Metallocene bis(perfluoroalkanesulfonate)s as air-stable cationic Lewis acids

Article abstract of DOI:10.1016/j.jorganchem.2008.12.057

Zirconocene and titanocene bis(perfluorooctanesulfonate)s were synthesized. In contrast to the corresponding triflates and perchlorates, these compounds are air- and water-stable. They were proved to be ionic on the basis of conductivity measurements and X-ray analysis, allowing these complexes to be stored for months. The strong Lewis acidity of these cationic metallocene species, which was proved by ESR study, enabled catalytic glycosylation.

Full text of DOI:10.1016/j.jorganchem.2008.12.057

Journal of Organometallic Chemistry 694 (2009) 1524–1528
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Metallocene bis(perfluoroalkanesulfonate)s as air-stable cationic Lewis acids
a
a
a
a
Renhua Qiu a, Guoping Zhang a, Xinhua Xu a, , Kangbin Zou , Lingling Shao , Dawei Fang , Yinhui Li ,
*
Akihiro Orita b, , Ryosuke Saijo , Hidetaka Mineyama , Tomoyoshi Suenobu , Shunichi Fukuzumi
,
b
b
c
c,
*
*
Delie An a, , Junzo Otera
b,
*
*
a Department of Chemistry, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, China
b Department of Applied Chemistry, Okayama University of Science, Ridai-cho, Okayama 700-0005, Japan
c Department of Material and Life Science, Graduate School of Engineering, Osaka University, SORST, Japan Science and Technology Agency (JST), Suita, Osaka 565-0871, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Zirconocene and titanocene bis(perfluorooctanesulfonate)s were synthesized. In contrast to the corre-
sponding triflates and perchlorates, these compounds are air- and water-stable. They were proved to
be ionic on the basis of conductivity measurements and X-ray analysis, allowing these complexes to
be stored for months. The strong Lewis acidity of these cationic metallocene species, which was proved
by ESR study, enabled catalytic glycosylation.
Received 19 November 2008
Received in revised form 24 December 2008
Accepted 24 December 2008
Available online 3 January 2009
Ó 2009 Elsevier B.V. All rights reserved.
Keywords:
Metallocenes
Perfluorooctanesulfonates
Lewis acids
1. Introduction
[11]. These species also cannot be isolated due to their hydrolytic
instability, and so they are usually generated in situ prior to reac-
The Lewis acid chemistry has played a major role in modern or-
ganic synthesis [1], yet the conflict between the following issues
remains still unsettled. The Lewis acid is desired to be as strongly
acidic as possible to acquire higher activity, while it becomes more
susceptible to hydrolysis upon increasing the acidity. Cationic
group 4 metallocene compounds, which have attracted increasing
attention recently [2], represent a typical example. The metallo-
cene bis(triflate) complexes of zirconium and titanium Cp2M(OTf)2
(Cp = C5H5, Tf = CF3SO2) were initially obtained by treatment of
Cp2MCl2 with AgOTf [3] and later from Cp2ZrMe2 and TfOH [4].
These complexes were successfully employed as catalysts for
Diels–Alder reaction [5], Mukaiyama–Aldol reaction [6], Hosomi–
Sakurai reaction [6a,7], [3+2] nitrone–olefin cycloaddition reaction
[8], and glycosylation [9]. Unfortunately, however, these metallo-
cene bis(triflate)s are not stable in open air [10], suffering from fac-
ile hydrolysis. Thus, these complexes must be handled under
strictly anhydrous conditions. Another notable species are putative
metallocene perchlorates Cp2M(ClO4)2 (M = Hf and Zr), which have
found extremely versatile application to glycosylation technology
tion by treating Cp2MCl2 with potentially explosive AgClO4.
Accordingly, improvement of the hygroscopic character of the cat-
ionic metallocene derivatives is highly demanding from the stand-
point of practical utilization as catalysts.
Recently, we disclosed that the perfluorooctanesulfonate group
worked as an effective counter-anion to provide cationic organotin
species [12], which were found air-stable and water-tolerant in
sharp contrast to the corresponding highly hygroscopic organotin
triflates [13]. This finding has led us to postulate that longer per-
fluoroalkanesulfonate groups could serve for overcoming the
hydrolytic instability of the cationic organometallic species in a
general sense. We report herein successful isolation of air-stable
cationic metallocene (M = Zr and Ti) bis(perfluoroalkanesulfo-
nate)s, which enabled facile assessment of Lewis acidity and cata-
lytic activity.
