The complexes [Co-2(mu-eta (2)-HC2C6H4X-4)(CO)(4)(dppm)] (X = H, NMe2, NO2,
CN or C=C{Ru(PPh3)(2)Cp}) and [Co-2(mu-eta (2)-RC2C=C{Ru(PPh3)(2)Cp})(CO)(
4)(dppm)] (R = H or SiMe3) have been prepared and characterised crystallogr
apically. Electrochemical and spectroscopic evidence has been used to help
formulate an empirical MO scheme and thereby explain the nature of the elec
tronic interactions that occur between the pendant group and the Co2C2 clus
ter core.