A highly modular and convergent approach for the synthesis of stimulant-responsive heteroligated cofacial porphyrin tweezer complexes

Article abstract of DOI:10.1021/ic702150y

The synthesis of new hemilabile phosphine ligands and their reaction with [Rh(COE)₂Cl]₂ to form dissymmetric heteroligated tweezer complexes using a halide-induced ligand rearrangement reaction are reported. These complexes can undergo reactions with small-molecule ligands and elemental anions quantitatively in situ, which serve to regulate the porphyrin-porphyrin distances and interactions within the assembly.

Full text of DOI:10.1021/ic702150y

Inorg. Chem. 2008, 47, 2755-2763
A Highly Modular and Convergent Approach for the Synthesis of
Stimulant-Responsive Heteroligated Cofacial Porphyrin Tweezer
Complexes
Christopher G. Oliveri, SonBinh T. Nguyen,* and Chad A. Mirkin*
Department of Chemistry and the International Institute for Nanotechnology, Northwestern
UniVersity, EVanston, Illinois 60208-3113
Received November 1, 2007
The synthesis of new hemilabile phosphine ligands and their reaction with [Rh(COE)2Cl]2 to form dissymmetric
heteroligated tweezer complexes using a halide-induced ligand rearrangement reaction are reported. These complexes
can undergo reactions with small-molecule ligands and elemental anions quantitatively in situ, which serve to
regulate the porphyrin-porphyrin distances and interactions within the assembly.
Introduction
the selective modification of the cavity formed by both
porphyrin moieties.9,11,15–17 Such control is necessary for
tuning the photophysical properties11,18,19 and, in certain
cases, the catalytic properties2–6 of these complexes. To
address these issues, our group has developed the weak-link
approach (WLA),20–22 for preparing highly flexible supramo-
lecular complexes capable of mimicking the properties of
allosteric biological systems.23–29 A key component of this
Cofacial porphyrin complexes1 are an important class of
molecules that have received a significant amount of attention
due to their interesting catalytic2–10 and photophysical
properties.11–14 While many approaches have been described
for the synthesis of both organic and coordination chemistry-
based cofacial porphyrin complexes, most of them yield
products which are structurally rigid and do not allow for
* To whom correspondence should be addressed. E-mail: chadnano@
northwestern.edu (C.A.M.), stn@northwestern.edu (S.T.N.).
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Rheingold, A. L. Angew. Chem., Int. Ed. 1998, 37, 465–467.
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Nguyen, S. T.; Mirkin, C. A. J. Am. Chem. Soc. 2007, 129, 10149–
10158.
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10.1021/ic702150y CCC: $40.75  2008 American Chemical Society
Inorganic Chemistry, Vol. 47, No. 7, 2008 2755
Published on Web 02/13/2008

Oliveri et al.
Scheme 1. Example of the Halide-Induced Ligand Rearrangement (HILR)
Scheme 2. Dissymmetric Heteroligated Cofacial Porphyrin Macrocycle and Tweezer Complexes
versatile approach is the ability to modify and regulate
supramolecular structures in situ via the introduction or
removal of external chemical stimuli.
complexes (8) with porphyrin arms would greatly facilitate
the realization of soluble coordination chemistry-based
cofacial porphyrins with structures that can be regulated in
situ via the addition of small-molecule chemical effectors.
Herein, we report the synthesis of new ether- and
thioether-phosphine hemilabile porphyrin ligands. Upon
reaction with a suitable RhI precursor, these ligands form
dissymmetric heteroligated porphyrin tweezer complexes in
quantitative yield (Scheme 2). Significantly, since these
tweezer complexes contain a single RhI regulatory site, they
can undergo significant geometrical distortions in situ when
triggered by external chemical stimuli. The extra mesityl
group on the porphyrin ring in 8, as compared with the
ligands used to form 7, greatly enhances the solubility of
this complex in organic solvents such as CH2Cl2 and THF,
enabling it to undergo reversible reactions with small-
molecule ligands without undesirable precipitation.
Through the course of our studies, we have discovered a
unique and novel halide-induced ligand rearrangement
(HILR) reaction30–32 that allows one to use two hemilabile
ligands (1 and 2) and a RhI precursor to form dissymmetric
heteroligated RhI complexes 3-6 (Scheme 1). This reaction
is quite general and has led to a highly convergent and
modular approach for the preparation of heteroligated dis-
symmetric cofacial porphyrin macrocycles (7; Scheme 2).33
A key feature of the assemblies that are formed via this
approach is their ability to react with small-molecule ligands
or halide-abstracting agents that allow for the selective
modification of both porphyrin-porphyrin distance and
orientation. In spite of these advantages, a limitation of the
heteroligated porphyrin macrocycles that we have studied
thus far is their low solubility in organic solvents. One
strategy for overcoming this problem is to remove one of
the two RhI regulatory sites in the supramolecular assemblies
and form tweezer complexes.26 This result led us to
hypothesize that a general approach for making tweezer-type
Results and Discussion
Design and Synthesis of Ether-Phosphine Ligand
13. While the aldehyde porphyrin precursor used to prepare
the thioether ligand in macrocycle 7 can be made in high
yield, the corresponding precursor for the ether analogue
required two additional steps and, consequently, a lower
overall yield.24 In designing the ether-containing hemilabile
ligand 13, we reasoned that direct incorporation of an aryl
aldehyde into the ligand framework, which could be delivered
via a Suzuki–Miyaura coupling reaction34,35 at the beginning
(29) Yoon, H. J.; Heo, J.; Mirkin, C. A. J. Am. Chem. Soc. 2007, 129,
14182–14183.
(30) Jeon, Y. M.; Heo, J.; Brown, A. M.; Mirkin, C. A. Organometallics
2006, 25, 2729–2732.
(31) Brown, A. M.; Ovchinnikov, M. V.; Mirkin, C. A. Angew. Chem.,
Int. Ed. 2005, 44, 4207–4209.
(32) Brown, A. M.; Ovchinnikov, M. V.; Stern, C. L.; Mirkin, C. A. J. Am.
Chem. Soc. 2004, 126, 14316–14317.
(33) Oliveri, C. G.; Heo, J.; Nguyen, S. T.; Mirkin, C. A.; Wawrzak, Z.
Inorg. Chem. 2007, 46, 7716–7718.
(34) Miyaura, N.; Suzuki, A. Chem. ReV. 1995, 95, 2457–2483.
2756 Inorganic Chemistry, Vol. 47, No. 7, 2008

Synthesis of Porphyrin Tweezer Complexes
Scheme 3. Synthesis of the Ether-Based Hemilabile Phosphine Tweezer Ligand 13a
a
Where, Mes ) mesityl. (i) KPPh2, THF; (ii) S8, THF, 85%; (iii) 4-formylphenylboronic acid, Pd(PPh3)4 (5 mol %), Na2CO3 (aq. 2 M), toluene/EtOH
(6:1, v/v), reflux, 95%; (iv) mesitaldehyde (1 equiv), 5-mesityldipyrromethane (2 equiv), BF3 ·OEt2, DDQ, NEt3, 22%; (v) Zn(OAc)2 ·2H2O, CHCl3/MeOH
(4:1, v/v), reflux, 98%; (vi) Cp2ZrHCl, THF, 92%.
of the ligand synthesis, would reduce the number of steps
required to synthesize 10 and increase its yield at the same
time. To this end, we combined the commercially available
4-(bromophenyl)-2-chloroethyl ether with KPPh2 in THF to
obtain the corresponding phosphine,32 which was then
protected with elemental sulfur to yield 9 in 85% yield
(Scheme 3). Compound 9 underwent Suzuki–Miyaura cou-
pling with 4-formylphenylboronic acid to afford 10 in 95%
yield. Significantly, using this approach allowed for the
synthesis of the ether-based aldehyde precursor 10 to be
reduced to three steps (from five for the analogous precursor
used in making macrocycle complex 7)24,33 with an increase
in yield from 31 to 77%.
