Bis(9‐borabicyclo[4.2.1]nonanes)

Solutions of bis(9‐borabicyclo[3.3.1]nonane) (1)2 at 150°C in the presence of quinuclidine (Q) yield the 1:1 adducts quinuclidine‐9‐borabicyclo[3.3.1]nonane (Q‐1) and quinuclidine‐9‐borabicyclo[4.2.1]nonane (Q‐2) which after rapid cooling are separable by fractional crystallization. The differing intermolecular interactions found in the crystalline amine‐boranes Q‐1 and Q‐2 (X‐ray analyses) reflect some of their solid state properties. From Q‐2 on reaction with diethyl ether–BF3 approximately equimolar mixture of syn‐ and anti‐bis(9‐borabicyclo[4.2.1]nonane) (2)2 is obtained. Q‐2 and therefore (2)2 are also preparable by adding Q to the initial hydroboration product mixture obtained from 1,5‐cyclooctadiene (3) and tetrahydrofuran–BH3.