The reaction of Me3CCOOBEt2 with pyrazole led to the formation of the stable addition complex 1, which was found to be monomeric in solution. The reaction of 9-H-9-borabicyclo [3.3. 1] nonane (9-H-9-BBN) 2 with pyrazole and pivalic acid yielded a similar complex Me3CCOO (9-BBN)-pzH 2. Crystallographic analysis of 2 revealed a dimeric structure due to the strong hydrogen bonding between azole hydrogen and carbonyl oxygen. The one ...