[joe900]

how it is possible that when i made TLC for my compound, chromium complex Cr(acac)3 and put it and its reference (pure complex) on the same plate, one of them has Rf=0.6 and the other has about 0.3? does contaminations change value of Rf and make it different? i think there should be two spots: from contamination and from product...

[MOTOBALL]

The very great difference in Rf values shows that your compound is not Cr(acac)3; the presence of impurities will not, in general, affect the Rf value of a compound.  Which Rf corresponds to the
Cr(acac)3 standard ?

What is the absorbent & the developing solvent ?

[joe900]

silicagel plate and dichloromethane-methanol (99:1), Rf for standard is 0.6. But the colour of the product is right...maybe i did some mistake during preparation

[kriggy]

Well color is not very good indicator. I had compound with same color as the pure one but it had like 60% impurities.

[MOTOBALL]

Chromatography on silica gel is based on adsorption to, and desorption from, the very polar solid phase.  Your unknown has Rf = 0.3, and is more strongly bound to the solid phase than the authentic Cr(acac)3; the unknown is therefore more polar than Cr(acac)3.

I don't know the synthesis of Cr(acac)3, but is it possible that your unknown is not fully substituted ??

Could your unknown be something like Cr(acac)2(OH)1 or Cr(acac)1(OH)2 ?