Studies of the synthesis and thermochemistry of coordinatively unsaturated chelate complexes (η5-C5Me5)IrL2 (L2 = TsNCH2CH2NTS, TsNCH2CO2, CO2CO2)

Article abstract of DOI:10.1021/ic990870l

A comparative synthetic, structural, and thermochemical study on a series of chelate complexes containing the fragment (η⁵-C₅Me₅)Ir [(η⁵-C₅Me₅)Ir(TsNCH₂CH₂NTs) (1), (η⁵-C₅Me₅)Ir(TsNCH₂CO₂) (2), (η⁵-C₅Me₅)Ir(CO₂CO₂) (3)] was performed to clarify the roles of carboxylato and sulfonamido ligands. Whereas 1 and 2 are monomeric in solution and in the solid state, 3 appears to exist as an oligomer or polymer, (3)(n), which can be broken up by addition of a ligand L such as a phosphine, CO, or 2-methoxypyridine to form (η⁵-C₅Me₅)Ir(L)(CO₂CO₂) (6). The synthesis of (3)(n) from [(η⁵-C₅Me₅)IrCl(μ-Cl)]₂ required the use of silver oxalate in CH₃CN, but if other solvents were used, the bridging oxalato complex (η⁵-C₅Me₅)IrCl(μ-η²-η²-C₂O₄)ClIr(η⁵-C₅Me₅) (7) was obtained and identified by X-ray diffraction. Enthalpies for reaction of THF-soluble monomers 1 and 2 with PMe₃ were determined to be - 28.7(0.5) and ~ 28.5(0.4) kcal mol^-1, respectively. The oligomerization behavior of 3 may be a result of reduced σ- or π-donation of carboxylato ligands compared to N-tosylamido ligands, because the values for v(CO) in oxalato and bissulfonamido complexes 6-CO and (η⁵-C₅Me₅)Ir(CO)(TsNCH₂CH₂NTs) (4-CO) were 2064 and 2042 cm^-1, respectively.

Full text of DOI:10.1021/ic990870l

Inorg. Chem. 2000, 39, 2493-2499
2493
Studies of the Synthesis and Thermochemistry of Coordinatively Unsaturated Chelate
Complexes (η5-C5Me5)IrL2 (L2 ) TsNCH2CH2NTs, TsNCH2CO2, CO2CO2)
Douglas B. Grotjahn,*,† H. Christine Lo,‡ Jason Dinoso,§ Charles D. Adkins,§ Chunbang Li,|
Steven P. Nolan,| and John L. Hubbard
Department of Chemistry, San Diego State University, 5500 Campanile Drive, San Diego, California
92182-1030, Department of Chemistry and Biochemistry, Arizona State University, Box 871604, Tempe,
Arizona 85287, Department of Chemistry, University of New Orleans, New Orleans, Louisiana 70148,
and Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300
ReceiVed July 22, 1999
A comparative synthetic, structural, and thermochemical study on a series of chelate complexes containing the
fragment (η5-C5Me5)Ir [(η5-C5Me5)Ir(TsNCH2CH2NTs) (1), (η5-C5Me5)Ir(TsNCH2CO2) (2), (η5-C5Me5)Ir(CO2-
CO2) (3)] was performed to clarify the roles of carboxylato and sulfonamido ligands. Whereas 1 and 2 are
monomeric in solution and in the solid state, 3 appears to exist as an oligomer or polymer, (3)n, which can be
broken up by addition of a ligand L such as a phosphine, CO, or 2-methoxypyridine to form (η5-C5Me5)Ir(L)(CO2-
CO2) (6). The synthesis of (3)n from [(η5-C5Me5)IrCl(µ-Cl)]2 required the use of silver oxalate in CH3CN, but if
other solvents were used, the bridging oxalato complex (η5-C5Me5)IrCl(µ-η2-η2-C2O4)ClIr(η5-C5Me5) (7) was
obtained and identified by X-ray diffraction. Enthalpies for reaction of THF-soluble monomers 1 and 2 with
PMe3 were determined to be -28.7(0.5) and -28.5(0.4) kcal mol-1, respectively. The oligomerization behavior
of 3 may be a result of reduced σ- or π-donation of carboxylato ligands compared to N-tosylamido ligands,
because the values for νCO in oxalato and bissulfonamido complexes 6-CO and (η5-C5Me5)Ir(CO)(TsNCH2CH2-
NTs) (4-CO) were 2064 and 2042 cm-1, respectively.
Introduction
Scheme 1
Here we report a comparative synthetic, structural, and
thermochemical study on a series of chelate complexes contain-
ing the metal fragment (η5-C5Me5)IrIII (1, 2, and 3). In 1994,
Grotjahn et al. reported a series of amino acid complexes
featuring Cp*Ir bound to an N-acyl or N-tosyl amino acid ligand,
deprotonated at N and carboxylate O.1 These complexes,
represented by N-tosylamidoglycine derivative 2, were note-
worthy for their high stability, coordinative unsaturation, and
rapid, stereoselective ligand additions when chiral amino acids
were involved.1-3 Spectroscopic and X-ray crystallographic
evidence pointed to significant π-donation from the acylated
or tosylated nitrogen in 2, which was reduced upon addition of
a ligand L and formation of 5 (Scheme 1).1,2 Even though some
π-donation from the carboxylato oxygen was assumed, no direct
evidence of this was available. Because sulfonamido ligands
are increasingly important in organometallic chemistry,4 it
seemed important to clarify structure and bonding in complexes
of type 2. Although π-donation from N or O ligands is now a
well-established phenomenon,5 the synthesis and study of the
title series of electronically and coordinatively unsaturated (η5-
C5Me5)Ir complexes (1-3) were expected to provide new
insights into the bonding in 2. Specifically, by comparing
compounds with η2-(N,N)-bis(sulfonamido), η2-(N,O)-sulfon-
amidocarboxylato, and η2-(O,O)-oxalato ligands (structures 1,
2, and 3, respectively), we expected to determine the relative
π-donating characteristics of the sulfonamido and carboxylato
ligands. As described below, complete comparison of 3 with 1
and 2 was precluded by the unusual oligomerization and
solubility behavior of 3. However, all three compounds gave
† San Diego State University (current e-mail: grotjahn@chemistry.sdsu.edu)
and Arizona State University.
‡ Arizona State University. Current address: The Scripps Research
Institute, Department of Molecular Biology, La Jolla, CA 92037.
§ San Diego State University.
