1,2σ(3)λ(3)-Oxaphosphetanes and Their P-Chalcogenides—A Combined Experimental and Theoretical Study

Although 1,2σ(5)λ(5)-oxaphosphetanes have been known for a long time, the “low-coordinate” 1,2σ(3)λ(3)-oxaphosphetanes have only been known since their first synthesis in 2018 via decomplexation. Apart from ligation of this P-heterocycle to gold(I)chloride and the oxidation using ortho-chloranil, nothing on their chemistry has been reported so far. Herein, we describe the synthesis of new 1,2σ(3)λ(3)-oxaphosphetane complexes (3a–e) and free derivatives (4a–e), as well as reactions of 4a with chalcogens and/or chalcogen transfer reagents, which yielded the P-chalcogenides (14–16a; Ch = O, S, Se). We also report on the theoretical results of the reaction pathways of C-phenyl-substituted 1,2 σ(3)λ(3)-oxaphosphetanes and ring strain energies of 1,2σ(4)λ(5)-oxaphosphetane P-chalcogenides.