Synthesis, characterization, reactivity and structure of some mono and binuclear (η6-p-cymene)ruthenium(II) complexes

Article abstract of DOI:10.1016/S0022-328X(98)00571-3

Reactions of [{Ru(η⁶-C₁₀H₁₄)Cl₂}₂] (η⁶-C₁₀H₁₄=p-cymene H₃C-C₆H₄-CH(CH₃)₂) with 4-cyanopyridine (referred hereafler as CNPy) in 1:1 and 1:2 molar ratios in dichloromethane yields the binuclear complex [{Ru(η⁶-C₁₀H₁₄)Cl₂} ₂(μ-CNPy)] and the mononuclear complex [Ru(η⁶-C₁₀H₁₄)Cl₂(CNPy)]. The latter complex further reacts with [{Ru(η⁶-C₆Me₆)Cl₂}₂] and [Ru(η⁵-C₅H₅)(PPh₃) ₂Cl] to give 4-cyanopyridine bridged complexes [Cl₂(η⁶-C₁₀H ₁₄)Ru(μ-CNPy)Ru(μ⁶-C₆Me ₆)Cl₂] and [Cl₂(η⁶-C₁₀H ₁₄)Ru(μ-CNPy)Ru(η⁵-C₅H ₅)(PPh₃)₂]⁺. The complex [Ru(η⁶-C₁₀H₁₄)Cl₂(CNPy)] also undergoes metathetical reactions with EPh₃ (E=P, As or Sb) to give complexes with the general formulations [Ru(η⁶-C₁₀H₁₄)Cl₂(EPh ₃)], however its reaction with diphenylphosphinomethane (dppm) in a 1:1 ratio gives the mononuclear complex [Ru(η⁶-C₁₀H₁₄)Cl₂(dppm)] in which the dppm ligand is present in uncommon coordination mode (η¹-dppm). The reaction products have been characterized by microanalyses and spectroscopic studies (IR, ¹H-, ¹³C-, ³¹P-NMR). The structure of [Ru(η⁶-C₁₀H₁₄)Cl₂(CNPy)] [a=10.984(1), b=14.052(1), c=12.189(1) A; β=114.810(1)°; V=1707.8(4) A³; D_calc=1.596 g cm^-3; monoclinic P2₁/c; Z=4] and confirmation of uncommon coordination mode of dppm, in [Ru(η⁶-C₁₀H₁₄)Cl₂(dppm)] [a=11.504(3), b=19.532(3), c=15.942(3) A; β=96.08(2)°; V=3562(2) A³; D_calc=1.446 g cm^-3; monoclinic P2₁/n; Z=4] has been determined by X-ray crystallography.

Full text of DOI:10.1016/S0022-328X(98)00571-3

Journal of Organometallic Chemistry 568 (1998) 13–20
Synthesis, characterization, reactivity and structure of some mono and
binuclear (p6-p-cymene)ruthenium(II) complexes
Dharmendra Kumar Gupta a, Abhaya Nand Sahay a, Daya Shankar Pandey a,*,
Narendra Kumar Jha b, Pankaj Sharma c, G. Espinosa c, A. Cabrera c, M. Carmen Puerta d,
Pedro Valerga d
a Department of Chemistry, A.P.S. Uni6ersity, Rewa-486003, India
b Department of Chemistry, Indian Institute of Technology, Delhi-110016, India
c Instituto de Quimica, UNAM, Deleq, Coyoacan, Mexico City DF 04510, Mexico
d Departmento de Quimica Inorganica, Uni6ersidad de Cadiz, Apartado 40, Puerto Real 11510, Spain
Received 14 October 1997
Abstract
Reactions of [{Ru(p6-C10H14)Cl2}2] (p6-C10H14=p-cymene H3CꢀC6H4ꢀCH(CH3)2) with 4-cyanopyridine (referred hereafler as
CNPy) in 1:1 and 1:2 molar ratios in dichloromethane yields the binuclear complex [{Ru(p6-C10H14)Cl2}2(v-CNPy)] and the
mononuclear complex [Ru(p6-C10H14)Cl2(CNPy)]. The latter complex further reacts with [{Ru(p6-C6Me6)Cl2}2] and [Ru(p5-
C5H5)(PPh3)2Cl] to give 4-cyanopyridine bridged complexes [Cl2(p6-C10H14)Ru(v-CNPy)Ru(v6-C6Me6)Cl2] and [Cl2(p6-
C10H14)Ru(v-CNPy)Ru(p5-C5H5)(PPh3)2]+. The complex [Ru(p6-C10H14)Cl2(CNPy)] also undergoes metathetical reactions with
EPh3 (E=P, As or Sb) to give complexes with the general formulations [Ru(p6-C10H14)Cl2(EPh3)], however its reaction with
diphenylphosphinomethane (dppm) in a 1:1 ratio gives the mononuclear complex [Ru(p6-C10H14)Cl2(dppm)] in which the dppm
