Preface

Volume 45 of the Royal Society of Chemistry Specialist Periodical Report in Organometallic Chemistry sees a change in the Editorial Team. We are delighted to take on this role after the successful tenure of Nathan J. Patmore and Paul I. P. Elliott. It is an honour to be part of this important resource that has been in publication since 1971 and has featured some of the giants of organometallic chemistry, both as editors and contributing authors. The founding editors were no less than Edward Abel and Gordon Stone, whose tenures were a substantial 25 and 20 years, respectively, highlighting their dedication to the field. The books started as regular annual reviews, capturing the most recent advances in specific topics such as organometallic compounds of a given group of the periodic table or a given class of ligand. The field has expanded substantially over the years, and the chapters have evolved with a focus on contemporary themes and areas in which there has been expansion. With this year’s volume we have focused on emerging investigators and future leaders as contributors. We present nine chapters which cover a broad range of topics including synthesis, catalytic application, photochemistry and computational investigation of transition metal and main group organometallic compounds. The chapters are designed to bring the readers up to speed on developing areas of research. We believe that these chapters provide a broad selection representing many of the different aspects of organometallic chemistry. There are, of course, so many different themes which could have been explored and we hope to explore these in later volumes.

One of the overarching themes of many of the chapters covered within this book is “cooperation”. This is where a secondary component is playing an additional role in facilitating a given transformation or tuning a given property within a certain complex. This is a developing and common theme across the broad field of organometallic chemistry, particularly with respect to homogeneous catalysis. Within the chapters, cooperation is exemplified in heterobimetallic systems, group 13 based ligands and external Lewis acids to promote reactivity. Additional themes include cooperative pathways in the activation of small inert molecules such as dinitrogen and carbon dioxide, transition metals in oxidation states lower than commonly seen for some metals or the use of organometallic complexes which are activated under photolytic conditions.

In the first chapter, Tiwari, Dey and Rit provide an update on bimetallic catalysts containing N-heterocyclic carbene ligands. The authors describe some synthetic challenges faced with bimetallic complexes and strategies to overcome them. They also provide several recent applications of bimetallic catalysts in homogeneous tandem catalysis involving cross-coupling-arylation, cyclisation–alkylation, oxidation-arylation, (hydro)dehalogenation-transfer hydrogenation, isomerisation-hydrophosphination, and imine synthesis from nitroarenes via tandem catalysis. They also describe examples where bimetallic complexes perform well in the activation of C–F bonds.

In the second chapter, Riddlestone describes the preparation of transition metal (M) complexes of group 10 supported by ligands containing elements (E) of group 13 containing the fragments M–E or M → E. The chapter highlights complexes where the ligand behaves as Z-type by accepting electron density from the metal centre indicated by M → E bond fragments, as well as how these bonds can be involved in the activation of small molecules such as dihydrogen. In addition, it also describes the use of such complexes in catalytic hydrogenation of unsaturated organic substrates by exploring cooperativity between the ligand and metal centre.

In the third chapter, Grills and Bhawal review the roles of Lewis acids in catalysis promoted by nickel complexes. The authors describe how Lewis acids facilitate the activation of strong bonds from a mechanistic point of view and how they have been instrumental in expanding the range of electrophiles that can be employed in Ni-catalysed cross-coupling reactions and related transformations.

In the fourth chapter, Grose and Willcox present an overview on the recent advances in iron catalysed hydroboration reactions in relation to a range of unsaturated carbon–carbon and carbon–heteroatom bonds. The review focuses on the different approaches that have been utilised across the literature including iron(ii) systems and more recent advances in low oxidation state catalysts. The chapter examines different ligand systems and how they affect the activity within catalysis with particular regard to regioselectivity.

In the fifth chapter, Joseph and Swarts highlight the potential of manganese(i) complexes in the context of hydrogen storage and release for a circular economy. The review focuses on the hydrogenation of CO₂ into formic acid, formate and methanol, emphasising the bifunctional mechanisms including ligand cooperativity. It also describes the dehydrogenation of these compounds as a potential source of hydrogen in a circular economy.

In the sixth chapter, Ariharasudhan, Devassy and Ayyappan provide a comprehensive overview of the research field of dinitrogen activation and functionalisation. The review focuses on four main approaches that have been utilised including (i) nitrogen–hydrogen bond forming transformations; (ii) nitrogen–carbon bond forming transformations; (iii) the utilisation of boron-based Lewis acids in combination with transition metals for the activation of dinitrogen; and (iv) metal-free strategies for the activation of dinitrogen. The review highlights some of the most promising pathways that could lead to efficient conversions of dinitrogen into compounds such as ammonia, 3-pyrazolidinone, N,N-bis(trimethylsilyl)aniline, nitriles, trimethylsilylisocyanate and other compounds containing N–C and N–B bonds.

In the seventh chapter, Fernández and Planas highlight recent advances in the use of photochemical methods to promote light-induced organometallic processes by main group elements from the s and p blocks. They also describe how these elements can engage in substrate coordination, activation of small molecules, and in some cases catalyse redox reactions, mirroring the behaviour of transition metals.

In the eighth chapter, Lewis, Billacura, Hamilton and Whiteoak provide an overview on the cycloaddition of three-membered saturated heterocycles with carbon dioxide catalysed by the heavier group 13 elements. Investigations involving the heavier elements have been relatively underexplored until recently. This chapter highlights recent developments focusing on activity, mechanistic pathways and a comparison with related aluminium systems.

In the nineth chapter, Souza and Fantuzzi introduce advanced quantum-mechanical computational methods and strategies to model excited states in organometallic systems. The authors describe applications of these theoretical approaches in organometallic chemistry and provide examples of applications in various contexts such as spin-crossover materials, photodevices, bioimaging, nanofabrication and artificial photosynthesis.

We would like to dedicate this volume to Professor Ian Manners (1961–2023) who was a true giant in organometallic chemistry.

Gareth R. Owen and Nildo Costa – University of South Wales

Rebecca Musgrave and Clare Bakewell – King’s College London