Angiola Chiesi-Villa

Titanium-carbon functionalities on an oxo surface defined by a calix [4] arene moiety and its redox chemistry

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 .

Decamethylvanadocene chemistry: synthesis, structure, and reactions of vanadium(II) and vanadium(III) derivatives with carbon monoxide and isocyanides

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

cis- and trans-Dichloro-derivatives of six- and seven-co-ordinate zirconium and hafnium bonded to quadridentate Schiff-base ligands. Crystal structures of [Zr(acen)Cl2(thf)], [M(salphen)Cl2(thf)]·0.5thf, [M(acen)Cl2], (M = Zr or Hf), and [Zr(msal)Cl2][acen =N,N′-ethylenebis(acetylacetoneiminate), salphen =N,N′-o-phenylenebis(salicylideneiminate), msal =N-methylsalicylideneiminate, and thf = tetrahydrofuran]

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.

Two phthalocyanine units ‘stapled’ by carbon–carbon σ bonds in a new sandwich-type molecule: {5,5′;19,19′-bi[phthalocyaninato (2–)]}titanium(IV). Synthesis, X-ray crystal structure, and properties

{5,5′;19,19′-Bi[phthalocyaninato(2–)]}titanium(IV)–1-chloronaphthalene(1/1 ), [TiL]·C10H7Cl, is obtained by the reaction of [Ti(pc)Cl2](pc = phthalocyaninato dianion, [C32H16N8]2–) with Na2(pc) in 1-chloronaphthalene at 190 °C, An X-ray single-crystal structure (monoclinic, space group C/2c, a= 16.327(3), b= 18.568(4), c= 19.022(4)A; β= 94.50(1)°, Z= 4) indicates for this complex a sandwich-type structure with the titanium atom in the centre of the molecule and the two phthalocyaninato units ‘stapled’ by two inter-ring C–C σ bonds [C(11)–C(11′) 1.556(6) and C(31)–C(31′) 1.575(6)A]. Due to the staggered orientations of the two macrocyclic rings (relative rotation 45°) the planes of the two inner N4 systems (each of which is slightly distorted from planarity) form a square-antiprism, with an average interplane distance of 2.32 A(much shorter than that found in similar ‘unstapled’ complexes), and Ti–N bond distances in the range 2.17–2.26 A. The complex shows high thermal stability and can be oxidized by nitric acid to give the species [TiL]NO3. The complexes [TiL] and [TiL]NO3 show differing solid-state electrical conductivity properties.

Tantalum–Carbon Functionalities Bonded to a Calix[4]arene-Oxo Matrix: The Chemistry of Mono-, Dialkyl, and Butadiene Derivatives of Tantalum(V)

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.

Molecular Batteries Based on Carbon–Carbon Bond Formation and Cleavage in Titanium and Vanadium Schiff Base Complexes

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.

Porphyrazines with Annulated Diazepine Rings, 1 Synthesis and Characterization of Tetrakis‐2,3‐(5,7‐diphenyl‐6H‐1,4‐diazepino)porphyrazine and Its MgII, CuII, and ZnII Complexes – X‐ray Crystal Structure of 2,3‐Dicyano‐5,7‐diphenyl‐6H‐1,4‐diazepine

A new class of porphyrazine macrocycles carrying peripheral diazepine rings, i.e. tetrakis-2,3-(5,7-diphenyl-6H-1,4-diazepino)porphyrazine [Ph2DzPzH2](H2O)4, and its metal derivatives of formula [Ph2DzPzM](H2O)x=2–7 [M = MgII(H2O), CuII, ZnII] have been prepared and characterized. Single crystal X-ray work on the monomeric precursor 5,7-diphenyl-2,3-dicyano-6H-1,4-diazepine, Ph2(CN)2Dz, and NMR spectra (CDCl3, (CD3)2SO) and UV/Vis spectra in solution of different media (basic, neutral, acid) of the monomer and its macrocyclic derivatives have provided information on the conformational flexibility of the diazepine ring as well as on the structural and electronic features of the entire porphyrazine skeleton.

