Ruthenium(ii) and rhodium(iii) porphyrin phosphine complexes: Influence of substitution pattern on structure and electronic properties

Article abstract of DOI:10.1039/c1nj20598f

A series of ruthenium(ii) and rhodium(iii) porphyrin complexes with diphenyl phenylacetylene phosphine (dpap) was synthesised and fully characterised by UV-vis, ¹H NMR and ³¹P{¹H} NMR spectroscopy, and in most cases also by single-crystal X-ray diffraction. The substitution pattern of the porphyrin was varied with increasing meso-phenyl substitution, from octa-ethyl porphyrin (OEP), through diphenyl di-ethyl porphyrin (DPP), to tetraphenyl porphyrin (TPP) and 3,5-di-^tbutyl tetraphenyl porphyrin (tbTPP). The dpap readily displaces the CO ligand from the parent Ru(CO)(porphyrin) and the iodide from the Rh(I)(porphyrin) to give bis-phosphine complexes M(dpap)₂(porphyrin). The UV-vis spectra reveal that some of the complexes are partially dissociated at concentrations of 10^-6 M, and the association constants were estimated to be in the range of 10⁶ to 10⁷ M^-1 for the first, and 10⁴ to 10⁶ M^-1 for the second binding event. The ¹H NMR chemical shifts of the complexes vary greatly despite the fact that they display very similar geometries in the solid state, and no correlation could be discerned between the crystal structures and the spectroscopic parameters in solution.

Full text of DOI:10.1039/c1nj20598f

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PAPER
Ruthenium(II) and rhodium(III) porphyrin phosphine complexes: influence
of substitution pattern on structure and electronic propertiesw
Andrew D. Bond,a Jeremy K. M. Sandersb and Eugen Stulz*c
Received (in Victoria, Australia) 8th July 2011, Accepted 18th August 2011
DOI: 10.1039/c1nj20598f
A series of ruthenium(II) and rhodium(III) porphyrin complexes with diphenyl phenylacetylene
1
phosphine (dpap) was synthesised and fully characterised by UV-vis, H NMR and
31P{1H} NMR spectroscopy, and in most cases also by single-crystal X-ray diffraction.
The substitution pattern of the porphyrin was varied with increasing meso-phenyl substitution,
from octa-ethyl porphyrin (OEP), through diphenyl di-ethyl porphyrin (DPP), to tetraphenyl
porphyrin (TPP) and 3,5-di-tbutyl tetraphenyl porphyrin (tbTPP). The dpap readily displaces the
CO ligand from the parent Ru(CO)(porphyrin) and the iodide from the Rh(I)(porphyrin) to give
bis-phosphine complexes M(dpap)2(porphyrin). The UV-vis spectra reveal that some of the
complexes are partially dissociated at concentrations of 10À6 M, and the association constants
were estimated to be in the range of 106 to 107 MÀ1 for the first, and 104 to 106 MÀ1 for the
1
second binding event. The H NMR chemical shifts of the complexes vary greatly despite the fact
that they display very similar geometries in the solid state, and no correlation could be discerned
between the crystal structures and the spectroscopic parameters in solution.
