Tricarbonyl complex

Chiral diene—iron tricarbonyl complexes were acylated using aluminum chloride to give acylated diene—iron complexes with high enantiomeric purity (>96% ee). For example, /ra/ j -piperjdene—iron tricarbonyl reacted with acyl haUdes under Friedel-Crafts conditions to give l-acyl-l,3-pentadiene—iron tricarbonyl complex without any racemization. These complexes can be converted to a variety of enantiomericaHy pure tertiary alcohols (180). 

Stabilization of Unstable Intermediates. Transition metals can stabilize normally unstable or transient organic intermediates. Cyclobutadiene has never been isolated as a free molecule, but it has been isolated and fully characterized as an iron tricarbonyl complex (138) ... 

The reactivity sequence furan > tellurophene > selenophene > thiophene is thus the same for all three reactions and is in the reverse order of the aromaticities of the ring systems assessed by a number of different criteria. The relative rate for the trifluoroacetylation of pyrrole is 5.3 x lo . It is interesting to note that AT-methylpyrrole is approximately twice as reactive to trifluoroacetylation as pyrrole itself. The enhanced reactivity of pyrrole compared with the other monocyclic systems is also demonstrated by the relative rates of bromination of the 2-methoxycarbonyl derivatives, which gave the reactivity sequence pyrrole>furan > selenophene > thiophene, and by the rate data on the reaction of the iron tricarbonyl-complexed carbocation [C6H7Fe(CO)3] (35) with a further selection of heteroaromatic substrates (Scheme 5). The comparative rates of reaction from this substitution were 2-methylindole == AT-methylindole>indole > pyrrole > furan > thiophene (73CC540). 

The possibility of activating the indole nucleus to nucleophilic substitution has been realized by formation of chromium tricarbonyl complexes. For example, the complex from TV-methylindole (215) undergoes nucleophilic substitution with 2-lithio-l,3-dithiane to give a product (216) which can be transformed into l-methylindole-7-carbaldehyde (217) (78CC1076). 

Germacyclopentadie ne, 1 - exo-fl uoro-1 -methyl-2,3,4,5-tetraphenyl-iron tricarbonyl complex structure, 1, 617 Germacyclopentane, 1-phenyl-bromination, 1, 607 Germacyclopentanes, 1, 605-609 chemical properties, 1, 607-608 synthesis, 1, 605-607 Germacyclopentenes synthesis, 1, 610-612 Germacyclopent-3-enes properties, 1, 612 reactions... 

The reaction of o-diphenylcyclobutadiene (generated in situ by oxidation of its iron tricarbonyl complex) with p-benzoquinone yields A as the exclusive product. With tetracyanoethylene, however, B and C are formed in a 1 7 ratio. Discuss these results, and explain how they relate to the question of the square versus rectangular shape of cyclobutadiene. 

The double bond transposition could also be achieved by the conversion of an intermediate for PGA2 synthesis into a 1,3-diene iron tricarbonyl complex from which PGC2 was synthesized in four steps. The Fe(CO)3 diene complex which survived the Wittig reaction was cleanly removed by Collins reagent in the subsequent step (Ref. 10). 

In the complexes of 1,3-boroles containing the unsaturated substituents (89CB633, 90CB2273, 94CB2393), the coordination mode is in the case of iron tricarbonyl complexes 10 and 11 (R = H, Me). 

The coupling reaction of an a ,/3-unsaturated chromium carbene complex, e.g. 1, and an alkyne 2, through coordination to the chromium center, is called the Dotz reaction. The initial product is the chromium tricarbonyl complex of a hydroquinone derivative 3, which can easily be converted to a free hydroquinone or quinone. 

Isopropyl l//-l,2-diazepine-l-carboxylate similarly gives tricarbonyl(4-7t/-l-isopropoxycar-bonyl-l//-1,2-diazepine)ironin45% yield (mp 106"C)and l-acetyl-3-methyl-l//-l,2-diazepine gives the corresponding iron tricarbonyl complex in 92% yield (mp 110 C).77... 

Ethyl 5-methyl-l//-l,2-diazepine-l-carboxylate and its 5-phenyl analog do not yield iron tricarbonyl complexes.77... 

Iron Tricarbonyl Complexes 19-21 of l-Troponyl-l//-l,2-diazepines and Their Decomplexation to 1-Tro-ponyl-127-1,2-diazepines 22-24 ... 

