Technological societies have seen a substantial increase in consumption of carbon based fuels since the onset of bulk manufacturing of goods and services beginning in the 18th century. This has created an inexhaustible carbon reserve in refractory CO2 with no efficient strategy for carbon recycling. This presentation describes how a multifunctional ligand scaffold is being studied alongside chromium, a metal that is often overlooked in CO2 reductive processes. Divalent chromium, Cr(N(SiMe3)2)2(THF)2, served as an attractive starting material to leverage acidic proton in bis-pyrazolylpyridine, H2L, to accomplish a goal of “pre-organized” metal complex for CO2 transformation. Indeed, reaction of Cr(N(SiMe3)2)2(THF)2 with H2L led to the formation of oligomeric Cr(II) products, including a rare tetra-chromium complex with four reducing equivalents “pre-loaded.” Chemically reduced [LCr]4 reacts with CO2 within five minutes to produce CO, CO32−, and in the presence of adventitious (SiMe3)2N−, a novel OC(O)OC(O)OCN− ligand. This work ultimately establishes that chemically reduced Cr supported by L2− is competent for CO2 reduction. In addition, chromium carbonyl complexes with a dianionic ligand are also described with the goal of converting carbon monoxide to value-added products.

Redox-active pincer ligands on chromium: Carbonate formation from a neglected metal

254th National Meeting (2017)

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