2. Results and discussion
The synthesis of zirconocene and titanocene bis(perfluoroal-
kanesulfonate)s is straightforward (Scheme 1). Treatment of metal-
locene dichlorides, Cp2MCl2 [M = Zr (1a), Ti (1b)] with silver
perfluorooctanesulfonate (AgOSO2C8F17 = AgOPFOS) (2 equiv.) in
THF or silver perfluorobutanesulfonate (AgOSO2C4F9 = AgOPFBS)
(2 equiv.) in Et2O or THF allowed us to isolate the corresponding
perfluoroalkanesulfonate derivatives Cp2M(OPFOS)2 Á nH2O Á THF
* Corresponding authors. Address: Department of Applied Chemistry, Okayama
University of Science, Ridai-cho, Okayama 700-0005, Japan. Tel./fax: +81 86 256
4292 (A. Orita).
E-mail addresses: xhx1581@yahoo.com.cn (X. Xu), orita@high.ous.ac.jp (A. Orita),
fukuzumi@chem.eng.osaka-u.ac.jp (S. Fukuzumi), deliean@sina.com (D. An),
otera@high.ous.ac.jp (J. Otera).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.12.057

R. Qiu et al. / Journal of Organometallic Chemistry 694 (2009) 1524–1528
1525
Previously, we have reported that the Lewis acidity of the metal
AgOPFOS (2 equiv)
THF, RT, 1 h
Cp2M(OPFOS)2 nH O
THF
2
complexes can be estimated by the binding energies (DE values) of
2a: M = Zr; n = 3
Lewis acid metal ions with O2ÅÀ on the basis of ESR spectra [16].
(recryst. from THF/hexane)
2b: M = Ti; n = 2
Thus, we measured the ESR spectra of OÅ2À–2a and O2ÅÀ–2b com-
Cp2MCl2
(recryst. from THF/hexane)
plexes to determine the
[16b]. The
E value of the titanium complex (OÅ2À–2b) is signifi-
cantly larger (Ti4+: gzz = 2.0289,
E = 1.06 eV) than that of Sc(OTf)3
(gzz = 2.0304, E = 1.00 eV) and is the largest among the E values
previously reported by our group [16]. The E of the zirconium
complex (OÅ2À–2a) exhibits relatively large value (Zr4+
gzz = 2.0331, E = 0.91 eV), which falls between those of Sc(OTf)3
and Y(OTf)3 (gzz = 2.0349, E = 0.85 eV). Since Lewis acids with
the E value larger than 0.88 were presumed to be capable for
DE values, which are shown in Fig. 2
1
D
D
AgOPFBS (2 equiv)
Et2O or THF, RT, 1 h
Cp2M(OPFBS)2 2H2O
3a: M = Zr
(recryst. from Et2O/toluene)
3b: M = Ti
(recryst. from THF/Et2O)
D
D
D
:
D
D
D
Cp2M(OPFOS)2 nH O
THF
2
inducing carbon–carbon bond-forming reactions [16b], it is rea-
sonably expected that the Lewis acidity of 2a and 2b is high en-
ough to trigger synthetically useful reactions.
Cp2M(OSO2Rf)2
Rf = C8F17; C4F9
or
in vacuo, 7 days
Cp2M(OPFBS)2 2H2O
With the above results in hand, we employed 2a as a catalyst in
synthetically important glycosylation reaction with glycosyl fluo-
ride donor. As shown in Scheme 2, the reaction proceeded
smoothly in the presence of 2a Á 3H2O Á THF (20 mol%) and molec-
ular sieves 4A (MS 4A) to give high yields of the glycosylation
products 5a–g. Remarkably, only a catalytic amount of 2a is en-
ough to complete the glycosylation. This presents a striking con-
trast to metallocene triflates or percholorates which are used in
large excess (2–5 equiv. relative to the donor) [9,11]. The O-glyco-
sylation products were obtained exclusively with p-methoxyphe-
nol and 2-naphthol in contrast to Cp2HfCl2/(AgClO4)2, which
induced rearrangement from O-glycosides to C-glycosides at
–20 °C with these phenols [11a,d]. Our catalyst is quite different
in this respect, implying a unique influence of the perfluorooctane-
sulfonate counter-anion [17]. The present protocol is applicable to
synthesis of disaccharide, and treatment of 4 with methyl 2,3,4-tri-
O-benzyl-glucopyranoside provided 5f in 89% yield. When 1,3,5-
trimethoxybenzene was utilized as acceptor, the C-glycosylation
took place exclusively from the b-face of 4 to afford 5g in high
yield.
