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The title complex, [Nb(C(7)H(12)N(3))(4)]PF(6), features chelating hpp anions (hpp is 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrim-idine) that define a distorted dodeca-hedral coordination geometry based on an N(8) donor set. The Nb atom is situated on a site of symmetry , and the PF(6) (-) anion has crystallographic fourfold symmetry.
We report a class of molecules with extremely low ionization enthalpies, one member of which has been determined to have a gas-phase ionization energy (onset, 3.51 electron volts) lower than that of the cesium atom (which has the lowest gas-phase ionization energy of the elements) or of any other known closed-shell molecule or neutral transient species… (More)
This study takes an in-depth look at the assessment of coherence and cohesion (CC) in the IELTS Academic Writing Task 2. It investigates the level of difficulty examiners experience, the features they look for, and the extent to which their marking of CC differs from their marking of other criteria. The impact of examiner qualifications, experience and… (More)