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Slideshow

From Molecular Gyroscopes to Homeomorphic Isomerization: Molecules that Turn Themselves Inside-Out

Portrait of Prof. John Gladysz, guest speaker
Professor John A. Gladysz
Distinguished Professor of Chemistry
Texas A&M University
iSTEM Building 2, Room 1218
Departmental Colloquium
R. B. King Lecture

Children never cease to be fascinated by toy gyroscopes, which commonly consist of (1) a rotating axis and disk, and (2) two to four spokes that connect the termini of the axis. This talk will describe syntheses of molecules that duplicate the connectivity, symmetry, and rotational ability of such gyroscopes. Complexes with trans R3P-MLn -PR3 linkages are first prepared, with R groups that terminate with a CH=CH2 moiety. Then alkene metathesis followed by hydrogenation is used to construct three-spoked cage molecules. Square planar, trigonal bipyramidal, and octahedral systems can be prepared.

Diagram illustrating alkene metathesis followed by hydrogenation used to construct three-spoked cage molecules.

Certain complexes can be demetallated to yield dibridgehead diphosphines, which can exist as three stereoisomers (phosphorus lone pairs in/in, out/out, or in/out). This provides a starting point for another very interesting story. It has proved possible to show that these molecules rapidly turn themselves "inside-out" by a dynamic process that has rarely been observed previously. These topologically novel equilibria interconvert what any chemist would regard as two configurational diastereomers by purely conformational processes.

Illustration of complexes demetallated to yield dibridgehead diphosphines, which can exist as three stereoisomers (phosphorus lone pairs in/in, out/out, or in/out).

Key References

(1) Lang, G. M.; Shima, T.; Wang, L.; Cluff, K. J.; Skopek, K.; Hampel, F.; Bl├╝mel, J.; Gladysz, J. A. J. Am. Chem. Soc. 2016, 138, 7649.

(2) Kharel, S.; Joshi, H.; Bierschenk, S.; Stollenz, M.; Taher, D.; Bhuvanesh, N.; Gladysz, J. A. J. Am. Chem. Soc. 2017, 139, 2172.

(3) Joshi, H.; Kharel, S.; Ehnbom, A.; Skopek, K.; Hess, G. D.; Fiedler, T.; Hampel, F.; Bhuvanesh, N.; Gladysz, J. A. J. Am. Chem. Soc. 2018, 140, 8463.

(4) Ehnbom, A.; Gladysz, J. A. Chem. Rev. 2021, 121, 3701.

(5) Estrada, A. L.; Wang, Y.; Hess, G.; Hampel, F.; Gladysz, J. A. Inorg. Chem. 2022, 61, 17012.

(6) Zhu, Y.; Stollenz, M.; Zarcone, S. R.; Kharel, S.; Hemant, J.; Bhuvanesh, N.; Reibenspiess, J. H.; Gladysz, J. A. Chem. Sci. 2022, 13, 13368.

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