New Bis‐ o ‐Benzoquinoid Ligands with Ethylene Bridge and Their Metal Complexes

The treatment of di‐ o ‐quinone 4,4′‐(ethane‐1,2‐diyl)‐bis(3,6‐di‐ tert ‐butyl‐ o ‐benzoquinone) (Q–CH 2 –CH 2 –Q, 1 ) leads to its rearrangement to form di‐ p ‐quinomethide 4,4′‐(ethane‐1,2‐diylidene)bis(2‐hydroxy‐3,6‐di‐ tert ‐butyl‐cyclohexa‐2,5‐dienone) ( 2 ). The subsequent oxidation of 2 by an alkaline solution of K 3 [Fe(CN) 6 ] yielded the new di‐ o ‐quinone 4,4′‐(ethene‐1,2‐diyl)bis(3,6‐di‐ tert ‐butyl‐ o ‐benzoquinone) (Q–CH=CH–Q, 3 ), which contains an ethylene bridge. The formation of mono‐ and poly‐reduced derivatives of 2 and 3 with potassium, thallium was studied by EPR technique. The dinuclear thallium derivative of 3 , Tl(SQ–CH=CH–SQ)Tl, was found to exist in the diamagnetic quinomethide form. The most stable derivatives of 2 and 3 are triphenyltin(IV) bis‐ p ‐quinomethide‐phenolate ( 4 ) and triphenylantimony(V) bis‐catecholate ( 5 ), which have been synthesized and isolated. The molecular structures of 2 , 3 , and 5 were characterized by single‐crystal X‐ray diffraction.