Reactivity of dinuclear rhodium(I) macrocycles formed via the weak-link approach

Article abstract of DOI:10.1021/om700926d

The reaction of a macrocyclic Rh(I) complex having hemilabile PO ligands with CI^- results in Rh - O bond breakage and yields a Cl-bridged tetranuclear Rh(I) complex, which was characterized by a single-crystal X-ray diffraction study. Reactivity of the complex with CO and halide abstracting agents is described.

Full text of DOI:10.1021/om700926d

Organometallics 2008, 27, 789–792
789
Notes
Reactivity of Dinuclear Rhodium(I) Macrocycles Formed via the
Weak-Link Approach
Junpei Kuwabara, Maxim V. Ovchinnikov, Charlotte L. Stern, and Chad A. Mirkin*
Department of Chemistry and the International Institute for Nanotechnology, Northwestern UniVersity,
2145 Sheridan Road, EVanston, Illinois 60208-3113
ReceiVed September 17, 2007
Scheme 1. Reactivity of the Dinuclear Rhodium(I)
Summary: The reaction of a macrocyclic Rh(I) complex haVing
hemilabile PO ligands with Cl- results in Rh-O bond breakage
and yields a Cl-bridged tetranuclear Rh(I) complex, which was
characterized by a single-crystal X-ray diffraction study.
ReactiVity of the complex with CO and halide abstracting agents
is described.
Macrocycles 1-5
Recent developments in the field of supramolecular coordina-
tion chemistry have resulted in several new and efficient
synthetic strategies for the preparation of two- and three-
dimensional structures that possess well-defined shapes, chiral-
ity, and function.1,2 Our group has been developing the weak-
link approach (WLA) to provide reliable methods to construct
supramolecular but structurally flexible coordination complexes.1a,3
The WLA allows one to synthesize condensed multimetallic
macrocycles with flexible hemilabile ligands that form both
strong and weak coordination bonds with a metal center. When
the condensed macrocycles are reacted with small molecules
or elemental ions that selectively break the weak links, they
* To whom correspondence should be addressed. Fax: (1) 847-467-5123.
E-mail: chadnano@northwestern.edu.
(1) (a) Holliday, B. J.; Mirkin, C. A. Angew. Chem., Int. Ed. 2001, 40,
2022. (b) Fujita, M. Acc. Chem. Res. 1999, 32, 53. (c) Fujita, M.; Tominaga,
M.; Hori, A.; Therrien, B. Acc. Chem. Res. 2005, 38, 371. (d) Leininger,
S.; Olenyuk, B.; Stang, P. J. Chem. ReV. 2000, 100, 853. (e) Seidel, S. R.;
Stang, P. J. Acc. Chem. Res. 2002, 35, 972. (f) Fiedler, D.; Leung, D. H.;
Bergman, R. G.; Raymond, K. N. Acc. Chem. Res. 2005, 38, 349. (g) Amijs,
C. H. M.; van Klink, G. P. M.; van Koten, G. Dalton Trans. 2006, 308. (h)
Thanasekaran, P.; Liao, R. T.; Liu, Y. H.; Rajendran, T.; Rajagopal, S.;
Lu, K. L. Coord. Chem. ReV. 2005, 249, 1085. (i) Kovbasyuk, L.; Krämer,
R. Chem. ReV. 2004, 104, 3161. (j) Kesanli, B.; Lin, W. Coord. Chem.
ReV. 2003, 246, 305. (k) Cotton, F. A.; Lin, C.; Murillo, C. A. Acc. Chem.
Res. 2001, 34, 759. (l) Swiegers, G. F.; Malefetse, T. J. Chem. ReV. 2000,
100, 3483. (m) Balzani, V.; Credi, A.; Raymo, F. M.; Stoddart, J. F. Angew.
