Incorporation of polybasic aromatic amines into ruthenium(II) chloro complexes

Article abstract of DOI:10.1016/j.poly.2004.05.016

The reactions of RuCl₂[P(C₆H₅) ₃]₃ with excesses of various aromatic amines led to six coordinate, pseudo-octahedral complexes. Thus, three equivalents of pyridazine or 3-methylpyridazine could be inc

Full text of DOI:10.1016/j.poly.2004.05.016

Polyhedron 23 (2004) 2725–2731
www.elsevier.com/locate/poly
Incorporation of polybasic aromatic amines into ruthenium(II)
chloro complexes
*
Benjamin G. Harvey, Atta M. Arif, Richard D. Ernst
Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, UT 84112-0850, USA
Received 20 April 2004; accepted 14 May 2004
Available online 15 July 2004
Abstract
The reactions of RuCl2[P(C6H5)3]3 with excesses of various aromatic amines led to six coordinate, pseudo-octahedral complexes.
Thus, three equivalents of pyridazine or 3-methylpyridazine could be incorporated, or two equivalents of pyrazole or phthalazine,
all as monodentate ligands. Reaction with 1,8-naphthyridine led to the incorporation of one bidentate ligand. X-ray structural data
were obtained for the pyridazine, phthalazine and 1,8-naphthyridine complexes.
Ó 2004 Elsevier Ltd. All rights reserved.
1. Introduction
The chemistry involving ruthenium complexes of ar-
N
N
N
N
2
N
N
omatic amines such as pyridine, 2,2-bipyridine and
pyrazine has been remarkably productive, yielding im-
portant contributions in a number of areas, including
mixed valence compounds and photochemistry [1].
However, in the vast majority of these compounds, the
ligand complements do not allow for direct Ru–Ru in-
teractions, although these may easily be generated using
a number of other ligands, such as the relatively simple
acetate ion and various analogues [2]. We have therefore
undertaken the preparations of ruthenium complexes
containing aromatic polyamine ligands which could
potentially lead to complexes with direct metal–metal
interactions. In this study, we have examined reactions
of RuCl2[P(C6H5)3]3 with several relatively simple
aromatic diamines, including pyridazine (1), 3-meth-
ylpyridazine (2), phthalazine (3), pyrazole (4) and 1,8-
naphthyridine (5).
1
3
N
N
N
N
H
4
5
2. Experimental
All reactions were carried out under an atmosphere
of nitrogen, using Schlenk techniques and apparatus.
Solvents were dried and deoxygenated by distillation
from CaH2 (for CH2Cl2) or sodium benzophenone ketyl
or by passing through columns of activated alu-
mina, under a nitrogen atmosphere in each case.
RuCl2[P(C6H5)3]3 was prepared by a published proce-
dure [3], while the diamines were all obtained from
commercial sources. Elemental analyses were obtained
from E&R Microanalytical Laboratories. NMR spectra
were obtained as previously described [4].
* Corresponding author. Tel.: +8015818639.
E-mail address: ernst@chem.utah.edu (R.D. Ernst).
0277-5387/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.05.016

2726
B.G. Harvey et al. / Polyhedron 23 (2004) 2725–2731
2.1. Dichlorotris(pyridazine)(triphenylphosphine)ruthe-
nium, RuCl2[P(C6H5)3](C4N2H4)3 (6)
2.3. Dichlorobis(phthalazine)bis(triphenylphosphine)ru-
thenium, RuCl2[P(C6H5)3]2(C8N2H6)2 (7)
To a magnetically stirred yellow-brown slurry of 1.0
g (1.0 mmol) RuCl2(PPh3)3 in 20 ml THF were added
0.40 ml (5.5 mmol) of pyridazine via syringe. The so-
lution rapidly changed color to a bright orange-red.
The flask was swirled several times until all solids
dissolved and then it was left undisturbed for 18 h.
After several hours, bright red crystals began to pre-
cipitate from the solution. These crystals were isolated
by removing the supernatant, washing with two 20 ml
and one 10 ml portions of ether, and drying in vacuo.
