4 Conclusions
Monometallic and heterobimetallic CBER mechanisms are a specific class of
synthetic systems which permit linear, quadratic and bilinear reaction rate terms.
It is possible to classify the basic structures. CBER mechanisms possess mononuclear sequences and a dinuclear sequence of intermediates. In addition there are
steps to transform mononuclear intermediates into dinuclear intermediates and
dinuclear intermediates back into mononuclear intermediates. One of the main
synthetic advantages of a CBER mechanism is associated with the potential for
tremendous rate increases due to the binuclear elimination step. This in turn can
lead to much more efficient synthetic use of a precious metal, either by taking
advantage of bilinear kinetics or quadratic kinetics.
A considerable emphasis of this chapter was to highlight the need for in situ
spectroscopic measurements in order to confirm the observable speciation present
and hence reaction network. Another strong emphasis was given to the fact that the
non-linear CBER mechanism provides a fertile area to apply quite advanced and
seldom used mathematical tools to catalysis. Thus the Feinberg criteria indicate that
these systems are stable and not oscillatory, the Horiuti criteria will help to decide
how many terms needed to be included in any comprehensive model by enumerating all independent pathways to products, and the Wegschieder criteria help to
clarify that the cycles in the CBER are not, by any means, independent. As catalysis
moves from simple unicyclic mechanisms to more complex and potentially
non-linear mechanisms, additional tools will be needed to meet the challenges of
better understanding these systems and to make better use of these systems
synthetically.
Acknowledgement The author would like to thank the Agency for Science Technology and
Research for generous support of this research. The author would also like to thank Dr Marco
Kla ¨hn for his recent and extensive computational work concerning CBER and allowing the
inclusion of Fig. 22.
References
1. van Santen RA, Neurock M (2006) Molecular heterogeneous catalysis: a conceptual and
computational approach. Wiley-VCH, Weinheim
2. Illanes A (ed) (2008) Enzyme biocatalysis: principles and applications hardcover. Springer,
Heidelberg
3. Waser M (2012) Asymmetric organocatalysis in natural product syntheses. Springer,
Heidelberg
4. Erker G, Stephen DW (2013) Frustrated Lewis Pairs II: expanding the scope. Springer,
Heidelberg
5. Parshall GW, Ittel SD (1992) Homogeneous catalysis: the applications and chemistry of
catalysis by soluble transition metal complexes. Wiley-Intersceince, New York
6. Molnar A (2013) Palladium-catalyzed coupling reactions: practical aspects and future developments. Wiley-VCH, Weinheim
The Catalytic Binuclear Elimination Reaction: Importance of Non-linear. . .
227
Monometallic and heterobimetallic CBER mechanisms are a specific class of
synthetic systems which permit linear, quadratic and bilinear reaction rate terms.
It is possible to classify the basic structures. CBER mechanisms possess mononuclear sequences and a dinuclear sequence of intermediates. In addition there are
steps to transform mononuclear intermediates into dinuclear intermediates and
dinuclear intermediates back into mononuclear intermediates. One of the main
synthetic advantages of a CBER mechanism is associated with the potential for
tremendous rate increases due to the binuclear elimination step. This in turn can
lead to much more efficient synthetic use of a precious metal, either by taking
advantage of bilinear kinetics or quadratic kinetics.
A considerable emphasis of this chapter was to highlight the need for in situ
spectroscopic measurements in order to confirm the observable speciation present
and hence reaction network. Another strong emphasis was given to the fact that the
non-linear CBER mechanism provides a fertile area to apply quite advanced and
seldom used mathematical tools to catalysis. Thus the Feinberg criteria indicate that
these systems are stable and not oscillatory, the Horiuti criteria will help to decide
how many terms needed to be included in any comprehensive model by enumerating all independent pathways to products, and the Wegschieder criteria help to
clarify that the cycles in the CBER are not, by any means, independent. As catalysis
moves from simple unicyclic mechanisms to more complex and potentially
non-linear mechanisms, additional tools will be needed to meet the challenges of
better understanding these systems and to make better use of these systems
synthetically.
Acknowledgement The author would like to thank the Agency for Science Technology and
Research for generous support of this research. The author would also like to thank Dr Marco
Kla ¨hn for his recent and extensive computational work concerning CBER and allowing the
inclusion of Fig. 22.
References
1. van Santen RA, Neurock M (2006) Molecular heterogeneous catalysis: a conceptual and
computational approach. Wiley-VCH, Weinheim
2. Illanes A (ed) (2008) Enzyme biocatalysis: principles and applications hardcover. Springer,
Heidelberg
3. Waser M (2012) Asymmetric organocatalysis in natural product syntheses. Springer,
Heidelberg
4. Erker G, Stephen DW (2013) Frustrated Lewis Pairs II: expanding the scope. Springer,
Heidelberg
5. Parshall GW, Ittel SD (1992) Homogeneous catalysis: the applications and chemistry of
catalysis by soluble transition metal complexes. Wiley-Intersceince, New York
6. Molnar A (2013) Palladium-catalyzed coupling reactions: practical aspects and future developments. Wiley-VCH, Weinheim
The Catalytic Binuclear Elimination Reaction: Importance of Non-linear. . .
227