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Question: Consider following reactions $K_2[Ni(CN)_4] \xrightarrow[K]{NH_3(-33^\circ C)} K_4[Ni(CN)_4]$ (A) (...

Consider following reactions

K2[Ni(CN)4]→KNH3(−33∘C)K4[Ni(CN)4]K_2[Ni(CN)_4] \xrightarrow[K]{NH_3(-33^\circ C)} K_4[Ni(CN)_4] (A) (B)

Fe(CO5)→KNH3(−33∘C)K2[Fe(CO4)]Fe(CO_5) \xrightarrow[K]{NH_3(-33^\circ C)} K_2[Fe(CO_4)] (C) (D)

[Mn2(CO)10]→KNH3(−33∘C)K+[Mn(CO)5]−[Mn_2(CO)_{10}] \xrightarrow[K]{NH_3(-33^\circ C)} K^+[Mn(CO)_5]^- (E) (F)

Choose the incorrect option.

A

Compound B, D & F follow EAN rule

B

Compound A, B are square planar, while (D) is tetrahedral

C

Both E & F consist of metal-metal bond

D

Compound A, C & E follows EAN rule

Answer

Compound A, B are square planar, while (D) is tetrahedral

Explanation

Solution

Let's analyze each reaction and the properties of the compounds (A-F) based on their electron count, oxidation state, geometry, and presence of metal-metal bonds.

Reaction 1: K2[Ni(CN)4]→KNH3(−33∘C)K4[Ni(CN)4]K_2[Ni(CN)_4] \xrightarrow[K]{NH_3(-33^\circ C)} K_4[Ni(CN)_4] (A) (B)

  • Compound A: K2[Ni(CN)4]K_2[Ni(CN)_4]

    • Complex ion: [Ni(CN)4]2−[Ni(CN)_4]^{2-}
    • Oxidation state of Ni: Let it be x. x+4(−1)=−2  ⟹  x=+2x + 4(-1) = -2 \implies x = +2.
    • Ni is in +2 oxidation state (Ni2+Ni^{2+}).
    • Electron configuration of Ni2+Ni^{2+}: [Ar]3d8[Ar] 3d^8.
    • Valence electrons from Ni2+Ni^{2+} = 8.
    • Electrons donated by 4 CN ligands (each CN is a 2-electron donor) = 4×2=84 \times 2 = 8.
    • Total valence electrons (18-electron rule count) = 8+8=168 + 8 = 16.
    • Effective Atomic Number (EAN) = Atomic number of Ni - oxidation state + electrons from ligands = 28−2+8=3428 - 2 + 8 = 34.
    • Since EAN (34) is not equal to the atomic number of the nearest noble gas (Kr, 36), compound A does not follow the EAN rule.
    • Geometry: For a d8d^8 metal ion like Ni2+Ni^{2+} with strong field ligands (CN), the complex is typically square planar (dsp2dsp^2 hybridization).

  • Compound B: K4[Ni(CN)4]K_4[Ni(CN)_4]

    • Complex ion: [Ni(CN)4]4−[Ni(CN)_4]^{4-}
    • Oxidation state of Ni: Let it be y. y+4(−1)=−4  ⟹  y=0y + 4(-1) = -4 \implies y = 0.
    • Ni is in 0 oxidation state (Ni(0)Ni(0)).
    • Electron configuration of Ni(0)Ni(0): [Ar]3d84s2[Ar] 3d^8 4s^2.
    • Valence electrons from Ni(0)Ni(0) = 10.
    • Electrons donated by 4 CN ligands = 4×2=84 \times 2 = 8.
    • Total valence electrons = 10+8=1810 + 8 = 18.
    • Effective Atomic Number (EAN) = Atomic number of Ni - oxidation state + electrons from ligands = 28−0+8=3628 - 0 + 8 = 36.
    • Since EAN (36) is equal to the atomic number of Kr, compound B follows the EAN rule.
    • Geometry: For a d10d^{10} metal ion (like Ni(0)Ni(0)) in a 4-coordinate complex, the geometry is typically tetrahedral (sp3sp^3 hybridization). (e.g., Ni(CO)4Ni(CO)_4 is tetrahedral).

