(Nitro-κN)[2-(phenyldiazenyl-κ N2)-pyridine-κN] (2,2′:6′, 2″-terpyridine-κ3N)ruthenium (II) tetrafluoroborate

Article abstract of DOI:10.1107/S0108270101007715

The Ru-N bond distances in the title complex, [Ru(NO₂)(C₁₁H₉N₃)(C₁₅ H₁₁N₃)]BF₄ or [Ru(NO₂)(tpy)(azpy)]-BF₄, [tpy is 2,2′:6′,2″-terpyridine and azpy is 2-(phenylazo)-pyridine], are Ru-N_py 2.063 (4), Ru-N_azo 2.036 (4), Ru-N_nitro 2.066 (3) A, and Ru-N_tpy 2.082(4), 1.982 (3) and 2.074 (4) A. The azo N atom is trans to the nitro group. The azo N=N bond length is 1.265 (5) A, which is the shortest found in such complexes to date. This indicates a multiple bond between Ru and the N atom of the nitro group, and π-backbonding [dπ(Ru) → π*(azo)] is decreased.

Full text of DOI:10.1107/S0108270101007715

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
1980), in order to extend the variety of such compounds and to
probe the nature of bonding in such complexes. In this report,
we describe the synthesis and the crystal and molecular
structures of the title complex, [Ru(NO2)(tpy)(azpy)]BF4, (I).
The aim of studying this compound is to explore how the co-
ligand, NO2 , affects the bonding in the complex molecule.
The coordination geometry around the Ru atom in (I) is
distorted octahedral. The equatorial positions are occupied by
three pyridine N atoms from the tpy ligand and one pyridine N
atom from the azpy molecule. In this complex, the nitrite
ligand is bound to Ru through the N atom, which is trans to the
azo nitrogen from azpy.
ISSN 0108-2701
(Nitro-jN)[2-(phenyldiazenyl-jN2)-
pyridine-jN](2,20:60,200-terpyridine-
j3N)ruthenium(II) tetrafluoroborate1
Kanidtha Hansongnern,a Uraiwan Saeteaw,a Jack Cheng,b
Fen-Ling Liaoc and Tian-Huey Lub*
As expected, the RuÐN bond to the central pyridyl ring of
Ê
the terpyridine ligand [Ru1ÐN5 1.982 (3) A] is the shortest
aDepartment of Chemistry, Faculty of Science, Prince of Songkla University, Hat-Yai,
Songkla 90112, Thailand, bDepartment of Physics, National Tsing Hua University,
Hsinchu, Taiwan 300, Taiwan, and cDepartment of Chemistry, National Tsing Hua
University, Hsinchu, Taiwan 300
bond, whereas the terminal Ru1ÐN3 [2.082 (4) A] and Ru1Ð
Ê
Ê
N4 [2.074 (4) A] bonds are lengthened, to relieve strain and
retain a typical terpyridine bite angle of 79ꢀ. This situation is
similar to that found in other ruthenium complexes containing
terpyridine ligands (Leising et al., 1990; Gerli et al., 1995;
Gulyas et al., 1996). The Ru1ÐN1(pyridine in azpy) distance
Correspondence e-mail: thlu@phys.nthu.edu.tw
Received 7 March 2001
Accepted 9 May 2001
Ê
of 2.063 (4) A is longer than the Ru1ÐN2(azo) distance of
Ê
2.036 (4) A. This indicates that there is a strong interaction
The RuÐN bond distances in the title complex,
[Ru(NO2)(C11H9N3)(C15H11N3)]BF4 or [Ru(NO2)(tpy)(azpy)]-
BF4, [tpy is 2,20:60,200-terpyridine and azpy is 2-(phenylazo)-
pyridine], are RuÐNpy 2.063 (4), RuÐNazo 2.036 (4), RuÐ
between Ru and Nazo as ꢀ-backbonding. Meanwhile, the azo
N2 atom trans to N6 from the nitro group gives rise to an
interesting result. The Ru1ÐN6(nitro) bond distance of
Ê
2.066 (3) A found in (I) is signi®cantly shorter than those
reported for other (nitro)ruthenium(II) complexes, for
Ê
Nnitro 2.066 (3) A, and RuÐNtpy 2.082 (4), 1.982 (3) and
Ê
2.074 (4) A. The azo N atom is trans to the nitro group. The
Ê
azo N N bond length is 1.265 (5) A, which is the shortest
found in such complexes to date. This indicates a multiple
bond between Ru and the N atom of the nitro group, and
ꢀ-backbonding [dꢀ(Ru) ! ꢀ*(azo)] is decreased.
Ê
example, 2.074 (6) A in trans-[Ru(tpy)(NO2)(PMe3)2]ClO4
(Leising et al., 1990). This could be due to some RuÐNnitro
multiple bonding in (I). On the other hand, the Ru1ÐN2(azo)
Ê
bond [2.036 (4) A] is longer than the values found in other
Comment
Complexes of ruthenium(II) with polypyridine ligands, such as
2,20:60,200-terpyridine (tpy) and bidentate ligands, have been
extensively studied. One reason for this is that they could lead
to high-valence ruthenium±oxo complexes, which act as
catalysts in the oxidation of carbohydrates. Thorp and co-
workers have demonstrated that the oxoruthenium(IV)
complex [RuIV(tpy)(bpy)O2+] (bpy is 2,20-bipyridine) is an
ef®cient DNA cleavage reagent (Grover et al., 1992). The
interesting properties of the class [Ru(tpy)(bpy)X]n+, where X
is monodentate, led us to synthesize ruthenium complexes
with other bidentate ligands which are better ꢀ-acceptors than
bpy, such as 2-(phenylazo)pyridine (azpy; Krause & Krause,
Figure 1
The molecular structure of (I) showing 30% probability displacement
ellipsoids and the atom-numbering scheme. H atoms have been omitted
for clarity.
1 Contribution No. 00 Au07.
ꢁ
Acta Cryst. (2001). C57, 895±896
# 2001 International Union of Crystallography
Printed in Great Britain ± all rights reserved 895