ligand is present in uncommon coordination mode (p1-dppm). The reaction products have been characterized by microanalyses
and spectroscopic studies (IR, 1H-, 13C-, 31P-NMR). The structure of [Ru(p6-C10H14)Cl2(CNPy)] [a=10.984(1), b=14.052(1),
3
c=12.189(1) A; i=114.810(1)°; V=1707.8(4) A ; Dcalc=1.596 g cm−3; monoclinic P21/c; Z=4] and confirmation of uncom-
˚
˚
6
˚
mon coordination mode of dppm, in [Ru(p -C10H14)Cl2(dppm)] [a=11.504(3), b=19.532(3), c=15.942(3) A; i=96.08(2)°;
V=3562(2) A ; Dcalc=1.446 g cm−3; monoclinic P21/n; Z=4] has been determined by X-ray crystallography. © 1998 Elsevier
3
˚
Science S.A. All rights reserved.
Keywords: Arene–ruthenium complexes; Mononuclear complexes; Bridged ruthenium complexes; Metathetic reactions
1. Introduction
tides and nucleobases have been studied extensively
[2–9]. However, its reactions with simple organonitriles
viz. 4-cyanopyridine, 1,4-dicyanobenzene, 1,4-piper-
azinedicarbonitrile, tetracyanoethylene, etc., possessing
two or more donor sites, have not been studied despite
detailed reports concerning complexes of these ligands
with a number of metal ions ([10]a–k). As a continua-
tion of our studies on these systems ([11]a–c), we
thought it worth while to make a detailed study of the
reactivity of [{Ru(p6-C10H14)Cl2}2] with 4-cyanopy-
ridine. Our prime concern in undertaking this study was
(a) to investigate relative donor capabilities of the two
Synthesis and characterization of arena–ruthenium
complexes have drawn special attention owing to their
catalytic potential and their use as precursors for the
synthesis of Ru(0) and Ru(II) complexes ([1]a–g). In
this regard, the p-cymene complex [{Ru(p6-
C10H14)Cl2}2] has been very important. Reactions of
this molecule with a variety of Lewis bases, monoden-
tate ligands, chiral bidentate ligands, aminoacids, pep-
* Corresponding author. Tel.: +91 7662 40740.
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00571-3

14
D.K. Gupta et al. / Journal of Organometallic Chemistry 568 (1998) 13–20
donor sites in the formation of mononuclear and/or,
polynuclear complexes, (b) to investigate the possibility
of formation of (p6-C10H14) containing ruthenium(II)
bi- and/or polynuclear bridged complexes. In this paper
we report the reproducible synthesis and characteriza-
tion of mononuclear pyridine N-bound complex
[Ru(p6-C10H14)Cl2(CNPy)] and binuclear complex
[{Ru(p6-C10H14)Cl2}2(v-CNPy)], in which the ligand
4-cyanopyridine serves as a bridge to two Ru(II) centers
through its nitrile nitrogen, along with a few other
related complexes. We also present the X-ray crystal
structure of [Ru(p6-C10H14)Cl2(CNPy)] and confirm the
presence of dppm ligand in an unusual coordination
mode in the complex [Ru(p6-C10H14)Cl2(dppm)] for the
first time by X-ray analysis.
for C16Cl2H18N2Ru: C, 46.82; H, 4.39; N, 6.82; Cl,
10.72. Found: C, 46.7; H, 4.29; N, 6.62; Cl, 10.80; IR
1
(KBr) 2039 cm−1 (wCꢁN); H-NMR (CDCl3): l 9.35
(d, hHꢀCNPy), 7.32 (d, iHꢀCNPy), 5.2–5.5 (AB pat-
tem, C6H4), 2.90 (m, CH(CH3)2), 1.63 (s, CꢀCH3), 1.57
(d, CH (CH3)2); 13C{1H}-NMR (CDCl3): 151.1
(hCꢀCNPy), 128.32 (iCꢀCNPy), 125.81 (kCꢀCNPy),
119.25 (CꢁN, CNPy), 104.52 (CꢀCHMe2), 96.4
(CꢀCH3), 83.03 and 80.45 (C6H4), 30.76 (CH(CH3)2),
22.26 (CH(CH3)2), 18 27 (CꢀCH3).