phosphinidene transfer reactions.7,8 Likewise, Rh(III) porphyrins
Introduction
have been studied in metallo radical chemistry9 and in olefin
hydrofunctionalisation,10 although these complexes are far less
Ruthenium and rhodium porphyrins have attracted considerable
interest in the recent years due to their characteristic electronic
commonly studied. More exotic ligands such as charged phospho-
ranido ligands on Rh(III) porphyrins have also been reported.11
properties, which make them suitable model compounds in
artificial photosynthesis and catalysis. The iso-electronic low-spin
Utilising the axial coordination chemistry of metallo por-
Fe(II) porphyrins are widely present in nature, in particular as
phyrins is a useful strategy to create supramolecular porphyrin
assemblies.12 As for many other metallo porphyrins, both
heme complexes (P450). The iron-heme complex is liable to
oxidation, readily forming inactive iron-oxo dimers, which is a
Ru- and Rh-porphyrins can readily form stable five- and six-
major issue when using iron-porphyrins to study their catalytic
coordinate complexes with nitrogen, sulfur and phosphorus
activity. The use of ruthenium eliminates this problem, hence
donor ligands. In particular, phosphine ligands are attractive
Ru(II) porphyrins have generally been employed as P450
for the construction of supramolecular assemblies because the
association constants are high, in the range of 106 to 108 MÀ1 13–15
,
model compounds for the study of bio-mimetic oxidation
reactions,1 as catalysts in hydrocarbon oxidation,2,3 as cata-
lysts for amidation4 and cycloaddition5 reactions, and in
photoinduced electron transfer reactions.6 Ru(II) porphyrin
and phthalocyanine complexes with primary and secondary
phosphines were reported for phosphine functionalization and
and are orthogonal to Zn-nitrogen and Sn-oxygen complexes.16–18
We have exploited this coordination chemistry to create supra-
molecular multi-porphyrin arrays.19–21 The bonding, however,
is not kinetically inert, and the ligand exchange can be used to
create dynamic combinatorial libraries.22,23 Other examples
of Ru- and Rh-porphyrin phosphine complexes in supra-
molecular assemblies are scarce, and normally nitrogen com-
plexation is favoured for the creation of supramolecular
assemblies with either ruthenium24–27 or rhodium28 porphyrins,
in particular also making use of the reversible coordination to
create dynamic switching systems.29,30
a Department of Physics and Chemistry, University of Southern
Denmark, Campusvej 55, 5230 Odense M, Denmark.
E-mail: adb@chem.sdu.dk
b University Chemical Laboratory, University of Cambridge,
Lensfield Rd, Cambridge CB2 1EW, UK. E-mail: jkms@cam.ac.uk
c School of Chemistry, University of Southampton, Highfield,
Southampton SO17 2HU, UK. E-mail: est@soton.ac.uk;
Fax: + 44 (0)23 8059 3131; Tel: + 44 (0)23 8059 9369
w Electronic supplementary information (ESI) available: Spectroscopic
analyses of the complexes. CCDC reference numbers 834653–834657.
For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c1nj20598f.
We have studied the coordination chemistry of various P(III)
ligands with both ruthenium and rhodium porphyrins,13–15
i.e. PPh3, phenyl-acetylene phosphines and phosphonites, as
model compounds for more complex supramolecular systems.
We found that a diphenyl phosphine with an acetylene
c
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described previously.19 The bis-phosphine complexes of the
Ru- and Rh-porphyrins, denoted P2-RuX or P2-RhX, are
readily available as reported earlier.13,15 Generally, it is suffi-
cient to mix the porphyrins with two equivalents of 1 in DCM,
and after evaporation of the solvent the pure complexes can
be obtained by re-crystallisation from DCM-MeOH. Other
methods to obtain phosphine complexes of Rh4 have also been
reported.32
UV-vis spectroscopy is very diagnostic for ligand complexa-
tion in metallo-porphyrins, since porphyrins show very charac-
teristic absorbance spectra (Fig. 1). These are dominated by a
strong B-band (Soret band) absorption at around 400–420 nm,
and weaker Q-band absorptions at higher wavelengths (500–
700 nm, Table 1). Upon ligand complexation, the absorbances
typically shift to higher wavelengths by about 10–40 nm, which is
diagnostic and can be used to monitor the binding event.
