Synthesis and Structure of Cyclic Aluminum Disiloxides

Synthesis and Reactivity of Aluminum Disilacyclopropenes. Cyclic AlSi2 Delocalized 2π Systems

The synthesis, structures, and reactivity of the first unsaturated AlSi2 three-membered ring systems were described. Reactions of dilithiodisilene [(NHB)LiSi═SiLi(NHB)] (1, NHB = diazaborolyl) with aluminum halides AlCl3, Ar(SiMe3)NAlCl2 (Ar = 2,6-iPr2C6H3), Cp*AlBr2 (Cp* = C5Me5), and TipAlBr2·Et2O (Tip = 2,4,6-iPr3C6H2) led to the formation of AlSi2 three-membered ring species, solvated (NHBSi)2AlCl(OEt2) (2) and solvent-free (NHBSi)2AlN(SiMe3) Ar (3), (NHBSi)2AlCp* (4), and (NHBSi)2AlTip (5), in good yields. X-ray diffraction studies and DFT calculations disclosed delocalized AlSi2 2π electron systems. Methanolysis of 4a resulted in cleavage of the Al-Si σ and Si-Si π bonds, giving trihydrodisilane (NHB)H(MeO)SiSiH2 (NHB) (6). Reaction of 4b with 4 equiv of N2O and H2C═CH2 resulted in the insertion of four oxygen atoms and four H2C═CH2 π bonds into all of the Al-Si and Si-Si bonds, yielding the O- and CH2CH2-bridged polycyclic species 7 and 8, demonstrating the synergistic reactivity of the Al-Si and Si-Si bonds in the AlSi2 ring system.

Alternative aluminum-based cocatalysts for the iron-catalyzed oligomerization of ethylene

Multinuclear aluminum cocatalysts have been obtained by the reaction of various phenols, alcohols or diols with trimethylaluminum and were used in situ or as isolated, well-defined species, for the activation of an iron(ii) or an iron(iii) pre-catalyst for the oligomerization of ethylene.

Heterometallic europium disiloxanediolates: synthesis, structural diversity, and photoluminescence properties

This contribution presents a full account of a structurally diverse class of heterometallic europium disiloxanediolates. The synthetic protocol involves in situ metalation of (HO)SiPh2OSiPh2(OH) (1) with either (n)BuLi or KN(SiMe3)2 followed by treatment with EuCl3 in suitable solvents such as 1,2-dimethoxyethane (DME) or tetrahydrofuran (THF). Reaction of EuCl3 with 2 equiv of (LiO)SiPh2OSiPh2(OLi) in DME afforded the Eu(III) bis(disiloxanediolate) "ate" complex [{(Ph2SiO)2O}2{Li(DME)}3]EuCl2 (2), which upon attempted reduction with Zn gave the tris(disiloxanediolate) [{(Ph2SiO)2O}3{Li(DME)}3]Eu (3). Treatment of EuCl3 with (LiO)SiPh2OSiPh2(OLi) in a molar ratio of 1:2 yielded both the ate complex [{(Ph2SiO)2O}3Li{Li(THF)2}{Li(THF)}]EuCl·Li(THF)3 (4) and the LiCl-free europium(III) complex [{(Ph2SiO)2O}2{Li(THF)2}2]EuCl (5). Compound 5 was found to exhibit a brilliant red triboluminescence. When (KO)SiPh2OSiPh2(OK) was used as starting material in a 3:1 reaction with EuCl3, the Eu(III) tris(disiloxanediolate) [{(Ph2SiO)2O}3{K(DME)}3]Eu (6) was isolated. Attempted ligand transfer between 5 and (DAD(Dipp))2Ba(DME) (DAD(Dipp) = N,N'-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene) afforded the unique mixed-valent Eu(III)/Eu(II) disiloxanediolate cluster [(Ph2SiO)2O]6Eu(II)4Eu(III)2Li4O2Cl2 (7). All new complexes were structurally characterized by X-ray diffraction. Photoluminescence studies were carried out for complex 5 showing an excellent color quality, due to the strong (5)D0→(7)F2 transition, but a weak antenna effect.