N-Bridged Pincer Iridium Complexes for Highly Efficient Alkane Dehydrogenation and the Relevant Linker Effects

Zhang, Xin1; Wu, Song-Bai4; Leng, Xuebing1; Chung, Lung Wa4; Liu, Guixia1,2; Huang, Zheng1,2,3

2020-06-05

10.1021/acscatal.0c00539

ACS Catalysis   影响因子和分区

2155-5435

A series of iridium complexes ((POCR)-P-R'NP)-HCl (4-HCl) and ((PSCR)-P-R'NP)Ir-HCl (5-HCl) (R = substituent on P; R' = substituent on N) supported by N-linked pincer ligands, with the other linker being O- or S-atom, have been synthesized. Among them, complexes with phosphino-iPr substituents ((POCR)-P-iPr'NP)Ir (4b, 4e, and 4g) exhibit very high catalytic activity for transfer dehydrogenation (TD) of both cyclic and linear alkanes. In the prototypical TD reaction of cyclooctane (COA) with tertbutylethylene (TBE), for example, 4g affords 14 720 turnovers at 200 degrees C, which are more than twofold of that obtained by the most efficient catalyst reported so far. Moreover, these complexes are highly effective for acceptorless dehydrogenation of 1,2,3,4-tetrahydronaphthalene, giving a turnover frequency of 8.8 min(-1) for H2- production within the first 4 h. The effects of the linkers at the positions ortho to the Ir center have been elucidated by a systematic comparison of electronic and steric properties of these O/ N- and S/N-linked pincer systems to those of C/C-linked (PCP)-P-iPr, O/O-linked (POCOP)-P-iPr, and S/O-linked (PSCOP)-P-iPr systems. Examination of the structure-activity relationships reveals that alkane C-H bond addition to the 14e (pincer)Ir fragment (the ratedetermining step in the TD reaction) is more favored by (POCR)-P-iPr'NP relative to other pincers, largely due to the strong N-linker -> C(aryl) pi-donation. Compared to the parent (POCOP)-P-iPr complex with similarly pi-donating O-linkers, the energy of the alkene-bound out-of-cycle resting state is raised by (POCR)-P-iPr'NP primarily due to steric factors. Consequently, the incorporation of the N-linker exerts an overall favorable effect on the catalytic rates. In addition, we found that the thermal stability of these catalysts with different linker combinations differs significantly.

alkane olefin dehydrogenation pincer ligand iridium homogeneous catalysis

SCI ; EI

英语

其他

National Basic Research Program of China[2016YFA0202900] ; National Natural Science Foundation of China[21825109][21821002][21572255][21732006] ; Chinese Academy of Sciences Key Research Program of Frontier Sciences[QYZDB-SSW-SLH016] ; Science and Technology Commission of Shanghai Municipality[17JC1401200]

Chemistry

Chemistry, Physical

WOS:000538766900053

AMER CHEMICAL SOC

20202808928076

Catalyst activity ; Synthesis (chemical) ; Catalysis ; Hydrogen production ; Olefins ; Ligands ; Iridium compounds ; Paraffins ; Thermodynamic stability

Gas Fuels:522 ; Thermodynamics:641.1 ; Physical Chemistry:801.4 ; Chemical Reactions:802.2 ; Chemical Agents and Basic Industrial Chemicals:803 ; Chemical Products Generally:804 ; Organic Compounds:804.1

Web of Science

1.Chinese Acad Sci, Univ Chinese Acad Sci, Shanghai Inst Organ Chem, State Key Lab Organometall Chem, Shanghai 200032, Peoples R China
2.East China Normal Univ, Chang Kung Chuang Inst, Shanghai 200062, Peoples R China
3.Univ Chinese Acad Sci, Sch Chem & Mat Sci, Hangzhou Inst Adv Study, Hangzhou 310024, Peoples R China
4.Southern Univ Sci & Technol, Shenzhen Grubbs Inst, Dept Chem, Shenzhen 518055, Peoples R China

Zhang, Xin,Wu, Song-Bai,Leng, Xuebing,et al. N-Bridged Pincer Iridium Complexes for Highly Efficient Alkane Dehydrogenation and the Relevant Linker Effects[J]. ACS Catalysis,2020,10(11):6475-6487.

Zhang, Xin,Wu, Song-Bai,Leng, Xuebing,Chung, Lung Wa,Liu, Guixia,&Huang, Zheng.(2020).N-Bridged Pincer Iridium Complexes for Highly Efficient Alkane Dehydrogenation and the Relevant Linker Effects.ACS Catalysis,10(11),6475-6487.

Zhang, Xin,et al."N-Bridged Pincer Iridium Complexes for Highly Efficient Alkane Dehydrogenation and the Relevant Linker Effects".ACS Catalysis 10.11(2020):6475-6487.