Diastereoselection through chiral conformations.
Chiral conformations of flexible mols. may develop in a concerted manner if the mol. is crowded enough to assure sufficient level of through-space contacts. Higher no. (>4) of groups connected to the same atom, as in many coordination compds., can be advantageous in this respect. The case study of [((R,S)-sBuO2CCH2)Co(CO)3(PPh3)] is presented here. X-ray diffraction shows that the possible no. of enantiomeric and diastereomeric conformations is reduced by 75% (from 8 to 2) by concerted development of the mol. conformations in cryst. phase. The complex was also studied by PM3 and d.-functional (B3LYP) methods.
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