The crystal structure of the title compound, [Pt(C(8)H(18)P(2))(C(9)H(21)P)(C(18)H(15)P)] or [(Ph(3)P)((t)Bu(2)PMe)Pt(eta(2)-(t)Bu(2)PP)], contains four molecules in the asymmetric unit with slightly different conformations. The P-P distances in the (t)Bu(2)PP ligands are similar for all four molecules [2.0661 (13)-2.0678 (13) A] and indicate a multiple character of the P-P bond in the (t)Bu(2)PP ligand. Molecules of the asymmetric unit can be assembled into a tetrahedron that fulfils the requirements for a rhombic disphenoid. The coordination of the Pt atom in all four molecules is square planar, with r.m.s. deviations from the PtP(4) planes in the range 0.03-0.05 A. All planes of the PtP(4) groups are approximately parallel to the ab plane of the unit cell. The structure represents an unusual unsymmetrical platinum phosphinidene derivative.