Nuclear magnetic resonance investigation of the nature of the boron-carbon bond in some vinylboranes

Rearrangement of Bis(dimethylamino)bis(1-indenyl)diborane(4) into Bis(dimethylamino)bis(3-indenyl)diborane(4)

“…The observed shielding corresponds to dialkylbis(dimethylamino)diboranes(4) [8] . 3-Indenyl groups should actually lead to a better shielding due to possible BϪC π bonding as observed for amino(vinyl)boranes [9] . Therefore, we can assume that the 3-indenyl group is not coplanar with the B 2 NC plane.…”

Boron-containing arylacetylene polymers as a novel carbon precursor: Synthesis, thermal curing and carbonisation

“…The substitution at carbon 4 causes a deshielding of 19.8 ppm, which is primarily due to the inductive effect of the boryl group. Most of the information regarding the electronic structure of the unsaturated systems is based on observing changes in the chemical shifts at the β-carbons [11] because the effects of any π electron back-donation to boron should be most obvious at these carbons. Therefore, the carbon 5 in the alkynyl group is deshielded by 41.1 ppm, which is 20 ppm more than the α-carbons.…”

Darstellung und Ligandeneigenschaften eines 1.2.5-Azadiborolen-Derivates [1] / Synthesis and Ligand Properties of an 1,2,5-Azadiborolene Derivative [1]

“…Der beobachtete Abschirmungsgewinn von etwa 3 ppm kann durch Rückbindung des ^-Systems erklärt werden. In Alkenylboranen ist durch mesomere Wechselwirkung das 13 C/3-Atom (150-160 ppm) bis zu 30 ppm stärker entschirmt als Ca (130-135 ppm) [14][15][16]. Für 3 und 1 werden <5 13 C = 156,2 und 175,2 ppm gefunden, was eine intensivere elektronische Wechselwirkung zwischen der > C=C<-Gruppe und den Boratomen in 1 als in 3 signalisiert.…”