Dehydrosilylation of ArNHSiH3 with Ytterbium(II) Amide: Formation of a Dimeric Ytterbium(II) Silanimine Complex

Rare-Earth-Catalyzed Hydrosilylation and Dehydrogenative Coupling of Hydrosilanes

Activation of Si–H bonds with rare-earth complexes could generate the highly reactive rare-earth hydrides or silyl complexes, which are key intermediates for hydrosilylation and cross-coupling reactions. This Account summarizes the recent advances in the rare-earth-catalyzed hydrosilylation of unsaturated substrates and dehydrogenative coupling of hydrosilanes with amines in our laboratory. The results demonstrated that rare-earth catalysts are unique in their reactivity and selectivity, enabling some unprecedented reactions.

1 Introduction

2 Dehydrogenative Coupling of Hydrosilanes with Amines

3 Catalytic Dehydrogenative Coupling of Hydrosilanes with Amines

4 Catalytic Hydrosilylation of Terminal Alkenes and Polymerization of Styrene

5 Catalytic Hydrosilylation of Internal Alkenes

6 Catalytic Dihydrosilylation of Internal Alkynes

7 Conclusions and Outlook

Using Functionalized Silyl Ligands To Suppress Solvent Coordination to Silyl Lanthanide(II) Complexes

The reaction of the potassium 1,3-trisilanediide Me₂Si[Si(Me₃Si)₂K]₂ with SmI₂ and YbI₂ was found to give the respective disilylated complexes Me₂Si[Si(Me₃Si)₂]₂Sm·2THF and Me₂Si[Si(Me₃Si)₂]₂Yb·2THF. Desolvation of coordinated solvent molecules in these complexes made their handling difficult. However, using a number of functionalized silanide ligands, complexes with a diminished number or even no coordinated solvent molecules were obtained ((R₃Si)₂Ln(THF)_x (x = 0–3)). The structures of all new lanthanide compounds were determined by X-ray single-crystal structure analysis. NMR spectroscopic analysis of some Yb–silyl complexes pointed at highly ionic interactions between the silyl ligands and the lanthanides. This bonding picture was supported by DFT calculations at the B3PW91/Basis1 level of theory. Detailed theoretical analysis of a disilylated Eu(II) complex suggests that its singly occupied molecular orbitals (SOMOs) are very close in energy to the ligand silicon lone pairs (HOMO), and SQUID magnetometry measurements of the complex showed a deviation from the expected behavior for a free Eu(II) ion, which might be due to a ligand–metal interaction.

Utilizing a number of functionalized silanides, disilylated Ln(II) complexes with a diminished number or even no coordinated solvent molecules were obtained.

Synthesis of divalent ytterbium terphenylamide and catalytic application for regioselective hydrosilylation of alkenes

Divalent ytterbium terphenylamide exhibited high regioselectivity and activity in the hydrosilylation of alkenes with low catalyst loadings.

Neutral "Cp-Free" Silyl-Lanthanide(II) Complexes: Synthesis, Structure, and Bonding Analysis

Complexes featuring lanthanide silicon bonds represent a research area still in its infancy. Herein, we report a series of Cp-free lanthanide (+II) complexes bearing σ-bonded silyl ligands. By reactions of LnI₂ (Ln = Yb, Eu, Sm) either with a 1,4-oligosilanyl dianion [K-Si(SiMe₃)₂SiMe₂SiMe₂Si(SiMe₃)₂-K)] (1) or with 2 (Me₃Si)₃SiK (3) the corresponding neutral metallacyclopentasilanes ({Me₂Si(Me₃Si)₂Si}₂)Ln·(THF)₄ (Ln = Yb (2a), Eu (2b), Sm (2c)), or the disilylated complexes ({Me₃Si}₃Si)₂Ln·(THF)₃ (Ln = Yb (4a), Eu (4b), Sm (4c)), were selectively obtained. Complexes 2b, 2c, 4b, and 4c represent the first examples of structurally characterized Cp-free Eu and Sm complexes with silyl ligands. In both series, a linear correlation was observed between the Ln–Si bond lengths and the covalent radii of the corresponding lanthanide metals. Density functional theory calculations were also carried out for complexes 2a–c and 4a–c to elucidate the bonding situation between the Ln(+II) centers and Si.

By reactions of LnI₂ (Ln = Yb, Eu, Sm) with oligosilanyl anions or dianions, either neutral disilylated complexes or metallacyclopentasilanes were obtained.

Reaction of a bulky amine borane with lanthanide trialkyls. Formation of alkyl lanthanide imide complexes

Lanthanide imidoborane complexes with terminal alkyl groups are synthesized from the reactions of simple lanthanide trialkyls with a bulky amine borane.

Multiple coupling of silanes with imido complexes of Mo

The bis(imido) complexes ((t)BuN[double bond, length as m-dash])2Mo(PMe3)(L) (L = PMe3, C2H4) react with up to three equivalents of silane PhSiH3 to give the imido-bridged disilyl silyl Mo(vi) complex ((t)BuN){μ-(t)BuN(SiHPh)2}Mo(H)(SiH2Ph)(PMe3)2 (3) studied by NMR, IR and X-ray diffraction. NMR data supported by DFT calculations show that complex 3 is an unusual example of a silyl hydride of Mo(VI), without significant SiH interaction. Mechanistic NMR studies revealed that silane addition proceeds in a stepwise manner via a series of Si-H∙∙∙M agostic and silanimine complexes whose structures were further elucidated by DFT calculations.