TY - JOUR
T1 - Rhodium(I) silyl complexes for C-F bond activation reactions of aromatic compounds
T2 - Experimental and computational studies
AU - Raza, Anna Lena
AU - Panetier, Julien A.
AU - Teltewskoi, Michael
AU - Macgregor, Stuart A.
AU - Braun, Thomas
PY - 2013/7/22
Y1 - 2013/7/22
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=84880523618&partnerID=8YFLogxK
U2 - 10.1021/om400150p
DO - 10.1021/om400150p
M3 - Article
AN - SCOPUS:84880523618
SN - 0276-7333
VL - 32
SP - 3795
EP - 3807
JO - Organometallics
JF - Organometallics
IS - 14
ER -