A Self-Assembled Trinuclear Co(II) Catalyst for Efficient C─H Activation of Benzaldehydes under Solvent-Free Condition

Abstract

A trinuclear, self-assembled Co(II) coordination solid with the formula [Co₃(BTC)₂(BPY)₄(H₂O)₁₀.]· BPY 4H₂O (1) [BTC = 1,3,5-benzenetricarboxylate, BPY = 4,4′-bipyridine] has been developed. Diffraction studies revealed that (1) features two crystallographically distinct Co²⁺ centers connected through BPY bridges, resulting in a trinuclear complex structure. The centrosymmetric trinuclear [Co₃(BTC)₂(BPY)₄] unit together with uncoordinated BPY molecules generate a 2D stacked structure. Theoretical calculations also support noncovalent interactions between the aromatic ring of uncoordinated BPY units and the trinuclear unit, as well as H-Bonding interactions. The compound 1 exhibits remarkable catalytic activity that facilitates the C─H activation of benzaldehyde in the presence of TBHP, yielding symmetric anhydrides. This green approach demonstrates a broad substrate scope under solvent-free conditions (water is added for solid reactant substrates). The investigated catalytic protocol is homogenous, straightforward, and efficient. In addition to that, mechanistic studies suggest that the catalytic reactions follow a radical pathway. This protocol also features short reaction time along with wide functional group tolerance, highlights its practical utility.