Insertion of a carbodiimide into the Ln-N σ-bond of organolanthanide complexes. Isomerization and rearrangement of organolanthanides containing guanidinate ligands

Article abstract of DOI:10.1021/om049866u

The reaction of (C₅H₅)YCl₂(THF) ₃ with LiNⁱPr₂ and subsequently with 2 equiv of N,N-diisopropylcarbodiimide (ⁱPrN=C=NⁱPr) in THF gave the organoyttrium guanidinates Y[ⁱPrNC(NⁱPr ₂)NⁱPr]₃ (1) and (C₅H ₅)₂Y[ⁱPrNC(NⁱPr₂)N ⁱPr] (2), which may be rationalized by the rearrangement reaction of the diinsertion product (C₅H₅)Y[ⁱPrNC(N ⁱPr₂)N'Pr]2. Treatment of ⁱPrN-C=N ⁱPr with lanthanocene primary amides [(C₅H ₅)₂LnNHR]₂ (R = ^tBu, Ln = Yb, Er, Dy, Y; R = Ph, Ln = Yb) gave the unexpected products (C₅H ₅)₂Yb[RNC(NHⁱPr)NⁱPr] (R = ^tBu, Ln = Yb (3), Er (4), Dy (5), Y(6); R = Ph, Ln = Yb (7)), indicating that a novel isomerization reaction involving a 1,3-hydrogen shift takes place along with the insertion of carbodiimide into the Ln-N a-bond, which provides an efficient synthesis of organolanthanide complexes with asymmetrical guanidinate ligands. All these complexes were characterized by elemental analysis and spectroscopic properties. The structures of complexes 1-5 and 7 were also determined by X-ray diffraction analysis.

Full text of DOI:10.1021/om049866u

Organometallics 2004, 23, 3303-3308
3303
In ser tion of a Ca r bod iim id e in to th e Ln -N σ-Bon d of
Or ga n ola n th a n id e Com p lexes. Isom er iza tion a n d
Rea r r a n gem en t of Or ga n ola n th a n id es Con ta in in g
Gu a n id in a te Liga n d s
J ie Zhang,† Ruifang Cai,† Linhong Weng,† and Xigeng Zhou*,†,‡
Department of Chemistry, Molecular Catalysis and Innovative Material Laboratory,
Fudan University, Shanghai 200433, People’s Republic of China, and State Key Laboratory
of Organometallic Chemistry, Shanghai 200032, People’s Republic of China
Received February 24, 2004
The reaction of (C5H5)YCl2(THF)3 with LiNiPr2 and subsequently with 2 equiv of N,N′-
diisopropylcarbodiimide (iPrNdCdNiPr) in THF gave the organoyttrium guanidinates
Y[iPrNC(NiPr2)NiPr]3 (1) and (C5H5)2Y[iPrNC(NiPr2)NiPr] (2), which may be rationalized by
the rearrangement reaction of the diinsertion product (C5H5)Y[iPrNC(NiPr2)NiPr]2. Treatment
i
t
of PrNdCdNiPr with lanthanocene primary amides [(C5H5)2LnNHR]2 (R ) Bu, Ln ) Yb,
Er, Dy, Y; R ) Ph, Ln ) Yb) gave the unexpected products (C5H5)2Yb[RNC(NHiPr)NiPr] (R
t
) Bu, Ln ) Yb (3), Er (4), Dy (5), Y(6); R ) Ph, Ln ) Yb (7)), indicating that a novel
isomerization reaction involving a 1,3-hydrogen shift takes place along with the insertion of
carbodiimide into the Ln-N σ-bond, which provides an efficient synthesis of organolanthanide
complexes with asymmetrical guanidinate ligands. All these complexes were characterized
by elemental analysis and spectroscopic properties. The structures of complexes 1-5 and 7
were also determined by X-ray diffraction analysis.
In tr od u ction
features, studies on the reactivities of complexes pos-
sessing guanidinate ligands are still relatively limited.
To our knowledge, the fluxional behaviors for the
guanidinates are rarely observed,7 and the intra-
guanidinate hydrogen shift has yet not been reported.
