Organometallic building blocks for crystal engineering. Synthesis, structure and hydrogen bonding interactions in [Fe(η5-C5H4CH2(CH3)OH)2], [Fe(η5-C5H3(CH3)COOH)2], [Fe(η5-C5H4CH(CH3)NH(η5-C5H4CH(CH3))] and in the diaminecyclohexane salt [Fe(η5-C5H4COO)2

The novel ferrocene-based compounds [Fe(η5-C5H4CH(CH3)OH)2] (1), [Fe(η5-C5H3(CH3)COOH)2] (2), [Fe(η5-C5H4CH(CH3)NH(η5-C5H4CH(CH3))] (3) and the diaminecyclohexane salt [Fe(η5-C5H4COO)2]2−[1S,2S-(NH3)2C6H10]2+·2[H2O] (4) have been synthesised and their molecular and supramolecular structures determined by single-crystal X-ray diffraction. The hydrogen bonding networks established by the COOH, CH(CH3)OH, and COO(−) groups have been studied and the structural parameters compared with those available for the prototypical dicarboxylic acid [Fe(η5-C5H4COOH)2].