Mono‐Dithiolene Molybdenum(IV) Complexes of cis‐1,2‐Dicyano‐1,2‐ethylenedithiolate (mnt²⁻): New Models for Molybdenum Enzymes

Abstract

New mono‐dithiolene molybdenum(IV) complexes of cis‐1,2‐dicyano‐1,2‐ethylenedithiolato [(mnt)2−] have been synthesized as models for molybdenum enzymes, with 4,4′‐di‐tert‐butyl‐2,2′‐bipyridine (Bu2bpy) and, N,N′‐tetraethylethylenediamine (Et4en) as ancillary ligands, and characterized by IR, UV/Vis, elemental analysis, ESI‐mass and electrochemical techniques. The temperature‐dependent 1H NMR spectra, recorded in CD3CN solution, indicated that [MoO(mnt)(Bu2bpy)] (1) has a rigid structure but [MoO(mnt)(Et4en)] (2) showed dynamic conformational inversion processes involving the chelating ethylenediamine unit. The complexes exhibited different reactivities toward molecular oxygen: 1 gave a single oxo‐bridged dimolybdenum dimer complex [Mo2O3(mnt)2(Bu2bpy)2] (3), while 2 did not react with O2 and kept its mononuclear structure. Both complexes have almost the same redox potential for MoIV/V, and so the steric bulkiness and conformational dynamics were thought to cause this marked contrast. The obtained dimolybdenum complex 3 was also structurally characterized and investigated, and found to be a new dimolybdenum complex with one dithiolene per molybdenum. The crystal structure of the starting complex 4 was also reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Oxo–Mo(IV)(dithiolene)thiolato Complexes: Analogue of Reduced Sulfite Oxidase

“…These show Mo(V) rhombic EPR signal and can be electrochemically reduced to Mo(IV), though the reduced complexes were not isolated. Some nondithiolene oxo–Mo(V) complexes were reported with a view to understand the EPR signature of SO. − Coordination of three sulfur atoms in the equatorial plane (two of which are from dithiolene) is the essential qualification for a compound to be considered as a structural analogue of reduced sulfite oxidase. No synthetic complex mimicking the fully reduced state of sulfite oxidase has been synthesized with dithiolene and thiolato ligation to date.…”

A New Class of Sulfido/Oxo(dithiolene)−Molybdenum(IV) Complexes Derived from Sulfido/Oxo-Bis(tetrasulfido)molybdenum(IV) Anions

“…In particular, significantly fewer are a type of mono(dithiolene)MoS complex, resulting in only one series of [Tp*Mo V/IV S(dithiolene)] 0/− complexes (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate); , this indicates that the incorporation of one terminal sulfido group into a mono(dithiolene)Mo center is a still difficult task. With respect to mono(dithiolene)MoO complexes, some types of the species have been synthesized with mono-, di-, or tridentate coligands. Therefore, development of new synthetic procedures for various types of mono(dithiolene)MoS/O complexes is necessary to expand the fields of bioinorganic chemistry as well as material science.…”

An Asymmetrically Substituted Aliphatic Bis-Dithiolene Mono-Oxido Molybdenum(IV) Complex With Ester and Alcohol Functions as Structural and Functional Active Site Model of Molybdoenzymes

“…In order to verify whether the slowness of the OAT reaction was indeed due to dimer formation, a solution of 3 mM complex 5 in the presence of oxidizing agent trimethylaminoxid (TMAO) in acetonitrile was prepared and monitored by UV-Vis spectroscopy under anaerobic condition. It was observed that after the initial formation of the transient Mo VI O 2 species (here very broad signal at λ max : 540 nm), it swiftly decomposed again while the signal for the catalytically inert Mo2VO 3 species (typical signal at λ max : 375 nm) (Villata et al, 2000; Sugimoto et al, 2003; Pal et al, 2007) exhibited a steady rise (see Figure S22). The change in the UV-vis with the progress of the reaction exhibits clean isosbestic points indicating the simultaneous presence of only two (not three) species.…”