Substituent effects on isocyanate insertion into a lanthanide-sulfur bond. unexpected construction of a coordinated thiazolate ring

Article abstract of DOI:10.1021/om0492606

[Cp₂Yb(o-H₂NC₆H₄S)] ₂·2THF (1) and Cp₂Yb(p-H₂NC ₆H₄S)(THF) (2) were prepared in good yields by the protonolysis of Cp₃Yb with the corresponding amino-substituted thiophenol in THF at room temperature, respectively. Treatment of [Cp ₂Yb(o-H₂NC₆H₄S)]₂· 2THF (1) with PhNCO gives the unexpected intermolecular addition/cyclization/ elimination product [(C₅H₅)_2- Yb(μ-η¹:η³-OSNC₇H₄)] ₂ (3), while Cp₂Yb(p-H₂NC₆H ₄S)(THF) (2) reacts with PhNCO under the same conditions to form the simple insertion product {Cp₂Yb[μ-η¹: η³-OC(p-H₂NC₆H₄S)NPh]} ₂·2THF (4), demonstrating that the neighboring NH₂ group participation could lead to unique isocyanate insertion reactivity. The structures of all the complexes were confirmed by X-ray single-crystal diffraction analysis, indicating that complexes 1 and 4 have an unusual intermolecular hydrogen bond interaction involving THF, and a novel intramolecular π-π weak interaction between aromatic rings is also observed in 4.

Full text of DOI:10.1021/om0492606

738
Organometallics 2005, 24, 738-742
Substituent Effects on Isocyanate Insertion into a
Lanthanide-Sulfur Bond. Unexpected Construction of a
Coordinated Thiazolate Ring
Jie Zhang,† Liping Ma,† Ruifang Cai,† Linhong Weng,† and Xigeng Zhou*,†,‡
Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative
Materials, Fudan University, Shanghai 200433, People's Republic of China, and State Key
Laboratory of Organometallic Chemistry, Shanghai 200032, People's Republic of China
Received September 23, 2004
[Cp2Yb(o-H2NC6H4S)]2‚2THF (1) and Cp2Yb(p-H2NC6H4S)(THF) (2) were prepared in good
yields by the protonolysis of Cp3Yb with the corresponding amino-substituted thiophenol in
THF at room temperature, respectively. Treatment of [Cp2Yb(o-H2NC6H4S)]2‚2THF (1) with
PhNCO gives the unexpected intermolecular addition/cyclization/elimination product [(C5H5)2-
Yb(µ-η1:η3-OSNC7H4)]2 (3), while Cp2Yb(p-H2NC6H4S)(THF) (2) reacts with PhNCO under
the same conditions to form the simple insertion product {Cp2Yb[µ-η1:η3-OC(p-H2NC6H4S)-
NPh]}2‚2THF (4), demonstrating that the neighboring NH2 group participation could lead
to unique isocyanate insertion reactivity. The structures of all the complexes were confirmed
by X-ray single-crystal diffraction analysis, indicating that complexes 1 and 4 have an
unusual intermolecular hydrogen bond interaction involving THF, and a novel intramolecular
π-π weak interaction between aromatic rings is also observed in 4.
Introduction
forming reactions,1b,3 very few studies have emphasized
the organolanthanide-promoted C-S bond formations.5
To the best of our knowledge, no example of organo-
lanthanide-promoted construction of sulfur-containing
heterocycles has been reported to date. Therefore, it
would be of great interest to determine if individual
C-S and C-N bond-forming and C-N bond-cleaving
steps could be coupled using a single lanthanide center
in a one-pot reaction. In this contribution, we present
the first example of the further interaction of the
adjacent NH2 group with an isocyanate unit inserted
into the lanthanide-sulfur bond, allowing the construc-
tion of a coordinated thiazole ring.
There is currently considerable interest in studying
insertions into lanthanide-ligand bonds, because they
permit unusual organolanthanide derivatives to be
prepared and provide new bond-forming methods for
organic synthesis with exquisite selectivity and ef-
fectiveness.1,2 In addition, the observation and isolation
of intermediate structures can provide glimpses of the
mechanism of lanthanide-promoted transformation of
organic functionalities.3 Although stoichiometric inser-
tions of small molecules into lanthanide-ligand bonds
have been studied extensively, surprisingly little is
known about the neighboring substituent participation
interaction.4 Furthermore, in contrast to the C-N bond-
Results and Discussion
* To whom correspondence should be addressed at Fudan Univer-
sity.
