Four Soft Donors and a Hard Centre: Rhodium Complexes of a Novel Tetrakis(NHC)‐Encapsulated Crown Ether Ligand

2,3,13,14‐Tetrakis(bromomethyl)dibenzo‐18‐crown‐6 ( 1 ) has been demonstrated to be a versatile synthetic intermediate for constructing multinucleating ligands with a hard‐donor, crown ether centre. By using this intermediate, novel salts of tetrakis(imidazoliomethyl)dibenzo‐18‐crown‐6, [H 4 L 1 ]X 4 ( 2 : X – = Br – ; 4 : X – = PF 6 – ), and tetrakis(benzimidazoliomethyl)dibenzo‐18‐crown‐6, [H 4 L 2 ]X 4 ( 3 : X – = Br – ; 5 : X – = PF 6 – ), were prepared. These salts are precursors to novel tetrakis(N‐heterocyclic carbene) complexes spanned by a crown ether bridge capable of binding various hard metal ions. Thetetrakis(imidazoliomethyl) salt 4 was used to prepare the bimetallic rhodium complexes [{(cod)Rh} 2 (μ‐L 1 )][PF 6 ] 2 ( 6 ) and [{(CO) 2 Rh} 2 (μ‐L 1 )][PF 6 ] 2 ( 7 ). These complexes selectively bind alkali metal ions.