On the other hand, in contrast to the extensive
chemistry of bis(cyclopentadienyl)lanthanide amido com-
plexes, little is known about the behavior of mono-
(cyclopentadienyl)lanthanide bis(amido) complexes, es-
pecially for the analogous insertion reactions.8,9 We have
previously reported the insertion of carbodiimide into
the Ln-N bond of organolanthanide secondary amido
complexes, which provides an efficient synthesis for
organolanthanide guanidinates.10,11 To better under-
stand the influence of the amido ligand and to further
develop the insertion reaction, in this work we present
an extension of this reaction to lanthanocene primary
amido complexes, by which a novel guanidinate isomer-
ization involving 1,3-hydrogen shift was established,
yielding the first organolanthanide complexes with
Guanidinate anions have recently received consider-
able attention as supporting ligands in organometallic
chemistry, due to their steric and electronic tunability1-5
and their potential as alternatives to the cyclopentadi-
enyl group with a view to the modification of alkene and
polar monomer polymerization catalysts.6 In principle,
each of the three nitrogen atoms of the guanidinate
ligand is capable of acting as a coordination site, and
the bonding modes are flexible. Despite these attractive
† Fudan University.
‡ State Key Laboratory of Organometallic Chemistry.
(1) (a) Ong, T. G.; Yap, G. P. A.; Richeson, D. S. Organometallics
2003, 22, 387. (b) Ong, T. G.; Yap, G. P. A.; Richeson, D. S.
Organometallics 2002, 21, 2839. (c) Ong, T. G.; Wood, D.; Yap, G. P.
A.; Richeson, D. S. Organometallics 2002, 21, 1. (d) Cotton, F. A.;
Daniels, L. M.; Huang, P. L.; Murillo, C. Inorg. Chem. 2002, 41, 317.
(e) Bazinet, P.; Wood, D.; Yap, G. P. A.; Richeson, D. S. Inorg. Chem.
2003, 42, 6225.
(2) (a) Duncan, A. P.; Mullins, S. M.; Arnold, J .; Bergman, R. G.
Organometallics 2001, 20, 1808. (b) Giesbracht, G. R.; Whitener, G.
D.; Arnold, J . Organometallics 2000, 19, 2809. (c) Thiruphthi, N.; Yap,
G. P. A.; Richeson, D. S. Chem. Commun. 1999, 2483. (d) Giesbracht,
G. R.; Whitener, G. D.; Arnold, J . J . Chem. Soc., Dalton Trans. 1999,
3601. (e) Thiruphthi, N.; Yap, G. P. A.; Richeson, D. S. J . Chem. Soc.,
Dalton Trans. 1999, 2947.
(3) (a) Aelits, S. L.; Coles, M. P.; Swenson, D. G.; J ordan, R. F.
Organometallics 1998, 17, 3265. (b) Chivers, T.; Parvez, M.; Schatte,
G. J . Organomet. Chem. 1998, 550, 213. (c) Maia, J . R. da S.; Gazard,
P. A.; Kilner, M.; Batsanova, A. S. J . Chem. Soc., Dalton Trans. 1997,
4625. (d) Robinson, S. D.; Sahajpal, A. J . Chem. Soc., Dalton Trans.
1997, 3349. (e) Bailey, P. J .; Bone, S. F.; Mitchell, L. A.; Parsons, S.;
Taylor, K. J .; Yellowlees, L. J . Inorg. Chem. 1997, 36, 867.
(4) (a) Bailey, P. J .; Mitchell, L. A.; Parsons, S. J . Chem. Soc., Dalton
Trans. 1996, 2389. (b) Dinger, M. B.; Henderson, W. Chem. Commun.
1996, 211. (c) Bailey, P. J .; Blake, A. L.; Kryszczuk, M.; Parsons, S.;
Reed, D. Chem. Commun. 1995, 1647.
(6) (a) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 429. (b) Marques, N.; Sella, A.; Takats, J . Chem.
