JEE Main · 2020mediumCORD-214

The isomer(s) of [Co(NH3)4Cl2] that has/have a Cl–Co–Cl angle of 90°, is/are:

Coordination Compounds · Class 12 · JEE Main Previous Year Question

Question

The isomer(s) of [Co(NH3)4Cl2][\mathrm{Co(NH_3)_4Cl_2}] that has/have a Cl–Co–Cl angle of 90°, is/are:

Options
  1. a

    meridional and trans

  2. b

    cis and trans

  3. c

    trans only

  4. d

    cis only

Correct Answerd

cis only

Detailed Solution

🧠 Cl–Co–Cl = 90° Means Cis

In octahedral [Co(NH3)4Cl2]+[\mathrm{Co(NH_3)_4 Cl_2}]^+:

  • cis: Cl atoms at adjacent positions → Cl–Co–Cl bond angle = 90°.
  • trans: Cl atoms at opposite positions → Cl–Co–Cl angle = 180°.

🗺️ Geometric Picture

In octahedral geometry:

  • Adjacent (cis) bonds make 90° angles.
  • Opposite (trans) bonds make 180° angles.

So a 90° Cl–Co–Cl angle is the signature of cis isomer.

Octahedral Bond Angles

| Position pair | Angle | |---|---| | Cis (adjacent) | 90° | | Trans (opposite) | 180° | | Diagonal (face) | 70.5° (mid of two 90° edges) |

⚠️ mer/fac Don't Apply to MA4B2MA_4 B_2

mer and fac are reserved for MA3B3MA_3 B_3 types. For MA4B2MA_4 B_2 ([Co(NH3)4Cl2]+[\mathrm{Co(NH_3)_4 Cl_2}]^+), only cis/trans terminology applies.

Answer: (4) cis only\boxed{\text{Answer: (4) cis only}}

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The isomer(s) of [Co(NH3)4Cl2] that has/have a Cl–Co–Cl angle of 90°, is/are: (JEE Main 2020) | Canvas Classes