Molybdenum complexes bimetallic

Fe—Fe bond can be assigned structures 201 or 202 based on spectral data. The other product of this reaction is 193 (R = r-Bu), however, it is produced in minor amounts. Complexes 199 (R = R = r-Bu, R = Ph, R = r-Bu) were obtained. Reaction of 146 (M = Mo, R = Ph, R = R = Ft, R = r" = Me) with (benzyli-deneacetone)iron carbonyl gives rise to the bimetallic complex 200 (M = Mo), which reacts further with the free phosphole to form the bimetallic heteronuclear sandwich 203. The preferable coordination of the molybdenum atom to the dienic system of the second phosphole nucleus is rather unusual. The molybdenum atom is believed to have a greater tendency to coordinate via the trivalent phosphorus atom than via the dienic system. 

Hydride transfer reactions from [Cp2MoH2] were discussed above in studies by Ito et al. [38], where this molybdenum dihydride was used in conjunction with acids for stoichiometric ionic hydrogenations of ketones. Tyler and coworkers have extensively developed the chemistry of related molybdenocene complexes in aqueous solution [52-54]. The dimeric bis-hydroxide bridged dication dissolves in water to produce the monomeric complex shown in Eq. (32) [53]. In D20 solution at 80 °C, this bimetallic complex catalyzes the H/D exchange of the a-protons of alcohols such as benzyl alcohol and ethanol [52, 54]. 

Molozonides see Primary ozonides Molybdenum(VI) complexes bimetallic complexes, 428 hydrogen peroxide determination, 635-6, 640... 

Reduction of the compounds of molybdenum and tungsten (VI). The first reaction of this group that was studied was the reduction of tungsten phenox-ide by the alkaline metals (Li, Na, K) in inert solvents that led to bimetallic complexes of W(V) [600] ... 

A bimetallic complex of molybdenum (V) was obtained on cathodic reduction of molybdenum (VI) oxomethoxide in the course of its electrochemical synthesis [902] ... 

The formation of the bimetallic complex of molybdenum and aluminium MoOjAljCOPhjg was revealed by mass-spectrometric study of viscous pastes,... 

The bimetallic complexes are not formed on direct interaction of either molybdenum or tantalum alkoxides. The introduction of steichiometric amounts of water into the solution of corresponding methoxides in methanol with subsequent evacuation and recrystallization from toluene leads to the formation with high yield of the bimetallic polyoxocomplex [Mo02Taj02(OMe)8]2 [847]. 

In addition to the bimetallic complexes of rhenium and alkaline metals formed as byproducts in the exchange reactions of rhenium halids with alkali alkoxides (such as, for example, LiReO(OPr )5 xLiCl(THF)2 [519]) there has been recently prepared a number ofbimetallic complexes ofrhenium and molybdenum, rhenium and tungsten, and rhenium and niobium [904, 1451]. The latter are formed either due to the formation of a metal-metal bond, arising due to combination of a free electron pair on rhenium (V) and a vacant orbital of molybdenum (VI) atom or via insertion of molybdenum or tungsten atoms into the molecular structure characteristic of rhenium (V and VI) oxoalkox-ides. The formation of the compounds with variable composition becomes possible in the latter case. 

The photochemical synthesis of the tungsten carbonyl metallocarborane [Eq. (18) ] is also effective in the preparation of the molybdenum carbonyl analog. The resulting air-sensitive complexes show chemical behavior similar to the cyclopentadienyl analogs, C5H5M(CO)3, in that they undergo protonation with anhydrous HOI and met.hylation with CH3I. They also react further with metal hexacarbonyls to afford bimetallic complexes 54) ... 

Redox activity of bimetallic complexes based on tris(3,5-dimethylpyrazolyl)-borato molybdenum(II) and tungsten(II) nitrosyls. Complexes derived from ethane-1,2-diol and the crystal structure of anti [Mo(NO) HB(3,5-Me2C3HN2)3 -(0CH2CH20)]24CHCl3... 

In bimetallic complexes, the oxidation state is calculated hy supposing that the metal-metal bond(s), if any, is/are broken homoly tic-ally. This procedure is justified by the fact that the electronegativities of the two metal centres are equal if they are identical, or similar in hetero-nuclear complexes (see Table 1.2(a)). The presence of one or more bonds between the metals therefore has no effect on their oxidation state. For example, the complex [Mo(Cl)2(PR3)2]2 can initially be considered to be decomposed into two monometallic neutral fragments [Mo(Cl)2(PR3)2] in which the oxidation state of molybdenum is +2. 

Treatment of TpMo( = CR)(CO)2 (R = C6H4Me-4) initially gives a mixture of TpMoFe( U-CR)(CO) (k = 5, 6), but the saturated molybdenum complex readily loses CO under a nitrogen atmosphere." Parallel reaction between bis(pyrazolyl) borate alkylidyne complexes and Fe2(CO)g similarly provides the 32-valence electron dimetal species BpWFe( -CR)(CO)6." These heteronuclear bimetallic complexes have a rich further chemistry, as summarised in Scheme 78. 

Treatment of Cp"Cr(Ti -Cot), Cp" = Cp, Cp with (EtCN)3M(CO)3, M = Mo, W and Fe2(CO)9 affords the complexes [(Cp Cr)(CO)3M][ i-Cot], M = Fe, Cr, W, Cp = Cp and I(Cp Cr)(CO)3Crl/i-Cot, Cot = Cyclooctatetrane, which have been spectroscopically characterised. Bimetallic complexes containing bis(tetramethylcyclopentadienyl) dimethylsilane bridges have been prepared from the reaction of arene tricarbonyl molybdenum complexes with the silyl substituted cyclopentadienyl derivative. The synthesis of pinanylcyclopentadienes followed by metallation and reaction with Mo(CO)s and Mel gives the chiral (-)-[(ii -C5Me4-3-pinanyl)(CO)3Me], which has been structurally characterised. The chiral methallyl complexes CpMo(NO)X(Ti -2-methallyl) X = camphorsulfonate have been resolved and the reactions of the... 

A1 Obaidi, N., Chaudhury, M., Clague, D., Jones, C.J., Pearson, J.C., McCleverty, J.A., and Salam S.S. (1987) Monometallic, homo- and hetero-bimetallic complexes based on redox-active tris(3,5-dimethylpyrazolyl)borato molybdenum and tungsten nitrosyls, part 4. The effects of ligating atom type on reduction potentials of monometallic complexes, J.ChemSoc., Dalton Trans., 1733-6. 

Complex formation of molybdenum and tungsten alkoxides with the alkoxides of other metals formation of bimetallic alkoxides... 

The complex formation of tungsten alkoxides with the alkoxides of other metals than the alkali, bismuth, and rhenium (see Section 12.21) has not been investigated in detail, and therefore the major attention below will be paid to the description of the bimetallic alkoxides of molybdenum. 

In contrast to the molybdenum complex, [CpCr(CO)3]2 gives ions only up to m/e 202 and 201, corresponding to [CpCr(CO)3H]+ and [CpCr(CO)3]+, respectively (151). The ions CpCr(CO)+ ( = 0-2) were also produced, but no bimetallic ions have been observed, suggesting that the compound may be monomeric in the vapor phase and implying a very weak metal-metal bond. 

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