Dalton Transactions Blog

Mechanochemistry has been used for centuries – according to some, as early as 371 B.C. The pestle and mortar still has a place in many chemistry labs but nowadays mechanically-induced chemistry is  performed with the help of a high-energy ball mill.

In their latest Dalton Transactions Perspective, Vladimir Šepelák, Sylvie Bégin-Colin and Gérard Le Caër describe how ball milling is used to effect transformations in oxides. Whilst understanding of the mechanochemical processes involved in ball-milling metalllic compounds is growing, for the more-complex oxide materials, the field is still relatively immature.

The authors explain the various uses of ball milling oxides which can be grouped into either homogeneous or heterogeneous processes (determined by whether there is a net exchange of atoms across boundaries or not). Homogeneous processes encompass polymorphic transformations and titania phase transformations; heterogeneous processes involve compound formations, decompositions and redox reactions.

To read more about the interesting nanocrystalline characteristics that ball milling offers, read the Perspective article now.

Transformations in oxides induced by high-energy ball-milling
Vladimir Šepelák, Sylvie Bégin-Colin and Gérard Le Caër

Interested in other mechanochemistry articles? Read the growing number of articles being added to the ChemComm web theme in mechanochemistry – guest edited by Stuart James and Tomislav Friščić.

Almost ten years ago, Piers et al. described how frustrated aminoboranes could be used to activate molecular hydrogen by exploiting their frustrated Lewis pairs.  Unfortunately the ansa-aminoborane they investigated proved incapable of activating H₂, and so this contribution was very much overlooked in the ongoing search for facile H₂ activation.

A frustrated Lewis pair, in this case, is a molecule that contains a Lewis acid group and a Lewis base group kept apart due to sterics.  Such compounds are, perhaps unsurprisingly, very reactive.  The most important practical application of FLPs is most likely to be the catalysed hydrogenation of polar double bonds under ambient conditions.

The Repo group at the University of Helsinki describe how they have overcome the problems encountered in 2003 to produce two new ansa-aminoboranes which are both capable of activating molecular hydrogen under ambient conditions.  One of their new compounds even shows selective reversible H₂ activation at room temperature, providing exciting new developments for FLP catalysis.

Read more about these new catalysts, including why they outperform their predecessors, in this HOT article.

Hydrogen activation by 2-boryl-N,N-dialkylanilines: a revision of Piers’ ansa-aminoborane
Konstantin Chernichenko, Martin Nieger, Markku Leskelä and Timo Repo

It’s estimated that there’s more than 4.5 billion tons of uranium in the ocean

US scientists have used a ligand that can form a complex with a uranyl ion to enable uranium to be extracted from seawater. The concentration of uranium in seawater is low at 3.3 parts per billion, but in the vast oceans, it’s estimated that there’s more than 4.5 billion tons of uranium; considerably more than the amount of uranium in terrestrial ores, say the researchers.

Extracting uranium from the sea is a challenge because it exists as a stable carbonate complex. Linfeng Rao from the Lawrence Berkeley National Laboratory, and colleagues, say that a cyclic imide dioxime ligand – glutarimidedioxime – can compete with carbonate to bind strongly to the uranyl ion to form the complex.

Rao says that there are two unique features in the structure of the uranium–glutarimidedioxime complex. ‘The protons of both oxime groups (–CH=N–OH) are rearranged from the oxygen atom to the nitrogen atom,’ he explains. ‘The middle imide group (–CH–NH–CH–) is deprotonated, resulting in a -1 charged ligand that coordinates to the uranyl cation in a tridentate mode (via the two oxime oxygen atoms and the imide nitrogen atom).’ With such a configuration, he adds, the electron density on the ligand could be delocalised, forming a conjugated system that coordinates strongly to the uranyl cation.

‘It will be interesting to learn how the ligand performs in competition with a peroxide anion, which forms an even stronger complex than carbonate with the uranyl ion in the natural marine photic zone,’ says Mark Antonio, a separation science expert from Argonne National Laboratory, US. He adds that the results from the investigation provide insights that may lead to a viable sequestration of uranium from amongst a myriad other cations.

‘Uranium availability becomes even more important as developing countries such as China and India are ramping up their nuclear power capacities,’ says Wenbin Lin, whose group from the University of North Carolina at Chapel Hill, US, focuses on addressing  fundamental chemical problems relevant to societal issues. ‘If an economically viable technology can be developed to extract uranium from seawater, nuclear power becomes a virtually sustainable clean energy source.’

