Forum Article pubs.acs.org/IC
Preface for the Advances in Main-Group Inorganic Chemistry Forum Philip P. Power*,† and Ching-Wen Chiu*,‡ †
Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States Department of Chemistry, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
‡
report on an o-phenylene-linked bis(N-heterocyclic olefin) (bisNHO) ligand and the corresponding isophosphindolylium cation, which features a cationic but nucleophilic phosphorus atom in an aromatic ring.2 Main-group Lewis acids and bases have a long-standing history in the stoichiometric and catalytic transformation of organic substrates. In the past several years, however, more and more studies have demonstrated that a combination of two reagents could be even more powerful, and a rapidly expanding field of study in main-group chemistry has focused on the cooperative activation of chemical bonds using frustrated Lewis pairs or bimetallic reagents. Thus, Hevia and co-workers showed that selective metalation under mild conditions by an organogallane species could be achieved in conjunction with a bulky lithium amide and a N-heterocyclic carbene via transmetal-trapping and a frustrated Lewis pair mechanism, respectively.3 In addition, two Forum Articles describe the design and reactivity of main-group Lewis acids. The Forum Article contributed by Melen and Lawson focuses on the recent advances of prototypical boron Lewis acids in borylation reaction,4 and transformations mediated by boron cations are also included. In a different vein, Gabbaı̈ and Yang have described work on the halogen-substituted stibonium cations, whose Lewis acidity originates from the low-lying σ* orbital of the Sb−halide bond.5 Such σ* Lewis acids are receiving considerable attention because of their performance as molecular sensors and Lewis acid catalysts. In addition to typical Lewis acid−base reactions, catalytic reactions akin to those mediated by transition-metal complexes can also be accomplished with main-group metals. The coordination chemistry of noninnocent ligands to d- and fblock metals has been extensively explored, but such a class of ligands can also be used in p-block metals. For example, Berben and co-workers have described the electrocatalytic H2 evolution by an aluminum complex, in which electron and proton transfer are facilitated by a bis(pyrazolyl)pyridine ligand.6 Similarly, Radosevich and co-workers utilize a redox-active bis(phenoxide) amide ligand to stabilize an open-shell phosphorane radical cation,7 which could see potential application in a cooperative multielectron process. While catalytic C−C and C−N bond coupling reactions assisted by d-block metals are pivotal for organic synthesis, catalytic bond-formation processes for main-group compounds remain less developed. Because the E−E coupling reaction generally relies on the efficient activation of an E−H bond, coordination and dissociation of main-group hydride derivatives to metal catalysts become important. In this regard, a Forum
U
p until the mid-1970s, the chemistry of s- and p-block element compounds had been viewed by many as unexciting because of their predictable molecular geometries, well-defined (but limited in number) oxidation states that were separated by large energies, and diamagnetic character. In essence, the perception that main-group element compounds are chemically less interesting and versatile than the transition metals was a tacit assumption. In addition, undergraduate inorganic chemistry courses were focused mainly, although not exclusively, on compounds of the transition elements and tended to reinforce the above perception. Ironically, maingroup elements are more diverse in their electronic character than transition metals. Furthermore, they are generally abundant and are involved everywhere in the modern economy as either bulk or specialty chemicals that find applications ranging from catalysis to electronic materials, cosmetics, and pharmaceuticals. For example, one of the most interesting research topics in the past 5 years, the halide perovskite solar cell, is based on the use of heavy-group 14 elements. These current applications, however, do not adequately define maingroup chemistry, and they certainly do not hinder main-group chemists from breaking the “rules” via exploratory synthesis. Since the mid-1970s, the desire to isolate new classes of compounds with unprecedented chemical bonds, geometries, and oxidation states of s- and p-block elements has become one of the main thrusts in main-group chemistry and has led to numerous new compound classes as well as insights on bonding. Furthermore, extension of the conjugated π system to heavier p-block elements has blurred the boundary between organic and main-group chemistry. In addition, the discovery of the activation of H2 and other small molecules by low-valent group 13 and 14 compounds or frustrated Lewis pairs removed a barrier between p-block elements and their d-block counterparts, as has the recent use of main-group compounds in catalysis. The inherent diversity in the electronic properties of s- and p-block elements and their compounds points to numerous developments to come. The intention of this Forum is to showcase some of the recent advances of main-group chemistry and to stimulate future innovations in inorganic chemistry. The continued expansion of developments in main-group chemistry is now driven mainly by the curiosity about the structure−reactivity relationships of an ever-expanding array of compound types. The isolation of what had hitherto been assumed to be unstable species has provided a great opportunity for the discovery of new reactions. We now highlight just a few of these. Gessner and Scharf describe the development of highly unstable metalated ylides, anionic analogues of bisylides that function as strong donating X,L-type ligands for both transition and main-group metals.1 Furthermore, Kinjo and co-workers © 2017 American Chemical Society
