Bimetallic complexes with porphyrins containing a cyclometalated phenylpyridine group

Article abstract of DOI:10.1016/j.jorganchem.2004.09.018

Treatment of Ni(HP¹) (H₃P¹ = meso-5-[4′-(2″-pyridyl)phenyl]-10,15,20-triphenyporphyrin) with K₂[PdCl₄] in EtOH afforded [Pd{Ni(P¹)}] ₂(μ-Cl)₂ that reacted with NaS₂CNEt ₂ to give Pd(S₂CNEt₂)[Ni(P¹)]. Reaction of Ni(HP¹) with [Ir(H)₂(PPh₃) ₂(Me₂CO)₂][BF₄] afforded Ir(H)Cl(PPh₃)₂[Ni(P¹)]. The crystal structures of Pd(S₂CNEt₂)[Ni(P¹)] and Ir(H)(Cl)(PPh ₃)₂[Ni(P¹)] have been determined.

Full text of DOI:10.1016/j.jorganchem.2004.09.018

Journal of Organometallic Chemistry 690 (2005) 253–260
www.elsevier.com/locate/jorganchem
Bimetallic complexes with porphyrins containing a cyclometalated
phenylpyridine group
Ka-Man Cheung, Qian-Feng Zhang, Wing-Leung Mak, Herman H.Y. Sung,
*
Ian D. Williams, Wa-Hung Leung
Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, PR China
Received 14 July 2004; accepted 10 September 2004
Available online 30 November 2004
Abstract
Treatment of Ni(HP1) (H3P1 = meso-5-[40-(200-pyridyl)phenyl]-10,15,20-triphenyporphyrin) with K2[PdCl4] in EtOH afforded
[Pd{Ni(P1)}]2(l-Cl)2 that reacted with NaS2CNEt2 to give Pd(S2CNEt2)[Ni(P1)]. Reaction of Ni(HP1) with [Ir(H)2(PPh3)2(Me2-
CO)2][BF4] afforded Ir(H)Cl(PPh3)2[Ni(P1)]. The crystal structures of Pd(S2CNEt2)[Ni(P1)] and Ir(H)(Cl)(PPh3)2[Ni(P1)] have been
determined.
Ó 2004 Elsevier B.V. All rights reserved.
Keywords: Bimetallic; Cyclometalated; Porphyrin; Nickel; Palladium; Iridium
1. Introduction
luminescent properties [9]. For example, Ir(III)–ppy
complexes have been used as phosphorescent dopants
for organic light-emitting diodes [10] and luminescent la-
bels for biomolecules [11]. In addition, owing to the ani-
onic nature of cyclometalated ligands, polynuclear metal
complexes with ppy–porphyrins are electrically neutral
and thus have high solubility in organic solvents. In this
connection, we seek to synthesize metal complexes with
porphyrin-ppy dyads that may have applications in pho-
toinduced electron transfer and bimetallic catalysis.
Herein, we report on the synthesis and structural char-
acterization of the first bimetallic complexes with
porphyrins containing a cyclometalated ppy group.
Polynuclear metalloporphyrins are of interest due to
their potential applications in photoinduced electron
transfer [1] and biomimetic redox catalysis [2]. Among
various synthetic routes to multiporphyrin arrays [3],
one convenient approach is to assemble ligand-ap-
pended porphyrins by coordination with appropriate
external metal ions. In the past decade, metal-assisted
self-assembly of pyridylporphyrins to give dimers and
oligomers with interesting architecture and spectral
properties has been studied extensively [3–5]. However,
analogous multiporphyrins based on cyclometalated
C^N ligands have not been well explored [6]. Recently,
Pd(II) [7] and Pt(II) [8] complexes with cyclometalated
N-confused porphyrins have been synthesized. Transi-
tion metal complexes containing cyclometalated N^C
ligands, particularly 2-phenylpyridine (ppy), have
attracted much attention due to their interesting photo-
2. Experimental
2.1. General information
Solvents were purified, distilled, and degassed prior
to use. NMR spectra were recorded on a Bruker ALX
300 spectrometer operating at 300 and 121.5 MHz for
*
Corresponding author. Tel.: +852 23587360; fax: +852 23581594.
E-mail address: chleung@ust.hk (W.-H. Leung).
