Selective synthesis of (3-ferrocenylprop-2-en-1-yl)-triphenylphosphonium iodide: crystal structure determination of two polymorphs

摘要

This work is part of a project studying the reactivity of a new ferrocenyl allylammonium salt, [3-(trimethylazaniumyl)prop-1-en-1-yl]ferrocene iodide, (1~+)·I~-, with different nucleophiles. With nitrogen-based nucleophiles, different ferrocenyl allylamine isomers have been synthesized successfully in good yield. Optimization of the basicity of the reaction medium has allowed selection of the best operating conditions to obtain the targeted isomer. In a similar way and in order to introduce phosphorus-containing functional groups, the reaction of ammonium salt (1~+)·I~- with a phosphorus nucleophile, namely triphenyl-phosphane, was attempted. It was then possible to isolate single crystals of (3-ferrocenylprop-2-en-1-yl)triphenylphosphonium iodide, [Fe(C_5H_5)(C_26H_23P)]I, which is shown to crystallize in two concomitant polymorphic forms, viz. a triclinic form, (I), in the space group P1, and a monoclinic form, (II), in the space group P2_1/c. In the inter-ion packing of polymorph (I), the cations form bilayer ribbons via C-H ??? pi and pi-pi stacking interactions. In polymorph (II), where pi-pi interactions do not occur, adjacent molecules are joined by C-H ??? pi interactions into a one-dimensional helical arrangement along the b axis.