Terphenylthiolate-Ligated Lanthanide Terminal Methyl Complexes Form Crystallographically Characterizable Terminal Acyls and Trimethylcyclopropanetriolates from Carbon Monoxide

The sterically bulky terphenylthiolate ligand {S[C6H3-2,6-(C6H2-2,4,6-iPr3)2]}1-, (SAriPr6)1-, has permitted the isolation of the terminal methyl complexes Ln(SAriPr6)2CH3, 1-Ln, Ln = La and Nd, from salt metathesis between Ln(SAriPr6)2I and methyllithium. These complexes react with carbon monoxide to afford the first structurally authenticated examples of terminal acyl complexes of the rare-earth elements, Ln(SAriPr6)2(η2-OCCH3), 2-Ln. However, in the presence of lithium iodide, the reaction between Ln(SAriPr6)2CH3 and CO forms the unique trimethylcyclopropanetriolate trianion, [cyclo-(OCCH3)3]3-, in the complex [Ln(SAriPr6)(μ-I)(μ-OCCH3)]3, 3-Ln. This CO insertion product arises from the formation of six C-C bonds, demonstrating the power of the (SAriPr6)1- ligand to generate new organometallic rare-earth metal reaction chemistry with CO.