To obtain porphyrin ligand 11, the aldehyde precursor 10
(1 equiv), 5-mesityldipyrromethane36 (2 equiv), and mesi-
taldehyde (1 equiv) were reacted under Lewis-acidic condi-
tions followed by oxidation. Importantly, 11 can be isolated
in gram quantities (22% yield) via simple chromatographic
separation over silica gel using only CH2Cl2 as the eluent.
The ZnII-porphyrin complex 12 was prepared in quantitative
yield by refluxing 11 in CHCl3/MeOH (4:1 v/v) with
Zn(OAc)2 · 2H2O. After metalation, the sulfide protecting
group was removed using Cp2ZrHCl, affording 13 in 92%
yield.
diphenylphosphine moiety with elemental sulfur to give
1-bromo-4-[2-(diphenylphosphinothioyl)ethylsulfanyl]ben-
zene (Scheme 4).24 This compound was then coupled to
4-formylphenylboronic acid to give 14 in 81% yield. Once
isolated, aldehyde 14 (1 equiv) was condensed with mesi-
taldehyde (1 equiv) and 5-mesityldipyrromethane36 (2 equiv)
under Lewis-acidic conditions to yield porphyrin 15 in 20%
yield after oxidation. Again, this compound can be isolated
in gram quantities via flash chromatography over silica gel
using only CH2Cl2 as the eluent. Compound 15 was then
metallated with ZnII (16a) or MgII (16b) using either
Zn(OAc)2 · 2H2O in CHCl3/MeOH (4:1, v/v) or MgBr2 and
NEt3 in CH2Cl2, respectively. Upon isolation of compounds
16a and 16b, the sulfide protecting groups were removed
by reaction with Cp2ZrHCl in THF followed by chromatog-
raphy over neutral alumina, which afforded ligands 17a and
17b in 90 and 89% yield, respectively.
Synthesis of Dissymmetric Heteroligated RhI Twee-
zer Complexes 18–25. The dissymmetric complexes 18 and
19 were prepared via the HILR using 2 equiv of the
appropriate ligands and 1 equiv of the RhI precursor,
[Rh(COE)2Cl]2. The reagents were dissolved in THF and the
mixture was sonicated for 1 h, resulting in the quantitative
formation of the desired RhCl(κ2-PS)(κ1-PO) products 18 and
19, as indicated by 31P{1H} NMR spectroscopy (Scheme 5).
The 31P{1H} NMR spectra for both compounds 18 and 19
Design and Synthesis of Thioether-Phosphine Li-
gands 17a and 17b. For the thioether-porphyrin ligand, we
employed a synthetic approach similar to the one used for
the ether-based ligand 13 (Scheme 4). Commercially avail-
able 4-bromothiophenol was alkylated with 1-chloro-2-
diphenylphosphinoethane followed by protection of the
show two resonances at δ 72 (dd, JRh-P ) 185 Hz, JP-P
)
41 Hz) and δ 29 (dd, JRh-P ) 166 Hz, JP-P ) 40 Hz), which
are highly diagnostic of this heteroligated RhICl(PS)(PO)
coordination environment.31 The matrix-assisted laser de-
sorption/ionization-time of flight (MALDI-TOF) mass
spectrum for 18 contains a peak at 2335.88 m/z corresponding
to the [M - Cl]+ ion. A similar trend is observed in the
(35) Suzuki, A. Acc. Chem. Res. 1982, 15, 178–184.
(36) Laha, J. K.; Dhanalekshmi, S.; Taniguchi, M.; Ambroise, A.; Lindsey,
J. S. Org. Process Res. DeV. 2003, 7, 799–812.
Inorganic Chemistry, Vol. 47, No. 7, 2008 2757

Oliveri et al.
Scheme 4. Synthesis of the Thioether-Based Hemilabile Phosphine Tweezer Ligands 17a and 17ba
a
Where, Mes ) mesityl. (i) 1-chloro-2-diphenylphosphinoethane, Cs2CO3, CH3CN, reflux; (ii) S8, THF; (iii) 4-formylphenylboronic acid, Pd(PPh3)4 (5
mol %), Na2CO3 (aq. 2 M), toluene/EtOH (6:1, v/v), reflux, 81%; (iv) mesitaldehyde (1 equiv), 5-mesityldipyrromethane (2 equiv), BF3 ·OEt2, DDQ, NEt3,
20%; (v) Zn(OAc)2 ·2H2O, CHCl3/MeOH (4:1, v/v), reflux, 97%; (vi) MgBr2, Net3, CH2Cl2, 96%; (vii) Cp2ZrHCl, THF (90% ZnII, 89% MgII).
MALDI-TOF mass spectrum of 19, with the [M - Cl]+ ion
at 2295.15 m/z and the [M - Mg - Cl]+ ion at 2270.21
m/z, as commonly observed.33 Together with the multinuclear
NMR data obtained for these complexes (Table 1), the
observations conclusively support our proposed structure for
18 and 19.
31P{1H} NMR spectroscopy. These transformations are near-
instantaneous and can be observed visually as the color
changes slightly for each transformation.
Upon introduction of CO (1 atm) to solutions of 20 and
21 in CD2Cl2, the semi-open [Rh(κ2-PS)(κ1-PO)(CO)][B(ArF)4]
adducts 22 and 23 are formed in quantitative yield according
to both 1H and 31P{1H} NMR spectroscopy (Scheme 5). The
31P{1H} NMR spectra for compounds 22 and 23 both show
two resonances at δ 61 (dd, JRh-P ) 114 Hz, JP-P ) 266
Hz) and 18 (dd, JRh-P ) 117 Hz, JP-P ) 266 Hz), whose
coupling constants clearly indicate a cis-to-trans conversion
of phosphine geometry (Table 1).31,33 The FTIR spectra of
compounds 22 and 23 in CH2Cl2 exhibit a νC≡O stretch at
1970 cm-1, which is also highly diagnostic of trans-
phosphine RhI(CO) complexes.31,33 Additionally, the meth-
ylene groups of the XCH2CH2PPh2 moieties (where X ) S
or O) provide an additional handle for following the partial
opening of the tweezer framework in situ. For example, the
The semi-open complexes 18 and 19 can be converted into
the closed complexes 20 and 21 quantitatively via abstraction
of Cl- upon sonication with Na[B(ArF)4] (1 equiv, where
B(ArF)4 ) tetrakis[(3,5-trifluoromethyl)phenyl]borate) in
CH2Cl2 (Scheme 5). The 31P{1H} NMR spectra for both 20
and 21 contain two resonances at δ 72 (dd, JRh-P ) 198 Hz,
JP-P ) 40 Hz) and 51 (dd, JRh-P ) 167 Hz, JP-P ) 41 Hz),
consistent with the formation of the [Rh(κ2-PS)(κ2-
PO)][B(ArF)4] adducts.31 The MALDI-TOF mass spectrum
for 20 contains a peak at 2336.99 m/z corresponding to the
desired M+ ion. In the case of 21, the MALDI-TOF mass
spectrum contains an M+ peak at 2295.22 m/z and the [M -
Mg]+ peak at 2270.92 m/z, as has been observed in previous
studies.33 Together, these characterization data strongly
support the formation of the desired closed complexes 20
and 21 (Table 1).
