Interaction of Rh(I) with meso-arylsapphyrins and -rubyrins: First structural characterization of bimetallic hetero-rubyrin complex

Article abstract of DOI:10.1021/ic000703h

The ligational behavior of meso-arylsapphyrins and rubyrins toward Rh(I) is investigated. Sapphyrins form monometallic complexes with coordination of one imine and amine type nitrogens of the bipyrrole unit in an η² fashion. The Rh(I) coordination is completed by the presence of two ancillary carbon monoxide ligands. Rubyrins form both monometallic and bimetallic complexes. Two types of bimetallic complexes have been isolated. In the first type, both rhodium atoms are projected above the mean rubyrin plane, while in the second type, one rhodium atom is projected above and the other below the mean plane. Detailed ¹H and 2D NMR spectral analyses along with IR and UV-visible spectra of the complexes confirm the proposed binding modes for the rhodium complexes. Furthermore, the single-crystal X-ray analysis of one of the bimetallic complexes of rubyrin shows a bowl-shaped symmetric structure where both Rh(I) atoms are projected above the mean rubyrin plane at an angle of 71.73°. The geometry around each rhodium center is approximately square planar [N1-Rh1-N2, 80.38(9)°; C15-Rh1-C16, 86.95(14)°; N1-Rh1-C15, 97.13(12)°; and N2-RH1-C16, 94.97(12)°]. The observed distance of 4.313 A between the two rhodium centers reveals very little interaction between the two rhodium atoms. This type of metal binding is accompanied by a 180° ring flip of the heterocyclic ring connecting the two bipyrrole units. In dioxarubyrin, where one of the pyrrole rings of the bipyrrole unit is inverted, Rh(I) binds at the periphery to the pyrrole nitrogen, leaving the rubyrin cavity empty. The absence of one amino and one imino nitrogen on the dipyrromethene subunits in the sapphyrins and rubyrins described here forces Rh(I) to bind to bipyrrole nitrogens.

Full text of DOI:10.1021/ic000703h

Inorg. Chem. 2001, 40, 1637-1645
1637
Interaction of Rh(I) with meso-Arylsapphyrins and -Rubyrins: First Structural
Characterization of Bimetallic Hetero-rubyrin Complex†
Seenichamy Jeyaprakash Narayanan, Bashyam Sridevi, and Tavarekere K. Chandrashekar*
Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India
Ulrich Englich and Karin Ruhlandt-Senge
Department of Chemistry, Syracuse University, Syracuse, New York 13244
ReceiVed June 27, 2000
The ligational behavior of meso-arylsapphyrins and rubyrins toward Rh(I) is investigated. Sapphyrins form
monometallic complexes with coordination of one imine and amine type nitrogens of the bipyrrole unit in an η2
fashion. The Rh(I) coordination is completed by the presence of two ancillary carbon monoxide ligands. Rubyrins
form both monometallic and bimetallic complexes. Two types of bimetallic complexes have been isolated. In the
first type, both rhodium atoms are projected above the mean rubyrin plane, while in the second type, one rhodium
1
atom is projected above and the other below the mean plane. Detailed H and 2D NMR spectral analyses along
with IR and UV-visible spectra of the complexes confirm the proposed binding modes for the rhodium complexes.
Furthermore, the single-crystal X-ray analysis of one of the bimetallic complexes of rubyrin shows a bowl-
shaped symmetric structure where both Rh(I) atoms are projected above the mean rubyrin plane at an angle of
71.73°. The geometry around each rhodium center is approximately square planar [N1-Rh1-N2, 80.38(9)°;
C15-Rh1-C16, 86.95(14)°; N1-Rh1-C15, 97.13(12)°; and N2-RH1-C16, 94.97(12)°]. The ïbserved distance
of 4.313 Å between the two rhodium centers reveals very little interaction between the two rhodium atoms. This
type of metal binding is accompanied by a 180° ring flip of the heterocyclic ring connecting the two bipyrrole
units. In dioxarubyrin, where one of the pyrrole rings of the bipyrrole unit is inverted, Rh(I) binds at the periphery
to the pyrrole nitrogen, leaving the rubyrin cavity empty. The absence of one amino and one imino nitrogen on
the dipyrromethene subunits in the sapphyrins and rubyrins described here forces Rh(I) to bind to bipyrrole nitrogens.
Introduction
receptor properties for anionic substrates,4 structural diversity,5
sapphyrin-nucleobase conjugates,6 capped sapphyrins,7 and
Sapphyrin, 1, and rubyrin, 2, belong to the family of expanded
heteroatom3d,5 substitution have been exploited by various
research groups.
â-Substituted rubyrin was first reported in 1991, and the X-ray
structure of the protonated form is a planar structure.8 On the
other hand, the meso-arylrubyrins with heteroatoms show
structural diversity where planar and inverted structures are
reported.9 Further, the substitution of one or more heteroatoms
(2) Bauer, V. J.; Clive, D. L. J.; Dolphin, D.; Paine, J. B., III.; Harris, F.
L.; King, M. M.; Loder, J.; Wang, S. C.; Woodward, R. B. J. Am.
Chem. Soc. 1983, 105, 6429-6436.
porphyrins and contain five and six pyrrole rings (heterocyclic
rings), respectively.1 Specifically, in sapphyrins, the five
heterocyclic rings are linked in a cyclic manner through four
meso carbon bridges in a 1.1.1.1.0 arrangement and they contain
22 conjugated π electrons. Rubyrins contain 26 π electrons,
and the six heterocyclic rings are arranged in a 1.1.0.1.1.0
fashion with four methine bridges. After the early discovery of
sapphyrins by Woodward and co-workers,2 considerable progress
has been made recently not only on syntheses of a range of
sapphyrins but also on their rich and diverse chemistry.3 Their
(3) (a) Broadhurst, M. J.; Grigg, R.; Johnson, A. W. J. Chem. Soc., Perkin
Trans. 1 1972, 2111-2116. (b) Sessler, J. L.; Cyr, M. J.; Lynch, V.;
McGhee, E.; Ibers, J. A. J. Am. Chem. Soc. 1990, 112, 2810-2813.
(c) Sessler, J. L.; Cyr, M. J.; Burrell, A. K. Synlett 1991, 127-134.
(d) Sessler, J. L.; Cyr, M. J.; Burrell, A. K. Tetrahedron 1992, 48,
9661-9672. (e) Sessler, J. L.; Lisowski, J.; Boudreaux, K. A.; Lynch,
V.; Barry, J.; Kodadek, T. J. J. Org. Chem. 1995, 60, 5975-5978. (f)
Paolesse, R.; Licoccia, S.; Spagnoli, M.; Boschi, T.; Khoury, R. G.;
Smith, K. M. J. Org. Chem. 1997, 62, 5133-5137. (g) Sessler, J. L.;
Hoehner, M. C.; Gebauer, A.; Andrievsky, A.; Lynch, V. J. Org. Chem.
1997, 62, 9251-9260. (h) Chmielewski, P. J.; Latos-Grazynski, L.;
Rachlewicz, K. Chem.sEur. J. 1995, 1, 68-72. (i) Bruckner, C.;
Sternberg, E. D.; Boyle, R. W.; Dolphin, D. Chem. Commun. 1997,
1689-1690. (j) Lash, T. D.; Richter, D. T. J. Am. Chem. Soc. 1998,
120, 9965-9966. (k) Srinivasan, A.; Mahajan, S.; Pushpan, S. K.;
Kumar, M. R.; Chandrashekar, T. K. Tetrahedron Lett. 1998, 39,
1961-1964. (l) Narayanan, S. J.; Sridevi, B.; Srinivasan, A.; Chan-
drashekar, T. K.; Roy, R. Tetrahedron Lett. 1998, 39, 7389-7392.
