Rare-earth silylamides of type [Ln{N(SiHMe 2 ) 2 } 3 (thf) x ] (Ln = Sc, Y, La, Nd, Er or Lu) have been prepared in high yield by reaction of 2.9 equivalents of Li[N(SiHMe 2 ) 2 ] with [LnCl 3 (thf) x ] in n-hexane or thf, depending on the solubility of the rare-earth halide precursor. The complexes [Ln{N(SiHMe 2 ) 2 } 3 (thf) 2 ] (Ln = Y, La to Lu) are isostructural in the solid state, adopting the preferred (3 ϩ 2, distorted) trigonal bipyramidal geometry, whilst [Sc{N(SiHMe 2 ) 2 } 3 (thf)] has a distorted tetrahedral co-ordination geometry and short Sc ؒ ؒ ؒ Si contacts in the solid state. The reaction of [Y{N(SiHMe 2 ) 2 } 3 (thf) 2 ] with varying amounts of AlMe 3 resulted in desolvation and alkylation with formation of AlMe 3 (thf), {AlMe 2 [µ-N(SiHMe 2 ] 2 } 2 and heterobimetallic (Y/Al) species. The generation of surface-bonded '(᎐ ᎐ ᎐ SiO) x Y[N(SiHMe 2 ) 2 ] y ' and '᎐ ᎐ ᎐ SiOSiHMe 2 ' moieties via the grafting of [Y{N(SiHMe 2 ) 2 } 3 (thf) 2 ] onto the mesoporous silicate MCM-41 is described in detail. Consideration is given to the factors governing the siloxide formation and silylation reactions, and the thermal stability of the surface species.Rare-earth amides, and in particular silylamides, 1 are of potential relevance in catalysis 2 and the material sciences. 3 Furthermore, the synthetic versatility of the Ln᎐N(SiMe 3 ) 2 moiety is well established in amine elimination reactions known as the silylamide route (Scheme 1). 1,4 Rare-earth amides are also capable of alkylation reactions via Lewis acid-base derived heterobimetallic species. 5,6 Advantages of the Ln᎐N(SiMe 3 ) 2 -based silylamide route are (i) facile availability of mono-and heterobi-metallic amide precursors, (ii) favourable (mild) reaction conditions including non-co-ordinating solvents, ambient temperature, smooth work-up procedures and 'quantitative' yield, (iii) avoidance of halide contamination and (iv) donor ligand-free products due to the weak donor capability of the released silylamine. 1 Complexes [Ln{N(SiHMe 2 ) 2 } 3 (thf) 2 ] derived from the sterically less bulky bis(dimethylsilyl)-amide ligand were introduced better to cope with the steric requirements of catalytically relevant, bulky and chelating ancillary ligands such as salen or linked cyclopentadienyl derivatives. 7 We report here a detailed synthetic and structural examination of these versatile synthetic building blocks. In addition, AlMe 3 -directed desolvation and alkylation reactions are discussed.Very recently, we found that many features of the homogeneously performed silylamide route can be transferred to a heterogeneous medium (Scheme 1). 8 Such a supramolecular approach allowed the grafting of rare-earth silylamide complexes onto a mesoporous aluminosilicate of type MCM-41 9,10 via surface organometallic chemistry. 11 The presence of 'Si᎐H' as a spectroscopic probe helped to unravel the chemical anchoring of the silylamides which proceeds via siloxide formation and silylation reactions. In this work more light will be shed on the surface organometallic chem...
The synthesis and X-ray crystal structures of Y[N(SiHMe2)2]3(carbene) x (carbene = 1,3-dimethylimidazolin-2-ylidene, x = 1, 2) are described. The donor capability of the strongly nucleophilic carbene ligand is expressed in both the displacement of two THF ligands by one carbene ligand in precursor compound Y[N(SiHMe2)2]3(THF)2 and by the addition of a second carbene ligand to yield the preferred (3 + 2) trigonal bipyramidal coordination geometry. In particular, the structural data reveal that the carbene ligands affect the coordination mode of the bis(dimethylsilyl)amide counterligands by forcing them to form close β-Si−H(silylamide)−yttrium agostic contacts. According to Pearson's terminology such carbene ligands have to be classified as hard donor ligands.
Since the fundamental works of D. C. Bradley and R. C. Mehrotra, metal alkoxides have attracted attention because of' tho diversity of their low-and high-molecular-weight structures; they are also generating increasing interest as precursor compounds for solving technical materiak problems. The understanding of the hydrolytic nucleation behavior is a prerequisite for the optimization of materials from sol --gel processes. For metal alkoxides to be precursors in chemical vapor deposition (CVD) processes in the preparation of inorganic oxidic materials, they should be strfficiently volatile, and sublimation should occur without decomposition at as low a temperature as possible ( < 150 'C). Only recently,using the "donor functionalization" concept, was a ligand type systematically developed that unifies the advantages of both steric demands and o-donor stabilization and so stabilizes low-molecularweight metal alkoxides. Even large metal ions of low charge (for example Ba") can thus form volatile alkoxides. 0-and N-donor functions in bidentate and multidentate alkoxo ligands are particularly advantageous; hence, for example, the vanadium derivative [V(OCMe,CH20Me),] is one of the most volatile metal alkoxides known to date. The first alkoxides of the alkaline earth metals calcium, strontium. and barium, which sublime without decomposition. have the formula [M,{OC(CHZOiPr),tBu),l. This article presents a critical inventory of the metal alkoxides with particular regard to the aspect of volatility. It also describes successes of the donor functionalization concept and shows-in perspective-how alkoxo ligands can be "tailor made" for metals according to their charge-toradius ratio by further development of the concept.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.