In summary, long perfluoroalkanesulfonate groups have proved
to work for stabilizing cationic metallocene complexes. The iso-
lated species were fully characterized by NMR spectroscopy,
X-ray diffraction, conductivity measurements, and ESR spectra.
The perfluorooctanesulfonate derivatives exhibited strong Lewis
acidity to trigger glycosylation in a catalytic manner. Further stud-
ies on synthesis of relevant compounds as well as their application
to other reactions such as Mukaiyama–Aldol reaction and allyla-
tion will be reported in a full paper.
Cp2M(OPFOS)2 nH O
THF
2
Cp2M(OSO2Rf)2 4H2O
Rf = C8F17; C4F9
or
in air, 2 days
Cp2M(OPFBS)2 2H2O
Scheme 1. Syntheses of Cp2M(OSO2C8F17
) and Cp2M(OSO2C4F9)2 (M = Ti, Zr).
2
[M = Zr (2a Á 3H2O Á THF), Ti (2b Á 2H2O Á THF)] (after recrystalliza-
tion from THF/hexane), Cp2Zr(OPFBS)2 Á 2H2O (3a Á 2H2O) (after
recrystallization from Et2O/toluene), and Cp2Ti(OPFBS)2 Á 2H2O
(3b Á 2H2O) (after recrystallization from THF/Et2O), as stable hy-
drated species. The hydration number (n) of 2 and 3 was variable
upon standing (Scheme 1). 1H NMR spectroscopy (in dry CH3CN)
and elemental analysis showed that freshly prepared samples after
recrystallization contained two or three water molecules along
with solvating THF for 2a and 2b while both 3a and 3b contained
two water molecules only. Pumping these complexes in vacuo for
a week at room temperature caused complete dehydration giving
rise to n = 0. Standing the freshly prepared compounds 2a and 2b
in open air for 2 days induced desolvation of the THF and the water
content increased to n = 4. Under the same circumstances, the
hydration number of 3a and 3b were also increased to n = 4. Such
durability, though being hydrated, presents a sharp contrast to
the corresponding triflate, Cp2Zr(OTf)2, which undergoes facile
hydrolysis to dinuclear Cp2Zr2(H2O)6(
l
2-OH)2(OTf)4 Á 4THF [3g].
Notably, 2 and 3 exhibited no sign of structural change after being
kept in open air for three months. The solid samples remained as
dry crystals or powder and suffered no color change. Therefore,
the metallocene perfluoroalkanesulfonates are storable in open
air, gaining a great advantage over the metallocene triflates or per-
chlorates from an operational point of view.
The cationic structure of 2a Á 3H2O Á THF in the solid state was
confirmed by X-ray analysis. The crystals suitable for the X-ray dif-
fraction were obtained by diffusion of hexane into saturated THF
solution. The crystal structure and packing together with selected
bond lengths and angles are shown in Fig. 1 [14]. The zirconium
atom is coordinated by three water molecules and not by THF.
Hence, the geometry of the [Cp2Zr(H2O)3]2+ moiety is similar to
that of [Cp2Zr(H2O)3]2+(OTf–)2 [3b]. The three H2O molecules lie
on the plane that bisects the angle between the Cp ring planes.
The Zr–O distances are 2.234(5), 2.236(6) and 2.247(6) Å. The
PFOSOÀ anions and the THF molecule are packed around the zirco-
nium cation in such a way that their oxygen atoms point towards
the H2O ligands. The C8F17 chains of the anion, on the other hand,
are clustered together so as to produce hydrophobic domains in
the crystal structure.
3. Experimental
3.1. General
All reactions were carried out under nitrogen atmosphere with
freshly distilled solvents unless otherwise noted. THF was distilled
from sodium/benzophenone. Acetonitrile was distilled from CaH2.
Acetone was refluxed for 4 h and distilled with KMnO4, and then
was dried with K2CO3, followed by distillation, and kept in the
dry box. NMR spectra were recorded at 25 °C on INOVA-400 M
(USA) calibrated with tetramethylsilane (TMS) as an internal refer-
ence. Elemental analyses were performed by VARIO EL III. Conduc-
tivity was measured on REX conductivity meter DDS-307. IR
spectra were recorded on NICOLET 6700 FTIR spectrophotometer
(Thermo Electron Corporation). X-ray single crystal diffraction
analysis was performed with SMART-APEX and RASA-7A by Shang-
hai Institute Organic Chemistry, Chinese Academy of Science.
