chlorophosphines

Chlorophosphines are a class of organophosphorus compounds characterized by a phosphorus-chlorine bond and two organic substituents on phosphorus, giving the general formula R2PCl. The P center is trivalent and the oxidation state of phosphorus is +1. Common examples include chlorodiphenylphosphine (Ph2PCl) and chlorodiisopropylphosphine (iPr2PCl). The R groups may be aryl or alkyl.

Synthesis: Chlorophosphines are typically prepared by chlorination of secondary phosphines R2PH using chlorinating agents such as thionyl chloride (SOCl2) or oxalyl chloride ((COCl)2) under inert conditions. They can also be obtained by chlorination of other phosphorus-containing precursors followed by selective oxidation, depending on the substrate.

Reactions and applications: The P–Cl bond is reactive toward nucleophiles, enabling substitution by Grignard or organolithium reagents to give tertiary phosphines (R2PR), as well as reaction with amines or alkoxides to form phosphoramide or phosphinite derivatives. This versatility makes chlorophosphines useful precursors for preparing a broad range of phosphorus ligands employed in homogeneous catalysis and organophosphorus synthesis. They can also be hydrolyzed by water to yield phosphine oxides or phosphinous acids and hydrogen chloride, reflecting their moisture sensitivity.

Handling and safety: Chlorophosphines are typically moisture- and air-sensitive. They should be prepared and stored under inert atmosphere, away from moisture. They can be toxic and corrosive, and hydrolysis products release HCl.