Linear Heterometallic Co 3 Li 2 and Co 4 Li 2 Siloxides: Precursors for the Plasma Synthesis of Adsorbent Materials

Multinuclear Clusters of Manganese and Lithium with Silsesquioxane-Derived Ligands: Synthesis and Ligand Rearrangement by Dioxygen- and Base-Mediated Si-O Bond Cleavage

The synthesis of manganese cluster complexes templated by polyhedral oligomeric silsesquioxane-derived ligands is described. Mn^II₃(Ph₇Si₇O₁₂)₂Pyr₄ (1) and Mn^II₄(Ph₄Si₄O₈)₂(Bpy)₂(Py)₂ (3) are prepared by replacement of the amide ligands of Mn(NR₂)₂ (R = SiMe₃) via ligand protolysis by the acidic proton of the respective silsesquioxane-derived silanols. Complex 1 is shown to undergo ligand rearrangement by reaction with O₂, which results in oxidation of the cluster to a mixed Mn^II/III cluster, concomitant with cleavage of the Si-O bonds of the ligand, releasing a [Ph₂Si-O]⁺ unit, opening a new ligating siloxide group, and resulting in the formation of Mn₃(Ph₆Si₆O₁₁)₂Pyr₄ (2). The ligand framework of 1 can also be perturbed by a base. The addition of LiOH/BuLi delivers a soluble equivalent of Li₂O to 1, resulting in cleavage of the Si-O bonds and linkage of the resulting exposed silicon atoms by the new oxide, giving a linked ligand variant that templates a Li₂Mn₃ cluster, Mn₃Li₂(Ph₇Si₇O₁₂OPh₇Si₇O₁₂)DMF₅Pyr (4). These systems are characterized by single-crystal X-ray diffraction, absorption spectroscopy, Fourier transform infrared, cyclic voltammetry, and CHN combustion analysis. Mechanistic implications for the Si-O bond cleavage events are discussed.

High-yield synthesis of a unique Mn(iii) siloxide complex through KMnO4 oxidation of a Mn(ii) precursor

A unique trivalent manganese siloxide complex, blue-violet Mn^IIILi₂Cl[(Ph₂SiO)₂O]₂(THF)₄·2THF (3) has been prepared by a straightforward two-step synthetic protocol. Lithiation of (Ph₂SiOH)₂O (1) followed by reaction with MnCl₂(THF)₂ gave the structurally remarkable Mn(ii) precursor Mn^IILi₄Cl₂[(Ph₂SiO)₂O]₂(THF)₅·2THF (2). Surprisingly, the final oxidation step could be achieved using KMnO₄ in THF to provide the Mn(iii) species 3 in high yield (91%). Both title compounds were structurally characterized by single-crystal X-ray diffraction.

Synthesis and structural study of new metallasilsesquioxanes of potassium and uranium

The first metallasilsesquioxanes comprising potassium and uranium have been synthesized and structurally characterized by single-crystal X-ray diffraction.

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.