0022-328X/$ - see front matter Ó 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.09.018

254
K.-M. Cheung et al. / Journal of Organometallic Chemistry 690 (2005) 253–260
1H and 31P, respectively. Chemical shifts (d, ppm) were
reported with reference to SiMe4 (1H) and H3PO4
(31P). Infrared spectra were recorded on a Perkin–Elmer
16 PC FT-IR spectrophotometer and mass spectra on a
Finnigan TSQ 7000 spectrometer. Elemental analyses
were performed by Medac Ltd., UK. Benzenedipyrro-
methane, 4-methylbenzenedipyrromethane [12], and
[Ir(H)2(PPh3)2(Me2CO)2][BF4] [13] were prepared
according to literature methods. 4-(20-Pyridyl)benzalde-
hyde was purchased from Aldrich Ltd.
J0 = 2 Hz, 1H, H3 or H4), 7.94 (m, 1H, H4 or H3),
8.10 (d, J = 8.0 Hz, 4H, 4-tol), 8.36 (d, J = 8.0 Hz, 4H,
H5 and H6), 8.86–8.92 (m, 9H, H1 and Hb). MS
(FAB): m/z 734 (M+ + 1). UV/Vis (CH2Cl2): kmax/nm
(e/104 Mꢀ1 cmꢀ1).
H4P4. Yield: 122 mg (17%). 1H NMR (300 MHz,
CDCl3): d ꢀ2.32 (s, 2H, NH), 2.72 (s, 6H, p-Me), 7.28
(t, J = 6.8 Hz, 2H, H2), 7.80 (m, 8H, 4-tol), 7.94 (d,
J = 7.8 Hz, 2H, H3 or H4), 8.09 (td, J = 8.0 Hz, 2H,
H3 or H4), 8.40 (m, 8H, H5 and H6), 8.72–8.79 (m,
10H, H1 and Hb). MS (FAB): m/z 798 (M+ + 1). UV/
Vis (CH2Cl2): kmax/nm (e/104 Mꢀ1 cmꢀ1) 420 (26), 452
(7.1), 516 (5.1), 554 (3.2), 592 (2.1), 650 (2.1).
2.2. Preparations of ppy-substituted porphyrins (Scheme
1)
A mixture of 4-(20-pyridyl)benzaldehyde (330 mg, 1.8
mmol) and benzenedipyrromethane (400 mg, 1.8 mmol)
in propionic acid (200 ml) was heated at reflux for 1 h.
The solvent was removed under reduced pressure and
the residue was extracted with dichloromethane and
purified by column chromatography (silica gel). H3P1
and H4P2 were eluted with Et2O/hexane (1:1) and
CH2Cl2/acetone (4:1), respectively. H3P3 and H4P4 were
prepared similarly using 4-methylbenzenedipyrrometh-
ane in place of benzenedipyrromethane. The hydrogen
atom labeling scheme for the porphyrin ligands is shown
below.
2.3. Preparations of nickel(II) porphyrins
Typically, a solution of Ni(acac)2 (Hacac = 2,4-pen-
tanedione) (112 mg, 0.44 mmol) in chloroform (20 ml)
was added ppy-substituted porphyrin (60 mg, 0.089
mmol) and the mixture was heated at reflux for 4 h.
The solvent was pumped off and the residue was
extracted with dichloromethane. Recrystallization from
methanol at room temperature in air afforded a purple
crystalline solid.
1
Ni(HP1). Yield: 50 mg (75%). H NMR (300 MHz,
CDCl3): d 7.34 (t, J = 6.0 Hz, 1H, ppy), 7.69 (m, 10H,
Ph), 7.88 (t, J = 7.0 Hz, 1H, ppy), 8.02 (m, 6H, Ph and
ppy), 8.14 (d, J = 8.0 Hz, 2H, H5), 8.30 (d, J = 8.0 Hz,
2H, H6), 8.75–8.83 (m, 9H, H1 and Hb). MS (FAB):
m/z 748 (M+ + 1). UV/Vis (CH2Cl2): kmax/nm (e/104
Mꢀ1 cmꢀ1) 416 (17), 529 (1.9).
Ar
H
H1
X = Ph, Ar = Ph (H3P1)
X = ppy, Ar = Ph (H4P2)
X = 4-tol, Ar = 4-tol (H3P3)
X = ppy, Ar = 4-tol (H4P4)
N
HN
N
N
H2
X
1
Ni(H2P2). Yield: 26 mg (41%). H NMR (300 MHz,
H3 H4 H5 H6
NH
CDCl3): d 7.35 (t, J = 6.0 Hz, 2H, ppy), 7.70 (m, 5H,
Ph), 7.89 (t, J = 5.0 Hz, 2H, ppy), 7.97–8.02 (m, 7H,
Ph and ppy), 8.14 (d, J = 8.0 Hz, 4H, H5), 8.31 (d,
J = 8.0 Hz, 4H, H6), 8.76 (d, J = 5.0 Hz, 4H, Hb), 8.82
(d, J = 5.0 Hz, 4H, Hb), 8.84 (d, J = 2.0 Hz, 2H, H1).
