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- Title
Walking Metals in d<sup>8</sup>⋅⋅⋅d<sup>8</sup> Hetero-bimetallic Complexes: An Original Dynamic Phenomenon.
- Authors
Nebra, Noel; Ladeira, Sonia; Maron, Laurent; Martin-Vaca, Blanca; Bourissou, Didier
- Abstract
In the course of our investigations on polymetallic complexes derived from 1,3-bis(thiophosphinoyl)indene (Ind(Ph2PS)2), we observed original fluxional behavior and report herein a joint experimental/computational study of this dynamic process. Starting from the indenylidene chloropalladate species [Pd{Ind(Ph2PS)2}Cl]− ( 1), the new PdII⋅⋅⋅RhI hetero-bimetallic pincer complex [PdCl{Ind(Ph2PS)2}Rh(nbd)] ( 2; nbd=2,5-norbornadiene) was prepared. X-ray crystallography and DFT calculations substantiate the presence of a d8⋅⋅⋅d8 interaction. According to multinuclear variable-temperature NMR spectroscopic experiments, the pendant {Rh(nbd)} fragment of 2 readily shifts in solution at room temperature between the two edges of the SCS tridentate ligand. To assess the role of the pincer-based polymetallic structure on this fluxional behavior, the related monometallic Rh complex [Rh{IndH(Ph2PS)2}(nbd)] ( 3) was prepared. No evidence for a metal shift was observed in that case, even at high temperature, thus indicating that inplane pincer coordination to the Pd center plays a crucial role. The previously described PdII⋅⋅⋅IrI bimetallic complex 4 exhibited fluxional behavior in solution, but with a significantly higher activation barrier than 2. This finding demonstrates the generality of this metal-shift process and the strong influence of the involved metal centers on the associated activation barrier. DFT calculations were performed to shed light onto the mechanism of such metal-shift processes and to identify the factors that influence the associated activation barriers. Significantly different pathways were found for bimetallic complexes 2 and 4 on one hand and the monometallic complex 3 on the other hand. The corresponding activation barriers predicted computationally are in very good agreement with the experimental observations.
- Publication
Chemistry - A European Journal, 2012, Vol 18, Issue 27, p8474
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201200359