0.56 g of product were isolated, corresponding to a
yield of 80%. Monoclinic crystals suitable for a single
crystal X-ray diffraction study were grown by layering
a solution of the compound in CH2Cl2 with an equal
volume of hexane. A similar procedure using a more
concentrated solution led to orthorhombic crystals
(space group Pbca, a ¼ 10:2872ð3Þ, b ¼ 23:6429ð12Þ,
To a stirred yellow-brown slurry of 0.50 g (0.52
mmol) RuCl2(PPh3)3 in 20 ml THF under nitrogen at
ambient temperature were added 0.15 g (1.1 mmol) of
phthalazine as a solid. The mixture rapidly converted to
a bright orange slurry. After 2 h of stirring, 50 ml of
hexane were added and the reaction mixture was stirred
for an additional 10 min. The resulting bright orange
precipitate was collected on a medium frit, washed with
3 ꢀ 10 ml ether and dried in vacuo. The yield is virtually
quantitative, with typical isolated yields greater than
90%. Crystals suitable for diffraction studies were grown
in a closed system by slow diffusion of ether vapors into
a concentrated CH2Cl2 solution of the product. A gen-
eral description of a similar apparatus has been pre-
sented [5]; in this application, a solution of the complex
was placed in one side and some ether was placed in the
other side, thus leading to vapor phase transfer of each
solvent to the other side. In other cases, simple evapo-
ration of one solvent may be achieved by placing diph-
enylmethane in the other side.
ꢀ
c ¼ 33:5918ð17Þ A at 293(1) K), having a higher sol-
vent content, and yielding a similar, but less satisfac-
tory, structural result.
1H NMR (CD2Cl2 ambient): d 10.74 (dt, 2H, H(1,9),
J ¼ 5:7, 1.4 Hz), 8.81 (dt, 1H, H5, J ¼ 6:0, 1.4 Hz), 8.33
(m, 3H, H(4,8,12)), 7.55 (tt, 6H, Ho(PPh3), J ¼ 8:1, 1.2
Hz), 7.43 (ddd, 2H, H(2,10), J ¼ 8:1, 7.1, 2.1 Hz), 7.22
(ddd, 2H, H(3,11), J ¼ 8:0, 6.5, 1.6 Hz), 7.12 (tq, 3H,
Hp(PPh3), J ¼ 7:4, 1.5 Hz), 6.97 (td, 6H, Hm(PPh3),
J ¼ 7:7, 1.8 Hz), 6.90 (ddd, 1H, H7, J ¼ 8:0, 4.9, 1.5
Hz), 6.45 (ddd, 1H, H6, J ¼ 8:1, 6.0, 2.1 Hz).
Anal. Calc. for C52H42P2Cl2N4Ru: C, 65.27; H, 4.42;
N, 5.86. Found: C, 65.23; H, 4.82; N, 5.41%.
2.4. Dichloro(1,8-naphthyridine)bis(triphenylphosphine)-
ruthenium, RuCl2[P(C6H5)3]2(1,8-C8N2H6) (8)
To a stirred yellow-brown slurry of 0.50 g (0.52
mmol) RuCl2(PPh3)3 in 20 ml of THF under nitrogen at
ambient temperature were added 80 mg (0.61 mmol) of
1,8-naphthyridine as a solid. A rapid color change to
bright purple was followed by the precipitation of a
purple solid. After stirring for approximately 10 min, the
supernatant appeared virtually colorless. The purple
precipitate was collected on a medium frit, washed with
3 ꢀ 10 ml ether and dried in vacuo. Yields for this re-
action appeared quantitative, with isolated yields typi-
cally above 90%. Crystals suitable for diffraction studies
were grown in a Schlenk tube by carefully layering
hexane onto a concentrated solution of the compound in
CH2Cl2.
Anal. Calc. for C30H27Cl2PN6Ru: C, 53.42; H, 4.03;
N, 12.46. Found: C, 53.77; H, 4.02; N, 12.13%.
