design,synthesis, and carbon- heteroatom coupling reactions of organometallic nickel(iv) complexes
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Design, synthesis, and carbon-heteroatom coupling reactions of organometallic nickel(IV) complexesNicole M. Camasso, and Melanie S. SanfordScienceVolume 347(6227):1218-1220March 13, 2015
Presented by- Anubhav RajpootArun KumarAshik BiswasInstructor-Dr. Swadhin MandalAssociate professor IISER Kolkata
Biologically importantNatures antioxidant ParamagneticCCM++
CC+MIntroduction to coupling reactionsCXM
CXM+++C-C Bonds between complex fragmentsCarbon-Heteroatom bondsBetween complex fragments
Biologically importantNatures antioxidantCoupling 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 stepTwo electron transfer processReductive Elimination:Final Product Regeneration of the catalystM(ii) M(0)
ObjectiveMetal atom having variable Ox. State ie. loose/gain electron relatively easilyCan accelerate many chemical reaction as catalystTune 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, 35943657)More sustainable and economicalFavourable 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
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 recrystallzationSolid state, Octahedral geometryHow to stabilise Ni(iv) complex
1.2 equiv NMe4OAc1.2 equiv NMe4X
X(78%)X=OPh,SPhComplicated mixtures of productsWhich Ni precursor to use forNucleophiles like OPh and SPh?Works only with Acetate!Precursor which gives neutral intermediateWhy?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.
Ni precursor with Tp ligand.(Tp=Trispyrazolylborate)
Application of Ni(IV) complex as catalyst
>Pharmaceuticals >Chemical industries. Dimethyl indole (is used as photorefractive material ) can be prepared by using nickel(IV) complex through alkyl azide formation
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, 898901(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, 35943657(6.)Wikipedia