Cationic Chains of Parent Arsanylboranes and Substituted Phosphanylboranes

摘要

The substituted monomeric phosphanylboranes Ph_2P-BH_2·NMe_3 (1) and tBuHP-BH_2·NMe_3 (2) have been used for the synthesis of cationic chain compounds built up by R_2P-BH_2 units. With a simple synthesis route, the highly stable cations [Me_3N·H_2B-PR_1R_2 -BH_2·NMe_3]~+ (1a, 2a) and [Me_3N·H_2B-PR_1R_2 -BH_2 -PR_1R_2 -BH_2·NMe_3]~+ (1b, 2b) (R_1 =R_2= Ph; R_1=H, R_2=tBu) are obtained as iodide (I-) salts. The reaction of H_2As-BH_2·NMe_3 (3) with IBH2·SMe2 leads to [Me_3N·H_2B-AsH_2 -BH_2 -AsH_2 -BH_2·NMe_3][I] (3a), the longest so far known arsanylborane chain. Compound 3a reacts with acetonitrile through a formal hydroarsination reaction to form [cyclo-{As(BH_2·NMe_3)(CMe=NH)_2(BH_2)}][I] (4). The reported synthetic strategy has proved to be a powerful tool for the formation of small, cationic oligomeric units. All products were comprehensively characterized by X-ray structure analysis, NMR, IR spectroscopy, and mass spectrometry in cooperation with DFT calculations.