Isolation and characterization of a covalent CeIV-Aryl complex with an anomalous 13C chemical shift
Grace B. Panetti, Dumitru‐Claudiu Sergentu, Michael R. Gau, Patrick J. Carroll, Jochen Autschbach, Patrick J. Walsh, Eric J. Schelter
Abstract
Abstract The synthesis of bona fide organometallic Ce IV complexes is a formidable challenge given the typically oxidizing properties of the Ce IV cation and reducing tendencies of carbanions. Herein, we report a pair of compounds comprising a Ce IV − C aryl bond [Li(THF) 4 ][Ce IV (κ 2 - ortho -oxa)(MBP) 2 ] ( 3-THF ) and [Li(DME) 3 ][Ce IV (κ 2 - ortho -oxa)(MBP) 2 ] ( 3-DME ), ortho -oxa = dihydro-dimethyl-2-[4-(trifluoromethyl)phenyl]-oxazolide, MBP 2– = 2,2′-methylenebis(6- tert -butyl-4-methylphenolate), which exhibit Ce IV − C aryl bond lengths of 2.571(7) – 2.5806(19) Å and strongly-deshielded, Ce IV − C ipso 13 C{ 1 H} NMR resonances at 255.6 ppm. Computational analyses reveal the Ce contribution to the Ce IV − C aryl bond of 3-THF is ~12%, indicating appreciable metal-ligand covalency. Computations also reproduce the characteristic 13 C{ 1 H} resonance, and show a strong influence from spin-orbit coupling (SOC) effects on the chemical shift. The results demonstrate that SOC-driven deshielding is present for Ce IV − C ipso 13 C{ 1 H} resonances and not just for diamagnetic actinide compounds.