1‑Aza-2,4-disilabicyclo[1.1.0]butanes with Superelongated C–N σ‑Bonds

Two silylene molecules oxidatively react under formal [1 + 2 + 1]-cycloaddition to the CN bond of nitriles to yield 1-aza-2,4-disilabicyclo­[1.1.0]­butanes (L)­(Cl)­Si­[μ-η1,2-NC­(p-RC6H4)]­Si­(Cl)­(L) (L = PhC­(NtBu)2, R = CF3 (2), F (3), Cl (4), Br (5)). The strongly folded bicyclic SiCNSi cores in 2–5 feature inverted bridgehead carbon atoms and superelongated C–N bonds [1.745(12) to 1.801(2) Å], exceeding the lengths of C–N single bonds in known silaaziridines by up to 23%. Detailed bonding analysis discloses C–N bonding interactions, sharing far-reaching similarities with the central C–C bond in [1.1.1]­propellane.