Sterically demanding diporphyrin ligands and rhodium(II) porphyrin bimetalloradical complexes

Article abstract of DOI:10.1021/ic0006302

A series of sterically demanding diporphyrins H₂(por)-X-(por)H₂ ligands that contain spacers (X) with different degrees of flexibility were synthesized from the trimesitylporphyrin derivatives 5-(4-hydroxyphenyl)-10,15,20-trimesitylporphyrin (TMP-OH)H₂ (1a) and 5-(2,6-dimethyl-4-hydroxyphenyl)-10,15,20-trimesityl-porphyrin, (DMTMP-OH)H₂ (1b). The monomeric porphyrins 1a,b, which have steric demands similar to that of tetramesitylporphyrin, (TMP)H₂, and carry a hydroxyl functional group at the para position of one of the mesophenyl substituents, were constructed from reaction of pyrrole with two aromatic aldehydes by a mixed aldehyde condensation approach. The diporphyrins with alkyl diether tethers were obtained stepwise from reactions of the hydroxy functionalized porphyrins 1a,b with dibromides Br(CH₂)(n)Br. The diporphyrin which contains a more rigid m-xylylene spacer, was made directly from reaction of 1b with α,α'-dibromo-m-xylene. Rhodium was inserted into the porphyrins using Rh₂(CO)₂Cl₂ and converted to dimethyl complexes Me-Rh(Por)-X-(Por)Rh-Me. The dirhodium(II) derivatives ·Rh(por)-X-(por)Rh· were generated by photolysis of the dimethyl complexes and observed to occur as stable bimetalloradicals because the ligand steric demands prohibit Rh(II)-Rh(II) bonding. EPR spectra of the dirhodium(II) derivatives, triphenyl phospine adducts, and dioxygen complexes are reported. The kinetic advantage of bimetalloradical complexes for substrate reactions that have two metal-centered radicals in the transition state is demonstrated by reactions of dihydrogen with dirhodium(II) bimetalloradical complexes.

Full text of DOI:10.1021/ic0006302

5318
Inorg. Chem. 2000, 39, 5318-5325
Sterically Demanding Diporphyrin Ligands and Rhodium(II) Porphyrin Bimetalloradical
Complexes
Xiao-Xiang Zhang and Bradford B. Wayland*
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323
ReceiVed June 12, 2000
A series of sterically demanding diporphyrins H2(por)-X-(por)H2 ligands that contain spacers (X) with different
degrees of flexibility were synthesized from the trimesitylporphyrin derivatives 5-(4-hydroxyphenyl)-10,15,20-
trimesitylporphyrin (TMP-OH)H2 (1a) and 5-(2,6-dimethyl-4-hydroxyphenyl)-10,15,20-trimesityl-porphyrin,
(DMTMP-OH)H2 (1b). The monomeric porphyrins 1a,b, which have steric demands similar to that of
tetramesitylporphyrin, (TMP)H2, and carry a hydroxyl functional group at the para position of one of the meso-
phenyl substituents, were constructed from reaction of pyrrole with two aromatic aldehydes by a mixed aldehyde
condensation approach. The diporphyrins with alkyl diether tethers were obtained stepwise from reactions of the
hydroxy functionalized porphyrins 1a,b with dibromides Br(CH2)nBr. The diporphyrin which contains a more
rigid m-xylylene spacer, was made directly from reaction of 1b with R,R′-dibromo-m-xylene. Rhodium was inserted
into the porphyrins using Rh2(CO)2Cl2 and converted to dimethyl complexes Me-Rh(Por)-X-(Por)Rh-Me.
The dirhodium(II) derivatives ‚Rh(por)-X-(por)Rh‚) were generated by photolysis of the dimethyl complexes
and observed to occur as stable bimetalloradicals because the ligand steric demands prohibit Rh(II)-Rh(II) bonding.
EPR spectra of the dirhodium(II) derivatives, triphenyl phospine adducts, and dioxygen complexes are reported.
The kinetic advantage of bimetalloradical complexes for substrate reactions that have two metal-centered radicals
in the transition state is demonstrated by reactions of dihydrogen with dirhodium(II) bimetalloradical complexes.
Introduction
of the termolecular transition state that favor the smaller
substrate.1,2,5
Metalloradical (M‚) reactions with substrates such as H2 and
CH4, where atom abstractions are highly endothermic, can
proceed by a concerted interaction of two metalloradicals with
the substrate through a four-centered transition state.1-8 Reac-
tions that utilize this type of pathway have relatively low
A strategy to improve the kinetics and retain the selectivity
of metalloradical reactions with substrates is to incorporate two
metal centered radical sites into a single molecular unit which
has the potential to convert the termolecular reaction into a
bimolecular process.7,8 This article reports on the design and
activation enthalpies because of extensive bond making in the
transition state but generally occur slowly because of the large
activation entropies associated with termolecular processes.1-5
Reactions of (tetramesitylporphyrinato)rhodium(II) ((TMP)RhII‚)
with CH4 and H2 are examples of processes that occur by this
termolecular pathway.1-3 One potentially important consequence
of this metalloradical mechanism is that there is a kinetic
preference for methane activation over C-H bond reactions with
all other aliphatic or aromatic hydrocarbons which is a different
selectivity order from all other systems that activate hydro-
carbons.9-13 This selectivity has its origin in the steric demands
procedures for the synthesis of a series of diporphyrin ligands
(9) (a) Hoyano, J. K.; McMaster, A.; Graham, W. A. G. J. Am. Chem.
Soc. 1983, 105, 7190. (b) Rest, A. J.; Whitewell, I.; Graham, W. A.
G.; Hoyano, J. K.; McMaster, A. D. J. Chem. Soc., Chem Commun.
1984, 624. (c) Ghosh, C. K.; Graham, W. A. G. J. Am.Chem. Soc.
1983, 109, 4726. (d) Janowicz, A. H.; Bergman, R. G. J. Am. Chem.
Soc. 1983, 105, 3929. (e) Wenzel, T. T.; Bergman, R. G. J. Am. Chem.
Soc. 1986, 108, 4856. (f) Hackett, M.; Whitesides, G. M. J. Am. Chem.
Soc. 1988, 110, 1449. (g) Harper, T. G.; Shinomoto, R. S.; Deming,
M. A.; Flood, T. C. J. Am. Chem. Soc. 1988, 110, 7915.
(10) (a) Watson, P. J. Am. Chem. Soc. 1983, 105, 6491. (b) Fendrick, C.
M.; Marks, T. J. J. Am. Chem. Soc. 1984, 106, 2214. (c) Fendrick, C.
M.; Marks, T. J. J. Am. Chem. Soc. 1986, 108, 625. (d) Thompson,
M. E.; Baxter, S. M.; Bulls, A. R.; Burger, B. J.; Nolan, M. C.;
Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J. E. J. Am. Chem. Soc.
1987, 19, 8109.
(1) Sherry, A. E.; Wayland, B. B. J. Am. Chem. Soc. 1990, 112, 1259.
(2) Wayland, B. B.; Ba, S.; Sherry, A. E. J. Am. Chem. Soc. 1991, 113,
5305.
(3) Wayland, B. B.; Ba, S.; Sherry, A. E. Inorg. Chem. 1992, 31, 148.
(4) Simandi, L. I.; Budo-Zahonyi, E.; Szeverenyi, Z.; Nemeth, S. J. Chem.
Soc., Dalton Trans. 1980, 276.
(5) Halpern, J.; Pribinic, M. Inorg. Chem. 1970, 9, 2626.
(6) (a) Halpern, J. Inorg. Chim. Acta 1982, 62, 31. (b) Halpern, J. Inorg.
Chim. Acta 1983, 77, L105.
(7) Zhang, X.-X.; Wayland, B. B. J. Am. Chem. Soc. 1994, 116, 7897.
(8) Zhang, X.-X.; Parks, G. F.; Wayland, B. B. J. Am. Chem. Soc. 1997,
119, 7938.
(11) Cummins, C. C.; Baxter, S. M.; Wolczanski, P. T. J. Am. Chem. Soc.
1988, 110, 8731.
(12) Periana, R. A.; Taube, D. J.; Evitt, E. R.; Lo`ffer, D. G.; Wentrcek, P.
R.; Voss, G.; Masuda, T. Science 1993, 259, 340.
10.1021/ic0006302 CCC: $19.00 © 2000 American Chemical Society
Published on Web 10/21/2000

Rhodium(II) Porphyrin Complexes
Inorganic Chemistry, Vol. 39, No. 23, 2000 5319
Figure 1. Schemes 1 and 2 for the preparation of diether-tethered diporphyrin ligands and the dirhodium(II) bimetalloradical derivatives.
that are used in forming dirhodium(II) porphyrin bimetalloradi-
cal species. Reactions of the diporphyrin bimetalloradical
complexes with H2 are used to illustrate the efficacy of this
stategy.
was separated by column chromatography. The first fraction
was identified as tetramesitylporphyrin, (TMP)H2. The second
fraction afforded the desired functionalized steric porphyrin
(TMP-OH)H2 (1a) or (DMTMP-OH)H2 (1b) in isolated yields
of 16% and 14%, respectively.
Results and Discussion
Formation of dimeric porphyrins with different spacers from
the functionalized steric porphyrins 1a,b was accomplished as
described in Schemes 1 and 2 (Figure 1). Reactions of porphyrin
1a or 1b with an excess of R,ω-dibromoalkanes by nucleophilic
substitution produced the bromoalkyl porphyrins (TMP-O(CH2)n-
Br)H2 (2a, n ) 6; 2b, n ) 11) and (DMTMP-O(CH2)nBr)H2
(2c, n ) 5; 2d, n ) 6) in 74% to 83% yields. Subsequent
reactions of the bromoalkyl porphyrins 2a-d with an excess
amount of the corresponding porphyrin 1 afforded the dipor-
phyrin ligands H2(por)O-X-O(por)H2 (3a-d) in 55-65%
yields. This stepwise synthesis of diporphyrins 3a-d (Scheme
1) provides a potential approach for preparing heterobimetal-
lodiporphyrins.15,16 An alternate single step procedure for the
synthesis of diporphyrin ligands is illustrated by the preparation
of compound 3e that contains a more rigid m-xylylene spacer
(Scheme 2). Reaction of an excess amount of porphyrin 1a with
R,R′-dibromo-m-xylene in DMF afforded the diporphyrin 3e in
87% yield.