Ar
H3P1. Yield: 58 mg (9%). 1H NMR (300 MHz,
CDCl3): d ꢀ2.83 (s, 2H, NH), 7.77 (m, 10H, Ph), 7.92
(m, 1H, H2), 8.05–8.13 (m, 2H, H3 and H4), 8.23 (m,
5H, Ph), 8.36 (dd, J = J0 = 9.0 Hz, 4H, H5 and H6),
8.85–8.94 (m, 9H, Hb and H1). MS (FAB): m/z 692
MS (FAB): m/z 826 (M+ + 1). UV/Vis (CH2Cl2): kmax
/
nm (e/104 Mꢀ1 cmꢀ1) 418 (16), 529 (1.9).
1
Ni(HP3). Yield: 51 mg (79%). H NMR (300 MHz,
CDCl3): d 2.66 (s, 9H, p-Me), 7.48 (d, J = 8.0 Hz, 6H,
4-tol), 7.74 (t, J = 7 Hz, 1H, ppy), 7.89 (d, J = 8 Hz,
6H, 4-tol), 8.16 (m, 2H, ppy), 8.19 (d, J = 6Hz, 2H,
H6), 8.39 (d, J = 8.0 Hz, 2H, H5), 8.71–8.79 (m, 8H,
Hb), 9.04 (d, J = 2 Hz, 1H, H1). MS (FAB): m/z 790
(M+ + 1). UV/Vis (CH2Cl2): kmax/nm (e/104 Mꢀ1 cmꢀ1
)
422 (18), 450 (3.5), 515 (2.6), 551 (2.0), 649 (1.3).
H4P2. Yield: 118 mg (17%). 1H NMR (300 MHz,
CDCl3): d ꢀ2.71 (s, 2H, NH), 7.38 (t, J = 7.0 Hz, 2H,
H2), 7.79–7.81 (m, 5H, Ph), 7.92 (t, J = 7.0 Hz, 2H, H4
or H3), 8.06 (d, J = 7.8 Hz, 2H, H3 or H4), 8.23–8.31
(m, 5H, Ph), 8.40 (dd, J = 8.0 Hz, 8H, H5 and H6),
8.80–8.86 (m, 8H, Hb), 8.87 (d, J = 2.0 Hz, 2H, H1).
(M+ + 1). UV/Vis (CH2Cl2): kmax/nm (e/104 Mꢀ1 cmꢀ1
417 (19), 529 (2.4).
)
2.4. Preparation of Pd(S2CNEt2)[Ni(P3)] (1)
MS (FAB): m/z 768 (M+ + 1). UV/Vis (CH2Cl2): kmax
/
A mixture of K2[PdCl4] (14 mg, 0.08 mmol) in
methanol (15 ml) and Ni(HP3) (60 mg, 0.08 mmol)
in MeOH/THF (3:1, 20 ml) was refluxed overnight.
The red precipitate, presumably [Pd{Ni(P3)}]2(l-Cl)2,
was collected, washed with Et2O, and stirred with
NaS2CNEt2 (36 mg, 0.16 mmol) in CHCl3/acetone at
nm (e/104 Mꢀ1 cmꢀ1) 420 (25), 451 (6.4), 516 (4.0), 554
(1.5), 650 (1.6).
H3P3. Yield: 44 mg (7%). 1H NMR (300 MHz,
CDCl3): d ꢀ2.48 (s, 2H, NH), 2.72 (s, 9H, p-Me) 7.37
(m, 1H, H2), 7.56 (m, 8H, 4-tol), 7.90 (td, J = 7.5 Hz,

K.-M. Cheung et al. / Journal of Organometallic Chemistry 690 (2005) 253–260
255
room temperature for 4 h. The solvent was pumped
2.6. Preparation of Pd(S2CNEt2)[Ni(HP2)] (3)
off and the residue was recrystallized from CH2Cl2/
MeOH to give a purple solid. Yield: 23 mg (29%).
