Synthesis of (O2CEPh)1- ligands (E = S, Se) by CO2 insertion into lanthanide chalcogen bonds and their utility in forming crystallographically characterizable organoaluminum complexes [Me 2Al(μ-O2CEPh

Article abstract of DOI:10.1021/ic0515610

CO₂ inserts into the Sm-S and Sm-Se bonds of [(C ₅Me₅)₂Sm(μ-EPh)]₂ (E - S, Se) to form the first crystallographically characterized (O₂CEPh) ^1- complexes, [(C₅Me₅

Full text of DOI:10.1021/ic0515610

Inorg. Chem. 2006, 45, 424−429
-
Synthesis of (O2CEPh)1 Ligands (E
Lanthanide Chalcogen Bonds and Their Utility in Forming
Crystallographically Characterizable Organoaluminum Complexes
[Me2Al( -O2CEPh)]2
) S, Se) by CO2 Insertion into
µ
William J. Evans,* Kevin A. Miller, and Joseph W. Ziller
Department of Chemistry, UniVersity of California, IrVine, California 92697-2025
Received September 12, 2005
CO2 inserts into the Sm
crystallographically characterized (O2CEPh)1- complexes, [(C5Me5)2Sm(
analogous to [(C5Me5)2Sm( -O2CR)]2 complexes, but they are less soluble. This feature was utilized in the reaction
of Me2AlCl with [(C5Me5)2Sm( -O2CEPh)]2, which forms crystallographically characterizable [Me2Al( -O2CEPh)]2
complexes. Such complexes could not be isolated from an analogous carboxylate reaction. [(C5Me5)2Sm( -O2-
−S and Sm
−
Se bonds of [(C5Me5)2Sm(
µ
-EPh)]2 (E
) S, Se) to form the first
µ-O2CEPh)]2. These complexes are structurally
µ
µ
µ
µ
CSePh)]2 decarboxylates in THF to form (C5Me5)2Sm(SePh)(THF). The loss of CO2 rather than COSe with formation
of (C5Me5)2Sm(OPh)(THF) was established by 13CO2 studies and independent synthesis of (C5Me5)2Sm(OPh)-
(THF) from (C5Me5)2Sm[N(SiMe3)2] and PhOH.
Introduction
complex from such a reaction, (C5Me5)2U(O2CStBu)2, which
was characterized by analytical and spectroscopic methods.8
The insertion of CO2 into reactive M-C bonds of
electropositive metals has been used for decades to convert
alkyl complexes into more stable, tractable carboxylate
derivatives.1-6 Insertion of CO2 into other types of metal-
ligand bonds (M-H, M-N, M-O) has also received
considerable attention,3,6 but to the best of our knowledge
there are few reports involving metal-chalcogen bonds,
M-E (E ) S, Se, Te).7,8 The only examples of this type of
reaction involve CO2 insertions into uranium-sulfur bonds.
The reaction of (C5H5)3U(SiPr) with CO2 to form (C5H5)3U(O2-
CSiPr) was reported to be the first insertion of CO2 into a
metal-sulfur bond of any kind.7 However, this complex
could not be isolated in pure form because of facile
decarboxylation. Subsequently, the reaction of (C5Me5)2U-
(StBu)2 with CO2, eq 1, was found to give the first isolatable
2CO2
(C5Me5)2U(StBu)2
8 (C5Me5)2U(O2CStBu)2 (1)
As part of a recent study of the ligand reduction chemistry
of the aryl chalcogenide metallocenes (C5Me5)2Sm(EPh)-
(THF) and [(C5Me5)2Sm(µ-EPh)]2 (E ) S, Se, Te),9 we
examined the reactivity of these complexes with CO2 to
determine if insertion would occur and be useful in deriva-
tizing Ln-S, Ln-Se, and Ln-Te bonds. We report here the
first crystallographically defined details on (O2CEPh)1- lig-
ands derived from M-E/CO2 insertion reactions. The utility
of the (O2CEPh)1- ligands in providing crystallizable orga-
noaluminum derivatives is also described, as well as the de-
carboxylation chemistry of [(C5Me5)2Sm(µ-O2CSePh)]2 in
THF.
* To whom correspondence should be addressed. Fax: 949-824-2210.
E-mail: wevans@uci.edu.
(1) Weidlein, J. Z. Anorg. Allg. Chem. 1970, 378, 245.
(2) Sneeden, R. P. A. In ComprehensiVe Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press:
New York, 1982; Chapter 50.4.
(3) Palmer, D. A.; Eldik, R. V. Chem. ReV. 1983, 83, 651.
(4) Braunstein, P.; Matt, D.; Nobel, D. Chem. ReV. 1988, 88, 747.
(5) Pandey, K. K. Coord. Chem. ReV. 1995, 140, 37.