2.2. Preparation of [{Ru(p6-C10H14)Cl2}2(v-CNPy)] (2)
This compound was prepared following the above
procedure except that [{Ru(p6-C10H14)Cl2}2] and 4-
cyanopyridine were taken in 1:1 molar ratio. The com-
pound separated as red–brown needles. Yield 65%:
m.p. 175°C (decom.); Anal. Calc. for C26C14H32N2Ru2:
C, 43.58; H, 4.47; N, 3.91; Cl, 16.83. Found: C, 43.72;
H, 4.25; N, 3.86; Cl, 20.52; IR (KBr) 2229 cm−1
2. Experimental
Analytical or chemically pure grade reagents were
used throughout. All the reactions were carried out
under nitrogen atmosphere. The solvents were dried
and distilled by standard procedures before use. 4-
Cyanopyridine (Aldrich) was purified from hot 90%
ethanol prior to its use. Triphenylphosphine, tripheny-
larsine, triphenylstibine, hexamethylbenzene, dicy-
clopentadiene, ammonium hexafluorophosphate and
RuCl3 ·xH2O (Aldrich) were used as-received.
1
(wCꢁN); H-NMR (CDCl3): l 9.30 (d, hHꢀCNPy), 7.54
(d, iHꢀCNPy), 5.36–5.60 (m, C6H4), 3.00 (m,
CH(CH3)2), 1.863 (s, CꢀCH3), 1.43 (m, CH(CH3)2);
13C{1H}-NMR (CDCl3): 156.1 (hCꢀCNPy), 129
(iCꢀCNPy), 125.9 (kCꢀCNPy), 121.7 (CꢁN, CNPy),
104.0 (CꢀCHMe2), 97.6 (CꢀCH3), 89.6, 89.5, 82.9, 81.7,
81.4, 81.2, 80.5 (C6H4), 30.7, 30.4 (CH(CH3)2), 22.2,
22.1 (CH(CH3)2), 18.2, 15.7 (CꢀCH3).
The starting complexes [{Ru(p6-C10H14)Cl2}2],
[{Ru(p6-C6Me6)Cl2}2] and [Ru(p5-C5H5)(PPh3)2Cl] were
prepared following the literature procedures [12,13].
Melting points of the complexes were recorded by a
Jyoti melting point apparatus in air. Microanalyses
were performed by the microanalytical laboratory of
R.S.I.C., Central Drug Research Institute, Lucknow.
IR spectra in the range 4000–200 cm−1 in KBr pellets,
1H-, 13C- and 31P-NMR with tetramethylsilane as the
internal standard were recorded with a Perkin-Elmer
577 Bruker WM-400 MHz and Bruker DRX-300 MHz
spectrometers. X-ray single crystal diffraction data for
the complex [Ru(p6-C10H14)Cl2(CNPy)] were obtained
on a Siemens P4 diffractometer and for the complex
[Ru(p6-C10H14)Cl2(dppm)] on an AFC6S-Rigaku
diffractometer.
2.3. Preparation of [Ru(p6-C10H14)Cl2(PPh3)] (3)
To a suspension of 1 (410 mg, 1.0 mmol) in methanol
(25 ml), triphenylphosphine (263 mg, 1.0 mmol) was
added and the solution was heated under reflux. The
suspension slowly dissolved and a bright red crystalline
compound started separating from the solution. It was
cooled to r.t. and the crystals were separated by filtra-
tion. These were washed several times with methanol,
diethylether and dried in vacuum. Yield 70%; m.p.
245°C (decom.); Anal. Calc. for C28C12H29PRu: C,
59.05; H, 5.09; Cl, 12.47. Found: C, 59.32; H, 5.25; Cl,
12.20; 1H-NMR (CDCl3): l 7.22–7.93 (br, m, Ar PPh3),
5.00–5.25 (AB pattern, C6H4). 2.84 (m, CH(CH3)2),
1.86 (s, CꢀCH3), 1.06 (d, CH(CH3)2).
