Reaktionen der Cyclobutadien‐homologen Diazadiboretidine

Abstract

Diazadiboretidine (RBNR')2 mit genugend groljen Resten R und R' lassen sich u. a. durch Cyclodimerisierung von Iminoboranen RB 3 NR' darstellen'). Sie sind rnit Cyclobutadien (RCCR')? isoelektronisch. Ihre rautenformige Vierringstruktur und ihre thermische Stabilitht macht sie rnit speziellen Cyclobutadienen, namlich denen vom sog. ,,pushp~ll''-Typ~,~', vergleichbar. Mit den Ligand-Kombinationen R/R' = Me/tBu, iPr/iPr erreicht man jenen Grenzwert des sterischen Anspruchs der Liganden, der im Bereich zwischen Raumtemperatur und ca. 100°C Gleichgewichte zwischen den Cyclooctatetraen-homologen Achtringen (RBNR')4 und den Vierringen (RBNR')2 ermoglicht; oberhalb 100°C sind die Vierringverbindungen ( 46.9 ppm gegeniiber 1 b (43.2 ppm) leicht tieffeldverschoben.

Synthesis and structures of monocyclic 1,4-diaza-2,3-diborine species

“…Of the C2B2N2 aromatic ring structures, 1,3-diaza-2,4-diborine structure, the thermodynamically most stable benzene analogue, was first synthesized by Paetzold and co-workers [4]. 2,3-diaza-1,4-diborine ring system was the first isolated example of an isoelectronic analogue of benzene with two BN units, despite computations suggesting that heterocycle is less stable than the 1,3-diaza-2,4-diborine ring by over 50 kcal/mol [3,5].…”

“…In this work, we report the synthesis and characterisation of new monocyclic 1,4-diaza-2,3-diborine derivatives 3ad, 3bc and 3ae and new bicyclic structure 8a. These diazadiborines were prepared individually from the [Li 2 (THF) 4 A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT [9], the corresponding 1,2-dichlorodiboranes 6c, 6d and 1,2-dichloro-1,2-diborolane 6e [10] in THF at -78 °C (Scheme 2). After the reaction, the mixture was brought to room temperature.…”

BN‐Achtringe (RBNR')4 aus BN‐Vierringen (RBNtBu)2 durch NtBu/NR'‐Austausch

“…(411. Die Reaktion nach G1. (4) iPr/CH2Ph iBu/CH,Ph 6, 14.7, 14.6, 13.7, 14.9, 14.0, 15.5 (4b, 1, 26.4, 26.8, 25.0 (4b, 7, 141.4, 145.8, 146.8 (iC), 127.9, 127.5, 127.3, 128.5 (oC), 128.1, 128.1, 128.2, 127.5 (m-C), 126.4, 126.2, 124.5, 126.2 (p-C (2) 925 (2) (14) 223 (13) 268 (14) 309 (15) 321 (15) 310 ( 15) 249 ( 14) 269 (14) 376 (16) / 260 (14) 201 ( 12) 281 (14) 322 (15) 301 (15) 267 (14) 229 (13) 293 (15) 351( 15) / 242 (14) 213 ( 13) 288 (14) 372 (16) 366 (16) 369 (16) 289 (14) 243 (14) 308 (14) ( 2) 8234 (2,) 6954 (2) 9093 (2) 9377 (3) 2034 ( 3) 7916 ( 2) 9439 (2) 9842 (2) 8772 (2) 8270 ( 3) 7332 (3) 6901 (3) 7406 (3) 8333 (3) 10622 ( 2) 10659 ( 3 ) 11845 (2) 8075 ( 3) 7864 …”

A σ‐Donor with a Planar Six‐π‐Electron B2N2C2 Framework: Anionic N‐Heterocyclic Carbene or Heterocyclic Terphenyl Anion?

“…1.53 and 1.38-1.40 =, respectively). [10] The B-N bonds in the latter derivatives are equal with those in borazines. As proposed by Bertrand and co-workers for the cationic precursor to D, [4d] the six π electrons in 2 appear to be distributed onto two allyllike fragments (B2C -and N2C + ) to form a zwitterionic structure, rather than delocalized over the entire ring framework.…”