Synthesis and Studies on the Reactivities of Dicyclopentadienylytterbium Derivatives Containing Carbazolate and Pyrazolate Ligands

Article abstract of DOI:10.1021/om0340342

Two ytterbocene derivatives containing aromatic nitrogen ligands, (C ₅H₅)₂YbCbz(THF) (1) and (C₅H ₅)₂YbPzMe₂(THF) (4), were synthesized, and their reactivities toward N,N′-diisopropylcarbodiimide, phenyl isothiocyanate, and phenyl isocyanate were studied. Abstraction of cyclopentadienyl from (C₅H₅)₃Yb with 1 equiv of carbazole (HCbz) in THF at room temperature gives 1. Reaction of 1 with N,N′-diisopropylcarbodiimide (ⁱPrN=C=NⁱPr) results in monoinsertion of ⁱPrN=C=NⁱPr into the Yb-N(Carbazolate) bond, yielding the ytterbocene guanidinate (C₅H₅) ₂Yb[ⁱPrN-C(Cbz)-NⁱPr] (2), while treatment of 1 with 1 equiv of phenyl isothiocyanate (PhNCS) gives the unexpected monocyclopentadienylytterbium complex (C₅H ₅)Yb[S-C(Cbz)-NPh]₂(THF) (3) and (C₅H ₅)₃Yb(THF), which may be rationalized by the ligand rearrangement of the monoinsertion product (C₅H₅) ₂Yb[S-C(Cbz)-NPh]. (C₅H₅)₃Yb reacts with 3,5-dimethylpyrazole (HPzMe₂) in a 1:1 ratio at ambient temperature to form complex 4. Reaction of 4 with PhNCO gives the insertion product (C₅H₅)₂Yb[OC(=NPh)PzMe ₂](THF) (5). In contrast to 1, however, complex 4 does not react with ⁱPrNCNⁱPr under the same conditions. All these complexes were characterized by elemental analysis and spectroscopic properties. The structures of complexes 2-5 were also determined by X-ray single-crystal diffraction analyses. These reactions present the first example of 1,3-heterocumulene insertions into the Ln-N(aromatic ring) bond and provide a new strategy for introducing a substituent at the nitrogen atom of organic heterocycle compounds.

Full text of DOI:10.1021/om0340342

Organometallics 2003, 22, 5385-5391
5385
Articles
Syn th esis a n d Stu d ies on th e Rea ctivities of
Dicyclop en ta d ien ylytter biu m Der iva tives Con ta in in g
Ca r ba zola te a n d P yr a zola te Liga n d s
J ie Zhang,† Ruifang Cai,† Linhong Weng,† and Xigeng Zhou*,†,‡
Molecular Catalysis and Innovative Material Laboratory, Department of Chemistry,
Fudan University, Shanghai 200433, People’s Republic of China, and State Key Laboratory of
Organometallic Chemistry, Shanghai 200032, People’s Republic of China
Received J uly 11, 2003
Two ytterbocene derivatives containing aromatic nitrogen ligands, (C5H5)2YbCbz(THF) (1)
and (C5H5)2YbPzMe2(THF) (4), were synthesized, and their reactivities toward N,N′-
diisopropylcarbodiimide, phenyl isothiocyanate, and phenyl isocyanate were studied. Abstrac-
tion of cyclopentadienyl from (C5H5)3Yb with 1 equiv of carbazole (HCbz) in THF at room
temperature gives 1. Reaction of 1 with N,N′-diisopropylcarbodiimide (iPrNdCdNiPr) results
in monoinsertion of iPrNdCdNiPr into the Yb-N(Carbazolate) bond, yielding the ytterbocene
guanidinate (C5H5)2Yb[iPrN.C(Cbz).NiPr] (2), while treatment of 1 with 1 equiv of phenyl
isothiocyanate (PhNCS) gives the unexpected monocyclopentadienylytterbium complex
(C5H5)Yb[S.C(Cbz).NPh]2(THF) (3) and (C5H5)3Yb(THF), which may be rationalized by
the ligand rearrangement of the monoinsertion product (C5H5)2Yb[S.C(Cbz).NPh]. (C5H5)3-
Yb reacts with 3,5-dimethylpyrazole (HPzMe2) in a 1:1 ratio at ambient temperature to form
complex 4. Reaction of 4 with PhNCO gives the insertion product (C5H5)2Yb[OC(dNPh)-
i
PzMe2](THF) (5). In contrast to 1, however, complex 4 does not react with PrNCNiPr under
the same conditions. All these complexes were characterized by elemental analysis and
spectroscopic properties. The structures of complexes 2-5 were also determined by X-ray
single-crystal diffraction analyses. These reactions present the first example of 1,3-
heterocumulene insertions into the Ln-N(aromatic ring) bond and provide a new strategy
for introducing a substituent at the nitrogen atom of organic heterocycle compounds.
In tr od u ction
On the other hand, there is currently considerable
interest in studying the reactivities of the Ln-N bond
of organolanthanide complexes, due to their applications
in organic synthesis and catalysis.4 However, research
efforts have been primarily focused on organolanthanide
amido complexes (amido ) NR1R2; R1, R2 ) H, alkyl,
aryl, silyl), and the reactivity of organolanthanide
complexes containing aromatic nitrogen ligands has
been much less studied.5,6e In most cases, aromatic
nitrogen ligands are only typically ancillary ligands
The carbazolate anion is an interesting ligand, be-
cause it can attach to a metal by several different modes,
such as η1, η3, and η5 coordination modes.1 Although
their organometallic complexes have been extensively
investigated in main-group-metal and transition-metal
chemistry,2 knowledge about their lanthanide complexes
is rather limited; only a few divalent lanthanide com-
plexes with carbazolate ligands have been synthesized
to date.3
† Fudan University.
(3) (a) Evans, W. J .; Rabe, G. W.; Ziller, J . W. Organometallics 1994,
13, 1641. (b) Deacon, G. B.; Forsyth, C. M.; Gatehouse, B. M.; White,
P. A. Aust. J . Chem. 1990, 43, 795. (c) Deacon, G. B.; Forsyth, C. M.;
Newham, R. H.; Polyhedron 1987, 6, 1143.
