Synergistic Cu2 Catalysts for Formic Acid Dehydrogenation

Hexanuclear copper hydride complexes, [Cu 6 (μ 3 -H) 2 ( meso - L 4 ) 3 (RNC) 4 ](PF 6 ) 4 (R = t Bu ( 6a ), Cy ( 6b )), were prepared by using a new linear tetraphosphine, meso -Ph 2 PCH 2 P(Ph)(CH 2 ) 4 P(Ph)CH 2 PPh 2 ( meso- L 4 ), and were converted into active catalysts of [Cu 2 (μ-O 2 CH)( meso - L 4 )(RNC) 2 ] + under the reaction conditions of formic acid dehydrogenation, where unsymmetric dinuclear copper sites supported by the tetradentate phosphine and isocyanide ligands were essential to demonstrate effective catalytic activity.