A dinitrosyl iron complex as a platform for metal-bound imidazole to N-heterocyclic carbene conversion

Hsieh, Chieh; Pulukkody, Randara; Darensbourg, Marcetta Y.

doi:10.1039/c3cc45091k

Cited by 21 publications

(20 citation statements)

References 25 publications

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“…It is noteworthy that the resulting DNIC contains an asymmetric NHC, thereby suggesting this to be a possible route for such syntheses, as well as further conversion to the corresponding TNIC, [(NHCMe-Mes)Fe(NO) 3 ] + by isoelectronic replacement of CO by NO + . 44 This model study demonstrated the impressive stability of the dinitrosyliron unit under base treatment, while supporting the isomerization of metal-bound imidazole to an NHC ligand. To our knowledge, only a few other examples of such interconversions exist in the organometallic literature.…”

Section: Patterns Between Nhc-dnics and Imidazole-dnicsmentioning

confidence: 54%

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Synthetic Advances Inspired by the Bioactive Dinitrosyl Iron Unit

Pulukkody

Darensbourg

2015

Acc. Chem. Res.

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Resulting from biochemical iron-NO interactions, dinitrosyl iron complexes (DNICs) are small organometallic-like molecules, considered to serve as vehicles for NO transport and storage in vivo. Formed by the interaction of NO with cellular iron sulfur clusters or with the cellular labile iron pool, DNICs have been documented to be the largest NO-derived adduct in cells, even surpassing the well-known nitrosothiols (RSNOs). Continuing efforts in biological chemistry are aimed at understanding the movement of DNICs in and out of cells, and their important role in NO-induced iron efflux leading to apoptosis in cells. Intrigued by the integrity of the unique dinitrosyl iron unit (DNIU) and the possibility of roles for it in human physiology or medicinal applications, the understanding of fundamental properties such as ligand effects on its ability to switch between two redox levels has been pursued through biomimetic complexes. Using metallodithiolates and N-heterocyclic carbenes (NHCs) as ligands to Fe(NO)2, the synthesis of a library of novel DNICs, in both the oxidized, {Fe(NO)2}(9), and reduced, {Fe(NO)2}(10), forms (Enemark-Feltham notation), offers opportunity to examine structural, reactivity, and spectroscopic features. The raison d'etre for the MN2S2·Fe(NO)2 synthesis development is for the potential to exploit the ease of accessing two redox levels on two different metal sites, a property presumably required for achieving two electron redox processes in base metals. Hence such molecules may be viewed as synthetic analogues of [NiFe]- or [FeFe]-hydrogenase active sites in nature, both of which use bridging thiolates for connection of the two centers. A particular success was the development of an Fe(NO)N2S2·Fe(NO)2(+/0) redox pair for proton reduction electrocatalysis. Monomeric, reduced NHC-DNICs of the L2Fe(NO)2 type are synthesized via the Fe(CO)2(NO)2 precursor, and oxidized thiolate-containing forms are derived from the dimeric (μ-RS)2[Fe(NO)2]2. Monomeric NHC-DNICs are four coordinate, pseudotetrahedral compounds with planar Fe(NO)2 units in which the slightly bent Fe-NO groups are directed symmetrically inward at both redox levels. They serve as stable analogues of biological histidine binding sites. In agreement with IR data, Mössbauer spectroscopic parameters, and DFT computations, the prototypic NHC-DNICs indicate extensive delocalization of the electron density of iron via π-backbonding. Such π-delocalization presents an unusual reaction path for the one electron process of RS(-)/RSSR interconversion. Comparisons with imidazole-DNICs find NHCs to be the "better" ligands to Fe(NO)2 and prompted investigations in (a) possible relationships between such imidazole- and NHC-containing DNICs, (b) systems that might mimic the reactivity of DNICs with the endogenous gaseotransmitter CO, and (c) mechanistic details of such processes. In a broader context, these studies aim to further describe the behavior of the {Fe(NO)2} unit as a single molecular entity when subjected to various ligand environments and r...

