Molybdenum complexes dithiocarbamates

Several complexes containing the W2S3 and W203 structural units have been prepared with thioxanthates and dithiocarbamates.178,179,180 Whether these have structures similar to the analogous molybdenum complexes is yet to be determined. 

One approach to limit dimer formation in model complexes involves the use of bulky ligands and weakly coordinating solvents. Holm and coworkers [196,198-201] have studied oxygen atom transfer reactions of 2,6-bis(2,2-diphe-nyl-2-thioethyl)pyridinate [2] molybdenum oxo complexes. In contrast to the structurally similar dithiocarbamate molybdenum complexes, the tendency of the 2,6-bis(2,2-dipheny 1-2-thioethy l)pyridinate MoIV monoxo complex to undergo di-... 

The various types of compound and their mechanisms of action have been reviewed by Mitchell . He concluded that the question of the extent to which the molybdenum additives decompose to produce molybdenum disulphide, if at all, was not yet resolved and certainly depended on the type of compound and the operating conditions. There was little doubt that molybdenum dithiocarbamates form molybdenum disulphide, probably by decomposition at hot spots caused by asperity interactions. It was less certain that molybdenum dithiophosphates form molybdenum disulphide, although mixtures of zinc dialkyidithiophosphate and molybdenum complexes had been shown to do so . 

NSC, Thiocyanate, gold complex, 26 90 NS2C5H11, Dithiocarbamic acid, diethyl-, molybdenum complex, 28 145 NSiC,H , Ethanamine, 1,1-dimethyl-A -(trimethylsilyl)-, 27 327 NSi2C4H , Silanamine, 1,1,1-trimethyl- -(trimethylsilyl)-, ytterbium complex, 27 148... 

S2NC5H, Dithiocarbamic acid, diethyl-, molybdenum complex, 28 145... 

More recendy, molecular molybdenum-sulfur complexes and clusters have been used as soluble precursors for M0S2 in the formulation of lubricating oils for a variety of appHcations (70). Presumably, the oil-soluble molybdenum—sulfur-containing precursors decompose under shear, pressure, or temperature stress at the wear surface to give beneficial coatings. In several cases it has been shown that the soluble precursors are trifunctional in that they not only display antifriction properties, but have antiwear and antioxidant characteristics as weU. In most cases, the ligands for the Mo are of the 1,1-dithiolate type, including dithiocarbamates, dithiophosphates, and xanthates (55,71). 

Electrochemical recognition, 39 80 anions, macrocyclic and acyclic polycobalti-cinium ligand systems, 39 134-140 cations, 39 81-133 ammonium cation, 39 128-133 crown ether and bis crow ether ligands containing bipyridyl transition metal recognition sites, 39 111 crown ether dithiocarbamate and dithi-olene complexes, 39 123-124 di-h-cyclopentadienyl-molybdenum(IV) and -tungsten(IV) crown ether complexes, 39 107-108... 

The reaction between [MoCl4(NCPr)2] and dithiocarboxylic acids is a general route to the preparation of eight-coordinate [Mo(S2CR)4] complexes.168 The crystal structure of [Mo(S2CPh)4] reveals these compounds to be isostructural with the dithiocarbamates, with a dodecahedral coordination around the molybdenum and average Mo—S distances of 2.475(1) and 2.543(1) A to the two different sulfur sites.170 Cyclic voltammetry has shown that in [Mo(acda)4] (Hacda = 2-aminocyclopent-l-ene-l-dithiocarboxylic acid) the Mo can be reversibly oxidized and reversibly reduced in one-electron processes.171... 

Dithiocarbamates, in Ru and Os half-sandwiches, 6, 493 Dithiocarbenes, Pt complexes, 8, 439 Dithiocarboxy ligands, in molybdenum carbonyls, 5, 447 Dithiolate-bridged compounds in dinuclear iron compounds with Fe-Fe bonds, 6, 238 as iron-only hydrogenase biomimetic models, 6, 239 Dithiolate diamides, with Zr(IV), 4, 784 Dithiolene—uranium complexes, synthesis and characterization, 4, 212 Ditopic receptors, characteristics, 12, 489 Ditungsten complexes, associated reactions, 5, 748 Divinyllead diacetates... 

Phosphorus is present in zinc dialkyldithiophosphate and deactivate platinum catalysts in engine exhaust systems. Using zinc, antimony and oxothiomolybdate dialkyl-dithiocarbamate (MoDTC) complexes alone or in combination with other lubricating oil additives appears to solve this problem. Antimony complexes are used also as extreme pressure agents while molybdenum ones as friction modifier additives (Hill et al., 1994). Analyses of Zn(dtc)2 decomposition using the thermogravimetric method, flash vacuum pyrolysis, and four-ball machine... 

Table 5.15. Protective tribofilm formation from degradation of molybdenum dithiocarbamate (MoDTC), molybdenum dithiophosphate (MoDDP) and molybdenum amine-ester complex (MoAC) directly and in combination with ZDDPs or sulfur compounds...

The (IsQ-coordinated species [Mo(CO)3(py)3] prepared from [Mo(CO)6] and pyridine is useful for the synthesis of various jr-allyl molybdenum compounds (68JOM(13)Pl, 970M5365). The 3-allyl complexes [( 3-allyl)Mo(CO)2Br(py)2] form [( 3-allyl)Mo(CO)2(S,S)(py)] with the anionic S,S-donors, dithiocarbamates and xanthates of sodium and potassium, M (S,S) (81JOM(218)185). [( 3-C3H5)Mo(CO)2(py)2Br] (68JO M(14)375) with thallium hexafluorophosphate in acetonitrile gives... 

Bisalkyne cyclopentadienyl derivatives of molybdenum and tungsten have been prominent in the development of Group VI alkyne chemistry in the 1980s. Unlike the dithiocarbamate systems where addition of a second alkyne produces a substitutionally inert bisalkyne derivative, interconversion of monoalkyne and bisalkyne cyclopentadienyl complexes is facile and synthetically useful. 

Electronic transitions assigned to the dir manifold produce the brilliant colors which characterize M(CO)(RC=CR)(B—B)2 complexes. A study of 20 dithiocarbamate derivatives reported transition energies ranging from 13,500 to 17,500 cm-1 with e between 70 and 120 Af-1 cm"1 for molybdenum while tungsten absorption maxima ranged from 15,800 to... 

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