Multi-site coordination of ferrocenylamido-naphthyridine conjugates [{(5,7-dimethyl-1,8-naphthyridin-2-yl)amino}carbonyl]ferrocene and 1,1′-bis[{(5,7-dimethyl-1,8-naphthyridin-2-yl)amino}carbonyl]ferrocene

Abstract

Ferrocenylamido-naphthyridine conjugates [{(5,7-dimethyl-1,8-naphthyridin-2-yl)amino}carbonyl]ferrocene (L¹)and 1,1′-bis[{(5,7-dimethyl-1,8-naphthyridin-2-yl)amino}carbonyl]ferrocene (L²) have been synthesized. Reaction of L¹ with [Cu(CH₃CN)₆][ClO₄]₂ affords [Cu(L¹)₂][ClO₄]₂ (1) demonstrating tridentate coordination of the ligand utilizing naphthyridine (NP) nitrogens and carbonyl oxygen. Hydroxo-bridged neutral dirhenium(I) compound [K⊂{{Re(CO)₃}₂(μ-OH)(Fc(CONHNP)(CO ̅N NP))₂}] (2) is reported in which the amido-NP arm of L² chelates a Re^I, and a K⁺ ion is encapsulated in a six-coordinate environment rendered by four NP nitrogens and two carbonyl oxygens involving all four arms of two L² ligands. Selective and reversible binding of K⁺ ion by the organometallic host has been recognized from electrochemical and fluorescence experiments. Partial hydrolysis of L² has provided a neutral metallamacrocycle [{Re(CO)₃}₂{Fc(CO₂)(CONHNP)(CONhnP)}₂] (3) consisting of alternate Fc and Re(CO)₃ units linked by carboxylate and amide-NP bridges. The rotational freedom of the ferrocenyl rings, the flexibility of the amide linker and the multi-site coordination of the ligands are demonstrated in the molecular structures of compounds 1–3.