2‐Bromophospholide Ions: Synthesis and Theoretical Study

DFT calculations at the B3 LYP/6–311++G(3df,2p) level indicate that the 2‐bromophospholide ion could be stable toward self‐arylation as a result of the lowered nucleophilicity of the in‐plane phosphorus lone pair (the corresponding σ P orbital is lowered by 0.7 eV compared with the corresponding orbital of the parent phospholide ion, and the negative charge at P is reduced from −0.435 to −0.369 e). Accordingly, the synthesis of 2‐bromo‐3,4‐dimethylphospholide was successfully carried out by quantitative base‐induced dealkylation of 2‐bromo‐1‐(2‐ethoxycarbonylethyl)‐3,4‐dimethylphosphole. This ion reacts with FeCl 2 to give the corresponding 2,2′‐dibromo‐3,3′,4,4′‐tetramethyl‐1,1′‐diphosphaferrocene as a poorly stable mixture of meso ‐ and rac ‐diastereomers in 18 % yield.