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A phosphite ligand such as $\mathrm{P}(\mathrm{OR}{)}_3$ binds through a phosphorus lone pair and can accept pi backbonding. Its donation and acceptance differ from those of both phosphine ligands and carbonyl ligands.

Triphenyl phosphite is $\mathrm{P}(\mathrm{OPh}{)}_3$, a neutral phosphorus donor used as a phosphite ligand.