(m) Pushpan, S. K.; Narayanan, S. J.; Srinivasan, A.; Mahajan, S.;
Chandrashekar, T. K.; Roy, R. Tetrahedron Lett. 1998, 39, 9249-
9252.
† Dedicated to Prof. S. S. Krishnamurthy on the occasion of his 60th
birthday.
* To whom correspondence should be addressed. E-mail: tkc@iitk.ac.in.
Fax: 0091-512-597436/590007.
(1) Sessler, J. L.; Weghorn, S. J. In The Porphyrin Handbook; Kadish,
K. M., Smith, K. M., Guilard, R., Eds.; Academic Press: San Diego,
2000; Vol. 2, pp 55-124.
10.1021/ic000703h CCC: $20.00 © 2001 American Chemical Society
Published on Web 02/21/2001

1638 Inorganic Chemistry, Vol. 40, No. 7, 2001
Narayanan et al.
Scheme 1 . Different Coordination Modes Reported for
alters the electronic structure of the ring, and this is reflected
in the spectral properties. The anion receptor properties of a
few rubyrins have also been reported very recently.10
Metallosapphyrins
Both sapphyrins and rubyrins contain heteroatoms in their
core and therefore are expected to bind transition metals in their
free base forms.11 However, the coordination chemistry of
sapphyrins and rubyrins is still in its infancy, where only a
handful of metal complexes have been structurally character-
ized.11 To the best of our knowledge, there are no reports on
the metal binding properties of rubyrins to date while a few
metal complexes of sapphyrins and hetero-sapphyrins containing
first- and third-row transition metals have been characterized.12
A summary of binding modes observed for sapphyrins is shown
2+
in Scheme 1. Only UO2 complex of monooxasapphyrin is
known to involve all the heteroatoms in the coordination mode
as in 3a.12e Most of the monometallic complexes exhibit binding
as in 3b where both in-plane and out-of-plane complexes have
been characterized.12a,c In the bimetallic complexes, the metal
atoms have been shown to bind as in 3c where each metal atom
is bridged between an imine and an amine nitrogen atom in an
approximately square planar environment around each metal
atom and where the metal planes are inclined at approximately
47° to the overall sapphyrin plane.12a,b The Co(II) ion coordi-
nates to N5 sapphyrin involving four pyrrole nitrogens (as in
3e),2 and the corresponding Zn(II) complex switches between
the symmetrical and unsymmetrical binding modes as in 3d and
3e.3c
A few metal complexes of other expanded porphyrins such
as pentaphyrin,13 hexaphyrin,14 amethyrin,15 and oxasmaragdyrin
have also been reported recently.16 These studies have set the
stage for thorough and systematic investigations on exploiting
expanded porphyrins as ligands. In this paper we report the
interaction of Rh(I) with a variety of hetero-sapphyrins and
-rubyrins. New modes of binding other than those in the
literature have been identified for hetero-sapphyrins, while for
the first time it has been shown that the hetero-rubyrins act as
ligands toward metals. In the monometallic complex, Rh(I) binds
to two nitrogens of the same bipyrrole ring to form an out-of-
plane complex in an η2 fashion. Two types of out-of-plane
bimetallic complexes, one having a bowl-shaped structure where
both the metals are projected above the plane of the macrocycle
and the second having one metal above and the other below
the plane, have been isolated. Furthermore, it has been shown
that the metal coordination in a particular mode is accompanied
by a 180° ring flip of the heterocyclic rings connecting the two
bipyrrole subunits. In dioxarubyrin where one of the pyrrole
rings of the bipyrrole unit is inverted, Rh(I) binds only at the
periphery coordinating to the pyrrole nitrogens of the inverted
ring, leaving the cavity empty.
(4) (a) Sessler, J. L.; Andrievsky, A.; Genge, J. W. AdV. Supramol. Chem.
1997, 4, 97-142. (b) Sessler, J. L.; Burrell, A. K.; Furuta, H.; Hemmi,
G. W.; Iverson, B. L.; Kral, V.; Magda, D. J.; Mody, T. D.; Shreder,
K.; Smith, D.; Weghorn, S. J. Transition Met. Supramol. Chem. 1994,
391-408. (c) Sessler, J. L.; Sansom, P. I.; Andrievsky, A.; Kral, V.
In Supramolecular Chemistry of Anions; Bianchi, A., James, K. B.,
Espana, E. G., Eds.; Wiley-VCH: New York, 1997; pp 355-419. (d)
Shionoya, M.; Furuta, H.; Lynch, V.; Harriman, A.; Sessler, J. L. J.
Am. Chem. Soc. 1992, 114, 5714-5722. (e) Sessler, J. L.; Andrievsky,
A.; Gale, P. A.; Lynch, V. Angew. Chem., Int. Ed. Engl. 1996, 35,
2782-2785. (f) Kral, V.; Furuta, H.; Shreder, K.; Lynch, V.; Sessler,
J. L. J. Am. Chem. Soc. 1996, 118, 1595-1607. (g) Iverson, B. L.;
Shreder, K.; Kral, V.; Sansom, P.; Lynch, V.; Sessler, J. L. J. Am.
Chem. Soc. 1996, 118, 1608-1616. (h) Sessler, J. L.; Andrievsky,
A.; Kral, V.; Lynch, V. J. Am. Chem. Soc. 1997, 119, 9385-9392. (i)
Sessler, J. L.; Kral, V.; Genge, J. W.; Thomas, R. E.; Iverson, B. L.
Anal. Chem. 1998, 70, 2516-2522.
(5) (a) Narayanan, S. J.; Sridevi, B.; Chandrashekar, T. K.; Vij, A.; Roy,
R. Angew. Chem., Int. Ed. 1998, 37, 3394-3397. (b) Narayanan, S.
J.; Sridevi, B.; Chandrashekar, T. K.; Vij, A.; Roy, R. J. Am. Chem.
Soc. 1999, 121, 9053-9068. (c) Srinivasan, A.; Anand, V. G.;
Narayanan, S. J.; Pushpan, S. K.; Kumar, M. R.; Chandrashekar, T.
K.; Sugiura, K.; Sakata, Y. J. Org. Chem. 1999, 64, 8693-8697. (d)
Srinivasan, A.; Pushpan, S. K.; Kumar, M. R.; Mahajan, S.; Chan-
drashekar, T. K.; Roy, R.; Ramamurthy, P. J. Chem. Soc., Perkin Trans
2 1999, 961-968. (e) Srinivasan, A.; Anand, V. G.; Pushpan, S. K.;
Chandrashekar, T. K.; Sugiura, K.; Sakata, Y. J. Chem. Soc., Perkin
Trans 2 2000, 1788-1793.
(6) (a) Kral, V.; Sessler, J. L.; Furuta, H. J. Am. Chem. Soc. 1992, 114,
8704-8705. (b) Sessler, J. L.; Furuta, H.; Kral, V. Supramol. Chem.
1993, 1, 209-220. (c) Kral, V.; Sessler, J. L. Tetrahedron 1995, 51,
539-554. (d) Sessler, J. L.; Sansom, P. I.; Kral, V.; O’Connor, D.;
Iverson, B. L. J. Am. Chem. Soc. 1996, 118, 12322-12330. (e) Sessler,
J. L.; Andrievsky, A. Chem. Commun. 1996, 1119-1120.
(7) (a) Sessler, J. L.; Brucker, E. A.; Kral, V.; Harriman, A. Supramol.
Chem. 1994, 4, 35-41. (b) Sessler, J. L.; Brucker, E. A. Tetrahedron
Lett. 1995, 36, 1175-1176.
