Mechanochemical assembly of hybrid organic–organometallic materials. Solid–solid reactions of 1,1′-di-pyridyl-ferrocene with organic acids

Manual kneading of the organometallic complex [Fe(η5-C5H4-C5H4N)2] with solid fumaric, succinic, tridecanedioic, terephthalic, trimesic and thiophene-2,5-dicarboxylic acids generated the corresponding adducts, whether salts or molecular complexes: [Fe(η5-C5H4-C5H4N)(η5-C5H4-C5H4NH)][HOOC(CH)2COO]·CH3OH, [Fe(η5-C5H4-C5H4N)(η5-C5H4-C5H4NH)][HOOC(CH2)2COO]·[HOOC(CH2)2COOH], [Fe(η5-C5H4-C5H4N)2]·[HOOC(CH2)11COOH]·2CH3OH, [Fe(η5-C5H4-C5H4N)2]·[HOOC(C6H4)COOH], [Fe(η5-C5H4-C5H4NH)2][C6H3(COOH)2(COO)]2 and 3{[Fe(η5-C5H4-C5H4N)(η5-C5H4-C5H4NH)][HOOC(SC4H2)COO]}·[Fe(η5-C5H4-C5H4N)2]·2[HOOC(SC4H2)COOH]. Direct reaction in solution yielded the same compounds, which were characterized by single crystal X-ray diffraction, thus allowing comparison of observed and calculated powder diffraction patterns. Kneading of the organometallic complex with maleic acid, on the other hand, yielded a different product from the one obtained via reaction in solution, which was characterized by single crystal X-ray diffraction as the salt [Fe(η5-C5H4-C5H4NH)2][HOOC(CH)2COO]2. The solid–solid processes described herein imply molecular diffusion through the lattice and breaking and reassembling of hydrogen bonded networks with or without proton transfer from acid to base.