[72]. Up to three methoxy substituents have been incorporated to the phenyl ring of
the C,N-bidentate chelating PYA (complexes 17b-e, Scheme 2). Under optimised
conditions, these complexes catalyse the TH of benzophenone using 2-propanol as a
hydrogen source. Incorporation of one methoxy substituent to the phenyl ring of the
PYA ligand markedly improved the catalytic activity from 27% conversion for 17a
to 99 and 96% for 17b and 17c, respectively, at 4 h of reaction. Incorporation of a
second methoxy group further enhances the catalytic rate (93% conversion for
Scheme 6 (continued)
80
M. Pilar Lamata et al.