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)(2)C:]; Dipp = [2,6-Pr2C6H3]), 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.