B(C6F5)3 or P4O10 in dichloromethane-d2 byproducts: H2O; under N2 or Ar; B(C6F5)3 or P4O10 added to soln. of borinic acid in CD2Cl2 at 178-184 K; reversible react.; not isolated; detd. by (1)H and (19)F NMR spectra;