The diamond face will pass through the diamond shape in the larger piece but it's too big to fit in the cut-out if both are laid flat. An enterprising jewelry maker, with more toggle experience than I have, might be able to fashion a toggle clasp out of the two pieces. Or, the pieces could simply be pendant and bead in a necklace.
The face diamond has a hole running from top point to the bottom point. There are no holes in the large piece but you could use a drill bit to make a hole if needed.