Solutions of the re-dissolved rhodium complexes in DCM show
absorbance spectra characteristic for fully intact complexes at
c = 5 Â 10À6 M because the B-band absorbances appear
sharp; an exception is P2-Rh5 where a small shoulder can be
observed at around 426 nm. Overall, the spectra are consistent
with earlier experiments where the association constant of
P2-Rh4 was determined to be Ka = 4.6 Â 104 MÀ1 13
,
and
Scheme 1 Structures of the phosphine ligand 1 and of the metallo-
porphyrins 2–5. M = Ru(II) or Rh(III)
the association constants in the present series were deter-
mined to be in the same order (Table 1). The complexes of
the Ru-series, on the other hand, do not show sharp porphyrin
absorbances, but shoulders, as in the case of P-Ru5, or even
two distinct absorbance maxima as in P-Ru2. This indicates
that these complexes dissociate partially at this concentration.
As reported earlier, the Ka-values for the ruthenium complexes
are about one order of magnitude lower compared to the
rhodium complexes.15 At lower concentrations, the rhodium
series also shows dissociation, and the B-band absorbances can
be de-convoluted into three distinct bands corresponding to the
free porphyrin, the mono-phosphine and the bis-phosphine
complexes (see ESI). From this, association constants can
be determined.15 The data show that the phosphine complex
with Ru2 is the weakest complex and dissociates readily at
phosphine substituent as synthon is most suitable from both a
synthetic and stability point of view; the stability is most likely
a combination of steric and electronic factors. Supramolecular
building blocks containing acetylenes are usually relatively
readily available, and transformation into the corresponding
phosphine is straightforward using chloro-diphenyl phos-
phine. Here, we report on the influence of the porphyrin
substitution pattern on the structural and electronic properties
of complexes with diphenyl phenyl-acetylene phosphine
(1, Scheme 1). To our knowledge, no systematic study involv-
ing different Ru- and Rh-porphyrins with one specific phos-
phine ligand has been reported. This, however, is important in
order to be able to make predictions for the suitability of a
phosphine porphyrin complex for a particular application
such as in catalysis or supramolecular chemistry. We have
varied the porphyrin structure with respect to its substitution
pattern with increasing meso-phenyl substituents, from octa-
ethylporphyrin (2, OEP), through diphenylporphyrin (3, DPP)
to tetraphenylporphyrin (4, TPP) and tetra(di-tbutyl-phenyl)-
porphyrin (5, tbTPP). The octahedral di-phosphine complexes
(dpap)2M(porphyrin) have been prepared, and their spectro-
scopic properties are evaluated using absorption and NMR
spectroscopy. One of the structures (P2-Rh4) obtained from
single crystal X-ray diffraction (XRD) has been published
elsewhere,13 as have the structures of some related complexes
of dpap with a rhodium di(di-tbutyl-phenyl) porphyrin.15
However, the majority of the crystal structures have not been
reported previously and are included in this paper.
Results and discussion
Synthesis and UV-vis spectroscopy
Fig. 1 UV-vis spectra of the porphyrin complexes; c = 5 Â 10À6
M
The synthesis and characterisation of dpap (1)31 and of the
metallo-porphyrins Ru2 to Ru5 and Rh2 to Rh5 has been
in DCM. (a) Rh-porphyrins; (b) Rh-bisphosphine complexes;
(c) Ru-porphyrins; (d) Ru-bisphosphine complexes.
c
2692 New J. Chem., 2011, 35, 2691–2696
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Table 1 Spectroscopic data for the porphyrin complexes
Complex
K
a1/[MÀ1
]
Ka2/[MÀ1
]
l
max/[nm] porphyrin
l
max/[nm]P1-complex
lmax/[nm]P2-complex
P2-Rh2
P2-Rh3
P2-Rh4
P2-Rh5
P2-Ru2
P2-Ru3
P2-Ru4
P2-Ru5
2.0 Â 107
1.7 Â 107
3.0 Â 107 a
9.3 Â 105
3.4 Â 105
2.5 Â 105
4.0 Â 107
1.4 Â 107
4.8 Â 105
8.4 Â 105
4.6 Â 104 a
6.3 Â 106
9.2 Â 104
1.9 Â 105
8.2 Â 105
3.5 Â 105
404, 518, 550
412, 526, 556
422, 533, 566
428, 534, 572
394, 516, 548
400, 522, 554
412, 530, 560
414, 532, 566
426, 499
430, 488
437, 504
435, 515
407, 528, 558
411, 536, 567
426
434, 538, 575
438, 537, 568
445, 557, 596
445, 562, 597
418
421
432
433
425, 546, 581
a
Data from ref. 13; P1-complex and P2-complex denote mono- and bis-phosphine complexes.
concentrations where the P2-Ru4 complex is still largely intact.