Anal. Calc. for C57H46N6NiPdS2 Æ MeOH Æ 1.5H2O:
C, 63.14; H, 4.84; N, 7.62. Found: C, 63.58; H,
4.75; N, 7.40%. 1H NMR (300 MHz, CDCl3): d
1.29 (overlapping t, 6H, Me), 2.65 (s, 9H, p-Me),
3.64–3.84 (m, 4H, CH2), 7.22 (t, J = 6.0 Hz, 1H,
ppy), 7.47 (d, J = 7.5 Hz, 6H, 4-tol), 7.70–7.94 (m,
11H, 4-tol and ppy), 8.53 (d, J = 6.0 Hz, 1H, H1),
8.75 (m, 6H, Hb), 8.87 (d, J = 5.4 Hz, 2H, Hb). MS
(FAB): m/z 1044 (M+). UV/Vis (CH2Cl2): kmax/nm
(e/104 Mꢀ1 cmꢀ1) 419 (23), 529 (2.7).
This compound was prepared similarly as for 1 using
Ni(H2P2) (60 mg, 0.08 mmol) in place of Ni(HP3).
Recrystallization from CH2Cl2/MeOH gave a purple so-
lid. Yield: 24 mg (29%). Anal. Calc. for C59H43N7NiPd-
S2 Æ 2.5H2O: C, 63.09; H, 4.22; N, 8.73. Found: C, 62.63;
H, 4.22; N, 8.87%. 1H NMR (300 MHz, CDCl3): d 1.14–
1.31 (overlapping t, 6H, Me), 3.65–3.84 (m, 4H, CH2),
7.34 (t, J = 6.0 Hz, 1H, ppy), 7.62–7.74 (m, 11H, Ph
and ppy), 7.88–8.01 (m, 6H, ppy), 8.13 (d, J = 7.8 Hz,
2H, H5), 8.30 (d, J = 8.2 Hz, 2H, H6), 8.54 (d, J = 5.4
Hz, 1H, ppy), 8.73–8.81 (m, 10H, Hb and H1). MS
(FAB): m/z 1079 (M+). UV/Vis (CH2Cl2): kmax/nm
(e/104 Mꢀ1 cmꢀ1) 422 (29), 529 (3.9).
2.5. Preparation of Pd(S2CNEt2)[Ni(P1)] (2)
This compound was prepared similarly as for 1
using Ni(HP1) in place of Ni(HP2). Recrystallization
from CH2Cl2/hexane afforded purple crystals that were
2.7. Preparation of Ir(H)(Cl)(PPh3)2[Ni(P3)] (4)
To a solution of [Ir(H)2(PPh3)2(Me2CO)2][BF4] (55
mg, 0.061 mmol) in CH2Cl2 (20 ml) was added one
equivalent of Ni(HP3) (48 mg, 0.061 mmol), and the
mixture was stirred at room temperature for 4 h. The
solvent was pumped off and the residue was washed with
hexane/Et2O and then extracted with CH2Cl2.
Recrystallization from CH2Cl2/hexane afforded a deep
red solid. Yield: 32 mg (40%). Anal. Calc. for
C88H67ClIrN5NiP2 Æ C6H14 Æ 2CH2Cl2 Æ 2H2O: C, 63.46;
H, 4.83; N, 3.85. Found: C, 63.96; H, 4.82; N, 3.58%.
1H NMR (300 MHz, acetone-d6): d ꢀ15.45 (t, J = 7.6
1
suitable for X-ray diffraction. Yield: 15 mg (27%). H
NMR (300 MHz, CDCl3): d 1.16 (t, J = 7.0 Hz, 3H,
Me), 1.28 (t, J = 6.6 Hz, 3H, Me), 3.62–3.69 (m, 2H,
CH2), 3.79–3.84 (m, 2H, CH2), 7.23 (t, J = 6.0 Hz,
1H, ppy), 7.66–7.75 (m, 10H, Ph), 7.84 (m, 2H,
ppy), 7.93–8.01 (m, 7H, Ph and ppy), 8.53 (d,
J = 4.8 Hz, 1H, ppy), 8.72 (m, 7H, H1 and Hb),
8.89 (d, J = 4.8 Hz, 2H, Hb). MS (FAB): m/z 1003
(M+ + 1). UV/Vis (CH2Cl2):
cmꢀ1) 417 (23), 529 (2.2).
