A Cationic Barium Hydride Complex Supported by an NNNN‐Type Macrocycle

The dibenzyl complex of barium [(Me 4 TACD)Ba(CH 2 Ph) 2 ] was prepared by reacting [Ba(CH 2 Ph) 2 ] with NNNN‐type macrocycle Me 4 TACD (Me 4 TACD=1,4,7,10‐tetramethyltetraazacyclododecane) and isolated as yellow crystals. Single crystal X‐ray diffraction revealed η 2 ‐ and η 3 ‐coordination of the benzyl groups. The benzylbarium cation in [(Me 4 TACD)Ba(CH 2 Ph)(thf)][B(C 6 H 3 ‐3,5‐Me 2 ) 4 ] was obtained upon protonolysis of the neutral bariumdibenzyl with the weak Brønsted acid [NEt 3 H][B(C 6 H 3 ‐3,5‐Me 2 ) 4 ] and isolated as colorless crystals. When the benzylbarium cation was reacted with H 2 (1 bar) in THF at room temperature, colorless crystals of the dinuclear hydride complex [(Me 4 TACD) 2 Ba 2 (μ‐H) 2 (thf) 4 ][B(C 6 H 3 ‐3,5‐Me 2 ) 4 ] 2 precipitated from the reaction mixture and characterized by single crystal X‐ray diffraction. The structural motif [Ba 2 (μ‐H) 2 ] 2+ was compared with that published in the literature. Hydrogenolysis of the dibenzyl [(Me 4 TACD)Ca(CH 2 Ph) 2 ] under the same conditions resulted in decomposition.