‡ State Key Laboratory of Organometallic Chemistry.
(1) (a) Hacker, R.; Kaufmann, E.; Schleyer, P. v. R.; Mahdi, W.;
Dietrich, H. Chem. Ber. 1987, 120, 1533. (b) Gregory, K.; Bremer, M.;
Schleyer, P. v. R.; Klusener, P. A. A.; Brandsma, L. Angew. Chem.,
Int. Ed. Engl. 1989, 28, 1224. (c) Mosges, G.; Hample, F.; Kaupp, M.;
Schleyer, P. v. R. J . Am. Chem. Soc. 1992, 114, 10880.
(2) (a) Riley, P. N.; Fanwick, P. E.; Rothwell, I. P. Dalton 2001, 181.
(b) Riley, P. N.; Parker, J . R.; Fanwick, P. E.; Rothwell, I. P.
Organometallics 1999, 18, 3679. (c) Riley, P. N.; Profilet, R. D.; Salberg,
M. M.; Fanwick, P. E.; Rothwell, I. P. Polyhedron 1998, 17, 773. (d)
Beswick, M. A.; Harmer, C. N.; Raithby, P. R.; Steiner, A.; Verhor-
evoort, K. L.; Wright, D. S. J . Chem. Soc., Dalton Trans. 1997, 2029.
(e) Bock, H.; Arad, C.; Nather, C.; Havlas, Z. J . Organomet. Chem.
1997, 548, 115. (f) Riley, P. N.; Profilet, R. D.; Fanwick, P. E.; Rothwell,
I. P. Organometallics 1996, 15, 5502. (g) Lambert, C.; Hampel, F.;
Schleyer, P. v. R. Angew. Chem., Int. Ed. Engl. 1992, 31, 1209.
(4) (a) Molander, G. A.; Romero, J . A. C. Chem. Rev. 2002, 102, 2161.
(b) Schumann, H.; Meese-Marktscheffel, J . A.; Esser, L. Chem. Rev.
1995, 95, 865. (c) Arredondo, V. M.; Tian, S.; McDonald, F. E.; Marks,
T. J . J . Am. Chem. Soc. 1999, 121, 3633. (d) Tian, S.; Arredondo, V.
M.; Marks, T. J . Organometallics 1999, 18, 2125. (e) Obora, Y.; Ohta,
T.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc. 1997, 119, 3745.
(5) (a) Fedushkin, I. L.; Petrovskaya, T. V.; Girgsdies, F.; Kohn, R.
D.; Bochkarev, M. N.; Schumann, H. Angew. Chem., Int. Ed. 1999,
38, 2262. (b) Evans, W. J .; Drummond, D. K. J . Am. Chem. Soc. 1994,
116, 2600. (c) Schumann, H.; Loebel, J .; Pickardt, J .; Qian, C.; Xie, Z.
Organometallics 1991, 10, 215. (d) Schumann, H.; Lee, P. R.; Dietrich,
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J . W. J . Am. Chem. Soc. 1989, 111, 3329.
10.1021/om0340342 CCC: $25.00 © 2003 American Chemical Society
Publication on Web 11/12/2003

5386 Organometallics, Vol. 22, No. 26, 2003
Zhang et al.
at room temperature, and the mixture was stirred for several
hours. The dark red solution became yellow-orange. After it
was stirred overnight, the reaction solution was concentrated
by reduced pressure to about 2 mL. Addition of 20 mL of
n-hexane resulted in the precipitation of a yellow solid. The
resulting mixture was centrifuged, and the solution was
decanted. The precipitate was washed with n-hexane and dried
under vacuum to afford a yellow powder. Recrystallization of
the powder from the solvent mixture of THF and n-hexane
gave 2 as yellow crystals. Yield: 0.60 g (57%). Anal. Calcd for
C29H32N3Yb: C, 58.48; H, 5.42; N, 7.05. Found: C, 58.23; H,
5.40; N, 7.11. 1H NMR: δ 6.29-7.98 (m, 8H), 3.57 (s, 5H),
2.49-2.69 (m, 2H), 0.89-1.42 (m, 12H), 0.4 (s, 5H). IR (Nujol,
cm-1): 3175 w, 1666 s, 1620 s, 1597s, 1514 m, 1402 m, 1331
m, 1312 m, 1233 s, 1198 m, 1170 s, 1148 m, 1058 s, 1011 s,
971 s, 770 s, 748 s, 684 m, 617 w. EI-MS (m/z (fragment,
relative intensity (%)): 596 (M, 13), 581 (M - CH3, 24), 430
(M - Cbz, 49), 304 (Cp2Yb, 47), 166 (Cbz, 37), 43 (Bu, 51).
which stabilize and construct but do not participate in
organometallic reactions.1-3,5
We have recently been interested in the reactivities
of organolanthanide complexes toward unsaturated
organic small molecules.6 The investigation results in
this field indicate that the occurrence of the insertion
strongly depends on the degree of the steric saturation
around the center metal ion and the nature of the
ligands. In a continuation of our recent investigation of
the lanthanide-ligand insertion and in order to learn
more about the aromatic nitrogen heterocycle anion as
a ligand, we herein report the synthesis of trivalent
ytterbocene carbazolate and pyrazolate complexes as
well as their reactivities toward carbodiimide, isocyan-
ate, and isothiocyanate, which present the first example
of 1,3-heterocumulene insertions into the Ln-N(aro-
matic ring) bond and provide a new strategy for intro-
ducing a substituent at the nitrogen atom of organic
heterocycles via formation of a new C-N(ring) bond.
Syn th esis of (C5H5)Yb[S.C(Cbz).NP h ]2(THF ) (3). To
a 20 mL THF solution of 1 (0.408 g, 0.76 mmol) was slowly
added phenyl isocyanate (0.104 g, 0.77 mmol) dropwise at -30
°C. After it was stirred for 30 min at low temperature, the
mixture was slowly warmed to room temperature and stirred
for several hours. Removal of the solvent left a yellow oily solid.
The resulting oily solid was extracted with 30 mL of toluene.