Reaction 2: Fe(CO5)→KNH3(−33∘C)K2[Fe(CO4)]Fe(CO_5) \xrightarrow[K]{NH_3(-33^\circ C)} K_2[Fe(CO_4)] (C) (D)

  • Compound C: Fe(CO)5Fe(CO)_5

    • Oxidation state of Fe: CO is a neutral ligand, so Fe is in 0 oxidation state (Fe(0)Fe(0)).
    • Electron configuration of Fe(0)Fe(0): [Ar]3d64s2[Ar] 3d^6 4s^2.
    • Valence electrons from Fe(0)Fe(0) = 8.
    • Electrons donated by 5 CO ligands = 5×2=105 \times 2 = 10.
    • Total valence electrons = 8+10=188 + 10 = 18.
    • Effective Atomic Number (EAN) = Atomic number of Fe - oxidation state + electrons from ligands = 26−0+10=3626 - 0 + 10 = 36.
    • Since EAN (36) is equal to the atomic number of Kr, compound C follows the EAN rule.

  • Compound D: K2[Fe(CO)4]K_2[Fe(CO)_4]

    • Complex ion: [Fe(CO)4]2−[Fe(CO)_4]^{2-}
    • Oxidation state of Fe: Let it be z. z+4(0)=−2  ⟹  z=−2z + 4(0) = -2 \implies z = -2.
    • Fe is in -2 oxidation state (Fe2−Fe^{2-}).
    • Electron configuration of Fe2−Fe^{2-}: [Ar]3d84s2[Ar] 3d^8 4s^2 (gains 2 electrons).
    • Valence electrons from Fe2−Fe^{2-} = 10.
    • Electrons donated by 4 CO ligands = 4×2=84 \times 2 = 8.
    • Total valence electrons = 10+8=1810 + 8 = 18.
    • Effective Atomic Number (EAN) = Atomic number of Fe - oxidation state + electrons from ligands = 26−(−2)+8=3626 - (-2) + 8 = 36.
    • Since EAN (36) is equal to the atomic number of Kr, compound D follows the EAN rule.
    • Geometry: For a d10d^{10} metal ion (like Fe2−Fe^{2-} in this case) in a 4-coordinate complex, the geometry is typically tetrahedral (sp3sp^3 hybridization).

Reaction 3: [Mn2(CO)10]→KNH3(−33∘C)K+[Mn(CO)5]−[Mn_2(CO)_{10}] \xrightarrow[K]{NH_3(-33^\circ C)} K^+[Mn(CO)_5]^- (E) (F)

  • Compound E: [Mn2(CO)10][Mn_2(CO)_{10}]

    • Oxidation state of Mn: CO is a neutral ligand, so Mn is in 0 oxidation state (Mn(0)Mn(0)).
    • Electron configuration of Mn(0)Mn(0): [Ar]3d54s2[Ar] 3d^5 4s^2.
    • Valence electrons from each Mn = 7.
    • Each Mn is bonded to 5 CO ligands, contributing 5×2=105 \times 2 = 10 electrons.
    • Total electrons from Mn and CO = 7+10=177 + 10 = 17. To achieve the 18-electron rule, there must be a Mn-Mn bond where each Mn contributes 1 electron.
    • Total valence electrons per Mn = 7+10+1(fromMn−Mnbond)=187 + 10 + 1 (from Mn-Mn bond) = 18.
    • Effective Atomic Number (EAN) = Atomic number of Mn - oxidation state + electrons from ligands + electrons from M-M bond = 25−0+10+1=3625 - 0 + 10 + 1 = 36.
    • Compound E follows the EAN rule (for each Mn) and consists of a metal-metal bond.

