Facially Dispersed Polyhydride Cu9 and Cu16 Clusters Comprising Apex‐Truncated Supertetrahedral and Square‐Face‐Capped Cuboctahedral Copper Frameworks

By using a linear tetraphosphine, meso-bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm), nona- and hexadecanuclear copper hydride clusters, [Cu₉ H₇ (μ-dpmppm)₃ ]X₂ (X=Cl (1 a), Br (1 b), I (1 c), PF₆ (1 d)) and [Cu₁₆ H₁₄ (μ-dpmppm)₄ ]X₂ (X₂ =I₂ (2 c), (4/3) PF₆ ⋅(2/3) OH (2 d)) were synthesized and characterized. They form copper-hydride cages of apex-truncated supertetrahedral {Cu₉ H₇ }²⁺ and square-face-capped cuboctahedral {Cu₁₆ H₁₄ }²⁺ structures. The hydride positions were estimated by DFT calculations to be facially dispersed around the copper frameworks. A kinetically controlled synthesis gave an unsymmetrical Cu₈ H₆ cluster, [Cu₈ H₆ (μ-dpmppm)₃ ]²⁺ (3), which readily reacted with CO₂ to afford linear Cu₄ complexes with formate bridges, leading to an unprecedented hydrogenation of CO₂ into formate catalyzed by {Cu₄ (μ-dpmppm)₂ } platform. The results demonstrate that new motifs of copper hydride clusters could be established by the tetraphosphine ligands, and the structures influence their reactivity.