Special Issue: Advances in Main-Group Inorganic Chemistry Published: August 7, 2017 8597
DOI: 10.1021/acs.inorgchem.7b01610 Inorg. Chem. 2017, 56, 8597−8598
Forum Article
Inorganic Chemistry
(3) Uzelac, M.; Kennedy, A. R.; Hevia, E. Trans-Metal-Trapping Meets Frustrated-Lewis-Pair Chemistry: Ga(CH2SiMe3)3-Induced C− H Functionalizations. Inorg. Chem. 2017, 56, 8615. (4) Lawson, J. R.; Melen, R. L. Tris(pentafluorophenyl)borane and Beyond: Modern Advances in Borylation Chemistry. Inorg. Chem. 2017, 56, 8627. (5) Yang, M.; Gabbaï, F. P. Synthesis and Properties of Triarylhalostibonium Cations. Inorg. Chem. 2017, 56, 8644. (6) Sherbow, T. J.; Fettinger, J. C.; Berben, L. A. Control of Ligand pKa Values Tunes the Electrocatalytic Dihydrogen Evolution Mechanism in a Redox-Active Aluminum(III) Complex. Inorg. Chem. 2017, 56, 8651. (7) Pistner, A. J.; Moon, H. W.; Silakov, A.; Yennawar, H. P.; Radosevich, A. T. A Stable Open-Shell Phosphorane based on a Redox ActiveAmidodiphenoxide Scaffold. Inorg. Chem. 2017, 56, 8661. (8) Hicken, A.; White, A. J. P.; Crimmin, M. R. Reversible Coordination of Boron−, Aluminum−, Zinc−, Magnesium−, and Calcium−Hydrogen Bonds to Bent {CuL2} Fragments: Heavy σ Complexes of the Lightest Coinage Metal. Inorg. Chem. 2017, 56, 8669. (9) Teichmann, J.; Bursch, M.; Köstler, B.; Bolte, M.; Lerner, H.-W.; Grimme, S.; Wagner, M. Trapping Experiments on a Trichlorosilanide Anion: a Key Intermediate of Halogenosilane Chemistry. Inorg. Chem. 2017, 56, 8683. (10) Friedfeld, M. R.; Stein, J. L.; Cossairt, B. M. Main-GroupSemiconductor Cluster Molecules as Synthetic Intermediates to Nanostructures. Inorg. Chem. 2017, 56, 8689. (11) Yogendra, S.; Hennersdorf, F.; Weigand, J. J. Nitrogen− Phosphorus(III)−Chalcogen Macrocycles for the Synthesis of Polynuclear Silver(I) Sandwich Complexes. Inorg. Chem. 2017, 56, 8698. (12) Li, S.-Y.; Sun, Z.-B.; Zhao, C.-H. Charge-Transfer Emitting Triarylborane π-Electron Systems. Inorg. Chem. 2017, 56, 8705. (13) Adler, R. A.; Wang, C.; Fukazawa, A.; Yamaguchi, S. Tuning the Photophysical Properties of Photostable Benzo[b]phosphole P-OxideBased Fluorophores. Inorg. Chem. 2017, 56, 8718.
Article from Crimmin and co-workers discusses the interaction of s- and p-block metal hydrides with β-diketiminate-supported copper(I) complexes,8 providing experimental and computational insights into σ complexes of main-group hydrides. Because main-group semiconducting materials continue to dominate solid-state electronics, investigation of the growth mechanism whereby molecular precursors are transformed to bulk material is of fundamental practical significance and lies at the interface of molecular and solid-state chemistry. The Forum Article of Wagner, Grimme, and co-workers describes trapping experiments on a trichlorosilanide anion,9 a key intermediate of the chloride-induced disproportionation of hexachlorodisilane to yield oligosilanes and silafulleranes. In addition, Cossairt and co-workers review the growth mechanisms of main-group semiconductor nanostructures from well-defined cluster precursors.10 Weigand and co-workers describe the synthesis and reactions of an inorganic macrocycle and demonstrate its potential as a multidentate ligand in stabilizing polynuclear metal complexes,11 which can be regarded as the transition phase between the mononuclear complex and cluster compound. The incorporation of p-block elements into organic conjugated systems has proven to be an effective approach to tuning the optoelectronic properties of organic fluorophores. In this context, two Forum Articles on main-group luminophores are featured. A Forum Article from Zhao and co-workers summarizes their recent progress in charge-transfer-emitting triarylboranes.12 In the contribution from Yamaguchi, Fukazawa, and co-workers, photobleaching-resisting red-emissive fluorophores for fluorescence imaging application are described.13 The rigid benzo[b]phosphole P-oxide dyes are not only strongly emissive but also possess photostability surpassing those of the currently used dyes. Unfortunately, this Forum is unable to cover all of the important breakthroughs in main-group chemistry that have occurred in recent years, and there remain several areas open for future main-group Forums. One exciting subject involves the reactivity, bonding, and catalytic ability of low-valent maingroup compounds that have been shown to resemble those of transition-metal complexes. Another such theme concerns main-group ligand-supported transition-metal complexes. We hope this collection of Forum Articles will stimulate further creativity in main-group chemistry and encourage researchers in all fields to apply those innovations.
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. ORCID
Philip P. Power: 0000-0002-6262-3209 Notes
Views expressed in this editorial are those of the authors and not necessarily the views of the ACS.
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REFERENCES
(1) Scharf, L. T.; Gessner, V. H. Metalated Ylides: A New Class of Strong Donor Ligands with Unique Electronic Properties. Inorg. Chem. 2017, 56, 8599. (2) Chong, C. C.; Rao, B.; Ganguly, R.; Li, Y.; Kinjo, R. Bis(Nheterocyclic olefin) Derivative: An Efficient Precursor for Isophosphindolylium Species. Inorg. Chem. 2017, 56, 8608. 8598
DOI: 10.1021/acs.inorgchem.7b01610 Inorg. Chem. 2017, 56, 8597−8598
