The complete molecule of title compound, C₅₈H₅₈P₄, is generated by a crystallographic twofold rotation axis that passes through the center of the C(methine)-C(methine) bond of length 1.582 (4) Å. The C-P bond lengths are 1.8824 (19) and 1.8991 (19) Å. The P-C-P angle of 109.69 (9)° is essentially equal to the expected value of 109.5° for a tetra­hedral C atom. Although the C(methine)-P-C(aromatic) bond angles range from 102.67 (9) to 107.04 (9)°, the C(aromatic)-P-C(aromatic) bond angles of 96.72 (9) and 97.29 (9)° are significantly smaller. The steric demands of the o-tolyl groups cause deviations from the bond lengths and angles reported for its phenyl analog.