A series of tethered diporphyrin ligands were designed
specifically to improve the rates for rhodium(II) porphyrin
reactions with substrates such as methane where two metal-
loradicals occur in the transition state. The two essential design
features needed to accomplish this objective are the following:
(1) The steric demands for the individual porphyrin units must
be large enough to preclude intra- and intermolecular Rh(II)-
Rh(II) bonding which makes an unfavorable contribution to the
thermodynamics and kinetics of substrate reactions. (2) The
length and flexibility of the tethering units must permit the two
metal centers to reach the required transition state for intra-
molecular substrate reactions. These features have been incor-
porated into a set of diporphyrin ligands by linking two sterically
demanding porphyrin units with a series of diether spacers
through reactions of the p-hydroxy functionality on a phenyl
group at the periphery of the porphyrin macrocycle (Figure 1,
Schemes 1 and 2).
The first step in the construction of the target diporphyrins
is to prepare porphyrins that have steric requirements similar
to that of tetramesitylporphyrin ((TMP)H2) and a functionality
on the periphery for tethering the two porphyrin units. Synthesis
of the functionalized sterically demanding porphyrins was
accomplished by use of a combination of the Lindsey methodol-
ogy14 and a mixed aldehyde condensation approach. The
condensation of mixtures of the desired aromatic aldehydes with
pyrrole produced a near statistical mixture of meso-substituted
porphyrins.
Formation of Rhodium(II) Porphyrin Bimetalloradical.
Rhodium is inserted in the diporphyrin ligands 3a-e by reaction
17
of Rh2(CO)2Cl2 in 1,2-dichloroethane and then converted to
the dimethyl derivatives H3C-Rh(por)O-X-O(por)Rh-CH3
(5a-e) in 80-85% isolated yields by the reaction sequence
given in Schemes 1 and 2. The Rh-CH3 groups in 5a-e
produce highly characteristic 1H NMR because of the shielding
effect from the aromatic porphyrin macrocycle and coupling
(15) (a) Guilard, R.; Lopez, M. A.; Tabard, A.; Richard, P.; Lecomte, C.;
Brandes, S.; Hutchison, J.; Collman, J. P. J. Am. Chem. Soc. 1992,
114, 9877. (b) Collman, J. P.; Hutchison, J. E.; Lopez, M. A.; Tabard,
A.; Guilard, R.; Seok, W. K.; Ibers, J. A.; L’Her, M. J. Am. Chem.
Soc. 1992, 114, 9869. (c) Collman, J. P.; Wagenknecht, P. S.;
Hutchison, J. E.; Lewis, N. S.; Lopez, M. A.; Guilard, R.; L’Her, M.;
Bothner-By, A.; Mishra, P. K. J. Am. Chem. Soc. 1992, 114, 5654.
(16) (a) Tabushi, I.; Kugimiya, S.; Kinnaird, M. G.; Saaski, T. J. Am. Chem.
Soc. 1985, 107, 4192. (b) Tabushi, I.; Saaski, T. J. Am. Chem. Soc.
1983, 105, 2901. (c) Tabushi, I.; Kugimiya, S.; Saaski, T. J. Am. Chem.
Soc. 1985, 107, 5159. (d) Tabushi, I.; Kugimiya, S. J. Am. Chem.
Soc. 1986, 108, 6926. (e) Tabushi, I. Pure Appl. Chem. 1988, 60,
581.
Condensation of 3 equiv of mesitaldehyde and 1 equiv of
4-hydroxybenzaldehyde or 2,6-dimethyl-4-hydroxybenzaldehyde
with 4 equiv of pyrrole in the presence of BF3‚Et2O (Figure 1,
Scheme 1) resulted in the intermediate porphyrinogens which
by oxidation with p-chloranil produced a porphyrin mixture that
(13) (a) Crabtree, R. H. Chem. ReV. 1995, 95, 987. (b) Arndtsen, B. A.;
Bergman, R. G.; Mobley, T. A.; Peterson, T. H. Acc. Chem. Res. 1995,
28, 154.
(14) (a) Lindsey, J. S.; Hsu, H. C.; Schreiman, I. C. Tetrahedron Lett. 1986,
27, 4969. (b) Lindsey, J. S.; Schreiman, I. C.; Hsu, H. C.; Marguerettaz,
A. M. J. Org. Chem. 1987, 52, 827.
(17) (a) Ogoshi, H.; Setsune, J.; Omura, T.; Yoshida, Z. J. Am. Chem. Soc.
1975, 97, 6461. (b) Ogoshi, H.; Omura, T.; Yoshida, Z. J. Am. Chem.
Soc. 1973, 95, 1666.

5320 Inorganic Chemistry, Vol. 39, No. 23, 2000
Zhang and Wayland
Figure 2. NMR spectra of H3C-Rh(por)O(CH2)6O(por)Rh-CH3 (5a)
in C6D6: (a) 1H NMR spectrum of diporphyrin unit; (b) 1H NMR
spectrum of Rh-CH3 group; (c) 1H NMR spectrum of Rh-13CH3 group;
(d) proton-coupled 13C NMR spectrum of Rh-13CH3 group.
Figure 3. (a) 1H NMR spectrum in the pyrrole region for ‚Rh(Por)O-
(CH2)6O(Por)Rh‚ (6a) in C6D6. (b) Temperature dependence for the
1
pyrrole H NMR paramagnetic shift of 6a in toluene-d8, displayed as
a plot of chemical shift, δ (ppm), versus 1/T (K-1).
from the 103Rh nucleus. Distinctive high field positions for the
1H and 13C NMR spectrum of the Rh-CH3 in 13CH3-Rh-
A(31P)g11 ) 1016 MHz, A(103Rh)g11 ) 61 MHz) are similar to
(por)O-(CH2)6-O(por)Rh-13CH3 (5a) (δCH ) -5.29; δ13CH
)
20
those observed for (TMP)Rh‚P(C6H5)3 and indicative of an
-13.58) and coupling (1J13C′H ) -141 Hz; 1J103Rh-13CH ) -29
(dxzdyz dxy)6 (dz2)1 electron configuration with substantial odd
electron spin density on the phosphine ligand. The triph-
enylphosphine adduct reacts with dioxygen (Po2 ∼ 200-600
Torr) to form a disuperoxo complex (Figure 4c) with the
anisotropic EPR spectrum exhibiting three distinct g values (g1
) 2.08, g2 ) 2.005, g3 ) 1.996) associated with low symmetry
(por)Rh(III)-O2- unit (Figure 4c). The small g value anisotropy
and near isotropic phosphorus couplings ( A (31P) ) 50.5 MHz)
are characteristic of superoxide complexes where the unpaired
electron is predominantly localized on the dioxygen unit.
Dirhodium(II) Bimetalloradical Reactions with Hydrogen.
The dirhodium(II) bimetalloradical complexes (‚Rh(por)O-X-
O(por)Rh‚) 6a-e react with hydrogen (PH2 ) 540 Torr; T )
296-353 K) in benzene to form the dihydride complex H-Rh-
(por)O-X-O(por)Rh-H (7a-e). Throughout the above range
of conditions each of these reactions effectively results in the
quantitative conversion of the bimetalloradicals (6) into dihy-
dride species (7).
2
Hz; J103Rh-CH ) 2.9 Hz) (Figure 2) provide convenient
observables for identifying the Rh-CH3 derivative in solution.
Facile photohomolysis (λ > 350 nm) of the Rh-CH3
units1,2,18 in 5a-e is an effective method to form dirhodium(II)
bimetalloradical complexes (‚RhII(por)O-X-O(por)RhII‚) 6a-e
(Schemes 1 and 2). The rhodium(II) complexes 6a-e exhibit
broad yet observable paramagnetically shifted 1H NMR spectra.
Temperature dependence for the pyrrole 1H NMR shift for the
dirhodium(II) complex 6a (‚Rh(por)O-(CH2)6-O(por)RhII‚) is
illustrated in Figure 3. The observed downfield shift for the
pyrrole hydrogens of 6a (δpyr(295 K) ) 18.2) is consistent with
a (dxy dxz,yz)6 (dz2)1 ground configuration placing positive spin
density in the porphyrin σ donor orbitals. Curie paramagnetism
for 6a is demonstrated by the linear dependence of the pyrrole
hydrogen shift with the inverse of temperature (δpyr vs T-1
)
(Figure 3).19 The observed Curie magnetic behavior clearly
demonstrates the absence of detectable RhII-RhII bonding down
to 190 K in toluene. The EPR spectrum for 6a in toluene glass
(90 K) (Figure 4) shows g values (g ) 2.64; g11 ) 1.90) very
close to that for (TMP)RhII‚ (g ) 2.65; g11 ) 1.915)20 resulting
from effectively independent RhII centers with (dxy dxz, yz)6 (dz2)1
electron configurations. The broadening of the EPR spectrum
which obscures the 103Rh coupling on the g11 transition of
the dirhodium(II) complex 6a relative that for (TMP)Rh‚
(A[103Rh(g11)] ) -197 MHz) may result from a small magnetic
interaction between the two rhodium(II) centers in the toluene
glass.
The reaction of H2 with the bimetalloradical complexes could
proceed by either an intramolecular or intermolecular use of
two RhII‚ centers to give bimolecular and termolecular processes,
respectively (Figure 5). The termolecular pathway shown in
Figure 5 is effectively the same as that used by (TMP)Rh‚ in
the reaction with H2.3 The intramolecular reaction two RhII‚
centers in 6 with H2 initially produces the same dihydride 7
which is the same hydride species that is present when the
reaction is complete. However, when RhII‚ centers from two
different molecules of 6 react with H2, the product that initially
forms has one Rh-H and one RhII‚ site in the molecule
(compound 8). Formation of the dihydride 7 by the inter-
molecular pathway thus would pass through an intermediate
species 8. More detailed reactivity studies of the bimetalloradical
species 6a and the dihydride 7a were undertaken in an effort to
distinguish between intra- and intermolecular pathways by both
kinetic studies and observing the time evolution of reaction
products.
