Call for papers: 2015 themed issues

Dalton Transactions coverWe are delighted to announce three new Dalton Transactions themed issues to be published in 2015:

Luminescent Complexes and Materials for Light-Emitting Devices
Guest Editor: Dr Eli Zysman-Colman (University of St. Andrews)
Deadline: 6th October 2014

Perovskites
Guest Editors: Professors Russell Morris, Philip Lightfoot (both University of St. Andrews) and J. Paul Attfield (The University of Edinburgh)
Deadline: 16th December 2014

Earth Abundant Element Compounds in Homogeneous Catalysis
Guest Editors: Professors Philip Mountford (University of Oxford), Laurel L. Schafer (University of British Columbia) and Warren E. Piers (University of Calgary)
Deadline: 14th January 2015

New Talent Asia
Guest Editor: Professor Hiroshi Nishihara (The University of Tokyo)
Deadline: 24th February 2015

Does your research fit into any of these subject areas? If so, we would welcome your contribution. For further details on issue scopes and on how to submit, see below:

How to submit

All types of manuscript – communications, full papers and Perspectives, will be considered for publication. The manuscript should be prepared according to our article guidelines and submitted via our online system.

All manuscripts will be subject to normal peer review and inclusion in the themed issue will be at the discretion of the Guest Editors. Please indicate in your submission which themed issue you would like to be considered for.

Issue scopes

Luminescent Complexes and Materials for Light-Emitting Devices
This themed issue will highlight the latest research in the field of luminescent complexes and materials for light-emitting devices. Suitable topics include the synthesis and fundamental photophysical studies of luminescent complexes as well as the fabrication and testing of devices which incorporate these materials. Contributions covering computational studies on relevant materials will also be appropriate.

Perovskites
This issue will focus on functional perovskites from the inorganic chemist’s perspective. It will include, but is not limited to: experimental studies on the synthesis, structure and physical/chemical properties of perovskites; chemistry-structure-property relationships; and the design and understanding of perovskite structure and functionality from a theoretical/computational perspective. Contributions are not limited to ‘classical’ inorganic perovskites but can also include hybrid perovskites, ‘MOF’ perovskites, layered perovskite families and related phases (eg. tungsten bronze types).

Earth Abundant Element Compounds in Homogeneous Catalysis
The aim of this themed issue is to showcase the latest research in the development of highly active and selective homogeneous catalysts utilizing earth abundant elements from across the Periodic Table. We believe this will reflect a recent trend in catalysis that seeks to find alternatives to catalysts based on precious metals like Ru, Rh, Pd, Ag, Re, Os, Ir, Pt, or Au and toxic elements like Hg, Bi, In and Pb. We are inviting contributions from researchers utilizing catalysts based on elements from both the s and p block, the more abundant first row transition metals and the lanthanides as catalysts for commodity chemical, fine chemical and polymer synthesis, to emphasise the broad range of activity in this area.

New Talent Asia
This themed issue will focus on all areas of inorganic and organometallic chemistry, inorganic materials science, bioinorganic chemistry and catalysis and aims to reflect the strength and vitality of new inorganic chemistry from the Asia-Pacific region.

Interested in submitting  paper? Please contact us for more information

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The influence of Michael Lappert on the chemistry landscape

Written by John Arnold, Penelope J. Brothers, Philip Mountford, Warren E. Piers, Christine M. Thomas and T. Don Tilley

Introduction

Michael F. Lappert, one of the giants of 20th century organometallic chemistry, passed away suddenly at the age of 85 on March 28, 2014. His storied career and status as a leader in the field have been commemorated elegantly elsewhere. Prof. Lappert published prolifically over his lengthy career, leaving the global community a legacy of almost 800 scholarly articles on original chemical research in organometallic chemistry from across the Periodic Table.

More than half of those papers, including many of his most highly cited articles, were published in Royal Society of Chemistry journals. To honour his memory and body of work, we have put together this web collection of selected contributions from the RSC Lappert canon (http://rsc.li/lappert). Together, these papers paint a picture of a chemist with extraordinarily broad interests and an uncanny knack for pursuing seminal research that has stood the test of time and influenced the field in significant ways.

The selected papers are grouped by Lappert’s major areas of interest and have been chosen by members of the Editorial Boards of Dalton Transactions and ChemComm, where much of Lappert’s work appeared over the years. They are available for viewing free of charge to interested chemists around the globe. We believe this is a fitting tribute to Prof. Lappert and hope the readers of Royal Society of Chemistry journals enjoy revisiting some of these seminal contributions.

Early contributions

Lappert’s very first paper in the chemical literature “Interaction of boron trichloride with optically active alcohols and ethers”, published in 1951 with his Ph. D. supervisor W. Gerrard, was followed in short order by a remarkable and prolific series of papers exploring the chemistry of boron halides with alcohols, ethers, pyridine, thioethers, extending into the chemistry of boronic acids, boronic esters, borinic acids, borinate esters and borates.

Indeed, almost every imaginable reaction of boron compounds with small organic molecules, and every combination of boron with halide, oxygen, nitrogen, sulfur, alkyl and aryl substituents and the corresponding Lewis acid–base complexes appear in these early papers.

Boronic acids feature in modern applications as diverse as the palladium-catalysed Suzuki–Miyaura cross-coupling reaction and as saccharide sensors; the foundation for these highly significant developments lies in the detailed, systematic work on the properties and chemistry of boron compounds reported in Lappert’s early papers.

