A stable free tetragermacyclobutadiene incorporating fused-ring bulky EMind groups.

The first free cyclobutadiene (CBD) germanium analogue was obtained as room-temperature stable dark red crystals via the reaction of the bulky EMind-substituted 1,2-dichlorodigermene with lithium naphthalenide. The cyclic 4π-electron antiaromaticity is essentially stabilized by the polar Jahn-Teller distortion in the germanium CBD producing a planar rhombic-shaped charge-separated structure.

1,2-Dihalodigermenes bearing bulky Eind groups: synthesis, characterization, and conversion to halogermylenoids.

1,2-Dihalodigermenes, (E)-(Eind)XGe[double bond, length as m-dash]GeX(Eind) (X = Br and Cl), bearing the fused-ring bulky Eind group (Eind = 1,1,3,3,5,5,7,7-octaethyl-s-hydrindacen-4-yl) have been isolated as orange-yellow crystals by the ligand redistribution reaction between the diarylgermylene, (Eind)2Ge:, and GeX2·dioxane in toluene via the cleavage and recombination of the Ge-C and Ge-X bonds. The dihalodigermenes have a Ge[double bond, length as m-dash]Ge double bond character in the crystalline state, but dissociate into halogermylenes, (Eind)XGe:, in solution. The addition of excess LiBr to the THF solution of the bromogermylene, (Eind)BrGe:, led to the formation of an equilibrium mixture containing the lithium bromogermylenoid, [Li+][(Eind)GeBr2]-. The bromogermylenoid can be isolated as a cryptand-separated potassium ion pair, [K+(crypt-222)][(Eind)GeBr2]-, which has been structurally characterized.

Synthesis and Structural Characterization of Lithium and Titanium Complexes Bearing a Bulky Aryloxide Ligand Based on a Rigid Fused-Ring s-Hydrindacene Skeleton.

The bulky aryl alcohols, (Rind)OH (1) [Rind = EMind (a) and Eind (b)], based on the rigid fused-ring 1,1,3,3,5,5,7,7-octa-R-substituted s-hydrindacene skeleton were prepared by the reaction of (Rind)Li with nitrobenzene followed by protonation. The treatment of 1 with (n)BuLi affords the lithium aryloxide dimers [(Rind)OLi(THF)]2 (2) or trimers [(Rind)OLi]3 (3), depending on the employed solvents (THF = tetrahydrofuran). The salt metathesis reaction of [(EMind)OLi(THF)]2 (2a) with TiCl4(THF)2 leads to the formation of the mononuclear diamagnetic mono- and bis(aryloxide) Ti(IV) complexes, [(EMind)O]TiCl3(THF) (4a) and [(EMind)O]2TiCl2 (5a). We also isolated a trace amount of the tris(aryloxide) Ti(IV) complex, [(EMind)O]3TiCl (6a). The reaction between 2a and TiCl3(THF)3 resulted in the isolation of the mononuclear paramagnetic mono- and bis(aryloxide) Ti(III) complexes, [(EMind)O]TiCl2(THF)2 (7a) and [(EMind)O]2TiCl(THF)2 (8a). The discrete monomeric structures of the titanium complexes 4a, 5a, 6a, 7a, and 8a were determined by X-ray crystallography.

Synthesis, structures and optical properties of trisilasumanene and its related compounds.

Novel trisilasumanenes that have no substituents on the exo carbon atoms, silicon analogues of sumanene, were prepared via repetitive lithiations of triphenylene followed by introduction of silicon functionalities. The optical properties of these trisilasumanenes and their related compounds were investigated by UV-vis and fluorescence spectroscopy.