Solid state NMR spectroscopy of metal carbonyls. The influence of site symmetry on the solid state spectrum of cis-(η5-C5H5)2Fe2(CO)4

Solid state carbon-13 NMR spectra of metal carbonyls are readily obtained using commercial instrumentation. The observed isotropic chemical shifts are in good agreement with solution values. Furthermore there is a one-to-one correspondence between crystallographically unique carbonyls and magnetically distinguishable carbonyls in the absence of accidental degeneracies. For cis-(η⁵-C₅H₅)₂Fe₂(CO)₄ the site symmetry is C₁ while the molecular symmetry is C_2ν. The lower solid state symmetry gives rise to more resonances in the solid spectrum than in solution. Magic angle tuning and chemical shifts were obtained using hexamethylbenzene as a standard.