Collman’s reagent, and

Recently, the group of Lammertsma developed an alternative route, using Collman s reagent and dichlorophosphine 17, to generate Fe(CO)4 complexed phosphinidene 18 in situ [61]. This reactive amino substituted species is trappable at about 0 °C with alkynes and terminal alkenes to give stable phosphirene... 

Addition of nucleophiles to a carbon monoxide ligand of pentacarbonyliron provides anionic acyliron intermediates which can be trapped by electrophiles (H+ or R—X) to furnish aldehydes or ketones [18]. However, carbonyl insertion into alkyl halides using iron carbonyl complexes is more efficiently achieved with disodium tetracarbonylferrate (Collman s reagent) and provides unsymmetrical ketones (Scheme 1.2) [19, 20]. Collman s reagent is extremely sensitive towards air and moisture, but offers a great synthetic potential as carbonyl transfer reagent. It can be prepared by an in situ procedure starting from Fe(CO)5 and Na-naphthalene [20]. 

Acyl transition metal species such as Collman s reagent and the Corey-Hegedus nickel carbonyl system, although also formally acyl anions, have not found wide use in synthesis, possibly... 

The salt Na2[Fe(CO)4] (eq. 24.18) is Collman s reagent, and has numerous synthetic applications. It is very air-sensitive and is best prepared in situ. In reactions 24.21-24.23, Na salts are the initial products, but the large cluster anions are isolated as salts of large cations such as [(Ph3P)2N]", [PluP]" " or [Ph4As]+ (see Box 24.1). 

Three neutral carbonyliron complexes of different reactivity are known pentacarbonyliron Fe(CO)5, nonacarbonyldiiron Fc2(CO)9, and dodecacarbonyltriiron Fej(CO)i2. Moreover, the anionic iron(-II) complex disodium tetracarbonylferrate Na2[Fe(CO)4] (Collman s reagent) and die higher analogs Na2[Fe2(CO)g] and Na2[Fej(CO)ii] also represent iron complexes bearing exclusively carbonyl ligands. With... 

Cowley s group reported in 1987 the condensation of a dichlorophosphine with Collman s reagent to form stable complex 12, for which they obtained an X-ray crystal structure [57]. However, the two nearly equally long P-N bond lengths of 1.777(7) and 1.764(7) indicate that 12 is not an unencumbered species. 

II (dw) 4 [Fe(CO)4]2- Tetrahedral Uncommon oxidation state, but familiar as Collman s reagent Na FefCO),] and other carbonyl anions 1... 

Highly strained bicyclic 2-aza-l-phosphiranes 211 and 213 were prepared as Fe/P-clusters by the reaction of Na2Fe(CO)4-l,5-dioxane (Collman s reagent) with corresponding dichloro(dialkylamino)phosphanes 210 and 212 in Et20 at — 30 °C. X-Ray studies demonstrated that saturated bicyclic complex 211 was remarkably stable <2005CEJ3631, 2005JOC8110>. 

Neutral a-alkyliron complexes are obtained upon reaction of Na[Cp(CO)2pe] (5) with alkyl halides (9) (Scheme 6), and as with Collman s reagent this occurs in an Sn2 fashion with inversion of coirfiguration at the carbon atom. Epoxides also participate in this reaction, but tertiary alkyl halides are poor substrates. Alternatively, complexes (9) may be prepared by reaction of an appropriate metal alkyl with Cp(CO)2PeX (6). Typically complexes of this type are prepared in order to gain access to the synthetically nseful cationic rf--alkene iron complexes (Section 4.1.2). Also, nucleophilic addition of (5) to heteroatom-snbstituted alkyl halides (snch as methoxymethylchloride or chloromethyl methyl snllide) affords complexes of type (9) that can be converted to cationic... 

Cycloalkanones. M6rour etaO have reported that Collman s reagent converts a y-ethylenic bromide or tosylate into a cyclohexanone and a -allenic bromide into a cyclopentenone in moderate yield. This carbonylation reaction represents a special O... 

Collman s reagent, 704 Complex formation, of molten salts, 377-378 Complex solids, 253—263 Concentration, and stability, 590-593 Conductivity... 