[Cp2Yb(o-H2NC6H4S)]2‚2THF (1) and Cp2Yb(p-H2NC6-
H4S)(THF) (2) were prepared by the protonolysis of
Cp3Yb with the corresponding amino-substituted thio-
phenol in THF at room temperature in 63 and 61%
yields, respectively. It is interesting to note that the
unexpected benzothiazole 2-oxide complex Cp2Yb(µ-
η1:η3-OSNC7H4)]2 (3) was obtained as yellow crystals in
53% yield when 1 reacted with 1 equiv of PhNCO in
THF at ambient temperature, indicating that the ad-
jacent NH2 group undergoes immediately a tandem
intramolecular hydroamination/PhNH2 elimination on
insertion of PhNCO into the Yb-S bond (Scheme 1).
Although a wide variety of metal-promoted transfor-
mation reactions of isocyanates have been studied,
indicating that both the CdN and the CdO double
bonds of isocyanates can participate in polar addition
† Fudan University.
‡ State Key Laboratory of Organometallic Chemistry.
(1) Reviews: (a) Evans, W. J.; Davis, B. L. Chem. Rev. 2002, 102,
2119. (b) Zhou, X. G.; Zhu, M. J. Organomet. Chem. 2002, 647, 28. (c)
Ferrence, G. M.; Takats, J. J. Organomet. Chem. 2002, 647, 84.
(2) (a) Kirillov, E.; Lehmann, C. W.; Razavi, A.; Carpentier, J. F.
Eur. J. Inorg. Chem. 2004, 943. (b) Zhang, J.; Cai, R. F.; Weng, L. H.;
Zhou, X. G. Organometallics 2004, 23, 3303. (c) Beetstra, D. J.;
Meetsma, A.; Hessen, B.; Teuben, J. H. Organometallics 2003, 22, 4372.
(d) Voth, P.; Arndt, S.; Spaniol, T. P.; Okuda, J.; Ackerman, L. J.;
Green, M. L. H. Organometallics 2003, 22, 65. (e) Kornienko, A. Y.;
Emge, T. J.; Brennan, J. G. J. Am. Chem. Soc. 2001, 123, 11933. (f)
Evans, W. J.; Fujimoto, C. H.; Ziller, J. W. Organometallics 2001, 20,
4529. (g) Evans, W. J.; Kozimor, S. A.; Nyce, G. W.; Ziller, J. W. J.
Am. Chem. Soc. 2003, 125, 13831. (h) Zhang, J.; Cai, R. F.; Weng, L.
H.; Zhou, X. G. Organometallics 2003, 22, 5385.
(3) (a) Molander, G. A.; Romero, J. A. C. Chem. Rev. 2002, 102, 2161
and references therein. (b) Hong, S. W.; Kawaoka, A. M.; Marks, T. J.
J. Am. Chem. Soc. 2003, 125, 15878. (c) Hong, S. W.; Tian, S.; Metz,
M. V.; Marks, T. J. J. Am. Chem. Soc. 2003, 125, 14768. (d) Molander,
G. A.; Pack, S. K. J. Org. Chem. 2003, 68, 9214. (e) Gribkov, D. V.;
Hultzsch, K. C.; Hampell, F. Chem. Eur. J. 2003, 9, 4796. (f) Hultzsch,
K. C.; Hampel, F.; Wagner, T. Organometallics 2004, 23, 2601. (g)
Hong, S.; Marks, T. J. Acc. Chem. Res. 2004, 37, 673.
(5) (a) Shen, Q.; Li, H. R.; Yao, C. S.; Yao, Y. M.; Zhang, L. L.; Yu,
K. B. Organometallics 2001, 20, 3070. (b) Zhang, C. M.; Liu, R. T.;
Zhou, X. G.; Chen, Z. X.; Weng, L. H.; Lin, Y. H. Organometallics 2004,
23, 3246.
(4) Evans, W. J.; Hughes, L. A.; Drummond, D. K.; Zhang, H.;
Atwood, J. L. J. Am. Chem. Soc. 1986, 108, 1722.
10.1021/om0492606 CCC: $30.25 © 2005 American Chemical Society
Publication on Web 01/13/2005

Isocyanate Insertion into a Lanthanide-Sulfur Bond
Organometallics, Vol. 24, No. 4, 2005 739
Scheme 1
the Yb-S bond rather than the N-H bond. The free
NH2 group at the para position is inert and undergoes
neither competitive addition to PhNCO nor further
addition to the newly formed OC(p-H2NC6H4S)NPh
ligand under the conditions involved. Recently, lan-
thanide thiolates were found to have high catalytic
activities for oligomerization of phenyl isocyanate,10 but
no oligomerization of phenyl isocyanate occurred and
only insertion chemistry is observed in the treatment
of PhNCO with 1 and 2.
