Diverse reactivity of rhodium β-(tetraphenyl)tetraphenyl porphyrin chlorides with benzonitrile: Formation of Rh porphyrin arene and imine complexes

Article abstract of DOI:10.1016/S0022-328X(99)00681-6

The reaction of rhodium trichloride with β-(tetraphenyl)tetraphenyl porphyrin, H₂(tpp)(Ph)₄, and β-(tetraphenyl)tetrakismesityl porphyrin, H₂(tmp)(Ph)₄, in refluxing benzonitrile gave novel rhodium porphyrin chl

Full text of DOI:10.1016/S0022-328X(99)00681-6

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 598 (2000) 80–86
Diverse reactivity of rhodium b-(tetraphenyl)tetraphenyl porphyrin
chlorides with benzonitrile: formation of Rh porphyrin arene and
imine complexes
Xiang Zhou, Man Kin Tse, De-Dong Wu, Thomas C.W. Mak, Kin Shing Chan *
Department of Chemistry, The Chinese Uni6ersity of Hong Kong, Shatin, N.T., Hong Kong, PR China
Received 23 June 1999; received in revised form 29 October 1999
Abstract
The reaction of rhodium trichloride with b-(tetraphenyl)tetraphenyl porphyrin, H2(tpp)(Ph)4, and b-(tetraphenyl)tetrakismesityl
porphyrin, H2(tmp)(Ph)4, in refluxing benzonitrile gave novel rhodium porphyrin chlorides, m-cyanophenyl and imine complexes.
The m-cyanophenyl and imine complexes were formed from chloride complexes by arene CꢀH activation via electrophilic
aromatic substitution and reductive nucleophilic addition with the solvent benzonitrile. © 2000 Elsevier Science S.A. All rights
reserved.
Keywords: Rhodium porphyrin; CꢀH activation; Diverse reactivity
facile preparation of the starting rhodium porphyrin
chloride complexes would be most advantageous.
RhI(CO)2Cl reacts with porphyrins in dichloro-
methane or benzene with subsequent oxidation, to yield
rhodium[III] porphyrin chlorides [1,3,11]. Novel rhodiu-
m[II] [11] and rhodium[IV] [12] porphyrins have also
been isolated depending the solvent of choice in the
reaction, and therefore exhibited the rich and diverse
chemistry both in the preparation and oxidation states
of rhodium porphyrins. Alternatively, when the more
accessible rhodium trichloride is employed as the
rhodium source in amide solvents such as dimethyl-
foramide or its derviatives [13], a formal CꢀN activation
of the amide bond is observed to yield small amounts of
rhodium porphyrin alkyls [13d]. Therefore, the solvent
of choice is crucial. We have reported recently that
benzonitrile may be used as a solvent for the introduc-
tion of rhodium trichloride into porphyrins to yield
rhodium porphyrin chlorides. Rhodium porphyrin aryls
were also resulted from intermolecular arene CꢀH acti-
vation of the solvent [8b]. We now report further
progress in the activation of benzonitrile solvent in the
course of the reaction of rhodium trichloride with
b-substituted porphyrins [14] to yield both arene activa-
tion products and a novel addition product involving
the nitrile.
1. Introduction
Rhodium porphyrins have been studied widely for
their unique structural and chemical reactivities [1–12].
Indeed the chemistry of rhodium[II] and [III] porphyrins
are rich and versatile. Rhodium[II] porphyrins form
novel non-bridged metal dimers [1,8a], Dimeric and
monomeric rhodium[II] porphyrin complexes react with
olefins and carbon monoxide to yield insertion products,
and with alkylaromatics to yield CꢀH activation prod-
ucts, all via radical pathways [3,4]. Monomeric rhodium
porphyrina undergo novel activation of methane
through termolecular transition states [3g]. Rhodum[III]
porphyrins serve as molecular recognition templates for
amino acids, nucleobases, and self-assembly units [2].
