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Issue 20, 2015
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Synthesis and structure of rhodium(I) silyl carbonyl complexes: photochemical C–F and C–H bond activation of fluorinated aromatic compounds

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Abstract

The rhodium(I) silyl carbonyl complexes [Rh{Si(OEt)3}(CO)(dippp)] (1) and [Rh{Si(OEt)3}(CO)(dippe)] (2) (dippp = 1,3-bis(diisopropylphosphino)propane, dippe = 1,2-bis-(diisopropylphosphino)ethane) were synthesized on treatment of the methyl compounds [Rh(CH3)(CO)(dippp)] (3) or [Rh(CH3)(CO)(dippe)] (4) with HSi(OEt)3 at low temperature. The methyl complexes 3 and 4 were prepared starting from the binuclear complexes [{Rh(μ-Cl)(dippp)}2] (5) and [{Rh(μ-Cl)(dippe)}2] (8), respectively. The silyl complexes 1 and 2 as well as the precursors [{Rh(μ-I)(dippp)}2] (6), [Rh(X)(CO)(dippp)] (3: X = CH3, 7: X = I) and [Rh(X)(CO)(dippe)] (4: X = CH3, 9: X = Cl) were characterized by NMR and IR spectroscopy and the structures in the solid state were determined by X-ray crystallography. The silyl complex 1 converts into the carbonyl-bridged complex [{Rh(μ-CO)(dippp)}2] (10) above temperatures of −30 °C by loss of the silyl ligand, whereas 2 is more thermally stable and a reaction to the binuclear complex [{Rh(μ-CO)(dippe)}2] (11) was observed at 50 °C. The silyl complex 2 reacted under irradiation with hexafluorobenzene and pentafluoropyridine to give the C–F activation products [Rh(C6F5)(CO)(dippe)] (12) and [Rh(2-C5F4N)(CO)(dippe)] (17), respectively. As additional products the silyl dicarbonyl complex [Rh{Si(OEt)3}(CO)2(dippe)] (13) and the cationic complex [Rh2(μ-H)(μ-CO)2(dippe)2]+[SiF5] (14) were identified. Compound 13 was synthesized independently by treatment of 2 with gaseous CO. In a similar manner, the dippp analogue [Rh{Si(OEt)3}(CO)2(dippp)] (15) was also prepared starting from 1. Photochemical reaction of 2 with pentafluorobenzene and 2,3,5,6-tetrafluoropyridine resulted selectively in C–H bond activation to afford 12 and [Rh(4-C5F4N)(CO)(dippe)] (18), respectively.

Graphical abstract: Synthesis and structure of rhodium(i) silyl carbonyl complexes: photochemical C–F and C–H bond activation of fluorinated aromatic compounds

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Publication details

The article was received on 26 Feb 2015, accepted on 14 Apr 2015 and first published on 27 Apr 2015


Article type: Paper
DOI: 10.1039/C5DT00819K
Citation: Dalton Trans., 2015,44, 9450-9469
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    Synthesis and structure of rhodium(I) silyl carbonyl complexes: photochemical C–F and C–H bond activation of fluorinated aromatic compounds

    L. Zámostná, S. Sander, T. Braun, R. Laubenstein, B. Braun, R. Herrmann and P. Kläring, Dalton Trans., 2015, 44, 9450
    DOI: 10.1039/C5DT00819K

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