Supramolecular Host-Selective Activation of Iodoarenes by Encapsulated Organometallics

Abstract

Supramolecular hosts offer defined micro-environments that facilitate selective host-guest interactions, enabling reactivity that would otherwise be challenging in bulk solution. While impressive rate enhancements and selectivities have been reported, similar reactivity can often be accessed through modifications of reaction conditions even in the absence of the host. We report here an oxidative addition of aryl halides across the metal centers in Cu(I) and Pd(II) organometallics that is assisted by the presence of a supramolecular host, realized via electrostatic stabilization and increased local substrate concentrations. When reaction conditions were screened to assess background reactivity, alternative reactivity (typically decomposition) resulted, indicating that encapsulation led to host-selective reaction trajectories.

A Promising Approach for Controlling the Second Coordination Sphere of Biomimetic Metal Complexes: Encapsulation in a Dynamic Hydrogen‐Bonded Capsule

“…From this experiment, no clear differenceb etween the four halide anions can be established. 19 FNMR experiments performed with NBu 4 Fs how al arge shift of the resonance of the fluoride anion (from À128.9 ppm for NBu 4 Ft oÀ113.0 ppm in presence of the encapsulated complex) andi ndicate an interaction between the capsule and the anion (FigureS38). These anions seem to be equally involvedi nt he final assembly [Zn(TMPA)ClÀX@1 6 ], al egitimate interpretation being that they are either co-encapsulated or parto ft he capsule itself by replacing aw ater molecule.…”

“…The 1 HNMR signals for the assemblies with the perchlorate or triflate complexes indicate mostly as ymmetrical speciesb ut while only one major isomer is detectable by lookinga tt he CH 2 region for the triflate case, up to three isomersa re present for the perchlorate (Figures S30 to S35). Interestingly, 19 FNMR experiments show that the chemical shift for the triflate anion is shiftedb yc a. + 1ppm in the presence of the capsule, indicating the possible co-encapsulation of the triflate anion (Figure S36).…”

“…[15] The Raymond andT oste groups have intensively studied the encapsulation of metal complexes in anionic tetrahedral coordination cages and have highlightedh ost-selective reaction pathways. [16][17][18][19] Other examples make use of ac apsule assembled from six resorcin [4]arene molecules and eight water molecules held together by al arge network of hydrogen bonds. [20] Hence, the groups of Reek and Scarso established that the encapsulation in this capsuleo famonocationic NHC-gold complex influenced its catalytic activity.…”

Modeling the Reaction of Carboxylic Acids and Isonitriles in a Self‐Assembled Capsule

“…In the presence of such hosts, selectivity, rate acceleration, and even catalysis have been observed for a wide range of chemical transformations not readily attained in solution. Examples include cyclizations, Diels–Alder reactions, C−X activation, rearrangements, cycloadditions, olefin oxidation and metathesis, ring opening, condensation, hydrolysis, and hydration . In short, confinement controls reactivity.…”

A Supramolecular Strategy for Selective Catalytic Hydrogenation Independent of Remote Chain Length

“…1–6 This has been demonstrated in a number of instances ranging from organic to organometallic trans-formations. 7–16 In one important example, supramolecular support of a metal-mediated hydroformylation reaction leads to a change in the selectivity of the transformation through the steric and secondary interactions achieved by a supramolecular scaffold (Figure 1a). 17–21 Our group has also demonstrated the ability of a host-encapsulated rhodium (1) and ruthenium catalyst to perform isomerization of allylic alcohols to aldehydes (Figure 1b).…”