ic9610243_si_001.pdf (398.65 kB)
Solution and Solid State Properties of [N-(2-Hydroxyethyl)iminodiacetato]vanadium(IV), -(V), and -(IV/V) Complexes1
journal contribution
posted on 1997-04-09, 00:00 authored by Mohammad Mahroof-Tahir, Anastasios D. Keramidas, Ron B. Goldfarb, Oren P. Anderson, Mary M. Miller, Debbie C. CransA mononuclear vanadium(IV), a mononuclear vanadium(V),
and a binuclear mixed valence vanadium(IV/V)
complex with the ligand N-(2-hydroxyethyl)iminodiacetic
acid (H3hida) have been structurally
characterized.
Crystal data for
[VO(Hhida)(H2O)]·CH3OH
(1): orthorhombic;
P212121; a
= 6.940(2), b = 9.745(3), c
= 18.539(4) Å; Z = 4. Crystal data for
Na[V(O)2(Hhida)2]·4H2O
(2): monoclinic; P21/c;
a = 6.333(2), b =
18.796(2),
c = 11.5040(10) Å; β = 102.53(2)°;
Z = 4. Crystal data for
(NH4)[V2(O)2(μ-O)(Hhida)2]·H2O
(3): monoclinic;
C2/c; a = 18.880(2), b
= 7.395(2), c = 16.010(2) Å; β =
106.33(2)°; Z = 4. The mononuclear
vanadium(IV)
and vanadium(V) complexes are formed from the monoprotonated
Hhida2- ligand, and their structural and
magnetic
characteristics are as expected for six-coordinate vanadium complexes.
An interesting structural feature in these
complexes is the fact that the two carboxylate moieties are coordinated
trans to one another, whereas the carboxylate
moieties are coordinated in a cis fashion in previously characterized
complexes. The aqueous solution properties
of the vanadium(IV) and -(V) complexes are consistent with their
structures. The vanadium(V) complex was
previously characterized; in the current study structural
characterization in the solid state is provided.
X-ray
crystallography and magnetic methods show that the mixed valence
complex contains two indistinguishable
vanadium atoms; the thermal ellipsoid of the bridging oxygen atom
suggests a type III complex in the solid state.
Magnetic methods show that the mixed valence complex contains a
free electron. Characterization of aqueous
solutions of the mixed valence complex by UV/vis and EPR spectroscopies
suggests that the complex may be
described as a type II complex. The
Hhida2- complexes have some similarities, but
also some significant
differences, with complexes of related ligands, such as
nitrilotriacetate (nta),
N-(2-pyridylmethyl)iminodiacetate
(pmida), and
N-(S)-[1-(2-pyridyl)ethyl]iminodiacetate
(s-peida). Perhaps most importantly, the mixed
valence
Hhida2- complex is significantly less stable
than the corresponding pmida and s-peida complexes of similar
overall
charge but very similar in stability to the nta and
V2O33+ complexes with higher
charges. Thus, there is the
potential for designing stable mixed valence dimers.