Chem., Int. Ed. 2000, 39, 3348. (n) Slone, R. V.; Benkstein, K. D.; Bélanger,
S.; Hupp, J. T.; Guzei, I. A.; Rheingold, A. L. Coord. Chem. ReV. 1998,
171, 221.
can be switched between structures with different shapes and
charges. These structurally tunable macrocycles have been
utilized to realize a new class of allosteric enzyme mimics,
which have led to novel amplification systems in chemical
sensing.4
The starting point for many of these systems is the binuclear
Rh(I) complex 1, assembled via phosphinoalkyl ether hemilabile
ligands and a Rh(I) precursor (Scheme 1). One interesting class
of structures includes those with bridging anthracene moieties.5
These structures are fluorescent and allow one to probe the
reactions that occur within the macrocycle. While it is well-
established that the reactions of rigid condensed macrocycles
such as 1 with CO leads to the formation of larger macrocycles
with flexible structures 23 and subsequent reactivity with Cl-
will lead to macrocycle 3,5 the direct reaction between con-
densed macrocycle 1 and Cl– has not yet been investigated. The
(2) (a) Yoshizawa, M.; Tamura, M.; Fujita, M. J. Am. Chem. Soc. 2004,
126, 6846. (b) Fiedler, D.; Pagliero, D.; Brumaghim, J. L.; Bergman, R. G.;
Raymond, K. N. Inorg. Chem. 2004, 43, 846. (c) Resendiz, M. J. E.;
Noveron, J. C.; Disteldorf, H.; Fischer, S.; Stang, P. J. Org. Lett. 2004, 6,
651. (d) Sibert, J. W.; Forshee, P. B.; Lynch, V. Inorg. Chem. 2005, 44,
8602. (e) Wu, C.-D.; Hu, A.; Zhang, L.; Lin, W. J. Am. Chem. Soc. 2005,
127, 8940. (f) Wu, H. C.; Thanasekaran, P.; Tsai, C. H.; Wu, J. Y.; Huang,
S. M.; Wen, Y. S.; Lu, K. L. Inorg. Chem. 2006, 45, 295. (g) Sathiyendiran,
M.; Liao, R. T.; Thanasekaran, P.; Luo, T. T.; Venkataramanan, N. S.; Lee,
G. H.; Peng, S. M.; Lu, K. L. Inorg. Chem. 2006, 45, 10052.
(3) (a) Gianneschi, N. C.; Masar, M. S.; Mirkin, C. A. Acc. Chem. Res.
2005, 38, 825. (b) Farrell, J. R.; Mirkin, C. A.; Guzei, I. A.; Liable-Sands,
L. M.; Rheingold, A. L. Angew. Chem., Int. Ed. 1998, 37, 465. (c) Holliday,
B. J.; Farrell, J. R.; Mirkin, C. A.; Lam, K.-C.; Rheingold, A. L. J. Am.
Chem. Soc. 1999, 121, 6316.
10.1021/om700926d CCC: $40.75
2008 American Chemical Society
Publication on Web 01/19/2008

790 Organometallics, Vol. 27, No. 4, 2008
Notes
Figure 1. Stick representation for the crystal structure of 4: (a) front view; (b)side view. Hydrogen atoms, solvent molecules (CH2Cl2), and
phenyl groups on phosphine in the side view have been omitted for clarity. Selected bond distances (Å) and angles (deg): Rh(1)-P(1) )
2.214(2), Rh(1)-P(2) ) 2.221(2), Rh(1)-Cl(1) ) 2.400(2), Rh(1)-Cl(1)* ) 2.4040(2); P(1)-Rh(1)-P(2) ) 96.14(7), P(1)-Rh(1)-Cl(1)
) 169.08(6), P(1)-Rh(1)-Cl(1)* ) 89.29(6), P(2)-Rh(1)-Cl(1) ) 94.53(7), P(2)-Rh(1)-Cl(1)* ) 174.33(7), Cl(1)-Rh(1)-Cl(1)* )
79.99(7), Rh(1)-Cl(1)-Rh(1)* ) 85.33(6).
Cl- anion in this system plays an important role in structure
Scheme 2. Possible Intermediates en Route To Form 4
regulation, since it can affect both macrocycle charge and overall
structure. Herein, we report the preparation and characterization
of the new tetranuclear Rh(I) complex 4, formed from the
reaction between 1 and Cl-, and its reactivity with CO and
halide abstracting agents.
