Extending CO Chains to [C5O5]5–

Extending CO Chains to [C5O5]5–

Author: ChemistryViews

Carbon monoxide can be a useful C1 building block. Understanding how C–C bonds can form between CO units and how the resulting chain-growth reactions work can be important, e.g., for industrial processes. Metal complexes have been used as soluble model systems in this context. For example, complexes of CO-chain-based ligands such as [C4O4]4– have been synthesized.

Mathew D. Anker, Martyn P. Coles, Victoria University of Wellington, New Zealand, and colleagues have performed a reduction and homologation of CO to give C4 and C5 chains using an aluminyl anion. The team exposed a solution of the complex (NONDipp)Al–K(TMEDA)2 (NONDipp = [O(SiMe2NDipp)2]2–, Dipp = 2,6-iPr2C6H3, TMEDA = tetramethylethylenediamine) to one atmosphere of CO. They obtained a complex with a [C4O4]4– ligand, i.e., K2[{Al(NONDipp)}2(C4O4)].

When the researchers reacted the dimeric potassium aluminyl [K{Al(NONDipp)}]2 with CO, they obtained a complex containing a [C5O5]5– ligand, which had been unknown so far (partial structure pictured). This complex crystallized as a mono-TMEDA adduct, i.e., K5[K(TMEDA)][{Al(NONDipp)}4(C5O5)2]. According to the team, this [C5O5]5– ligand represents the first non-cyclic C5-oligomer of CO.


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