AgOSO2C8F17 and AgOSO2C4F9 were prepared according to meth-
ods, which we reported earlier [13].
The ionic dissociation of 2 and 3 in solution was apparent from
conductivity measurements (Table 1). The large molar conductivity
values are consistent with complete ionization into a 1:2 electro-
lyte [15].

1526
R. Qiu et al. / Journal of Organometallic Chemistry 694 (2009) 1524–1528
Fig. 1. An ORTEP view showing 50% probability ellipsoids and packing of Cp2Zr(H2O)3(OSO2C8F17
)
2 Á 3H2O Á THF (2a Á 3H2O Á THF). Selected bond distances (Å) and angles (°):
Zr–O(2), 2.234 (5); Zr–O(3), 2.236 (6); Zr–O(1), 2.247 (6); Zr–C(10), 2.467 (9); Zr–C(2), 2.469 (10); Zr–C(6), 2.479 (9); Zr–C(1), 2.479 (10); Zr–C(4), 2.491 (10); Zr–C(5), 2.494
(9); Zr–C(9), 2.498 (9); Zr–C(3), 2.504 (11); Zr–C(7), 2.511 (9); O(2)–Zr–O(3) 69.3 (2); O(2)–Zr–O(1), 72.0 (2); O(3)–Zr–O(1), 141.2 (2). The torsion angle between the two Cp
ring planes is 53.83°.
gzz = 2.0289
Table 1
Conductivity of cationic metallocene perfluoroalkanesulfonates.a
Compound
Conductivity (l )
S cmÀ1
a
b
2a Á 3H2O Á THF
2b Á 2H2O Á THF
3a Á 2H2O
136.1
114.5
98.5
gzz = 2.0331
3b Á 2H2O
95.1
a
In CH3CN (1.0 mmol LÀ1) at 15 °C.
20 G
3.2. Cp2Zr(OSO2C8F17)2 Á 3H2O Á THF (2a Á 3H2O Á THF)
To a solution of Cp2ZrCl2 (292 mg, 0.99 mmol) in THF (20 mL)
was added a solution of AgOSO2C8F17 (1.21 g, 2.0 mmol) in THF
(10 mL). The mixture was stirred in the dark at room temperature
for 1 h, and filtrated. The filtrate was combined with dry hexane
(40 mL). Then, the solution was stored in the refrigerator for 24 h
to furnish colorless crystals (794 mg, 65%): M.p. 133–136 °C. 1H
NMR (300 MHz, CD3CN) d 1.77–1.81 (m, 4H, THF), 2.19 (s, 6H,
Fig. 2. ESR spectra of (a) OÅ2À/Ti4+ (2b Á 2H2O Á THF) and (b) O2ÅÀ/Zr4+
(2a Á 3H2O Á THF).
H2O), 3.63 (t, J = 6.7 Hz, 4H, THF), 6.52 (s, 10H, Cp). 19F NMR (283
MHz, CD3CN) d À81.45 (t, J = 9.6 Hz, 3F, CF3-), À114.84 (s, 2F,
-CF2-), À120.86 (s, 2F, -CF2-), À122.01 to À122.25 (m, 6F, -(CF2)3-),

R. Qiu et al. / Journal of Organometallic Chemistry 694 (2009) 1524–1528
OBn
1527
diluted with Et2O (2 mL) and toluene (5 mL). The solution was kept
standing in a refrigerator for 24 h. White crystals were obtained
(308 mg, 72%): M.p. 100–104 °C. 1H NMR (500 MHz, CD3CN) d
2.36 (s, 4H, H2O), 6.52 (s, 10H, Cp). 19F NMR (283 MHz, CD3CN) d
À81.67 (s, 3F, CF3-), À115.52 (s, 2F, -CF2-), À112.19 (s, 2F, -CF2-),
À126.56 (s, 2F, -CF2-). IR (KBr) 3535.3, 3503.1, 3476.3, 3466.0,
3446.2, 3403.2, 3337.3, 2437.7, 1677.6, 1440.4, 1354.6, 1270.1,
1137.9, 1064.7, 1018.9, 835.0, 806.8, 739.6, 700.4, 685.2, 659.3,
617.5, 526.1, 439.0 cmÀ1. Elemental Anal. for Cp2Zr(OSO2C4F9)2
(3a) after pumping for a week: Calc. for C18H10F18O6S2Zr: C,
26.38; H, 1.23; found: C, 26.28; H, 1.31%. Elemental Anal. for
Cp2Zr(OSO2C4F9)2 Á 4H2O (3a Á 4H2O) after standing in open air for
2 days: Calc. for C18H18F18O10S2Zr: C, 24.25; H, 2.03; found: C,
24.37; H, 2.09%.