metal-organic compounds
Ê
ruthenium±azpy complexes, such as 1.977 (4) and 1.984 (4) A
Ê
in [Ru(azpy)2Cl2] (Seal & Ray, 1984), and 1.971 (7) A in
[Ru(tpy)(azpy)(CH3CN)]2+ (Pramanik et al., 1998).
In addition, the observed variation of the N N bond
lengths is indicative of ꢀ-backbonding between Ru and the
Nazo atom. In the complex ion of (I), the N N bond distance
Table 1
Selected geometric parameters (A, ).
ꢀ
Ê
Ru1ÐN5
Ru1ÐN2
Ru1ÐN1
Ru1ÐN6
Ru1ÐN4
1.982 (3)
2.036 (4)
2.063 (4)
2.066 (3)
2.074 (4)
Ru1ÐN3
BÐF3
BÐF2
BÐF1
BÐF4
2.082 (4)
1.334 (6)
1.342 (5)
1.362 (6)
1.367 (8)
Ê
is 1.265 (5) A, which is shorter than the values observed in
other complexes (Seal & Ray, 1984; Pramanik et al., 1998) and
close to the value found in the uncoordinated azpy ligand
N5ÐRu1ÐN2
N5ÐRu1ÐN1
N2ÐRu1ÐN1
N5ÐRu1ÐN6
N2ÐRu1ÐN6
N1ÐRu1ÐN6
N5ÐRu1ÐN4
N2ÐRu1ÐN4
103.04 (13)
176.31 (17)
75.57 (13)
85.04 (15)
171.88 (14)
96.40 (13)
79.38 (14)
94.32 (13)
N1ÐRu1ÐN4
N6ÐRu1ÐN4
N5ÐRu1ÐN3
N2ÐRu1ÐN3
N1ÐRu1ÐN3
N6ÐRu1ÐN3
N4ÐRu1ÐN3
97.26 (15)
87.86 (12)
79.03 (15)
92.53 (14)
104.37 (15)
88.24 (14)
158.31 (11)
Ê
[1.248 (4) A; Panneerselvam et al., 2000]. The lengthening of
the Ru1ÐN2(azo) distance suggests less Ru±N ꢀ interaction
at this centre, possibly due to a greater Ru±NO2 ꢀ interaction.
This con®rms that the nitro group also has considerable ꢀ
interactions with the Ru centre, as seen clearly from this
complex. Therefore, the N N bond length can be a useful
probe for the relative strength of the RuÐN(azo) bond.
H atoms were placed with geometrical constraints (CÐH =
Ê
0.93 A) and re®ned as riding, with Uiso(H) = 1.2Ueq(C).
Data collection: SMART (Bruker, 1999); cell re®nement: SMART;
data reduction: SHELXTL (Bruker, 1999); program(s) used to solve
structure: SHELXS97 (Sheldrick, 1990); program(s) used to re®ne
structure: SHELXL97 (Sheldrick, 1997); molecular graphics:
NRCVAX (Gabe et al., 1989); software used to prepare material for
publication: SHELXTL.
Experimental
Commercial ruthenium trichloride was purchased from Aldrich and
2,20:60200-terpyridine was obtained from Fluka. [Ru(tpy)Cl3] and
2-(phenylazo)pyridine were synthesized according to the methods of
Sullivan et al. (1980) and Campbell et al. (1953). [Ru(tpy)(azpy)Cl]Cl
was synthesized using a modi®cation of the procedure published by
Takeuchi et al. (1984). The synthesis of [Ru(NO2)(tpy)(azpy)]BF4,
(I), was as follows: [Ru(tpy)(azpy)Cl]Cl (52 mg) and silver nitrate
