Catalytic reactions that enable the formation of new bonds to carbon centres play a pervasive role in the state-of-the-art synthesis of organic molecules and macromolecules. In contrast, the development of analogous processes as routes to main group compounds and materials has been much slower. Nevertheless, recent advances have led to a broad expansion of this field and now allow access to a wide range of catenated structures based on elements across the p block. These breakthroughs have already impacted areas such as hydrogen storage and transfer, functional inorganic polymers and ceramic thin films. Dehydrogenation and dehydrocoupling processes are particularly well developed and may be mediated by either transition metal or main group catalysts. Such pathways represent an increasingly attractive and convenient alternative to traditional routes, such as salt metathesis and reductive coupling reactions. An overview of this emerging area is presented in this Review with a focus on recent developments and future challenges.

Catalysis in service of main group chemistry offers a versatile approach to p-block molecules and materials

Thanks to rational ligand design, the first gold(I) complexes to undergo oxidative addition of aryl iodides were discovered. The reaction proceeds under mild conditions and is general. The ensuing aryl gold(III) complexes have been characterized by spectroscopic and crystallographic means. DFT calculations indicate that the bending induced by the diphosphine ligand plays a key role in this process.

Facile oxidative addition of aryl iodides to Gold(I) by ligand design: Bending turns on reactivity

Classically closo-carborane anions, particularly [HCB11H11]− and [HCB9H9]−, and their derivatives have primarily been used as weakly coordinating anions to isolate reactive intermediates, platforms for stoichiometric and catalytic functionalization, counteranions for simple Lewis acid catalysis, and components of materials like liquid crystals. The aim of this article is to educate the reader on the contemporary nonclassical applications of these anions. Specifically, this review will cover new directions in main group catalysis utilized to achieve some of the most challenging catalytic reactions such as C–F, C–H, and C–C functionalizations that are difficult or impossible to realize with transition metals. In addition, the review will cover the utilization of the clusters as dianionic C σ-bound ligands for coordination chemistry, ligand substituents for coordination chemistry and advanced catalyst design, and covalently bound spectator substituents to stabilize radicals. Furthermore, their applications a...

Nonclassical Applications of closo-Carborane Anions: From Main Group Chemistry and Catalysis to Energy Storage

We report here the remarkable properties of PAd3, a crystalline air-stable solid accessible through a scalable SN1 reaction. Spectroscopic data reveal that PAd3, benefiting from the polarizability inherent to large hydrocarbyl groups, exhibits unexpected electron releasing character that exceeds other alkylphosphines and falls within a range dominated by N-heterocyclic carbenes. Dramatic effects in catalysis are also enabled by PAd3 during Suzuki–Miyaura cross-coupling of chloro(hetero)arenes (40 examples) at low Pd loading, including the late-stage functionalization of commercial drugs. Exceptional space-time yields are demonstrated for the syntheses of industrial precursors to valsartan and boscalid from chloroarenes with ∼2 × 104 turnovers in 10 min.

Tri(1-adamantyl)phosphine: Expanding the Boundary of Electron-Releasing Character Available to Organophosphorus Compounds

We report the development of a new class of phosphorescent zwitterionic bis(heteroleptic) Ir(III) compounds containing pyridyl ligands with weakly coordinating nido-carboranyl substituents. Treatment of phenylpyridine-based Ir(III) precursors with C-substituted ortho-carboranylpyridines in 2-ethoxyethanol results in a facile carborane deboronation and the formation of robust and highly luminescent metal complexes. The resulting nido-carboranyl fragments associate with the cationic Ir(III) center through primarily electrostatic interactions. These compounds phosphoresce at blue wavelengths (450–470 nm) both in a poly(methyl methacrylate) (PMMA) matrix and in solution at 77 K. These complexes display structural stability at temperatures beyond 300 °C and quantum yields greater than 40%. Importantly, the observed quantum yields correspond to a dramatic 10-fold enhancement over the previously reported Ir(III) congeners featuring carboranyl-containing ligands in which the boron cluster is covalently attached t...

Blue Phosphorescent Zwitterionic Iridium(III) Complexes Featuring Weakly Coordinating nido-Carborane-Based Ligands.

Extremely Electron-Rich, Boron-Functionalized, Icosahedral Carborane-Based Phosphinoboranes

The experiments described here examined the effects of reaction conditions, various additives, and local sequence on the formation and stability interstrand cross-links (ICLs) derived from the reaction of an apurinic/apyrimidinic (AP) site with the exocyclic amino group of an adenine residue on the opposing strand in duplex DNA. Cross-link formation was observed in a range of different buffers, with faster formation rates observed at pH 5. Inclusion of the base excision repair enzyme alkyladenine DNA glycosylase (hAAG) which binds tightly to AP-containing duplexes decreased, but did not completely prevent, formation of the dA-AP ICL. Formation of the dA-AP ICL was not altered by the presence of the biological metal ion Mg2+ or the biological thiol, glutathione. Several organocatalysts of imine formation did not enhance the rate of dA-AP ICL formation. Duplex length did not have a large effect on dA-AP yield, so long as the melting temperature of the duplex was not significantly below the reaction temperature (the duplex must remain hybridized for efficient ICL formation). Formation of the dA-AP ICL was examined in over 40 different sequences that varied the neighboring and opposing bases at the cross-linking site. The results indicate that ICL formation can occur in a wide variety of sequence contexts under physiological conditions. Formation of the dA-AP ICL was strongly inhibited by the aldehyde-trapping agents methoxyamine and hydralazine, by NaBH3CN, by the intercalator ethidium bromide, and by the minor groove-binding agent netropsin. ICL formation was inhibited to some extent in bicarbonate and Tris buffers. The dA-AP ICL showed substantial inherent stability under a variety of conditions and was not a substrate for AP-processing enzymes APE1 or Endo IV. Finally, we characterized cross-link formation in a small (11 bp) stem-loop (hairpin) structure and in DNA-RNA hybrid duplexes.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.2c05736

Effects of Local Sequence, Reaction Conditions, and Various Additives on the Formation and Stability of Interstrand Cross-Links Derived from the Reaction of an Abasic Site with an Adenine Residue in Duplex DNA

Calvin D. Lewis

Papers

Extremely Electron-Rich, Boron-Functionalized, Icosahedral Carborane-Based Phosphinoboranes

Effects of Local Sequence, Reaction Conditions, and Various Additives on the Formation and Stability of Interstrand Cross-Links Derived from the Reaction of an Abasic Site with an Adenine Residue in Duplex DNA