"For cyanide to kill you" is constructed from the sentence "cyanide kills you", and obeys exactly the same rules. It predicates an action (killing) of a particular agent (cyanide), though it is not bound to any particular time. If "kills you" is a "predicate" in the finite clause, then "to kill you" is also a predicate in the nonfinite clause. Can you make the argument that it isn't without special pleading?