Iridium PC(sp³)P Pincer Complexes with Hemilabile Pendant Arms: Synthesis, Characterization, and Catalytic Activity

Abstract

A series of new PC­(sp3)P pincer ligands possessing hemilabile alkoxyl side arms as well as their iridium complexes are reported. All new organometallic compounds were structurally characterized including X-ray analysis. The hemilability of the side arms was probed by reactions with CO, revealing the reversible coordination. The catalytic activity of the new complexes was tested by iridium-catalyzed transfer dehydrogenation of alkanes under mild conditions.

The underappreciated influence of ancillary halide on metal–ligand proton tautomerism

“…For the 6 complexes with H and CO trans to each other, d Ir-H (t) is reported between À5 and À10, and 2 J H-P between 14-18 Hz. [45][46][47][48][49][50][51] With d Ir-H (t) À17.22 and 2 J H-P ¼ 12 Hz for the neutral [H-L Ir-Cl], the data are most consistent with H and Cl trans to each other (as depicted in Scheme 1).…”

Regioselective Isomerization of Terminal Alkenes Catalyzed by a PC(sp3)Pincer Complex with a Hemilabile Pendant Arm

“…Catalysis . Initial alkene isomerization studies were conducted using five complexes reported by us in the past as catalysts for the transfer dehydrogenation of alkanes [17a,b] . Compounds 1 – 4 possess hemilabile coordinating alkoxyl groups: 1 – 3 are characterized by mer‐ configuration of the PC( sp 3 )ligand and a rigid coordination of the sidearm having a different steric bulk complex, whereas 4 is a more flexible analogue with fac ‐coordination of the ligand.…”

Poison or Promoter? Investigating the Dual-Role of Carbon Monoxide in Pincer-Iridium-Based Alkane Dehydrogenation Systems via Operando Diffuse Reflectance Infrared Fourier Transform Spectroscopy

“…One class of complexes that continues to receive attention both as very successful homogeneous as well as, increasingly, heterogenized catalysts, is that of pincer-metal, and particularly pincer-iridium, species of the form [M( R4 PCP)Ln] ( R4 PCP = κ 3 -C6H3-2,6-(CH2PR2)2). 24 The modularity of these species has made them especially amenable to catalyst development, 15,[25][26][27] with multiple derivatives having been synthesized based on the R4 PCP framework, 28 as well as other derivative frameworks including ( R4 anthraphos), 29 ( R4 POCOP), [30][31] ( R4 PCOP), 32 ( R4 PSCOP), 33 ( R4 PC(sp 3 )P), [34][35][36][37] ( R4 PNP), 38 (Phebox), [39][40] (Pybox), 41 and "pincercrown ether" ligands ( 15-crown-5 NCOP iPr2 ), 42 among many others.…”