Dalton Transactions Blog

Posted on behalf of Stuart Bartlett, web writer for Dalton Transactions

Sustainable chemistry is a key area of research, with catalysis leading the way by performing many chemical transformations while only requiring stoichometric amounts. Yet, a problematic area of homogeneous catalysis is high amounts of organic and toxic solvents required, where the catalyst must be separated, and in almost all cases destroyed, in order to recover the product.

This research, carried out at the University of Girona, in Spain, looked at the hydration of harmful nitriles using a ruthenium based homogeneous catalyst, to its non-toxic amide. This is the first instance of these types of catalysts doing this hydration in solely water or glycerol. This could have a big impact on producing industrially important chemicals much more cheaply and in a sustainable way, while also allowing the removal of toxic chemicals in environmentally friendly media.

Two catalysts were investigated: [RuCl₂(pypz-H)(DMSO)₂] (2), and [RuCl₂(pz-H)(DMSO)₃] (3). (pypz-H = asymmetric didentate 2-(3-pyrazolyl) pyridine ligand; pz-H = monodentate pyrazole ligand; DMSO = dimethyl sulfoxide) Both were tested in H₂O at 80^oC, at 1 mol % of ruthenium. The substrates included various small organics with a nitrile and another functional group. The conversion of the substrate was above 80% in many cases and selectivity to the corresponding amide, over 98% in almost all cases. In general, catalyst (3) performed better, reasoned as greater flexibility of the catalytic intermediate, having only monodentate ligands. This means more labile sites for the reactants to coordinate. Free DMSO was found after the reaction suggesting these are the labile sites at the metal centre. A further study demonstrated how using glycerol allows recycling of the catalyst with no loss of conversion, where the products go into organic media and the catalyst remains in the glycerol.

This is an excellent study displaying how homogeneous catalysis can move one step further into the field of green chemistry by using non-toxic and plentiful solvents, such as water. Many of these delicate transformations are performed by expensive metals, such as ruthenium, and this work demonstrates how keeping the catalyst in its original media allows for sequential runs, meaning overall lower amounts of the catalyst are required.

Find out more from the paper:

Ru(II) complexes containing dmso and pyrazolyl ligands as catalysts for nitrile hydration in environmentally friendly media
Íngrid Ferrer, Jordi Rich, Xavier Fontrodona, Montserrat Rodríguez and Isabel Romero
Dalton Trans., 2013,42, 13461-13469
DOI: 10.1039/C3DT51580J, Paper

Stuart Bartlett is currently doing a 1 year postdoc position with David Cole-Hamilton at the University of St Andrews, focusing on the conversion of renewable oils towards fine chemical production using metathesis. He obtained his PhD from the University of Southampton investigating the mechanism of ethene oligomerisation catalysis using NMR and X-ray Absortion Spectroscopy.

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

When you hear the phrase “at the click of a button” you expect that something can be done both simply and efficiently. Likewise, the original aim of Click Chemistry as stated by Nobel laureate K. Barry Sharpless in 2001 was to develop simple, efficient chemical reactions that would yield a wide range of new molecules to be tested for applications in pharmaceuticals or materials.

The particular type of reaction most often associated with Click Chemistry is the azide/alkyne cycloaddition, wherein a molecule containing a carbon-carbon triple bond is reacted with a molecule containing a terminal (azide) group of three nitrogen atoms such that they join together resulting in a five-membered “triazolate” heterocycle incorporating the two carbon and three nitrogen atoms.

Over the past twelve years chemists have developed a diverse range of molecules that feature these two functional groups and thus can be combined using this reaction. The variation on this chemistry presented here by the group of Adam S. Veige includes gold and platinum metal atoms in the starting molecules. The grand goal, they state, would be to use this reaction to synthesize perfectly regular polymers incorporating metal atoms linked by the triazolate bridges for possible use in materials.