2.1. Preparation of [Ru(p6-C10H14)Cl2(CNPy)] 1
2.4. Preparation of [Ru(p6-C10H14Cl2(AsPh3)] (4)
[{Ru(p6-C10H14)Cl2}2] (612 mg, 1.0 mmol) dissolved
in dichloromethane (50 ml) was treated with 4-cyanopy-
ridine (208 mg, 2.0 mmol) and the solution was heated
under reflux for 1 h. The orange–red solution was
cooled to r.t., filtered through celite and evaporated to
dryness under reduced pressure. The solid residue was
washed several times with petroleum ether, crystallized
from dichloromethane–petroleum ether and dried in
vacuum. Yield 655 mg (80%); m.p. 200°C; Anal. Calc.
This compound was obtained in the form of red
microcrystals following the above procedure for 3 start-
ing from 1 and triphenylarsine. Yield 60%; m.p. 195°C;
Anal. Calc. for AsC28Cl2H29Ru: C, 54.90; H, 4.74; Cl,
1
11.60. Found: C, 54.92; H, 4.54; Cl, 11.22; H-NMR
(CDCl3): l 7.2–7.8 (br, m, Ar AsPh3), 5.12–5.36 (AB
pattern, C6H4), 2.92 (m, CH(CH3)2), 1.84 (s, CꢀCH3),
1.21 (d, CH(CH3)2).

D.K. Gupta et al. / Journal of Organometallic Chemistry 568 (1998) 13–20
15
2.5. Preparation of [Ru(p6-C10H14)Cl2(SbPh3)] (5)
(hHꢀCNPy), 7.50 (iHꢀCNPy), 5.22–5.50 (AB pattern
C6H4), 2.99 (m CH(CH3)2), 2.15 (s, CH3 of C6(CH3)6),
1.65 (s, CꢀCH3), 1.24 (d, CH(CH3)2).
This compound was also prepared following the pro-
cedure used for 3 starting from 1 and triphenylstibine.
It separated out as red crystals. Yield 60%; m.p. 180°C
(decom.); Anal. Calc. for C28Cl2H29RuSb: C, 50.98; H,
4.40; Cl, 10.77. Found: C, 51.02; H, 4.22; Cl, 11.22;
1H-NMR (CDCl3): l 7.25–7.82 (br, m, Ar SbPh3),
5.20–5.32 (AB pattern, C6H4), 2.86 (m, CH(CH3)2),
1.86 (s, CꢀCH3), 1.16 (d, CH(CH3)2).
2.8. Preparation of [Cl2(p6-C10H14)Ru(v-CNPy)
Ru(p5-C5H5)(PPh3)2]PF6 (8)
[Ru(p5-C5H5)(PPh3)2Cl] (250 mg, 0.34 mmol) in
methanol (20 ml) was treated with AgPF6 (85 mg, 0.33
mmol) and the solution was stirred at r.t. for 0.5 h. It
was centrifuged to remove the white precipitate of AgCl
and the yellow/orange filtrate was treated with [Ru(p6-
C10H14)Cl2(CNPy)] (125 mg, 0.33 mmol). It was stirred
at r.t. Slowly, a brown microcrystalline compound sep-
arated. It was filtered, washed several times with
methanol, diethylether and dried in vacuum. Yield 65%;
m.p. 225°C; Anal. Calc. for C57Cl4H53N2P2Ru2: C,
54.97; H, 4.25; N, 2.29. Found: C, 54.82; H, 4.46; N,
1.84; IR (KBr) 2226 cm−1 (wCꢁN); 1H-NMR (Acetone-
d6): l 9.20 (hHꢀCNPy), 7.25–7.85 (br, m, iHꢀCNPy
and Ar PPh3), 5.32, 5.84 (AB pattern C6H4), 4.6 (s,
(C5H5), 2 89 (m, CH(CH3)2), 2.16 (s, CꢀCH3), 1.25 (d,
CH(CH3)2).
2.6. Preparation of [Ru(p6-C10H14)Cl2(dppm)] ·CH2Cl2
(6)
To a suspension of [Ru(p6-C10H14)Cl2(CNPy)] (205
mg, 0.5 mmol) in methanol (25 ml), 1,2-bis(-
diphenylphosphino)methane (142 mg, 0.5 mmol) was
added and the solution was heated to reflux for 1 h.
The deep red solution thus obtained was cooled to r.t.,
filtered to remove any solid residue and rotaporated.