On the basis of these experimental results, a possible
reaction pathway for the formation of 3 is proposed in
Scheme 1. Coordination of PhNCO and migration of
o-H2NC6H4S give the insertion intermediate I. A se-
quential addition of the activated N-H to the CdN
double bond results in cyclization via a four-centered σ
bond metathesis process. Reductive elimination of
PhNH2 generates the thiazolate ring. Obviously, the
present hydroamination/cyclization pathway is differ-
ent from the mechanism of the previously reported
organolanthanide-catalyzed construction of azacyclic
skeletons: for the latter the hydroamination/cyclization
reaction generally proceeds via a turnover-limiting C-C
multiple-bond insertion into the lanthanide-nitrogen
bond.3g However, attempts to isolate the intermediate
II have been unsuccessful, due to the thermodynamic
instability. A tandem addition/cyclization/elimination
reaction is observed in the treatment of 1 with PhNCO,
whereas for 2 no subsequent reaction is observed, even
with a longer reaction time. It is possible that both the
activation of the metal on the NH2 group and the
formation of a more stable aromatic thiazolate skeleton
contribute to the occurrence of the hydroamination/
cyclization/amine-elimination reaction of the putative
amido intermediate I. Furthermore, this reaction also
represents the first example in organolanthanide chem-
istry of direct N-H addition to a ligand functionality.
Complexes 1-4 have been characterized by elemental
analysis and IR and mass spectroscopy, which were in
good agreement with the proposed structures. Interest-
ingly, in the IR spectra compound 2 displays three
medium-intensity bands at 3554, 3409, and 3318 cm-1
attributable to ν(N-H) vibrations, while the corre-
sponding bands due to the H-bond interaction in 4 are
observed near 3430, 3343, and 3230 cm-1, respectively.
In the case of 1 the absorptions of N-H bonds are
shifted to lower frequencies with a medium band at 3238
cm-1 and a weaker band at 3170 cm-1 as compared with
4, which may be attributed to the additional chelating
coordination as established by X-ray diffraction. The
structures of all the complexes were also confirmed by
X-ray single-crystal diffraction analysis. Crystal struc-
ture analysis confirmed that complex 1 is a centrosym-
metric dimeric structure, with the o-aminothiophenoxyl
ligand as both a bridging and side-on donating group.
Each Yb atom is coordinated by two cyclopentadienyl
rings, two bridging sulfur atoms, and one chelating
nitrogen atom to form an edge-bridged tetrahedral
geometry. The Yb-N distance (2.459(2) Å; Table 2) is
reactions, in most cases only single-addition products
are isolated, and the sequential CdO and CdN bis-
addition processes are rarely observed.1,6 To our knowl-
edge, only one stepwise addition reaction of organo-
metallic reagents to isocyanates has been reported,
where the isocyanate unit inserted into the Zr-H bond,
forming a formamido ligand, with further addition of a
second Zr-H bond.7 The further addition reaction of an
organic functionality to the isocyanate unit inserted into
the metal-ligand bond is unprecedented. On the other
hand, organolanthanides have been applied success-
fully to the intra-/intermolecular hydroamination and
hydrophosphination of a variety of unsaturated sub-
strates, including aminoolefins, aminoalkynes, phos-
phinoalkenes, and phosphinoalkynes, providing a mild
and efficient method for the construction of aza- and
phosphacyclic skeletons.3,8 To our knowledge, the present
regiospecific, tandem C-S and C-N bond-forming and
subsequent C-N bond-cleaving reaction is unprec-
edented in organolanthanide chemistry and provides an
effective method for the construction of the thiazole
skeleton, despite the fact that it is stoichiometric with
respect to the metal fragment.
To obtain additional insight into the mechanism and
scope of the reaction, we examined the behavior of
Cp2Yb(p-H2NC6H4S)(THF) (2) toward PhNCO. In marked
contrast to [Cp2Yb(o-H2NC6H4S)]2‚2THF, where mul-
tiple pathways occur for PhNCO, treatment of 2 with 1
equiv of PhNCO under the same conditions provided
only the dinuclear insertion product {Cp2Yb[µ-η1:η3-
OC(p-H2NC6H4S)NPh]}2‚2THF (4) (eq 1). The direct
addition of amines to isocyanates is a convenient
transformation in organic synthesis.9 However, this
result indicates that PhNCO is preferentially added by
(8) (a) Douglass, M. R.; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc.
