New expeditions in polar organometallic chemistry

Since Frankland’s seminal discovery of ZnEt₂ in 1849, when he reacted elemental zinc with ethyl iodide in a sealed tube, polar organometallic reagents have become essential tools in the synthetic chemist’s toolbox. The longest servants amongst this family of compounds are organolithium and Grignard reagents, whose exceptionally high reactivity (due primarily to the large polarization of their metal–carbon bonds) makes them valuable reagents, capable of promoting numerous fundamental organic transformations, being in fact indispensable to any laboratory worldwide where synthetic chemistry is carried out. Despite their long-standing and ubiquitous utility, the true identities of many organometallic intermediates still remain unresolved and a matter of debate, while the ways of tuning their reactivity still attract widespread interest. Furthermore, studies on f-block chemistry, as well as new developments in the chemistry of the elements of other groups, such as 1, 2, 12 and 13, have made the family of polar organometallic reagents, and subsequently their applications, grow exponentially over the past ten or so years.

With this background, it is a genuine pleasure to introduce this Dalton Transactions themed issue on “New Expeditions in Polar Organometallic Chemistry”, which is privileged to contain a series of stimulating invited contributions from leading experts researching within different sub-areas of the polar organometallic chemistry landscape. The main aim of this issue is to showcase recent developments in this evolving field, ranging from fundamental aspects related to the synthesis and characterization of novel organometallic reagents to their direct applications in organic synthesis, catalysis, supramolecular chemistry and materials science.

Comprising 30 manuscripts, the contents of the issue include an eye-catching frontier article by Capriati (DOI: 10.1039/C4DT01004C), which highlights the pivotal role that organolithium chemistry has played and continues to play in organic synthesis, as well as providing a personal outlook on the challenges and future prospects of commodity organometallic reagents. Several other articles are dedicated to the chemistry of group 1, shedding new light on the intricate behaviour that some of these compounds show in solution with the aid of advanced NMR techniques and DFT calculations (by Harrison-Marchand, DOI: 10.1039/C4DT01156B and Lopez–Ortiz, DOI: 10.1039/C4DT00927D), as well as focusing on the key structural features that influence the reactivities of novel group 1 compounds (Robertson, DOI: 10.1039/C4DT00808A; Stasch, DOI: 10.1039/C4DT01185F and Gessner, DOI: 10.1039/C4DT01466A). Reflecting its emerging importance, a remarkable number of contributions (by Coles, DOI: 10.1039/C4DT01097C; Hill, DOI: 10.1039/C3DT53542H; Carpentier, DOI: 10.1039/C4DT01206B; Okuda, DOI: 10.1039/C4DT00916A; Trifonov, DOI: 10.1039/C4DT00806E and Wang, DOI: 10.1039/C4DT01364F) reveal new catalytic applications of s- and f-block compounds, a domain that has traditionally been monopolized by transition-metal catalysis. The synthesis of an intriguing Mg–hydride cluster, which can release H₂ at high temperatures is reported by Harder (DOI: 10.1039/C4DT00835A). Cooperative bimetallic chemistry, investigating the effects on the structure and reactivity of compounds when two metals of markedly different polarities (such as an alkali metal with Mg, Zn, Al or Cu) are combined, is covered in several papers (by Davies, DOI: 10.1039/C4DT00965G; Mulvey, DOI: 10.1039/C4DT00914B; O'Hara, DOI: 10.1039/C4DT00921E; Gonzalez-Mosquera, DOI: 10.1039/C4DT00952E and Hernan-Gomez, DOI: 10.1039/C4DT01131G), as well as in a perspective article by Wheatley and Uchiyama (DOI: 10.1039/C4DT01130A) summarizing recent achievements in applying lithium cuprates to promote direct Cu–H exchange reactions of organic substrates. Applications of polar organometallic reagents for the functionalization of N-heterocyclic carbenes (by Robinson, DOI: 10.1039/C4DT00933A; Goicoechea, DOI: 10.1039/C4DT00954A and Sadow, DOI: 10.1039/C4DT01011F), and to promote new bond activation processes (by Love, DOI: 10.1039/C4DT01442A; Uhl, DOI: 10.1039/C4DT00922C; Liddle, DOI: 10.1039/C4DT00909F and Hou, DOI: 10.1039/C4DT01725K) are also included, along with several more excellent contributions focusing on the coordination chemistry of this family of compounds (by Westerhausen, DOI: 10.1039/C4DT00949E; Kays, DOI: 10.1039/C4DT00647J; Stalke, DOI: 10.1039/C4DT01008F and Chung, DOI: 10.1039/C4DT00689E).

In summary, the collection of articles included in this themed issue offers a glimpse of the breadth and depth of current research in this vibrant area, not only in terms of the fundamental synthesis and characterization of these intriguing compounds, but also towards developing new applications in order to provide solutions to the present challenges in modern synthesis and catalysis.

I would like to sincerely thank all the authors for their enthusiastic responses to this themed issue and for their fine contributions. I would also like to acknowledge the excellent work of all the anonymous reviewers that have been involved in assessing the scientific quality and rigor of all the submissions and the staff from the Dalton Transactions office, who were extremely helpful throughout the whole process. Finally, this editorial would also like to remember two true pioneers in the field (and other fields!), who sadly passed away during the production of this themed issue, namely Professors Ken Wade and Mike Lappert. Through many seminal discoveries, they both played a major role in advancing polar organometallic chemistry, and undoubtedly their legacy will continue inspiring many new generations of synthetic chemists yet to come.

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