Interactions of Verkade's Superbase with Strong Lewis Acids: From Labile Mono- and Binuclear Lewis Acid-Base Complexes to Phosphenium Cations

A series of mono- and binuclear Lewis acidbase complexes of the formulas N[CH2CH2N(Pr-i)](3)P -> LA [LA = BH3 (8), Ga(C6F5)(3) (10), GaCl3 (11)], LA -> N[CH2CH2N(Pr-i)](3)P [LA = Al(C6F5)(3) (6a), AlMe3 (6b), AlEt3 (6c), AlBu3i (6d), BF3 (13)], and LA <- N[CH2CH2N(Pri)](3)P -> LA [Lewis acid (LA) = Al(C6F5)(3) (7a), AlMe3 (7b), AlEt3 (7c), AlBu3i (7d), AlCl3 (7e), BH3 (9)] were generated from reactions of Verkades base, N[CH2CH2N(Pr-i)](3)P (1), with various boron-, aluminum-, and gallium-containing Lewis acids, and characterized by multinuclear NMR spectroscopy. {N[CH2CH2N(Pr-i)](3)P -> C7H7}[BF4] (5) was synthesized via the treatment of 1 with [C7H7][BF4]. The reaction of 1 with B(C6F5)(3), followed by the addition of [Ph3C](2)[B12Cl12], gave rise to the rearranged borate salt [PN4C9H17(Pr-i)(2)][B(12)Cl(1)2] (3), while treating 1 with [Ph3C]2[B12Cl12] exclusively afforded {N[CH2CH2N(Pr-i)](3)PH}(2)[B12Cl12] (4). Reactions of 1 with 2 equiv of GaCl3 and BF3, respectively, afforded the novel phosphenium gallate and borate salts 12a, 12b, and 15. The solid-state structures of 1, 35, 6b, 7a, 7b, 7e, 8, 10, 11, 12b, 13, and 15 were determined by X-ray crystallography.