Half-Sandwich Alkyl, Amido, and Iodo Samarium(II) Complexes: Non-Conventional Sterically Governed Oxidation of (tBu4Carb)2Sm

π-Carbazolyl supported bis(alkyl) complexes of Sc, Y and La for α-olefin polymerization and hydrogenation

A series of new half-sandwich bis(alkyl) rare-earth metal complexes coordinated by a sterically demanding 1,3,6,8-tetra-tert-butyl-carbazol-9-yl ligand [tBu₄Carb]La(CH₂C₆H₅)₂(THF) (1-La), [tBu₄Carb]Ln(o-NMe₂C₆H₄CH₂)₂ (Ln = Sc (2-Sc), Y (2-Y), La (2-La), [tBu₄Carb]Ln(CH₂SiMe₃)₂(THF) (Ln = Sc (3-Sc), Y (3-Y)), were synthesized. 1-La, 2-La, and 2-Y were prepared by an alkane elimination protocol, while 2-Sc, 3-Sc, and 3-Y became accessible only when salt metathesis reactions of tBu₄CarbK with R₂Ln(THF)_n⁺[BPh₄]^- were employed. X-ray analysis revealed that in all complexes the carbazolyl ligand exhibits π-coordination with metal ions. 2-Sc and 3-Sc when activated with [Ph₃C][B(C₆F₅)₄] demonstrate excellent activity in α-olefin (octene-1, nonene-1, decene-1 and 1,1-diphenyl-but-1-ene) polymerization. When H₂ was used as a chain transfer agent (1 bar, rt) in the presence of 3-Sc/[Ph₃C][B(C₆F₅)₄] or 2-Y, 2-La olefin hydrogenation occurred with quantitative conversion.

Ln(ii) alkyl complexes: from elusive exotics to catalytic applications

The synthesis, structures and reactivity of isolable Ln^II (Ln = Sm, Eu, Yb) alkyl complexes are discussed. The application of Ln^II alkyl derivatives in a variety of catalytic reactions is considered as well.

Samarium(II) Monoalkyl Complex Supported by a β-Diketiminato-Based Tetradentate Ligand: Synthesis, Structure, and Catalytic Hydrosilylation of Internal Alkynes

The synthesis and catalytic applications of trivalent rare-earth metal alkyl complexes have been well developed, but the chemistry of divalent rare-earth metal alkyl complexes lagged much behind. Herein, we report the synthesis, structure, and catalytic applications of a samarium(II) monoalkyl complex supported by a β-diketiminato-based tetradentate ligand, [LSmCH(SiMe₃ )₂ ] (L=[MeC(NDipp)CHC(Me)NCH₂ CH₂ N(Me)CH₂ CH₂ NMe₂ ]^- , Dipp=2,6-(iPr)₂ C₆ H₃ ). This complex is synthesized by the salt metathesis reaction of samarium iodide [LSm(μ-I)]₂ and KCH(SiMe₃ )₂ in 63 % yield. Its structure is characterized by single-crystal X-ray diffraction, showing a distorted square-pyramid coordination geometry. This samarium(II) monoalkyl complex exhibits high catalytic activity in the hydrosilylation of aryl and methyl-substituted unsymmetrical internal alkynes with secondary hydrosilanes, selectively providing the α-(E) products in high yields.

Thermally Stable Ln(II) and Ca(II) Bis(benzhydryl) Complexes: Excellent Precatalysts for Intermolecular Hydrophosphination of C-C Multiple Bonds

A series of Ln(II) and Ca(II) bis(alkyl) complexes with bulky benzhydryl ligands, [( p- tBu-C₆H₄)₂CH]₂M(L _n) (M = Sm, L = DME, n = 2 (1); M = Sm, Yb, Ca, L = TMEDA, n = 1 (2, 3, 4), were synthesized by the salt-metathesis reaction of MI₂(THF) _n ( n = 0-2) and [( p- tBu-C₆H₄)₂CH]^-Na⁺. In complex 1, the benzhydryl ligands are bound to the metal center in η²-coordination mode. Unlike complex 1, in isomorphous complexes 3 and 4, due to the coordination unsaturation of the metal center, the both benzhydryl ligands coordinate to the metal in η³-fashion. In complex 2, one ligand is η³-coordinated while the second one is η⁴-coordinated to the Sm(II) ion. Complexes 2-4 demonstrated unprecedented thermal stability: no evidence of decomposition was observed after heating their solutions in C₆D₆ at 100 °C during 72 h. Complex 1 behaves differently: thermolysis in C₆D₆ solution at 75 °C results in total decomposition in 8 h. Addition of DME promotes decomposition of 2-4 and makes it feasible at 40 °C. Complexes 1-4 demonstrated high catalytic activity and excellent regio- and chemoselectivities in intermolecular hydrophosphination of double and triple C-C bonds with both primary and secondary phosphines. Complexes 2 and 3 enable addition of PhPH₂ toward the internal C═C bond of Z- and E-stilbenes with 100% conversion under mild conditions. Double sequential hydrophosphination of phenylacetylene with Ph₂PH and PhPH₂ was realized due to the application of Yb(II) complex as a catalyst.