(30 mg) were heated at re¯ux in an acetone±water solution (12 ml;
3:1 v/v). The resulting silver chloride was ®ltered off and the ®ltrate
was heated for 15 min and NaNO2 (40 mg) added. The reaction
mixture was heated for a further 1 h and then NH4BF4 (45 mg) was
added. After standing for 5 d, the solid was ®ltered off and washed
with cool water and diethyl ether (yield 88%). Crystals of (I) suitable
for X-ray analysis were recrystallized from a solution in a mixture of
methanol and acetone (1:1 v/v).
The authors would like to thank the Higher Education
Development Project ± Postgraduate Education and Research
Program in Chemistry for partial support. They are also
indebted to the National Science Council, People's Republic
of China, for support under grant No. NSC89-2112-M-007-083.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: VJ1141). Services for accessing these data are
described at the back of the journal.
Crystal data
3
[Ru(NO2)(C11H9N3)-
(C15H11N3)]BF4
Mr = 650.37
Dx = 1.665 Mg m
Mo Kꢂ radiation
Cell parameters from 8214
re¯ections
References
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Monoclinic, Pc
a = 9.2347 (13) A
ꢃ = 2.1±28.3ꢀ
ꢄ = 0.67 mm
T = 296 (2) K
Ê
1
Ê
b = 9.6814 (13) A
Ê
c = 14.588 (2) A
ꢁ = 95.948 (2)ꢀ
V = 1297.2 (3) A
Z = 2
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3
Ê
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Siemens SMART CCD area-
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Oscillation scans
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(North et al., 1968)
3233 independent re¯ections (plus
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4484 re¯ections with I > 2ꢅ(I)
Rint = 0.036
ꢃ
max = 28.3ꢀ
Tmin = 0.788, Tmax = 0.916
7966 measured re¯ections
h = 10 ! 12
k = 12 ! 12
l = 18 ! 18
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Re®nement
Re®nement on F2
R[F2 > 2ꢅ(F2)] = 0.027
wR(F2) = 0.068
S = 1.01
4727 re¯ections
w = 1/[ꢅ2(Fo2) + (0.0468P)2]
where P = (Fo2 + 2Fc2)/3
(Á/ꢅ)max = 0.001
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3
Ê
Áꢆmax = 0.42 e A
È
3
Ê
0.34 e A
Áꢆmin
=
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370 parameters
H-atom parameters constrained
Absolute structure: Flack (1983)
Flack parameter = 0.06 (2)
ꢁ
896 Kanidtha Hansongnern et al.
[Ru(NO2)(C11H9N3)(C15H11N3)]BF4
Acta Cryst. (2001). C57, 895±896