Question

Why the rate of substitution reactions on square planar d8 complexes goes in the order: Ni>Pd>>Pt ?

Answer 1

weakness of the M-X bond or metal-ligand bond for square planar species. (NOTE: a higher Zeff leads to stronger metal ligand bonds which in turn effects the rate).
Also, look at the atomic size difference (increase as you go down) from Ni to Pd, to Pt.

Answer 2

@abb0t if we focus on the leaving group, Ni is more electronegative than the others, so it will not release Cl minus easier than them. am I right?

Answer 3

Actually, Nickel is less electronegative than Pd or Pt.
Nickel as I see is about 1.9, Pd is 2.2 and Pt is 2.3

Answer 4

remember that electronegativity is due to the tendency of an atom or radical to attract electrons in the formation of an ionic bond. But like I said, it's larger as you move down so that electron attraction is less because the atomic size is much larger making the bonding weaker hence, the Ligand can leave faster cuz there is less attraction going on between electrons.

Answer 5

@ardalan - Be sure to hand out a medal in appreciation of the effort! Its good karma.

Answer 6

@abb0t I am not convinced about the EN that you have explained. sincerely in a group from top to bottom, EN decreases. so we have to be cautious about CFT and VBT.

Answer 7

Well, for your example, you haven't provided me with any ligands, which will affect it's crystal field splitting.

Answer 8

before that. Thanks for your delicate attention and your efforts. it worths more than a virtual medal.

I meant the substitution reaction mostly in organometallic chemistry.

Answer 9

dear @abb0t I searched for the answer and i barely found it. do you like to know it?

Answer 10

Sure. it might help others who may be seeking answers to a similiar type question :)
I'm a little rusty on my inorganic. Gotta review.

Answer 11

so we cannot trust to EN absolutely.

Answer 12

In a sense, you can't ONLY rely on EN because it is only one of many other factors that influence the rate of substitution of transition metals. Does that make sense?

Answer 13

yes you are right.
actually I understood that the tendency to have coordination number of 5 is the main factor that influences this reaction rate.

Answer 14

Yeah, look at the crystal field splitting for square planar geometry for a \(\large d^8\) species.