Triphenylphosphine coordinates with the rhodium(II) centers
of the bimetalloradical 6a and exhibits an anisotropic EPR
spectrum in toluene glass (90 K) associated with a di mono
triphenyl phosphine adduct (Figure 4b). The g values (g
)
2.17, g11 ) 2.00) and hyperfine couplings (A(31P)g ) 756 MHz,
(18) (a) Wayland, B. B.; Sherry, A. E.; Poszmik, G.; Bunn, A. G. J. Am.
Chem. Soc. 1992, 114, 1673. (b) Sherry, A. E.; Wayland, B. B. J.
Am. Chem. Soc. 1989, 111, 5010.
(19) Drago, R. S. Physical Methods for Chemists, 2nd ed.; Saunders College
Publishing: Philadelphia, PA, 1992; Chapter 12, p 508.
(20) Wayland, B. B.; Sherry, A. E.; Bunn, A. G. J. Am. Chem. Soc. 1993,
115, 7675.
The substantial rate enhancement for the reaction of the
bimetalloradical 6a with H2 compared to (TMP)RhII‚ is il-
lustrated in Figure 6. Plots of the disappearance of RhII‚ centers

Rhodium(II) Porphyrin Complexes
Inorganic Chemistry, Vol. 39, No. 23, 2000 5321
Figure 5. Sequence of hydride complexes formed by intramolecular
and intermolecular reactions of two RhII‚ centers with H2.
Figure 6. Change in the [RhII‚] centers with time for reactions of
hydrogen ([H2] ) 2.1 × 10-3 M) with (TMP)RhII‚ (k(296) ) 2.7 M-1
s-1) and ‚Rh(por)(CH2)6O(por)Rh‚ (6a) (k(296) ) 9.3 × 10-3 M-1 s-1
(6a) ) 2.82 × 10-3 M).
)
at 296 K ([(TMP)]i ) 2.82 × 10-3 M; [6a]i ) 1.41 × 10-3 M, [RhII‚]i
to a second-order process provide convincing evidence that the
most productive path for the reaction of 6a with H2 involves
the intramolecular use of two RhII‚ centers.
Additional direct evidence for the intramolecular path was
obtained by observing the sequence of Rh-H species formed
in the reactions of 6a with H2 at low concentration. When a
benzene solution of the bimetalloradical 6a is put in contact
with a low pressure of H2 such that there is less than a
stoichiometric amount of H2 for the complete reaction (PH i
∼
2
1
3 Torr) the H NMR spectrum of the Rh-H region observed
over an extended period of time reveals a sequence of rhodium
hydride species (Figure 7). The initially formed hydride complex
Figure 4. (a) Anisotropic EPR spectrum for ‚Rh(Por)O(CH2)6O(Por)-
Rh‚ (6a) (toluene glass, 90 K): g1,2 ) 2.64, g3 ) 1.90. (b) Anisotropic
EPR spectrum for the triphenyl phosphine adduct of 6a (toluene glass,
90 K): g1,2 ) 2.17, A(31P)g1,2 ) 756 MHz; g3 ) 2.00, A(31P)g3 ) 1016
MHz, A(103Rh)g3 ) 61 MHz. (c) Anisotropic EPR spectrum for the
superoxo complex of the bis(triphenyl phosphine) adduct of 6a (toluene
glass, 90 K): g1 ) 2.080, A(31P)g1 ) 50.9 MHz; g2 ) 2.005, A(31P)g2
) 50.5 MHz; g3 ) 1.996, A(31P)g3 ) 50.3 MHz.
1
has a H NMR spectrum identical with that of the dihydride
7a. After a period of several days a second hydride species
appears and builds up in concentration with the decline in
concentration of 7a. We ascribe these observations to a relatively
fast initial bimolecular reaction of 6a with H2 to produce the
dihydride 7a in a single step followed by a slower intermolecular
hydrogen atom transfer from 7a to 6a to produce 8a (‚Rh-
(por)O-(CH2)6-O(por)Rh-H) (Figure 8). Degenerate hydrogen
atom transfer between (OEP)Rh-H and (OEP)Rh‚ is relatively
fast but this type of process is much slower for the (TMP)RhII‚
system where the ligand steric demands inhibit attaining the
transition state for atom transfer.
as a function of time for the reactions of the dirhodium(II)
complex 6a and (TMP)RhII‚ with H2 in C6D6 (296 K) are shown
in Figure 6. The kinetics for the reaction of 6a with H2 are
fitted to a bimolecular process with a second-order rate constant
of 9.3 × 10-1 M-1 s-1 (T ) 296 K) (Figure 7). The
disappearance of (TMP) RhII‚ by reaction with H2 as a function
of time at the same concentration and temperature as the reaction
of 6a is calculated and plotted in Figure 6 using the previously
determined third-order rate constant of 2.7 M-2 s-1 at 296 K.1
The large increase in the rate of reaction of 6a with H2 compared
to (TMP)RhII‚ and the fitting of the concentration-time profile
The ligand steric demands designed into the bimetalloradical
radical complexes are similar to that of TMP and thus relatively
slow intermolecular hydrogen atom transfer is expected between
6a and 7a. Support for this interpretation was obtained from a

5322 Inorganic Chemistry, Vol. 39, No. 23, 2000
Zhang and Wayland
as benzene and toluene were degassed by freeze-pump-thaw cycles
to remove oxygen and then refluxed over sodium/benzophenone ketyl
to remove water as indicated by turning purple. Chloroform, methylene
chloride, and 1,2-dichloroethane used in synthetic procedures were
purified by washing three times with water followed by chromatography
on grade 1 alumina for the removal of ethanol and water. Prepurified
nitrogen and argon gases used for the inert-atmosphere box were
purchased from Airco or MG industries.
Proton NMR spectra were obtained on a Bruker WP200SY, a Bruker
AC-250, or a Bruker AMX-500 interfaced to an Aspect 300 computer
at ambient temperature. All spectra were referenced using the residual
solvent peak as an internal standard (benzene-d6, δ ) 7.155; toluene-
d8, δ ) 2.09; chloroform-d1, δ ) 7.24). Carbon-13 NMR spectra were
obtained on the AMX-500 instrument equipped with a carbon-13 probe.
Variable-temperature 1H NMR spectra were obtained on an IBM-Bruker
AF200SY or IBM Bruker WP200SY spectrometer equipped with a
Bruker VI-1000 temperature controller or boil-off from liquid nitrogen
when temperature needed is below 220 K. The probe was cooled with
a FTS systems refrigerator unit equipped with a temperature controller.
The temperatures in the probe were referenced against an external
samples of methanol and ethylene glycol for low- and high-temperature
experiments, respectively. The samples were protected from light prior
to and during the experiments.
Electron paramagnetic resonance spectra were obtained by use of
ER 100 D X-band spectrometer. Temperature measurements were
calibrated with a Bruker model VT unit using N2 as the cooling source
(283-90 K). All EPR experiments were performed at 90 K unless
otherwise noted and calibrated using diphenylpicrylhydrazine (DPPH,
g ) 2.0036) as an external standard. Fast atom bombardment mass
spectrometry (FAB-MS) data were recorded on a VG-ZAB-E spec-
trometer with a cesium ion gun. Electronic spectra were recorded with
a Hewlett-Packard UV 8452 instrument interfaced to an IBM PC.
5-(4-Hydroxyphenyl)-10,15,20-trimesitylporphyrin, (TMP-OH)-
H2 (1a). A 2 L three-neck round-bottomed flask fitted with a septum,
reflux condenser, and nitrogen inlet port was charged with CHCl3 (1
L) (distilled from K2CO3), 4-hydroxybenzaldehyde (305 mg, 2.5 mmol),
mesitaldehyde (1.106 mL, 7.5 mmol), and pyrrole (694 µL, 10 mmol).
After the solution was purged with N2 for 5 min, BF3‚OEt2 (1.32 mL)
was added via syringe. The room-temperature reaction was monitored
by removing 50-mL aliquots and oxidizing with excess p-chloranil,
followed by UV-vis absorption spectroscopy. At the end of 60 min,
p-chloranil (1.844 g, 7.5 mmol) was added in powder form and the
reaction mixture was gently refluxed (∼60 °C) for 1 h. The reaction
mixture was then cooled to room temperature, and the precipitates were
filtered off. The filtrate was rotary evaporated to dryness under reduced
pressure. The crude dry product was purified by column chromatog-
raphy on silica gel with chloroform first and then with dichloromethane
as eluents. The first fraction was identified as (TMP)H2. The second
fraction was evaporated and dried to give 1a as a purple solid in 16%
yield. 1H NMR (C6D6), δ (ppm): 8.92 (d, 2H, 3JH-H ) 4.8 Hz, pyrrole),
1
Figure 7. Sequence of H NMR for the 103Rh-H region for C6D6
solutions for 6a exposed to a small initial pressure of H2 (PH2i ) 3
Torr).
Figure 8. Sequence of Rh-H species formed when a C6D6 solutions
of 6a reacts with a less than stoichiometric quantity of H2. The dihydride
7a forms first, and then is slowly converted to a second hydride species
8a.
separate experiment where isolated samples of the dihydride
7a and bimetalloradical 6a were mixed in C6D6 solvent. The
initial H NMR spectrum obtained by mixing 6a and 7a was
that of the dihydride 7a, but a second hydride species with H
NMR identical with 8a grew in over a period of days. The
sequence of hydride species formed in the reaction of 6a with
H2 clearly indicates that the intramolecular reaction of two RhII‚
centers with H2 has a large kinetic preference compared to the
intermolecular pathway where RhII‚ centers in two molecules
of 6a are used. Both kinetic studies and the sequence of Rh-H
species formed indicate that the reaction of the bimetalloradical
complex 6a with dihydrogen occurs through a bimolecular
process that involves the intramolecular use of two RhII‚ centers.
