Rhodium(I) silyl complexes for C-F bond activation reactions of aromatic compounds: Experimental and computational studies

Anna Lena Raza, Julien A. Panetier, Michael Teltewskoi, Stuart A. Macgregor*, Thomas Braun

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


The rhodium(I) silyl complexes [Rh{Si(OEt)3}(PEt 3)3] (2a) and [Rh{Si(OMe)3}(PEt 3)3] (2b) were synthesized by treatment of [Rh(CH 3)(PEt3)3] (1) with the corresponding silanes HSi(OEt)3 and HSi(OMe)3 at low temperature. The intermediate oxidative addition products fac-[Rh(H)(CH3){Si(OR) 3}(PEt3)3] (R = Et, 6a; R = Me, 6b) were observed by low-temperature NMR spectroscopy. A reaction of 2a with CO afforded trans-[Rh(CO){Si(OEt)3}(PEt3)2] (7) by the replacement of the phosphine ligand in the position trans to the silyl group. Treatment of 2a,b with pentafluoropyridine led to C-F activation reactions at the 2-position, yielding [Rh(2-C5F4N)(PEt 3)3] (11). The silyl complexes [Rh{Si(OR) 3}(PEt3)3] (2a,b) gave with 2,3,5,6-tetrafluoropyridine the C-F activation product [Rh(2-C5F 3HN)(PEt3)3] (10), whereas complex 7 reacted by C-H activation to furnish trans-[Rh(CO)(4-C5F4N)(PEt 3)2] (12). The C-F activation of pentafluoropyridine at 2b was studied with density functional theory calculations using a [Rh{Si(OMe)3}(PMe3)3] model complex (2′). The calculations indicate that a silyl-assisted C-F activation mechanism, analogous to related ligand-assisted processes at metal-phosphine and metal-boryl bonds, is more accessible than a C-F oxidative addition/Si-F reductive elimination pathway. The silyl-assisted process also proceeds with a kinetic preference for activation at the 2-position, as the transition state in this case derives extra stabilization through a Rh⋯N interaction. The C-F oxidative addition transition states show a significant degree of phosphine-assisted character and are not only higher in energy than the silyl-assisted process but also favor activation at the 4-position.

Original languageEnglish
Pages (from-to)3795-3807
Number of pages13
Issue number14
Publication statusPublished - 22 Jul 2013


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