(4) (a) Noyori, R.; Hashiguchi, S. Acc. Chem. Res. 1997, 30, 97-102.
(b) Pritchett, S.; Woodmansee, D. H.; Gantzel, P.; Walsh, P. J. J. Am.
Chem. Soc. 1998, 120, 6423-6424. (c) Pritchett, S.; Woodmansee,
D. H.; Davis, T. J.; Walsh, P. J. Tetrahedron Lett. 1998, 39, 5941-
5942. (d) Armistead, L. T.; White, P. S.; Gagne´, M. R. Organometallics
1998, 17, 216-220. (e) Denmark, S. E.; O’Connor, S. P.; Wilson, S.
R. Angew. Chem., Int. Ed. Engl. 1998, 37, 1149-1151.
| University of New Orleans.
Utah State University.
(1) Grotjahn, D. B.; Groy, T. J. Am. Chem. Soc. 1994, 116, 6969-6970.
(2) Grotjahn, D. B.; Groy, T. Organometallics 1995, 14, 3669-3682.
(3) Grotjahn, D. B.; Joubran, C. Tetrahedron: Asymmetry 1995, 6, 745-
752.
10.1021/ic990870l CCC: $19.00 © 2000 American Chemical Society
Published on Web 05/20/2000

2494 Inorganic Chemistry, Vol. 39, No. 12, 2000
Grotjahn et al.
0.153 mmol, 1.07 equiv), and THF (20 mL) was added. The mixture
was stirred for 4 d, after which time it was noted that the mixture had
lightened somewhat from orange to yellow, but that most of the yellow
color was in the solid phase. Therefore, CH3CN (20 mL) was added,
and the mixture was stirred for an additional 13 h, after which more
but not all color was in the solution. The mixture was filtered in air
through a pad of Celite in a fritted funnel, and the filter cake was washed
with warm CH3CN, followed by CH2Cl2 in several portions. Combined
filtrates were concentrated by rotary evaporation, and the yellow solid
residue (135 mg) was recrystallized from CH2Cl2-THF, allowing the
solvent to slowly evaporate through a syringe needle in a septum. Pale
orange crystals of 7 (102.0 mg, 87%) were isolated. Suitable single
crystals for X-ray diffraction were obtained by recrystallization from
CH2Cl2-THF: mp 298 °C dec; (when sample heated starting at 286
corresponding CO adducts (4-CO, 5-CO, and 6-CO), whose
IR spectroscopic data showed that π-donation of carboxylato
ligands is less than that of N-tosylamido ligands.
Experimental Section
General Procedures. Unless otherwise specified, NMR spectra were
recorded at 200, 300, 400, or 500 MHz with Varian spectrometers at
1
room temperature. H and 13C NMR chemical shifts are reported in
parts per million downfield from tetramethylsilane and referenced to
residual solvent resonances (1H NMR, 7.27 for CHCl3 in CDCl3; 13C
1
NMR, 77.00 for CDCl3), where H NMR signals are given followed
by multiplicity, coupling constants J in hertz, and integration in
parentheses. For complex coupling patterns, the first coupling constant
listed corresponds to the first splitting listed; e.g., for (dt, J ) 3.2, 7.9,
1 H) the doublet exhibits the 3.2 Hz coupling constant. 31P{1H} NMR
chemical shifts were referenced to external 85% H3PO4(aq).
IR spectra were obtained on either a Perkin-Elmer series 1600 or a
Mattson Instruments model 2020 Galaxy series FT-IR spectrophotom-
eter. Elemental analyses were performed at NuMega Resonance Labs
(San Diego), Atlantic Microlab, Inc. (Georgia), or the Department of
Chemistry, Arizona State University.
1
°C); IR (KBr) 1620 cm-1 (vs); H NMR (CDCl3) δ 1.62 (s). Anal.
Calcd for C22H30Cl2Ir2O4 (813.86): C, 32.46; H, 3.72. Found: C, 32.43;
H, 3.67.
Synthesis of (3)n. To a stirred suspension of [(η5-C5Me5)IrCl(µ-
Cl)]2 (257.7 mg, 0.323 mmol) in CH3CN (3 mL) in the glovebox was
added Ag2C2O4 (229.6 mg, 0.756 mmol, 1.17 equiv). The mixture was
stirred for 39 h before it was diluted with an equal volume of CH2Cl2
and filtered through Celite, and the filter cake was rinsed with CH2Cl2
in portions. Combined filtrates were concentrated by rotary evaporation.
To the yellow syrupy residue was added CH2Cl2, and the resulting
mixture was concentrated. To the residue were added CH2Cl2 and THF,
and some of the solvent was allowed to evaporate slowly. The
supernatant was pipetted away, and the remaining yellow solid was
stored over P4O10 under vacuum, leaving 232.0 mg (78%): IR (KBr)
1699, 1675, 1633, 1595 cm-1 (all vs). Anal. Calcd for C12H15-
IrO4‚0.5CH2Cl2 (415.49 + 42.47): C, 32.79; H, 3.52. Found: C, 32.88;
H, 3.47.
1H and 13C{1H} NMR and IR data (νCO) for the chelated complexes
are listed in Table 1.
Synthesis of 1. A 50 mL Schlenk flask was charged with a stirbar,
TsNHCH2CH2NHTs6 (53.9 mg, 0.146 mmol), [(η5-C5Me5)IrCl(µ-Cl)]2
7
(58.0 mg, 0.0728 mmol), and K2CO3 (40.5 mg, 0.293 mmol), and the
flask was evacuated and filled with nitrogen. THF (10 mL) was then
added via syringe under N2. The resulting orange-yellow mixture was
allowed to stir for 36 h at room temperature, after which time the color
had changed to dark red. The solvent was removed on a high vacuum
line to afford a red residue along with some pale green crystalline solid.
A portion of CH2Cl2 (about 5 mL) was used to dissolve the residue,
and the resulting solution was washed with an equal amount of H2O
and then concentrated on a high-vacuum line. The residue was purified
by recrystallization from CH2Cl2-Et2O, followed by refrigeration at
-15 °C to give the title complex as dark red needles (99.0 mg, 98%):
IR (KBr) 2918, 2859, 1599, 1495, 1447 cm-1. Anal. Calcd for C26H33-
IrN2O4S2 (693.92): C, 45.00; H, 4.80; N, 4.04. Found: C, 44.84; H,
4.76; N, 4.01.
