PCP Pincer Iridium Chemistry – Coordination of Pyridines to [(tBuPCP)IrH(Cl)]. Issue 1 (23rd November 2015)

• Record Type: Journal Article
• Authors: Titova, Ekaterina M.; Silantyev, Gleb A.; Filippov, Oleg A.; Gulyaeva, Ekaterina S.; Gutsul, Evgenii I.; Dolgushin, Fedor M.; Belkova, Natalia V.
• Is Part Of: European journal of inorganic chemistry. Issue 1(2016)
• Page Start: 56
• Page End: 63
• Publication Date: 2015-11-23
• Subjects: Iridium -- Pincer complexes -- Dihydrogen bonding -- Hydride ligands -- N ligands -- Ligand effects; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201501083
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: The complexes of [( t Bu PCP)IrH(Cl)] {1, t Bu PCP = 1, 3‐bis[(di‐ tert ‐butylphosphanyl)methyl]benzene} with pyridine (py, 2 ), 4‐aminopyridine (4apy, 3 ) and 2‐aminopyridine (2apy, 4 ) have been synthesized and fully characterized by variable‐temperature spectroscopy (NMR, IR, and UV/Vis). In each case, the reaction yields a mixture of cis ‐ and trans ‐hydrido–chlorido isomers. The stereochemistry of the latter was confirmed by single‐crystal X‐ray analysis of2a and3a, which showed that the pyridine ligands coordinated opposite the aryl ring do not produce an additional twist of the pincer ligand but lead to the elongation of all bonds involving the iridium atom. The chlorido ligand becomes substantially labilized owing to the strong trans effect of the hydrido ligand, and that in3a it is prone to intermolecular N–H··· Cl hydrogen bonding in the solid state. In the 2‐aminopyridine complex4, the intramolecular hydrogen bond to the chlorido ligand (isomer4a′ ) is slightly more preferred over the N–H··· H bond (isomer4a ). The structures of the cis ‐hydrido–chlorido isomers2b –4b were established with the help of 15 N‐labeled pyridine. These isomers undergo fast ligand exchange on the NMR timescale that slows as the temperature decreases. The decoalescence temperature is the lowest for the 2‐aminopyridine derivative4b ; therefore, it is the least stable. The repulsion between the tert ‐butyl groups of the pincer ligand and the o ‐NH2 group is the main reason for the lower stability of4b . Abstract : The complexes of [(t Bu PCP)IrH(Cl)] with pyridine, 2‐aminopyridine, and 4‐aminopyridine are characterized by variable‐temperature spectroscopy. Each reaction yields a mixture of cis ‐ and trans isomers. The stereochemistry of the latter was confirmed by single‐crystal X‐ray analysis. The adducts with 2‐aminopyridine feature intramolecular hydrogen bonds with the chlorido or hydrido ligands.