This difference in complex stability can most probably be
attributed to the electronics of the porphyrins. The lower
stability of the complex in P2-Ru5 compared to P2-Ru4 is
more likely to arise from a steric influence of the additional
tert-butyl groups on the meso-phenyl substituents. In the
rhodium series, P2-Rh4 seems to be the least stable complex.
NMR spectroscopy
Since the ruthenium and rhodium metallo-porphyrins are
1
diamagnetic, both H NMR and 31P{1H} NMR spectroscopy
can be used to ascertain the integrity of the complexes. It
should be noted that at the concentrations used for NMR
spectroscopy (1–5 mM) the complexes are fully associated at
room temperature which is different from the low concentra-
tion UV-vis measurements, where the complexes may disso-
ciate. We have discussed the NMR studies of the kinetic
lability and ligand exchange reactions of both phosphine-
ruthenium and rhodium porphyrin complexes previously.13,15
Analogously, in the complexes here ligand exchange is slow on
the NMR time scale, and the chemical shifts represent the
associated complexes which are concentration independent.
In the 1H NMR spectra, the most characteristic chemical shifts
indicative of complex formation are observed for the phenyl
substituents on phosphorus (Fig. 2). Due to their positioning
above the shielding region of the porphyrin, the resonances
appear upfield shifted. The tbTPP-complexes are generally
very poorly soluble in CDCl3, therefore the spectra appear
very noisy for P2-Ru5 and P2-Rh5 even in the presence of 10%
CD3OD. The 31P{1H} NMR chemical shifts (Table 2) are
indicative of the composition of the complex, i.e. if the metal is
coordinated by one phosphine or by two. The 31P{1H} NMR
chemical shifts of the mono-phosphine complexes were obtained
by adding one equivalent of the ligand to the porphyrin solu-
tion. These complexes can, however, not be isolated due to the
lability of the carbonyl or iodide ligand on the ruthenium and
rhodium, respectively.13,15 The chemical shifts are consistent
with previous measurements of similar complexes, and do not
show any particular trends within the porphyrin series; in fact,
they vary only by a few ppm within the rhodium or ruthenium
series. Hence, the differences in chemical shifts as observed by
1H NMR spectroscopy are not observed for the phosphorus
nucleus.
Fig. 2 Part of the 1H NMR spectra displaying the chemical shift
differences in the bis-dpap complexes.
when comparing the different complexes. First, the shift differ-
ences from the free phosphine to the complexed ligand vary with
porphyrin structure, with OEP (2) showing the largest shift and
TPP/tbTPP (4/5) showing the smallest shifts (Fig. 2). This is not
in line with the binding constants, where the OEP complexes
normally show smaller Ka values than TPP complexes. How-
ever, additional shielding or deshielding effects arising from
the meso-phenyl substituents must be taken into account;
these would explain the differences observed with increasing
number of meso-phenyl groups. Second, the ortho protons in
the ruthenium series show a smaller high-field shift, whereas
the meta and para protons show a larger shift compared to the
Interestingly, the ruthenium and rhodium phosphine com-
plexes show quite different chemical shifts for the phenyl protons
in the ortho, meta and para positions. Two trends can be seen
c
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Table 2 NMR data of the porphyrin complexes
Single-crystal X-ray diffraction
1
31P/[ppm] (JRh-P/[Hz])a
d H/[ppm]
The X-ray crystal structure of P2-Rh4 has been reported
previously.13 The structures of P2-Rh2 and P2-Ru5 have not
been satisfactorily determined to date. Crystallographic data
for the remaining five complexes are summarised in Table 3.
