Carbon dioxide binding at a Ni/Fe center: synthesis and characterization of Ni(η¹-CO₂-κC) and Ni-μ-CO₂-κC:κ²O,O′-Fe

Abstract

The degree of CO₂ activation can be tuned by incorporating a distinct electronic coordination environment at the nickel center. A mononuclear nickel carboxylate species (Ni-CO₂, <b>3</b>) and a dinuclear nickel-iron carboxylate species (Ni-CO₂-Fe, <b>5</b>) were prepared. The structure of <b>3</b> reveals a rare η¹-κ<i>C</i> binding mode of CO₂, while that of <b>5</b> shows bridging CO₂ binding (μ₂-κ<i>C</i>:κ²<i>O</i>,<i>O</i>') between the nickel and iron, presented as the first example of a nickel-μ-CO₂-iron species. The structural analyses of <b>3</b> and <b>5</b> based on XRD and DFT data reveal a higher degree of CO₂ activation in <b>5</b>, imparted by the additional interaction with an iron ion.