**Triple Bonds between Bismuth and Group 13 Elements: Theoretical Designs and Characterization**

Jia-Syun Lu, Ming-Chung Yang, Shih-Hao Su, Xiang-Ting Wen, Jia-Zhen Xie and Ming-Der Su

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/67220

#### Abstract

The effect of substitution on the potential energy surfaces of RE13≡BiR (E13 = B, Al, Ga, In, and Tl; R = F, OH, H, CH3, SiH3, Tbt, Ar\*, SiMe(SitBu3)2, and SiiPrDis2) is investigated using density functional theories (M06-2X/Def2-TZVP, B3PW91/Def2-TZVP, and B3LYP/LANL2DZ+dp). The theoretical results suggest that all of the triply bonded RE13≡BiR molecules prefer to adopt a bent geometry (i.e., ∠RE13Bi ≈ 180° and ∠E13BiR ≈ 90°), which agrees well with the bonding model (model (B)). It is also demonstrated that the smaller groups, such as R = F, OH, H, CH3, and SiH3, neither kinetically nor thermodynamically stabilize the triply bonded RE13≡BiR compounds, except for the case of H3SiB≡BiSiH3. Nevertheless, the triply bonded RʹE13≡BiRʹ molecules that feature bulkier substituents (Rʹ = Tbt, Ar\*, SiMe(SitBu3)2, and SiiPrDis2) are found to have the global minimum on the singlet potential energy surface and are both kinetically and thermodynamically stable. In other words, both the electronic and the steric effects of bulkier substituent groups play an important role in making triply bonded RE13≡BiR (Group 13–Group 15) species synthetically accessible and isolable in a stable form.

Keywords: bismuth, group 13 elements, triple bond, multiple bond, density functional theory

## 1. Introduction

Triply bonded molecules are of great interest in structural and synthetic inorganic chemistry as well as in fundamental science. Molecules that have triple bonds, however, pose a more difficult challenge than analogous doubly bonded molecules from a synthetic viewpoint [1–8]. Acetylene is one of the most commonly triply bonded molecules in traditional organic chemistry. Thanks to Kira, Power, Sekiguchi, Tokitoh, Wiberg and many coworkers, the stable

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homonuclear alkyne analogues of all of the heavier group 14 elements have now been isolated and characterized [9–19]. Recently, heteronuclear ethyne-like molecules that possess C≡Ge [20, 21], C≡Sn [22], and C≡Pb [23] triple bonds have also been theoretically predicted and have been published elsewhere.

Nevertheless, to the authors' best knowledge, neither experimental nor theoretical studies have been performed on acetylene-like compounds that feature an E13≡Bi (E = B, Al, Ga, In, and Tl) triple bond. It is surprising how little is known about the stability and molecular properties of E13≡Bi, considering the importance of bismuth compounds [24] that contain group 13 elements in inorganic chemistry [25–35] and material chemistry [36–45].

The aim of this study is to theoretically determine the existence and relative stability of RE13≡BiR triply bonded molecules, which can be synthesized as stable compounds when they are properly substituted. For the first time, the structures of RE13≡BiR with various substituents are reported. That is, theoretical calculations of RE13≡BiR are performed, using both smaller ligands (such as, R = F, OH, H, CH3, and SiH3) and larger ligands with bulky aryl and silyl groups (i.e., Rʹ = Tbt, Ar\*, SiMe(SitBu3)2, and SiiPrDis2; Dis = CH(SiMe3)2; Scheme 1) [46–51]. As a result, the effect of substituents on these bismuth-group-13 element triple bonds is systematically investigated using density functional theory (DFT) calculations. It is expected that the theoretical interpretations of the effect of substituents, presented in this work, will help in the experimental preparation of the many precursors of RE13≡BiR.