2001, 123, 10221. (b) Kawaoka, A. M.; Douglass, M. R.; Marks, T. J.
Organometallics 2003, 22, 4630.
(6) Braunstein, P.; Nobel, D. Chem. Rev. 1989, 89, 1927.
(7) Gambarotta, S.; Strologo, S.; Floriani, C.; Chiesi-Villa, A.;
Guastini, C. J. Am. Chem. Soc. 1985, 107, 6278.
(9) Ozaki, S. Chem. Rev. 1972, 72, 457.
(10) Deng, M. Y.; Yao, Y. M.; Zhou, Y. F.; Zhang, L. F.; Shen, Q.
Chin. J. Chem. 2003, 21, 574.

740 Organometallics, Vol. 24, No. 4, 2005
Table 1. Crystal and Data Collection Parameters of Complexes 1-4
Zhang et al.
1
2
3
4
formula
mol wt
C
40H48N2O2S2Yb2
C
20H24NOSYb
C42H44N2O4S2Yb2
1050.99
C54H50N4O4S2Yb2
999.00
499.50
1237.24
orange
cryst color
cryst dimens (mm)
cryst syst
space group
unit cell dimens
a (Å)
red
orange
orange
0.35 × 0.25 × 0.20
monoclinic
P21/c
0.10 × 0.08 × 0.05
triclinic
P1h
0.25 × 0.10 × 0.08
monoclinic
P21/n
0.35 × 0.20 × 0.10
triclinic
P1h
10.9171(12)
10.6077(12)
16.9229(18)
7.768(2)
8.653(3)
14.462(4)
84.112(4)
83.848(4)
89.238(4)
961.4(5)
2
14.052(4)
8.375(3)
17.511(5)
11.112(6)
11.338(6)
12.039(6)
115.778(5)
101.400(7)
100.963(7)
1271.7(11)
1
b (Å)
c (Å)
R (deg)
â (deg)
103.9650(10)
1901.8(4)
105.223(4)
1988.6(11)
γ (deg)
V (Å3)
Z
2
2
Dc (g cm-3
)
1.745
5.033
980
1.726
1.755
4.822
1028
1.615
µ (mm-1
F(000)
)
4.978
3.785
490
614
radiation (λ ) 0.710 730 Å)
temp (K)
Mo KR
298.2
ω-2θ
293.2
298.2
298.2
scan type
θ range (deg)
h,k,l range
2.29-26.51
1.42-26.01
-8 e h e 9
-10 e k e 8
-17 e l e 17
4432
1.66-25.01
1.97-25.01
-6 e h e 13
-13 e k e 12
-12 e l e 13
4617
4166 (Rint ) 0.0290)
92.8 (θ ) 25.01°)
0.7034 and 0.3509
-13 e h e 11
-12 e k e 13
-20 e l e 21
8904
-15 e h e 16
-8 e k e 9
-20 e l e 20
7971
no. of rflns measd
no. of unique rflns
3921 (Rint ) 0.0204
99.5 (θ ) 26.51°)
0.4326 and 0.2718
3709 (Rint ) 0.0201)
97.6 (θ ) 26.01°)
0.7889 and 0.6359
3481 (Rint ) 0.0383)
99.8 (θ ) 25.01°)
0.6990 and 0.3786
completeness to θ (%)
max and min transmissn
refinement method
no. of data/restraints/params
goodness of fit on F2
final R indices (I > 2σ(I))
full-matrix least squares on F2
3921/0/218
0.989
R1 ) 0.0189,
wR2 ) 0.0435
R1 ) 0.0236,
wR2 ) 0.0445
0.667 and -0.609
3709/0/217
0.988
R1 ) 0.0338,
wR2 ) 0.779
R1 ) 0.410,
wR2 ) 0.796
1.347 and -1.008
3481/0/210
0.947
4166/0/273
1.081
R1 ) 0.0457,
wR2 ) 0.1287
R1 ) 0.0505,
wR2 ) 0.1353
1.749 and -1.430
R1 ) 0.0440,
wR2 ) 0.1156
R1 ) 0.0676,
wR2 ) 0.1214
0.937 and -0.950
R indices (all data)
largest diff peak and hole (e Å-3
)
Table 2. Selected Bond Lengths (Å) and Angles
(deg) for Complex 1