Rev. 2002, 102, 2137. (c) Luo, Y. J .; Yao, Y. M.; Shen, Q. Macromol-
ecules 2002, 35, 8670. (d) Luo, Y. J .; Yao, Y. M.; Shen, Q.; Yu, K. B.
Eur. J . Inorg. Chem. 2003, 318. (e) Chen, J . L.; Yao, Y. M.; Luo, Y. J .;
Zhou, L. P.; Shen, Q. J . Organomet. Chem. 2004, 689, 1019.
(7) (a) Mullins, S. M.; Duncan, A. P.; Bergman, R. G.; Arnold, J .
Inorg. Chem. 2001, 40, 6952. (b) Thirupathi, N.; Yap, G. P. A.; Richeson,
D. S. Organometallics 2000, 19, 2573.
(8) Molander, G. A.; Romero, J . A. C. Chem. Rev. 2002, 102, 2161
and references therein.
(9) Arndt, S.; Okuda, J . Chem. Rev. 2002, 102, 1953 and references
therein.
(10) Zhang, J .; Cai, R. F.; Weng, L. H.; Zhou, X. G. J . Organomet.
Chem. 2003, 672, 94.
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2003, 22, 5385.
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10.1021/om049866u CCC: $27.50 © 2004 American Chemical Society
Publication on Web 05/25/2004

3304 Organometallics, Vol. 23, No. 13, 2004
Zhang et al.
Syn th esis of (C5H5)2Yb[tBu NC(NHiP r )NiP r ] (3). To a 20
mL THF solution of [(C5H5)2YbNHtBu]2 (0.346 g, 0.46 mmol)
was slowly added N,N′-diisopropylcarbodiimide (0.116 g, 0.92
mmol) dropwise at -30 °C. After it was stirred for 30 min,
the reaction mixture was slowly warmed to ambient temper-
ature and stirred for 12 h. The solution was concentrated and
cooled to -20 °C to give an orange powder. Recrystallization
of the powder from a mixture of THF and toluene gave 3 as
yellow crystals. Yield: 0.249 g (54%). Mp: 144 °C dec. Anal.
Calcd for C21H34N3Yb: C, 50.29; H, 6.83; N, 8.38. Found: C,
asymmetrical guanidinate ligands. Furthermore, we
also studied the reaction of organolanthanide bis(amido)
complexes with carbodiimide, which led to the formation
of a homoleptic tris(guanidinate) lanthanide complex.
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 THF, toluene, and n-hexane
were refluxed and distilled over sodium benzophenone ketyl
under nitrogen immediately prior to use. (C5H5)YCl2(THF)3,12a
1
50.40; H, 6.95; N, 8.51. H NMR: δ 6.30 (s, 10H), 3.51-3.62
(m, 2H), 2.69 (s, 1H), 0.91-1.42 (m, 21H), 1.10 (s, 9H). IR
(Nujol, cm-1): 3448 m, 1649 s, 1529 m, 1304 m, 1171 s, 1130
m, 1013 s, 890 s, 767 s, 701 s, 663 w. EI-MS (m/z (fragment,
relative intensity (%)): 502 (M, 17), 436 (M - CpH, 24), 422
(M - Cp - CH3, 100), 379 (M - Cp - NHiPr, 11), 198 (L, 8),
12c
(C5H5)Y(NiPr2)2,12b [(C5H5)2LnNHtBu]2, and [(C5H5)2YbNHPh]2
were prepared by slightly modified literature methods. N,N′-
Diisopropylcarbodiimide was purchased from Aldrich and was
used without purification. Melting points were determined in
a sealed nitrogen-filled capillary and are uncorrected. Elemen-
tal analyses for C, H, and N were carried 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 tech-
niques with a source temperature of 200 °C. The values of m/z
i
142 (L - NiPr + H, 8) (L ) PrNC(NHiPr)NtBu).