(8) Sessler, J. L.; Morishima, T.; Lynch, V. Angew. Chem., Int. Ed. Engl.
1991, 30, 977-980.
(9) (a) Narayanan, S. J.; Srinivasan, A.; Sridevi, B.; Chandrashekar, T.
K.; Senge, M. O.; Sugiura, K.; Sakata, Y. Eur. J. Org. Chem. 2000,
2357-2360. (b) Srinivasan, A.; Pushpan, S. K.; Kumar, M. R.;
Chandrashekar, T. K.; Roy, R. Tetrahedron 1999, 55, 6671-6680.
(10) (a) Srinivasan, A.; Reddy, M. V.; Narayanan, S. J.; Sridevi, B.;
Pushpan, S. K.; Kumar, M. R.; Chandrashekar, T. K. Angew. Chem.,
Int. Ed. Engl. 1997, 36, 2598-2601. (b) Furuta, H.; Morishima, T.;
Kral, V.; Sessler, J. L. Supramol. Chem. 1993, 3, 5-8. (c) Srinivasan,
A.; Anand, V. G.; Pushpan, S. K.; Chandrashekar, T. K.; Sugiura, K.;
Sakata, Y. J. Chem. Soc., Perkin Trans. 2 2000, 1788-1793.
(11) (a) Sessler, J. L., Weghorn, S. J., Eds. In Expanded, Contracted &
Isomeric Porphyrins; Tetrahedron Organic Chemistry Series, Vol. 15;
Pergamon: New York, 1997. (b) Jasat, A.; Dolphin, D. Chem. ReV.
1997, 97, 2267-2340.
(12) (a) Burrell, A. K.; Sessler, J. L.; Cyr, M. J.; McGhee, E.; Ibers, J. A.
Angew. Chem., Int. Ed. Engl. 1991, 30, 91-93. (b) Lisowski, J.;
Sessler, J. L.; Lynch, V. Inorg. Chem. 1995, 34, 3567-3572. (c)
Sessler, J. L.; Burrell, A. K.; Lisowski, J.; Gebauer, A.; Cyr, M. J.;
Lynch, V. Bull. Soc. Chim. Fr. 1996, 133, 725-734. (d) Burrell, A.
K.; Cyr, M. J.; Lynch, V.; Sessler, J. L. Chem. Commun. 1991, 1710-
1713. (e) Sessler, J. L.; Gebauer, A.; Hoehner, M.; Lynch, V. Chem.
Commun. 1998, 1835-1836.
Results and Discussion
The modes of Rh(I) binding to the different sapphyrins and
rubyrins are characterized by mass spectra and 1H NMR, UV-
(13) (a) Gossauer, A. Chimia 1984, 38, 45-46. (b) Burrell, A. K.; Hemmi,
G.; Lynch, V.; Sessler, J. L. J. Am. Chem. Soc. 1991, 113, 4690-
4692. (c) Kral, V.; Brucker, E. A.; Hemmi, G.; Sessler, J. L.; Kralova,
J.; Bose, H. J. Bioorg. Med. Chem. 1995, 3, 573-578.
(14) Charriere, R.; Jenny, T. A.; Rexhausen, H.; Gossauer, A. Heterocycles
1993, 36, 1561-1575.
(15) (a) Sessler, J. L.; Weghorn, S. J.; Hiseada, Y.; Lynch, V. Chem.s
Eur. J. 1995, 1, 56-67. (b) Weghorn, S. J.; Sessler, J. L.; Lynch, V.;
Baumann, T. F.; Sibert, J. W. Inorg. Chem. 1996, 35, 1089-1090.
(c) Sessler, J. L.; Gebauer, A.; Scherer, M.; Lynch, V. Inorg. Chem.
1998, 37, 2703-2706.
(16) Sridevi, B.; Narayanan, S. J.; Chandrashekar, T. K.; Englich, U.; Senge,
K. R. Inorg. Chem. 2000, 39, 3669-3677.

Characterization of Hetero-rubyrin Complex
Inorganic Chemistry, Vol. 40, No. 7, 2001 1639
Figure 2. UV-visible spectra for 5 (2.126 × 10-6 M) and 8 (5.276
× 10-6 M) in CH2Cl2 in the Soret and Q-band regions.
pyrrole proton is localized on one of the bipyrrole nitrogens,
destroying the symmetry that results in the appearance of
individual doublets for each proton. The metal coordination as
in 7 also results in the presence of a symmetry axis, and as a
1
result of this, one would expect that the H NMR spectrum of
7 should be similar to that of 4 at room temperature. This is
exactly what has been observed. The metal coordination results
in the shifts of specific protons. The bipyrrole protons d and e
experience a significant shielding upon metal coordination [0.43
and 0.91 ppm for 7, 0.37 and 0.85 for 8, and 0.19 and 0.62 for
9], while the thiophene protons c and b and pyrrole protons a,
whose heteroatoms are not involved in the coordination to the
metal, experience small shifts. This observation is in agreement
with the earlier literature reports.12,16,18 This mode of metal
binding is different from other hetero-sapphyrins reported in
the literature. In general the metal binds to one imine and amine
type of nitrogen present on the dipyrromethene subunit of the
sapphyrin.12,16 But in the present case, lack of one imine and
one amine type nitrogen on the dipyrromethene subunit due to
the presence of heteroatom, the metal is forced to bind to the
imine and amine type of nitrogen present on the bipyrrole unit.
The UV-visible spectra of 5 and 8 shown in Figure 2 also
confirm the metal coordination. Both the Soret and Q bands
experience red shifts upon metal binding (for 7-9 Soret and
Q-band shifts are 35-40 nm and 25-30 nm, respectively),
which is consistent with the earlier reports.12c,19
Figure 1. 1H NMR (CDCl3) spectra of 4 (a) and 7 (b).
Scheme 2 . Synthesis of Rh(I) Complex of Modified
Sapphyrins
The metal binding mode of 10 is shown in Scheme 3. 10
shows an unusual inverted structure where one of the pyrrole
rings of each bipyrrole unit is inverted and there is a slow
flipping of these rings at room temperature, giving rise to broad
1H NMR resonances.9a Because of this ring inversion, the
pyrrole -NH protons are localized; hence, there is no tautom-
erism possible. This is confirmed by the appearance of a pyrrole
-NH signal in the shielded region (-2.5 ppm) at room
visible, and IR methods. The single-crystal X-ray structure of
one of the bimetallic complexes of rubyrin further confirms the
suggested mode of binding.
Scheme 2 shows the metal coordination to three sapphyrins,
4, 5, and 6. Rhodium binds to two bipyrrole nitrogens in a η2
fashion as in 7-9, and the coordination is completed by the
presence of two carbonmonoxide ligands in an approximate
square planar geometry. This mode of binding is arrived at by
a comparison of 1H NMR spectra of free base 4 and the rhodium
complex 7 shown in Figure 1. In 4, the bipyrrole protons d, d′
and e, e′ are equivalent among themselves because of the rapid
tautomerism at room temperature of the inner hydrogen between
the two bipyrrole nitrogens, resulting in the presence of a
symmetry axis passing between the bipyrrole ring and the
opposite pyrrole ring.5b,17 When the temperature is lowered, the
1
temperature. A comparison of H NMR spectra of 10 and its
metal derivatives is made in Figure 3. The peak assignments
1
that are marked are based on correlations observed in H-1H
correlation spectroscopy (COSY). An inspection of the figure
indicates (a) sharpening of the resonances upon metal binding,
(b) doubling of the resonances where all the peaks appear in
pairs, and (c) the appearance of peaks for the inner pyrrole -NH
protons (g, g′) in the shielded region. The sharpening of the
(18) It is documented in the literature that the â-CH protons of the ring
experience significant shielding upon metal binding to the heteroatom
of the ring. If the heteroatom is not involved in coordination, the â-CH
protons experience a deshielding.
