The reactions of alkylamino substituted phosphines with I2 and (Ph2Se2I2)2: structural features of alkylamino phosphonium cations.

TLDR: The reactions of the tris-dialkylamino phosphines and (nPr2N)3P, and the pyrrolidinyl substituted phosphines, with I2 and (Ph2Se2I2)2, have been reported and the crystal structures have all been determined.

Abstract: The reactions of the tris-dialkylamino phosphines (Et2N)3P and (nPr2N)3P, and the pyrrolidinyl substituted phosphines (C4H8N)3P and tBuP(NC4H8)2, with I2 and (Ph2Se2I2)2, have been reported. The reactions with diiodine lead to the formation of [R3PI]I adducts, which are essentially ionic, but show a tendency to display long, soft–soft, I⋯I interactions in the solid state. The crystal structures of [(Et2N)3PI]I, (1), [(nPr2N)3PI]I, (2), and [(C4H8N)3PI]I, (3), have all been determined, and display I⋯I interactions varying between 3.5170(6) and 3.6389(14) A. The analogous reactions with (Ph2Se2I2)2 lead to the formation of phenylseleno-phosphonium salts, [R3PSePh]I. The structures of [(C4H8N)3PSePh]I, (6) and [(C4H8N)2tBuPSePh] I, (7), have been determined and do not display any soft–soft interactions between the selenium and iodine atoms. All of the phosphonium salts represent examples of structures containing tris-dialkylamino phosphine fragments which show no “special” nitrogen atom, i.e. all three nitrogen atoms are planar. This type of arrangement is usually observed when a C3 symmetric conformation is observed, (which is the case for 1 and 2), but not for the (C4H8N)3P adducts 3 and 6, where the conformation is closer to Cs, although the nitrogen atoms are still essentially planar. The P–N bonds in all the compounds reported herein are short, ranging between 1.599(12) A and 1.643(12) A, and are consistent with the previously reported short P–N bonds in phosphonium salts featuring tris-dialkylamino substituted phosphines.