Activation of Small Molecules by the Metal-Amido Bond of Rhodium(III) and Iridium(III) (η5-C5Me5)M-Aminopyridinate Complexes
We report the synthesis and structural characterization of five-coordinate complexes of rhodium and iridium of the type [(η5-C5Me5)M(N^N)]+ (3-M+), where N^N represents the aminopyridinate ligand derived from 2-NH(Ph)-6-(Xyl)C5H3N (Xyl = 2,6-Me2C6H3). The two complexes were isolated as salts of the...
| Authors: | , , , , |
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| Format: | article |
| Status: | Versión enviada para evaluación y publicación |
| Publication Date: | 2018 |
| Country: | España |
| Institution: | Universidad de Sevilla (US) |
| Repository: | idUS. Depósito de Investigación de la Universidad de Sevilla |
| OAI Identifier: | oai:idus.us.es:11441/87894 |
| Online Access: | https://hdl.handle.net/11441/87894 https://doi.org/10.1021/acs.inorgchem.7b02283 |
| Access Level: | Open access |
| Summary: | We report the synthesis and structural characterization of five-coordinate complexes of rhodium and iridium of the type [(η5-C5Me5)M(N^N)]+ (3-M+), where N^N represents the aminopyridinate ligand derived from 2-NH(Ph)-6-(Xyl)C5H3N (Xyl = 2,6-Me2C6H3). The two complexes were isolated as salts of the BArF anion (BArF = B[3,5-(CF3)2C6H3]4). The M-Namido bond of complexes 3-M+ readily activated CO, C2H4, and H2. Thus, compounds 3-M+ reacted with CO under ambient conditions, but whereas for 3-Rh+, CO migratory insertion was fast, yielding a carbamoyl carbonyl species, 4-Rh+, the stronger Ir-Namido bond of complex 3-Ir+ caused the reaction to stop at the CO coordination stage. In contrast, 3-Ir+ reacted reversibly with C2H4, forming adduct 5-Ir+, which subsequently rearranged irreversibly to [Ir](H)(=C(Me)N(Ph)-) complex 6-Ir+, which contains an N-stabilized carbene ligand. Computational studies supported a migratory insertion mechanism, giving first a β-stabilized linear alkyl unit, [Ir]CH2CH2N(Ph)-, followed by a multistep rearrangement that led to the final product 6-Ir+. Both β- and α-H eliminations, as well as their microscopic reverse migratory insertion reactions, were implicated in the alkyl-to-hydride-carbene reorganization. The analogous reaction of 3-Rh+ with C2H4 originated a complex mixture of products from which only a branched alkyl [Rh]C(H)(Me)N(Ph)- (5-Rh+) could be isolated, featuring a β-agostic methyl interaction. Reactions of 3-M+ with H2 promoted a catalytic isomerization of the Ap ligand from classical κ2-N,N′ binding to κ-N plus η3-pseudoallyl coordination mode. |
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