The residue was washed several times with petroleum
ether, extracted with dichloromethane and filtered. The
dichloromethane extract was layered with light
petroleum ether (40–60°C) and left for slow crystalliza-
tion. Red needle-shaped crystals separated. These were
filtered, washed several times with petroleum ether and
dried under vacuum. Yield 65%: m.p. 158°C Anal.
Calc. for C36Cl4H38P2Ru: C, 55.74; H, 4.65, Cl, 18.32.
Found: (C, 55.82; H. 4.62; Cl, 18.75; 1H-NMR
(CDCl3): l 6.99–7.95 (br, m, Ar Ph2PCH2PPh2), 5.14,
2.9. X-ray diffraction studies
Data collection, crystal and refinement parameters
are given in Table 1. Atomic co-ordinates and selected
bond lengths and angles are given in Table 2. ORTEP
views for 1 and 6 are given in Figs. 1 and 2,
respectively.
5.32
(AB
pattern,
C6H4),
3.40–3.44
(dd,
Ph2PCH2PPh2), 248 (m, CH(CH3)2), 1.87 (s, CꢀCH3),
0.76 (d, CH(CH3)2); 13C{1H}-NMR (CDCl3): 128.1–
138.2 (Ar Ph2PCH2PPh2), 107.6 (CꢀCHMe2), 93.7 (C-
CH3), 90.3 and 85.6 (C6H4) 54.5 (Ph2PCH2PPh2), 29.9
(CH(CH3)2), 21.2 (CH(CH3)2), 17.7 (CꢀCH3); 31P{1H}-
NMR (CDCl3): 26.1 (dd Ru-bound P of Ph2PCH2PPh2)
−27.6 (d Pendant P of Ph2PCH2PPh2).
Table 1
Crystal data for 1 and 6
1
6
2.7. Preparation of [Cl2(p6-C10H14)Ru(v-CNPy)
Ru(p6-C6Me6)Cl2] (7)
Formula
C
410.3
Red, irregular
monoclinic
P21/c
16H18Cl2N2Ru C36H38Cl4P2Ru
Formula weight
Color, habbit
Crystal system
Space group
775.5
Red, irregular
Monoclinic
P21/n
[{Ru(p6-C6Me6)Cl2}2] (334 mg, 0.5 mmol) was added
to a suspension of [Ru(p6-C10H14)Cl2(CNPy)] (410 mg
1.0 mmol) in methanol (40 ml) and heated under reflux
for ca. 5 h. After cooling to r.t., the orange solution
was filtered to remove any solid residue. The filtrate
was concentrated to ca. 15 ml under reduced pressure
and left for slow crystallization. After a few hours, a
golden red microcrystalline compound separated out
from the solution. It was filtered, washed several times
with, methanol, diethylether and dried under vacuum.
Yield 45%; m.p. 195°C (decom); Anal. Calc. for
C28Cl4H36N2Ru2: C, 45.16; H, 4.83; N, 3.76; Cl, 19.09.
Found: C, 44.82; H, 4.87; N, 3.42; Cl, 19.22; IR (KBr)
Unit cell dimensions
˚
a (A)
10.984(1)
14.052(1)
12.189(1)
114.810(0)
1707.8(4)
4
1.596
12.25
3155
11.504(3)
19.532(3)
15.942(3)
96.08(2)
3562(2)
4
1.446
8.46
5645
˚
b (A)
˚
c (A)
i (°)
V (A )
3
˚
Z
Dcalc (g cm−3
)
Absorption coeff. (cm−1
Reflections collected
)
Independent reflections
2997 (Rint
0.146)
2339
=
5418 (Rint=0.085)
Observed reflections
GOF
3507
1.96
1.33
2230 cm−1 (wCꢁN); 1H-NMR (CDCl3):
l 9.33

16
D.K. Gupta et al. / Journal of Organometallic Chemistry 568 (1998) 13–20
ꢀ w(Fo−Fc)2 where w−1=|2(F)−0.0008F2 resulting
in R=0.0649, wR=0.1766 and S=1.33.
Table 2
˚
Selected bond lengths (A) and angles (°) with estimated S.D. in
parentheses for 1 and 6
2.9.2. Complex 6
1
6
Diffraction data for 6 were collected from red irregular
crystals of dimensions 0.28×0.12×0.35 mm in ꢀ-2q
scan mode (2q range from 5.0 to 50.0°) using Mo–Kh
radiation (u=0.71073) at a speed of 4.0° min−1 in ꢀ.
