Contrasting Reactivities of Silicon and Germanium Complexes Supported by an N‑Heterocyclic Guanidine Ligand

We report the synthesis of an acyclic two-coordinate germylene supported by two bulky and electron donating N-heterocyclic guanidine [IPrN]⁻ ligands (IPr = [(HCNDipp)₂C:]; Dipp = [2,6-ⁱPr₂C₆H₃]), and its reactivity with molecular hydrogen to form IPrNH, which presumably proceeds via the unstable intermediate [H₂Ge­(NIPr)₂]. Our attempts to isolate the corresponding silylene [:Si­(NIPr)₂] led to an unexpected ligand activation/rearrangement process involving N–C­(aryl) bond cleavage within the N-heterocyclic guanidine ligand; this transformation was also studied by computational methods.