Synthesis, Characterization, and Electrochemistry of the Homoleptic f Element Ketimide Complexes [Li]₂[M(N═C^tBuPh)₆] (M = Ce, Th)

Abstract

Reaction of [Ce(NO3)3(THF)4] with 6 equiv of Li(N=C t BuPh), followed by addition of 0.5 equiv of I2, affords the homoleptic Ce(IV) ketimide, [Li]2[Ce(N=C t BuPh)6] (1), which can be isolated in 44% yield after work-up. Similarly, reaction of [ThCl4(DME)2] with 6 equiv of Li(N=C t BuPh) in THF affords the isostructural Th(IV) ketimide, [Li]2[Th(N=C t BuPh)6] (2), which can be isolated in 53% yield after work-up. Both 1 and 2 were fully characterized, including analysis by X-ray crystallography, allowing for a detailed structural and spectroscopic comparison. The electronic structures of 1 and 2 were also explored with density functional theory (DFT) and multi-configurational wavefunction calculations. Additionally, the redox chemistry of 1 was probed by cyclic voltammetry, which revealed a highly cathodic Ce(IV)/Ce(III) reduction potential, providing evidence for the ability of the ketimide ligand to stabilize high oxidation states of the lanthanides.This material is available free of charge via the Internet at http://pubs.acs.org.

Comparison of tetravalent cerium and terbium ions in a conserved, homoleptic imidophosphorane ligand field

“… 31 This experiment not only lends confirmation to the previous theoretical and reactivity studies that demonstrate that a homoleptic imidophosphorane ligand sphere can push the Ce 3+/4+ redox couple to negative values, these studies also confirm the most negative shift in redox potential from that of the free Ce ion observed electrochemically in any cerium coordination complex. 38 – 40 The quasi-reversible oxidation event occurs at –1.44 V for 1-Ce(PN*) and at –1.63 V for 2-Ce(PN*) vs. Fc/Fc + at 200 mV s –1 . This difference could be the result of a cation binding effect due to presence of a potassium ion in 1-Ce(PN*) but not in 2-Ce(PN*) .…”

Cerium(iv) complexes with guanidinate ligands: intense colors and anomalous electronic structures

“…Moreover, the PBE calculations reproduce the trend in the spectroscopic n f values ( Figure S73). Since the 4f population increased to a lesser extent compared to the decrease of 5d population, there is an overall decrease of the ligand-to-metal electron donation and increase of the Ce charge from 1-Cl 75 were obtained from the NBO analyses.…”

“…To further understand the differences in 4f and 5d population and metal–ligand covalency in the Ce( iv ) guanidinate complexes, 2-Cl , [3+] , and [4+] , natural localized molecular orbitals (NLMOs) 75 were obtained from the NBO analyses. Fig.…”

Synthesis and Characterization of a Linear, Two-Coordinate Pt(II) Ketimide Complex

“…[24][25][26][27][28][29][30] Homoleptic ketimide complexes are also known for copper, boron, aluminum, uranium, and cerium. [31][32][33][34][35] In this context, the absence of a homoleptic group 10 ketimide is notable, especially given the foundational role that these elements have played in the development of organometallic chemistry. 36 To rectify this oversight, we explored the reactivity of a series of Pt(II) salts with Li(N=C t Bu2).…”