Addition of PMe3 to 1 To Give 4-PMe3. In a glovebox, a flame-
dried J. Young NMR tube was charged with 1 (12.6 mg, 0.0182 mmol)
and CDCl3 (0.7 mL) to make a dark red solution. To this solution was
added PMe3 (in excess), and a yellow solution resulted immediately.
The reaction mixture was then subjected to chromatography with a
Chromatotron (SiO2, EtOAc-hexanes, 1:1) to give the title complex
(13.4 mg, 96%) as a yellow solid: 31P{1H} NMR (202.3 MHz, CDCl3)
δ 26.01; IR (KBr) 2917, 1269, 1136 cm-1. Anal. Calcd for C29H42-
IrN2O4PS2 (769.99): C, 45.24; H, 5.50; N, 3.64. Found: C, 44.09; H,
5.42; N, 3.9.
Addition of PMe3 to (3)n To Give 6-PMe3. To a suspension of
(3)n‚0.5CH2Cl2 (16.7 mg, 0.0349 mmol) in CDCl3 (ca. 1 mL) in a J.
Young NMR tube was added PMe3 (4.5 µL). Not all cloudiness
disappeared on addition of the phosphine, so an additional 1.0 µL was
added (total 5.5 µL, 0.053 mmol). After acquisition of NMR spectra
the contents of the tube were filtered through a cotton plug in a pipet,
the cotton rinsed with CH2Cl2, and the filtrate concentrated to leave a
yellow solid (12.9 mg, 0.0262 mmol, 75%). Anal. Calcd for C15H24-
IrO4P (491.55): C, 36.65; H, 4.92. Found: C, 36.53; H, 4.90.
Addition of PEt3 to (3)n To Give 6-PEt3. In a manner similar to
that used to make 6-PMe3, a suspension of (3)n‚0.5CH2Cl2 (14.8 mg,
0.0323 mmol) in CDCl3 (ca. 1 mL) in an NMR tube was treated with
PEt3 (4.0 mg, 0.034 mmol). Not all cloudiness disappeared on addition
of the phosphine, so an additional 1.0 µL was added (total ca. 0.04
1
mmol). The presence of the product was shown by H, 13C{1H}, and
31P{1H} NMR spectroscopies. Filtration and recrystallization from
CDCl3-CH2Cl2-hexane provided yellow crystals of 6-PEt3 (16.5 mg,
96%): mp 248 °C dec (apparatus preheated to 240 °C); 31P{1H} NMR
(CDCl3, 80.95 MHz) δ 7.46. Anal. Calcd for C18H30IrO4P (533.63):
C, 40.52; H, 5.67. Found: C, 40.46; H, 5.64.
Synthesis of 7 [(η5-C5Me5)IrCl(µ-η2-η2-C2O4)ClIr(η5-C5Me5)]. In
the glovebox, a 50 mL Schlenk flask was charged with a stirbar, [(η5-
C5Me5)IrCl(µ-Cl)]2 (115.0 mg, 0.144 mmol), and Ag2C2O4 (46.6 mg,
Addition of PPh3 to (3)n To Give 6-PPh3. In a manner similar to
that used to make 6-PMe3, a suspension of (3)n‚0.5CH2Cl2 (14.8 mg,
0.0323 mmol) in CDCl3 (ca. 1 mL) in an NMR tube was treated with
PPh3 (9.0 mg, 0.034 mmol). The presence of the product was shown
by 1H, 13C{1H}, and 31P{1H} NMR spectroscopies. Filtration and
recrystallization from CDCl3-CH2Cl2-hexane provided yellow crystals
of 6-PPh3 (21.3 mg, 97%): mp 253 °C dec (apparatus preheated to
236 °C). Anal. Calcd for C30H30IrO4P (677.76): C, 53.16; H, 4.46.
Found: C, 52.79; H, 4.29.
Addition of 2-Methoxypyridine to (3)n To Give 6-NC5H4OMe.
In a way manner to that used to make 6-PMe3, a suspension of (3)n‚
0.5CH2Cl2 (46.6 mg, 0.112 mmol) in CH2Cl2 (ca. 1 mL) in a vial was
treated with 2-methoxypyridine (22.4 mg, 0.205 mmol). Within 2 min
a slightly cloudy yellow solution formed. The mixture was filtered
through a bit of Celite on a glass wool plug in a pipet, and the Celite
was rinsed with additional CH2Cl2. The filtrates were concentrated by
rotary evaporation and the yellow residue stored under oil pump
vacuum, leaving yellow solid 6-NC5H4OMe (51.8 mg, 88%). Anal.
Calcd for C18H22IrNO5 (524.60): C, 41.21; H, 4.23; N, 2.67. Found:
C, 40.75; H, 3.96; N, 2.61.
(5) Reviews: (a) Bryndza, H. E.; Tam, W. Chem. ReV. 1988, 88, 1163-
1188. (b) Fryzuk, M. D.; Montgomery, C. D. Coord. Chem. ReV. 1989,
95, 1-40. Alkoxide π-donation: (c) Lunder, D. M.; Lobkovsky, E.
B.; Streib, W. E.; Caulton, K. G. J. Am. Chem. Soc. 1991, 113, 1837-
1838. (d) Hubbard, J. L.; McVicar, W. K. Inorg. Chem. 1992, 31,
910-913. (e) Poulton, J. T.; Sigalas, M. P.; Folting, K.; Streib, W.
E.; Eisenstein, O.; Caulton, K. G. Inorg. Chem. 1994, 33, 1476-1485.
(f) Bickford, C. C.; Johnson, T. J.; Davidson, E. R.; Caulton, K. G.
Inorg. Chem. 1994, 33, 1080-1086. Amide complexes: (g) Villan-
ueva, L. A.; Abboud, K. A.; Boncella, J. M. Organometallics, 1994,
13, 3921-3931. (h) Rahim, M.; Ahmed, K. J. Organometallics, 1994,
13, 1751-1756. (i) Dewey, M. A.; Knight, D. A.; Arif, A.; Gladysz,
J. A. Chem. Ber. 1992, 125, 815-824 and references therein. Amide
complexes in which there appears to be no π-donation: (k) Joslin, F.
L.; Johnson, M. P.; Mague, J. T.; Roundhill, D. M. Organometallics
1991, 10, 2781-2794.
(6) Wessig, P.; Legart, F.; Hoffmann, B.; Hennig, H.-G. Liebigs Ann. 1991,
979-982.
