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An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures. Related Article: Akachukwu D. Obi, Diane A. Dickie, Robert J. Gilliard, Jr.|2022|CSD Communication||| 

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures. Related Article: Akachukwu D. Obi, Diane A. Dickie, Robert J. Gilliard, Jr.|2022|CSD Communication||| 

Selective and site-specific boron-doping of polycyclic aromatic hydrocarbon frameworks often give rise to redox and/or photophysical properties that are not easily accessible with the analogous all-carbon systems. Herein, we report ligand-mediated control of boraphenanthrene closed- and open-shell electronic states, which has led to the first structurally characterized examples of neutral bis(9-boraphenanthrene) (2–3) and its corresponding biradical (4). Notably, compounds 2 and 3 show intramolecular charge transfer absorption from the 9-boraphenanthrene units to p-quinodimethane, exhibiting dual (red-shifted) emission in solution due to excited state conjugation enhancement (ESCE). Moreover, while boron-centered monoradicals are ubiquitous, biradical 4 represents a rare type of open-shell singlet compound with 95% biradical character, among the highest of any reported boron-based polycyclic species with two radical sites. 

Abstract A combined synthetic and theoretical investigation of N‐heterocyclic carbene (NHC) adducts of magnesium amidoboranes is presented, which involves a rare example of reversible migratory insertion within a normal valents‐block element. The reaction of (NHC)Mg(N(SiMe₃)₂)₂(1) and dimethylamine borane yields the tris(amide) adduct (NHC−BN)Mg(NMe₂BH₃)(N(SiMe₃)₂) (2; NHC−BN = NHC−BH₂NMe₂). In addition to Me₂N=BH₂capture at the^NHCC−Mg bond, mechanistic investigations suggest the likelihood of aminoborane migratory insertion from an RMg(NMe₂BH₂NMe₂BH₃) intermediate. To elucidate these processes, the carbene complexes (NHC)Mg(NMe₂BH₃)₂(8) and (NHC)Mg(NMe₂BH₂NMe₂BH₃)₂(9) were synthesized, and a dynamic migration of Me₂N=BH₂between Mg−N and^NHCC−Mg bonds was observed in9. This unusual reversible migratory insertion is presumably induced by dissimilar charge localization in the⁻{NMe₂BH₂NMe₂BH₃} anion, as well as the capacity of NHCs to reversibly capture Me₂N=BH₂in the presence of Lewis acidic magnesium species.