(6) Xiaolang, Y.; Moss, J. R. Coord. Chem. ReV. 1999, 181, 27.
(7) Leverd, P. C.; Ephritikhine, M.; Lance, M.; Vigner, J.; Nierlich, M.
J. Organomet. Chem. 1996, 507, 229.
Experimental Section
The manipulations described below were performed under argon
or nitrogen with rigorous exclusion of air and water using Schlenk,
vacuum line, and glovebox techniques. Solvents were saturated with
UHP grade argon (Airgas), and were dried by passage through
Glasscontour drying columns before use. NMR solvents were dried
over NaK, and vacuum transferred before use. NMR spectra were
(8) Lescop, C.; Arliguie, T.; Lance, M.; Nierlich, M.; Ephritikhine, M. J.
Organomet. Chem. 1999, 580, 137.
(9) Evans, W. J.; Miller, K. A.; Lee, D. S.; Ziller, J. W. Inorg. Chem.
2005, 44, 4326.
424 Inorganic Chemistry, Vol. 45, No. 1, 2006
10.1021/ic0515610 CCC: $33.50
© 2006 American Chemical Society
Published on Web 11/15/2005

Synthesis and Utility of (O2CEPh)1- Ligands
recorded with a Bruker DRX 500 MHz system. Infrared spectra
were recorded as thin films obtained from deuterotoluene or deu-
terobenzene on an ASI ReactIR 1000 instrument.10 (C5Me5)2Sm-
(EPh)(THF) (E ) Se),9 [(C5Me5)2Sm(µ-EPh)]2 (E ) S, Se),9 and
(C5Me5)2Sm[N(SiMe3)2]11 were prepared as previously described.
PhOH was purchased from Aldrich, and was sublimed before use.
CO2 and 13CO2 were purchased from Airgas and Cambridge Isotope
Laboratories, Inc., respectively. Me2AlCl (1.0 M in hexanes) was
purchased from Aldrich. Complete elemental analyses were per-
formed by Analytische Laboratorien (Lindlar, Germany). Com-
plexometric analyses were carried out as previously described.12
[(C5Me5)2Sm(µ-O2CSPh)]2, 1. In an argon-filled glovebox free
of coordinating solvents, an orange solution of [(C5Me5)2Sm(µ-
2 Hz), 6.89 (m, 3H), 7.09 (m, 2H). 13C (125.7 MHz, benzene-d6):
δ -11.5 (CH3), 129.9 (phenyl), 130.9 (phenyl), 135.5 (phenyl);
the ipso carbon was not located. IR: 2961s, 2930s, 2856m, 1613s,
1583s, 1478w, 1444s, 1382s, 1332s, 1262s, 1197s, 1158w, 1092s,
1096s, 1019s, 915w, 861s, 803s, 703s cm-1. Anal. Calcd for C18H22-
Al2O4S2: C, 51.42; H, 5.27; Al, 12.83. Found: C, 51.19; H, 5.36;
Al, 12.64.
[Me2Al(µ-O2CSePh)]2, 4. As described for 3, 4 was obtained
from Me2AlCl (64 µL, 0.692 mmol) and [(C5Me5)2Sm(µ-O2-
1
CSePh)]2 (2; 215 mg, 0.173 mmol) in toluene (4 mL). H NMR
spectroscopy showed complete consumption of the starting material
and formation of only the previously characterized (C5Me5)2Sm-
13
(µ-Cl)2AlMe2 and resonances for 4 isolated as described below.
9
The red solid was dissolved in hexane, and cooled to -35 °C. After
2 days, 4 was obtained as colorless crystals (37 mg, 42%). Crystals
suitable for X-ray diffraction were grown from hexane at -35 °C.
1H NMR (500 MHz, benzene-d6): δ -0.67 (s, 6H, ∆ν1/2 ) 2 Hz),
6.90 (m, 3H), 7.22 (m, 2H). 13C NMR (125.7 MHz, benzene-d6):
δ -11.2 (CH3), 130.1 (phenyl), 130.4 (phenyl), 136.6 (phenyl);
the ipso carbon was not located. IR: 2930s, 2895m, 2853w, 1606s,
1567s, 1478m, 1440s, 1339s, 1289s, 1262s, 1200s, 1158w, 1092s,
1019s, 911w, 803s, 703s cm-1. Anal. Calcd for C18H22Al2O4Se2:
C, 42.04; H, 4.31; Se, 30.72; Al, 10.49. Found: C, 41.89; H, 4.26;
Se, 30.25; Al, 10.63.
SPh)]2 (31 mg, 0.029 mmol) in benzene-d6 (1 mL) was added to
a J-Young NMR tube. The solution was degassed by three freeze-
pump-thaw cycles. The NMR tube was subsequently charged with
1 atm of CO2 gas. The solution became yellow, and orange crystals
suitable for X-ray diffraction were observed after 12 h. Removal
of solvent yielded 1 as an orange crystalline powder (31 mg, 94%).
