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

The redox reaction between the europium(III) amide [(Me3Si)(2)N](3)Eu-III(mu-Cl)Li(THF)(3) and pyrrolyl-functionalized secondary amines was found for the first time. The interactions of 2-(2,6-R2C6H3NHCH2)C4H3NH (R = CH3 (1), R = Pr-i (2)) with 2 equiv of europium(III) amide [(Me3Si)(2)N](3)Eu-III(mu-Cl)Li(THF)(3) led to oxidation of the secondary amine with isolation of imino-functionalized pyrrolyl lithium complexes {[eta(2):eta(1)-2-(2,6-R2C6H3N=CH)C4H3N]Li(THF)}(2) (R = CH3 (4), R = Pr-i (5)). When the deuterated compounds 2-(2,6-R2C6H3NHCHD)C4H3NH (R = CH3 (1a), R = Pr-i (2a)) were respectively treated with 2 equiv of europium(III) amide [(Me3Si)(2)N](3)Eu-III(mu-Cl)Li(THF)(3), the corresponding mixture of deuterated imino-functionalized pyrrolyl lithium complexes {[eta(2):eta(1)-2-(2,6-Me2C6H3N=CD)C4H3N]Li(THF)}(2) (4a), and 4 and {[eta(2):eta(1)-2-(2,6-(PR2C6H3N)-P-i=CD)C4H3N]Li(THF)}(2) (5a) and 5 were produced upon analyses of the NMR spectra of the complexes. Treatment of 2-(2,6-(PR2C6H3NHCHD)-P-i)C4H3NH (2a) with excess (Me3Si)(2)NLi gave the only pyrrole deprotonated product, {[eta(5):eta(2):eta(1)-2-(2,6-(PR2C6H3NHCHD)-P-i)-C4H3N]Li2N(SiMe3)(2)}(2) (6). When 2-(2,6-(PR2C6H3NHCH2)-P-i)C4H3NH (2) was treated with ytterbium(III) amide [(Me3Si)(2)N](3)Eu-III(mu-Cl)Li(THF)(3), a dinuclear ytterbium(III) amide with formula {[mu-eta(5):eta(1)):eta(1)-2-[(2,6-(Pr2C6H3)-Pr-i)NCH2]C4H3N]YbN(SiMe3)(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 (Me2SiO)(3), 2-(2,6-(PR2C6H3NHCH2)-P-i)C4H3NH (2), and europium(III) amide [(Me3Si)(2)N](3)Eu-III(mu-Cl)Li(THF)(3), after workup, afforded the europium(II) complex {[mu-eta(5):eta(1):eta(1)-2-(ArN(Me2SiO)CH2)C4H3N]Eu-II[eta(5)-2-(ArN=CH)C4H3N]Li-2[N(SiMe3)(2)]}(2) (Ar = 2,6-(PR2C6H3)-P-i) (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-Bu-t-C4H2NH-2-CH2NHCH2](2) (3) with [(Me3Si)(2)N](3)Eu-III(mu-Cl)Li(THF)(3) produced a novel centrosymmetric macrocyclic complex with six europium(II) ions and six lithium ions, {[(5-Bu-t-C4H2N-2-CH=NCH2)(2)](4)[(5-Bu-t-2-CH3N=CH(C4H2N)]Eu3Li3}(2) (9) with observation of redox chemistry between europium(III) and the linked secondary amine. When the linked secondary diamine [5-Bu-t-C4H2NH-2-CH2NHCH2](2) (3) was treated with [(Me3Si)(2)N](3)Dy-III(mu-Cl)Li(THF)(3) to produce a novel four-sandwiched-lithium-supported tetranuclear dysprosium(III) complex, {eta(2):eta(2)-[eta(1):eta(1)-(mu-eta(5):eta(5)-[5-Bu-t-C4H2N-2-CH2NCH2CH2N-2-CH2-5-Bu-t-C4H2N]Li)2]Dy-2(mu(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.