808764-81-0Relevant articles and documents
Synthetic analogues of the active site of the A-cluster of acetyl coenzyme A synthase/CO dehydrogenase: Syntheses, structures, and reactions with CO
Harrop, Todd C.,Olmstead, Marilyn M.,Mascharak, Pradip K.
, p. 3424 - 3436 (2006)
Two metallosynthons, namely (Et4N)2[Ni(NpPePS)] (1) and (Et4N)2[Ni(PhPepS)] (2) containing carboxamido-N and thiolato-S as donors have been used to model the bimetallic M p-Nid subsite of the A-cluster of the enzyme acetyl coenzyme A synthase/CO dehydrogenase. A series of sulfur-bridged Ni/Cu dinuclear and trinuclear complexes (3-10) have been synthesized to explore their redox properties and affinity of the metal centers toward CO. The structures of (Et4N)2[Ni(PhPepS)] (2), (Et4N)[Cu(neo) Ni(NpPePS)]·0.5Et2O·0.5H2O (3·0.5Et2O·0.5H2O), (Et4N)[Cu- (neo)Ni(PhPepS)]·H2O (4·H2O), (Et 4N)2[Ni{Ni(NpPepS)}2]·DMF (5·DMF), (Et4N)2[Ni(DMF)2{Ni(NpPepS)} 2]·3DMF (6·3DMF), (Et4N)2[Ni(DMF) 2(Ni(PhPePS)}2] (8), and [Ni(dppe)Ni(PhPepS)] ·CH2Cl2 (10·CH2Cl2) have been determined by crystallography. The Nid mimics 1 and 2 resist reduction and exhibit no affinity toward CO. In contrast, the sulfur-bridged Ni center (designated NiC) in the trinuclear models 5-8 are amenable to reduction and binds CO in the Ni(I) state. Also, the sulfur-bridged NiC center can be removed from the trimers (5-8) by treatment with 1,-10-phenanthroline much like the labile Ni from the enzyme. The dinuclear Ni-Ni models 9 and 10 resemble the Nip-Ni d subsite of the A-cluster more closely, and only the modeled Ni p site of the dimers can be reduced. The Ni(I)-Ni(II) species display EPR spectra typical of a Ni(I) center in distorted trigonal bipyramidal and distorted tetrahedral geometries for 9red and 10red, respectively. Both species bind CO, and the CO-adducts 9red-CO and 10red-CO display strong νco at 2044 and 1997 cm -1, respectively. The reduction of 10 is reversible. The CO-affinity of 10 in the reduced state and the νco value of 10 red-CO closely resemble the CO-bound reduced A-cluster (νco = 1996 cm-1).
Structural models of the bimetallic subunit at the A-cluster of acetyl coenzyme A synthase/CO dehydrogenase: Binuclear sulfur-bridged Ni-Cu and Ni-Ni complexes and their reactions with CO
Harrop, Todd C.,Olmstead, Marilyn M.,Mascharak, Pradip K.
, p. 14714 - 14715 (2007/10/03)
The Ni(II)-dicarboxamido-dithiolato complexes (Et4N)2[Ni(NpPepS)] (1) and (Et4N)2[Ni(PhPepS)] (2) were used as Nid metallosynthons in the construction of higher nuclearity dinuclear Ni-Cu and Ni-Ni species to model the bimetallic Mp-Nid site of the A-cluster of acetyl coenzyme A synthase/CO dehydrogenase (ACS/CODH). Reaction of 1 with [Cu(neo)Cl] and [Ni(terpy)Cl2] in MeCN affords the dinuclear complexes (Et4N)[Cu(neo)Ni(NpPepS)] (3) and [Ni(terpy)Ni(NpPepS)] (4), respectively. Reaction of 2 with [Ni(dppe)Cl2] in MeCN yields [Ni(dppe)Ni(PhPepS)] (6). The Ni-Cu complex 3 exhibits no redox chemistry at the Nid site and no reaction with CO. In contrast, the Nip sites in 4 and 6 are readily reduced (characterized by their Ni(I) EPR spectra) and bind CO, exhibiting νco bands at 2044 and 1997 cm-1, respectively, indicating terminal CO binding. The present Ni-Ni systems replicate the structural and chemical properties of the A-cluster site in ACS/CODH and support the presence of Ni at Mp in the catalytically active enzyme. Copyright