(7) White, C.; Yates, A.; Maitlis, P. M. Inorg. Synth. 1992, 29, 230.

Table 1. 1H and 13C{1H} NMR and IR Data for Chelate Complexesa
1H
13C{1H}
complex
C5(CH3)5
chelate
L
C5(CH3)5
89.63
C5(CH3)5
chelate
L
IR (KBr, cm-1) νCO
1
1.78 (s, 15 H)
2.39 (s, 6 H, ArsCH3)
2.76 (s, 4 H, CH2CH2)
7.20 (d, J ) 8.0, 4 H)
7.63 (d, J ) 8.0, 4 H)
2.40 (s, 3 H, ArsCH3)
3.35 (s, 2 H, NCH2CO)
7.26 (d, J ) 8, 2 H)
10.34
21.37 (ArsCH3)
53.95 (CH2CH2)
127.15, 129.46 (HsCAr)
139.65, 142.08 (CAr)
21.2 (ArsCH3)
52.9 (NCH2CO2)
127.4, 129.7 (HsCAr)
136.3, 143.2 (CAr)
186.0 (CdO)
2b
1.81 (s, 15 H)
87.7
9.9
1684
7.64 (d, J ) 8, 2 H)
(3)n
1.66 (s, 15 H)
NDc
ND
NDc
ND
NDc
1595, 1633,
1675, 1699
4-PMe3
1.78 (d, J ) 2.0, 15 H) 2.27 (m, 2 H)
2.36 (s, 6 H)
1.85 (d, J ) 9.8, 9 H)
1.59 (d, J ) 11.0, 9 H)
1.44 (d, J ) 11.2)
ND
ND
2.72 (m, 2 H)
7.17 (d, J ) 8.1, 4 H)
7.66 (d, J ) 8.1, 4 H)
2.32-2.38 (m, 2 H)
2.39 (s, 6 H)
4-CO
1.99 (s, 15 H)
101.64
9.48
9.3
21.39 (ArsCH3)
54.84 (CH2CH2)
127.72, 129.16 (HsCAr)
137.28, 141.62 (CAr)
167.96 (CO)
2042d
2.58-2.66 (m, 2 H)
7.18 (d, J ) 8, 2 H)
7.62 (d, J ) 8, 2 H)
b
5-PMe3
5-COb
1.72 (d, J ) 2.1, 15 H) 2.36 (s, 3 H)
3.70 (d, J ) 16.5, 1 H)
91.3 (d, J ) 2.3)
21.1 (ArsCH3)
52.9 (NCH2CO2)
127.0, 129.2 (HsCAr)
139.7, 141.4 (CAr)
185.1 (CO2)
13.8 (d, J ) 37.8, PCH3)
169.2 (CO)
1650 (OCdO)
3.95 (d, J ) 16.5, 1 H)
7.20 (d, J ≈ 8, 2 H)
7.62 (d, J ≈ 8, 2 H)
2.40 (s, 3 H)
3.54 (d, J ) 16.6, 1 H)
3.79 (d, J ) 16.6, 1 H)
7.25 (d, J ) 8.2, 2 H)
7.68 (d, J ) 8.2, 2 H)
1.94 (s, 15 H)
100.9
9.0
21.2 (ArsCH3)
1671 (OCdO)
2033 (CO)
53.9 (NCH2CO2)
128.1, 129.7 (HsCAr)
135.9, 142.7 (CAr)
185.0 (CO2)
165.63 (CO2CO2)
165.76 (CO2CO2)
1651d,e (OCdO)
2049d,e (CO)
6-PMe3
6-PEt3
1.64 (d, J ) 1.5, 15 H)
1.64 (d, J ) 1.7, 15 H)
90.10
8.95
8.77
12.47 (d, J ) 35.2, PCH3)
12.85 (d, J ) 32.8, PCH2)
6.34 (d, J ) 3.1, PCH2CH3)
127.64 (d, J ) 54.1)
128.63 (d, J ) 10.5)
131.19 (d, J ) 2.5)
134.18 (d, J ) 10.6)
57.55 (CH3O)
1677, 1698
1677, 1697
1.75 (quintet, J ) 7.7, 6 H) 90.08 (d, J ) 3.0)
1.04 (dt, J ) 16, 7.6, 9 H)
7.45-7.62 (m, 15 H)
6-PPh3
1.35 (d, J ) 2.0, 15 H)
90.90 (d, J ) 2.5)
8.23
164.69 (CO2CO2)
166.30 (CO2CO2)
1677, 1694
6-NC5H4OMef 1.54 (s, 15 H)
3.96 (s, 3 H)
83.60
8.72
1677, 1697
6.90-6.98 (m, 2 H)
108.41 (C-3)
118.66 (C-5)
7.77 (t, J ) 7.0, 1 H)
8.18 (d, J ) 5.6, 1 H)
142.53 (C-4)
149.97 (C-6)
164.04 (C-2)
168.50 (CO)
6-CO
1.88 (s, 15 H)
99.16
8.95
164.31 (CO2CO2)
1673d
1707d
2064d
a CDCl3 solvent, chemical shifts δ relative to those of CHCl3 ) (7.27 ppm) and CDCl3 (77.00 ppm). Coupling constants J in hertz. ND ) not determined. b NMR and IR data from refs 1 and 2 unless
f
otherwise noted. c Poor solubility precluded observation of the 13C{1H} NMR spectrum. d In CDCl3. e IR data in CDCl3 from this work. NC5H4OMe ) 2-methoxypyridine. 13C resonances assigned with
the aid of GHMQC and GHMBC experiments.

2496 Inorganic Chemistry, Vol. 39, No. 12, 2000
Grotjahn et al.
