Ruthenocene, directed metalation

Another interesting comparison of Group VIII metallocenes concerns their ease of protonation in boron trifluoride hydrate (14). It appears that the proton is attached directly to the metal atom, and that ruthenocene and osmocene are protonated to a lesser extent than ferrocene. 

The effect of metal replacement has not been established with certainty. Direct comparison of ferrocene complexes with analogous ruthenocene complexes is only possible for the parent compounds, with ruthenocene having a slightly larger cubic nonlinearity.1819 This result needs to be treated cautiously, as the technique employed (OPL) is susceptible to thermal contributions (see earlier) and the low nonlinearities of the complexes induce substantial errors. The differing fundamental frequencies employed... 

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