The extract was evaporated to ca. 5 mL, and yellow crystals
of 3 were slowly formed at room temperature. Yield: 0.25 g
(36% based on Yb). Anal. Calcd for C47H39N4OS2Yb: C, 61.83;
Exp er im en ta l Section
Gen er a l P r oced u r e. All operations involving air- and
moisture-sensitive compounds were carried out under an inert
atmosphere of purified argon or nitrogen using standard
Schlenk techniques. The solvents of THF, toluene, and n-
hexane were refluxed and distilled over sodium benzophenone
ketyl under nitrogen immediately prior to use. (C5H5)3Yb was
prepared by the literature procedure.7 Carbazole, 3,5-dimeth-
ylpyrazole, N,N′-diisopropylcarbodiimide, and phenyl isocy-
anate were purchased from Aldrich and were used without
purification. Elemental analyses for C, H, and N were carried
1
H, 4.31; N, 6.14. Found: C, 61.91; H, 4.30; N, 6.23. H NMR:
δ 6.30-8.02 (m, 10H), 3.57 (s, 5H), 0.93-2.69 (b, 24H). IR
(Nujol, cm-1): 3175 w, 1664 m, 1616 w, 1595 s, 1574 m, 1518
s, 1320 m, 1301 m, 1225 s, 1203 m, 1154 s, 1091 s, 1071 m,
1009 s, 895 m, 851 m, 770 s, 747 s, 690 s, 663 w. EI-MS (m/z
(fragment, relative intensity (%)): 304 (Cp2Yb, 15), 286 (L +
H, 28), 167 (Cbz, 52), 119 (L - Cbz, 23), 71 (THF - H, 100),
66 (CpH, 61) (L ) SC(Cbz)NPh). Further crystallization by
diffusion of n-hexane into the above mother liquor yielded a
mixture of yellow crystals and dark crystals. The latter was
identified to be (C5H5)3Yb(THF) by comparison of the X-ray
crystallographic analysis data with literature values.5c
out on
a Rapid 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 HP5989A instrument operating in EI mode. Crystalline
samples of the respective complexes were rapidly introduced
by the direct inlet techniques with a source temperature of
200 °C. The m/z values are referred to the isotopes 12C, 1H,
1
14N, 16O, and 174Yb. H NMR data were obtained on a Bruker
Syn th esis of (C5H5)2YbP zMe2(THF ) (4). (C5H5)3Yb (0.968
g, 2.63 mmol) and 3,5-dimethylpyrazole (0.252 g, 2.63 mmol)
were mixed in 50 mL of THF. The solution slowly turned from
dark green to yellow over several hours. After the mixture was
stirred overnight at room temperature, all volatile substances
were removed under vacuum to give a yellow powder. Recrys-
tallization of the powder from the mixture of THF and toluene
gave 4 as orange crystals. Yield: 0.88 g (72%). Anal. Calcd for
DMX-500 NMR spectrometer and were referenced to residual
aryl protons in C6H6 (δ 7.16).
Syn th esis of (C5H5)2YbCbz(THF ) (1). (C5H5)3Yb (2.35 g,
6.38 mmol) and carbazole (1.07 g, 6.39 mmol) were mixed in
100 mL of THF. The solution slowly turned from dark green
to dark red over several hours. After the mixture was stirred
for 24 h at room temperature, all volatile substances were
removed under vacuum to give a red powder. Yield: 3.32 g
(90%). Recrystallization of the powder from the mixture of THF
C
19H25N2OYb: C, 48.51; H, 5.36; N, 5.95. Found: C, 48.39; H,
5.31; N, 6.02. IR (Nujol, cm-1): 3175 w, 3090 w, 1655 s, 1602
m, 1570 s, 1571 s, 1347 m, 1250 m, 1171 s, 1109 s, 1073 s,
1013 s, 963 m, 922 s, 872 s, 772 s, 675 m, 661 w. EI-MS (m/z
(fragment, relative intensity (%)): 399 (M - THF, 15), 334
(M - THF - Cp, 28), 267 (M - THF - 2Cp, 38), 96 (HPzMe2,
33), 65 (Cp, 100).
and toluene gave 1 as red crystals. Anal. Calcd for C26H26
-
NOYb: C, 57.67; H, 4.84; N, 2.59. Found: C, 57.34; H, 4.69;
N, 2.64. 1H NMR: δ 6.29-7.99 (m, 8H), 2.11 (s, 10H). IR
(Nujol, cm-1): 3175 w, 1620 s, 1584 m, 1336 m, 1322 m, 1263
s, 1122 m, 1148 s, 1074 s, 1015 s, 959 m, 903 m, 848 s, 759 m,
663 w. EI-MS (m/z (fragment, relative intensity (%)): 470 (M
- THF, 8), 304 (Cp2Yb, 46), 167 (CbzH, 100), 72 (THF, 17), 65
(CpH, 66).
Syn th esis of (C5H5)2Yb[iP r N.C(Cbz).NiP r ] (2). To a
30 mL THF solution of 1 (0.946 g, 1.76 mmol) was slowly added
N,N′-diisopropylcarbodiimide (0.222 g, 1.76 mmol) dropwise
Syn th esis of (C5H5)2Yb[OC(dNP h )P zMe2](THF ) (5). To
a 30 mL THF solution of 4 (0.534 g, 1.13 mmol) was slowly
added phenyl isocyanate (0.135 g, 1.14 mmol) dropwise at room
temperature, and the mixture was stirred overnight. The
reaction solution was concentrated to ca. 3 mL by reduced
pressure. Yellow crystals of 5 were obtained at -20 °C for
several days. Yield: 0.43 g (64%). Anal. Calcd for C26H30N3O2-
Yb: C, 52.97; H, 5.13; N, 7.13. Found: C, 52.88; H, 5.21; N,
7.04. 1H NMR: δ 9.27 (s, 1H), 7.01-7.73 (m, 5H), 5.17 (b, 5H),
2.49-2.69 (m, 4H), 2.04 (b, 5H), 1.36 (s, 6H), 0.92-1.20 (m,
4H). IR (Nujol, cm-1): 3175 w, 1655 s, 1590 s, 1529 s, 1301 m,
1268 s, 1179 m, 1155 s, 1126 m, 1067 s, 1020 s, 984 m, 917 s,
873 m, 770 m, 698 s, 670 w, 630 w, 585 w. EI-MS (m/z
(fragment, relative intensity (%)): 590 (M, 5), 518 (M - THF,
2), 399 (M - THF - PhNCO, 11), 334 (M - THF - PhNCO -
(6) (a) Zhang, J .; Cai, R. F.; Weng, L. H.; Zhou, X. G. J . Organomet.