Syn th esis of (C5H5)2Er [tBu NC(NHiP r )NiP r ] (4). To a 20
mL THF solution of [(C5H5)2ErNHtBu]2 (0.429 g, 0.58 mmol)
was slowly added N,N′-diisopropylcarbodiimide (0.146 g, 1.16
mmol) dropwise at -30 °C. The reaction mixture was subse-
quently worked up by the method described above. Pink
crystals of 4 were obtained in 67% yield (0.385 g). Mp: 162 °C
dec. Anal. Calcd for C21H34N3Er: C, 50.88; H, 6.91; N, 8.48.
Found: C, 50.76; H, 6.98; N, 8.57. IR (Nujol, cm-1): 3449 m,
1649 s, 1531 m, 1301 m, 1169 s, 1131 m, 1009 s, 892 s, 769 s,
702 s, 663 w. EI-MS (m/z (fragment, relative intensity (%)):
494 (M, 21), 428 (M - CpH, 34), 422 (M - Cp - CH3, 71), 371
(M - Cp - NHiPr, 34), 198 (L, 14), 142 (L - NiPr+H, 10) (L
1
refer to the isotopes 12C, H, 14N, 89Y, 164Dy, 166Er, and 174Yb.
1H NMR data were obtained on a Bruker DMX-500 NMR
spectrometer and were referenced to residual aryl protons in
C6H6 (δ 7.16).
i
) PrNC(NHiPr)NtBu).
Syn th esis of Y[iP r NC(NiP r 2)NiP r ]3 (1) a n d (C5H5)2Y-
[iP r NC(NiP r 2)NiP r ] (2). To a solution of (C5H5)YCl2(THF)3
(0.862 g, 1.95 mmol) in 30 mL of THF was added LiNiPr2 (0.418
g, 3.90 mmol) at -30 °C. After it was stirred at this temper-
ature for 3 h, the mixture was warmed to room temperature
and was stirred for 12 h. Then, the solution was cooled to -30
°C and treated with N,N′-diisopropylcarbodiimide (0.492 g,
3.90 mmol). After it was stirred for 3 h at -30 °C, the reaction
mixture was slowly warmed to ambient temperature and was
further stirred for 24 h. Removal of the solvent left a pale
yellow solid. The resulting solid was extracted with 30 mL of
toluene. The extract was evaporated to ca. 5 mL. Pale yellow
crystals of 1 were slowly formed at room temperature. Yield:
0.539 g (36%). Mp: 194 °C dec. Anal. Calcd for C39H84N9Y: C,
60.99; H, 11.02; N, 16.41. Found: C, 60.91; H, 10.95; N, 16.42.
1H NMR (C6D6): 3.57 (m, 12H, CH(CH3)2), 1.36 (d, 24H, CH-
(CH3)2), 1.20 (d, 24H, CH(CH3)2), 0.91 (d, 24H, CH(CH3)2). IR
(Nujol, cm-1): 3175 w, 1631 s, 1160 w, 1301 m, 1222 m, 1160
s, 1118 s, 1056 m, 1019 w, 974 m, 913 w, 859 s, 822 w, 768 w,
681 w, 665 s. EI-MS (m/z (fragment, relative intensity (%)):
Syn th esis of (C5H5)2Dy[tBu NC(NHiP r )NiP r ] (5). By the
procedure described for 3, reaction of [(C5H5)2DyNHtBu]2 (0.314
g, 0.43 mmol) with N,N′-diisopropylcarbodiimide (0.109 g, 0.86
mmol) gave 5 as pale yellow crystals. Yield: 0.321 g (76%).
Mp: 168 °C dec. Anal. Calcd for C21H34N3Dy: C, 51.37; H, 6.98;
N, 8.56. Found: C, 51.20; H, 7.04; N, 8.73. IR (Nujol, cm-1):
3443 m, 1649 s, 1530 m, 1301 m, 1169 s, 1130 m, 1009 s, 890
s, 765 s, 703 s, 663 w. EI-MS (m/z (fragment, relative intensity
(%)): 491 (M, 13), 425 (M - CpH, 21), 411 (M - Cp - CH3,
86), 368 (M - Cp - NHiPr, 27), 198 (L, 17), 142 (L - NiPr +
i
H, 22) (L ) PrNC(NHiPr)NtBu).