1H NMR (500 MHz, toluene-d8): δ 1.44 (s, 30H, C5Me5, ∆ν1/2
)
3
3
4 Hz), 4.13 (d, 2H, JHH ) 7 Hz, o-H), 5.08 (t, 2H, JHH ) 7 Hz,
3
m-H), 5.41 (t, 1H, JHH ) 7 Hz, p-H). 13C NMR (125.8 MHz,
toluene-d8): δ 18.8 (C5Me5), 116.5 (C5Me5), 132.2 (o-phenyl), 126.7
(m-phenyl), 127.2 (p-phenyl); the ipso carbon was not located. IR:
3057w, 2961s, 2918s, 2856s, 2729s, 2235s, 1598s, 1532s, 1475s,
(C5Me5)2Sm(OPh)(THF), 5. In a nitrogen-filled glovebox,
PhOH (22 mg, 0.231 mmol) in 3 mL of THF was added dropwise
to a stirred solution of orange (C5Me5)2Sm[N(SiMe3)2]11 (134 mg,
0.230 mmol) in THF (5 mL). A clear yellow solution immediately
formed. After the mixture was stirred overnight, the yellow solution
was evaporated to dryness to yield 5 as a yellow powder (131 mg,
97%). Crystals of 5 suitable for X-ray diffraction were grown at
-35 °C from a concentrated hexane solution. 1H NMR (500 MHz,
THF-d8): δ 1.25 (s, 30H, C5Me5, ∆ν1/2 ) 2 Hz), 7.12 (t, 1H, 3JHH
1440s, 1378s, 1262s, 1089s, 1023s, 799s, 741s, 691s, 587w cm-1
.
Anal. Calcd for C54H70O4S2Sm2‚2C6H6: C, 60.78; H, 6.34, S, 4.92;
Sm, 23.06. Found: C, 60.75; H, 6.27; S, 4.82; Sm, 22.90.
[(C5Me5)2Sm(µ-O2CSePh)]2, 2. As described for 1, 2 was
obtained as an orange crystalline powder (32 mg, 96%) from [(C5-
9
Me5)2Sm(µ-SePh)]2 (31 mg, 0.025 mmol) in benzene-d6 (1 mL).
Orange crystals suitable for X-ray diffraction were observed after
1
12 h. H NMR (500 MHz, toluene-d8): δ 1.40 (s, 30H, C5Me5,
) 7 Hz, p-H), 7.15 (d, 2H, 3JHH ) 7 Hz, o-H), 7.27 (t, 2H, 3JHH
)
3
3
∆ν1/2 ) 4 Hz), 4.25 (d, 2H, JHH ) 7 Hz, o-H), 5.13 (t, 2H, JHH
7 Hz, m-H). 13C NMR (125.7 MHz, THF-d8): δ 17.8 (C5Me5),
115.4 (C5Me5), 115.9 (p-phenyl), 119.4 (o-phenyl), 131.0 (m-
phenyl); the ipso carbon was not located. IR: 2964s, 2907s, 2856s,
1590s, 1486s, 1444s, 1378w, 1293s, 1258s, 1162s, 1092s, 1065s,
1019s, 861s, 826s, 803s, 757s, 695s cm-1. Anal. Calcd for
C30H43O2Sm: C, 61.49; H, 7.40; Sm, 25.66. Found: C, 61.21; H,
7.29; Sm, 25.40.
3
) 7 Hz, m-H), 5.48 (t, 2H, JHH ) 7 Hz, p-H). 13C NMR (125.8
MHz, toluene-d8): δ 18.6 (C5Me5), 116.7 (C5Me5), 132.9 (o-
phenyl), 126.6 (m-phenyl), 126.5 (p-phenyl); the ipso carbon was
not located. IR: 3057w, 2961s, 2910s, 2856s, 2223w, 2181w,
1945w, 1532s, 1475s, 1436s, 1401s, 1378s, 1258s, 1092s, 1065s,
1019s, 842s, 803s, 733s, 691s, 668s, 575w cm-1. Anal. Calcd for
C54H70O4Se2Sm2: Sm, 26.2. Found: 26.2. 13C-labeled 2-13CO2 was
synthesized in an analogous fashion.
Reaction of 2-13CO2 + THF. THF-d8 (1 mL) was condensed
into a J-Young tube containing [(C5Me5)2Sm(µ-O213CSePh)]2 (15
mg, 0.012 mmol) at -196 °C, and the J-young tube was sealed.
As the tube warmed to room temperature, bubbles were observed.
