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The compound LiAl(OC(Ph) (CF 3 ) 2 ) 4 (1), prepared from LiAlH 4 and HOC(Ph)(CF 3 ) 2 , is an active Lewis acid catalyst in toluene solution for the 1,4conjugate addition of silyl ketene acetals to R,β-unsaturated carbonyl compounds and for the direct substitution of allylic acetates by silyl ketene acetals. The structure of 1 contains a rare trigonal prismatic coordination sphere around the Li + cation, with two Li-O(C, Al) bonds and four Li-F(C) bonds.One of the most important uses of new weakly coordinating anions (WCAs) is to enhance the catalytic activity of metal cations. 2 Two examples that have received considerable attention recently are metallocene-catalyzed olefin polymerization 3 and lithiumcatalyzed Diels-Alder reactions and 1,4-conjugate addition reactions. 4 The best Li + -based catalysts, including LiClO 4 , 4a,b,d LiN(O 2 SCF 3 ) 2 , 4e,g and LiCo(C 2 B 9 H 11 ) 2 , 4c exhibit higher activity as the coordinating ability of the solvent decreases from, for example, diethyl ether to 1,2dichloroethane (DCE). Due to restrictions or hazards associated with DCE and other weakly coordinating halogenated solvents, 5 hydrocarbon-soluble and hydrocarbon-active catalysts would be desirable for large-scale industrial use. However, few lithium salts of WCAs are soluble in hydrocarbon solvents, and none that we know of is catalytically active.We now report that the Li + salt of a new tetrakis-(polyfluoroalkoxy)aluminate shows great promise as a hydrocarbon-active catalyst for 1,4-conjugate addition reactions and the direct substitution of allylic acetates by silyl ketene acetals. The new hydrocarbon-soluble compound LiAl(OC(Ph)(CF 3 ) 2 ) 4 , 1, was prepared by adding 4 equiv of HOC(Ph)(CF 3 ) 2 to LiAlH 4 in toluene solution: 6 The hygroscopic, volatile, white solid, which was purified by vacuum sublimation at 138 °C, is extremely soluble in hydrocarbon solvents including hexane and toluene. Diffraction-quality crystals were grown by cooling a hexane solution of 1. 7 The solid-state structure, shown in Figure 1, consists of discrete LiAl(OC-(Ph)(CF 3 ) 2 ) 4 molecules. The Al atom is tetrahedrally coordinated by four 1,1,1,3,3,3-hexafluoro-2-phenyl-2propoxide ligands. The O1-Al-O2 angle of 91.8(1)°is smaller than the five other O-Al-O angles, which range from 105.4(1) to 116.7(1)°. The Al(OC(Ph)(CF 3 ) 2 ) 4anion is a hexadentate chelating ligand for the Li + cation. The O1-Al-O2 unit forms a four-membered chelate ring with Li + , with Li-O(Al,C) bond distances of 1.966(8) and 1.978(8) Å. Four C-F bonds from four different CF 3 groups form five-membered O-Li-F-C-C chelate rings, with Li-F(C) bond distances of 1.984(9), 2.082(9), 2.098(11), and 2.354 (10) Å. The overall LiO 2 F 4 coordination sphere can best be described

The tert-butyl substituted compounds of gallium have been synthesized and characterized: (10), and [Li(HO i Pr) 4 ][( t Bu) 2 GaCl 2 ] (11). X-Ray crystallographic characterization was obtained for compounds 1-6 and 8-11. Compounds 10 and 11 exhibit three-dimensional hydrogen bonded networks in which augmentation of the O-H ؒ ؒ ؒ Cl hydrogen bond is proposed to be due to the increased acidity of alcohols bonded to the Lewis acidic lithium ions. A discussion of the dependence of the puckering of the chair-like conformation in eight-membered cyclic compounds of the Group 13 metals is presented.

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