Syn th esis of (C5H5)2Y[tBu NC(NHiP r )NiP r ] (6). By the
procedure described for 3, reaction of [(C5H5)2YNHtBu]2 (0.284
g, 0.49 mmol) with N,N′-diisopropylcarbodiimide (0.124 g, 0.98
mmol) gave 6 as colorless crystals. Yield: 0.288 g (71%). Mp:
155 °C dec. Anal. Calcd for C21H34N3Y: C, 60.42; H, 8.21; N,
10.07. Found: C, 60.29; H, 8.17; N, 10.19. 1H NMR: δ 6.28 (s,
10H), 3.68 (s, 1H), 3.43-3.48 (m, 2H), 1.45-1.67 (m, 12H), 1.10
(s, 9H). IR (Nujol, cm-1): 3445 m, 1649 s, 1528 m, 1303 m,
1170 s, 1130 m, 1011 s, 889 s, 765 s, 701 s, 661 w. EI-MS (m/z
(fragment, relative intensity (%)): 417 (M, 31), 436 (M - CpH,
43), 422 (M - Cp - CH3, 100), 379 (M - Cp - NHiPr, 24), 198
i
226 (L, 17), 184 (L - Pr+H, 100), 127 (L - NiPr2, 14), 100
i
(NiPr2, 31), 43 (iPr, 98) (L ) PrNC(NiPr2)NiPr).
Further crystallization by diffusion of n-hexane into the
mother liquor yielded pale yellow crystals of 2, which were
isolated by filtration followed by a subsequent washing with
a minimal amount of a mixture of THF and n-hexane. Yield:
0.269 g (31%). Mp: 158 °C dec. Anal. Calcd for C23H38N3Y: C,
i
(L, 8), 142 (L - NiPr + H, 10) (L ) PrNC(NHiPr)NtBu).
Syn th esis of (C5H5)2Yb[P h NC(NHiP r )NiP r ] (7). By the
procedure described for 3, reaction of [(C5H5)2YbNHPh]2 (0.498
g, 0.63 mmol) with N,N′-diisopropylcarbodiimide (0.159 g, 1.26
mmol) gave 7 as orange crystals. Yield: 0.453 g (69%). Mp:
176 °C dec. Anal. Calcd for C23H30N3Yb: C, 52.97; H, 5.80; N,
8.06. Found: C, 52.84; H, 5.81; N, 8.13. IR (Nujol, cm-1): 3381
m, 1641 m, 1591 s, 1567 m, 1301 m, 1162 s, 1010 s, 963 m,
889 s, 771 s, 695 s, 663 w. EI-MS (m/z (fragment, relative
intensity (%)): 522 (M, 55), 457 (M - Cp, 58), 399 (M - Cp -
NHiPr, 61), 218 (L′, 54), 161 (L′ - NiPr, 10), 119 (L′ - NiPr -
1
62.01; H, 8.60; N, 9.43. Found: C, 61.89; H, 8.65; N, 9.48. H
NMR (C6D6): δ 6.49 (m, 5H, C5H5), 6.29 (m, 5H, C5H5), 3.61
(m, 2H, CH(CH3)2), 3.38 (m, 2H, CH(CH3)2), 1.31 (d, 12H, CH-
(CH3)2), 1.23 (d, 6H, CH(CH3)2), 0.91 (d, 6H, CH(CH3)2). IR
(Nujol, cm-1): 3166 w, 1631 s, 1157 w, 1305 m, 1231 m, 1155
s, 1122 s, 1051 w, 1014 s, 959 m, 913 w, 890 s, 768 m, 663 s.
EI-MS (m/z (fragment, relative intensity (%)): 430 (M - CH3,
7), 365 (M - Cp - CH3, 21), 226 (L, 46), 219 (Cp2Y, 10), 184
i
iPr + H, 51) (L′ ) PrNC(NHiPr)NPh).
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 1-5 and
7 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-
monochromated Mo KR (λ ) 0.710 73 Å) radiation. During the
intensity data collection, no significant decay was observed.
i
(L - Pr + H, 17), 127 (L - NiPr2, 25), 100 (NiPr2, 40), 66 (L,
i
58), 43 (iPr, 100) (L ) PrNC(NiPr2)NiPr).
