Issue 6, 2022

Solvent coordination to palladium can invert the selectivity of oxidative addition

Abstract

Reaction solvent was previously shown to influence the selectivity of Pd/PtBu3-catalyzed Suzuki–Miyaura cross-couplings of chloroaryl triflates. The role of solvents has been hypothesized to relate to their polarity, whereby polar solvents stabilize anionic transition states involving [Pd(PtBu3)(X)] (X = anionic ligand) and nonpolar solvents do not. However, here we report detailed studies that reveal a more complicated mechanistic picture. In particular, these results suggest that the selectivity change observed in certain solvents is primarily due to solvent coordination to palladium. Polar coordinating and polar noncoordinating solvents lead to dramatically different selectivity. In coordinating solvents, preferential reaction at triflate is likely catalyzed by Pd(PtBu3)(solv), whereas noncoordinating solvents lead to reaction at chloride through monoligated Pd(PtBu3). The role of solvent coordination is supported by stoichiometric oxidative addition experiments, density functional theory (DFT) calculations, and catalytic cross-coupling studies. Additional results suggest that anionic [Pd(PtBu3)(X)] is also relevant to triflate selectivity in certain scenarios, particularly when halide anions are available in high concentrations.

Graphical abstract: Solvent coordination to palladium can invert the selectivity of oxidative addition

Supplementary files

Article information

Article type
Edge Article
Submitted
25 Okt. 2021
Accepted
21 Dec. 2021
First published
22 Dec. 2021
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2022,13, 1618-1628

Solvent coordination to palladium can invert the selectivity of oxidative addition

E. K. Elias, S. M. Rehbein and S. R. Neufeldt, Chem. Sci., 2022, 13, 1618 DOI: 10.1039/D1SC05862B

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