Mixed ligation to vanadium(III): Synthesis, spectra and structures of bis(acetylacetonato)(o-phenanthroline)vanadium(III) fluoroborate and bis(acetylacetonato)(o-phenanthroline)vanadium(III) perchlorate

Article abstract of DOI:10.1016/j.ica.2005.12.020

Two mixed ligand vanadium(III) complexes bis(acetylacetonato) (phenanthroline)vanadium(III) fluoroborate (1) and bis(acetylacetonato) (phenanthroline)vanadium(III) perchorate (2) have been prepared and characterized by UV-Vis, IR, ¹H NMR spectroscopic techniques and single crystal X-ray diffraction. The electronic spectra are as expected for V(III) in an octahedral environment. The ¹H NMR spectra are typical of paramagnetic V(III) species. The complexes have crystallized with dichloromethane solvate and are isomorphous. The coordination sphere is composed of vanadium in a distorted octahedral environment, ligated to two bidentate chelating acetylacetonate ligands through the oxygen atoms and two phenanthroline nitrogens.

Full text of DOI:10.1016/j.ica.2005.12.020

Inorganica Chimica Acta 359 (2006) 1314–1320
www.elsevier.com/locate/ica
Note
Mixed ligation to vanadium(III): Synthesis, spectra and structures
of bis(acetylacetonato)(o-phenanthroline)vanadium(III)
fluoroborate and bis(acetylacetonato)(o-phenanthroline)vanadium(III)
perchlorate
a
a,
*
Savaridasson Jose Kavitha , Krishnaswamy Panchanatheswaran
,
b
b
Mark R.J. Elsegood , Sophie H. Dale
a
School of Chemistry, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu, India
Chemistry Department, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK
b
Received 20 July 2005; received in revised form 29 November 2005; accepted 7 December 2005
Available online 20 January 2006
Abstract
Two mixed ligand vanadium(III) complexes bis(acetylacetonato)(phenanthroline)vanadium(III) fluoroborate (1) and bis(acetylaceto-
nato)(phenanthroline)vanadium(III) perchorate (2) have been prepared and characterized by UV–Vis, IR, 1H NMR spectroscopic tech-
niques and single crystal X-ray diffraction. The electronic spectra are as expected for V(III) in an octahedral environment. The 1H NMR
spectra are typical of paramagnetic V(III) species. The complexes have crystallized with dichloromethane solvate and are isomorphous.
The coordination sphere is composed of vanadium in a distorted octahedral environment, ligated to two bidentate chelating acetylacet-
onate ligands through the oxygen atoms and two phenanthroline nitrogens.
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: Mixed-ligand complexes; Vanadium(III); 1,10-Phenanthroline complexes
1. Introduction
complex [V2(l-O)(phen)4Cl2]Cl2 [10] prepared by the
action of VCl3 on o-phenanthroline was shown to interact
with DNA leading to its degradation [7,11]. Synthesis of
monomeric V(III)-phenanthroline complexes has long been
a challenge in V(III) coordination chemistry. Reaction of
ammonium vanadium sulfate [12] and vanadium(III) sul-
fate [13] with 1,10-phenanthroline gave purple complexes
containing V(IV). Rikkou et al., have reported the synthe-
sis of a series of mononuclear bis(L-L)dichloro V(III) com-
plexes (L-L = bipyridine and phenanthroline) by the
reduction of non-oxo V(IV) precursors [14]. However, to
our knowledge there are no structural reports on non-
oxo V(III)-phenanthroline mononuclear complexes so far.
Herein, we describe the synthesis, spectra, electrochem-
istry and first structural reports on mononuclear non-oxo
V(III)-phenanthroline complexes, viz. [V(acac)2(phen)]BF4,
[V(acac)2(phen)]ClO4 (acac = acetylacetonate; phen = o-
phenanthroline).