The 1H and 13C NMR spectra of the orange solution showed
complete consumption of the starting material and formation of
(C5Me5)2Sm(SePh)(THF) in approximately 80% yield. Free 13CO2
was observed at 126.1 ppm.
X-ray Data Collection, Structure Solution, and Refinement
of 1. A yellow crystal of approximate dimensions 0.07 mm × 0.15
mm × 0.32 mm was mounted on a glass fiber and transferred to a
Bruker CCD platform diffractometer. The SMART14 program
package was used to determine the unit-cell parameters and for
data collection (25 s/frame scan time for a sphere of diffraction
data). The raw frame data were processed using SAINT15 and
SADABS16 to yield the reflection data file. Subsequent calculations
were carried out using the SHELXTL17 program. There were no
systematic absences or any diffraction symmetry other than the
Friedel condition. The centrosymmetric triclinic space group P1h
was assigned and later
[Me2Al(µ-O2CSPh)]2, 3. In an argon-filled glovebox free of
coordinating solvents, Me2AlCl (69 µL, 0.746 mmol) was added
dropwise to an orange slurry of [(C5Me5)2Sm(µ-O2CSPh)]2 (1; 214
mg, 0.186 mmol) in toluene (4 mL). A clear red solution
immediately formed. After the mixture was stirred overnight, the
red solution was evaporated to dryness and yielded a red micro-
crystalline solid. 1H NMR spectroscopy showed complete consump-
tion of the starting material and formation of only the previously
characterized red complex, (C5Me5)2Sm(µ-Cl)2AlMe2;13 the spectra
also showed resonances for 3, isolated as described below. The
red solid was dissolved in hexane, and cooled to -35 °C. After 2
days, 3 was obtained as colorless crystals (30 mg, 38%). Crystals
suitable for X-ray diffraction were grown from hexane at -35 °C.
1H NMR (500 MHz, benzene-d6): δ -0.63 (s, 6H, CH3, ∆ν1/2
)
(10) Evans, W. J.; Johnston, M. A.; Ziller, J. W. Inorg. Chem. 2000, 39,
3421.
(11) Evans, W. J.; Keyer, R. A.; Ziller, J. W. Organometallics 1993, 12,
2618.
(12) Evans, W. J.; Engerer, S. C.; Coleson, K. M. J. Am. Chem. Soc. 1981,
103, 6672.
(13) Evans, W. J.; Champagne, T. M.; Giarikos, D. G.; Ziller, J. W.
Organometallics 2005, 24, 570.
(14) SMART Software Users Guide, version 5.1; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 1999.
Inorganic Chemistry, Vol. 45, No. 1, 2006 425

Evans et al.
Table 1. X-ray Data Collection Parameters for
[(C5Me5)2Sm(µ-O2CEPh)]2 (E ) S, 1; E ) Se, 2)
empirical formula
fw
T (K)
C54H70O4S2Sm2‚2(C6H6) 1 C54H70O4Se2Sm2‚2(C6H6) 2
1304.14
163(2)
1397.94
163(2)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
triclinic
P1h
triclinic
P1h
10.0448(8)
11.3453(9)
14.8839(12)
71.0950(10)
73.9510(10)
69.1850(10)
1474.8(2)
1
10.0816(9)
11.4143(10)
14.9377(12)
71.1060(10)
73.6160(10)
69.2800(10)
1493.6(2)
1
Z
F
calcd (Mg/m3)
1.468
2.089
0.0189
0.0467
1.554
3.211
0.0176
0.0437
µ (mm-1
)
R1 [I > 2.0σ(I)]a
wR2 (all data)a
Figure 1. Molecular structure of [(C5Me5)2Sm(µ-O2CSPh)]2, 1, with
thermal ellipsoids drawn at the 50% probability level. [(C5Me5)2Sm(µ-O2-
CSePh)]2, 2, is isomorphous.
2
2
2
a wR2 ) [∑[w(Fo - Fc )2]/∑[w(Fo )2]]1/2, R1 ) ∑||Fo| - |Fc||/∑|Fo|.
refined against 6953 data points. As a comparison for refinement
on F, R1 ) 0.0176 for those 6637 data points with I > 2.0σ(I).
