Ring-Opening Polymerization of a Strained [3]Nickelocenophane: A Route to Polynickelocenes, a Class of S = 1 Metallopolymers

Abstract

We report the synthesis, reactivity studies, and ring-opening polymerization of a tricarba[3]nickelocenophane. The resulting green polynickelocene (5) possesses a -(CH2)3- spacer between the nickelocene units and is shown to be of high molecular weight. SQUID magnetometry measurements indicate that 5 is a macromolecular material with an S = 1 repeat unit.

Main-chain metallopolymers at the static–dynamic boundary based on nickelocene

“…Paramagnetic polynickelocene 7 was also found to exhibit significant antiferromagnetic spin-spin interactions, with evidence for intramolecular spinspin coupling along the polymer chains. 29 Herein we demonstrate that, as a consequence of the weaker Ni-Cp bonds (M-Cp dissociation energy is 250 kJ mol -1 for nickelocene vs. 305 kJ mol -1 for ferrocene), 31 polynickelocene 7 can exist in either a static or labile state, and in the latter case forms a dynamic equilibrium with monomer 5 and small amounts of cyclic oligomers 6x, under a range of conditions (Fig. 1d).…”

“…The β protons of monomer 5 were observed at -29.0 ppm (α protons are not observed, as reported previously). 29 Integration of the shifts corresponding to Cp protons at high field after 24 h indicated that ca. 69% of the [3] (Fig.…”

“…The studies also showed that the rate of polymer chain scission is relatively slow, even in polar and coordinating solvents, and this was confirmed by microrheological studies, which indicated that the polynickelocene 7 behaves as a static material on the relatively short rheological timescale at room temperature. Polynickelocene 7 is a rare example of a readily accessible and easily handled soluble magnetic polymetallocene, and further development of this and analogous materials will be of considerable interest with respect to their responsive, magnetic, 29 and redox properties (see Supplementary Figs 20-22). …”

“…In contrast, we recently showed that tricarba [3]nickelocenophane (5) is significantly more tilted (α = 16.6°) and undergoes spontaneous ROP in pyridine at ambient temperature to yield the soluble magnetic main chain polynickelocene 7, containing S = 1 spin centres. 29 This material was shown to be of high molar mass (weight average molar mass Mw = ca. 40,000 g mol -1 ) based on dynamic light scattering (DLS) studies in THF, and analysis by MALDI-TOF indicated the presence of both cyclic and linear components.…”

Synthesis and Solution Self‐Assembly of Polyisoprene‐block‐poly(ferrocenylmethylsilane): A Diblock Copolymer with an Atactic but Semicrystalline Core‐Forming Metalloblock

“…1 Thus, analogues of PFS with other elements in the bridge or containing different metals to iron (in some cases in combination with alternative π-hydrocarbon ligands) have been prepared and their ROP has been successfully demonstrated in a growing number of cases. This provides a route to new and fascinating metallopolymers with modified properties, 222,[399][400][401][402][403][404][405] and studies of these materials are likely to constitute a broad new area of future research.…”