Molybdenum complexes bromides

A closely related formation of >/3-cydopropenyl molybdenum complex Cp P(OMe)3)2Mo( 3-C3Ph2Me), possibly involving an interamolecular ligand cycloaddition within a carbyne-acetylene intermediate complex, has been accomplished by treating the acetylenic cation complex [Cp f P(OMe)3 2Mo( 2-PhC=CPh)]BF4 with vinylmagne-sium bromide in THF (equation 253)321. 

Similarly, metathetical exchange of the labile acetonitrile ligands in the octahedral molybdenum complex (CO)2(MeCN)2BrMo( 3-C3Ph3) with a variety of bidentate amines led to the corresponding amino complexes (equation 267)311. These form crystalline acetonitrile solvates suitable for X-ray determination, which confirm the octahedral structure of these complexes and the occurrence of the cyclopropenyl and bromide groups in a tram-relationship. 

Lithium benzenetellurolate or bromomagnesium benzcnetellurolate and cycloheptatrienyl-(dicarbonyl)molybdenum bromide produced the benzenetellurolato-bridged dinuclear molybdenum complex, dicarbonylbis[l-7-r -cycloheptatrienyl -bis[p-benzeneteUurolato] di-molybdenum( II)1. 

Even polymeric molybdenum (III) bromide is soluble through complex forma-tion i. ... 

In a similar manner, Jt-allyl complexes of manganese, iron, and molybdenum carbonyls have been obtained from the corresponding metal carbonyl halides [5], In the case of the reaction of dicarbonyl(r 5-cyclopentadienyl)molybdenum bromide with allyl bromide, the c-allyl derivative is obtained in 75% yield in dichloromethane, but the Jt-allyl complex is the sole product (95%), when the reaction is conducted in a watenbenzene two-phase system. Similar solvent effects are observed in the corresponding reaction of the iron compound. As with the cobalt tetracarbonyl anion, it is... 

Scheme 2.29 depicts two of the first examples of microwave-assisted carbonylation reactions7. In these reactions, the temperature controls the rate of the CO release. Thus, during heating at 150°C in sealed vessels, carbon monoxide was smoothly emitted from the molybdenum carbonyl complex into the reaction mixture (Fig. 2.1, Profile A). As a result, aryl iodides and bromides underwent efficient amino carbonylation with non-hindered, aliphatic, primary and secondary amines in only 15 min, using Herrmann s palladacycle as pre-catalyst7 (Scheme 2.29). In contrast, at a reaction temperature of 210°C, carbon monoxide was liberated almost instantaneously (Fig. 2.1, Profile B).

Anionic chromium hydride complexes proved to be efficient hydrogen atom donors. Newcomb determined PPN+ HCr(CO)5 to be an efficient radical initiator and reducing agent for radicals and determined the kinetics of the hydrogen abstraction reaction [214]. In line with the observation that 3d metal complexes are much more prone to radical pathways than the corresponding 4d and 5d complexes, an increase of the extent of competing S -pathways for the bromide abstraction was found for molybdenum and tungsten complexes compared to the chromium complex. 

Propynylnaphthalene 15 furnishes dinaphthylacetylene 20 in near quantitative yield. On the other hand, the Mori system performs somewhat less well if heteroatoms are present in the substrates, suggesting that the catalytic system is poisoned by the presence of the heteroatom through complexation and/or chelation of the active molybdenum center. Cyano groups and bromides/iodides inhibit the reactivity of the catalyst system. However, both propynylated phenols (16) and esters (17) give satisfactory dimerization results (21, 22). 

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