3
3
8.85 (d, 2H, JH-H ) 4.8 Hz, pyrrole), 8.84 (d, 2H, JH-H ) 4.8 Hz,
3
3
1
pyrrole), 8.82 (d, 2H, JH-H ) 4.8 Hz, pyrrole), 7.78 (d, 2H, JH-H
)
8.2 Hz, o-phenyl), 7.11 (s, 6H, m-phenyl), 6.42 (d, 2H,3JH-H ) 8.2
Hz, m′-phenyl), 4.25 (br s, 1H, -OH), 2.45 (s, 6H, p-CH3), 2.41 (s,
3H, p′-CH3), 1.96 ( s, 12H, o-CH3), 1.84 (s, 6H, o′-CH3), -1.73 (br s,
2H, -NH). UV-vis (CH2Cl2), λmax (nm): 650, 592, 548, 514, 414.
FAB-HRMS (M+): calcd for C53H48N4O, m/e 756.3829; found, m/e
756.3894.
1
5-(2,6-Dimethyl-4-hydroxyphenyl)-10,15,20-trimesitylporphy-
rin, (DMTMP-OH)H2 (1b). The porphyrin 1b was prepared in 14%
yield by a procedure analogous to that given for porphyrin 1a using
2,6-dimethyl-4-hydroxybenzaldehyde instead of 4-hydroxybenzalde-
hyde. 1H NMR (C6D6), δ (ppm): 8.81 (s, 4H, pyrrole H), 8.79 (s, 4H,
pyrrole H), 7.13 (s, 4H, arom), 6.59 (s, 4H, arom), 4.12 (broad s, 1H,
-OH), 2.43 (s, 9H, p-CH3), 1.89 (s, 18H, o-CH3), 1.79 (s, 6H, o-CH3),
-1.64 (broad s, 2H, -NH). UV-vis (CH2Cl2), λmax (nm): 646, 592,
546, 514, 416. FAB-HRMS (M+): calcd for C55H52N4O, m/e 784.4141;
found, m/e 784.4076.
Experimental Section
General Procedures and Methods. All manipulations were per-
formed on a high-vacuum line equipped with a Welch Duo-Seal vacuum
pump or in an inert-atmosphere box filled with argon unless otherwise
noted. All reagents were purchased from Aldrich or Strem Chemical
Co. and used as received. Pyrrole was distilled prior to use. [Rh-
(CO)2Cl]2 was sublimed prior to use. Deuterated NMR solvents such
5-[4-(6-Bromo-1-hexoxy)phenyl]-10,15,20-trimesitylporphyrin,
[TMP-O(CH2)6Br]H2 (2a). A mixture of porphyrin 1a (635 mg, 0.84
mmol), 1,6-dibromohexane (1.72 mL, 11.16 mmol), and anhydrous K2-

Rhodium(II) Porphyrin Complexes
Inorganic Chemistry, Vol. 39, No. 23, 2000 5323
CO3 (1.69 g, 12.23 mmol) was magnetically stirred with DMF (17 mL,
dried over 4 Å molecular sieves). The reaction was monitored by TLC
(silica gel, CH2Cl2). After 30 h, the reaction mixture was rotary
evaporated to dryness under reduced pressure. A mixture of water (96
mL) and methanol (17 mL) was added to treat the residue. Upon
centrifuging of the sample, the precipitates were collected and dried in
vacuo at 100 °C to remove excess 1,6-dibromohexane and then purified
by column chromatography (silica gel, CH2Cl2) to give porphyrin 2a
in 83% yield. 1H NMR (C6D6), δ (ppm): 9.02 (d, 2H, 3JH-H ) 4.8 Hz,
1.36 (m, 8H, -CH2CH2CH2CH2-), -1.68(br s, 4H, -NH). UV-vis
(CH2Cl2), λmax (nm): 648, 592, 548, 514, 418. FAB-HRMS (M+): calcd
for C112H106N8O2, m/e 1594.8441; found, m/e 1594.8312.
5,10,15-Trimesityl-20-[4-[11-[p-(10,15,20-trimesityl-5-porphinyl)-
phenoxy]u ndecoxy]phenyl]porphine, H2[TMP-O(CH2)11O-TMP]-
H2 (3b). The diporphyrin 3b was prepared in 63% yield from the
reaction of porphyrin 1a with 2b by a procedure analogous to that given
1
3
for diporphyrin 3a. H NMR (C6D6), δ (ppm): 9.02 (d, 4H, JH-H
)
3
4.8 Hz, pyrrole), 8.88 (d, 4H, JH-H ) 4.8 Hz, pyrrole), 8.87 (d, 4H,
3
3
3JH-H ) 4.8 Hz, pyrrole), 8.83 (d, 4H, JH-H ) 4.8 Hz, pyrrole), 7.97
3
pyrrole), 8.88 (d, 2H, JH-H ) 4.8 Hz, pyrrole), 8.87 (d, 2H, JH-H
)
3
3
4.8 Hz, pyrrole), 8.83 (d, 2H, JH-H ) 4.8 Hz, pyrrole), 7.96 (d, 2H,
3JH-H ) 8.5 Hz, o-phenyl), 7.16 (s, 6H, m-phenyl), 7.10 (d, 2H, 3JH-H
) 8.5 Hz, m′-phenyl), 3.74 (t, 2H, 3JH-H ) 6.3 Hz, -OCH2-), 2.98 (t,
(d, 4H, JH-H ) 8.5 Hz, o-phenyl), 7.16 (s, 12H, m-phenyl), 7.12 (d,
4H, 3JH-H ) 8.5 Hz, m′-phenyl), 3.88 (t, 4H, 3JH-H ) 6.1 Hz, -OCH2-),
2.44 (s, 12H, p-CH3), 2.42 (s, 6H, p′-CH3), 1.97 (s, 24H, o-CH3), 1.85
(s, 12H, o′-CH3), 1.54-1.36 (m, 8H, -(CH2)9-), -1.68(br s, 4H, -NH).
UV-vis (CH2Cl2) λmax (nm): 645, 591, 548, 514, 416. FAB-HRMS
(MH+): calcd for C117H116N8O2, m/e 1665.9301; found, m/e 1665.9358.
5,10,15-Trimesityl-20-[4-[5-[p-(10,15,20-trimesityl-5-porphinyl)-
2,6-dimeth ylphenoxy]pentoxy]-2,6-dimethylphenyl]porphine, H2-
[DMTMP-O (CH2)5O-DMTMP]H2 (3c). The diporphyrin 3c was
prepared in 55% yield from the reaction of porphyrin 1b with 2c by a
procedure analogous to that given for diporphyrin 3a. 1H NMR (CDCl3)
3
2H, JH-H ) 6.7 Hz, -CH2Br), 2.45 (s, 6H, p-CH3), 2.41 (s, 3H, p′-
CH3), 1.97 (s, 12H, o-CH3), 1.85 (s, 6H, o′-CH3), 1.55-1.16 (m, 8H,
-CH2CH2CH2CH2-), -1.69 (br s, 2H, -NH). UV-vis (CH2Cl2), λmax
(nm): 650, 592, 548, 516, 418. FAB-HRMS (M+): calcd for C59H59N4-
Obr, m/e 918.3837; found, m/e 918.3840.
5-[4-(11-Bromo-1-undecoxy)phenyl]-10,15,20-trimesitylporphy-
rin, [TMP-O(CH2)11Br]H2 (2b). The porphyrin 2b was prepared in
80% yield by a procedure analogous to that given for porphyrin 2a
using 1,11-dibromoundecane instead of 1,6-dibromohexane. 1H NMR
δ (ppm): 8.65 (d, 4H, 3JH-H ) 4.7 Hz, pyrrole), 8.62 (d, 4H, 3JH-H
)
3
(C6D6), δ (ppm) 9.02 (d, 2H, JH-H ) 4.8 Hz, pyrrole), 8.88 (d, 2H,
4.7 Hz, pyrrole), 8.61 (s, 8H, pyrrole),7.25 (s, 12H, arom), 7.05 (s,
4H, arom), 4.34 (t, 4H, 3JH-H ) 5.8 Hz, -CH2O), 2.60 (s, 18H, p-CH3),
2.16 (m, 6H, -CH2CH2CH2-), 1.87 (s, 12H, o-CH3), 1.84 (s, 36H,
o′-CH3), -2.52 (s, 4H, -NH). UV-vis (CH2Cl2), λmax (nm): 646, 592,
546, 514, 414. FAB-HRMS (M+): calcd for C115H112N8O2, m/e
1636.8910; found, m/e 1636.8921.
3
3JH-H ) 4.8 Hz, pyrrole), 8.87 (d, 2H, JH-H ) 4.8 Hz, pyrrole), 8.83
3
3
(d, 2H, JH-H ) 4.8 Hz, pyrrole), 7.96 (d, 2H, JH-H ) 8.5 Hz,
3
o-phenyl), 7.16 (s, 6H, m-phenyl), 7.11 (d, 2H, JH-H ) 8.5 Hz, m′-
phenyl), 3.86 (t, 2H, 3JH-H ) 6.2 Hz, -OCH2-), 2.99 (t, 2H, 3JH-H
)
6.7 Hz, -CH2Br), 2.45 (s, 6H, p-CH3), 2.42 (s, 3H, p′-CH3), 1.97 (s,
12H, o-CH3), 1.85 (s, 6H, o′-CH3), 1.55-1.16 (m, 8H, -(CH2)9-),
-1.68 (br s, 2H, -NH). UV-vis (CH2Cl2), λmax (nm): 646, 592, 547,
514, 416. FAB-HRMS (M+): calcd for C59H59N4Obr, m/e 918.3837;
found, m/e 918.3840.