Alternative Synthesis of 6-PMe3. To a suspension of [(η5-C5Me5)-
IrCl(µ-Cl)]2 (68.8 mg, 0.0863 mmol) in dry THF (2 mL) was added
PMe3 (25 µL, 1.4 equiv), whereupon the solid dissolved rapidly. After
5 min, the orange solution was concentrated on the vacuum line, leaving
an orange solid: 1H NMR (200 MHz, CDCl3) δ 1.71 (d, J ) 2 Hz, 15
H), 1.66 (d, J ) 11.2 Hz, 9 H). In the glovebox, the residue was
dissolved in CH3CN (2 mL), and Ag2C2O4 (62.2 mg, 0.205 mmol, 1.19
equiv) was added. The flask was covered with foil, the contents were
stirred for 14 h before CH2Cl2 (2 mL) was added outside the glovebox,
and the now-yellow solution and white powder were filtered through
a plug of Celite in a pipet. The plug was rinsed with CH2Cl2 in small
portions, and combined filtrates were concentrated by rotary evapora-
tion. The yellow solid remaining exhibited the same spectral properties
as those reported above. The solid was dissolved in CH2Cl2 (ca. 1 mL),
and a layer of THF (2 mL) was carefully added. Yellow crystals of
6-PMe3 (78.6 mg, 93%) were isolated by pipetting off the supernatant
and storage under high vacuum. NMR spectral properties matched those
of the sample prepared from (3)n and the literature values.8
Alternative Synthesis of 6-PEt3. In a manner similar to that used
for the PMe3 analogue, [(η5-C5Me5)IrCl(µ-Cl)]2 (52 mg) and PEt3 (0.02
mL) were combined in THF (5 mL); after isolation, the resulting
intermediate was stirred in THF with Ag2C2O4 (38.1 mg). The mixture
was worked up as in the synthesis of 6-PMe3 and the crude product
crystallized from CH2Cl2-hexanes to give yellow crystals of 6-PEt3
(54.9 mg, 55%).
Alternative Synthesis of 6-PPh3. In a manner similar to that used
for the PMe3 analogue, [(η5-C5Me5)IrCl(µ-Cl)]2 (50.0 mg, 0.0628 mmol)
and PPh3 (32.9 mg, 0.126 mmol) were combined in CH2Cl2 (5 mL);
after 1 d, to the resulting solution was added Ag2C2O4 (38.2 mg, 0.126
mmol). After the mixture was stirred for 1 d, 1H NMR spectral analysis
of an aliquot revealed unreacted dichloro complex, so more Ag2C2O4
(38.0 mg) was added and the mixture stirred for an additional 1 d before
workup and crystallization gave yellow crystals of 6-PPh3 (47.5 mg,
53%).
Thermochemistry. General Considerations. All manipulations
involving organoiridium complexes were performed under argon using
standard high-vacuum or Schlenk tube techniques, or in a MBraun
glovebox containing less than 1 ppm oxygen and water. Trimethylphos-
phine was purchased from Aldrich and used as received. Solvents were
dried and distilled under argon before use employing standard drying
agents.9 Only materials of high purity as indicated by NMR spectros-
copy were used in the calorimetric experiments. NMR spectra were
recorded using a Varian Gemini 300 MHz spectrometer. Calorimetric
measurements were performed using a Calvet calorimeter (Setaram
C-80) which was periodically calibrated using the TRIS reaction10 or
the enthalpy of solution of KCl in water.11 The experimental enthalpies
for these two standard reactions compared very closely to literature
values. This calorimeter has been previously described,12 and typical
procedures are described below. Experimental enthalpy data are reported
with 95% confidence limits.
Table 2. Crystallographic Data for 7
empirical formula
fw
space group
unit cell dimens
C22H30Cl2Ir2O4
813.8
P21/c
a ) 8.205(2) Å
b ) 8.945(4) Å
c ) 16.714(6) Å
â ) 94.22(2)°
1223.3(10)
V (Å3)
Z
2
temp (°C)
radiation
density (calcd)
-100
Mo KR (λ ) 0.710 73 Å)
2.209
11.072
abs coeff (mm-1
)
quantity minimized
∑w(Fo - Fc)2
R1 ) 2.31%, wR2 ) 3.36%
R1 ) 3.49%, wR2 ) 3.93%
final R indicesa (obsd data)
R indices (all data)
a R1 ) ∑||Fo| - |Fc||∑|Fo|. wR2 ) [∑[w(Fo2 - Fc2)2]/∑[w(Fo )2]]1/2
.
2
GOF ) [∑[w(Fo2 - Fc2)2]/(n - p)]1/2, where n ) number of reflections
2
and p ) number of parameters refined. w ) 1/[σ2(Fo ) + (0.0326P)2
2
+ 224.2319P], where P ) (Fo + 2Fc2)/3.
the glovebox. A 20 mg sample of 2 was accurately weighed into the
lower vessel, which was closed and sealed with 1.5 mL of mercury. A
4 mL sample of a stock solution of PMe3 (250 mg of PMe3 in 20 mL
of THF) was added, and the remainder of the cell was assembled,
removed from the glovebox, and inserted into the calorimeter. The
reference vessel was loaded in an identical fashion with the exception
that no organoiridium complex was added to the lower vessel. After
the calorimeter had reached thermal equilibrium at 30.0 °C (about 2
h), the calorimeter was inverted, thereby allowing the reactants to mix.
After the reaction had reached completion and the calorimeter had once
again reached thermal equilibrium (ca. 2 h), the vessels were removed
from the calorimeter. Conversion to 5-PMe3 was found to be
quantitative under these reaction conditions. Control reactions with Hg
and PMe3 showed no reaction. Enthalpy data are the average of five
individual calorimetric determinations. The final enthalpy value (-28.5
( 0.4 kcal/mol) represents the enthalpy of reaction with all species in
solution. This methodology represents a typical procedure involving
all organoiridium compounds and all reactions investigated in the
present study.
Enthalpy of Solution of 2. To consider all species in solution, the
enthalpy of solution of 2 had to be directly measured. This was
performed by using a procedure similar to the one described above
with the exception that no PMe3 was added to the reaction cell. The
enthalpy of solution, 4.1 ( 0.2 kcal/mol, represents the average of five
individual determinations.
Crystal Structure of 7. A yellow crystal of suitable size was
mounted vertically in a 0.3 mm X-ray capillary and centered optically
on a Siemens P4 autodiffractometer, precooled to -100 °C with the
LT-2a low-temperature device. The centering of 25 randomly chosen
reflections with 15° g 2θ g 30° led to the selection of a primitive
monoclinic cell. Data were collected at -100 °C (Table 2). The space
group was chosen on the basis of the systematic absences (0k0, k odd;
h0l, l odd). The structure was solved using Patterson methods, and
refinement of the non-hydrogen atoms to convergence was carried out
using the SHELXTL Plus package of programs from Siemens (Madison,
WI). Hydrogen atoms were generated in idealized positions with fixed
isotropic thermal parameters. The asymmetric unit represents half of
the centrosymmetric dinuclear complex that is generated through the
inversion center of the molecule. An empirical absorption correction
using the ψ scan data was attempted, but no improvement in the
refinement or in the minimization of the peaks in the vicinity of the Ir
atom could be attained. See Table 3 for the most important bond lengths
and angles.
