Persistent π-arene interactions in bulky formamidinate complexes of potassium

The reaction of potassium hexamethyldisilazide (K-HMDS) with 1 equiv. of the bulky formamidine N(Diep)=C(H)NH(Diep) (Diep-FormH, Diep = 2,6-Et2C6H3) in THF yields the half deprotonated compound [K(DiepForm)(DiepFormH)] (1), which exhibits suppressed reactivity with the hexamethyldisilazide anion. Reaction of 1 with n-BuLi gives the polymer [{Li(THF)(2)K(DiepForm)(2)}(n)] (2). Preparation of 1 in the presence of the chelating solvents 1,2-dimethoxyethane (DME) or N,N,N',N",N"-pentamethyldiethylenetriamine (PMDETA) gives the fully deprotonated species [{K-3(DiepForm)(3)(DME)(3)}(n)](3) and [{K(PMDETA)K(DiepForm)(2)}(n)] (6). The syntheses of compounds 1-3, 6 and related compounds, e.g. [{K-3[N(Dimp)C(H)N(Dimp)}(3)(DME)(3)}(n)] (4) (Dimp=2,6-Me2C6H3), are described. (c) 2007 Elsevier B.V. All rights reserved.