Yb(1)-N(1)
Yb(1)-C(8)
Yb(1)-C(4)
Yb(1)-C(10)
Yb(1)-C(9)
Yb(1)-C(6)
Yb(1)-C(7)
Yb(1)-C(5)
Yb(1)-C(3)
2.459(2)
2.590(4)
2.599(3)
2.602(3)
2.606(4)
2.606(3)
2.608(4)
2.624(3)
2.626(3)
Yb(1)-C(2)
Yb(1)-C(1)
Yb(1)-S(1)
S(1)-C(11)
S(1)-Yb(1A)
N(1)-C(16)
N(1)‚‚‚O(1)
O(1)‚‚‚H(1B)
2.654(3)
2.669(3)
2.724(1)
1.762(3)
2.864(1)
1.442(3)
2.992(4)
2.13
N(1)-Yb(1)-S(1)
C(11)-S(1)-Yb(1)
67.4(1) C(16)-N(1)-Yb(1) 117.0(2)
101.6(1) C(16)-C(11)-S(1) 117.3(2)
C(11)-S(1)-Yb(1A) 131.6(1) C(11)-C(16)-N(1) 117.2(2)
Yb(1)-S(1)-Yb(1A) 113.4(1) N(1)-H(1B)‚‚‚O(1) 159.9
comparable with the Yb-N donor bond distance of
Cp2Yb[OC(dNPh)PzMe2](THF) (2.473(2) Å).2h An in-
teresting feature of the crystal structure of 1 is the
N(1)-H(1B)‚‚‚O(1) hydrogen bonding between the chelat-
ing coordinated NH2 group and the uncoordinated THF,
as shown in Figure 1. The hydrogen-bond interaction
is common in inorganic complexes of rare earths.11 For
the lanthanocene system, however, a similar interaction
is quite uncommon12 and no example of a hydrogen-bond
interaction involving THF has been reported.
Figure 1. ORTEP diagram of [Cp2Yb(o-H2NC6H4S)]2‚
2THF (1) with the ellipsoids drawn at the 30% probability
level.
distances in 1, in which the sulfur atoms are in bridging
positions. This shortening of 0.083-0.223 Å is quite
normal on going from bridging to nonbridging and is in
the range observed for organolanthanide chloride com-
plexes (0.04-0.27 Å).13
Complex 2 is a solvated monomeric structure (Figure
2) and has normal metrical parameters (Table 3). The
Yb-S distance of 2.641(2) Å is shorter than the Yb-S
The molecular structure of 3 is shown in Figure 3.
Selected bond lengths and angles of 3 are listed in Table
4. The X-ray crystal analysis results show that the
benzothiazole 2-oxide ligand in 3 exhibits an unusual
(11) Liang, Y. C.; Cao, R.; Su, W. P.; Hong, M. C.; Zhang, W. J.
Angew. Chem., Int. Ed. 2000, 39, 3304.
(12) Shapiro, P. L.; Henling, L. M.; Marsh, R. E.; Bercaw, J. E. Inorg.
Chem. 1990, 29, 4560.
(13) Evans, W. J.; Peterson, T. T.; Rausch, M. D.; Hunter, W. J.;
Atwood, J. L. Organometallics 1985, 4, 554.

Isocyanate Insertion into a Lanthanide-Sulfur Bond
Organometallics, Vol. 24, No. 4, 2005 741
Figure 4. ORTEP diagram of {Cp2Yb[µ-η1:η3-OC(p-
H2NC6H4S)NPh]}2‚2THF (4) with the ellipsoids drawn at
the 30% probability level.
Table 4. Selected Bond Lengths (Å) and Angles
(deg) for Complex 3
Figure 2. ORTEP diagram of Cp2Yb(p-H2NC6H4S)(THF)
(2) with the ellipsoids drawn at the 30% probability level.
