UNSYMMETRICAL POLYPYRAZOLYLBORATE VIA BORON CATIONS

Convenient new procedures were developed for preparing unsymmetric pyrazolylborate, [H2B(pz)(pz')]-. Reaction of 3,5-dimethylpyrazole with BH3.THF complex gives 3,5-dimethylpyrazole borane. Treatment of this compound with I2 at room temperature gives the cation [H2B(3,5-Me2pzH)2]+. When the reaction temperature was lowered to -30-degrees-C we obtained the compound [H2B(3,5-Me2pzH)(I)], whose reactions with different pyrazoles in THF give the unsymmetric [H2B(3,5-Me2pzH)(pzH')]+I-. Reaction of the boronium iodides with NaH produces [H2B(3,5-Me2pz)(pz')]-Na+.