Molybdenum(VI) and molybdenum(V) complexes with N,N'-dimethyl-N,N'-bis(2-mercaptophenyl)ethylenediamine. Electrochemical and electron paramagnetic resonance models for the molybdenum(VI/V) centers of the molybdenum hydroxylases and related enzymes

Abstract

Electrochemical one‐electron reduction of dioxomolybdenum complexes with tetradentate N2O2 or N2S2 ligands containing sec. amino groups result in deprotonation of the amino groups and loss of an oxo ligand as H2O. This biomimetically undesirable result is circumvented by synthesis of the ligand (VI) and its complexes (VIII) (which can be prepared also from dioxobis(acetylacetonato)molybdenum and (VI) with 80% yield) and (X).

Pulsed EPR studies of the exchangeable proton at the molybdenum center of dimethyl sulfoxide reductase

“…All spectra consist of several lines that are interpreted as follows. It may originate from 14 N of the pterin ligands or from 35 Cl introduced during the sample preparation. The broad lines with a positive amplitude situated symmetrically with respect to m D , at frequencies of about m a =0.9-1.4 MHz and m b =6.4-6.8 MHz (depending on B 0 that determines the mw excitation position within the EPR spectrum), are the fundamental lines of the nearby exchangeable deuteron.…”

cis-Dioxomolybdenum(VI) complexes of sterically encumbered phenol-based tetradentate N2O2 ligands: Structural, spectroscopic, and electrochemical studies

“…As a result, the Mo-N(1) [15]. Comparable structural features have been reported for cis-MoO 2 L complexes of related N 2 O 2 and N 2 S 2 ligands [25,26].…”

“…Such process in cis-MoO 2 complexes are generally irreversible [25,27,28] due to the formation of EPR silent µ-oxo-dimolybdenum(V) compound [29]. One interesting exception is the cis-MoO 2 L 3 complex (H 2 L 3 being the corresponding tetradentate N 2 S 2 ligand), which undergoes a reversible Mo(VI)/Mo(V) reduction at a much positive potential E 1/2 = − 0.98 V vs SCE [26]. The result is consistent with the effect of O→S substitution on the potentials of Mo complexes involving otherwise identical ligands [30,31].…”

“…The reversibility of Mo VI O 2 →Mo V O 2 electron transfer in 2 and 3 thus offer a rare example of steric solution [11,26] to the comproportionation-dimerization problem encountered frequently in the development of valid biomimetic models for the active sites of oxomolybdenum enzymes.…”

Biomimetic Chemistry of Molybdenum

“…9.4(a)] is typical of those that have been structurally characterized (the Structure of cis.trans-aJ-NjSJM^-67 Q>) Structure of m,ciV(L 2 -N 2 S 2 )MoOCl (the cis.trans isomer has also been structurally characterized) 70. stereochemical prefix refers firstly to the relative positions of the oxo groups and secondly to the relative positions of the thiolate groups) [66][67][68][69]. The d(Mo=0), d(Mo-S) and Z_(0-Mo-0) values are typically ca.…”