Results and Discussion
The reaction to form 4 from 1 and Cl- was monitored by
The known condensed macrocycle 1 was synthesized from
9,10-bis(2-(diphenylphosphino)ethoxy)anthracene3c and a Rh(I)
precursor according to literature methods.5 Addition of 2 equiv
of [PPN]Cl (PPN ) [Ph3PdNdPPh3]+) to a solution of the
condensed macrocycle 1 results in a slight color change from
red to orange and the eventual formation of the tetranuclear
complex 4. After 48 h, complex 4, which is insoluble in CH2Cl2,
THF, and diethyl ether, is collected as small crystals in the
bottom of the reaction vessel (49% yield). A single-crystal X-ray
diffraction study of one of these crystals reveals the Cl-bridged
tetranuclear Rh(I) structure of 4 (Scheme 1 and Figure 1). The
structure consists of two bridging [Rh(µ-Cl)]2 units and four
flexible 9,10-bis(2-(diphenylphosphino)ethoxy)anthracene ligands.
Each Rh(I) center exhibits a distorted-square-planar geometry
with cis-Cl and cis-phosphine ligands. The anthracenes located
diagonally from each other are parallel to each other, while the
angle between the anthracenes that are not parallel is 56.3°
(Figure 1b). Although the [Rh(µ-Cl)(PR3)2]2 (R ) alkyl, aryl)
motif is quite common,6 it is rare to see a molecule with [Rh(µ-
Cl)]2 units that are connected with flexible bidentate P ligands
to form a tetranuclear Rh(I) macrocycle.7 Because of the low
solubility of compound 4, its structure in solution could not be
determined.
31P{1H} NMR spectroscopy at low temperature. 31P{1H} NMR
spectroscopy of the reaction mixture shows two well-resolved
sets of resonances at 52.3 ppm (dd, JRh-P ) 192, JP-P ) 48
Hz) and 35.1 ppm (dd, JRh-P ) 190, JP-P ) 48 Hz) at -10 °C,
which can be assigned to a phosphine of the chelated κ2P,O
ligand and the unchelated κ1P,O ligand, respectively, on the
basis of previous reports of model Rh-Cl complexes with κ2P,S
and κ1P,O ligands.8 The intermediate to form 4 is at least one
of two possible isomeric structures (Scheme 2). On the basis
of the spectroscopic data of this fleeting intermediate, it is
impossible to differentiate the two possibilities. However, both
possible intermediates, which may be in dynamic equilibrium
with one another, contain weak Rh-O linkages and would be
expected to lead to the same observed product 4 upon dimer-
ization through the Cl ligands. The reaction to form 4 can be
reversed simply by adding LiB(C6F5)4 · Et2O under sonication
conditions. The sonication is important because of the low
solubility of complex 4.
Interestingly, when 4 is added to CD2Cl2 and sonicated in
the presence of CO (1 atm), open neutral complex 3 forms in
quantitative yield (Scheme 1). In this transformation, the π-acid
CO displaces the bridging Cl groups of the tetranuclear complex
to form the dinuclear complex 3.9 Addition of 2 equiv of
LiB(C6F5)4 · Et2O to compound 3 in CD2Cl2 under CO (1 atm)
results in the rapid formation of cationic complex 2. Complex
2 is a known compound and was characterized on the basis of
1H and 31P{1H} NMR, FTIR, and ESI MS and a comparison
of that data with literature data. Complex 2 also can be made
(4) (a) Gianneschi, N. C.; Bertin, P. A.; Nguyen, S. T.; Mirkin, C. A.;
Zakharov, L. N.; Rheingold, A. L. J. Am. Chem. Soc. 2003, 125, 10508.
(b) Gianneschi, N. C.; Cho, S. H.; Nguyen, S. T.; Mirkin, C. A. Angew.
Chem., Int. Ed. 2004, 43, 5503. (c) Gianneschi, N. C.; Nguyen, S. T.; Mirkin,
C. A. J. Am. Chem. Soc. 2005, 127, 1644. (d) Oliveri, C. G.; Gianneschi,
N. C.; Nguyen, S. T.; Mirkin, C. A.; Stern, C. L.; Wawrzak, Z.; Pink, M.
J. Am. Chem. Soc. 2006, 128, 16286. (e) Heo, J.; Mirkin, C. A. Angew.
Chem., Int. Ed. 2006, 45, 941. (f) Masar, M. S.; Gianneschi, N. C.; Oliveri,
C. G.; Stern, C. L.; Nguyen, S. T.; Mirkin, C. A J. Am. Chem. Soc. 2007,
129, 10149.