Table 2. X-ray Data Collection Parameters for [Me2Al(µ-O2CEPh)]2 (E
) S, 3; E ) Se, 4) and (C5Me5)2Sm(OPh)(THF), 5
X-ray Data Collection, Structure Solution, and Refinement
of 3. A colorless crystal of approximate dimensions 0.15 mm ×
0.20 mm × 0.21 mm was handled as was described for 1. There
were no systematic absences or any diffraction symmetry other than
the Friedel condition. The centrosymmetric triclinic space group
P1h was assigned and later determined to be correct. The molecule
was located about an inversion center. At convergence, wR2 )
0.0777 and GOF ) 1.027 for 162 variables refined against 2495
data points. As a comparison for refinement on F, R1 ) 0.0288
for those 2138 data points with I > 2.0σ(I). See Table 2 for
parameters relating to 3, 4, and 5.
empirical formula
fw
T (K)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
C18H22Al2O4S2 3 C18H22Al2O4Se2 4 C30H43O2Sm 5
420.44
163(2)
triclinic
P1h
514.24
163(2)
triclinic
P1h
585.99
163(2)
monoclinic
P21/c
7.3848(7)
7.8025(7)
9.7743(9)
95.896(2)
90.289(2)
108.727(2)
530.12(8)
1
7.5821(8)
7.8593(9)
9.7855(11)
95.797(2)
90.635(2)
109.368(2)
546.69(10)
1
9.6264(10)
17.0880(18)
17.0045(18)
90
102.183(2)
90
2734.2(5)
4
1.424
Z
F
calcd (mg/m3)
1.317
1.562
µ (mm-1
)
0.353
0.0288
0.0777
3.481
0.0208
0.0508
2.171
0.0209
0.0535
R1 [I > 2.0σ(I)]a
X-ray Data Collection, Structure Solution, and Refinement
of 4. A colorless crystal of approximate dimensions 0.09 mm ×
0.27 mm × 0.50 mm was handled as was described for 1. There
were no systematic absences or any diffraction symmetry other than
the Friedel condition. The centrosymmetric triclinic space group
P1h was assigned and later determined to be correct. The molecule
was located about an inversion center. At convergence, wR2 )
0.0508 and GOF ) 1.040 for 162 variables refined against 2613
data points. As a comparison for refinement on F, R1 ) 0.0208
for those 2451 data points with I > 2.0σ(I).
X-ray Data Collection, Structure Solution, and Refinement
of 5. A yellow crystal of approximate dimensions 0.18 mm × 0.32
mm × 0.39 mm was handled as described for 1. The diffraction
symmetry was 2/m, and the systematic absences were consistent
with the centrosymmetric monoclinic space group P21/c, which was
later determined to be correct. At convergence, wR2 ) 0.0535 and
GOF ) 1.083 for 439 variables refined against 6666 data points.
As a comparison for refinement on F, R1 ) 0.0209 for those 6064
data pointswith I > 2.0σ(I).
wR2 (all data)a
2
2
2
a wR2 ) [∑[w(Fo - Fc )2]/∑[w(Fo )2]]1/2, R1 ) ∑||Fo| - |Fc||/∑|Fo|.
determined to be correct. The structure was solved by direct
methods, and refined on F2 by full-matrix least-squares techniques.
The analytical scattering factors18 for neutral atoms were used
throughout the analysis. Hydrogen atoms were located from a
difference Fourier map and refined (x, y, z and Uiso). The molecule
was a dimer, and was located about an inversion center. There were
two molecules of benzene solvent present per dimeric formula unit.
At convergence, wR2 ) 0.0467 and GOF ) 1.063 for 498 variables
refined against 6877 data points. As a comparison for refinement
on F, R1 ) 0.0189 for those 6431 data points with I > 2.0σ(I).
See Table 1 for parameters related to 1 and 2.
X-ray Data Collection, Structure Solution, and Refinement
of 2. A yellow crystal of approximate dimensions 0.11 mm × 0.32
mm × 0.32 mm was handled as was described for 1. There were
no systematic absences or any diffraction symmetry other than the
Friedel condition. The centrosymmetric triclinic space group P1h
was assigned and later determined to be correct. The molecule was
a dimer, and was located about an inversion center. There were
two molecules of benzene solvent present per dimeric formula unit.
At convergence, wR2 ) 0.0437 and GOF ) 1.050 for 498 variables
Results and Discussion
[(C5Me5)2Sm(µ-O2CEPh)]2 (E ) S, 1; E ) Se, 2).
Reaction of [(C5Me5)2Sm(µ-EPh)]2 (E ) S, Se) with 1 atm
of CO2 in benzene-d6 produced the orange crystalline
products 1 and 2 for S and Se, respectively, in high yields.
1
The H and 13C NMR data in each case showed a single
(15) SAINT Software Users Guide, version 6.0; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 1999.
(16) Sheldrick, G. M. SADABS, version 2.10; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 2001.
(17) Sheldrick, G. M. SHELXTL, version 6.12; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 2001.
(18) International Tables for X-ray Crystallography 1992; Kluwer Aca-
demic Publishers: Dordrecht, The Netherlands; 1992. Vol. C.
C5Me5 resonance in the typical region for trivalent metal-
locenes. X-ray quality crystals of both compounds were
obtained directly from the reaction mixtures and provided
crystallographic confirmation, Figure 1, of CO2 insertion
according to eq 2.