Since tweezer complexes 18-21 are much more soluble
in organic solvent compared to their macrocyclic analogues,
one can reversibly address the RhI hinge sites in situ with
selected small-molecule ligands and elemental anions. For
example, the addition of (n-Bu)4NCl (1 equiv) to a CH2Cl2
solution of complex 20 or 21 results in their quantitative
conversion to complexes 18 and 19, respectively. Impor-
tantly, this transformation is reversible and complexes 20
and 21 can be quantitatively reformed upon the addition of
a stoichiometric amount of Na[B(ArF)4] as evidenced by
1
methylene protons in the H NMR spectra of both 22 and
23 exhibit four well-resolved resonances (SCH2CH2P,
SCH2CH2P, OCH2CH2P, and OCH2CH2P) as compared with
the broad, overlapping resonances observed for the methylene
protons in 20 and 21.
Although the ether moieties in complexes 20 and 21 can
be selectively displaced from the Rh centers via the introduc-
tion of CO (1 atm), displacing the thioether moieties in 20
and 21 requires the use of both halides and CO. For instance,
introducing CO (1 atm) to a CD2Cl2 solution of half-open
complexes 18 or 19 quantitatively yielded the fully open,
highly flexible tweezer complexes 24 and 25 as indicated
by 31P{1H} NMR spectroscopy (Scheme 5). These complexes
2758 Inorganic Chemistry, Vol. 47, No. 7, 2008

Synthesis of Porphyrin Tweezer Complexes
Scheme 5. Synthesis and In Situ Regulation of Dissymmetric Porphyrin Tweezer Complexes 18–25a
a Mes ) mesityl and X– ) tetrakis[(3,5-trifluoromethyl)phenyl]borate. (i) [Rh(COE)2Cl]2 (0.5 equiv), THF (18 ) 93%; 19 ) 94%); (ii) Na[B(ArF)4]
(1 equiv), CH2Cl2 (20 ) 93%; 21 ) 93%); (iii) (n-Bu)4NCl (1 equiv), CH2Cl2 (18 ) 19 ) quant); (iv) CO (1 atm), CD2Cl2 (22 ) 23 ) quant); (v)
Na[B(ArF)4] (1 equiv), CH2Cl2 (22 ) 23 ) quant); (vi) CO (1 atm), CD2Cl2 (24 ) 25 ) quant); (vii) (n-Bu)4NCl (1 equiv), CO (1 atm), CD2Cl2 (24
) 25 ) quant).
Table 1. Comparison of 31P{1H} Chemical Shifts and Coupling
Constants for Porphyrin Complexes 18–25 vs Analogous Model
Complexes (3–6, Scheme 4)
can be generated in situ from the closed complexes 20 and
21 upon the addition of a stoichiometric amount of (n-
Bu)4NCl and CO (1 atm). In both cases, the 31P{1H} NMR
spectra of 24 and 25 yield broad multiplets at δ 23, which
arise due to the overlap of two doublets of doublets (Table
1). The presence of a CO-bound RhI species in 24 and 25
has also been confirmed by FTIR spectroscopy (νC≡O ) 1967
and 1971 cm-1, respectively).
Attempts to isolate diffraction-quality single crystals of
the complexes presented herein have thus far proven unsuc-
cessful. In the instances where small crystals formed, they
quickly lose solvent upon being removed from the mother
liquor. Nevertheless, their solution structures can be readily
JRh-P
JP-P
JRh-P JP-P
δ(PS)a (PS)b
(PS)b
δ(PO)a (PO)b (PO)b
3
4
5
6
73
73
63
185 41
200 41
116 268
broad multiplet at
approx δ 24
185 41
198 40
30
51
19
168
168
121
41
41
268
18 and 19
20 and 21
22 and 23
24 and 25
72
72
61
29
51
18
166
167
117
40
41
266
114 266
broad multiplet at
approx δ 23
a Data is reported in part per million. All chemical shifts have been
rounded to the nearest whole number. b Data is reported in Hertz.
Inorganic Chemistry, Vol. 47, No. 7, 2008 2759

Oliveri et al.
Micromass Q-TOF Ultima mass spectrometer. Electron-impact mass
spectra (EIMS) were recorded on a Fisions VG 70-250 SE mass
spectrometer. Matrix-assisted laser desorption/ionization-time of
flight (MALDI-TOF) mass spectra were recorded on a PE Voyager
DE-Pro MALDI-TOF mass spectrometer. Elemental analyses were
performed by Quantitative Technologies Inc., Whitehouse, NJ.
1-Bromo-4-[2-(diphenylphosphinothioyl)ethoxy]benzene (Com-
pound 9). In a 100-mL Schlenk round-bottom flask, [2-(4-
bromophenoxy)ethyl]diphenylphosphane (7.00 g, 18.2 mmol) and
elemental sulfur (583 mg, 18.2 mmol) were stirred in THF (70 mL)
under N2 at rt for 3 h. The remaining steps were then performed
under ambient conditions. The reaction mixture was concentrated
in vacuo and the resulting oil was dissolved in a minimal amount
of CH2Cl2 and precipitated from solution with pentane to afford 9
established based upon the large spectroscopic database that
we have obtained for fully characterized RhI model tweezer
complexes without porphyrins. As illustrated in Table 1,
31P{1H} NMR spectroscopic data provide a powerful means
for unequivocally identifying the product that results from
each in situ reaction. For example, the chemical shifts and
coupling constants for both complexes 18 and 19 only vary
by ∼2 ppm and 2 Hz, respectively, when compared to model
complex 3 (Scheme 1), definitively indicating formation of
the desired cis-phosphine, thioether-bound RhI complex.
Conclusions
In conclusion, we have demonstrated how the HILR can
be used to quantitatively assemble porphyrin-based hemila-
bile ligands and simple transition metal precursors into
dissymmetric, heteroligated tweezer complexes. In contrast
with their macrocyclic analogues, which contain two regula-
tory sites, these tweezer complexes have a single site that
can be used to modulate the porphyrin-porphyrin interac-
tions. The addition or removal of small-molecule ligands and
elemental anions can be used to interconvert the open and
closed conformations of the tweezer complexes in situ. The
enhanced solubility of these tweezer complexes allows for
such transformations to proceed in a completely reversible
manner, in contrast to the macrocyclic analogues, which often
precipitate during analogous transformations. Therefore, the
tweezer complexes and their corresponding reactivity with
small molecules and ions provide a convenient means for
manipulating the interactions between both porphyrins.
Efforts to utilize these transformations in the regulation of
both catalytic and photophysical properties are currently
underway.
1
as a white solid (6.48 g, 85% yield). H NMR (CD2Cl2): δ 2.93
(m, 2H, CH2PdS), 4.33 (m, 2H, OCH2), 6.57 (d, 2H, JH-H ) 8.7
Hz, ArH), 7.70 (d, 2H, JH-H ) 9.3 Hz, ArH), 7.47–7.57 (br m,
8H, ArH), 7.83–7.90 (br m, 6H, ArH). 31P{1H} NMR (CD2Cl2): δ
39.2 (s). 13C{1H} NMR (CD2Cl2): δ 32.2 (d, CH2P ) S, JC-P
)
56.4 Hz), 62.8 (OCH2), 116.4, 128.7, 128.8, 131.0, 131.1, 131.8,
132.5. HREIMS (m/z): Calcd. 415.9999. Found 416.0005. Elemental
analysis for C20H18BrOPS: Calcd. C, 57.56; H, 4.35. Found C,
58.31; H, 4.20.
