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)double bond; length as m-dashC(H)NH(Diep) (DiepFormH, 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)2K(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 [{K3(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. [{K3{N(Dimp)C(H)N(Dimp)}3(DME)3}n] (4) (Dimp = 2,6-Me2C6H3), are described.