Synthesis, Structure, and Reactivity of a Pyridine-Stabilized Germanone

The first isolable pyridine-stabilized germanone has been prepared and its reactivity toward trimethylaluminum has been investigated. The germanone adduct results from a stepwise conversion that starts from 4-dimethylaminopyridine (DMAP) and the ylide-like N-heterocyclic germylene LGe: (L=CH{(C=CH2)(CMe)[N-(aryl)](2)}, aryl=2,6- iPr(2)C(6)H(3)) (1) at room temperature, and gives the corresponding germylene-pyridine adduct L(DMAP)Ge: (2) in 91% yield. The latter reacts with N2O at room temperature to form the desired germanone complex L(DMAP)Ge=O (3) in 73% yield. The Ge-O distance of 1.646(2) angstrom in 3 is the shortest hitherto reported for a Ge=O species. The reaction of 3 with trimethylaluminum leads solely to the addition product LGe(Me)O[Al(DMAP)Me-2] (4). The latter results from insertion of the Ge=O subunit into an Al Me bond of AlMe3 and concomitant migration of the DMAP ligand from germanium to the aluminum atom. Compounds 2-4 have been fully characterized by analytical and spectroscopic methods. Their molecular structures have been established by single-crystal X-ray crystallographic analysis.