The molecular units are shown in Fig. 4, and selected geo-
metrical parameters are summarised in Table 4. Except for
P2-Ru4, all of the porphyrin complexes lie on crystallographic
inversion centres. P2-Ru4 contains two independent com-
plexes, one lying on an inversion centre and one on a general
position. The two complexes exhibit different orientations of
the dpap ligands with respect to the porphyrin core (described
below). The former exhibits disorder for one phenyl substi-
tuent on P, modelled in two orientations related by rotation of
ca 301 about the P–C(ipso) bond. For P2-Rh5, there is one
d
P1-complex
P2-complex
Ho
Hm
Hp
Complex
P2-Rh2
P2-Rh3
P2-Rh4
P2-Rh5
P2-Ru2
P2-Ru3
P2-Ru4
P2-Ru5
À7 (119)
À8 (118)
À9 (115)
À7 (114)
À15
À9 (88)
3.82
3.99
4.14
4.18
4.2
4.41
4.57
4.6
6.36
6.47
6.56
6.58
6.29
6.41
6.5
6.83
6.91
6.95
6.96
6.63
6.7
À10 (89)
À9 (87)
À8 (85)
À1
À14
2
À12
0
3
6.77
6.76
À11
6.5
a
dpap: d –32 ppm.
rhodium series. This is best demonstrated in the overlay of the
partial 1H NMR spectra of the DPP (2) complexes (Fig. 3).
From a structural point of view, the XRD structures do not
show large variations in the relative geometries, i.e. the
distances of the protons to the porphyrin plane are compar-
able, at least in the solid state (vide infra and inset in Fig. 3).
Also, the symmetry seen in the 1H NMR spectra indicate
relatively unhindered rotation of the metal-phosphorus bonds
and of the phenyl groups. Since the differences in chemical
shift cannot be assigned to the geometry or the presence of the
meso-phenyl groups (as the number is the same in the corres-
ponding complex), the electronics in the individual complexes
must be quite different. It seems that the de-shielding effect is
large for rhodium on the ortho protons (close to the porphyrin
plane) but weak on the para protons (further away from the
porphyrin plane). This raises the question as to whether the
magnetic fields induced through the ring currents are strongly
influenced by the metals, and whether this magnetic field
can have magnitudes that vary strongly with distance from
the porphyrin planes depending on the metal. Generally it
is accepted that porphyrins have similar to identical ring
currents, unless they are structurally distorted.33,34 However,
the differences seen in the absorbances indicate changes in the
energy splitting of the ground and excited states. Also, calcu-
lations on free-base and Mg porphine show that metallation
can have an effect on the ring current of the porphyrin.35 The
s- and p-effects of the metal should also be considered. The
question about the origin of these unusual chemical shift
effects might be answered with computational methods, which
are beyond our current scope.
%
porphyrin complex per unit cell in space group P1. The single
iodide site in the unit cell was refined with 50% site occupancy,
consistent with charge balance. Additional electron density
in this region could be modelled satisfactorily as a pentane
molecule having 50% site occupancy. Thus, there is one iodide
anion and one pentane molecule per unit cell (i.e. per P2-Rh5
complex). In P2-Ru3, the chloroform molecule is disordered
about a crystallographic inversion centre.
In all determined structures within the series (including
P2-Rh413) the porphyrins are essentially flat, and the M–P
and M–N bond distances are closely comparable (Table 4).
In P2-Ru2 and P2-Rh3/Ru3, the acetylenic arm of dpap lies
over the unsubstituted meso positions of the porphyrin and
the phenyl substituents on P lie above the pyrrole rings
(Fig. 4). In P2-Rh4/Ru4 and P2-Rh5, the dpap ligand is rotated
by ca 451 from this orientation so that the acetylenic arm
lies over one pyrrole ring, one phenyl substituent lies over another
pyrrole ring and the other phenyl substitutent lies over one meso
position of the porphyrin. In P2-Ru4, the non-centrosymmetric
complex has similar orientations for the acetylenic arms of the
two dpap ligands, but they are rotated ca 901 to each other viewed
in projection along the P–Ru–P axis.
