Abstract
Diastereomer separation by fractional crystallization is the most important method for the resolution of enantiomers in research as well as in industry. Herein we describe two different types of diastereomer co-crystallization, which impede diastereomer separation. The two diastereomers (R-Fe,R-C)- and (S-Fe,R-C)-[CpFe(Prophos)PPh(OMe)(2)]PF6, differing only in the metal atom configuration, form ...
Abstract
Diastereomer separation by fractional crystallization is the most important method for the resolution of enantiomers in research as well as in industry. Herein we describe two different types of diastereomer co-crystallization, which impede diastereomer separation. The two diastereomers (R-Fe,R-C)- and (S-Fe,R-C)-[CpFe(Prophos)PPh(OMe)(2)]PF6, differing only in the metal atom configuration, form 1:1 co-crystals with a racemate-like lattice. Between the (R-Fe,R-C) and (S-Fe,R-C) diastereomers there is an almost-inversion center and the (R-Fe,R-C)/(S-Fe,R-C) pair repeats as a kind of dimer in the lattice. Crystallization of a 50:50 diastereomer mixture of (R-Ru,R-C)- and (S-Ru,R-C)-[MeCpRu(Prophos)Cl] gave (R-Ru,R-C)/(S-Ru,R-C) 7:93 co-crystals, and another crystallization afforded diastereomerically pure (S-Ru,R-C)-[MeCpRu(Prophos)Cl]. In the co-crystal, the 93% component (S-Ru,R-C)-[MeCpRu(Prophos)Cl] dictates the build-up of a conglomerate-like lattice, and the 7% component (R-Ru,R-C)-[MeCpRu(Prophos)Cl] has to adopt its M-Prophos chelate ring conformation, although diastereomerically pure (R-Ru,R-C)-[MeCpRu(Prophos)Cl] has a completely different chelate ring conformation.
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