Dalton Transactions Blog

In this HOT article, Ribas and co-workers build on previous studies on the mechanism of Ullmann cross coupling reactions using a well-defined aryl-copper(III) complex. Fundamental mechanistic knowledge of these couplings is still scarce but is gaining renewed interest due to the cost and toxicity benefits in comparison to Pd-based methodologies for the synthesis of key intermediates in the pharmaceutical industry. The reactivity of well defined aryl–Cu^III species in front of phenol-type nucleophiles was found to differ substantially from the reactivity with corresponding phenolates, and a significant enhancement was found to produce the same aryl–O coupling product. Mechanistic studies showed that easy deprotonation of coordinated secondary amines was responsible for the intense LMCT band at 545 nm; indeed, this pH-dependent reactivity of the pincer-like coordinated ligand somewhat enhanced its reactivity.

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Aryl–O reductive elimination from reaction of well-defined aryl–Cu^III species with phenolates: the importance of ligand reactivity
Alicia Casitas, Nikolaos Ioannidis, George Mitrikas, Miquel Costas and Xavi Ribas
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10428D

This Dalton Transactions Hot article looks at the use of zinc complexes in cancer treatment. This exciting compound, made by Soumitra Choudhuri and colleagues, was found to act against drug resistant cancers.

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An in vitro and in vivo study of a novel zinc complex, zinc N-(2-hydroxyacetophenone)glycinate to overcome multidrug resistance in cancer Ruma Dey Ghosh, Satyajit Das, Avishek Ganguly, Kaushik Banerjee, Paramita Chakraborty, Avijit Sarkar, Mitali Chatterjee, Ashis Nanda, Kiran Pradhan and Soumitra K. Choudhuri
Dalton Trans., 2011, DOI: 10.1039/C1DT10501A

Since their first publication, zwitterionic benzo quinonemonoimines such as have attracted much attention, because of the remarkable electronic delocalization of their pi-system which forms two chemically connected but electronically separated 6pi-electron subunits. Their potential antiaromaticity is of theoretical interest, and the unique properties that such ligands may confer to their metal complexes extend to coordination chemistry, optical recording, homogenous catalysis and supramolecular chemistry.

In this Dalton Transactions Hot Article, Thomas Kauf and Pierre Braunstein compare the properties of TCNE and TCNQ zwitterionic benzoquinonemonoimine derivatives to find some interesting results. Be the first to read their communication here – free for you to view for 4 weeks:

Contrasting behaviour of TCNE and TCNQ zwitterionic benzoquinonemonoimine derivatives and coordination of a tricyanoethenyl substituent to Pd(0)
Thomas Kauf and Pierre Braunstein
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10804B

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In this Dalton Transactions Hot article, Chebrolu P. Rao from the Indian Institute of Technology, Bombay and colleagues investigate the anticancer activity of the organometallic compound, copper (II) anthracenyl-terpyridine.

This compound is particularly exciting because it kills cells in a way not seen before with copper complexes.

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Synthesis, characterization, plasmid cleavage and cytotoxicity of cancer cells by a copper(II) complex of anthracenyl-terpyridine
Amit Kumar, Jugun Prakash Chinta, Amrendra Kumar Ajay, Manoj Kumar Bhat and Chebrolu P. Rao
Dalton Trans., 2011, DOI: 10.1039/C1DT10201J

In this HOT article, a very careful synthetic and catalytic study of the use of di- and trisulfonated phosphines with o, m and o, m, m substitution patterns is described. Pd complexes of these were tested for  copolymerizations with polar monomers. This led to a novel anionic phosphine sulphonate Pd(II)-based pre-catalyst salt for polymerisation reactions.  Although, polymerisation in the presence of methyl acrylate, acrylonitrile and vinyl acetate led to reduced incorporation values compared to the available literature reports in combination with problems that are attributed to aggregation of the catalyst in most cases, the facile synthesis of chelating highly polar ligands which show high water solubility could be of significant interest for homogeneous catalysis by application in other systems.

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Synthesis of non-symmetrically sulphonated phosphine sulphonate based Pd(II) catalyst salts for olefin polymerisation reactions
Timo M. J. Anselment, Carly E. Anderson, Bernhard Rieger, M. Bele Boeddinghaus and Thomas F. Fässler
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10372E

In this Dalton Transactions Hot Article, Maria-Angels Carvajal and colleagues probe the photomagnetic properties of a copper octacyanomolybdate complex using high level ab initio calculations.

The authors describe in detail the photomagnetic process arising from a local Mo d-d excitation in the complex. They also show that there is a small energy barrier for the reverse reaction and that it can be induced by light. They also investigate the temperature dependence of the magnetic susceptibility and compare it with experimental values.

Photomagnetic materials are of interest as candidates for use in memory devices and optical switches.

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Insights on the photomagnetism in copper octacyanomolybdates
Maria-Angels Carvajal, Rosa Caballol and Coen de Graaf
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10120J, Paper

In this Dalton Transactions Hot Article, Graham Bowmaker from the University of Auckland and colleagues, synthesised three new disilver(I) carbonate/tertiary phosphine complexes.

Solution and mechanochemical methods were used. The use of the mechanochemical synthesis demonstrates an additional aspect of this type of method. The study also demonstrates the value of ATR IR and CPMAS NMR for monitoring the progress of mechanochemical synthesis.

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Solution and mechanochemical syntheses, and spectroscopic and structural studies in the silver(I) (bi-)carbonate: triphenylphosphine system
Graham A. Bowmaker, Effendy, John V. Hanna, Peter C. Healy, Scott P. King, Claudio Pettinari, Brian W. Skelton and Allan H. White
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10416K, Paper

In this HOT article, the authors have extended their work in understanding enantioselective catalysis by coordination compounds. The role of steric hindrance in controlling the binding mode of propylene oxide to a novel vanadyl salen-type complex N,N‘-bis(5-tert-butylsalicylidene)-1,2-cyclohexanediamino-vanadium(IV) oxide, [VO(3)], has been investigated using CW/pulse EPR, ENDOR and HYSCORE spectroscopy and compared to that of the parent complex N,N‘-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediamino-vanadium(IV) oxide, [VO(1)]. Removal of the ‘inner tert-butyl groups from the salicylidene rings reduces the steric hindrance between the ligand and epoxide substrate. As a result the selectivity for binding single enantiomers of propylene oxide in these complexes is reversed in [VO(3)] relative to [VO(1)].

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Structure and pulsed EPR characterization of N,N‘-bis(5-tert-butylsalicylidene)-1,2-cyclohexanediamino-vanadium(IV) oxide and its adducts with propylene oxide
E. Carter, I. A. Fallis, B. M. Kariuki, I. R. Morgan, D. M. Murphy, T. Tatchell, S. Van Doorslaer and E. Vinck
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10378D