In‐Situ Analysis of Anionic Coordination Polymerizations by Electrospray‐Ionization Mass Spectrometry

Abstract
Anionic coordination polymerizations proceed via highly reactive intermediates, whose in situ analysis has remained difficult. Here, we show that electrospray‐ionization mass spectrometry is a promising method to obtain detailed information on the polymerization process. Focusing on polymerization reactions of 1,3‐dienes initiated by CoCl2/RLi (R=Me, nBu, tBu, Ph), we directly observe the growing polymer chains and characterize the active anionic cobalt centers by gas‐phase fragmentation experiments. On the basis of these results, we suggest a plausible mechanism for the polymerization reaction. Moreover, the ESI mass spectra permit the determination of molecular weight distributions, which are in good agreement with those derived from NMR‐spectroscopic as well as MALDI mass‐spectrometric measurements, and afford a wealth of kinetic data.

Negative‐ion mode ESI mass spectrometry permits the direct observation of anionic polymers resulting from the reaction of 1,3‐dienes with CoCl2 and organolithium reagents.

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