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T. C. Johnstone
Most notable is the reversible activation of H 2 and the catalytic hydrogenation chemistry it enables [4, 5]. Other important examples include the capture of NO and N 2 O
[6, 7] and the capture and reduction of SO 2 [8], CO [9], and CO 2 [10].
Although this chemistry will inevitably find important synthetic applications,
perhaps the greatest contribution of FLP chemistry has been in providing chemists
with a new paradigm through which to view, interpret, and predict chemical reactivity
[11]. Despite having firm roots in main-group inorganic chemistry, an ever-widening
scope of systems continues to be interpreted in an FLP manner, including transitionmetal chemistry, enzymatic catalysis, and heterogeneous catalysis [12]. By allowing
chemical systems to be viewed in a new light, the FLP concept is enabling the
discovery of new chemistry [13, 14].
Investigation into the very nature of FLP chemistry has complemented the
discovery of new chemical transformations with equally important novel fundamental knowledge. Theoretical and experimental investigations into the mechanism
of H 2 activation led to the postulation of the encounter complex, which might play
a role across a range of different chemistries [15–18]. Recent studies that uncovered the single-electron counterpart to classical two-electron FLP chemistry have
also suggested that these two paradigms might simply reflect extreme limits of a
unifying underlying continuum [19–22]. In a similar manner, investigation into the
FLP reactivity of Lewis pairs that are not fully frustrated has revealed that the key to
observing FLP chemistry is accessing the dissociated acid and base [23–25]. In the
case of a classical FLP, steric bulk drives the dissociation to completion, but in cases
far from this limit, FLP chemistry can be observed, provided that the Lewis adduct
is in equilibrium with the dissociated acid and base. The presence and importance of
these equilibria, as well as the potential role of dispersive interactions in stabilizing
encounter complexes, provide a clear path for introducing FLP chemistry into the
undergraduate inorganic chemistry curriculum.
Although there are no reports in the chemical education literature on best practices for teaching FLP chemistry, anecdotal data suggest that it has generally been
reserved for graduate or upper-division undergraduate courses. In these contexts,
it is frequently introduced as an example of cutting-edge research. FLP chemistry certainly qualifies as such and incorporating research topics into undergraduate instruction can be a valuable strategy for not only engaging students, but also
engaging faculty as well [26]. In very recent years, FLP chemistry has even started
to appear in undergraduate inorganic chemistry textbooks, often as an “advanced
topic” or “research application” of the fundamental Lewis acid–base chemistry being
discussed [27]. One of the most compelling features of FLP chemistry is, however,
its simplicity. Lower-division undergraduate students have already been exposed to
all of the key material needed to grasp the FLP concept. If the students have the tools
to understand the material, the instructor’s primary task is to find a compelling and
constructive way to introduce them to that material.
As noted above, research into the role that dynamic equilibrium plays in the
FLP chemistry exhibited by associated Lewis pairs revealed that FLP chemistry
is a natural—even inevitable—extension of classical Lewis acid–base chemistry.
Consideration of these equilibria provides a means of smoothly incorporating the
T. C. Johnstone
Most notable is the reversible activation of H 2 and the catalytic hydrogenation chemistry it enables [4, 5]. Other important examples include the capture of NO and N 2 O
[6, 7] and the capture and reduction of SO 2 [8], CO [9], and CO 2 [10].
Although this chemistry will inevitably find important synthetic applications,
perhaps the greatest contribution of FLP chemistry has been in providing chemists
with a new paradigm through which to view, interpret, and predict chemical reactivity
[11]. Despite having firm roots in main-group inorganic chemistry, an ever-widening
scope of systems continues to be interpreted in an FLP manner, including transitionmetal chemistry, enzymatic catalysis, and heterogeneous catalysis [12]. By allowing
chemical systems to be viewed in a new light, the FLP concept is enabling the
discovery of new chemistry [13, 14].
Investigation into the very nature of FLP chemistry has complemented the
discovery of new chemical transformations with equally important novel fundamental knowledge. Theoretical and experimental investigations into the mechanism
of H 2 activation led to the postulation of the encounter complex, which might play
a role across a range of different chemistries [15–18]. Recent studies that uncovered the single-electron counterpart to classical two-electron FLP chemistry have
also suggested that these two paradigms might simply reflect extreme limits of a
unifying underlying continuum [19–22]. In a similar manner, investigation into the
FLP reactivity of Lewis pairs that are not fully frustrated has revealed that the key to
observing FLP chemistry is accessing the dissociated acid and base [23–25]. In the
case of a classical FLP, steric bulk drives the dissociation to completion, but in cases
far from this limit, FLP chemistry can be observed, provided that the Lewis adduct
is in equilibrium with the dissociated acid and base. The presence and importance of
these equilibria, as well as the potential role of dispersive interactions in stabilizing
encounter complexes, provide a clear path for introducing FLP chemistry into the
undergraduate inorganic chemistry curriculum.
Although there are no reports in the chemical education literature on best practices for teaching FLP chemistry, anecdotal data suggest that it has generally been
reserved for graduate or upper-division undergraduate courses. In these contexts,
it is frequently introduced as an example of cutting-edge research. FLP chemistry certainly qualifies as such and incorporating research topics into undergraduate instruction can be a valuable strategy for not only engaging students, but also
engaging faculty as well [26]. In very recent years, FLP chemistry has even started
to appear in undergraduate inorganic chemistry textbooks, often as an “advanced
topic” or “research application” of the fundamental Lewis acid–base chemistry being
discussed [27]. One of the most compelling features of FLP chemistry is, however,
its simplicity. Lower-division undergraduate students have already been exposed to
all of the key material needed to grasp the FLP concept. If the students have the tools
to understand the material, the instructor’s primary task is to find a compelling and
constructive way to introduce them to that material.
As noted above, research into the role that dynamic equilibrium plays in the
FLP chemistry exhibited by associated Lewis pairs revealed that FLP chemistry
is a natural—even inevitable—extension of classical Lewis acid–base chemistry.
Consideration of these equilibria provides a means of smoothly incorporating the