OBn
2a•3H2O•THF
(0.2 eq)
O
O
+ ROH
or ArH
BnO
BnO
BnO
BnO
OR or Ar
F
CH2Cl2,
MS 4A, rt
OBn
5
OBn
4
D/A (donor/acceptor)
= 1: 1.3
ROH = cyclohexanol, 0.5 h, 5a, 94% (36/64)a
t-butyl alcohol, 0.5 h, 5b, 92% (54/46)a
cyclohexylmethanol, 0.5 h, 5c, 95% (43/57)a
p-methoxyphenol, 0.5 h, 5d, 87% (42/58)a
2-naphthol, 0.5 h, 5e, 90% (45/55)a
HO
2.5 h, 5f, 89% (68/32)a
O
BnO
OMe
BnO
BnO
ArH =1,3,5-trimethoxybenzene (D/A = 1: 5), 4 h, 5g, 84% (0/100)a
aRatio of α and β adduct.
3.5. Cp2Ti(OSO2C4F9)2 Á 2H2O (3b Á 2H2O)
Scheme 2. Glycosylation with glycosyl fluoride catalyzed by 2a.
To a solution of Cp2TiCl2 (124 mg, 0.50 mmol) in THF (10 mL)
was added a solution of AgOSO2C4F9 (427 mg, 1.05 mmol) in THF
(5 mL). The mixture was stirred in the dark at room temperature
for 1 h, and filtered. Evaporation furnished a residue, which was di-
luted with THF (1 mL) and Et2O (5 mL). The yellow solid was ob-
tained (276 mg, 68%): M.p. 117–121 °C. 1H NMR (300 MHz,
CD3CN) d 3.39 (s, 4H, H2O), 6.95 (s, 10H, Cp). 19F NMR (283 MHz,
CD3CN) d À81.77 (t, J = 9.6 Hz, 3F, CF3-), -115.41 to –115.45 (m,
2F, -CF2-), À122.26 (s, 2F, -CF2-), À126.47 to –126.70 (m, 2F,
-CF2-). IR (KBr): 3503.3, 3119.2, 1695.8, 1447.6, 1357.4, 1297.1,
1237.0, 1137.3, 1065.4, 1017.0, 850.4, 807.8, 740.8, 700.8, 658.1,
620.3, 598.5, 526.8 cmÀ1. Elemental Anal. for Cp2Ti(OSO2C4F9)2
(3b) after pumping for a week: Calc. for C18H10F18O6S2Ti: C,
27.85; H, 1.30; found: C, 27.88; H, 1.37%. Elemental Anal. for
Cp2Ti(OSO2C4F9)2 Á 4H2O (3b Á 4H2O) after standing in open air for
two days: Calc. for C18H18F18O10S2Ti: C, 25.49; H, 2.14; found: C,
25.68; H, 2.03%.
À123.10 (s, 2F, -CF2-), À126.48 to –126.55 (m, 2F, -CF2-). IR (KBr)
3543.8, 3505.8, 3474.8, 3420.8, 3409.8, 3905.2, 3229.0, 2359.0,
1662.9, 1427.7, 1370.6, 1331.5, 1242.4, 1150.7, 1074.1, 1041.1,
943.0, 819.6, 747.0, 707.5, 649.7, 628.8, 559.8, 531.6, 500.9 cmÀ1
.
Cp2Zr(OSO2C8F17)2 Á 4H2O (2a Á 4H2O) 1H NMR (300 MHz, CD3CN)
d 2.19 (s, 8H, H2O), 6.52 (s, 10H, Cp). 19F NMR (283 MHz, CD3CN)
d À81.47 (t, J = 9.6 Hz, 3F, CF3-), À114.91 (s, 2F, -CF2-), À120.90
(s, 2F, -CF2-), À122.00 to À122.27 (m, 6F, -(CF2)-), À123.13 (s, 2F,
-CF2-), À126.54 to 126.65 (m, 2F, -CF2-). Elemental Anal. for
Cp2Zr(OSO2C8F17 2 (2a) after pumping for a week: Calc. for
)
C26H10F34O6S2Zr: C, 25.60; H, 0.83; found: C, 25.67; H, 0.82%. Ele-
mental Anal. for Cp2Zr(OSO2C8F17)2 Á 4H2O (2a Á 4H2O) after stand-
ing in open air for 2 days: Calc. for C26H18F34O10S2Zr: C, 24.18; H,
1.40; found: C, 24.34; H, 1.33%.
