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Abstract: Essentially no information is known about the behavior of individual molecular catalysts under reaction conditions. This is a result of the averaging inherent to traditional analytical techniques. Herein, a combined fluorescence microscopy and 1H NMR spectroscopy study reveals that unique (that is, non‐ensemble averaged) distributions and time‐variable kinetics from molecular ruthenium catalysts within growing polynorbornene occur and are detectable between 10−9  m and 10−6  m of substrate, surprisingly just 1000‐fold less concentrated than a typical laboratory bench‐scale reaction. The kinetic states governing single‐turnover events are determinable by overlay of the signal arising from individual monomer insertion reactions with that from polymer growth from neighboring catalysts. [ABSTRACT FROM AUTHOR]

Abstract: Catalytic cycles are typically depicted as possessing time‐invariant steps with fixed rates. Yet the true behavior of individual catalysts with respect to time is unknown, hidden by the ensemble averaging inherent to bulk measurements. Evidence is presented for variable chemical kinetics at individual catalysts, with a focus on ring‐opening metathesis polymerization catalyzed by the second‐generation Grubbs’ ruthenium catalyst. Fluorescence microscopy is used to probe the chemical kinetics of the reaction because the technique possesses sufficient sensitivity for the detection of single chemical reactions. Insertion reactions in submicron regions likely occur at groups of many (not single) catalysts, yet not so many that their unique kinetic behavior is ensemble averaged. [ABSTRACT FROM AUTHOR]

Multiple active individual molecular ruthenium catalysts have been pinpointed within growing polynorbornene, thereby revealing information on the reaction dynamics and location that is unavailable through traditional ensemble experiments. This is the first single-turnover imaging of a molecular catalyst by fluorescence microscopy and allows detection of individual monomer reactions at an industrially important molecular ruthenium ring-opening metathesis polymerization (ROMP) catalyst under synthetically relevant conditions (e.g. unmodified industrial catalyst, ambient pressure, condensed phase, ca. 0.03 m monomer). These results further establish the key fundamentals of this imaging technique for characterizing the reactivity and location of active molecular catalysts even when they are the minor components. [ABSTRACT FROM AUTHOR]