December 11, 2024, 07:42:50 AM
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Topic: Failed to synthesize [Co(Me)(py)(DMG)2]  (Read 455 times)

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Offline luscofusco

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Failed to synthesize [Co(Me)(py)(DMG)2]
« on: November 20, 2024, 06:18:29 PM »
This week at the lab I tried to synthesize [Co(Me)(py)(DMG)2] this is a summary of the procedure:

Day 1:
 
  - Dissolved 2.7g of DMG in 100mL of EtOH with heat and stirring. 
  - Added 2.5g of CoCl₂·6H₂O, forming a dark green solution. 
  - Added 2mL of py and let it cool to room temperature. 
  - Passed air through the mixture for 30 minutes, turning the solution light brown (three phases were observed: a dark brown layer on top, a light brown suspension in the middle, and a small dark green phase at the bottom). 
  - Filtered under vacuum and washed with water, then ethanol, and finally ether, obtaining a brown powder. 

---

- **Day 2** 

  - Assembled a system with a Liebig condenser and a 2-neck round bottom flask, purging it with nitrogen for 5 minutes. 
  - Added 10mL of MeOH and deoxygenated it for another 5 minutes. 
  - Added 0.8g of the compound obtained on Day 1 (presumably [Co(Cl)(py)(DMG)₂]) and 2mL of methyl iodide, forming a dark-colored solution. 
  - Slowly added 0.4g of NaBH₄. Upon addition, an orange layer formed on top but disappeared once the NaBH₄ was consumed. 
  - Added a small quantity of water to precipitate the product. 
  - Filtered the solution, obtaining a brown-orange powder. This brown was different from the one obtained on Day 1 but still brown (maybe incomplete or partial reaction?) 

  - Repeated the procedure of day 2 step by step, starting with 0.8g of [Co(Cl)(py)(DMG)₂] provided by another lab mate (which appeared identical to the compound I obtained on day 1). This time, the expected orange powder, likely [Co(Me)(py)(DMG)₂], was obtained

I guess I did something wrong on day 1. The only different step on day 2 from the first try to the second try was that on the second the stirring was more intense (not a lot tho).

Any ideas? If cobalt had not been oxidized on day 1 it should've remained green instead of brown right?

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