2.2. Dichlorotris(3-methylpyridazine)(triphenylphos-
phine)ruthenium, RuCl2[P(C6H5)3](3-CH3C4N2H3)
To a stirred yellow-brown slurry of 0.50 g (0.52
mmol) RuCl2(PPh3)3 in 20 ml of THF under nitrogen at
ambient temperature were added 0.25 g (2.7 mmol) of 3-
methylpyridazine via syringe. The reaction mixture
rapidly converted to a bright red solution and was stir-
red overnight. After ca. 18 h, 50 ml of hexane were
added with stirring to precipitate the product. The
bright red-orange precipitate was collected on a medium
frit, washed with 3 ꢀ 10 ml ether, and dried in vacuo.
Yield: 285 mg, 75%.
1H NMR (CDCl3 ambient): d 10.74 (d, 2H, Ho-Me-
pyd, J ¼ 5:7 Hz), 8.52 (d, 1H, Ho-Mepyd, J ¼ 5:7 Hz),
7.66 (t, 6H, Hm-PPh3, J ¼ 8:4 Hz), 7.26 (dd, 2H, Hm-
Mepyd, J ¼ 7:8, 6.0 Hz), 7.09 (t, 3H, Hp-PPh3, J ¼ 6:9
Hz), 7.02–6.90 (m, 8H, Ho-PPh3 and Hp-Mepyd), 6.68
(d, 1H, Hp-Mepyd, J ¼ 7:8 Hz), 6.48 (dd, 1H, Hm-Me-
pyd, J ¼ 7:8, 6.0 Hz), 2.09 (s, 6H, Me), 1.90 (s, 3H, Me).
Anal. Calc. for C33H33PCl2N6Ru: C, 55.31; H, 4.64;
N, 11.73. Found: C, 55.22; H, 4.53; N, 11.51%.
Anal. Calc. for C44H36P2Cl2N2Ru: C, 63.93; H, 4.39;
N, 3.39. Found: C, 63.85; H, 4.53; N, 3.18%.
2.5. Dichlorobis(pyrazole)bis(triphenylphosphine)ruthe-
nium, RuCl2[P(C6H5)3]2(C3N2H4)2 (9)
To a magnetically stirred slurry of 0.50 g (0.52 mmol)
RuCl2(PPh3)3 in 20 ml THF were added 0.10 g (1.5
mmol) of pyrazole. A rapid color change to red was
observed, followed by a slower (2–3 min) transition to
yellow. The color change to yellow occurred much more
rapidly if a large excess of pyrazole was used. The so-
lution was stirred for 18 h and the solvent removed in

B.G. Harvey et al. / Polyhedron 23 (2004) 2725–2731
2727
vacuo to yield a thick yellow oily solid. The solid was
washed with 3 ꢀ 10 ml pentane and dried in vacuo. The
powdery residue was extracted with 3 ꢀ 10 ml CH2Cl2
and filtered through a coarse frit with a Celite pad. The
bright yellow filtrate was concentrated to ca. 10 ml and
carefully layered with 50 ml hexane. After the flask had
been left undisturbed for 24 h, yellow crystals were de-
posited on the sides of the flask. The supernatant was
removed and the crystals were washed with 3 ꢀ 10 ml
ether and dried in vacuo. 0.370 g of product were iso-
lated, corresponding to a yield of 85%. Solutions of the
product rapidly turn green upon exposure to air.
1H NMR (chloroform-d1, ambient): d 11.70 (s, 2H,
N–H), 8.13 (t, 4H, py–H(2,4), J ¼ 1:5 Hz), 7.35 (t, 12H,
Ho(PPh3), J ¼ 8:3 Hz), 7.17 (t, 6H, Hp(PPh3), J ¼ 7:4
Hz), 7.00 (q, 12H, Hm(PPh3), J ¼ 7:0 Hz), 5.94 (q, 2H,
py–H3, J ¼ 2:2 Hz).
Section 2.1), but the solvent was poorly behaved, and a
less satisfactory structure was obtained. The hydrogen
atoms in 7 were also refined isotropically, except for
those associated with the solvent molecules. These at-
oms were allowed to ride on their respective carbon
atoms. Two CH2Cl2 molecules, one of half occupancy,
were incorporated into this lattice. For 8, all but one
hydrogen atom, H44, could be refined isotropically.
