Abstract
Chem 鈥� Eur. J. 2021, 27, 8195-8202
Mechanochemical Formation, Solution Rearrangements, and Catalytic Behavior of a Polymorphic Ca/K Allyl Complex
Koby RJ, Doerr AM, Rightmire NR, Schley ND, Brennessel WW, Long BK, Hanusa TP
Without solvents present, the often far-from-equilibrium environment in a mechanochemically driven synthesis can generate high-energy, non-stoichiometric products not observed from the same ratio of reagents used in solution. Ball milling 2?equiv. K[A鈥橾 (A鈥�=[1,3-(SiMe3)2C3H3]?) with CaI2 yields a non-stoichiometric calciate, K[CaA鈥�3], which initially forms a structure (1) likely containing a mixture of pi- and sigma-bound allyl ligands. Dissolved in arenes, the compound rearranges over the course of several days to a structure (2) with only ?3-bound allyl ligands, and that can be crystallized as a coordination polymer. If dissolved in alkanes, however, the rearrangement of 1听迟辞 2聽occurs within minutes. The structures of 1听补苍诲 2聽have been modeled with DFT calculations, and 2聽initiates the anionic polymerization of methyl methacrylate and isoprene; for the latter, under the mildest conditions yet reported for a heavy Group 2 species (one-atm pressure and room temperature).