Redox chemistry between europium(III) amide and pyrrolyl-functionalized secondary amines. synthesis and structural characterization of lithium and novel lanthanide complexes incorporating functionalized pyrrolyl ligands

摘要

The redox reaction between the europium(III) amide [(Me_3Si) _2N]3Eu~(III)(μ-Cl)Li(THF)_3 and pyrrolyl-functionalized secondary amines was found for the first time. The interactions of 2-(2,6-R_2C_6H_3NHCH _2)C_4H_3NH (R = CH_3 (1), R = ~iPr (2)) with 2 equiv of europium(III) amide [(Me_3Si) _2N]3Eu~(III)(μ-Cl)Li(THF)_3 led to oxidation of the secondary amine with isolation of imino-functionalized pyrrolyl lithium complexes {[η~2:η~1-2-(2,6-R _2C_6H_3N=CH)C4H3N]Li(THF)} _2 (R = CH_3 (4), R = ~iPr (5)). When the deuterated compounds 2-(2,6-R_2C_6H_3NHCHD)C _4H_3NH (R = CH_3 (1a), R =~ iPr (2a)) were respectively treated with 2 equiv of europium(III) amide [(Me _3Si)_2N]3Eu~(III)(μ-Cl)Li(THF) _3, the corresponding mixture of deuterated imino-functionalized pyrrolyl lithium complexes {[η~2:η~1-2-(2,6-Me _2C_6H_3N=CD)C_4H_3N]Li(THF)} _2 (4a) and 4 and {[η~2:η~1-2-(2,6- ~iPr_2C_6H_3N=CD)C_4H _3N]Li(THF)}_2 (5a) and 5 were produced upon analyses of the NMR spectra of the complexes. Treatment of 2-(2,6-~iPr _2C_6H_3NHCHD)C_4H_3NH (2a) with excess (Me_3Si)_2NLi gave the only pyrrole deprotonated product, {[η~5:η~2:η~1-2-(2,6- ~iPr_2C_6H_3NHCHD)C_4H _3N]Li_2N(SiMe_3)_2}_2 (6). When 2-(2,6-~iPr_2C_6H_3NHCH _2)C_4H_3NH (2) was treated with ytterbium(III) amide [(Me_3Si)_2N]_3Yb~(III)(μ-Cl) Li(THF)_3, a dinuclear ytterbium(III) amide with formula {[(μ-η~5:η1):η~1-2-[(2,6- ~iPr_2C_6H_3)NCH_2]C _4H_3N]YbN(SiMe_3)_2}_2 (7) was isolated and no oxidation of the secondary amine was observed. Reduction of ytterbium or imino-functionalized pyrrolyl compound was not observed by refluxing the toluene solution of complex 7 for 2 days. Treatment of equal equivalents of grease (Me_2SiO)_3, 2-(2,6- ~iPr_2C_6H_3NHCH_2)C_ 4H_3NH (2), and europium(III) amide [(Me _3Si)_2N]_3Eu~(III)(μ-Cl)Li(THF) _3, after workup, afforded the europium(II) complex {[μ-η~5:η~1:η~1-2-(ArN(Me _2SiO)CH_2)C_4H_3N]Eu ~(II)[η~5-2-(ArN=CH)C_4H_3N]Li _2[N(SiMe_3)_2]}_2 (Ar = 2,6- ~iPr_2C_6H_3) (8) with reduction of europium(III) to europium(II) and oxidation of the secondary amine to an imino group. Reaction of a pyrrolyl-functionalized linked secondary diamine [5- ~tBu-C_4H_2NH-2-CH_2NHCH _2]_2 (3) with [(Me_3Si)_2N] _3Eu~(III)(μ-Cl)Li(THF)_3 produced a novel centrosymmetric macrocyclic complex with six europium(II) ions and six lithium ions, {[(5-~tBu-C_4H_2N-2-CH=NCH_2) _2]_4[(5-~tBu-2-CH_3N=CH(C _4H_2N)]Eu_3Li_3}_2 (9) with observation of redox chemistry between europium(III) and the linked secondary amine. When the linked secondary diamine [5-~tBu-C_4H _2NH-2-CH_2NHCH_2]_2 (3) was treated with [(Me_3Si)_2N]_3Dy~(III)(μ-Cl) Li(THF)_3 to produce a novel four-sandwiched-lithium-supported tetranuclear dysprosium(III) complex, {η~2:η~2- [η~1:η~1-(μ-η~5: η~5-[5-~tBu-C_4H_2N-2-CH _2NCH_2CH_2N-2-CH_2-5- ~tBu-C_4H_2N]Li)_2]Dy _2(μ_3-Cl)Li}_2 (10), no redox chemistry was observed. All compounds were characterized by spectroscopic methods and elemental analyses; complexes 4-10 were also characterized by X-ray structure analyses.