From Boron to Bismuth: The Pre-transmetalation Complex in the Aryl Transfer

TL;DR

This paper reports the first structural evidence of pre-transmetalation complexes in aryl transfer from boron to bismuth.

Contribution

The study identifies two new pre-transmetalation complexes bridged by F– or OH– and proposes two general transmetalation pathways.

Findings

Two unprecedented pre-transmetalation complexes linking B and Bi were structurally characterized.

Two general transmetalation pathways (neutral and ionic) were established based on d-block element studies.

The findings provide guidelines for successful transmetalation of diverse arylboron species.

Abstract

B-to-Bi transmetalation is increasingly encountered as
a key organometallic
step in Bi-based protocols. Yet, akin to transition metal complexes,
obtaining structural evidence of pre-transmetalation intermediates
that lead to the aryl transfer from B to a metal is challenging and
rare. Herein, we provide structural characterization of two unprecedented
pre-transmetalation complexes linking B and Bi through a F–
or an OH– bridge. Inspired by earlier studies on d-block elements,
we establish two general pathways by which transmetalation can occur:
the neutral and the ionic pathway. These studies delineate the requirements for successful transmetalation
of a wide range of unprecedented arylboron species.

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