The Structure of the Carbene Stabilized Si₂H₂ May Be Equally Well Described with Coordinate Bonds as with Classical Double Bonds

The cyclic alkyl­(amino) carbene stabilized Si₂H₂ has been isolated in the molecular form of composition (Me-cAAC:)₂Si₂H₂ (1) and (Cy-cAAC:)₂Si₂H₂ (2) at room temperature. Compounds 1 and 2 were synthesized from the reduction of HSiCl₃ using 3 equiv of KC₈ in the presence of 1 equiv of Me-cAAC: and Cy-cAAC:, respectively. These are the first molecular examples of Si₂H₂ characterized by single crystal X-ray structural analysis. Moreover, electrospray ionization mass spectrometry and ¹H as well as ²⁹Si NMR data are reported. Furthermore, the structure of compound 1 has been investigated by theoretical methods. The theoretical analysis of 1 explains equally well its structure with coordinate bonds as with classical double bonds of a 2,3-disila-1,3-butadiene.