Cationic barium benzyl and hydride complexes that contain an eighteen-membered N,N,N,N,N,N-type macrocycle

Abstract

Using the eighteen-membered polyamine macrocycle Me6HACO (Me6HACO = 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane, Me6[18]aneN6), the synthesis of a hydride cation [(Me6HACO)BaH)]+ was attempted by hydrogenolysis of the benzyl cation. Protonolysis of [Ba(CH2Ph)2] with the conjugate acid of the macrocyclic ligand [(Me6HACO)H][B(C6H3-3,5-Me2)4] afforded the benzyl cation [(Me6HACO)Ba(CH2Ph)][B(C6H3-3,5-Me2)4], which was recrystallized from THF/n-pentane at −40 °C. Single crystal X-ray diffraction analysis showed a seven-coordinate metal center with an η1-coordinated benzyl ligand, subtending a long Ba-C distance of 2.85 Å. The macrocyclic ligand is folded with two opposite methyl groups pointing away from the metal center, while the other four methyl groups are oriented towards the metal center. Hydrogenolysis of the benzyl cation indicated the formation of toluene and a hydride species with a 1H NMR signal at δ = 8.82 ppm but the product could not be isolated.