Bismuth has recently
been shown to be able to maneuver between
different oxidation states, enabling access to unique redox cycles
that can be harnessed in the context of organic synthesis. Indeed,
various catalytic Bi redox platforms have been discovered and revealed
emerging opportunities in the field of main group redox catalysis.
The goal of this perspective is to provide an overview of the synthetic
methodologies that have been developed to date, which capitalize on
the Bi redox cycling. Recent catalytic methods via low-valent Bi(II)/Bi(III),
Bi(I)/Bi(III), and high-valent Bi(III)/Bi(V) redox couples are covered
as well as their underlying mechanisms and key intermediates. In addition,
we illustrate different design strategies stabilizing low-valent and
high-valent bismuth species, and highlight the characteristic reactivity
of bismuth complexes, compared to the lighter
p
-block
and
d
-block elements. Although it is not redox catalysis
in nature, we also discuss a recent example of non-Lewis acid, redox-neutral
Bi(III) catalysis proceeding through catalytic organometallic steps.
We close by discussing opportunities and future directions in this
emerging field of catalysis. We hope that this Perspective will provide
synthetic chemists with guiding principles for the future development
of catalytic transformations employing bismuth.