 (O) 2 Ti(R)] (R = Me ( 7 ); CH 2 Ph ( 8 ), p -MeC 6 H 4 ( 9 ) and [ p -Bu t -calix[4]-(OMe)(O) 3 Ti(R)] (R = Me ( 10 ); CH 2 Ph ( 11 ); p -MeC 6 H 4 ( 12 )). Complexes 7 and 9 undergo a thermal oxidative conversion into 10 and 12 , occurring with the demethylation of one of the methoxy groups. A solid state structural property of 9 and 12 has been revealed by X-ray analysis showing a self-assembly of the monomeric units into a columnar polymer, where the p -tolyl substituent at the metal functions as a guest group for an adjacent titanium-calixarene. Reductive alkylation of 3 with Mg(CH 2 Ph) 2 gave 8 instead of forming the corresponding dialkyl derivative. Two synthetic routes have been devised for the synthesis of the Ti(III)-Ti(III) dimer [ p -Bu t -calix[4]-(OMe)(O) 3 Ti] 2 ] ( 13 ): the reduction of 4 and the reaction of TiCl 3 (thf) 3 with the lithiated form of 6 . A very strong antiferromagnetic coupling is responsible for the peculiar magnetic behavior of 13 . The proposed structures have been supported by the X-ray analyses of 4, 9, 12 and 13 .
Chemistry: A European Journal | 1999
Carlo Floriani
Olefin rearrangements to alkylidynes and alkylidenes driven by acids, bases, or light, and dinitrogen cleavage to nitride (depicted here) are all possible with the aid of transition metals anchored to a preorganised oxo surface, illustrated by calix[4]arene anions.
Inorganic Chemistry | 1984
Sandro Gambarotta; Carlo Floriani; Angiola Chiesi-Villa; Carlo Guastini
Determination des structures cristallines des composes (cp*) 2 V (avec cp*=η 5 -C 5 Me 5 ), (cp*) 2 V(CO), (cp*) 2 V(CN)(CNC 6 H 11 ) et (cp*) 2 V(CN). Spectres IR et moments magnetiques
Angewandte Chemie | 1999
Jean-Marc Benech; Lucia Bonomo; Euro Solari; Rosario Scopelliti; Carlo Floriani
Stepwise dealkylation of meso-octaethylporphyrinogen 1 yields porphomethene 2 and porphodimethene 3, providing access to large quantities of these valuable intermediates. The synthetic sequence relies on SnCl4⋅2 THF, Li, and H2O; the extent of dealkylation depends on the amount of SnCl4⋅2 THF employed.
Journal of The Chemical Society-dalton Transactions | 1990
Fabio Corazza; Euro Solari; Carlo Floriani; Angiola Chiesi-Villa; Carlo Guastini
The reaction of MCl4·2thf (thf = tetrahydrofuran) with the sodium salt of quadridentate Schiff bases [L =N,N′-ethylenebis(acetylacetoneiminate)(acen), N,N′-ethylenebis(salicylideneiminate)(salen), N,N′-ethylenebis(α-methylsalicylideneiminate)(dmsalen), or N,N′-o-phenylenebis(salicylideneiminate)(salphen)] yields the complexes [MLCl2(thf)]. X-Ray analyses showed for all of them that the metal ion is seven-co-ordinate with a pseudo-pentagonal bipyramidal geometry. Details of the structures of [Zr(acen)Cl2(thf)](5), [Zr(salphen)Cl2(thf)]·0.5thf (10), and of the corresponding isostructural hafnium complex [Hf(salphen) Cl2(thf)]·0.5thf (11) are reported. The equatorial plane of the bipyramid is defined by the N2O2 donor atoms and by the oxygen atom from thf, while the two chlorine atoms are trans to each other [Cl–Zr–Cl 169.1 (1), (5); 165.2(1), (10); Cl–Hf–Cl 166.3(1)°, (11)]. Recrystallization of the seven-co-ordinate complexes from toluene removed the thf leading to six-co-ordinate complexes. The structural determination of the isostructural [Zr(acen)Cl2](12) and [Hf(acen)Cl2](13) showed the six-co-ordination of the metal with the two chlorines assuming a cis arrangement [Cl–Zr–Cl 87.2(1), (12); Cl–Hf–Cl 87.4(1)°, (13)]. Bond lengths within the co-ordination sphere are significantly shorter in the six-co-ordinate complexes. The cis and trans isomers do not interconvert in solutions of non-co-ordinating solvents, i.e. C6H6 or CH2Cl2, as shown by their distinctive 