Limiting radius ratio

I recently came across this question while studying Solid State.  

The coordination no. of [Ni(CN)4]2- is 4 as **Ni** is bonded to 4 **CN**s and is planar in structure.Hence its Limiting Radius Ratio must be between 0.225 and 0.414 . But the answer given in the book is 0.414 to 0.732 (which is the limiting radius ratio for coordination no. 6) .  

How is this true?Some sites agree with my answer .  

Is the answer given in the book wrong or have I made any mistake in the reasoning?




Here, limiting radius ratio is for geometry of this complex is square planar because $\ce{CN-}$ is a strong field ligand and causes pairing of unpaired electrons. So we can relate that $\ce{Ni^2+}$ occupies a square planar void of the $\ce{CN-}$ lattice. The square planar void is a cross section of the octahedral void.


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