Bis(phthalocyaninato)niobium(IV): a new sandwich-type molecule ‘stapled’ by two inter-ligand C-C σ bonds

Bis(phthalocyaninato)niobium(IV), [Pc2Nb], a new sandwich-type molecule of unusual light-brown colour, has been obtained from the reaction of PcNbCl2 with PcNa2 in α-chloronaphthalene. Information at hand, including IR and UV-Vis spectral data, strongly suggests the presence in the complex of highly distorted Pc fragments ‘stapled’ by interligand C-C σ bonds, a peculiar feature so far observed only in its Ti(IV) analogue, [Pc2Ti]

Zinc chloride homogeneous catalysis in the tritylation of hydroxyl- and amide-bearing molecules

A tritylation protocol based on the transfer of the triphenylmethylcarbenium ion from trityl acetate to substrates having hydroxyls, in the presence of catalytic amounts of ZnCl(2), is described. The advantages of this method are broad scope, mild conditions, and easy handling. The comparison with the procedure based on the use of equimolar mixture of TrCI and ZnCl(2) in the presence of TEA shows that comparable results are obtained. However, only this method allows reactions of secondary or benzylic alcohols such as oxidation or formation of symmetric ethers to be suppressed. Both procedures are successfully extended to simple and substituted amides. Irrespective of its low solubility in acetonitrile, even asparagine can be directly tritylated on its amide group. (C) 2010 Elsevier Ltd. All rights reserved

Novel families of phthalocyanine-like macrocycles—Porphyrazines with annulated strongly electron-withdrawing 1,2,5-thia/selenodiazole rings

Tetrakis(thiadiazole)porphyrazines and tetrakis(selenodiazole)porphyrazines, first described in the years 1998–2001, have later attracted the attention of different scientific groups in the world. Since the beginning and in the most recent times, a number of aspects concerning their relevance as phthalocyanine-like macrocycles, their distinct structural, electronic and UV–visible spectroscopic features, and electrochemical behavior have brought to knowledge the important role played by the externally annulated electron-withdrawing thia- and selenodiazole rings. Much has been learned about the acid–base properties of the new macrocycles, their facile electron uptake and negative charge redistribution capability within the entire macrocyclic framework. Further work has been directed to the synthesis and characterization of several low-symmetry species carrying peripherally annulated benzene or substituted benzene rings and thia- or selenodiazole rings and the structural and electronic effects caused by the progressive annulation of the heterocyclic rings in a basic phthalocyanine structure has been examined. Deselenation processes at the annulated selenodiazole rings in symmetrical and low-symmetry macrocycles and the formation of vicinal diamino functionalities have allowed diversified derivatization procedures with formation of new porphyrazine macrocycles by ring reclosure or designed external sites for exocyclic metalation in dinuclear species

Further Structural Information on the Intra- and Interunit Contacts in Dimeric Ruthenium Phthalocyanine

Previous EXAFS and further LAXS studies fully confirm that solid amorphous ruthenium phthalocyanine, as obtained from its DMSO, pyridine, and isoquinoline adducts, is dimeric with dimers chained to form aggregates of formula [(PcRu)(2)](n) (average n = 6) and with short intradimer Ru-Ru (2.40 Angstrom) and long interdimer (4.30-4.40 Angstrom) bond distances, in contrast with recent different EXAFS findings (very short Ru-Ru interdimer contacts, 3.52 Angstrom) and an associated structural model

The chameleon-like coordinating ability of 2,3-di(pyridyl)pyrazine-type ligands

This survey is dedicated to the multifaceted modes of binding of metal ions by polyazine N donors like 2,3-di(2-pyridyl)pyrazine (dpp), 5,6-di(2-pyridyl)quinoxaline (dpq) and 9,10-di(2-pyridyl)benzoquinoxaline (dpbq) and related substituted analogs, covered until the end of 2016. These compounds display the potential coordination of the dipyridinopyrazine block consisting of two pyridine and two pyrazine N donor atoms. This report illustrates the structural features of the mono-, di- and multinuclear complexes, whenever crystallographic information was available. In the absence of X-ray work, as is the case for tri-, tetra-, and multinuclear systems, the overall organization of the complex systems is that proposed by the authors. Synthetic procedures, physicochemical properties, especially UV–visible spectroscopic and electrochemical behaviour, are given some attention. © 2017 Elsevier B.V

Iron(II) complexes of hexaphenyl(1,2,5-thia/selenadiazolo)porphyrazine: the direct replacement of Se by S in the 1,2,5-selenadiazole ring

Iron(II) complexes of hexaphenyl(1,2,5-thia/selenadiazolo)porphyrazines have been prepared as bis(pyridine) adducts [PY2Fe(XN2)PAPh(6)] (X = S, Se) from the corresponding Mg-II complexes obtained by template co-cyclotetramerization of diphenylfumarodinitrile with 1,2,5-thia/selenadiazolo-3,4-dicarbonitriles, and the unusual direct replacement of Se by S in the reaction of [Py2Fe(SeN2)PAPh(6)] with H2S has been observed