Coordination Chemistry Of Molybdenum Research Articles

Oxidative cleavage of 3-phenyllactic acid in presence of molybdenum complexes

Molybdenum(V) starting material, (PyH) 5 [Mo V OCl 4 (H 2 O)] 3 Cl 2 , reacted in acetonitrile with 3-phenyllactic acid (2-hydroxy-3-phenylpropanoic acid) in the presence of tetraphenylphosphonium counterions to {(C 6 H 5 ) 4 P} 2 [(Mo VI O 2 Cl 2 ) 2 (C 2 O 4 )] (C 2 O 4 2− = oxalate anion). By the X-ray structure analysis of the product, the oxidation of the metal to + 6 oxidation state and the oxidative cleavage of 3-phenyllactic acid to oxalate ion were undoubtedly confirmed. Several other products of the transformation of the organic substrate were identified by 1 H NMR spectroscopy: phenylacetic acid, benzaldehyde, phenylacetaldehyde and lactone, 3,4-diphenyl-2,5-dihydrofuran-2-one. 3-phenyllactic acid undergoes in the presence of molybdenum(V) species a series of transformation reactions which produce oxalate, benzaldehyde, phenylacetaldehyde, phenylacetic acid and 3,4-diphenyl-2,5-dihydrofuran-2-one. ► Oxidation products of 3-phenyllactic acid. ► Oxidation of α -hydroxycarboxylic acids. ► Coordination chemistry of molybdenum and α -hydroxycarboxylic acids. ► X-ray structure of {(C 6 H 5 ) 4 P} 2 [(MoO 2 Cl 2 ) 2 (C 2 O 4 )].

Synthesis, crystal structure and magnetic properties of an oxalato-bridged ReIVMoVIheterobimetallic complex

The Re(IV)-Mo(VI) compound of formula (PPh(4))(2)[ReCl(4)(μ-ox)MoO(2)Cl(2)] (1) constitutes the first example of a heterodinuclear oxalato-bridged complex in the coordination chemistry of molybdenum.

STRUCTURAL ENVIRONMENTS AROUND MOLYBDENUM IN SILICATE GLASSES AND MELTS. I. INFLUENCE OF COMPOSITION AND OXYGEN FUGACITY ON THE LOCAL STRUCTURE OF MOLYBDENUM

The coordination chemistry of molybdenum was investigated in nine series of synthetic silicate glasses, including sodium disilicate (NS2), sodium trisilicate (NS3), albite (Ab), anorthite (An), Ab50An50, Ab30An70, diopside (DI), rhyolite (RH), and basalt (BA), using electron paramagnetic resonance (EPR) and X-ray absorption fine structure (XAFS) spectroscopies. The Mo content of these glasses ranges from 300 ppm to 3 wt.%. On the basis of results derived from high-resolution X-ray absorption near-edge structure (XANES) spectroscopy, molybdenum is present primarily as molybdate moieties [Mo(VI)O42−] in most of the glass compositions prepared at f (O2) values ranging from 1 atm to 10−12 atm (temperatures ranging from 1100 to 1700°C, i.e., from air to IW+4). Analysis of extended XAFS (EXAFS) spectra of these glasses indicates an average Mo–O distance of ~1.76(1) A. No evidence for second-neighbor Si or Al around Mo was found in any of the glasses, confirming that molybdate moieties are not connected to the tetrahedral framework, in agreement with Pauling bond-valence predictions. The presence of molybdate moieties in regions of these glasses enriched in network modifiers helps explain why crystalline molybdates can nucleate easily in silicate glasses (and, by extension, in the corresponding melts). In the highly polymerized glass compositions (such as “Ab” or “RH”), Mo(VI)O66− moieties also exist, but at minor levels (<20% of the total Mo). In glasses prepared at low f (O2) (near IW), reduced species of Mo occur, such as molybdenyl [Mo(V) and Mo(IV)]. In glasses prepared at even lower f (O2) (near IW+4), Mo is present as a metallic precipitate. The prevalence of molybdate moieties in silicate glasses until relatively low oxygen fugacities (IW) are achieved appears to be at variance with the fact that molybdenite, Mo(IV)S2, is the dominant Mo-bearing mineral in the Earth’s crust. In a companion paper, we re-examine the speciation of molybdenum in more complex systems that are closer to geochemical reality, such as high-temperature melts, densified (high-pressure) glasses, and silicate glass compositions enriched in volatiles.

