Syntheses and characterization of [(η6-C6Me 6)Ru(μ-N3)(X)]2 (X = N3 and Cl) complexes and their reactions towards mono- and bidentate ligands

Article abstract of DOI:10.1016/j.jorganchem.2004.10.039

The reaction of the complex [{(η⁶-C₆Me ₆)Ru(μ-Cl)Cl}₂] 1 with sodium azide ligand gave two new dimers of the composition [{(η⁶-C₆Me ₆)Ru(μ-N₃)(N₃)}₂

Full text of DOI:10.1016/j.jorganchem.2004.10.039

Journal of Organometallic Chemistry 690 (2005) 885–894
www.elsevier.com/locate/jorganchem
Syntheses and characterization of [(g6-C6Me6)Ru(l-N3)(X)]2
(X = N3 and Cl) complexes and their reactions towards
mono- and bidentate ligands q
a
P. Govindaswamy , Patrick J. Carroll , Yurij A. Mozharivskyj ,
b
c
a,
*
Mohan Rao Kollipara
a
Department of Chemistry, North-Eastern Hill University, Shillong 793 022, India
b
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, PA 19104, USA
c
Ames Laboratory, Iowa State University of Science and Technology, Ames, Iowa, IA 50011, USA
Received 25 August 2004; accepted 16 October 2004
Available online 21 November 2004
Abstract
The reaction of the complex [{(g6-C6Me6)Ru(l-Cl)Cl}2] 1 with sodium azide ligand gave two new dimers of the composition
[{(g6-C6Me6)Ru(l-N3)(N3)}2] 2 and [{(g6-C6Me6)Ru(l-N3)Cl}2] 3, depending upon the reaction conditions. Complex 3 with excess
of sodium azide in ethanol yielded complex 2. These complexes undergo substitution reactions with monodentate ligands to yield
monomeric complexes of the type [(g6-C6Me6)Ru(X)(N3)(L)] {X = N3, Cl, L = PPh3 (4a, 9a); PMe2Ph (4b, 9b); AsPh3 (4c, 9c);
X = N3, L = pyrazole (Hpz) (5a); 3-methylpyrazole (3-Hmpz) (5b) and 3,5-dimethyl-pyrazole (3,5-Hdmpz) (5c)}. Complexes 2
and 3 also react with bidentate ligands to give bridging complexes of the type [{(g6-C6Me6)Ru(N3)(X)]2(l-L)} {X = N3, Cl,
L = 1,2-bis(diphenylphosphino)methane (dppm) (6, 10); 1,2-bis(diphenylphosphino)ethane (dppe) (7, 11); 1,2-bis(diphenylphosph-
ino)propane (dppp) (8, 12); X = Cl, L = 4,4-bipyridine (4,40-bipy) (13)}. These complexes were characterized by FT-IR and
FT-NMR spectroscopy as well as by analytical data.The molecular structures of the representative complexes [{(g6-
C6Me6)Ru(l-N3)(N3)}2] 2, [{(g6-C6Me6)Ru(l-N3)Cl}2] 3,[(g6-C6Me6)Ru(N3)2(PPh3)] 4a and [{(g6-C6Me6)Ru(N3)2}2 (l-dppm)] 6
were established by single crystal X-ray diffraction studies.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Hexamethylbenzene; Azide; Phosphines; Pyrazoles and ruthenium
1. Introduction
having a coordination group which is p electron bonded
(like the cyclopentadienyl ligand) have attracted atten-
tion from the viewpoints of improving and elucidating
catalytic processes such as olefin polymerization [2–5].
A lot of interest has been generated in these complexes
due to the synthesis of water-soluble arene ruthenium
complexes which exhibit antibiotic, antiviral [6] and cat-
alytic activities [7]. Recently, the first half-sandwich
arene ruthenium(II)–enzyme complex was isolated by
the reaction of g6-p-cymene Ru(II) complexes with
hen egg-white lysozyme [8]. We have been interested in
supramolecular arene ruthenium complexes based on
In recent years, the coordination chemistry of che-
lated ligands containing mixed functionalities on transi-
tion metal centers has been an extremely active area of
research [1]. In particular, transition metal complexes
q
A part of the initial results was published as a note in J.
Organomet. Chem., 689 (2004) 3108.
*
Corresponding author. Tel.: +91 364 272 2620; fax: 91 364
2550076.
E-mail addresses: kmrao@nehu.ac.in, mrkollipara@yahoo.com
(M.R. Kollipara).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.10.039

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P. Govindaswamy et al. / Journal of Organometallic Chemistry 690 (2005) 885–894
quasi-octahedral geometries, since a new type of supra-
molecular series could be developed by introduction of
these organic moieties [9]. Recently, Chang et al. [10] re-
ported cyclopentadienyl ruthenium azide [(g5-
C5H5)Ru(PPh3)2(N3)] complexes and their reactions
with acetylenes yielded triazoles and tetrazoles. We have
recently communicated syntheses of azide dimeric com-
plexes of ruthenium(II) [11] along with their reactions
with monodentate ligands. We have also reported reac-
tivity studies of chloro arene ruthenium dimers [{(g6-
arene)Ru(l-Cl)Cl}2] with diphenyl-2-pyridyl-phosphine
(PPh2Py) and pyrazoles to yield neutral, cationic phos-
phine compounds and amidine complexes, as well as
disubstituted pyrazole complexes [12]. No reports are
available yet on the reactivity of these complexes with
azide groups.
