Metal-bridging vs. chelating Me2Si(C5H4)2 ligands in dinuclear complexes

Dehydrogenative Coupling of Terminal Alkynes with O/N-Based Monohydrosilanes Catalyzed by Rare-Earth Metal Complexes

Newly synthesized rare-earth metal alkyl complexes bearing a tripyrrolyl ligand act as excellent precatalysts for the cross-dehydrogenative coupling between various terminal alkynes and O/N-based monohydrosilanes of HSi(OEt)₃/HSi(NMe₂)₃, leading to the formation of a variety of alkoxysilylalkyne and aminosilylalkyne derivatives in good to high yields. The precatalysts LRE(CH₂SiMe₃)(thf)₂ (RE = Y(1a), Er(1b), Yb(1c), L = 2,5-[(2-C₄H₃N)CPh₂]₂(C₄H₂NMe), thf = tetrahydrofuran) were easily prepared in high yields via the reactions of RE(CH₂SiMe₃)₃(thf)₂ with the proligand H₂L in a single step. Mechanistic studies reveal that treatment of 1 with phenylacetylene could generate the active catalytic species: dinuclear rare-earth metal alkynides (L(thf)_n[RE(μ-C≡CPh)]₂L) (RE = Y(5a), n = 1; Yb(5c), n = 0), which could react with HSi(OEt)₃ to produce the coupling product 4aa and the dinuclear rare-earth metal hydrides (L (thf)[RE(μ-H)]₂L) (RE = Y(6a); Yb(6c)). By contrast, prior treatment of 1c with HSi(OEt)₃ proceeds via cleavage of the Si-O bond to produce the dinuclear ytterbium alkoxide (LYb(μ-OEt))₂ 7c, which is inert in the dehydrogenative coupling reaction. The results of the mechanistic studies are consistent with the observation that the reaction is greatly influenced by the addition sequence of precatalyst/alkynes/silanes.

Rare-earth metal hydrides supported by silicon-bridged boratabenzene fluorenyl ligands: synthesis, structure and reactivity

The first boratabenzene derivatives of rare-earth metal hydrides were synthesized, and their reactivity was studied.

Bridged Aminotroponiminate Complexes of Lanthanum

The reaction of the new ligand 1,3-di(2-(N-isopropylamino)troponimine)propane, H(2)[(iPr)TP], with KH affords K(2)[(iPr)TP]. The salt of this new ligand is a useful starting material for the preparation of the lanthanum compounds [[(iPr)TP](3)La(2)(THF)](2) and [[(iPr)TP]LaCl(THF)](2), respectively. These metal complexes were characterized by NMR and X-ray crystallography. In contrast to macrocyclic ligands the [(iPr)TP](2)(-) anion shows a higher flexibility upon coordination and features two different coordination modes. Further reaction of [[(iPr)TP]LaCl(THF)](2) with 2 equiv of LiCH(SiMe(3))(2) or KN(SiMe(3))(2) in toluene affords the alkyl or amide derivatives [[(iPr)TP](2)LaE(SiMe(3))(2)] (E = CH, N) in high yield. Crystal data: [[(iPr)TP](3)La(2)(THF)](2), space group P2(1)/c, a = 19.860(2) Å, b = 17.691(3) Å, c = 21.333(3) Å, beta = 102.211(8) degrees, Z = 4, V = 7325.8 Å(3); [[(iPr)TP]LaCl(THF)](2), space group P2(1)/n, a = 12.848(3) Å, b = 32.902(7) Å, c = 16.215(3) Å, beta = 110.38(3) degrees, Z = 4, V = 6425(2) Å(3).