All the more remarkably, this work was done on the basis of careful isolation and characterisation of products via melting and boiling points, refractive indices, elemental analyses and optical rotations, but without the aid of the routine spectroscopic techniques we now take for granted.

By the late 1950s, IR spectroscopy was becoming more widely used and a 1958 paper reports and assigns B–O, B–Cl, B–aryl, B–H3, B–N and B–H vibrational frequencies. Both IR and 1H NMR spectroscopy were used to determine whether organic amide complexes of BCl3 and TiCl4 were N-bound or O-bound, concluding that the latter was favoured, and also observing restricted rotation about the amide C–N bond. Almost all of Lappert’s 80 or so papers published from 1951 to 1965 were concerned with the chemistry of boron.

The paper on amide complexes also shows his interest in the Lewis acid properties of boron halides extending to other elements. This theme quickly extended to a range of metals, for example using IR (and to a limited extent, 1H NMR) spectroscopy to investigate complexes of ethylacetate with a wide range of metal halides (boron, aluminium, silicon, germanium, tin, gallium, indium, titanium, zirconium and iron), commenting on the donor ability of the esters, stereochemistry and group trends for both the metals and the halides.

Now established as a leader in exploring the systematic preparative and descriptive chemistry of elements across the periodic table, Lappert began to report new reaction types that were to set the stage for organometallic chemistry into the present. After preparing a range of new tin amine compounds, in 1965 Lappert reported the first well-established aminostannylation reactions, in which an unsaturated substrate inserts into a tin-nitrogen bond. For example, CO2 inserts into Me3SnNMe2 to give the carbamato complex Me3SnOC(O)NMe2.

This paper described the aminostannylation reaction for CO2, CS2, ketene, PhNCO, PhNCS, PhCN, SO2 and other unsaturated small molecules. We now accept, of course, such main group addition reactions such to be of central importance in both academic and industrial chemistry. As well as establishing a major new reaction paradigm, this chemistry also illustrated Lappert’s early success in tin and, more broadly, group 14 chemistry, as his next major set of papers demonstrates.

Interaction of boron trichloride with optically active alcohols and ethers
W. Gerrard and M. F. Lappert
J. Chem. Soc., 1951, 1020-1024

Stability, solvolysis, and co-ordination reactions of esters of boronic acids and their halogen derivatives
L. J. Bellamy, W. Gerrard, M. F. Lappert and R. L. Williams
J. Chem. Soc., 1958, 2412-2415

Infrared spectra of boron compounds
L. J. Bellamy, W. Gerrard, M. F. Lappert and R. L. Williams
J. Chem. Soc., 1958, 2412-2415

Spectra and structure of amide complexes
W. Gerrard, M. F. Lappert, H. Pyszora and J. W. Wallis
J. Chem. Soc., 1960, 2144-215

Co-ordination compounds having carboxylic esters as ligands. Part II. Relative acceptor strengths of some Group III and IV halides
M. F. Lappert
J. Chem. Soc., 1962, 542-548

Amino-derivatives of metals and metalloids. Part II. Aminostannylation of unsaturated substrates, and the infrared spectra and structures of carbamato- and dithiocarbamato-trimethylstannanes and related compounds
T. A. George, K. Jones and M. F. Lappert
J. Chem. Soc., 1965, 2157-2165

Divalent group 14 compounds

The second group of papers concerns Lappert’s longstanding interest in the “carbene analogs” of the heavier group 14 elements. Debuting in 1976 in a pair of articles in J. Chem. Soc., Dalton Trans., the study of these compounds was a major theme in Lappert’s research efforts in the 1970s and 80s. The first paper is one of his most highly cited (>400), and has certainly been quite influential. It summarizes studies on subvalent alkyl and amido derivatives of the group 14 elements Ge, Sn, and Pb, described in earlier communications going back to 1973. These compounds feature bulky –CH(SiMe3)2 and –N(SiMe3)2 groups that stabilize the divalent compounds in their monomeric forms in solution.

These compounds have since been extensively used as synthetic starting points for low-valent group 14 chemistry, and they represent important milestones in the study of main group compounds and heavy element–element bonded compounds. In particular, with the solid-state structure of {Sn[CH(SiMe3)2]2}2, this work provided the first description of the now well-established trans-bent structure for a E2R4 group 14 compound, and offered a simple rationale for the bonding in such species. In the accompanying paper, the utility of the SnR2 compounds as donor ligands for transition metals and as starting materials for tin(IV) derivatives was explored extensively.

Subsequent studies in this area focused on detailed structural studies and culminated in a paper that provides a more complete understanding of E2R4 species, with more extensive structural data, and establishment of key periodic trends in structure and bonding for these subvalent group 14 compounds. Especially with the aid of molecular orbital calculations, this work provided insight into how localized electron density on the group 14 elements increasingly “bends” the E2R4 structure as E becomes heavier: C < Si < Ge < Sn < Pb.

While the above work focused mainly on the heavier elements in the group, in 1995 Lappert also prepared one of the first well-described silylene derivatives, a class of compounds that has become prominent in recent years as ligands in homogeneous catalysis. These silylenes utilized an “N-heterocyclic” strategy for stabilizing the silylene moiety—a widely familiar approach for the stabilization of divalent species in the lightest group 14 element, carbon. Indeed, Lappert was an early adopter of N-heterocyclic carbenes as ligands for transition metals.