(8) (a) Brown, A. M.; Ovchinnikov, M. V.; Stern, C. L.; Mirkin, C. A.
J. Am. Chem. Soc. 2004, 126, 14316. (b) Brown, A. M.; Ovchinnikov, M. V.;
Mirkin, C. A. Angew. Chem., Int. Ed. 2005, 44, 4207. (c) Jeon, Y.-M.;
Heo, J.; Brown, A. M.; Mirkin, C. A. Organometallics 2006, 25, 2729. (d)
Ulmann, P. A.; Brown, A. M.; Ovchinnikov, M. V.; Mirkin, C. A.;
DiPasquale, A. G.; Rheingold, A. L. Chem. Eur. J. 2007, 13, 4529. (e)
Oliveri, C. G.; Heo, J.; Nguyen, S. T.; Mirkin, C. A.; Wawrzak, Z. Inorg.
Chem. 2007, 46, 7716.
(5) Kuwabara, J.; Stern, C. L.; Mirkin, C. A. J. Am. Chem. Soc. 2007,
129, 10074.
(6) (a) Osborn, J. A.; Jardine, F. H.; Young, J. F.; Wilkinson, G. J. Chem.
Soc. A 1966, 1711. (b) Tolman, C. A.; Meakin, P. Z.; Lindner, D. L.; Jesson,
J. P. J. Am. Chem. Soc. 1974, 96, 2762. (c) Bleeke, J. R.; Donaldson, A. J.
Organometallics 1986, 5, 2401.
(7) (a) Chandrasekaran, P.; Mague, J. T.; Balakrishna, M. S. Organo-
metallics 2005, 24, 3780. (b) Chandrasekaran, P.; Mague, J. T.; Balakrishna,
M. S. Inorg. Chem. 2005, 44, 7925.
(9) (a) Bunten, K. A.; Farrar, D. H.; Poë, A. J.; Lough, A. Organome-
tallics 2002, 21, 3344. (b) Krüger, P.; Werner, H. Eur. J. Inorg. Chem.
2004, 481.

Notes
Organometallics, Vol. 27, No. 4, 2008 791
) 1,5-cyclooctadiene) was purchased from Strem Chemicals
and used as received. 9,10-Bis(2-(diphenylphosphino)ethoxy)-
anthracene)3c and [(µ2-9,10-bis(2-(diphenylphosphino)ethoxy)-
anthracene)2Rh2Cl2(CO)2] (3)5 were synthesized according to
literature methods. All other chemicals were used as received from
Aldrich Chemical Co. 1H NMR spectra were recorded on a Varian
Mercury 300 MHz FT-NMR spectrometer and referenced relative
to residual proton resonances in CD2Cl2.31P{1H} NMR spectra were
recorded on a Varian Mercury 300 MHz FT-NMR spectrometer at
121.53 MHz and referenced relative to an external 85% H3PO4
standard. All chemical shifts are reported in ppm. FT-IR spectra
were obtained using a Thermo Nicolet Nexus 670 FT-IR. Electro-
spray ionization mass spectra (ESI-MS) were recorded on a
Micromas Quatro II triple quadrupole mass spectrometer. Elemental
analyses were performed by Quantitative Technologies Inc. White-
house, NJ.
Figure 2. Stick representation for the crystal structure of 5.
Hydrogen atoms, counteranions, and solvent molecules (CH2Cl2)
have been omitted for clarity. Selected bond distances (Å) and
angles (deg): Rh(1)-P(1) ) 2.3223(9), Rh(1)-P(2)* ) 2.3517(9),
Rh(1)-C(1) ) 1.868(4), Rh(1)-C(2) ) 1.958(3); P(1)-Rh(1)-P(2)*
) 176.58(4), P(1)-Rh(1)-C(1) ) 87.0(1), P(1)-Rh(1)-C(2) )
91.0(1), P(2)*-Rh(1)-C(1) ) 92.6(1), P(2)*-Rh(1)-C(2) )
89.1(1), C(1)-Rh(1)-C(2) ) 173.9(2).
