Structure of 1,5-diisopropyl-4-phenyl-4,5-dihydrotetraazaborole

Synthesis of Complex Boron–Nitrogen Heterocycles Comprising Borylated Triazenes and Tetrazenes Under Mild Conditions

“…The formation of tetrazaboroles ,− is a representative example of the classical reactivity of iminoboranes, which are BN-isosteres of alkynes. In this chemistry, extensively explored by Paetzold et al, iminoboranes can be obtained by thermolysis of boron azides and can be treated (or trapped) with organic azides to yield tetrazaboroles. ,,,− ,− , Although well established, the tetrazaborole chemistry has yielded little structural data. ,, …”

“…The structural parameters for the tetrazaborole core in 6b and 8 are comparable to those of the reported tetraazaboroles. 53,54 The N−N single bond distances in 8 are both significantly shorter than in 6b (N1−N2 1.367(3) and N3−N4 1.355(3) Å). In 8, the −B(X)Mes moiety is coordinatively saturated by the dative bond with the second tetrazaborole ring, thus preventing any π-interaction with the neighboring ring-nitrogen atoms (endocyclic B−N distances B1−N1 1.431(4) and B1−N4 1.439(5) Å, statistically identical; exocyclic B−N distances of B2−N1 1.558(5) and N2−B2′ 1.604(3) Å).…”

Synthesis and Trapping of Iminoboranes by M=B/C=N Bond Metathesis

“…Thes tructure of 6b was ascertained by single-crystal X-ray diffraction (Figure 3), which showed the compound to be a1 ,4-diphenyltetraazaborole,t he product of af ormal cycloaddition of an iminoborane with as econd equivalent of phenylazide.P aetzold and co-workers have shown that tetraazaboroles are products of [2+ +3] cycloadditions of azides with iminoboranes (with 11 BNMR signals at d B % 27 ppm); [13] however,o nly one structurally characterized example of such acompound exists,namely 1,5-diisopropyl-4phenyltetraazaborole (E). [14] TheB ÀNd istances of 6b (avg. 1.435 )a re slightly longer than those of E (1.411, 1.422 ), which was attributed to the extreme steric hindrance of the boron-bound group in 6b.Incontrast, the central N = Nbonds of 6b and E are effectively identical in length within experimental uncertainty.N otably,t he BN 4 and boronbound aryl planes of 6b are tilted only by approximately 498 8,a llowing for slipped p-p stacking between the mesityl and phenyl groups on both sides of the molecule,w ith centroid-centroid distances of 3.56-3.92 .…”

“…The structure of 6 b was ascertained by single‐crystal X‐ray diffraction (Figure ), which showed the compound to be a 1,4‐diphenyltetraazaborole, the product of a formal cycloaddition of an iminoborane with a second equivalent of phenylazide. Paetzold and co‐workers have shown that tetraazaboroles are products of [2+3] cycloadditions of azides with iminoboranes (with 11 B NMR signals at δ B ≈27 ppm); however, only one structurally characterized example of such a compound exists, namely 1,5‐diisopropyl‐4‐phenyltetraazaborole ( E ) . The B−N distances of 6 b (avg.…”

Synthese und Nachweis von Iminoboranen durch M=B/C=N‐Bindungsmetathese

“…Die Isolierung ist nur fürdas sterisch anspruchsvollste der postulierten Iminoborane (2a)u nd das kleinste 1,3-Diazaboretidin (5b) [13] allerdings konnte bisher nur eine Verbindung dieses Typs strukturell charakterisiert werden:1,5-Diisopropyl-4-phenyltetraazaborol (E). [14] Die B-N-Abstände in 6b (Mittelwert:1.435 )sind etwas grçßer als die in E (1.411, 1.422 ), was durch den extremen sterischen Anspruch des borgebundenen Restes in 6b erklärt werden kann. Dagegen ist die zentrale N-N-Doppelbindung in 6bund E,i mR ahmen der Messgenauigkeit, gleich lang.B emerkenswert ist die Verdrehung der BN 4 -Einheit gegenüber der Ebene des borgebundenen Arylrings um ca.…”