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The chemistry of aluminacyclopentadienes, also known as alumoles, has experienced a resurgence in recent years, resulting in the preparation of a number of new entries in this class of compound. In contrast, their reactivity remains relatively unexplored. Thus far, their Lewis acid-base chemistry has been studied, as well as various ring-insertion reactions with unsaturated species such as alkynes and azides. Herein we present a range of new ring expansion reactions of an alumole with heteroatom-containing unsaturated species, providing novel six-, seven- and eight-membered cyclic products with high heteroatom content. Additionally, an unusual reaction was observed when the alumole was treated with morpholine-N-oxide, involving a stepwise insertion of two oxygen atoms, first into the exocyclic Al-C bond and then the endocyclic Al-C bond.

The combination of electron-rich diaminoalkynes and ditopic Lewis acids diboranes(4) leads to unusual uncatalysed diboration reactions involving internal Lewis adduct, zwitterion, and C-C bond formation. The products are novel multicyclic, charge-separated compounds with intramolecular dative bonds.

Convenient solution-phase syntheses of tetrahalodiboranes(4) B 2 F 4 , B 2 Cl 4 and B 2 I 4 are presented herein from common precursor B 2 Br 4 . In addition, the dimethylsulfide adducts B 2 Cl 4 (SMe 2 ) 2 and B 2 Br 4 (SMe 2 ) 2 are conveniently prepared in one-step gram and multigram scale syntheses from the commercially-available starting material B 2 (NMe 2 ) 4 . The results provide simple access to the full range of tetrahalodiboranes(4) for the exploration of their untapped synthetic potential.

Herein we report a facile and selective synthetic route to monocyclic NHC-stabilized boriranes. We have succeeded in obtaining two highly stable new boriranes through salt elimination of NHC-stabilized dichloroboranes with the dianion of trans-stilbene, Na2[C14H12]. One borirane was observed to undergo reaction with [Pt(PEt3)3], in which the Pt(0) center oxidatively adds a backbone C-H bond of the NHC, leading to the isolation of the Pt(II) complex trans-[(Et3P)2PtH{C=CH(NMe)2C·BPh(C14H12)}]. The remarkable inertness of the NHC-boriranes suggests a strong stabilising effect of quaternization of the boron atom.