Sodium ferrate, preparation

Preliminary to the preparation of the gel of ferrous hydroxide, it will be necessary to prepare a solution of sodium ferrate, NazFeCh. This can be done electro-lytically according to the directions in Exercise 22. 

Bis[tetraethylammonium] Tetrakis(benzenetellurolate] ferrate(II)3 Under an atmosphere of nitrogen, 1.83 g (4.0 mmol) bis[tetraethylammonium] tetrachloroferratc(II) dissolved in 25 ml acetone are mixed with a solution of 16 mmol sodium benzenetellurolate prepared from 3.27 g (8.0 mmol) diphenyl ditellurium and 0.61 g (16 mmol) sodium borohydride, in 10 m/ ethanol. The immediately formed red precipitate is filtered and dried under a vacuum yield 100%. 

A solution of sodium dicarbonyl(cyclopentadienyl)ferrate prepared from the dicarbonyl(T] -cyclopentadienyl)iron dimer [Cp(CO)2pe]2 (4.11 g, 11.6 mmol) and sodium amalgam (2%, 35.3 g) in tetrahydrofuran (80 mL) is added slowly at -78 °C to a solution of 4-bromo-2//-chromene-3-carbaldehyde (5.5 g, 23 mmol) in tetrahydrohiran (70 mL). The mixture is stirred at -78 °C for 1 h and then allowed to warm to room temperature over a period of 1 h. The solvent is evaporated in vacuo, and the residue is dissolved in diethyl ether/acetone (1 1) and subsequently purified by column chromatography on silica gel. With petroleum ether/diethyl ether (2 1) tetracarbonyl(dicyclopentadienyl)diiron is separated, whereas with diethyl ether/acetone (1 1) the alkenyl-Fp complex is obtained. The solvent is evaporated and the yellow-brown solid is dissolved in dichloromethane (200 mL), dried (magnesium sulfate), and the solution concentrated in vacuo to yield the q -alkenyl-Fp complex as a yellow-brown, amorphous solid 6.9 g (89%). ... 

To 2 ml of the fusion add 2-3 drops of a freshly prepared dilute solution (c 0.1%) of di-sodium pentacyanonitrosyl ferrate Na2[Fe(CN)5NO]. (The latter may be prepared by adding a minute crystal of the solid to about 2 ml of water.) A purple coloration indicates sulphur the coloration slowly fades on standing. 

Tris[tetraethylammonium] Tetrakis [benzenetellurolate(tellurido) ferrate]3 Under an atmosphere of nitrogen, 4.54 g (4 mmol) of bis[tetraethylammonium] tetrakis[benzenetellurolato]ferrate(II) dissolved in 40 m/ acetonitrile are dropped into a solution of sodium hydrogen telluride in 30 ml acetonitrile. (The sodium hydrogen telluride was prepared from 0.51 g (4.0 mmol) tellurium powder and a three-fold excess of sodium borohydride in ethanol, evaporation of the ethanol, and dissolution of the residue in 30 ml acetonitrile.) The... 

Sodium per ferrate, Na2Fc04, may be prepared in an analogous manner to the potassium salt already described. It also results when ferric oxide is fused with sodium peroxide and the cooled mass treated with ice. Sodium perferrate then passes into solution.3... 

Sodium ruthenate, Na2Ru04, is prepared in situ from ruthenium tetroxide (in solution in carbon tetrachloride) and 1 M sodium hydroxide by shaking for 2 h at room temperature. The reagent remains in the aqueous layer, which acquires bright-orange color [937]. It oxidizes primary alcohols to carboxylic acids and secondary alcohols to ketones and is comparable with but stronger than potassium ferrate [937]. 

To a stirred suspension of 1,2-diphenylcyclopropenylium perchlorate (2.6 g, 8.95 mmol) in THF (10 mL), cooled at — 78 C, was slowly added a solution of sodium dicarbonyl(t -cyclopentadienyl)ferrate in THF (10 mL), which was prepared from dicarbonyl( -cyclopcntadienyl)iron dimer (1.7 g, 4.8 mmol) and 2% sodium amalgam (17 g). After warming the mixture to — 10 °C, the solvent was removed under vacuum, the residue was taken up in EtjO/dioxane (2 1, 15 mL), and the solution was cooled to — 10 C and rapidly filtered through a glass filter. The filtrate was evaporated at — 10 C under high vacuum, the... 

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... 

The tetrachlorodiester (431), prepared from the photoaddition product of dichloro-ethylene and dichloromaleic anhydride, reacts directly with sodium tetracarbonyl-ferrate to give the functionalized cyclobutadiene complex (432) in 30—40% yield. The vicinal diester groups have been modified to give a wide variety of 1,2-disubsti-tuted cyclo butadiene complexes. 

Acyl carbonyl ferrates are involved as intermediates in two preparations of aldehydes. Alkyl bromides react with sodium tetracarbonyl ferrate(—ii) (from iron pentacarbonyl and sodium) by a process of oxidative addition to furnish the ferrate(—i) (124) this species rearranges on treatment with triphenylphosphine to a phosphonium-substituted acyl ferrate(—i) (125), which is subsequently cleaved by acetic acid to the homologous aldehyde, as outlined in Scheme 46. A related procedure employs reaction of an acid halide with sodium tetracarbonyl ferrate(—ii) to afford the acyl ferrate(—i) (126) directly this species is also cleaved by acetic acid, and affords yet another method for the reduction of acid halides to aldehydes. 

Cross-conjugated dihydroacepentalene complexes 156 (NR2 = NEt2, piperidino, 3,5-dimethylpiperidino, morpholino) and 159 were prepared by de Meijere and Butenschon [179, 180] by treatment of the ligands with either Fe2(CO)9 or CpCo(H2CCH2)2 in yields up to 70%. When complex 156 was reduced with sodium, the persistent radical anion was detected with spin density on the iron atom as indicated by electron spin resonance (ESR) spectroscopy. Further reduction with sodium afforded the ferrate(-2) 158, which is diamagnetic and could be characterized by NMR investigations (Scheme 10.56). 

A 4% sodium amalgam is prepared from the careful addition of sodium (3 g, 130 mmol), in small portions, to mercury (650 g, 3.25 mol), which is rapidly stirred. The amalgam is allowed to return to room temperature over 1 h, and then a tetrahydro-furan (100 mL) solution of tetracarbonyl(dicyclopentadienyl)diiron (10.62 g, 30 mmol) is added in one portion and is efficiently stirred for 2 h. The amber tetrahydrofuran solution of sodium dicarbonyl(cyclopentadienyl)ferrate is separated from the amalgam and transferred to a new flask via syringe. This solution is cooled to 0 °C and l-bromo-2,2-di-methoxypropane (llg, 60 mmol) in tetrahydrofuran (10 mL) is added dropwise over 30 min. The yellow-brown solution is stirred at 0 °C for a further 30 min and then at room temperature for 3 h. The solvent is removed, and the residue is extracted with pentane (ca. 

---