Synthesis and Characterization of a Series of Diarylgermylenes and Dihalodigermenes Having Fused-Ring Bulky “Rind” Groups

A series of diarylgermylenes, (Rind)2Ge: (1) [Rind = EMind (a), Eind (b), and MPind (c)], bearing the fused-ring bulky 1,1,3,3,5,5,7,7-octa-R-s-hydrindacen-4-yl (Rind) groups has been obtained as purple to blue crystals by the reaction of GeCl2·dioxane with 2 equiv. of (Rind)Li. A similar reaction using 1 equiv. of (Rind)Li affords the 1,2-dibromodigermenes, (Rind)BrGe=GeBr(Rind) (2) [Rind = Eind (b) and MPind (c)], as yellow to orange crystals. The ligand redistribution reaction between 1 and GeCl2·dioxane in toluene leads to the formation of the 1,2-dichlorodigermenes, (Rind)ClGe=GeCl(Rind) (3) [Rind = EMind (a), Eind (b), and MPind (c)]. The molecular structures of 1a, 1c, 2c, and 3c have been newly determined by X-ray crystallographic analysis. The 1,2-dihalodigermenes, (Rind)XGe=GeX(Rind) [X = Br (2) and Cl (3)], show a dimeric form with a Ge=Ge double bond in the solid state, but exist as a monomeric halogermylene, (Rind)XGe: [X = Br (4) and Cl (5)], in solution. The electronic properties of the Rind-based diarylgermylenes, dihalodigermenes, and halogermylenes have been experimentally and theoretically investigated.