Chem. 2003, 672, 94. (b) Zhang, J .; Ruan, R. Y.; Saho, Z. H.; Cai, R.
F.; Weng, L. H.; Zhou, X. G. Organometallics 2002, 21, 1420. (c) Zhou,
X. G.; Zhu, M. J . Organomet. Chem. 2002, 647, 28. (d) Zhou, X. G.;
Zhang, L. B.; Zhu, M.; Cai, R. F.; Weng, L. H.; Huang, Z. X.; Wu, Q. J .
Organometallics 2001, 20, 5700. (e) Zhou, X. G.; Huang, Z. E.; Cai, R.
F.; Zhang, L. B.; Zhang, L. X.; Huang, X. Y. Organometallics 1999, 18,
4128.
(7) Wilkinson, G.; Birmingham, J . M. J . Am. Chem. Soc. 1954, 78,
42.

Dicyclopentadienylytterbium Derivatives
Organometallics, Vol. 22, No. 26, 2003 5387
Ta ble 1. Cr ysta l a n d Da ta Collection P a r a m eter s of Com p lexes 2-5
2
3
4
5
formula
mol wt
C
29H22N3Yb
C47H39N4OS2Yb
912.98
C19H25N2OYb
470.45
C26H30N3O2Yb
589.57
595.62
cryst color
cryst dimens (mm)
cryst syst
space group
unit cell dimens
a (Å)
yellow
yellow
orange
yellow
0.45 × 0.40 × 0.10
monoclinic
P21/n
0.20 × 0.15 × 0.10
0.20 × 0.15 × 0.10
monoclinic
P21/c
0.40 × 0.20 × 0.20
monoclinic
P21/c
triclinic
P1h
9.535(3)
8.276(2)
32.545(9)
12.957(11)
14.860(12)
14.880(12)
74.266(12)
71.540(11)
66.508(11)
1886.3(6)
2
8.1826(15)
14.503(3)
16.187(3)
17.804(2)
7.9199(9)
18.910(2)
b (Å)
c (Å)
R (deg)
â (deg)
96.933(4)
100.886(3)
114.7940(10)
γ (deg)
V (Å3)
2549.6(12)
4
1.552
3.689
1188
1886.3(6)
4
1.657
4.963
924
2420.7(5)
4
1.618
3.890
1172
Z
Dc (g cm-3
)
1234
2.021
918
µ (mm-1
F(000)
)
radiation
temp (K)
scan type
θ range (deg)
h,k,l range
Mo KR (λ ) 0.710 730 Å)
298.2
ω-2θ
2.17-25.01
-10 e h e 11
-9 e k e 9
-33 e l e 38
10 294
298.2
ω-2θ
298.2
298.2
ω-2θ
2.17-26.76
-17 e h e 22
-9 e k e 9
-23 e l e 23
11 433
ω-2θ
1.46-25.01
2.53-25.01
-9 e h e 9
-17 e k e 17
-15 e l e 19
7801
-15 e h e 15
-17 e k e 17
-16 e l e 17
11 683
no. of rflns measd
no. of unique rflns
4479 (Rint ) 0.0704)
99.8 (θ ) 25.01)
0.7093 and 0.2876
11 683 (Rint ) 0.0000)
96.4 (θ )25.01)
0.8234 and 0.6879
3308 (Rint ) 0.0350)
99.5 (θ )25.01)
0.6367 and 0.4368
5092 (Rint ) 0.0265)
99.2 (θ )26.76)
0.5101 and 0.3052
completeness to θ (%)
max and min rransmissn
refinement method
full-matrix least squares on F2
no. of data/restraints/params
goodness of fit on F2
final R indices (I > 2σ(I))
4479/0/302
0.933
11 683/60/396
0.978
3308/30/243
1.035
5092/0/291
0.944
R1 ) 0.0504
wR2 ) 0.1135
R1 ) 0.0712
wR2 ) 0.1202
2.015 and -1.219
R1 ) 0.0885
wR2 ) 0.2152
R1 ) 0.1157
wR2 ) 0.2338
2.215 and -1.422
R1 ) 0.0394
wR2 ) 0.0869
R1 ) 0.0505
wR2 ) 0.0918
1.083 and -1.034
R1 ) 0.0228
wR2 ) 0.0505
R1 ) 0.0292
wR2 ) 0.0519
0.855 and -0.455
R indices (all data)
largest diff peak and hole (e Å-3
)
Cp, 28), 269 (YbPzMe2, 21), 119 (PhNCO, 85), 96 (HPzMe2,
72), 72 (THF, 11), 66 (CpH, 100).
Siemens SAINT program to yield a total of 11 683 reflections.
All of them were independent. Laue symmetry revealed a
triclinic crystal system, and the final unit cell parameters were
determined from the full-matrix least-squares refinement on
F2 of three-dimensional centroids of 11 683 reflections. Further
refinement led to final convergence at R ) 0.0885.
X-r a y Da ta Collection , Str u ctu r e Deter m in a tion , a n d
Refin em en t. Suitable single crystals of complexes 2-5 were
sealed under argon in Lindemann glass capillaries for X-ray
structural analysis. Diffraction data were collected on a Bruker
SMART Apex CCD diffractometer using graphite-monochro-
mated Mo KR (λ ) 0.710 73 Å) radiation. During the intensity
data collection, no significant decay was observed. The intensi-
ties were corrected for Lorentz-polarization effects and em-
pirical absorption with the SADABS program.8 The structures
were solved by direct methods using the SHELXL-97 pro-
gram.9 All non-hydrogen atoms were found from the difference
Fourier syntheses. The 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. All calculations were performed using the Bruker
Smart program. A summary of the crystallographic data and
selected experimental information is given in Table 1.