Throughout the data collection, intensities of three
standard reflections were measured every 100 reflections
as a check of the stability of the crystal. A total of 5645
reflections (5418 unique) were measured.
The structure was solved by the Patterson method and
refined by block-matrix least-square procedures using
3507 reflections with I\3.0|(I). All the non-hydrogen
atoms were refined with anisotropic thermal parameters
by a full-matrix least-square method. Position of the
hydrogen atoms were calculated at the ideal positions
and were not refined. The function minimized was
ꢀ w(Fo−Fc)2, where w−1=|2(F). Final values of R=
0.051 wR=0.067 and S=1.96 were obtained. All calcu-
lations for data reduction, structure solution and
refinement were carried out on a VAX 3520 computer at
the Servicio Central de Ciencia y Technologia de la
Universidad de Cadiz, using the TEXSAN [16] software
system.
˚
Bond lengths (A)
Ru(1)ꢀCl(1)
Ru(1)ꢀCl(2)
Rr(1)ꢀN(1)
Ru(1)ꢀC(8)
Ru(1)ꢀC(9)
Ru(1)ꢀC(10)
Ru(1)ꢀC(11)
Ru(1)ꢀC(12)
Ru(1)ꢀC(13)
C(1)ꢀN(1)
2.405(2) Ru(1)ꢀCl(1)
2.404(2) Ru(1)ꢀCl(2)
2.127(6) Ru(1)ꢀP(1)
2.173(7) Ru(1)ꢀC(1)
2.176(7) Ru(1)ꢀC(2)
2.197(8) Ru(1)ꢀC(3)
2.219(7) Ru(1)ꢀC(4)
2.178(7) Ru(1)ꢀC(5)
2.121(7) Ru(1)ꢀC(6)
1.136(16)
2.409(2)
2.414(2)
2.348(2)
2.226(8)
2.184(8)
2.149(8)
2.200(9)
2.239(9)
2.248(9)
Bond angles (°)
Cl(1)ꢀRu(1)ꢀCl(2)
Cl(1)ꢀRu(1)ꢀN(1)
Cl(2)ꢀRu(1)ꢀN(1)
C(9)ꢀC(8)ꢀC(14)
C(13)ꢀC(8)ꢀC(14)
88.0(1)
85.3(1)
87.0(1)
Cl(1)ꢀRu(1)ꢀCl(2)
Cl(1)ꢀRu(1)ꢀP(1)
Cl(2)ꢀRu(1)ꢀP(1)
89.05(8)
84.26(8)
86.64(8)
121.5(7)
120.1(8)
C(10)ꢀC(11)ꢀC(15) 118.2(7)
C(12)ꢀC(11)ꢀC(15) 123.2(6)
2.9.1. Complex 1
Diffraction data for 1 were collected from red irregular
crystals of dimensions 0.48×0.32×0.18 mm, in ꢀ scan
mode (2q range from 3.0 to 50.0°). Intensities were
measured by 2q-ꢀ scan method using Mo-Kh radiation
(u=0.71073). A variable scan speed between 4.00 and
100.0° min−1 in ꢀ was used. Throughout the data
collection, intensities of three standard reflections were
measured every 297 reflections as a check of the stability
of the crystal. A total of 3155 reflections (2qB50.0°)
3. Results and discussion
The reaction of [{Ru(p6-C10H14)Cl2}2] with 4-
cyanopyridine in dichloromethane in 1:1 and 1:2 molar
ratios gives the mononuclear complex 1 and the binuclear
complex 2 in quantitative yields.
Complex 1 is an air stable, non-hygroscopic, red
crystalline solid, soluble in most of the common organic
solvents like acetone, benzene, dichloromethane, chloro-
form, dimethylformamide and dimethylsulfoxide;
slightly soluble in methanol, ethanol and insoluble in
diethylether and petroleum ether. Its IR spectrum
showed the w(CꢁN) of the co-ordinated CNPy at 2239
were measured and out of these, 2339 reflections with
F\4.0|(F) were used in solution and struture refine-
ment.