Rhodium[III] porphyrin cations undergo arene CꢀH
activation through electrophilic aromatic substutition
[1d,8b]. Rhodium[III] porphyrin hydrides insert into
carbon monoxide to give novel stable formyl complexes
[3a–c,4]. Rhodium porphyrin halides catalyze cyclo-
propanation and insertion reactions [5,6]. Structurally
and electronically modified complexes would be impor-
tant for the fine tuning of the reactivity. Consequently,
* Corresponding author. Fax: +86-852-26035057.
E-mail address: ksc@cuhk.edu.hk (K.S. Chan)
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00681-6

X. Zhou et al. / Journal of Organometallic Chemistry 598 (2000) 80–86
81
2. Result and discussion
2.2. Spectroscopic characterization of rhodium
porphyrins
2.1. Reaction of rhodium porphyrin with PhCN
The rhodium porphryins were well-characterized by
spectroscopic methods. The infrared absorption of 3
and 8 at 2222 and 2223 cm−1, respectively confirmed
the presence of a CN group while that of 4 at 1727,
3390 cm−1 supported CꢁN and NꢀH stretching fre-
quencies, respectively and therefore an imine group.
Porphyrin complexes 3 and 8 showed high-field aro-
matic proton resonances of the meta-cyanophenyl
group (l=1.07, 1.09, 5.05, and 5.64 ppm and 1.18
(overlapped signals), ꢀ4.90, and 5.63 ppm, respec-
tively) due to porphyrin ring current effect in their
1H-NMR spectra.
When b-(tetraphenyl)tetraphenyl porphyrin (1),
H2(tpp)(Ph)4 [14b], was reacted with two equivalents of
RhCl3 in refluxing benzonitrile for 48 h in air, the
expected product ClRh(tpp)(Ph)4 (2), the arene CꢀH
activation product (mcph)Rh(tpp)(Ph)4 (3), the unex-
pected nitrile addition product (CNHPh)Rh(tpp)(Ph)4
(4), and 2,4,6-triphenyl-1,3,5-triazine (5) were obtained
in 42, 21, 8 and 47% yields, respectively (Scheme 1).
Likewise RhCl3 reacted with sterically hindered b-(te-
traphenyl)tetrakismesitylporphyrin (6), H2(tmp)(Ph)4
[14c] to give ClRh(tmp)(Ph)4)(7), and (mcph)Rh(tmp)-
(Ph)4 (8), in 42 and 20% yields, respectively (Scheme 2).
All rhodium porphyrin complexes were isolated and
separated by silica gel chromatography in air.
1
The H-NMR of 3 showed that an ethanol molecule
coordinated weakly to the rhodium atom. Two signals
at 1.03 and 3.38 ppm were assigned to the methyl and
methylene protons of coordinated EtOH, respectively.
When a CDCl3 solution of 3 was left at RT for a
month, a new spectrum in CDCl3 of the same solid was
taken. These two singals disappeared.
The structures of 3 and 4 were further established by
single crystal X-ray crystallography. Atomic coordi-
nates, bond lengths and angles, and thermal parameters
for compounds 3 and 4 have been deposited at the
Cambridge Crystallographic Data Centre (Section 5).
Raw data intensities were collected on a Rigaku
RAXIS-II camera with rotating source (50 kV 90 mA)
at room temperature (293 K). The structures were
solved by direct method, and all non-hydrogen atoms
were located on an E-map. All computations were
performed using SHELXTL PC program package on a
PC 486 computer [15,16]. Reddish–brown plate crystals
of (mcph)Rh(tpp)(Ph)4 (3) and red blocks crystals of
(CNHPh)Rh(tpp)(Ph)4 (4) were prepared by slow diffu-
sion of ethanol into CHCl3 solution. The collection and
refinement data for 3 and 4 are listed in Table 1. The
selected bond lengths and angles are listed in Tables 2
and 3, respectively.
Scheme 1.
