if such an adapter would exist it would not focus to infinity !
The Hasselblad H has 61,63mm, the Mamiya 645 has 63,3 mm, the Hasselblad V has 74,9 mm. A Leica S2 has only 53mm
An adapter from H to M645 could be a max of 1,57mm thick which is technically not possible.
for more infos on possible combinations see here:http://www.graphics.cornell.edu/~westin/misc/mounts-by-register.html