(12) (a) Zhou, X. G.; Wu, Z. Z.; Ma, H, Z.; Xu, Z. You, X. X.
Polyhedron 1994, 13, 375. (b) Booij, M.; Kiers, N. H.; Heeres, H. J .;
Teuben, J . H. J . Organomet. Chem. 1989, 364, 79. (b) Bercaw, J . E.;
Davies, D. L.; Wolczanski, P. T. Organometallics 1986, 5, 443.

Organolanthanides Containing Guanidinate Ligands
Organometallics, Vol. 23, No. 13, 2004 3305
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 a n d 7
2
3
4
5
7
formula
mol wt
C
23H38N3Y
C21H34N3Yb
501.55
C21H34N3Er
495.77
C21H34N3Dy
491.01
C23H30N3Yb
521.54
445.47
cryst color
cryst dimens (mm)
cryst syst
space group
unit cell dimens
a (Å)
colorless
red
pink
yellow
red
0.50 × 0.20 × 0.10 0.45 × 0.40 × 0.05 0.10 × 0.10 × 0.20 0.10 × 0.20 × 0.30 0.20 × 0.10 × 0.05
monoclinic
P21/n
orthorhombic
Pbac
orthorhombic
Pbac
orthorhombic
Pbac
monoclinic
P21
8.803(4)
30.028(12)
9.573(4)
108.416(5)
2401.0(16)
4
1.232
2.440
944
11.068(7)
15.049(9)
26.599(16)
11.058(5)
15.086(7)
26.498(12)
11.145(4)
15.116(6)
26.522(10)
9.0720(14)
8.4415(13)
14.682(2)
98.600(2)
1111.8(3)
2
1.558
4.217
518
b (Å)
c (Å)
â (deg)
V (Å3 )
4430(5)
8
1.504
4.229
2008
4420(3)
8
1.490
3.804
1992
4468(3)
8
1.640
3.352
1976
Z
Dc (g .cm-3
)
µ (mm-1
F(000)
)
radiation
temp (K)
scan type
θ range (deg)
h,k,l range
Mo KR (λ ) 0.710 730 Å)
293.2
ω-2θ
2.34-25.00
-10 e h e 10
-27 e k e 35
-11 e l e 10
10 006
298.2
ω-2θ
2.39-26.01
-13 e h e 12
-18 e k e 18
-15 e l e 32
16 294
293.2
298.2
298.2
ω-2θ
1.40-26.01
-11 e h e 10
-10 e k e 10
-18 e l e 16
5134
ω-2θ
ω-2θ
1.54-25.01
-12 e h e 13
-17 e k e 17
-31 e l e 14
17 287
1.54-25.01
-10 e h e 13
-17 e k e 16
-31 e l e 31
17 487
no. of rflns measd
no. of unique rflns
4222 (Rint
0.0458)
)
4350 (Rint
0.0380)
)
3892 (Rint
0.0372)
)
3935 (Rint
)
3876 (Rint )
0.0300)
0.0317)
completeness to θ, %
max and min transmissn
refinement method
99.3% (θ ) 25.00)
99.6% (θ ) 26.01)
100% (θ ) 25.01)
100% (θ )25.01)
99.5% (θ )26.01)
0.8168 and 0.4859
0.7924 and 0.3750 0.8164 and 0.2520 none
none
full-matrix least squares on F2
no. of data/restraints/params 4222/0/252
4350/1/238
0.955
3892/0/227
1.102
3935/0/233
1.114
3876/1/248
0.993
goodness of fit on F2
1.014
final R indices (I > 2σ(I))
R1
0.0495
0.0987
0.0282
0.0623
0.0359
0.0730
0.0294
0.0640
0.0356
0.0823
wR2
R indices (all data)
R1
0.0820
0.0427
0.0464
0.0428
0.0397
wR2
0.1065
0.0659
0.0782
0.0693
0.0847
largest diff peak and
0.273 and -0.390
0.984 and -1.211
1.105 and -1.377
0.629 and -0.890
1.179 and -0.717
hole (e Å-3
)
Sch em e 1
The intensities were corrected for Lorentz-polarization effects
and empirical absorption with the SADABS program.13 The
structures were solved by direct methods using the SHELXL-
97 program.14 The absolute configuration of complex 7 was
established by anomalous dispersion effects in diffraction
measurements on the crystal. All non-hydrogen atoms were
found from the difference Fourier syntheses. The H atoms were
included in calculated positions with isotropic thermal param-
eters 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 crystal-
lographic data and selected experimental information are given
in Table 1.
