Metallopolymers via Thermal Dealkylation of Unstrained Bisphosphanylferrocene Precursors

Abstract

Ferrocenylene-bridged polyphosphanes [Fc'P 2 ] n t Bu 2 and [Fc'P 2 ] n (Fc' = 1,1'-ferrocenediyl; t Bu = tert-butyl, previously prepared via thermal ring expansion polymerization from strained ferrocenophane precursors, are reported to be accessible from unstrained secondary phosphanes. Thermal reaction and polymerization of Fe(C 5 H 4 -PH t Bu) 2 proceed through the elimination of t BuH, and consequent formation of t Bu-substituted diphospha[2]FCP, along with ferrocene substituted cyclic P 4 -species, and di-t Bu-substituted linear P 4 -species. The resulting polymer shows similar 13 C and 31 P solid-state NMR, IR, and UV-Vis spectra, as well as elemental analyses, when compared to those of authentic samples of previously published [Fc'P 2 ] n t Bu 2 and [Fc'P 2 ] n obtained via strained ferrocenophanes. On the contrary, thermal reaction of all-t Bu-substituted tertiary phosphane Fc'(P t Bu 2 ) 2 entails loss of the P-containing moiety along with formation of Fc t Bu instead of polymeric material. Thermodynamic assessment of the decomposition pathways of both precursors based on density functional theory calculations is consistent with the experimental findings. Overall, the unstrained 1,1'-ferrocenylene bridged secondary bisphosphane provides a simplified approach for thermal polymerization to linear onedimensional P n -chains.