CS238920B1 - A method for preparing bis / triphenylphosphane oxide / tribromo ferric complex - Google Patents

Abstract

The invention relates to a method of preparing a bis-/triphenylphosphane oxide/tribromoiron complex of the formula FeBr,/Ph,P0/-, where Ph stands for phenyl. J J The essence of the method according to the invention consists in the fact that iron compounds selected from the group including the elemental metal and salts of strong inorganic acids, such as sulfates, are allowed to react with hydrobromic acid or alkali metal bromides and triphenylphosphane PhjP in acetonitrile in the presence of dioxygen. The said complex is used as a catalyst for the oxidation of triphenylphosphane with dioxygen to triphenylphosphane oxide.

Description

The invention relates to a method of preparing the bis/triphenylphosphane oxide/tribromoferric complex Example FeBrj/Ph^PO/j, where Ph always means phenyl.

The above complex is used as a catalyst for the oxidation of triphenylphosphate Ph^P by dioxygen to triphenylphosphine oxide Ph-jÉO according to the invention AO No. 205 483 and is simultaneously a potential catalyst for the oxidation of other substrates such as tertiary phosphanes and arsanes, olefins, styrene, alkylbenzenes.

The compound of the composition FeBr ₃ /Ph ₃ PO/ ₂ is prepared according to J. Chem. Soc. /A/ 1971, 859 by direct reaction of anhydrous FeBr ₃ with triphenylphosphine oxide and according to AO No. 214 985 by reaction of anhydrous FeBr ₃ with triphenylphosphine in the presence of O ₂ .

The disadvantage of the first method of preparation is that it starts from Ph ₃ PO, which must be prepared by oxidation of PhjP. In the second method, Ph ₃ PO is no longer the starting material, but anhydrous FeBr^ must also be used.

The above disadvantages can be eliminated by the method of preparing bis(triphenylphosphine oxide), tribromoiron complex according to the invention, the essence of which consists in that iron compounds selected from the group comprising an elemental metal and salts of strong inorganic acids such as sulfates are reacted with hydrobromic acid or alkali metal bromides and triphenylphosphine Ph ₃ P in a molar ratio of 1:3:2 in acetonitrile in the presence of dioxygen at temperatures of 20 to 80 °C.

If the molar ratio of the above substances is not maintained, then in addition to the FeBr ₃ /Ph ₃ PO/ ₂ complex, after the reaction is complete, a portion of unreacted starting substances is present in the reaction mixture, except for triphenylphosphine, which is catalytically oxidized to triphenylphosphine oxide.

In the case of using ferrous bromide, ferric oxide is formed as a by-product, the formation of which can be suppressed to a minimum by adding bromide anions to the solution. In the case of starting materials of ferrous or ferrous sulfate hydrates, the by-product is always alkali metal sulfate.

After the reaction is complete, the reaction mixture is filtered and, after cooling, brownish-red crystals of the composition FeBr ₃ /Ph ₃ PO/ ₂ gradually crystallize from the filtrate, which are recrystallized.

At a concentration of iron in oxidation state III, II or 0 equal to approximately 0.1 M in acetonitrile /approx. 30 cm/, while maintaining the above-mentioned molar ratio, the FeBr ₃ /Ph ₃ PO/ ₂ complex can be obtained with the addition of oxygen in 3 to 40 hours, depending on the starting iron compound used.

Increasing the temperature above 50 °C accelerates the reaction, but it is necessary to collect the acetonitrile by cooling. Lowering the temperature below 50 °C prolongs the reaction time.

The subject matter of the invention is described in the following examples of solutions.

Example: ”4

In a temperature-controlled reaction vessel (50 C) flushed with oxygen, 2.5.10 mol -3 -3 of ferric sulfate hydrate Fe ₂ /SO^/ ₃ .9H ₂ O, 1.5.10 mol of potassium bromide KBr and 10 mol of triphenylphosphine Ph,P are placed and after connecting to the apparatus for measuring dioxygen consumption, 10 cm of acetonitrile is dosed per 3 ^J.

By monitoring the dependence of O ₂ consumption on time, it was found that the oxidation of 1*h ₃ P took place in 5 hours. After filtering off the cured potassium sulfate K ₂ SO ₄ from the solution, the compound FeBr ₃ /Ph ₃ PO/ ₂ , i.e. bis/triphenylphosphine oxide/ tribromoiron complex, crystallized.

The obtained crystals were rinsed with acetonitrile after filtration and recrystallized if necessary.

rolled and dried at room temperature. lysis. the purity of the complex was determined by elemental analysis Analysis results: Fe Br C H calculated /%/ 6.55 28.13 50.74 3.55 found /%/ 6.51 28.10 51.12 3.65 The yield was 80% • - Translation 2 To the reactionary banks will weigh 1.1 g Fe 2/SO^/ ₂ .9H ₂ 0y 2.1 g Ph ₃ P and 1.4 g KBr. After adding 3 50 cm of acetonitrile is the mixture is heated at 55 °C on approach Oj 7 hours. After filtering

of solids from the reaction mixture, after evaporation of acetonitrile from the filtrate, a brown-red powder was obtained, which was recrystallized.