(a ) (C5H5)2Yb[iP r N.C(Cbz).NiP r ] (2). Frames were
integrated to the maximum 2θ angle of 50.02° with the
Siemens SAINT program to yield a total of 10 294 reflections,
of which 4479 were independent (Rint ) 0.0704). Laue sym-
metry revealed a monoclinic crystal system, and the final unit
cell parameters were determined from the full-matrix least-
squares refinement on F2 of three-dimensional centroids of
4479 reflections. Further refinement led to final convergence
at R ) 0.0504.
(c) (C5H5)2YbP zMe2(THF ) (4). Frames were integrated to
the maximum 2θ angle of 50.02° with the Siemens SAINT
program to yield a total of 7801 reflections, of which 3308 were
independent (Rint ) 0.0350). Laue symmetry revealed a
monoclinic crystal system, and the final unit cell parameters
were determined from the full-matrix least-squares refinement
on F2 of three-dimensional centroids of 3308 reflections.
Further refinement led to final convergence at R ) 0.0394.
(d ) (C5H5)2Yb[OC(dNP h )P zMe2](THF ) (5). Frames were
integrated to the maximum 2θ angle of 53.52° with the
Siemens SAINT program to yield a total of 11 433 reflections,
of which 5092 were independent (Rint ) 0.0265). Laue sym-
metry revealed a monoclinic crystal system, and the final unit
cell parameters were determined from the full-matrix least-
squares refinement on F2 of three-dimensional centroids of
5092 reflections. Further refinement led to final convergence
at R ) 0.0228.
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of th e Tr iva len t
Ytter bocen e Ca r ba zola te Com p lex (C5H5)2YbCbz-
(THF ) (1). The known divalent lanthanide carbazolate
complex was synthesized by the metathetic reaction of
SmI2(THF)4 with KCbz5a or the protolysis reactions of
Ln(C6F6)2 (Ln ) Yb, Eu) with carbazole (CbzH).5b,c To
our knowledge, no trivalent organolanthanide carba-
zolate was reported. Here we synthesized complex 1 by
(b) (C5H5)Yb[S.C(Cbz).NP h ]2(THF ) (3). Frames were
integrated to the maximum 2θ angle of 50.02° with the
(8) Sheldrick, G. M. SADABS, Program for Empirical Absorption
Correction; University of Go¨ttingen, Go¨ttingen, Germany, 1998.
(9) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
Crystal Structures; University of Go¨ttingen, Go¨ttingen, Germany,
1997.

5388 Organometallics, Vol. 22, No. 26, 2003
Zhang et al.
Sch em e 1
Sch em e 2
However, attempts to isolate the intermediate (C5H5)2-
Yb[S.C(Cbz).NPh] were unsuccessful at room tem-
perature. In organolanthanide chemistry, mono(cyclo-
pentadienyl)lanthanide derivates are usually thermo-
dynamically unstable, liable to rearrange to the more
thermodynamic stable bis(cyclopentadienyl)lanthanide
derivates due to the large radius of the metal ion and
high coordination number.11 However, very few ligand
rearrangement reactions from bis(cyclopentadienyl)-
lanthanide derivates to mono(cyclopentadienyl)lan-
thanide derivates have been observed.5c
Syn th esis of th e Ytter bocen e P yr a zola te Com -
p lex (C5H5)2YbP zMe2(THF ) (4). To further study the
reactivity of organolanthanides containing aromatic
nitrogen ligands, we have also synthesized the complex
(C5H5)2YbPzMe2(THF) (4) by the reaction of (C5H5)3Ln
with HPzMe2 in THF at room temperature (eq 2).
the protolysis reaction of (C5H5)3Yb with 1 equiv of CbzH
in THF at room temperature, as shown in the reaction
equation
THF
Cp YbCbz(THF)
Cp3Yb + CbzH room temp8
(1)
2
1
Complex 1 is air- and moisture-sensitive. It is soluble
in THF and toluene and slightly soluble in n-hexane.
Complex 1 has been characterized by elemental analysis
1
and infrared, H NMR, and mass spectroscopy, which
were in good agreement with the proposed formula. The
mass spectrum of 1 displays a series of peaks clearly
representing fragments derived from the parent mol-
ecule. In the IR spectra, complex 1 exhibits two char-
acterized absorptions at 1620 and 1584 cm-1, which may
be attributed to the ring stretching modes of the
carbazolate ligand5a and two well-defined bands at 1074
and 903 cm-1 for the coordinated THF. Unfortunately,
the crystal structure of 1 has not been solved by X-ray
analysis due to poor crystal quality.
THF
Cp YbPzMe (THF)
Cp3Yb + HPzHMe2 room temp8
(2)
2
2
2
Rea ction of Com p lex 4 w ith P h NCO. Although
organometallic pyrazolates have been extensively in-
vestigated, examples of M-N insertion based on the
chelating pyrazolate ligand are very rare.12,16b To further
investigate the effects of the steric factors and bonding
mode of the aromatic nitrogen ligand on the insertion,
reactions of complex 4 with isocyanate and carbodiim-
ide, respectively, have been studied. The results indicate
that PhNCO can be monoinserted into the Ln-N(η2-
pyrazolate) bond of 4 to yield (C5H5)2Yb[OC(dNPh)-
PzMe2](THF) (5) (Scheme 2), but no further reaction
involving phenyl isocyanate was observed, even in the
presence of excess PhNCO with a higher reaction
temperature and a longer reaction time. This is different
from the observation of PhNCO insertion into the Ln-N
σ-bond of (CH3C5H4)2Ln(NiPr2)(THF) (Ln ) Y, Yb, Er),
where excess PhNCO can be catalyzed to give a poly-
mer.13 This may be attributed to the differences of steric
hindrance and the bonding mode between 5 and
(CH3C5H4)2Ln[OC(NiPr2)NPh](THF), as shown in Fig-
ure 4 (vide infra).
i
Rea ction s of Com p lex 1 w ith P r NdCdNiP r a n d
P h NCS. Recently, we and other groups have found that
carbodiimide readily inserts into the Ln-NR2 (R )
alkyl, silyl) σ-bonds of lanthanide amido complexes,
yielding the corresponding guanidinate complexes.6a,10
However, it has been unclear up to now whether
carbodiimide molecules can be inserted into the Ln-
N(aromatic ring) bond. To study the effect of the nature
of the organic nitrogen ligand on the insertion and
explore the reactivity of complex 1, we first investigated
the reaction of 1 with carbodiimide. When N,N′-diiso-
propylcarbodiimide was added to a THF solution of 1
at room temperature, the corresponding guanidinate
complex (C5H5)2Yb[iPrN.C(Cbz).NiPr] (2) was ob-
tained in moderate yield, indicating that one carbodi-
imide molecule is inserted into the Ln-N(Cbz) bond
(Scheme 1).