k
max/nm (e/104 Mꢀ1
Table 1
Crystallographic data and experimental details for 2 Æ C6H14 Æ 0.5CH2Cl2 and 5 Æ C6H14
2 Æ C6H14 Æ 0.5CH2Cl2
5 Æ C6H14
Empirical formula
Formula weight
Crystal system
Space group
C60.5H55ClN6NiPdS2
1130.79
Triclinic
C91H75ClIrN5NiP2
1572.75
Monoclinic
C2/c
ꢀ
P1
˚
a (A)
14.615(3)
17.205(4)
22.069(5)
77.385(4)
75.225(4)
66.922(4)
4892(2)
4
65.13(1)
9.585(2)
24.185(5)
90
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
90.72(3)
90
3
˚
V (A )
15097(5)
8
1.396
Z
Dcalcd (g cmꢀ3
T (K)
)
1.535
100(2)
100(2)
2.139
l(Mo Ka) (mmꢀ1
F(000)
)
0.942
2332
6464
13142
8189
Reflections collected
Independent reflections
Ra, wRb (I > 2r(I))
R1, wR2 (all data)
Goodness-of-fit (GoF)c
3
Maximum residual density (e/A )
19080
12653
0.0590, 0.1563
0.0997, 0.1727
0.996
0.0462, 0.0901
0.1012, 0.1009
0.906
˚
1.391
1.254
P
P
a
b
c
R1 = iFo| ꢀ |Fci/ |Fo|.
P
P
2
2 1=2
wR2 ¼ ½ wðjF 2oj ꢀ jF c2Þ = wjF 2oj ꢁ
:
P
GoF = [ w(|Fo| ꢀ |Fc|)2/(Nobs ꢀ Nparam)]1/2
.

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K.-M. Cheung et al. / Journal of Organometallic Chemistry 690 (2005) 253–260
Ar
Ar
Ar
N
N
HN
HN
Ar
X
X +
X
EtCO2H
N
H
N
H
NH
N
NH
N
Ar
Ar
Ar = Ph (H3P1) 9%
= 4-tol (H3P3) 7%
Ar = Ph (H4P2) 17%
= 4-tol (H4P4) 17%
X =
N
H
Scheme 1. Syntheses of ppy-substituted porphyrins.
Hz, 1H, IrH), 2.81 (s, 9H, p-Me), 7.39–7.76 (m, 42H, Ph
and 4-tol), 8.08 (m, 6H, ppy), 8.15 (d, J = 5.0 Hz, 2H,
Hb), 8.73 (d, J = 5.0 Hz, 2H, Hb), 8.93 (br. s, 4H, Hb),
9.74 (d, J = 5.8 Hz, 1H, H1). 31P{1H} NMR (121.5
MHz, CDCl3): d 17.26 (s). MS (FAB): m/z 1506
(M+ ꢀ Cl). IR (KBr, cmꢀ1): 2154 [m(Ir–H)]. UV/Vis
(CH2Cl2): kmax/nm (e/104 Mꢀ1 cmꢀ1) 421 (35), 529 (4.2).
3. Results and discussion
3.1. Synthesis
In an attempt to prepare ppy-substituted porphyrins,
4-(20-pyridyl)benzaldehyde was reacted with an equimo-
lar amount of arenedipyrromethane (arene = benzene or
4-methylbenzene) in refluxing propionic acid. However,
in addition to the expected bis-ppy porphyrins 5,15-
bis[40-(200-pyridyl)phenyl]-10,20-diarylporphyrin (H4P2
and H4P4), the mono-ppy porphyrins 5-[40-(200-pyr-
idyl)phenyl]-10,15,20-triarylporphyrin (H3P1 and H3P3)
were isolated as minor products (Scheme 1). It seems
likely that the formation H3P1 and H3P3 involves the
rearrangement of arenedipyrromethane to arenetripyr-
rolemethane. Metal insertion of these porphyrins with
Ni(acac)2 (Hacac = 2,4-pentanedione) afforded the cor-
responding Ni(II) porphyrins (see Section 2). Analogous
2.8. Preparation of Ir(H)(Cl)(PPh3)2[Ni(P1)] (5)
This compound was prepared similarly as for 4 using
Ni(HP1) in place of Ni(HP3). Recrystallization from
CH2Cl2/hexane afforded deep red crystals that were suit-
1
able for X-ray crystallography. Yield: 29 mg (27%). H
NMR (300 MHz, CDCl3): d ꢀ16.3 (t, J = 7.6 Hz, 1H,
IrH), 6.57 (t, J = 7.0 Hz, 1H, ppy), 7.04–7.10 (m, 5H,
Ph), 7.18 (m, 15H, Ph), 7.38–7.48 (m, 15H, Ph), 7.71–
7.89 (m, 11H, Ph and ppy), 7.98 (m, 6H, Hb and ppy),
8.34 (d, J = 4.8 Hz, 1H, H5), 8.38 (d, J = 4.8 Hz, 1H,
H6), 8.74–8.90 (m, 5H, Hb and H1). 31P{1H} NMR
(121.5 MHz, CDCl3): d 13.40 (s). FAB (MS): m/z 1465
(M+ ꢀ Cl). IR (KBr, cmꢀ1): 2170 [m(Ir–H)]. UV/Vis
(CH2Cl2): kmax/nm (e/104 Mꢀ1 cmꢀ1): 422 (37), 529 (4.8).
