Novel approach for the synthesis of chiral organometallic complexes - first series of lithium 2-amino-indenide ligands bearing pendant donor groups and a unique helical -zirconocene

A broad series of mono- and bis-2-aminoindenyl ligands, bearing pendant donor sec -amine groups was synthesized via the reaction of indan-2-one with the corresponding secondary mono- and bis -amines: 1 -H from pyrrolidine, 2 -H from piperidine, 3 -H from morpholine, 4 -H from thiomorpholine, 5 -H from dibenzylamine, 6 -H 2 from N , N ′-diethyldiaminopropane-1,3, 7 -H 2 from piperazine, 8 -H 2 from S -(+)-prolinol, 9 -H from O -methyl- S -(+)-prolinol, 10 -H from O -ethyl- S -(+)-prolinol and 11 -H 2 from R -(-)- N -(2-anilinomethyl)-pyrrolidine. Direct metallation of 3 -H, 4 -H and 9 -H by n BuLi led to the formation of the corresponding mono-lithiated species 3 -Li, 4 -Li and 9 -Li. Trans -Metallation of 4 -Li by ZrCl 4 led to the formation of the presumably monomeric [( η 5 - 4 )ZrCl 3 ] 12 . Partial hydrolysis of 12 occurred after several attempts to crystallize it and led to the formation of its 1 : 1 adduct with the free ligand 4 -H, [( η 5 - 4 )ZrCl 3 (μ- N , S - 4 -H)] 13 . Direct metallation of 8 -H 2 with [Zr(NEt 2 ) 4 ] led to the formation of a chiral bent -zirconocene with a helical structure [( η 5 ,μ- O - 8 ) 2 Zr] 14 . The molecular structure of enantiomerically pure 9 -Li was determined using X-ray crystallographic studies. Alternating Li + and chelating indenyl anions are linked in infinite chains. The coordination environment of Li + consists of the η 5 -bonded five-membered ring of the indenyl fragment, the η 1 -bonded adjacent ligand and the donor sp 3 nitrogen and oxygen atoms of the chelating side chain. Direct metallation of chiral 2-amino-indenyl ligands leads to a lithiated species linked in infinite chains and a unique helical bent zirconocene.