Na2Fe 4 Collman

Carbonylate anions are the most suitable starting material for the synthesis of silylmetal compounds. A prerequisite for the preparation of compounds with a formal M = Si double bond is the use of metallate dianions like Na2Fe(CO)4 (Collman s reagent) together with the respective dichlorosilanes [96]. 

The reaction (Eq. (5)) in THF yields labile THF adducts which are converted into the more stable HMPA adducts by addition of HMPA. The various equilibria existing between Na2Fe(CO)4 and several donor solvents are described in a detailed paper by Collman in HMPA, the solvent-separated supernucleophilic ion pair [Na+x HMPA x Fe(CO)4 ] is the kinetically dominant species, with no kinetic contribution from free [Fe(CO)J2 . In THF, Na2Fe(CO)4 is much less dissociated, with tight-ion paired [NaFe(CO)4] as the kinetically important species [96],... 

The first synthesis of a formyl complex was described in 1973 (27, 28). In a landmark paper, Collman and Winter reported that the reaction of Na2Fe(CO)4 with formic acetic anhydride [Eq. (4)] afforded the anionic formyl Na+(CO)4Fe(CHOU (subsequently isolated as its [(CeHs PjiN or PPN+ salt) in good yield. Formic acetic anhydride is an excellent formylat-ing agent. This seemingly unusual reagent was selected because many HCOX species (X = Cl, 02CH) are unstable at room temperature (4 ). 

Sodium reacts with iron pentacarbonyl to produce a salt known as sodium tetracarbonylferrate(—II)2, Na2Fe(CO)4, which has been shown by J. P. Collman and co-workers to have considerable potential as a reagent for organic synthesis. 

Reaction of the nucleophilic Collman s reagent (Na2Fe[CO]4) with two alkyl halides affords ketones via successive oxidative additions (Scheme 1.2) [7]. However, no catalytic cycle is achieved because the reaction conditions applied do not lead to regeneration of the reagent. 

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>. 

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 ... 

Synthesis of aliphatic ketones. Collman et al. have described four similar but distinct syntheses of unsymmetrical ketones using Na2Fe(CO)4 as the reagent as outlined in (a)-(d). 

Na2Fe(CO)4—A transition-metal analogue of a Grignard reagent (J. P. Collman, Accounts Chem. Res., 1975, 8, 342. 

Applications of carbonylate reactions in organic synthesis are numerous. Particularly noteworthy are schemes involving tetracaibonylferrate( -11) (referred to as Collman s reagent), which can be isolated as a sodium salt, Na2Fe(CO)4-1.5 dioxane, and is commercially available. The highly nucleophilic [Fe(CO)4]2 reacts readily with alkyl halides to yield alkyl iron carbonylates ... 

Review. Collman cites a new practicable method of preparation of Na2Fe(CO)4 from Fe(CO)s and molten sodium in the presence of benzophenone ketyl in boiling dioxane. 

A.iii. Sodium Tetracarbonyl Ferrate. An extremely useful organoiron reagent is sodium tetra-carbonyl ferrate [Na2Fe(CO)4], usually prepared by reduction of iron pentacarbonyl. The synthetic utility of this reagent lies in its ability to react with alkyl halides in a stepwise manner, including the reaction with two different alkyl halides, as reported independently by Cooke and by Collman and co-workers. - When sodium tetracarbonyl ferrate reacted with 1-bromooctane, a trigonal bipyramidal complex (715) was formed... 

Interestingly, bimetallic complexes including the [Fe(CO)4] moiety are also recovered after treatment of Cp2M(PPhHCl)(CO)J+Cr salts with Collman s reagent Na2Fe(CO)4 ° ... 

COLLMAN S REAGENT Na2Fe(CO)4. COUPLING WITH CO INSERTION... 

C2H5I + Na2Fe(CO)4 + BrECHJ COOCaHs -> C H COICH COOC H Ethyl 5-bromovalerate added under Ng to a soln. of Na-tetracarbonylferrate(-II) in N-methyl-2-pyrrolidone, stirred 1 hr., ethyl iodide added, and the product isolated after 24 hrs. ethyl 6-ketooctanoate. Y 74%. - The most remarkable feature of the above reagent is its toleration of functional groups. F. e., also with tosylates, whidi minimize eliminations, s. J. P. Collman, S. R. Winter, and D. R. Clark, Am. Soc. 94, 1788 (1972). 

Amino acids can also be prepared by a stoichiometric condensation of the Collman reagent Na2Fe(CO)4 with a starting mixture of acyl chloride and imidoyl chloride [166] ... 

---