Synthesis and Coordination of the Cagelike Siloxane Compounds E2{(SiMe2)2O}3 (E = As, Sb, Bi)

Abstract

AbstractThe cage compounds [E2{(SiMe2)2O}3] for E = P, As, Sb, and Bi (1, 4, 5, and 6, respectively) are readily accessible in moderate yields by the reaction of Na3E (for E = P, As, Sb, Bi) or [Li(dme)EH2] (for E = P, As; dme = dimethoxyethane) with 1,3‐dichloro‐1,1,3,3‐tetramethyldisiloxane. These compounds were isolated and characterized by X‐ray crystallographic analysis. The major structural parameters such as the E–Si bond length and the Si–E–Si angles are discussed and compared with those of similar compounds. The small Si–E–Si angles in these compounds are attributable to steric and electronic reasons. Further, the R3M–E[(SiMe2)2O]3E–MR3 (M = Al, E = As, Sb; M = Ga, E = Sb) Lewis acid–base adducts were formed as well as the W(CO)5 adduct of compound 1 and a heteroleptic Na[Al(ORF)4] (RF = C(CF3)3) adduct with 4 to investigate the coordination properties of the cage compounds. The structural changes caused by coordination follow the Haaland model, which gives qualitative information on the adduct stability. The assumptions made by the Haaland model are valid for a versatile set of Lewis acids. To investigate coordination on the inside of the cage, a reaction of 4 with Li[Al(ORF)4] was performed to yield a new dimeric ligand of the constitution As4[(SiMe2)2O]6.