The molecular structure and atomic labellings for
(mcph)Rh(tpp)(Ph)4 are shown in Fig. 1. The Rh atom
,
is displaced 0.03 A from the mean plane of porphyrin
,
ring and displaced 0.05 A from the four nitrogen atoms
,
plane. The average distance of RhꢀN is 2.005 A for
non-substituted pyrrole and 2.060 A for substituted
pyrrole. The NꢀCa bond length is also affected by
rhodium insertion (average bond length 1.383 A for
rhodium complex, 1.371 A for porphyrin ligand). The
distance between C45 and C51 is 2.992 A, and that of
C51 and C57 is 2.988 A with paralleling arrangement.
The largest deviation relative to the mean plane of four
,
,
,
,
,
,
pyrrole rings is at C5 (0.13 A), whereas N3 lies approx-
,
imately above the mean plane by about 0.008 A.
The dihedral angles between meso-phenyl plane and
Scheme 2.
the mean porphyrin plane are 91.7, 83.5, 91.8 and

82
X. Zhou et al. / Journal of Organometallic Chemistry 598 (2000) 80–86
Table 1
91.8, 83.5, 81.7, 71.9°, respectively. The eight phenyl
Crystal data for compound 3 and 4
groups are in a parallel arrangement. The dihedral
angles between NC4 pyrroles and mean plane are 3.6,
0.2, 2.8 and 6.7°, respectively. The dihedral angle be-
tween benzonitrile and mean plane is 96°. The selected
bond lengths and bond angles are given in Table 2.
The molecular structure and atomic labellings for
(CNHPh)Rh(tpp)(Ph)4 (4) are shown in Fig. 2. The Rh
Formula
(C68H44N4)
(C6H4CN)
(C2H5OH)Rh
(C68H44N4)
(C6H5CNH)Rh
Crystal system
Space group
Formula weight
Monoclinic
P21/n (no. 14)
1168.2
Orthorhombic
P1 (no. 2)
1124.1
,
atom is displaced by 0.07 A from the mean plane of
porphyrin ring which is longer than that of
,
a (A)
22.25690(8)
11.9499(6)
24.8388(9)
13.736(1)
13.846(1)
15.855(2)
101.64(1)
100.81(1)
101.58(1)
1
7008
2814.1(14)
1.327
,
b (A)
,
c (A)
,
(mcph)Rh(tpp)(Ph)4 (0.03 A). The average distance of
RhꢀN is 2.015 A for non-substituted pyrrole and 2.056
h (°)
i (°)
k (°)
Z
,
115.392(3)
Table 3
4
2516
5868.7(4)
1.300
0.05×0.12×0.12
Rigaku RAXIS-II Rigaku RAXIS-II
Mo–Ka Mo–Ka
(u=0.71073 A)
Graphite
,
Selected bond lengths (A) bond angles (°) of (CNHPh)Rh(tpp)(Ph)4
F(000)
3
(4)
,
V (A )
Dcalc. (g cm−3
)
Bond lengths
Crystal size (mm)
Diffrractometer
Radiation
0.05×0.12×0.12
Rh(1)ꢀN(1)
Rh(1)ꢀN(3)
Rh(1)ꢀC(75)
2.057(3)
2.055(3)
1.963(5)
Rh(1)ꢀN(2)
Rh(1)ꢀN(4)
2.017(4)
2.012(4)
,
,
(u=0.71073 A)
Graphite
10088
Monochromator
No. of unique
reflections
Bond angles
10774
N(1)ꢀRh(1)ꢀN(2)
N(2)ꢀRh(1)ꢀN(3)
N(2)ꢀRh(1)ꢀN(4) 171.0(2)
N(1)ꢀRh(1)ꢀC(75) 93.3(2)
N(3)ꢀRh(1)ꢀC(75) 88.9(2)
89.7(1)
90.0(1)
N(1)ꢀRh(1)ꢀN(3)
N(1)ꢀRh(1)ꢀN(4)
N(3)ꢀRh(1)ꢀN(4)
N(2)ꢀRh(1)ꢀC(75)
N(4)ꢀRh(1)ꢀC(75)
177.9(2)
89.9(1)
90.0(1)
99.9(2)
89.1(2)
No. of reflections
No. of variables
5228 (I\3|)
748
7312 (I\6|)
726
R, Rw (observed data) 0.057, 0.050 a
0.052, 0.052 b
1.56
Goodness-of-fit
2.13
largest and mean shift 0.004, −0.001
(|)
0.12, 0.01
Res extrema in final
+0.70 to −0.53
+0.52 to −0.63
difference map
−3
,
(e A
)
2 −1
a w=[|2ꢀFoꢀ+0.001ꢀFoꢀ ]
.
