The boron chelate compd. I is obtained by the reaction of vinamidine MeN:C(Me)CH:C(Me)NHMe with Et2O.BF3. Protonation with HBF4 gives the cation II. Comparison of the calcd. and exptl. detd. structures demonstrates I and II to be heterocyclic analogs of cyclohexadienide and 1,4-cyclohexadiene resp.