Preparation, spectra and structure of [Fe-2(eta-C5H5)(2)(L)(CN)(mu-CO)(mu-CN(R')R)], [Fe-2(eta-C5H5)(2)(CO)(CN)(2)(mu-CNMe(2))(2)](+) and [Fe-2(eta-C5H5)(2)(CN)(2)(mu-CNMe(2))(2)] zwitterions (L=CO or organoisocyanide) and their reactions with alkyl and protic electrophiles

The thermal, photolytic or chemical activation of [Fe-2(eta-C5H5)(2)(CO)(2)(mu-CO)(mu-CNMe(2))]X and cis-[Fe-2(eta-C5H5)(2)(Co)(CNMe)(mu-CO)(mu-CNMe(2))]X and related salts (X(-)=I- or [SO3CF3](-)) allows replacement of one t-CO ligand by L=CN-, CNMe or CNC(6)H(3)Et(2)-2,6 to give respectively [Fe-2(eta-C5H5)(2)(CO)(L)(mu-CO)(mu-CNMe(2))](+) and [Fe-2(eta-C5H5)(2)(L)(CNMe)(mu-CO)(mu-CNMe(2))](+) derivatives. Similar reactions of cis-[Fe-2(eta-C5H5)(2)(CO)(2)(mu-CNMe(2))(2)][SO3CF3](2) allows the replacement of one or both t-CO groups in turn by L=CN-, CNMe or CNC6H11 to give respectively [Fe-2(eta-C5H5)(2)(CO)(L)(mu-CNMe(2))(2)](2+) and [Fe-2(eta-C5H5)(2)(L)(2)(mu-CNMe(2))(2)](2+) derivatives. Some of these substitution reactions take place with isomerism of the Fe-2(L)(2)(mu-L')(2) framework cis[-] trans, but the cis isomers always predominate no matter what the precursor. However, alkylation of the t-CN ligand by ROSO(2)CF(3), but not RI, proceeds without any such isomerism, which allows correlation of spectra with structure for a number of different types of compound. Protonation of the t-CN ligands of [Fe-2(eta-C5H5)(5)(CO)(CN)(mu-CNMe(2))(2)](+) and [Fe-2(eta-C5H5)(2)(CN)(2)(mu-CNMe(2))(2)] to give complexes containing t-CNH ligands may be effected by HOSO2CF3, but this straight-forward approach does not work for [Fe-2(eta-C5H5)(2)(CO)(CNH)(mu-CO)(mu-CNMe(2))](+) which is best prepared by the reaction of [Fe-2(eta-C5H5)(5)(Co)(CN)(mu-CO)(mu-CNMe(2))] with EtOSO(2)CF(3) in wet chloroform. The spectra of the various compounds are reported and discussed, There is no exchange between cis and trans isomers or bridging and terminal ligands, or rotation about the C=N bonds of the mu-C=NR(2) ligands in any of the complexes reported below 80 degrees C.