Yb(1)-O(1A)
Yb(1)-O(1)
Yb(1)-N(1)
Yb(1)-C(8)
Yb(1)-C(9)
Yb(1)-C(3)
Yb(1)-C(7)
Yb(1)-C(6)
Yb(1)-C(10)
2.288(6)
2.414(7)
2.461(6)
2.583(10)
2.590(11)
2.593(10)
2.593(10)
2.595(11)
2.598(11)
Yb(1)-C(5)
Yb(1)-C(4)
Yb(1)-C(1)
S(1)-C(12)
S(1)-C(11)
O(1)-C(11)
N(1)-C(11)
N(1)-C(17)
2.601(12)
2.602(11)
2.604(12)
1.741(9)
1.764(8)
1.264(10)
1.286(10)
1.434(10)
O(1A)-Yb(1)-N(1)
O(1A)-Yb(1)-O(1)
N(1)-Yb(1)-O(1)
C(12)-S(1)-C(11)
C(11)-O(1)-Yb(1)
119.4(2) C(17)-N(1)-Yb(1) 154.2(6)
65.5(2) O(1)-C(11)-N(1)
53.9(2) O(1)-C(11)-S(1)
88.7(4) N(1)-C(11)-S(1)
92.1(5) O(1)-C(11)-Yb(1)
120.2(7)
124.3(7)
115.4(7)
61.1(4)
Yb(1A)-O(1)-Yb(1) 114.5(2) N(1)-C(11)-Yb(1)
59.1(4)
C(11)-N(1)-C(17)
C(11)-N(1)-Yb(1)
112.1(7) S(1)-C(11)-Yb(1)
174.3(5)
93.7(5)
Table 5. Selected Bond Lengths (Å) and Angles
(deg) for 4
Figure 3. ORTEP diagram of [Cp2Yb(o-H2NC6H4S)]2 (3)
Yb(1)-O(1)
Yb(1)-O(1A)
Yb(1)-N(1A)
Yb(1)-C(9)
Yb(1)-C(1)
Yb(1)-C(5)
Yb(1)-C(2)
Yb(1)-C(3)
Yb(1)-C(4)
Yb(1)-C(10)
Yb(1)-C(8)
2.268(5)
2.372(5)
2.414(5)
2.583(9)
2.583(9)
2.594(9)
2.603(9)
2.614(8)
2.616(9)
2.622(9)
2.617(9)
Yb(1)-C(7)
S(1)-C(18)
S(1)-C(11)
N(1)-C(11)
N(1)-C(12)
N(1)-Yb(1A)
O(1)-C(11)
O(1)-Yb(1A)
N(2)‚‚‚O(2A)
O(2)‚‚‚H(2A)
2.621(8)
1.774(9)
1.778(7)
1.262(9)
1.415(9)
2.414(5)
1.309(8)
2.372(5)
3.10(2)
with the ellipsoids drawn at the 30% probability level.
Table 3. Selected Bond Lengths (Å) and Angles
(deg) for Complex 2
Yb(1)-O(1)
Yb(1)-C(7)
Yb(1)-C(2)
Yb(1)-C(6)
Yb(1)-C(1)
Yb(1)-C(3)
Yb(1)-C(8)
2.287(4)
2.583(6)
2.584(6)
2.589(7)
2.594(6)
2.597(6)
2.610(6)
Yb(1)-C(10)
Yb(1)-C(4)
Yb(1)-C(9)
Yb(1)-S(1)
Yb(1)-C(5)
S(1)-C(11)
2.614(7)
2.620(6)
2.625(7)
2.641(2)
2.645(6)
1.786(6)
2.38
O(1)-Yb(1)-O(1A)
O(1)-Yb(1)-N(1A)
O(1A)-Yb(1)-N(1A)
C(18)-S(1)-C(11)
C(11)-N(1)-C(12)
C(11)-N(1)-Yb(1A)
66.0(2) Yb(1)-O(1)-Yb(1A) 114.0(2)
O(1)-Yb(1)-S(1)
99.4(1)
C(11)-S(1)-Yb(1)
106.7(2)
120.2(2) N(1)-C(11)-O(1)
54.3(2) N(1)-C(11)-S(1)
102.6(4) O(1)-C(11)-S(1)
123.2(6) N(1)-C(11)-Yb(1A)
94.2(4) O(1)-C(11)-Yb(1A)
116.4(6)
128.8(5)
114.7(5)
59.1(4)
bonding mode, which acts as both a bridging and side-
on chelating group. Both the O(1)-C(11) and N(1)-
C(11) distances of 1.264(10) and 1.286(10) Å lie between
single- and double-bond distances.14 This suggests some
electronic delocalization over the O-C-N unit. Con-
sistent with this, the Yb(1)-N(1) distance of 2.461(6) Å
is between those expected for a Yb3+-N single bond and
a Yb3+r:N donor bond (2.19-2.69 Å),15 and there is a
weak interaction between Yb(1) and C(11).
