om500686c_si_001.cif (48.69 kB)

Homoleptic Tris(α,ω-alkanediyl)yttriates of the Type [{Li(dme)}3{Y(CH2‑X-CH2)3}] (X = C2H4, C3H6, Si(CH3)2)

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posted on 12.01.2015, 00:00 by Reinald Fischer, Stefan Bode, Mathias Köhler, Jens Langer, Helmar Görls, Martin D. Hager, Ulrich S. Schubert, Matthias Westerhausen
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.