Abstract
Oxalic acid reacts with sandwich compounds such as decamethyl ferrocene, decamethyl cobaltocene, bis-benzene chromium and cobaltocene, in the presence of oxygen, via a multi-step process involving oxidation, deprotonation and precipitation, to form crystalline superstructures containing columns of organometallic sandwich cations and hydrogen oxalate anions. Five novel crystalline compounds are reported, namely [Fe(η5-C5Me5)2][HC2O4]·[H2C2O4]0.5, 1a, [Co(η5-C5Me5)2][HC2O4]·[H2C2O4]0.5, 1b, [Fe(η5-C5Me5)2][HC2O4]·[H2C2O4], 2, [Cr(η6-C6H6)2][HC2O4]·[H2O], 3, and [Co(η5-C5H5)2][HC2O4]·[H2C2O4]0.5[H2O] 4. The anionic network in [M(η5-C5Me5)2][HC2O4]·[H2C2O4]0.5 (M = Fe, Co) is based on an unusual deca-atomic ring formed by hydrogen oxalate anions linked side-to-side via(−)O–H⋯O(−) hydrogen bonding interactions. The magnetic behaviour of compounds 1a, 2, and 3 has been investigated by SQUID magnetometry. Both compounds 1a and 2 present weak antiferromagnetic interactions, which are significantly stronger in 1a. The structure of the chloride salt [(η5-C5H5)2Co][Cl]·[H2C2O4][H2O], 5, is also described.
Published Version
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