Fosfiinit

Fosfiinit, or phosphines, are a class of organophosphorus compounds characterized by a phosphorus atom bonded to three substituents and bearing a lone pair of electrons. The simplest member is phosphine (PH3); more practically encountered are tertiary phosphines such as triphenylphosphine (PPh3) and trialkylphosphines (e.g., PMe3, PCy3). They are typically colorless liquids or gases and are notable for their ability to act as ligands in coordination chemistry.

Structurally, phosphines feature a trigonal pyramidal geometry at phosphorus and serve as Lewis bases due to their lone pair. Electronic and steric properties can be tuned by changing the substituents on phosphorus, influencing both donor strength and steric demand. This tunability is summarized in concepts such as the Tolman cone angle, which captures the steric profile of a phosphine ligand.

Synthesis of fosfiinit generally involves alkylation or arylation of phosphorus halides, reduction of phosphine oxides, or related transformations. Common laboratory routes include converting phosphorus trihalides (like PCl3) with organomagnesium or organolithium reagents to give tertiary phosphines after workup. Phosphines can also be prepared by reducing phosphine oxides with suitable hydride or silane reagents.

Applications of fosfiinit are dominated by their role as ligands in homogeneous catalysis. They are used to stabilize metal centers in a wide range of reactions, including hydroformylation, hydrogenation, and various cross-coupling processes. The ability to tailor both electronic and steric properties makes phosphines among the most versatile ligands in organometallic chemistry.

Safety and handling note that many phosphines are air-sensitive and can be toxic or malodorous. PH3, in particular, is highly toxic and flammable. They are typically handled under inert atmosphere and stored to minimize oxidation to phosphine oxides.