2 −1
b w=[|2ꢀFoꢀ+0.0001ꢀFoꢀ ]
.
R=ꢁꢀFoꢀ−ꢀFoꢀ/ꢁꢀFoꢀ,
wR=
2 1/2
[ꢁ w2(ꢀFoꢀ−ꢀFcꢀ)2/ꢁ w2ꢀFoꢀ ]
.
Table 2
,
Selected bond lengths (A) and bond angles (°) of (mcph)Rh(tpp)(Ph)4
(3)
Bond lengths
Rh(1)ꢀN(1)
Rh(1)ꢀN(3)
Rh(1)ꢀO(1)
N(1)ꢀC(3)
N(2)ꢀC(8)
N(3)ꢀC(13)
N(4)ꢀC(1)
C(1)ꢀC(2)
C(2)ꢀC(3)
C(3)ꢀC(4)
2.073(6)
2.046(6)
2.349(7)
1.376(11) N(1)ꢀC(6)
1.386(7) N(2)ꢀC(11)
1.394(10) N(3)ꢀC(16)
1.379(11) N(3)ꢀC(18)
1.397(10) C(1)ꢀC(20)
Rh(1)ꢀN(2)
Rh(1)ꢀN(4)
Rh(1)ꢀC(69)
2.010(5)
1.998(5)
1.985(9)
1.378(7)
1.374(11)
1.403(7)
1.373(8)
1.443(9)
1.496(13)
1.366(10)
1.390(8)
1.463(10) C(4)ꢀC(5)
C(2)ꢀC(21)
Bond angles
N(1)ꢀRh(1)ꢀN(2) 90.1(2)
N(2)ꢀRh(1)ꢀN(3) 89.6(2)
N(1)ꢀRh(1)ꢀC(69) 90.3(3)
N(3)ꢀRh(1)ꢀC(69) 88.2(2)
N(1)ꢀRh(1)ꢀN(3)
N(1)ꢀRh(1)ꢀN(4)
N(2)ꢀRh(1)ꢀC(69)
N(4)ꢀRh(1)ꢀC(69)
176.4(3)
90.1(2)
93.2(3)
88.5(3)
Fig. 1. (a). Molecular structure and atomic labelings of (mcph)-
Rh(tpp)(Ph)4. (b) Edge-on view plot of the skeleton of (mcph)-
Rh(tpp)(Ph)4. Hydrogen atoms are omitted for clarity. Thermal ellip-
soids are drawn at 50% probability level.
83.5°, respectively (Fig. 1). The dihedral angles between
b-substituted phenyls and the porphyrin mean plane are

X. Zhou et al. / Journal of Organometallic Chemistry 598 (2000) 80–86
83
108.9°, respectively. The dihedral angles between NC4
pyrroles and mean plane are 9.6, 5.5, 9.5 and 10.1°,
respectively. The dihedral angle between benzonitrile
and mean plane is 96°.
,
The bond length between Rh(1) and C(69) is 1.985 A
,
in 3 and Rh(1) and C(75) is 1.963 A in 4. These are
typical of a RhꢀC bond distance and are somewhat
shorter than a RhꢀC(sp3) bond length [11,17].
From the arrangements of the porphyrins in the unit
cells of 3 and 4, the porphyrins pack in parallel layers.
