Another Mode of Cooperative Racemization with Solvent Benzene

3 Another Mode of Cooperative Racemization with Solvent Benzene 

When the crystal of [/ -l-(methoxycarbonyl)ethyl](cyclopentylamine)-cobaloxime, (i -l-mce)(cpa)cobaloxime, 8, was exposed to visible light, another mode of racemization was observed [42], The crystal belongs to the monoclinic system and the space group is P2i. There are two crystaUographically independent molecules, A and B, and one solvent benzene molecule in the asymmetric unit as shown in Fig. 3.32. There is a pseudo inversion center between A and B. A disordered benzene molecule is situated on the pseudo inversion center between the chiral 1-mce groups of A and B. The molecular stractures of A and B are shown in Fig. 3.33. The 1-mce groups of A and B take syn and anti conformations, respectively. This structure is very similar to that of the previous cha complex except that the two 1-mce groups have different conformations. 

3 Racemizations of Alkyl Groups in Cobaloxime Complex Crystals 

When the axial base was replaced with benzylamine (ba, 9), some interesting results were obtained. The crystals were grown from methanol [38,42,44], ethanol [44], acetonitril [44], and methyl acetate [45], Four kinds of crystals with different solvent molecules were obtained. Each crystal revealed the photo-racemization. However the processes were different with each other. The details of the racemiza-tion processes with the solvent molecules were recently reviewed [46]. 

The above results clearly indicate that the existence of the solvent and the relative position between the reactive group and the solvent molecule should control the reaction pathway and may produce the different products. 

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