In 1974, Lappert’s lab elegantly demonstrated that a wide range of transition metal N-heterocyclic carbenes could be synthesized via C=C bond cleavage of electron-rich olefins by low valent metals. His 1973 review on transition metal carbenes covers the synthesis, electronic properties, and reactivity of carbenes, as well as their potential role in a range of organic reaction mechanisms. Although written in the early days of metal-carbene chemistry, the basic themes and principles discussed in this review remain pervasive in modern Organometallic Chemistry textbooks.

Subvalent Group 4B metal alkyls and amides. Part I. The synthesis and physical properties of kinetically stable bis[bis(trimethysilyl)methyl]-germanium(II), -tin(II), and -lead(II)
P. J. Davidson, D. H. Harris and M. F. Lappert
J. Chem. Soc., Dalton Trans., 1976, 2268–2274

Subvalent Group 4B metal alkyls and amides. Part II. The chemistry and properties of bis[bis(trimethylsilyl)methyl]tin(II) and its lead analogue
J. D. Cotton, P. J. Davidson and M. F. Lappert
J. Chem. Soc., Dalton Trans., 1976, 2275–2286

Molecular structures of the main group 4 metal(II) bis(trimethylsilyl)-amides M[N(SiMe3)2]2 in the crystal (X-ray) and vapour (gas-phase electron diffraction)
T. Fjeldberg, H. Hope, M. F. Lappert, P. P. Power and A. J. Thorne
J. Chem. Soc., Chem. Commun., 1983, 639–641

Chemistry, including the X-ray structure, of bis[bis(trimethylsilyl)methylgermanium(II)], R2GeGeR2[R = CH(SiMe3)2], a stable compound having a metal–metal ‘double bond,’ a dimetallene
P. B. Hitchcock, M. F. Lappert, S. J. Miles and A. J. Thorne
J. Chem. Soc., Chem. Commun., 1984, 480–482

Subvalent Group 4B metal alkyls and amides. Part 9. Germanium and tin alkene analogues, the dimetallenes M2R4[M = Ge or Sn, R = CH(SiMe3)2]: X-ray structures, molecular orbital calculations for M2H4, and trends in the series M2R′4[M = C, Si, Ge, or Sn; R′= R, Ph, C6H2Me3-2,4,6, or C6H3Et2-2,6]
D. E. Goldberg, P. B. Hitchcock, M. F. Lappert, K. M. Thomas, A. J. Thorne, T. Fjeldberg, A. Haaland and B. E. R. Schilling
J. Chem. Soc., Dalton Trans., 1986, 2387–2394

Synthesis, structures and reactions of new thermally stable silylenes
B. Gehrhus, M. F. Lappert, J. Heinicke, R. Boese and D. Blaser,
J. Chem. Soc., Chem. Commun., 1995, 1931–1932

Carbene complexes. Part VIII. Chromium(0), iron(0), rhodium(I), iridium(I), nickel(II), palladium(II), platinum(II), and gold(I) mono- and oligo-carbene species from electron-rich olefins
B. Cetinkay, P. Dixneuf and M. F. Lappert
J. Chem. Soc., Dalton Trans., 1974, 1827–1833

The chemistry of transition-metal carbene complexes and their role as reaction intermediates
D. J. Cardin, B. Cetinkaya, M. J. Doyle and M. F. Lappert,
Chem. Soc. Rev., 1973, 2, 99–144

Metallocenes

Lappert did not restrict himself to the main group part of the Periodic Table! Transition metal metallocenes occupy a central position in Organometallic Chemistry and early in his career, Lappert was active in the development of improved synthetic routes to the group metallocene dihalides and the development of their organometallic chemistry. In “Part 1” of a series on metallocene dihalides, the Lappert group established routes to zirconocenes and hafnocenes of all the halides and provided detailed spectroscopic data.

The crucial role these compounds were to play in “single site” olefin polymerization catalysis was still on the horizon, but these key early studies provided foundational work for these later developments. The Lappert group continued working with metallocenes for several years; subsequent studies on group 4 compounds included the preparation and characterization of a wide variety of alkyl derivatives. In an example from group 5, the report of an η2-CO2 complex of an alkyl niobocene complements the famous nickel complex of Aresta et al. and demonstrated the first such complex for an early transition metal. Remarkably, the CO2 does not insert into the Nb–C bond of the alkyl group. Given the recent intense interest in the chemistry of CO2, this early discovery serves as a fundamental example of M–CO2 bonding.

Lappert was also interested in the organometallic chemistry of the group 3 metals and the lanthanides (vide infra), including metallocene derivatives of these metals. He was among the first to demonstrate that alkyl groups could serve as bridging ligands in these highly Lewis acidic species. Through careful synthesis and structural analysis, the disclosure of these unusual, highly reactive compounds provided fundamental insight into the organometallic chemistry of the lanthanide metals. Finally, in another prescient contribution, the Lappert group highlighted the bis-(trimethylsilyl) cyclopentadienyl ligand as a bulky, solubilizing Cp donor for the preparation of a variety of lanthanocene chlorides. This ligand is a well-utilized alternative to the ubiquitous (pentamethyl) cyclopentadienyl donor, particularly for the lanthanide and actinide elements.