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Section: Patterns Between Nhc-dnics and Imidazole-dnicsmentioning

confidence: 54%

“…44 The changes that accompanied this process were monitored by IR spectroscopy. As shown in Figure 11, deprotonation at the C2 position of the imidazole ring of 11 by the base resulted in the formation of unstable intermediate species, proposed as 12a/12b.…”

Section: Patterns Between Nhc-dnics and Imidazole-dnicsmentioning

confidence: 99%

Synthetic Advances Inspired by the Bioactive Dinitrosyl Iron Unit

Pulukkody

Darensbourg

2015

Acc. Chem. Res.

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“…In 2013 Darensbourg evidenced the occurrence of a base-promoted conversion of a Nalkylimidazole ligand to the corresponding NH-NHC mediated by a dinitrosyl iron complex. 152…”

Section: Scheme 30 Isomerization Of a Benzimidazole Derivative To Itmentioning

confidence: 99%

Dearomatization of Transition Metal-Coordinated N-Heterocyclic Ligands and Related Chemistry

Arévalo

Espinal‐Viguri

Huertos

et al. 2016

Advances in Organometallic Chemistry

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Contents 1. Introduction 2. Addition of Main Group Organometallic Reagents to Pyridines and Related Heteroaromatics 3. Reaction of Pyridines with Early Transition Metal Complexes 4. The Elusive Nucleophilic Attack on Transition Metal-Coordinated 2,2'-Bipyridine and 1,10-Phenanthroline 5. Reactivity of Carbonyl rhenium and Molybdenum Complexes 5.1 Reactions of the Phosphido Complex [Re(PPh 2)(CO) 3 (phen)] with Activated Acetylenes and Olefins 5.2 Dearomatization by Deprotonation of Complexes with N-alkylimidazole Ligands 5.3 Couplings and Dearomatization Initiated by Deprotonation of C(sp 3)-H Bonds

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“…Following with the latter recipe, protic NHCs (pNHCs) consist of the presence of a N-bound H atom. Although most of the studies on NHCs together with metal moieties are based on the interaction of the carbene carbon of the NHC with the metal [ 23 – 26 ], the high instability due the NH group of the pNHCs can induce secondary interactions leading to bifunctional catalysis [ 27 – 28 ], substrate recognition [ 29 ] and/or biological systems [ 30 – 31 ]. Among the synthetic methodologies to access to pNHC metal complexes [ 32 – 40 ], recently N -arylimine functionalized pNHC iridium complexes were obtained using excess of [Ir(cod)(µ-Cl)] 2 [ 41 ], and next deprotonation of the pNHC leads to an equilibrium between a mononuclear complex containing a C-bound anionic imidazolide [ 42 – 44 ] and its dimer [ 45 – 58 ], where the NHC moiety binds in a µ-C,N bridging mode (see Scheme 1 ) [ 44 ].…”

Section: Introductionmentioning

confidence: 99%

Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes

Poater¹

2016

Beilstein J. Org. Chem.

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SummaryBearing the versatility of N-heterocyclic carbene (NHC) ligands, here density functional theory (DFT) calculations unravel the capacity of coordination of a deprotonated NHC ligand (pNHC) to generate a doubly C2,N3-bridged dinuclear complex. Here, in particular the discussion is based on the combination of the deprotonated 1-arylimidazol (aryl = mesityl (Mes)) with [M(cod)(μ-Cl)] (M = Ir, Rh) generated two geometrical isomers of complex [M(cod){µ-C3H2N2(Mes)-κC2,κN3}]2). The latter two isomers display conformations head-to-head (H-H) and head-to-tail (H-T) of C S and C 2 symmetry, respectively. The isomerization from the H-H to the H-T conformation is feasible, whereas next substitutions of the cod ligand by CO first, and PMe3 later confirm the H-T coordination as the thermodynamically preferred. It is envisaged the exchange of the metal, from iridium to rhodium, confirming here the innocence of the nature of the metal for such arrangements of the bridging ligands.

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A dinitrosyl iron complex as a platform for metal-bound imidazole to N-heterocyclic carbene conversion

Cited by 21 publications

References 25 publications

Synthetic Advances Inspired by the Bioactive Dinitrosyl Iron Unit

Synthetic Advances Inspired by the Bioactive Dinitrosyl Iron Unit

Dearomatization of Transition Metal-Coordinated N-Heterocyclic Ligands and Related Chemistry

Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes

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