NEt2
C
Ar
S
S
N
Pd
N
N
2.9. X-ray diffraction studies
i, ii
Ar
Ni
N
N
A summary of crystallographic data and experimen-
tal details for complexes 2 Æ C6H14 Æ 0.5CH2Cl2 and
5 Æ C6H14 are compiled in Table 1. Intensity data were
collected on a Bruker SMART APEX 1000 CCD dif-
fractometer using graphite-monochromated Mo Ka
Ar
Ni(HP1)
or
Ni(HP3)
4-tol
Ph
1
2
Ar
Ar
˚
H
Cl
radiation (k = 0.71073 A) at 100(2) K. The collected
L
Ir
L
iii
frames were processed with the software SAINT [14].
Structures were solved by the direct methods and refined
by full-matrix least-squares on F2 using the SHELXTL
[15] software package. Non-hydrogen atoms were
refined anisotropically. The hydrogen atoms of C–H
bonds were added in idealized positions. For 5, the car-
bon atoms in the hexane solvent molecules were disor-
dered and their site occupancies were set to be 0.5.
The disordered carbon atoms were refined with fixed
C–C bond distances and described without hydrogen
atoms.
N
N
N
Ar
Ni
N
N
L = PPh3
Ar
Ar
4-tol
Ph
4
5
Scheme 2. Syntheses of bimetallic complexes with cyclometalated
porphyrins: (i) K2[PdCl4], EtOH, RT; (ii) Na(Et2NCS2), acetone/
CH2Cl2, RT; (iii) [Ir(H)2(PPh3)2(Me2CO)2][BF4], CH2Cl2, RT.

K.-M. Cheung et al. / Journal of Organometallic Chemistry 690 (2005) 253–260
257
(a)
(b)
˚
Fig. 1. ORTEP diagram of 2: (a) top view and (b) side view. The ellipsoids are drawn at 30% probability level. Selected bond distances (A) and angles
(°): Ni(1)–N(2) 1.954(4), Ni(1)–N(3) 1.947(4), Ni(1)–N(4) 1.952(4), Ni(1)–N(5) 1.947(4), Pd(1)–S(1) 2.291(1), Pd(1)–S(2) 2.401(2), Pd(1)–N(1)
2.054(4), Pd(1)–C(11) 2.002(5); C(11)–Pd(1)–N(1) 81.2(2), S(1)–Pd(1)–S(2) 75.13(5), N(2)–Ni(1)–N(3) 90.0(2), N(3)–Ni(1)–N(4) 90.0(2), N(4)–Ni(1)–
N(5) 90.0(2), N(5)–Ni(1)–N(2) 90.0(2).
i
i
˚
Fig. 2. Part of the crystal packing diagram for 2 Æ C6H14 Æ 0.5CH2Cl2 showing intermolecular Pdꢂ ꢂ ꢂPd [3.827(2) A] and Pdꢂ ꢂ ꢂS [3.833(2) and 3.890(2)
˚
A] contacts.

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K.-M. Cheung et al. / Journal of Organometallic Chemistry 690 (2005) 253–260
Fe(III) and Co(II) porphyrins could be prepared simi-
larly using FeCl2 and Co(CH3CO2), respectively.
plexes 2 and 5 are non-emissive in CH2Cl2 solution at
room temperature.