5,10,15-Trimesityl-20-[4-[6-[p-(10,15,20-trimesityl-5-porphinyl)-
2,6-dimeth ylphenoxy]hexoxy]-2,6-dimethylphenyl]porphine, H2-
[DMTMP-O(CH2)6O-DMTMP]H2 (3d). The diporphyrin 3d was
prepared in 60% yield from the reaction of porphyrin 1b with 2d by a
procedure analogous to that given for diporphyrin 3a. 1H NMR (C6D6),
5-[4-(5-Bromo-1-pentoxy)-2,6-dimethylphenyl]-10,15,20-tri-
mesitylporphyrin, [DMTMP-O(CH2)5Br]H2 (2c). The porphyrin 2c
was prepared in 74% yield by a procedure analogous to that given for
porphyrin 2a using porphyrin 1b and 1,5-dibrompentane instead of
porphyrin 1a and 1,6-dibromohexane. 1H NMR (CDCl3), δ (ppm): 8.63
(s, 4H, pyrrole H), 8.62 (s, 4H, pyrrole H), 7.27 (s, 6H, arom), 7.00 (s,
δ (ppm): 8.89 (d, 4H, 3JH-H ) 4.7 Hz, pyrrole), 8.83 (d, 4H, 3JH-H
)
4.7 Hz, pyrrole), 8.82 (s, 8H, pyrrole), 7.13 (s, 16H, m-phenyl), 3.98
(t, 4H, 3JH-H ) 6.1 Hz, -OCH2-), 2.42 (s, 18H, p-CH3), 1.93 (s, 12H,
o-CH3), 1.90 (s, 36H, o′-CH3), 1.66-1.45 (m, 8H, -CH2CH2CH2CH2-),
-1.62(br s, 4H, -NH). UV-vis (CH2Cl2), λmax (nm): 646, 590, 546,
514, 418. FAB-HRMS (M+): calcd for C116H114N8O2, m/e 1650.9067;
found, m/e 1650.8982.
5,10,15-Trimesityl-20-[4-[r,r′-[p-(10,15,20-trimesityl-5-porphinyl)-
phenoxy] xyloxy]phenyl]porphine, H2[TMP-O(m-CH2C6H4CH2)O-
TMP]H2 (3e). A mixture of porphyrin 1a (225 mg, 0.297 mmol) and
R,R′-dibromo-m-xylene (39 mg, 0.149 mmol) was stirred with anhy-
drous K2CO3 (406 mg, 2.94 mmol) in DMF (20 mL) at 110 °C. The
reaction was monitored by TLC (silica gel, toluene/petroleum ether
(v/v) ) 2.5/1). After 24 h, the reaction mixture was poured into a solvent
mixture containing water (90 mL) and methanol (10 mL). The
precipitates were filtered off using a Buchner funnel (type D) and
washed with a small amount of methanol. The residue was dried in an
oven at 100 °C and was purified by column chromatography (silica
gel, toluene/petroleum ether (v/v) ) 2.5/1). The second fraction was
identified as diporphyrin 3e and obtained in 87% yield. 1H NMR (C6D6),
3
3
2H, arom), 4.24 (t, 2H, JH-H ) 6.1 Hz, -CH2O), 3.54 (t, 2H, JH-H
) 6.7 Hz, -CH2Br), 2.62 (s, 9H, p-CH3), 1.95-2.10 (m, 6H, -CH2-
CH2CH2-), 1.86 (s, 24H, o-CH3), -2.52 (s, 2H, -NH). UV-vis (CH2-
Cl2), λmax (nm): 646, 592, 548, 514, 416. FAB-HRMS (M+): calcd
for C60H61N4Obr, m/e 932.4030; found, m/e 932.4061.
5-[4-(6-Bromo-1-hexoxy)-2,6-dimethylphenyl]-10,15,20-tri-
mesitylporphyrin, [DMTMP-O(CH2)6Br]H2 (2d). The porphyrin 2d
was prepared in 75% yield using porphyrin 1b instead of 1a by a
procedure analogous to that given for the porphyrin 2a. 1H NMR (C6D6),
δ (ppm): 8.88 (d, 2H, 3JH-H ) 4.7 Hz, pyrrole), 8.83 (d, 2H, 3JH-H
)
4.7 Hz, pyrrole), 8.82 (s, 4H, pyrrole), 7.13 (s, 6H, m-phenyl), 7.06 (s,
3
2H, m′-phenyl), 3.84 (t, 2H, JH-H ) 6.2 Hz, -OCH2-), 3.00 (t, 2H,
3JH-H ) 6.7 Hz, -CH2Br), 2.42 (s, 9H, p-CH3), 1.90 (s, 24H, o-CH3),
1.67-1.25 (m, 8H, -CH2CH2CH2CH2-), -1.63 (br s, 2H, -NH). UV-
vis (CH2Cl2), λmax (nm): 646, 592, 546, 514, 416. FAB-HRMS (M+):
calcd for C61H63N4OBr, m/e 946.4183; found, 946.4149.
δ (ppm): 9.02 (d, 4H, 3JH-H ) 4.7 Hz, pyrrole), 8.89 (d, 4H, 3JH-H
)
3
4.7 Hz, pyrrole), 8.85 (d, 4H, JH-H ) 4.7 Hz, pyrrole), 8.83 (d, 4H,
3JH-H ) 4.7 Hz, pyrrole), 7.97 (d, 4H, 3JH-H ) 8.4 Hz, o-phenyl), 7.72-
7.16 (multiple s, 16H, phenyl), 7.00 (d, 4H, 3JH-H ) 8.4 Hz, m′-phenyl),
4.95 (s, 4H, -OCH2-), 2.42 (s, 18H, p-CH3), 1.98 (s, 24H, o-CH3),
1.86 (s, 12H, o′-CH3), -1.68 (br s, 4H, -NH). UV-vis (CH2Cl2), λmax
(nm): 645, 591, 548, 514, 418. FAB-HRMS (MH+): calcd for
5,10,15-Trimesityl-20-[4-[6-(p-(10,15,20-trimesityl-5-porphinyl)-
phenoxy)he xoxy]phenyl]porphine, H2[TMP-O(CH2)6O-TMP]H2
(3a). A mixture of 1a (293 mg, 0.387 mmol) and porphyrin 2a (119
mg, 0.129 mmol) were stirred with anhydrous K2CO3 (640 mg, 4.63
mmol) in DMF (10 mL). The reaction was monitored by TLC (silica
gel, toluene/petroleum ether (v/v) ) 2.5/1). After 28 h, the reaction
mixture was evaporated under reduced pressure to dryness and treated
with dichloromethane and water to remove inorganic salts. The organic
layer was concentrated in vacuo and purified by column chromatog-
raphy (silica gel, toluene/petroleum ether (v/v) ) 2.5/1). The second
fraction was identified as diporphyrin 3a and obtained in 65% yield.
1H NMR (C6D6), δ (ppm): 9.04 (d, 4H, 3JH-H ) 4.8 Hz, pyrrole), 8.89
(d, 4H, 3JH-H ) 4.8 Hz, pyrrole), 8.86 (d, 4H, 3JH-H ) 4.8 Hz, pyrrole),
C114H103N8O2, m/e 1615.8204; found, m/e 1615.8132.
I-Rh[TMP-O(CH2)6O-TMP]Rh-I (4a). In a three-neck flask fitted
with a reflux condenser and an addition funnel, a solution of
[Rh(CO)2Cl]2 (88 mg, 0.226 mmol) in dry 1,2-dichloroethane (10 mL)
were added dropwise under argon to a suspension containing dipor-
phyrin 3a (52.4 mg, 0.033 mmol) and anhydrous NaOAc (44 mg, 0.536
mmol) in 1,2-dichloroethane (18 mL). The resulting reaction mixture
was refluxed (∼80 °C) under argon for 48 h. After the mixture was
cooled to room temperature, I2 was added in two stages, 44 mg (0.173
mmol) initially and an additional 44 mg (0.173 mmol) after 2 h. The
reaction mixture was stirred overnight at room temperature under argon.
3
3
8.83 (d, 4H, JH-H ) 4.8 Hz, pyrrole), 7.98 (d, 4H, JH-H ) 8.5 Hz,
o-phenyl), 7.18 (s, 12H, m-phenyl), 7.14 (d, 4H,3JH-H ) 8.5 Hz, m′-
phenyl), 3.88 (t, 4H, 3JH-H ) 6.1 Hz, -OCH2-), 2.45 (s, 12H, p-CH3),
2.41 (s, 6H, p′-CH3), 1.97 (s, 24H, o-CH3), 1.85 (s, 12H, o′-CH3), 1.54-

5324 Inorganic Chemistry, Vol. 39, No. 23, 2000
Zhang and Wayland
Filtration and concetration gave a crude material which was treated
with CH2CI2 and a saturated Na2S2O3 aqueous solution for removal of
excess iodine. The organic phase was concentrated and purified by
column chromatography (silica gel, CH2CI2/hexane (v/v) ) 5/1) to give
iodorhodium(III) diporphyrin complex 4a in 75% yield. 1H NMR
mg, 0.375 mmol) in aqueous NaOH (0.1 M, 2.0 mL) to the above
solution under argon effected a color change from deep red to dark
brown, indicating the formation of the RhI[TMP-O(CH2)6O-TMP]RhI
dianion. The resulting solution was stirred for 1.5 h. Addition of CH3I
(0.2 mL, 3.2 mmol) resulted in the formation of methylrhodium(III)
diporphyrin complex 5a as a light orange precipitate, which was
collected by filtration and purified by column chromatography (silica
gel, C6H6) to give 5a in 85% yield. The addition of 13CH3I instead of
CH3I afforded the 13C derivative of the complex 5a, H313C-Rh[TMP-
3
(C6D6), δ (ppm): 9.05 (d, 4H, JH-H ) 4.9 Hz, pyrrole), 8.90 (d, 4H,
3JH-H ) 4.9 Hz, pyrrole), 8.87 (s, 8H, pyrrole), 8.17 (dd, 2H, 3JH-H
)
4
3
8.4 Hz, JH-H ) 2.1 Hz, o-phenyl), 7.94 (dd, 2H, JH-H ) 8.4 Hz,
4JH-H ) 2.1 Hz, o′-phenyl), 7.28 (dd, 2H,3JH-H ) 8.4 Hz, 4JH-H ) 2.6
3
4
1
Hz, m-phenyl), 7.10 (dd, 2H, JH-H ) 8.4 Hz, JH-H ) 2.6 Hz, m′-
phenyl), 7.25 (s, 4H, m′′-phenyl), 7.21 (s, 2H, m′′′-phenyl), 7.09 (s,
O(CH2)6O-TMP]Rh-13CH3. H NMR (C6D6), δ (ppm): 9.00 (d, 4H,
3
3JH-H ) 4.9 Hz, pyrrole), 8.82 (d, 4H, JH-H ) 4.9 Hz, pyrrole), 8.78
3
3
4
2H, m′′′′-phenyl), 7.05 (s, 4H, m′′′′′-phenyl), 3.88 (t, 4H, JH-H ) 6.1
(s, 8H, pyrrole), 8.19 (dd, 2H, JH-H ) 8.4 Hz, JH-H ) 2.1 Hz,
3 4
Hz, -OCH2-), 2.45 (s, 18H, p-CH3), 2.37 (s, 12H, o-CH3), 2.26 (s,
6H, o′-CH3), 1.82 (s, 6H, o′′-CH3), 1.79 (s, 12H, o′′′-CH3), 2.01 (m,
4H, -OCCH2-), 1.63 (m, 4H, -CCH2CH2C-). UV-vis (CHCl3), λmax
(nm): 532, 420. FAB-MS for C112H102N8O2Rh2I2: m/e 2052 (M+), 1925
o-phenyl), 8.02 (dd, 2H, JH-H ) 8.4 Hz, JH-H ) 2.1 Hz, o′-phenyl),
3 4
7.31 (dd, 2H, JH-H ) 8.4 Hz, JH-H ) 2.6 Hz, m-phenyl), 7.18 (dd,
3
4
2H, JH-H ) 8.4 Hz, JH-H ) 2.6 Hz, m′-phenyl), 7.24 (s, 4H, m′′-
phenyl), 7.20 (s, 2H, m′′′-phenyl), 7.10 (s, 2H, m′′′′-phenyl), 7.08 (s,
-
-
3
(M+ I), 1798 (M+ 2I).
