Ligand Derivatives

Growing polymers from ligands and metal complexes requires modification of ligands with initiator sites.  Despite their widespread uses in so many branches of chemistry, bipyridines, even simple derivatives, can present special challenges for synthesis. 

“Bipyridines” Fraser, C. L.; Smith, A. P; Comprehensive Coordination Chemistry II; Meyer, T. J.; McCleverty, J. A., Eds; Elsevier Ltd.:  Oxford, UK, 2004; Vol. 1, Ch. 1, pp. 1-23.

This prompted us to develop new routes to common electrophilic halide and nucleophilic alcohol derivatives, including monofunctional reagents via a Negishi cross coupling strategy.

Negishi scheme coming soon

“Efficient Synthesis of 4-, 5-, and 6-Methyl-2,2'-bipyridine by a Negishi Cross Coupling Strategy Followed by High-Yield Conversion to Bromo- and Chloromethyl-2,2'-bipyridines” Savage, S. A.; Smith, A. P.; Fraser, C. L. J. Org. Chem. 1998, 63, 10048-51.

“Synthesis of Methyl-2,2'-bipyridines by a Negishi Cross-Coupling Strategy” Smith, A. P.; Savage, S. A.; Fraser, C. L.  Org. Synth. 2001, 78, 51-62.

“Synthesis of 4-, 5-, and 6-Methyl-2,2’-bipyridine by a Negishi Cross-Coupling Strategy: 5-Methyl-2,2’-bipyridine,” Smith, A. P.; Savage, S. A.; Love, J. C.; Fraser, C. L. in Thematic Collections of Organic Synthesis, Vol. 1, Palladium, Nickel and Iron-Catalyzed Reactions, Danheiser, R., Ed.; Wiley:  New York, 2008.

Chloride scheme coming soon

“Synthesis of Halomethyl and Other Bipyridine Derivatives by Reaction of 4,4'-Bis[(trimethylsilyl)methyl]-2,2'-bipyridine with Electrophiles in the Presence of Fluoride Ion” Fraser, C. L.; Anastasi, N. R.; Lamba, J. J. S.  J. Org. Chem. 1997, 62, 9314-7.

“Efficient Synthesis of Halomethyl-2,2'-Bipyridines” Smith, A. P.; Lamba, J. J. S.; Fraser, C. L. Org. Synth.  2001, 78, 82-90.

Alcohol scheme coming soon

“An Improved Synthesis of Hydroxymethyl Bipyridines” Smith, A. P.; Corbin, P. S.; Fraser, C. L. Tetrahedron Lett.  2000, 41, 2787-9.

Macroligands

When halide, alcohol or other functionalized ligands are used as initiators for controlled polymerization, macroligands result. Block copolymer macroligands are accessible when polymeric ligands are used as macroinitiators.  These systems can be coordinated to metals to form polymeric metal complexes.

Macroligand scheme coming soon

“Synthesis of Bipyridine-Centered Diblock Copolymers” Smith, A. P.; Fraser, C. L. Macromolecules, 2003, 36, 2654-60.

Metalloreagents

In some cases it is better to effect ligand modifications after, not before binding to metal centers.  This situation arises when reactive ligand functionalities are not stable to typical coordination conditions, as is the case for halomethyl bipyridines and Ru tris(bpy) complexes.  Thus, we developed methods for generating alcohol functionalized metal complexes for use as precursors to Ru complexes with pendant chloride sites.  Different numbers of functionalities are possible in these reagents, leading to materials with different architectures.  Both alcohol and chloride derivatives are versatile reagents. They can be utilized as metalloinitiators for controlled polymerization reactions and starting points for futher derivatization.

Ru scheme coming soon

“Ruthenium(II) a-Diimine Complexes with One, Two and Three 4,4'-Bis(hydroxymethyl)-2,2'-bipyridine and 4,4'-Bis(chloromethyl)-2,2'-bipyridine Ligands:  Useful Starting Materials for Further Derivatization” Collins, J. E.; Lamba, J. J. S.; Love, J. C.; McAlvin, J. E.; Ng, C.; Peters, B. P.; Wu, X.; Fraser, C. L. Inorg. Chem. 1999, 38, 2020-4.