We here report the preparation of new azide ruthe-
nium(II) dimers containing the hexamethylbenzene
group and their reactions with a variety of mono- and
bidentate ligands. We have isolated mononuclear and
binuclear complexes in these reactions. Representative
complexes have been characterized by single crystal X-
ray study.
pound was filtered, washed with dry ethanol and dieth-
ylether and dried under vacuum (yield 95 mg, 92%).
IR (KBr pellets, cmꢀ1): 2064s (l-mN3), 2024s (terminal
1
m
N3). H NMR (CDCl3, d): 2.06 (s, 36H, HMB). Ele-
mental analysis (%) for C24H36Ru2N12: Calculated –
C, 33.87; H, 5.90; N, 27.43. Found: C, 33.32; H, 6.21;
N, 27.33.
2.3. Synthesis of [(g6-C6Me6)Ru(l-N3)(Cl)]2 (3)
A mixture of [(g6-C6Me6)RuCl2]2 1 (100 mg, 0.149
mmol) and twofold excess of sodium azide (18 mg,
0.288 mmol) was stirred in dry acetone (20 ml) for 10
h whereby the orange-red colored product was sepa-
rated out. The compound was filtered, washed with
dry ethanol and diethylether and dried under vacuum
(yield 87 mg, 85%).
IR (KBr pellets, cmꢀ1): 2057s (l-mN3). 1H NMR
(CDCl3, d): 2.09 (s, 36H, HMB). Elemental analysis
(%) for C24H36Ru2N6 Cl2: Calculated – C, 42.2; H,
5.32; N, 12.32. Found: C, 42.38; H, 5.09; N, 12.44.
2.4. Synthesis of complex 2 (second method)
A mixture of complex 3 (100 mg, 0.146 mmol) and ex-
cess of sodium azide (38 mg, 0.587 mmol) was stirred in
dry ethanol (20 ml) for 2 h, whereby the orange-colored
product was separated out. The compound was filtered,
washed with diethylether and dried under vacuum (yield
86 mg, 84%).
2. Experimental
2.1. General considerations
All chemicals used were of reagent grade. The sol-
vents were dried and distilled before use following the
standard procedures. Ruthenium trichloride trihydrate
(Arora Matthey Ltd.), hexamethylbenzene (Acros
Organics), PPh3, PPhMe2, AsPh3, 1,2-bis-(diph-
enylphosphino)methane (dppm), 1,2-bis(diphenylphos-
phino)ethane (dppe), 1,2-bis-(diphenylphosphino)-
propane (dppp) (Aldrich), sodium azide (Loba),
4,40-bipyridine (4,40-bipy), pyrazole (Hpz), and 3-meth-
ylpyrazole (3-Hmpz) (Merck) were used as received.
The ligand 3,5-dimethylpyrazole and the precursor com-
2.5. Synthesis of [(g6-C6Me6)Ru(N3)2 (L)]
{L = PPh3 (4a), PMe2Ph (4b) AsPh3 (4c)}
A mixture of complex 2 (60 mg, 0.086 mmol) and lig-
and L (0.260 mmol) was stirred in dry acetone (10 ml)
for 12 h, whereby the orange-colored product was sepa-
rated out. The compound was filtered, washed with
diethylether and dried under vacuum.
plex [{(g6-C6Me6)Ru(l-Cl)Cl}2]
1
were prepared
2.5.1. Complex 4a
according to the literature procedures [12b,13]. Elemen-
tal analyses of the complexes were performed in a Per-
kin–Elmer-2400 CHN/O analyzer. Infrared spectra
were recorded on a Perkin–Elmer 983 spectrophotome-
Yield 45 mg (43%). IR (KBr pellets, cmꢀ1): 2030s
(terminal mN3). 1H NMR (CDCl3, d): 1.88 (s, 18H,
HMB), 7.41–7.55 (m, 15H, Ph). 31P {1H} NMR (CDCl3,
d): 34.66. Elemental analysis (%) for C30H33RuN6P: Cal-
culated – C, 59.10; H, 5.45; N, 13.78. Found: C, 59.36;
H, 5.14; N, 13.92.
1
ter. H and 31P {1H} NMR spectra were recorded on
a Bruker-ACF-300 (300 MHz) NMR spectrometer and
referenced to tetramethylsilane and H3 PO4 (85%),
respectively. Coupling constants J are given in hertz (Hz).
2.5.2. Complex 4b
Yield 36 mg (43%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 1.66 (s, 6H,
CH3), 1.89 (s, 18H, HMB), 7.47–7.69 (m, 5H, Ph). 31P
{1H} NMR (CDCl3, d): 29.33. Elemental analysis (%)
for C20H29RuN6P: Calculated – C, 49.43; H, 6.02; N,
17.31. Found: C, 49.36; H, 5.86; N, 7.92.
2.2. Synthesis of [(g6-C6Me6)Ru(l-N3)(N3)]2 (2)
A mixture of [(g6-C6Me6)RuCl2]2 (100 mg, 0.149
mmol) and excess of sodium azide (60 mg, 0.897 mmol)
was stirred in dry ethanol (25 ml) for 4 h whereby the
orange-colored product was separated out. The com-

P. Govindaswamy et al. / Journal of Organometallic Chemistry 690 (2005) 885–894
887
2.5.3. Complex 4c
hot hexane and diethyl ether, and finally dried under
vacuum.
