The Strong Acidity and the Process for Deprotonation of (η6-Toluene)Fe(H)2(SiCl3)2

The acidity and the process for deprotonation of (η6-toluene)Fe(H)2(SiCl3)2 in acetonitrile were studied with pyridine derivatives. (η6-Toluene)Fe(H)2(SiCl3)2 is a very strong acid and deprotonates in acetonitrile. The formation of hydrogen-bonded complexes M−H···N prior to deprotonation is observed when pyridine, 2,6-lutidine, and 2,2‘-bipyridine are used. With 1 equiv of bipyridine, the hydrogen-bonded species is quite stable, two hydrides are deprotonated, and [bpyH2]2+ is formed. The small 57Fe−hydride coupling constant (3.6 Hz) for (η6-toluene)Fe(H)2(SiCl3)2 is consistent with strong acidity of the compound. The 10.8 Hz coupling between 57Fe and the hydride in [(η6-toluene)Fe(H)(SiCl3)2]- and (η6-toluene)Fe(H)(py)(SiCl3) is similar to those observed in other Fe(II) hydrido compounds. The observation of the coupling only between p-H and the hydride in [(η6-toluene)Fe(H)(SiCl3)2]- and (η6-toluene)Fe(H)(py)(SiCl3) indicates that the configuration with the hydride trans to p-H is dominant in solution and the rotation of the toluene is not fast at room temperature.