Ring-expanded iridium and rhodium N-heterocyclic carbene complexes: a comparative DFT study of heterocycle ring size and metal center diversity

KARACA E. Ö., Akkoc M., Oz E., Altin S., Dorcet V., Roisnel T., ...More

JOURNAL OF COORDINATION CHEMISTRY, vol.70, no.7, pp.1270-1284, 2017 (SCI-Expanded, Scopus)

  • Publication Type: Article / Article
  • Volume: 70 Issue: 7
  • Publication Date: 2017
  • Doi Number: 10.1080/00958972.2017.1287906
  • Journal Name: JOURNAL OF COORDINATION CHEMISTRY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1270-1284
  • Keywords: Iridium, rhodium, N-Heterocyclic carbene, DFT calculation, X-ray, CROSS-COUPLING REACTIONS, SUZUKI-MIYAURA, PALLADIUM COMPLEXES, ROOM-TEMPERATURE, IR(I) COMPLEXES, LIGANDS, REACTIVITY, CATALYSIS, CHLORIDES, BEARING
  • Inonu University Affiliated: Yes

Abstract

A new series of ring-expanded six-and seven-membered N-heterocyclic carbene precursors (re-NHCs) and their transition metal complexes were synthesized. The basic properties of the synthesized materials were investigated by density functional theory (DFT). The six- and seven-membered re-NHCs were synthesized in good yield via reaction of the corresponding alkyldibromides or alkyldiiodides with N,N'-bis-(2-phenylbenzene)formamidine in the presence of K2CO3 under aerobic conditions. Complexes, represented by the formula [ML1,2(COD)Cl] (where M = Ir or Rh and L is a ring-expanded N-heterocyclic carbene ligand), were synthesized in the presence of the corresponding free carbene and iridium or rhodium metal precursors in tetrahydrofuran. All new re-NHC complexes were characterized by different analytical techniques, including NMR spectroscopy, X-ray diffraction, UV spectroscopy and elemental analysis. According to molecular electrostatic potential calculations, the electrophilic properties of the complexes were aligned, from highest to lowest, as Ir-6-DiPh, Rh-6-DiPh and Ir-7-DiPh. The HOMO, LUMO and energy gaps of the complexes were calculated by DFT. On the basis of the DFT analysis, it can be predicted that Rh-6-DiPh is the most stable complex and Ir-7-DiPh is more reactive than Ir-6-DiPh.