Bioinorganic chemistry of molybdenum and tungsten enzymes: A structural–functional modeling approach

Synthesis, Characterization of New Tungsten(IV)?Pterin Complexes and their Reactivity Studies towards Trimethylamine N-Oxide, Sodium Borohydride and Potassium Ferricyanide

“…For the pterin ligand (1) ( Figure 1 shows the structural formulas of its tautomers) two medium intensity broad bands at 1363 cm -1 and 1209 cm -1 could be assigned to the δ(N-H) and δ(N-H)+ν(C-N) vibrations respectively, of its NH(3) and NH(5) groups [28]. Absence of such vibrations in the corresponding complexes (2,3,4) indicate deprotonation of such functional groups in forming the pterin ligand anion, L 2- (Figure 2). On the other hand, a new distinct band of variable intensity is observed at 1261 cm -1 for the present complexes, which may be assigned to the ν(C-O) mode of the O(4) phenoxide group [28].…”

“…The low solubility problem associated with pterin compounds, is overcome to a large extent here by replacing one of the hydrogen atoms of the pterin NH 2 (2) group by a pivaloyl group [(CH 3 ) 3 CCO] through reaction with pivalic anhydride [10,11]. Careful control of the reaction conditions, e,g.…”

“…Pterins (2-amino-4-oxopteridines) are important in a wide range of biological functions including a large number of metal-containing enzymes (e.g., Fe, Mo, W) [1][2][3]. The redox noninnocent nature of the pterin ring is associated with the ability of its pyrazine ring to exist in a number of oxidation states [4].…”

Electronic Fine‐Tuning of Oxygen Atom Transfer Reactivity of cis‐Dioxomolybdenum(VI) Complexes with Thiosemicarbazone Ligands

“…[2][3][4][5][6] Whereas bidentate dithiolene ligands model the S,S donor set found in the molybdopterin cofactor of the enzymes, [7,8] bidentate ligands with N,S, N,N and N,O donor have also been found to catalyze OAT. Examples include pyridine thiolates, [9] iminopyrrolato, [10,11] diketiminate (NacNac), [12] and β-ketiminato [13] ligands.…”

“…Biomimetic model complexes, however, tend not to have additional redox centers incorporated, as found in the molybdoenzymes, and hence both the oxidative and reductive half-reaction take place at the molybdenum center (Scheme 1). [23] The catalytic activity of these complexes is therefore often limited by slow kinetics due to charge buildup at the molybdenum center and the formation of inactive Mo V dimers as a result of the comproportionation of Mo IV and Mo VI (Scheme 1). In this context, we are interested in the development of chelate ligands that allow the electronic properties of their donor atoms to be tuned so as to facilitate OAT.…”