<i>N</i>,<i>N</i>‘-Diferrocenyl-<i>N</i>-heterocyclic Carbenes and Their Derivatives Benno Bildstein Michael Malaun Holger Kopacka Klaus Wurst Martin Mitterböck Karl-Hans Ongania Giuliana Opromolla Piero Zanello 10.1021/om990377h.s003 https://acs.figshare.com/articles/journal_contribution/_i_N_i_i_N_i_-Diferrocenyl-_i_N_i_-heterocyclic_Carbenes_and_Their_Derivatives/3785166 In continuation of our work on Wanzlick/Arduengo carbenes containing redox-active ferrocenyl substituents we report on the synthesis of <i>N</i>,<i>N</i>‘-diferrocenyl imidazol(in)ium salts as precursors of imidazol(in)-2-ylidenes. The necessary starting material for this chemistry is aminoferrocene, which was prepared by an improved and large-scale synthesis by the sequence solid lithioferrocene, iodoferrocene, <i>N</i>-ferrocenylphthalimide, aminoferrocene. The preparation of <i>N</i>,<i>N</i>‘-diferrocenyl heterocycles involves condensation of aminoferrocene with glyoxal to afford <i>N</i>,<i>N</i>‘-diferrocenyldiazabutadiene [Fc-DAB], reduction, condensation with formaldehyde, and oxidation with trityl salts to yield <i>N</i>,<i>N</i>‘-diferrocenylimidazol(in)ium salts. In situ deprotonation and trapping with electrophiles yielded the expected metal complexes and derivatives in some cases [Ag<sup>+</sup> or S<sub>8</sub>], but attempted reaction with other transition metals [e.g., Pd(II)] failed to give the corresponding complexes, due to (i) steric hindrance by the two <i>N</i>-ferrocenyl substituents, (ii) reduced acidity of the imidazol(in)ium precursors, and (iii) inaccessibility of the free carbenes. Spectroscopic [IR, Raman, UV−vis, MS, NMR (<sup>1</sup>H, <sup>13</sup>C, <sup>109</sup>Ag)], structural [X-ray], and electrochemical [CV] properties are reported and compared to those of other <i>N</i>-heterocyclic carbene derivatives. 1999-09-16 00:00:00 metal complexes heterocyclic carbene derivatives 13 C ferrocenyl substituents trityl salts aminoferrocene precursor heterocyclic Carbenes MS transition metals diferrocenyl synthesis 1 H imidazol CV NMR UV steric hindrance IR condensation Ag