Different url structure on a Network

Hi,
I have a multisite configured to work with subfolders, but I would need to create a sub-site with a different domain. Is this possible?
In a network, you can create “infinite” blogs (table wp_blogs in the db), but the site always remains one (table wp_site): strictly speaking, I think that creating a new site (not a blog) can also use another structure for the url…

E.g:
main site: catalogo.it (site_id=1, blog_id=1)
sub site: catalogo.it/extra/ (site_id=1, blog_id=2)
new site: nuovo.it (???)