Metallocene halides. Part I. Synthesis, spectra, and redistribution equilibria of di-π-cyclopentadienyldihalogeno-titanium(IV),-zirconium-(IV), and -hafnium(IV)
P. M. Druce, B. M. Kingston, M. F. Lappert, T. R. Spalding and R. C. Srivastava
J. Chem. Soc. A, 1969, 2106–2110

Metallocene derivatives of early transition metals. Part 2. Substituted cyclopentadienyl Group 4A dichloro-metallocene complexes [M(η-C5H4R)2Cl2](M = Zr or Hf; R = Me, Et, Pri, But, or SiMe3), their mono- and di-alkyl derivatives [M(η-C5H4R)2R′X](X = Cl or R′; R′= CH2SiMe3 or CH2CMe3), and their d1 reduction products
M. F. Lappert, C. J. Pickett, P. I. Riley and P. I. W. Yarrow
J. Chem. Soc., Dalton Trans., 1981, 805–813

A novel carbon dioxide complex: synthesis and crystal structure of [Nb(η-C5H4Me)2(CH2SiMe3)(η2-CO2)]
G. S. Bristow, P. B. Hitchcock and M. F. Lappert
J. Chem. Soc., Chem. Commun., 1981, 1145–1146

Alkyl-bridged complexes of the d- and f-block elements. Part 2. Bis[bis(η-cyclopentadienyl)methylmetal(III)] complexes, and the crystal and molecular structure of the yttrium and ytterbium species
J. Holton, M. F. Lappert, D. G. H. Ballard, R. Pearce, J. L. Atwood and W. E. Hunter
J. Chem. Soc., Dalton Trans., 1979, 54–61

Use of the bis(trimethylsilyl)cyclopentadienyl ligand for stabilising early (f0–f3) lanthanocene chlorides; X-ray structure of [(Pr{η-[C5H3(SiMe3)2]}2Cl)2] and of isoleptic scandium and ytterbium complexes
M. F. Lappert, A. Singh, J. L. Atwood and W. E. Hunter
J. Chem. Soc., Chem. Commun., 1981, 1190–1191

Homoleptic compounds of Lewis acidic metals

The use of steric bulk in ligand sets to stabilize reactive species pervades the work of Lappert, and in the development of routes to homoleptic alkyls of the early metals and lanthanides he used this strategy to great effect. In addition to the metallocene work described above, the Lappert group produced a strong body of work concerning homoleptic alkyl and amido derivatives of these elements.

The earliest forays into this area built on the group 4 metallocene chemistry described above. 1973 saw publication of the first of his full papers on trimethylsilylmethyl and trimethylgermylmethyl complexes of group 4 metals, including the homoleptic derivatives. Over a decade later, these complexes inspired some of Arnold’s postdoctoral research with Wilkinson into related homoleptic aryls and their reactivity. As is now well appreciated, alkyl ligands of the type used by Lappert provide a number of important and attractive features: in addition to the stability they impart by virtue of the lack of beta hydrogen atoms, they are easy to prepare and handle and they provide excellent solubility, and crystallinity to the resulting metal complexes.

Also in 1973, Lappert and Pearce put out a brief report in J. Chem. Soc., Chem. Commun. Concerning the preparation of scandium and yttrium tris(alkyl) complexes as their bis-THF adducts. This simple paper has served as an inspiration for many groups working in this area, and these alkyl complexes are now routinely used to prepare post-metallocene organometallic compounds of these reactive, Lewis acidic metals directly via facile alkane elimination protocols. Use of even bulkier –CH(SiMe2)2 groups (the same groups used to prepare the divalent group 14 metallenes described above) allowed for isolation of truly homoleptic lanthanide(III) alkyls, even those of larger, more kinetically labile lanthanides such as La and Sm. The key to success in this endeavour was addition of a second trimethylsilyl group to the alpha carbon, which provided much needed steric protection along with electronic stabilization. His interest in this area was not just restricted to synthesis; he also went far beyond his usual standard synthesis and characterization techniques to explore the thermochemistry of metal alkyl complexes, establishing standard heats of formation for metal–carbon bonds in homoleptic species.

In addition to homoleptic alkyls, the Lappert group prepared amido and alkoxo derivatives of these metals that have proven useful over time. In a seminal paper from 1968 by Lappert and Chandra a number of such complexes were initially reported. Many working in the area of group 4 chemistry take the protonolysis reactions of metal amides for granted as synthetic routes to metalcyclopentadienyl, -alkoxide and –thiolate derivatives. It is this classic contribution by Lappert which provides the foundation of so much chemistry deriving from the early transition metals, from applications in olefin polymerisation catalysis to CVD precursors to hydroelementation chemistry. In a related communication 15 years later, Lappert and Singh describe new classes of hydrocarbon-soluble group 3 and lanthanoid complexes of bulky aryloxide ligands.

Remarkably, before this time only a handful of three- and four-coordinate rare earth compounds were known. Today, many working in this area of rare earth and alkaline earth (i.e. large and electropositive) metal chemistry accept the use of bulky phenolate-based ligands as a sine qua non for controlling coordination numbers and nuclearity. Not surprisingly, with 183 citations, this is one of the top 3% most cited papers from Lappert’s many contributions.

