What you're describing is an incomplete pass. The foot is still continuing in one motion which is OOB. If he comes down with the toe and then lifts it without the heel touching OOB, it would be a catch provided he completes it as he goes to the ground.
The rule states(2-4-3): "If one FOOT.." (not toe) "...lands IB and the receiver has poss and firm control of the ball, it is a catch...even though a SUBSEQUENT step or fall takes the rec OOB."
Heel is part of the foot, if it comes down OOB, player is OOB. Also, 2-4-3-f says that "When in question, the catch...is not completed."