The closest center to center approach of the porphyrin
,
,
rings is 10.55 A for 3 and 4.20 A for 4. The least-square
,
distances between two layers are 5.00 A for 3 and 5.62
,
A for 4. The intermolecular contacts of 3 and 4 are
greater than 4 A [18]. Therefore, no evidence for p–p
,
interaction between neighboring molecules was found in
these structures. This indicates that the observed planar-
ity and non-planarity [18] does not arise from crystal
packing forces but from a minimization of steric repul-
sions between the peripheral phenyl rings. The confor-
mation of the macrocycle and the tilting of the phenyl
rings into the porphyrin plane effectively minimize unfa-
vorable contacts between the peripheral substituents.
2.3. Mechanistic reaction
Fig. 2. (a). Molecular structure and atomic labellings of (CNHPh)-
Rh(tpp)(Ph)4. (b). Edge-on view plot of the skeleton of (CNHPh)-
Rh(tpp)(Ph)4 Hydrogen atoms are omitted for clarity. Thermal ellip-
soids are drawn at 50% probability level.
meta-Cyanophenyl rhodium complexes 3 and 8 were
likely formed via a SEAr pathway from the selective
carbon hydrogen activation of the PhCN at a meta-po-
sition with 2 and 7 [8b]. When 2 was refluxed in PhCN
either in air or under nitrogen for 48 h, 3 and 4 were
formed in 38 and 10% yield, respectively supporting that
2 is an intermediate for the formation of 3 and 4 (Fig.
2). Assisted by the highly polar and donating PhCN, 2
likely ionized into Rh[III] porphyrin cation before its
electrophilic reaction with PhCN [1d] (Scheme 2). Fur-
thermore, the meta-substituted pattern is typical of an
electrophilic substitution product of an electron defi-
cient arene [1d].
Possible CꢀH activation of other arenes was invesit-
gated. ClRh(tpp)(Ph)4 (2) was refluxed with toluene,
pyridine or anisole, but no reactions occurred with 2
recovered only. As the proposed reaction intermediate
carries a positive charge, a polar solvent favors its
formation. PhCN serves both as a good solvent and
reagent since it is a high boiling and highly polar solvent
that can stabilize intermediates well.
Co(tpp)Cl was dissolved and refluxed in benzonitrile
for 72 h both in air and under nitrogen, no desired CꢀH
activation product was obtained. Co(tpp)Cl was recov-
ered in 96% yield. Presumably, the ionization of cobalt
porphyrin chloride to cobalt porphyrin cation is less
favorable than that of rhodium porphyrins.
The origin of the formation of 4 is less clear. The
formation of 4 from 2 in refluxing PhCN both in air or
under nitrogen (Scheme 3) suggests that 2 was possibly
Scheme 3.
,
A for substituted pyrrole. Insertion of rhodium into the
b-substituted porphyrins decreases the porphyrin core
size more compared with that of b-substituted por-
phyrin. The NꢀCa bond length was also shortened by
,
rhodium inserting (average bond length of 1.383 A in
,
rhodium complex, 1.371 A in porphyrin ligand). The
largest deviations relative to the mean plane of four
,
pyrrole rings is at C13 (0.42 A), whereas N3 lies approx-
,
imately above the mean plane by about 0.03 A. The
atom deviations from the mean plane in PhCN are
larger than those of (mcph)Rh(tpp)(Ph)4, which showed
larger deviation than that of (mcph)Rh(tpp)(Ph)4. The
selected bond lengths and bond angles are given in
Table 3.
The dihedral angles between meso-phenyl and the
porphyrin mean plane are 71.2, 79.4, 109.6, and 74.7°,
respectively. The dihedral angles between b-substituted
phenyls and mean plane are 108.0, 79.9, 104.2, and

84
X. Zhou et al. / Journal of Organometallic Chemistry 598 (2000) 80–86
reduced to give either rhodium(I) or rhodium(II) por-
phyrins. A preliminary experiment of the reduction of 3
by Na/Hg in toluene with subsequent reaction with
PhCN yielded small amount of 4. The highly nucleo-
philic rhodium(I) porphyrins [1b,c] added to the elec-
trophilic nitrile carbon and subsequent protonation
yielded 4. Alternatively, the rhodium(II) porphyrin rad-
ical [1b,d,e] generated added to the nitrile carbon to
give nitrogen centered radical; subsequent hydrogen
atom abstraction yielded 4.
