Imino(silyl)disilenes: application in versatile bond activation, reversible oxidation and thermal isomerization

Abstract

Two novel disilenes of type ABSiSiAB bearing N-heterocyclic imino (A = NI^tBu) and trialkylsilyl (B = Si^tBu₃1, B = Si^tBu₂Me 2) groups are reported. The reduced steric demand in 2 results in a highly stable, nonetheless flexible system, wherefore (E/Z) isomerization is observed from room temperature up to 90 °C. The proposed isomerization mechanism proceeds via monomeric silylenes in line with experimental results. Despite enhanced stability, disilene 2 retains high reactivity in the activation of small molecules, including H₂. The rare example of a disilene radical cation 7 is isolated and shows reversible redox behavior. White phosphorous (P₄) selectively reacts with 2 to give the unique cage-compound 8. Selective thermal rearrangement of 2 at higher temperatures yields the A₂SiSiB₂-type disilene 9 (A = NI^tBu, B = Si^tBu₂Me), which bears characteristics of a zwitterionic and a dative central Si–Si bond. The proposed mechanism proceeds via an initial NHI migration followed by silyl migration.