CO2/13CO2 Dynamic Exchange in the Formate Complex [(2,9-(tBu)2-phen)Cu(O2CH)] and its Catalytic Activity in the Dehydrogenation of Formic Ac-id

Formate complexes of copper(I) are rare. We report here the synthesis, characterization, and crystal structure of the simple tricoordinate [(phen*)CuI(O2CH)] (1) supported with the bulky phenanthroline ligand 2,9-di-terbutyl-1,10-phenanthroline (phen*). Complex 1 decarboxylates at 100°C to give H2 and Cu(0) deposit with free phen*. To ensure that the degradation process goes through the hypothetical hydride [(phen*)CuH], Lewis acidic boron BR3 compounds (R = C6F5, Et) or organic scavengers have been introduced to trap it. In most case degradation occurs except with B(C6F5)3 that give the cationic complex [{(phen*)Cu}2(-HCO2)][(HCO2)B(C6F5)3] (2) which has been crystallized. While 1 does not react with CS2 when heated, it undergoes under 1 atm of 13CO2, a dynamic decarboxyla-tion/carboxylation process that indicates transient formation of the hydride. The catalytic activity of complex 1 in the dehydrogenation of formic acid is revealed.