Tridentate Lewis Acids Based on Tribenzotriquinacene Chalices.

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((ethy-nyl)phenyl)tribenzotriquinacene. The resulting poly-Lewis acids were tested for their acceptor abilities in host-guest experi-ments 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)-phenyl-si--lane.

Bis(µ-diisopropyl-hydoxylaminato)-κ(2) O:N;κ(2) O:O-bis-[(diisopropyl-hydoxylaminato-κO)beryllium].

The title compound, [Be2(C6H14NO)4], was prepared from a solution of BeCl2 in diethyl ether and two equivalents of O-lithia-ted N,N-diisopropyl-hydoxyl-amine. The mol-ecular structure is composed of a dinuclear unit forming a central five-membered planar Be-O-Be-O-N ring (sum of inter-nal angles = 540.0°; r.m.s. deviation from planarity = 0.0087 Å). Both Be atoms show the unusual coordination number of three, with one Be atom coordinated by three O atoms and the other by two O atoms and one N atom, both in distorted trigonal-planar environments. The Be-O distances are in the range 1.493 (5)-1.600 (5) Šand the Be-N distance is 1.741 (5) Å.