Homoleptic Tris(<i>α,ω</i>-alkanediyl)yttriates of the Type [{Li(dme)}<sub>3</sub>{Y(CH<sub>2</sub>‑X-CH<sub>2</sub>)<sub>3</sub>}] (X = C<sub>2</sub>H<sub>4</sub>, C<sub>3</sub>H<sub>6</sub>, Si(CH<sub>3</sub>)<sub>2</sub>)
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The metathesis reaction of anhydrous yttrium(III) chloride with ethereal solutions of 1,4-dilithiobutane, 1,5-dilithiopentane as well as bis(lithiomethyl)dimethylsilane in the molar ratio of 1:3 yields the homoleptic yttriates [{Li(dme)}3{Y(C4H8)3}] (2), [{Li(dme)}3{Y(C5H10)3}] (3), and [{Li(dme)}3(Y{CH2Si(CH3)2CH2}3)] (4) after addition of 1,2-dimethoxyethane (DME). The molecular structures of 2 and 3 show hexa-coordinate yttrium atoms in distorted octahedral environments of three bidentate chelating α,ω-alkanediyl ligands. Three Li(dme) units occupy bridging positions between two α-CH2 fragments of different ligands. These complexes decompose at 0 °C in THF-d8 solution leading to the formation of methyl vinyl ether as well as n-butane and n-pentane, respectively. The 13C{1H} NMR experiment of 2 at −40 °C shows a doublet for the α-CH2 fragment with a 1JC,Y coupling constant of 21.6 Hz. For the thermally more stable complex 4 (NMR measurement at r.t.), a 1JC,Y coupling constant of 16.9 Hz was observed. Bis(lithiomethyl)dimethylsilane crystallizes as the cage compound [(Et2O)4{(LiCH2)2Si(CH3)2}3(LiCl)]2 (1) with a shell-like structure around the central chloride ions. YCl3 reacts with an excess of phenyllithium in diethyl ether to a product mixture. Lithium chloride can be removed with tetrahydropyran (THP) as [(thp)2LiCl]2 (5). After the addition of THF to the residue, [Ph3Y(thf)3] (6, 1JC,Y = 48.7 Hz) could be identified in the solution. The applicability of complexes 2, 3, and 4 as initiators for styrene polymerization is studied in THF solution at −70 °C.
