Coordination templated [2+2+2] cyclotrimerization in a porous coordination framework

Abstract

Controlling chemical reactions by the supramolecular confinement effects of nanopores has attracted great attention. Here we show that open metal sites in porous coordination frameworks can constitute more powerful and strict templates for precision syntheses. A Fe(III) dicarboxylate framework functionalized with triangularly arranged metal sites is used to accomplish [2+2+2] cyclotrimerization reactions for organonitrile, alkyne and alkene monomers bearing a geometrically suitable pyridyl group. In situ single-crystal X-ray diffraction facilitates the direct observation of such a coordination templated reaction, before cylcotrimerization, the monomer coordinates at the Fe(III) centre by its pyridyl donor, which forces three unsaturated groups to gather around a position very similar with that of the desired covalent cyclic trimer. After the reaction, the trimers serve as tripodal ligands to perfectly fix the Fe(III) ions and the whole crystal to generate an exceptionally rigid and porous material with large surface area coupled with guest-proof zero thermal expansion.

A Strategy for Constructing Pore‐Space‐Partitioned MOFs with High Uptake Capacity for C2 Hydrocarbons and CO2

“…For comparison, we also sought to use 4, 4′‐dipyridyldisulfide (dpds) as PPA, but found that the same dps‐pacs could be obtained. These results showed that MIL‐88 type structure might have better fit for dps …”

Pore‐Environment Engineering in Multifunctional Metal‐Organic Frameworks

“…Wei et al . used the PSE&I strategy to remove and insert ligands in MIL‐88 . The regular hexagonal channels in MIL‐88 make the open metal sites formed after the removal of the coordinated water molecules in the Fe 3 (μ 3 ‐O) cluster by heating.…”

“…The trimeric products (MIL‐88B) with 4‐pyCN (a), 4‐pyC 2 H (b), and 4‐pyC 2 H 3 (c) as monomers. Reproduced with permission . Copyright © 2015, Springer Nature.…”

Conceptual Advances from Werner Complexes to Metal–Organic Frameworks

“…This alignment is ideally suited to fix three molecules in the ideal configuration to facilitate trinuclear reactions such as [2 + 2 + 2] cycloadditions. 31 The power of this approach was illustrated by the successful incorporation and trimerization of three different kinds of linker: 4-cyanopyridine, 4-ethynylpyridine, and 4-vinylpyridine. Heating of the ligand exchanged MOF initiates the [2 + 2 + 2] cycloaddition reactions of the incorporated molecules in the pores which leads to the formation of triazine, benzene, and cyclohexane moieties, respectively ( Figure 4 c–e).…”