Catalytic Properties Of Nickel Chelate On Hydrosilication Of Unsaturated Compounds

Catalytic reactions occupy an important position in the synthesis of novel organic compounds,and the use of catalysts can increase the rate of reactions and reduce the occurrence of side reactions.The design of novel catalysts includes many aspects,one of which is very critical to design suitable ligands that is used to modulate the electronic properties of the central metal atom as well as the spatial environment.Commonly used ligands include conventional phosphine ligands,stable N-heterocyclic carbinol ligands,and promising S-containing ligands.Researchers are innovative and imaginative in designing ligands,as evidenced by many examples,such as derivatives from the tartaric acid backbone,ferrocene homologs,heteropolynaphthol frameworks and their variants,phosphazenes,and oxazolidines.These ligands can be represented precisely because of their unique and outstanding properties and wide applicability.Ligands can be broadly classified into mono dentate and multi dentate ligands based on the number of coordination sites bound to the central atom,with multi dentate ligands attracting the attention of many chemists because of their unique stability and versatility.Among the transition metal complexes that has/had been used in industry,the ligands are mainly multi-dentate ligands with precious metals such as Rh,Pt,Ir,and Pd as the central metal atoms.Precious metals have the disadvantages of high price,high toxicity and low abundance,which have led chemists to actively explore cheap transition metal complexes that can replace precious metals.The instability of unsaturated bonds makes unsaturated compounds have a variety of reaction possibilities,which has caused more and more chemists to use unsaturated compounds as raw materials to synthesize new compounds,and the alkylation of unsaturated compounds has been an important way to obtain silicone materials,such as aldehydes and ketones alkylation,olefins alkylation,and allies alkylation.At present,these reactions are still dominated by noble metal catalysts,therefore,in recent years,chemists have been working on cheap transition metals to replace noble metals for silica hydrogenation reactions,which are mainly based on iron,cobalt and nickel.The catalytic potential for metallic nickel complexes is very high for nickel as a cognate element of platinum.The abundance of nickel as well as its low cost is important reasons why it is worth studying,and especially in recent years,nickel catalysis has been gradually developed.In this paper,polydentate nickel complexes were constructed by constructing polydentate ligands with different parts,and their catalytic properties on the hydrosilication of unsaturated compounds were investigated in detail.It is divided into the following two parts:1.Eight[CNN]-pincer asymmetric ligands were prepared by reacting with Ni(DME)Cl2 based on the eight[CNN]-clamped asymmetric ligands that have been synthesized by the group.The catalytic activities of these nickel complexes were investigated for the silly hydrogenation of aldehydes and ketones as well as olefins,among which the catalytic activities for the silly hydrogenation of aldehydes and ketones were prominent.In olefin silly hydrogenation,different types of additives reacted with different silanes with different effects.It is worth mentioning that all the eight[CNN]pincer nickel-chloride complexes synthesized in this paper can be stabilized in the air.It was shown that the catalytic activity of the complex[MeCNN(CH)3-Ni-Cl]for the alkylation of aldehydes and ketones was good,and the catalytic reaction could be completely converted at room temperature when NaBHEt3 was used as an additive.By screening the pre-reaction time,it was found that the reaction time could be greatly shortened after 30 mins of pre-reaction with silane,and the aldehyde was completely reacted after 1.5 h.Especially for ketone catalysis,the time is only 2.5 h for complete conversion.And the catalytic system also has good substrate universality and good functional group tolerance.The study of the reaction mechanism shows that the nickel-chloride complex is firstly NaBHEt3 to nickel-hydrogen complex,and then the nickel-hydrogen complex will firstly react with PhSiH3 to release H2 to form nickel-silyl complex,then react with aldehydes and ketones to form intermediates,and finally react with PhSiH3 to obtain silly ethers.In the subsequent exploration of olefin silly hydrogenation,it was found that[nBuCNN(CH3)2-Ni-Cl]has good catalytic activity and the catalyst loading can be reduced to 0.01 mol%.2.The reaction of the[P,S]bidentate ligand with Ni(PMe3)4,which has been synthesized by our group,was used to obtain nickel-hydrogen complexes,which later reacted stoichiometrically with linkenes containing different substituents and obtained the corresponding nickel complexes,expanding the variety of linkenes that should be developed with this nickel-hydrogen complex.These new nickel-linked alkene complexes have been fully characterized.We hope to explore the chemical properties of these nickel-linked alkene complexes.