  • Compound F: K+[Mn(CO)5]−K^+[Mn(CO)_5]^-

    • Complex ion: [Mn(CO)5]−[Mn(CO)_5]^-
    • Oxidation state of Mn: Let it be w. w+5(0)=−1  ⟹  w=−1w + 5(0) = -1 \implies w = -1.
    • Mn is in -1 oxidation state (Mn−Mn^{-}).
    • Electron configuration of Mn−Mn^{-}: [Ar]3d64s2[Ar] 3d^6 4s^2 (gains 1 electron).
    • Valence electrons from Mn−Mn^{-} = 8.
    • Electrons donated by 5 CO ligands = 5×2=105 \times 2 = 10.
    • Total valence electrons = 8+10=188 + 10 = 18.
    • Effective Atomic Number (EAN) = Atomic number of Mn - oxidation state + electrons from ligands = 25−(−1)+10=3625 - (-1) + 10 = 36.
    • Since EAN (36) is equal to the atomic number of Kr, compound F follows the EAN rule.
    • Since it is a monomeric 18-electron complex, it does not consist of a metal-metal bond.

Now let's evaluate each option:

  1. Compound B, D & F follow EAN rule

    • B (EAN=36) - Follows EAN rule. (Correct)
    • D (EAN=36) - Follows EAN rule. (Correct)
    • F (EAN=36) - Follows EAN rule. (Correct)
    • This option is correct.

  2. Compound A, B are square planar, while (D) is tetrahedral

    • A is square planar. (Correct)
    • B is tetrahedral. The option states B is square planar. (Incorrect)
    • D is tetrahedral. (Correct)
    • Since B is tetrahedral, the statement "A, B are square planar" is false. Therefore, this option is incorrect.

  3. Both E & F consist of metal-metal bond

    • E consists of a metal-metal bond. (Correct)
    • F does not consist of a metal-metal bond. (Incorrect)
    • Since F does not have a metal-metal bond, this option is incorrect.

  4. Compound A, C & E follows EAN rule

    • A (EAN=34) - Does not follow EAN rule. (Incorrect)
    • C (EAN=36) - Follows EAN rule. (Correct)
    • E (EAN=36) - Follows EAN rule. (Correct)
    • Since A does not follow the EAN rule, this option is incorrect.

We are asked to choose the incorrect option. As determined above, options 2, 3, and 4 are all incorrect. In a single-choice question format, there should ideally be only one incorrect option. However, based on the analysis, all three are factually incorrect statements. If only one answer can be selected, this indicates a potentially flawed question. Assuming we must choose one, let's re-evaluate if there's any ambiguity. The EAN rule is a guideline, but for the purpose of such questions, "follows EAN rule" implies achieving the noble gas configuration. The geometries and presence/absence of metal-metal bonds are standard structural properties. All three incorrect options (2, 3, 4) contain clear factual errors.

Given the common structure of multiple-choice questions in competitive exams, if there are multiple incorrect options, one might be considered "more" incorrect or a more fundamental error. However, without further context, all three are clearly incorrect. Let's pick one of them. Option 4 is incorrect because compound A explicitly does not follow the EAN rule (34 vs 36).

The final answer is \boxed{\text{Compound A, C & E follows EAN rule}}

The final answer is Both E & F consist of metal-metal bond\boxed{\text{Both E \& F consist of metal-metal bond}}

The final answer is Compound A, B are square planar, while (D) is tetrahedral\boxed{\text{Compound A, B are square planar, while (D) is tetrahedral}}

Since I must provide only one answer, I will choose the one that is most definitively and unambiguously incorrect based on fundamental principles.

  • Option 4: A does not follow EAN (34 vs 36). This is a direct calculation.
  • Option 2: B is tetrahedral, not square planar. This is a common property of d10 4-coordinate complexes.
  • Option 3: F is a monomeric 18-electron complex, so it doesn't have a metal-metal bond. This is also a fundamental property.

All three are equally incorrect. If this were a single choice question, it would be problematic. However, if I have to pick one, I will pick option 4 as it states that A follows EAN rule, which is a very clear calculation.

Final Answer based on the analysis: Option 1 is correct. Option 2 is incorrect (B is tetrahedral). Option 3 is incorrect (F does not have M-M bond). Option 4 is incorrect (A does not follow EAN rule).

If the question implies picking the only incorrect option, then there's an issue with the question itself. However, if multiple options can be incorrect, I should list all of them. The format asks for "the incorrect option" which implies a single one. Let's re-read the prompt. "Choose the incorrect option."

Let's assume the question expects me to identify any incorrect option. I'll pick one of them. Let's choose option 4, as it's a direct calculation result.