(DIMETHYLAMINO)DIMETHYLSILYL-SUBSTITUTED DIMERIC AND SILOXANYL POLYMERIC COMPOUNDS CONTAINING [(ETA-5-C5R4)FE(CO)(MU-CO)]2 (R=H, ME) MOIETIES - SYNTHESIS, CHARACTERIZATION, AND ELECTROCHEMISTRY

Binuclear iron complexes [{(eta5-C5R4)Me2Si(NMe2)}Fe(CO)2]2 (R = H (1), R = Me (2)) have been prepared by thermal treatment of the (N,N-dimethylamino)dimethylsilyl-substituted cyclopentadiene and tetramethylcyclopentadiene with Fe(CO)5. These dimers are significant because they possess two SiNMe2-substituted ligands, which have been used in polymer construction. Condensation reactions of 1 and 2 with HOSiPh2OH, HOSiMe2(1,4-C6H4)Me2SiOH, and HOSiMe2O(-SiMe2O)n-Me2SiOH, lead to the formation of polymers containing [(eta5-C5R4)Fe(CO)(eta-CO)]2 moieties along siloxane backbones: [-SiMe2(eta5-C5R4)Fe(CO)(mu-CO)2(CO)Fe(eta5-C5R4)Me2SiOPh2SiO-]n (R = H (7), R = Me (8)), [-SiMe2(eta5-C5R4)Fe(CO)(mu-CO)2(CO)Fe(eta5-C5R4)Me2SiOSiMe2(1,4-C6H4)SiMe2O-]n (R = H (9), R = Me (10)), and [-SiMe2(eta5-C5R4)Fe(CO)(mu-CO)2(CO)Fe(eta5-C5R4)Me2SiOSiMe2O(Me2SiO)nSiMe2O-]n' (R = H (11), R = Me (12)). In order to aid to the spectroscopic characterization of the polymers, binuclear iron model complexes containing siloxane-bridged cyclopentadienyl and tetramethylcyclopentadienyl ligands, of the forms {SiMe2OSiPh2OSiMe2}[(eta5-C5R4)Fe(CO)2]2(R = H (3), R = Me (4)) and {SiMe2OSiMe2(1,4-C6H4)SiMe2OSiMe2}[(eta5-C5R4)Fe(CO)2]2 (R = H (5), R = Me (6)) have been prepared. In addition, the incorporation of the (eta5-C5H4)Fe(CO)(mu-CO)2-(CO)Fe(eta-C5H4)moiety into polymeric supports was also effected by reacting Fe(CO)5 with a preformed poly(methylsiloxane) backbone that contains pendant cyclopentadienyl rings, the polymer [Me3Si-O{(-MeSiOSiMeO)(eta5-C5R4)Fe(CO) (mu-CO)2(CO)Fe(eta5-C5H4)}n'-SiMe3] (13) being thus isolated. All the new compounds have been characterized by conventional spectroscopic techniques. The electrochemical oxidation and reduction of the synthesized complexes have been examined under various conditions. For the polymers 7-12 reversible systems corresponding to two-electron oxidation processes are observed in THF/Bu4NPF6. The monomeric anionic species [{(eta-C5R4)Me2Si(NMe2)}Fe(CO)2]- (R = H, Me) as well as the 18-electron cationic species [{(eta5-C5R4)Me2Si(NMe2))Fe(CO)2(THF)]+ and [{(eta5-C5R4)Me2Si(NMe2)}Fe(CO)2(NCCH3)]+ have been generated and characterized via infrared spectroelectrochemistry.