(19) (a) Ravikanth, M.; Chandrashekar, T. K. Struct. Bonding 1995, 82,
105-188. (b) Gouterman, M. In The Porphyrins; Dolphin, D., Ed.;
Academic Press: New York, 1978; Vol. III, pp 1-165.
(17) (a) Rachlewicz, K.; Sprutta, N.; Latos-Grazynski, L.; Chmielewski,
P. J.; Szterenberg, L. J. Chem. Soc., Perkin Trans. 1998, 959-967.
(b) Rachlewicz, K.; Sprutta, N.; Chmielewski, P. J.; Latos-Grazynski,
L. J. Chem. Soc., Perkin Trans. 1998, 969-975.

1640 Inorganic Chemistry, Vol. 40, No. 7, 2001
Narayanan et al.
Figure 4. UV-visible spectra for 10 (3.934 × 10-6 M) and 11 and
12 (12.27 × 10-6 M) in CH2Cl2 in the Soret and Q-band regions.
Scheme 4 . Synthesis of Mono- and Bimetallic Rh(I)
Complexes of Heteroatom Rubyrins
Figure 3. 1H NMR (CDCl3) spectra of 10 (a) and 11 and 12 (b).
Scheme 3 . Synthesis Scheme for Rh(I) Interaction with
Dioxarubyrins
proved to be futile. Significant shielding of c and d protons
(0.24 and 0.36 ppm for cc′ protons and 0.56 and 0.54 ppm for
dd′ protons) and deshielding of a and b protons (0.94 and 1.42
ppm for aa′ and 0.54 and 0.6 ppm for bb′ protons) upon metal
coordination further support the suggested binding mode. Also,
the appearance of these protons as quartets suggests the presence
of three-bond coupling between the -NH protons and the a
and b protons [3J ) 2 Hz]. The e and f protons, which are away
from the metal center, experience minimum shifts upon metal
binding. The two isomers 11 and 12 are different only with
respect to the presence of CO ligands in cis and trans geometry
with respect to the rhodium atom. This mode of periphery metal
binding is very unusual and is somewhat similar to that proposed
for Pd2+ binding to the isomeric mixture of hexaphyrins14 where
the two pyrrole rings rotate outward by 180° prior to the
coordination to form the periphery-bound Pd2+ hexaphyrin
complex. The UV-visible spectra (Figure 4) further confirm
the formation of metal complexes. Small shifts (8 nm for Soret
band and ∼10-12 nm for Q bands) are observed upon metal
binding in the electronic spectrum. However, the magnitude of
observed shifts are much smaller than those observed for hetero-
sapphyrins, confirming the metal ion binding at the periphery
rather than inside the cavity.12
resonances upon metal binding suggests that the flipping of one
of the pyrrole rings of bipyrrole units observed for the free base
10 is no longer present in the complex. The appearance of peaks
for the inner pyrrole -NH protons (g, g′) in the shielded region
rules out the metal coordination inside the rubyrin cavity. This
leads us to suggest that the metal is bound to the pyrrole nitrogen
of the inverted ring as shown in 11 and 12, and the mass spectra
confirmed the presence of two rhodium atoms in the complex.
The doubling of resonances for all the protons suggests the
presence of two species in solution that do not interconvert into
one another on the NMR time scale. We identify these species
as isomers 11 and 12, and our attempts to separate these isomers
Reaction of 2 equiv of [Rh(CO)2Cl]2 with free base rubyrins
13, 14, and 15 in dichloromethane for about 20-30 min gave
a mixture of products (Scheme 4) containing both mono- and
bimetallic complexes. The major product monometallic com-
plexes 22, 23, and 24 were isolated in about 25-30% yield.
Two types of bimetallic complexes were isolated; complexes
16, 17, and 18 in ∼6% yield and complexes 19, 20, and 21 in

Characterization of Hetero-rubyrin Complex
Inorganic Chemistry, Vol. 40, No. 7, 2001 1641
∼1% yield. These mixtures of products can be easily separated
on the column because of their differing polarity. In a typical
reaction, 16 came first as a blue band followed by 19 (violet
band) and 22 (came last as a magenta band).
In monometallic complexes the Rh(I) binds to two nitrogens
of the same bipyrrole unit, forming an out-of-plane complex.
Furthermore, the heterocyclic rings linking the two bipyrrole
units remain inverted as in the corresponding free bases. In the
bimetallic complexes each Rh(I) also binds to two nitrogens of
a bipyrrole unit in an η2 fashion but the difference between the
two types, being in one case as in 16, is that both rhodium atoms
are pointing above the plane of the macrocycle, and this type
of coordination is accompanied by a 180° ring flip of the
heterocyclic ring linking the two bipyrrole units. In the second
case, as in 19, the two rhodium atoms are in two different planes
where one rhodium is projected above and the other one below
the mean rubyrin plane. In this type of binding the heterocyclic
ring linking the two bipyrrole units remain inverted as in the
corresponding free base.
The proposed structures for complexes 16-24 are based on
the structural data available in the literature for the Rh(I)
complexes of hetero-sapphyrins12 and amethyrin15c as well as
on the single-crystal X-ray structure of the complex 16 (vide
infra). In the bis-Rh(I) complexes of heterosapphyrins, the metal
binds to two nitrogens of dipyrromethane subunits such that
one rhodium atom is projected above and the other rhodium is
projected below the mean sapphyrin plane with an approxi-
mately square planar arrangement around each metal center.12b,c
In amethyrin, the X-ray structure of the bis-rhodium complex
is a bowl-shaped structure where both the metals are projected
above the plane of the amethyrin skeleton, imparting a symmetry
to the complex.15c However, in solution, variable-temperature
proton NMR studies reveal the presence of two species where
in one case both the rhodium atoms are projected above the
plane of the macrocycle as in the solid state. In the other species,
the two rhodium atoms are found above and below the plane
as in hetero-sapphyrins. It was not possible to separate the two
species. However, in the present study, we were successful in
the separation of two types of bimetallic complexes, and one
of them has been structurally characterized.
Figure 5. 1H NMR (CDCl3) spectra of 17 (a) and 20 (b).
revealed by X-ray structure analysis (vide infra). This makes
the selenophene protons (a) equivalent, and they resonate as a
sharp singlet at 9.39 ppm. Also, the bipyrrole protons (b and c)
become equivalent and resonate as a doublet of doublet in the
region 8.3-8.5 ppm. These assignments were confirmed by the
correlations seen in the 1H-1H COSY results. Furthermore, the
nonappearance of any peaks in the shielded region confirms
the ring flipping upon rhodium coordination. The coordination
of Rh(I) results in the characteristic shielding of bipyrrole
protons relative to free base.18 Similar spectra were observed
for the complexes 16 and 18.