3.3. Cp2Ti(OSO2C8F17)2 Á 2H2O Á THF (2b Á 2H2O Á THF)
3.6. Determination of hydration number
To a solution of Cp2TiCl2 (249 mg, 0.99 mmol) in THF (20 mL)
was added a solution of AgOSO2C8F17 (1.21 g, 2.0 mmol) in THF
(10 mL). The mixture was stirred in the dark at room temperature
for 1 h, and filtered. The filtrate was combined with dry hexane
(40 mL). Then, the solution was stored in the refrigerator for 24 h
to furnish yellow needle crystals (693 mg, 54%): M.p. 206–210 °C.
1H NMR (300 MHz, CD3CN) d 1.78–1.83 (m, 4H, THF), 3.56 (s, 4H,
H2O), 3.65 (t, J = 6.6 Hz, 4H, THF), 6.96 (s, 10H, Cp). 19F NMR
(283 MHz, CD3CN) d À81.33 (t, J = 9.6 Hz, 3F, CF3-), À114.93 (s,
2F, -CF2-), À120.98 (s, 2F, -CF2-), À122.11 (m, 6F, -(CF2)-),
À122.99 (s, 2F, -CF2-), À126.42 (m, 2F, -CF2-). IR (KBr) 3648.9,
3586.9, 3536.4, 3505.3, 3443.4, 3416.5, 3120.1, 2363.6, 1662.9,
1440.4, 1370.1, 1246.3, 1152.6, 1073.9, 823.9, 642.0, 561.4,
Molecular sieves (4 Å, 11.0 g, dried at 355 °C in a muffle furnace
for 5 h) were added to CD3CN (25.0 g), and the mixture was kept
under nitrogen atmosphere overnight. In this CD3CN, water was
not detected by 1H NMR spectroscopy. The dehydrated CD3CN
was added to a freshly prepared (2a Á 3H2O Á THF) (10.0 mg, recrys-
tallized from THF/hexane (3:4) followed by drying under reduced
pressure for a week), and the solution was analyzed by 1H NMR
spectroscopy. Then the sample was subjected to elemental
analysis.
3.7. ESR detection of OÅ2À–2a complex
526.5 cmÀ1
.
Cp2Ti(OSO2C8F17)2 Á 4H2O (2b Á 4H2O) 1H NMR
A quartz ESR tube (4.5 mm i.d.) containing an oxygen-saturated
solution of dimeric 1-benzyl-1,4 dihydronicotinamide (BNA)2
(1.0 Â 10À2 M) and 2a Á 3H2O Á THF (1.0 Â 10À3 M) in MeCN was
irradiated in the cavity of the ESR spectrometer with the focused
light of a 1000 W high-pressure Hg lamp through an aqueous filter.
Dimeric (BNA)2, which was used as an electron donor to reduce
oxygen, was prepared according to the literature. The ESR spectra
of OÅ2À–2a complex in frozen MeCN were measured at 143 K with
a JEOL X-band apparatus under nonsaturating microwave power
conditions. The g values were calibrated precisely with an Mn2+
marker, which was used as a reference.
(300 MHz, CD3CN) d 3.19 (s, 8H, H2O), 6.97 (s, 10H, Cp). 19F NMR
(283 MHz, CD3CN) d À81.32 (t, J = 9.6 Hz, 3F, CF3-), À114.82 (s,
2F, -CF2-), À120.90 (s, 2F, -CF2-), À121.92 to –122.05 (m, 6F,
-(CF2)-), À122.91 (s, 2F, -CF2-), À126.29 to À126.34 (m, 2F, -CF2-).
Elemental Anal. for Cp2Ti(OSO2C8F17)2 (2b) after pumping for a
week: Calc. for C26H10F34O6S2Ti: C, 26.55; H, 0.86; found: C,
26.76; H, 0.86%. Elemental Anal. for Cp2Ti(OSO2C8F17)2 Á 4H2O
(2b Á 4H2O) after standing in open air for 2 days: Calc. for
C26H18F34O10S2Ti: C, 25.02; H, 1.45; found: C, 25.28; H, 1.42%.
