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.