The structure was solved by direct methods with
SIR-92 [14] and refined by block-matrix least-square
procedures using SHEXTL [15]. All the non-hydrogen
atoms were refined with anisotropic thermal parameters
by a full-matrix least-square method. Positions of the
hydrogen atoms were calculated at the ideal positions
and were not refined. The function minimized was
1
cm−1. In the H-NMR spectrum, the arene (p6-C10H14)
signals were observed at l 1.32 (d), 2.18 (s), 2.92 (sp),
5.25, 5.49 ppm (AB pattern) and the h and i protons of
the CNPy resonated at l 9.38 and 7.35 ppm. The arene

D.K. Gupta et al. / Journal of Organometallic Chemistry 568 (1998) 13–20
17
Fig. 1. ORTEP drawing of [Ru(p6-C10H14)Cl2(CNPy)] (1) with 50% probability thermal ellipsoids.
unexpected and it could result from the difference in
the local electron density on the (p6-C10H14) protons,
which could arise from the nature of M–L bonding of
the two Ru(II) centers (one bonded to an aromatic
nitrogen atom and the other bonded to the nitrile
nitrogen atom). In the 13C{1H}-NMR spectrum of 2,
the nitrile carbon atom resonated at lowfield (l 121.5
ppm) as compared with that in 1 (l 119.25 ppm) and
free ligand (l 116 ppm). On comparison with the
elemental and spectral data of 2 with 1 it was elucidated
that it is a binuclear complex, in which the CNPy acts
as a bridge between two Ru(II) centers. Treatment of
an equimolar amount of complex 1 with EPh3 (E=
P, As, Sb) gave brick-red to red-brown crystalline com-
plexes 3, 4 or 5. The IR spectra of these complexes did
not show any band in the nitrile stretching frequency
region assignable to w(CꢁN), however, they exhibited
characteristic bands due to EPh3. In the 1H-NMR
spectra of 3, 4 or 5, signals due to the arene (p6-C10H14)
and EPh3 were observed; however, resonances corre-
sponding to h and i protons of CNPy were absent. It
therefore suggested that, in the presence of good Lewis
bases like EPh3, the ligand CNPy gets substituted to
give metathetical products 4, 5 or 6. Further support of
this view point comes from the reaction of 1 with a
bidentate phosphine such as dppm, yielding complex 6.
The IR spectrum of 6 did not show any band assignable
protons and 4-cyanopyridine (h and i) protons exhib-
ited a downfield shift as compared with that in the
precursor complex [{Ru(p6-C10H14)Cl2}2] [12] and in
the free ligand 4-cyanopyridine ([17]a,b). The 13C{1H}-
NMR spectrum of 1 follows the trends observed in the
1H-NMR spectrum, with the nitrile carbon of the
CNPy resonating at lowfield (l 119.25 ppm) as com-
pared with that in the free ligand (l 116 ppm). The IR,
1H and 13C{1H} spectral data of 1 strongly suggested
the linkage of the CNPy with the metal center ruthe-
nium, through its aromatic ring nitrogen ([18]a–f). It
was further confirmed by single crystal X-ray analysis.
It is worth noting that due to the presence of the
pendant nitrile group in 1, it could be used as a
metallo-ligand or as synthon for the synthesis of homo/
heterobimetallic complexes. The IR spectra of 2 showed
a band assignable to n(CꢁN) at 222 cm−1. This band
exhibited a decrease in the position of nitrile stretching
frequency w(CꢁN) as compared with that in 1 (2239
1
cm−1) and free ligand (2242 cm−1). In the H-NMR
spectra of 2 splitted resonances were observed in the
same region as that for 1 (l 9.30, 7.54, 5.36–5.60,
2.34–3.00, 1.86–2.18, 1.30–1.43 ppm). Both, the arene
(p6-C10H14) and 4-cyanopyridine (h and i) protons
exhibited a downfield shift relative to those in complex
1 and free ligand. The splitting of the signals is not

18
D.K. Gupta et al. / Journal of Organometallic Chemistry 568 (1998) 13–20
Fig. 2. ORTEP drawing of [Ru(p6- C10H14)Cl2(dppm)] (6) with 50% probability thermal ellipsoids. Hydrogen atoms are omitted for clarity.
1
to w(CꢁN). The H-NMR spectra of the complex dis-
played aromatic resonances overlapping between d
7.61–6.99 ppm along with the resonances due to the
arene (p6-C10H14). However, signals assignable to h and
i photons of CNPy were not observed. In the 13C{1H}-
NMR spectrum of 6, signals assignable to aromatic and
methylene carbons of dppm, and those for arene (p6-
C10H14) were observed in their usual positions, signals
corresponding to h, i and k carbons of CNPy were not
observed. The 31P{1H}-NMR spectrun of 6 exhibited
two separated peaks at l −27.6 (d) and 26.1 (dd) ppm,
suggesting that the two phosphorus nuclei of the dppm
ligand are present in different chemical environments.
