| العنوان: |
Synthesis and Structures of Crystalline Lithium, Sodium, Potassium, and Magnesium Silylmethyls Derived from the Ligands [CH(SiMe3){SiMe3-n(OMe)n}]- (n = 1, 2), [CH(SiMe2OMe)2]-, and [CH(SiMe3)(SiMe2Ph)]- |
| مستخلص: |
The paper deals with metal complexes of the silylmethyl ligands [CH(SiMe3){SiMe3-n(OMe)n}]- (n = 1, 2), [CH(SiMe3)(SiMe2Ph)]-, and [CH(SiMe2OMe)2]-. Treatment of the precursor alkanes with LiBut in pentane, or of CH2(SiMe3)(SiMe2OMe) with NaCH2Ph in benzene, afforded the crystalline complexes [Li{CH(SiMe3)(SiMe2OMe)}]8 (2), [Li{CH(SiMe3)(SiMe(OMe)2)}]∞ (7), [Li{CH(SiMe2OMe)2}]∞ (9), and [Na{CH(SiMe3)(SiMe2OMe)}]∞ (3), respectively. The yield of each, except 9, was almost quantitative, but (under conditions which had given 2 and 7) CH2(SiMe2OMe)2 and LiBut remarkably gave [Li{μ-C(SiMe2OMe)3}]2 (10) as the major product. The compound [K{CH(SiMe3)(SiMe2OMe)}]∞ (4) was obtained from 2 and KOBut in hexane, and addition of Et2O to 4 gave the crystalline compound [K{CH(SiMe3)(SiMe2OMe)}(OEt2)]∞ (5). The crystalline compounds [Li{(CH(SiMe3)(SiMe2Ph))(TMEDA)}] (12) and [Mg(μ-Br){CH(SiMe3)(SiMe2Ph)}(OEt2)] (14) were prepared from CH(Br)(SiMe3)(SiMe2Ph) in Et2O and Li followed by TMEDA or Mg, respectively. Compound 7 and MgBr2 in THF yielded the crystalline cluster compound [Li2Mg5(OMe)8{CH(SiMe3)(SiMe(OMe)2)}4] (15). The molecular structures of 2, 3, 5, 7, 9, 12, 14, and 15 are described, as are the variable-temperature 1H NMR spectra of 2 in toluene-d8. In 2, 3, and 5, the alkyl is C,O-centered and is essentially a planar chelate toward the Li, Na, or K cation, respectively. In 7, the alkyl ligand core is planar and functions as an O,O-centered bridge to adjacent Li cations, with rather long Li−C distances, whereas in 15 the alkyl acts as a C,O-centered bridge to peripheral Mg and Li cations. The central core of 15 is a Mg atom surrounded by a roughly hexagonal planar array of four Mg and two transoid Li cations joined by six bridging OMe anions. Crystalline 9 is a polymer, in which successive LiOSiCSiO rings are linked by Li−C bonds of unequal lengths, of ca. 2.18 and 2.50 Å. The ligand [CH(SiMe3)(SiMe2Ph)]- is bound to Li in 14 or Mg in 12, in a terminal fashion. |
