Europium is Different: Solvent and Ligand Effects on Oxidation State Outcomes and C-F Activation in Reactions Between Europium Metal and Pentafluorophenylsilver

Zhifang Guo; Victoria L. Blair; Glen B. Deacon; Peter C. Junk

doi:10.1002/chem.202103865

Europium is Different: Solvent and Ligand Effects on Oxidation State Outcomes and C-F Activation in Reactions Between Europium Metal and Pentafluorophenylsilver

Zhifang Guo
, Victoria L. Blair
, Glen B. Deacon
, Peter C. Junk

School of Chemistry

Research output: Contribution to journal › Article › Research › peer-review

8 Citations (Scopus)

Abstract

Unique outcomes have emerged from the redox transmetallation/ protolysis (RTP) reactions of europium metal with [Ag(C₆F₅)(py)] (py=pyridine) and pyrazoles (RR′pzH). In pyridine, a solvent not normally used for RTP reactions, the products were mainly Eu^II complexes, [Eu(RR′pz)₂(py)₄] (RR′pz=3,5-diphenylpyrazolate (Ph₂pz) 1; 3-(2-thienyl)-5-trifluoromethylpyrazolate (ttfpz) 2; 3-methyl-5-phenylpyrazolate (PhMepz) 3). However, use of 3,5-di-tert-butylpyrazole (tBu₂pzH) gave trivalent [Eu(tBu₂pz)₃(py)₂] 4, whereas the bulkier N,N′-bis(2,6-difluorophenyl)formamidine (DFFormH) gave divalent [Eu(DFForm)₂(py)₃] 5. In tetrahydrofuran (thf), the usual solvent for RTP reactions, C−F activation was observed for the first time with [Ag(C₆F₅)(py)] in such reactions. Thus trivalent [{Eu₂(Ph₂pz)₄(py)₄(thf)₂(μ-F)₂}{Eu₂(Ph₂pz)₄(py)₂(thf)₄(μ-F)₂}] (6), [Eu₂(ttfpz)₄(py)₂(dme)₂(μ-F)₂] (7), [Eu₂(tBu₂pz)₄(dme)₂(μ-F)₂] (8) were obtained from the appropriate pyrazoles, the last two after crystallization from 1,2-dimethoxyethane (dme). Surprisingly 3,5-dimethylpyrazole (Me₂pzH) gave the divalent cage [Eu₆(Me₂pz)₁₀(thf)₆(μ-F)₂] (9). This has a compact ovoid core held together by bridging fluoride, thf, and pyrazolate ligands, the last including the rare μ₄-1η⁵(N₂C₃): 2η²(N,N′): 3κ(N): 4κ(N′) pyrazolate binding mode. With the bulky N,N′-bis(2,6-diisopropylphenyl)formamidine (DippFormH), which often favours C−F activation in RTP reactions, neither oxidation to Eu^III nor C−F activation was observed and [Eu(DippForm)₂(thf)₂] (10) was isolated. By contrast, Eu reacted with Bi(C₆F₅)₃ and Ph₂pzH or tBu₂pzH in thf without C−F activation, to give [Eu(Ph₂pz)₂(thf)₄] (11) and [Eu(tBu₂pz)₃(thf)₂] (12) respectively, the oxidation state outcomes corresponding to that for use of [Ag(C₆F₅)(py)] in pyridine.

Original language	English
Article number	e202103865
Number of pages	11
Journal	Chemistry - A European Journal
Volume	28
Issue number	3
DOIs	https://doi.org/10.1002/chem.202103865
Publication status	Published - 13 Jan 2022

Keywords

C−F activation
europium
pentafluorophenylsilver
redox transmetallation/protolysis (RTP)
trispentafluorophenylbismuth

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10.1002/chem.202103865

Cite this

@article{8f593c70f8994a38a70d701958f459b0,

title = "Europium is Different: Solvent and Ligand Effects on Oxidation State Outcomes and C-F Activation in Reactions Between Europium Metal and Pentafluorophenylsilver",

