Molybdenum II dimer

The unique ligating behavior of the bridging 2,6-dimethoxyphcnyl ligand with respect to promoting a substantial decrease in the metal atom separation for molybdenum(II) dimers is even more prominent in the case of chromium. The chromium-chromium distance of 1.847(1) A in Cr2(DMP)4 (90) is more than 0.1 A less than the corresponding value in any other chromous dimer yet reported. To compare homonuclear multiple bonds among elements with inherently different atomic radii, Cotton, Koch, and Millar proposed a normalized value for intemuclear distances based on Pauling s atomic radius of the element in question (209). A simple definition of formal shortness as t/(M—M)/2r(M) then follows as a measure of the relative compactness of the attractive interaction (90). The formal shortness ratio of 0.778 for the quadruple bond in... 

The oxomolybdenuni(IV) porphyrin treated with trimethylsilylchloride produces the trans dichloro derivative Mo(OEP)Cl2 which gives Mo(OEP)(PhC=CPh) by reduction with LiAlH4 in the presence of diphenylacetylene. The dimer is then obtained by vacuum pyrolysis of this five coordinate complex. Molybdenum(II) dimers are also obtained by heating a mixture of MoCl2(CO)4 and H2(Por) in oxygen-free toluene (Eq. 26) where Por is OEP, its 5-formyl-, 5-amino-, and 5-isocyanato derivative, or 5,15-dimethyletiopor-phyrin II. 

Although supported Pd catalysts have been the most extensively studied for butadiene hydrogenation, a number of other catalysts have also been the object of research studies. Some examples are Pd film catalysts, molybdenum sulfide, metal catalysts containing Fe, Co, Ni, Ru, Rh, Os, Ir, Pt, Cu, MgO, HCo(CN) on supports, and LaCoC Perovskite. There are many others (79—85). Studies on the weU-characteri2ed Mo(II) monomer and Mo(II) dimer on siUca carrier catalysts have shown wide variations not only in catalyst performance, but also of activation energies (86). 

The coals used were PSOC 1098 Illinois 6 and Beulah-Zap North Dakota lignite from the Argonne coal bank. The analytical data of these coals are shown in Table I. The ratio of catalyst to coal was approximately 0.6 mmoles of metal per gram of coal. The organometallic catalysts were molybdenum(II) acetate dimer, Mo2(OAc)4, obtained from Strem, molybdenum(II) allyl dimer Mo2(OAc)4, was prepared by die method of Cotton and Pipal (25). The NiMo supported catalyst was prepared by addition of bis(l,5-cyclooctadiene) Ni(0) (Strem) to sulfided Mo on alumina (. Cp2Mo2( l-SH)2(p.-S)2, referred to as MoS2(OM), was prepared by modification of method of Dubois et al. (26), and Cp2Mo2Co2( i3-S)2(li4-S)(CO)4, CoMo(OM) was prepared by the method of Curtis et al. (27). Pentacarbonyl iron was obtained from Aldrich,... 

Few monomeric d4 bisalkyne complexes with only monodentate ligands in the coordination sphere have been reported. The only molybdenum(II) complex in this category is Mo(PhC=CR)2(CO)(NCMe)I2 (R = Ph, Me), which was included in a reaction scheme illustrating products accessible from cleavage of the iodide bridges in dimeric [Mo(PhC=CR)(/r-I)-(I)(CO)(CNMe)]2 reagents (51). Efforts to convert Mo(RC=CR)(CO)-L2X2 complexes to bisalkyne derivatives were not successful (46). 

Molybdenum(II) and molybdenum(III) form an extensive array of multiply bonded dimers, which contain Mo-Mo quadruple and triple bonds respectively. Much of the organometallic chemistry of this class of compound has come principally from the work of one research group. Homoleptic compounds suchas [Mo2Me8]" , [Mo() -allyl)4], which contains bridging and terminal allyl ligands (see Bridging Ligand), are readily synthesized from [Mo2(OAc)4]... 

Handa, M., Kasamatsu, K., Kasuga, K., Mukuriya, M., and Fujii, T., Linear chain compounds of molybdenum(II) acetate dimer linked by linear-bidentate ligands, pyr-azine,4,4 -bipyridine, and l,4-diazabicycloj2.2.2]octane, Chem. Lett., 1753-1756 (1990). 

Ryan TR, McCarley RE (1982) Synthesis and characterization of rectangular tetranuclear cluster complexes of molybdenum(II) by condensation of quadruply bonded dimers. Inorg Chem 21 2072-2079... 

C20H31CIM0N2O2, Chlorodicarbonyl(N,N -dicyclohexylethylenediimine)-(7r-2-methylallyl)molybdenum(II ), 42B, 667 C20H3 2CI4RU2, Dichloro(2,7-dimethyl-octa-2,6-diene-1,8-diyl)ruthen-ium(IV) dimer, 37B, 447... 

The kinetics and mechanism of substitution of the quadruply bonded molybdenum(II) aqua dimer with thiocyanate and oxalate have been reported/... 

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