Triphos

Bis(diphenylphosphinoethyl)phenylphosphine

Bis(diphenylphosphinoethyl)phenylphosphine is called triphos, is a linear tridentate triphosphine. It is prepared by the free-radical-catalysed addition of phenylphosphine to vinyldiphenylphosphine:

2 Ph₂PCH=CH₂ + H₂PPh → [Ph₂PCH₂CH₂]₂PPh

This isomer of triphos is flexible and can bind to an octahedral metal center give either a facial or meridional isomers. Some derivatives are square planar complexes of the type [MX(triphos)]⁺ (M = Ni, Pd, Pt; X = halide).

1,1,1-Tris(diphenylphosphinomethyl)ethane

1,1,1-Tris(diphenylphosphinomethyl)ethane is also called triphos. It is a tripodal ligand ("three-legged") of idealized C3v symmetry. It is prepared by the reaction of sodium diphenylphosphide and CH₃C(CH₂Cl)₃:

3 Ph₂PNa + CH₃C(CH₂Cl)₃ → CH₃C[CH₂PPh₂]₃ + 3 NaCl

It forms complexes with many transition metals. It usually functions as a tripodal ligand that occupies three adjacent coordination sites. Triphos complexes often exhibit high thermal stability. Such complexes are used to analyze mechanistic aspects of homogeneous catalysts. For example, rhodium forms complexes with CH₃C[CH₂PPh₂]₃ like [(triphos)RhCl(C₂H₄)], [(triphos)RhH(C₂H₄)], and [(triphos)Rh(C₂H₅)(C₂H₄)], provide model intermediates in the catalytic cycle for hydrogenation of alkenes.

Triphos sometimes behaves as a bidentate-chelating ligand. Illustrative cases include fac-[Mn(CO)₃Br(η²-triphos)] and [M(CO)₄(η²-triphos)],where M is Cr, Mo, or W. Triphos serves as a tridentate-bridging ligand in an icosohedral Au₁₃ cluster. The phosphine bridges three chlorogold(I) groups to form the tripod molecule of trichloro-1,1,1-(diphenylphosphinomethyl)ethanetrigold(I), CH₃C[CH₂PPh₂AuCl]₃.

Bis(diphenylphosphinophenyl)phenylphosphine

Like bis(diphenylphosphinoethyl)phenylphosphine, bis(diphenylphosphinophenyl)phenylphosphine is a linear tridentate ligand, but it is more rigid and more air stable. It is prepared from o-lithiated triphenylphosphine:

2 LiC₆H₄PPh₂ + PhPCl₂ → PhP[C₆H₄PPh₂]₂