Molybdenum complexes dicarbonyl

The retrosynthetic analysis of the 2-oxygenated carbazole alkaloids, 2-methoxy-3-methylcarbazole (37), O-methylmukonal (glycosinine) (38), 2-hydroxy-3-methylcar-bazole (52), and mukonal (53) based on the molybdenum-mediated approach led to the molybdenum-complexed cation (663) and 3-methoxy-4-methylaniline (655) as precursors (Scheme 5.51). The cationic molybdenum complex, dicarbonyl (ri -cyclohexadiene)(r -cyclopentadienyl)molybdenum hexafluorophosphate (663), required for the electrophilic substitution, was easily prepared quantitatively through known literature procedures (586,587). 

Allyl(dicarbonyl)molybdenum complexes 5 are also prepared from 4 via the methyl derivative... 

A single example of a rr-alkyl molybdenum complex was serendipitously prepared from a solution of the very light-sensitive dicarbonyl complex Mo(TPP)(CO)2. 

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. 

Finally, an unusual reaction between methylenecyclopropane and tricarbonyl( -indenyl)methylmolybdenum gave, after prolonged standing at room temperature, the allylic dicarbonyl( -indenyl)( -l-methyl-2-acetylallyl)molybdenum complex (equation 344)406 suggested that the reaction involves the initial formation of f/ -methyl-... 

Most preparations of the intermediate racemic 3-allyl(dicarhonyl)cyclopentadieny molybdenum complexes7 2 start from sodium or potassium tricarbonyl(cyclopentadienyl)molybdate8 9 10 (4) for a simple preparation see ref 11, p 493. The allylation of 4 hy homoallylic halides, such as 4-hromo-l-butene, is accompanied by rearrangement and decarhonylationI2. (Z)-if-2-butenyl(dicarbonyl)cyclopentadienylmolybdenum (5), like other comparable complexes, exists as a mixture of endo/exo- conformers, which interconvert rapidly at room temperature12. 

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... 

Experimental Procedure 3.1.4. Preparation of a Molybdenum Vinylidene Complex from a Carbyne Complex Tetrabutylanunoniuih Cyano(ethoxycarbonyl) vinylidene (dicarbonyl) hydro-tris(3,5-dimethyl-1 -pyrazblyl)borato molybdenum [526] [37] pp 151 and 188... 

In addition to the successful reductive carbonylation systems utilizing the rhodium or palladium catalysts described above, a nonnoble metal system has been developed (27). When methyl acetate or dimethyl ether was treated with carbon monoxide and hydrogen in the presence of an iodide compound, a trivalent phosphorous or nitrogen promoter, and a nickel-molybdenum or nickel-tungsten catalyst, EDA was formed. The catalytst is generated in the reaction mixture by addition of appropriate metallic complexes, such as 5 1 combination of bis(triphenylphosphine)-nickel dicarbonyl to molybdenum carbonyl. These same catalyst systems have proven effective as a rhodium replacement in methyl acetate carbonylations (28). Though the rates of EDA formation are slower than with the noble metals, the major advantage is the relative inexpense of catalytic materials. Chemistry virtually identical to noble-metal catalysis probably occurs since reaction profiles are very similar by products include acetic anhydride, acetaldehyde, and methane, with ethanol in trace quantities. 

A number of unusual structural features have been noted. The ruthenium porphyrin formed by reaction of triruthenium dodecacarbonyl with an N, AT-vinyl-bridged tetraphenylporphyrin involves disruption of a pyrrole C-N bond to give a product in which the ruthenium is bound to two pyrrole N atoms, the C and N atoms of the ruptured pyrrole ring, and two mutually cis carbonyl ligands. The remaining pyrrole N is uncoordinated.613 Mutually cis configurations have also been found for the dicarbonyl complex of molybdenum tetraphenylporphyrin and for some dinitrosyl porphyrins. 