Henze’s discovery that certain ascidians or sea-squirts
accumulate V(III) to a greater extent in their blood cells,
spurred the interest of chemists in the chemistry of V(III)
compounds [1]. Due to lack of suitable starting materials
which can be handled under normal laboratory conditions
and the pronounced tendency of the trivalent state to
undergo oxidation, V(III) chemistry is not well explored.
Nevertheless, vanadium(III) is reported to form neutral,
cationic, anionic and oxo-bridged complexes [2–5].
o-Phenanthroline(1,10-phenanthroline) or its congener
bipyridyl forms complexes with vanadium in 0, +3, +4
and +5 oxidation states [6–9]. The vanadium(III) cationic
*
Corresponding author. Tel.: +91 431 2407053; fax: +91 431 2407045.
E-mail address: panch_45@yahoo.co.in (K. Panchanatheswaran).
0020-1693/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2005.12.020

S.J. Kavitha et al. / Inorganica Chimica Acta 359 (2006) 1314–1320
1315
2. Experimental
2.3. Preparation of V(acac)3
2.1. Reagents
Bis(acetylacetonato)oxovanadium(IV) (8 g) was reduced
with tin in the presence of excess of acetylacetone. The mix-
ture was refluxed under nitrogen atmosphere for 3 h. Brown
crystals separated out on cooling the reaction mixture. The
product was pure and more easily isolated than using the
reported procedure in which zinc was employed as the reduc-
ing agent [16]. Yield 7.5 g, 71.70%, m.p. 184 °C. (m.p.
reported 184 °C). IR (KBr disk, m/cmꢀ1): 1567, 1523, 1423,
1383, 1362, 1274, 1191, 1018, 930, 776, 668, 586, 447, 412.
1H NMR (400 MHz, methanol): d 45.77(18H), 40.41(3H).
The chemicals were purchased from Sigma–Aldrich.
Methanol was dried by distillation from magnesium turn-
ings and iodine. Bis(acetylacetonato)oxovanadium(IV)
was prepared as reported [15]. The vanadium(III)
starting material, tris(acetylacetonato)vanandium(III)
was prepared by reducing bis(acetylacetonato)oxovana-
dium(IV) with tin in the presence of excess of acetylace-
tone by modifying the reported procedure [16].
o-Phenanthrolinium salts were prepared by the action
of the corresponding acids on o-phenanthroline monohy-
drate. Perchloric acid and perchlorate derivatives
were used with caution in small quantities to avoid
explosion.
2.3.1. Preparation of 1,10-phenanthrolinium chloride
To a solution of 1,10-phenanthroline monohydrate
(0.50 g; 2.52 mmol) in ethanol, concentrated hydrochloric
acid (0.25 ml; 2.52 mmol) in ethanol was added and heated
over a water bath. The colorless product obtained was iso-
lated and had the same melting point (225 °C) as that of
the commercially available sample. Yield : 0.50 g, 91.67%.
m.p. 225 °C. IR (KBr disk, m/cmꢀ1): 3342, 3029, 1631,
1598, 1543, 1519, 1453, 1425, 1371, 1339, 1317, 1285, 1248,
2.2. Measurements
Elemental analysis was carried out using model 2400
Perkin–Elmer CHN analyzer at the Loughborough
University, Loughborough, Leicestershire, UK. The IR
spectra were recorded on a JASCO 400 plus spectropho-
tometer using a KBr disk technique. Electronic spectra
were recorded in DMF on a CARY 300 Bio UV–Vis Var-
ian spectrophotometer. The 1H NMR spectra were
recorded using BRUKER 200 MHz and BRUKER
400 MHz instruments using TMS as an internal reference
at the Sophisticated Instruments Facility, Indian Institute
of Science, Bangalore, India. Cyclic voltammograms were
obtained on CH instruments electrochemical analyzer.
The measurements were carried out at 100 mV/s under
oxygen free condition using a three-electrode cell in which
glassy carbon electrode was the working electrode, satu-
rated Ag/AgCl electrode was the reference electrode and
platinum wire was used as the auxiliary electrode.
