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

Two crystalline complexes of bis(η1-methylcyclopentadienyl)zinc, [Zn(C5H4Me)2(py)2] (1), where py is pyridine, and [Zn(C5H4Me)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(C5H4Me)2 complexes reported in the literature; both structures display η1-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(C5H4Me)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.