Synthesis of oxomolybdenum bis(dithiolene) complexes related to the cofactor of the oxomolybdoenzymes †

Abstract

A synthetic strategy is reported for a general route to asymmetric dithiolenes. This has been used for the generation of [MoO(dithiolenepyridin-2-yl, pyridin-3-yl, pyridin-4-yl, quinoxalin-2-yl or 2-(dimethylaminomethyleneamino)-3-methyl-4-oxopteridin-6-yl], which have been characterised by analysis, spectroscopy and electrochemistry. The prototypical compound [PPh 4 ] 2 [MoO(sdt) 2 ]ؒEtOH, where sdt = α,β-styrenedithiolate (R = phenyl), crystallises in the space group P2 1 /c with a = 13.217(4), b = 31.820(8), c = 14.534(7) Å, β = 113.8(2)Њ and Z = 4. The MoOS 4 moiety is square-based pyramidal with the O atom at the apex [Mo᎐ ᎐ O, 1.700(5) Å] and contains a cis geometry of the phenyl groups. The physical properties of all the compounds are consistent with a retention of the MoOS 4 centre and the variation in the dithiolene 1 H NMR resonances, infrared ν(Mo᎐ ᎐ O) and ν(C᎐ ᎐ C) stretching frequencies and the E ₂  ₁ values for the Mo V -Mo IV couple are rationalised by a consideration of the nature of the R substituent. The complexes with the pterin [2-amino-4(1H)-pteridinone] substituent have a particular relevance to the Mo centre in oxomolybdoenzymes, and are the closest structural models to date for these enzymes containing two molybdopterin ligands per metal. † Based on the presentation given at Dalton Discussion No. 2, 2nd-5th

A Bioinspired Molybdenum Complex as a Catalyst for the Photo‐ and Electroreduction of Protons

“…This ligand was directly reacted with K 3 Na[MoO 2 (CN) 4 ]·6 H 2 O [12] under alkaline conditions at 45 8 8Cfor 30 minutes, [13] followed by cation exchange with Bu 4 NBr,t oa fford the mononuclear complex (Bu 4 N) 2 [Mo IV O(qpdt) 2 ](1)in67% yield. As aresult of the sensitivity of the complex to air,s olid samples were kept within an anaerobic box.…”

The Electronic Structure and Spectroscopy of Metallo‐Dithiolene Complexes

“…[Adapted from (16).] research has focused on how simple variations in the donor ability of a coordinated dithiolene affect the reduction (7,8,20,22) and ionization potentials of oxo-molybdenum dithiolenes. Photoelectron spectroscopy has revealed that the Mo d xy redox orbital of (L-N 3 )MoO(qdt) is stabilized by $0.8 eV compared to that of (L-N 3 )MoO(tdt) (20,22).…”

Unexpected Reaction Promoted by NH+···O=Mo Hydrogen Bonds in Nonpolar Solvents

“…[16] Especially, the acidic ammonium protons of Et 3 NH + and pyridinium (PyH + ) counterions formed relatively strong hydrogen bonds and weakened the M=O (M = V, Mo) bond in the solid state. [17][18][19] The absorption spectra of one of these complexes in dichloromethane solution suggested that the NH + ···O=Mo hydrogen bond was retained and it should decrease the electron density of Mo; however, the results of electrochemical measurements showed a negative shift, which was inconsistent with the expectation.…”