4′-[2-(Diphenylphosphinothioyl)ethoxy]biphenyl-4-carbalde-
hyde (Compound 10). In a 500-mL Schlenk round-bottom flask,
9 (10.0 g, 23.9 mmol), 4-formylphenylboronic acid (3.63 g, 26.3
mmol), and Pd(PPh3)4 (5 mol %, 1.38 g) were stirred in a degassed
6:1 toluene/ethanol (400 mL) solution under N2. To this flask, a
degassed solution of Na2CO3 in H2O (2 M, 60 mmol, 30 mL) was
added and the contents were refluxed under N2 for 20 h. All
purification was then carried out under ambient conditions. The
solvent was removed in vacuo and the residue was dissolved in
CH2Cl2 (300 mL) and washed with H2O (2 × 100 mL). The organic
solvent was separated and evaporated to yield a crude brown oil
that was purified via column chromatography (2:1 hexanes/ethyl
acetate as eluent) to yield 10 as beige solid which was further
purified by precipitation from a CH2Cl2 solution with pentane (10.1
g, 95% yield). 1H NMR (CD2Cl2): δ 2.98 (m, 2H, CH2PdS), 4.42
(m, 2H, OCH2), 6.80 (d, 2H, JH-H ) 6.6 Hz, ArH), 7.50–7.57 (br
m, 8H, ArH), 7.70 (d, 2H, JH-H ) 8.4 Hz, ArH), 7.85–7.93 (br m,
6H, ArH), 10.0 (1H, CHO). 31P{1H} NMR (CD2Cl2): δ 39.1 (s).
13C{1H} NMR (CD2Cl2): δ 32.2 (d, CH2P ) S, JC-P ) 56.7 Hz),
62.7 (OCH2), 115.1, 127.1, 128.6, 128.8, 128.9, 130.3, 131.1, 131.2,
131.8, 131.8, 132.4, 132.6, 133.7, 135.0, 146.6, 158.8, 191.9.
HREIMS (m/z): Calcd. 442.1156. Found 442.1139. Elemental
analysis for C27H23O2PS: Calcd. C, 73.28; H, 5.24. Found C, 72.73;
H, 4.96.
General Methods and Instrument Details
All reactions were carried out under an inert atmosphere of
dinitrogen using standard Schlenk techniques or an inert-atmosphere
glovebox unless otherwise noted. Tetrahydrofuran (THF), diethyl
ether (Et2O), dichloromethane (CH2Cl2), and hexanes were purified
according to published methods.37 All solvents were deoxygenated
with nitrogen prior to use. Deuterated solvents (Cambridge Isotope
Laboratories Inc.) were obtained from commercial sources and used
as received. 5-Mesityldipyrromethane,36 2-(4-bromophenoxy)ethyl)-
diphenylphosphine,32 2-(4-bromophenylthio)ethyl)diphenylphos-
phine,32 and 1-bromo-4-[2-diphenylphosphinothioyl)ethylsulfa-
nyl]benzene24 were prepared according to literature procedures. All
other chemicals were used as received from Aldrich Chemical Co.
1H NMR (300.22 or 400.18 MHz) spectra were recorded on either
a Varian Mercury 300 MHz FTNMR spectrometer or a Varian
Mercury 400 MHz FTNMR spectrometer and referenced relative
to residual proton resonances. 31P{1H} NMR (121.53 or 161.95
MHz) spectra were recorded on either a Varian Mercury 300 MHz
or a Varian Mercury 400 MHz NMR spectrometer and referenced
relative to an external 85% H3PO4 standard. 13C{1H} (100.16 MHz)
spectra were recorded on a Varian Mercury 400 MHz FTNMR
spectrometer. All chemical shifts are reported in part per million.
Electrospray ionization mass spectra (ESIMS) were recorded on a
Micromass Quatro II triple quadrupole mass spectrometer or a
5-{4′-[2-(Diphenylphosphinothioyl)ethoxy]biphenyl-4-
yl}-10,15,20-mesitylporphyrin (Compound 11). In an aluminum
foil-wrapped 1000-mL Schlenk round-bottom flask, 10 (2.21 g, 5.00
mmol), 5-mesityldipyrromethane (2.64 g, 10.0 mmol), and mesi-
taldehyde (0.725 mL, 5.00 mmol) were dissolved in degassed CHCl3
(800 mL) and stirred under N2 over activated 4Å molecular sieves.
To this solution, BF3 ·OEt2 (2 mL) was added at once and the
solution stirred in the absence of light for 3 h at room temperature.
The flask was opened to ambient conditions at which point DDQ
(2.64 mg, 12 mmol) and NEt3 were added and allowed to stir for
an additional 30 min. The solvent was removed and the crude
product was purified via column chromatography (CH2Cl2 as eluent)
1
to yield 11 as a purple solid (1.21 g, 22%). H NMR (CD2Cl2): δ
-2.58 (s, 2H, NH), 1.86 (s, 18H, mesityl CH3), 2.62 (s, 9H, mesityl
CH3), 3.05 (m, 2H, CH2PdS), 4.50 (m, 2H, OCH2), 6.92 (d, 2H,
JH-H ) 8.4 Hz, ArH), 7.31 (s, 4H, ArH), 7.54 (m, 6H, ArH), 7.80
(37) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518–1520.
2760 Inorganic Chemistry, Vol. 47, No. 7, 2008

Synthesis of Porphyrin Tweezer Complexes
(d, 2H, JH-H ) 8.7 Hz, ArH), 7.91 (m, 10H, ArH), 8.26 (d, 2H,
JH-H ) 8.1 Hz, ArH), 8.65 (s, 4H, ArH), 8.69 (d, 2H, JH-H ) 4.5
Hz, ArH), 8.89 (d, 2H, JH-H ) 4.5 Hz, ArH). 31P{1H} NMR
(CD2Cl2): δ 39.4 (s). ESIMS (m/z): Calcd. 1077.4. Found 1077.7.
Elemental analysis for C73H65OPS: Calcd. C, 81.38; H, 6.08; N,
5.20. Found C, 80.26; H, 5.97; N, 5.45.
5-{4′-[2-(Diphenylphosphinothioyl)ethylsulfanyl]biphenyl-4-
yl}-10,15,20-mesitylporphyrin (Compound 15). In an aluminum
foil-wrapped 1000-mL Schlenk round-bottom flask, 14 (2.29 g, 5.00
mmol), 5-mesityldipyrromethane (2.64 g, 10.0 mmol), and mesi-
taldehyde (0.725 mL, 5.00 mmol) were dissolved in degassed CHCl3
(800 mL) and stirred under N2 over activated 4Å molecular sieves.
To this solution, BF3 ·OEt2 (2 mL) was added at once and the
solution stirred in the absence of light for 3 h at room temperature.
The flask was opened to ambient conditions at which point DDQ
(2.64 g, 12 mmol) and NEt3 were added and allowed to stir for an
additional 30 min. The solvent was removed and the crude product
was purified via column chromatography (CH2Cl2 as eluent) to yield
15 as a purple microcrystalline solid (1.11 g, 20%). 1H NMR
(CD2Cl2): δ -2.59 (s, 2H, NH), 1.84 (s, 18H, mesityl CH3), 2.60
(s, 9H, mesityl CH3), 2.84 (m, 2H, CH2PdS), 3.24 (m, 2H, SCH2),
7.29 (s, 4H, ArH), 7.47 (m, 10H, ArH), 7.84 (m, 6H, ArH), 7.98
(d, 2H, JH-H ) 8.7 Hz, ArH), 8.28 (d, 2H, JH-H ) 8.1 Hz, ArH),
8.62 (s, 4H, ArH), 8.67 (d, 2H, JH-H ) 4.8 Hz, ArH), 8.86 (d, 2H,
JH-H ) 4.5 Hz, ArH). 31P{1H} NMR (CD2Cl2): δ 41.5 (s). ESIMS
(m/z): Calcd. 1093.4. Found 1093.7. Elemental analysis for
C73H65N4PS2: Calcd. C, 80.19; H, 5.99; N, 5.12. Found C, 79.52;
H, 5.86; N, 4.91.
