Linkage isomers nitropentaamminecobalt(iii)chloride shows 2 bands at 1065 and 1470 nitritopentaamminecobalt(iii)chloride shows 2 bands at 1300 and 1430 on infrared spectrum. How do you account for these differences?

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Answer 1 · 2016-02-06T20:15:43

Nitro is coordinated by the #"N"#, while nitrito is coordinated through an #"O"#.

I think you may have reversed the IR assignments.

The structures of the two isomers are

The two #"N-O"# bonds in the nitro group are equivalent.

Their stretching vibrations are coupled to give #ν_"as" = "1430 cm"^(-1)# and #ν_(text(s)) = "1300 cm"^(-1)#.

The asymmetric stretch is very strong, and the symmetric stretch is weak.

The nitrito isomer has an #"N=O"# bond and an #"N-O"# bond.

Both peaks are very strong and well separated, with #ν_"(N=O)" = "1470 cm"^(-1)# and #ν_"(N-O)" = "1065 cm"^(-1)#