426 Inorganic Chemistry, Vol. 45, No. 1, 2006

Synthesis and Utility of (O2CEPh)1- Ligands
Table 3. Selected Bond Distances (Å) and Angles (deg) for
[(C5Me5)2Sm(µ-O2CEPh)]2 (E ) S, 1; E ) Se, 2)
1
2
Sm(1)-O(1)
Sm(1)-O(2′)
Sm(1)-Cnt1
Sm(1)-Cnt2
E(1)-C(22)
E(1)-C(21)
O(1)-C(21)
2.3286(13)
2.3771(13)
2.427
2.3307(13)
2.3812(12)
2.425
2.442
2.440
1.778(2)
1.7916(18)
1.258(2)
1.9153(19)
1.9472(17)
1.251(2)
Cnt1-Sm(1)-O(1)
Cnt2-Sm(1)-O(1)
Cnt1-Sm(1)-Cnt2
O(1)-Sm(1)-O(2′)
C(21)-O(1)-Sm(1)
O(2)-C(21)-O(1)
O(1)-C(21)-E(1)
C(22)-E(1)-C(21)
106.4
107.5
133.4
85.84(5)
163.89(13)
127.61(17)
111.82(14)
104.19(9)
106.4
107.6
133.6
82.33(5)
164.80(12)
128.62(16)
111.20(12)
102.05(7)
Complex 2 can also be obtained in high yield from the
THF-solvated precursor, (C5Me5)2Sm(SePh)(THF), under 1
atm of CO2 in benzene.
[(C5Me5)2Sm(µ-TePh)]2 appears to react similarly with
CO2, but crystallographic confirmation of the product has
not yet been obtained. The product does have a single C5-
Me5 1H NMR resonance at 1.41 ppm that is similar to those
of 1 and 2 in toluene, at 1.44 and 1.40 ppm, respectively.
Attempts to make a mixed chalcogenide analogue from [(C5-
Me5)2Sm(µ-SPh)]2 and[(C5Me5)2Sm(µ-TePh)]2 gave crystals
of [(C5Me5)2Sm(µ-O2CEPh)]2 that were isomorphous with
1 and 2 and that refined with site occupancy factors for E of
suggested that the (O2CEPh)1- ligands could be useful in
providing less soluble, more crystalline forms of complexes
analogous to carboxylates. This was tested with the analogue
of the reaction shown in eq 3. Equation 3 was studied as a
90% for S and 10% for Te.
As shown in Figure 1, both 1 and 2 have a square planar
arrangement of (C5Me5)1- ring centroids that is typical of
metallocenes bridged by large groups.19-21 Perpendicular to
the plane of the four (C5Me5)1- ring centroids is an eight-
membered SmOC(E)OSmOC(E)O ring. These atoms are
coplanar within 0.12 Å in 1 and 2. The aryl rings attached
to the chalcogen have a trans arrangement with respect to
each other. The overall structure is similar to that of the ben-
zylcarboxylate [(C5Me5)2Sm(µ-O2CCH2Ph)]2, 6, obtained by
insertion of CO2 into the Sm-benzyl bond in (C5Me5)2Sm-
(CH2Ph).21 In this sense, the S and Se atoms of 1 and 2 are
analogous to the CH2 unit in 6. Because of the larger sizes
of S and Se, the attached phenyl rings are farther from the
Sm2(µ-O2CR)2 cores. In this regard, the (O2CEPh)1- ligands
may be valuable for the construction of bimetallic lanthanide
complexes that keep C-H bonds distant from the metals, a
desirable feature in terms of fluorescence quenching.22 The
Sm‚‚‚Sm distances in 1 and 2 are 5.565 and 5.604 Å,
respectively, compared to 5.034 and 5.231 Å in the [(C5-
model for the activation of lanthanide carboxylates with alkyl
aluminum reagents to make catalysts for the polymerization
of isoprene to high cis-1,4-polyisoprene.13 Unfortunately,
even in this carboxylate model system, the aluminum
byproduct could not be fully characterized, in part because
of its high solubility.
To determine if the reduced solubility of (O2CEPh)1-
complexes could help in this case, we examined the
analogous reaction of 1 and 2 with Me2AlCl. This reaction
produced the expected organosamarium product, (C5Me5)2-
Sm(µ-Cl)2AlMe2, analogous to that in eq 3. However, in this
case the organoaluminum byproducts, [Me2Al(µ-O2CEPh)]2
(E ) S, 3; E ) Se, 4), could be isolated as colorless crystals
and fully characterized (eq 4). Cooling the reaction mixtures
Me5)2Sm(µ-EPh)]2 precursors.9
The 1.242(2)-1.258(2) Å C(21)-O(1) and C(21)-O(2)
distances (see Table 3 ) in 1 and 2 indicate a delocalized
structure for the carboxylate portion of the (O2CEPh)1- lig-
ands. The 1.792(2) and 1.947(2) Å C(21)-E distances in 1
and 2, respectively, are in the single-bond range.23 The O2C-
E-C(ipso carbon) angles of 104.19(9) and 102.05(7)° in 1
and 2, respectively, are consistent with sp3 hybridization
around E.
