Treating bis(9-borobicyclo[3.3.1]nonane) (I) with quinuclidine (II) in hydrocarbon solvents at 150 Deg gives quinuclidino-9-borabicyclo[3.3.1]- (III) and -[4.2.1]nonane (IV), which are sepd. by fractional crystn. after rapid cooling. The differing intermol. interactions found in cryst. III and IV by x-ray anal. reflect some of their solid-state properties. IV reacts with BF3.OEt2 to give an approx. equimolar mixt. of syn- (V) and anti-bis(9-borabicyclo[4.2.1]nonane) (VI). IV, and therefore VI, are also prepd. by adding II to the initial hydroboration product mixt. obtained from 1,5-cyclooctadiene and THF.BH3.