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Formation of an Isolable Divinylborinium Ion through Twofold 1,2‐Carboboration between a Diarylborinium Ion and Diphenylacetylene
Author(s) -
Tanaka Naoki,
Shoji Yoshiaki,
Hashizume Daisuke,
Sugimoto Manabu,
Fukushima Takanori
Publication year - 2017
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201701730
Subject(s) - diphenylacetylene , chemistry , boron , delocalized electron , ion , valence (chemistry) , valence electron , crystallography , atom (system on chip) , photochemistry , inorganic chemistry , computational chemistry , electron , organic chemistry , physics , quantum mechanics , catalysis , computer science , embedded system
Abstract Borinium ions, that is, two‐coordinate boron cations, are the most electron‐deficient isolable boron compounds. As borinium ions have only four formal valence electrons on boron, they should show a strong tendency to accept electron pairs on the boron atom to fill its valence shell. Thus chemical reactions of borinium ions are expected to give products in which the coordination number of boron is increased from two to three or four. However, contrary to this expectation, we found that the dimesitylborinium ion (Mes 2 B + ) undergoes twofold 1,2‐carboboration reactions with two equivalents of diphenylacetylene to yield an unprecedented borinium ion ( 1 + ) with two substituted vinyl groups on the boron center. NMR spectroscopy and X‐ray diffraction analysis of 1 + , together with electronic‐structure calculations, revealed that the positive charge is delocalized over the entire π‐conjugated system. The fact that the chemical transformation of a borinium ion gives rise to a different borinium ion without a change in the coordination number is remarkable and should provide new insight into the chemistry of the Group 13 elements.