Cyclometalation of the meso-ppy groups in the Ni(II)
porphyrins afforded bimetallic complexes. However,
metalation of the bis-ppy compounds Ni(H2P2) and
Ni(H2P4) usually yielded mixtures of products that
could not be separated easily. Thus, this work focussed
on cyclometalation of Ni(II) mono-ppy porphyrins
(Scheme 2). Treatment of Ni(HP3) with K2[PdCl4] in
methanol led to formation of a brown precipitate, pre-
sumably the chloro-bridged diporphyrin complex
[Pd{Ni(P3)}]2(l-Cl)2, which is sparingly soluble in
most organic solvents except DMF. Treatment of
[Pd{Ni(P3)}]2(l-Cl)2 with NaS2CNEt2 in CH2Cl2/ace-
tone afforded the Pd(II)/Ni(II) complex Pd(S2CNEt2)
[Ni(P3)] (1). Pd(Et2NCS2)[Ni(P1)] (2) was prepared sim-
ilarly from Ni(HP1) and has been characterized by X-ray
crystallography. Attempts to prepare a trinuclear por-
phyrin complex by reacting Ni(H2P2) with excess
K2[PdCl4]/NaS2CNEt2 and longer reaction time were
unsuccessful. Only the mono-cyclometalated complex
Pd(Et2NCS2)[Ni(HP2)] (3) was isolated. The bis-palla-
dated compound was not formed possibly due to the
low solubility of the [Pd{Ni(HP2)}]2(l-Cl)2 intermediate
that prevented further cyclometalation of the porphyrin.
Similar to 7,8-benzoquinoline and its derivatives [16],
the ppy-substituted porphyrins could be cyclometalated
readily by Ir(III) hydride compounds. For example,
treatment of [Ir(H)2(PPh3)2(Me2CO)2][BF4] [13] with
Ni(HP3) and Ni(HP1) afforded Ir(H)(Cl)(PPh3)2[Ni(P3)]
(4) and Ir(H)(Cl)(PPh3)2[Ni(P1)] (5), respectively
(Scheme 2). The chloride in 4 and 5 was apparently de-
rived from the CH2Cl2 solvent. The presence of the hy-
dride ligand was confirmed by IR [m(Ir–H) at 2154 and
3.2. Crystal structures
The solid-state structures of complexes 2 and 5 have
been established by X-ray crystallography. Fig. 1 shows
the molecular structure of 2. The porphyrin macrocycle
˚
in 2 is essentially planar with a deviation of 0.01 A from
the mean N4 plane and the geometry around Pd is close
to square planar. The plane containing Pd and its
coordinating atoms is approximately perpendicular to
the porphyrin plane (dihedral angle of ca. 88.4(2)°).
The Ni–N distances (av. 1.950(4) A) are comparable to
those in Ni(TPP) (H2TPP = meso-5,10,15,20-tetra-
˚
(a)
1
2170 cmꢀ1] and H NMR (d ꢀ15.45 and ꢀ16.20 ppm,
respectively) spectroscopy. Consistent with the solid-
state structure (vide infra), the hydride for each com-
1
pound appears as a triplet in the H NMR spectrum
due to coupling with the two equivalent PPh3 ligands.
The observation of the hydride resonance at ca. d ꢀ16
ppm suggests that the hydride is trans to the pyridyl
instead of the phenyl group [13]. An attempt to prepare
a trimetallic porphyrin complex by reaction of Ni(H2P2)
with two equivalent of [Ir(H)2(PPh3)2(Me2CO)2][BF4]
was not successful.
The optical spectrum of 2 in CH2Cl2 displays the Sor-
et band at 417 nm, which is similar to that of Ni(HP1)
(416 nm). On the other hand, the Soret band for 5 is
red-shifted by ca. 6 nm and has a higher intensity (ca.
2 times) compared with that for Ni(HP1). The red shift
for 5 probably arises from the deformation of the por-
phyrin macrocycle (vide infra) [17]. The cyclic voltamm-
ogram of 4 in CH2Cl2 exhibits couples at 0.58 and 0.86
V vs. Cp2Fe+/0 that are assigned as the porphyrin-cen-
tered oxidations because similar oxidation potentials
were also found for the free porphyrin ligand. Com-
(b)
Fig. 3. ORTEP diagram of 5: (a) top view and (b) side view. The
ellipsoids are drawn at 30% probability level. Selected bond distances
˚
(A) and angles (°): Ni(1)–N(2) 1.910(5), Ni(1)–N(3) 1.926(5), Ni(1)–
N(4) 1.915(6), Ni(1)–N(5) 1.904(5), Ir(1)–P(1) 2.302(2), Ir(1)–P(2)
2.316(2), Ir(1)–N(1) 2.146(5), Ir(1)–C(11) 2.023(6); C(11)–Ir(1)–N(1)
79.7(2), C(11)–Ir(1)–P(1) 87.0(2), C(11)–Ir(1)–P(2) 94.9(2), N(1)–
Ir(1)P(1) 93.8(1), N(1)–Ir(1)–P(2) 94.4(1), P(1)Ir(1)–P(2) 171.8(1),
N(2)–Ni(1)–N(3) 90.2(2), N(3)–Ni(1)–N(4) 90.1(2), N(4)–Ni(1)–N(5)
89.8(2), N(5)–Ni(1)–N(2) 89.8(2).