4H, m′′′′′-phenyl), 3.92 (t, 4H, JH-H ) 6.1 Hz, -OCH2-), 2.45 (s,
18H, p-CH3), 2.33 (s, 12H, o-CH3), 2.23 (s, 6H, o′-CH3), 1.78 (s, 6H,
o′′-CH3), 1.73 (s, 12H, o′′′-CH3), 1.86 (m, 4H, -OCCH2-), 1.58 (m,
I-Rh[TMP-O(CH2)11O-TMP]Rh-I (4b). The iodorhodium(III) di-
porphyrin complex 4b was prepared in 73% yield from diporphyrin
2
4H, -CCH2CH2C-), -5.29 (dd, 6H, Rh-13CH3, J103Rh-H ) 2.9 Hz,
1
3b by a procedure analogous to that given for complex 4a. H NMR
1J13C-H ) 141.5 Hz). 13C NMR (CD3C6D5), δ (ppm): -13.58 (qd,
1J103Rh-13C ) 29 Hz, 1JH-13C ) 141.5 Hz). UV-vis (C6H6), λmax (nm):
522, 414. FAB-HRMS (M+): calcd for C11213C2H108N8O2Rh2, m/e
1828.6773; found, m/e 1828.6842.
3
(C6D6), δ (ppm): 9.06 (d, 4H, JH-H ) 4.9 Hz, pyrrole), 8.91 (d, 4H,
3JH-H ) 4.9 Hz, pyrrole), 8.89 (s, 8H, pyrrole), 8.20 (dd, 2H, 3JH-H
)
4
3
8.4 Hz, JH-H ) 2.1 Hz, o-phenyl), 7.92 (dd, 2H, JH-H ) 8.4 Hz,
4JH-H ) 2.1 Hz, o′-phenyl), 7.24 (dd, 2H, 3JH-H ) 8.4 Hz, 4JH-H ) 2.6
3
4
Hz, m-phenyl), 7. 07 (dd, 2H, JH-H ) 8.4 Hz, JH-H ) 2.6 Hz, m′-
phenyl), 7.25 (s, 4H, m′′-phenyl), 7.21 (s, 2H, m′′′-phenyl), 7.09 (s,
H3C-Rh[TMP-O(CH2)11O-TMP]Rh-CH3 (5b). The methylrhod-
ium(III) diporphyrin complex 5b was prepared in 82% yield from the
iodorhodium(III) diporphyrin complex 4b by a procedure analogous
to that given for complex 5a. 1H NMR (C6D6), δ (ppm): 8.98 (d, 4H,
3
2H, m′′′′-phenyl), 7.05 (s, 4H, m′′′′′-phenyl), 3.88 (t, 4H, JH-H ) 6.1
Hz, -OCH2-), 2.45 (s, 18H, p-CH3), 2.33 (s, 12H, o-CH3), 2.25 (s,
6H, o′-CH3), 1.81 (s, 18H, o′′-CH3), 2.10 (m, 4H, -OCCH2-), 1.55-
1.32 (m, 14H, -C(CH2)7C-). UV-vis (CHCl3), λmax (nm): 530, 422.
3
3JH-H ) 4.9 Hz, pyrrole), 8.81 (d, 4H, JH-H ) 4.9 Hz, pyrrole), 8.78
3
4
(s, 8H, pyrrole), 8.17 (dd, 2H, JH-H ) 8.4 Hz, JH-H ) 2.1 Hz,
-
3
4
FAB-MS for C117H112N8O2Rh2I2: 1868 (M+ 2I).
o-phenyl), 8.04 (dd, 2H, JH-H ) 8.4 Hz, JH-H ) 2.1 Hz, o′-phenyl),
3 4
7.28 (dd, 2H, JH-H ) 8.4 Hz, JH-H ) 2.6 Hz, m-phenyl), 7.14 (dd,
I-Rh[DMTMP-O(CH2)5O-DMTMP]Rh-I (4c). The iodorhod-
ium(III) diporphyrin complex 4c was prepared in 70% yield from
diporphyrin 3c by a procedure analogous to that given for complex
4a. 1H NMR (C6D6), δ (ppm): 8.93 (d, 4H, 3JH-H ) 4.9 Hz, pyrrole),
8.86 (d, 4H, 3JH-H ) 4.9 Hz, pyrrole), 8.84 (s, 8H, pyrrole), 7.23, 7.08,
7.03 (three s, 16H, arom), 4.00 (t, 4H, 3JH-H ) 6.1 Hz, -CH2O), 2.44
(s, 18H, p-CH3), 2.39, 2.36 (two s, 24H, o-CH3), 2.16 (m, 6H, -CH2-
CH2CH2-), 1.80, 1.75 (two s, 24H, o-CH3). UV-vis (CH2Cl2), λmax
(nm): 528, 420. FAB-MS for C115H108N8O2Rh2I2: m/e 2093 (M+), 1965
3
4
2H, JH-H ) 8.4 Hz, JH-H ) 2.6 Hz, m′-phenyl), 7.24 (s, 4H, m′′-
phenyl), 7.20 (s, 2H, m′′′-phenyl), 7.10 (s, 2H, m′′′′-phenyl), 7.08 (s,
3
4H, m′′′′′-phenyl), 3.92 (t, 4H, JH-H ) 6.0 Hz, -OCH2-), 2.45 (s,
18H, p-CH3), 2.34 (s, 12H, o-CH3), 2.23 (s, 6H, o′-CH3), 1.78 (s, 6H,
o′′-CH3), 1.73 (s, 12H, o′′′-CH3), 1.87 (m, 4H, -OCCH2-), 1.58 (m,
2
4H, -C(CH2)7C-), -5.29 (dd, 6H, Rh-13CH3, J103Rh-H ) 2.9 Hz,
1J13C-H ) 141.5 Hz). 13C NMR (CD3C6D5), δ (ppm): -13.58 (qd,
1J103Rh-13C ) 29 Hz, 1JH-13C ) 141.5 Hz). UV-vis (C6H6), λmax (nm):
523, 413. FAB-HRMS (MH+): calcd for C11713C2H118N8O2Rh2, m/e
1899.7653; found, m/e 1899.7697.
-
-
(M+ I), 1838 (M+ 2I).
I-Rh[DMTMP-O(CH2)6O-DMTMP]Rh-I (4d). The iodorhodium-
(III) diporphyrin complex 4d was in 65% yield prepared from
diporphyrin 3d by a procedure analogous to that given for complex
4a. 1H NMR (C6D6), δ (ppm): 8.87 (d, 4H, 3JH-H ) 4.9 Hz, pyrrole),
8.84 (d, 4H, 3JH-H ) 4.9 Hz, pyrrole), 8.81 (s, 8H, pyrrole), 7.23, 7.08,
7.03 (three s, 16H, arom), 4.00 (t, 4H, 3JH-H ) 6.1 Hz, -CH2O), 2.44
(s, 18H, p-CH3), 2.39, 2.36 (two s, 24H, o-CH3), 2.16 (m, 6H, -CH2-
CH2CH2-), 1.80, 1.75 (two s, 24H, o-CH3). UV-vis (CH2Cl2), λmax
(nm): 529, 420. FAB-MS for C116H110N8O2Rh2I2: m/e 2107 (M+), 1979
H3C-Rh[DMTMP-O(CH2)5O-DMTMP]Rh-CH3 (5c). The me-
thylrhodium(III) diporphyrin complex 5c was prepared in 84% yield
from the iodorhodium(III) diporphyrin complex 4c by a procedure
1
analogous to that given for complex 5a. H NMR (C6D6), δ (ppm):
3
3
8.84 (d, 4H, JH-H ) 4.9 Hz, pyrrole), 8.78 (d, 4H, JH-H ) 4.9 Hz,
pyrrole), 8.76 (s, 8H, pyrrole), 7.22 (s, 8H, arom), 7.08 (s, 4H, arom),
4.01 (t, 4H, 3JH-H ) 6.1 Hz, -OCH2-), 2.44 (s, 18H, p-CH3), 2.30 (s,
6H, o-CH3), 2.27 (s, 18H, o′-CH3), 1.90 (m, 6H, -CH2CH2CH2-), 1.78
(M+ I), 1852 (M+ 2I).
