Iron(II) Chloride1


[7758-94-3]  · Cl2Fe  · Iron(II) Chloride  · (MW 126.75)

(synthesis of ferrocene2 and derivatives;3 Sandmeyer reaction;4 alkane C-H functionalizations;6,7 alkyne reductions;5 catalytic additive8)

Alternate Name: ferrous chloride.

Physical Data: mp 670-674 °C; sublimes; d 3.16 g cm-3.

Solubility: 64.4 g/100 mL cold water (10 °C), 105.7 g/100 mL hot water (100 °C); 100 g/100 mL alcohol; sol acetone; insol ether.

Form Supplied in: green to yellow solid; widely available, can be obtained as 99.999% ultra dry material.

Preparative Methods: chlorobenzene (1 kg) and sublimed (anhydrous) Iron(III) Chloride is refluxed for 3.5 h. The iron(II) chloride is filtered and washed with anhydrous benzene (97% yield).1

Handling, Storage, and Precautions: incompatible with strong oxidizing agents; hygroscopic; may decompose on exposure to air, HCl being produced. It is an irritant. Use in a fume hood.

Ferrocene Synthesis.

Iron(II) chloride reacts with sodium cyclopentadienide in THF to give ferrocene (eq 1). This method has been described in detail2 and is applicable to many ferrocene derivatives.3

Sandmeyer Reaction.

The Sandmeyer reaction has been performed with iron(II) chloride, in place of Copper(II) Chloride. The reactions proceed in good yield, except with methyl substituents, where phenols are obtained (eq 2).4

FeCl2-Lipoamide-NaH Reductions.

Iron(II) chloride in combination with simple dithiols are effective catalysts for the reduction of alkynes to alkenes with Sodium Borohydride (22-93% yields) (eq 3).5 The best reaction conditions employ 5 equiv NaBH4, 7.5 mol% lipoamide, and 10 mol% FeCl2 stirred at rt for 8 h.

Amination of the C-H Bond.

Reaction of Chloramine-T with rigorously dry FeCl2 and adamantane in dichloromethane under nitrogen, and column chromatography of the crude reaction mixture after 2 h, gives a 63% yield of the tertiary sulfonamide (eq 4).6

GifIV Oxidation Catalyst.

FeCl2.4H2O is one of the catalysts used in the GifIV oxidation of saturated hydrocarbons using molecular oxygen. However, many iron catalysts have been used with varying results. FeCl2 provides a good ratio of secondary to tertiary hydroxylation with a reasonable turnover (30). A combination of adamantane (2 mmol), Zinc (20 mmol), and FeCl2 (7 mmol) in pyridine-acetic acid is stirred for 18 h, open to the atmosphere, to yield oxidation products (eq 5).7

Raney Cobalt Catalyst Additive.

Unsaturated alcohols can be obtained from a,b-unsaturated aldehydes via hydrogenation with Raney cobalt catalyst. FeCl2 addition to the catalyst increases yields.8

Related Reagents.

Sodium Triethylborohydride-Iron(II) Chloride.

1. FF 1967, 1, 145.
2. Wilkinson, G. OSC 1963, 4, 473.
3. Wilkinson, G.; Birmingham, J. M. JACS 1954, 76, 4281.
4. Nakatani, Y. TL 1970, 4455 (CA 1971, 74, 31 594d).
5. Kijima, M.; Nambu, Y.; Endo, T. CL 1985, 1851.
6. Barton, D. H. R.; Hay-Motherwell, R. S.; Motherwell, W. B. JCS(P1) 1983, 445.
7. Barton, D. H. R.; Boivin, J.; Gastiger, M.; Morzycki, J.; Hay-Motherwell, R. S.; Motherwell, W. B.; Ozbalik, N.; Schwartzentruber, K. M. JCS(P1) 1986, 947.
8. Hotta, K.; Kubomatsu, T. BCJ 1969, 42, 1447.

Andrew D. White

Parke-Davis Pharmaceutical Research, Ann Arbor, MI, USA

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