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|Title:||Synthetic and Electrochemical Studies of Novel Iron Nitrosyl Complexes|
McGlinchey, M. J.
|Abstract:||<p> Dinitrosyliron complexes have gained importance as a result of their biological and chemical relevance. Their biological significance stems from the roles exhibited by nitric oxide, including its ability to regulate blood pressure, to act as a biological messenger and because of its involvement in memory storage. Other functions that these dinitrosyliron-based complexes have displayed include their ability to transfer molecular oxygen to alkenes or phosphines, and its use in the polymerization of olefins. One area not yet extended to iron dinitrosyl complexes involves the synthesis of polymeric materials containing a conjugated backbone in the polymer. Thus, the next logical approach was to apply this idea, while investigating their potential to demonstrate unique properties such as optical, redox, and/or conducting behaviour exemplified by other inorganic and organometallic polymeric species. Hence, reactions involving Fe(NO)2(CO)2 and bidentate diphosphine ligands, bis(diphenylphosphino)methane (DPPM), trans-1,2-bis(diphenylphosphino)ethylene (t-DPPEN), 1,1 '-bis(diphenylphosphino) ferrocene (FcP2), bis(diphenylphosphino)acetylene (DPPA) and 1,4- bis(diphenylphosphino)benzene (DPPB) have been investigated. Three types of compounds arose from these reactions: the monometallic system Fe(DPPM)(N0)2(CO) 9, linear dimetallic molecules of the type Fe2(μ-L)(N0)4(CO)2 (L = PPh2CHzPPh2 10, PPh2C≡CPPh2 11, PPh2(p -6H4)PPh2 12, PPhzCH=CHPPhz 13, and PPh2((C5H4)2Fe) PPh2 14), and cyclic dimetallic species of the type Fe2(μ-L)(NO)4 (L = PPh2(p-C6H4)PPh2 15, PPh2CH2PPh2 16, and PPh2C≡CPPh2 17). These systems were isolated and characterized by the use of NMR and IR spectroscopy. The structures of compounds 10, 11, 16 and 17 were also determined by X-ray crystallography. The linear dimetallic compounds, 11, 13 and 14, were treated with tetracyanoethylene (TCNE) to afford compounds of the type Fe2(μ-L)(N0)4(TCNE)2 (L = PPhzC≡CPPh2 18 and PPh2((C5H4)2- Fe)PPh2 19) and [(TCNE)(NO)2Fe(μ-L)[Fe(NO)2(CO)] (L = PPh2CH=CHPPh2 20). These TCNE adducts were probed by means of cyclic voltammetry to investigate their potential redox properties; only compound 18 revealed communication between the two iron centres. </p> <p> Dinitrosyldicarbonyliron, Fe(NO)2(CO)2 and other four-coordinate dinitrosyliron systems have been extensively examined in terms of nucleophilic substitution, including the effects of both hard and soft bases. These findings prompted us to ask whether electrophiles attack dinitrosyliron complexes. Hence, Fe(NO)2(CO)2 1, and also the phosphine complexes Fe(NO)2(CO)(PPh3) 21, and Fe(NO)2(PPh3)2 22, have been treated with a variety of electrophiles (HCl, SiMe3Cl, Et30^+SbCl6-, trifluoroacetic acid (TFA) and trifluoromethanesulfonic acid (TFSA)) to probe the nucleophilic character of the iron centres. Moreover, another approach involved examining the nucleophilic nature of the iron nitrosyl salts, [PPN^+][Fe(CO)3(NO)], 24 and [N(Bu)4+][Fe(C0)3(NO)], 25. </p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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