Silylmethyl and related complexes. Part I. Kinetically stable alkyls of titanium(IV), zirconium(IV), and hafnium(IV)
M. R. Collier, M. F. Lappert and R. Pearce
J. Chem. Soc., Dalton Trans., 1973, 445–451

Stable silylmethyl and neopentyl complexes of scandium(III) and yttrium(III)
M. F. Lappert and R. Pearce
J. Chem. Soc., Chem. Commun., 1973, 126–126

Synthesis and structural characterisation of the first neutral homoleptic lanthanide metal(III) alkyls: [LnR3][Ln = La or Sm, R = CH(SiMe3)2]
P. B. Hitchcock, M. F. Lappert, R. G. Smith, R. A. Bartlett and P. P. Power
J. Chem. Soc., Chem. Commun., 1988, 1007–1009

Standard heats of formation and M–C bond energy terms for some homoleptic transition metal alkyls MRn
M. F. Lappert, D. S. Patil and J. B. Pedley
J. Chem. Soc., Chem. Commun., 1975, 830–831

Amido-derivatives of metals and metalloids. Part VI. Reactions of titanium(IV), zirconium(IV), and hafnium(IV) amides with protic compounds
G. Chandra and M. F. Lappert
J. Chem. Soc. A, 1968, 1940–1945

Three- and four-co-ordinate, hydrocarbon-soluble-aryloxides of scandium, yttrium, and the lanthanoids; X-ray crystal structure of tris(2,6-di-t-butyl-4-methylphenoxo)scandium
P. B. Hitchcock, M. F. Lappert and A. Singh
J. Chem. Soc., Chem. Commun., 1983, 1499–1501

β-Diketiminato (“NacNac”) ligands

Few ancillary ligand classes develop into widely adopted platforms for chemistry. Cyclopentadienyl ligands, phosphine donors, pincer frameworks come to mind when thinking about such ligand sets, and it can be argued that the β-diketiminato ligands deserve to be thought of in these terms. Lappert was again ahead of the curve on this and was among the first to recognize that these ligands should be suitable for supporting a wide range of coordination chemistry, providing the advantage of steric protection of a metal center in comparison to the widely used acetylacetonate, or acac, ligand.

This was amply demonstrated in two closely related communications that were published on the same year (1994) and attracted 114 citations each. They describe straightforward preparation of two highly lipophilic monoanionic ligands, namely azaallyl and β-diketiminate, and introduce these ligands into early transition and main group metal chemistry. Later, β-diketiminate ligands (also more widely known as “NacNac”) became particularly popular ancillary group in various fields of organometallic and coordination chemistry with significant contributions using Lappert’s bis(trimethylsilyl) substituted β-diketiminate.

Lappert himself continued to publish prodigiously in this area until late in his career and, along with Bourget-Merle and Severn, published a definitive review on the subject of NacNac ligands in coordination chemistry. Recent results include the use of the NacNac ligand system to support low valent Ln(II) compounds and the exploration of non-spectator roles for the NacNac ligand in chemical reactivity.

Transformation of the bis(trimethylsilyl)methyl into a β-diketinimato ligand; the X-ray structure of [Li(L′L′)]2, SnCl(Me)2(L′L′) and SnCl(Me)2(LL), [L′L′= N(R)C(Ph)C(H)C(Ph)NR, LL = N(H)C(Ph)C(H)C(Ph)NH, R = SiMe3)
P. B. Hitchcock, M. F. Lappert and D. S. Liu
J. Chem. Soc., Chem. Commun., 1994, 1699–1700

Transformation of the bis(trimethylsilyl)methyl into aza-allyl and β-diketinimato ligands; the X-ray structures of [Li{N(R)C(But)CH(R)}]2 and [Zr{N(R)C(But)CHC(Ph)N(R)}Cl3](R = SiMe3)
P. B. Hitchcock, M. F. Lappert and D. S. Liu
J. Chem. Soc., Chem. Commun., 1994, 2637–2638

Heteroleptic ytterbium(II) complexes supported by a bulky β-diketiminato ligand
P. B. Hitchcock, A. V. Khvostov, M. F. Lappert and A. V. Protchenko
Dalton Trans., 2009, 2383–2391

New reactions of β-diketiminatolanthanoid complexes: sterically induced self-deprotonation of β-diketiminato ligands
P. B. Hitchcock, M. F. Lappert and A. V. Protchenko
Chem. Commun., 2005, 951–953

Final thoughts

None of us was formally associated with Prof. Lappert, but each has encountered his work again and again as our own careers have developed. In choosing these papers, we have focused on those that we believe to have been the most influential on the field (mostly as measured by the number of citations, but also based on our own experiences) while reflecting the impressive breadth of Lappert’s interests. As such, the selection is somewhat biased towards his early career work and we may have missed some chestnuts from later on in his career.

Realizing that such choices are personal and reflective of our own experiences, it is entirely possible that many of you reading this will have opinions of your own as to what contributions by Mike Lappert should be recognized. In this case, we invite you to add to the conversation by leaving your comments here. In the meantime, we hope you accept this collection in the spirit it is meant: to honour the work and legacy of a fine chemist.

Happy reading!

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The Rare BH5

In fall 2008 I visited Boston, where a good friend gave me a tour of Harvard’s chemical laboratories.  Passing by a small office, I saw through the window a thin elderly man in glasses hunched over a desk.  He was turned away from me but the sign on his office said William N. Lipscomb.

Since Lipscomb’s astonishing groundwork beginning in the 1940’s, boranes have provided fascinating examples of the diversity and possibilities of chemical bonding.  Today, boron’s Lewis acidity is widely exploited in catalysis and Frustrated Lewis Pair (FLP) chemistry.

The BH5 molecule, described as BH3 with sigma-bonded dihydrogen bound in an H2 manner, lies at the confluence of many currents of boron chemistry: the activation of hydrogen by FLP’s using borane Lewis acids; three-centre-two-electron bonding; H2 complexes, and the comparison of main group and transition metal chemistry.