NMR Titrations. Prior to every set of calorimetric experiments
involving PMe3, an accurately weighed amount ((0.1 mg) of the
organoiridium complex was placed in a Wilmad screw-capped NMR
tube and THF-d8 was subsequently added. The solution was titrated
with a solution of PMe3 by injecting the latter in aliquots through the
septum with a microsyringe, followed by vigorous shaking. The
1
reactions were monitored by 31P and H NMR spectroscopy, and the
reactions were found to be rapid, clean, and quantitative. These
conditions are necessary for accurate and meaningful calorimetric results
and were satisfied for all organometallic reactions investigated.
Solution Calorimetry. Calorimetric Measurement of Reaction
between 2 and PMe3. The mixing vessels of the Setaram C-80 were
cleaned, dried in an oven maintained at 120 °C, and then taken into
(8) Freedman, D. A.; Mann, K. R. Inorg. Chem. 1991, 30, 836-840.
(9) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals, 3rd ed.; Pergamon Press: New York, 1988.
(10) Ojelund, G.; Wadso¨, I. Acta Chem. Scand. 1968, 2, 1691-1699.
(11) Kilday, M. V. J. Res. Natl. Bur. Stand. (U.S.) 1980, 85, 467-481.
(12) (a) Nolan, S. P.; Hoff, C. D.; Landrum, J. T. J. Organomet. Chem.
1985, 282, 357-362. (b) Nolan, S. P.; Lopez de la Vega, R.; Hoff, C.
D. Inorg. Chem. 1986, 25, 4446-4448.
Results and Discussion
Syntheses and Ligand Additions. η2-(N,N)-Bis(sulfonamido)
chelate complex 1 was prepared in much the same way as 2:1,2
TsNHCH2CH2NHTs6 reacted with solid K2CO3 and 0.5 mol of

Synthesis and Thermochemistry of Chelate Complexes
Inorganic Chemistry, Vol. 39, No. 12, 2000 2497
Table 3. Selected Bond Lengths (Å) and Bond Angles (deg) for 7
Scheme 2
Ir-Cl
2.381(2)
2.145(5)
2.157(5)
1.255(9)
1.250(9)
2.115(7)
2.121(7)
2.123(7)
2.117(7)
2.131(8)
Cl-Ir-O(1)
85.5(2)
85.0(2)
76.9(2)
116.7(8)
125.3(7)
118.0(8)
114.3(4)
113.5(5)
Ir-O(1)
Ir-O(2)
O(1)-C(6)
O(2)-C(6a)
Ir-C(1)
Ir-C(2)
Ir-C(3)
Ir-C(4)
Ir-C(5)
Cl-Ir-O(2)
O(1)-Ir-O(2)
O(1)-C(6)-C(6a)
O(1)-C(6)-O(2a)
C(6a)-C(6)-O(2a)
Ir-O(1)-C(6)
Ir-O(2)-C(6a)
7
the dimer [(η5-C5Me5)IrCl(µ-Cl)]2 in CH2Cl2 to form 1 as a
deep burgundy solid in 98% yield. The 1H NMR spectroscopic
data for 1 in CDCl3 revealed a singlet at δ 2.76 ppm for all
four methylene protons (Table 1), consistent with a monomeric
structure like that of crystallographically characterized 2, in
which the C5Me5 centroid and the five atoms of the chelate
ring lie nearly in the same plane.1,2 When a dark red solution
of 1 in CDCl3 was treated with PMe3, the color immediately
and removal of solvent from the filtrate and recrystallization
from CH2Cl2-THF, a yellow powdery solid giving correct
combustion data for 3‚0.5 CH2Cl2 could be obtained in 78%
yield. The yellow color of the product and its curiously low
solubility in CDCl3 strongly suggested that the compound was
not the monomeric 16-electron structure represented by 3, but
rather was an oligomer or polymer in which each metal center
achieved coordinative saturation as schematically illustrated in
structure (3)n (Scheme 2). By comparison, 18-electron amino
acid complexes 5 are all yellow solids, whereas their coordi-
natively unsaturated precursors 2 are red.1,2 Furthermore, as
adduced by comparison of IR spectra,1,2 related complex 8
appears to exist as a red monomer in CH2Cl2 solution, but as a
yellow oligomer or polymer, (8)n, involving bridging by the
amide group in the solid state. To gain more information about
the structure of (3)n, its ligand addition chemistry was explored.
A suspension of presumed (3)n in CDCl3 exhibited a weak
singlet at δ 1.66 ppm from the small amount of dissolved
compound. The yellow solid dissolved within 1 min when PMe3
1
changed to yellow, and H NMR spectroscopy revealed two
multiplets at 2.27 and 2.72 ppm, each integrating for two
protons, changes expected to accompany formation of 4-PMe3
1
and its AA′MM′ spin system. Similar changes in H NMR
spectroscopic data and color occurred when 4-CO was formed
from 1 by bubbling CO through a CDCl3 solution of 1 for about
2 min.
Installation of the oxalato ligand on (η5-C5Me5)Ir proved to
be more problematic, requiring the use of silver oxalate13 on
the dimer [(η5-C5Me5)IrCl(µ-Cl)]2. Even with use of excess
silver oxalate, however, in reaction solvent CH2Cl2 or THF only
half the chloride ligands were exchanged and yellow-orange
crystals of oxalato-bridged dimer 7, which is somewhat soluble
1
was added. In the H NMR spectrum of the resulting yellow
solution, doublets at δ 1.65 (J ) 1.5 Hz, 15 H) and 1.45 (J )
11.2 Hz, 9 H) were consistent with the presence of the known8
complex 6-PMe3, which was isolated in 75% yield. The same
complex could also be made in 93% yield by initial addition of
PMe3 to [(η5-C5Me5)IrCl(µ-Cl)]2 to form (η5-C5Me5)IrCl2-
(PMe3),16 followed by reaction with Ag2C2O4 in CH3CN. In
6-PMe3 the presence of the oxalato ligand was confirmed by
a singlet in the 13C NMR spectrum at δ 165.63 ppm. However,
the most striking spectroscopic differences between (3)n and
6-PMe3 appeared in IR spectra. Whereas the IR spectrum of
6-PMe3 in KBr showed two absorptions at 1677 and 1698
cm-1, attributable to the symmetrical and asymmetrical stretch-
ing of the carbonyl groups,13,14 the spectrum of (3)n in KBr
showed four very strong absorptions at 1595, 1633, 1675, and
1699 cm-1, which would be consistent with oxalato ligands in
both bridging and terminal coordination modes in (3)n. There-
fore, comparison of the IR data for (3)n and 6 strongly suggests
the conversion of bridging oxalato ligands in (3)n to a chelating
one in 6.
