ic9908672_si_001.cif (233.23 kB)
Synthesis and Structures of Bis(dithiolene)molybdenum Complexes Related to the Active Sites of the DMSO Reductase Enzyme Family
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posted on 1999-12-29, 00:00 authored by Booyong S. Lim, James P. Donahue, R. H. HolmStructural analogues of the reduced (Mo(IV)) sites of members of the DMSO reductase family of molybdoenzymes
are sought. These sites usually contain two pterin−dithiolene cofactor ligands and one protein-based ligand. Reaction
of [Mo(MeCN)3(CO)3] and [Ni(S2C2R2)2] affords the trigonal prismatic complexes [Mo(CO)2(S2C2R2)2] (R =
Me (1), Ph (2)), which by carbonyl substitution serve as useful precursors to a variety of bis(dithiolene)molybdenum(IV,V) complexes. Reaction of 1 with Et4NOH yields [MoO(S2C2Me2)2]2- (3), which is readily oxidized to
[MoO(S2C2Me2)2]1- (4). The hindered arene oxide ligands ArO- afford the square pyramidal complexes
[Mo(OAr)(S2C2R2)2]1- (5, 6). The ligands PhQ- afford the trigonal prismatic monocarbonyls [Mo(CO)(QPh)(S2C2Me2)2]1-
(Q = S (8), Se (12)) while the bulky ligand ArS- forms square pyramidal [Mo(SAr)(S2C2R2)2]1- (9, 10). In
contrast, reactions with ArSe- result in [Mo(CO)(SeAr)(S2C2R2)2]1- (14, 15), which have not been successfully
decarbonylated. Other compounds prepared by substitution reactions of 1 and 2 include the bridged dimers [Mo2(μ-Q)2(S2C2Me2)4]2- (Q = S (7), Se (11)) and [Mo2(μ-SePh)2(S2C2Ph2)4]2- (13). The complexes 1, 3−5, 7−10,
12−14, [Mo(S2C2Me2)3] (16), and [Mo(S2C2Me2)3]1- (17) were characterized by X-ray structure determinations.
Certain complexes approach the binding arrangements in at least one DMSO reductase (5/6) and its Ser/Cys
mutant, and in dissimilatory nitrate reductases (9/10). This investigation provides the initial demonstration of the
new types of bis(dithiolene)molybdenum(IV) complexes available through [Mo(CO)2(S2C2R2)2] precursors, some
of which will be utilized in reactivity studies. (Ar = 2,6-diisopropylphenyl or 2,4,6-triisopropylphenyl.)
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dissimilatory nitrate reductasesCertain complexes approachS 2 C 2 Ph 2Et 4 NOH yieldsprismatic monocarbonylsbridged dimersligand ArScarbonyl substitutionS 2 C 2 R 2DMSO Reductase Enzyme Family Structural analoguescomplexes 1S 2 C 2DMSO reductase familyMoligands PhQprismatic complexesDMSO reductasebinding arrangementsarene oxide ligands ArOCOreactivity studiessubstitution reactionsActive Sitesforms squareOther compounds
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