The synthesis of bona fide organometallic CeIV complexes is a daunting challenge as it is a combination of the typically oxidizing CeIV cation and reducing carbanions. Despite this obstacle, we report a pair of compounds comprising the first examples of a CeIV–Caryl bond from the reaction of an electron rich CeIV starting material and a bidentate aryl lithium. The products exhibit CeIV–Caryl bond lengths of 2.571(7) – 2.5806(19) Å and strongly-deshielded CeIV–Cipso 13C{1H} NMR resonances at 255.6 ppm. All other NMR signals are within the diamagnetic region. Computational analyses indicate that the Ce contribution to the CeIV–Caryl bond is ~12%, which is unexpectedly high for lanthanide-ligand bonds. Furthermore, computations reproduce the characteristic 13C position, where the strong influence from spin-orbit coupling (SOC) effects move the signal outside of the diamagnetic region. According to a natural localized molecular orbital analysis, the SOC deshielding is primarily influenced by the sizable covalency of the CeIV–Cipso bond. The results demonstrate that SOC-driven deshielding can be present in 4f CeIV–Cipso 13C resonances in addition to diamagnetic 5f actinide compounds.

Isolation and characterization of a covalent CeIV-Aryl complex with an anomalous 13C chemical shift

ACS Spring Meeting 2021

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