[5-{4′-[2-(Diphenylphosphinothioyl)ethoxy]biphenyl-4-yl}-
10,15,20-mesitylporphyrinato]zincII (Compound 12). In a 250-
mL round-bottom flask, 11 (500 mg, 0.464 mmol), and Zn(OAc)2 ·
2H2O (1.02 g, 4.64 mmol) were refluxed in 4:1 CHCl3/MeOH (200
mL) for 3 h. Upon completion, the solution was washed with H2O
(2 × 100 mL) and dried over Na2SO4. The contents were filtered
and the solvent was removed in vacuo yielding 12 as a purple solid
1
(518 mg, 98% yield). H NMR (CD2Cl2): δ 1.84 (s, 18H, mesityl
CH3), 2.62 (s, 9H, mesityl CH3), 3.07 (m, 2H, CH2PdS), 4.49 (m,
2H, OCH2), 6.92 (d, 2H, JH-H ) 8.7 Hz, ArH), 7.31 (s, 6H, ArH),
7.57 (m, 6H, ArH), 7.80 (d, 2H, JH-H ) 8.7 Hz, ArH), 7.90 (m,
6H, ArH), 8.26 (d, 2H, JH-H ) 8.1 Hz, ArH), 8.70 (m, 6H, ArH),
8.94 (d, 2H, JH-H ) 4.5 Hz, ArH). 31P{1H} NMR (CD2Cl2): δ 39.4
(s). ESIMS(m/z): Calcd. 1140.7. Found 1141.3. Elemental analysis
for C73H63OPSZn: Calcd. C, 76.86; H, 5.57; N, 4.91. Found C,
76.90; H, 6.02; N, 4.42.
[5-{4′-[2-(Diphenylphosphinothioyl)ethylsulfanyl]biphenyl-4-
yl}-10,15,20-mesityl-porphyrinato]zincII (Compound 16a). In a
250-mL round-bottom flask, 15 (500 mg, 0.457 mmol) and
Zn(OAc)2 ·2H2O (1.00 g, 4.57 mmol) were refluxed in CHCl3/
MeOH (200 mL, 4:1 v/v) for 3 h. Upon completion, the solution
was washed with H2O (2 × 100 mL) and dried over Na2SO4. The
contents were filtered and the solvent was removed in vacuo
yielding 16a as a purple microcrystalline solid (513 mg, 97% yield).
1H NMR (CD2Cl2): δ 1.84 (s, 18H, mesityl CH3), 2.62 (s, 9H,
mesityl CH3), 2.82 (m, 2H, CH2PdS), 3.22 (m, 2H, SCH2), 7.30
(s, 4H, ArH), 7.46 (m, 10H, ArH), 7.81 (m, 6H, ArH), 7.98 (d,
2H, JH-H ) 8.1 Hz, ArH), 8.29 (d, 2H, JH-H ) 8.4 Hz, ArH), 8.71
(s, 4H, ArH), 8.75 (d, 2H, JH-H ) 4.5 Hz, ArH), 8.94 (d, 2H, JH-H
) 4.8 Hz, ArH). 31P{1H} NMR (CD2Cl2): δ 41.3 (s). ESIMS
(m/z): Calcd. 1154.3. Found 1154.5 Elemental analysis for
C73H63PS2Zn: Calcd. C, 75.79; H, 5.49; N, 4.84. Found C, 75.09;
H, 5.13; N, 4.51.
[5-[4′-(2-Diphenylphosphanylethoxy)biphenyl-4-yl]-10,15,20-
mesitylporphyrinato]zincII (Compound 13). In a 50-mL Schlenk
round-bottom flask, 12 (405 mg, 0.355 mmol) and Cp2ZrHCl (293
mg, 1.14 mmol) were stirred under N2 in THF (30 mL) at 60 °C
for 4 h. Upon completion, the solvent was removed and the contents
were purified via column chromatography on neutral alumina (THF
as eluent) under an atmosphere of N2 to yield 13 as a purple solid
1
(361 mg, 92% yield). H NMR (CD2Cl2): δ 1.85 (s, 18H, mesityl
CH3), 2.60 (s, 9H, mesityl CH3), 2.65 (m, 2H, CH2P), 4.20 (m,
2H, OCH2), 7.02 (d, 2H, JH-H ) 8.4 Hz, ArH), 7.28 (s, 6H, ArH),
7.36 (d, 2H, JH-H ) 6.9 Hz, ArH), 7.51 (m, 6H, ArH), 7.83 (d,
2H, JH-H ) 9.3 Hz, ArH), 7.94 (d, 2H, JH-H ) 7.8 Hz, ArH), 8.20
(d, 2H, JH-H ) 7.8 Hz, ArH), 8.61 (s, 4H, ArH), 8.63 (d, 2H, JH-H
) 4.8 Hz, ArH), 8.83 (d, 2H, JH-H ) 4.2 Hz, ArH). 31P{1H} NMR
(CD2Cl2): δ -23.8 (s). ESIMS (m/z): Calcd. 1106.4. Found 1106.4.
Elemental analysis for C73H63OPZn: Calcd. C, 79.08; H, 5.73; N,
5.05. Found C, 78.09; H, 5.55; N, 4.77.
[5-{4′-[2-(Diphenylphosphinothioyl)ethylsulfanyl]biphenyl-4-
yl}-10,15,20-mesityl-porphyrinato]magnesiumII (Compound 16b).
Under ambient conditions, 15 (602 mg, 0.550 mmol), MgBr2 (4.03
g, 21.9 mmol), and NEt3 (12.2 mL, 88.0 mmol) were combined in
a 500-mL round-bottom flask and stirred for 6 h at rt in CH2Cl2
(350 mL). The solution was then washed with H2O (2 × 100 mL)
and extracted with CH2Cl2 (200 mL). The organic layer was further
washed with H2O (100 mL), dried over MgSO4, and concentrated
to give 16b as a crude purple microcrystalline solid which was
further purified via column chromatography on neutral alumina
(CH2Cl2 as eluent to yield a small amount of unreacted freebase
porphyrin then THF to elute product) which provided 16b (608
mg, 96% yield). 1H NMR (CD2Cl2): δ 1.84 (s, 18H, mesityl CH3),
2.62 (m, 9H, mesityl CH3), 2.87 (m, 4H, CH2PdS), 3.25 (m, 4H,
SCH2), 7.29 (s, 6H, ArH), 7.47 (br m, 10H, ArH), 7.82 (br m, 6H,
ArH), 7.97 (d, 2H, JH-H ) 7.5 Hz, ArH), 8.30 (d, 2H, JH-H ) 7.8
Hz, ArH), 8.60 (s, 4H, ArH) 8.66 (d, 2H, JH-H ) 4.2 Hz, ArH),
8.85 (d, 2H, JH-H ) 4.2 Hz, ArH). 31P{1H} NMR (CD2Cl2): δ 41.5
(s). EIMS (m/z): Calcd. 1114.4. Found 1114.4. Elemental analysis
for C73H63MgPS2: Calcd. C, 77.95; H, 5.65; N, 4.98. Found C,
77.14; H, 5.72; N, 4.53.
