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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| Authors: | Dr. Zhifang Guo Dr. Victoria L. Blair Prof. Glen B. Deacon Prof. Peter C. Junk |
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| Affiliation: | 1. School of Chemistry, Monash University, Clayton, 3800 Australia College of Science & Engineering, James Cook University, Townsville, 4811, Qld Australia;2. School of Chemistry, Monash University, Clayton, 3800 Australia;3. College of Science & Engineering, James Cook University, Townsville, 4811, Qld Australia |
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| 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. |
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| Keywords: | C−F activation europium pentafluorophenylsilver redox transmetallation/protolysis (RTP) trispentafluorophenylbismuth |
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