[Me2Al(µ-O2CEPh)]2 (E ) S, 3; E ) Se, 4). The fact
that 1 and 2 readily crystallized from the reaction mixture
(19) Evans, W. J.; Gonzales, S. L.; Ziller, J. W. J. Chem. Soc. 1991, 26,
9880.
(20) Evans, W. J. J. Alloys Compd. 1993, 192, 205.
(21) Evans, W. J.; Perotti, J. M.; Ziller, J. W. J. Am. Chem. Soc. 2005,
127, 3894.
(22) Gamelin, D. R.; Gu¨del, H. U. Acc. Chem. Res. 2000, 33, 235.
(23) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen, A.
G. J. Chem. Soc., Perkin Trans. 2 1987, S1.
to -35 °C allowed for the separation of 3 and 4 from (C5-
Inorganic Chemistry, Vol. 45, No. 1, 2006 427

Evans et al.
Figure 3. Molecular structure of (C5Me5)2Sm(OPh)(THF), 5, with thermal
ellipsoids drawn at the 50% probability level.
Figure 2. Molecular structure of [Me2Al(µ-O2CSPh)]2, 3, with thermal
ellipsoids drawn at the 50% probability level. [Me2Al(µ-O2CSePh)]2, 4, is
isomorphous.
However, since the lanthanides are highly oxophilic, it is
possible that COSe was lost and (C5Me5)2Sm(OPh)(THF)
was the byproduct. This would require that the H NMR
spectrum of (C5Me5)2Sm(OPh)(THF) be identical to that of
(C5Me5)2Sm(SePh)(THF).
1
Table 4. Selected Bond Distances (Å) and Angles (deg) for
[Me2Al(µ-O2CEPh)]2 (E ) S, 3; E ) Se, 4)
3
4
To rule out the formation of (C5Me5)2Sm(OPh)(THF), we
synthesized this complex independently. Reaction of (C5-
Me5)2Sm[N(SiMe3)2]11 with PhOH produced a yellow crys-
talline product in high yield. (C5Me5)2Sm(OPh)(THF), 5, was
characterized by elemental analysis and 1H NMR, 13C NMR,
and IR spectroscopy. It was completely identified by X-ray
crystallography (eq 6; Figure 3). The complex has a 1H NMR
Al(1)-O(1)
Al(1)-O(2)
Al(1)-C(3)
Al(1)-C(2)
S(1)-C(1)
S(1)-C(4)
O(1)-C(1)
O(2)-C(1′)
1.8570(10)
1.8255(10)
1.9400(16)
1.9566(16)
1.7548(13)
1.7767(14)
1.2642(16)
1.2585(15)
1.8595(13)
1.8290(12)
1.9374(19)
1.959(2)
1.9017(16)
1.9193(16)
1.2646(19)
1.2564(19)
O(2)-Al(1)-O(1)
O(1)-Al(1)-C(3)
O(1)-Al(1)-C(2)
C(3)-Al(1)-C(2)
C(1)-E(1)-C(4)
C(1)-O(1)-Al(1)
O(1)-C(1)-E(1)
101.93(4)
106.20(6)
106.91(6)
124.45(8)
102.27(6)
128.43(9)
114.07(10)
101.58(5)
105.67(8)
106.99(8)
124.55(10)
99.43(7)
128.96(11)
114.18(11)
Me5)2Sm(µ-Cl)2AlMe2 in each case. Complexes 3 and 4 were
characterized by elemental analysis and 1H NMR, 13C NMR,
and IR spectroscopy. They were completely identified by
X-ray crystallography (Figure 2).
C5Me5 resonance at 1.25 ppm that is similar to those of the
previously characterized complexes (C5Me5)2Sm(EPh)(THF)
(E ) S, Se, Te; 1.19, 1.18, and 1.23 ppm, respectively).9
However, the NMR spectrum of the product of eq 6 was
distinct from that of (C5Me5)2Sm(SePh)(THF).
Further confirmation that 2 decomposed in THF by loss
of CO2 was obtained by synthesis of the carbon-labeled
analogue [(C5Me5)2Sm(µ-O213CSePh)]2. Addition of this
complex to THF-d8 generated an organolanthanide product
with 1H and 13C NMR spectra consistent with (C5Me5)2Sm-
(SePh)(THF) as well as a 13C NMR peak at 126.1 ppm,
which matches the resonance of free 13CO2 at 1 atm in THF-
d8 (eq 7).