4′-[2-(Diphenylphosphinothioyl)ethylsulfanyl]biphenyl-4-car-
baldehyde (Compound 14). In a 500-mL Schlenk round-bottom
flask, 1-bromo-4-[2-(diphenylphosphinothioyl)ethylsulfanyl] ben-
zene (10.0 g, 23.1 mmol), 4-formylphenylboronic acid (3.51 g, 25.3
mmol), and Pd(PPh3)4 (5 mol %, 1.34 g) were stirred in a degassed
6:1 toluene/ethanol (400 mL) solution under N2. To this solution,
a degassed solution of Na2CO3 in H2O (2 M, 58 mmol, 29 mL)
was added and the contents were refluxed under N2 for 20 h. All
purification was then carried out under ambient conditions. The
solvent was removed in vacuo and the residue was washed with
H2O (2 × 100 mL), extracted with CH2Cl2 (300 mL), and the
solvent was evaporated to yield a crude brown oil. The oil was
purified via column chromatography (2:1 hexanes/ethyl acetate as
eluent) to yield 14 as a beige solid, which was further purified by
precipitation from a CH2Cl2 solution with pentane (8.63 g, 81%
yield). 1H NMR (CD2Cl2): δ 2.75 (m, 2H, CH2PdS), 3.17 (m, 2H,
SCH2), 7.34 (d, 2H, JH-H ) 8.4 Hz, ArH), 7.45–7.60 (br m, 8H,
ArH), 7.76–7.85 (br m, 6H, ArH), 7.94 (d, 2H, JH-H ) 8.7 Hz,
ArH), 10.0 (s, 1H, CHO). 31P{1H} NMR (CD2Cl2): δ 41.5 (s).
13C{1H} NMR: δ 26.4 (SCH2), 32.3 (CH2PdS, JC-P ) 51.8 Hz),
127.1, 128.0, 128.9, 129.0, 129.3, 130.4, 131.1, 131.2, 131.9, 132.0,
132.4, 133.0, 135.5, 136.3, 137.5, 146.2, 191.8. HREIMS (m/z):
Calcd. 458.0927. Found 458.0929. Elemental analysis for
C27H23OPS2: Calcd. C, 70.72; H, 5.06. Found C, 70.81; H, 4.75.
5-[4′-(2-Diphenylphosphanylethylsulfanyl)biphenyl-4-yl]-
10,15,20-mesitylporphyrinato]zinc(II) (Compound 17a). In a 50-
mL Schlenk round-bottom flask, 16a (431 mg, 0.372 mmol) and
Inorganic Chemistry, Vol. 47, No. 7, 2008 2761

Oliveri et al.
Cp2ZrHCl (307 mg, 1.19 mmol) were stirred under N2 in THF (30
mL) at 60 °C for 4 h. Upon completion, the solvent was removed
and the contents were purified via column chromatography on
neutral alumina (THF as eluent) under an atmosphere of N2. The
product was isolated and the solvent was removed to yield 17a as
a purple microcrystalline solid (373 mg, 90% yield). 1H NMR
(CD2Cl2): δ 1.85 (s, 18H, mesityl CH3), 2.45 (m, 2H, CH2P), 2.60
(s, 9H, mesityl CH3), 3.04 (m, 2H, SCH2), 7.29 (s, 4H, ArH),
7.39–7.48 (br m, 14H, ArH), 7.88 (d, 2H, JH-H ) 8.4 Hz, ArH),
8.00 (d, 2H, JH-H ) 7.8 Hz, ArH), 8.24 (d, 2H, JH-H ) 8.4 Hz,
ArH), 8.61 (s, 4H, ArH), 8.64 (d, 2H, JH-H ) 4.8 Hz, ArH), 8.82
(d, 2H, JH-H ) 4.8 Hz, ArH). 31P{1H} NMR (CD2Cl2): δ -15.8
(s). ESIMS (m/z): Calcd. 1124.7. Found 1125.6. Elemental analysis
for C73H63PSZn: Calcd. C, 77.95; H, 5.65; N, 4.98. Found C, 77.14;
H, 5.72; N, 4.53.
36H, mesityl CH3), 2.46 (br m, 2H, SCH2CH2P), 2.57–2.62 (m,
18H, mesityl CH3), 2.72 (m, 2H, SCH2CH2P), 2.81 (m, 2H,
OCH2CH2P), 4.62 (m, 2H, OCH2CH2P), 7.09 (d, 2H, JH-H ) 8.4
Hz ArH), 7.21–7.35 (br m, 20H, ArH), 7.42 (br t, 4H), 7.53 (t, 4H,
ArH), 7.70 (t, 4H, ArH), 7.87 (d, 2H, JH-H ) 8.4 Hz, ArH),
7.97–8.08 (br m, 6H, ArH), 8.22 (d, 2H, JH-H ) 8.7 Hz, ArH),
8.33 (d, 2H, JH-H ) 8.1 Hz, ArH), 8.40 (d, 2H, JH-H ) 8.1 Hz,
ArH), 8.56–8.70 (m, 12H, ArH), 8.87 (d, 2H, JH-H ) 4.2 Hz, ArH),
8.92 (d, 2H, JH-H ) 4.2 Hz, ArH). 31P{1H} NMR (CD2Cl2): δ 72.6
(dd, JRh-P ) 184 Hz, JP-P ) 38 Hz), 28.6 (dd, JRh-P ) 167 Hz,
JP-P ) 41 Hz). MALDI-TOF MS (m/z): Calcd. 2295.23 [M - Cl-].
Found 2295.15; Calcd. 2270.93 [M - Mg - Cl-)]. Found 2270.21.
[(13)(17a)Rh][B(ArF)4] (Compound 20). Compound 18 (200.0
mg, 0.0843 mmol) and Na[B(ArF)4] (74.7 mg, 0.0843 mmol) were
added to a 20-mL vial and sonicated in CH2Cl2 (15 mL) for 1 h.
The solution was placed in a freezer at -30 °C for 1 h to ensure
complete precipitation of NaCl. The solution was passed through
a plug of Celite (to remove NaCl) into a 25-mL Schlenk flask, and
the solvent was removed under vacuum to yield 20 as an
air-sensitive purple solid (251 mg, 93% yield). 1H NMR (CD2Cl2):
δ 1.67–1.85 (m, 36H, mesityl CH3), 2.51–2.84 (br m, 24H, mesityl
CH3, SCH2CH2P, SCH2CH2P and OCH2CH2P), 4.17 (m, 2H,
OCH2CH2P), 7.34–8.03 (br m, 56H, ArH), 7.74 (br s, 12H, ArH),
8.37 (br s, 4H, ArH), 8.65–8.96 (br m, 16H, ArH). 31P{1H} NMR
(CD2Cl2): δ 72.7 (dd, JRh-P ) 198 Hz, JP-P ) 40 Hz), 51.0 (dd,
JRh-P ) 167 Hz, JP-P ) 41 Hz). MALDI-TOF MS (m/z): Calcd.
2336.31 [M - B(ArF)4-]. Found 2336.99.
5-[4′-(2-Diphenylphosphanylethylsulfanyl)biphenyl-4-yl]-
10,15,20-mesitylporphyrinato] magnesiumII (17b). In a 50-mL
Schlenk round-bottom flask, 16b (438 mg, 0.393 mmol) and
Cp2ZrHCl (406 mg, 1.26 mmol) were stirred in THF under N2 (30
mL) at 60 °C for 4 h. The solvent was removed and the reaction
was purified via column chromatography on neutral alumina (THF
as eluent) in a glovebox under an atmosphere of N2. The solvent
was removed in vacuo to yield 17b as a purple microcrystalline
1
solid (378 mg, 89% yield). H NMR (THF-d8): δ 1.86 (s, 18H,
mesityl CH3), 2.64 (m, 2H, CH2P), 2.60 (s, 9H, mesityl CH3), 3.07
(m, 2H, SCH2), 7.28 (s, 6H, ArH), 7.36 (d, 6H, JH-H ) 4.5 Hz,
ArH), 7.45 (br d, 6H, JH-H ) 6.6 Hz, ArH), 7.88 (d, 2H, JH-H
)
[(13)(17b)Rh][B(ArF)4] (Compound 21). Compound 19 (200.0
mg, 0.0858 mmol) and Na[B(ArF)4] (75.6 mg, 0.0858 mmol) were
added to a 20-mL vial and sonicated in CH2Cl2 (15 mL) for 1 h.