That one was refined with a fixed thermal parameter. A
summary of crystal and data collection parameters is
given in Table 1, while pertinent bonding parameters for
6–8 are listed in Tables 2–4.
3. Results and discussion
The reactions of RuCl2[P(C6H5)3]3 with excesses of
pyridazine, 3-methylpyridazine, phthalazine, pyrazole
and 1,8-naphthyridine in each case led to a six-coordi-
nate ruthenium(II) complex, as summarized in Scheme
1. The reactions involving pyridazine or 3-methylpy-
ridazine resulted in the incorporation of three equiva-
lents of the ligand, together with expulsion of two
phosphine ligands. In contrast, the reactions with
phthalazine, pyrazole or 1,8-naphthyridine brought
about the loss of only one phosphine ligand, leading
only to the incorporation of two phthalazines, two
pyrazoles or one (chelating) 1,8-naphthyridine ligand(s).
The constitutions of these complexes have been estab-
lished through analytical data, NMR spectroscopy when
solubility permitted, and for 6–8, through single crystal
X-ray diffraction studies. In each case where meaningful
Anal. Calc. for C42H38Cl2P2N4Ru: C, 60.58; H, 4.60;
N, 6.73. Found: C, 60.49; H, 4.76; N, 6.49%.
2.6. Crystallographic studies
Single crystals for X-ray diffraction study were fixed
to glass fibers using Paratone oil and thereafter trans-
ferred to a Nonius Kappa CCD diffractometer for
study. Structures were solved using direct method pro-
grams provided in the SIR-97 or SHELXL-97 program
packages. All non-hydrogen atoms were subjected to
anisotropic refinement. For 6, the hydrogen atoms were
refined isotropically, including those in a molecule of
solvent CH2Cl2. It can be noted that crystals having a
higher CH2Cl2 content could also be obtained (see
Table 1
Crystallographic parameters for RuCl2[P(C6H5)3](C4N2H4)3, RuCl2[P(C6H5)3]2(C8N2H6)2, and RuCl2[P(C6H5)3]2(1,8-C8N2H6)
Empirical formula
Formula weight
Temperature (K)
C31H29Cl4N6PRu
759.44
150(1)
C53:5H45Cl5N4P2Ru
1084.19
150(1)
C44H36Cl2N2P2Ru
826.66
200(1)
ꢀ
k (A)
0.71073
monoclinic
P21=c
0.71073
triclinic
0.71073
triclinic
Crystal system
Space group
Unit cell dimensions
ꢁ
ꢁ
P1
P1
ꢀ
a (A)
15.5365(3)
11.7054(3)
17.4477(3)
90
11.7277(1)
13.8433(2)
17.2485(3)
87.2876(6)
74.6044(6)
65.5332(10)
2451.10(6)
2
11.3392(3)
12.4477(3)
13.5955(4)
90.0120(12)
82.0268(12)
74.1443(11)
1826.64(8)
2
ꢀ
b (A)
ꢀ
c (A)
a (°)
b (°)
c (°)
93.8557(13)
90
3
ꢀ
Volume (A )
3165.87(12)
4
1.593
Z
Dcalc
1.469
6.99
1.503
6.99
Absorption coefficient (cmꢁ1
)
9.17
3.8–27.5
ꢁ20 6 h 6 20,
h Range (°)
Limiting indices
3.5–27.5
ꢁ14 6 h 6 15,
2.5–27.9
ꢁ14 6 h 6 14,
ꢁ14 6 k 6 15, ꢁ22 6 l 6 22 ꢁ17 6 k 6 17, ꢁ19 6 l 6 22 ꢁ16 6 k 6 15, ꢁ15 6 l 6 17
Reflections collected
Independent reflections; n: I > nðIÞ
12360
17109
12433
7235; 2
0.0289
0.0594
10929; 2
0.0437
0.1052
8467; 2
0.0469
0.0858
RðF Þ
Rw(F 2)
Maximum/minimum difference Fourier peak (e A )
3
ꢀ
0.41/)0.65
2.07/)1.29
0.64/)0.94

2728
B.G. Harvey et al. / Polyhedron 23 (2004) 2725–2731
Table 2
Pertinent bonding parameters for RuCl2[P(C6H5)3](C4N2H4)3 (6)
The product of the reaction with excess pyridazine
was found to adopt a mer,cis arrangement of ligands in a
pseudooctahedral coordination environment (6), Fig. 1.
