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Which of the following statements about coordination compounds are CORRECT? (Select all that apply.) (A) Both [PtCl2(NH3)2] and [Cu(NH3)4]²+ adopt a square planar geometry. (B) The complex [Fe(C2O4)3]³- does not show geometrical isomerism but does exhibit optical isomerism. (C) The C-O bond order decreases in the order [Ni(CO)4] > [Co(CO)4]⁻ > [Fe(CO)4]²-. (D) [NiCl2(PPh3)2] can exist as two geometrical isomers.

1. A and B only
2. B and D only
3. A, B, and D only
4. B, C, and D only

Correct answer: B and D only

Solution

[Cu(NH3)4]²+ is actually square planar (Jahn-Teller distorted d⁹), so A is correct. [Fe(C2O4)3]³- is a tris-bidentate octahedral complex with no geometric isomers but has optical isomers (D and L). C is incorrect because higher negative charge -> more back-bonding -> lower C-O bond order, so the correct trend is Ni(CO)4 > Co(CO)4⁻ > Fe(CO)4²- in C-O bond order, making C actually CORRECT as stated. D is correct as [NiCl2(PPh3)2] can be cis or trans.

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