Abstract Reaction of the imidazolium‐stabilized diphosphete‐diide IDP with trityl phosphaalkyne affords a mixture which contains the molecules 1 a and 1 b with a central C3P3 core, which formally carries a two‐fold negative charge. In order to avoid the formation of an antiaromatic 8π electron system within a conjugated dianionic six‐membered C3P32− ring, 1 a adopts a bicyclic 3.1.0 and 1 b a tricyclic 2.2.0.0 structure which are in a dynamic equilibrium. 1 a, b can be reversibly oxidized to a triphosphinine dication 52+ with a central flat aromatic six‐membered C3P3 ring. This two‐electron redox reaction occurs in two single‐electron transfer steps via the 7π‐radical cation 4⋅+, which could also be isolated and fully characterized. The profound reversible structural change observed for the two‐electron redox couple 52+/1 a, b is in sharp contrast to the C6H6/C6H62− couple, which undergoes only a modest structural deformation.
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