I have XP3.5 so for what it’s worth the help there says
“You can use the Dynamics engine first introduced in Cinema 4D R12 with X-Particles. To do so, you must:
add a Generator object or a Sprite object to the scene and link it to an emitter (you must generate objects for Dynamics to work, the engine will not work on bare particles)
if using a Generator object, add an object to be generated; if using Sprites, select the type of sprite you want – note that this will not work if you generate lights, since they have no geometry
set up Dynamics tags on the objects you want particles to collide with in the usual way
add a Dynamics tag to the Sprite or Generator object, NOT to the object to be generated – this is important!
set the required options in the Dynamics tag
finally, in the Dynamics tag, Collision tab, set ‘Individual Elements’ to ‘Top Level’ (or any of the options in the drop-down other than ‘Off’) – if you don’t do this you won’t get any dynamics effects
Now your particles and their objects can be used with the inbuilt Dynamics system.
You should be aware that Cinema’s Dynamics will take control of the generated object away from X-Particles. The particles themselves remain under the control of the emitter, but the objects may be completely divorced from their source particle. Unfortunately there is nothing we can do about this, as the Cinema 4D SDK does not provide any functions for controlling dynamics or accessing the dynamics data.”
It’s possible with XP3.5 but if it does work with 2.5 you’d have to go to Project/Dynamics/Gravity to 0 since trying to set the Mass of your spare to 0 won’t work it will still drop when your collisions do work.