TY - JOUR
T1 - Stability and C–H Bond Activation Reactions of Palladium(I) and Platinum(I) Metalloradicals
T2 - Carbon-to-Metal H-Atom Transfer and an Organometallic Radical Rebound Mechanism
AU - Krämer, Tobias
AU - Gyton, Matthew
AU - Bustos, Itxaso
AU - Sinclair, Matthew
AU - Tan, Sze-yin
AU - Wedge, Christopher
AU - Macgregor, Stuart
AU - Chaplin, Adrian
N1 - Funding Information:
We thank the EPSRC (EP/K035681/1, T.K., S.A.M.; DTP studentship to M.J.G.S.), European Research Council (ERC grant agreement 637313, M.R.G., A.B.C.), Spanish Ministry of Universities and European Union (Margarita Salas grant funded by the European Union-NextGenerationEU, I.B.), and Royal Society (UF100592, UF150675, A.B.C.) for financial support. T.K. and S.A.M. acknowledge the DJEI/DES/SFI/HEA Irish Centre for High-End Computing (ICHEC) and ARCHER2 UK National Supercomputing Facility for the provision of high-performance computing facilities and support. EPR facilities were provided by the Spectroscopy RTP at the University of Warwick. High-resolution mass-spectrometry data were collected using instruments purchased through support from Advantage West Midlands and the European Regional Development Fund. Crystallographic data were collected using an instrument that received funding from the ERC under the European Union’s Horizon 2020 research and innovation program (grant agreement No. 637313). T.K. thanks Dr. Ragnar Bjornsson (CEA Grenoble) for insightful discussions.
Publisher Copyright:
© 2023 The Authors. Published by American Chemical Society.
PY - 2023/6/28
Y1 - 2023/6/28
N2 - One-electron oxidation of palladium(0) and platinum(0) bis(phosphine) complexes enables isolation of a homologous series of linear d9 metalloradicals of the form [M(PR3)2]+ (M = Pd, Pt; R = tBu, Ad), which are stable in 1,2-difluorobenzene (DFB) solution for >1 day at room temperature when partnered with the weakly coordinating [BArF4]− (ArF = 3,5-(CF3)2C6H3) counterion. The metalloradicals exhibit reduced stability in THF, decreasing in the order palladium(I) > platinum(I) and PAd3 > PtBu3, especially in the case of [Pt(PtBu3)2]+, which is converted into a 1:1 mixture of the platinum(II) complexes [Pt(PtBu2CMe2CH2)(PtBu3)]+ and [Pt(PtBu3)2H]+ upon dissolution at room temperature. Cyclometalation of [Pt(PtBu3)2]+ can also be induced by reaction with the 2,4,6-tri-tert-butylphenoxyl radical in DFB, and a common radical rebound mechanism involving carbon-to-metal H-atom transfer and formation of an intermediate platinum(III) hydride complex, [Pt(PtBu2CMe2CH2)H(PtBu3)]+, has been substantiated by computational analysis. Radical C–H bond oxidative addition is correlated with the resulting MII–H bond dissociation energy (M = Pt > Pd), and reactions of the metalloradicals with 9,10-dihydroanthracene in DFB at room temperature provide experimental evidence for the proposed C–H bond activation manifold in the case of platinum, although conversion into platinum(II) hydride derivatives is considerably faster for [Pt(PtBu3)2]+ (t1/2 = 1.2 h) than [Pt(PAd3)2]+ (t1/2 ∼ 40 days).
AB - One-electron oxidation of palladium(0) and platinum(0) bis(phosphine) complexes enables isolation of a homologous series of linear d9 metalloradicals of the form [M(PR3)2]+ (M = Pd, Pt; R = tBu, Ad), which are stable in 1,2-difluorobenzene (DFB) solution for >1 day at room temperature when partnered with the weakly coordinating [BArF4]− (ArF = 3,5-(CF3)2C6H3) counterion. The metalloradicals exhibit reduced stability in THF, decreasing in the order palladium(I) > platinum(I) and PAd3 > PtBu3, especially in the case of [Pt(PtBu3)2]+, which is converted into a 1:1 mixture of the platinum(II) complexes [Pt(PtBu2CMe2CH2)(PtBu3)]+ and [Pt(PtBu3)2H]+ upon dissolution at room temperature. Cyclometalation of [Pt(PtBu3)2]+ can also be induced by reaction with the 2,4,6-tri-tert-butylphenoxyl radical in DFB, and a common radical rebound mechanism involving carbon-to-metal H-atom transfer and formation of an intermediate platinum(III) hydride complex, [Pt(PtBu2CMe2CH2)H(PtBu3)]+, has been substantiated by computational analysis. Radical C–H bond oxidative addition is correlated with the resulting MII–H bond dissociation energy (M = Pt > Pd), and reactions of the metalloradicals with 9,10-dihydroanthracene in DFB at room temperature provide experimental evidence for the proposed C–H bond activation manifold in the case of platinum, although conversion into platinum(II) hydride derivatives is considerably faster for [Pt(PtBu3)2]+ (t1/2 = 1.2 h) than [Pt(PAd3)2]+ (t1/2 ∼ 40 days).
KW - Palladium(I)
KW - Platinum(I)
KW - Synthetic organic chemistry
UR - http://www.scopus.com/inward/record.url?scp=85163731475&partnerID=8YFLogxK
U2 - 10.1021/jacs.3c04167
DO - 10.1021/jacs.3c04167
M3 - Article
VL - 145
SP - 14087
EP - 14100
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 25
ER -