Metallodithiolates as Ligands to Dinitrosyl Iron Complexes: Toward the Understanding of Structures, Equilibria, and Spin Coupling

doi:10.1021/ic501117f

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Title:	Metallodithiolates as Ligands to Dinitrosyl Iron Complexes: Toward the Understanding of Structures, Equilibria, and Spin Coupling
Authors:	Pinder Tiffany A.;Montalvo Steven K.;Hsieh, Chung-Hung;Lunsford Allen M.;Bethel Ryan D.;Pierce Brad S;Darensbourg Marcetta Y.
Contributors:	淡江大學化學學系
Date:	2014-01-01
Issue Date:	2014-08-27 09:29:19 (UTC+8)
Publisher:	American Chemical Society
Abstract:	Metallodithiolate ligands are used to design heterobimetallic complexes by adduct formation through S-based reactivity. Such adducts of dinitrosyl iron were synthesized with two metalloligands, namely, Ni(bme-daco) and V≡O(bme-daco) (bme-daco = bismercaptoethane diazacyclooctane), and, for comparison, an N-heterocyclic carbene, namely, 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (Imes), by cleavage of the (μ-I)2[Fe(NO)2]2 dimer of electronic configuration {Fe(NO)2}9 (Enemark–Feltham notation). With Fe(NO)2I as Lewis acid acceptor, 1:1 adducts resulted for both the IMes·Fe(NO)2I, complex 2, and V≡O(bme-daco)·Fe(NO)2I, complex 4. The NiN2S2 demonstrated binding capability at both thiolates, with two Fe(NO)2I addenda positioned transoid across the NiN2S2 square plane, Ni(bme-daco)·2(Fe(NO)2I), complex 3. Enhanced binding ability was realized for the dianionic vanadyl dithiolate complex, [Et4N]2[V≡O(ema)], (ema = N,N′-ethylenebis(2-mercaptoacetamide)), which, unlike the neutral (V≡O)N2S2, demonstrated reactivity with the labile tungsten carbonyl complex, cis-W(CO)4(pip)2, (pip = piperidine), yielding [Et4N]2[V≡O(ema)W(CO)4], complex 1, whose ν(CO) IR values indicated the dianionic vanadyl metalloligand to be of similar donor ability to the neutral NiN2S2 ligands. The solid-state molecular structures of 1–4 were determined by X-ray diffraction analyses. Electron paramagnetic resonance (EPR) measurements characterize the {Fe(NO)2}9 complexes in solution, illustrating superhyperfine coupling via the 127I to the unpaired electron on iron for complex 2. The EPR characterizations of 3 [Ni(bme-daco)·2(Fe(NO)2I)] and 4 [V≡O(bme-daco)·Fe(NO)2I] indicate these complexes are EPR silent, likely due to strong coupling between paramagnetic centers. Within samples of complex 4, individual paramagnetic centers with localized superhyperfine coupling from the 51V and 127I are observed in a 3:1 ratio, respectively. However, spin quantitation reveals that these species represent a minor fraction (<10%) of the total complex and thus likely represent disassociated paramagnetic sites. Computational studies corroborated the EPR assignments as well as the experimentally observed stability/instability of the heterobimetallic DNIC complexes.
Relation:	Inorganic Chemistry 53(17), pp.9095–9105
DOI:	10.1021/ic501117f
Appears in Collections:	[Graduate Institute & Department of Chemistry] Journal Article

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