(s, 6H, o′′-CH3), 1.74 (s, 18H, o′′′-CH3), -5.24 (d, 6H, RhCH3, 2JRh-CH
-
-
3
1
) 2.8 Hz). 13C NMR (CD3C6D5), δ (ppm): -13.58 (qd, J103Rh-13C
)
I-Rh[TMP-O(m-CH2C6H4CH2)O-TMP]Rh-I (4e). The iodo-
rhodium(III) diporphyrin complex 4e was prepared in 74% yield from
diporphyrin 3e by a procedure analogous to that given for complex
4a. 1H NMR (C6D6), δ (ppm): 9.02 (d, 4H, 3JH-H ) 4.9 Hz, pyrrole),
8.88 (d, 4H, 3JH-H ) 4.9 Hz, pyrrole), 8.83 (s, 8H, pyrrole), 8.14 (dd,
1
29 Hz, JH-13C ) 141.5 Hz). UV-vis (C6H6), λmax (nm): 522, 414.
-
FAB-MS for C117H114N8O2Rh2: m/e 1869 (M+), 1854 (M+ CH3),
1839 (M+ - 2CH3). FAB-HRMS (MH+): calcd for C117H114N8O2Rh2:
m/e 1868.7177; found, m/e 1868.7102.
3
4
3
2H, JH-H ) 8.3 Hz, JH-H ) 2.2 Hz, o-phenyl), 8.00 (dd, 2H, JH-H
H3C-Rh[DMTMP-O(CH2)6O-DMTMP]Rh-CH3 (5d). The me-
thylrhodium(III) diporphyrin complex 5d was prepared in 80% yield
from the iodorhodium(III) diporphyrin complex 4d by a procedure
4
3
) 8.3 Hz, JH-H ) 2.2 Hz, o′-phenyl), 7.27 (dd, 2H, JH-H ) 8.3 Hz,
4JH-H ) 2.6 Hz, m-phenyl), 7.10 (dd, 2H, 3JH-H ) 8.3 Hz, 4JH-H ) 2.6
Hz, m′-phenyl), 7.24 (s, 6H, m′′-phenyl), 7.20 (s, 2H, m′′′-phenyl), 7.10
(s, 2H, m′′′′-phenyl), 7.08 (s, 6H, m′′′′′-phenyl), 5.00 (s, 4H, -OCH2-),
2.45 (s, 18H, p-CH3), 2.33 (s, 12H, o-CH3), 2.22 (s, 6H, o′-CH3), 1.77
(s, 6H, o′′-CH3), 1.72 (s, 12H, o′′′-CH3). UV-vis (CHCl3), λmax (nm):
532, 420. FAB-MS for C114H98N8O2Rh2I2: m/e 2071 (MH+), 1925
1
analogous to that given for complex 5a. H NMR (C6D6), δ (ppm):
3
3
8.84 (d, 4H, JH-H ) 4.9 Hz, pyrrole), 8.77 (d, 4H, JH-H ) 4.9 Hz,
pyrrole), 8.76 (s, 8H, pyrrole), 7.21 (s, 8H, m-phenyl), 7.07 (s, 8H,
3
m′-phenyl), 4.00 (t, 4H, JH-H ) 5.8 Hz, -OCH2-), 2.44 (s, 18H,
p-CH3), 2.29 (s, 6H, o′-CH3), 2.27 (s, 18H, o′′-CH3), 1.78 (s, 6H, o′′′-
CH3), 1.74 (s, 18H, o′′′′-CH3), 1.85 (m, 4H, -OCCH2-), 1.66 (m, 4H,
-CCH2CH2C-), -5.25 (dd, 6H, Rh-13CH3, 2J103Rh-H ) 2.9 Hz, 1J13C-H
) 141.5 Hz). 13C NMR (C6D6), δ (ppm): -14.00 (qd, 1J103Rh-13C ) 29
Hz, 1JH-13C ) 141.5 Hz). UV-vis (C6H6), λmax (nm): 522, 415. FAB-
HRMS (M+): calcd for C118H116N8O2Rh2, m/e 1882.7333; found, m/e
1882.7403.
-
-
(MH+
I), 1798 (MH+
2I). FAB-HRMS (MH+): calcd for
C114H98N8O2Rh2I2, m/e 2071.4090; found, m/e 2071.4163.
H3C-Rh[TMP-O(CH2)6O-TMP]Rh-CH3 (5a). The iodorhodium-
(III) diporphyrin complex 4a (69.8 mg, 0.034 mmol) was dissolved in
ethanol (25 mL) by stirring at 60 °C for 40 min. The resulting deep
red solution was filtered in air into a two-neck round-bottom flask and
flushed with argon for 40 min. Addition of an excess of NaBH4 (14.2
H3C-Rh[TMP-O(m-CH2C6H4CH2)O-TMP]Rh-CH3 (5e). The

Rhodium(II) Porphyrin Complexes
Inorganic Chemistry, Vol. 39, No. 23, 2000 5325
methylrhodium(III) diporphyrin complex 5e was prepared in 85% yield
from the iodorhodium(III) diporphyrin complex 4e by a procedure
analogous to that given for complex 5a. H NMR (C6D6), δ (ppm):
temperature dependence study. EPR (90 K, toluene): g1,2 ) 2.64, g3
) 1.90, A(103Rh)g3 ∼ 158 MHz.
1
Reactions of 6a-e with Hydrogen. Weighed samples of CH3-(TMP-
O(CH2)nO-TMP)Rh-CH3 (5) (∼0.5 mg) were placed in vacuum-
adapted NMR tubes and evacuated prior to vacuum transfer of C6D6
(∼0.5 mL) as solvent. The solutions were photolyzed for 6 h in a
Rayonet photoreactor (λ > 350 nm) which is known to result in the
complete conversion of CH3-(TMP-O(CH2)nO-TMP)Rh-CH3 (5) to
‚Rh(TMP-O(CH2)nO-TMP)Rh‚ (6). The benzene-d6 solution of ‚Rh-
(TMP-O(CH2)nO-TMP)Rh‚ (6) was evacuated to dryness followed by
sequential vacuum transfer of C6D6 (∼0.6 mL) and hydrogen gas (P
) 540 Torr). The products were identified as H-(TMP-O(CH2)nO-
TMP)Rh-H (8).
3
3
8.97 (d, 4H, JH-H ) 4.9 Hz, pyrrole), 8.81 (d, 4H, JH-H ) 4.9 Hz,
pyrrole), 8.77 (s, 8H, pyrrole), 8.16 (dd, 2H, 3JH-H ) 8.3 Hz, 4JH-H
)
3
4
2.2 Hz, o-phenyl), 8.03 (dd, 2H, JH-H ) 8.3 Hz, JH-H ) 2.2 Hz,
o′-phenyl), 7.33 (dd, 2H, 3JH-H ) 8.3 Hz, 4JH-H ) 2.6 Hz, m-phenyl),
3
4
7.17 (dd, 2H, JH-H ) 8.3 Hz, JH-H ) 2.6 Hz, m′-phenyl), 7.24 (s,
6H, m′′-phenyl), 7.20 (s, 2H, m′′′-phenyl), 7.10 (s, 2H, m′′′′-phenyl),
7.08 (s, 6H, m′′′′′-phenyl), 5.00 (s, 4H, -OCH2-), 2.45 (s, 18H, p-CH3),
2.33 (s, 12H, o-CH3), 2.22 (s, 6H, o′-CH3), 1.77 (s, 6H, o′′-CH3), 1.72
(s, 12H, o′′′-CH3), -5.31 (dd, 6H, Rh-13CH3, J103Rh-H ) 2.9 Hz,
2
1J13C-H ) 141.5 Hz). 13C NMR (CD3C6D5), δ (ppm): -13.6 (qd,
1J103Rh-13C ) 29 Hz, 1JH-13C ) 141.5 Hz). FAB-HRMS (MH+): calcd
for C11413C2H104N8O2Rh2, m/e 1849.6537; found, m/e 1849.6530.
(1) H-Rh[TMP-O(CH2)6O-TMP]Rh-H (7a): 1H NMR (C6D6)
δ 8.96 (d, 2H, 3JH-H ) 4.9 Hz, pyrrole), 8.81 (d, 2H, 3JH-H ) 4.9 Hz,
[‚RhII[TMP-O(CH2)6O-TMP]RhII‚] (6a). Degassed benzene solu-
tion of the methylrhodium(III) diporphyrin complex 5a (0.5-0.8 mg/
0.3 mL) in a vacuum-adapted NMR tube was photolyzed (λ > 350
nm) for 6 h in a Rayonet photoreactor. The solvent along with methane
and toluene formed in the reaction were removed under vacuum to
3
3
pyrrole), 8.80 (d, 2H, JH-H ) 4.9 Hz, pyrrole), 8.79 (d, 2H, JH-H
)
3
4
4.9 Hz, pyrrole), 8.15 (dd, 1H, JH-H ) 8.4 Hz, JH-H ) 2.1 Hz,
o-phenyl), 7.92 (dd, 1H, JH-H ) 8.4 Hz, JH-H ) 2.1 Hz, o′-phenyl),
3
4
3
4
7.28 (dd, 1H, JH-H ) 8.4 Hz, JH-H ) 2.6 Hz, m′-phenyl), 7.10 (dd,
3
4
1H, JH-H ) 8.4 Hz, JH-H ) 2.6 Hz, m′-phenyl), 7.23 (s, 4H, m′′-
phenyl), 7.19 (s, 2H, m′′′-phenyl), 7.11 (s, 6H, m′′′′-phenyl), 3.92 (t,
1
give 6a as a solid in quantitative yield. H NMR (C6D6, 296 K), δ
(ppm): 18.57 (br s, 16H, pyrrole), 11.36 (br s, 8H, o-H + m-H), 8.90
(s, 12H, m′-H), 5.10 (s, 4H, -OCH2-), 3.58 (br s, 36H, o-CH3), 3.52
(s, 18H, p-CH3), 2.77 (s, 8H, -CH2CH2CH2CH2-). A linear relationship
between the pyrrole chemical shift vs the inverse temperature was
obtained from the temperature dependence study. EPR (90 K, tolu-
ene): g1,2 ) 2.64, g3 ) 1.90, A(103Rh)g3 ∼ 158 MHz. EPR for the
triphenylphosphine adduct 7a (90 K, toluene): g1,2 ) 2.17, g3 ) 2.00,
A(31P)g1,2 ) 756 MHz, A(31P)g3 ) 1016 MHz, A(103Rh)g3 ) 61 MHz.
