2,3,5,6-Tetramethyl-1H,4H-3a,6a-diaza-1,4-diphosphapentale ne and Its 1,4-Dichloro Derivative: Specifics of Synthetic Approaches

Reaction of 2-butanone azine with PCl3 in THF or methylene chloride gives a mixture of isomeric diazadiphosphapentalene dichlorides. Carrying out the reaction without solvent leads to 1,4-dichloro-2,5,3,6-tetramethyl-1H,4H-3a,6a-diaza-1,4-diphosphapentalene (DDPCl2) (32%) and the cleavage product of the heteropentalene backbone - 4,5-dimethyl-2H-1,2,3-diazaphospholium chloride (29%), while in acetonitrile the only reaction product is dichloride DDPCl2 (60%). The reduction of the latter with manganese powder in tetrahydrofuran leads to 2,5,3,6-tetramethyl-1H,4H-3a,6a-diaza-1,4-diphosphapentalene in 57% yield. The products were investigated by X-ray diffraction analysis and cyclic voltammetry method.