A similar structure can be assumed for the 3-meth-
ylpyridazine complex, and this would be consistent with
the NMR results which revealed two types of amine li-
gands in a 2:1 ratio. As would be expected, there is some
evidence of inter-ligand steric repulsion involving the
phosphine ligand, as the P–Ru–N angles all exceed 90°
(91.22(5)–97.06(5)°), thereby leading to generally acute
N–Ru–Cl2 angles (85.56(5)–90.05(5)°). While other an-
gles also deviate from their ideal values, the presence of
six aromatic rings in the complex can be expected to
result in C–H/p [6] and/or p=p [7] interactions, whether
intramolecular or intermolecular [8], which could play
an even larger role than the steric effects and therefore
complicate further comparisons.
ꢀ
Bond distances (A)
Ru–N1
Ru–N3
Ru–N5
2.0760(17)
2.0735(17)
2.0604(16)
Ru–P1
Ru–Cl1
Ru–Cl2
2.2976(5)
2.4309(5)
2.4665(5)
Bond angles (°)
N1–Ru–N3
N1–Ru–N5
N1–Ru–P1
N1–Ru–Cl1
N1–Ru–Cl2
N5–Ru–P1
N5–Ru–Cl1
N5–Ru–Cl2
Ru–P1–C13
93.51(7)
175.72(7)
92.85(5)
89.45(5)
85.83(5)
91.22(5)
89.22(5)
90.05(5)
118.82(7)
N3–Ru–N5
N3–Ru–P1
N3–Ru–Cl1
N3–Ru–Cl2
P1–Ru–Cl1
P1–Ru–Cl2
Cl1–Ru–Cl2
Ru–P1–C19
Ru–P1–C25
87.33(7)
97.06(5)
172.44(5)
85.56(5)
89.73(2)
177.14(2)
87.72(2)
115.48(7)
116.23(7)
Table 3
Pertinent bonding parameters for RuCl2[P(C6H5)3]2(C8N2H6)2 (7)
Although there seem to be no other examples of
structurally characterized ruthenium complexes con-
taining both phosphine and the simple pyridazine li-
gands, and just a few for transition metals generally [9],
some comparisons may be made with various more
common poly(amine) species. Thus, the Ru–N distances
ꢀ
Bond distances (A)
Ru–P1
Ru–Cl1
Ru–N1
2.4085(7)
2.4421(7)
2.055(2)
Ru–P2
Ru–Cl2
Ru–N2
2.3855(7)
2.4661(7)
2.057(2)
Bond angles (°)
N1–Ru–N3
N1–Ru–P1
N1–Ru–P2
N1–Ru–Cl1
N1–Ru–Cl2
P1–Ru–Cl1
P1–Ru–Cl2
Cl1–Ru–Cl2
Ru–P1–C17
Ru–P1–C23
Ru–P1–C29
ꢀ
of 2.060(2)–2.076(2) A in 6 are similar to values of
89.16(9)
86.16(7)
94.36(7)
N3–Ru–P1
N3–Ru–P2
N3–Ru–Cl1
N3–Ru–Cl2
P1–Ru–P2
P2–Ru–Cl1
P2–Ru–Cl2
Ru–P2–C35
Ru–P2–C41
Ru–P2–C47
95.80(7)
88.17(7)
ꢀ
2.049(2) and 2.084(3) A in neutral pyridyl-substituted
pyridazine complexes [10], as well as to those in a mixed
valence Ru(II,III) complex [11], but longer than those in
ꢀ
related cationic species (1.986(10)–2.031(7) A) [12], and
shorter than Ru–N bonds in trimetallic carbonyl com-
plexes in which pyridazine coordinates to two adjacent
ꢀ
ruthenium(0) centers (2.11(1)–2.136(4) A) [13]. Likewise,
ꢀ
the Ru–Cl distances of 2.4309(5) and 2.4665(5) A are
reasonably similar to values ranging from 2.392(1) to
177.21(7)
87.70(7)
89.24(7)
176.22(7)
86.37(2)
92.06(3)
176.01(3)
89.67(2)
87.65(3)
93.98(2)
112.79(9)
116.23(10)
120.68(10)
116.47(10)
112.85(10)
119.76(10)
ꢀ
2.431(1) A in the related cationic or carbonyl-containing
ꢀ
Table 4
Pertinent bonding parameters for RuCl2[P(C6H5)3]2(1,8-C8N2H6) (8)
complexes. The Ru–P distance of 2.2976(5) A may be
ꢀ
compared to values in the range of 2.23–2.44 A found
for two modifications of RuCl2[P(C6H5)3]3 [14].
