Drew-Pfitzner type

In 1939, Drew83 proposed structures for 2 1 chromium complexes of o,octahedrally coordinated to the central chromium ion (81). Pfitzner71 independently arrived at the same conclusion and 2 1 chromium complexes having this equatorial or meridional (mer) configuration have been described84 as Drew—Pfitzner types. This configuration permits only an enantiomeric pair of isomers. 

In contrast, chromium (ITT) and cobalt(III) form 2 1 dye metal complexes that have nonplanar stmctures. Geometrical isomerism exists. The (9,(9 -dihydroxyazo dyes (22) form the Drew-Pfitzner or y rtype (23) (A = C = O) whereas o-hydroxy—o -carboxyazo dyes (24) form the Pfeiffer-Schetty or fac type (25), where A = CO 2 and C = O. 

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See also in sourсe #XX -- [ ]

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