Dual Activation of H2 and CO2 by a Pincer-Type Ni-Zn Heterobimetallic Complex.

Various Ni-based metalloenzymes employ synergistic heterometallic cooperativity where a Ni center and a second metal ion cofacilitate small-molecule conversion. Inspired by these biological systems, synthetic model complexes have been developed that exploit bimetallic cooperativity to achieve analogous reactivity. In this work, we report a bimetallic Ni-Zn complex comprising a pincer-type diamido-diaminodiphosphine ligand, in which a weakly Lewis acidic Zn(II) center stabilizes a T-shaped Ni(0) site. Subsequent reactivity with H2 led to the isolation of a rare Ni dihydride complex, which dynamically interconverts between Zn(μ-H)Ni(H) and trans-Ni(H)2 motifs via rotational rocking about the P-Ni-P axis. The Ni dihydride complex is a competent alkene hydrogenation catalyst (5 mol% loading, 70°C, 2 bar H2) for terminal olefins. Also, the Ni dihydride inserts CO2 to give a rare Ni hydrido formate. This product further reacts with a second equivalent of CO2 through a carboxylate shift mechanism that unveils a nucleophilic Zn(II) amide group that inserts CO2 to give carbamate. Collectively, our experimental and computational results highlight the role of Zn(II) as a weakly Lewis acidic partner, which promotes the dual activation of H2 and CO2 by a single Ni center in the absence of any external base.