Scope and Mechanism of Cooperativity at the Intersection of Organometallic and Supramolecular Catalysis

Abstract

ABSTRACT:The scope and mechanism of the microenvironmentcatalyzed C(sp 3 )−C(sp 3 ) reductive elimination from transition metal complexes [Au(III), Pt(IV)] is explored. Experiments detailing the effect of structural perturbation of neutral and anionic spectator ligands, reactive alkyl ligands, solvent, and catalyst structure are disclosed. Indirect evidence for a coordinatively unsaturated encapsulated cationic intermediate is garnered via observation of several inactive donorarrested inclusion complexes, including a crystallographically characterized encapsulated Au(III) cation. Finally, based on stoichiometric experiments under catalytically relevant conditions, a detailed mechanism is outlined for the dual supramolecular and platinumcatalyzed C−C coupling between methyl iodide and tetramethyltin. Determination of major platinum species present under catalytic conditions and subsequent investigation of their chemistry reveals an unexpected interplay between cis−trans isomerism and the supramolecular catalyst in a Pt(II)/Pt(IV) cycle, as well as several off-cycle reactions.

Gold Catalysis in (Supra)Molecular Cages to Control Reactivity and Selectivity

“…The reductive elimination reaction inside the Ga 4 L 6 cage was studied in more detail in a follow‐up paper . The influence of the spectator ligand PR 3 appeared not only to be of influence in the binding process of the decomposition product, but also the transition state of the reductive elimination was stabilized in the cavity to a larger extend when using PEt 3 instead of PMe 3 .…”

“…Nitschke presented an M 4 L 6 cage in which the ligands contained an NHC moiety that is coordinated to a gold chloride complex (Figure 9). [47] The resulting cage structure contains six gold complexes that each closely resemble the established gold catalyst [Au(IPr)Cl]. However, removal of the six chlorides using silver salts resulted in decomposition of the cage and the formation of gold nanoparticles, making this cage unsuitable for catalysis.…”

Gold‐Catalyzed Cross‐Coupling Reactions: An Overview of Design Strategies, Mechanistic Studies, and Applications

“…Using an anionic supramolecular assembly to encapsulate and activate the CÀCb ond-formingt ransitions tate was recently demonstrated as ap ractical way to accomplish fast dialkyl reductive elimination from low-coordinating Au and Pt centers. [330] The size of the phosphine li-Scheme66. Following Michaelis-Menten kinetics, rate enhancement on the order of approximately 10 7 ,reaching the activity of biological enzymes hasb een observed under optimal reactionc onditions.…”

“…(b) n-Butane elimination from cis-Me 3 PAuEt 2 I [330]. The cationic intermediate complex undergoes facile unimolecular reductive elimination to produce MeI.Synthesis of fluorinated molecules with selectiveC ÀFb onds is ahighly useful and challenging process.…”

Encapsulation of a Quinhydrone Cofactor in the Inner Pocket of Cobalt Triangular Prisms: Combined Light‐Driven Reduction of Protons and Hydrogenation of Nitrobenzene

“…[1] To match the high efficiency and selectivity of enzymatic systems,c hemists have used small molecules with defined hydrophobic cavities [2,3] that mimic the remarkable properties of enzyme active sites and emulate their enzymatic activities in catalyzing specific chemical transformations.S upramolecular chemistry using Werner-type hosts has displayed interesting recognition properties and reactivity reminiscent of natural enzymes, [4] such as the high kinetic rates of reactions performed in the confined spaces,o wing to the proximity effects imposed by the architectural pocket. [5,6] On the other hand, nature has developed millions of redox systems in which redox processes are catalyzed by numerous species of coenzymes. [7] Thef undamental transformations of biological syntheses include large numbers of redox events.…”