Collman s reagent

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]. 

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. 

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... 

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. 

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]. 

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... 

Selective reduction of unsaturated aldehydes. Collman s reagent is effective for the selective reduction of the a,/8 -unsaturation of aldehyde 1. The dihydro aldehyde 2 is an intermediate in the synthesis of 9,10-dihydroretinals (e.g., 4). 

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... 

The electropilic phosphinidine complex 29 can be generated in situ by the reaction of dichloro(diisopropyl-amino)phosphine with Collman s reagent. By trapping reactions with various alkynes, amine-substituted phosphirene complexes 30 are accessible (Equation 24) <2000T137>. 

Thus Collman s reagent functions much like a Cngnard reagent in its ability to convert alkyl halides into a wide variety of organic compounds. 

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. 

Cobalt(III) fluoride, 397 Cobalt(II) phthalocyanine, 102-103 Collman s reagent, 174-175 6-Coniceine, 398 Coniferyl alcohol, 351 Cope rearrangement, 31,311 Copper(ll) acetate, 103, 211 Copper(fl) acetate-Iron(II) sulfate, 103-104 Copper(I) bromide-Diinethyl sulfide, 104-105... 

The most commercially important metal carbonyl anion, [Fe(CO)4]2, contained in Collman s reagent (shown below), can be prepared from the following reaction in dioxane solvent.14... 

---