Ga. Van Albada et al., Synthesis, structure, spectroscopy, and magnetism of unique propeller-typelinear trinuclear Cu-II complexes with in-situ prepared formamidine ligands, EUR J INORG, (12), 1999, pp. 2269-2275
Three new copper(II) linear trinuclear compounds are reported, all of which
were synthesized in-situ, with the general formula [Cu-3(L)(4)](CF3SO3)(2)
(Y)(x), where L is the dehydronated ligand: N,N'-bis(pyridine-2-yl)formamid
ine (abbreviated as Hpdf), N, N'-bis(pyrimidine-2-yl)form amidine (abbrevia
ted as Hpmf) and N,N'-bis(5-methylpyridine-2-yl)formamidine (abbreviated as
Hmpdf), Y = EtOH or H2O and x = 0.5-1.5. The compounds were characterized
by X-ray diffraction, IR, LF, and EPR spectroscopy and by magnetic suscepti
bility down to 4 K. The structure of the compound [Cu-3(pmf)(4)](CF3SO3](2)
(H2O)(1/2) was determined by X-ray crystallography; it was found to crystal
lise in the triclinic space group P-l with a: = 8.529(5), b = 15.760(5), c
= 19.639(5) A, alpha = 101.793(5), beta = 101.263(5), gamma = 102.389(5)deg
rees, Z = 2. The structure [Cu-Cu-Cu angle 174.96(11)degrees] consists of f
our nearly Rat molecules of the ligand, which contribute to the propeller-t
ype structure around the Cu-Cu-Cu axis. A strong antiferromagnetic interact
ion between the Cu-II ions is observed with calculated J values, based on t
he Hamiltonian H = -2J(S-1.S-2 + S-2.S-3)-2J'.S-1.S-3, of -174(1) cm(-1), -
120(1) cm(-1), and -167(1) cm(-1) for the compounds studied with L = pdf, p
mf, and mpdf, respectively. These values are in agreement with an S = 1/2 g
round state below temperatures of 120-160 K.