In contrast, the spectra of 20 (Figure 5b) turned out to be
quite complicated because of the presence of rhodium atoms
above and below the mean rubyrin plane, destroying the
symmetry. In this case, all 12 â-CH protons become inequivalent
and resonate as individual doublets, suggesting the highly
nonplanar nature of the complex. All the assignments marked
Distinction between the Two Types of Bis-rhodium
1
Complexes in Solution. An understanding of the H NMR
spectra of free base rubyrins is essential for distinguishing
between the two types of metal complex structures. We have
recently shown that the two heterocyclic rings connecting the
two bipyrrole subunits in the hetero-rubyrins are rotating at room
temperature, giving rise to broad, unresolved 1H NMR signals.5a,b
However, when the sample is cooled to -50 °C, this rotation
can be arrested, and at this temperature the heterocyclic rings
remain inverted, which has been confirmed by the presence of
the â-CH proton signals of the inverted rings in the high-field
region. Single-crystal X-ray structures also support such a
conclusion.5b
1
in the spectrum are based on the correlations seen in the H-
1H COSY. The important feature is the appearance of sele-
nophene protons (i, j, k, and l) in the shielded region, suggesting
that the ring inversion is retained upon metal binding. However,
the chemical shifts observed for these protons suggest that the
ring is not completely inside the plane of the macrocycle but is
tilted slightly above such that these protons are away from the
ring current region relative to the corresponding free base.
The 1H NMR spectra of monometallic complex 24 is shown
in Figure 6a. The mode of metal binding suggested here results
in the formation of an out-of-plane rhodium complex, and the
A distinction between the two types of complexes can be
made on the basis of the chemical shift of â-CH protons of the
heterocyclic rings. If the heterocyclic ring is fully inverted, the
â-CH protons should experience the ring current and are
expected to resonate in the high-field region. If it is not inverted,
these protons are expected to resonate in the aromatic region.3h,5c
1
assignments marked are based on H-1H COSY (Figure 6b).
The appearance of the selenophene protons (a and b) in the
region -1.4 to -1.9 ppm clearly reveals that these rings are
inverted as in the corresponding free base upon metal coordina-
tion. The rhodium coordination results in the typical shielding
of bipyrrole protons (c and e) relative to bipyrrole protons (f
and d) as observed for the rhodium sapphyrins 7, 8, and 9 (vide
supra). Furthermore, the appearance of inner -NH proton (q)
1
A comparison of H NMR spectra of bis-rhodium complexes
17 and 20 made in Figure 5 clearly distinguishes between the
two types.
The 1H NMR spectra of 17 (Figure 5a) turned out to be very
simple because of the presence of symmetry in the complex as

1642 Inorganic Chemistry, Vol. 40, No. 7, 2001
Narayanan et al.
Figure 6. (a) 1H NMR (CDCl3) spectrum of 24 and (b) 1H-1H
correlation spectrum (CDCl3) of 24.
Figure 8. ORTEP diagram illustrating the cis orientation of two
Rh(I) atoms in 16: (a) plane view; (b) side view. Phenyl rings are
omitted for clarity.
for monometallic complexes while higher for bimetallic com-
plexes relative to the corresponding free base. For example, the
monometallic complexes show a ∼30 nm red shift for the Soret
band and a ∼22 nm shift for the Q type bands, while in the
bimetallic complexes these shifts are ∼58 and 50 nm, respec-
tively. These shifts are much larger compared to the shifts
observed for dioxarubyrin metalation where the Rh(I) is coor-
dinated at the periphery of the rubyrin. This kind of periphery
coordination should not perturb the π electron delocalization,
while the rhodium coordinated inside the rubyrin cavity is
expected to perturb the delocalization pathway, and this is
reflected in the larger optical absorption band shifts.19
X-ray Crystal Structure. The structure of complex 16 is
shown in the Figure 8. The complex adopts a bowl-shaped
structure in which both rhodium atoms are projected above the
plane of the rubyrin skeleton and the coordination at the rhodium
center is completed by the presence of two ancillary carbonyl
ligands. Each rhodium atom is bound to one amine and one
imine type of nitrogen present on the same bipyrrole unit.
Furthermore, the two thiophene rings that link the two bipyrrole
units have undergone a 180° ring flip relative to the corre-
sponding free base upon Rh(I) coordination. This is reflected
in drastic changes in the torsional angle S1-C4-C5-C6. For
example, in free base rubyrin 14,5b this angle was found to be
-173.1(12)° while upon rhodium coordination this angle is
reduced to -17.6°. The rhodium atoms are found 0.781 Å above
the mean plane defined by the meso carbons, and the molecule
is found to be symmetric. The metal plane (defined by N1, N2,
Rh1, C15, C16, O1, and O2) is inclined by 71.73° (Figure 8,
side view) with respect to the mean rubyrin plane, and this is
Figure 7. UV-visible spectra for 14 (14.179 × 10-6 M) (a), 17 (7.37
× 10-6 M) (b), and 23 (14.55 × 10-6 M) (c) in CH2Cl2 in the Soret
and Q-band regions.
at -0.65 ppm at low temperature further confirms the mode of
coordination. For complexes 22 and 23, the peaks of sele-
nophene appeared broader (line widths of ∼13 Hz) at room
temperature, suggesting the flipping of the heterocyclic rings.
A comparison of UV-visible spectra of free base 14 and
rhodium complexes 17 and 23 is made in Figure 7. In general,
the metal complexation is accompanied by a red shift of both
Soret and Q type bands. The magnitudes of shifts are smaller

Characterization of Hetero-rubyrin Complex
Inorganic Chemistry, Vol. 40, No. 7, 2001 1643
Table 2. Crystallographic Data for 16
Table 1. Comparison of Selected Bond Lengths and Bond Angles
for 16 and Dirhodium Complexes of Thiasapphyrin and Amethyrin
16
dirhodium
complex of
dirhodium
complex of
amethyrin15c
solvent for crystallization
empirical formula
temp (K)
benzonitrile/methanol
C56H32N4O4Rh2S2
95(2)
complex
16
thiasapphyrin12c
cryst syst
monoclinic
C2/c
4517.64(12)
13.2046(2)
16.8107(3)
20.3873(3)
90
93.3860(10)
90
4
1.610
17354/5494
0.0519
Bond Length (Å)
space group
Rh1-N1
Rh1-N2
Rh1-C15
Rh1-C16
C9-C10
Rh‚‚‚Rh
2.099(2)
2.087(2)
1.861(3)
1.851(3)
1.405(4)
4.313
2.083(2)
2.083(2)
1.847(3)
1.854(3)
1.434(4)
2.066(8)
2.054(7)
1.836(10)
1.869(11)
1.450(2)
4.1
vol (Å3)
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
Bond Angle (deg)
γ (deg)
N1-Rh1-N2
C15-Rh1-C16
N1-Rh1-C15
N2-Rh1-C16
80.38(9)
88.09(8)
85.8(3)
89.4(4)
91.5(4)
92.5(4)
Z
86.95(14)
97.13(12)
94.97(12)
88.26(12)
91.09(10)
92.17(11)
calcd density (g/cm3)
reflns collected/unique
R(int)
F(000)
limiting indices
2200
much higher than observed for metal sapphyrins (∼47°). The
metal coordination results in the deviation of heterocyclic rings
from the mean rubyrin plane constructed with four meso
carbons. Specifically, the dihedral angles are 34.41° for
thiophene ring, 48.12° for pyrrole ring containing N1, and 46.10°
for pyrrole ring containing N2. The torsional angles C4-C5-
C51-C52 and C1A-C14-C141-C146 are -37.5° and 56.3°
and are found to be drastically reduced relative to those of the
corresponding free base (65.0° and 57.6°), suggesting that the
meso phenyl rings are almost coplanar with the rest of the
macrocycle, increasing the delocalization pathway and justi-
fying the red shifts observed upon metal coordination in the
UV-vis spectra. The aromatic nature of the complexes is
evident from the CR-Câ distances (C6-C7, 1.434(4) Å;
C8-C9, 1.411(4) Å) being longer than the Câ-Câ distances
(C7-C8, 1.360(4) Å).8
A comparison of relevant bond angles and bond distances
observed for complex 16 along with bis-rhodium complexes of
thiasapphyrin and amethyrin is made in Table 1. In general the
Rh-N distances observed for 16 is slightly longer than observed
for the corresponding sapphyrin and amethyrin complexes. The
Rh-C distances of the CO ligand in all the cases are
comparable, and the two rhodium atoms are well separated in
16, suggesting that there is very little interaction between the
two rhodium centers. A comparison of bond angles around the
Rh(I) center reveals some interesting observations. Specifically,
the N1-Rh1-N2 bond angle is more than 8° lower while the
angle N1-Rh1-C15 is about 7° higher than observed for the
corresponding bis-rhodium thiasapphyrin (Table 1). This is
attributed to the difference in the coordination modes. In rubyrin
complex 16 the metal is bound to two nitrogens of the bipyrrole
unit, making the bond angle of N1-Rh1-N2 smaller at the
expense of the bond angle N1-Rh1-C15, while in the
thiasapphyrin complex the rhodium is bound to two nitrogens
of the dipyrromethene unit. Furthermore, the effect of this mode
of binding is reflected in significant lowering of the C9-C10
bond distance by 0.03 and 0.045 Å relative to the corresponding
distances in the thiasapphyrin12c and amethyrin15c complexes,
respectively.
