Molecular structures of free quinuclidine and its adducts with metal trihydrides, MH3 (M = B, Al or Ga), studied by gas-phase electron diffraction, X-ray diffraction and quantum chemical calculations

Abstract

The structure of quinuclidine, HC(CH(2)CH(2))(3)N, has been re-investigated by quantum chemical calculations and by gas-phase electron diffraction (GED). The GED data, together with published rotational constants, have been analysed using the SARACEN method to determine the most reliable structure (r(h1)) for the gaseous molecule. The structures of two adducts of quinuclidine with group 13 trihydride molecules, MH(3) (M=B, Al), have also been determined by GED and quantum chemical calculations. The effect of the coordination of these hydrides to the quinuclidine nitrogen atom has been investigated, and the structural changes and energetics of adduct formation are discussed. We also present the crystal structure of quinuclidine borane.

Increasing the Reactivity of Nitrogen Catalysts

“…The dynamic conformational behaviour of this molecule has been studied: some degree of freedom is still present, since it displays two twisted conformations in rapid equilibrium (Scheme 26). [92] These enantiomeric clockwise and anticlockwise helices are energetic wells, since eclipsed CH interactions are minimised. For our topic of interest, it should be noted that hyperconjugation, of the three C À C bonds with the nitrogen lone pair can only occur in the C 3v symmetrical transition Scheme 24.…”

“…In 1986, Hine and Chen [104] measured the rate constants for the nucleophilic addition of nitrogen bases onto alkyl tosylates (Table 13). The idea was that steric decongestion around the active lone pair in bridged bicyclic structures, such as 1-azabicycloA C H T U N G T R E N N U N G [2.2.1]heptane (92), would enhance the nucleophilicity.…”

Lewis base complexes of AlH3: structural determination of monomeric and polymeric adducts by X-ray crystallography and DFT calculations

“…7 The trimethylamine (TMA) and QUIN addicts have also been characterised structurally in the vapour phase by gas electron diffraction (GED), where they are each reported to be pseudotetrahedral at the Al centre. 18,20,21 Bidentate phosphine ligands have also produced pseudo 1 : 1 adducts; for example, 1,2-bis(di-isopropyl)phosphinoethane (DIPE) 7 and 1,2-bis-(dicyclohexylphosphino)ethane (DCPE), where the phosphine ligand bonds with two alane moieties. 8 Carbenes predominantly form 1 : 1 adducts with alane, which may be attributed to the steric bulk of the carbene moiety.…”

“…The amine derivatives are generally volatile and sublime readily at ambient temperature, but are metastable in the gas phase. 20,40,41 Upon thermolysis (>100 °C), the adduct dissociates to leave polymeric alane, which then immediately decomposes via an autocatalytic process, releasing hydrogen and forming an aluminium mirror (eqn (10)). 10,27,34 The availability of high purity Al though this process has stimulated a large body of research into the use of these adducts in chemical vapour deposition (CVD) to produce Al thin films.…”

Self-Aggregation and Liquid Crystalline Behavior of New Ester-Functionalized Quinuclidinolium Surfactants

“…The quinuclidine moiety can be considered having a twisted C 3 -symmetry 34 which has molecular cavities between the extended carbon arms. The similar carbon arm of adjacent quinuclidinolium moiety probably positions itself tightly in this cavity maintaining a distance due to electrostatic repulsion between similarly charged headgroups.…”