The active sites of molybdenum- and tungsten-containing enzymes

Protein X-ray crystallography has revealed the structures of the active sites of several molybdenum- and tungsten-containing enzymes that catalyze formal hydroxylation and oxygen atom transfer reactions. Each molybdenum (or tungsten) atom is coordinated by one (or two) ene-dithiolate groups of a novel pterin (molybdopterin), and the active sites are further differentiated from one another by the number of acid residues. These active-site structures have no precedent in the coordination chemistry of molybdenum and tungsten.

Coordination chemistry of molybdenum with novel thiolate ligands. The crystal and molecular structures of a binuclear complex with a MoMo triple bond [Mo 2(SC 6H 4 oPPh 2) 3Cl 3] and of [Mo(SC 6H 3-2-SiMe 3-6-P(O)Ph 2) 2Cl 2], a species exhibiting [MoO 2S 2Cl 2] coordination

Coordination chemistry of molybdenum with novel thiolate ligands. The crystal and molecular structures of a binuclear complex with a MoMo triple bond [Mo 2(SC 6H 4 oPPh 2) 3Cl 3] and of [Mo(SC 6H 3-2-SiMe 3-6-P(O)Ph 2) 2Cl 2], a species exhibiting [MoO 2S 2Cl 2] coordination

ChemInform Abstract: The Coordination Chemistry of Molybdenum and Tungsten. Part 17. Oxomolybdenum(V) Complexes Containing Sulphur and Nitrogen Donor Ligands.

AbstractAlle Komplexe wurden durch Reaktion von MoOCl3 (THF)2 mit dem Liganden im Verhältnis 1:1, bzw. 2:1 für (II), in THF dargestellt.

The coordination chemistry of molybdenum and tungsten. Part XIV. Dioxomolybdenum(VI) complexes of bidentate, tridentate, and tetradentate Schiff bases containing oxygen, nitrogen and sulphur donors

A large number of bidentate, tridentate, tetradentate Schiff base ligands containing oxygen, nitrogen, and sulphur donor atoms have been complexed to the cis-MoO 2 moiety. The structures of the resulting complexes are postulated on the basis of infrared and proton n.m.r. arguments previously developed by Yamada. In the case of the complexes of the tetradentate ligands, the nature of the backbone between the imine groups determines which cis isomer is found.

Coordination chemistry of molybdenum and tungsten—VIII. Oxomolybdenum(V) complexes of 8-hydroxyquinoline and relevance of EPR spectra to binding sites in flavoenzymes

MoOCl 3(THF) 2 (THF = tetrahydrofuran) reacts with 8-hydroxyquinoline (QH) to form [MoOCl 3(QH) 2], which contains neutral monodentate ligands, [MoOCl(Q) 2], and anionic bidentate ligands, and the dimeric [Mo 2O 3(Q) 4], which contains anionic bidentate ligands and both terminal and bridging oxo donors. In dichloromethane [MoOCl 3(QH) 2] dissolves to give three species, and epr measurements identify these as unchanged [MoOCl 3(QH) 2], [MoOCl(Q) 2] and a third species characterised by a value of 1.979. No g value of this magnitude has previously been obtained for molybdenum(V) complexes which do not contain sulphur donors, and the significance of epr measurements as an indication of the nature of molybdenum coordination in flavoenzymes must be questioned. These complexes have also been characterised by vibrational and electronic spectral measurements.