EPR for the superoxo complex of the triphenylphosphine adduct 8a
(90 K, toluene): g1 ) 2.08, g2 ) 2.005, g3 ) 1.996, A(31P)g1 ) 50.9
MHz, A(31P)g2 ) 50.5 MHz, A(31P)g3 ) 50.3 MHz.
3
4H, JH-H ) 6.1 Hz, -OCH2-), 2.45 (s, 12H, p-CH3), 2.43 (s, 6H,
p′-CH3), 2.28 (s, 12H, o′-CH3), 2.05 (s, 6H, o′-CH3), 1.87 (s, 6H, o′′-
CH3), 1.76 (s, 12H, o′′′′-CH3), 1.86 (m, 4H, -OCCH2-), 1.57 (m, 4H,
1
-CCH2CH2C-), -40.07 (d, 1H, Rh-H, J103Rh-H ) 43.4 Hz,); FAB
-
MS for C112H104H8O2Rh2, m/e 1798 (M+ H).
(2) H-Rh[TMP-O(CH2)11O-TMP]Rh-H (7b): 1H NMR (C6D6) δ
3
3
8.94 (d, 2H, JH-H ) 4.9 Hz, pyrrole), 8.81 (d, 2H, JH-H ) 4.9 Hz,
3
3
pyrrole), 8.80 (d, 2H, JH-H ) 4.9 Hz, pyrrole), 8.79 (d, 2H, JH-H
4.9 Hz, pyrrole), 8.12 (dd, 1H, JH-H ) 8.4 Hz, JH-H ) 2.1 Hz,
o-phenyl), 7.88 (dd, 1H, JH-H ) 8.4 Hz, JH-H ) 2.1 Hz, o′-phenyl),
7.26 (dd, 1H, JH-H ) 8.4 Hz, JH-H ) 2.6 Hz, m-phenyl), 7.06 (dd,
1H, JH-H ) 8.4 Hz, JH-H ) 2.6 Hz, m′-phenyl), 7.23 (s, 6H, m′′-
phenyl), 7.11 (s, 6H, m′′′-phenyl), 7.11 (s, 6H, m′′′′-phenyl), 3.92 (t,
4H, JH-H ) 6.1 Hz, -OCH2-), 2.45 (s, 12H, p-CH3), 2.43 (s, 6H,
)
3
4
3
4
3
4
[‚Rh(II)[TMP-O(CH2)11O-TMP]Rh(II)‚] (6b). The rhodium(II)
porphyrin bimetalloradical complex 6b was prepared in quantitative
yield from the methylrhodium(III) diporphyrin complex 5b by a
3
4
3
1
procedure analogous to that given for bimetalloradical 6a. H NMR
p′-CH3), 2.28 (s, 12H, o′-CH3), 2.05 (s, 6H, o′-CH3), 1.87 (s, 6H, o′′-
CH3), 1.75 (s, 12H, o′′′-CH3), 1.87 (m, 4H, -OCCH2-), 1.58 (m, 4H,
(C6D6, 296 K), δ (ppm): 18.57 (br s, 16H, pyrrole), 11.36 (br s, 8H,
o-H + m-H), 8.90 (s, 12H, m′-H), 5.10 (s, 4H, -OCH2-), 3.58 (br s,
36H, o-CH3), 3.52 (s, 18H, p-CH3), 2.77 (s, 18H, -(CH2)9-). A linear
relationship between the pyrrole chemical shift vs the inverse temper-
ature was obtained from the temperature dependence study. EPR (90
K, toluene): g1,2 ) 2.64, g3 ) 1.90, A(103Rh)gz ∼ 158 MHz.
1
-C(CH2)7C-), -40.07 (d, 1H, Rh-H, J103Rh-H ) 43.5 Hz).
(3) H-Rh[DMTP-O(CH2)5O-DMTMP]Rh-H (7c): 1H NMR
(C6D6) δ 8.86-8.75 (m, 16H, pyrrole H), 7.22, 7.08 (two s, 16H, arom),
4.01 (t, 4H, -CH2O), 2.44 (s, 18H, p-CH3), 2.29-2.15 (five s, 24H,
o-CH3), 1.90 (m, 6H, -CH2CH2CH2-), 1.84, 1.80 (two s, 24H, o-CH3),
-40.00 (d, 1H, Rh-H, JRh-H′ ) 43.4 Hz).
[‚Rh(II)[DMTMP-O(CH2)5O-DMTMP]Rh(II)‚] (6c). The rhod-
ium(II) porphyrin bimetalloradical complex 6c was prepared in
quantitative yield from the methylrhodium(III) diporphyrin complex
(4) H-Rh[DMTMP-O(CH2)6O-DMTMP]Rh-H (7d): 1H NMR
(C6D6) δ 8.85-8.75 (m, 16H, pyrrole H), 7.22 (s, 8H, m-phenyl), 7.08
(s, 8H, m-phenyl), 4.00 (t, 4H, -CH2O), 2.43 (s, 18H, o′-CH3), 2.29
(s, 6H, o′-CH3), 2.27 (s, 18H, o′′-CH3), 1.80 (s, 6H, o′′′-CH3), 1.74 (s,
18H, o′′′′-CH3), 1.85 (m, 4H, -OCCH2-), 1.66 (m, 4H, -CCH2CH2C-),
-40.00 (d, 1H, Rh-H, JRh-H′ ) 43.4 Hz).
1
5c by a procedure analogous to that given for bimetalloradical 6a. H
NMR (C6D6), δ (ppm): 18.45 (broad, 16H, pyrrole H), 8.88 (broad,
16H, arom), 3.57 (br s, 48H, o-CH3), 3.51 (s, 18H, p-CH3). A linear
relationship between the pyrrole chemical shift vs the inverse temper-
ature was obtained from the temperature dependence study. UV-vis
(C6H6), λmax (nm): 538, 426. FAB-MS for C115H107N8O2Rh2: m/e 1840
(MH+).
(5) H-Rh[TMP-O(m-CH2C6H4CH2)O-TMP]Rh-H (7e): 1H NMR
3
3
(C6D6) δ 8.93 (d, 4H, JH-H ) 4.9 Hz, pyrrole), 8.81 (d,4H, JH-H
)
3
[‚Rh(II)[DMTMP-O(CH2)6O-DMTMP]Rh(II)‚] (6d). The rhod-
ium(II) porphyrin bimetalloradical complex 6d was prepared in
quantitative yield from the methylrhodium(III) diporphyrin complex
5d by a procedure analogous to that given for bimetalloradical 6a. 1H
NMR (C6D6, 296 K), δ (ppm): 18.50 (br s, 16H, pyrrole), 8.87 (s,
16H, m-phenyl), 5.22 (s, 4H, -OCH2-), 3.57 (br s, 48H, o-CH3), 3.51
(s, 18H, p-CH3), 2.90 (s, 8H, -CH2CH2CH2CH2-). A linear relationship
between the pyrrole chemical shift vs the inverse temperature was
obtained from the temperature dependence study. UV-vis (C6H6), λmax
(nm): 538, 426. FAB-MS for C116H110N8O2Rh2: m/e 1854 (MH+).
4.9 Hz, pyrrole), 8.80 (d, 4H, JH-H ) 4.9 Hz, pyrrole), 8.79 (d, 4H,
3JH-H ) 4.9 Hz, pyrrole), 8.12 (dd, 2H, JH-H ) 8.4 Hz, JH-H ) 2.2
3
4
3
4
Hz, o-phenyl), 7.89 (dd, 2H, JH-H ) 8.3 Hz, JH-H ) 2.2 Hz, o′-
phenyl), 7.30 (dd, 2H, JH-H ) 8.3 Hz, JH-H ) 2.6 Hz, m-phenyl),
3
4
3
3
7.15 (dd, 2H, JH-H ) 8.3 Hz, JH-H ) 2.6 Hz, m′-phenyl), 7.75 (s,
1H, spacer-phenyl), 7.43 (d, 2H, 3JH-H ) 7.4 Hz, spacer-phenyl), 7.35
(t, 1H, 3JH-H ) 7.4 Hz, spacer-phenyl), 7.22 (s, 4H, m′′-phenyl), 7.20
(s, 2H, m′′′-phenyl), 7.11 (s, 2H, m′′′′-phenyl), 7.10 (s, 4H, m′′′′′-
phenyl), 5.00 (s, 4H, -OCH2-), 2.44 (s, 12H, p-CH3), 2.43 (s, 6H,
p′-CH3), 2.28 (s, 12H, o-CH3), 2.04 (s, 6H, o′-CH3), 1.87 (s, 6H, o′′-
CH3), 1.75 (s, 12H, o′′′-CH3), -40.09 (d, 1H, Rh-H, JRh-H ) 43.5
Hz).
[‚Rh(II)[TMP-O(m-CH2C6H4CH2)O-TMP]Rh(II)‚] (6e). The rhod-
ium(II) porphyrin bimetalloradical complex 6e was prepared in
quantitative yield from the methylrhodium(III) diporphyrin complex
1
5e by a procedure analogous to that given for bimetalloradical 6a. H
Acknowledgment. This research was supported by the
Department of Energy Division of Chemical Sciences, Office
of Science, through Grant DE-FG02-86ER-13615. <<
NMR (C6D6), δ (ppm): 18.4 (br s, 16H, pyrrole), 11.3 (br s, 8H, o-H
+ m-H), 8.90 (s, 16H, m′-H), 5.10 (s, 4H, -OCH2-), 3.58 (br s, 36H,
o-CH3), 3.51 (s, 18H, p-CH3). A linear relationship between the pyrrole
chemical shift vs the inverse temperature was obtained from the
IC0006302