K.-M. Cheung et al. / Journal of Organometallic Chemistry 690 (2005) 253–260
259
Fig. 4. Part of the crystal packing diagram for 5 Æ C6H14 showing N(pyrrole)ꢂ ꢂ ꢂHC(meso-phenyl) hydrogen bonds between two molecules [C(52B)–
˚
H(52B) 0.95, H(52B) ꢂ ꢂ ꢂ N(4A) 2.593(2), C(52B)ꢂ ꢂ ꢂN(4A) 3.356(3) A; C–H ꢂ ꢂ ꢂ N 164.0(2)°].
˚
phenylporphyrin, 1.931(2) A) [18]. The two PdAS bonds
4. Conclusions
˚
are not symmetric (2.401(2) and 2.291(2) A) due to trans
influence of the phenyl group. The crystal packing dia-
gram of 2 Æ C6H14 Æ 0.5CH2Cl2 shows that the lattice
consists of pairs of molecules with the Pdꢂ ꢂ ꢂPd* and
Pdꢂ ꢂ ꢂS* separations of 3.827(2) and 3.833(2) and
In summary, we have synthesized and characterized a
new type of bimetallic complex with porphyrins contain-
ing a cyclometalated 2-phenylpyridine group. Given the
rich coordination chemistry of cyclometalated N^C lig-
ands, the ppy–porphyrin dyad may serve as a useful
building block for porphyrin dimers and oligomers with
interesting structures and properties. With judicious
choice of metal ions in the porphyrin and ppy coordina-
tion sites, such bimetallic complexes could find applica-
tions in redox catalysis and photoinduced electron
transfer.
˚
3.890(2) A, respectively (Fig. 2).
The molecular structure of 5 is shown in Fig. 3. To
our knowledge, this is the first structurally characterized
metalloporphyrin that contains a transition metal hy-
dride at its periphery. Unlike 2, the porphyrin macrocy-
cle in 5 displays a saddle deformation [17] with the mean
˚
displacement of the pyrrolic carbons of 0.34 A, which is
comparable to that for other Ni(II) non-planar porphy-
rin complexes, e.g., Ni(DTPP) (H2DTPP = 2,3-diethy-
˚
nyl-5,10,15,20-tetraphenyl-porphyrin; 0.32 A) [19].
5. Supporting information
Given the planarity of the porphyrin in 2, the saddle
geometry for 5 is probably due to crystal packing effects
and/or steric bulk of the PPh3 ligands. The crystal
packing diagram of 5 Æ C6H14 reveals intermolecular
hydrogen bonding between a pyrrolic nitrogen and a
meso-phenyl group of another porphyrin molecule
Crystallographic data for 2 Æ C6H14 Æ 0.5CH2Cl2 and
5 Æ C6H14 have been deposited with the Cambridge Crys-
tallographic Data Centre, CCDC 213142 and 213143,
respectively, in CIF format. Copies of this information
may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
(fax: +44 1223 336033; e-mail: deposit@ccdc.
cam.ac.uk).
˚
(Cꢂ ꢂ ꢂN 3.356(3) A) (Fig. 4). The average Ni–N distance
˚
of 1.914 A is slightly shorter than that in 2. The separa-
˚
tion between the Ir(III) and Ni(II) centers is ca. 8.6 A.
Similar to [Ir(bq)(PPh3)2(H)(H2O)][SbF6] (Hbq = 7,8-
benzoquinoline) [16a], the geometry around Ir is pseu-
do-octahedral with two mutually trans-PPh3 ligands.
The hydride is trans to the pyridyl instead of the phenyl
group due to the trans influence of the latter that results
Acknowledgements
˚
in a rather long Ir–Cl bond (2.4858(2) A). The Ir–P, Ir–
N, and Ir–C distances (av. 2.309(2), 2,146(5), and
The financial support from the Hong Kong
Research Grants Council and the Hong Kong Uni-
versity of Science and Technology is gratefully
acknowledged.
˚
2.023(6) A, respectively) are similar to those in
[Ir(bq)(PPh3)2(H)(H2O)][ SbF6] [16a].

260
K.-M. Cheung et al. / Journal of Organometallic Chemistry 690 (2005) 253–260
[6] A porphyrin derived from an Os(II)–ppy complex has been
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