The formation 2,4,6-triphenyl-1,3,5-triazine, might be
due to the catalytic trimerization of PhCN either by
HCl generated in the ligand substitution reaction [19]
or a rhodium complex.
Beta substituents of porphyrins do not seem to affect
the yields of the formation of rhodium porphyrin chlo-
rides and aryl rhodium porphyrins (Scheme 2). The
formation of imine 4 seems to be unique to 2. Other
beta-substituted planar or non-planr porphyrins pro-
duced no imine product [8b].
The formation of novel rhodium porphyrins in vari-
ous solvent have been reported and exihibit diverse
chemcial reactivities. Rhodium[II] [11] and rhodium[IV]
[12] porphyrins have been formed in acetic acid and
benzene when [RhI(CO)2Cl]2 was reacted with te-
traphenyl porphyrin. Oxidation of rhodium[I] por-
phyrin insertion intermediate [1a–b] to rhodium[II] [12]
likely accounts its formation. Electrophilic aromatic
substitution of resultant rhodium[III] porphyrin with
benzene might account the formation of rhodium[IV]
complex [11]. Novel reaction of a rhodium[III] por-
phyrin chloride with boiling diethylacetamide yielded
ethyl rhodium porphyrin via the interemediacy of
aminoethyl rhodium porphyrin [13d]. While the mecha-
nism of these novel chemistry remains unclear, the rich
chemistry of rhodium porphyrins with solvents to yield
rhodium(II), (III), and (IV) species exists.
(250 MHz) spectrometers or a Bruker ARX 500 (500
MHz) spectrometer. Chemical shifts were referenced
with tetramethylsilane l=0.00 ppm. Mass spectra were
obtained in FAB mode using m-nitrobeznyl alcohol
(NBA) as the matrix with a Bruker APEX 47e Mass
Spectrometer. Elemental analysis were performed by
the Medac Ltd., Department of Chemistry, Brunel Uni-
versity, UK. Unless otherwise noted, all materials were
obtained from commercial suppliers and used without
further purification. Flash chromatography was per-
formed with silica gel (70–230 or 230–400 mesh).
4.1. Synthesis of rhodium porphyrin complexes:
(2,3,5,10,12,13,15,20-octaphenylporphyrinato)-
(3-cyanophenyl)rhodium(III) chloride (2), (2,3,5,10,12,
13,15,20-octaphenylporphyrinato)-(3-cyanophenyl)-
rhodium(III) (3) and (2,3,5,10,12,13,15,20-octaphenyl-
porphyrinato)(h-phenylimine) rhodium(III) (4)
H2(tpp)(Ph)4 (100 mg, 0.109 mmol) and RhCl3·3H2O
(57.5 mg, 0.218 mmol) were refluxed in PhCN (15 ml)
in air for 48 h. After removal of the solvent, the
reaction mixture was purified by chromatography using
a solvent mixture of CH2Cl2–hexane (2:1) as the eluent
and the different fractions were collected for 2, 3, and
4. ClRh(tpp)(Ph)4 (2) (48 mg, 42% yield). Rf=0.12
1
(hexane: CH2Cl2=2:1). H-NMR(250 MHz, CDCl3) l
5.46 (t, 2 H, J=6.7, 7.2 Hz), 6.48 (d, 2 H, J=7.5 Hz),
6.84–7.24 (m, 32 H), 7.57 (bs, 4 H), 7.80 (bs, 4 H), 8.39
(s, 4 H). Anal. Calc. for RhC68H44N4Cl·3H2O: C, 73.61;
H, 4.54; N, 5.05. Found: C, 73.80; H, 4.60; N, 5.21.
UV–vis umax (CH2Cl2, nm, log m): 436.0 (5.08), 545.0
(4.13), 582.0 (3.49). FABMS (matrix: NBA) m/e: 1020
(M+ꢀCl). (mcph)Rh(tpp)(Ph)4 (3) (26 mg, 21% yield).
