Perhydrocarbyl ReVII complexes: Comparison of molecular and surface complexes

Mathieu Chabanas, Anne Baudouin, Christophe Copéret, Jean-Marie Maurice Basset, Wayne Lukens, Anne Lesage, Sabine Hediger, Lyndon Emsley*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

100 Scopus citations

Abstract

The molecular complex [Re(≡CtBu)(=CHtBu) (CH2tBu)2] (1) reacts with a silica partially dehydroxylated at 700 °C to give syn-2,[(≡SiO)Re(≡CtBu)(=CHtBu) (CH2tBu)], as a single isomer according to mass-balance analysis, IR, and solid-state NMR spectroscopy. 1D and 2D solid-state NMR (HETCOR and long-range HETCOR) on a 13C-labeled-2 has allowed us to observe the chemical shifts of all carbons (including those that are not labeled) and ascertain their assignments. Moreover, EXAFS data are consistent with the presence of two carbons at a relatively short distance (1.79 A), which cannot be deconvoluted, but which are consistent with the presence of alkylidene and alkylidyne carbons along with two other first neighbors at a longer distance (2.01 Å), the alkyl carbon and the O atom by which the Re is attached to the surface. Moreover, the data also suggest the presence of a siloxane bridge of the silica surface at 2.4 Å in the coordination sphere of the Re center. Thermal and photochemical treatment allow us to observe the anti isomer, which was also fully characterized by 1 D and 2D solid-state NMR. This behavior parallels the reactivity of molecular Re complexes, and their respective 1H and 13C chemical shifts match those of the corresponding molecular analogues syn- and anti-2m and n. Finally, the grafting of 1 onto silica involves the reaction of both the alkyl and the alkylidene ligand with an equiprobability, leaving the alkylidyne as a spectator ligand. Noteworthy is the formation of 2 [(≡SiO)Re(≡CtBu)(=CHtBu) (CH2tBu)], rather than the corresponding trisneopentyl-neopentylidyne Re complex, monografted on silica, [(≡SiO)Re(≡CtBu)(CH2- tBu)3], which would have been expected from the reactivity of 1 with various molecular Brönsted acids and which also suggests that a proximal siloxane bridge forces the α-H abstraction process, leading to syn-2a.

Original languageEnglish (US)
Pages (from-to)492-504
Number of pages13
JournalJournal of the American Chemical Society
Volume125
Issue number2
DOIs
StatePublished - Jan 15 2003

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Fingerprint

Dive into the research topics of 'Perhydrocarbyl Re<sup>VII</sup> complexes: Comparison of molecular and surface complexes'. Together they form a unique fingerprint.

Cite this