BO Chemistry Comes Full Circle

Superseding β‐Diketiminato Ligands: An Amido Imidazoline‐2‐Imine Ligand Stabilizes the Exhaustive Series of B=X Boranes (X=O, S, Se, Te)

“…[10] Braunschweig and Yamashita exploited the strategy of stabilizing entities with B À Om ultiple bonds within the coordination sphere of at ransition metal. [11,12] Examples of heavier B=Xc halcogenoboranes (X = S, Se,T e) are even rarer than oxoboranes and strategies to stabilize them include (i)either N,N'-chelation by bis imidazoline-2-imines by Inoue, [13] NacNac type by Cui or Singh, [14] or diamido ligands by Aldridge [9] or (ii)NHC-coordination by Braunschweig [15] to afford neutral or cationic uncomplexed thio-or selenoboranes.Incontrast to N,N'-stabilized B=Xboranes (X = S, Se), which are stable in the monomeric form, the NHC-substituted species are prone to arapid dimerization in solution with the formation of four-membered boracycles.T elluroboranes with the structural B = Te double bond entity are extremely rare and only one example could be prepared by Braunschweig, and required stabilization with aL ewis acidic manganese core originating from the borylene complex it was formed from. [15] Herein, we present ac onsistent contribution to the currently patchy area of ketone analogous boranes including heavier chalcogens with the special focus on the neutral species.S of ar there is no ligand system, which has afforded ac omplete series of chalcogenoboranes with the structural B=Xe ntity (X = O, S, Se,T e), and the reported neutral oxoboranes and telluroboranes could only be isolated as complexes to (strong) Lewis acids.T herefore,w eseto ut to design an ovel ligand system, which affords the full scope of Lewis acid free,monomeric chalcogenoboranes.T he obvious predominance of N,N'-chelating NacNac ligands in attempts to stabilize the B=Xe ntity can be traced back to the successful history of this ligand class in the production of low valent main group compounds and their applications in bond and substrate activation processes with prominent examples being NacNac stabilized Mg I ,Al I or Ga I species.…”

Quantum Chemical and Biochemical Study on Antioxidant Properties of Halogenated Boroxine K2[B3O3F4OH]

“…To form these bonds, boron atoms presumably need to activate their valence electrons from the inner shell, close to the nucleus. This phenomenon affects the number and the delocalization of unpaired electrons over the entire molecule and results in the local bond configuration change from trigonal sp 2 to tetrahedral sp 3 hybridization.…”

“…Boroxines are boronic acid anhydrides, consisting of 6-membered, heterocyclic compounds composed of alternating oxygen and singly hydrogenated boron atoms. [2] Due to their unique electron configurations, boroxines react readily with Lewis basis and are potentially selective enzyme inhibitors. They have the ability to bind to the active sites of enzymes and thus, prevent the catalytic reactions.…”

[BO2]− as a Synthon for the Generation of Boron‐Centered Carbamate and Carboxylate Isosteres

“…This lacuna is reminiscent of oxoborane (BO) chemistry prior to Braunschweigs report of trans-[(Cy 3 P) 2 BrPt(BO)], which achieved the in situ generation of a terminal BO ligand through the reversible elimination of Me 3 SiBr from the B-Br oxidative addition product of Br 2 BOSiMe 3 and [Pt(PCy 3 ) 2 ]. [4,12] In this contribution, we demonstrate the accessibility of [BO 2 ] À as a synthon through alkene elimination from isolable magnesium pinacolatoboryl species and its in situ trapping to provide boron-centered analogues of carbamate and carboxylate anions.…”

“…[3] These observations are a thermodynamic consequence of the strong B À O bond (809 kJ mol À1 ) and the latent Lewis acidity of the boron center. [4] A number of noteworthy recent advances in the chemistry of lower nuclearity oxoborane derivatives, however, have been achieved either through the incorporation of kinetically stabilizing substituents, [5] for example in Aldridges isolated oxoborane anion (1, Figure 1 a), [6] or by saturation of the Lewis basic oxo and Lewis acidic boron units. [7,8] This latter approach is exemplified by Rivard and coworkers isolation of [(IPr)(HO)B = OB(C 6 F 5 ) 3 ] (2, IPr = N,N'bis(2,6-di-isopropylphenylimidazol-2-ylidene, Figure 1 a) in which the stability of the HOB=O unit is maintained through the donor-acceptor combination of an N-heterocyclic carbene (NHC) and the potent Lewis acid, B(C 6 F 5 ) 3 .…”