Yield 45 mg (40%). IR (KBr pellets, cmꢀ1): 2027s. 1H
NMR (CDCl3, d): 1.86 (s, 18H, HMB), 7.31–7.72 (m,
15H, Ph).Elemental analysis (%) for C30H33RuN6 As:
Calculated – C, 55.13; H, 5.09; N, 12.85. Found: C,
55.28; H, 5.35; N, 12.45.
2.7.1. Complex 6
Yield 79 mg (85%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 1.82 (s, 36H,
HMB), 2.14–2.17 (m, 2H, CH2), 7.10–7.34 (m, 20H,
Ph). 31P {1H} NMR (CDCl3, d): 32.62 (s). Elemental
analysis (%) for C49H58Ru2N12P2: Calculated – C,
54.57; H, 5.42; N, 15.58. Found: C, 53.97; H, 5.09; N,
15.35.
2.6. Synthesis of [(g6-C6Me6)Ru(N3)2 (L)]
{L = Hpz (5a), 3-Hmpz (5b), 3,5-Hdmpz (5c)}
A mixture of complex 2 (60 mg, 0.086 mmol) and lig-
and L (0.260 mmol) was stirred in dry acetone (10 ml)
for 10 h at room temperature. The solvent was removed
under reduced pressure. The solid mass was dissolved in
dichloromethane and then filtered. The solution was
concentrated for 2 ml and excess of hexane was added
for precipitation. The orange yellow product was sepa-
rated out, washed with diethyl ether and dried under
vacuum.
2.7.2. Complex 7
Yield 75 mg (80%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 1.75 (s, 36H,
HMB), 2.14–2.18 (m, 4H, CH2), 7.41–7.53 (m, 20H,
Ph). 31P {1H} NMR (CDCl3, d): 31.13 (s). Elemental
analysis (%) for C50H60Ru2N12P2: Calculated – C,
54.94; H, 5.54; N, 15.38. Found: C, 54.63; H, 5.09; N,
15.42.
2.6.1. Complex 5a
Yield 45 mg (63%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 2.11 (s, 18H,
HMB), 6.42 (t, 1H, J = 3.18, CHpz), 7.59 (d, 1H,
J = 2.89, CHpz ), 7.78 (d, 1H, J = 3.43, CHpz), 11.71
(s, 1H, NH). Elemental analysis (%) for C15H22RuN8:
Calculated – C, 43.36; H, 5.33; N, 26.97. Found: C,
43.09; H, 5.62; N, 26.12.
2.7.3. Complex 8
Yield 81 mg (85%). IR (KBr pellets, cmꢀ1): 2037s (ter-
1
minal mN3). H NMR (CDCl3, d): 1.75 (s, 36H, HMB),
2.14–2.16 (m, 6H, CH2), 7.27–7.47 (m, 20H, Ph). 31P
{1H} NMR (CDCl3, d): 28.12 (s). Elemental analysis
(%) for C51H62Ru2N12P2: Calculated – C, 55.36; H,
5.64; N, 15.19. Found: C, 55.52; H, 5.46; N, 15.02.
2.6.2. Complex 5b
2.8. Syntheses of [(g6-C6Me6)Ru(N3)(Cl)(L)]
{L = PPh3 (9a), PMe2Ph (9b), AsPh3 (9c)}
Yield 42 mg (57%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 2.04 (s, 18H,
HMB), 2.76 (s, 3H, CH3), 6.38 (d, 1H, J = 2.66, CHpz),
7.96 (d, 1H, J = 2.92, CHpz), 11.86 (s, 1H, NH). Ele-
mental analysis (%) for C16H24RuN8: Calculated – C,
44.74; H, 5.63; N, 26.08. Found: C, 44.31; H, 5.38; N,
26.17.
These complexes were synthesized using the same
procedure given above (see 2.5), except that complex
[(g6-C6Me6)Ru(-N3)(Cl)]2 3 (60 mg, 0.088 mmol) was
used as the starting material instead of complex 2.
2.8.1. Complex 9a
2.6.3. Complex 5c
Yield 41 mg (39%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 1.82 (s, 18H,
HMB), 6.94–7.56 (m, 15H, Ph). 31P {1H} NMR (CDCl3,
d): 33.68. Elemental analysis (%) for C30H33RuN3ClP:
Calculated – C, 59.74; H, 5.51; N, 6.96. Found: C,
59.39; H, 5.87; N, 7.06.
Yield 51 mg (67%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 2.05 (s, 18H,
HMB), 2.13 (s, 6H, CH3), 6.45 (s, 1H, CHpz), 11.42
(s, 1H, NH). Elemental analysis (%) for C17H26RuN8:
Calculated – C, 46.03; H, 5.91; N, 25.26. Found: C,
46.16; H, 5.73; N, 25.37.
2.8.2. Complex 9b
2.7. Synthesis of [{(g6-C6Me6)Ru(N3)2}2 (l-L)]
{L = dppm (6), dppe (7) and dppp (8)}
Yield 37 mg, (44%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 1.54 (s, 6H,
CH3), 1.76 (s, 18H, HMB), 7.43–7.51 (m, 5H, Ph). 31P
{1H} NMR (CDCl3, d): 30.43. Elemental analysis (%)
for C20H29RuN3ClP: Calculated – C, 50.15; H, 6.10;
N, 8.77. Found: C, 49.12; H, 5.86; N, 8.43.
A mixture of complex 2 (60 mg, 0.086 mmol) and lig-
and L (0.086 mmol) was stirred in dry acetone (10 ml)
for 3 h at room temperature. The solvent was rotary
evaporated. The solid was dissolved in dichloromethane
and then filtered. The solution was concentrated for 2 ml
and excess of hexane was added for precipitation. The
orange-yellow product was separated out, washed with
2.8.3. Complex 9c
Yield 46 mg, (41%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 1.78 (s, 18H,

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P. Govindaswamy et al. / Journal of Organometallic Chemistry 690 (2005) 885–894
HMB), 6.91–7.65 (m, 15H, Ph). Elemental analysis (%)
for C30H33RuN3ClAs: Calculated – C, 55.68; H, 5.14;
N, 6.49. Found: C, 55.37; H, 4.97; N, 6.62.
analysis (%) for C34H44Ru2N8Cl2: Calculated – C, 48.74;
H, 5.27; N, 13.37. Found: C, 48.82; H, 5.41; N, 13.53.
2.9. Synthesis of [{(g6-C6Me6)Ru(N3)Cl}2 (l-L)]
{L = dppm (10), dppe (11) and dppp (12)}
3. Structure analysis and refinement
Single crystals of complexes 2, 3, 4a and 6 suitable for
X-ray analyses were grown by slow diffusion of diethyl-
ether into their solution in a mixture of dichloromethane
and acetone. X-ray intensity data were collected on a Ri-
gaku Mercury CCD area detector employing graphite-
A mixture of complex 3 (60 mg, 0.086 mmol) and lig-
and L (0.086 mmol) was stirred in dry acetone (10 ml)
for 3 h at room temperature. The solvent was rotary
evaporated. The solid was dissolved in dichloromethane
and then filtered. The solution was concentrated for 2 ml
and excess of hexane added for precipitation. The or-
ange-yellow product was separated out, washed with
hot hexane and diethyl ether, and finally dried under
vacuum.
˚
monochromated Mo Ka radiation (k = 0.71069 A) at a
temperature of 143 K. Indexing was performed from a
series of twelve 0.5ꢁ rotation images with exposures of
30 s. Rotation images were processed using crystal clear
[14], producing a listing of unaveraged F2 and r (F2) val-
ues, which were then passed on to the crystal structure
[14] program package for further processing and struc-
ture solution on a Dell Pentium III computer. The inten-
sity data were corrected for Lorentz and polarization
effects and for absorption using the REQAB program
[15].
The structure was solved by direct methods (SIR-97)
[16]. Refinement was performed by a full-matrix least-
squares method based on F2 using SHELXL-97 [17]. All
reflections were used during refinement (F2 that were
experimentally negative were replaced by F2 = 0). The
2.9.1. Complex 10
Yield 81 mg, (86%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 1.74 (s, 36H,
HMB), 2.13–2.15 (m, 2H, CH2), 7.23–7.42 (m, 20H,
Ph). 31P {1H} NMR (CDCl3, d): 30.56(s). Elemental
analysis (%) for C49H58Ru2N6Cl2P2: Calculated – C,
55.26; H, 5.48; N, 7.89. Found: C, 55.48; H, 5.04; N,
8.01.
2.9.2. Complex 11
Yield 85 mg, (89%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 1.82 (s, 36H,
HMB), 2.13–2.20 (m, 4H, CH2), 7.38–7.61 (m, 20H,
Ph). 31P {1H} NMR (CDCl3, d): 30.34 (s). Elemental
analysis (%) for C50H60Ru2N6Cl2P2: Calculated – C,
55.64; H, 5.60; N, 7.78. Found: C, 55.35; H, 5.41; N,
7.97.
weighting
scheme
used
was
W ¼ 1=½r2ðF 2oÞþ
0:0235P2 þ 1:7407Pꢁ for the complex 2, W ¼
1=½r2ðF 2oÞ þ 0:0308P2 þ 2:5803Pꢁ for complex 4a, and
W ¼ 1=½r2ðF 2oÞ þ 0:0559P2 þ 2:6157Pꢁ for complex 6,
where P ¼ ðF 2o þ 2F 2cÞ=3. Non-hydrogen atoms were re-
fined anisotropically, while hydrogen atoms were refined
using a ‘‘riding’’ model. Refinement converged at a final
value of R = 0.0245, 0.0411, 0.0302 and 0.0366 for the
complexes 2, 3, 4a and 6, respectively (for observed data
F), and at values of wR2 = 0.0576, 0.0950, 0.0724 and
0.0957 for complexes 2, 3, 4a and 6, respectively (for un-
ique data F2) (see Scheme 1).
2.9.3. Complex 12
Yield 82 mg, (85%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 1.74 (s, 36H,
HMB), 2.14–2.19 (m, 6H, CH2), 7.24–7.48 (m, 20H,
Ph). 31P {1H} NMR (CDCl3, d): 27.46 (s). Elemental
analysis (%) for C51H62Ru2N6Cl2P2: Calculated – C,
56.02; H, 5.71; N, 7.68. Found: C, 56.25; H, 5.48; N,
7.52.
Table 1 lists the cell information, data collection
parameters and refinement data. Figs. 1–4 are ORTEP
[18] representations of complexes 2, 3, 4a and 6 with
30% probability thermal ellipsoids displayed (except
complex 3 with 50% probability).
2.10. Synthesis of [{(g6-C6Me6)Ru(N3)Cl}2 (l-4,4-
bipy)] (13)
4. Results and discussion
A mixture of complex 3 (60 mg, 0.088 mmol) and 4,4-
bipyridine (0.088 mmol) in dry acetone (15 ml) was stir-
red for 3 h, and the solvent was removed under vacuum.
The solid product was washed with diethylether (10
ml · 2) and then dried under vacuum to give the yellow
solid complex 13.
Yield 62 mg, (84%). IR (KBr pellets, cmꢀ1): 2037s
(terminal mN3). 1H NMR (CDCl3, d): 2.05 (s, 36H,
HMB), 7.55–7.69 (m, 4H), 8.75–8.94 (m, 4H). Elemental
4.1. Dimeric complexes
The chloro arene ruthenium dimer 1 reacted with ex-
cess of sodium azide in ethanol gave an orange-colored
tetraazido complex 2 in 92% yield. When the reaction
was carried out with the complex 1 and sodium azide
in 1:2 molar ratios in acetone, the orange-red di-azido
complex 3 was obtained in 85% yield. The similar

P. Govindaswamy et al. / Journal of Organometallic Chemistry 690 (2005) 885–894
889
Cl
3 with excess of sodium azide gave the complex 2. These
complexes are stable in air and soluble in polar solvents
such as chloroform and dichloromethane, but insoluble
in non-polar solvents such as hexane and pentane.
The infrared spectrum of complex 2 shows two char-
acteristic stretching bands – one in the region of the ter-
minal azide ligands at 2024 cmꢀ1 and another in the
region of the bridging azide ligands at 2064 cmꢀ1 [20]
indicating the complex 2 have two types of azide groups.
Where as in the case of complex 3 exhibit the character-
Cl
Ru
Cl
Ru
Cl
complex 1
1:2
1:6
NaN
3
NaN
3
EtOH
N
N
N
acetone
N
N
N
N
N
N
Cl
Ru
Excess
Ru
N
Ru
Ru
Cl
istic band for the bridging azide groups at 2057 cmꢀ1
,
NaN
3
N
N
N
demonstrating that no terminal azide ligands are pre-
sent. This is further confirmed by the elemental analysis,
which indicates only two azide groups. The proton
NMR spectrum of the complex 2 exhibits a strong peak
at 2.06 ppm for the hexamethylbenzene protons,
whereas in the case of complex 3 the signal is observed
at 2.09 ppm.
N
EtOH
N
N
N
N
complex 3
complex 2
Scheme 1.
reaction in the case of p-cymene dimer [(g6-
C10H14)Ru(l-Cl)Cl]2 invariably yielded only the bridged
disubstituted azido complex [(g6-C10H14)Ru(l-N3)Cl]2
analogous to complex 3 [19a]. It is very interesting to
see the difference of the reactivity of these dimers (2
and 3) towards azide as observed in the case pyrazole
reactions [12b]. In the case of pyrazole reactions, one
can understand the difference of the reactivity of these
dimers towards pyrazoles on the basis of steric factor
of pyrazoles as well as hexamethylbenzene. The complex
4.2. Mononuclear complexes
The dimeric complexes 2 and 3 undergo bridge cleav-
age reactions with a twofold excess of ligand L in ace-
tone, giving the mononuclear complexes 4, 5, and 9
(Scheme 2).
The infrared spectra of complexes 4 and 9 show a
strong band in the range of 2037–2026 cmꢀ1 due to
the terminal azide group [21] along with strong bands
due to the phenyl groups of the phosphine ligands.
Table 1
Crystal data and structure refinement for complexes 2, 3, 4a and 6 acetone
Formula
C
24H36N12Ru2
C24H36Cl2N6Ru2
C30H33N6PRu
C52H64N12P2ORu2
Mr
694.79
681.63
0.71073
Triclinic
609.66
1137.23
0.71069
Triclinic
˚
Wavelength (A)
Crystal system
Space group
0.71069
Monoclinic
P21/n
0.71069
Monoclinic
P21/c
ꢀ
ꢀ
P1
P1
Unit cell dimensions
˚
a (A)
˚
8.6152(5)
16.1555(10)
10.4889(7)
90
9.169(2)
9.178(2)
9.365(2)
111.208(4)
102.294(4)
106.566(4)
658.6(3)
1
18.037(2)
8.5409(7)
17.9964(13)
90
11.5469(5)
13.1587(4)
18.6027(5)
69.563(3)
83.811(4)
78.166(4)
2590.3(2)
2
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
110.468(1)
90
100.383(2)
90
3
˚
V (A )
1367.7(2)
2
2726.9(4)
4
Z
Crystal size (mm3)
Dcalc (g cmꢀ 3)
F(000)
0.35 · 0.12 · 0.06
1.687
704
0.05 · 0.04 · 0.03
1.718
344
0.32 · 0.30 · 0.04
1.485
1256
0.32 · 0.20 · 0.10
1.458
1172
2h (ꢁ)
Reflections collected
Independent
5.04–54.96
7973
2971
4.96–56.36
5765
5155
5.3–54.96
35422
6111
5.36–54.96
32462
11506
Reflections [R(int)]
l (Mo Ka)/cmꢀ1
No. parameters
Goodness of-fit on F2
R1 (I > 2r(I)), wR2
R1, R2 (all data)
0.0152
11.43
0.0164
1.374
0.0239
6.65
0.0197
6.95
179
1.097
296
0.983
350
1.0124
635
1.055
0.0245, 0.0576
0.0266, 0.0592
+1.152, ꢀ0.550
0.0411, 0.0950
0.0523, 0.1006
+0.807, ꢀ0.403
0.0302, 0.0724
0.0330, 0.0737
+0.804, ꢀ0.853
0.0366, 0.0957
0.0406, 0.0998
+1.691, ꢀ1.134
ꢀ3
˚
Largest diff. peak and hole (e A
)

890
P. Govindaswamy et al. / Journal of Organometallic Chemistry 690 (2005) 885–894
Fig. 1. ORTEP diagram of the complex 2 with 30% probability
˚
thermal ellipsoids. Selected bond lengths (A) and bond angles (ꢁ)
Fig. 2. ORTEP diagram of the complex 3 with 50% probability
thermal ellipsoids. Hydrogens are omitted for clarity of the figure.
˚
Bond lengths (A)
˚
Selected bond lengths (A) and bond angles (ꢁ)
Ru(1)–N(1)
Ru(1)–N(4)
N(1)–N(2)
N(2)–N(3)
N(4)–N(5)
N(5)–N(6)
Ru–C*
2.148(2)
2.141(2)
1.208(3)
1.140(3)
1.084(3)
1.191(4)
1.663
˚
Bond lengths (A)
Ru(A)–C*
1.714
1.614
Ru(B)–C*
Ru(A)–Cl(A)
Ru(A)–N(1)
Ru(A)–N(4)
Ru(B)–Cl(B)
Ru(B)–N(1)
Ru(B)–N(4)
N(1)–N(2)
N(2)–N(3)
N(4)–N(5)
N(5)–N(6)
2.394(5)
2.120(14)
2.138(13)
2.421(5)
2.151(12)
2.168(14)
1.189(19)
1.11(2)
Bond angles (ꢁ)
N(4)–Ru(1)–N(1)
N(1)#(1)–Ru(1)–N(1)
N(4)–Ru(1)–N(1)#(1)
84.33(8)
73.26(8)
82.59(9)
*
Ruthenium to centroid of HMB.
1.23(2)
1.17(2)
Bond angles (ꢁ)
The monomeric compounds exhibit only one IR band
due to terminal azide group which is slightly higher
wave number with comparison to the starting dimer.
The 1H NMR spectra of these complexes exhibit a
strong peak for hexamethylbenzene at 1.88 ppm for
complex 4a,1.89 ppm for complex 4b and 1.86 ppm for
complex 4c, indicating an upfield shift from 2.08 ppm
for the HMB protons in the starting complex. This is
due to the increased electron density on the ruthenium
atom induced by the two azide groups. The aromatic
protons of the ligands L appear as multiplets at around
6.91–7.69 ppm for these complexes. The 31P {1H} NMR
spectra of these complexes exhibit a singlet at around
29.33–34.66 ppm for the terminal phosphine group.
The 1H NMR spectra of the complexes 9a–c also exhibit
N(1)–Ru(A)–Cl(A)
N(4)–Ru(A)–Cl(A)
N(1)–Ru(A)–N(4)
N(1)–Ru(B)–Cl(B)
N(4)–Ru(B)–Cl(B)
N(1)–Ru(B)–N(4)
87.4(4)
87.6(4)
71.9(4)
84.4(4)
86.5(4)
70.7(4)
*
Ruthenium to centroid of HMB.
strong signals for the hexamethylbenzene protons in the
range at 1.76–1.89 ppm and multiplets in the range of
7.0–7.7 ppm for the phenyl groups of the phosphine lig-
ands. The methyl protons of PMe2Ph appear around
1.66 ppm in the case of complex 4b and around 1.54
ppm in the case of complex 9b.

P. Govindaswamy et al. / Journal of Organometallic Chemistry 690 (2005) 885–894
891
Fig. 4. ORTEP diagram of the complex 6 with 30% probability
thermal ellipsoids. Hydrogens are omitted for clarity of the figure.
˚
Selected bond lengths (A) and bond angles (ꢁ)
˚
Bond lengths (A)
Ru(1)–N(4)
Ru(1)–N(1)
Ru(1)–P(1)
P(1)–C(25)
P(2)–C(25)
Ru(2)–N(10)
Ru(1)–C*
Ru(2)–N(7)
Ru(2)–P(2)
Ru(2)–C*
2.145(2)
2.105(2)
2.3756(6)
1.158(3)
1.836(2)
2.127(2)
2.238
2.089(2)
2.3594(6)
2.233
Fig. 3. ORTEP diagram of the complex 4a with 30% probability
thermal ellipsoids. Hydrogens are omitted for clarity of the figure.