ꢀ
Bond distances (A)
Ru–P1
Ru–Cl1
Ru–N1
2.2819(7)
2.4242(9)
2.217(3)
Ru–P2
Ru–Cl2
Ru–N2
2.3040(8)
2.4050(9)
2.222(2)
Notably, the reaction of RuCl2[P(C6H5)3]3 with
phthalazine led only to the incorporation of two
equivalents of ligand, rather than three. As the resulting
RuCl2[P(C6H5)3]2(C8H6N2)2 complex contains an extra
phosphine ligand compared to 6, the additional steric
crowding may block access of a third amine ligand to
the metal center; alternatively it could be that the lower
solubility of this complex compared to its hypothetical
pyridazine analogue led to 7’s precipitation before a
third incorporation could take place. Consequently, it
could be possible to bring about the third incorporation
using other solvents and/or more forcing conditions. A
structural determination revealed the complex to have a
cis,trans,cis pseudooctahedral geometry (Fig. 2), so the
chloride ligands have remained cis to each other. The
two P(C6H5)3 ligands are located trans to each other,
with one phenyl group from each pointed between the
two chloride ligands. This results in the other phenyl
groups being directed towards the phthalazine ligands,
Bond angles (°)
N1–Ru–N2
N1–Ru–P1
N1–Ru–P2
N1–Ru–Cl1
N1–Ru–Cl2
P1–Ru–Cl1
P1–Ru–Cl2
Cl1–Ru–Cl2
Ru–N1–C1
Ru–N1–C8
Ru–N2–C8
Ru–N2–C7
60.81(9)
100.96(7)
161.41(7)
80.95(7)
85.27(7)
97.77(3)
90.87(3)
164.89(3)
148.6(2)
94.3(2)
N2–Ru–P1
N2–Ru–P2
N2–Ru–Cl1
N2–Ru–Cl2
P1–Ru–P2
P2–Ru–Cl1
P2–Ru–Cl2
Ru–P1–C9
Ru–P1–C15
Ru–P1–C21
Ru–P2–C27
Ru–P2–C33
Ru–P2–C39
160.60(7)
101.17(7)
86.35(8)
81.53(7)
97.45(3)
94.09(3)
97.06(3)
108.74(9)
125.39(11)
117.42(10)
106.79(11)
124.08(10)
119.71(10)
94.1(2)
148.8(2)
NMR data could be recorded, the spectral results were
indicative of the presence of only one isomer, which was
also consistent with the structural results.

B.G. Harvey et al. / Polyhedron 23 (2004) 2725–2731
2729
H
H
N
N
N
N
Ru
N
Cl
Cl
Cl
N
N
N
Ru
N
Ph3P
Ph3P
PPh3
Cl
N
9
6
RuCl2[P(C6H5)3]2
N
Ph3P
Ru
Cl
Ru
Cl
Ph3P
Ph3P
Cl
Cl
N
N
N
N
Ph3P
N
8
7
Scheme 1.
presumably in order to optimize C–H/p and p=p inter-
actions. It seems quite possible that these interactions
could play a role in stabilizing the observed cis,trans,cis
isomer, and if the additional fused rings of the phthal-
azine ligands do not engage in any substantial stabilizing
intermolecular interactions, such an arrangement could
be found for the analogous pyridazine complex which
would be a likely intermediate in the formation of 6.
