Supramolecular Chemistry Based on Frustrated Lewis Pairs – Reactions of an Al/P FLP with Potassium Formate and Cesium Fluoride

Reactions of the Al/P‐based frustrated Lewis pair Mes 2 P–C(Al t Bu 2 )=C(H)–Ph ( 1 ) with the Brønstedt acids HBr, HI, and HCO 2 H resulted in the formation of the corresponding H X adducts Mes 2 (H)P–C[Al( X ) t Bu 2 ]=C(H)–Ph [ X = Br ( 4 ), I ( 5 ), OC(H)O ( 6 )]. Despite the well‐known sensitivity of Al–C bonds towards protolysis, the products were isolated in good yields. Short intramolecular distances between H and Br, I or O are consistent with the presence of P–H ··· X hydrogen bonds. Treatment of 1 with potassium formate or CsF yielded in poor to moderate yields the adducts Mes 2 P–C(Al t Bu 2 )=C(H)Ph · (KO 2 CH) ( 7 ) and Mes 2 P–C(Al t Bu 2 )=C(H)Ph · (CsF) ( 8 ). The potassium compounds required the presence of additional solvent molecules to obtain isolable crystalline products. Two monomeric units were joined by interactions of each K + cation with two formate anions. Supramolecular entities resulted by the additional coordination of the K + cations to solvent molecules ( 7a , toluene; 7b , 1,2‐difluorobenzene; 7c , THF), weak contacts to a mesityl group and in case of 7b and 7c to a t Bu group and the P atom. The CsF adduct 8 crystallizes as a double‐stranded chain with the coordination of the Cs + cation to F – , a mesityl group (η 6 ), a Ph group (η 6 ; leads to an infinite chain), and a t Bu group (connects two chains to a double strand) of two different neighboring molecules. The Cs–F bond length is with 274.7(1) pm comparatively short, and the adduct may be viewed as a CsF molecule trapped by the FLP functionality.