The obtained crystals of the composition FeBr ₂ /Ph.jPO/ ₂ were dried and subjected to analysis.

Analysis results

Fe Br C H calculated /%/ 6.55 28.13 50.74 3.55 found /%/ 6.52 28.00 49.90 3.60

The yield was 80%.

Example 3

0.08 to 0.09 g of iron powder is placed in a temperature-controlled reaction vessel /40 °C/, about 3

Dioxygen is introduced into 0.8 g of triphenylphosphine and 0.6 cm of 46% hydrobromic acid in 30 cm of acetonitrile with constant stirring. The oxidation of Fe° to Fe ¹¹¹ and Ph^P to Ph^PO took place in about 10 hours. After cooling, brownish-red crystals of the composition FeBr^/PhjPO/j crystallized from the solution, which can be recrystallized.

Analysis results

Fe •Br C H calculated /%/ 6.55 28/13 50.74 3.55 found /%/ 6.48 28.02 50.03 3.57

The yield was 85%.

Example 4

Anhydrous iron(II) bromide (0.33 g), 3 3 triphenylphosphine (0.8 g) and 0.2 cm of 46% hydrobromic acid in 25 cm of acetonitrile are placed in a reaction vessel heated to 50°C and O2 is introduced with constant stirring.

The oxidation of Fe ¹¹ to Fe ¹¹¹ and Ph 2 P to Ph 2 PO took about 3 hours. After filtering off any solids, FeBr 2 /I 2 _O 2 crystallized from the solution. Analogously to Example 1, the dried sample was subjected to analysis.

To a reaction flask containing iron(II) bromide FeBr ₂ /5.10 ^-3 moles/, triphenylphosphine

Ph.jP (7.10 ³ moles) and 80 cm ³ of acetonitrile are fed with dioxygen at 40 °C with stirring for 1 day.

The reaction produced, in addition to FeBr ₃ /Ph ₃ PO/ ₂ , a small amount of uncoordinated triphenylphosphine oxide.

PhjPO and iron oxide Fe ₂ O ₃ , which was filtered off.

Analysis results:

calculated /%/ found /%/ The yield was 75%.

Fe Br C H 6.55 28.13 50.74 3.55 6.5 0 27.99 50.18 3.50

Example

Brownish-red crystals crystallized from the filtrate, which, after recrystallization, were subjected to an analysis similar to that in Example 1.

Analysis results:

Fe Br C H calculated /%/ 6.55 28.13 50.74 3.55 found /%/ 6.56 28.16 50.00 3, 51 The yield was 50%. Example 6

In a reaction vessel heated to 65 °C, ferrous sulfate heptahydrate FeSO ₄ .7H ₂ O (0.6 g), triphenylphosphine PhjP (1.0 g) and 0.75 cm ^{3 of} 46% hydrobromic acid HBr (or 0.7 g KBr), 30 cm ³ of acetonitrile are added and oxygen dioxide is added with constant stirring.

The oxidation of Fe to Fe and Ph ₃ P to Ph ₃ PO _f lasted 40 hours. After filtering off the solids (K ₂ SO ₄ , traces of Fe ₂ O ₃ , possibly unreacted FeSO ₄ .7H ₂ O) and evaporating the acetonitrile from the filtrate, a brownish-red powder was obtained, which was recrystallized. The obtained crystals of FeBr ₃ ~ ,yph ₃ PO/ ₂ were dried and analyzed.

Analysis results:

Fe Br C H calculated /%/ 6.55 28.12 50.74 3.55 found /%/ 6.49 28.18 50.80 3.65

The yield was 60%.

Identification of the preparations of Examples 1 to 6 was carried out by measuring the electron and infrared spectra. The end of the oxidation of PhjP to Ph ₃ PO was determined by comparing the electron spectrum of the product with the spectrum of pure triphenylphosphine oxide PhjPO, which has 4 absorption bands with maximum absorption in the region of 254, 260, 265 and 272 nm in acetonitrile solution.

The presence of coordinated PhjPO in the sample was proven by measuring infrared spectra /Q _p _ ₀ = ¹ 343 cm ¹ /. For uncoordinated IhjPD is \J ρ_θ = 1 190 cm ¹ . The course of the oxidation of Ph3P to Ph-jPO can also be followed by measuring the O ₂ consumption at constant temperature and atmospheric pressure. After oxidation, the amount of C> ₂ consumed stabilized at a constant value identical to the calculated amount of C> ₂ . ...

Claims (1)

SUMMARY OF THE INVENTION A method of preparing a bis / triphenylphosphane oxide / tribromo ferric complex of formula FeBr 3 / Ph 3 PO / 2, wherein Ph is phenyl, wherein iron compounds selected from the group include an elemental metal and salts of strong inorganic acids such as sulfates, are reacted with hydrobromic acid or alkali metal bromides and triphenylphosphate PhpP in a molar ratio of 1: 3 · 2 in acetonitrile in the presence of diacid at temperatures of 20 to 80 ° C.