While there are no other structurally characterized
(phthalazine)ruthenium complexes to compare with 7,
and only a few transition metal complexes containing
both phosphine and phthalazine ligands [9c,15], one can
note that the Ru–N distances for 7 are slightly shorter
than those for 6. The two Ru–P bonds are lengthened
relative to the one in 6, but are similar to the nearly trans
Ru–P bonds in RuCl2[P(C6H5)3]3 [14], whereas as noted
before, the unique Ru–P bond in RuCl2[P(C6H5)3]3 (ca.
ꢀ
2.23 A) is similar to the Ru–P distance in 6. The
lengthening of the Ru–P bonds in 7 thus appears to be
electronic in origin. The Ru–Cl bond distances for 6 and
7 are not significantly different from each other, but are
ꢀ
longer than the values of ca. 2.38–2.39
RuCl2[P(C6H5)3]3.
A
in
C3
C21
C4
N2
C49
C22
C50
C48
C2
C43
C20
C51
C44
C42
C16
C39
C6
C15
C23
C40
C52
C38
C47
C35
C36
C19
C14
C5
C45
C41
C7
N1
C37
C24
Cl1
C46
C17
C1
P2
C18
C13
Cl2
N3
C8
Cl1
N1
Ru1
N6
N4
P1
Ru1
C16
C9
C3
C1
N4
C15
C14
C2
C26
N3
C13
C4
Cl2
C25
C30
C31
C10
N2
C5
C11
C27
C12
C7
C22
P1
N5
C6
C8
C17
C29
C30
C23
C24
C27
C32
C21
C25
C34
C12
C28
C28
C9
C33
C29
C26
C18
C20
C11
C10
C19
Fig. 1. Perspective view and numbering scheme for RuCl2-
[P(C6H5)3](C4N2H4)3 (6).
Fig. 2. Perspective view and numbering scheme for RuCl2-
[P(C6H5)3]2(C8N2H6)2 (7).

2730
B.G. Harvey et al. / Polyhedron 23 (2004) 2725–2731
bpy)2(1,8-C8N2H6)2þ average 2.11(1) A for the naph-
thyridine ligand [16], while in a more complicated,
amino-substituted 1,8-naphthyridine complex [17], a
highly asymmetric coordination is observed, with Ru–N
ꢀ
C29
C32
C30
C43
C28
C42
C31
C44
C39
C27
ꢀ
distances of 2.066(6) and 2.377(7) A. More common
than the observed monometallic chelating coordination
mode are the monodentate bonding mode (with Ru–N
C41
C7
Cl1
C6
C4
C34
C35
P2
C40
C19
N2
ꢀ
distances to date of 2.078(9)–2.137(6) A) [16,18] and a
C5
C33
C38
C20
C15
C36
C18
Ru1
bridging mode in which the nitrogen centers are coor-
dinated to different ruthenium centers which generally
would be connected by a Ru–Ru bond [17,19,20]. In
these cases, the Ru–N distances range from 2.00(3) to
C8
C37
C3
N1
C16
P1
C26
C17
C21
Cl2
C1
C2
ꢀ
2.21(3) A. Likewise, the monodentate coordination
C25
C10
C9
mode has been observed in phosphine-containing com-
plexes of gold [21] and platinum [22], while the bridging
mode has been observed in a dicopper phosphine
complex [23].
C14
C24
C22
C23
C11
C13
C12
The reaction of an excess of the five-membered ring
ligand pyrazole with RuCl2[P(C6H5)3]3 led only to the
incorporation of two equivalents, and the expulsion of
one phosphine ligand, analogous to the reaction in-
volving phthalazine rather than to that of pyridazine.
