Tetrylenes based on 1,10-phenanthroline-containing diol: the synthesis and application as initiators of ε-caprolactone polymerization

Treatment of 4,7-dichloro-2,9-dimethyl-1,10-phenanthroline with two equivalents of p-tert-butylphenol in the presence of К2СО3 afforded 4,7-di(4-tert-butylphenoxy)-2,9-dimethyl-1,10-phenanthroline (1). Monolithiation of 1 with lithium diisopropylamide followed by treatment with benzophenone resulted in 1-(4,7-bis-p-tert-butylphenoxy-9-methyl-1,10- phenanthrolin-2-yl)methyl-1,1-diphenylethanol (2). 1-(4,7-Bis-p-tert-butylphenoxy-9-hydroxy (diphenyl)methyl-1,10-phenanthrolin-2-yl)-1,1-diphenylethanol (3), a tetradentate ONNO ligand, was prepared analogously from 2. The interaction of 3 with 1 eq. of Lappert’s germylene or stannylene M[N(SiMe3)2]2 (M = Ge, Sn) led to the corresponding germylene 4 and stannylene 5 in moderate yields. According to 1Н, 13С, and 119Sn NMR spectroscopy data, stannylene 5 is monomeric in solution and the coordination number of tin atom is 4. Tetrylenes 4 and 5 demonstrated high activity as initiators of bulk polymerization of ε-caprolactone which leads to high-molecular-weight polymers with relatively narrow molecular weight distribution.