The solution was placed in a freezer at -30 °C for 1 h to ensure
complete precipitation of NaCl. The solution was passed through
a plug of Celite (to remove NaCl) into a 25-mL Schlenk flask, and
the solvent was removed under vacuum to yield 21 as an
air-sensitive purple solid (253 mg, 93% yield). 1H NMR (CD2Cl2):
δ 1.71–1.84 (m, 36H, mesityl CH3), 2.55–2.84 (br m, 24H, mesityl
CH3, SCH2CH2P, SCH2CH2P and OCH2CH2P), 4.17 (m, 2H,
7.8 Hz, ArH), 7.99 (d, 2H, JH-H ) 7.2 Hz, ArH), 8.25 (d, 2H,
JH-H ) 7.8 Hz, ArH), 8.53–8.57 (br m, 6H, ArH), 8.74 (d, 2H,
JH-H ) 3.6 Hz, ArH). 31P{1H} NMR (THF-d8): δ -15.8 (s). EIMS
(m/z): Calcd. 1082.4 [M+]. Found 1082.6. Elemental analysis for
C73H63MgPS (2 THF): Calcd. C, 79.36; H, 6.33; N, 4.57. Found
C, 78.19; H, 6.15; N, 4.58.
(13)(17a)RhCl (Compound 18). Ligand 13 (147 mg, 0.133
mmol), ligand 17a (150 mg, 0.133 mmol), and [Rh(COE)2Cl]2 (47.8
mg, 0.0667 mmol) were added to a 20-mL vial and dissolved in
THF (15 mL). This solution was transferred to a 50-mL Schlenk
flask and sonicated for 1 h. Upon completion, the solvent was
removed under vacuum to yield a purple solid which was sonicated
in hexanes (20 mL) for 1 h, filtered, washed with fresh hexanes (2
× 10 mL) and dried under vacuum to yield 18 as an air-sensitive
OCH2CH2P), 7.21–7.98 (br m, 56H, ArH), 8.38 (d, 4H, JH-H
)
6.6 Hz, ArH), 8.64–8.97 (br m, 16H, ArH). 31P{1H} NMR (CD2Cl2):
δ 72.4 (dd, JRh-P ) 198 Hz, JP-P ) 40 Hz), 51.0 (dd, JRh-P ) 167
Hz, JP-P ) 41 Hz). MALDI-TOF MS (m/z): Calcd. 2295.22 [M -
B(ArF)4-]. Found 2295.2. Calcd. 2270.92 [M - Mg - Cl-)]. Found
2270.92.
1
solid (146 mg, 93% yield). H NMR (CD2Cl2): δ 1.78–1.83 (m,
36H, mesityl CH3), 2.45 (br m, 2H, SCH2CH2P), 2.57–2.61 (m,
18H, mesityl CH3), 2.71 (m, 2H, SCH2CH2P), 2.80 (m, 2H,
OCH2CH2P), 4.64 (m, 2H, OCH2CH2P), 7.09 (d, 2H, JH-H ) 8.4
Hz, ArH), 7.20–7.35 (br m, 20H, ArH), 7.41 (br m, 4H), 7.53 (t,
4H, ArH), 7.70 (t, 4H, ArH), 7.88 (d, 2H, JH-H ) 8.4 Hz, ArH),
7.97–8.08 (br m, 6H, ArH), 8.21 (d, 2H, JH-H ) 8.1 Hz, ArH),
8.32 (d, 2H, JH-H ) 7.8 Hz, ArH), 8.41 (d, 2H, JH-H ) 8.1 Hz,
ArH), 8.67-8.70 (m, 10H, ArH), 8.73 (d, 2H, JH-H ) 4.2 Hz, ArH),
8.92 (d, 2H, JH-H ) 4.8 Hz, ArH), 8.95 (d, 2H, JH-H ) 4.2 Hz,
ArH). 31P{1H} NMR (CD2Cl2): δ 72.6 (dd, JRh-P ) 185 Hz, JP-P
) 41 Hz), 28.8 (dd, JRh-P ) 166 Hz, JP-P ) 40 Hz). MALDI-TOF
MS (m/z): Calcd. 2336.31 [M - Cl-]. Found 2335.88.
[(13)(17a)Rh(CO)][B(ArF)4] (Compound 22). Compound 22
can be prepared according to two separate methods.
Method A. Compound 20 (15.0 mg, 0.00468 mmol) was added
to a 5-mL vial, dissolved in CD2Cl2 (2 mL), and transferred to a
10-mL Schlenk flask. The flask was attached to a Schlenk line where
the N2 atmosphere was evacuated and replaced with CO (1 atm).
The contents were sonicated for 30 s at which point the flask was
brought into a glovebox and transferred to a J-Young air-free NMR
tube. The yield of 22 was determined to be quantitative as indicated
by 31P{1H} NMR spectroscopy.
Method B. In a glovebox, compound 18 (20.0 mg, 0.00843
mmol) was added to a 5-mL vial, dissolved in CD2Cl2 (1 mL) and
transferred to a 10-mL Schlenk flask. The Schlenk flask was placed
on a Schlenk line where the N2 atmosphere in the flask was
evacuated and replaced with an atmosphere of CO (1 atm), resulting
in the in situ generation of compound 24. The flask was brought
back into the glovebox where Na[B(ArF)4] (7.47 mg, 0.00843
mmol) was added to the solution, at which point the solution was
transferred to a J-Young air-free NMR tube. The resulting mixture
was sonicated for 30 min which provided compound 22 in
(13)(17b)RhCl (Compound 19). Ligand 13 (147 mg, 0.133
mmol), ligand 17b (144 mg, 0.133 mmol), and [Rh(COE)2Cl]2 (47.8
mg, 0.0667 mmol) were added to a 20-mL vial and dissolved in
THF (15 mL). This solution was transferred to a 50-mL Schlenk
flask and sonicated for 1 h. Upon completion, the solvent was
removed under vacuum to yield a purple solid which was sonicated
in a hexanes (20 mL) for 1 h, filtered, washed with fresh hexanes
(2 × 10 mL), and dried under vacuum to yield 19 as an air-sensitive
1
solid (146 mg, 94% yield). H NMR (CD2Cl2): δ 1.78–1.86 (m,
2762 Inorganic Chemistry, Vol. 47, No. 7, 2008

Synthesis of Porphyrin Tweezer Complexes
quantitative yield as was indicated by 31P{1H} NMR spectroscopy.
1H NMR (CD2Cl2): δ 1.83 (br s, 36H, mesityl CH3), 2.62 (br s,
18H, mesityl CH3), 2.88 (m, 2H, SCH2CH2P), 3.03 (m, 2H,
SCH2CH2P), 3.17 (m, 2H, OCH2CH2P), 4.52 (m, 2H, OCH2CH2P),
6.98–7.97 (br m, 52H, ArH), 8.29 (m, 4H, ArH), 8.39 (m, 4H, ArH),
8.71 (br s, 12H, ArH), 8.94 (br s, 4H, ArH). 31P{1H} NMR
(CD2Cl2): δ 61.0 (dd, JRh-P ) 114 Hz, JP-P ) 266 Hz), 18.5 (dd,
JRh-P ) 117 Hz, JP-P ) 266 Hz). FTIR (CH2Cl2): νCO ) 1970
flask was sonicated for 30 s and the solution was transferred to a
J-Young air-free NMR tube. Analysis of this solution by 1H NMR
and 31P{1H} NMR spectroscopy indicated the quantitative conver-
sion of 20 to 24. 1H NMR (CD2Cl2): δ 1.80–1.84 (m, 36H, mesityl
CH3), 2.57–2.61 (m, 18H, mesityl CH3), 3.02 (br m, 2H,
SCH2CH2P), 3.24 (m, 2H, SCH2CH2P), 3.39 (m, 2H, OCH2CH2P),
4.69 (m, 2H, OCH2CH2P), 7.06 (d, 2H, JH-H ) 8.4 Hz, ArH),
7.24–7.28 (br m, 12H, ArH), 7.43 (d, 2H, JH-H ) 8.1 Hz, ArH),
7.52 (br s, 12H, ArH), 7.80–7.87 (br m, 12H, ArH), 7.93 (d, 4H,
JH-H ) 8.4 Hz, ArH), 8.24 (br t, 4H, ArH), 8.68–8.74 (br m, 12H,
ArH), 8.92 (m, 4H, ArH). 31P{1H} NMR (CD2Cl2): δ 21.6 (eight
peaks which arise from overlap of two dd’s: δ 21.6, 22.4, 22.6,
cm-1
.