Attempts to incorporate a third equivalent of pyrazole
using a large (10 equiv.) excess of pyrazole under reflux
conditions did not lead to any observable change. The
1H NMR spectrum demonstrated that the two phos-
phine ligands were equivalent, as were the two pyraz-
Fig. 3. Perspective view and numbering scheme for RuCl2-
[P(C6H5)3]2(1,8-C8N2H6) (8).
The reaction of RuCl2[P(C6H5)3]3 with 1,8-naph-
thyridine was unique in leading to the incorporation of
only one ligand, at least under mild conditions, although
a bidentate coordination mode was adopted in the
product (8). Perhaps as a result of the smaller spatial
requirements of the chelating diamine as compared to
the two phthalazine ligands in 7, the phosphine ligands
in 8 adopt a cis rather than trans orientation, with the
chlorides becoming trans (Scheme 1, Fig. 3). Nonethe-
less, the marked asymmetry in the Ru–P–C angles (Ta-
ble 3) seems to reveal the presence of some steric
interactions between the phosphine ligands. In contrast,
the Ru–P–C angles in the other complexes were more
regular, although RuCl2[P(C6H5)3]3 also displays a dis-
tortion [14]. In any event, this arrangement leads to an
apparently favorable orientation for intramolecular C–
H/p interactions between two of the naphthyridine hy-
drogen atoms and two of the phosphine phenyl groups
[6]. The N1–Ru–N2 angle is of necessity quite small, at
60.81(9)°, thereby allowing for the P1–Ru–P2 angle to
expand to 97.45(3)°. The chloride ligands are bent away
from the phosphines toward the diamine, with a Cl1–
Ru–Cl2 angle of 164.89(3)°. Presumably due to the lack
of alignment between the nitrogen lone pairs and the
metal center, the Ru–N distances in 8 (2.217(3), 2.222(2)
oles.
The
overall
complex
stoichiometery,
RuCl2[P(C6H5)3]2(C3N2H4)2, again corresponds to a
six-coordinate, pseudo-octahedral complex. A structural
study has revealed that it adopts a different arrangement
than that of 7 (Scheme 1) [24].
4. Summary
The complex RuCl2[P(C6H5)3]3 has been found to be
a useful starting material for the formation of polybasic
aromatic amine complexes of ruthenium. Despite the
potential abilities of pyridazine, pyrazole, phthalazine
and 1,8-naphthyridine to bridge more than one metal
center, none of the complexes involved such bridging,
although the 1,8-naphthyridine ligand did chelate a
single metal center. Each complex retained one or two of
the triphenylphosphine ligands, whose steric bulk may
have prevented the formation of dimetallic complexes.
To some extent the product that was isolated was de-
termined by solubility considerations, suggesting that
additional incorporations could be achieved in some
cases. Likewise, for at least pyrazole and pyridazine, it
appears possible to limit the extent of incorporation
through stoichiometry [24]. Notably, initial attempts to
incorporate additional metal centers into the pyridazine
complex have tended to lead instead to ligand exchange
reactions [24], as has been seen for pyrazine complexes
[25]. Possibly the use of less acidic metal centers or the
ꢀ
A) are notably longer than those in 6 and 7. In turn,
however, the opposite trend is observed for 8’s Ru–Cl
ꢀ
(2.4050(9), 2.4242(9) A) and Ru–P bonds (2.2819(7),
ꢀ
2.3040(8) A).
Although there seem to be no structurally charac-
terized examples of ruthenium complexes containing
both phosphine and 1,8-naphthyridine ligands, two re-
ports of chelating (naphthyridine)ruthenium complexes
have appeared. The Ru–N distances in Ru(2,20 -

B.G. Harvey et al. / Polyhedron 23 (2004) 2725–2731
2731
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deprotonation of coordinated pyrazole, which would
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5. Supplementary material
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC, Nos. 236487-236489 for com-
pounds 8, 7 and 6, respectively. Copies of this infor-
mation may be obtained free of charge from The
Director, CCDC, 12, Union Road, Cambridge CB2 1EZ
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