Dalton Transactions Blog

With TONs up to 9000 H₂/Co this Hot Communication by Peter Hamm and Roger Alberto et al. is worth a read.

The team have developed a stable, water reducing catalyst which operates under acidic conditions and indicates poly-pyridyl ligand frameworks are superior to some of the other commonly used chelators. They also show the cobalt complex retains catalytic activity when resin bound, meaning it is active as both a homogeneous and heterogeneous catalyst. For full details download the article below.

A highly stable polypyridyl-based cobalt catalyst for homo- and heterogeneous photocatalytic water reduction
Miguel Guttentag, Alexander Rodenberg, Cyril Bachmann, Anna Senn, Peter Hamm and Roger Alberto
Dalton Trans., 2012, Advance Article

The catalytic potential of metal nanoparticles is widely understood and some are already used for heterogeneous catalysis.  In a dedication to Professor Cole-Hamilton, Karine Philippot and Bruno Chaudret et al. report the synthesis and characterisation of uniquely stabilised RuPt nanoparticles.

A diphenylphospine was used to stabilise bimetallic RuPt nanoparticles, both decorating them and affecting their chemical composition.  Neither an ordered alloy nor a core-shell structure was produced; instead, as proven by scattering and spectroscopic techniques, very disordered nanoparticles with Ru cores and alloy shells were observed. The mechanism that produces such an “onion” structure is thought to involve the reaction of the diphosphine ligands with Ru at the beginning of the reaction.

The use of reactive ligands in the synthesis of bimetallic nanoparticles can modify their structure, suggesting the possibility of finely tailoring the structure and surface of such nanoparticles in the future.  These modifications have already shown promise, with CO poisoning of RuPt nanoparticles having much less of an effect on hydrogenation reactions than with analagous pure Ru examples.

To find out more about these new bimetallic nanoparticles, download this HOT article now.

On the influence of diphosphine ligands on the chemical order in small RuPt nanoparticles: combined structural and surface reactivity studies
Patricia Lara, Tuğçe Ayvalı, Marie-José Casanove, Pierre Lecante, Alvaro Mayoral, Pier-Francesco Fazzini, Karine Philippot and Bruno Chaudret

Konstantin Shuvaev, Annie K. Powell and colleagues have designed a ligand containing the nitronyl nitroxide radical.  The ligand can self-assemble with copper(II) ions to give a [2 x 2] grid complex.

The nitronyl nitroxide radical coordinated via the oxo-atom of the N+-O- fragment in a chelating fashion and lies in the equatorial plane of the metal ion.

The high reactivity of organic radicals makes them difficult to use but the nitronyl nitroxide radical is one of the most stable and so can be used in the design of paramagnetic polytopic ligands as building blocks for supramolecular grids.  Most previous supramolecular grids have been made using diamagnetic ligands but the team found that being able to use a paramagnetic ligand resulted in a grid with interesting spin coupling and magnetic properties.

Read more for free at…

A self-assembled Cu(II)4 [2 × 2] grid with organic radicals
Konstantin V. Shuvaev, Stephen Sproules, J. Mikko. Rautiainen, Eric J. L. McInnes, David Collison, Christopher E. Anson and Annie K. Powell
Dalton Trans., 2012
DOI: 10.1039/C2DT31946B, Paper

Scientists in Mexico and Spain have synthesised a ruthenium complex using a N-heterocyclic CNC pincer ligand.

Lutidine-derived pincer complexes are well established amongst organometallic chemists. More traditionally, the pincer ligand motif, PNX has been utilised (where P is a phosphine and X is either a phosphine or N donor ligand) but substitution of phosphines with stronger electron-donating N-heterocyclic carbenes has meant that more active catalytic species have been made for promoting hydrogenation of non-active esters. Mostly speaking, these ligands follow a CNN coordination pattern. According to the researchers, the only CNC pincer complex reported coordinates to the ruthenium centre in a mer geometry.

In their latest Dalton Transactions Communication, the team report on the synthesis of a CNC ligand which coordinates to ruthenium in an usual fac mode. They proved that the resultant complex can be used to catalyse the hydrogenation of imines by firstly deprotonating one of the ligand methylene bridges.

To read more about this development, read the full article now…

Hydrogenation of imines catalysed by ruthenium(II) complexes based on lutidine-derived CNC pincer ligands
Martín Hernández-Juárez, Mónica Vaquero, Eleuterio Álvarez, Verónica Salazar and Andrés Suárez
Dalton Trans., 2012, Advance Article

As Jason Love described in his 2009 ChemComm Feature Article, pyrrole-based macrocycles are ideal ligands for creating pre-organised metal binding sites to enable the multielectron redox chemistry so required for transforming small molecules such as O₂, carbon dioxide and water.

Here in their latest Dalton Transactions article, Love and colleagues take this a step further.

The team note how their previous attempts to make mononuclear transition metal complexes with the donor ligands were unsuccessful. Despite significant efforts, they could only make bimetallic complexes – well, until now that is…

The newest set of ligands now incorporate N₄^¬ with either O₅ or ONO donors which are separated through aryl spacers. Upon binding of a singular metal atom, the complexes fold to form a Pacman-like cleft structure. Love and colleagues expect the structure to play host to guest molecules which can benefit from metal coordination as well as hydrogen bonding interactions to the oxygen and nitrogen atom acceptors.

To read more, download the article now… 

Synthesis and structures of transition metal pacman complexes of heteroditopic Schiff-base pyrrole macrocycles
James W. Leeland, Colin Finn, Bérengère Escuyer, Hiroyuki Kawaguchi, Gary S. Nichol, Alexandra M. Z. Slawin and Jason B. Love