Complex 4 is a dimeric structure (Figure 4). The
structural data reveal that PhNCO has inserted into
the Yb-S bond to form a thiolate-substituted amido
anion. Characteristically, the unusual intermolecular
hydrogen-bond interaction between the noncoordinated
57.4(3)
C(12)-N(1)-Yb(1A) 141.6(5) S(1)-C(11)-Yb(1A) 172.1(4)
C(11)-O(1)-Yb(1)
C(11)-O(1)-Yb(1A)
150.6(5) N(2)-H(2A)‚‚‚O(2A) 141.5
94.9(4)
NH2 and noncoordinated THF molecules is also ob-
served in 4. Bond lengths and angles involving the
amido functions indicate their bonding in an µ-η1:η3
fashion. The Yb(1)-O(1), Yb(1)-O(1A), Yb(1)-N(1A),
and Yb(1)-C(11A) distances of 2.268(5), 2.372(5),
2.414(5), and 2.806(7) Å (Table 5) are similar to the
corresponding distances of 2.288(6), 2.461(6), 2.414(7),
and 2.808(5) Å in 3, respectively. The distance between
the centers of two aromatic rings containing C(12) and
C(18) is 3.775 Å, and the dihedral angle between the
least-squares planes amounts to 17.9°. These data
demonstrate that the two aromatic rings are close
together so that intramolecular π-π interactions are
(14) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G. J. Chem. Soc., Perkin Trans. 1987, S1.
(15) Zhou, X. G.; Zhang, L. B.; Zhu, M.; Cai, R. F.; Weng, L. H.
Organometallics 2001, 20, 5700.

742 Organometallics, Vol. 24, No. 4, 2005
Zhang et al.
possible.16 Similar π-π stacking interactions were
observed for lanthanide complexes with the doubly
deprotonated form of the bibracchial lariat ether N,N′-
bis(2-salicylaldiminobenzyl)-1,10-diaza-15-crown-5.17
In conclusion, the present work demonstrates the
novel reactivity of organolanthanides with bifunctional
ligands toward PhNCO. It is interesting to note that
the further interaction of the neighboring NH2 group
with an isocyanate unit inserted into the lanthanide-
sulfur bond could lead to unique reactivity and selectiv-
ity trends, allowing a mild and efficient construction of
the coordinated benzothiazole 2-oxide ligand. In contrast
to the known organolanthanide-promoted hydroamina-
tion/cyclization reactions, where the general mechanism
involves turnover-limiting C-C multiple-bond insertion
into the lanthanide-heteroatom bond followed by a
rapid protonolysis by other amine substrates,3,8 in the
present case, the hydroamination/cyclization proceeds
via intramolecular amine addition to the CdN double
bond. Moreover, the X-ray crystal structure analyses
have revealed an unusual intermolecular hydrogen-bond
interaction involving THF and an interesting intra-
molecular π-π weak interaction between aromatic
rings.
2.41 mmol) with p-aminothiophenol (0.302 g, 2.41 mmol) gave
2 as orange crystals. Yield: 0.734 g (61%). Anal. Calcd for
C20H24NOSYb: C, 48.09; H, 4.84; N, 2.80. Found: C, 48.16;
H, 4.92; N, 2.91. IR (Nujol): 3554 m, 3409 m, 3318 m, 1619 s,
1599 s, 1074 s, 1008 s, 911 m, 775 s, 664 m cm-1. EI-MS (m/z
(%)): 428 (15) [M - THF].
Reaction of Complex 1 with PhNCO. To a 30 mL THF
solution of 1 (0.524 g, 0.57 mmol) was slowly added phenyl
isocyanate (0.135 g, 1.14 mmol) at room temperature and
stirred for 24 h. The reaction solution was concentrated to ca.
3 mL by reduced pressure. Yellow crystals of [(C5H5)2Yb(µ-η1:
η3-OSNC7H4)]2 (3) were obtained at -20 °C for several days.
Yield: 0.318 g (53%). Anal. Calcd for C42H44N2O4S2Yb2: C,
48.00; H, 4.22; N, 2.67. Found: C, 47.83; H, 4.11; N, 2.85. IR
(Nujol): 3161 m, 1613 s, 1589 s, 1538 m, 1565 m, 1074 s, 1009
s, 920 m, 770 s, 735 s, 670 m, 657 m cm-1. EI-MS (m/z (%)):
454 (25) [M/2]. The PhNH2 produced was identified by GC/
MS.
Reaction of Complex 2 with PhNCO. By the above
procedure described for 3, reaction of 2 (0.460 g, 0.92 mmol)
with phenyl isocyanate (0.109 g, 0.92 mmol) gave {Cp2Yb[µ-
η1:η3-OC(p-H2NC6H4S)NPh]}2‚2THF (4) as orange crystals.