Synthetic Methods. Synthesis of [(K2:µ2:K2-9,10-bis(2-(diphenyl-
phosphino)ethoxy)anthracene)2Rh2][B(C6F5)4]2 (1). Complex 1
was synthesized in a manner similar to that used for [(κ2:µ2:κ2-
9,10-bis(2-(diphenylphosphino)ethoxy)anthracene)2Rh2][B(3,5-
5
C6H3(CF3)2)4]2 using
9,10-bis(2-(diphenylphosphino)ethoxy)-
directly from compound 1 via CO addition through literature
procedures. Interestingly, bubbling N2 through the solution of
complex 2 results in loss of a single CO ligand at each Rh center
and formation of the new complex 5 (Scheme 1). Low-
temperature 31P{1H} NMR spectroscopy of the reaction mixture
allows one to easily follow this transformation. As the single
resonance for 2 (26.0 ppm, JRh-P ) 72 Hz) rapidly disappears,
a new resonance for 5 (14.9 ppm, JRh-P ) 107 Hz) appears. In
addition, the 31P{1H} NMR spectrum of complex 5 formed from
13C-labeled CO shows a doublet of triplets, consistent with a
complex with two rather than three CO ligands at each Rh center
(JRh-P ) 108 Hz and JP-C ) 16 Hz). The loss of one carbonyl
ligand from each Rh(I) center is consistent with the reactivity
observed for related monometallic Rh(I) complexes.10
The solid-state structure of complex 5 was confirmed by a
single-crystal X-ray diffraction study (Figure 2). The Rh(I)
center exhibits a distorted-square-planar geometry with trans-
CO and trans-P coordination environments. The two anthracenyl
rings in 5 are parallel with each other with a 3.79 Å separation,
consistent with a π-π stacking interaction.11 Similar π-π
stacking interactions have been observed in other metallamac-
rocycles,12 but one sees a much larger distance (e.g., >6 Å) in
analogous binuclear Rh(I) macrocycles, where there are three
CO ligands per trigonal-bipyramidal Rh center.3 The extra CO
ligand may inhibit the π-π stacking interactions observed for
the complexes with square-planar Rh centers and only two CO
ligands.
anthracene) (31.8 mg, 0.050 mmol), [RhCl(cod)]2 (12.6 mg, 0.025
mmol), and LiB(C6F5)4(Et2O) (38.0 mg, 0.050 mmol) in 92% yield
(65.2 mg). H NMR (CD2Cl2): δ 8.11 (m, C14H8, 4H), 7.73 (m,
PC6H5, 8H), 7.52 (m, PC6H5, 4H), 7.43 (m, PC6H5, 8H), 7.32 (m,
C14H8, 4H), 3.97 (m, OCH2, 4H), 2.88 (m, CH2PPh2, 4H). 31P{1H}
NMR (CD2Cl2): δ 62.5 (d, JRh-P ) 213 Hz). ESI-MS (m/z): [M -
2B(C6F5)4]2+ 738.1 (calcd for [C84H72O4P4Rh2]2+ 737.6). Anal.
Calcd for C132H72B2F40O4P4Rh2: C, 55.96; H, 2.56. Found: C, 56.08;
H, 2.55.
1
Formation of [(µ2-9,10-bis(2-(diphenylphosphino)ethoxy)-
anthracene)2Rh2(CO)6][B(C6F5)4]2 (2). An NMR tube was loaded
with a CD2Cl2 solution (0.5 mL) of [(κ2:µ2:κ2-9,10-bis(2-
(diphenylphosphino)ethoxy)anthracene)2Rh2][B(C6F5)4]2 (1; 14.2
mg, 5 µmol) and charged with CO (1 atm). The resulting solution
1
changed from red to yellow. H and 31P{1H} NMR spectroscopic
data of the solution are consistent with the quantitative formation
of [(µ2-9,10-bis(2-(diphenylphosphino)ethoxy)anthracene)2Rh2-
1
(CO)6][B(C6F5)4]2 (2). H NMR (CD2Cl2, -76 °C): δ .8–7.0 (m,
PC6H5 and C14H8, 24H), 6.92 (m, C14H8, 4H), 3.96 (br, OCH2, 4H),
3.56 (br, CH2PPh2, 4H). 31P{1H} NMR (CD2Cl2, -76 °C): δ 6.0
(d, JRh-P ) 72 Hz). ESI-MS (m/z): [M - 4CO - 2B(C6F5)4]2+
766.0 (calcd for [C86H72O6P4Rh2]2+ 765.6). FTIR (CH2Cl2): νCO
2039 cm-1(s). The lability of the CO ligands made it impossible
to obtain an elemental analysis for the complex.
