Reactivity of a Diplatinum-Templated BNBN Analogue of Butatriene Toward Azides

The A-frame complex [Pt₂(μ-BN≡BN(TMS)₂)(μ-dmpm)₂] (V, TMS = trimethylsilyl, dmpm = bis(dimethylphosphino)methane) undergoes a wide array of reactions with azides. For electron-rich (N₃Ar^ED) or bulky aryl azides (N₃Ar^big), initial γ-adduct formation at the sp-boron center and Pt chelation yields the unstable complexes 2-Ar^ED/big. These lose N₂ in a Staudinger-type reaction, generating a basic >B═NAr^ED/big moiety, which C-H-borylates the neighboring dmpm CH₂ bridge. Finally, [2 + 3] cycloaddition of the remaining B≡N moiety with N₃Ar^ED/big yields the diplatinum(I) complexes 1-Ar^ED/big, bridged by one tetrazaborolyl-substituted dmpm ligand. For electron-poor aryl azides (N₃Ar^EW), the adducts 2-Ar^EW decompose to the unstable nitrene-bridged A-frame complexes 4-Ar^EW. With additional N₃Ph^F5 (Ph^F5 = C₆F₅), 2-Ph^F5 undergoes a (B-Pt)-to-(N-Pt) shift, followed by a Staudinger-type reaction at B1, yielding the (ArN₂)NBN(BNAr)-bridged A-frame complex 3-Ph^F5, which decomposes to VIII. With N₃TMS, B≡N azidosilylation and TMSBr elimination lead to the unsymmetrical (azidoborylimino)boryl diplatinum(I) complex 5. With N₃BPh₂, V undergoes a Staudinger reaction at the sp-boron center, followed by a (Pt-B)-to-(Pt-N) shift, generating the 1,3-diazadiboretidine-1,2-diyl-bridged A-frame complex 6-BPh₂. With the more polarized N₃BCat (Cat = catecholato), a B≡N azidoboration yields the boranediyl-bridged A-frame complex 7-BCat. While X-ray crystallography provides structural evidence for the majority of products, in-situ multinuclear NMR spectroscopy and calculations provide valuable insights into reaction mechanisms and selectivity.