Synthesis and crystal structure of the organogermanium complex of ytterbium [(Ph2Ge)4Yb(THF)4]·4THF with a five-membered Ge4Yb cycle

[(thf)5Ln(Ge9{Si(SiMe3)3}2)] (Ln = Eu, Sm, Yb): Capping Metalloid Germanium Cluster with Lanthanides

We report the synthesis of three neutral complexes with different coordination modes of a di-silylated metalloid germanium cluster to divalent lanthanides [(thf)₅Ln(ηⁿ-Ge₉(Hyp)₂)] (Ln = Yb (1, n = 1); Eu (2, n = 2, 3), Sm (3, n = 2, 3); Hyp = Si(SiMe₃)₃) by the salt metathesis of LnI₂ with K₂[Ge₉(Hyp)₂] in THF. The complexes were characterized by elemental analysis, nuclear magnetic resonance and UV-vis-NIR spectroscopy, and single-crystal X-ray diffraction. In thf solution, the formation of contact or solvate-separated ion pairs depending on the concentration is assumed. Compound 2 exhibits a blue luminescence typical for Eu²⁺. The solid-state magnetic measurements of compounds 2 and 3 confirm the presence of divalent europium and samarium, respectively.

Bonding analysis in ytterbium(II) distannyl and related tetryls

The syntheses of the ytterbium(II) distannyl [Yb{Sn(SiMe₃)₃}₂·(thf)₄] (Yb-Sn) and of its digermyl analogue [Yb{Ge(SiMe₃)₃}₂·(thf)₃] (Yb-Ge) are presented. The compounds were characterised by multinuclear high-resolution solution NMR spectroscopy, including ¹⁷¹Yb NMR, and by X-ray diffraction crystallography. The bonding and electronic properties of the two complexes, along with those of the known ytterbium(II) disilyl derivative [Yb{Si(SiMe₃)₃}₂·(thf)₃] (Yb-Si) and those of the congeneric calcium distannyl [Ca{Sn(SiMe₃)₃}₂·(thf)₄] (Ca-Sn), were investigated in detail by DFT calculations. This analysis points at a primarily ionic Yb-tetrel bonding, with a small covalent contribution, attributed principally to the 5d(Yb) participation. This weak covalent character is found to be larger for the distannyl Yb-Sn than for its lighter Si- and Ge-derivatives. The covalent component is also found to be greater in Yb-Sn than in Ca-Sn, due to the availability of the 5d(Yb) orbitals for bonding.

(thf)2Ln(Ge9{Si(SiMe3)3}3)2 (Ln = Eu, Sm): the first coordination of metalloid germanium clusters to lanthanides

We report the synthesis, structure and magnetic properties of the first rare earth complexes of metalloid group 14 clusters [(thf)2Ln(Ge9Hyp3)2] (Ln = Eu, Sm, Hyp = Si(SiMe3)3). X-Ray crystallographic analysis and DFT calculations reveal a novel η2-coordination mode of the Ge9Hyp3 units and a slight distortion of the Ge9 cage.

Yttrium germole dianion complexes with Y-Ge bonds

The reactions of dipotassium 3,4-dimethyl-2,5-bis(trimethylsilyl)-germole dianion K2[1] with YCl3 and Cp*YCl2 (Cp* = cyclopentadienyl) in THF at room temperature afforded the dianion salt [(K-cryptand-222)2][1-YCl3] (K2[2]) and the dimeric complex [1-Y-Cp*]2 (3), respectively. While the polymeric complex {[(1)2-Y-K(toluene)]2}n (4) was obtained from the reaction of K2[1] and half molar equivalent of YCl3(THF)3.5 in toluene at 80 °C. The germole dianions in complexes 3 and 4 feature η5/η1 coordination interactions with the yttrium atoms. They represent the first examples of rare earth (RE) complexes containing RE-Ge bonds other than the RE-GeR3 structural type.

f-Element silicon and heavy tetrel chemistry

The last three decades have seen a significant increase in the number of reports of f-element carbon chemistry, whilst the f-element chemistry of silicon, germanium, tin, and lead remain underdeveloped in comparison. Here, in this perspective we review complexes that contain chemical bonds between f-elements and silicon or the heavier tetrels since the birth of this field in 1985 to present day, with the intention of inspiring researchers to contribute to its development and explore the opportunities that it presents. For the purposes of this perspective, f-elements include lanthanides, actinides and group 3 metals. We focus on complexes that have been structurally authenticated by single-crystal X-ray diffraction, and horizon-scan for future opportunities and targets in the area.

