Which of the following complex compounds will exhibit highest paramagnetic behaviour ?
(At.No. : Ti=22,Cr=24,Co=27,Zn=30)
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AIPMT-2011 Main
A
[Co(NH3)6]3+
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B
[Cr(NH3)6]3+
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C
[Zn(NH3)6]3+
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D
[Ti(NH3)6]3+
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Solution
The correct option is B[Cr(NH3)6]3+ (1) [Ti(NH3)6]3+:3d1 Configuration and thus has one unpaired electron.
(2) [Cr(NH3)6]3+ : The complex is inner orbital complex but 3d3 configuration has three unpaired electrons with weak as well as with strong field ligand.
(3) [Co(NH3)6]3+ : The cobalt ion in +3 oxidation state with 3d6 configuration represented as shown below.
It has no unpaired electron.
(4) [Zn(NH3)6]3+ : Because of 3d10 configuration no (n-1)d orbital is available for d2sp3 hybridisation and thus forms outer orbital complex. The complex is diamagnetic.
Thus, complex in option (b) has more unpaired electron so it has highest magnetic moment.