Dalton Transactions

doi: 10.1039/c003543mpmid: N/A

doi: 10.1039/c003544kpmid: N/A

doi: 10.1039/c003545apmid: N/A

doi: 10.1039/b926640mpmid: 20221526

Hu, Yilin; Fay, Aaron W.; Lee, Chi Chung; Wiig, Jared A.; Ribbe, Markus W.

doi: 10.1039/b922555bpmid: 20221527

Nitrogenase catalyzes the nucleotide-dependent conversion of dinitrogen to ammonia at the iron-molybdenum cofactor (FeMoco) center of its molybdenum-iron (MoFe) protein component. Biosynthesis of FeMoco is arguably one of the most complex processes in the field of bioinorganic chemistry, which involves the participation of a number of nif (nitrogen fixing) gene products. One key player in this process, NifEN (encoded by nifE and nifN), is homologous to the MoFe protein with regard to both the primary sequences and the types of the metal centers. Recently, an all-iron precursor has been identified on NifEN, which closely resembles the Fe/S core structure of the mature cofactor. Such a precursor-bound form of NifEN has not only served as an excellent platform for the investigation of FeMoco assembly, but also facilitated the examination of the capacity of NifEN as a catalytic homolog of MoFe protein. This perspective will focus on the recent advances toward elucidating the dual functions of NifEN in nitrogenase assembly and catalysis, and the insights afforded by these advances into the evolution and mechanism of nitrogenase.

Dance, Ian

doi: 10.1039/b922606kpmid: 20221528

In seeking to mimic the hydrogenation of N2 to NH3 as effected under mild conditions by the enzyme nitrogenase, three classes of known metal sulfide clusters that resemble the NFe7MoS9 core of FeMo-co, the active site of nitrogenase, have been assessed theoretically. The assessment has been made in the context of the previously proposed mechanism for nitrogenase, in which protons are relayed to FeMo-co, where, as hydrogen atoms accumulated on Fe and S atoms, they transfer to bound N2 and subsequent intermediates in a critical sequence of intramolecular hydrogenations, probably accelerated by H atom tunneling. The three model systems possess the XcFe4S4 face which is the key active site of FeMo-co (X is most probably N in FeMo-co, and is S in the models). The most promising functional models are based on clusters M1, {(tpb)Mo(μ3-S)3Fe2(Fe-L)Sc(μ-S)2(Fe-L)Fe2(μ3-S)3Mo(tpb)} [tpb = tris(1-pyrazolyl)hydroborate], for which syntheses are well developed. The assessment is based on the ability of the models to mimic the intermediates in the FeMo-co mechanism, as determined by density functional simulations. The elaborations of M1 required to mimic the FeMo-co behaviour are described. These include modification of the tpb ligands to control the coordination at the Fe atoms, to provide for the proton relay functionality, and to prevent unwanted reactivity at other Fe and S atoms. Literature references with prescriptions for synthesis of the predicted homogeneous catalysts are provided. Further, in view of the similarities between the model systems and the P-cluster of nitrogenase, it is speculated that the P-cluster could be a relic catalytic site for N2 reduction.

Kuwata, Shigeki; Ikariya, Takao

doi: 10.1039/b927357cpmid: 20221529

Bifunctional catalysts, in which two functionalities cooperate in substrate activation and transformation, promote a number of chemical and biological reactions quite efficiently. This perspective mainly describes our efforts to extend the concept of the metal/NH bifunctional mononuclear catalysts to dinuclear systems. The late transition metal dinuclear complexes with bridging sulfonylated nitrogen donors and parent amides (NH2) are focused on particularly, while the chemistry of related nitrogen-bridged polynuclear complexes is also mentioned.

Ichikawa, Koji; Nonaka, Kyoshiro; Matsumoto, Takahiro; Kure, Bunsho; Yoon, Ki-Seok; Higuchi, Yoshiki; Yagi, Tatsuhiko; Ogo, Seiji

doi: 10.1039/b926061gpmid: 20221530

This communication reports the successful merging of the chemical properties of a natural [NiFe]hydrogenase (Desulfovibrio vulgaris Miyazaki F) and our previously reported [NiRu] hydrogenase-mimic. The catalytic activity of both the natural enzyme and the mimic is almost identical, with the exception of working pH ranges, and this allows us to use them simultaneously in the same reaction flask. In such a manner, isotope exchange between D2 and H2O could be conducted over an extended pH range (about 2–10) in one pot under mild conditions at ambient temperature and pressure.

Matsumoto, Tsuyoshi; Ito, Mikinao; Kotera, Mai; Tatsumi, Kazuyuki

doi: 10.1039/b924915jpmid: 20221531

The dinuclear Ni(ii)-Ni(i) complex NiII(dadtEt)NiI(SDmp)(PPh3) was synthesized as a Ni(ii)d–Ni(i)p model of the A-cluster in acetyl CoA synthase. This complex was reacted with Co(dmgBF2)2(Me)(Py) and KSDmp successively to afford Ni(dadtEt)Ni(Me)(SDmp), which further reacts with CO to afford the acetylthioester CH3C(O)SDmp via reductive elimination.

Mahammed, Atif; Gross, Zeev

doi: 10.1039/b916590hpmid: 20221532

A water soluble bipolar aluminium(iii) corrole enhances the chemiluminescence of luminol, accepts the released energy, and emits it at tissue-penetrating wavelengths.