In a recent paper in Dalton Transactions, authors Szieberth, Szpisjak, Turczel and Konczol describe BH5 as “rare.”  This is an understatement.  As they report, its existence was confirmed in 1994 by infra-red spectroscopy in an argon matrix at 10-25K temperatures.

In this paper, they present the modelling of the BH5 complex using Natural Bond Order analysis.  Although this has been reported before, the authors use this paper to discern a unique and significant contribution to the stability of η2 H2 borane complexes: the back-donation of electron density from the B-H (or B-R) s-bonds into the σ* orbital of the bound H2, just as electron density from d-orbitals is donated to the H-H σ* orbital in transition metal H2 complexes.  Their description of the Lewis structure of BH5 as a BH3/H2 adduct featuring a three-centre-two electron bond accounts for 99.1% of the electron density.

William Lipscomb passed away on April 14, 2011 at the age of 91.  But I am sure he would be pleased that work within his research area remains vigorously active.

Read the original paper:

The stability of η2-H2 borane complexes – a theoretical investigation
László Könczöl, Gábor Turczel, Tamás Szpisjaka and Dénes Szieberth
Dalton Trans., 2014,43, 13571-13577


Ian Mallov 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.
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September’s HOT articles

Enjoy a read of Autumn’s crop of HOT articles which are free to access for 4 weeks only!

Our HOT articles have also been compiled into a collection and are available for viewing on our website.

Metal-mediated coupling of amino acid esters with isocyanides leading to new chiral acyclic aminocarbene complexes
Tatyana B. Anisimova, M. Fátima C. Guedes da Silva, Vadim Yu. Kukushkin, Armando J. L. Pombeiro and Konstantin V. Luzyanin
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT01917B

Graphical Abstract

Free to access until 27th October 2014


Photoinduced hydrogen evolution by a pentapyridine cobalt complex: elucidating some mechanistic aspects
Elisa Deponti, Alessandra Luisa, Mirco Natali, Elisabetta Iengo and Franco Scandola
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT02269F

Graphical Abstract

Free to access until 27th October 2014


Efficient halogen photoelimination from dibromo, dichloro and difluoro tellurophenes
Elisa I. Carrera and Dwight S. Seferos
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT01751J

Graphical Abstract

Free to access until 17th October 2014


Synthesis, structure and catalytic activity of a gold(I) complex containing 1,2-bis(diphenylphosphino)benzene monoxide
Christine Hahn, Leticia Cruz, Amanda Villalobos, Liliana Garza and Samuel Adeosun
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT02116A

Graphical Abstract

Free to access until 17th October 2014


1,3,5-Triferrocenyl-2,4,6-tris(ethynylferrocenyl)-benzene – a new member of the family of multiferrocenyl-functionalized cyclic systems
Ulrike Pfaff, Grzegorz Filipczyk, Alexander Hildebrandt, Marcus Korb and Heinrich Lang
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT02307B

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Free to access until 17th October 2014

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Expanding the Utility of Expanded NHCs

Posted on behalf of Marcus Drover, web writer for Dalton Transactions

In their recent paper in Dalton Transactions, Stasch, Jones and co-workers describe the use of bulky ring-expanded N-heterocyclic carbenes (NHCs) for the stabilisation of Group 15 trichlorides, ECl3; E = P, As, Sb.

The authors show that mixing 1:1 solutions of the ring-expanded, 2,6-diisopropylphenyl-subsitutied NHC “6-Dipp” with ECl3 (E = P, As, and Sb) affords satisfactory yields of the corresponding [(6-Dipp)ECl3] adduct, noting that the use of the alternatively-substituted mesityl-substituted carbene (6-Mes) led to a mixture of products thus highlighting the importance of the 6-Dipp ligand for stabilising the adducts.

Adduct formation

The group characterised each adduct using standard means, including NMR spectroscopy and electron-impact (EI) mass spectrometry. In the cases of P and Sb, they were able to use X-ray crystallography to determine the solid state structures of those compounds and observed that each pnictogen centre adopted a saw-horse geometry.

When the researchers tried to reduce these adducts using either KC8 or a Mg(I) derivative, they were mostly unsuccessful, however they were able to reduce [(6-Dipp)PCl3] using the former reagent to form a unique dicationic carbene-stabilized P4 unit. Once again, the authors attributed the stability of this species to the steric profile of the 6-Dipp ligand framework. The X-ray crystal structure of the complex shows a P4-butterfly geometry stabilised by two carbene moieties.

P4 compound

During the course of their reactivity studies, the group identified (6-MesH)2 as a byproduct resulting from reaction of in-situ generated [(6-Mes)PCl3] with KC8. With further optimisation, they revealed that this moiety could be accessed from treatment of [6-MesH]Br with KC8 – marking the first successful reductive coupling of cyclic amidinium ions. Along with NMR and X-ray crystal data, a cyclic voltammetry (CV) study was also performed on (6-MesH)2 to fully characterise this unique species.

The successful syntheses of all these p-block NHC complexes pave the way for new discoveries in fundamental reactivity, bonding, and catalysis employing main group elements, further demonstrating the potential of these elements to perform exciting chemistry.

