Computational Study of Cyclobutane-1,3-diylidene Dicarbenes: Ground-State Spin Multiplicity and New Strategy toward the Synthesis of Bicyclo[1.1.0]but-1(3)-enes

• Yoshiki Fujita

  Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526

• Manabu Abe

  Department of Chemistry, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526

• Yoshihito Shiota

  Institute for Materials Chemistry and Engineering, Kyushu University, Moto-oka, Nishi-ku, Fukuoka 819-0395

• Tatsuya Suzuki

  Institute for Materials Chemistry and Engineering, Kyushu University, Moto-oka, Nishi-ku, Fukuoka 819-0395

• Kazunari Yoshizawa

  Institute for Materials Chemistry and Engineering, Kyushu University, Moto-oka, Nishi-ku, Fukuoka 819-0395

Abstract

Coupled-cluster calculations were performed for cyclobutane-1,3-diylidene dicarbenes 2 at the CCSD(T)//CCSD/cc-pVDZ level of theory, in which the ground-state spin multiplicity and the structures of unique molecules were investigated in detail. The closed-shell singlet state 2(Sσπ) with a bicyclo[1.1.0]but-1(3)-ene (BBE) structure found to be the ground-state was much lower in energy than the corresponding singlet dicarbene structure 2(S**), the quintet state 2(Q), and the triplet state 2(T), suggesting that the hitherto experimentally unknown BBE structure can be synthesized by the intramolecular dimerization of two carbene units. The energy gap between the BBE structures 2(Sσπ) and corresponding quintet states 2(Q) with electron-withdrawing substituents (X = F) at the C2 and C4 positions was found to be larger than that with electron-donating substituents (X = SiH3), i.e., ca. 100 kcal mol−1 for 2b (X = F) > ca. 85 kcal mol−1 for 2a (X = H) > ca. 70 kcal mol−1 for 2c (X = SiH3). Two unique structures, 2(Tσ) with a C1–σ–C3 bond and 2(Tπ) with a C1–π–C3 bond, were found to be the equilibrium structures for the triplet state of cyclobutane-1,3-diylidene dicarbenes 2.

Journal

• Bulletin of the Chemical Society of Japan

  Bulletin of the Chemical Society of Japan 89 (7), 770-778, 2016-04-13

  Oxford University Press (OUP)

Keywords

• General Chemistry

Details

• CRID: 1360283694073738112
• NII Article ID: 130005253040
• DOI: 10.1246/bcsj.20160051
• ISSN: 13480634
• ISSN: 00092673
• Web Site: https://academic.oup.com/bcsj/article-pdf/89/7/770/56279631/bcsj.20160051.pdf
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