To gain more insight into the reactivity of complex 1,
the reaction of 1 with phenyl isothiocyanate was also
studied. Significantly, it is found that reaction of
complex 1 with 1 equiv of phenyl isothiocyanate results
in the formation of the unexpected product (C5H5)Yb-
[S.C(Cbz).NPh]2(THF) (3) along with the formation
of a small amount of (C5H5)3Yb(THF). Presumably,
complex 3 might result from the rearrangement of the
monoinsertion product (C5H5)2Yb[S.C(Cbz).NPh].
Notably, in contrast to organolanthanide amido
complexes,6a,10 complex 4 does not react with N,N′-
diisopropylcarbodiimide under the same conditions. This
may be attributed to the chelating coordination mode
of the pyrazolate ligand, which is disfavored for the
interaction of the carbodiimide molecule with the central
metal and results in a decrease in the Ln-N bond
reactivity.6e
(11) Arndt, S.; Okuda, J . Chem. Rev. 2002, 102, 1953.
(12) Ahn, S.; Mayr, A. J . Am. Chem. Soc. 1996, 118, 7408.
(13) Mao, L.; Shen, Q.; Xue, M.; Sun, J . Organometallics 1997, 15,
33711.
(10) Giesbrecht, G. R.; Whitener, G. D.; Arnold, J . Dalton 2001, 923.

Dicyclopentadienylytterbium Derivatives
Organometallics, Vol. 22, No. 26, 2003 5389
F igu r e 1. ORTEP diagram of 2 with the probability
ellipsoids drawn at the 30% level. Hydrogen atoms are
omitted for clarity.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 2
F igu r e 2. ORTEP diagram of 3 with the probability
ellipsoids drawn at the 30% level. Hydrogen atoms are
omitted for clarity.
Yb(1)-N(1)
Yb(1)-N(2)
Yb(1)-C(5)
Yb(1)-C(9)
Yb(1)-C(4)
Yb(1)-C(3)
Yb(1)-C(6)
Yb(1)-C(2)
Yb(1)-C(1)
2.292(6)
2.305(6)
Yb(1)-C(10)
Yb(1)-C(8)
Yb(1)-C(7)
N(1)-C(11)
N(2)-C(11)
N(3)-C(29)
N(3)-C(18)
N(3)-C(11)
2.566(9)
2.580(9)
2.590(9)
1.297(10)
1.303(9)
1.367(10)
1.396(11)
1.431(9)
2.535(10)
2.545(10)
2.545(12)
2.546(12)
2.553(10)
2.561(11)
2.562(11)
Ta ble 3. Bon d Len gth s (Å) a n d An gles (d eg) for 3
Yb(1)-O(1)
Yb(1)-N(1)
Yb(1)-N(3)
Yb(1)-C(5)
Yb(1)-C(4)
Yb(1)-C(1)
Yb(1)-C(3)
Yb(1)-C(2)
Yb(1)-S(2)
2.365(13)
2.390(7)
2.532(8)
2.580(15)
2.597(14)
2.600(18)
2.628(16)
2.630(17)
2.709(5)
Yb(1)-S(1)
Yb(1)-C(6)
Yb(1)-C(25)
S(1)-C(6)
S(2)-C(25)
C(6)-N(1)
C(6)-N(2)
C(25)-N(3)
C(25)-N(4)
2.766(6)
2.937(19)
2.995(9)
1.782(17)
1.687(9)
1.27(2)
1.42(2)
1.345(12)
1.433(12)
N(1)-Yb(1)-N(2)
C(11)-N(1)-Yb(1)
C(11)-N(2)-Yb(1)
C(29)-N(3)-C(18)
C(29)-N(3)-C(11)
C(18)-N(3)-C(11)
58.0(2)
92.3(5)
91.6(5)
108.8(7)
125.7(6)
122.0(7)
N(1)-C(11)-N(2)
N(1)-C(11)-N(3)
N(2)-C(11)-N(3)
N(1)-C(11)-Yb(1)
N(2)-C(11)-Yb(1)
N(3)-C(11)-Yb(1)
118.1(7)
120.5(7)
121.4(7)
58.8(4)
59.3(4)
178.6(5)
O(1)-Yb(1)-N(1)
O(1)-Yb(1)-N(3)
N(1)-Yb(1)-N(3)
N(1)-Yb(1)-S(2)
N(3)-Yb(1)-S(2)
N(1)-Yb(1)-S(1)
N(3)-Yb(1)-S(1)
N(1)-Yb(1)-C(6)
N(3)-Yb(1)-C(6)
S(2)-Yb(1)-C(6)
S(1)-Yb(1)-C(6)
N(1)-Yb(1)-C(25)
N(3)-Yb(1)-C(25)
S(2)-Yb(1)-C(25)
147.4(4)
79.7(4)
76.6(3)
93.8(2)
60.4(2)
61.2(2)
85.4(2)
24.9(4)
78.9(4)
115.2(4)
36.3(4)
82.0(2)
26.5(2)
C(6)-S(1)-Yb(1)
C(25)-S(2)-Yb(1)
N(1)-C(6)-N(2)
N(1)-C(6)-S(1)
N(2)-C(6)-S(1)
N(1)-C(6)-Yb(1)
N(2)-C(6)-Yb(1)
S(1)-C(6)-Yb(1)
C(6)-N(1)-Yb(1)
N(3)-C(25)-S(2)
N(4)-C(25)-S(2)
N(3)-C(25)-Yb(1)
77.1(7)
82.4(4)
124.3(13)
119.3(13)
116.1(13)
52.6(7)
173.5(11)
66.6(6)
102.4(8)
120.6(7)
120.8(7)
57.2(4)
Complexes 2-5 were characterized by elemental
analysis and spectroscopic properties, which were in
good agreement with the proposed structures. Their
mass spectra display the molecular ion peaks or a series
of peaks clearly representing fragments derived from
the parent molecule. Significantly, the MS data of 5
show that the loss of the PhNCO fragment occurs more
readily than the direct loss of the PzMe2 group. This
differs from the observed results in other PhNCO
insertion products.6d,13 In the IR spectra of 2, the
characterized absorption at ca. 2100 cm-1 for the
νas(NdCdN) stretch of free carbodiimide is absent, but
a new strong band at ca. 1666 cm-1 attributable to the
delocalized -N.C.N- stretching mode is present.14
The structures of complexes 2-5 were further confirmed
by X-ray single-crystal structure determinations.
