Which of the following complexes exhibit the highest paragmagnetic behavior? a. [Co(ox)2(OH)2]^- b. [Ti(NH3)6]^3+ c. [V(gly)2(OH)2(NH3)2]^+ d. [Fe(en)(bpy)(NH3)2]^2+
1 Answer
I found
I would first reference your text to check the charge of the ligands, but you would have to memorize these in an exam. I have a naming guide here.
"ox"ox is oxalato, a-2−2 bidentate ligand."gly"gly is glycine, a neutral ligand at"pH"pH 77 . Since it has a carboxyl group, it is possible that it bindseta^2η2 . It is also possible that it binds bidentate at basic"pH"pH ."OH"OH is hydroxide, a-1−1 monodentate ligand."en"en and"bipy"bipy are both neutral bidentate ligands.
From that, we can then determine the oxidation states on each metal and thus their number of unpaired electrons.
["Co"("ox")_2("OH")_2]^(-)[Co(ox)2(OH)2]− has two-2−2 bidentate and two-1−1 monodentate ligands, giving a+3+3 oxidation state on cobalt, making it ad^6d6 metal in the octahedral ligand field.
Since
"ox"^(2-)ox2− and"OH"^(-)OH− are both fairly weak-field ligands (weaker sigma donors than water), this is likely a high spind^6d6 complex, with four unpaired electrons.
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["Ti"("NH"_3)_6]^(3+)[Ti(NH3)6]3+ has three neutral ammine ligands, each strong-field, making this a low-spin complex involving ad^1d1 metal. Only one unpaired electron. -
["V"("gly")_2("OH")_2("NH"_3)_2]^(+)[V(gly)2(OH)2(NH3)2]+ has two-1−1 hydroxo ligands, two neutral ammine ligands, and two neutral monodentateeta^2η2 glycine ligands (at"pH"pH 77 ), making this"V"^(+3)V+3 , ad^2d2 metal with two unpaired electrons in the octahedral ligand field splitting diagram.
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I did not need to think about strong- or weak-field for either of the previous two complexes. Why is that?
["Fe"("en")("bpy")("NH"_3)_2]^(2+)[Fe(en)(bpy)(NH3)2]2+ has two neutral bidentate ligands (ethylenediamine and 2,2'-bipyridine), and two neutral monodentate ammine ligands, making iron a+2+2 oxidation state. We therefore have ad^6d6 metal in an octahedral ligand field consisting of three species of strong-field ligands, giving a low-spind^6d6 configuration, having diamagnetism.