Mononuclear dicarbonyl(cyclopentadienyl)hydridoiron complexes, characteristics, 6, 173 Mononuclear a-donor ligands, in molybdenum carbonyls,... 

It is, however, impossible to use this route to obtain cyanocarbonyl metalates having more than three CN ligands. The /e/racyanodicarbonyl metalates(O) of chromium, molybdenum, and tungsten (126) are readily accessible from the dicarbonyl complexes M(CO)2bipy2 (M = Cr, Mo, W), Cr(CO)2[(Ph2P)2CH J2, or Cr(CO)1I(Ph,P) C2H4]2 (125) with KCN in liquid NH3 at 120°C. 

Upon UV irradiation in hydrocarbon solution, the hexacarbonyls of chromium, molybdenum, and tungsten react differently with conjugated dienes like 1,3-butadiene (la), ( )-l,3-pentadiene (lb), 2-methyl-1,3-butadiene (lc), ( , )-2,4-hexadiene (Id), ( )-2-methyl-l,3-pentadiene (le), 2-ethyl-1,3-butadiene (If), or 1,3-cyclohexadiene (Ig). Chromium hexacarbonyl (2) yields, with the acyclic dienes la-lf, tetracarbonyl-r/2-dienechromium(0) complexes (3a-3f) in a smooth reaction (8-10). With 1,3-cyclohexadiene, in addition to 3g, dicarbonylbis(>/4-l,3-cyclohexadiene)chromium(0) (4g) is obtained [Eqs. (7) and (8)j. During chromatography on silica gel, the 1,3-cyclohexadiene complex 3g dismutates readily to [Cr(CO)6] and 4g [Eq. (9)]. Under the same conditions with 2 1,3-cyclopentadiene (lh) yields, in a hydrogen-transfer reaction, the stable dicarbonyl- / 5-cyclopentadienyl-r/ 3-cyclopent-enylchromium (5) (11-13) [Eq. (10)]. 

Due to low solubility in hydrocarbon solvents at low temperatures, [(>75-C5H5)Mo(CO)3]2 is not well suited for photoreactions. In order to increase the solubility, the methylcyclopentadienyl derivative, [(t/5-CH3C5H4)-Mo(CO)3]2 (102), has been used. After photoreaction with la-lc and It in n-pentane solution, the reaction mixtures contain two products each, di-nuclear tricarbonylbis(f/5-methylcyclopentadienyl)( /4-diene)molybdenum (103) and dicarbonyl-t -enyl- 5-methylcyclopentadienylmolybdenum complexes (104) (141) [Eq. (56)]. 

One of the chlorides in this complex can be exchanged for perchlorate on treatment of a solution of the complex in dichloromethane/acetonitrile with silver perchlorate2. Dicarbonyl(chloromethylidyne)[hydrotris(pyrazol-l-yl)borato]molybdenum(IV) reacted with sodium telluride in aqueous methanol to produce the anionic dicarhonyl[hydro-tris(pyrazol-l-yl)borato telluracarbonylmolybdate(0), which was isolated as the moderately air-stable tetraethylammonium salt. This salt reacted with methyl iodide in acetonitrile to form dicarbonyl[hydrotris(pyrazolo)borato](methyltelluromethylidyne) molybdenum(IV)3. 

The chemistry of the dicarbonyl(7 -cyclopentadienyl)nitrosyl and the chloro-(i7 -cyclopentadienyl)dinitrosyl complexes of chromium, molybdenum, and tungsten [i.e., fT -CsHs)M(CO)j(NO)] and [(i7 -CsHs)M(NO)2Cl] has not been studied extensively, partly because of the various difficulties associated with their preparation. The procedures described below are of general applicability to all three metals and lead to the desired compounds in high yields. The carbonyl nitrosyl complexes are the synthetic precursors of the chloro nitrosyl complexes and so their preparation is described first. 

A. DICARBONYL(t -CYCLOPENTADIENYL)NITROSYL complexes of CHROMIUM, MOLYBDENUM, AND TUNGSTEN... 

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