Complexes 3 and 4 are isomorphous and dimeric in the
solid state. As in 1 and 2, the phenyl groups adopt a trans
orientation with respect to each other. The bond distances
and angles in 3 and 4 are similar to those in [Me2Al(µ-O2-
CNiPr2)]2 (see Table 4).24 The O-Al-O and C(Me)-Al-O
angles fall into the narrow range 101.58(5)-108.20(8)°,
whereas the C1-E-C4 angles, 102.27(6)° for 3 and 99.43-
(7)° for 4, are similar to those of the analogues in 1 and 2.
Decarboxylation of 2. Although [(C5Me5)2Sm(µ-O2-
CSePh)]2, 2, can be synthesized from the THF solvate (C5-
Me5)2Sm(SePh)(THF) in benzene, dissolving 2 in THF
1
generates a gas and a product that has the same H NMR
spectrum as (C5Me5)2Sm(SePh)(THF). If this reaction was
analogous to the decarboxylation of (C5H5)3U(O2CSiPr) that
prevented its isolation,7 the products of the decomposition
would be as shown in eq 5.
[(C5Me5)2Sm(µ-O213CSePh)]2 THF8
2(C5Me5)2Sm(SePh)(THF) + 213CO2 (7)
The structure of (C5Me5)2Sm(OPh)(THF) is not isomor-
phous with those of the (C5Me5)2Sm(EPh)(THF) complexes.9
THF8
[(C5Me5)2Sm(µ-O2SePh)]2
2
(24) Chang, C. C.; Srinivas, B.; Mung-Liang, W.; Wen-Ho, C.; Chiang,
2(C5Me5)2Sm(SePh)(THF) + 2CO2 (5)
M. Y.; Chung-Sheng, H. Organometallics 1995, 14, 5150.
428 Inorganic Chemistry, Vol. 45, No. 1, 2006

Synthesis and Utility of (O2CEPh)1- Ligands
Table 5. Selected Bond Distances (Å) and Angles (deg) for
(C5Me5)2Sm(OPh)(THF), 5
structure of 5 is the 160.7(2)° Sm-O-C(ipso) angle. The
analogous angles in the S, Se, and Te complexes are much
more acute: 120.8(2), 118.5(1), and 112.49(6)°, respectively.
Another difference in 5 is that the (OPh)1- ligand is
symmetrically positioned between the rings with 106.8 and
107.3° (C5Me5 ring centroid)-Sm-O(1) angles. In the S,
Se, and Te analogues, these two angles differ by 13-16°.
Sm(1)-O(1)
Sm(1)-O(2)
Sm(1)-Cnt1
Sm(1)-Cnt2
O(1)-C(21)
2.1645(14)
2.4729(15)
2.453
2.445
1.345(2)
Cnt1-Sm(1)-O(1)
Cnt2-Sm(1)-O(1)
Cnt1-Sm(1)-Cnt2
C(21)-O(1)-Sm(1)
Cnt1-Sm(1)-O(2)
Cnt2-Sm(1)-O(2)
O(1)-Sm(1)-O(2)
107.3
106.8
135.0
160.66(15)
103.9
Conclusion
CO2 insertion reactions can be used to derivatize aryl
chalcogenide ligands and provide (O2CEPh)1- ligands. These
groups readily form crystallographically characterizable
complexes with lanthanide metallocenes that decarboxylate
in THF. Complexation of the (O2CEPh)1- ligands to a
dimethylaluminum fragment gives a dimeric complex that
is fully characterizable by X-ray crystallography, in contrast
to the more soluble carboxylate analogue.
104.7
89.73(6)
The metallocene parts of all four of these complexes are
similar: a 135.0° (C5Me5 ring centroid)-Sm-(C5Me5 ring
centroid) angle vs 133.7-135.2° and a 2.453 Å Sm-centroid
distance vs 2.442-2.452 Å.
The Sm-O(OPh) distance of 2.164(1) Å (see Table 5) is
much shorter than that of the Sm-E(EPh) analogues (2.760-
(1)-3.1239(3) Å), as expected on the basis of the sizes of
the donor atoms.25 The Sm-O(THF) distance of 2.473(2)
Å in 5 may be slightly longer than that in the analogues
(2.443(3)-2.449(2) Å) as a consequence of 5 having more
steric bulk close to the metal. The main difference in the
Acknowledgment. We thank the National Science Foun-
dation for support of this research.
Supporting Information Available: X-ray diffraction details
(CIF) and X-ray data collection, structure solution, and refinement
of compounds 1-5 (PDF). This material is available free of charge
via the Internet at http://pubs.acs.org.
(25) Shannon, R. D. Acta Crystallogr. 1976, A32, 751.
IC0515610
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