Tetra(n-butyl)ammonium perchlorate was used as the sup-
porting electrolyte.
1191, 1079, 960, 885, 848, 779, 718, 621. UV kmax/nm(emax
/
1
molꢀ1 cm2): 264(19800), 225(27200). H NMR (200 MHz,
D2O): 8.59 (dd, J = 1.46, 4.96, 2H), 8.22 (dd, J = 1.54,
8.32 2H), 7.66 (dd, J = 4.98, 8.22, 2H), 7.33 (s, 2H).
2.3.2. Preparation of 1,10-phenanthrolinium
fluoroborate Æ 1,10-phenanthroline
To a solution of 1,10-phenanthroline monohydrate
(0.50 g; 2.52 mmol) in ethanol, a solution of HBF4
(0.44 ml; 2.52 mmol) in ethanol was added and heated over
a water bath. Colorless crystals were obtained on cooling
the solution to room temperature. Yield 0.64 g, 95.5%,
m.p. 247 °C. Anal. Calc. for C24H17BF4N4: C, 64.31; H,
3.82; N, 12.50. Found: C, 64.21; H, 3.98; N, 12.58%. IR
(KBr disk, m/cmꢀ1): 3424, 1617, 1598, 1543,1506,
1469,1418, 1137, 1078, 1055, 1038, 840, 765, 732, 713.
UV kmax/nm(emax/molꢀ1 cm2): 263(25900), 230(34700).
1H NMR (200 MHz, dmso-d6): d 9.28 (dd, J = 1.36, 4.84,
2H), 9.05 (dd, J = 1.38, 8.24, 2H), 8.33 (s, 2H), 8.20 (dd,
J = 4.88, 8.20, 2H).
X-ray data were collected using a Bruker SMART
1000 CCD diffractometer using Mo Ka radiation
˚
(k = 0.71073 A) with narrow frames (0.3° in x) [17].
The structures were solved by direct methods and refined
by full-matrix least squares methods on F2 [18]. Atoms
2.3.3. Preparation of 1,10-phenanthrolinium perchlorate
To a solution of 1,10-phenanthroline monohydrate
(0.50 g; 2.52 mmol) in ethanol, perchloric acid (0.21 ml;
2.52 mmol) in ethanol was added and heated over a water
bath. Colorless crystals were obtained on cooling the solu-
tion to room temperature. Yield 0.54 g, 75.8%. m.p. chars
at 195 °C. Anal. Calc. for C12H9ClN2O4: C, 51.35; H,
3.23; N, 9.98. Found: C, 51.61; H, 3.48; N, 10.19%. IR
(KBr disk, m/cmꢀ1): 3446, 1620, 1594, 1547, 1451, 1419,
1143, 1091, 879, 840, 761, 731, 718, 623. UV: kmax/nm-
(emax/molꢀ1 cm2): 263(19000), 231(33900). 1H NMR
(200 MHz, dmso-d6): d 9.21 (dd, J = 1.56, 4.24, 2H), 8.80
(dd, J = 1.56, 8.20, 2H), 8.18 (s, 2H), 8.01 (dd, J = 4.68,
8.20, 2H).
ꢀ
F(2), F(3) and F(4) of the BF4 anion are disordered
over two sets of positions in 1, the major component
being 88.4(6)%. In 2, the oxygen atoms of the ClO4
ꢀ
anion adopt two sets of positions with the major compo-
nent being 77.2(15)%. In both the structures, atoms
C(23) and Cl(2) of the solvent of crystallisation are dis-
ordered over two sets of positions with the major com-
ponents being 56.4(7)% for 1 and 84.9(11)% for 2. The
disorder was modeled with restraints on geometry and
anisotropic displacement parameters. Hydrogen atoms
were included in a riding model with Uiso set to be 1.2
times that of the carrier atom. Further details are given
in Table 2.

