Synthesis and Reactivity of 2-Iodophosphinines

The synthesis of 2-iodophosphinines 5 ( a, parent compound; b, 4,5-dimethyl derivative) and of their pentacarbonyltungsten complexes 7 is described starting from dichloro(diiodomethyl)phosphine ( 2 ), which was prepared via alkylation of phosphorus trichloride with (diiodomethyl)magnesium chloride ( 1 ). The halogen−metal exchange reactions of 5a / b and 7a / b are reported: the lithiation reactions of 5a / b with n -BuLi were not successful. In contrast, the complexes 7a / b were converted to the corresponding lithium derivatives 11a / b with n -BuLi in THF at −100 °C. Derivatization of 11a / b with triphenyltin chloride furnished 13a / b, respectively. The reaction of 5b with magnesium in THF at room temperature led to the formation of 3,4-dimethylphosphinine ( 18 ) (41.5%), 4,4‘,5,5‘-tetramethyl-2,2‘-biphosphinine ( 16 ) (1.3%), and 2-(iodomagnesio)-4,5-dimethylphosphinine ( 17 ) (19.2%); 37% of the starting material had decomposed. In a reaction with zinc, 5b gave the organozinc derivatives 20 or 21 in THF/TMEDA or DMF, respectively. The same zinc insertion procedures were applied to 7b but did not furnish the pentacarbonyltungsten complexes 22 or 24 in a clean fashion. However, 22 could be prepared via complexation of 20 with (acetonitrile)pentacarbonyltungsten ( 6 ).