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Title: The bonding, synthesis and electrochemistry of some iron-sulphur-nitrosyl compounds
Author: Lambert, Ronald J. W.
ISNI:       0000 0001 3604 3625
Awarding Body: University of St Andrews
Current Institution: University of St Andrews
Date of Award: 1990
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Salts of the bls(μ-thiosulphato-S)-bis(dinitrosylferrate)(2-) anion, [Fe2(S2o3)2(NO)4]2- can be prepared by the reaction of iron(ll)/thiosulphate mixtures with nitrite ion. The crystal structure of {(Ph3P)2N}2[ Fe2(S203)2(NO)4] reveals it to adopt a trans structure. 15N n.m.r. studies of this salt also show it to adopt the trans structure in solution. The anion reacts with thiolate ion, RS-, to provide good yields of Fe2(SR)2(NO)4; e.p.r. studies show the mononitrosyl [Fe(N0)(SR)3]3− to be a major intermediate in this reaction. Salts of the Black Roussin ion, [Fe4S3(NO)7]- react with aryldiazonium salts, ArN2+ , to produce Fe2(SAr)2(NO)4. 13C n.m.r. studies of Fe2(SC6H4F)2(NO)4 reveal it to exist in a 1:1 ratio of cis and trans isomers. Reaction of the Black anion with trialkylsulphonium or sulphoxonium salts leads to the metathesis product. The crystal structure of Me3S[Fe4S3(NO)7] shows no evidence for the closure of the iron-sulphur cage by the sulphur of the Me3S cation. Reaction of the Black anion with trialkyloxonium salts provides good yields of Fe2(SR)2(NO)4. Electrochemical studies on Fe2(SR)2(NO)4 by conventional cyclic voltammetry shows two chemically and electrochemically reversible one electron reductions to produce [Fe2(SR)2(NO)4]− and [Fe2(SR)2(NO)4]2−. The monoanion is a paramagnetic complex with g= 1.995; coupling to four equivalent nitrogens shows the presence of a delocalised electron. The electrochemical behaviour of the dianion is dependent on the electrode material; reversible on a glassy carbon electrode but quasi-reversible on platinum. Fe2(SR)2(NO)4 also exhibits a three electron oxidation; the anodic current of which increases in the presence of primary amines. Electrochemical studies on the Black Roussin ion and its selenium analogue [Fe4Se3(NO)7]− show similar electrochemical responses: three reversible one electron reductions and an irreversible multielectron oxidation. Extended Huckel molecular orbital calculations on [Fe2S2(NO)4]2− , Fe2(SMe)2(NO)4 and [Fe2(S203)2(N0)4]2− reveal little direct Fe-Fe interaction in these complexes. Reduction or oxidation would result in the addition or removal of electron density from orbitals of mainly Fe-S character. An electrochemical study of Fe(NO)(S2C N R2)2 by cyclic voltammetry shows a reversible one electron reduction and an Irreversible oxidation in tetrahydrofuran and dichloromethane. In acetonitrile the reduction of the complex is coupled to a chemical step making the reduction chemically irreversible at low scan rates. The observed variation of E with R is due to the inductive effect of R.
Supervisor: Glidewell, Christopher Sponsor: Association of International Cancer Research
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD305.N8L2 ; Nitro compounds