Hidetoshi Watanabe

Reduction of the 1,4,5,8-tetrasila-1,4,5,8-tetrahydroanthracene derivative with lithium metal. Isolation and characterization of the tetralithium salt of a tetraanion, and observation of an Si–H⋯Li+ interaction

Abstract Treatment of 2,3,6,7-tetrakis(dimethylsilyl)-1,1,4,4,5,5,8,8-octamethyl-1,4,5,8-tetrasila-1,4,5,8-tetrahydroanthracene (1) with lithium metal in diethyl ether yields dark red crystals of the tetralithium salt of the tetraanion, 2, in which the two tetrasilylethylene units are subjected to a two-electron reduction. The molecular structure of 2, determined by X-ray crystallography, is discussed in comparison with that of the neutral molecule 1. Evidence for the interaction between Si–H and the Li+ ion of 2, in both solid state and solution, is also given.

Tetrasilyl-substituted cyclobutadiene dianion dilithium salt: synthesis and structure

The reaction of tetrakis(trimethylsilyl)cyclobutadienylcyclopentadienyl cobalt complex (Me3Si)4C4CoCp with lithium metal in THF yielded the dilithium salt of cyclobutadiene dianion CBD2– stabilized by four trimethylsilyl groups, Li+2[(Me3Si)4C4]2–. The bridged CBD2– dianion was also synthesized by a similar procedure starting from the bridged cobalt complex, which was prepared from the reaction of 2,2,5,5,8,8,11,11-octamethyl-2,5,8,11-tetrasilacyclododeca-1,6-diyne with CpCo(CO)2 in refluxing octane. The aromaticity of the CBD2– is discussed on the basis of the structural characteristics and magnetic properties.

Cyclobutadiene Dianion Dilithium: a New Aromatic Ring System

The reaction of tetrakis(trimethylsilyl)- (or cis-diphenyl) cyclobutadiene cobalt complexes with lithium metal in THF at room temperature produced the dilithium salts of tetrakis(trimethylsilyl)- (or cis-diphenyl) cyclobutadiene dianion, which were isolated as pale yellow (or pale orange) solids stable in the absence of air. NMR spectra and X-ray crystallography of these dianions provide the evidence for an aromatic character with a six π-electron system.