The co-ordination chemistry of molybdenum and tungsten. Part 9. Oxomolybdenum-(IV) and -(V) complexes of methyl-substituted bidentate Group 5B ligands

The preparation of oxomolybdenum(V) complexes [MoOCl3(L–L)] with the bidentate ligands (L–L) 1,3-bis(dimethylphosphino)propane, 1,3-bis(dimethylarsino)propane, (3-dimethylphosphinopropyl)dimethylarsine, o-phenylenebis( dimethylarsine), and (2-dimethylarsinophenyl)dimethylstibine are descried. On the basis of their e.s.r. spectra the first three complexes have fac structures. Oxomolybdenum(IV) cations [MoO(Cl)(L–L)2]+ have been prepared from [MoOCl2(PMe2Ph)3] and L–L, and are shown by 1H n.m.r. to have trans-pseudo-octahedral structures.

The coordination chemistry of molybdenum and tungsten. Part V. Open-chain tetrathioether complexes of molybdenum(IV) and (V) and tungsten(IV) and (V)

The tetrathioethers α, ω-bis(methylthioalkylthio)alkanes, CH 3S(CH 2) nS(CH 2) mS(CH 2) nSCH 2 (n = m = 2; n = 2, m = 3; n = 3, m = 2, n = m = 3, ligand), yield seven-co-ordinate [MCl 4(ligand) (M = Mo, W), seven-coordinate [WoCl 3(ligand)] in which the thioethers act as tridentate ligands, and six-coordinate [MoOCl 3) 2(ligand)] in which the ligand acts in a tetraligate bimetallic manner. 2-5-Dithiahexane (dth) similarly yielded [MCl 4(dth)(RCN)] and [MoOCl 3(dth)]. The electronic, infrared and electron paramagnetic resonance spectral properties of these complexes are reported and discussed.

Co-ordination chemistry of molybdenum. Part II. Oxomolybdenum(IV) and -(V) complexes of diphosphine, diarsine, and arsine-phosphine ligands

Reaction of [MoCl3O(thf)2](thf = tetrahydrofuran) with bidentate ligands [L–L = Ph2PCH2CH2PPh2(dppe); Ph2AsCH2CH2AsPh2(dpae); cis-Ph2PCHCHPPh2(dppen); cis-Ph2AsCHCHAsPh2(dpaen) : Ph2AsCH2CH2PPh2(dadpn); cis-Ph2AsCHCHPPh2(dadpen); C6H4(PPh2-o)2(pdpp); and C6H4(AsPh2-o)(PPh2-o)(pdadp)] has led to the isolation of [MoCl3O(L–L)] complexes. Refluxing these complexes in methanol leads to partial reduction to form [MoIVClO(L–L)2][MoVCl4O], but reflux in methanol in the presence of L–L and Na[BPh4] results in complete reduction to [MoClO(L–L)2][BPh4]. These complexes have been characterised by the use of i.r., electronic-absorption, and e.p.r. spectroscopy. E.p.r. spectra suggest that the [MoCl3O(L–L)](L–L = dppe or dppen) species have a fac structure in dichloromethane. Considerable hyperfine structure, and g values ca. 1.97, have been observed for the e.p.r.-active species.

Coordination chemistry of molybdenum. Part III. EPR spectra of molybdenum(V) 8-hydroxyquinoline complexes and their relevance to the nature of molybdenum coordination in flavoenzymes

Coordination chemistry of molybdenum. Part III. EPR spectra of molybdenum(V) 8-hydroxyquinoline complexes and their relevance to the nature of molybdenum coordination in flavoenzymes

The co-ordination chemistry of molybdenum—I: Some complexes of molybdenum(V) with 2:2′-dipyridyl

The preparations and chemical magnetic and spectroscopic properties of the following complexes of molybdenum(V) with 2:2′-dipyridyl are described: MoO 2Cldipy (I), Mo 2O 3Cl 4(dipy) 2 (II), and MoOCl 3dipy(III). According to the magnetic moments I and II are polymerized and III is a monomer. Possible structures of the complexes are discussed.