Both the N-heterocyclic carbene (NHC) 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr) and its corresponding hydrochloride salt (SIPrHCl) were each reacted with either GeCl2·dioxane or SnCl2, resulting in the isolation of SIPr-ECl2 or SIPrHECl3 respectively (where E = Ge, Sn). Two procedures to isolate group 14 trihalide salts have been done, one allowing for manipulation in air without concern for moisture in its preparation. Attempts have been made to isolate the corresponding carbene adducts of reduced, zero oxidation state germanium and tin dimeric compounds ((SIPrE0)2). The target compounds appear considerably unstable, and the only indication of the formation of this type of compound is for (SIPrGe0)2 which could be identified using single crystal X-ray crystallography on one of the few small red crystals that were isolated alongside starting material.
George et al. (Wed,) studied this question.