Modulation Of Multi-active Sites In Atomic Pt Catalysts For C-N Formation

C-N formation is of great significance to synthetic chemistry,as the N-containing products are widely used in chemical,medication,and biology.Addition of an amine to unsaturated carbon-carbon bond is a simple yet effective route to produce new C-N bonds.But how to effectively conduct an anti-Markovnikov addition in high selectivity has been of great challenge.Here this work reports a highly active and selective heterogeneous anti-Markovnikov hydroamination with supported atomically-dispersed Pt as catalyst.The main innovative research findings and conclusions are as follows:1.It is still a great challenge to fabrite atomically-dispersed Pt in a simple and effective method.It is proposed that Pt can be induced by surface of LDHs,and thus the atomically-dispersed Pt can be obtained by a simple impregnation method.The atomically-dispersed Pt supported on Zn(Al)O has been prepared by the lattice inducement of LDHs.The atomically-dispersed Pt supported on Zn(Sn)(Al)O has been prepared by the inducement of Sn sites which are confined in the lattice of LDHs.The atomic Pt on Zn(Al)O exists as Pt10 and Pt1?+,and the ratio of Pt10 centers increases with the increase of atomic Pt loading.The atomic Pt on Zn(Sn)(Al)O exists as Pt10,due to the strong interaction of Pt-Sn.2.In order to improve the anti-markov selectivity of hydroamination of olefins,atomic Pt supported on Zn(Al)O was applied to catalyze the hydroamination of olefin and amine,and high anti-markov selectivity and high activity were obtained(an anti-Markovnikov selectivity of 92%and a TON of 331).The reaction mechanism has been studied by EPR spectra and in situ FT-IR spectra of adsorption/desorption of styrene and/or pyrrolidine.It has been demonstrated that Pt10 activates amine to be electrophilic while Pt1?+activates C=C by ?-bonding to make ?-C nucleophilic.The attack of nucleophilic ?-C to electrophilic amine affords the anti-Markovnikov addition.3.To further improve the activity of anti-Markovnikov C-N formation of olefins and amines,the atomic Pt supported by Zn(Sn)(Al)O was applied to catalyze hydroamination of olefin and amine.By modulation the ratio of atomic Pt0 to coordination-unsaturated Sn?,a cooperating catalysis between atomic Pt0 and coordination unsaturated Sn? in anti-Markovnikov hydroamination reaction has been revealed.Atomic Pt0 activates amine to be electrophilic while coordination-unsatUrated Sn? serves as an active site favoring the ?-binding of C=C to make ?-C nucleophilic.The attack of nucleophilic ?-C to electrophilic amine affords a selectivity of 99%to anti-Markovnikov product in the addition of styrene and pyrrolidine.4.The atomic Pt catalyst was used repeatedly for 10 times in the hydroamination reaction,and its activity and anti-Markovnikov selectivity remained unchanged.HADDF-STEM images and in situ FT-IR spectra of CO adsorption were carried out on the used catalyst,and it was found that the Pt sites remained atomically dispersed in the reaction process.This strategy was successfully applied to the anti-Markovnikov hydroamination of aromatic olefin with aromatic amine or aliphatic amine,aromatic amine with aliphatic olefin,and linear aliphatic olefin with secondary amine.