Metallorganische verbindungen der lanthanoide

Unusual Complex Chemistry of Rare‐Earth Elements: Large Ionic Radii—Small Coordination Numbers

“…The yttrium atoms achieve the low coordination numbers with phosphorus atoms, which are about the same size as chloro ligands, through the steric bulk of the SiMe 3 (TMS) groups. CN=4 complexes of the type [Ln(CMe 3 ) 4 ] − , 6 with voluminous tert ‐butyl ligands, are also known, whereas the methyl ligands in [LnMe 6 ] 3− ions lead to octahedral coordination 10. Coordination numbers 8 and 9 are found in crystalline trihalides, which form bi‐ and tricapped trigonal‐prismatic coordination polyhedra 14.…”

CeCl3/n‐BuLi: Unraveling Imamoto's Organocerium Reagent

“…Homoleptic anionic tert ‐butyl complexes were previously reported for [Li(thf) x ][Ln( t ‐Bu) 4 ] (Ln=Sm, Er: x= 4; Y: x= 3), [27a] [Li(OEt 2 ) 4 ][Er( t ‐Bu) 4 ], [22c] [Li(tmeda) 2 ][Ln( t ‐Bu) 4 ] (Ln=Tb, Lu),[ 22c , 27b ] and [Li(dme) 3 ][Ln( t ‐Bu) 4 ] (Ln=Tb, Er). [27c] Crystal structures were obtained for [Li(tmeda) 2 ][Lu( t ‐Bu) 4 ] [27b] and [Li(dme) 3 ][Er( t ‐Bu) 4 ], [27c] whereas the enhanced thermal instability of derivatives of the “lighter” rare‐earth metals was pointed out. In order to test our low‐temperature set‐up for organocerium derivatives prone to β‐H elimination, [33] we targeted the anionic fragment [Ce( t ‐Bu) 4 ].…”

NMR spectroscopic study of the adduct formation and reactivity of homoleptic rare earth amides with alkali metal benzyl compounds, and the crystal structures of [Li(TMEDA)2][Nd{N(SiMe3)2}3(CH2Ph)] and [{Li(TMP)}2{Li(Ph)}]2

“…The rare earth elements, with their large ionic radii, high coordination numbers and interactions dominated by ionic bonding, also have a well-developed 'ate' chemistry producing charge separated lanthanide complexes when additional anionic ligands bind to the Ln metal centres. [20] Examples of charge-separated organometallic lanthanide 'ate' compounds include [Li(L)n][LnR4] {R = t Bu, [21][22][23] CH2SiMe3; [22,24,25] We were interested in lanthanide motifs with two different bridging atoms similar to I, because only a handful of structurally characterised examples are known (Figure 2, bottom) that show lanthanide complexes with mixed alkyl/amide bridging interactions (type II, Figure 1). [31][32][33] These include cyclometallated complexes that result from N″ ligand deprotonation, [34][35][36] such as [K][Y(N″)2{κ 2 -CH2Si(Me)2N(SiMe3)}] [30] that becomes a solvent separated ion pair when a co-ligand such as 18-crown-6 is used.…”