iterm2 and tmux: Keyboard conflicts
Do you have the command keys mapped to option in the Keys tab and the option keys set to act as meta in the Profiles tab? If you do, set the option keys to act as "+Esc" in the preferences:



When the option keys are set to act as meta, they are not recognized in tmux.

Edit: \e[1;5D and \e[1;5C are not recognized by tmux either. You could just map ⌘B  to \eb and ⌘F to \ef: