Synthesis of arene ruthenium triazolato complexes by cycloaddition of the corresponding arene ruthenium azido complexes with activated alkynes or with fumaronitrile

Article abstract of DOI:10.1016/j.jorganchem.2006.05.001

The neutral arene ruthenium azido complexes [(η⁶-p-cymene)Ru(LL)(N₃)], [LL = acetylacetonato (acac) (4), benzoylacetonato (bzac) (5) diphenylbenzoyl methane (dbzm) (6)] undergo [3+2] cycloaddition reaction with a series of activated alkynes and fumaronitrile to produce the arene ruthenium triazolato complexes: [(η⁶-p-cymene)Ru(LL){N₃C₂(CO₂R)₂}] [LL = (acac), R = Me (7); LL = (bzac), R = Me (8); LL = (dbzm), R = Me (9); LL = (acac), R = Et (10); LL = (bzac), R = Et (11); LL = (dbzm), R = Et (12) and [(η⁶-p-cymene)Ru(LL)(N₃C₂HCN)]; LL = acac (13), bzac (14); dbzm (15). However, cationic azido complexes, [(η⁶-p-cymene)Ru(dppe)(N₃)]⁺ and [(η⁶-p-cymene)Ru(dppm)(N₃)]⁺ do not undergo such cycloaddition reactions. The complexes were characterized on the basis of microanalyses, FT-IR and NMR spectroscopic data. Crystal structures of representative complexes were determined by single crystal X-ray diffraction.

Full text of DOI:10.1016/j.jorganchem.2006.05.001

Journal of Organometallic Chemistry 691 (2006) 3509–3518
www.elsevier.com/locate/jorganchem
Synthesis of arene ruthenium triazolato complexes by cycloaddition
of the corresponding arene ruthenium azido complexes with activated
alkynes or with fumaronitrile
a
b
b
a,
*
Keisham Sarjit Singh , Kevin A. Kreisel , Glenn P.A. Yap , Mohan Rao Kollipara
a
Department of Chemistry, North-Eastern Hill University, Shillong 793022, India
Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA
b
Received 9 March 2006; received in revised form 1 May 2006; accepted 1 May 2006
Available online 5 May 2006
Abstract
The neutral arene ruthenium azido complexes [(g6-p-cymene)Ru(LL)(N3)], [LL = acetylacetonato (acac) (4), benzoylacetonato (bzac)
(5) diphenylbenzoyl methane (dbzm) (6)] undergo [3+2] cycloaddition reaction with a series of activated alkynes and fumaronitrile to
produce the arene ruthenium triazolato complexes: [(g6-p-cymene)Ru(LL){N3C2(CO2R)2}] [LL = (acac), R = Me (7); LL = (bzac),
R = Me (8); LL = (dbzm), R = Me (9); LL = (acac), R = Et (10); LL = (bzac), R = Et (11); LL = (dbzm), R = Et (12) and [(g6-p-cym-
ene)Ru(LL)(N3C2HCN)]; LL = acac (13), bzac (14); dbzm (15). However, cationic azido complexes, [(g6-p-cymene)Ru(dppe)(N3)]+ and
[(g6-p-cymene)Ru(dppm)(N3)]+ do not undergo such cycloaddition reactions. The complexes were characterized on the basis of
microanalyses, FT-IR and NMR spectroscopic data. Crystal structures of representative complexes were determined by single crystal
X-ray diffraction.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: p-Cymene; Diethylacetylenedicarboxylate; Dimethylacetylenedicarboxylate; Azide; Ruthenium; Fumaronitrile; Acetylacetonate; Benzoylacet-
onate; Diphenylbenzoyl methane
1. Introduction
complexes undergo [3+2] cycloaddition reactions with nitr-
iles [7–19] and isonitriles [7,8,20–23] to produce tetrazolato
complexes. Similar reactions with alkynes produce triazo-
lates complexes [12,24–26]; alkenes, however, react very
slowly and mostly afforded mixture of products [8,12].
Although such reactions are studied extensively in syn-
thetic organic chemistry, dipolar cycloaddition reactions
of azide coordinated metal complexes are relatively unex-
plored. A few reports appeared on cycloaddition of alkynes
to ruthenium azido complexes in recent years [27–29].
However, to the best of our knowledge cycloaddition reac-
tion of arene ruthenium azido complexes have not been
studied. Our study reveals that such cycloaddition reac-
tions are favorable in neutral complexes, but do not occur
in cationic arene ruthenium azido complexes. Bennett et al.
[30] reported the synthesis of [(g6-arene)Ru(acac)Cl] by the
reaction of a arene ruthenium dimer with acac in presence
In organic chemistry 1,3-dipolar cycloaddition reactions
are common processes. The process involves the reaction
between 1,3-dipoles or a propargynellyl type with dipolaro-
philes. One of the most useful synthetic applications of
azides is the preparation of 1,2,3-triazoles via 1,3-dipolar
cycloaddition reactions of azides with substituted acetylene
compounds [1–4]. The dipolar cycloaddition reactions
between acetylenes and azides are very important and the
most efficient route to synthesize 1,2,3-triazoles [4,5]. In
analogy, a coordinated azide group in metal complexes
can also undergo such cycloaddition reactions [6]. Azido
*
Corresponding author. Tel.: +91 364 272 2620; fax: +91 364 255 0076.
E-mail addresses: mohanrao59@hotmail.com, mohanraokollipara@
yahoo.co.in (M.R. Kollipara).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.05.001

3510
K.S. Singh et al. / Journal of Organometallic Chemistry 691 (2006) 3509–3518
of base and its reactions with various ligands. Here, we
report the preparation of p-cymene ruthenium b-diketo-
nato azido complexes [(g6-arene)Ru(LL)(N3)]. These azido
complexes undergo [3+2] cycloaddition reactions with a
series of activated alkynes and fumaronitrile to produce
p-cymene ruthenium triazolato complexes. The spectral
and structural characterizations of these complexes are
presented.
added and kept at room temperature. A yellow crystalline
solid was precipitated out. The precipitate was collected
and dried. The spectroscopic data are consisted with the
reported values.
2.2.2. Preparation of [(g6-p-cymene)Ru(acac)(N3)] (4)
Two routes were used to prepare this complex:
Route (a): The complex [(g6-p-cymene)Ru(acac)Cl]
(100 mg, 0.270 mmol) and NaN3 (35 mg, 0.54 mmol) were
stirred in 30 ml of ethanol for 6 h. The solvent was
removed on rotary-evaporator and the residue was dis-
solved in diethyl ether then filtered. The filtrate on evapo-
2. Experimental
Caution: All the azide reactions should perform with
extreme care.
rating at room temperature affords
a bright red
crystalline solid of the complex. Yield: 83 mg, 82%.
Route (b): The complex [{(g6-p-cymene)Ru(l-N3)Cl}2]
(100 mg, 0.160 mmol) and [Na(acac) Æ H2O] (56 mg,
0.40 mmol) were stirred in 30 ml of ethanol for 5 h, and
then solvent was removed. The residue was dissolved in
dichloromethane and then filtered. The filtrate on concen-
tration and addition of excess hexane afford red crystalline
solid of the complex.
2.1. Physical methods and materials
All solvents were dried in appropriate drying agents and
distilled prior to use [31]. RuCl3 Æ 3H2O (Arora Matthey
Limited) and dimethylacetylenedicarboxylate (Aldrich)
and diethylacetylenedicarboxylate (Acros) were purchased
and used as received. NMR spectra were recorded on a
Bruker AMX-400 MHz spectrometer at 400.13 (1H),
100.61 MHz (13C) with SiMe4 as internal reference and cou-
pling constants are given in hertz. Infrared spectra were
recorded as a KBr pellets on a Perkin–Elmer model 983 spec-
trometer. Elemental analyses were carried out at the SAIF,
NEHU, Shillong, using a Perkin–Elmer 2400 CHN/S ana-
lyzer. The precursor complexes [{(g6-p-cymene)RuCl2}2]
[32], [{(g6-p-cymene)Ru(l-N3)Cl}2] [33,34], [(g6-p-cym-
ene)Ru(bzac)Cl] (2) and [(g6-p-cymene)Ru(dbzm)Cl] (3)
were prepared by following a literature method [34]. While
the complex [(g6-p-cymene)Ru(acac)Cl] (1) was prepared
by minor modification of reported method [35]. The follow-
ing nomenclature was used in the text.
Analytical and spectroscopic data are as follows: Anal.
Calc. for C15H21O2N3Ru: C, 47.86; H, 5.58; N, 11.16.
Found: C, 47.39; H, 5.78; N, 10.87%. IR (KBr, cmꢀ1):
1
2037 (mN3), 1577, 1519 (mC@O + mC@C). H NMR (CDCl3,
d): 1.31 (d, 6H, JH–H = 6.92, CHMe2), 1.98 (s, 6H, (acac-
Me)), 2.20 (s, 3H, CH3), 2.83 (m, 1H, CHMe2), 5.11 (s,
1H, acac-cH), 5.13 (d, 2H, JH–H = 4.88, C6H4), 5.39 (d,
2H, JH–H = 5.92, C6H4). 13C {1H} NMR (CDCl3, d):
17.33 (s, CH3), 22.30 (s, Me, CHMe2), 27.17 (s, (acac-
0
Me)), 30.62 (s, CH, CHMe2), 78.87 (s, CAA ) 82.73 (s,
i
0
C
BB ), 96.91 (s, CMe), 98.63 (acac-cC), 99.36 (s, CPr ),
186.93 (s, acac-CO).
2.2.3. Preparation of [(g6-p-cymene)Ru(bzac)N3] (5)
This complex was prepared by following a similar
method as described in the preparation of complex 4 (route
b) using [Na(bzac) Æ H2O] instead of [Na(acac) Æ H2O].
Yield: 82 mg, 81%.
Anal. Calc. for C20H23N3O2Ru: C, 54.78; H, 5.25; N,
9.58. Found: C, 54.26; H, 4.98; N, 9.27%. IR (KBr,
cmꢀ1): 2015 m(N3), 1587, 1560, 1528 (mC@O + mC@C). 1H
NMR (CDCl3, d): 1.35 (d, 6H, JH–H = 6.9, CHMe2), 1.98
(s, 3H, (bzac-Me)), 2.24 (s, 3H, Me), 2.83 (m, 1H, CHMe2),
5.21 (s, 1H, bzac-cH), 5.36 (d, 2H, JH–H = 5.8), 5.52 (d, 2H,
JH–H = 5.8), 7.35 (m, 3H), 7.78 (d, 2H, JH–H = 6.8).
R
R
A
B
Me
Me
Me
O
O Na
H
A'
B'
Na[acac]: R, R = Me,
Na[bzac]: R, R = Me,
Na[dbzm]: R, R = Ph,
Me
Ph
Ph
2.2.4. Preparation of [(g6-p-cymene)Ru(dbzm)N3] (6)
This complex was prepared by following a similar
method as described in the preparation of complex 4 (route
b) using [Na(dbzm) Æ H2O] instead of [Na(acac) Æ H2O].
Yield: 86 mg (84%).
2.2. Synthesis of complexes
2.2.1. Preparation of [(g6-p-cymene)Ru(acac)Cl] (1)
The complex [{(g6-p-cymene)RuCl2}2] (100 mg, 0.163
mmol) and Na(acac) (57 mg, 0.40 mmol) were stirred in
dry methanol 20 ml for 3 h. The solution turned into
bright yellow, the solvent was removed by rotary-
evaporator and the residue was dissolved in dichlorometh-
ane and filtered to remove sodium chloride. The solution
was concentrated to ca. 5 ml and excess of hexane was
IR (KBr, cmꢀ1): 2030 m(N3), 1593, 1533 (mC@O + mC@C).
1HNMR (CDCl3, d) : 1.36 (d, 6H, JH–H = 5.8), 2.36 (s, 3H,
Me), 2.89 (m, 1H, CHMe2), 5.34 (d, 2H, JH–H = 6.2), 5.56
(d, 2H, JH–H = 6.4), 6.32 (s, 1H), 7.46 (m, 6H), 7.92 (m,
4H).

K.S. Singh et al. / Journal of Organometallic Chemistry 691 (2006) 3509–3518
3511
2.2.5. Preparation of triazolato complexes [(g6-p-
cymene)Ru(LL){N3C2(CO2R)2}] (LL = acac, R = Me
(7), LL = bzac, R = Me (8); LL = (dbzm), R = Me (9),
LL = acac, R = Et (10); LL = (bzac), R = Et (11),
LL = dbzm, R = Et (12))
21.19 (s, Me, CHMe2), 30.75 (s, CH, CHMe2), 51.42 (d,
0
CH3, JC–H = 20.72 (CO2CH3)2), 80.63, 80.98 (s, CAA ),
85.21, 85.54 (s, C0BB), 95.87 (s, dbzm-cC), 98.80 (s, CPri),
127.34–130.93 (m, Ph), 139.30 (s, C(CO2Me)2), 153.83 (s,
CO2) 182.13, 182.78 (s, CO).
General procedure: A round bottom flask charged with
corresponding azido complex (4) (100 mg, 0.26 mmol) or
(5) (100 mg, 0.22 mmol) or (6) (100 mg, 0.20 mmol) was
added fivefold excess of dimethylacetylenedicarboxylate/
diethylacetylenedicarboxylate and CH2Cl2 (20 ml). The
mixture was stirred at room temperature and then the solu-
tion was reduced to ca. 3 ml on rotary evaporator. To this
solution was added 30 ml of hexane, whereby the com-
pound precipitated out as a yellow solid. The solid was col-
lected by centrifuged and washed with 2 · 20 ml of hexane
and dried under vacuum to gave the triazolato complexes
[(g6-p-cymene)Ru(LL){N3C2(CO2R)2}] (7–12).
Complex 10. LL = (acac), R = Et, 8 h, 77% (113 mg).
Anal. Calc. for C23H31N3O6Ru: C, 50.77; H, 5.88; N,
7.72%. Found: C, 50.25; H, 5.36; N, 7.87%. IR (KBr,
1
cmꢀ1): 1716 (mC@O), 1578, 1552, 1517 (mC@O + mC@C). H
NMR (CDCl3, d): 1.22 (t, 6H, JH–H = 4.8, CH2(CH3)2),
1.32 (t, 6H, JH–H = 4.0, CHMe2), 1.92 (s, 6H, acac-Me),
2.17 (s, 3H, Me (cym)), 2.78 (m, 1H, CHMe2), 4.30 (qt,
4H, JH–H = 7.12), 4.97 (s, 1H, acac-cH), 5.29 (dd, 2H,
JH–H = 10.52, JH–H = 6.04), 5.55 (dd, 2H, JH–H = 11.28,
JH–H = 6.12). 13C {1H} NMR (CDCl3, d): 14.21 (s, Me
(–CH2Me)), 17.68 (s, Me, CMe), 22.34 (s, Me, CHMe2),
26.67 (d, JC–H = 16.50, Me, acac-Me), 30.66 (s, CH,
0
Reaction time, yield, analytical and spectroscopic data
are as follows:
CHMe2), 60.55 (s, –CH2– (–CH2Me)), 80.11 (s, CAA ),
0
84.97 (d, CBB JC–H = 24.54), 98.98 (d, CH, acac-cC,
Complex 7. LL = (acac), R = Me, 12 h, 93% (128 mg).
Anal. Calc. for C21H27N3O6Ru: C, 48.59; H, 5.21; N,
8.10. Found: C, 48.25; H, 5.16; N, 7.87%. IR (KBr,
JC–H = 15.59), 99.72 (s, CMe), 101.28 (s, CPri), 140.26 (s,
C(CO2Et)2), 162.78 (s, (CO2)), 187.15 (s, CO).
Complex 11. LL = (bzac), R = Et, 10 h, 82% (114 mg).
Anal. Calc. for C28H33N3O6Ru: C, 55.12; H, 5.41; N, 6.89.
Found: C, 54.87; H, 5.23; N, 6.95%. IR (KBr, cmꢀ1): 1716
(mC@O), 1578, 1552, 1517 (mC@O + mC@C). 1H NMR (CDCl3,
d): 1.26 (m, 6H, Me), 1.28 (m, 6H, CHMe2), 2.07 (s, 3H
(bzac-Me)), 2.17 (s, 3H, Me (Cym)), 2.82 (m, 1H, CHMe2),
4.26, 4.29 (qt, 4H, JH–H = 3.2, –CH2– (CO2Et)), 5.62 (d,
2H, JH–H = 8.4), 5.65 (d, 2H, JH–H = 5.84), 5.58 (s, 1H,
cH-bzac), 7.31–7.35 (m, 3H), 7.71 (m, 2H). 13C {1H} NMR
(CDCl3, d): 14.15 (s, Me (CO2CH2Me)), 17.66 (Me-cymene),
22.21 (d, Me JC–H = 30.28, CHMe2), 27.61 (s, Me (bzac-
Me)), 30.68 (s, CH, CHMe2), 60.45, 61.19 (s, –CH2–
1
cmꢀ1): 1723 (mC@O), 1579, 1560, 1517 (mC@O + mC@C). H
NMR (CDCl3, d): 1.21 (d, 6H, JH–H = 6.92, CH(CH3)2),
1.91 (s, 6H, acac-Me), 1.94 (s, 3H), 2.75 (m, 1H,
CH(CH3)2), 3.86 (s, 6H, (OCH3)), 4.95 (s, 1H, acac-cH),
5.29 (m, 2H), 5.60 (m, 2H). 13C {1H} NMR (CDCl3, d):
17.65 (s, Me, CMe), 22.32 (s, Me, CH(Me)2), 26.60 (s,
acac-Me), 30.68 (s, CH, CHMe2), 51.66 (s, CH3,
0
0
CO2(CH3)), 80.07 (s, CAA ), 84.99 (s, CBB ), 98.93 (s, CH,
acac-c C), 99.75 (s, C, CMe), 101.30 (s, CPri), 140.22 (s,
C(CO2Me)2), 162.90 (s, (CO2)), 187.12 (s, acac-CO).
Complex 8. LL = (bzac), R = Me, 18 h, 84% (112 mg).
Anal. Calc. for C26H29N3O6Ru: C, 53.65; H, 4.98; N, 7.22.
Found: C, 53.18; H, 4.73; N, 6.95%. IR (KBr, cmꢀ1): 1716
(mC@O), 1578, 1552, 1517 (mC@O + mC@C). 1H NMR (CDCl3,
d): 1.24 (d, 6H, JH–H = 4, CH(CH3)2), 1.98 (s, 3H, bzac-Me),
2.06 (s, 3H, cym), 2.79 (m, 1H, CH(CH3)2), 3.49 (s, 6H,
0
0
,
(CO2Et)), 80.30 (t, CAA , JC–H = 16.50), 85.02 (d, CBB
JC–H = 40.34), 96.17 (s, CH, bzac-cC), 99.71 (s, CMe),
101.20 (s, CPri), 127.10–130.84 (m, Ph), 138.90, 140.05 (s,
C(CO2Et)), 162.80 (s, CO2), 180.87 (s, CO), 189.12 (s, CO).
Complex 12. LL = (dbzm), R = Et: 12 h, 81% (109 mg).
Anal. Calc. for C33H35N3O6Ru: C, 59.09; H, 5.22; N,
6.26. Found: C, 58.75; H, 4.98; N, 6.12%. IR (KBr,
0
(OCH3)), 5.33 (m, 2H, HAA ), 5.48 (s, 1H, bzac-H), 5.62
0
(m, 2H, HBB ), 7.30 (m, 3H, bzac-Ph), 7.68 (m, 2H, bzac-
1
Ph). 13C {1H} NMR (CDCl3, d): 17.67 (s, Me, CMe),
22.21 (d, Me, JH–H = 31.80, CHMe2), 27.58 (s, Me, bzac-
Me), 30.73 (s, CH, CHMe2), 51.62 (s, Me, CO2Me), 80.30
cmꢀ1): 1723 (mC@O), 1579, 1560, 1517 (mC@O + mC@C). H
NMR (CDCl3, d): 1.26 (m, 6H, Me, CO2Et), 1.29 (m, 6H,
CHMe2), 2.17 (s, 3H, Me (Cym.)), 2.82 (m, 1H, CHMe2),
4.26 (qt, 4H, JH–H = 3.2, –CH2– (CO2Et)), 5.46 (d, 1H,
JH–H = 6), 5.67 (d, 1H, JH–H = 6), 5.72 (d, 2H, JH–H = 6),
6.18 (s, 1H, dbzm-cH), 7.35 (m, 6H), 7.77 (m, 4H). 13C
{1H} NMR (CDCl3, d): 14.10 (s, Me (CO2Et)2), 17.72 (s,
Me (cym)), 22.21 (d, JC–H = 30.28, Me (CHMe2)), 30.68
(s, CH, (CHMe2)), 61.19 (s, –CH2– (CO2Et)), 80.87 (d,
CAA , JC–H = 29.88), 85.13 (d, CBB JC–H = 30.99), 94.85
(s, CH (dbzm-cC)), 99.54 (s, CMe), 101.19 (s, CPri),
127.34–130.98 (m, Ph), 139.91 (s, C(CO2Et)), 162.81 (s,
(CO2)), 181.94, 182.58 (s, CO).
0
0
(d, CAA , JC–H = 19.60), 85.45 (d, CBB , JC–H = 19.60),
96.79 (s, CH, bzac-cC), 99.79 (s, CMe), 101.30 (s, CPri),
127.12–130.81 (m, Ph), 140.05 (s, C(CO2Me)), 162.99 (s,
CO2), 180.94 (s, CO), 189.13 (s, CO).
Complex 9. LL = (dbzm), R = Me, 18 h, 87% (111 mg).
Anal. Calc. for C31H31N3O6Ru: C, 57.93; H, 4.82; N,
6.53. Found: C, 57.48; H, 4.66; N, 6.28%. IR (KBr,
0
0
1
cmꢀ1): 1723 (mC@O), 1579, 1560, 1517 (mC@O + mC@C). H
NMR (CDCl3, d): 1.29 (d, 6H, JH–H = 6.92, CHMe2),
2.17 (s, 3H, Me - cymene), 2.87 (m, 1H, CHMe2), 3.77 (s,
6H, (CO2Me)2), 5.42 (d, 1H, JH–H = 6), 5.46 (d, 1H,
JH–H = 6), 5.67 (d, 1H, JH–H = 6), 5.72 (d, 1H, JH–H = 6),
6.16 (s, 1H, dbzm-cH), 7.35 (m, 6H, Ph), 7.77 (m, 4H,
Ph). 13C {1H} NMR (CDCl3, d): 17.79 (s, CH3, CMe),
2.2.6. [(g6-p-cymene)Ru(acac){N3C2HCN}] (13)
Caution: These reactions should perform under well ven-
tilation hoods.

3512
K.S. Singh et al. / Journal of Organometallic Chemistry 691 (2006) 3509–3518
A round bottom flask was charged with the azido com-
ene)), 21.36 (s, CH3, CHMe2), 30.76 (s, CH, CHMe2),
0
0
plex 4 (100 mg, 0.26 mmol) and fumaronitrile (100 mg,
1.28 mmol) and 20 ml of dichloromethane. The mixture
was stirred at room temperature for 8 h. The solvent was
reduced to 3 ml and added excess of n-pentane or n-hexane
to give a yellow precipitate. The yellow solid was collected
and washed with 2 · 10 ml of n-pentane and dried under
vacuum. Yield: 81% (92 mg).
80.63, 80.98 (s, CAA ), 85.21, 85.54 (s, CBB ), 94.87 (s,
dbzm-cC), 98.80 (s, CPri), 114.27 (s, CN) 128.74–132.53
(m, Ph), 139.30 (s, C(CN)), 183.58 (s, CO).
3. Structural analysis and refinement
X-ray quality crystals of complex 4 were grown by slow
evaporation of diethyl ether solution of complex 4 at room
temperature while the crystals of 7, 11, 12 and 13 were
obtained by diffusion of hexane into acetone solution of
the complexes. X-ray diffraction data were measured at
120(2) K on a Bruker AXS Apex CCD area detector
employing graphite monochromated Mo Ka radiation
Anal. Calc. for C18H22N4O2Ru: C, 50.57; H, 5.15; N,
13.11. Found: C, 50.26; H, 4.93; N, 12.87%. IR (KBr,
1
cmꢀ1): 2223 (mC„N), 1571, 1520 (mC@O + mC@C). H NMR
(CDCl3, d): 1.23 (d, 6H, Me, CHMe2), 1.94 (d, 6H,
JH–H = 2.92), 2.08 (s, 3H, Me, CMe), 2.79 (m, 1H), 5.19
(s, 1H, acac-cH), 5.27 (d, 1H, JH–H = 5.92), 5.34 (d, 1H,
JH–H = 5.92), 5.57 (d, 1H, JH–H = 5.92), 5.61 (d, 1H,
JH–H = 5.96), 6.92 (s, 1H, CH). 13C {1H} NMR (CDCl3,
˚
(k = 0.71073 A). Absorption correction were made by
modeling a transmission surface by spherical harmonics
employing equivalent reflections with I > 2r(I) (SADBAS)
[36]. The structures were solved by direct methods and
refined by full matrix least squares base on F2 [37,38].
Non-hydrogen atoms were refined anisotropically and
hydrogen atoms were refined using a ‘‘riding’’ model. The
selected bond lengths and angles are tabulated in Tables
1, 2 and summary of collection parameters and refinement
data is presented in Table 3 respectively.
d): 17.25 (d, Me, CMe), 22.09 (d, Me, CMe2, JC–H
=
13.88), 26.94 (d, JC–H = 22.13, CMe), 30.49 (s, CH,
0
0
CHMe2), 80.64 (s, CAA ), 81.24 (s, CBB ), 83.15 (s), 84.34
(s), 84.77 (s), 99.04 (d, JC–H = 26.35, acac-cCH), 100.08
(s, CPri), 114.88 (s, CN), 128.93 (s), 134.91 (s, CH),
138.56 (s, C(CN)), 187.50 (s, CO).
2.2.7. [(g6-p-cymene)Ru(bzac){N3 C2HCN}] (14)
Caution: These reactions should perform under well ven-
tilation hoods.
4. Result and discussions
This compound was prepared in analogy to that of (13)
using the compound (5) instead of (4). Yield: 78% (90 mg).
Anal. Calc. for C23H24N4O2Ru: C, 56.43; H, 4.90; N,
11.45. Found: C, 56.17; H, 4.69; N, 11.27%. IR (KBr,
4.1. Synthesis of arene ruthenium azido complexes
Treatment of the complexes [(g6-p-cymene)Ru(LL)Cl]
with NaN3 in ethanol afforded the azido complexes [(g6-
p-cymene)Ru(LL)(N3)] in fairly good yield (Scheme 1).
The formation of the azido complexes can be readily con-
firmed by the appearance of a strong characteristic band
of the terminal azide stretching frequency at around
2015–2036 cmꢀ1. Alternatively, the azido complexes can
also be prepared by the reaction of azide dimer [{(g6-p-
cymene)Ru(l-N3)Cl}2] with sodium salts of b-diketonate.
The absence of the bridging azido band at 2057 cmꢀ1 of
the starting complex and appearance of a new band in
1
cmꢀ1): 2220 (mC„N), 1571, 1520 (mC@O + mC@C). H NMR
(CDCl3, d): 1.26 (d, 6H, Me, CHMe2), 2.12 (s, 3H (bzac-
Me)), 2.18 (s, 3H, Me (cym)), 2.84 (m, 1H, CHMe2), 5.60
(d, 2H, JH–H = 8.2), 5.64 (d, 2H, JH–H = 8.4), 5.72 (s, 1H,
cH-bzac), 6.98 (s, 1H, CH), 7.26–7.68 (m, 5H). 13C {1H}
NMR (CDCl3, d): 18.26 Me (cymene), 22.28 (d, Me
JC–H = 30.28, (CHMe2)), 27.73 (s, Me (bzac-Me)), 30.68
0
0
(s, CH, (CHMe2)), 82.30 (t, CAA ), 84.02 (d, CBB ), 97.13 (s,
CH, bzac-cC), 99.21 (s, CMe), 101.28 (s, CPri), 114.38
(s, CN), 127.10–132.84 (Ph), 138.90 (s, C(CN)), 180.67 (s,
CO), 189.32 (s, CO).
2.2.8. [(g6-p-cymene)(dbzm)Ru{N3C2HCN}] (15)
Caution: These reactions should perform under well ven-
tilation hoods.
Table 1
˚
Selected bond lengths (A) and bond angles (ꢁ) for the complex 4 with
estimated standard deviations (esds) in parenthesis
Molecule 1
Molecule 2
This complex was prepared by adopting a similar
method as described in the preparation of (13) using the
compound (6) instead of (4). Yield: 77% (85 mg,
0.185 mmol).
˚
Bond lengths (A)
Ru(1)–Cent
Ru(1)–O(1)
Ru(1)–O(2)
Ru(1)–N(1)
N(1)–N(2)
N(2)–N(3)
1.652 (4)
2.077(3)
2.057(3)
2.102(4)
1.151(5)
1.153(6)
Ru(2)–Cent
Ru(2)–O(3)
Ru(2)–O(4)
Ru(2)–N(4)
N(4)–N(5)
N(5)–N(6)
1.657 (5)
2.066(3)
2.071(3)
2.095(4)
1.162(5)
1.134(6)
Anal. Calc. for C28H26N4O2Ru: C, 60.97; H, 4.71; N,
10.16. Found: C, 60.58; H, 4.39; N, 9.87%. IR (KBr,
1
cmꢀ1): 2220 (mC„N), 1571, 1520 (mC@O + mC@C). H NMR
(CDCl3, d): 1.31 (d, 6H, JH–H = 6.92), 2.17 (s, 3H), 2.87
(m, 1H), 5.54 (d, 1H, JH–H = 6.38), 5.61 (d, 1H, JH–
H = 6.42), 5.67 (d, 1H, JH–H = 6), 5.72 (d, 1H, JH–H = 6),
6.16 (s, 1H, dbzm-cH), 6.89 (s, 1H), 7.25 (m, 6H), 7.48
(m, 4H). 13C {1H} NMR (CDCl3, d): 17.48 (s, CH3 (cym-
Bond angles (ꢁ)
O(1)–Ru(1)–O(2)
Ru(1)–N(1)–N(2)
O(1)–Ru(1)–N(1)
O(2)–Ru(1)–N(1)
88.56(12)
131.0(3)
80.33(15)
84.86(18)
O(3)–Ru(2)–O(4)
Ru(2)–N(4)–N(5)
O(3)–Ru(2)–N(4)
O(4)–Ru(2)–N(4)
85.96(15)
124.1(3)
85.96(15)
85.74(14)

K.S. Singh et al. / Journal of Organometallic Chemistry 691 (2006) 3509–3518
3513
Table 2
˚
Selected bond lengths (A) and bond angles (ꢁ) for the complexes 7, 11, 12
and 13 with estimated standard deviations (esd’s) in parenthesis
Complex 7
Complex 11 Complex 12 Complex 13
˚
Bond lengths (A)
Ru–Cent
Ru–N(1)
Ru–N(2)
Ru–O(1)
Ru–O(2)
N(1)–N(2)
N(2)–N(3)
1.660(3)
1.667(4)
2.101(4)
1.670 (2)
2.0969(19)
1.656(5)
2.099(2)
2.091(3)
2.074(3)
2.079(3)
1.353(6)
1.330(6)
Scheme 1. Reaction pathway of starting materials.
2.0627(18)
2.0581(18)
1.338(3)
2.068(3)
2.063(3)
1.356(4)
1.314(4)
2.0642(16)
2.0647(16)
1.364(2)
the region 2015–2030 cmꢀ1 confirmed the formation of the
azido complexes [(g6-p-cymene)Ru(LL)(N3)].
1.334(3)
1.320(3)
Bond angles (ꢁ)
O(1)–Ru–O(2)
N(1)–N(2)–N(3) 113.46(19)
88.81(8)
88.32(11)
109.5(3)
88.89(6)
109.23(17)
87.93(14)
108.4(4)
4.2. Reaction of ruthenium azido complexes with DMD or
DED
O(2)–Ru–N(2)
O(1)–Ru–N(2)
O(1)–Ru–N(1)
O(2)–Ru–N(1)
83.69(7)
86.68(7)
85.64(15)
83.86(15)
84.97(11)
83.44(11)
84.45(7)
85.11(7)
The reaction of azido complexes 4–6 with a fivefold
excess of the substituted acetylenes dimethylacetylene-
Table 3
Summary of crystal structure determination and refinement parameters for complexes 4, 7, 11, 12 and 13
Complex 4
Complex 7
Complex 11
Complex 12
Complex 13
Empirical formula
Formula weight
Temperature (K)
C
376.42
298(2)
0.71073
Monoclinic
P2(1)/c
15H21N3O2Ru
C21H27N3O6Ru
519.53
120(2)
0.71073
Monoclinic
P2(1)/c
C28H33N3O6Ru
608.64
120(2)
0.71073
Monoclinic
P2(1)/c
C33H35N3O6Ru
670.71
120(2)
0.71073
Orthorhombic
P2(1)2(1)2(1)
C18H22N4O2Ru
427.47
298(2)
0.71073
Monoclinic
P2(1)/n
˚
Wavelength (A)
Crystal system
Space group
Unit cell dimensions
˚
a (A)
20.110(18)
9.192(8)
19.953(18)
8.500(3)
11.099(4)
23.147(9)
10.060(9)
13.284(12)
19.707(18)
11.221(6)
11.300(6)
23.783(12)
90
90
90
9.964(4)
12.378(5)
15.629(6)
˚
b (A)
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
117.246(13)
91.109(4)
100.273(15)
103.848(6)
3
˚
Volume ( A )
3279(5)
8
2183.2(15)
4
2591(4)
4
3016(3)
4
1871.6(12)
4
Z
Calculated density
(Mg/m3)
1.525
1.581
1.560
1.477
1.517
Absorption coefficient
0.964
0.761
0.654
0.570
0.856
(mmꢀ1
)
F(000)
1536
1068
1256
1384
872
Crystal size (mm)
h Range for data
collection (ꢁ)
0.21 · 0.15 · 0.10
2.04–28.48
0.41 · 0.36 · 0.18
1.76–28.32
0.34 · 0.26 · 0.19
1.86–28.32
0.38 · 0.31 · 0.27
1.71–28.26
0.19 · 0.12 · 0.06
2.12–28.22
Limiting indices
ꢀ25 6 h 6 26,
ꢀ11 6 k 6 12,
ꢀ25 6 l 6 26
ꢀ10 6 h 6 10,
ꢀ14 6 k 6 14,
ꢀ29 6 l 6 29
ꢀ13 6 h 6 12,
ꢀ16 6 k 6 17,
ꢀ26 6 l 6 26
ꢀ14 6 h 6 14,
ꢀ14 6 k 6 14,
ꢀ30 6 l 6 31
ꢀ12 6 h 6 11,
ꢀ15 6 k 6 14,
ꢀ20 6 l 6 20
Reflections collected/
34013/7729 [0.0681]
11902/4819 [0.0370]
25517/6076 [0.0953]
28487/6897 [0.0530]
10451/4178 [0.0691]
unique [Rint
]
Completeness to h (%)
28.48–93.0
28.32–88.6
28.32–94.0
28.26–95.2
28.22–90.5
Absorption correction
Semi-empirical
equivalents
Refinement method
Full-matrix least
squares on F2
7729/3/405
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices
[I > 2sigma(I)]
R indices (all data)
4819/0/287
6076/0/349
6897/0/393
4178/0/231
1.032
1.044
1.055
1.034
1.027
R1 = 0.0497,
wR2 = 0.1199
R1 = 0.0632, wR2 = 0.1304
R1 = 0.0343,
wR2 = 0.0852
R1 = 0.0404,
wR2 = 0.0895
0.876 and ꢀ0.861
R1 = 0.0666,
wR2 = 0.1704
R1 = 0.0714,
wR2 = 0.1752
1.988 and ꢀ2.236
R1 = 0.0277
wR2 = 0.0667
R1 = 0.0302
wR2 = 0.0680
0.670 and ꢀ0.319
R1 = 0.0572,
wR2 = 0.1306
R1 = 0.0834
wR2 = 0.1482
0.826 and ꢀ0.482
Largest difference peak
1.663 and ꢀ0.377
ꢀ3
˚
and hole (e A
)

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K.S. Singh et al. / Journal of Organometallic Chemistry 691 (2006) 3509–3518
dicarboxylate (MeO2CC2CO2Me) (DMD) or diethylacety-
lenedicarboxylate (EtO2CC2CO2Et) (DED) in dichloro-
methane at room temperature afforded the yellow
ruthenium triazolato complexes in good yield (Scheme 2).
The formation of the triazolato complexes can be readily
confirmed by observing the disappearance of azide band
and the appearance of new bands due to C@O stretching
frequencies at 1726 cmꢀ1. In addition to the C@O stretch-
ing frequencies, the IR spectra of these complexes showed a
pair of strong bands at around 1517–1578 cmꢀ1 which are
assignable to coupled (C@O) + (C@C) modes of the
b-diketonate [39,40]. Surprisingly, the triazolato complexes
formed from the two acetylenes differ in their mode of
bonding. The dimethylacetylenedicarboxylate exclusively
produced N(2) bonded triazolato complexes while diethyl-
acetylenedicarboxylate produced exclusively N(1) bonded
triazolato complexes. This has been confirmed by the
X-ray analysis of the complexes 7, 11 and 12.
It should be noted that the triazole anion could be coor-
dinated by a metal through either its N(1) or N(2) nitrogen
atoms [7,26] which are essentially isoenergetic as indicated
by molecular orbital calculations [26,27]. Evidence
obtained to date indicates that either of the two isomers
N(1) and N(2)-bonded are formed simultaneously
[7,12,16,26,27] or only the N(2) bound isomer is produced
exclusively [7,12,16,17]. In our cases both the N(1) and
N(2) bonded isomers are formed depending on the substit-
uents of the triazolato ring. Thus, methoxy-substituted
acetylene produced exclusively N(2) bonded isomer while
ethoxy-substituted acetylene exclusively produced N(1) iso-
mer. Ellis et al. have reported the initial formation of N(1)
bonded complex via azide attack on the coordinated nitrile
carbon of pentamethylamine cobalt complexes which
slowly isomerized to the N(2) bonded complex [41]. It is
believed that the triazolato complexes initially form the
N(1) bonded complexes which then isomerize to the N(2)
bonded complexes. Isomerization from N(1) to N(2) is
favored as far as steric factors are concerned while elec-
tronic factors favor no isomerization.
It has been reported that the N(1) nitrogens of the tria-
zolato anions are more nucleophilic than the N(2) nitro-
gens [27]. The N(1) to N(2) linkage isomerization
reaction appears to be driven by the steric congestion
between the triazole ring substituents. An inspection of
molecular models of the linkage isomers indicates that this
congestion would be totally relieved in the N(2) bonding
isomer. Thus, formation of exclusively N(1) bonded triazo-
lato complexes 10–12 could not be due to steric factors but
it is believed that it is due to electronic factors. As men-
tioned previously, a consideration of ring nitrogen nucleo-
philicity favors N(1) coordination for substituted triazolato
complexes [27]. Thus, in the case of the ethoxy substituted
triazolato complexes (10–12) no isomerization takes place
from the N(1) to N(2) bonded complexes due to the high
inductive effect of the ethoxy group which favors the
N(1) bonded triazolato complexes. But the methoxy substi-
tuted triazolato complexes isomerize from the N(1) to N(2)
bonded isomers and produce exclusively the N(2) bonded
triazolato complexes (7–9). In order to confirm the mode
of bonding, the crystal structures of the representative
complexes have been determined. On the basis of spectro-
scopic data and X-ray analysis, the methoxy-substituted
triazolato complex has been proposed N(2) bonded while
ethoxy-substituted triazolato complexes are proposed to
be N(1) bonded triazolato complexes.
The 1H NMR spectrum of complex 7 is shown in Fig. 1.
The 1H NMR spectra of the complexes 7–9 exhibit, in
addition to the p-cymene resonances, singlet resonances
Scheme 2. Synthetic pathway of complexes.

K.S. Singh et al. / Journal of Organometallic Chemistry 691 (2006) 3509–3518
3515
while the carbons of the b-diketonate group appear at d
183–189.
4.3. Reaction of ruthenium azido complexes with
fumaronitrile
The reaction of the azido complexes 4–6 with excess
fumaronitrile at room temperature for 10–15 h affords the
N(2) bound 4-cyano-1,2,3-triazolato complexes (13–15) in
good yield. The formation of the triazolato complexes is
readily confirmed by the absence of the starting azide
stretching frequency and the appearance of a strong band
at around 2220 cmꢀ1 corresponding to the stretching fre-
quency of the C„N group of the coordinated triazolato
1
group. The H NMR spectra of these complexes showed
characteristic singlet resonances at d 6.9 assigned to the
CH group of the triazolato ring proton and a singlet in
the region d 5.19–6.16 attributed to c-proton of the b-
1
diketonato group. In addition, the H NMR spectra con-
tains doublet resonances corresponding to the p-cymene
group in the region d 5.3 arising from the protons of the
arene ring, a multiplet at ca. d 2.87 due to CHMe2, a singlet
at d 2 for methyl group and a doublet at d 1.2 for the
methyl protons of isopropyl group. In principle, the cyclo-
addition of fumaronitrile to the coordinated azide can take
place via C@C or C„N. The reaction of coordinated azide
in Ni(II) with CH2@CHCN gave a triazolinato complex
[7]. A pathway via direct cyclization of HC„CCN with
azide resulting in the formation of triazolato has also
occurred [27,42]. Complexes 13–15 are clearly formed by
[3+2] cyclization between the azido ligand and the C@C
double bond following removal of a HCN molecule. The
proposed structures of the complexes are confirmed by a
determination of molecular structure of representative
complex 13 by single crystal X-ray diffraction.
Fig. 1. 1H NMR Spectrum of complex [(g6-p-cymene)Ru(acac)-
{N3C2(CO2Me)2}] (7).
corresponding to the b-diketonate ligand in the region d
4.9–6.2 for c-proton and a singlet at ca. d 3.8 assignable
to the methoxy carbonyl group protons of the triazolato
group.
1
The H NMR spectra of complexes 10–12 exhibited a
quartet at ca. d 4.29 and a triplet ca. d 1.28 due to the
methylene and methyl protons of the ethoxy carbonyl
group. The 13C {1H} NMR of these complexes exhibited
a single resonance at d 162 due to carbon of CO2 group
Fig. 2. Molecular structure of complex [{(g6-p-cymene)Ru(acac)N3}] (4). Thermal ellipsoids are depicted with 30% probability level.

3516
K.S. Singh et al. / Journal of Organometallic Chemistry 691 (2006) 3509–3518
5. Crystal structures
The complex crystallizes in the P2(1)/c space group. The
ruthenium atom is coordinated by a p-cymene ligand in g6-
fashion occupying three facile coordination sites. The
remaining coordination sites are occupied by the O-atoms
of the acetylacetonate ligand and azide group. The unit cell
consists of two molecules. The two molecules differ only in
the orientation of the azide groups. In one molecule
5.1. Crystal structure of [(g6-p-cymene)Ru(acac)N3] (4)
The ORTEP drawing of complex 4 with the atom label-
ing scheme is shown in Fig. 2. The selected bond lengths
and angles are listed in Table 1.
Fig. 3. Molecular structure of [(g6-p-cymene)Ru(acac){N3C2(CO2Me)2}] (7). Thermal ellipsoids are depicted with 30% probability level.
Fig. 4. Molecular structure of [(g6-p-cymene)Ru(bzac){N3C2(CO2Et)2}] (11). Thermal ellipsoids are depicted with 30% probability level.

K.S. Singh et al. / Journal of Organometallic Chemistry 691 (2006) 3509–3518
3517
the –N@N@N group is directed horizontally while in the
other it directed vertically. The distance between the ruthe-
nium and the centroid of the p-cymene ligand in both mol-
˚
ecules is comparable, the values being 1.652(4) A (Ru1–
˚
Cent) and 1.657(5) A, (Ru2–Cent). The Ru1–O(1)
˚
˚
[2.077(3) A] and Ru1–O(2) [2.057(3) A], in one of the mol-
ecules is comparable to that of the other and the values are
in the range of reported Ru–O bond lengths of other ruthe-
nium b-diketnoate systems [43].
The N–N bond lengths in the molecules are in the range
˚
of 1.134 (6)–1.162 (5) A, which are comparable to other
reported N–N bond lengths. However, the ruthenium and
˚
nitrogen of the azide bond distance, 2.102(4) A, is slightly
longer than that of other reported complexes such as rho-
dium [44] and copper [6b] complexes.
5.2. Crystal structures of
[(g6-p-cymene)Ru(acac){N3C2(CO2Me)2}] (7);
[(g6-p-cymene)Ru(bzac){N3C2(CO2Et)2}] (11);
[(g6-p-cymene)Ru(dbzm){N3C2(CO2Et)2}] (12) and
[(g6-p-cymene)Ru(acac){N3C2(H)(CN)}] (13)
Fig. 6. Molecular structure of [(g6-p-cymene)Ru(acac){N3C2(H)(CN)}]
(13). Thermal ellipsoids are depicted with 30% probability level.
The structure of the compounds 7, 11, 12 and 13 consists
of a neutral arene ring bonded to the ruthenium, along with
anionic b-diketonato and triazolato ligands. The molecular
structures of complexes 7, 11, 12 and 13 with atom labeling
scheme are shown in Figs. 3–6. Selected bond lengths and
angles are presented in Table 2. The complexes 7, 11 and
13 crystallized in the P2(1)/c space group while complex
12 crystallized in the P2(1)2(1)2(1) space group. The p-
cymene ligand is bonded to the ruthenium atom in g6-fash-
ion with ruthenium to centroid of the ring being 1.660 (3),
˚
1.667 (4), 1.670 (2) and 1.656 (5) A, for complex 7, 11, 12
and 13, respectively. The complexes adopt a typical three-
legged piano stool conformation with the N and the two
O-atoms as the legs. The Ru–O(1) and Ru–O(2) bond dis-
tances of the triazolato complexes 7, 13 are comparable to
the starting azido complex 4. The remarkable difference in
the structure between the methoxy substituted complex 7
and that of ethoxy substituted complexes 11 and 12 is the
mode of coordination of the triazolato unit to the ruthe-
nium atom. In complex 7, the triazolato group is bonded
to the metal through N(2) – while in complexes 11 and 12,
it is bonded through N(1) – atom of the triazolato group.
It is notable that most cycloaddition reactions of coordi-
nated azide with acetylenes to produce triazoles exclusively
form the N(2)-isomer. To the best of our knowledge, com-
plexes 11 and 12 represent first structurally characterized
N(1)-bound isomer obtained from such cycloaddition reac-
tion. There is no significant difference in the bond distances
of the heterocyclic ring indicating delocalization of elec-
trons in the ring. The Ru–O (1) and Ru–O(2) bond dis-
˚
tances in the complexes range from 2.0581 to 2.079 A
which is comparable to those of the reported Ru–O bond
lengths [43]. The O(1)–Ru–O(2) bond angles of the complex
˚
7 (88.81(8) A) are comparable to that of complexes 11
˚
˚
(88.32(11) A) and 12 (88.89(6) A).
6. Conclusions
Fig. 5. Molecular structure of [(g6-p-cymene)Ru(dbzm){N3C2(CO2Et)2}]
(12). Thermal ellipsoids are depicted with 30% probability level.
Previously, we reported the syntheses of indenyl
ruthenium triazolato complexes. In these complexes the

3518
K.S. Singh et al. / Journal of Organometallic Chemistry 691 (2006) 3509–3518
(b) W. Beck, M. Bander, W.P. Fehlhammer, P. Pollamann, H.
Schachl, Inorg. Nucl. Chem. Lett. 4 (1968) 143.
[10] T. Kemmerich, W. Beck, C. Spencer, R. Mason, Z. Naturforsch.,
Teil B 27 (1972) 745.
[11] W. Rigby, P.M. Bailey, J.A. McCleverty, P.M. Maitlis, J. Chem.
Soc., Dalton Trans. (1979) 371.
[12] T. Kemmerich, J.H. Nelson, N.E. Takach, H. Boeheme, B. Jablonski,
W. Beck, Inorg. Chem. 21 (1982) 1226.
[13] P.H. Kreutzer, J.C. Weis, H. Bock, J. Erbe, W. Beck, Chem. Ber. 116
(1983) 2691.
[14] S.S. Washburne Jr., W.R. Peterson, J. Organomet. Chem. 21 (1970)
427.
[15] K. Sisido, K. Nabika, T. Isida, S. Kozima, J. Organomet. Chem. 33
(1971) 337.
triazolato ligand binds to the metal through the N(2) atom
irrespective of acetylenes are used. Where as in the present
study the bonding depend on the acetylene. In the case of
dimethylacetylenedicarboxylate the bonding is through
N(2) whereas in the case of diethylacetylenedicarboxylate
the bonding is through N(1). Even though we expected
the chemistry to be similar to indenyl ruthenium systems,
we observed the formation of new bonding modes in the
arene ruthenium system. Complexes 11 and 12 are the first
examples of structurally characterized N(1)-bound isomers
obtained from such cycloaddition reactions.
[16] A.P. Gaughan, K.S. Browman, Z. Dori, Inorg. Chem. 11 (1972) 601.
[17] W. Beck, K. Schropp, Chem. Ber. 108 (1975) 3317.
[18] J. Erbe, W. Beck, Chem. Ber. 116 (9) (1983) 3867.
[19] L. Busetto, A. Palazzi, R. Ros, Inorg. Chim. Acta 13 (1975) 233.
[20] P.M. Treichel, W.J. Knebel, R.W. Hess, J. Am. Chem. Soc. 93 (1971)
5424.
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Acknowledgments
We thank Sophisticated Instruments Facility (SIF), In-
dian Institute of Science, IISc., Bangalore for providing
NMR facility. K.M.R. highly appreciates the referees for
their comments and suggestions to make the manuscript
in the present form.
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Appendix A. Supplementary material
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Kollipara, J. Coord. Chem. 59 (2006) in press.
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[32] (a) M.A. Bennett, T.N. Huang, T.W. Matheson, G.B. Robertson,
A.K. Smith, Inorg. Synth. 21 (1985) 74;
Crystallographic data for the structural analysis have
been deposited at the Cambridge Crystallographic Data
Centre (CCDC), CCDC No. 287034 for complex 4, CCDC
No. 287035 for complex 7, CCDC No. 287036 for complex
11, CCDC No. 287037 for complex 13 and CCDC No.
290263 for complex 12, respectively. Copies of this infor-
mation may be obtained free of charge from the director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (fax:
+44 1223 336 033; e mail: deposit@ccdc.cam.ac.uk or
http://www.ccdc.cam.ac.uk). Supplementary data associ-
ated with this article can be found, in the online version,
at doi:10.1016/j.jorganchem.2006.05.001.
(b) M.A. Bennett, T.W. Matheson, G.B. Robertson, A.K. Smith,
P.A. Tucker, Inorg. Chem. 19 (1980) 1014.
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(b) The azide dimer was synthesized using sodium azide salt instead of
trimethylsilyl azide.
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