Conclusions
We have analysed a range of ruthenium and rhodium por-
phyrin bis-phosphine complexes, which are readily available
by ligand displacement on the parent porphyrins. The weaker
second binding of the phosphine indicates that one ligand can
be displaced preferentially and potentially be substituted with
another ligand. This is of importance in catalysis applications
where efficient ligand exchange is crucial. The electronic para-
meters vary greatly in the different complexes, in particular the
1
absorbances change within the series of porphyrins. H NMR
spectra reveal that the shielding effects are more complex
than might be expected, and the differences cannot easily be
explained from structural aspects. It is evident that more
electronic parameters have to be taken into account, in
particular arising from metallation of the porphyrin. More
quantum mechanical analyses are thus required to understand
fully the electronic behaviour of metallo porphyrins and their
complexes, in particular their activity towards substrates in
catalysis.
Fig. 3 Part of the 1H NMR spectra of P2-Rh2 (black) and P2-Ru2
(red) displaying the chemical shifts of the phosphine-phenyl group.
The overlaid structures are taken from the XRD structures; other
substituents on the DPP and dpap are omitted for clarity.
c
2694 New J. Chem., 2011, 35, 2691–2696
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Table 3 Selected crystallographic data for P2-Rh3, P2-Rh5, P2-Ru2, P2-Ru3 and P2-Ru4
P2-Rh3 P2-Rh5 P2-Ru2
P2-Ru3
P2-Ru4
Empirical formula
Formula weight
Crystal system
Space group
T/K
a/A
b/A
c/A
a (1)
[C84H74N4P2Rh]+IÀÁCH2Cl2 [C116H122N4P2Rh]+IÀÁC5H12 C76H74N4P2Ru C84H74N4P2RuÁCHCl3 C84H58N4P2Ru
1516.15
Monoclinic
C2/c
1936.07
Triclinic
1206.40
Triclinic
1421.85
Triclinic
1286.35
Monoclinic
C2/c
%
P1
220(2)
%
P1
180(2)
%
P1
180(2)
180(2)
26.5305(5)
12.1202(3)
22.0169(4)
90
94.010(2)
90
7062.3(3)
4
1.426
180(2)
23.5610(2)
13.1750(1)
61.8138(5)
90
99.249(1)
90
18938.5(3)
12
1.353
12.0257(3)
15.2154(3)
16.3438(5)
102.144(1)
98.439(1)
111.559(1)
2635.21(12)
1
11.5833(3)
12.2478(3)
13.1535(3)
96.180(1)
110.866(1)
113.422(1)
1530.93(6)
1
11.0429(2)
13.5072(2)
13.9191(3)
62.832(1)
80.910(1)
68.659(1)
1720.36(5)
1
b (1)
g (1)
V/A3
Z
Dc/g cmÀ3
m(Mo-Ka)
Total data
Unique data
Rint
1.220
0.535
1.309
0.357
1.372
0.442
0.850
0.351
18 772
4581
0.059
21 481
8901
0.076
7512
0.071
0.217
18 951
6976
0.045
6232
0.037
0.087
19 763
7847
0.044
6551
0.043
0.093
37 279
14 306
0.040
10 783
0.046
0.121
Observed data [I 4 2s(I)] 3760
R1 [I 4 2s(I)]
wR2 (all data)
Goodness of fit, S
0.034
0.098
1.14
À0.74, 0.69
1.05
À1.65, 1.18
1.05
À0.70, 0.45
1.03
À0.63, 0.35
1.07
À0.59, 0.45
r
min, rmax e AÀ3
Experimental
General
All manipulations were performed using standard inert atmo-
sphere techniques, and freshly distilled and degassed solvents:
methylene chloride (CH2Cl2), chloroform (CHCl3) from CaH,
methanol (MeOH) from Mg; CDCl3 was filtered over basic
alumina and degassed by purging with Ar prior to use. dpap (1),
Ru2 to Ru5 and Rh2 to Rh5 have been synthesised as described
elsewhere.19,31 NMR spectra were recorded on a Bruker
DPX400 NMR spectrometer at 400.13 MHz (1H, residual
undeuterated solvent as internal standard) or 161.98 MHz
(31P{1H}, H2PO4 external standard); all spectra were recorded
in CDCl3 except for P2Rh5 and P2Ru5 (CDCl3-CD3OD 10: 1).
