1,1,1-Tris(diphenylphosphinomethyl)ethane, also called Triphos, is an organophosphorus compound with the formula CH<sub>3</sub>C[CH<sub>2</sub>PPh<sub>2</sub>]<sub>3</sub>. An air-sensitive white solid, it is a tripodal ligand ("three-legged") of idealized C<sub>3v</sub> symmetry. It was originally prepared by the reaction of sodium diphenylphosphide and CH<sub>3</sub>C(CH<sub>2</sub>Cl)<sub>3</sub>:
It forms complexes with many transition metals, usually as a tripodal ligand. Such complexes are used to analyze mechanistic aspects of homogeneous catalysts. For example, rhodium forms complexes with CH<sub>3</sub>C[CH<sub>2</sub>PPh<sub>2</sub>]<sub>3</sub> like [(triphos)RhCl(C<sub>2</sub>H<sub>4</sub>)], [(triphos)RhH(C<sub>2</sub>H<sub>4</sub>)], and [(triphos)Rh(C<sub>2</sub>H<sub>5</sub>)(C<sub>2</sub>H<sub>4</sub>)], provide model intermediates in the catalytic cycle for hydrogenation of alkenes.
Triphos sometimes behaves as a bidentate ligand. Illustrative cases include fac-[Mn(CO)<sub>3</sub>Br(÷<sup>2</sup>-triphos)] and [M(CO)<sub>4</sub>(÷<sup>2</sup>-triphos)], where M is Cr, Mo, or W. Triphos serves as a tridentate-bridging ligand in an icosahedral Au<sub>13</sub> cluster. The phosphine bridges three chlorogold(I) groups to form the tripod molecule of trichloro-1,1,1-(diphenylphosphinomethyl)ethanetrigold(I), CH<sub>3</sub>C[CH<sub>2</sub>PPh<sub>2</sub>AuCl]<sub>3</sub>.