How do you want to "interact"? I have set Capture One to be the default editor (Photo Mechanic Plus > Preferences > Launching, Deafult application to edit photos) and in Photo Mechanic Plus > Preferences > IPTC/XMP have clicked on the lightning symbol at the bottom right and have selected [Capture One]. All of that seems to work well for me (i.e., adding metadata and having it recognised in Capture One, opening files to edit inCapture One).
It might be helpful to explain what more you want.
Stephen