Bis(2-cyanoethyl) (3'-methoxy-3-oxo-3H-spiro[isobenzofuran-1,9'-xanthen]-6'-yl) Phosphinylidenephosphite is an intermediate in the synthesis of 3-O-Methylfluorescein Phosphate Bis-Cyclohexylammonium Salt (M227495), which is used in fluorimetric studies. It can be used as reactant in multifunctional phosphate-​based inorganic-​organic hybrid nanoparticles.