A Dicerium(IV) Nitride Complex with a Linear CeNCe Core Stabilized by Bulky Cyclohexyltriamide Ligands

Lanthanide nitrides remain rare, being restricted to the singular example with a CeN(Li 2 )Ce core stabilized by two Lewis acidic lithium ions. Here, we introduce a new cyclohexyltriamide ligand [Tach DMBS ] to lanthanide chemistry, which enables us to isolate a lanthanide nitride complex [{(Tach DMBS )Ce} 2 (μ–N)][Na(12–crown–4) 2 ] ( 6 ) with a linear CeNCe core without any alkali metal interaction. Complex 6 was prepared by the reaction of a rare dinuclear tuck-in–tuck-over cerium(IV) metallacycle [{(CH 2 CHNSiMe 2 t Bu) 2 (CHNSiMe t Bu(μ–CH 2 )Ce} 2 ] ( 4 ) with one equivalent of NaNH 2 in benzene in the presence of two equivalents of 12–crown–4, yielding 48%. The Ce–N(nitride) bond distances in 6 (2.051(19) Å) are close to the shortest Ce–N bonds reported so far, and a linear Ce–N–Ce bond angle in 6 (180.00°) is disclosed. The isostructural oxo analogue [{(Tach DMBS )Ce} 2 (μ–O)] ( 7 ) was prepared for comparison. Computational analysis of 6 and 7 reveals Ce═N multiple-bonding character consisting of two 2c–2e σ-bonds and two orthogonal 3c–2e π-bonds in 6, showing a similar bonding trend to that in the known CeN(Li 2 )Ce linkage, but single bonds for Ce–O in 7, confirming the stronger donating capability of N 3– vs O 2– in the bridging mode and highlighting the importance of supporting ligands in stabilizing the unsupported CeNCe core.