abstract = "Unique outcomes have emerged from the redox transmetallation/ protolysis (RTP) reactions of europium metal with [Ag(C6F5)(py)] (py=pyridine) and pyrazoles (RR′pzH). In pyridine, a solvent not normally used for RTP reactions, the products were mainly EuII complexes, [Eu(RR′pz)2(py)4] (RR′pz=3,5-diphenylpyrazolate (Ph2pz) 1; 3-(2-thienyl)-5-trifluoromethylpyrazolate (ttfpz) 2; 3-methyl-5-phenylpyrazolate (PhMepz) 3). However, use of 3,5-di-tert-butylpyrazole (tBu2pzH) gave trivalent [Eu(tBu2pz)3(py)2] 4, whereas the bulkier N,N′-bis(2,6-difluorophenyl)formamidine (DFFormH) gave divalent [Eu(DFForm)2(py)3] 5. In tetrahydrofuran (thf), the usual solvent for RTP reactions, C−F activation was observed for the first time with [Ag(C6F5)(py)] in such reactions. Thus trivalent [\{Eu2(Ph2pz)4(py)4(thf)2(μ-F)2\}\{Eu2(Ph2pz)4(py)2(thf)4(μ-F)2\}] (6), [Eu2(ttfpz)4(py)2(dme)2(μ-F)2] (7), [Eu2(tBu2pz)4(dme)2(μ-F)2] (8) were obtained from the appropriate pyrazoles, the last two after crystallization from 1,2-dimethoxyethane (dme). Surprisingly 3,5-dimethylpyrazole (Me2pzH) gave the divalent cage [Eu6(Me2pz)10(thf)6(μ-F)2] (9). This has a compact ovoid core held together by bridging fluoride, thf, and pyrazolate ligands, the last including the rare μ4-1η5(N2C3): 2η2(N,N′): 3κ(N): 4κ(N′) pyrazolate binding mode. With the bulky N,N′-bis(2,6-diisopropylphenyl)formamidine (DippFormH), which often favours C−F activation in RTP reactions, neither oxidation to EuIII nor C−F activation was observed and [Eu(DippForm)2(thf)2] (10) was isolated. By contrast, Eu reacted with Bi(C6F5)3 and Ph2pzH or tBu2pzH in thf without C−F activation, to give [Eu(Ph2pz)2(thf)4] (11) and [Eu(tBu2pz)3(thf)2] (12) respectively, the oxidation state outcomes corresponding to that for use of [Ag(C6F5)(py)] in pyridine.",

keywords = "C−F activation, europium, pentafluorophenylsilver, redox transmetallation/protolysis (RTP), trispentafluorophenylbismuth",

author = "Zhifang Guo and Blair, \{Victoria L.\} and Deacon, \{Glen B.\} and Junk, \{Peter C.\}",

note = "Funding Information: GBD and PCJ gratefully acknowledge the ARC for funding (DP190100798). This research was undertaken in part using the MX1 beamline at the Australian Synchrotron, part of ANSTO. [42] Publisher Copyright: {\textcopyright} 2021 Wiley-VCH GmbH",

year = "2022",

month = jan,

day = "13",

doi = "10.1002/chem.202103865",

language = "English",

volume = "28",

journal = "Chemistry - A European Journal",

issn = "1521-3765",

publisher = "Wiley-VCH Verlag GmbH \& Co. KGaA",

number = "3",

}

Europium is Different: Solvent and Ligand Effects on Oxidation State Outcomes and C-F Activation in Reactions Between Europium Metal and Pentafluorophenylsilver. / Guo, Zhifang; Blair, Victoria L.; Deacon, Glen B. et al.
In: Chemistry - A European Journal, Vol. 28, No. 3, e202103865, 13.01.2022.

Research output: Contribution to journal › Article › Research › peer-review

TY - JOUR

T1 - Europium is Different

T2 - Solvent and Ligand Effects on Oxidation State Outcomes and C-F Activation in Reactions Between Europium Metal and Pentafluorophenylsilver

AU - Guo, Zhifang

AU - Blair, Victoria L.

AU - Deacon, Glen B.

AU - Junk, Peter C.

N1 - Funding Information: GBD and PCJ gratefully acknowledge the ARC for funding (DP190100798). This research was undertaken in part using the MX1 beamline at the Australian Synchrotron, part of ANSTO. [42] Publisher Copyright: © 2021 Wiley-VCH GmbH

