Cis- und trans-1-Phosphabicyclo[4.4.0]decan

Cis- and trans-1-Phosphabicyclo[4.4.0]decane A mixture of cis-( 5a ) and trans-1-phosphabicyclo [4.4.0] decane 5b has been prepared by free-radical cyclization of (CH₂ = CH? CH₂? CH₂)₂CH? PH₂ 10 . The isomers could be separated in a pure state. Stereostructures have been assigned by ¹³C n.m.r. at 153—302 K. Equilibration of 5a and 5b by u.v. irradiation gave ?G°₃₅ ≈? 0 kJ ° mol^?1 · Activation parameters for ring inversion of “cis” stereoisomer 5a and its “cis” P-sulfid 17a are found to be ΔG° = 41.9 kJ · mol^?1 and 39.7 kJ · mol^?1, respectively. Treatment of 5a and 5b with H₂O₂, sulfur, selenium, HSO₃F, CH₃I, CS₂, and Ni(CO)₄, respectively, yield the corresponding derivatives. ¹H, ¹³C, ³¹P, ⁷⁷Se n.m.r. and i.r. data are reported.