Read the full article to find out more:

Expanded Ring N-Heterocyclic Carbene Adducts of Group 15 Element Trichlorides: Synthesis and Reduction studies
Anastas Sidiropoulos, Brooke Osborne, Alexandr Simonov, Deepak Dange, Alan Bond, Andreas Stasch and Cameron Jones
Dalton Trans., 2014, DOI: 10.1039/C4DT02074J


Marcus Drover is a Ph.D. student, co-supervised by Professors Laurel Schafer and Jennifer Love at the University of British Columbia. His research is focused on the preparation of low-coordinate RhI and IrI complexes for use in small-molecule reactivity. He grew up in St. John’s, Newfoundland and graduated from Memorial University (MUN) before beginning graduate school in 2012.
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August’s HOT papers

Enjoy a read of our fresh batch of HOT articles which are free to access for 4 weeks only!

Our HOT articles have also been compiled into a collection and are available for viewing on our website.

Unusual assembly of lacunary heteropolymolybdates with cyanometalate fragment
Ya Wang, Ning Jiang, Fengyan Li, Yanzhen Zheng, Lin Xu and Minghui Sun
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT01875C

Graphical Abstract

Free to access until 17th October 2014


Structure, stability and photocatalytic H2 production by Cr-, Mn-, Fe-, Co-, and Ni-substituted decaniobate clusters
Jung-Ho Son, Jiarui Wang and William H. Casey
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT02020K

Graphical Abstract

Free to access until 17th October 2014


Light-induced spin-state switching in the mixed crystal series of the 2D coordination network {[Zn1−xFex(bbtr)3](BF4)2}: optical spectroscopy and cooperative effects
Pradip Chakraborty, Cristian Enachescu, Arnaud Humair, Leo Egger, Teresa Delgado, Antoine Tissot, Laure Guénée, Céline Besnard, Robert Bronisz and Andreas Hauser
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT01728E

Graphical Abstract

Free to access until 11th September 2014


Two-photon sensitized visible and near-IR luminescence of lanthanide complexes using a fluorene-based donor–π-acceptor diketonate
Adam W. Woodward, Andrew Frazer, Alma R. Morales, Jin Yu, Anthony F. Moore, Andres D. Campiglia, Evgheni V. Jucov, Tatiana V. Timofeeva and Kevin D. Belfield
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT01507J

Graphical Abstract

Free to access until 11th September 2014


Low temperature activation of S8, Sered and α-Te with [CpBIGFe(CO)2] radicals
S. Heinl and M. Scheer
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT01764A

Graphical Abstract

Free to access until 9th September 2014


Large structural changes upon protonation of Fe4S4 clusters: the consequences for reactivity
Ian Dance and Richard A. Henderson
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT01687D

Graphical Abstract

Free to access until 9th September 2014

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Dalton Transactions in Japan

Members of our Editorial Board recently awarded Dalton Transactions certificates to two attendees at conferences in Japan.

The XXVI International Conference on Organometallic Chemistry (ICOMC 2014) was held in Sapporo on 13th – 18th July with over 1100 participants in attendance.

Professors Fryzuk & Mountford

Professor Michael Fryzuk recieving his certificate from Professor Philip Mountford

Professor Philip Mountford (University of Oxford), Chair of the Dalton Transactions Editorial Board, was on hand to present Professor Michael Fryzuk (University of British Columbia) with a certificate commemorating his Dalton Transactions-sponsored lecture.

Professor Fryzuk gave an excellent talk on nitrogen fixation using organometallic species which was well attended by conference delegates.

After the conference, a number of speakers attended a post-ICOMC symposium at Osaka University on 19th July 2014. The meeting was attended by 150 students and local professors and featured talks from Professors Jun Okuda and Matthias Tam (both members of the Dalton Transactions Advisory Board), Professor John Arnold (Dalton Transactions Associate Editor) and Professor Mountford.

John Arnold, Philip Mountford and Kento Kawakita

Mr Kento Kawakita (right) recieving his certificate from Professors John Arnold (left) and Philip Mountford (centre).

50 posters were presented during the conference, with Mr Kento Kawakita, from the group of Professor Kazushi Mashima (Osaka University and Dalton Transactions Advisory Board), being awarded a Dalton Transactions prize for best poster by Professors Mountford and Arnold.

Congratulations to both Professor Fryzuk and Mr Kawakita!

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Breaking zirconacycles is hard to do

In their recent paper in Dalton Transactions, Erker and co-workers describe B(C6F5)3 as an unorthodox probe for the detection of σ ligand character and allenoid-type bonding in substituted zirconocenes.

Chemists have studied the strong Lewis acid, B(C6F5)3 for the past decade, particularly for its uses in frustrated Lewis pairs (FLPs). This small molecule has, however, gained popularity in other areas of chemistry. In catalysis, B(C6F5)3 is commonly employed to generate cationic metal centres by alkyl group abstraction (σ-ligand abstraction) to activate molecular pre-catalysts for use in polymerisation.

Zirconocene cleavage

Expanding the scope beyond alkyl groups, Erker and co-workers showed that B(C6F5)3 can mediate cleavage of Zr-C(sp3) bonds in zirconacycles, creating unique allene coordination complexes. In one instance, they used an unsubstituted zirconacycloallenoid (Zr-CH2-) to synthesise a zwitterionic (η2-allenyl)zirconocene with an allene bond angle close to linearity.

In a second case, they reacted a 4-phenyl substituted zirconacycloallenoid (Zr-CHPh-) to produce a zwitterionic allene-coordinated zirconocene.

In demonstrating such reactivity, the authors lead the way for B(C6F5)3 to act as a standard probe for detecting latent σ ligand character in other molecules.

