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)]-

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))}](infinity) (7), [Li{CH(SiMe2OMe)(2)}](infinity) (9), and [Na{CH(SiMe3)(SiMe2-OMe)}](infinity) (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{mu-C(SiMe2OMe)(3)}](2) (10) as the major product. The compound [K{CH(SiMe3)(SiMe2OMe)}](infinity) (4) was obtained from 2 and KOBut in hexane, and addition of Et2O to 4 gave the crystalline compound [K{CH(SiMe3)(SiMe2OMe)}(OEt2)](infinity) (5). The crystalline compounds [Li{(CH-(SiMe3)(SiMe2Ph))(TMEDA)}] (12) and [Mg(mu-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 [Li-2-Mg-5(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 H-1 NMR spectra of 2 in toluene-d(8), 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 Angstrom. The ligand [CH(SiMe3)(SiMe2Ph)](-) is bound to Li in 14 or Mg in 12, in a terminal fashion.