Sequestering uranium from seawater: binding strength and modes of uranyl complexes with glutarimidedioxime
Guoxin Tian,  Simon Teat,  Zhiyong Zhang and Linfeng Rao
Dalton Trans., 2012
DOI: 10.1039/C2DT30978E

Scientists in Mexico have devised a new synthetic pathway to a nitrogen-containing ligand, which, when bound to divalent nickel or manganese, is a 1000 times more effective than the leading clinical drug at reducing the profileration of the parasite responsible for amoebiasis. This disease causes 70 thousand deaths a year.

The same ligand bound to other divalent metal ions also shows remarkable anti-cancer properties with activities superior to cisplatin.

Want to know more? Download the article now…
Potential cytotoxic and amoebicide activity of first row transition metal compounds with 2,9-bis-(2′,5′-diazahexanyl)-1,1-phenanthroline (L1)
Juan Carlos García-Ramos, Yanis Toledano-Magaña, Luis Gabriel Talavera-Contreras, Marcos Flores-Álamo, Vanessa Ramírez-Delgado, Emmanuel Morales-León, Luis Ortiz-Frade, Anllely Grizett Gutiérrez, Adriana Vázquez-Aguirre, Carmen Mejía, Julio César Carrero, Juan Pedro Laclette, Rafael Moreno-Esparza and Lena Ruiz-Azuara

Gigantic multinuclear transition metal cluster complexes have unique properties and reactivities.

Metalladithiolenes, along with their cluster complexes, are excellent compounds for studying multinucleation and electronic communication in mixed-valent states.  Electronic communication in mixed-valent states is particularly important for single-molecule magnets, enzymes and for the creation of molecular devices.  Ryota Sakamoto, Satoru Tsukada and Hiroshi Nishihara detail synthetic strategies for the successful multinucleation of metalladithiolenes in this Hot Perspective. 

Download it today…
Multinuclear metalladithiolenes: focusing on electronic communication in mixed-valent states
Ryota Sakamoto, Satoru Tsukada and Hiroshi Nishihara

Here are some of the authors’ other recent Dalton Transactions publications:

Synchronized motion and electron transfer of a redox-active rotor
Shoko Kume and Hiroshi Nishihara
Dalton Trans., 2011,40, 2299-2305
DOI: 10.1039/C0DT01084G

Conjugation of Au11 cluster with Cys-rich peptides containing the α-domain of metallothionein
Shinya Ariyasu, Akira Onoda, Ryota Sakamoto and Takeshi Yamamura
Dalton Trans., 2009, 3742-3747
DOI: 10.1039/B900570F

Development of a versatile synthesis method for trinuclear Co(III), Rh(III), and Ir(III) dithiolene complexes, and their crystal structures and multi-step redox properties
Yusuke Shibata, Baohua Zhu, Shoko Kume and Hiroshi Nishihara
Dalton Trans., 2009, 1939-1943
DOI: 10.1039/B815560G

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Unique cooperation has been observed between rhenium atoms and non-innocent N-confused porphyrin ligands in new oxorhenium(V) complexes.

The simplest porphyrin, porphine (left), and the N-confused porphyrin used to synthesize unique oxorhenium complexes.

Hiroyuki Furuta et al. have synthesised two new porphyrin oxorhenium(V) complexes which have been shown to be remarkably effective at oxygen atom transport. Through a catalytic process the oxygen atom from pyridine N-oxide can be transferred to PPh₃ in a 97% yield, notably higher than that of some other rhenium(V) complexes. The authors propose that the reason for their success is the existence of a Re-C bond, believing that this bond is important for efficient oxygen transport.

Atom transport is at the heart of successful catalysis, and as usual nature has already beaten us to it. Galactose oxidase for example converts a primary alcohol into an aldehyde by transporting a hydrogen atom from one part of the enzyme to another. But if the oxygen atom transfer seen in these synthetic N-confused porphyrin oxorhenium(V) complexes can be extended to other systems, exciting advancements in the field of catalysis could be on the horizon.

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To find out more about these exciting new complexes and the atom transport they facilitate, take a look at the full Dalton Transactions communication.

Cooperation between metal and ligand in oxygen atom transport by N-confused porphyrin oxorhenium(V) complexes
Takaaki Yamamoto, Motoki Toganoh and Hiroyuki Furuta

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By Katie Renouf, Web Writer