Cp 2 Ti(κ 2 - t BuNCN t Bu): A Complex with an Unusual κ 2 Coordination Mode of a Heterocumulene Featuring a Free Carbene

• Published in: Journal of the American Chemical Society Vol. 142; no. 17; pp. 8006 - 8018
• Main Authors: Beaumier, Evan P, Gordon, Christopher P, Harkins, Robin P, McGreal, Meghan E, Wen, Xuelan, Copéret, Christophe, Goodpaster, Jason D, Tonks, Ian A
• Format: Journal Article
• Language: English
• Published: United States 29.04.2020
• Subjects: Humans; Methane - analogs & derivatives; Methane - chemistry; Molecular Structure; Organometallic Compounds - chemistry; Titanium - chemistry
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.0c02487

Although there are myriad binding modes of heterocumulenes to metal centers, the monometallic κ -ECE (E = O, S, NR) coordination mode has not been reported. Herein, the synthesis, isolation, and physical characterization of Cp Ti(κ - BuNCN Bu) ( ) (Cp = cyclopentadienyl, Bu = -butyl), a strained 4-membered metallacycle bearing a free carbene, is described. Computational (DFT, CASSCF, QT-AIM, ELF) and solid-state CP-MAS C NMR spectroscopic analysis indicate that is best described as a free carbene with partial Ti-C bonding that results from Ti-N π-bonding mixing with N-C-N σ-bonding of the bent N-C-N framework. Reactivity studies of corroborate its carbene-like nature: protonation with [LutH]I results in the formation of a Ti-formamidinate ( ), while oxidation with S yields a Ti-thioureate ( ). Additionally, a related bridged dititanamidocarbene, (Cp Ti) (μ-η ,η -CyNCNCy) ( ) (Cy = cyclohexyl) is reported. Taken together, this work suggests that the 2-electron reduction of heterocumulene moieties can allow access to unusual free carbene coordination geometries given the proper stabilizing coordination environment from the reducing transition metal fragment.