Chemical Behavior and Structure of Triply Bridged Pyrazaboles of the Type RB(Mu-pz)2(Mu-OBRO)BR

摘要

Triply bridged pyrazaboles of the type RB(mu-pz)2(mu-OBRO)BR(1, R = C2H5, C6H5; Hpz pyrazole) are thermally quite stable and can be sublimed without decomposition even under atmospheric pressure. At room temperature they are resistant to water but are not soluble. Dissolution of 1 in protonic solvents occurs with complete breakdown of the molecules. Halogenation of 1 (R = C2H5) with SOC2 yields the pyrazable RCIB(mu-pz)2BRCL. The latter compound is a valuable material for the preparation of various other pyrazaboles. Thus, reaction with alkali metal alkoxide or with alcohol in the presence of triethylamine gives access to R(RO)B(mu-pz)2BR(OR') (R' = CH3, C2H5), the first examples of B-alkoxypyrazaboles; and with (CX3CO)2O (X = H, F) the species with R' = CX3CO are obtained. The crystal and molecular structures of 1 with R = C2H5 were determined. The molecule crystallizes in space group P2 sub 1.