AbstractThe bis(diorganoboryl) chalcogenides (R2B)2O [R = C2H5(3); R2= 1,5‐C8H14(1)], (R2B)2S [R2= 1,5‐C8H14(5)], and (R2B)2Se [R2= 1,5‐C8H14(7)] react with pyrazole (Pz) and its derivatives 3‐methylpyrazole (3‐MePz) and indazole (benzo‐Pz) to form in high yields (65–92%) stable 1:1 adducts [e.g.2(El = O),4(El = O),6(El = S) and8(El = Se)].1H‐,13C‐,11B‐NMR spectra and X‐ray analyses (of2and6) show a basic structure with a central B2ElN2(El = O, S, Se) heterocycle. The reaction of2with R2BH and the thermolysis of4give the dimeric 1‐pyrazolylboran