STRUCTURAL AND REACTION CHEMISTRY OF NICKEL-COMPLEXES IN RELATION TO CARBON-MONOXIDE DEHYDROGENASE - A REACTION SYSTEM SIMULATING ACETYL-COENZYME-A SYNTHASE ACTIVITY
STRUCTURAL AND REACTION CHEMISTRY OF NICKEL-COMPLEXES IN RELATION TO CARBON-MONOXIDE DEHYDROGENASE - A REACTION SYSTEM SIMULATING ACETYL-COENZYME-A SYNTHASE ACTIVITY
复制标题
DOI：
10.1021/ja00022a041
复制
发表时间：
1991-10-23
影响因子：
15
通讯作者：
HOLM, RH
中科院分区：
文献类型：
--
作者：
STAVROPOULOS, P;MUETTERTIES, MC;HOLM, RH
以三足配体NS3R = N(CH2CH2SR)3 （R = i-Pr, t-Bu）为基础，制备了一系列镍配合物[Ni(NS3R)L]+，以研究一氧化碳脱氢酶（CODH）中镍位点相关物质的稳定性和反应。[Ni(NS3R)Cl]+与MeMgCl反应生成[Ni(NS3R)Me]+，与CO反应生成[Ni(NS3R)COMe]+。[Ni(NS3tBu)Cl]+与NaBH4反应得到[Ni(NS3tBu)H]+和Ni(I)种[Ni(NS3tBu)]+。通过去除平衡体系[Ni(NS3tBu)Et]+/[Ni(NS3tBu)H]+/C2H4中的乙烯，得到了Ni(I)污染最小的氢化物配合物。[Ni(NS3tBu)]+与CO反应得到[Ni(NS3tBu)CO]+，而[Ni(NS3tBu)H]+在相同条件下得到Ni(CO)4和质子化配体。所有反应均在THF中进行，所有配合物均以bph4盐分离。本系列包括在没有非生理（C/P/As）配体的情况下稳定ni -甲基，-酰基，-氢化物和-羰基配体的罕见例子。用x射线晶体学证明了L = Cl, Me, COMe， H和CO的五种配合物的三角-双锥体立体化学。在THF中，[Ni(NS3R)COMe]+与硫醇反应后，与一氧化碳的甲基/酰基转化和硫酯R' s COMe （R' = Et, CH2Ph, Ph）的高产率形成是两个先前未记载的在缺乏非生理性（C/P/As）连接的Ni（II）位点介导的过程。这些都与目前对热醋酸梭菌CODH催化反应循环的看法有关。Ni(II)-H和Ni(I)-CO可能与CODH的CO/CO2活性有关。详细介绍了所有的制备、其他反应和结构。这项工作是将CODH的反应化学置于合理基础上的初步尝试，并为酶的当前反应循环提供了一些可行性。
A series of nickel complexes [Ni(NS3R)L]+ derived from the tripodal ligand NS3R = N(CH2CH2SR)3 (R = i-Pr, t-Bu) has been prepared in order to investigate the stabilities and reactions of certain species potentially relevant to the nickel sites in carbon monoxide dehydrogenase (CODH). Reaction of [Ni(NS3R)Cl]+ with MeMgCl affords [Ni(NS3R)Me]+, which with CO yields [Ni(NS3R)COMe]+. Reaction of [Ni(NS3tBu)Cl]+ with NaBH4 gives [Ni(NS3tBu)H]+ and the Ni(I) species [Ni(NS3tBu)]+. The hydride complex was obtained with minimal Ni(I) contamination by removal of ethylene from the equilibrium system [Ni(NS3tBu)Et]+/[Ni(NS3tBu)H]+/C2H4. Reaction of [Ni(NS3tBu)]+ with CO affords [Ni(NS3tBu)CO]+, whereas [Ni(NS3tBu)H]+ under the same conditions gives Ni(CO)4 and protonated ligand. All reactions were performed in THF, and all complexes were isolated as BPh4-salts. This series includes rare examples of the stabilization of Ni-methyl, -acyl, -hydride, and -carbonyl ligands in the absence of nonphysiological (C/P/As) coligands. Trigonal-bipyramidal stereochemistry has been demonstrated for five complexes with L = Cl, Me, COMe, H, and CO by X-ray crystallography. The methyl/acyl transformations with carbon monoxide and the formation in high yield of the thioesters R'SCOMe (R' = Et, CH2Ph, Ph) upon reaction of [Ni(NS3R)COMe]+ with thiols in THF are two previously undocumented processes mediated at Ni(II) sites lacking non-physiological (C/P/As) ligation. These are relevant to current views of the catalytic reaction cycle of Clostridium thermoaceticum CODH, which is presented. The Ni(II)-H and Ni(I)-CO species may be pertinent to the CO/CO2 activity of CODH. Full details of all preparations, other reactions, and structures are presented. This work is an initial attempt to place the reaction chemistry of CODH on a rational basis, and provides some viability for the present reaction cycle of the enzyme.