Divalent europium and ytterbium complexes supported by a bulky 2-pyridyl amido ligand: synthesis, structure and reactivity studies

Abstract

Metallation of the N-arylated 2-pyridyl amine [HN(C6H3Pr(i)2-2,6)(2-C5H3N-6-Me)] (1) with potassium hydride in Et2O and THF yielded potassium amides [{KL(OEt2)}2] [L = N(C6H3Pr(i)2-2,6)(2-C5H3N-6-Me)] (2) and KL(THF)2 (3), respectively. Treatment of LnI2(THF)2 (Ln = Eu, Yb) with 2 afforded the corresponding Ln(II) amido complexes [EuL(μ-L)2K(THF)] (4) and [YbL2(THF)2] (5). In contrast, an analogous reaction of SmI2(THF)2 with 2 only led to the isolation of homoleptic Sm(III) triamide [SmL3] (6). The reaction chemistry of divalent complexes 4 and 5 was examined. Oxidation of the Eu(II) amido complex 4 by iodine yielded the trivalent [EuL3] (7), whereas addition of Yb(II) diamide 5 to iodine led to the isolation of the bis(amido) Yb(III) iodide complex [YbL2(I)(THF)] (8). Complex 8 could also be prepared by the reaction of 5 with copper(I) iodide. A subsequent reaction of 8 with KOBut gave, unexpectedly, the Yb(III) triamide [YbL3] (9). Reactions of complex 5 with diphenyl dichalcogenides PhEEPh (E = S, Se, Te) also gave [YbL3] (9) as the only isolable product. The solid-state structures of complexes 2 and 4–9 were elucidated by X-ray diffraction analysis.

Synthesis and Reactivity of Bis(silylene)‐Coordinated Calcium and Divalent Lanthanide Complexes

“…Only af ew examples of multidentate anionic silylene ligandsh ave been reported in the last 10 years, most of them being accessed by intramolecular CÀHo rS i ÀHb ond activation when using low-valent transition metal precursors. [2c, 3d, 4k, 21] The distance between the Yb atom and the pyridine nitrogen atom in 3 (2.314(4) )i ss lightly longer than the distance with the amide nitrogen donor (2.256(4) ), suggesting that the anionic charge is localized att he amide N-atoma nd supporting an amidopyridine (rather than aminopyridinato) [22] coordination mode of the ligand.Asimilard istribution of bond lengths (YbÀN pyr > YbÀN amido )w as found in related Yb III amidopyridine complexes. [23] In addition, the neutral NHSi moiety is coordinated to the Yb atom with as ignificantly shortened YbÀSi bond (3.0426(15) )c ompared to the divalent Yb complex 2 (3.1505(11) and 3.1999(11) ).…”

“…The bondings ituation of Ca with the pyridyl-amido moiety is different from that in the Yb III complex 3.T he CaÀN amido bonds( Ca1ÀN5 2.524(2) and Ca2ÀN112 .532(2) )a re slightly longert han the CaÀN pyr bonds (Ca1ÀN4 2.468(2) and Ca2ÀN10 2.451(2) ), suggesting ah igherw eight of the aminopyridinato resonance form. [22] Despite the popularity and versatility of amidinate-coordinated Ca complexes, only ah andful of Ca complexes bearing pyridyl-amido ligands has been reported. [28] The very poor yield of 4 in this procedure precludedf urther spectroscopic studies.…”

Rare-earth metal complexes with redox-active formazanate ligands

“…Such reactivity has been presented in the literature, as a similar redox reaction was observed when potassium amide [{KN(C 6 H 3 i Pr 2 -2,6)(2-C 5 H 3 N-6-Me(OEt 2 )} 2 ] was reacted with [SmI 2 (thf) 2 ] and afforded a homoleptic Sm( iii ) trisamide. 44 To further test the above mentioned hypothesis, L 2 H was treated directly with the divalent Sm compound [Cp* 2 Sm(thf) 2 ], 45 a similar behavior to the Yb complex was observed, as the trivalent Sm complex 4 formed, which could be identified according to the 1 H NMR spectrum (Scheme 4).…”

“…Such reactivity has been presented in the literature, as a similar redox reaction was observed when potassium amide [{KN(C 6 H 3 iPr 2 -2,6)(2-C 5 H 3 N-6-Me(OEt 2 )} 2 ] was reacted with [SmI 2 (thf ) 2 ] and afforded a homoleptic Sm(III) trisamide. 44 To further test the above mentioned hypothesis, L 2 H was treated directly with the divalent Sm compound [Cp* 2 Sm(thf ) 2 ], 45 a similar behavior to the Yb complex was observed, as the trivalent Sm complex 4 formed, which could be identified according to the 1 H NMR spectrum (Scheme 4).…”

Cobalt(ii) amido complexes derived from a monodentate arylamido ligand featuring a highly electron-withdrawing C6F5 substituent

“…17,23 We are interested in the chemistry of metal amides, especially the synthesis and reaction chemistry of amido complexes of divalent 3d metals and lanthanide metals. [29][30][31][32][33] Earlier, we have reported on the chemistry of a few Fe(II) and Co(II) complexes supported by the monodentate N-silylated and N-alkylated arylamido system [N(R)(C 6 H 3 R′ 2 -2,6)] − (R = SiMe 3 , CH 2 Bu t ; R′ = Me, Pr i ). 32 It was noted that minor modifications in the steric and electronic properties of the R and R′ substituents in this system can change the metal-ligand stoichiometry of the corresponding metal amides.…”