Creation of Optically Pure Crystals from a Meso-Type Gold(I) Metalloligand with d- and l-Amino Acids: A Coordination Trick.

Abstract

A unique example of a coordination system that creates optically pure crystals from a meso compound with d- and l-amino acids is reported. The 1:1 reaction of a newly prepared meso digold(I) complex, [Au2 (dcpe)(d-Hpen)(l-Hpen)] ([H2 1]), with Co(OAc)2 under aerobic conditions yielded a cationic AuI2 CoIII trinuclear complex, [Au2 Co(dcpe)(d-pen)(l-pen)]+ [2]+ , in which [1]2- acts as a hexadentate-N2 ,O2 ,S2 metalloligand to a CoIII center. Similar reactions with M(OAc)2 (M=Ni and Zn) produced analogous but neutral AuI2 MII complexes, [Au2 M(dcpe)(d-pen)(l-pen)] ([3M ]). Complexes [2]+ and [3M ] are chiral (C vs. A) at the octahedral CoIII and MII centers due to the arrangement of the N2 ,O2 ,S2 donor set. In addition, through spontaneous resolution, [3M ] gave optically pure C-[3M ] and A-[3M ] crystals, showing the creation of homochirality from meso-[1]2- and achiral M2+ through crystallization. Such a phenomenon was not observed for [2]+ , which gave a racemic compound containing both C-[2]+ and A-[2]+ .