Acylation of Homoatomic Ge₉ Cages and Subsequent Decarbonylation

The direct acylation of Ge₉ Zintl clusters by the reaction of K[Ge₉{Si(SiMe₃)₃}₃] with acyl chlorides in hexane or toluene solutions is presented, leading to the neutral, carbonyl-derivatized products [{Si(SiMe₃)₃}₃Ge₉(CO)R′] (R′=Me, iPr, tBu, Ph, Bz, cyclopropylmethyl, phenethyl, 4-vinylphenyl). This reaction is applicable to a wide range of acyl chlorides and allows for diverse functionalization of Ge₉ Zintl clusters. [{Si(SiMe₃)₃}₃Ge₉(CO)tBu] readily releases CO at ambient conditions under formation of [{Si(SiMe₃)₃}₃Ge₉tBu]. This temperature-dependent decarbonylation most likely proceeds via a radical Norrish-type I α-bond cleavage. Except for R′=tBu and Bz all obtained acyl-derivatized Ge₉ cluster compounds do not release CO even at elevated temperatures. All compounds were characterized by NMR spectroscopy. [{Si(SiMe₃)₃}₃Ge₉(CO)R′] (R′=tBu, Ph, Me, iPr) as well as [{Si(SiMe₃)₃}₃Ge₉tBu] were further structurally characterized by single crystal X-ray diffraction.