Über Pterinchemie. 90. Mitteilung. Synthese und Kristallstruktur des ersten chinoiden Dihydropterinmolybdän (IV)‐Komplexes

Abstract

Synthesis and Crystal Structure of the First Quinoid Dihydropterinmolybdenum(1V) ComplexThe first molybdenum(1V) complex with a quinoid dihydropterin, i.e. 2, was isolated and characterized by IR, UV and NMR data and single-crystal X-ray diffraction. The reaction of MoV'02CI, with the biologically important 6B-5,6,7,8-tetrahydro-~-biopterin') (7) in MeOH gave almost quantitatively trichloro(l,5-quinoid-7,8dihydro-6H-~-biopterin)oxomolybdenum(IV) (2). The complex crystallizes with one molecule of MeOH in the noncentrosymmetric orthorhombic space group P2,2,2, (No. 19) with unit cell dimensions a = 1009.3(3), h = 1104.7(3), and c = 1484.5(4) pm and Z = 4. The Mo-atom has a distorted octahedral geometry (Fig. 1). It is coordinated by N(5) and O(4) of the pterin ligand. The distance of the Mo-N(5) bond (202 pm) is unusually short compared to similar complexes. O(4) is located trans to a terminal 0x0 ligand. The octahedral coordination is completed by three C1-atoms in a meridional arrangement. Complex 2, with the Mo-atom in the enzyme-relevant oxidation state +1V and the pterin in the intermediate quinoid dihydro form, should lead to an extension of the proposed 'common molybdenum cofactor' model.

Synthesis, characterization, and spectroscopy of model molybdopterin complexes

“…We [20][21][22][23][24] and others [25][26] have studied the redox interplay between pterins and transition metals, including Mo. Reduced pterins react with many oxidized Mo(6+) complexes to produce Mo-coordinated pterin compounds where the electronic distribution is highly covalent [24].…”

Pterin Chemistry, Part 91. Synthesis and Crystal Structure of the First Molybdenum (IV)-q-dihydro-L-Biopterin Complex

“…The tables of the bond distances and angles, the experimental and the "C-NMR data were published in Helvetica Chimica Acta (1).…”

Organometallic Rhodium(III) and -(I) Complexes with 1,3-Diniethyllumazine(DML). The Crystal Structure of [(η2- (O4,N5)DML)(η5-C5Me5)ClRh](PF6)

“…There are some model complexes with regard to the m olybdopterin system [4,9,10], including a In case of the related lumazine derivatives the 0 4,N5 chelate coordination has been suggested for a number of complexes between well soluble 1,3-dimethyllumazine (DML) and ruthenium (II), copper(I), rhenium(I) [11,12] and tungsten(V) or -(VI) complex fragments [13]. Folate as another pterin ligand system also forms 0 4,N5 coordinated complexes with [Ru(bpy)2]2+ [14].…”

“…sulfite oxidase, ni trate reductase) operate with the help of a cofac tor which is assumed to be a special metal-binding pterin, the molybdopterin (1) [2][3][4][5]. While there is much agreement on the nature of the chromoReprint requests to Prof. Dr. W. Kaim. phore in that cofactor [4,5] and on the metal oxi dation states (+VI,+V,+IV) involved, the metal co ordination is not obvious although the dithiolenetype sulfur atoms have frequently been invoked [4,5]; coordination at N5 and/or O 4 of the pterin ring system (2) has also been suggested [9]. …”