Oligomer (3)n appears to be a versatile precursor to other
complexes. For example, 6-PEt3 and 6-PPh3 could be made
in over 90% yield in one step from (3)n and the appropriate
phosphine. Independent syntheses were accomplished from
initial reaction of dimer [(η5-C5Me5)IrCl(µ-Cl)]2 with the
appropriate phosphine, followed by introduction of silver
oxalate. The IR and NMR spectroscopic data for the two new
phosphine complexes resembled those of 6-PMe3 (Table 1).
in CH2Cl2, were formed. The dimeric structure was suggested
by the observation of a single very strong infrared absorption
at 1620 cm-1, similar to the spectral data for other µ-η2-η2-
C2O4 complexes14,15 and different from the two bands seen
between 1650 and 1750 cm-1 for most η2-C2O4 complexes.13-15
Furthermore, the combustion analyses for C and H were in
accord with the proposed structure, although the calculated
values for 7 and 3 were fairly close. An X-ray diffraction study
on crystals grown from CH2Cl2-THF identified the structure
of 7 (vide infra).
On the other hand, if CH3CN was used as reaction solvent
for silver oxalate and [(η5-C5Me5)IrCl(µ-Cl)]2, after filtration
(13) Paonessa, R. S.; Prignano, A. L.; Trogler, W. C. Organometallics 1985,
4, 647-657.
(14) Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coor-
dination Compounds, Part B, 5th ed.; Wiley: New York, 1997; pp
74-77.
(15) (a) Overview: Oldham, C. In ComprehensiVe Coordination Chemistry;
Wilkinson, G., Gillard, R. D., McCleverty, J. A., Eds.; Pergamon:
Oxford, 1987; Vol. 2, pp 443-446. Examples of related µ-η4 and η2
complexes: (b) Coucouvanis, D.; Demadis, K. D.; Kim, C. G.;
Dunham, R. W.; Kampf, J. W. J. Am. Chem. Soc. 1993, 115, 3344-
3345. (c) Yan, H.; Su¨ss-Fink, G.; Neels, A.; Stoeckli-Evans, H. J.
Chem. Soc., Dalton Trans. 1997, 4345-4350. (d) Castro, I.; Calatayud,
M. L.; Sletten, J.; Lloret, F.; Julve, M. J. Chem. Soc., Dalton Trans.
1997, 811-817. (e) Oro, L. A.; Pinillos, M. T.; Jarauta, M. P.
Polyhedron 1985, 4, 325-331. Examples of η2 complexes: (f)
Reference 8. (g) Prignano, A. L.; Trogler, W. C. Inorg. Chem. 1986,
25, 4454-4456. (h) Dovletoglou, A.; Adeyemi, S. A.; Meyer, T. J.
Inorg. Chem. 1996, 35, 4120-4127. (i) Shinozaki, K.; Takahashi, N.
Inorg. Chem. 1996, 35, 3917-3924. (j) Real, J.; Bayo´n, J. C.; Lahoz,
F. J.; Lo´pez, J. A J. Chem. Soc., Chem. Commun. 1989, 1889-1890.
(16) Kang, J. W.; Moseley, K.; Maitlis, P. M. J. Am. Chem. Soc. 1969, 91,
5970-5977.

2498 Inorganic Chemistry, Vol. 39, No. 12, 2000
Grotjahn et al.
yellow solutions of 6. We noted that (3)n dissolved in CH3CN,
but on removal of solvent, only (3)n remained, free of CH3CN.
Similar behavior has been observed for (η5-C5Me5)Ru(proline).19
Comparison of IR spectral data for (3)n and 6 strongly suggest
the conversion of unsymmetrical bridging oxalato ligands to
chelating ones. Although the insolubility of (3)n precluded
extension of thermochemical studies to include the entire series
1-3, we thought that the carboxylato ligand was smaller and a
poorer donor than the N-tosylamido ligand, leading to the
propensity for 3 to oligomerize. The importance of electronic
properties is suggested by comparison of the acidities of bound
water molecules in Ru complexes, which led other workers15h
to conclude that an acetylacetonato ligand is a better π-donor
than an oxalato ligand.
Figure 1. A view of the structure of complex 7.
In addition, 2-methoxypyridine added readily to provide
6-NC5H4OMe in 88% yield, and saturation of a suspension of
(3)n in CDCl3 with CO provided 6-CO after 0.5 h.
To determine the role of electronic factors, the CO adducts
of 1-3 (4-CO, 5-CO, and 6-CO) were examined by IR
spectroscopy in CDCl3 solution.20 Others have used νCO as a
probe of the electron density of a metal center.21 The observed
values of νCO in 4-CO (2042 cm-1), 5-CO (2049 cm-1), and
6-CO (2064 cm-1) clearly indicate that the sulfonamido ligands
are better donors than the oxalato ligand. Interestingly, the
replacement of one sulfonamido group in 4-CO with a
carboxylato group results in a slight change (7 cm-1), whereas
replacement of the sole sulfonamido in 5-CO with a carboxy-
lato group produces a larger change (15 cm-1). The π-donating
abilities of sulfonamide and carboxylate substituents in organic
compounds have been compared using variants of the Hammett
equation.22 Focusing on the effect of an aromatic substituent
on the para position, which is taken as a measure of π-donation
or -acceptance, it appears that the -NHSO2Ph group (σP )
-0.01 or +0.01) is a better donor than the O2CCH3 substituent
(σP ) 0.31). However, in electronically saturated 18-electron
metal centers such as those found in 4-CO, 5-CO, and 6-CO,
there is typically no significant π-interaction between the metal
and oxo and amide ligands.5 Therefore, although π-donation is
important in formally 16-electron complexes 1-3,1,2 the dif-
ferences in IR data for the three electronically saturated CO
complexes may be ascribed to superior σ-donation of the
sulfonamido ligand compared with that of the carboxylato
ligand. Relevant literature examples of spectroscopic changes
accompanying changes in pure σ-donating ability are (dien)-
Finally, upon addition of PMe3, dimer 7 disproportionated
to give a mixture of (η5-C5Me5)IrCl2(PMe3)16 and 6-PMe3.