3.4. Cp2Zr(OSO2C4F9)2Á2H2O (3a Á 2H2O)
3.8. Crystal data refinements details
To a solution of Cp2ZrCl2 (146 mg, 0.50 mmol) in Et2O (10 mL)
was added a solution of AgOSO2C4F9 (427 mg, 1.05 mmol) in Et2O
(5 mL). The mixture was stirred in the dark at room temperature
for 1 h, and filtered. Evaporation furnished a residue, which was
Refinement of F2 was against all reflections. The weighted R-fac-
tor wR and goodness of fit S are based on F2, conventional R-factors
R are based on F, with F set to zero for negative F2. The threshold

1528
R. Qiu et al. / Journal of Organometallic Chemistry 694 (2009) 1524–1528
(f) U. Thewalt, W. Lasser, J. Organomet. Chem. 276 (1984) 341;
expression of F2 > 2
etc. and is not relevant to the choice of reflections for refine-
ment. R-factors based on F2 are statistically about twice as large
as those based on F, and R-factors based on ALL data will be even
r
(F2) is used only for calculating R-factors(gt)
(g) W. Lasser, U. Thewalt, J. Organomet. Chem. 311 (1986) 69;
(h) J.S. Angus-Dunne, Transition Met. Chem. 31 (2006) 268.
[4] (a) G.A. Luinstra, J. Organomet. Chem. 517 (1996) 209;
(b) Synthesis of Cp2Zr(OSO2C8H17
)
from Cp2ZrMe2 and two equiv. of
2
HOSO2C8H17 has been already reported as well.N.S. Hîñgen, G.A. Luinstra,
Inorg. Chim. Acta 259 (1997) 185.
larger. Data collection: Bruker SMART; cell refinement: Bruker SMART
;
data reduction: Bruker SHELXTL; program(s) used to solve structure:
SHELXS97 (Sheldrick, 1990); program(s) used to refine structure:
SHELXL97 (Sheldrick, 1997); molecular graphics: Bruker SHELXTL; soft-
[5] (a) T.K. Hollis, N.P. Robison, B. Bosnich, Organometallics 11 (1992) 2745;
(b) T.K. Hollis, N.P. Robinson, B. Bosnich, J. Am. Chem. Soc. 114 (1993) 5464;
(c) J.B. Jaquith, C.J. Levy, G.V. Bondar, S. Wang, S. Collins, Organometallics 17
(1998) 914;
ware used to prepare material for publication: Bruker SHELXTL
.
(d) J.B. Jaquith, J. Guan, S. Wang, S. Collins, Organometallics 14 (1995) 1079;
(e) Y. Hong, B.A. Kuntz, S. Collins, Organometallics 12 (1993) 964;
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111 (1989) 6070.
3.9. Glycosylation
[6] (a) T.K. Hollis, B. Bosnich, J. Am. Chem. Soc. 117 (1995) 4570;
(b) S. Lin, G. Bondar, C.J. Levy, S. Collins, J. Org. Chem. 63 (1998) 1885.
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(b) H. Yamada, H. Takimoto, T. Ikeda, H. Tsukamoto, T. Harada, T. Takahashi,
Synlett (2001) 1751;
A
suspension of 2a Á 3H2O Á THF (9.9 mg, 7.38 mmol) and
powdered molecular sieves 4A (30.0 mg, dried in vacuo at 180 °C
for 5 min prior to use) in CH2Cl2 (1.0 mL) was stirred at room
temperature for 30 min. In another flask, a suspension of 4
(20.0 mg, 0.0369 mmol), methyl 2,3,4-tri-O-benzyl-glucopyrano-
side (22.2 mg, 0.0480 mmol), and powdered molecular sieves 4A
(20.0 mg, dried in vacuo at 180 °C for 5 min prior to use) in CH2Cl2
(2.0 mL) was stirred at room temperature for 10 min. To the sus-
pension of 2a Á 3H2O Á THF was transferred the suspension of 4
and methyl 2,3,4-tri-O-benzyl-glucopyranoside by a syringe, and
the mixture was stirred at rt for 2.5 h. After aqueous solution of
NaHCO3 had been added, the mixture was filtered through a thin
pad of Celite. The filtrate was extracted three times with ethyl ace-
tate, and the combined organic layer was washed with brine and
dried over MgSO4. After evaporation, CH2Cl2 was added to the res-
idue, and the mixture was filtered. After evaporation, the residue
was purified by preparative TLC (silica gel, ethyl acetate/hexane
(20%)) to give 5f as colorless syrup (32.2 mg, 89%).
