Spontaneous resolution of a bis( η1-methylcyclopentadienyl)zinc complex

Abstract

Two crystalline complexes of bis( η 1-methylcyclopentadienyl)zinc, [Zn(C 5H 4Me) 2(py) 2] ( 1), where py is pyridine, and [Zn(C 5H 4Me) 2(teeda)], 2, where teeda is N, N, N′, N′-tetraethylethylenediamine have been isolated. The crystal structures of 1 and 2 are the first crystal structures for Zn(C 5H 4Me) 2 complexes reported in the literature; both structures display η 1-coordination of the methylcyclopentadienyl ring to zinc, and both compounds display chirogenic α-carbon atoms. While 1 forms racemic crystals, 2 undergoes spontaneous resolution and crystals of 2 are thus enantiomerically pure. 1H NMR showed that Zn(C 5H 4Me) 2 is stereochemically labile in solution with only one signal for the Cp-protons. This fact opens up the possibility for total spontaneous resolution and absolute asymmetric synthesis.