Synthesis, Structures, and Reactivities of BCN-Heterocyclic B-N Chains.

The BCN-heterocyclic B-N chain compounds, the sodium and potassium salts of 3 and 4 anions (Na 3 , Na 4 , and K 4 ), were synthesized by reactions of ethane 1,2-diamineborane (BH 3 NH 2 CH 2 CH 2 NH 2 BH 3 , 1 ) and propane 1,2-diamineborane (BH 3 NH 2 CH 2 CH 2 CH 2 NH 2 BH 3 , 2 ) with MH (M = Na and K). Then, the neutral B-N chain compounds 5 and 6 were prepared with dehydrogenation of [NH 4 ] 3 and [NH 4 ] 4 , formed by metathesis reactions of Na 3 and Na 4 with NH 4 Cl or NH 4 SCN, respectively. Compounds 7 and 8 , analog 5 , were also prepared using pyridine and 4-methoxypyridine instead of NH 3 in 5 . These synthesized compounds were characterized spectroscopically, and the singe-crystal structures of the Na 3 ·18-crown-6 and K 4 ·18-crown-6 adducts were determined. Furthermore, the reactions of Na 3 and Na 4 with cationic B-N chain compounds, [NH 3 BH 2 NH 3 ]Cl and [NH 3 BH 2 NH 2 BH 2 NH 3 ]Cl, could not form longer BCN-heterocyclic B-N chain. The solubility of metal hydrides, the ability for proton abstracting, the basicity of Lewis bases, and the chelate effect may influence these reactions even though the reaction mechanism is not fully understood.