In this study, we
are interested in preparing Fe(III), Pd(II),
and Cu(II) complexes from new thiazole derivatives. All syntheses
were elaborately elucidated to estimate their molecular and structural
formulae, which agreed with those of mononuclear complexes. The square-planer
geometry of Pd(II) complex (MATYPd) was the starting point for its
use as a heterocatalyst in preparing pyrazole-4-carbonitrile derivatives 4a–o using ultrasonic irradiation through a facile
one-pot reaction. The simple operation, short-time reaction (20 min),
and high efficiency (97%) were the special advantages of this protocol.
Furthermore, this green synthesis strategy was advanced by examination
of the reusability of the catalyst in four consecutive cycles without
significant loss of catalytic activity. The new synthesis strategy
presented remarkable advantages in terms of safety, simplicity, stability,
mild conditions, short reaction time, excellent yields, and use of
a H2O solvent. This catalytic protocol was confirmed by
the density functional theory (DFT) study, which reflected the specific
characteristics of such a complex. Logical mechanisms have been suggested
for the successfully exerted essential physical parameters that confirmed
the superiority of the Pd(II) complex in the catalytic role. Optical
band gap, electrophilicity, and electronegativity features, which
are essential parameters for the catalytic behavior of the Pd(II)
complex, are based mainly on the unsaturated valence shell of Pd(II).