No. The flange focal distance (lens register distance) of the Pentax 645 is shorter: 70.87mm, vs. 74.1mm for the Pentacon 6/Kiev 60/88. The end of the 645 lens would need to extend 3.23mm within the Kiev lens mount ring, and the diameter of the lens would not allow that.
Pentax 67 FFD is 84.95mm, so theoretically an adapter would work, but because of the design of the 67 lenses and the P6/Kiev bodies, they wouldn't allow infinity focus. See
The Pentacon Six System for details.
Also, aren't the Pentax lenses, either 645 or 67, as expensive or more expensive than the equally good lenses made for the Kiev and Pentacon?
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