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2.3.4. Preparation of [V(acac)2(phen)]BF4 Æ CH2Cl2
Tris(acetylacetonato)vanandium(III) (0.3 g, 0.86 mmol)
was refluxed with 1,10-phenanthrolinium fluoroborate Æ phe-
nanthroline (0.25 g , 0.58 mmol) under nitrogen atmosphere
in methanol. A bright orange solid separated out on cooling.
The solid was recrystallised by vapor diffusion of petroleum
ether into dichloromethane solution resulting in the forma-
tion of [V(acac)2(phen)][BF4] Æ CH2Cl2. Yield 0.48 g, 64.7%.
m.p. chars at 225 °C. Anal. Calc. for [C22H22N2O4V]BF4 Æ
0.65CH2Cl2: C, 47.61; H, 4.11; N, 4.90. Found: C, 47.72;
H, 4.11; N, 4.92%. IR(KBr disk, m/cmꢀ1): 3436, 1628, 1521,
1427, 1332, 1285, 1082, 961, 850, 720, 614,
459, 444. UV kmax/nm(emax/molꢀ1 cm2): 231(20650), 273
(33010), 349(7375), 454(2075), 652(15). 1H NMR
(200 MHz, CDCl3): d 68.12 (br, 12H), 17.47 (br, 2H), 6.93
(br, 2H), 1.85 (br, 2H), ꢀ23.30 (br, 2H).
anthrolinium perchlorate. The 1H NMR data of these salts
are similar to those of o-phenanthroline itself, indicating
that the salts dissociate in solution.
The reaction of o-phenanthrolinium salts with V(acac)3
may be described by the initial dissociation of the o-phen.
salts to the base and free acid, followed by the action of
acid on V(acac)3 to displace the ligand and subsequent
coordination of o-phenanthroline (Scheme 1).
Elemental analyses indicate the presence of unproto-
nated o-phenanthroline in the fluoroborate salt, whose stoi-
chiometry can be represented as (C12H9N2)(C12H8N2)BF4.
The presence of two acetylacetonate ligands and one o-phe-
nanthroline ligand in both the vanadium complexes is indi-
cated by their corresponding elemental analysis. The
complexes are insoluble in water, completely soluble in
chloroform and dichloromethane, and partially soluble in
methanol.
2.3.5. Preparation of [V(acac)2(phen)]ClO4 Æ CH2Cl2
The above procedure was repeated with 1,10-phenanthr-
olinium perchlorate(0.26 g, 0.86 mmol) resulting in the for-
mation of [V(acac)2(phen)]ClO4 Æ CH2Cl2. Yield 0.36 g
65.83%. m.p. chars at 225 °C. Anal. Calc. for
[C22H22N2O4V]ClO4 Æ 0.75CH2Cl2: C, 46.11; H, 4.00; N,
4.73. Found: C, 46.62; H, 4.24; N, 4.79%. IR(KBr disk,
m/cmꢀ1): 3424, 1623, 1526, 1421, 1331, 1285, 1141, 1090,
1016, 927, 846, 721, 621, 577, 466. UV kmax/nm(emax/molꢀ1
cm2): 231(18950), 273(38850), 349(7718), 454(2179),
3.2. Spectroscopic characterization
In the IR spectra of 1 and 2 the peaks at 1521 and
1526 cmꢀ1, respectively, correspond to mCO stretch of acacꢀ
ligand. The mC@C/mC@N stretching frequencies at 1427 cmꢀ1
in 1 and 1421 cmꢀ1 in 2 are characteristic of the phenan-
throline moiety. In the electronic spectra, the intense UV
bands at 231 and 273 nm are characteristic of chelated phe-
nanthroline ligand and are due to intra- ligand (p–p*)
transitions.
1
671(18). H NMR (200 MHz, CDCl3): d 68.53 (br,12H),
17.56 (br, 2H), 6.91 (br, 2H), 1.64 (br, 2H), ꢀ23.43 (br, 2H).