Yield: 0.262 g (46%). Anal. Calcd for C54H58N4O4S2Yb2: C,
52.42; H, 4.73; N, 4.52. Found: C, 52.39; H, 4.71; N, 4.59. IR
(Nujol): 3437 m, 3343 m, 3222 m, 1634 s, 1593 s, 1550 s, 1062
s) 1010 s, 928 s, 773 s, 710 m, 695 m, 658 m cm-1. EI-MS (m/z
(%)) 547 (12) [M/2].
X-ray Data Collection, Structure Determination, and
Refinement for 1-4. A suitable crystal for each of the
complexes was selected and sealed under argon in a Linde-
mann glass capillary for X-ray structural analysis. Diffraction
data were collected on a Bruker SMART CCD diffractometer
using graphite-monochromated Mo KR (λ ) 0.710 73 Å)
radiation. The intensities were corrected for Lorentz-polariza-
tion effects and empirical absorption with the SADABS
program.18 A summary of the crystallographic data is given
in Table 1.
The structure was solved bydirect methods using the
SHELXL-97 program.19 All non-hydrogen atoms were found
from the difference Fourier syntheses. H atoms were included
in calculated positions with isotropic thermal parameters
related to those of the supporting carbon atoms but were not
included in the refinement. There is one solvent molecule
present per formula unit for 3. All calculations were performed
using the Bruker Smart program.
Experimental Section
All operations involving air- and moisture-sensitive com-
pounds were carried out under an inert atmosphere of purified
nitrogen using standard Schlenk techniques. All solvents were
refluxed and distilled over sodium benzophenone ketyl under
nitrogen immediately prior to use. Elemental analyses for C,
H, and N were carried out on a Vario EL CHN-O analyzer.
Infrared spectra were obtained on a Nicolet FT-IR 360
spectrometer with samples prepared as Nujol mulls. Mass
spectra were recorded on a Philips Agilent MS5973N or Philips
HP5989A instrument operating in EI mode. Crystalline samples
of the respective complexes were rapidly introduced by direct-
inlet techniques.
Synthesis of [Cp2Yb(o-H2NC6H4S)]2‚2THF (1). (C5H5)3-
Yb (0.968 g, 2.63 mmol) and o-aminothiophenol (0.329 g, 2.63
mmol) were mixed in 100 mL of THF. The solution color slowly
turned from dark green to red in several hours. After the
mixture was stirred for 24 h at room temperature, all volatile
substances were removed under vacuum to give an orange
powder. Orange crystals of 1‚2THF were obtained by recrys-
tallization from THF at -20 °C for several days. Yield: 0.768
g (63%). Anal. Calcd for C40H48O2N2S2Yb2: C, 48.09; H, 4.84;
N, 2.80. Found: C, 47.93; H, 4.79; N, 2.97. IR (Nujol): 3238
m, 3170 w, 1657 m, 1587 m, 1565 m, 1061 s, 1013 s, 910 m,
770 s, 681 m cm-1. EI-MS (m/z (%)): 428 (52) [M/2].
Acknowledgment. We thank the NNSF of China,
the NSF of Shanghai, the Fund of the New Century
Distinguished Scientist of the Education Ministry of
China, and the Research Fund for the Doctoral Program
of Higher Education of China for financial support.
Supporting Information Available: Figures giving ad-
ditional views and CIF files giving details of crystal structure
determinations and structure data for all complexes. This
material is available free of charge via the Internet at
http://pubs.acs.org.
Synthesis of Cp2Yb(p-H2NC6H4S)(THF) (2). Following
the procedure described for 1, reaction of (C5H5)3Yb (0.888 g,
(16) (a) Hobza, P.; Selzle, H. L.; Schlag, E. W. J. Am. Chem. Soc.
1994, 116, 3500. (b) Zhang, X.-X.; Boedunov, A. V.; Bradshaw, J. S.;
Dalley, N. K.; Kou, X.; Izatt, R. M. J. Am. Chem. Soc. 1995, 117, 11507.
(c) Ranganathan, D.; Haridas, V.; Gilardi, R.; Karle, I. L. J. Am. Chem.
Soc. 1998, 120, 10793.
(17) Gonza´lez-Lorenzo, M.; Platas-Iglesias, C.; Avecilla, F.; Geraldes,
C. F. G. C.; Imbert, D.; Bu¨nzli, J.-C. G.; de Blas, A.; Rodr´ıguez-Blas,
T. Inorg. Chem. 2003, 42, 6946.
OM0492606
(18) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
Correction; University of Go¨ttingen, Go¨ttingen, Germany, 1998.
(19) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
the Crystal Structure; University of Go¨ttingen, Go¨ttingen, Germany,
1997.