An iron tricarbonyl complex 19-21 (0.338 g, 1 mmol) and freshly sublimed Me3NO (0.6 g, 8 mmol) in acetone was left at rt for 4h. Evaporation, followed by flash chromatography (alumina, Et20), gave the corresponding unstable l-troponyl-l//-l,2-diazepines 22-24 in 76, 76 and 44% yield, respectively. 

In a number of cases, alkenes that are too unstable for isolation have been isolated in the form of metal complexes. As example is norbomadienone, which was isolated in the form of its iron-tricarbonyl complex (11). The free dienone spontaneously decomposes to carbon monoxide and benzene (see 17-29). 

Complete diastereoselection is observed in the HDA reaction of Danishefsky s diene with o-substituted benzaldehyde chromium tricarbonyl complexes. Decomplexation is facile and good yields of 2-aryl-2,3-dihydropyran-4-ones result <96SL258>. Cis-2,3-disubstituted pyranones are accessible from the Lewis-acid catalysed HDA reaction between (triisopropylsilyloxy) dienes and aldehydes and dehydrogenation of the resulting dihydropyrans <96JOC7600>. 

Unlike the parent tricarbonyls, complexes of the type CpMo(CO)2LR do not appear to undergo CO insertion. Attempts at the carbonylation of CpMo(CO)2(PPh3)Me under 78 atm of CO were unsuccessful (17) passing CO through a solution of the dicarbonyl in THF at reflux afforded only some CpMo(CO)jMe (20),... 

One of the most useful types of it complexes of aromatic compounds from the synthetic point of view are chromium tricarbonyl complexes obtained by heating benzene or other aromatics with Cr(CO)6. 

Not all carbon nucleophiles will add to arene chromium tricarbonyl complexes. For example, alkyllithium reagents and simple ketone enolates do not give adducts.325... 

Benzocyclobutene, when generated by oxidation of its iron tricarbonyl complex, can function as the dipolarophile in 1,3-dipolar cycloaddition reactions with arylnitrile oxides (Scheme 113).177 Unfortunately the synthetic versatility of this type of process is limited because of the unreactivity of other 1,3-dipolar species such as phenyl azide, benzonitrile N-phenylimide, and a-(p-tolyl)benzylidenamine N-oxide.177... 

A platinum-rhenium composite catalyst supported on the granular activated carbon (Pt-Re/C, 5 wt-Pt%, mixed molar ratio of Pt/Re = 2) [10] was prepared by a "dry-migration method" [33,34] as follows (1) The Pt/C catalyst prepared earlier (5 wt-metal%) was evacuated at 180°C for 1 h (2) The mixture (molar ratio of Pt/Re = 2) of the Pt/C catalyst and a cyclopentadienylrhenium tricarbonyl complex (Re(Cp)(CO)3) were stirred under nitrogen atmosphere at room temperature for 1 h and then heated at 100° for 1 h, with the temperature kept at a constant (3) This mixture was further stirred under hydrogen atmosphere at 240°C for 3 h and finally (4) the Pt-Re/C composite catalyst was evacuated at 180°C for 1 h. A platinum-tungsten composite catalyst supported on the granular activated carbon (Pt-W/C, 5 wt-Pt%, mixed molar ratio of Pt/W = 1) [5,6] was also prepared similarly by the dry-migration method. All the catalysts were evacuated inside the reactor at 150°C for 1 h before use. 

Treatment of a polyfunctional chromium-tricarbonyl-complexed hydroxy aldehyde with an excess of Et3SiFFTFA for 4.5 hours gives an 82% yield of fully reduced product with both the formyl and hydroxy groups completely and selectively reduced (Eq. 193).352... 

The synthesis of the trismethylenemethane iron tricarbonyl complex [(CH2)3C]-Fe(CO)3 was reported by Emerson et al. in 1966 (27). The geometry of this compound in the gas phase was investigated by Almenningen et al. (28) using electron diffraction methods. These authors pointed out some structural peculiarities which were not amenable to a simple explanation, in particular, why the hypothetical planar (CH2)3C radical is distorted when bound to the Fe(CO)3 conical fragment in such a way that the carbon atoms of the CH2 groups are displaced toward — the iron atom (Fig. 9). 

Other cyclic olefine-manganese tricarbonyl complexes were investigated by Whitesides and Lichteriberger (64), and include (77schd)Mn(CO)3,0 sced)Mn(CO)3, and (i7scet)Mn(CO)3. In all three complexes, the ionizations of the six d-electrons fall at 8 eV, giving rise to a broad band, while 7r orbitals of the cyclic ligands produce two bands, at 8.5 and 10 eV. 

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