.: Current Research Activities :.


Metallodithiolates as Ligands in Coordination,
Bioinorganic, and Organometallic Chemistry

Unique, readily accessible, bidentate metallodithiolate ligands, here illustrated
by NiN2S2, possess S-based nucleophilicity used as a central building block for
the preparation of polymetallic complexes including C2, C3, C4 paddlewheels
(Jason Denny, Chem. Rev. 2015).

Hemilabile Bridging Thiolates as Proton Shuttles in
Bioinspired H2Production Electrocatalysts



Catalysis and Mechanism of H2 Release from
Amine-Boranes by Diiron Complexes

Hydrogen release from amine-boranes by diiron complexes with bridging dithiolates
is found to be influenced by the nature of the S to S linker. Time-resolved FTIR studies
monitor the dissociation of amine-borane from adducts of photolytically produced
coordinatively unsaturated diiron intermediates. Substituents on the S to S bridge
capable of agostic interactions with nearby iron diminishes residence time of the
substrate and impedes dehydrogenation, whereas a nitrogen functionality assists
via heterolytic H2 formation.



Complexes of MN2S2•Fe(η5-C5R5)(CO) as Platform
for Exploring Cooperative Heterobimetallic
Effects in HER Electrocatalysis  

Salient features in the computationally proposed mechanistic path for
electrocatalytic H2 production catalyzed by MN2S2•[Fe(η5-C5H5)(CO)]+
as  catalyst. (Ding, Ghosh, Lunsford, J. Am. Chem. Soc. 2016)

The ligand unwrapping/rewrapping pathway that exchanges
metals in S-acetylated, hexacoordinate N2S2O2 complexes

The effect of S-acetylation in MN2S2 complexes on metal exchange reactivity was
examined in a series of MN2S2O2 complexes. While clean exchange processes do not
occur for the MN2S2 derivatives where formation of S-bridged aggregates predominate,
acetylation permits the metal exchange with hierarchy that follows the Irving–Williams
series of stability for first row transition metals: Fe2+ < Co2+ < Ni2+ < Cu2+ > Zn2+.
The enhanced metal exchange deriving from S-acetylation is of significance to probes
and detection of cysteine-S metallo-proteins and metallo-enzyme active sites,
and highlights a new role for S-acetylation. (Jason Denny, Chem. Sci. 2015)

Toward biocompatible dinitrosyl iron complexes:
sugar-appended thiolates

Both monomeric and dimeric tetraacetylglucose-containing {Fe(NO)2}9 dinitrosyl
iron complexes (DNICs) were prepared and examined for NO release in the presence
of both chemical NO-trapping agents and endothelial cells. (Chem. Commun. 2016)

Interaction of hydrogen, Gold, and Nickel with a Reduced 2Fe2S Cluster

The Ph3PAu+ cation, renowned as an isolobal analogue of H+, is found to serve as a proton surrogate and form a stable Au2Fe2 complex, (μ-SAuPPh3)2[Fe(CO)3]2,
analogous to the highly reactive di-hydrosulfide, (μ-SH)2[Fe(CO)3]2. In the solid state, X-ray diffraction analysis finds both the SAuPPh3 and SH bridges in anti
configurations. VT NMR studies, supported by DFT computations, confirmed substantial barriers, ca. 25 kcal/mol, to intramolecular interconversions between
the three stereo-isomers of (μ-SH)2[Fe(CO)3]2. In contrast, the largely dative bond of S to Au in μ-SAuPPh3 facilitates inversion at S and accounts for the facile
equilibration of the -SAuPPh3 units with barriers half that of the -SH analogue. Reactivity of the gold-protected sulfurs of (μ-SAuPPh3)2[Fe(CO)3]2, is accessed
by strong acid release of the gold, generating in situ the (μ-SH)2[Fe(CO)3]2 precursor of the well-known [FeFe]-H2ase active site biomimetic,
2-SCH2(NR)CH2S)[Fe(CO)3]2. (Danielle Crothers, Angew. Chem. 2015)

Synthetic Advances Inspired by Bioactive Dinitrosyl
Iron Unit:

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.
(Randara Pulukkody, Accts. Chem. Res. 2015)


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