The bands at 652 nm in 1 and 671 nm in 2 in the visible
3
3
region are due to T1g(F) ! T2g transition and the bands
3. Results and discussion
at 349 nm in 1 and 350 nm in 2 are assigned to
3
3T1g(F) ! T1g(P) transition [19]. The 1H NMR spectra
3.1. Synthesis and stoichiometry
of both the complexes give relatively sharp signals. The sig-
nals due to the –CH3 protons of the acetylacetonate ligand
appear at d 68.12 ppm in 1 and 68.53 ppm in 2, consider-
ably downfield with respect to the corresponding signal (d
45.77 ppm) in V(acac)3. The CH proton of the acetylaceto-
Both the mixed ligand complexes were obtained by the
displacement of acetylacetone by acidic progenic ligands,
namely, o-phenanthrolinium fluoroborate and o-phen-
6
5
_
7
4
2
X
+
HX
+
HX
+
3
8
N
N
N
N
N
N
9
1
10
H
(in solution)
_
_
X
BF
,
ClO
=
4
4
N
N
O
V
atm.
N
2
O
O
O
_
+
O
V
acacH
+
X
+
+
HX
N
N
O
O
reflux
O
O
O
Scheme 1. Synthesis of mixed ligand complexes 1 and 2.

S.J. Kavitha et al. / Inorganica Chimica Acta 359 (2006) 1314–1320
1317
Table 1
colinic acids (+0.635 and +0.560 V, respectively) [2,20]
indicating that 1 and 2 are stable to oxidation.
1H NMR chemical shifts and their assignments for [V(acac)2(phen)]BF4
(1) and [V(acac)2(phen)]ClO4 (2)
d/ppm
3.4. Crystal structures
2,9-H
3,8-H
4,7-H
5,6-H
(Me group)
The molecular structures and atom numbering scheme
of 1 and 2 are shown in Figs. 1a and 1b. Table 2 shows
the crystal data and refinement parameters for the com-
plexes. Complexes 1 and 2 are isomorphous and have
dichloromethane molecules as the solvent of crystalliza-
tion. The vanadium(III) ion is in a distorted octahedral
environment. The V–N bond distances (Table 3) agree clo-
sely with those reported for [{V(phen)2Cl}2O]2+ [7]. The
N–V–N bite angle in the phenanthroline moiety is
77.37(10)° and the average O–V–O bite angle in the acetyl-
acetonate chelate ring is 88.37(9)°. Thus, the substitution of
acetylacetonate ligand by the phenanthroline ligand causes
less steric crowding, opening up the possibility for the
approach of another atom to coordinate to vanadium,
which would aid in the preparation of seven-coordinate
V(III) complexes. With this aim, the reaction of V(acac)3
with o-phenanthrolinium chloride was carried out using
the same solvent and conditions mentioned for the prepa-
ration of 1 and 2. The initial red product gradually hydro-
lysed to form green crystals. The unit cell parameters for
this complex were found to be in close agreement with
the reported values (a = 17.950(5), b = 10.574(1),
1
2
1.85
1.64
17.47
17.56
ꢀ23.30
ꢀ23.43
6.93
6.91
68.12
68.53
Solvent: CDCl3.
Protons are numbered as in Ref. [10] and included in Scheme 1.
The assignments are based upon those given in Ref. [10].
nate ligand observed at d 40.41 ppm in V(acac)3 is not
observed both in 1 and 2. The phenanthroline protons
appear as four groups. This pattern is similar to that
observed in the symmetrical complex cis-[V2Cl2(phen)4(l-
O)]Cl2. The assignment of signals in the above complex
1
was confirmed by comparison with the H NMR spectra
of analogous methyl substituted phenanthroline-vana-
dium(III) complexes [10]. The chemical shifts for com-
plexes 1 and 2 are listed in Table 1 along with their
assignments.