Dysprosium complexes bearing unsupported DyIII-GeII/SnII metal-metal bonds as single-ion magnets

Two dysprosium complexes bearing unsupported Dy-Ge/Sn metal-metal bonds are reported here, wherein the Dy-Ge and Dy-Sn bonds both contain relatively large covalency. The complexes exhibit slow relaxation of magnetization at zero field with energy barriers of 485 and 620 K, respectively, and the blocking temperature of 6 K.

Non-traditional ligands in f-block chemistry

The molecular chemistry of the f-elements, i.e. the lanthanides and actinides, is traditionally dominated by the use of carbon, nitrogen, oxygen or halide ligands. However, the use of metal-based fragments as ligands is underdeveloped, which contrasts to the field of d-block metal–metal complexes that have developed extensively over the last 50 years. Consequently, the use of metal-based fragments as ligands to the f-elements may be regarded as ‘non-traditional’. This review outlines the development of compounds that possess f-element–metal bonds that may be described as polarized covalent or donor–acceptor in nature. For this review, the f-element is defined as (i) a group 3 or lanthanide metal: scandium, yttrium and lanthanum to lutetium or (ii) an actinide metal: thorium or uranium, and the metal is defined as a d-block transition metal, or a p-block triel (group 13, aluminium or gallium), a tetrel (group 14, silicon, germanium or tin), or a pnictide (group 15, antimony or bismuth) metal. Silicon, germanium and antimony are traditionally classified as metalloids, but we include them in this review for completeness. This review focuses on complexes that have been unambiguously structurally authenticated by single crystal X-ray diffraction studies, and novel aspects of their syntheses, properties and reactivities are highlighted.

Synthesis and structural characterization of Sm(II) and Yb(II) complexes containing sterically demanding, chelating secondary phosphide ligands

Metathesis between [(Me3Si)2CH)(C6H4-2-OMe)P]K and SmI2(THF)2 in THF yields [([Me3Si]2CH)(C6H4-2-OMe)P)2Sm(DME)(THF)] (1), after recrystallization. A similar reaction between [(Me3Si)2CH)(C6H3-2-OMe-3-Me)P]K and SmI2(THF)2 yields [([Me3Si]2CH)(C6H3-2-OMe-3-Me)P)2Sm(DME)].Et2O (2), while reaction between [(Me3Si)2CH)(C6H4-2-CH2NMe2)P]K and either SmI2(THF)2 or YbI2 yields the five-coordinate complex [([Me3Si]2CH)(C6H4-2-CH2NMe2)P)2Sm(THF)] (3) or the solvent-free complex [([Me3Si]2CH)(C6H4-2-CH2NMe2)P)2Yb] (4), respectively. X-ray crystallography shows that complex 2 adopts a distorted cis octahedral geometry, while complex 1 adopts a distorted pentagonal bipyramidal geometry (1, triclinic, P1, a = 11.0625(9) A, b = 15.924(6) A, c = 17.2104(14) A, alpha = 72.327(2) degrees, beta = 83.934(2) degrees, gamma = 79.556(2) degrees, Z = 2; 2, monoclinic, P2(1), a = 13.176(4) A, b = 13.080(4) A, c = 14.546(4) A, beta = 95.363(6) degrees, Z = 2). Complex 3 crystallizes as monomers with a square pyramidal geometry at Sm and exhibits short contacts between Sm and the ipso-carbon atoms of the ligands (3, monoclinic, C2/c, a = 14.9880(17) A, b = 13.0528(15) A, c = 24.330(3) A, beta = 104.507(2) degrees, Z = 4). Whereas preliminary X-ray crystallographic data for 4 indicate a monomeric structure in the solid state, variable-temperature 1H, 13C(1H), 31P(1H), and 171Yb NMR spectroscopies suggest that 4 undergoes an unusual dynamic process in solution, which is ascribed to a monomer-dimer equilibrium in which exchange of the bridging and terminal phosphide groups may be frozen out at low temperature.