Bis(4‐benzhydryl‐benzoxazol‐2‐yl)methane – from a Bulky NacNac Alternative to a Trianion in Alkali Metal Complexes

A novel sterically demanding bis(4‐benzhydryl‐benzoxazol‐2‐yl)methane ligand 6 ((4−BzhH2)BoxCH(2)) was gained in a straightforward six‐step synthesis. Starting from this ligand monomeric [M((4‐BzhH2)BoxCH)] (M=Na (7), K (8(1) )) and dimeric [{M((4‐BzhH2)BoxCH)}(2)] (M=K (8(2) ), Rb (9), Cs (10)) alkali metal complexes were synthesised by deprotonation. Abstraction of the potassium ion of 8 by reaction with 18‐crown‐6 resulted in the solvent separated ion pair [{(THF)(2)K@(18‐crown‐6)}{bis(4‐benzhydryl‐benzoxazol‐2‐yl)methanide}] (11), including the energetically favoured monoanionic (E,E)‐((4‐BzhH2)BoxCH) ligand. Further reaction of (4−BzhH2)BoxCH(2) with three equivalents KH and two equivalents 18‐crown‐6 yielded polymeric [{(THF)(2)K@(18‐crown‐6)}{K@(18‐crown‐6)K((4‐Bzh)BoxCH)}](n) (n→∞) (12) containing a trianionic ligand. The neutral ligand and herein reported alkali complexes were characterised by single X‐ray analyses identifying the latter as a promising precursor for low‐valent main group complexes.