Thermochemistry of Ligand Addition. The enthalpies of
solution for 1 and 2 in THF were +5.0(0.3) and +4.1(0.2) kcal
mol-1, respectively. Enthalpies of reaction between PMe3 and
1 and 2 were -23.7(0.5) and -24.4(0.3) kcal mol-1, respec-
tively. Therefore, the enthalpies of reaction with all species in
solution amounted to -28.7(0.5) and -28.5(0.4) kcal mol-1
for 1 and 2, the same within experimental uncertainty. Unfor-
tunately, the analogous oxalato complex formulated as (3)n
exhibited negligible solubility in THF and could not be used in
these experiments. Very few systems of this kind have been
studied, so given the limited data it is not clear why the enthalpy
difference between two ligand additions is experimentally
negligible.
Crystal Structure of 7. Yellow plates of 7 suitable for an
X-ray diffraction study were obtained from CH2Cl2-THF. The
structure (Figure 1) verifies the basic constitution of the
molecule and is centrosymmetric, containing an inversion center.
Many such structures are known,15,17 and the one reported agrees
well with the literature examples. For example, within experi-
mental uncertainty, the bond lengths C(6)-O(1) and C(6a)-
O(2) are identical [1.255(9) and 1.250(9) Å, respectively], and
are the same as values reported for other µ-η2-η2-C2O4
complexes.15,17 In contrast, in mononuclear η2-C2O4 oxalato
complexes the average lengths of the CdO and CsO bonds
are 1.224 and 1.279 Å, respectively.18
Mo(CO)3 (1883 and 1723 cm-1 23a
and the analogous perm-
)
Comparisons of Carboxylato and N-Tosylamido Ligands.
Color, solubility, and IR spectral data are key indicators of the
structure of the complexes considered in this paper and,
ultimately, of the behavior of ligands on the (η5-C5Me5)IrIII
fragment. We have previously shown that 2 is a red monomer
in the solid state.1,2 From the work described here, complexes
1 and 2, which both have sulfonamido ligands, show very similar
properties: both are red in color and formally 16-electron
species, either in solution or in the solid state. In comparison,
previous work1,2 showed that related amidato complex 8
(Scheme 2) is red in solution but yellow in the solid state.
Changes in IR absorptions pointed to oligomerization or
polymerization in the solid state with concomitant formation
of coordinatively saturated Ir centers in (8)n.
ethylated complex of Me2NCH2CH2N(Me)CH2CH2NMe2 (1907,
1774, and 1755 cm-1),23b or the Mo(CO)3 complexes of 1,4,7-
triazacyclononane (1850 and 1740-1700 cm-1 24a
and a per-
)
alkylated analogue (1895, 1759, and 1729 cm-1).24b Taken
together with the large difference in structure between monomer
21,2 (with one carboxylato ligand) and oligomer (3)n (with two
carboxylato ligands per monomer), we conclude that one
sulfonamido group provides sufficient donation, whether in σ-
or π-fashion, to stabilize the monomeric form.
Finally, we note that the removal of all chloride ligands from
(19) Koelle, U. Chem. ReV. 1998, 98, 1313-1334.
(20) For 5-CO in KBr, νCO had been reported as 2033 cm-1.2 In the work
reported here, the values for IR absorptions have estimated uncertain-
ties of (2 cm-1
.
In the present study, attempted formation of 3 led to isolation
of a yellow, poorly soluble solid, formulated as an oligomer or
polymer, (3)n, which dissolves only on addition of a two-electron
donor such as a phosphine, CO, or 2-methoxypyridine, forming
(21) Moloy, K. G.; Petersen, J. L. J. Am. Chem. Soc. 1995, 117, 7696-
7710 and refs 10-12 and 15 therein.
(22) Exner, O. In Correlation Analysis in Chemistry; Chapman, N. B.,
Shorter, J., Eds.; Plenum: New York, 1978; Chapter 10, pp 439-
540, especially pp 468 and 472.
(23) (a) Abel, E. W.; Bennett, M. A.; Wilkinson, G. J. Chem. Soc. 1959,
2323-2327. (b) Zanotti, V.; Rutar, V.; Angelici, R. J. J. Organomet.
Chem. 1991, 414, 177-191.
(24) (a) Chaudhuri, P.; Wieghardt, K.; Tsai, Y.-H.; Kru¨ger, C. Inorg. Chem.
1984, 23, 427-432. (b) Beissel, T.; Dellavedova, B. S. P. C.;
Wieghardt, K.; Boese, R. Inorg. Chem. 1990, 29, 1736-1741.
(17) (a) Felthouse, T. R.; Laskowski, E. J.; Hendrickson, D. N. Inorg. Chem.
1977, 16, 1077-1079. (b) Cheng, P.-T.; Loescher, B. R.; Nyburg, S.
C. Inorg. Chem. 1971, 10, 1275-1281.
(18) Orpen, A. G.; Brammer, L.; Allen, F. H.; Kennard, O.; Watson, D.
G.; Taylor, R. J. Chem. Soc., Dalton Trans. 1989, S1-S83.

Synthesis and Thermochemistry of Chelate Complexes
Inorganic Chemistry, Vol. 39, No. 12, 2000 2499
[(η5-C5Me5)IrCl(µ-Cl)]2 in the synthesis of oxalato complex (3)n
required the use of silver ion and the polar, coordinating solvent
CH3CN, whereas synthesis of chelate complexes 1 and 2 could
be accomplished using only potassium carbonate, even in
dichloromethane, perhaps a reflection of the relative nucleo-
philicities of the conjugate bases of oxalic acid and N-
sulfonamides.
sulfonamido ligands to catalysis.4 Furthermore, (3)n is a versatile
precursor to monomeric complexes 6 by simple ligand addition.
Acknowledgment. D.B.G., C.A., and J.D. acknowledge San
Diego State University for partial support of this work. S.P.N.
acknowledges the National Science Foundation (Grant CHE
9985213). We thank Professor Patrick Walsh for suggesting the
study of the CO complexes.
Conclusions
Supporting Information Available: An X-ray crystallographic file
in CIF format for the structure of 7. This material is available free of
charge via the Internet at http://pubs.acs.org.
The characterization of monomers 1 and 2 and oligomer or
polymer (3)n and IR spectroscopic data on the corresponding
CO adducts point to the competence of the N-tosylamido ligand
as a π- or σ-donor, which has bearing on the application of the
IC990870L