The reaction of select
copper(II) monocarboxylates Cu(RCOO)2(H2O)
x
(R = C4H3O, C6H5, H; x = 2, 4) with pyrazole
(Hpz), carried out in protic solvents, yields
mono- or dinuclear species [Cu(RCOO)2(Hpz)
n
]
m
(n = 2, 4; m = 1, 2), always accompanied by tri- or
hexanuclear derivatives based on the triangular [Cu3(μ3-OH)(μ-pz)3]2+ fragment. The molecular
structures of all isolated compounds have been established through
XRD determinations. In some cases, the mono-, or dinuclear species
act as secondary building units, self-assembling into 1D or 3D coordination
polymers. The hexanuclear benzoate cluster contains coordinated and
crystallization MeOH molecules, whose removal generates a crystalline
1D coordination polymer that can be reconverted into the hexanuclear
cluster by soaking in MeOH. The relatively high pK
b values of carboxylate anions employed in the syntheses
are responsible for the preferential formation of mono- or dinuclear
species rather than tri- or hexanuclear ones.