Stepwise construction of a 4-hydroxyphenyl functionalized O,N,N-tridentate ferrocene-containing enaminone: Spectral, analytical and structural studies

Tetrahydropyranylation of methyl-4-hydroxybenzoate proceeds with formation of its corresponding THP aromatic ether THP-O-p-C6H4CO2CH3 (1; THP = tetrahydropyranyl, C5H9O). Reaction with in situ generated carbanion of acetylferrocene gave the protected organometallic complex Fc-C(=O) CH=C(OH) (p-C6H4-O-THP) (2, Fc=(eta(5)-C5H5)Fe(eta(5)-C5H4)) featuring keto-enol functionality; subsequent acidic treatment of 2 afforded the 4-hydroxyphenyl substituted counterpart Fc-C(=O) CH=C(OH)(p-C6H4OH) (3) that exists as a 73/27 mixture of keto-enol/beta-diketone tautomers in DMSO solution. The functionalized tridentate metalloligand Fc-C(=O) CH=C(p-C6H4OH) N(H)CH2CH2NH2 (4) incorporating O,N,N-donors is readily obtained upon Schiff base condensation of 3 with 1,2-diaminoethane. Complex 4 exists exclusively as its ferrocenyl-enaminone tautomer in solution and in the solid state. Compounds 1-4 were characterized by NMR (H-1, C-13) and IR spectroscopy as well as by elemental analysis and single-crystal X-ray diffraction. (C) 2012 Elsevier B. V. All rights reserved.