-17 e h e 17, -22 e k e 16,
-19 e l e 26
GOF (F2)
final R indices {I > 2σ(I)}
R indices (all data)
1.044
R1 ) 0.0384, wR2 ) 0.0776
R1 ) 0.0609, wR2 ) 0.0833
in binding to nitrogen relative to S or Se by coordinating to
bipyrrole nitrogens; this is limited to only monometallic com-
plexes. The present study also describes for the first time, the
coordination behavior of hetero-rubyrins and the formation of
a bowl-like structure for the bimetallic complexes where both
metals are pointing away from the mean plane in the same
direction as in amethyrin,15c the second structure where metals
are projected in two different planes as in hetero-sapphyrins12
and where the formation of periphery-bound bimetallic com-
plexes as in dioxarubyrin clearly highlights the versatility of
rubyrin as a ligand. Furthermore, the 180° ring flip upon Rh(I)
binding is quite unusual and suggests the flexibility of the ligand.
The present study has exploited the interaction of only Rh(I),
but other metal ions are also expected to interact with these
macrocycles to form unique complexes that can further the
domain of coordination chemistry of expanded porphyrins in
general. Studies in this direction are in progress in this
laboratory.
Experimental Section
Instrumentation. Electronic spectra were recorded on a Perkin-
Elmer-Lambda 20 UV-vis spectrophotometer. IR spectra were obtained
from a Perkin-Elmer 1320 infrared spectrophotometer. Proton NMR
spectra were obtained on a 400 MHz JEOL spectrometer using CDCl3
or CD2Cl2 as solvent. Chemical shifts are expressed in parts per million
relative to residual CHCl3 (7.258 ppm) or CH2Cl2 (5.3 ppm). FAB mass
spectra were obtained on a JEOL SX-120/DA6000 spectrometer.
Materials. All NMR solvents were used as received. Dichlo-
romethane was dried under calcium hydride and distilled under nitrogen
before use. Silica gel (100-120 mesh) or neutral alumina or basic
alumina (Merck, usually Brockmann grade III) was used for column
chromatography. Di-µ-chloro-bis[dicarbonyl rhodium(I)] was purchased
from Aldrich and was used as received. Various free base sapphyrins
and rubyrins were synthesized and characterized as reported earlier from
this laboratory.5b
Conclusions
X-ray Diffraction Analysis. (C56H32N4O4Rh2S2) 16. Small, golden-
brown crystals were obtained by diffusion of methanol into a benzoni-
trile solution of 16. The data crystal was a block with approximate
dimensions of 0.20 × 0.18 × 0.06 mm3. Crystal data and details of
the data collection and structure refinement are listed in Table 2 and
Supporting Information. The data were collected at 95(2) K on a
Siemens SMART system, complete with a three-circle goniometer and
CCD area detector.20 The data collection nominally covered over a
hemisphere of reciprocal space by a combination of three sets of
The present results reveal that both meso-arylsapphyrins and
-rubyrins can be used as ligands toward Rh(I). Generally, the
heterosapphyrins reported in the literature form both mono-
metallic and bimetallic complexes with Rh(I) by binding to
nitrogens of dipyrromethene subunits. However, the sapphyrins
described here contain one heteroatom (S or Se) in each di-
pyrromethene subunit, and hence, Rh(I) shows its preference

1644 Inorganic Chemistry, Vol. 40, No. 7, 2001
Narayanan et al.
exposures; each set had a different φ angle for the crystal, and each
exposure covered 0.3° in ω. The crystal to detector distance was 4.936
cm. Coverage of the unique set is over 97% complete to at least 26° in
θ. Crystal decay was monitored by repeating the initial frames at the
end of data collection and analyzing the duplicate reflections. No decay
was observed. The data reduction was performed using SAINT, version
4, software.21 The structure was solved by a combination of direct
methods and refined on F2 by full-matrix least-squares methods with
anisotropic thermal parameters for the non-H atoms.22 Hydrogen atoms
were placed geometrically and refined with a riding model (including
free rotation about C‚‚‚C bonds for methyl groups) and with U(iso)
constrained to be 1.2 times U(eq) of the carrier atom. The conventional
R(F) for 5494 reflections with I > 2σ(I) was equal to 0.0384.
General Procedure for Syntheses of Rhodium Complexes. 1.
(5,10,15,20-Tetraphenyl-26,28-dithiasapphyrinato)-25,29-dicarbo-
nylrhodium(I) (7). Sapphyrin 4 (0.035 g, 0.049 mmol) was dissolved
in alcohol-free dichloromethane (50 mL). Anhydrous sodium acetate
(0.032 g, 0.49 mmol) was added to the solution followed by di-µ-chloro-
bis[dicarbonylrhodium(I)] (0.019 g, 049 mmol), and the mixture was
stirred for 20 min. The solvent was evaporated in vacuo, and the residue
was chromatographed on a basic alumina column. The brown-red
fraction eluted with petroleum ether/dichloromethane (3:1) gave a green
solid identified as 7 (0.035 g, 82%), which decomposes above 250 °C.
1H NMR (400 MHz, CDCl3, 25 °C): δ 7.79(m, 4H), 7.92(m, 8H), 8.34-
(m, 4H), 8.58(s, 2H), 8.62(m, 4H), 8.86(d, J ) 4.4 Hz, 2H), 9.02(d, J
) 4.4 Hz, 2H), 9.73(d, J ) 5.2 Hz, 2H), 9.95(d, J ) 5.2 Hz, 2H).
UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4): 513 (11.23), 623 (1.29), 684
(0.28), 774 (0.15), 864 (1.33). IR (KBr) ν(CO): 1994, 2063 cm-1. FAB-
MS: m/z 872(30%) [M+].
(s, 4H), 7.67(s, 2H), 8.97(dd, J ) 4.4 Hz, 3J ) 2 Hz, 2H), 9.20(d, J )
3
4.4 Hz, 2H), 9.28(d, J ) 4.4 Hz, 2H), 10.90(dd, J ) 4.4 Hz, J ) 2
Hz, 2H) for cis isomer. 1H NMR (400 MHz, CDCl3, 25 °C): δ -3.71-
(s, 2H), -2.53(d, J ) 4.4 Hz, 2H), -2.46(d, J ) 4.4 Hz, 2H), 2.01(s,
6H), 2.03(s, 6H), 2.17(s, 6H), 2.69(s, 6H), 2.68(s, 12H), 7.38(s, 4H),
7.52(s, 2H), 7.59(s, 2H), 9.01(dd, J ) 4.4 Hz, 3J ) 2 Hz, 2H), 9.26(d,
J ) 4.4 Hz, 2H), 9.37(d, J ) 4.4 Hz, 2H), 11.29(dd, J ) 4.4 Hz, 3J )
2 Hz, 2H) for trans isomer. UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4):
527(9.16), 569(5.24)(sh), 702(0.71), 772(0.71), 860(0.31), 979(2.83).
