819050-89-0Relevant articles and documents
Characterization of a reactive Rh2 nitrenoid by crystalline matrix isolation
Das, Anuvab,Chen, Yu-Sheng,Reibenspies, Joseph H.,Powers, David C.
, p. 16232 - 16236 (2019)
The fleeting lifetimes of reactive intermediates in C-H functionalization chemistry often prevent their direct characterization. For example, the critical nitrenoid intermediates that mediate Rh2-catalyzed C-H amination have eluded characterization for more than 40 years. In the absence of structural characterization of these species, methodological development is often computationally guided. Here we report the first X-ray crystal structure of a reactive Rh2 nitrenoid, enabled by N2 elimination from an organic azide ligand within a single-crystal matrix. The resulting high-resolution structure displays metrical parameters consistent with a triplet nitrene complex of Rh2. The demonstration of facile access to reactive metal nitrenoids within a crystalline matrix provides a platform for structural characterization of the transient species at the heart of C-H functionalization.
PROCESSES FOR PREPARING COMPLEXES COMPRISING RHODIUM(II) AND CARBOXYLATE LIGANDS
-
, (2019/02/15)
There is provided herein a process for the preparation of a complex of formula (I): Rh(II)2 Xn, wherein X and n have meanings provided in the description, comprising the step of reacting: (a) a source of Rh(III); and (b) a source of
Dirhodium catalysts that bear redox noninnocent chelating dicarboxylate ligands and their performance in intra-and intermolecular C-H amination
Kornecki, Katherine P.,Berry, John F.
, p. 562 - 568 (2012/03/12)
We report two new analogues of the well-known C-H amination catalyst [Rh2(esp)2] (1) (esp = α,α,α′, α′-tetramethyl-1,3-benzenedipropanoate) that bear redox-active supporting ligands that are structurally similar to esp. The redox-active ligands are 2-[3-(1-carboxy-1-methylethoxy)phenoxy]-2-methylpropanoic acid (H2L1) and (3-methoxycarbonyl-2,5-di-tert-butylphenoxy)ethanoic acid (H2L2), which react with Rh2(OAc)4 to form the catalysts [Rh2(L1)2] (2) and [Rh2(L2) 2] (3). Both 2 and 3 have been characterized by X-ray crystallography and cyclic voltammetry, inter alia. Compounds 2 and 3 are structurally similar to 1 but show more complex electrochemical features. Whereas 1 has a single reversible redox wave that corresponds to the Rh2II,II/ Rh2II,III couple, 2 and 3 show multiple oxidations that are characteristic of ligand-centered oxidation. Catalysts 1, 2, and 3 perform well in a model intramolecular C-H amination reaction, and all three catalysts perform equally well during the first four hours of a model intermolecular reaction. After this point, 2 and 3 cease to function, whereas 1 continues to be active. These results support the hypothesis that intermolecular C-H amination utilizes two distinct mechanisms: (1) a nitrene interception/insertion mechanism that is fast but ceases to be operative after four hours, and (2) a one-electron mechanism that is more robust over extended time periods, but requires the catalyst to be able to undergo Rh2-centered oxidation. Copyright