PY - 2022/1/13

Y1 - 2022/1/13

N2 - Unique outcomes have emerged from the redox transmetallation/ protolysis (RTP) reactions of europium metal with [Ag(C6F5)(py)] (py=pyridine) and pyrazoles (RR′pzH). In pyridine, a solvent not normally used for RTP reactions, the products were mainly EuII complexes, [Eu(RR′pz)2(py)4] (RR′pz=3,5-diphenylpyrazolate (Ph2pz) 1; 3-(2-thienyl)-5-trifluoromethylpyrazolate (ttfpz) 2; 3-methyl-5-phenylpyrazolate (PhMepz) 3). However, use of 3,5-di-tert-butylpyrazole (tBu2pzH) gave trivalent [Eu(tBu2pz)3(py)2] 4, whereas the bulkier N,N′-bis(2,6-difluorophenyl)formamidine (DFFormH) gave divalent [Eu(DFForm)2(py)3] 5. In tetrahydrofuran (thf), the usual solvent for RTP reactions, C−F activation was observed for the first time with [Ag(C6F5)(py)] in such reactions. Thus trivalent [{Eu2(Ph2pz)4(py)4(thf)2(μ-F)2}{Eu2(Ph2pz)4(py)2(thf)4(μ-F)2}] (6), [Eu2(ttfpz)4(py)2(dme)2(μ-F)2] (7), [Eu2(tBu2pz)4(dme)2(μ-F)2] (8) were obtained from the appropriate pyrazoles, the last two after crystallization from 1,2-dimethoxyethane (dme). Surprisingly 3,5-dimethylpyrazole (Me2pzH) gave the divalent cage [Eu6(Me2pz)10(thf)6(μ-F)2] (9). This has a compact ovoid core held together by bridging fluoride, thf, and pyrazolate ligands, the last including the rare μ4-1η5(N2C3): 2η2(N,N′): 3κ(N): 4κ(N′) pyrazolate binding mode. With the bulky N,N′-bis(2,6-diisopropylphenyl)formamidine (DippFormH), which often favours C−F activation in RTP reactions, neither oxidation to EuIII nor C−F activation was observed and [Eu(DippForm)2(thf)2] (10) was isolated. By contrast, Eu reacted with Bi(C6F5)3 and Ph2pzH or tBu2pzH in thf without C−F activation, to give [Eu(Ph2pz)2(thf)4] (11) and [Eu(tBu2pz)3(thf)2] (12) respectively, the oxidation state outcomes corresponding to that for use of [Ag(C6F5)(py)] in pyridine.

AB - Unique outcomes have emerged from the redox transmetallation/ protolysis (RTP) reactions of europium metal with [Ag(C6F5)(py)] (py=pyridine) and pyrazoles (RR′pzH). In pyridine, a solvent not normally used for RTP reactions, the products were mainly EuII complexes, [Eu(RR′pz)2(py)4] (RR′pz=3,5-diphenylpyrazolate (Ph2pz) 1; 3-(2-thienyl)-5-trifluoromethylpyrazolate (ttfpz) 2; 3-methyl-5-phenylpyrazolate (PhMepz) 3). However, use of 3,5-di-tert-butylpyrazole (tBu2pzH) gave trivalent [Eu(tBu2pz)3(py)2] 4, whereas the bulkier N,N′-bis(2,6-difluorophenyl)formamidine (DFFormH) gave divalent [Eu(DFForm)2(py)3] 5. In tetrahydrofuran (thf), the usual solvent for RTP reactions, C−F activation was observed for the first time with [Ag(C6F5)(py)] in such reactions. Thus trivalent [{Eu2(Ph2pz)4(py)4(thf)2(μ-F)2}{Eu2(Ph2pz)4(py)2(thf)4(μ-F)2}] (6), [Eu2(ttfpz)4(py)2(dme)2(μ-F)2] (7), [Eu2(tBu2pz)4(dme)2(μ-F)2] (8) were obtained from the appropriate pyrazoles, the last two after crystallization from 1,2-dimethoxyethane (dme). Surprisingly 3,5-dimethylpyrazole (Me2pzH) gave the divalent cage [Eu6(Me2pz)10(thf)6(μ-F)2] (9). This has a compact ovoid core held together by bridging fluoride, thf, and pyrazolate ligands, the last including the rare μ4-1η5(N2C3): 2η2(N,N′): 3κ(N): 4κ(N′) pyrazolate binding mode. With the bulky N,N′-bis(2,6-diisopropylphenyl)formamidine (DippFormH), which often favours C−F activation in RTP reactions, neither oxidation to EuIII nor C−F activation was observed and [Eu(DippForm)2(thf)2] (10) was isolated. By contrast, Eu reacted with Bi(C6F5)3 and Ph2pzH or tBu2pzH in thf without C−F activation, to give [Eu(Ph2pz)2(thf)4] (11) and [Eu(tBu2pz)3(thf)2] (12) respectively, the oxidation state outcomes corresponding to that for use of [Ag(C6F5)(py)] in pyridine.

KW - C−F activation

KW - europium

KW - pentafluorophenylsilver

KW - redox transmetallation/protolysis (RTP)

KW - trispentafluorophenylbismuth

UR - https://www.scopus.com/pages/publications/85120806111

U2 - 10.1002/chem.202103865

DO - 10.1002/chem.202103865

M3 - Article

AN - SCOPUS:85120806111

SN - 1521-3765

VL - 28

JO - Chemistry - A European Journal

JF - Chemistry - A European Journal

IS - 3

M1 - e202103865

ER -

Europium is Different: Solvent and Ligand Effects on Oxidation State Outcomes and C-F Activation in Reactions Between Europium Metal and Pentafluorophenylsilver

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Keywords

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CTREC: Challenging targets in rare earth metal-organic chemistry

Australian Synchrotron

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Europium is Different: Solvent and Ligand Effects on Oxidation State Outcomes and C-F Activation in Reactions Between Europium Metal and Pentafluorophenylsilver

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Keywords

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CTREC: Challenging targets in rare earth metal-organic chemistry

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Australian Synchrotron

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