ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2010, Vol. 36, No. 5, pp. 330–332. © Pleiades Publishing, Ltd., 2010. Original Russian Text © L.A. Aslanov, V.N. Zakharov, M.A. Zakharov, A.L. Kamyshny, Sh. Magdassi, A.V. Yatsenko, 2010, published in Koordinatsionnaya Khimiya, 2010, Vol. 36, No. 5, pp. 330–332. 330 Silicon clusters of size 1 to 5 nm (so-called nanosil- icon NS) show properties that are of interest for opto- electronics, manufacture of high-efficiency solar cells, and design of new protein, DNA, and virus markers in medicine and for other purposes [1]. Nanosilicon is produced by destruction of large sil- icon crystals or from silicon compounds but in any case, stabilization of NS is needed, as nanoparticles are readily agglomerated, oxidized with oxygen, and react with air moisture. The NS particles are stabilized by hydrogen to give silane groups on the nanoparticle surface [1], by alkoxyl or alkyl ligands [2–8], or by implanting them into SiO 2 . Stabilization by alkyl ligands has a number of advantages: it does not change with time as compared with hydrogen stabilization and gives products that are easily dispersed in organic sol- vents. Alkyl ligands surround the silicon nanoparticles by a thin layer unlike rather thick and dense SiO 2 lay- ers. The preparation of NS by destruction of large crys- tals of silicon or using silicon chemical compounds is accompanied by the formation of a large bulk of sili- con particles larger than 5 nm, which are of no use for the indicated purposes, i.e., the silicon-containing raw material is used inefficiently. Therefore, a topical task is to restrict the nanoparticle size to within 1–5 nm, which is needed for practical use. It is known [9] that carbene ligands based on 1,3-dialkyl(diaryl)imidazol- 2-ylidenes create steric hindrance for crystal growth and restrict their size. The purpose of this work is to test the effect of steric restrictions produced by carbenes diring the formation of NS particles on the particle size. As carbenes, imi- dazol-2-ylidene (I-2-I) derivatives with different sub- stituents were employed. EXPERIMENTAL Synthesis of NS. The complexation of NS with car- benes can be represented by the following scheme: R 1 , R 2 -I-2-I were prepared by the reduction of alkylmethylimidazolium with active metals (sodium, magnesium, zinc). A Schlenk vessel with a reflux con- denser and a calcium chloride tube was prefilled with argon; the synthesis and sampling were carried out in an argon flow. The experiments were carried out at 110°С or at room temperature. The reaction mixture was vigorously magnetically stirred. a) Stabilization of NS by I-2-I derivatives. Dried solvent, xylene or diglyme (7–12 ml); an ionic liquid, 1,3-dimethylimidazolium iodide (MmimI), 1-butyl- 3-methylimidazolium bromide or 1-decyl-3-meth- ylimidazolium bromide, prepared as described previ- ously [10] (2.3–8.7 mmol); Na (20.2 mmol) or Mg, Zn (9.2 mmol); and SiBr 4 (4.0 mmol) were placed in the reactor. The reaction was performed at 110°С for 1–2 h or at room temperature for 24 h. b) Stabilization of NS by alkyl groups. A solvent, diglyme, toluene, or octane (8–15 ml); silicon tetra- halide, most often SiBr 4 (4–6.6 mmol); MeSiHal 3 , (Me) 2 SiHal 2 , (Me) 3 SiHal, or (Et) 2 SiHal 2 (9.2– 16.0 mmol); sodium in 10% excess (8.8–14.5 mmol) or zinc (magnesium) (7.5 mmol) in different disperse states (bits, metal drops pre-dispersed in a solvent, dust, or chips) were added to the reactor. The reaction was carried out at 110°С 1 for 1.5–2 h and then the setup was cooled. At room temperature, the reaction N CH N R R N C : N R R N C N R R 1 1 1 2 2 2 + +M, +SiBr 4 –M + , –H 2 , –Br – Si R 1 , R 2 -I-2-I Stabilization of Silicon Nanoparticles by Carbenes L. A. Aslanov a, *, V. N. Zakharov a , M. A. Zakharov a , A. L. Kamyshny b , Sh. Magdassi b , and A. V. Yatsenko a a Moscow State University, Vorob’evy gory, Moscow, 119899 Russia b Casali Institute of Applied Chemistry, The Hebrew University, Israel E-mail: aslanov@struct.chem.msu.ru Received September 23, 2009 Abstract—Sodium reduction of a mixture of tetrabromosilane with imidazole ionic liquids in organic sol- vents gives dispersions of silicon nanoparticles stabilized by carbene ligands. It was shown that the size of sil- icon nanoclusters depends on the size of substituents at nitrogen atoms of 1,3-dialkylimidazol-2-ylidenes. DOI: 10.1134/S1070328410050027