Polydentate ligand exchange via formation of a dimetallic complex. Crystal structures of [(thf)Fe(acen)MCl2](M = Fe or Zn), [ClFe(salphen)FeCl(thf)2], [Ti(acen)(thf)2][CoCl3(thf)], and [Ti(acen)(thf)2]2[Fe3Cl8(thf)2][acen =N,N′-ethylenebis(acetylacetoneiminate), salphen =N,N′-o-phenylenebis(salicylideneiminate), and thf = tetrahydrofuran]

Complexation of metal halides M′Cln by square-planar Schiff-base complexes, i.e. ML [M = Fe, Co, Ni, or Cu; L = acen =N,N′-ethylenebis(acetylacetoneiminate), salen =N,N′-ethylenebis(salicylideneiminate), or salphen =N,N′-o-phenylenebis(salicylideneiminate)] led to adducts which are intermediates in the exchange of the quadridentate ligand between M and M′. Exchange occurs if M′ is in an higher oxidation state than M. Concomitant redox and ionization reactions are observed. Reaction of [Fe(acen)], (1) with MCl2·nthf (M = Fe or Zn) led to the bimetallic adducts [(thf)Fe(acen)MCl2[M = Fe, (2); Zn, (3)] containing a square-pyramidal iron, while M has a tetrahedral co-ordination geometry. A complex analogous to (2), [ClFe(salphen)FeCl(thf)2](4)(thf = tetrahydrofuran), was obtained by treating FeCl2·1.5 thf with H2 salphen in a 2:1 molar ratio in the presence of Na(OMe). This reaction gave some insight into the ligand-exchange pathway. The reaction of [M(acen)](M = Fe, Co, or Ni) complexes with TiCl4·2thf in thf led to migration of the acen ligand to titanium and formation of [Ti(acen)Cl2], (7) and the corresponding metal halide MCl2·nthf. Related results have been obtained in the reaction of [M(acen)] and TiCl3·3thf. When M = Ni or Cu complex (7) was obtained by exchange of the acen ligand and oxidation of titanium(III) by the corresponding metal halides. In the absence of a redox reaction, complexes of titanium (III) have been obtained: [Ti(acen)(thf)2][CoCl3(thf)], (10), and [Ti(acen)(thf)2]2[Fe3Cl8(thf)2], (11), respectively. The structures of complexes (2)–(4), (10), and (11) have been determined by X-ray analysis: (2) space group P, a= 14.029(2), b= 9.854(1), c= 8.092(1)A; α= 98.48(1), β= 90.96(1), γ= 107.44(1)°, Z= 2, and R= 0.065 for 1 360 observed reflections; (3), space group P, a= 14.006(3), b= 9.823(2), c= 8.077(2)A, α= 98.49(1), β= 90.90(1), γ= 107.57(1)°Z= 2, and R= 0.072 for 2 347 observed reflections; (4), space group P21/c, a= 12.882(2), b= 11.940(2), c= 21.701 (3)A, β= 95.40(1)°, Z= 4, R= 0.054 for 1991 observed reflections; (10), space group P, α= 12.735(3), b= 15.105(3), c= 8.935(2)A, α= 95.30(2), β= 94.26(2), γ= 67.91 (2)°, Z= 2, and R= 0.055 for 2 576 observed reflections; (11), space group P, α= 14.109(3), b= 14.713(3), c= 9.203(2)A, α= 99.98(2), β= 104.76(2), γ= 63.08(2)°Z= 1 for C48H84Cl8Fe3N4O10Ti2 formula unit, and R= 0.050 for 2 685 observed reflections.

The π-Pyrrole Complexation of Alkali Metal Ions by Zirconiummeso-Octaalkylporphyrinogens: Encapsulation of Li4H4 and Li2O in Sandwich Structures

Complexation of metal ion and counterion by the same compound is possible with zirconium meso-octaalkylporphyrinogens (structure of a dimeric complex with four encapsulated equivalents of LiH is depicted): they carry salts in the molecular ion-pair form in hydrocarbons, and function as acid-base bifunctional compounds.

The π and σ bonding modes of meso-octaethylporphyrinogen to transition metals: the X-ray structure of a meso-octaethylporphyrinogen–zirconiuml(IV) complex and of the parent meso-octaethylporphyrinogen ligand

The meso-octaethylporphyrinogen tetraanion provides σ and π binding pyrrolyl anions to electron poor transition metals, as shown in the structure of the meso-octaethylporphyrinogen–zirconium(IV) complex containing two η5 and two σ metal-bonded pyrrolyl anions.