1370557-20-2Relevant academic research and scientific papers
Tuning the electronic properties of carbenes: A systematic comparison of neighboring amino versus amido groups
Blake, Garrett A.,Moerdyk, Jonathan P.,Bielawski, Christopher W.
scheme or table, p. 3373 - 3378 (2012/06/04)
A related series of six-membered carbenes featuring adjoining amino and/or amido groups (i.e, a diaminocarbene, a monoamido-aminocarbene (3), and a a diamidocarbene (6)) were systematically compared using crystallographic, spectroscopic, electrochemical, and density functional theory methods. The solid-state structure of 3 was found to exhibit inequivalent nitrogen-carbon bond lengths (Ccarbene-Namide = 1.395(4) A vs C carbene-Namine = 1.323(4) A). Moreover, the C carbene-Namide distance was longer than that measured in the solid-state structure of 6 (1.371(3) A), while the C carbene-Namine distance was similar to that measured in the solid-state structure of a cyclic alkyl-aminocarbene (1.315(3) A). Iridium complexes of the aforementioned carbenes were also evaluated, and the collected data revealed that the introduction of carbonyl groups to the carbene-containing scaffold had a nearly linear, additive effect on the E 1/2 potential of the carbene-ligated iridium I/II redox couple (+165 mV per carbonyl added) as well as the Tolman electronic parameter value of the corresponding carbene-Ir(CO)2Cl complex (ca. 7 cm-1 per carbonyl added). Beyond attenuated ligand donicity, the introduction of carbonyl groups was found to broaden the chemical reactivity: unlike prototypical N-heterocyclic carbenes, including diaminocarbenes, the monoamido-aminocarbene was found to couple to isonitriles to form the respective ketenimines.
