Collman reagent

Collman reagent S.8.2.9.2 Reactions with alkyl or acyl halides ... 

The same electrochemical flow cell has also been used in combination with IR spectroscopy in a stopped-flow system [68, 69]. The purpose was to study the electrogeneration of the Collman reagent Fe(CO)4 obtained from the two-electron reduction of Fe(CO)5. It was possible to monitor the consumption of Fe(CO)s and... 

Figure 26. Application of flow-cell and IR spectroscopy to study the reaction between the electrogenerated Collman reagent, Fe(CO)4 (v = 1741 cm ) and Fe(CO)s = 2018 and 1993 cm ) to generate Fe2(CO)g (v = 1914 and 1883 cm ). Fe(CO)5 (1 mM) is reduced in the flow cell to ImM Fe(CO)4 , which is mixed with 10 mM Fe(CO)s in the IR cuvette. The medium was aceto-nitrile/0.1 M BU4NBF4. From C. Amatore, J. N. Verpeaux, and S. U. Pedersen, in Novel Trends in Electroorganic Synthesis (S. Torii, Ed.), Kodansha, Tokyo, 1995, p. 205.

From the other side, the carbonylation of alkyl halides needs stoichiometric amounts of iron salt, such as the Collman reagent [Na2pe(CO)4]. The first... 

Using alkyl halides the scope of the reaction is limited to benzylic compounds unless one uses stoichiometric amounts of the versatile Collman reagent Na2pe(CO)4 (Table II). 

Use of the stoichiometric Collman reagent allows dialkyl ketone synthesis via ... 

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] ... 

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... 

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. 

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... 

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