UV-vis spectra were recorded on a Varian Cary 100 Bio
spectrophotometer. X-ray diffraction data were collected using
a Nonius Kappa CCD diffractometer. Structures were solved
by direct methods using either SHELXS-9736 or SIR-9237 and
refined against all F2 data using SHELXL-97.36
Fig. 4 Molecular units in the X-ray crystal structures of P2-Rh3,
P2-Rh5, P2-Ru2, P2-Ru3 and P2-Ru4. Displacement ellipsoids are
shown at 30% probability and H atoms are omitted. All molecules lie
on crystallographic inversion centres except P2-Ru4 (mol2). For P2-Ru4
(mol2), disorder of one phenyl substituent on dpap is not shown.
Table 4 Selected geometrical data (A,1) for P2-Rh3, P2-Rh5, P2-Ru2, P2-Ru3 and P2-Ru4. All molecules except P2-Ru4 (mol2) lie on
crystallographic inversion centres
P2-Rh3
P2-Rh5
P2-Ru2
P2-Ru3
P2-Ru4 (mol1)
P2-Ru4 (mol2)
sa
0.048
86.4
0.031
89.1
0.030
87.7
0.036
88.8
0.022
88.6
0.083
89.8
89.1
ab
bb
M–P1
M–P2
M–N1
M–N2
M–N3
M–N4
2.3688(10)
2.3694(12)
2.3777(5)
2.3610(5)
2.3684(9)
2.3597(10)
2.3784(10)
2.051(3)
2.048(3)
2.060(3)
2.059(3)
2.051(3)
2.046(3)
2.035(3)
2.041(4)
2.0589(15)
2.0561(15)
2.0644(18)
2.0638(17)
2.056(3)
2.046(3)
a
b
s denotes the average perpendicular deviation of the porphyrin core atoms from the least-squares plane through all 24 core atoms. a and b
denote the angle formed by the Rh–P1/P2 bond with the least-squares porphyrin plane.
c
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New J. Chem., 2011, 35, 2691–2696 2695

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General procedure for the synthesis of the complexes
Notes and references
The porphyrin (50 mg) was suspended in CHCl3 (5 ml), and neat
dpap (5 eq.) was added. The solution was stirred at room
temperature under an Ar atmosphere for 15 min., and the solvent
was removed on a rotary evaporator. The residue was re-dissolved
in 5 ml CHCl3, stirred at room temperature for 10 min, then the
solvent removed in vacuo. The orange solid was dissolved in a
minimum amount of hot CH2Cl2 (ca 2 ml), and 10 ml MeOH
were carefully layered over the solution. After standing overnight,
orange/bronze coloured crystals were collected on a sintered
funnel, washed with MeOH and dried in vacuo. Yields are in the
range of 90 to 98%. Crystals suitable for XRD analysis were
grown from a saturated CHCl3 solution layered with MeOH.
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P2Rh2: H NMR d 1.79 (t, 24H, J = 7.5 Hz, ethyl-CH3),
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1
P2Ru2: H NMR d 1.61 (t, 12H, J = 7.4 Hz, ethyl-CH3),
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2696 New J. Chem., 2011, 35, 2691–2696
This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011