(c) H. Tanaka, M. Adachi, H. Tsukamoto, T. Ikeda, H. Yamada, T. Takahashi, Org.
Lett. 4 (2002) 4213;
(d) H. Tanaka, N. Matoba, H. Tsukamoto, H. Takimoto, H. Yamada, T. Takahashi,
Synlett (2005) 824.
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(b) K. Suzuki, H. Maeta, T. Matsumoto, G. Tsuchihashi, Tetrahedron Lett. 29
(1988) 3571;
(c) T. Matsumoto, H. Maeta, K. Suzuki, Tetrahedron Lett. 29 (1988) 3575;
(d) T. Matsumoto, M. Katsuki, K. Suzuki, Tetrahedron Lett. 29 (1988) 6935;
(e) T. Matsumoto, M. Katsuki, K. Suzuki, Tetrahedron Lett. 30 (1989) 833;
(f) K. Suzuki, H. Maeta, T. Matsumoto, Tetrahedron Lett. 30 (1989) 4853;
(g) T. Matsumoto, M. Katsuki, K. Suzuki, Chem. Lett. 30 (1989) 437;
(h) T. Matsumoto, M. Katsuki, H. Jona, K. Suzuki, Tetrahedron Lett. 30 (1989)
6185;
(i) T. Matsumoto, T. Hosoya, K. Suzuki, Synlett (1991) 709;
(j) M.I. Matheu, R. Echarri, S. Castillon, Tetrahedron Lett. 34 (1993) 2361;
(k) P. Wipf, J.T. Reeves, Tetrahedron Lett. 40 (1999) 4649;
(l) P. Wipf, J.T. Reeves, J. Org. Chem. 66 (2001) 7910;
All the glycosylation products, glycosyl donors and acceptor 4
[18], 5a [19], 5b [18], 5c [20], 5d [21], 5e [22], 5f [23] and 5g
[24], were characterized spectroscopically by comparison of 1H
and 13C NMR spectral data reported.
(m) W.M. Macindoe, H. Iijima, Y. Nakahara, T. Ogawa, Tetrahedron Lett. 35
(1994) 1735;
(n) H. Kuyama, T. Nukada, Y. Ito, Y. Nakahara, T. Ogawa, Carbohydr. Res. 268
(1995) C1.
[12] (a) X. Li, A. Kurita, S. Man-e, A. Orita, J. Otera, Organometallics 24 (2005) 2567;
(b) D.-L. An, Z. Peng, A. Orita, A. Kurita, S. Man-e, K. Ohkubo, X. Li, S. Fukuzumi,
J. Otera, Chem. Eur. J. 12 (2006) 1642.
Acknowledgment
This work was partially supported by the National Natural Sci-
ence Foundation of China (20372020 and 20672033).
[13] (a) T. Sato, J. Otera, H. Nozaki, J. Am. Chem. Soc. 112 (1990) 901;
(b) T. Sato, Y. Wakahara, J. Otera, H. Nozaki, Tetrahedron Lett. 31 (1990) 1581;
(c) T. Sato, Y. Wakahara, J. Otera, H. Nozaki, Tetrahedron 47 (1991) 7625.
[14] Full crystallographic data have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication no. CCDC 631296.
[15] For an example of an A2+B2– electrolyte, the molar conductivity of Cd(ClO4)2 is
112 (10 mmol/L CH3CN): G.J. Janz, R.P.T. Tomkins, Nonaqueous Electrolytes
Handbook, vol. 1, Academic Press, New York, 1972, p. 419.
[16] (a) S. Fukuzumi, K. Ohkubo, Chem. Eur. J. 6 (2000) 4532;
(b) K. Ohkubo, S.C. Menon, A. Orita, J. Otera, S. Fukuzumi, J. Org. Chem. 68
(2003) 4720.
[17] Use of C8F17SO3H in place of 2a gave no desired product but a complex
mixture. It follows that the free acid was not liberated from the catalyst during
the reaction, or not responsible for the glycosylation, if any. For possible
influence of free acid derived from metal triflates, see: R. Dumeunier, I. Markó,
Tetrahedron Lett. 45 (2004) 825.
Appendix A. Supplementary material
CCDC 631296 contains the supplementary crystallographic data
for 2a Á 3H2O Á THF. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.a-
c.uk/data_request/cif. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.jorganchem.2008.12.057.
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