1
Rf=0.48 (hexane: CH2Cl2=2:1). H-NMR (500 MHz,
CDCl3) l 1.03 (t, 3 H, J=6.9 Hz, cordinated Me group
of EtOH), 1.07 (s, 1 H), 1.09 (d, 1 H, J=9.3 Hz), 3.38
(q, 2 H, J=6.7 Hz, cordinated methylene group of
EtOH), 5.05 (t, 1 H, J=7.8 Hz), 5.64 (d, 1 H, J=7.5
Hz), 6.70–6.82 (m, 17 H), 7.02–7.21 (m, 15 H), 7.58 (d,
4 H, J=7.4 Hz), 7.74 (d, 4 H, J=7.2 Hz), 8.31 (s, 4
H). Anal. Calc. for RhC75H48N5·C2H5OH: C, 79.17; H,
4.66; N, 5.99. Found: C, 78.86; H, 4.60; N, 5.94.
FABMS (matrix: NBA) m/e: 1122.1 (M++1). UV–vis
umax (CH2Cl2, nm, log m): 426.0 (5.13), 531.0 (4.20).
IR(film) wCN (cm−1): 2222. (CNHPh)Rh(tpp)(Ph)4, 4.
(6 mg, 48% yield). Rf=0.86 (hexane: CH2Cl2=1: 2).
1H NMR (250 MHz, CDCl3) l 2.94 (d, 2 H, J=7.9
Hz), 3.50 (bs, 1 H) 6.21 (t, 2 H, J=7.8 Hz), 6.59 (t, 1
H, J=7.4 Hz), 6.81–6.93 (m, 21 H), 7.07–7.23 (m, 11
H), 7.62 (d, 4 H, J=7.4 Hz), 7.70 (d, 4 H, J=7.0 Hz),
8.28 (s, 4 H). Anal. Calcd for RhC75H50N.5H2O: C,
78.87; H, 4..62; N, 5.91. Found: C, 78.87; H, 4.59; N,
6.13. FABMS (matrix: NBA) m/e: 1124 (M+). UV–vis
umax (CH2Cl2, nm, log m): 425.0 (4.92), 531.0(4.01), 644.0
(3.03). IR(film) wCNH (cm−1): 1462, 1727, 3390.
3. Conclusion
We have discovered that RhCl3 reacted with por-
phyrins in refluxing benzonitrile to yield rhodium aryl
and imine complexes 3 and 4. Rhodium porphyrin aryls
were formed from arene CꢀH activation from the reac-
tion of rhodium porphyrin chlorides with benzonitrile
solvent. The imine complex 4 was formed likely from a
reduced rhodium porphyrin for only the chloride com-
plex 2.
4. Experimental
IR spectra were recorded on a FT-IR spectrophoto-
1
meter as neat films on KBr plates. H-NMR spectra
were recorded on a Bruker WM 250 super-conducting

X. Zhou et al. / Journal of Organometallic Chemistry 598 (2000) 80–86
85
4.2. (2,3,12,13-Tetrakis-phenyl-5,10,15,20-tetra-
mesitylporphyrin)(3-cyanophenyl)rhodium(III) chloride
(7) and (2,3,12,13-tetrakis-phenyl-5,10,15,20-tetra-
mesitylporphyrin)(3-cyanophenyl) rhodium(III) (8)
Grants Council of Hong Kong kindly supports the high
field NMR facilities.
References
H2(tmp)(Ph)4 (90 mg, 0.083 mmol) and RhCl3·3H2O
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the different fractions were collected for 7 and 8.
ClRh(tmp)(Ph)4 (7) (43 mg, 42% yield). Rf=0.10 (hex-
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1
ane:CH2Cl2=1:2). H-NMR (250 MHz, CDCl3) l 1.81
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6.75–6.94 (m, 21 H), 8.24 (s, 4 H). UV–vis umax
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5. Supplementary material
X-ray diffraction data (crystal and data collection
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Acknowledgements
We thank the Croucher Foundation (CF 92/10/23)
for financial support and the Johnson Matthey Com-
pany for a generous loan of RhCl3. The Research

86
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