Main-group-based rings and polymers

Chemistry of Boratophosphazenes: Synthesis of Borazine-Phosphazene Hybrid Cations, and New Inorganic Heterocycles by Skeletal Substitution Reactions

“…[29] Because of our differing observations, we have studied the reaction of 1 with BCl 3 in more detail. An NMR-scale reaction between 1 and a slight excess of BCl 3 (20 %) in CD 2 Cl 2 was performed, and analysis by 11 B NMR spectroscopy showed a sharp signal at d 12.3 and a broad resonance at d 29.9, which is consistent with that previously observed for [2] . The 31 P NMR spectrum exhibited a singlet resonance at d 34.7, which is consistent with [2] , and a resonance at d 30.0, which lies closer to that for 1 than [2] , and is consistent with the presence of adduct 3.…”

“…The product was analyzed by 31 P NMR in CDCl 3 , which showed the presence of a dominant singlet at d 30.6. This resonance was not consistent with the formation of the analogue of [2] with 11 B NMR. Colorless crystals were obtained by slow evaporation of solvent from a solution of the product in dichloromethane/hexanes (1:1).…”

“…[10,11] With this in mind we have chosen to investigate boroncontaining heterophosphazenes, which represent an underdeveloped area of inorganic chemistry and may provide access to new inorganic polymers through ROP. In fact, very few examples of rings constructed from boron, nitrogen, and phosphorus atoms are known, [12] which is surprising since borazines and phosphazenes represent two of the most wellstudied textbook classes of inorganic ring systems.…”

“…However, analysis of the product by 11 B NMR spectroscopy showed that 1 [d 5.4 (t)] was completely consumed and that a new product [2][AlCl 4 ] with a broad singlet resonance at d 29.6 in CDCl 3 was formed (Scheme 2). This downfield shift and the broadening of the 11 B NMR resonance for [2][AlCl 4 ] suggests the presence of a planar rather than tetrahedral environment at boron. Significantly, the 11 B NMR chemical shift for [2] is similar to that for the borazine (ClBNMe) 3 (d 31.2).…”

“…3), and the unexpected ring-expansion product 4. [28] Although only 4 made spectroscopic sense because of the observation of a single 11 B NMR resonance, it was concluded that 3 was the most likely product. [29] Because of our differing observations, we have studied the reaction of 1 with BCl 3 in more detail.…”