The peak at l 26.1 ppm has been assigned to the
ruthenium-bound phosphorus atom, while the one at l
−27.6 ppm to the pendant phosphorus [19,20]. These
data suggested (i) the formation of 6 takes place by
substitution of CNPy in 1 by dppm and (ii) dppm acts
as monodentate ligand in the complex. The unusual
binding mode of the dppm ligand in 1 has been confi-

D.K. Gupta et al. / Journal of Organometallic Chemistry 568 (1998) 13–20
19
slightly larger than RuꢀN bond length in the 4-MePy
complex [Ru(p6-C6H6)(LꢀL)(2-MePy)][PF6] [26],1, and
in octahedral complexes like [Ru(NH3)5(pz)](BF4)2 and
[Ru(NH3)5(pz)](CF3SO3)2·H2O [27]. The nitrile CꢁN
rmed by single crystal X-ray analysis. It is one of the
few examples of ruthenium complexes in which dppm is
in uncommon monodentate binding mode ([21]a–f).
Complex 6 therefore, represents a unique opportunity
of behaving as a metallo-ligand and as a synthon for
the development of homo/heterobimetallic systems.
The presence of a pendant nitrile group in 1
prompted us to exploit the nucleophilicity of this group
in the synthesis of binuclear complexes. Basically, treat-
ment of 1 with [{Ru(p6-C6Me6)Cl2}2] resulted in the
formation of golden red, shiny crystalline complex 7
and with [Ru(p5-C5H5)(PPh3)2Cl] in the presence of
[PF6]− gave a cationic red-brown complex [Cl2(p6-
C10H14)Ru(v-CNPy)Ru(p5-C5H5)(PPh3)2]PF6 8. The
analytical and spectral data of 7 and 8 corresponds to
CNPy bridged binuclear complexes.
˚
bond length is 1.136(16) A which is very close to the
one characteristic for sp-N bond type and comparable
with the one reported for CH3CN complexes [Ru(p6-
C6H6)(CH3CN)3]2+ and [Ru(p5-C5H5)(CH3CN)3]2+
[28].
˚
The RuꢀP(1) distance in 6 is 2.348(2) A which is close
to RuꢀP distances in [Ru(p5-C5H5)(p1-dppm)2Cl] and
other related systems [19,20].
4. Conclusions
In the present study, we have developed two systems,
complex 1 and 6, bearing pendant donor groups. These
systems therefore, behave as metallo-ligands and as
synthons, these are potential precursors for the synthe-
sis of homo/heterobimetallic complexes. Works on the
synthesis of homo/heterobimetallic complexes starting
from both complexes is in progress.
3.1. Crystal structures of [Ru(p6-C10H14)Cl2(CNPy)]
(1) and [Ru(p6-C10H14)Cl2(dppm)] ·CH2Cl2 (6)
Both complexes adopted a typical ‘piano-stool’ ge-
ometry with the tetrahedral arrangement of the p-
cymene and the other three ligands about the metal
center ruthenium. These have a similar arrangement to
that of [Ru(p6-C10H14)RuCl2(MePPh2)] and [Ru(p6-
C10H14)RuCl(pz)2]PF6 ([22]a,b). For both compounds,
the p-cymene rings are planar with mean deviation
Acknowledgements
˚
from the planes of 0.0087 and 0.0082 A, respectively.
Thanks are due to the Council of Scientific and
Industrial Research, New Delhi and the Director CSM-
CRI, Bhavnagar for financial assistance (HRDG-
01(1375)/95/EMR-II). The Head, Department of
Chemistry for extending facilities, The Head, R.S.I.C.
CDRI, Lucknow for providing spectral and analytical
data and Professor U.C. Agawala for his helpful sug-
gestions and encouragement.
The ruthenium to carbon distances in 1 are almost
˚
equal, with an average RuꢀC=2.177(7) A [range
˚
2.121(7)–2.219(7) A] with an exception of RuꢀC(11)
˚
which is slightly larger [2.219(7) A] compared with the
others. In 6, all the RuꢀC distances are almost equal
˚
with an average RuꢀC 2.207(9) A [range 2.149(8)–
˚
˚
2.248(9) A]. The RuꢀC distances of 1.6539 A in 1 and
˚
1.6947 A are very close to those reported for other
Ru(II) arene complexes ([23]a–c), but for 1 it is shorter
˚
than the average of 1.678 A.
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