Cr ysta l Str u ctu r es of 2-5. The X-ray structural
analysis results show that 2 (Figure 1, Table 2) is a
solvent-free monomer with the ytterbium atom bonded
to two η5-cyclopentadienyl rings and one chelating
guanidinate ligand to form a distorted-tetrahedral
geometry. The coordination number of the central Yb3+
is 8. As expected, the coordinated guanidinate group
forms essentially a planar four-membered ring with the
Yb atom within experimental errors. The bond angles
around C(11) are consistent with sp2 hybridization. The
cent-Yb-cent (cent ) the center of the cyclopentadienyl
ring) plane relative to the YbNCN plane is approxi-
mately perpendicular. This disposition may result from
the steric interaction between two bulky isopropyl
groups and two cyclopentadienyl ligands. The C(11)-
N(1) (1.297(10) Å) and C(11)-N(2) (1.303(9) Å) distances
are approximately equivalent and significantly shorter
N(4)-C(25)-Yb(1) 174.9(6)
33.93(19) S(2)-C(25)-Yb(1)
S(1)-Yb(1)-C(25) 110.3(2)
63.7(3)
96.3(5)
C(25)-N(3)-Yb(1)
than the C-N single-bond distances, indicating that the
π-electrons of the CdN double bond in the present
structure are delocalized over the N-C-N unit.15
Consistent with this case, the Yb-N(1) and Yb-N(2)
distances, 2.292(6) and 2.305(6) Å, are intermediate
between the values observed for the Yb-N single-bond
distance and the Yb-N donor-bond distances (2.19-2.69
Å)16 and are comparable to the corresponding values
found in [(C5H4Me)Yb(PzMe2)(OSiMe2PzMe2)]2 (average
2.293(6) Å)16b and {CyNC[N(SiMe3)2]NCy}2YbN(SiMe3)2
(average 2.317(13) Å).17
Figure 2 shows the molecular structure of 3. Selected
bond distances and angles are listed in Table 3. The
ytterbium atom carries one η5-cyclopentadienyl group
(15) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G. J . Chem. Soc., Perkin Trans. 1987, S1.
(16) (a) Zhou, X. G.; Huang, Z. E.; Cai, R. F.; Zhang, L. X.; Hou, X.
F.; Feng, X. J .; Huang, X. Y. J . Organomet. Chem. 1998, 563, 101. (b)
Zhou, X. G.; Ma, H. Z.; Huang, X. Y.; You, X. Z. J . Chem. Soc., Chem.
Commun. 1995, 2483. (c) Evans, W. J .; Drummond, D. K.; Chamber-
lain, L. A.; Doeden, R. J .; Bott, S. G.; Zhang, H.; Atwood, J . L. J . Am.
Chem. Soc. 1988, 110, 4983.
(17) Zhou, Y.; Yap, G. P. A.; Richeson, D. S. Organometallics 1998,
17, 4387.
(14) Wilkins, J . D. J . Organomet. Chem. 1974, 80, 349.

5390 Organometallics, Vol. 22, No. 26, 2003
Zhang et al.
F igu r e 3. ORTEP diagram of 4 with the probability
ellipsoids drawn at the 30% level. Hydrogen atoms are
omitted for clarity.
F igu r e 4. ORTEP diagram of 5 with the probability
ellipsoids drawn at the 30% level. Hydrogen atoms are
omitted for clarity.
