Only one example is known, bis(trifluoromethyl)phosphinous acid, (CF)POH.  It is prepared in several steps from phosphorus trichloride (Et = ethyl):
:PCl  +  2 EtNH  →  PClNEt  +  EtNHCl
:2 P(NEt)  +  PClNEt  +  2 CFBr  →  P(CF)NEt  +  2 BrClP(NEt)
:P(CF)NEt  +  HO  →   P(CF)OH  +  HNEt