Are these color changes consistent with the expected positions of the ligands in

Question

Are these color changes consistent with the expected positions of the ligands in the spectrochemical series? Explain. A rhodium complexes of the formula, (Rh(CO)(Phosphine)_2Cl) have the C-O stretching bands shown below. Match the infrared bands with the appropriate phosphine. Phosphine: P(p-C_6H-4F)_3,P(p-C_6H_4Mc)_3,P(t - C_4H_9)_3, P(C_6F_5)_3 u(CO) cm^-1;1923, 1965, 1984, 2004 Briefly explain your answer. Provide plausible reason/s for the difference in the C-O frequencies in the following compounds. V(CO)_6 = 1859cm^-1, Cr(CO)_6 = 1981 cm^-1, Mn(CO)^+_6 = The more negative change on the more electrons enter in the an tab co group, the lower C-O stre chin So V(Co)^-

Explanation / Answer

i hope that you wanted to knwo the reason for

a)

[Rh CO (phosphine)2 Cl] ...depending on the type of phosphine the CO stretching frequency will change...let me give you the trend...CO in free state has stretchinh frquency around 2250 cm-1

when it's atached to the metal ...if the electron density on themetal is increased ... then the M-CO bond will be stronger...which results in decrese in the frequency of CO ...so if a electron donating phosphine is attached to the metal then the CO frequency will decrease...and if the electron withdrawing phosphine is attched to the metal ..the M-CO bond becomes weak and hence CO bond tends to free CO stretching.

i have numbered them according to the series given

so

so the series of electron withdrawing chcracter of phosphine is given as

4> 1> 2> 3

hence there correspondioinig stretching frequency should be

4- 2004 cm-1

1 - 1984 cm-1

2- 1965cm-1

3 - 1915 cm-1

please leave a comment i was not clear!!!

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