.: Current Research Activities :.

Cyanide-Bridged Iron Complexes as Biomimetics of Tri-iron Arrangements in Maturases of the H cluster of the Diiron Hydrogenase: Our work addresses the cyanide docking process, with possible linkage isomerization as the coupling of two biomimetics is made. (Allen Lunsford, submitted, 2015)

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, Chemical Sciences 2015)

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, (μ2-SCH2(NR)CH2S)[Fe(CO)3]2. (Danielle Crothers, Angew. Chem. 2015)

Synthetic Advances Inspired by the 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)

Isomers of edge-bridged square pyramids produced by alternate addition of electrophilic (NO+) and nucleophilic (PMe3) to a diiron complex relate to the active site of [FeFe]-hydrogenase. Computations support experiments that define a third CO substitution with regioselectivity on the iron containing prebound NHC and NO ligands; the NO+/CO substitution process on the complex disubstituted with NHC and PMe3 on each iron yields the rotated structure that exposes an open face on iron. (Ryan Bethel, Inorg. Chem. 2014)

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).

Chemistry Department -- Texas A&M University -- 3255 TAMU, College Station, TX 77843 -- 979.845.5417