ABC26IN0285 · Organometallic Compounds
Subject: Inorganic Chemistry · Chapter: Organometallic Compounds · Topic: Organometallic Compounds – General · Exam: CSIR-NET 2020 · Marks: 2 · Difficulty: Hard
The order of rate of substitution of chloride by pyridine (in ethanol) in the following complexes is 
I II III
I II III(a)I $>$ II $>$ III
(b)I $\approx$ III $\approx$ II
(c)I $>$ II $\approx$ III
(d)I $<$ II $\approx$ III
Answer
Answer (as printed): A
Explanation
Square planar complexes undergo associative pathway. So, ligand substitution process can be better understood in terms of crystal field activation energy (CFAE). Considering trigonal bipyramid or square pyramidal geometry in Transition state (T.S.), C.F.A.E. can be calculated. C.F.A.E. $(D_q)$ = C.F.S.E. $(D_q)$ of T.S. − C.F.S.E. $(D_q)$ of square planar complex. The $D_q$ value increases of the heavier congeners and it makes heavier congeners more inert. So rate of substitution will be $\mathrm{Ni^{II}} > \mathrm{Pd^{II}} > \mathrm{Pt^{II}}$