IR (KBr) ν(CO): 1993, 2068 cm-1. FAB-MS: 1302(18%), [(M - 2)+].
5. (5,10,19,24-Tetraphenyl-30,33-dithiarubyrinato)-29,34,31,32-
tetracarbonyl-cis-dirhodium(I) (16), (5,10,19,24-Tetraphenyl-30,-
33-dithiarubyrinato)-29,34,31,32-tetracarbonyl-trans-dirhodium-
(I) (19), and (5,10,19,24-Tetraphenyl-30,33-dithiarubyrinato)-29,34-
dicarbonylrhodium(I) (22). The above procedure was followed using
rubyrin 13 (0.1 g, 0.129 mmol) with sodium acetate (0.105 g, 1.29
mmol) and di-µ-chloro-bis[dicarbonyl rhodium(I)] (0.1 g, 0.258 mmol).
The solvent was evaporated, and the residue was chromatographed in
the neutral alumina column. The first blue band that eluted with a
petroleum ether and dichloromethane mixture (4:1) gave a golden-brown
solid identified as 16 (yield, 0.005 g, 3.5%), which decomposes above
1
280 °C. H NMR (400 MHz, CDCl3, 25 °C): δ 7.87(m, 4H), 7.98(m,
8H), 8.02(d, J ) 4.4 Hz, 4H), 8.12(d, J ) 4.4 Hz, 4H), 8.66(m, 8H),
8.93(s, 4H). UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4): 579(8.54), 736-
(0.66), 825(0.76), 1060(1.89). IR (KBr) ν(CO): 2003, 2069 cm-1. FAB-
MS: 1094(18%), [M+]. The second violet band that eluted with a
petroleum ether and dichloromethane mixture (2:1) gave a golden-brown
solid in very low yield (<1%) and is identified as 19. The last pink
band that eluted with dichloromethane/ethyl acetate (9:1) gave a
magenta solution. Upon evaporation a green solid was formed and was
identified as 22 (yield, 0.02 g, 16.5%), which decomposes above 280
°C. 1H NMR (400 MHz, CDCl3, 25 °C): δ -5.88(brs, 1H), -2.81(brs,
2H), -2.48(brs, 2H), 7.80(m, 4H), 7.92(m, 8H), 8.05(m, 4H), 8.49-
(brs, 2H), 8.54(m, 4H), 8.65(brs, 2H), 8.71(brs, 2H), 9.14(brs, 2H).
UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4): 563(8.64), 704(0.89), 771-
(0.58), 901(0.41), 1039(2.00). IR (KBr) ν(CO): 2008, 2069 cm-1. FAB-
MS: 937(31%), [M+].
2. (5,10,15,20-Tetraphenyl-26,28-diselenasapphyrinato)-25,29-di-
carbonylrhodium(I) (8). The above procedure was followed using 5
(0.030 g, 0.037 mmol), sodium acetate (0.030 g, 0.372 mmol), and
di-µ-chloro-bis[dicarbonylrhodium(I)] (0.022 g, 0.056 mmol). The
rhodium complex 8 was obtained in 62% (0.018 g) yield and
1
decomposes above 250 °C. H NMR (400 MHz, CDCl3, 25 °C): δ
7.89(m, 8H), 7.94(m, 4H), 8.41(m, 4H), 8.53(m, 4H), 8.85(s, 2H), 8.99-
(d, J ) 4.4 Hz, 2H), 9.16(d, J ) 4.4 Hz, 2H), 10.17(d, J ) 5.2 Hz,
2H), 10.38(d, J ) 5.2 Hz, 2H). UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4):
514 (5.56), 627 (0.84), 672 (0.39), 767 (0.15), 856 (0.82). IR (KBr)
ν(CO): 2000, 2065 cm-1. FAB-MS: m/z 968(20%) [(M + 2)+].
6. (5,10,19,24-Tetraphenyl-30,33-diselenarubyrinato)-29,34,31,-
32-tetracarbonyl-cis-dirhodium(I) (17), (5,10,19,24-Tetraphenyl-30,-
33-diselenarubyrinato)-29,34,31,32-tetracarbonyl-trans-dirhodium-
(I) (20), and (5,10,19,24-Tetraphenyl-30,33-diselenarubyrinato)-
29,34-dicarbonylrhodium(I) (23). These compounds were prepared
similarly as above from 14 (0.1 g, 0.115 mmol), sodium acetate (0.095
g, 1.15 mmol), and di-µ-chloro-bis[dicarbonylrhodium(I)] (0.04 g, 0.23
mmol). In the chromatographic separation on neutral alumina, the first
blue band that eluted with petroleum ether and dichloromethane (3:2)
gave 17 as a golden-brown solid (yield 0.006 g, 5%), which decomposes
3. (5,10,15,20-Tetramesityl-26,28-diselenasapphyrinato)-25,29-
dicarbonylrhodium(I) (9). The above procedure was followed using
the sapphyrin 6 (0.030 g, 0.031 mmol), sodium acetate (0.025 g, 0.310
mmol), and di-µ-chloro-bis[dicarbonyl rhodium(I)] (0.012 g, 0.031
mmol). The rhodium complex 9 was obtained in 57% (0.020 g) yield
1
and decomposes above 260 °C. H NMR (400 MHz, CDCl3, 25 °C):
δ 1.53(s, 6H), 1.65(s, 6H), 2.25(s, 6H), 2.34(s, 6H), 2.69(s, 6H), 2.73-
(s, 6H), 7.30(s, 2H), 7.43(s, 2H), 7.45(s, 2H), 7.46(s, 2H), 8.80(s, 2H),
8.98(d, J ) 4.8 Hz, 2H), 9.25(d, J ) 4.0 Hz, 2H), 10.15(d, J ) 5.6
Hz, 2H), 10.22(d, J ) 4.4 Hz, 2H). UV-vis (CH2Cl2) λmax (nm) (ꢀ ×
10-4): 511(14.62), 623(2.41), 669(1.23), 763(0.53), 852(2.19). IR (KBr)
ν(CO): 2002, 2068. FAB-MS: m/z 1136(35%) [(M + 2)+].
1
above 290 °C. H NMR (400 MHz, CDCl3, 25 °C): δ 7.91(m, 4H),
8.02(m, 8H), 8.30(d, J ) 4.4 Hz, 4H), 8.37(d, J ) 4.4 Hz, 4H), 8.70-
(m, 8H), 9.39(s, 4H). UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4): 595-
(9.61), 695(0.55), 745(0.74), 835(1.29), 1076(2.47). IR (KBr) ν(CO):
2003, 2069 cm-1. FAB-MS: 1188(32%), [M+]. The second violet band
that eluted with petroleum ether/dichloromethane (1:1) gave a brown
solid that was identified as 20 (yield 0.004 g, 3%), which decomposes
above 280 °C. 1H NMR (400 MHz, CDCl3, 25 °C): δ 3.42(d, J ) 5.8
Hz, 1H), 3.44(d, J ) 4.4 Hz, 1H), 3.72(d, J ) 5.8 Hz, 1H), 3.78(d, J
) 4.4 Hz, 1H), 7.50(m, 8H), 7.72(m, 4H), 7.79(m, 10H), 7.85(d, J )
4.8 Hz, 1H), 7.88(d, J ) 4.8 Hz, 1H), 7.91(d, J ) 4.8 Hz, 1H), 7.95(d,
J ) 4.4 Hz, 1H), 8.08(d, J ) 4.4 Hz, 1H), 8.19(d, J ) 4.4 Hz, 1H).
UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4): 606(6.06), 757(0.74), 929-
(0.97). IR (KBr) ν(CO): 2014, 2073 cm-1. FAB-MS: 1188(10%) [M+].
The fourth magenta band that eluted with 2% ethyl acetate in
dichloromethane mixture gave 23 as a green solid (yield 0.04 g, 33%),
which decomposes above 270 °C. 1H NMR (400 MHz, CDCl3, 25 °C):
δ -2.81(brs, 2H), -2.76(brs, 2H), 7.81(m, 4H), 7.89(m, 8H), 8.00(m,
4H), 8.47(d, J ) 6.0 Hz, 2H), 8.53(m, 4H), 8.58(d, J ) 6.0 Hz, 2H),
8.63(brs, 2H), 8.95(brs, 2H). UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4):
564(13.3), 708(1.06), 775(0.96), 906(0.57), 1045(3.09); IR (KBr)
ν(CO): 2003, 2069 cm-1. FAB-MS: 1032(10%) [(M + 1)+].
4. (5,10,19,24-Tetramesityl-30,33-dioxarubyrinato)-31,34-cis-tet-
racarbonyldichlorodirhodium(I) (11) and (5,10,19,24-Tetramesityl-
30,33-dioxarubyrinato)-31,34-trans-tetracarbonyldichlorodirhodium-
(I) (12). These complexes were prepared by the reaction of 10 (0.044
g, 0.048 mmol) with sodium acetate (0.039 g, 0.480 mmol) and di-µ-
chloro-bis[dicarbonylrhodium(I)] (0.047 g, 0.120 mmol) by a similar
procedure described above. The crude product upon chromatographic
separation on silica gel with dichloromethane gave the inseparable
mixture of 11 and 12 as a green solid. Yield 0.03 g, 48%; decomposes
1
above 280 °C. H NMR (400 MHz, CDCl3, 25 °C): δ -3.52(s, 2H),
-2.36(d, J ) 4.4 Hz, 2H), -2.15(d, J ) 4.4 Hz, 2H), 1.70(s, 6H),
1.86(s, 6H), 2.21(s, 6H), 2.75(s, 12H), 2.74(s, 6H), 7.37(s, 2H), 7.42-
(20) SMART Software Reference Manual; Siemens Analytical X-ray
Instruments: WI, 1994.
(21) SAINT, Software Reference Manual, version 4; Siemens Analytical
X-ray Instruments: WI, 1995.
(22) Sheldrick, G. M. SHELXTL, Reference Manual, version 5; Siemens
Analytical X-ray Instruments: WI, 1994.
7. (5,10,19,24-Tetramesityl-30,33-diselenarubyrinato)-29,34,31,-
32-tetracarbonyl-cis-dirhodium(I) (18), (5,10,19,24-Tetramesityl-30,-

Characterization of Hetero-rubyrin Complex
Inorganic Chemistry, Vol. 40, No. 7, 2001 1645
33-diselenarubyrinato)-29,34,31,32-tetracarbonyl-trans-dirhodium-
(I) (21), and (5,10,19,24-Tetramesityl-30,33-diselenarubyrinato)-
29,34-dicarbonylrhodium(I) (24). These compounds were prepared
similarly as above from 15 (0.1 g, 0.097 mmol), sodium acetate (0.08
g, 0.97 mmol), and di-µ-chloro-bis[dicarbonyl rhodium(I)] (0.075 g,
0.194 mmol). The residue obtained from the reaction mixture was
chromatographed on the silica gel column. The first blue band that
eluted with a petroleum ether and dichloromethane mixture (4:1) gave
18 as a golden-brown solid (yield 0.004 g, 3%), which decomposes
Hz, 2H), 8.79(d, J ) 4.0 Hz, 2H), 9.24(d, J ) 4.4 Hz, 2H), 9.51(d, J
) 4.0 Hz, 2H). UV-vis (CH2Cl2) λmax (nm) (ꢀ × 10-4): 555(27.29),
698(2.61), 767(3.57), 890(1.68), 1028(6.68); IR (KBr) ν(CO): 1997,
2064 cm-1. FAB-MS: 1201(25%) [(M + 2)+].
Acknowledgment. This work was supported by grants from
the Department of Science and Technology (DST) and the
Council of Scientific and Industrial Research (CSIR), Govern-
ment of India, New Delhi, to T.K.C. and a grant from the
National Science Foundation to K.R.S. (Grant CHE-9702246).
Purchase of the X-ray diffractometer equipment was made
possible with grants from NSF (Grant CHE-95-27898), the
W.M.Keck Foundation, and Syracuse University. T.K.C. is also
grateful to the Alexander von Humboldt foundation for an
equipment grant.
1
above 290 °C. H NMR (400 MHz, CDCl3, 25 °C): δ 2.09(s, 6H),
2.17(s, 6H), 2.39(s, 12H), 2.75(s, 12H), 7.40(s, 4H), 7.59(s, 4H), 8.61-
(d, J ) 4.4 Hz, 4H), 8.63(d, J ) 4.4 Hz, 4H), 9.46(s, 4H). UV-vis
(CH2Cl2) λmax (nm) (ꢀ × 10-4): 592(7.31), 740(0.68), 819(1.06), 919-
(0.25), 1052(2.06). IR (KBr) ν(CO): 2012, 2071 cm-1. FAB-MS: 1358-
(60%) [(M + 1)+]. The second violet band that eluted with a petroleum
ether and dichloromethane mixture (2:1) gave the 21 in <1% yield.
The last pink band that eluted with dichloromethane gave 24 in 42%
yield (0.055 g), which decomposes above 260 °C. 1H NMR (400 MHz,
CDCl3, 25 °C): δ -1.82(d, J ) 5.6 Hz, 2H), -1.49(d, J ) 5.2 Hz,
2H), 1.31(s, 6H), 1.71(s, 6H), 2.63(s, 6H), 2.65(s, 6H), 2.70(s, 6H),
2.85(s, 6H), 7.15(s, 2H), 7.23(s, 2H), 7.46(s, 2H), 7.49(s, 2H), 8.62(d,
J ) 4.4 Hz, 2H), 8.68(d, J ) 4.4 Hz, 2H), 9.13(d, J ) 4.4 Hz, 2H),
Supporting Information Available: Tables of crystal data, struc-
ture solution and refinement, atomic coordinates, bond lengths and
angles, and anisotropic thermal parameters for compound 16, FAB mass
spectra for 7, 11, 12, 17, and 22, IR spectra for 9, 11, 12, 20, and 22,
1H NMR (CDCl3, -50 °C) spectra for 24, and 2D 1H-1H COSY results
for 7, 17, and 20. This material is available free of charge via the
Internet at http://pubs.acs.org.
1
9.38(d, J ) 4.4 Hz, 2H). H NMR (400 MHz, CDCl3, -50 °C): δ
-2.12(d, J ) 4.8 Hz, 2H), -1.78(d, J ) 4.8 Hz, 2H), -0.65(brs, 1H),
1.30(s, 6H), 1.68(s, 6H), 2.66(s, 6H), 2.67(s, 6H), 2.74(s, 6H), 2.89(s,
6H), 7.19(s, 2H), 7.28(s, 2H), 7.52(s, 2H), 7.54(s, 2H), 8.72(d, J ) 4.0
IC000703H