(THF)n was studied. It was found that the reaction of
(C5H5)YCl2(THF)3 with LiNiPr2 and subsequently with
2 equiv of N,N′-diisopropylcarbodiimide (iPrNdCdNi-
Pr) in THF gave Y[iPrNC(NiPr2) NiPr]3 (1) and (C5H5)2Y-
[iPrNC(NiPr2)NiPr] (2). Presumably, complexes 1 and
2 could result from the rearrangement of the diinsertion
product CpY[iPrNC(NiPr2)NiPr]2, as shown in Scheme
1. However, attempts to isolate the intermediate CpY-
[iPrNC(NiPr2)NiPr]2 were unsuccessful. The reactions
of bis- or poly(amido) metal complexes with carbodiim-
ides have been studied extensively,15 but multiple-
insertion products are observed in only a few cases. For
example, only one of the M-N bonds is reactive to
carbodiimide, even under more drastic conditions for
M(NMe2)5 (M ) Ta, Nb).16 The present observation
might be attributed to two favorable factors: (i) the
presence of a vacant coordination site at the larger
lanthanide metal center satisfies the need for coordina-
Y[iP r NC(NiP r 2)NiP r ]3 (1). The data on crystals of 1 were
sufficient to provide atom connectivity but not high-precision
metrical information, due to the poor quality of data collected.
Cell constants for the triclinic system at 293(2) K are as
follows: a ) 13.302(5) Å, b ) 13.375(5) Å, c ) 17.960(6) Å, R
) 105.460(5)°, â ) 92.172(5)°, γ ) 119.811(4)°; V ) 2616.1-
(16) Å3, Z ) 2; Dc ) 0.868 g cm-3
.
Resu lts a n d Discu ssion
Rea ction of (C5H5)Y(NiP r 2)2 w ith N,N′-Diisop r o-
p ylca r bod iim id e. To gain more insight into the inser-
tion of carbodiimide into the Ln-N bond, the reaction
of N,N′-diisopropylcarbodiimide with (C5H5)Y(NiPr2)2-
(13) Sheldrick, G. M. SADABS, A Program for Empirical Absorption
Correction; University of Go¨ttingen, Go¨ttingen, Germany, 1998.
(14) Sheldrick, G. M. SHELXL-97, Program for the Refinement of
Crystal Structures; University of Go¨ttingen, Go¨ttingen, Germany,
1997.
(15) (a) Giesbrecht, G. R.; Whitener, G. D.; Arnold, J . Dalton 2001,
923. (b) Chandra, G.; J enkins, A. D.; Lappert, M. F.; Srivastava, R. C.
J . Chem. Soc. A 1970, 2550.
(16) Tin, M. T. K.; Yap, G. P. A.; Richeson, D. S. Inorg. Chem. 1999,
38, 998.

3306 Organometallics, Vol. 23, No. 13, 2004
Zhang et al.
Sch em e 2
tion of the carbodiimide molecule to precede insertion;
(ii) the stronger ionic characteristics of the Ln-N σ bond
enhance the migratory aptitude of the amino ligands.