3.3. Electrochemistry
The cyclic voltammogram of 1 in the potential window
of +1.2 to ꢀ1.0 V, indicates a reversible (DE = 50 mV)
one electron reduction at ꢀ0.885 V and a quasireversible
(DE = 230 mV) one electron oxidation at 1.007 V. The cyc-
lic voltammogram of 2 in the range of +0.9 to ꢀ0.1 V
shows a reversible (DE = 92 mV) one electron reduction
at ꢀ0.900 V and a quasireversible (DE = 275 mV) oxida-
tion at +1.025 V. A blank run with the ligands gave no
peak in the potential range +0.0 to +1.2 V. The peak
potentials for V(III)/V(IV) couple are much higher than
usually observed in V(III) complexes of picolinic and dipi-
˚
c = 28.817(8) A, orthorhombic, space group Pbcn) for
[{V(phen)2Cl2}O]2+ [7]. We conclude that the initial red
product gradually undergoes hydrolysis forming the above
oxo-bridged dimer. In order to study the effect of non-coor-
dinating anions upon complex stability, we used fluorobo-
rate and perchlorate salts for the above reaction and
obtained mixed ligand complexes 1 and 2 containing
ꢀ
ꢀ
ꢀ
BF4 and ClO4ꢀ, respectively. Both BF4 and ClO4 ions
interact with o-phenanthroline and acetylacetonate groups
Fig. 1a. Crystal structure of 1.

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S.J. Kavitha et al. / Inorganica Chimica Acta 359 (2006) 1314–1320
Fig. 1b. Crystal structure of 2.
Table 2
Crystal data and structure refinement parameters for 1 and 2
1
2
Formula
M
C
601.09
23H24BCl2F4N2O4V
C23H24Cl3N2O8V
613.73
Temperature (K)
Radiation, wavelength (A)
Crystal system
150(2)
Mo Ka, 0.71073
monoclinic
150(2)
Mo Ka, 0.71073
monoclinic
˚
Space group
a (A)
P21/n
7.7281(6)
P21/n
7.7134(8)
˚
˚
b (A)
15.4506(12)
21.5225(17)
94.207(2)
2562.9(3)
15.3004(16)
21.925(2)
93.785(2)
2581.9(5)
˚
c (A)
˚
b (A)
3
˚
V (A )
Z
4
4
Dc (g/cm3)
1.558
0.658
1224
1.579
0.746
1256
l (mmꢀ1
F(000)
)
Crystal colour
red
red
h Range for data collection
Index ranges
Reflections collected
Independent reflections
Rint
1.62–28.78°
1.62–27.50°
h ꢀ 9 to 10, k ꢀ 19 to 20, l ꢀ 28 to 29
h ꢀ 9 to 9, k ꢀ 19 to 19, l ꢀ 28 to 28
21499
6076
0.0286
21251
5852
0.0526
Reflections with F2 > 2r(F2)
Absorption correction
Minimum and maximum transmission
R1 [F2 > 2r(F2)]
4878
4147
semi-empirical from equivalents
0.726 and 0.793
0.0626
semi-empirical from equivalents
0.721 and 0.936
0.0735
wR2 (all data)
0.1749
1.080
0.810
ꢀ1.046
0.1960
1.098
1.029
ꢀ0.490
Goodness-of-fit on F2
ꢀ3
˚
˚
Largest difference peak (e A
Largest difference hole (e A
)
ꢀ3
)
through C–H. . .F and C–H. . .O hydrogen bonding interac-
tions, indicating the role of anions in stabilizing the solid
state structures of 1 and 2 (Figs. 2 and 3). The H. . .F dis-
diffraction studies [21]. The observed H. . .F distances are
much less than the reported value of 2.6 A, deduced from
˚
the CSD survey [22] of a number of structures. The D–
H. . .A angles vary from 143.0° to 165.6° in 1. In compound
2, C–H. . .O interactions occur, the H. . .O distances rang-
˚
tances range from 2.28 to 2.54 A which are comparable
