Application of 2,6-dihydroxypyridine hydrochloride_Industrial additives

Application background and overview of 2,6-dihydroxypyridine hydrochloride

2,6-Dihydroxypyridine hydrochloride is a chemical raw material that can be used to prepare a pincer phosphine ligand iridium metal catalyst. The metal catalyst is highly responsive to carbon dioxide in the electrocatalytic reduction of carbon dioxide, and can effectively and selectively reduce carbon dioxide to formic acid, and among all reduction products, formic acid accounts for a very high proportion.

Applications of 2,6-dihydroxypyridine hydrochloride

Preparation of clamp-shaped phosphine ligand iridium metal catalyst specifically includes the following steps:

Application of 2,6-dihydroxypyridine hydrochloride (1) Preparation of clamp ligands

In the glove box, pour the reactant 2,6-dihydroxypyridine hydrochloride (1513.2mg, 10mmol) into a 100mlSchl pure pyridine enk bottle, add 50ml THF to obtain suspension a, di-tert-butyl chloride Phosphine (3440 μL, 18.12 mmol) and triethylamine (7.68 mL, 55.12 mmol) were dropped into mixture a to obtain mixture b; take the Schlenk bottle out of the glove box, put it into an oil bath, reflux, and stir , the reactor containing mixture b was heated to 70°C under a nitrogen atmosphere. After 7 days of reaction, the eggplant bottle was taken out and cooled to 25°C to obtain mixture c. The Schlenk bottle was pumped into the glove box, filtered, and the liquid was vacuum distilled to obtain an oily solid. After freezing and solidification, the pincer-shaped ligand was obtained as a white solid with a yield of 71%. The purity was determined to be 99.8% by GC-MS. The nuclear magnetic properties are as follows: ¹H NMR (d8-THF, MHz, 253K): δ7.50 (t, J＝7.2Hz, Ar-H, 1H), 6.75 (d, J＝7.6Hz ,Ar-H,2H),1.15(d,J＝11.2Hz,-C(CH3)3,36H).³¹P NMR(d8-THF,MHz,253K): δ156.51 (s).

Application of 2,6-dihydroxypyridine hydrochloride (2) The synthesis method of pincer phosphine ligand iridium complexes is as follows:

Weigh the ligand (480 mg, 1.2 mmol) prepared in step (1) into a 25 ml single-mouth bottle in the glove box, and add 10 ml of acetonitrile to form solution A, [Ir(coe)₂ Add 5 ml THF to Cl]₂ (1.2 mmol) to form suspension B. Slowly drop suspension B into solution A, stirring continuously throughout the process. During the dripping process, it was found that the suspension continued to dissolve and eventually turned into a transparent orange-yellow solution C. The reactor containing the orange-yellow solution C was pressurized to 2.5MPa under a hydrogen atmosphere, and heated to 90°C to continue. Stir for 12 hours until the reaction is complete, then cool to 25°C to obtain mixture D. Pump the reaction bottle containing D into the glove box, filter, and take the liquid for vacuum distillation to obtain a light yellow solid. The solid powder was recrystallized with acetonitrile and diethyl ether, and light yellow crystals were precipitated. The solid was separated from the liquid, and the solid was drained to obtain E. The yield was 90%. Dissolve E (314mg, 500μmol) in THF, add NaH (845mg, 35mmol), stir continuously for 20h until the reaction is complete, filter, take the liquid and perform vacuum distillation to obtain yellow solid F, which is the product pincer phosphine ligand iridium metal. Catalyst, the yield is 85%. The structural formula of the pincer phosphine ligand iridium metal catalyst is as follows:

The nuclear magnetic properties are as follows: ¹H NMR (d8-THF, MHz, 253K): δ7.58 (t, J＝8Hz, Ar-H, 1H), 6.68 (d, J＝ 8Hz,Ar-H,2H),1.55(t,J＝7.2Hz,-C(CH3)3,36H),-10.57(td＝17.6Hz,4.8Hz,Ir-H,2H),-16.72(m ,Ir-H,1H);³¹P NMR (d8-THF, MHz, 253K): δ204.87.

References

[1] [Chinese invention] CN fluoroboric acid 201811508523.1 A clamp-shaped phosphine ligand iridium metal catalyst and its preparation method and application