Synthesis and structures of metallocene complexes of iron(II) and ruthenium(II) derived from 9,9′-spirobifluorene

Reaction between 9,9′-spirobifluorene and [CpM]+ (where M = Fe and Ru) equivalents gives the complexes [CpRu(η6-SBF)][PF6] (1), [(CpRu)2(η6,η6-SBF)][PF6]2 (2) and [(CpFe)2(η6,η6-SBF)][PF6]2 (3), respectively. Single crystal X-ray structures of 1 and 3 show that the metal atoms exhibit distorted η6-coordination to SBF phenyl moieties primarily as a consequence of steric interactions between Cp and SBF. The structure of 3 contains each of the possible C2 enantiomers whereas NMR spectroscopy shows signals consistent with a 1:1 mixture of C2 and C1 stereoisomers for both 2 and 3. In conjunction with electrochemical data the observations are consistent with SBF acting as a molecule containing two independent biphenyl moieties.