Kuburat Saliu

A Rare‐Earth Metal Variant of the Tebbe Reagent

Tebbe reagent [Cp2Ti{(m-CH2)(m-Cl)Al(CH3)2}] (A ; Cp = cyclopentadienyl) belongs to the most enigmatic organometallic compounds. Its successful synthesis, resulting from the careful investigation of the reaction of [Cp2TiCl2] with two equivalents Al(CH3)3, was triggered by important discoveries in two fundamentally different areas of homogeneous catalysis. Indeed, the initial studies of methane (and methylidene) formation from [Cp2TiCl2]/Al(CH3)3 mixtures were conducted in the context of Ziegler–Natta polymerization catalysis, but the methylene unit was structurally characterized by X-ray crystallography for the first time in tantalum alkylidene complexes, such as [Cp2Ta(CH2)(CH3)], [3] and tungsten methylene compounds, related to proposed catalysts for olefin metathesis. Although catalytically active in olefin metathesis, the Tebbe reagent is currently used for efficient carbonyl methylenation reactions. In his initial studies, Tebbe also commented on the synthesis of the structurally similar all-methyl derivative [Cp2Ti{(m-CH2)(m-CH3)Al(CH3)2}] (B) from the labile [Cp2Ti(CH3)2] and Al(CH3)3, suggesting [Cp2Ti(CH3)2{Al(CH3)3}] (B ) as a stabilized intermediate. Although the structures of the bis(neopentyl) derivative [Cp2Ti{(m-CH2)(m-Cl)Al(CH2C(CH3)3)2}] [7] and a zirconium analogue [Cp2Zr{(m-CHCH2C(CH3)3)(m-Cl)Al(CH2CH(CH3)2)2}] [8] have been reported, there are no X-ray structures of the Tebbe reagent nor of discrete metallacycles of the type [M(m-CH2)(m-R)Al(CH3)2] (R = Cl, CH3). [9, 10] Previous studies from our laboratories on rare-earthmetal(III) tetramethylaluminate complexes [LxLn{Al(CH3)4}y] (y = 1, 2, 3; x + y = 3, L = monovalent ancillary ligand, Ln = lanthanides and Sc, Y, La) as polymerization catalysts 12] led to the isolation of Ln clusters with methylene, 14] methine, and carbide functionalities. We also found that complex [Cp*3Y3(m-Cl)3(m3-Cl)(m3-CH2)(thf)3] (Cp* = C5(CH3)5) displayed Tebbe-like reactivity. [13]

Crystal structure of tri­benzyl­bis­(tetra­hydro­furan-κO)lutetium(III)

In the compound [Lu(C7H7)3(C4H8O)2], the Lu ion is coordinated by three benzyl and two tetrahydrofuran ligands. Two of the benzyl groups are bonded in a classical η1-fashion through the methylene via the ipso-carbon atom of the benzyl ligand in addition to bonding through the methylene C atom, resulting in a modified trigonal–bipyramidal coordination geometry about the Lu center.

Bis[tris(3-tert-butyl-5-methyl­pyrazol-1-yl)hydridoborato]ytterbium(II) toluene solvate

In the title compound, [Yb(C24H40BN6)2]·C7H8, the Yb atom is coordinated by two tris(3-tert-butyl-5-methylpyrazol-1-yl)hydridoborate [TptBu,Me] ligands. One ligand binds in the κ3 mode, throuh three N atoms of the pyrazolyl rings, the other ligand coordinates through two N atoms of the pyrazolyl rings and the H atom attached to the central B via an agostic-type interaction through the B—H group of the second TptBu,Me ligand, giving an overall distorted octahedral geometry. One of the tert-butyl groups is disordered over two sites, with occupancies of 0.65 and 0.35.