Ta ble 4. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 4
Ta ble 5. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for 5
Yb(1)-N(2)
Yb(1)-N(1)
Yb(1)-O(1)
Yb(1)-C(28)
Yb(1)-C(29)
Yb(1)-C(27)
2.264(4)
2.309(5)
2.337(5)
2.531(3)
2.558(3)
2.567(3)
Yb(1)-C(24)
Yb(1)-C(4)
Yb(1)-C(25)
Yb(1)-C(10)
Yb(1)-C(30)
Yb(1)-C(3)
2.575(3)
2.582(3)
2.588(3)
2.607(3)
2.610(3)
2.616(3)
Yb(1)-O(1)
Yb(1)-O(2)
Yb(1)-N(1)
Yb(1)-C(5)
Yb(1)-C(7)
Yb(1)-C(1)
Yb(1)-C(6)
Yb(1)-C(4)
Yb(1)-C(10)
2.192(2)
2.420(2)
2.473(2)
2.602(3)
2.603(3)
2.605(4)
2.606(3)
2.619(4)
2.623(3)
Yb(1)-C(8)
Yb(1)-C(3)
Yb(1)-C(2)
O(1)-C(14)
N(1)-C(11)
N(1)-N(2)
N(2)-C(14)
N(3)-C(14)
N(3)-C(17)
2.627(4)
2.632(4)
2.632(4)
1.269(3)
1.328(4)
1.376(3)
1.434(4)
1.269(4)
1.403(4)
N(2)-Yb(1)-N(1)
35.11(15) N(1)-Yb(1)-O(1) 82.70(18)
N(2)-Yb(1)-O(1) 116.39(15)
and one THF molecule and is chelated by two SC(Cbz)-
NPh ligands. The most important feature of the struc-
ture is that two SC(Cbz)NPh ligands have distinctly
different Yb-N and Yb-S distances. The Yb(1)-N(1)
distance of 2.390(7) Å is significantly shorter than the
Yb(1)-N(3) distance of 2.532(9) Å, while the Yb(1)-S(1)
distance of 2.766(6) Å is longer than the Yb(1)-S(2)
distance of 2.709(5) Å. This may be attributed to the
large interligand steric interruption. Both N(1)-C(6)-
S(1)-Yb(1) and N(3)-C(25)-S(2)-Yb(1) units are es-
sentially planar within experimental error. All bond
distances involving the ytterbium atom are in the
normal ranges.16,18
The overall structure of 4 is similar to that of the
complex (C5H5)2ErPzMe2(THF)6e (Figure 3). Selected
bond distances and angles are given in Table 4. The
ytterbium atom is coordinated to two η5-cyclopentadi-
enyl groups, two nitrogen atoms of the 3,5-dimeth-
ylpyrazolate ligand, and one oxygen atom from the
tetrahydrofuran molecule. The coordination number of
the central metal Yb is 9. The Yb-N distances of 2.264-
(4) and 2.309(5) Å are in the range expected for an
Ln-N bond interaction with partial single- and donor-
bond character.16
O(1)-Yb(1)-O(2)
O(1)-Yb(1)-N(1)
73.91(7)
66.31(8)
N(1)-N(2)-C(14)
117.1(2)
C(14)-N(3)-C(17) 120.0(3)
C(14)-O(1)-Yb(1) 129.3(2)
N(3)-C(14)-O(1)
112.22(17) N(3)-C(14)-N(2)
110.9(3) O(1)-C(14)-N(2)
130.7(3)
116.1(3)
113.2(3)
N(2)-N(1)-Yb(1)
C(13)-N(2)-N(1)
C(13)-N(2)-C(14) 131.9(3)
) the center of cyclopentadienyl ring) plane relative to
the Yb-N(1)-O(1) plane is approximately perpendicu-
lar (89.3°). The cent-Yb-cent angle is 137.2°. The
N(3)-C(14) distance (1.269(4) Å) is comparable to the
accepted value for the N(sp2)dC(sp2) double bond (1.28
Å).19 The Yb-N(1) distance (2.473(2) Å) is comparable
to the values observed for the Yb-N donor-bond dis-
tance16 and is slightly and significantly longer than the
corresponding values found in [(C5H4Me)Yb(PzMe2)-
(OSiMe2PzMe2)]2 (Yb-N(bridge pyrazolate) ) 2.402(7)
Å).16b The Yb-O(1) distance (2.192(2) Å) is smaller than
the corresponding values found in [(C5H4Me)Yb(Pz-
Me2)(OSiMe2PzMe2)]2 (Yb-O ) 2.250(5) Å).16b The Yb-
O(THF) distance (2.420(2) Å) is longer than the corre-
sponding value in 3 (2.365(13) Å).16c
All the Yb-C(Cp) distances in these complexes are
in the normal ranges observed for lanthanocene com-
plexes.20
As shown in Figure 4, complex 5 is a solvated
monomer. Selected bond distances and angles are given
in Table 5. It is interesting that the inserted PhNCO
unit is bonded to the lanthanide ion only through
oxygen, while the moiety in other PhNCO insertion
products is generally η2 bonded to the metal by oxygen
and nitrogen.6d,13 This difference may be attributed to
the stronger chelating coordination of the nitrogen atom
of the pyrazolate group, which prohibits the bonding of
the Yb3+ ion and the nitrogen atom of PhNCO. Consis-
tent with this, in the mass spectrum of 5, the loss of
the PhNCO fragment occurs more readily than the
direct loss of the PzMe2 group. The cent-Yb-cent (cent
Con clu sion s
The present results demonstrate that N,N′-diisopro-
pylcarbodiimide can insert into the Yb-N bond of
(C5H5)2YbCbz(THF) (1) under mild conditions but it does
not react with (C5H5)2YbPzMe2(THF) even under more
rigorous conditions, which is different from the results
reported for organolanthanide amido complexes. PhNCS
is also found to insert into the Yb-N(Cbz) bond of 1.
Interestingly, the insertion product derived from PhNCS
(19) March, J . In Advanced Organic Chemistry; McGraw-Hill: New
York, 1997; Vol. 2, p 24.
(20) (a) Zhou, X. G.; Wu, Z. Z.; J in, Z. S. J . Organomet. Chem. 1992,
431, 289. (b) Evans, W. J .; Dominguez, R.; Hanusa, T. P. Organome-
tallics 1986, 5, 263.
(18) Zalkin, A.; Henly, T. J .; Anderson, R. A. Acta Crystallogr. 1987,
C43, 233.

Dicyclopentadienylytterbium Derivatives
Organometallics, Vol. 22, No. 26, 2003 5391
with 1 is unstable at room temperature and rearranges
easily to the unexpected (C5H5)Yb[S.C(Cbz).NPh]2-
(THF), revealing an unusual rearrangement reaction of
cyclopentadienyl lanthanide complexes. Furthermore,
the insertion of phenyl isocyanate into the Yb-N(η2-
pyrazolate) bond presents the first example of unsatur-
ated organic molecule insertion into the Ln-N(η2) bond
of the chelating pyrazolate complexes. However, in
contrast to the reactivity of organolanthanide amido
complexes, where the monoinsertion product catalyzed
excess PhNCO to form a polymer, in the present case,
no further reaction was observed. All observed differ-
ences indicate that organolanthanides containing aro-
matic nitrogen ligands exhibit lower activity to N,N′-
diisopropylcarbodiimide, phenyl isothiocyanate, and
phenyl isocyanate compared with the corresponding
amido complexes. These reactions provide a new strat-
egy for introducing a substituent at the nitrogen atom
of organic heterocyclic compounds.
Ack n ow led gm en t. We thank the National Natural
Science Foundation of China and the Research Funds
of Excellent Young Teacher and the New Century
Distinguished Scientist of National Education Ministry
of China for financial support.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and thermal parameters and all bond distances
and angles for complexes 2-5; these data are also available
as CIF files. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM0340342