˚
Selected bond lengths (A) and bond angles (ꢁ)
˚
Bond lengths (A)
Ru(1)–N(1)
Ru(1)–N(4)
N(1)–N(2)
N(2)–N(3)
N(4)–N(5)
N(5)–N(6)
Ru(1)–P(1)
Ru–Ca
2.145(2)
2.105(2)
1.203(3)
1.203(3)
1.192(3)
1.158(3)
2.3604(5)
2.242
Bond angles (ꢁ)
N(4)–Ru(1)–N(1)
N(4)–Ru(1)–P(1)
N(1)–Ru(1)–P(1)
N(7)–Ru(2)–N(10)
N(7)–Ru(2)–P(2)
N(10)–Ru(2)–P(2)
83.09(9)
84.95(6)
81.18(6)
83.56(9)
86.80(6)
82.21(6)
Bond angles (ꢁ)
N(4)–Ru(1)–N(1)
N(4)–Ru(1)–P(1)
N(1)–Ru(1)–P(1)
84.03(7)
87.77(5)
86.32(5)
*
Average distance between ruthenium and HMB.
a
Average distance between ruthenium and HMB.
of orange colored, air-stable binuclear complexes 6–8
and 10–12 (Scheme 3). The formation of these com-
The IR spectrum of complex 5 shows a strong band at
2037 cmꢀ1 due to the terminal azide mode of the complex
which is higher wave number comparatively to starting
1
plexes is confirmed by the H NMR spectra. The IR
spectra of these complexes show the terminally bound
azide ligands at 2037 cmꢀ1 [21] along with strong bands
due to the phenyl groups of the phosphine ligands.
The aromatic protons of the ligand L appear as
multiplets at around 7.10–7.61 ppm for these complexes.
The multiplets in the range 2.13–2.20 ppm are assigned
to the methylene groups of the phosphine ligands. The
31P {1H} NMR spectra of these complexes exhibit a sin-
glet at around 27.46–32.62 ppm for the bridged phos-
phine group indicating the symmetric nature of the
complexes.
1
complex. Peak integration of the H NMR spectrum of
complex 5 shows these complexes are mononuclear in nat-
ure. The methyl protons of hexamethylbenzene appear as
a strong singlet at around 2.04–2.11 ppm. The NH proton
of the pyrazole ligands shifts downfield and appears at
around 11.5 ppm [12b]. The ring CH protons of pyrazoles
appear in the aromatic region.
4.3. Binuclear bridging complexes
The reaction of the complex 2 and 3 with bridging
phosphine ligands in acetone resulted in the formation
The reaction of the complex 3 with 4, 40-bipyridine
ligand in acetone resulted in the formation of the orange

892
P. Govindaswamy et al. / Journal of Organometallic Chemistry 690 (2005) 885–894
N
N
X
N
L
Ru
Ru
N
N
N
Ru
acetone
N
X
X
L
N
X = N , L = PPh (4a)
3
3
N
X = Cl, L = PPh (9a)
3
X = N , L = PMe Ph (4b)
3
2
X = Cl, L = PMe Ph (9b)
2
X = N (2)
3
X = Cl (3)
X = N , L = AsPh (4c)
3
3
X = Cl, L = AsPh (9c)
3
X = N , L = Hpz (5a)
3
X = N , L = 3-Hpz (5b)
3
X = N , L = 3,5-Hdmpz (5c)
3
Scheme 2.
N
N
N
N
N
X
X
N
L
Ru
Ru
Ru
L
Ru
acetone
N
N
X
X
N
N
X = N , L = dppm (6)
N
3
N
X = N , L = dppe (7)
3
X = N , L = dppp (8)
3
X = N (2)
3
X = Cl(3)
X = Cl, L = dppm (10)
X = Cl, L = dppe (11)
X = Cl, L = dppp (12)
X = Cl, L = 4,4'-bipy (13)
Scheme 3.
colored binuclear complex 13 (Scheme 3). The infrared
spectrum of complex 13 shows a strong band at 2037
equals 84.33(8)ꢁ, a little lower than that for other re-
ported compounds. The bond distance between the cent-
1
cmꢀ1 due to the terminal azide group. The H NMR
roid of HMB and Ru is 1.663 A, while the Ru–N bond
˚
˚
distances are 2.148(2) A for the Ru(1)–N(1) bond and
˚
2.141(2) A for the Ru(1)–N(4) bond, which are within
the limits observed for reported complexes [22]. The ter-
minal azide nitrogens have N–N bond distances of
spectrum of complex 13 exhibits a strong singlet for
hexamethyl-benzene protons at 2.05 ppm. The ligand
bipy protons are observed as four doublets in the region
7.55–8.94 ppm.
˚
˚
1.084(3) A for the (N4)–(N5) bond and 1.191(3) A for
the (N5)–(N6) bond. The N–N bond distances in the
˚
bridging azide nitrogens are 1.208(3) A for the (N1)–
5. Molecular structures
˚
(N2) bond and 1.140(3) A for the (N2)–(N3) bond. In
Single crystals of the complexes 2, 3, 4a and 6 were
subject to X-ray crystal studies. A summary of the sin-
gle-crystal X-ray structure analyses is shown in Table
1. The ORTEP drawings of the complexes 2, 3, 4a and
6 are shown in Figs. 1–4, respectively. The geometry
around the ruthenium atom in these complexes 2, 3,
4a and 6 is octahedral, where the hexamethylbenzene
ligand occupies three coordination positions.
The complex [{(g6-C6Me6)Ru(l-N3)(N3)}2] 2 crystal-
lizes in the monoclinic space group P2(1)/n with centro-
symmetry. The compound has a structure describable as
the joining of two piano stools together by their legs.