Synthesis of [(µ2-9,10-bis(2-(diphenylphosphino)ethoxy)-
anthracene)2Rh2Cl2]2 (4). [PPN]Cl (22.8 mg, 40 µmol) in CH2Cl2
(3 mL) was added to a solution of [(κ2:µ2:κ2-9,10-bis(2-
(diphenylphosphino)ethoxy)anthracene)2Rh2][B(C6F5)4]2 (1; 56.8
mg, 20 µmol) in CH2Cl2 (3 mL). After 48 h, the crystals were
collected and washed with CH2Cl2 (3 mL × 2). The red crystals of
4 were obtained in 49% yield (15.3 mg). Due to its low solubility,
the product was characterized only by single-crystal X-ray diffrac-
Experimental Section
General Methods and Instrument Details. All reactions were
carried out under an inert atmosphere of nitrogen using standard
Schlenk techniques or an inert-atmosphere glovebox unless other-
wise noted. Diethyl ether, CH2Cl2, and hexanes were purified by
published methods.13 All solvents were deoxygenated with nitrogen
prior to use. Deuterated solvents were purchased from Cambridge
Isotope Laboratories Inc. and used as received. [RhCl(cod)]2 (cod
tion and elemental analysis. Anal. Calcd for
C168H144-
Cl4O8P8Rh4 · 4CH2Cl2: C, 60.20; H, 4.46. Found: C, 60.14; H, 4.19.
Crystals of 4 · 7CH2Cl2 suitable for X-ray diffraction analysis were
directly obtained by the reaction in CH2Cl2. Although the structure
determined from the crystallographic data has seven CH2Cl2 solvent
molecules, the elemental analysis shows four solvated CH2Cl2
molecules for the compound. This difference is likely due to the
drying of the sample under reduced pressure prior to EA.
(10) (a) Lindner, E.; Wang, Q.; Mayer, H. A.; Fawzi, R.; Steimann, M.
Organometallics 1993, 12, 1865. (b) Singewald, E. T.; Shi, X.; Mirkin,
C. A.; Schofer, S. J.; Stern, C. L. Organometallics 1996, 15, 3062.
(11) Janiak, C. Dalton Trans. 2000, 3885.
Synthesis of [(µ2-9,10-bis(2-(diphenylphosphino)ethoxy)-
anthracene)2Rh2(CO)4][B(C6F5)4]2 (5). A CD2Cl2 solution of
[(µ2-9,10-bis(2-(diphenylphosphino)ethoxy)anthracene)2Rh2(CO)6]-
[B(C6F5)4]2 (2; 5 µmol) was bubbled with N2 gas for several
minutes. The solution changed from yellow to pale orange. 1H and
31P{1H} NMR spectroscopic data show the quantitative formation
(12) (a) Xu, F. B.; Li, Q. S.; Zeng, X. S.; Leng, X. B.; Zhang, Z. Z.
Organometallics 2004, 23, 632. (b) Wan, X. J.; Xu, F. B.; Li, Q. S.; Song,
H. B.; Zhang, Z. Z. Organometallics 2005, 24, 6066.
(13) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J. Organometallics 1996, 15, 1518.

