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

Abstract

Although the metathesis of metal-boron double bonds with elemental chalcogenides is an established process, no similar reactivity has been observed with element-nitrogen bonds. Such a reaction would provide a new route to iminoborane compounds (RB≡NR'), which have recently experienced renewed synthetic interest. Herein, we present the first observation of M=B/C=N metathesis reactions, which led to the isolation of a stable iminoborane in addition to further iminoborane cycloaddition products.

Release of Isonitrile‐ and NHC‐Stabilized Borylenes from Group VI Terminal Borylene Complexes

“…Combination of terphenyldihaloboranes (TerPhBCl 2 ) 1 a – c with the Group VI dimetallates Na 2 [M(CO) 5 ] (M=Cr, W) gives rise to a family of terminal Group VI borylene complexes (Scheme ). Extremely broad 11 B NMR signals are observed for complexes 2 a – f , which fall in the range of 145–155 ppm, as has been previously reported in similar terminal arylborylene complexes . Compounds 2 b , 2 d and 2 e have been characterized by X‐ray crystallographic studies (Figure ), whereas the molecular structures of 2 a and 2 c were published in our original reports .…”

“…Compounds 2 b , 2 d and 2 e have been characterized by X‐ray crystallographic studies (Figure ), whereas the molecular structures of 2 a and 2 c were published in our original reports . The metal–boron distances for the Cr borylenes are identical within experimental error, ranging from 1.913(2) Å in 2 a to 1.904(5) Å in 2 c , whereas the M−B distances of the W borylenes are 2.069(12) and 2.079(4) Å in 2 d and 2 e , which are within the ranges reported for terminal borylene M−B distances ,. Solid‐state IR spectroscopy reveals A 1 symmetric carbonyl vibrational modes between 2063–2067 cm −1 for 2 a – 2 c and 2073–2078 cm −1 for 2 d – 2 f , which is indicative of the relative electron deficiency of the metal center in relation to known σ‐donor complexes ([(1,3‐dimethylimidazol‐2‐ylidene)Cr(CO) 5 ] has an A 1 symmetric stretching frequency of 2056 cm −1 ) .…”

“…Extremely broad 11 BNMR signals are observed for complexes 2a-f,w hich fall in the range of 145-155ppm, as has been previously reported in similart erminal arylborylene complexes. [5,7] Compounds 2b, 2d and 2e have been characterizedb yX -ray crystallographic studies (Figure 3), whereas the molecular structureso f2a and 2c were published in our originalr eports. [8] The metal-boron distances for the Cr borylenes are identicalw ithin experimentale rror,r anging from 1.913(2) in 2a to 1.904 (5) in 2c,w hereas the MÀBd istances of the W borylenes are 2.069(12)a nd 2.079(4) in 2d and 2e,w hich are within the ranges reported for terminal borylene MÀBd istances.…”

Germaborenes: Borylene Transfer Agents for the Synthesis of Iminoboranes

“… [5a] A color change from deep red to yellow was observed and after extraction with n ‐hexane and crystallization at −30 °C germyl substituted iminoboranes 3 and 4 were isolated and characterized by NMR spectroscopy and single crystal X‐ray diffraction. Short B−N bond lengths of 1.245(4) Å ( 3 , Figure 1) and 1.231(5) Å ( 4 , see Supporting Information) which can be compared with other B–N triple bonds [1.190(4)–1.265(7) Å] were found in both molecular structures [3c, 6] . The high bond order between boron and nitrogen is further indicated by the linear alignment of the Ge‐B‐N‐R fragments with two angles close to 180° [Ge‐B‐N: 168.0(3)° ( 3 ), 165.1(3)° ( 4 ); B‐N‐R: 174.6(2)° ( 3 ), 177.0(3)° ( 4 )].…”

Eine Bor‐Tellur‐Doppelbindung: direkte Insertion in eine Mn=B‐Doppelbindung

“…Die Synthese und Isolierung von Verbindungen mit besonderen Bindungsmodi ist ein wichtiges Gebiet in der Grundlagenforschung . In den letzten Jahrzehnten konnten bereits einige Verbindungen mit formalen Mehrfachbindungen zwischen Bor und verschiedenen Elementen, unter anderem Übergangsmetallen (ÜMs), Bor, Kohlenstoff, Silicium, Stickstoff, Phosphor und Arsen, synthetisiert und charakterisiert werden. Ein interessanter Aspekt ist hierbei, dass bislang lediglich Mehrfachbindungen mit Bor und Elementen bis maximal zur 4.…”