German historian Wolfram Siemann, in his well received new biography of Metternich, claims that Metternich's peace ouvertures to Napoleon in 1813 were not genuine but a ploy to buy time:
"Siemann explains that Metternich correctly foresaw, in a series of reports to the Austrian emperor, that Napoleon was quite incapable of agreeing to a negotiated peace. Indeed, Siemann judges all of Metternich’s attempts to reach an agreement with Napoleon, including his celebrated tête-à-tête at the Marcolini Palace in Dresden in 1813, merely as efforts to buy more time while the Austrians rearmed. Metternich never believed that Napoleon would agree to lasting concessions."
(Source: Mark Jarrett's Review of the book in Literary Review December 2019-January 2020)
On the merits of the book itself Jarrett adds:
"Wolfram Siemann, professor emeritus of history at the University of Munich. Siemann has spent years doing original archival research in Vienna and Prague, and historians of central Europe have been falling over themselves in praise of the German edition."
Michael Broers also praised the work in the second volume of his biography of Napoleon:
"Wolfram Siemann’s life of Metternich, definitive not only in its authority, but for having changed the game forever, through its assiduous research."
The idea that peace overtures were a means of buying time doesn't entirely surprise me, but does that necessarily mean that they weren't entered into in good faith? If Napoleon had surprised everyone and agreed to terms, then surely there was scope to try and build a lasting settlement? The terms that he was offered were, as far as I'm aware, fairly reasonable, even quite good.