Dalton Transactions Blog

The current issue of Dalton Transactions is a themed issue on boranes and borohydrides, of which one of the cover articles  by Chunfang Jiang and Douglas W. Stephan explores phosphinimine-boranes in frustrated Lewis pair chemistry. Frustrated Lewis pairs are entities that consist of a Lewis acid and a Lewis base which, because of sterics, do not form an adduct. These systems are very reactive and are able to activate H₂, CO₂, and olefins amongst others without the need for a transition metal catalyst.

In this article, a series of phosphinimines (species contanining a phosphorous-nitrogen double bond) were combined with B(C₆F₅)₃ and in one case a Lewis acid-base adduct was formed. The reactivity of the adduct was compared to the other cases where frustrated Lewis pairs were generated. Remarkably, the researchers discovered that both the adduct and the frustrated Lewis pairs were able to activate H₂, CO₂ and phenylacetylene.

This work paves the way for discovering even more acid base combinations that could be used in frustrated Lewis pair systems for catalysis without the need for transition metals.

To find out more, read the full Dalton Transactions article:

Phosphinimine–borane combinations in frustrated Lewis pair chemistry
Chunfang Jiang and Douglas W. Stephan
Dalton Trans., 2013, 42, 630-637

Developing facile and economical technologies for utilizing CO and CO₂ as C1 building blocks remains a lucrative challenge, and this area has recently enjoyed a surge in interest and development.  The current paradigm for activating these abundant carbon oxides invokes reduction of the strong C-O multiple bonds, typically facilitated by low-valent transition-metal and f-element complexes, to yield oligomerized ([CO_x]^n– ) units or (CO)-incorporated organic materials.

Polly Arnold and co-workers have recently demonstrated that the discreet U(III) tris-amide complex [U(N(SiMe₃)₂)₃] is indeed a versatile reducing agent for such carbon oxide activation chemistry, cleanly reacting with CO to yield a stable ynediolate ([OCCO]^2-) adduct which features a newly formed C-C bond.

Reporting in Dalton Transactions, Arnold and co-workers now describe a modified U(III) platform which incorporates a hemi-labile, bidentate alkoxy-tethered NHC ligand, and divergent activation of carbon oxides at U(III).  This report serves to underscore the potency of ligand design as an instrument for encouraging novel and unusual chemical transformations, in addition to describing a variety of new complexes incorporating activated carbon oxides.

Check out the full article to read more about these divergent carbon oxide activation pathways.

Carbon monoxide and carbon dioxide insertion chemistry of f-block N-heterocyclic carbene complexes
Polly L. Arnold, Zöe R. Turner, Anne I. Germeroth, Ian J. Casely, Gary S. Nichol, Ronan Bellabarba and Robert P. Tooze

Dalton Trans., 2013, Advance Article
DOI: 10.1039/C2DT31698F