AbstractThe tetraorganodiboroxanes R2BOBR2[R = C2H5(1); R2= 1,5‐C8H14(2)] react with N‐bases [pyridine (P); 4‐methylpyridine (4‐MeP),4‐EtP, 4‐tBuP, 3,5‐Me2P, DMAP; quinuclidine (Q); 1,5‐diazabicyclo[4.3.0]non‐5‐ene (DBN)] to form stable liquid (N‐base‐1) and solid (N‐base‐2) 1:1 adducts (e.g.P‐2, Q‐2, andDBN‐2). In solution, the rates of fluctuation of the N‐base between the two boron atoms of the R2B groups depend on the Lewis acidities of1and2, the basicities of the bases, as well as the steric factors of the donor‐acceptor pairs. At low temperatures (e.g. ≤ −20°C forP‐2and ≤ −50°C forP‐1), bonding of the base to only one of the boron atoms is indicated. WhenQ‐2is dissolved in CDCl3or [D8]toluene at room temperature it dissociates completly (11B and13C NMR). Below −60°C interaction between the base and the borane was observed. Low‐temperature (‐50°C)11B‐NMR data indicate that in the presence