The 24-year-old, Larrondo, will be making his move after much speculation, while Under-21 Montenegrin starlet Bakic, who is currently on loan at Torino, will join the Viola in the summer.
The Italian club believe the players will be ones for the future after a deal was struck to gain the services of the two midfielders this week.
“Larrondo will join Fiorentina in a co-ownership deal,” Siena director Stefano Antonelli told Fiorentinanews.com.
Meanwhile, Siena are also hoping to boost their chances of avoiding relegation and are interested in acquiring the services of two players from Vincenzo Montella's squad.
Antonelli added: “We really like Ruben Olivera and Francesco Della Rocca in Fiorentina’s squad, but I think these will be two different and distinct negotiations."