Design, synthesis, and carbon-heteroatom coupling reactions of organometallic nickel(IV) complexes

Nicole M. Camasso, and Melanie S. SanfordScience

Volume 347(6227):1218-1220March 13, 2015

Presented by- Anubhav RajpootArun KumarAshik Biswas

Instructor-Dr. Swadhin MandalAssociate professor IISER Kolkata

Biologically important

Nature’s antioxidant

Paramagnetic

C C M+ +M

CC

C C + M

Introduction to coupling reactions

C X M

M

XCC X M++ +

C-C Bonds between complex fragments

Carbon-Heteroatom bondsBetween complex fragments

Biologically important

Nature’s antioxidant

Coupling Reaction: Traditional Catalytic Cycle

Oxidative Addition: M(0) M(ii) Addition of Organic halide

to the M

Transmetalation: Transfer of alkyl/aryl group from one metal to another High activation energy Rate determining step Two electron transfer

process

Reductive Elimination: Final Product Regeneration of the

catalyst M(ii) M(0)

Objective

Metal atom having variable Ox. State ie. loose/gain electron relatively easily

Can accelerate many chemical reaction as catalyst

Tune the coordination environment around metal

Can be used in coupling reactions.

Concept of Nickel(IV) Complexes

Pd & Ni share same group so, they should have similar analogy.

Can Ni(IV) be prepared & equally

useful?

Pd(IV) has mediated many important C-X coupling reactions.

Why Ni instead of Pd?

Fig:Price of the elements (in $/kg) Vs. their annual production (in kg/yr).(Chem. Rev. 2016, 116, 3594−3657)

More sustainable and economical

Favourable intrinsic properties

Lower atomic radius

More Number

of oxidation

states.Lesselectronegativity

Does Ni(IV) complex accessible?

Cyclic voltammogram of (bpy)Ni(II)(CH2CMe2-o-C6H4)

study of Ni(ii) complex:

two oxidative waves at –0.61 V and +0.27 V versus Fc/Fc+ (Fc, ferrocene).

NiIII/NiIV NiII/NiIII

Reaction Scheme

(3)

-[Ni]

-[Ni]

VERY TRANSIENT.NO NMR.

At RT or -400 C

Ni(IV) complex is stable due to presence of

strong EWG.

Which oxidant to use ?

Tridentate instead of bidentate ligand

-[NiII]

>Immediate colour chan from dark red to

yellow. >much stable than bidentate ligand Ni

complex.92% yield isolated by recrystallzation

Solid state, Octahedral geometry

How to stabilise Ni(iv) complex

1.2 equiv NMe4OAc

1.2 equiv NMe4 X

X

(78%)X=OPh,SPh

Complicated mixtures of products

Which Ni precursor to use forNucleophiles like OPh and SPh?

Works only with Acetate!

Precursor which gives neutral intermediate

Why?

Due to positive charge on Ni(IV) Intermediate!

Reactivity of NiIV complex

The Ni(IV) intermediate does not have any charge on it

Lesser side product.Good selectivity.

Ni precursor with Tp ligand.(Tp=Trispyrazolylborate)

Application of Ni(IV) complex as catalyst

-N2

Adventitious water-Ni(II)

>Pharmaceuticals

>Chemical industries.

Dimethyl indole (is used as photorefractive material ) can be prepared by using nickel(IV) complex through alkyl azide formation

Conclusion

A series of Organometallic Niiv complexes are designed, synthesized . Niiv complexes undergo highly selective carbon(sp3)-oxygen, carbon(sp3)-nitrogen, and carbon(sp3)-sulfur coupling reactions with exogenous nucleophiles. Observed reactivity has the potential for direct applications in the development of nickel-catalyzed carbon-heteroatom coupling reactions.

Reference……… (1.) Yoshinori Aihara and Naoto Chatani, J. Am. Chem. Soc. 2014, 136, 898−901

(2.) Sarah Z. Tasker1*, Eric A. Standley1* & Timothy F. Jamison1,N AT U R E, V O L 5 0 9 ,2 0 1 4

(3.) Xile Hu*, Chem. Sci., 2011, 2, 1867

(4.) RSC Catalysis Series No. 21,New Trends in Cross-Coupling: Theory and Applications

(5.)Shao M, Chang Q, Dodelet J, Chenitz R, Chem. Rev. 2016, 116, 3594−3657

(6.)Wikipedia