Unsaturated Four-Membered Phosphorus-Carbon Rings: From Organic to Coordination Chemistry

Abstract
The chemistry of 1,2-dihydrophosphetes and 1,2-dihydro-1,2-diphosphetes is comprehensively reviewed. Several applications such as the synthesis of tetraphosphafulvalenes and 1,3-diphospholyl anions are mentioned. The interconversion with open-chain 1-phospha- and 1,4-diphosphadienes is emphasized. The various coordination modes are discussed.