Heterometallic bismuth carboxylates and polyaminocarboxylates have
proved to be attractive as precursors for bimetallic or multimetallic oxide and
sulphide materials. Bismuth-containing inorganic materials are of great interest
for many technological applications. They have been associated with high Tc
superconductivity, oxide-ion conduction, ferroelectrics, dielectrics, catalysts
and inorganic pigments. Coordination compounds of Bi(III) with polydentate
ligands have a large variety of crystal structures due to high coordination
number (8-10) of bismuth atom. Coordination chemistry of Bi(III) is limited by
the high hydrolytic tendency of bismuth compounds. The importance of bismuthcontaining
inorganic materials, the lack of well-characterised single-source
precursors and the advantage of using chemical routs in obtaining precursors
with preselected Bi-Me ratio have prompted us to propose the investigation of
synthesis and characterisation of heterometallic complexes of bismuth with pand
d-elements.
Sixteen compounds of general formula Me(BiEDTA)2⋅nH2O and
Me(BiDTPA)⋅nH2O, where Me=Co2+, Ni2+, Mn2+, Cd2+ Cu2+, Zn2+, Pb2+, VO2+ (n
=4-9) have been synthesized, identified and characterized by element and
thermogravimetric analysis, IR spectroscopy, single crystal and high temperature
(HTXRD) X-ray diffraction studies[1]. The compound [Cu(H2O)6][BiEDTA]2⋅3H2O
is isomorphous to Bi-Co and Bi-Ni complexes. Upon thermal degradation it
yields a mixed oxide CuBi2O4 after a much shorter time (100-120 times), at
lower temperature (1.9-2.1 times) and composed of smaller particles (5-
10 times) when compared to classical state reaction[2]. Bismuth containing
mixed- oxide systems are good ionic conductors, while the initial heterometallic
coordination compounds proved to be dielectrics[3] as well as efficient catalysts
in radiolitic water decomposition. Thus, the emission of hydrogen in presence of
[Cu(H2O)6][BiEDTA]2⋅3H2O is 40.2 times higher than compared to noncatalytic
process[4].
Aiming at enlarging the information on crystal structures of bismuth(III)
coordination compounds, we have synthesized and characterized by different
physico-chemical methods four heterometallic Bi(III)-Co(III) coordination
compounds with EDTA: [Co(NH3)4CO3][BiEDTA]⋅3H2O I, 1,6-[Co(NH3)4(NO2)2
]2[Bi2(EDTA)2(H2O)2]⋅4H2O II, [Co(NH3)5NCS][BiEDTA]2⋅2H2O III and [Co(DH)
2(thio)2][BiEDTA(thio)2]⋅2H2O IV (thio=thiocarbamide). Four different modes of
EDTA coordination have been found in these compounds. The anionic part in
I consists of a polymeric chain with oxygen atoms of carboxylic groups acting
as bridging ligands. In II and III the anions are formed of two different dimmers

[Bi2(μ-EDTA)2(H2O)2]2-. In IV two sulphur atoms complete the coordination
number of Bi to eight. Eight more Bi(III)-Co(III) complexes with DTPA of general
formula: [Co(thios)3]2[BiDTPA]2X⋅nH2O and [Co(thios)3][BiEDTA]X⋅nH2O, where
X= SO4
2-, 2NCS-, 2NO3
-, 2ClO4
- thios=thiosemicarbazide. The crystal structure
of the compound [Co(thios)3]2[BiDTPA]2SO4⋅6H2O denotes the presence of
tridimensional networks consisting of complex cations [Co(thios)3]3+, complex
anions [BiDTPA]2- and SO4
2- anions placed in the through hollows[5]. These
systems are stabilized by numerous hydrogen bonds.
Knowing the coordination number of copper atom to vary from 4 to
6 and having noncoordinated acetate fragments in APC ligands we have
synthesised several Bi(III)-Cu(II) coordination compounds of general formula:
[CuL]y[BiAPC]⋅nH2O, where L=tridentate thiosemi- or semicarbazone of salicylic
aldehyde; APC=EDTA, DTPA: Y=1,2; n=6 or 12. The obtained compounds of
copper(II) with bulky bismuth aminopolycarboxilates anions crystallise better
than the ones with nitrate, chloride or sulphate anions.
[1]S. Sobanska, J.-P. Wignacourt, P. Conflant, M. Drache, I. Bulimestru, A. Gulea,
Eur.J. Solid State Inorg. Chem. 1996, 37, 701-712.
[2]Gulea A., Stavila V., Bulimestru I., Wignacourt J.-P., Tsapcov V. Moldova Patent
Nr.1559, Publ. BOPI Nr.11, 2000.
[3]Gulea A., Stavila V., Bulimestru I., Tsapcov V. Moldova Patent. Nr.2479. Publ.
BOPI Nr.6 2004.
[4]Gulea A., Cecal A., Paraschivescu A., Bulimestru I., Wignacourt J.-P.,Tsapcov
V. Moldova Patent Nr.2476, Publ. BOPI Nr.6 2004.
[5]Bulimestru I., Petrenco P., Gulea A., Gdaniec M., Simonov Yu. Russian Journal
of Coordination Chemistry. 2005. V. 31. №5.