Impressively, they synthesize in high yield a molecule featuring a gold-platinum-gold motif where the gold and platinum atoms are indeed linked by triazolate bridges using this reaction. They also present other less high-yielding, but nonetheless interesting reactions, including one wherein they link the two gold atoms within a very similar molecule using a bis(diphenylphosphino)methane bridge, forcing the two gold atoms to bend symmetrically to the same side of the molecular plane.

To sum up with an alliteration, such manipulations of multi-metallic molecules may move masterfully towards many materials.

Find out more from the paper:

Inorganic click (iClick) synthesis of heterotrinuclear Pt^II/Au^I₂ complexes
Andrew R Powers, Xi Yang, Trevor J del Castillo, Ion Ghiviriga, Khalil A Abboud and Adam Steven Veige
Dalton Trans., 2013, Accepted Manuscript
DOI: 10.1039/C3DT52105B, Communication

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

Chemotherapy remains the most widely used therapeutic approach to treating cancer. Such drugs work by targeting and killing rapidly dividing cells (a major characteristic of most cancer cells) by impairing mitosis (cell division).¹ These drugs are often highly effective at suppressing or even eliminating cancer in the patient, however, they can also lead to many severe side effects such as immunosuppression and infertility. Free radicals and reactive oxygen species (ROS), a by-product of the chemotherapy process, are frequently implicated as a cause of some of the side effects experienced.² Hence, a drug which simultaneously kills cancer cells and scavenges free radicals and ROS could hypothetically reduce the side effects of chemotherapy while remaining effective against the disease.

In this article, the authors combine two biologically active species into discrete potential drug molecules; hydroxyl-substituted Schiff bases, known to have good free radical scavenging and anti-cancer activity,³ and ferrocene, previously shown to increase the anti-cancer activity of other chemotherapeutic drugs.⁴

Using established methods, the authors thoroughly tested their new compounds for anti-free radical and anti-cancer activity. The results showed that one molecule in particular (“Compound 1”) has good free radical scavenging activity against ABTS.- and DPPH. (assessed by changes in UV-Vis absorbance), as well as displaying cytoprotective activity against radical attacks, delaying free radical oxidative damage to membrane cells. “Compound 1” was also shown to possess good anti-cancer activity against HeLa cancer cell lines, even out-performing clinically used anti-cancer drug Resveratrol. These early findings show promise for the development of chemotherapy treatments which combine antioxidant and anti-cancer activities.

To read more, see:

Synthesis and biological evaluation of hydroxyl-substituted Schiff-bases containing ferrocenyl moieties
Wansong Chen, Weizhu Ou, Liqiang Wang, Yuanqiang Hao, Jianshun Cheng, Juan Li and You-Nian Liu,
Dalton Trans., 2013, DOI: 10.1039/C3DT51977E, Paper

¹ V. Malhorta, M. C. Perry, Cancer Biol. Ther., 2003, 2 (Suppl. 1), S2-4.
² E.-S. E. El-Awady, Y. M. Moustfa, D. M. Abo-Elmatty and A. Radwan, Eur. J. Pharmacol., 2011, 650, 335-341.
³ Y.-F. Li and Z.-Q. Liu, Eur. J. Pharm. Sci., 2011, 44, 158-163.
⁴ B. Zhou, J. Li, B.-J. Feng, Y. Ouyang, Y.-N. Liu and F. Zhou, J. Inorg. Biochem., 2012, 116, 19-25.

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.

Congratulations to Philip Power, who has been awarded the inaugural Dalton Distinguished Lectureship in recognition of his work on transition metal and main group chemistry.

Supported by Dalton Transactions, this lectureship is awarded yearly to an outstanding senior researcher in the field of inorganic chemistry. Besides providing recognition for high quality chemistry research, it also facilitates interaction between researchers in different institutions.

Philip will be presenting his lecture at University of California, Berkeley on the 7th February 2014.

Philip received his B.A. from the University of Dublin in 1974, and commenced on his PhD research at the University of Sussex under M.F. Lappert. After graduating in 1977, he spent two years working as a postdoctoral researcher in Stanford under R.H. Holm. In 1981, he started a faculty position at University of California, Davis, where he is currently a Professor.