Abstract: Examination of the temperature dependence of the proton nmr spectrum of 2- isopropylp, henylbis (4, 4'-dimethyl-2, 2'-biphenylylene) phosphorane (1) suggests that pseudorotation of this compound does not occur by a simple Berry process but rather by a mechanisminvolving a square pyramidal intermediate (Scheme I). The permutation of the 4- and 4'-biphenylylene sites resulting from this intermediate is the same as that which would ...
