Electronic and steric factors have been investigated in the thermalr ing expansion of borolesw ith organic azides,areaction that providesa ccess to highly arylated 1,2-azaborinines,BNanalogues of benzene.Reactions of avariety of boroles and organic azides demonstrate that the synthetic methodi sq uite generali nf urnishing 1,2-azaborinines,b ut the respective reaction rates reveal as trongd ependence on the substituents on the two reactants. The productsh ave been characterizedb yU V/Vis, electrochemical, NMR, and Xray diffractionm ethods, clarifying their constitutions and highlighting substituent effects on the electronic structure of the 1,2-azaborinines. Furthermore, analysiso fs everalp ossible mechanistic pathways for 1,2-azaborinine formation,a s studied by DFT,r evealed that at wo-step mechanism involving azide-borole adduct formation and nitrene insertion is favored.

The diborene 1 was synthesized by reduction of a mixture of 1,2-di-9-anthryl-1,2-dibromodiborane(4) (6) and trimethylphosphine with potassium graphite. The X-ray structure of 1 shows the two anthryl rings to be parallel and their π(C ) systems perpendicular to the diborene π(B=B) system. This twisted conformation allows for intercalation of the relatively high-lying π(B=B) orbital and the low-lying π* orbital of the anthryl moiety with no significant conjugation, resulting in a small HOMO-LUMO gap (HLG) and ultimately a C-H borylation of the anthryl unit. The HLG of 1 was estimated to be 1.57 eV from the onset of the long wavelength band in its UV/Vis absorption spectrum (THF, λ =788 nm). The oxidation of 1 with elemental selenium afforded diboraselenirane 8 in quantitative yield. By oxidative abstraction of one phosphine ligand by another equivalent of elemental selenium, the B-B and C -H bonds of 8 were cleaved to give the cyclic 1,9-diborylanthracene 9.

The reactions of terminal acetylenes with doubly Lewis base-stabilised diborenes resulted in different outcomes depending on the nature of the ligands at boron and the conformation of the diborene (cyclic...

(Di)boranediyl-bridged diplatinum A-frame complexes were synthesised by the twofold oxidative addition of dihalo(di)boranes to a bis(diphosphine)-bridged diplatinum(0) precursor and were characterised by NMR spectroscopy and X-ray crystallography.