The two could have met in Acco in 1799 at the battle of Acco. The still young French Revolution wanted to fight or die for freedom. The French Royalists were on the side of the Louverture as opposed to the nationalists who wanted the black soldiers back on the plantations! The banner of freedom had passed to the British and Napoleon's old plan to give Jerusalem to the Jews was now still born like his plan to invade England. This is why Rabbi Nachman could not meet Napoleon.
Rabbi Nachman defeated Napoleon when he wrote the Petek on 28.7.5566 (discovered this on the 5th day of Hannoukka and my telephone number is 0556628753). Three years before the burning of the Sefer ha Nischaf. This is the precise day of the Battle of Trafalgar.