PChem Seminar – Dr. Ivan Popov, WSU Chemistry Assistant Professor

About the event

Speaker: Dr. Ivan Popov, Assistant Professor

Host: Dr. Ursula Mazur

Title: Structural and Electronic Transformations in Group 13 Hydrides: To Share or Not to Share Electrons?

Abstract:

The term “electron deficiency” is traditionally employed to describe compounds which do not have enough valence electrons to form localized two-center two-electron (2c-2e) bonds joining all atoms. Diborane, B2H6, is a classical example of such species, where two 3c-2e B-H-B bonds are necessary to distribute 12 valence electrons over 8 B-H contacts.1,2 An electron-deficient nature of B gives rise to electron delocalization which may involve more than three centers, as previously demonstrated by various exotic gas-phase clusters exhibiting multicenter bonding.3 In turn, electron delocalization may invoke aromatic properties, correlating with the extra stability and decreased reactivity of such compounds. While over 100 individual B hydrides are known,4 the hydride chemistry of the heavier congeners (Al, Ga, In, Tl) remains more cryptic, which is primarily attributed to their lower thermal stability.5 As the orbitals become more diffuse down the group from B to Tl, the properties of these hydrides begin to change qualitatively, revealing a dichotomy in their structures and electron distributions depending on the number of H atoms. In my talk, I will describe the evolution of the changes in the geometric and electronic structures of Group 13 hydrides as a function of H saturation. Specifically, I will identify their global minimum structures, assess thermodynamic stability towards hydrogen dissociation and compare the degree of electron delocalization from B to Tl in Z2Hx and Z3Hy (Z = B-Tl; x=0-6; y=0-9).6-9

References:

1. H. C. Longuet-Higgins, M. A., D. Phil. Q. Rev. Chem. Soc., 1957,11, 121–133.
2. W. N. Lipscomb, Boron Hydrides; Benjamin Inc.: New York, NY, USA, 1963.
3. T. Jian, X. Chen, S.-D. Li, A. I. Boldyrev, J. Li, L. S. Wang, Chem. Soc. Rev. 2019, 48, 3550–3591.
4. N. N. Greenwood, Chem. Soc. Rev. 1992, 21, 49–57.
5. A. J. Downs, C. R. Pulham, Chem. Soc. Rev. 1994, 23, 175–184.
6. A. S. Pozdeev, P. Rublev, S. Scheiner, A. I. Boldyrev, Molecules 2023, 28, 183.
7. A. S. Pozdeev, P. Rublev, A. I. Boldyrev, Y. Rao, ChemPhysChem 2023, 24, e202300332.
8. A. S. Pozdeev, I. A. Popov, Chem. Phys. Rev. 2024, 5, 011401.
9. A. S. Pozdeev, I. A. Popov, J. Phys. Chem. A2025, 129, 6391−6403.