Dalton Transactions Blog

We are pleased to announce the inclusion of Altmetrics on Dalton Transactions.

With a constantly changing publishing landscape and changes to the way people use scientific literature, altmetrics is a measure that can monitor the level of conversation and interest in a particular piece of research at the article level. Thus altmetrics provides an additional modern metric for our authors to measure the impact of their work, rather than rely solely on citations and impact factor.

To view the altmetrics on Dalton Transactions articles, use the Metrics tab as pictured below on the article landing page.

A press release from Altmetrics is available on our website.

What do you think? We are interested to hear your feedback on this new development and how you are utilising these new types of metrics. Please leave your comments below.

Posted on behalf of Ian Mallov, web writer for Dalton Transactions

We often invoke the analogy of using building blocks when we talk about constructing large, complex molecules.  Adding small building blocks often allows for finer control in design, and diatomic hydrogen is the most used small building block.

To add hydrogen to other molecules, hydrogen molecules themselves are split into a proton and hydride; these are then transferred to the target molecule.  Recently, main group compounds involving frustrated Lewis pairs have been used in both steps instead of transition metal catalysts.  There are also a few main group molecules where hydrogen is split at a single atomic site.  Silylenes – the silicon analogue of carbenes, and the subject of this paper, with two bonds, a pair of electrons, and an empty p-orbital, are one type of these select few. This paper mentions the argument that non-transition metal catalysts may be “greener,” but a thorough life-cycle analysis of extraction, reaction and disposal would be necessary to indicate this. 

Authors, Kuriakose and Vanka use Density Functional Theory to explore the question of why some silylenes split hydrogen and some don’t.  Specifically, they want to test the hypothesis that whether or not hydrogen is split at the silicon centre depends on if an adjacent atom “interferes,” leading to undesired products.  They create a profile of the energies of reaction (with hydrogen gas) of three distinct types of silylene: a boryl amido silylene (I), a silyl amido silylene (II) and a dithiolate silylene (III).  I and II have activated hydrogen, while III hasn’t been observed to do so. 

The free energy profiles for the reaction of silylene, III, with hydrogen  

After optimizing geometry they model the HOMO and LUMO of the silylenes, since donation of electrons from the HOMO and acceptance of electrons into the LUMO are necessary for hydrogen activation.  In the case of I and II, the LUMO is localized on the silicon atom, while in III, it is not. Correspondingly, the reaction pathway of splitting hydrogen is energetically favoured for I and II, and disfavoured for III.  They also examine effects of other features, such as the angle of the two substituents. 

Have a read of the full article now:

New insights into small molecule activation by acyclic silylenes: a computational investigation
Nishamol Kuriakose and Kumar Vanka
Dalton Transactions, DOI: 10.1039/c3dt52817k

Ian Mallov is currently a Ph.D. student in Professor Doug Stephan’s group at the University of Toronto. His research is focused on synthesizing new Lewis-acidic compounds active in Frustrated Lewis Pair chemistry. He grew up in Truro, Nova Scotia and graduated from Dalhousie University and the University of Ottawa, and worked in chemical analysis in industry for three years before returning to grad school.

Posted on behalf of Liana Allen, web writer for Dalton Transactions

As more information becomes known about the negative impacts that humans are having on the Earth’s environment, increasing focus is being put on ways of decreasing these effects in all aspects of our lives. For the chemical industry, there are already several key areas which have been identified as needing particular attention with respect to decreasing our effect on the environment. In the last decade, this challenge has become so important that it is now recognized as a field in its own right, referred to as ‘Green Chemistry’. Some of the overall themes of green chemistry are: decrease of the amount of waste by-products generated by a reaction (i.e. avoiding poor atom economy reagents), reduction of reagents which pose safety hazards (i.e. explosives and known toxic compounds), and ‘cleaner’ solvent choices (i.e. avoiding chlorinated solvents, or volatile solvents whose vapours pose an environmental problem).¹

One of the most important reactions used in chemical industry is formation of carbon-carbon bonds.² The methodology most commonly used to form such bonds is a group of reactions called palladium-catalysed cross-couplings. One of this set of vital reactions is called the Sonogashira coupling. This reaction is used to couple terminal alkynes with aryl or vinyl halides to form di-substituted alkynes, and requires a copper co-catalyst (in addition to a palladium catalyst), heating conditions, and a solvent such as DMF.

In their recent Dalton Transactions article, Wang and colleagues take significant steps towards applying the principles of green chemistry to the Sonogashira reaction by optimizing new conditions where; (a) a copper co-catalyst is not required, thus increasing the atom efficiency of the reaction, (b) the reaction can be run at room temperature, eradicating the energy cost normally required for heating and (c) the solvent is readily available and environmentally benign water.

To read more, see:

Copper-free Sonogashira Cross-Coupling Reaction Promoted by Palladium complexes of Nitrogen-containing Chelating Ligand in Neat Water at Room Temperature
Hong Zhong, Jinyun Wang, Liuyi Li and Ruiha Wang, Dalton Trans. 2013, DOI:10.1039/C3DT52970C

Dr C. Liana Allen is currently a post-doctoral research associate in the group of Professor Scott Miller at Yale University, where she works on controlling the enantio- or regioselectivity of reactions using small peptide catalysts. Liana received her Ph.D. in organic chemistry at Bath University with Professor Jonathan Williams, where she worked on developing novel, efficient syntheses of amide bonds.