Lithium Derivatives of 5-Methyl-5,10-dihydroindeno[1,2-b]indole and 1,3,5-Trimethyl-6H-dihydroindeno[2,1-b]indole: Synthesis and Molecular Structure

The reaction of 1,3-dimethyl-5,6-dihydroindeno[2,1-b]indole with methyl iodide in the presence of cetyltrimethylammonium bromide produced 1,3,5-trimethyl-6H-indeno[2,1-b]indole (L1H). The molecular structure of the compound was confirmed by X-ray diffraction analysis. The ligands L1H and 5-methyl-5,10-dihydroindeno[1,2-b]indole (L2H) were metallated with n-butyllithium in diethyl ether at 0°C to give the corresponding lithium derivatives L1Li(Et2O)2 (I) and L2Li(Et2O)2 (II). According to the X-ray diffraction data, lithium complex II has a monomeric structure, and the asymmetric unit contains two crystallographically independent molecules of the complex. In molecule IIb, the lithium cation is coordinated to the five-membered ring of the ligand in an η5-type, whereas in molecule IIa, coordination occurs in an η3-type manner.