The possibility of electron binding to the HPPH3 and H2PPH2 tautomers of diphosphine was studied at the coupled cluster level of theory with single, double, and noniterative triple excitations. The HPPH3 tautomer, with a dipole moment of 3.7 D, binds an electron by 333 cm(-1), whereas the H2PPH2 tautomer forms neither a dipole- nor valence-bound anionic state. It is suggested that the HPPH3 tautomer, which is kinetically stable but thermodynamically unstable relative to H2PPH2, may be formed by photodetachment from the P2H4- species examined in this work. An unusual aspect of the (HPPH3)(-) anion is that electron correlation contributes 82% to the electronic stability and effects beyond the fourth order of the Moller-Plesset perturbation theory contribute 55%.