The first time this lab was performed, the waste container developed a deep red color. While it is difficult to say with certainty what compound was the cause of this color (there were a lot of substances in that mixture!), one possibility is the [Ni(CN)5]–3 ion, which is in fact a deep red. Unusually for a transition meta
the spectrochemical series allows us to explain the variety of
colors observed in
the properties of compounds can occasionally be frustrated by various complicating factors.
For instance, the nitrite ligand is presented as having a high field strength, but that is only when
it is the nitrogen of the nitrite that is coordinating to the metal center. Nitrite is also capable of
binding to the metal center through an oxygen, and when this happens, nitrite is a low field
strength ligand. Furthermore, many metals initially precipitate as simple ionic salts before they
have a chance to form more soluble complex ions. And occasionally, unexpected redox
reactions can lead to complex mixtures.
Despite these complications, the spectrochemical series remains a powerful predictive
tool for inorganic chemists. New ligands are being developed all the time, and each new ligand
needs to be placed, at least approximately, on the spectrochemical series. In the second part of
this lab, determine, as much as possible, the position of a new ligand, dimethylglyoxime, relative to other ligands on the series.
It is possible to rank ligands more quantitatively by calculating the value of the d-orbital
splitting, Δ. If the absorbance for a complex across the range of UV-vis light is measured, the
wavelength of maximum absorbance can be determined and the energy associated with that
transition can be calculated.
Question 1: The first time this lab was performed, the waste container developed a deep red color. While it is difficult to say with certainty what compound was the cause of this color (there were a lot of substances in that mixture!), one possibility is the [Ni(CN)5]–3 ion, which is in fact a deep red. Unusually for a transition metal complex, it has trigonal bipyramidal geometry. If we assume that two of the ligands approach along the z axis, and the other three are symmetrically distributed around the atom in the xy plane, use the pictures of the five d orbitals in the notes (or the Transition Metal Practice worksheet) to predict the splitting pattern for this complex. Based on this prediction, as well as the number of d electrons present and the position of the ligand on the spectrochemical series, how many unpaired electrons do you predict this complex to have? Explain your answers.
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