Interested in finding out more? Read the full article:

Reaction of Five-membered Zirconacycloallenoids with the Strong Lewis Acid B(C6F5)3
Gerald Kehr, Gerhard Erker, Constantin Gabriel Daniliuc, Birgit Wibbeling and Georg Bender
Dalton Trans. 2014, DOI: 10.1039/C4DT01137F


Marcus Drover Marcus Drover is a Ph.D. student, co-supervised by Professors Laurel Schafer and Jennifer Love at the University of British Columbia. His research is focused on the preparation of low-coordinate RhI and IrI complexes for use in small-molecule reactivity. He grew up in St. John’s, Newfoundland and graduated from Memorial University (MUN) before beginning graduate school in 2012.
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HOT articles for July

July brings us a new batch of HOT articles – free to access for 4 weeks only!

Our HOT articles have also been compiled into a collection and are available for viewing on our website.

A series of 3D metal organic frameworks based on [24-MC-6] metallacrown clusters: structure, magnetic and luminescence properties
Kai Wang, Hua-Hong Zou, Zi-Lu Chen, Zhong Zhang, Wei-Yin Sun and Fu-Pei Liang
Dalton Trans., 2014, 43, 12989-12995
DOI: 10.1039/C4DT01593B

Graphical Abstract

Free to access until 20th August 2014


Mechanism of water oxidation by non-heme iron catalysts when driven with sodium periodate
Alexander R. Parent, Takashi Nakazono, Shu Lin, Satoshi Utsunomiya and Ken Sakai
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT01188K

Graphical Abstract

Free to access until 13th August 2014


Hybrid photocatalysts using graphitic carbon nitride/cadmium sulfide/reduced graphene oxide (g-C3N4/CdS/RGO) for superior photodegradation of organic pollutants under UV and visible light
Rajendra C. Pawar, Varsha Khare and Caroline Sunyong Lee
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT01278J

Graphical Abstract

Free to access until 13th August 2014


NAMI-A is highly cytotoxic toward leukaemia cell lines: evidence of inhibition of KCa 3.1 channels
Serena Pillozzi, Luca Gasparoli, Matteo Stefanini, Mirco Ristori, Massimo D’Amico, Enzo Alessio, Federica Scaletti, Andrea Becchetti, Annarosa Arcangeli and Luigi Messori
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT01356E

Graphical Abstract

Free to access until 7th August 2014


Shape evolution of Au nanoring@Ag core–shell nanostructures: diversity from a sole seed
Jingsong Sun, Jindi Wang, Ying Zhang, Pengbo Wan, Liang Luo, Feng Wang and Xiaoming Sun
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT00992D

Graphical Abstract

Free to access until 4th August 2014


Aqueous stability of alumina and silica perhydrate hydrogels: experiments and computations
Yitzhak Wolanov, Avital Shurki, Petr V. Prikhodchenko, Tatiana A. Tripolskaya, Vladimir M. Novotortsev, Rami Pedahzur and Ovadia Lev
Dalton Trans., 2014, Advance Article
DOI: 10.1039/C4DT01024H 

Graphical Abstract
  

Free to access until 4th August 2014

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Hang on to your carbene

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

What we think of as “organic chemistry” doesn’t often focus on the structure and bonding environments of the carbon atom, unlike inorganic chemistry which often does so with heteroatoms.  So I don’t think I’m going far out on a limb when I say that perhaps the key development in the structure and bonding of carbon over the last quarter century has been the isolation and use of the persistent carbene. 

Arduengo carbene

Arduengo carbene

A carbene is a divalent carbon atom possessing two electrons.  Once thought to be unisolable, its history is recent enough that almost all important figures in its development are not only still living to this day, but still working.  Ron Breslow proposed that carbenes could be isolated in 1957, Guy Bertrand isolated a liquid dicarbene in 1989 and, in 1991, Anthony Arduengo reported the first comprehensive solid-state data of the type of carbene that now bears his name (pictured above).  

So why waste the words of a short post blog on historical perspective?

Because the uses of the carbene have fallen almost entirely in one direction.  Primarily, the carbene has been used as a strong s 2-electron donor – attached to many transition metal atoms it forms very stable complexes, and it is relatively easy to vary its size. 

Only recently have the uses of the carbene diverged. 

In a recent Dalton Transactions paper, Arnold, Love and co-workers present work on labile carbenes tethered to rare earth metals by an alkoxy arm.  On rare earth metals – which are much harder Lewis acids than late transition metals – the soft carbene donor and hard metal acceptor are poorer matches.  Thus the carbon-metal bond may break, freeing the carbene for reactivity, while the hard alkoxy arm keeps the ligand tethered to the metal.

carbene reactivity

Reactivity of tethered alkoxycarbene complexes 

The authors present some examples of reactivity, including co-operative activation of pyrroles and alkynes by the carbene and metal centres, as well as outer-sphere interactions in the form of hydrogen bonding between pyrroles and the metal-bound O atom in solution.   Despite these being small steps, they are nonetheless important if the carbene is to find new roles outside stabilising late transition metal centres.

Interested in finding out more? Read the full paper:

Homo- and heteroleptic alkoxycarbene f-element complexes and their reactivity towards acidic N–H and C–H bonds
Polly L. Arnold, Thomas Cadenbach, Isobel H. Marr, Andrew A. Fyfe, Nicola L. Bell, Ronan Bellabarba, Robert P. Tooze and Jason B. Love
Dalton Trans., 2014, DOI10.1039/C4DT01442A


Ian Mallov 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.
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