With the exception of H1 (5),
all hydrogen atoms bonded to sp2 (sp3
) carbon atoms were
assigned ideal positions and refined using a riding model with
Uiso constrained to 1.2 (1.5) times the Ueq value of the parent
carbon atom; the position of the Al-bonded hydrogen atom
H1 (5) was taken from the difference map and refined freely
(Table 2).