[(13)(17b)Rh(CO)][B(ArF)4] (Compound 23). Compound 23
can be prepared according to two separate methods.
Method A. Compound 21 (15.0 mg, 0.00475 mmol) was added
to a 5-mL vial, dissolved in CD2Cl2 (2 mL), and transferred to a
10-mL Schlenk flask. The flask was attached to a Schlenk line where
the N2 atmosphere was evacuated and replaced with CO (1 atm).
The contents were sonicated for 30 s at which point the flask was
brought into a glovebox and transferred to a J-Young air-free NMR
tube. The yield of 23 was determined to be quantitative as indicated
by 31P{1H} NMR spectroscopy.
23.3, 23.7, 24.5, 24.8, 25.6). FTIR (CH2Cl2): νCO ) 1967 cm-1
.
(13)(17b)RhCl(CO) (Compound 25). Compound 25 can be
prepared according to two separate methods. Since method A relies
only on the addition of CO (1 atm) to the sample, the product from
this reaction was used for all of the necessary characterization.
Method A. Compound 19 (20.0 mg, 0.00858 mmol) was
weighed out into a 5-mL vial, dissolved in CD2Cl2 (1 mL) and
transferred to a 10-mL Schlenk flask. The flask was placed on a
Schlenk line where the N2 atmosphere was removed and replaced
with CO (1 atm). The flask was sonicated for 30 s and the solution
was transferred to a J-Young air-free NMR tube. Analysis of this
Method B. In a glovebox, compound 19 (20.0 mg, 0.00858
mmol) was added to a 5-mL vial, dissolved in CD2Cl2 (1 mL), and
transferred to a 10-mL Schlenk flask. The Schlenk flask was placed
on a Schlenk line where the N2 atmosphere in the flask was
evacuated and replaced with an atmosphere of CO (1 atm), resulting
in the in situ generation of compound 25. The flask was brought
back into the glovebox where Na[B(ArF)4] (7.60 mg, 0.00858
mmol) was added to the solution, at which point the solution was
transferred to a J-Young air-free NMR tube. The resulting mixture
was sonicated for 30 min which provided compound 23 in
quantitative yield as was indicated by 31P{1H} NMR spectroscopy.
1H NMR (CD2Cl2): δ 1.83-1.85 (br s, 36H, mesityl CH3), 2.61
(br s, 18H, mesityl CH3), 2.89 (m, 2H, SCH2CH2P), 3.04 (m, 2H,
SCH2CH2P), 3.17 (m, 2H, OCH2CH2P), 4.52 (m, 2H, OCH2CH2P),
7.02 (d, 4H, JH-H ) 8.4 Hz, ArH), 7.29 (br s, 12H, ArH), 7.50–7.98
(br m, 40H, ArH), 8.27 (d, 4H, JH-H ) 8.4 Hz, ArH), 8.61–8.85
(br m, 12H, ArH), 8.92 (d, 4H, JH-H ) 8.4 Hz, ArH). 31P{1H}
NMR (CD2Cl2): δ 61.0 (dd, JRh-P ) 113 Hz, JP-P ) 266 Hz), 18.6
(dd, JRh-P ) 118 Hz, JP-P ) 266 Hz). FTIR (CH2Cl2): νCO ) 1970
1
solution by H NMR and 31P{1H} NMR spectroscopy indicated
the quantitative conversion of 19 to 25.
Method B. Compound 21 (20.0 mg, 0.00633 mmol) and (n-
Bu)4NCl (1.76 mg, 0.00633 mmol) were weighed out into a 5-mL
vial, dissolved in CD2Cl2 (1 mL), and transferred to a 10-mL
Schlenk flask. The flask was placed on a Schlenk line where the
N2 atmosphere was removed and replaced with CO (1 atm). The
flask was sonicated for 30 s and the solution was transferred to a
J-Young air-free NMR tube. Analysis of this solution by 1H NMR
and 31P{1H} NMR spectroscopy indicated the quantitative conver-
sion of 21 to 25. 1H NMR (CD2Cl2): δ 1.79–1.84 (m, 36H, mesityl
CH3), 2.58–2.62 (m, 18H, mesityl CH3), 3.02 (br m, 2H,
SCH2CH2P), 3.24 (m, 2H, SCH2CH2P), 3.39 (m, 2H, OCH2CH2P),
4.68 (m, 2H, OCH2CH2P), 7.06 (d, 2H, JH-H ) 9.1 Hz, ArH),
7.24–7.28 (br m, 12H, ArH), 7.43–7.52 (br s, 14H, ArH), 7.79–7.86
(br m, 12H, ArH), 7.94 (d, 4H, JH-H ) 7.8 Hz, ArH), 8.25 (d, 4H,
JH-H ) 7.2 Hz, ArH), 8.60–8.75 (br m, 12H, ArH), 8.85 (m, 2H,
ArH), 8.94 (m, 2H, ArH). 31P{1H} NMR (CD2Cl2): δ 21.4 (seven
peaks which arise from overlap of two dd’s: δ 21.4, 22.4, 23.5,
cm-1
.
(13)(17a)RhCl(CO) (Compound 24). Compound 24 can be
prepared according to two separate methods. Since method A relies
only on the addition of CO (1 atm) to the sample, the product from
this reaction was used for all of the necessary characterization.
Method A. Compound 18 (20.0 mg, 0.00843 mmol) was
weighed out into a 5-mL vial, dissolved in CD2Cl2 (1 mL), and
transferred to a 10-mL Schlenk flask. The flask was placed on a
Schlenk line where the N2 atmosphere was removed and replaced
with CO (1 atm). The flask was sonicated for 30 s, and the solution
was transferred to a J-Young air-free NMR tube. Analysis of this
23.6, 24.4, 24.6, 25.4). FTIR (CH2Cl2): νCO ) 1971 cm-1
.
Acknowledgment. C.G.O. would like to thank Michael
J. Wiester for preparation of the Supporting Information
document. C.A.M. and S.T.N. acknowledge the NSF, ARO,
AFOSR, and DDRE for support of this research.
1
solution by H NMR and 31P{1H} NMR spectroscopy indicated
the quantitative conversion of 18 to 24.
Supporting Information Available: 1H and 31P{1H} NMR
spectra for compounds 19, 21, 23, and 25 and MALDI-TOF spectra
for compounds 19 and 21. This material is available free of charge
via the Internet at http://pubs.acs.org.
Method B. Compound 20 (20.0 mg, 0.00625 mmol) and (n-
Bu)4NCl (1.74 mg, 0.00625 mmol) were weighed out into a 5-mL
vial, dissolved in CD2Cl2 (1 mL), and transferred to a 10-mL
Schlenk flask. The flask was placed on a Schlenk line where the
N2 atmosphere was removed and replaced with CO (1 atm). The
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