Main‐Group Rings, Chains, and Polymer Compounds

Abstract

Although research in the field of main‐group rings, chains, and polymers is a less mature area of chemistry than that of carbon‐based rings, chains, and polymers, it is currently very fertile, as evidenced by the significant increase in available monocyclic main‐group rings in the past two decades, including neutral, anionic, cationic, and radical homocycles and heterocycles. Furthermore, recent advances in main‐group polymer chemistry have been substantial with access to high‐molecular‐weight polyaminoboranes and polyphosphinoboranes enabled by efficient dehydropolymerization catalysts, as well as the production of advanced cross‐linked polysulfide materials. Facile preparation and stabilization of low coordinate main‐group centers, synthesis of new reactive main‐group precursors, and the development of new routes to link main‐group elements together have been keys in moving the field forward. The scope of main‐group complexes has increased drastically, with multiple routes available to access the compounds, enabling a wide range of derivatives possible. In addition, compared to the carbon‐based systems, main‐group compounds feature more bonding options due to the different electronics and sterics afforded by the noncarbon atom(s) and, therefore, modified reactivity. As a result, existing theories such as aromaticity are challenged when new main‐group cycles are created. In this article, the most common routes to prepare the different types of main‐group rings, chains, and polymers are summarized, along with selected classic examples and recent additions to the field from across the p‐block (Groups 13–16). Both homonuclear and heteronuclear systems are covered, and some relevant information on characterization, properties, and uses of the compounds is also included.

Trivalent Titanocene Alkyls and Hydrides as Well-Defined, Highly Active, and Broad Scope Precatalysts for Dehydropolymerization of Amine-Boranes

“…Amine-boranes have elicited considerable attention due to their potential as hydrogen storage and transfer agents, − as precursors to single-layer h-BN and related materials, and as precursors to new main-group polymers such as polyaminoboranes [NHR-BHR′] n . − The latter can be viewed as isoelectronic analogues of common polyolefins, , but they possess distinct properties and potential applications as, for example, precursors to boron-based ceramics and as piezoelectric materials. − Since the first report of Ir-catalyzed dehydropolymerization of primary N -alkylamine-boranes RNH 2 ·BH 3 , significant progress has been made in terms of the range of transition metal precatalysts, − the depth of mechanistic understanding, and the development of metal-free stoichiometric methodologies. , …”