The Mechanism of the Stille Reaction Investigated by Electrospray Ionization Mass Spectrometry

Abstract

On-line monitoring of Stille reactions was performed via direct infusion electrospray ionization mass spectrometry (ESI-MS) and its tandem version (ESI-MS/MS). When operated in the positive ion mode, ESI(+)-MS was able to transfer, directly from solution to the gas phase, the species involved in all main steps of a Stille reaction, that is, the catalytically active palladium species Pd(PPh3)2, in its molecular ion form as well as the key cationic Pd(II) intermediates, including cyclic IPd-(CH2CH)Sn species. When searching for anionic species, ESI(-)-MS monitoring showed I- as the only anion detectable in the reaction medium. A detailed catalytic cycle for a Stille reaction was elaborated in which reaction intermediates and the previously elusive catalytically active Pd(0) species are shown in association with the respective ionic species intercepted by ESI-MS and further characterized by ESI-MS/MS.

Online Monitoring of Polymerizations: Current Status

“…Mostly the mixing tee is connected to the ionization probe with a fused-silica capillary providing residence times from 0.7 to 28 s in a continuous flow mode by varying the length of the transfer capillary. [66][67][68][69][70][71][72] Continuous online MS monitoring of polymerization reactions was first made available by Santos and Metzger. They investigated the mechanism of the homogeneously catalyzed Ziegler-Natta polymerization of ethane and Brookhart polymerization of alkenes in early stages of the polymerization.…”

Palladium Intermediates in Solution

“…However, Santos, Eberlin et al[37] undertook an ESI-MS/MS investigation of a Stille cross-coupling in their study of 3,4-dichloroiodobenzene (40c) and vinyltributyltin (41) using Pd(PPh 3 ) 4 as the catalyst (Scheme 7.18 and…”

Stille cross‐coupling reaction using Pd/BaSO4 as catalyst reservoir

“…A dimethylglioxime test for Pd species in the ethanol-water solution after decantation and product extraction gave a positive, Quite recently Eberlin's group [26] disclosed their results on the investigation of the mechanism of the Stille reaction and detected several different intermediates, including palladiumcontaining phosphines, including Pd(PPh 3 ) 2 species, [27] and palladium complexes with acetonitrile. The present reaction pathway must be very similar, although it was proved in the present paper that the reaction proceeded well in the absence of phosphines (Scheme 2).…”