Fe(CO)4] is an extremely useful organometallic nucleophile. Cooke and Collman developed the synthesis for the parent compound of this nucleophile, Na2Fe(CO>4, commonly known as Collman s reagent, by reacting sodium with Fe(CO)5 in dioxane ... 

Applications of carbonylaie reactions in organic synthesis are numerous. Particularly noteworthy are schemes involving tetracarbonylferrate( - ID (referred to as Collman s reagent), which can be isolated as a. sodium salt, NanFe(CO)4-1.5 dioxane, and is commercially available. The highly nucleophilic [Fe(CO)4p reacts readily with alkyl halides to yield alkyl iron carbonylates ... 

Cyclocarbonylation (9, 205-206). McMurry and Andrus have examined the scope of the reaction of Collman s reagent with unsaturated tosylates as a route to cycloalkanones and have concluded that the reaction is useful for preparation only of cyclopentanones and cyclohexanones from olefinic tosylates in which the double bond is monosubstituted. Yields are higher with primary tosylates than with secondary tosylates. 

In solution, Na2[Fe(CO)4] can dissociate to yield anions such as [NaFe(CO)4 and species in which solvent molecules are attached to the anions. Collman s reagent has broad applications in chemical synthesis. 

Disodium tetracarbonylferrate (Collman s reagent) is prepared by the reduction of Fe(CO)5 with sodium naphthalene in THF or sodium benzophenone ketyl in dioxane. Though it can be isolated as a white precipitate, it is usually used in THF or dioxane solution without isolation because of its highly air-sensitive and pyrophoric character. It is reported that the solubility of Na2[Fe(CO)4] is 7 x 10 M in THF and that it can be stored for moderate periods in an inert atmosphere in the dark [36]. X-ray crystallography of Na2[Fe(CO)4] (Fig. 10.2) shows that the C—Fe—C bond angle opposite to the sodium cations is significantly distorted (129.7°) [37]. However, this distortion is reduced for the potassium analogue [38]. 

The salt Na2[Fe(CO)4] (equation 23.16) is Collman s reagent which has numerous synthetic applications it is very air-sensitive and is best prepared in situ. In reactions 23.19-... 

This compound is nonpyrophoric and easier to handle than commercial Collman s reagent. Its preparation in essentially quantitative yield from Fe(CO)s involves treatment with KOH in MeOH for 0.5 h, and with BujP in refluxing THF. The pure product can be stored under argon for months. 

In contrast to the OH and MeO reagents, which are able to achieve both a substitution and a deprotonation reaction (or vice versa, see Scheme 8), Collman s reagent, because of its lower basic character, affords only the chloride displacement. 

Alkylation of the enolate of (138) with methallyliodide gave the product (149) whose stereochemistry was assigned on the basis of equilibration experiment. It was converted to the dione (150) by oxidation with osmium tetrooxide and sodiumperiodate. The aldol cyclization of (150) effected with sodium hydride and trace of t-amyl alcohol in refluxing benzene afforded the enone (151) in 88% yield. Normal protic conditions (sodium hydroxide, ethanol) were not effective in this transformation. All attempts for its conversion to aphidicolin (148) by intermolecular additions proved fruitless and therefore were turned to intramolecular methods. Molecular models show clearly that the top face of the carbonyl group is less hindered to nucleophilic attack than is the bottom face. Thus the reduction of (151) with lithium aluminium hydride afforded the alcohol (152) whose vinyl ether (153) was subjected to pyrolysis for 2 hr at 360 C in toluene solution containing a small amount of sodium t-pentoxide to obtain the aldehyde (154) in 69% yield. Reduction and then tosylation afforded the alcohol (155) and tosylate (156) respectively. Treatment of this tosylate with Collman s reagent [67] (a reaction that failed in the model system) afforded the already reported ketoacetonide (145) whose conversion to aphidicolin (148) has been described in "Fig (12)". 

Unsaturated Ring Ketones.—Acetylene hexacarbonyldicobalt complexes react with ethene, alkenes, and cycloalkenes to provide a general synthetic route to cyclopentenones. Unfortunately most monosubstituted ethenes react non-specifically. 2-Bromoethylallene gives 2-methylcyclopent-2-enone on treatment with Collman s reagent. 

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