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Which of these statements about [ [ [ Co(CN) 6 ] 3 − _6]^{3-} 6 ] 3 − is true?
medium
Coordination Compounds
2015
chemistry
[Co(CN) 6 _6 6 ] 3 − ^{3-} 3 − has four unpaired electrons and will be in a low-spin configuration.
Explanation To solve this problem, we need to analyze the electronic configuration of the complex [ [ [ Co(CN) 6 ] 3 − . _6]^{3-}.
\newline 6 ] 3 − . 1. Determine the oxidation state of cobalt in [ [ [ Co(CN) 6 ] 3 − : _6]^{3-}:
\newline 6 ] 3 − :
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]
has four unpaired electrons and will be in a high-spin configuration.
[Co(CN) 6 _6 6 ] 3 − ^{3-} 3 − has no unpaired electrons and will be in a high-spin configuration.
[Co(CN) 6 _6 6 ] 3 − ^{3-} 3 − has no unpaired electrons and will be in a low-spin configuration.
• Let the oxidation state of Co be
• Each CN ligand carries a charge of
• The overall charge of the complex is
• Therefore, the equation is:
x + 6 ( − 1 ) = − 3. x + 6(-1) = -3.
\newline x + 6 ( − 1 ) = − 3. • Solving for
x : x − 6 = − 3 x = + 3 x:
\newline x - 6 = -3
\newline x = +3
\newline x : x − 6 = − 3 x = + 3 2. Electronic configuration of Co
• The atomic number of cobalt (Co) is 27.
• The electronic configuration of neutral Co is
Ar
] 3 d 7 4 s 2 . ] \, 3d^7 \, 4s^2.
\newline ] 3 d 7 4 s 2 . • For Co
3 + , r e m o v e t h r e e e l e c t r o n s : t w o f r o m 4 s a n d o n e f r o m 3 d . ^{3+}, remove three electrons: two from 4s and one from 3d.
\newline 3 + , re m o v e t h reee l ec t ro n s : tw o f ro m 4 s an d o n e f ro m 3 d . • The configuration becomes
Ar
] 3 d 6 . ] \, 3d^6.
\newline ] 3 d 6 . 3. Determine the spin state:
• CN
is a strong field ligand, which causes pairing of electrons.
• In a low-spin configuration, the 3d electrons will pair up.
• The 3d^6 configuration in a low-spin state results in all electrons being paired.
4. Analyze the options:
• Option 1: Four unpaired electrons and low-spin configuration. This is incorrect.
• Option 2: Four unpaired electrons and high-spin configuration. This is incorrect.
• Option 3: No unpaired electrons and high-spin configuration. This is incorrect.
• Option 4: No unpaired electrons and low-spin configuration. This is correct.
Therefore, the correct option is Option 4.