to the corresponding distances ranging from 2.07 to
˚
˚
2.50 A in [Cp(PMe3)2RuH2]BF4 as determined by neutron
ing from 2.32 to 2.50 A. These are much lower than sum

S.J. Kavitha et al. / Inorganica Chimica Acta 359 (2006) 1314–1320
1319
Table 3
˚
Selected bond distances and angles for 1 and 2 (A and °)
1
2
V(1)–O(1)
V(1)–O(2)
V(1)–O(3)
V(1)–O(4)
V(1)–N(1)
V(1)–N(2)
1.958(3)
1.971(3)
1.947(3)
1.969(3)
2.134(3)
2.142(3)
1.949(4)
1.965(3)
1.945(4)
1.969(3)
2.142(4)
2.140(4)
O(1)–V(1)–O(2)
O(3)–V(1)–O(4)
N(1)–V(1)–N(2)
O(3)–V(1)–N(1)
O(4)–V(1)–O(2)
O(1)–V(1)–N(2)
O(1)–V(1)–O(3)
O(1)–V(1)–O(4)
O(1)–V(1)–N(1)
O(2)–V(1)–N(2)
O(2)–V(1)–N(1)
O(3)–V(1)–N(2)
O(3)–V(1)–O(2)
O(4)–V(1)–N(2)
O(4)–V(1)–N(1)
88.83(11)
88.06(11)
77.42(12)
172.78(12)
179.80(12)
168.63(12)
95.75(12)
91.02(11)
91.22(12)
90.65(11)
90.21(11)
95.62(12)
91.81(11)
89.52(11)
89.93(11)
88.82(14)
87.78(14)
77.32(16)
172.89(16)
179.03(15)
167.87(16)
96.44(15)
90.91(15)
90.54(16)
91.16(14)
90.19(15)
95.69(16)
91.33(14)
89.30(14)
90.74(15)
Fig. 3. A view of the C–H. . .O hydrogen bonding interactions in 2.
10-phenanthroline [25] and other aromatic N containing
ligands [26]. The two rings are parallel with zero dihedral
angles in both 1 and 2. Least-squares plane calculations
indicate that within the molecule, the acetylacetonate
ligands are planar as is the phenanthroline moiety in both
the structures.
4. Conclusions
The present work reveals the possibility of preparing
cationic mixed ligand complexes of vanadium(III) stabi-
lized by suitable anions. The complexes are indefinitely sta-
ble to air both in solution and solid state. The stability of
the crystal structures is traceable to C–H. . .O, C–H. . .F
and p–p interionic interactions. However, the contributing
factor for the molecular stability is attributed to the non-
coordinating nature of the anions. Work on the prepara-
tion of ternary complexes of vanadium(III) containing
three different bidentate ligands is in progress.
Fig. 2. A view of the packing showing the C–H. . .F interactions in 1.
˚
of van der Waals radii (2.6 A) of oxygen and hydrogen.
The D–H. . .A angles in 2 range from 129.4° to 161.0°. Such
interactions have been noticed in [(phen)2H]ClO4 [23] and
many organic molecules [24]. The crystal structure of 1
consists of chains along the b-axis (Fig. 2) while that of 2
is made up of rings (Fig. 3). p–p interactions in 1 and 2 also
contribute to the crystal stability, the closest distance
between the centroids of adjacent molecules being
5. Supplementary material
Crystallographic data for the structures reported in this
paper have been deposited with the Cambridge Crystallo-
graphic Data Centre as Supplementary data, Nos. 259448
and 259447.
˚
3.506(2) and 3.531(3) A, respectively, for the non-nitrogen
phenanthroline rings C(4)–C(9) at (x,y,z) and C(4)–C(9) at
(2 ꢀ x,2 ꢀ y,1 ꢀ z). The ring normal and the vector
between the ring centroids forms an angle of about 8° in
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