The bond angle N(1)–Ru(1)–N(4) around ruthenium
the case of terminal azide, the N(4)–N(5) bond distance
is slightly smaller than the bridging azide N(1)–N(2),
whereas the N(5)–N(6) distance of the terminal azide
is slightly longer than the bridging azide N(2)–N(3) dis-
tances. However, these bond distances for the bridging
and terminal azide N–N bonds are close to other re-
ported values [19].
The complex [{(g6-C6Me6)Ru(l-N3)Cl}2]3 crystal-
ꢀ
lizes in the triclinic space group P1. It consists of each
Ru(II) atom bonded to a hexamethylbenzene ligand,
two nitrogen atoms of azide groups and one chlorine
atom, maintaining centrosymmetry. The Ru–Cl bond
˚
distances are 2.394(5) and 2.421(5) A, which are close

P. Govindaswamy et al. / Journal of Organometallic Chemistry 690 (2005) 885–894
893
to those in the starting dimeric complex 1 [23]. The
6. Concluding remarks
Ru–N bond lengths involving the bridging nitrogen
moieties Ru(A)–N(1), Ru(A)–N(4), Ru(B)–N(1) and
Ru(B)–N(4) are 2.120(14), 2.138(13), 2.151(12) and
It is thus interesting to note that there is a difference
in reactivity between the p-cymene dimeric complex
[(g6-p-cymene)Ru(l-Cl)Cl]2 and the hexamethylbenzene
dimeric complex [(g6-C6Me6)Ru(l-Cl)Cl]2 towards
azides and pyrazoles [3b]. The former gives only the
disubstituted p-cymene ruthenium l-azido dimer [(g6-
C10H14)Ru(l-N3)Cl]2 irrespective of sodium azide
concentration [19a], whereas the latter gives both disub-
stituted l-azido and tetrazido substituted complexes.
These complexes can undergo a variety of substitution
reactions with monodentate and bidentate ligands to
yield monomeric compounds as well as bridged dimeric
compounds. Complex 3 gives chiral complexes after sub-
stitution of neutral ligands. These complexes are very
good starting materials for the synthesis of new azido
compounds.
˚
2.168(14) A, respectively, very similar to those found
in the complex 2. This structure gives N–N bond dis-
˚
tances of 1.189(19), 1.11(2), 1.23(2) and 1.17(2) A,
which are slightly shorter than in the complex 2. The
geometry of the complex is octahedral with the hexa-
methylbenzene ligand occupying three coordination
sites. This is evident from the nearly 90ꢁ values for
the N–Ru–Cl bond angles, which are 87.4(4)ꢁ for the
N(1)–Ru(A)–Cl(A) angle and 87.6(4)ꢁ for the N(4)–
Ru(A)–Cl(A) angle. The average distance between
ruthenium and the hexamethylbenzene carbons is
˚
˚
2.207 A for the Ru(A)–C(arene) bonds and 2.128 A
for the Ru(B)–C(arene) bonds. The distances between
the centroid of the arene and the metal atoms are
˚
1.714 and 1.614 A for Ru(A)–C(arene) and Ru(B)–
C(arene), respectively.
The structure of the complex [(g6-C6Me6)R-
u(N3)2(PPh3)] 4a consists of a Ru (II) atom g6-coordi-
nated to a hexamethylbenzene molecule, to the two
nitrogen atoms of the azide group, and to a PPh3 ligand
through the P atom, leading to a Ôthree-legged piano
stoolÕ type of structure. The two Ru–N distances
Acknowledgement
We thank Professor R.H. Duncan Lyngdoh for his
help in preparing the manuscript.
Appendix A. Supplementary material
˚
(2.105(2) and 2.145(2) A) are slightly different, as found
in related structures with phosphine complexes (2.177(2)
Crystallographic data for the structural analysis have
been deposited at the Cambridge Crystallographic Data
Centre (CCDC), CCDC No. 235560 for complex 2,
CCDC No. 247740 for complex 3, CCDC No. 247738
for complex 4a, and CCDC No. 247739 for complex 6.
Copies of this information may be obtained free of
charge from the director, CCDC, 12 Union Road, Cam-
bridge, CB2 1EZ, UK (fax: +44-1223-336033; e-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.ca-
m.ac.uk). Supplementary data associated with this arti-
cle can be found, in the online version at doi:10.1016/
j.jorganchem.2004.10.039.
˚
˚
A) [24]. The average Ru–C(arene) distance is 2.242 A.
The arene ring is nearly planar and shows C–C bond
distances that appear to be normal. The N(4)–Ru(1)–
N(1) bond angle of 84.05(7)ꢁ is similar to that found
in the related rhodium(III) azido complex [Rh2(C5Me5)2-
(N3C4F6)3(N3)] (82.0(3)ꢁ) [19b]. The N(1)–Ru(1)–P(1)
and N(4)–Ru(1)–P(1) bond angles (86.32(5) and
87.77(5)ꢁ, respectively) also indicate a piano stool type
of structure.
The complex 6 crystallized with one molecule of ace-
tone for each complex molecule. The geometry around
each ruthenium center of 6 is close to octahedral, with
the hexamethylbenzene ligand occupying three coordi-
nation sites. The complex crystallizes in the triclinic
space group P1. as shown in figure 4. The ruthenium
atom is -bonded to the hexamethylbenzene ligand with
the average distance between ruthenium and the six
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