1H n.m.r. spectra. In the absence of geometrical constraints zirconium(IV) prefers six-co-ordination and a cis arrangement of the chloride ligands. This was confirmed by synthesizing [Zr(msal)2Cl2](15)(msal =N-methylsalicylideneiminate), [Cl–Zr–Cl 97.9(1)°] containing a bidentate Schiff-base ligand. Its crystallization from thf gave the unsolvated six-co-ordinated form. Crystallographic details: complex (5), space group P, a= 8.401 (1), b= 15.987 (2), c= 7.805(1)A, α= 98.41 (1), β= 90.32(1), γ= 76.65(1)°, Z= 2, and R 0.042 for 3 713 observed reflections; (10), space group P, a= 12.759(2), b= 13.332(2), c= 7.587(1)A, α= 91.60(2), β= 98.45(1), γ= 85.30(1)°, Z= 2, and R 0.033 for 3 813 observed reflections; (11), space group P, a= 12.737(7), b= 13.269(7), c= 7.564(4)A, α= 91.48(1), β= 98.56(1), γ= 85.26(1)°Z= 2, and R 0.027 for 4 227 observed reflections; (12), space group P21/n, a= 24.150(5), b= 9.160(2), c= 7.282(1)A, β= 90.90(1)°, Z= 4, and R 0.034 for 1 894 observed reflections; (13), space group P21/n, a= 24.096(10), b= 9.161 (4), c= 7.262(3)A, β= 90.87(1)°, Z= 4, and R 0.024 for 2 124 observed reflections; (15), space group P, a= 13.024(3), b= 14.522(3), c= 9.797(2)A, α= 90.10(1), β= 93.14(1), γ= 96.09(1)°, Z= 4, and R 0.044 for 3 294 observed reflections.
Journal of The Chemical Society, Chemical Communications | 1978
Giuseppe Fachinetti; Carlo Floriani; Sergio Pucci
The reaction of carbon monoxide with bis(η5-cyclopentadienyl)hydridochlorozirconium(IV), cp2Zr-(H)Cl, at room temperature and atmospheric pressure, leads to a dinuclear zirconium(IV) derivative (cp2ZrCl)2CH2O; replacing CO by CO2 in this reaction results in the quantitative formation of cp2ZrCl(OMe) and (cp2ZrCl)2O.
Journal of The Chemical Society-dalton Transactions | 1977
Giuseppe Fachinetti; Giovanni Fochi; Carlo Floriani
Carbonylation of toluene solutions of bis(η-cyclopentadientyl)diphenyl-zirconium(IV) and -hafnium(IV), [M(cp)2(Ph)2](cp =η-C5H5; M = Zr or Hf), with CO at atmospheric pressure gave acyl derivatives [M(cp)2(COPh)(Ph)][ν(CO)= 1 500 cm–1]. The same results were obtained for [M(cp)2R2](M = Zr or Hf; R = CH2Ph or Me), but in these cases the carbonyl insertion was found to be reversible. The isolation of [M(cp)2(COR)R][ν(CO)= 1 530–1 550 cm–] was possible only for zirconium, while under the same conditions equilibrium constants and thermodynamic data were obtained for CO insertion into the Hf–Me (ΔH⊖=–12.7 ± 1.6 kcal mol–1; ΔS⊖=–33.0 ± 5.6 cal K–1 mol–1) and Hf–CH2Ph (ΔH⊖=–11.5 ± 0.2 kcal mol–1; ΔS⊖=–28.7 ± 0.6 cal K–1 mol–1) bonds. All the acyls show a low CO stretching frequency, which indicates an η-acyl bonded group, as was confirmed by X-ray structural data.
Chemistry: A European Journal | 1999
Barbara Castellano; Euro Solari; Carlo Floriani; Nazzareno Re; Angiola Chiesi-Villa; Corrado Rizzoli
Tantalum–carbon functionalities bonded over an oxo matrix (here calix[4]arene anions) undergo a variety of multiple migratory insertion reactions which lead to the metal-assisted formation of C–C and CC bonds.
Chemistry: A European Journal | 1999
Federico Franceschi; Euro Solari; Carlo Floriani; Marzio Rosi; Angiola Chiesi-Villa; Corrado Rizzoli
A novel mode of storing and releasing electrons, based on the reversible formation and cleavage of C−C bonds, has been created. The C−C bonds formed by the reductive coupling of imino groups across two [M(salophen)] complexes (see structure) function as shuttle for two electrons, permitting long-range electron transfer to a variety of substrates (e.g. quinone, dioxygen, and azides). This electron transfer is mediated by the metal, which becomes the reactive site, while the C–C functionality is never directly involved.