phosphinebased

Phosphine-based compounds refer to chemical substances that contain the phosphine functional group PR3 or are derived from it. The term is most often used to describe phosphine ligands, which are neutral, two-electron donors that coordinate to metal centers in coordination and organometallic chemistry. Common examples include triphenylphosphine (PPh3) and many substituted phosphines used to tune reactivity and selectivity in catalysis.

Structurally, phosphines vary by the size and electronics of the R substituents. They can be primary, secondary, or tertiary; steric bulk is described by parameters such as the cone angle, while electronic properties are characterized by metrics like the Tolman electronic parameter. They are typically air-sensitive and can be oxidized to phosphine oxides upon exposure to air and moisture; many phosphines require inert atmosphere handling.

In metal complexes, phosphine ligands donate electron density to the metal through the P lone pair and can engage in back-donation from metal d-orbitals, stabilizing low-oxidation-state metals and enabling catalytic steps such as oxidative addition and reductive elimination. Phosphine-based ligands are central to many catalytic processes, including hydrogenation, hydroformylation, cross-coupling (Suzuki, Negishi, Kumada), and other C–H activation reactions. Notable examples include Wilkinson's catalyst with triphenylphosphine ligands and chiral phosphines such as BINAP used in enantioselective hydrogenations. Bidentate and multidentate phosphines (e.g., dppe, dppf, BINAP) create defined bite angles that influence reactivity and selectivity.

Synthesis and handling: phosphines are prepared by phosphorylation or substitution of precursor chlorophosphines. They are often air- and moisture-sensitive, requiring inert-atmosphere techniques; safety considerations include potential toxicity of some phosphines and the hazardous nature of phosphine gas if released.