Molybdenum complexes cycloheptatriene

Cobaltaie(l -), dodecacarbonylirontri-, tetraethylammonium, 27 188 Cobaltate(l -), dodecacarbonylirontri-, (triphenylphosphine)gold(l -(-), 27 188 -------, dodecacarbonylrutheniumtri-, tetraethylammonium, 26 358 Copper, (acetonitrile)dodecacarbonyltrico-balt ruthenium-, 26 359 Crystal growth, 26 377 Cyanate, tungsten complex, 26 42 Cycloheptatriene, molybdenum complex, 27 4... 

Later on, it was demonstrated that these heterocycles can undergo Diels-Alder reactions in the presence of an electrophile (Ss or Mel) and dienophiles <2002T1573, 2003HAC560>. These phosphoms-containing heterocycles were found to produce, upon reaction with tricarbonyl(cycloheptatriene)molybdenum(0) or tricarbonyl(mesitylene) tungsten(O), cr-complexes of the type L2M(CO)4 or I,(M(CO)( instead of 7t-complexes <1998EJI1079>. Some derivatives of this heterocycle were also found to display remarkable antibacterial activity <2005BML937>. 

As described in many reviews, Trost and his co-workers have carried out a pioneering work on the molybdenum-and tungsten-catalyzed allylic alkylation of allylic esters regioselectivity of the reaction is often complementary to the palladium-catalyzed allylic alkylation. The first asymmetric version was disclosed by Pfaltz and Lloyd-Jones in 1995 (Equation (63)). They used a catalytic amount of a novel tungsten complex, prepared from [W(CO)3(MeCN)3] or [W(cycloheptatriene) (COIs] and optically active (diphenylphosphino)phenyloxazolines 57, for the allylic alkylation of 3-aryl-2-propenyl phosphate with dimethyl sodiomalonate to isolate the corresponding branched alkylated compounds as a major isomer with an excellent enantioselectivity (96% ee). Unexpectedly, 3-aryl-2-propenyl carbonates are shown to be unreactive. It is worth noting that an isostructural molybdenum complex does not promote the catalytic alkylation under the same reaction conditions. In contrast, Lloyd-Jones and Lehmann reported the stereocontrolled... 

The structure of cycloheptatriene-molybdenum tricarbonyl (XXX, M = Mo) was subsequently confirmed by x-ray analysis (76). The six olefinic carbon atoms were found to be approximately planar and symmetrically bonded to the metal, with the methylene carbon bent away from the latter. Carbon-carbon ring distances indicated alternate double and single bonds in the planar portion of the molecule, rather than a delocalized TT-electron system, as was originally suggested. The analogous complex (C7H8)W(C0)3 was subsequently described in the literature (62, 164). 

Although Able et al. (2, 8) had originally set out to prepare 7r-cyclo-heptatrienyl complexes of metals, the cycloheptatriene complexes they actually obtained served as key intermediates in forming the former complexes. In 1958 Dauben and Honnen (61) reported that cycloheptatriene-molybdenum tricarbonyl reacted with triphenylmethyl tetrafluoroborate in methylene chloride solution with abstraction of hydride ion from the molybdenum complex. The reaction products, obtained in nearly quantitative yields, were triphenylmethane and the 7r-cycloheptatrienyl complex [(7r-C7H7)Mo(CO)3]+BF4 . 

If the number of olefins in the polyene is greater than two, then the number of steps in the overall displacement reaction is simply larger. For example, M(CO)3(l,3,5-cyclo-heptatriene) (wherein which M = Cr, Mo, and W) reacts with three equivalents of PhCN to form Mo(CO)3(NCPh)3 and 1,3,5-cycloheptatriene by a stepwise process. The rate law for reaction of Cr(CO)3(l,3,5-cycloheptatriene) is first order in complex and first order in benzonitrile. However, the reaction of Mo(CO)3(l,3,5-cycloheptatriene) is first order in complex and second order in benzonitrile. The kinetic data for reaction of the molybdenum complex have been rationalized by a stepwise pathway in which the first benzonitrile... 

In 1958 Dauben and Honnen prepared the fluoroborate salt of cyclo-heptatrienyl-molybdenum tricarbonyl through reaction of cycloheptatriene-molybdenum tricarbonyl with triphenylmethyl fluoroborate (88), Fischer and Fischer (89) have shown that an analogous reaction between cyclo-hexadiene-iron tricarbonyl (LXX) and the triphenylmethyl cation leads to the formation of a salt of the cyclohexadienyliron tricarbonyl cation (LXXI), Eq. 9. In the cation (LXXI), and in the analogous complexes described below, it is assumed that there are five ip -type carbon atoms simultaneously bonded to the iron atom. 

Cycloheptatrienes with chromium, 5, 337 in molybdenum carbonyls, 5, 480 tj7-Cycloheptatrienyl complexes, with tungsten carbonyls and isocyanides, 5, 693 Cycloheptatrienyl compounds actinide complexes, 4, 227 with actinides, 4, 226 lanthanide complexes, 4, 122... 

When the hydrocarbon C13Hi6 (50g), obtained from 44 by displacement with trimethylphosphite, is coordinated to molybdenum [Eq. (31)], the resulting complex contains a rearranged hydrocarbon ligand, whose structure conforms with the [6 + 4] cycloadduct of 1,3-cyclohexadiene to 1,3,5-cycloheptatriene. Obviously, during the complexation reaction, C—C bonds are cleaved and otherwise reconstituted in the coordination sphere of the molybdenum (73). 

Bis[dw-butyLphosphano] tellurium replaces norbornadiene, cycloheptatriene, acetonitrile, and dimethyl(methylene)oxosulfurane in chromium, molybdenum, and tungsten complexes. The P —Te compound acts as a bidentate ligand with the two phosphorus atoms coordinated to the metal atom1. The tetracarbonylchromium complex [R = CH(CH3)J can be recrystallized without loss of tellurium2. 

At present, there are only NMR data available for 7r-arene and TT-cycloheptatriene complexes of chromium, molybdenum, and tungsten (80,158,161) (see Table XXV). The chemical shifts of the complexed... 

Ph3P=NH acts as a neutral donor, displacing carbonyl and other ligands from molybdenum and tungsten complexes. Thus m-[(Ph3P NH)2M ( 0)4] (M = Mo, W) and [(Ph3P NFl)2Mo(CO)3]2 were obtained from the hexacarbonyls, [(cycloheptatriene)Mo(CO)3], or [(C4pIjNCN)2Mo(CO)4]... 

A number of olefins which may act as 6-electron ligands are shown in Table 17. Cycloheptatriene may act as both a 4-electron (see p. 138) and 6-electron ligand. With the Group VI metal heracarbonyls and clohepta-triene the complexes CtHsM(CO)3 are formed [93a]. The structure of ( cloheptatriene molybdenum tiicarbonyl, S.IO, has been determined by X-ray analysis [93]. 

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