Dimesitylboryl- and Amino-substituted Acetylene Having Butatriene-type Resonance Contribution

Abstract

Boryl- and amino-substituted acetylenes would have a butatriene-type resonance contribution due to the interaction between boron empty orbital and nitrogen lone pair. However, a few examples of boryl- and amino-substituted acetylenes have been synthesized up to date, and structural analysis by X-ray crystallography has remained unknown. Here we report the synthesis and characterization of dimesitylboryl- and diethylamino-substituted acetylene. In addition to the spectroscopic studies, the X-ray crystallography of the acetylene revealed the lengthening of the triple bond and the shortening of C–B and C–N bonds, being consistent with the butatriene-type resonance contribution.

Stable Push–Pull Disilene: Substantial Donor–Acceptor Interactions through the Si═Si Double Bond

“…Both the HOMO and the LUMO involve a substantial contribution from the 2p orbital of the N atom and the 2p orbital of the B atom, which reflects the π-donor effect of the amino group and the π-acceptor effect of the boryl group on the SiSi double bond. These orbital features are similar to those observed in 1-amino-2-borylacetylene . The TDDFT calculations support the assignment of the absorption band of 1 at 482 nm to the HOMO → LUMO transition.…”

“…These orbital features are similar to those observed in 1-amino-2-borylacetylene. 16 The TDDFT calculations support the assignment of the absorption band of 1 at 482 nm to the HOMO → LUMO transition. Although the HOMOs of 1 (−4.45 eV) and 2 (−4.42 eV) are virtually identical in energy, the LUMO of 1 (−1.53 eV) is substantially stabilized relative to that of 2 (−0.74 eV).…”

Boron‐ versus Nitrogen‐Centered Nucleophilic Reactivity of (Cyano)hydroboryl Anions: Synthesis of Cyano(hydro)organoboranes and 2‐Aza‐1,4‐diborabutatrienes

“…5 a/b R may thus be regarded as the first examples of 2‐aza‐1,4‐diborabutatrienes. Other reported azaborabutatrienes include a 1‐aza‐2‐borabutatriene rhodium complex generated by borylene transfer from a molybdenum aminoborylene complex to a rhodium vinylidene, [39] as well as a couple of aminoborylacetylenes Et 2 N−C≡C−BY 2 (Y=Mes, NMe 2 ),[ 40 , 41 ] which show significant contribution from their 1‐aza‐4‐borabutatriene resonance forms, Et 2 N=C=C=BY 2 .…”

9-[(Z)-2-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)ethenyl]-9H-carbazole

“…However, the contribution of the ionic canonical structure is very small when p-phenylene is inserted into the N-B bond (Yuan et al, 2006). By contrast, there is a significant contribution of the ionic canonical structure when a C C bond is inserted into the N-B bond (Onuma et al, 2015). The crystal structure of one isomer of the C C bond-inserted system, namely 9-[(E)-2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)ethenyl]-9H-carbazole has been reported (Hatayama & Okuno, 2012), which is an E-isomer of the title compound.…”