Origins of Batch-to-Batch Variation: Organoindium Reagents from Indium Metal

Abstract

Yields of organoindium reagents synthesized from indium metal were previously reported to be highly dependent on metal batch and supplier due to the presence or absence of anticaking agent. Here, single-particle fluorescence microscopy established that MgO, an additive in some batches nominally for anticaking, significantly increased the physisorption of small-molecule organics onto the surface of the resulting MgO-coated indium metal particles. An inert and relatively nonpolar boron dipyrromethene fluorophore with a hydrocarbon tail provided a sensitive probe for this surface physisorption. SEM images revealed markedly different surface properties of indium particles either with or without MgO, consistent with their different physisorption properties observed by fluorescence microscopy. We further documented incomplete commercial bottle labeling regarding the presence and composition of this anticaking agent, both within our laboratory and previously in the literature, which may complicate reproducibility between laboratories. Trimethylsilyl chloride pretreatment, a step employed in a subset of reported synthetic procedures, removed the anticaking agent and produced particles with similar physisorption properties as commercial batches of indium powder distributed without the anticaking agent. These data indicate the possibility of an additional substrate/catalyst physisorption mechanism by which the anticaking agent may be influencing synthetic procedures that generate organoindium reagents from indium metal, in addition to simple anticaking.

Trimethylsilyl Chloride Aids in Solubilization of Oxidative Addition Intermediates from Zinc Metal

“…The dramatically lower lifetime of 2 compared to 1 is attributed to quenching by the zinc surface. [37,38] The substantially increased lifetime of 4 (τ solution = 4.6 ns) compared to 2 (τ surface � 0.8 ns) is attributed to removal of the organozinc from its proximity to the quenching zinc metal surface; the shorter lifetime of 4 (τ solution = 4.6 ns) compared to 1 (τ solution = 5.5 ns) is attributed to the presence of zinc(II) in molecular 4. [42,43] (See Scheme S3 for the regions of interest used for each measurement.…”

Exploring chemistry with single-molecule and -particle fluorescence microscopy

“…As chemists, we still do not generally know the answers to these questions. Single-particle fluorescent microscopy studies found differences in reactivity behaviors between individual nanoparticles [17,32], zeolite particles [13,53], metallic zinc [4,35], indium [58], particles in powders in addition to the growing polymer aggregates [41,42]. In fascinating recent work, Sambur identified that individual particles displayed different electrochromic dynamics, impacting the durability and speed of tinting of smart windows on the macroscale [22]; on account of the natural spectral changes of these particles, addition of a fluorescent imaging agent was not required for these measurements.…”

Reactivity Differences of Rieke Zinc Arise Primarily from Salts in the Supernatant, Not in the Solids

“… − The mechanistic causes of these reactivity differences remain, however, poorly understood . Without the ability to understand the cause of variation in different batches of Rieke zinc, , the rational selection of the best preparation by users is not straightforward, and the expansion of this useful chemistry to access new carbon–(pseudo)­halide bond insertion, polymers, and nanomaterials is impeded.…”