Octalithium, Tetrasodium, and Decalithium Compounds Based on Pyrrolyl Ligands: Synthesis, Structures, and Activation of the C-H Bonds of Pyrrolyl Rings and CN Bonds of a Series of Ligands by Organolithium Reagents

The organometallic compounds of lithiumions have garnered continuousinterest as indispensable precursors for the syntheses of organometalliccomplexes of main-group metals, transition metals, lanthanide metals,and actinide metals. In this work, we present a strategy for the preparationof a series of polynuclear lithium complexes. This methodology featuresthe utilization of organolithium reagents both as metal sources tocoordinate with the ligands and as nucleophilic reagents to undergonucleophilic addition to the C N bonds of the ligands. Reactionof a ligand HL1 [HL1 = 2-(((1-(2-(dimethylamino)ethyl)-1H-pyrrol-2-yl)methylene)amino)phenol] with n-BuLiproduced complex [Li-8(L1a)(4)]& BULL;1.5Tol (1 & BULL;1.5Tol) [H ( 2 ) L1a = 2-((1-(1-(2-(dimethylamino)ethyl)-1H-pyrrol-2-yl)pentyl)amino)phenol]. One prominent feature regardingthe formation of 1 & BULL;1.5Tol is the occurrence of nucleophilicaddition of n-BuLi to the C N bond of HL1,leading to the generation of a new [L1a](2-) ligandthat contains both aminophenol and 1-(2-pyrrolyl)alkylamine scaffolds.The developed protocol can be adapted to a series of organolithiumreagents. Compounds [Li-8(L1b)(4)] (2) and [Li-8(L1c)(4)] (3) were affordedby treatment of HL1 with sec-BuLi and LiCH2SiMe3, respectively. Reaction of an analogous ligand HL2[HL2 = 2-(((1-(2-(dimethylamino)ethyl)-1H-pyrrol-2-yl)methylene)amino)-4-methylphenol]with n-BuLi generated compound [Li-8(L2a)(4)] (4). C N bond activation was not observedin the reaction of HL1 with (NaOBu)-Bu- t , andthe complex [Na-4(L1)(4)]& BULL;Tol (5 & BULL;Tol) was obtained. A decanuclear complex [Li-10(L3a)(2)(L3b)(2)] (6) was also prepared viathe reaction of HL3 [HL3 = 2-(2-((((1H-pyrrol-2-yl)methylene)amino)methyl)-1H-pyrrol-1-yl)-N,N-dimethylethan-1-amine]with t-BuLi. A remarkable feature in terms of thesynthesis of 6 is the simultaneous occurrence of hydrogenatom abstraction from the C-H bond of the pyrrolyl ring andnucleophilic addition to the C N bond of the HL3 ligand by t-BuLi. A series of amines containing biologically and physiologicallyimportant moieties were achieved by hydrolysis of the crude productsfrom the reactions of the HL1-HL3 ligands and organolithiumreagents. This work provides an efficient approach to high-nuclearitylithium compounds as well as a series of amines. A series of polynuclear lithium compounds based on a classof pyrrolyl-containing Schiff-base ligands were prepared and characterized.The nucleophilic addition of organolithium reagents to the C Nbond of the ligands occurred during the processes for the formationsof the octalithium and decalithium compounds. A series of amines containingbiologically and physiologically important moieties were achievedby hydrolysis of the crude products from the reactions of the ligandsand organolithium reagents.