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Two tri‐ and two hexadentate poly‐Lewis acids (PLAs) with calyx‐like structures of C3 symmetry containing aluminum‐ and boron‐containing Lewis acidic functions were prepared by tin‐metal exchange reactions. The triply hydrosilylated [12]annulene served as basic framework. It forms a calyx‐like structure by the stereo‐ and regioselective attachment of three SiMeCl2 groups to the planar [12]annulene. The PLA precursors were generated by attaching three or six trimethylstannylethynyl groups to the silicon atoms. Lewis acid functions were introduced using the reagents bis‐(bis(trimethylsilyl)methyl)aluminium hydride (HAl[CH(SiMe3)2]2) and catecholatochloroborane (ClBCat). The complexation behavior of the PLAs towards different Lewis bases was investigated by NMR. Bases included pyridine, polydentate nitrogen‐ and phosphorus‐containing bases. Additionally, three molecules of a bidentate phosphorus‐containing base were captured with hexadentate PLAs. Diffusion NMR experiments provided insight into the aggregation processes: some of the adducts had a significantly larger volume than expected, indicating the formation of larger adducts than the expected 1 : 1 adduct, including larger 2 : 2 adduct cages. The distances between the Lewis acid units and the steric requirement of the attached substituents determine the complexation behavior of the PLAs. Thus, the weak Lewis acidic BCat units show no (tridentate case) or a strong (hexadentate case) interaction with PMe2‐containing bases, if they can act cooperatively. [ABSTRACT FROM AUTHOR]

Chalice‐shaped tridentate poly‐Lewis acids (PLA) based on the tribenzotriquinacene (TBTQ) scaffold have been synthesised. Stannylation of the alkyne units, attached via phenyl‐spacers to the benzhydrylic positions to the TBTQ scaffold, with Me2NSnMe3 afforded the trimethyltin substituted TBTQ derivative. Replacement of these tin functions with other elements resulted in rigid boron‐ and aluminium‐functionalised PLAs. More flexible PLAs were obtained by hydrometallation reactions of the terminal alkyne groups of 4b,8b,12b‐tris((ethynyl)phenyl)tribenzotriquinacene. The resulting poly‐Lewis acids were tested for their acceptor abilities in host‐guest experiments with suitable bases. Preliminary tests with pyridine led to the synthesis of a large tridentate base with three pyridyl groups attached to a TBTQ backbone. Complexation of this Lewis base with the PLAs resulted in the formation of aggregates, which were studied in solution in more detail by 1H DOSY NMR experiments regarding their size. Further experiments were performed with the tridentate bases 1,4,7‐trimethyl‐1,4,7‐triazacyclononane and tris((dimethylphosphino)methyl)phenylsilane. [ABSTRACT FROM AUTHOR]

Hexadentate poly-Lewis acids (PLA) based on the bowl-shaped tribenzotriquinacene (TBTQ) have been synthesised. The introduction of three n-propyl groups into the benzhydrylic positions of the TBTQ backbone has significantly increased the solubility of the subsequently derived compounds. Semi-flexible PLAs containing boron and aluminium were obtained by hydrometallation of the corresponding 2,3,6,7,10,11-hexaalkynyl-TBTQ. Other rigid hexadentate PLAs were synthesised by stannylation of the corresponding alkyne units with Me3SnNMe2 followed by tin-element exchange reactions. The Lewis acidity of these PLAs was investigated in host–guest experiments with pyridine. Further experiments with bidentate bases showed correlations between their flexibility, their Lewis basicity and the complexation behaviour towards the synthesised PLAs. Addition of bis((dimethylphosphino)methyl)dimethylsilane (BisPhos) to solutions of the rigid alkynyl PLAs led to the formation of 3 : 1 adducts. Single crystal X-ray diffraction was used to further elucidate the host–guest connectivtiy. In addition, a sixfold pnictogen-bonding donor was synthesised by tin-antimony exchange. [ABSTRACT FROM AUTHOR]