792 Organometallics, Vol. 27, No. 4, 2008
Notes
Table 1. Crystallographic Data
4 · 7CH2Cl2
5 · 4CH2Cl2
empirical formula
formula wt
temp (K)
C
175H162Cl18O8P8Rh4
C
140H80B2Cl8F40O8P4Rh2
3690.55
153(2)
3284.96
293(2)
wavelength (Å)
cryst syst, space group
a (Å)
b (Å)
c (Å)
0.710 73
0.710 73
triclinic, P1
11.439(1)
16.356(2)
18.746(2)
j
monoclinic, C2/m
24.845(3)
25.051(3)
16.168(2)
R (deg)
90.305(2)
ꢀ (deg)
127.172(2)
100.456(2)
105.572(2)
3317.3(7)
1, 1.644
0.574
γ (deg)
V (Å3)
8018.0(16)
2, 1.529
0.844
3764
Z, calcd density (Mg/m3)
abs coeff (mm-1
F(000)
)
1640
cryst size (mm)
0.13 × 0.13 × 0.04
0.28 × 0.15 × 0.10
1.11-28.81
30 627/15 378 (R(int) ) 0.0921)
θ range for data collecn (deg)
no. of collected/unique rflns
abs cor
1.31-28.83
37 143/9951 (R(int) ) 0.0941)
numerical
max, min transmission
refinement method
0.9761, 0.9122
0.9531, 0.8687
full-matrix least squares on F2
no. of data/restraints/params
goodness of fit on F2
final R indices (I > 2σ(I))
R indices (all data)
16 168/0/949
1.078
R1 ) 0.0887, wR2 ) 0.2296
R1 ) 0.1444, wR2 ) 0.2500
1.373, -0.814
15 378/2/893
0.818
R1 ) 0.0546, wR2 ) 0.1294
R1 ) 0.0930, wR2 ) 0.1444
1.246, -0.814
largest diff peak, hole (e/Å-3
)
of [(µ2-9,10-bis(2-(diphenylphosphino)ethoxy)anthracene)2Rh2(CO)4]-
[B(C6F5)4]2 (5). 1H NMR (CD2Cl2, -76 °C): δ 7.8–7.0 (m, PC6H5
and C14H8, 24H), 6.92 (m, C14H8, 4H), 3.96 (br, OCH2, 4H), 3.56
(br, CH2PPh2, 4H). 31P{1H} NMR (121 MHz, CD2Cl2, -76 °C):
δ 14.9 (d, JRh-P ) 107 Hz). ESI-MS (m/z): [M - 6CO -
2B(C6F5)4]2+ 737.0 (calcd for [C84H72O4P4Rh2]2+ 737.1). FTIR
(KBr): νCO 2039 (s), 2005 cm-1 (w). Anal. Calcd for
correction was also applied using the numerical method. The
structures were solved by direct methods provided by the program
package SHELXTL. All of the non-hydrogen atoms were refined
anisotropically. CH2Cl2 solvent molecules are highly disordered and
were treated by SQUEEZE.14The electron count from the SQUEEZE
model converged to electron 353 count/cell (4 · 7CH2Cl2) and 72
count/cell (5 · 4CH2Cl2). Hydrogen atom positions were calculated
and included in the final cycle of refinement (see Table 1 for
crystallographic data).
C136H72B2F40O8P4Rh2: C, 55.46; H, 2.46. Found: C, 55.77; H, 2.70.
Crystals of 5 · 4CH2Cl2, suitable for single crystal X-ray diffraction
analysis, were obtained by recrystallization of the product from
2:1 CH2Cl2-hexane. Although the structure determined from the
crystallographic study has four CH2Cl2 solvent molecules, the
elemental analysis shows no CH2Cl2 in the compound. This
difference is likely due to the drying of the sample under reduced
pressure prior to EA.
X-ray Crystallography. Crystals of 4 · 7CH2Cl2 and 5 · 4CH2Cl2,
suitable for single-crystal X-ray diffraction studies, were mounted
on a glass fiber using oil (Infineum V8512). All measurements were
made on a CCD area detector with graphite-monochromated Mo
KR (λ ) 0.710 73 Å) radiation on a Bruker SMART-1000
diffractometer. The raw data collected were processed to produce
conventional intensity data by the program SAINT. The intensity
data were corrected for Lorenz and polarization effects. Absorption
Acknowledgment. We acknowledge the NSF, AFOSR,
ARO, and DDRE for financial support of this research.
C.A.M. is grateful for a NIH Director’s Pioneer Award.
Supporting Information Available: CIF files giving X-ray
crystallographic data for the structure determinations of 4 · 7CH2Cl2
and 5 · 4CH2Cl2. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM700926D
(14) van der Sluis, P.; Spek, A. L. Acta Crystallogr., Sect. A 1990, A46,
194.