Mechanochemical Synthesis of Phosphazane‐Based Frameworks

Abstract

Mechanochemistry is emerging as a powerful solvent-free approach to chemical synthesis, having been applied to metal oxides, pharmaceutical materials, organic compounds and to a lesser extent, coordination complex synthesis. Notably, examples of applications of mechanochemical methodologies in the synthesis of main-group compounds are few and far between. Herein, we demonstrate that ball milling enabled the solvent-free synthesis of a range of phosphazane frameworks with a broad substrate scope, yielding seven new acyclic and macrocyclic species. The strength of this methodology is highlighted by a fast, selective and high-conversion product generation from poorly soluble starting materials, thereby demonstrating mechanochemistry as a real alternative to solution-based methods in synthetic main-group chemistry.

Completely Solvent-free Protocols to Access Phase-Pure, Metastable Metal Halide Perovskites and Functional Photodetectors from the Precursor Salts

“…As part of the sustainable energy and green chemistry efforts in our team, we have recently been developing multi-dimensional lead and tin halide perovskites for light absorption and emission purposes (Koh et al., 2016, Thirumal et al., 2017) and creating innovative energy solutions based on artificial photosynthesis (Dokic and Soo, 2018, Gazi et al., 2017, Hong et al., 2019, Lim et al., 2018, Ng et al., 2018). Simultaneously, we have also been developing more eco-friendly, essentially solvent-free, mechanochemical approaches for the synthesis, functionalization, and transformation of main group compounds (Shi et al., 2016, Sim et al., 2017, Sim et al., 2018) and complexes (Geciauskaite and Garcia, 2017, Tan and Garcia, 2019, Wang et al., 2016, Wang et al., 2017). In a joint endeavor, we sought to use mechanochemistry to address the challenges encountered in solution-based syntheses of purportedly unstable metal halide perovskites.…”

Main group mechanochemistry

“…Theoretical and systematic studies that elucidate the kinetic and thermodynamic driving forces of mechanochemical reactions are undergoing and will be imperative to achieving this goal [ 106 , 112 – 114 ]. Areas in which we anticipate mechanochemistry will show particular strength in: (i) the synthesis of highly air- and moisture-sensitive compounds, since many are incompatible with a wide range of protic solvents [ 95 ]; and (ii) the synthesis of unsolvated species, where chemical reactivity might be hindered by the presence of strongly bound solvent molecules within their coordination sphere [ 98 ].…”

“…However, these species remain typically arduous to synthesize and isolate, since phosphazane arrangements are generally highly air- and moisture-sensitive [ 93 – 94 ], and their halogenated precursors are incompatible with protic solvents. Mechanochemistry therefore offers an elegant synthetic route by circumventing solvent compatibility issues, the tedious processes associated with the use of strict anhydrous solvents, and by minimizing unwanted side-products (see Scheme 6 ) [ 95 ].…”

Direct and Telescopic Mechanochemical Synthesis of Higher-order Organic-Inorganic Hybrid Cocrystals: Tuning Order, Functionality and Size in Cocrystal Design

“…In a previous study, it has been demonstrated that airand moisture-stable cyclodiphosph(V)azane compounds can be readily accessed via simple oxidation of the phosphorus(III) centers to phosphorus(V) using chalcogenic elements. [51][52][53] Within the cyclodiphosph(V/V)azane species, the cis-oxidized frameworks the terminal substituents can adopt several topological arrangements giving rise to different conformations (Scheme 1). Of particular interest is the exo, exo (Z, Z) conformation, which acts as a versatile bifurcated hydrogen bond (HB) donor, owing to the two terminal NH groups that are oriented in a converging manner.…”