TY - JOUR
T1 - Metallodithiolates as ligands to dinitrosyl iron complexes
T2 - Toward the understanding of structures, equilibria, and spin coupling
AU - Pinder, Tiffany A.
AU - Montalvo, Steven K.
AU - Hsieh, Chung Hung
AU - Lunsford, Allen M.
AU - Bethel, Ryan D.
AU - Pierce, Brad S.
AU - Darensbourg, Marcetta Y.
PY - 2014/9/2
Y1 - 2014/9/2
N2 - 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 (CO) IR values indicated the dianionic vanadyl metalloligand to be of similar donor ability to the neutral NiN 2S2 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.
AB - 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 (CO) IR values indicated the dianionic vanadyl metalloligand to be of similar donor ability to the neutral NiN 2S2 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.
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U2 - 10.1021/ic501117f
DO - 10.1021/ic501117f
M3 - Article
C2 - 25144614
AN - SCOPUS:84961983731
SN - 0020-1669
VL - 53
SP - 9095
EP - 9105
JO - Inorganic chemistry
JF - Inorganic chemistry
IS - 17
ER -