To our knowledge, few homoleptic tris(guanidinate)
metal complexes have been reported in the literature,
and all these compounds have been prepared by me-
tathesis reactions.6e,22
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. Bon d Len gth s (Å) a n d An gles (d eg) for 2
Syn th eses a n d Ch a r a cter iza tion s of (C5H5)2Yb-
t
[RNC(NHiP r )NiP r ] (R ) Bu , Ln ) Yb (3), Er (4),
Y(1)-N(2)
Y(1)-N(1)
Y(1)-C(3)
Y(1)-C(2)
Y(1)-C(4)
Y(1)-C(9)
Y(1)-C(7)
Y(1)-C(8)
Y(1)-C(1)
Y(1)-C(5)
2.316(3)
2.321(3)
2.618(5)
2.628(5)
2.638(6)
2.639(5)
2.640(5)
2.641(5)
2.643(5)
2.646(6)
Y(1)-C(6)
2.654(5)
2.657(5)
1.326(4)
1.464(5)
1.340(4)
1.464(5)
1.419(6)
1.421(5)
1.481(5)
Y(1)-C(10)
N(1)-C(11)
N(1)-C(12)
N(2)-C(11)
N(2)-C(15)
N(3)-C(21)
N(3)-C(11)
N(3)-C(18)
Dy (5), Y (6); R ) P h , Ln ) Yb (7)). Lanthanocene
primary amido complexes [(C5H5)2LnNHR]2 were al-
i
lowed to react with PrNdCdNiPr to give the unex-
pected products (C5H5)2Yb[RNC(NHiPr)NiPr] (R ) tBu,
Ln ) Yb (3), Er (4), Dy (5), Y (6); R ) Ph, Ln ) Yb (7))
(Scheme 2).
Significantly, in contrast to the observation of sym-
metrical coordinated guanidinate complexes in other
insertions of carbodiimides into the lanthanide-nitro-
N(2)-Y(1)-N(1)
57.70(10) N(1)-C(11)-N(2) 114.1(3)
C(11)-N(1)-C(12) 123.1(3)
N(1)-C(11)-N(3) 122.6(3)
N(2)-C(11)-N(3) 123.3(3)
i
gen bonds,10-11,15 reactions of [(C5H5)2LnNHR]2 with -
C(11)-N(1)-Y(1)
C(11)-N(2)-Y(1)
C(21)-N(3)-C(11) 120.5(4)
C(11)-N(3)-C(18) 119.2(3)
94.2(2)
94.0(2)
PrNdCdNiPr gave the asymmetrically coordinated
N(1)-C(11)-Y(1)
N(2)-C(11)-Y(1)
57.17(19)
56.96(19)
guanidinate complexes (C5H5)2Ln[RNC(NHiPr)NiPr] (R
t
N(3)-C(11)-Y(1) 178.4(2)
) Bu, Ln ) Yb (3), Er (4), Dy (5), Y (6); R ) Ph, Ln )
Yb (7)). The formation of complexes 3-7 suggests that
a novel isomerization involving a 1,3-hydrogen shift
takes place along with the insertion of carbodiimide into
the Ln-N bond. To our knowledge, although guanidi-
nate complexes have been extensively studied, only one
example of the guanidinate rearrangement from sym-
metrical to asymmetrical coordination has been reported
to date.7a A 1,3-hydrogen internal shift of guanidinate
ligands has not observed before. This may give a new
insight into the fluxionality of guanidinate ligands.
Two possible pathways for the formation of these
complexes are depicted in Scheme 1. Pathway A involves
1,3-migration of the NHR group to the carbon atom of
coordinated carbodiimide to form the intermediate I,
analogous to the reactivity of lanthanocene secondary
amido derivatives with carbodiimide,10 followed by
tautomerization to the title compounds. The alternative
pathway, B, involves intramolecular coupling, followed
by 1,3-hydrogen migration. Insertion of carbodiimide
into a Ln-N bond has been observed before, and the
tautomerization of the initial product of the carbodiim-
ide insertion, via a formal 1,3-hydrogen shift, bears
some resemblance to the rearrangement that follows
insertion of acetonitrile into the Sc-N bond.17 Thus,
pathway A may be more plausible.
terized by elemental analysis and spectroscopic meth-
ods. In the mass spectra, all complexes exhibit the
molecule ion peak, and complexes 3-7 are also char-
acterized by the easy loss of the cyclopentadienyl and
the NHiPr groups. Complexes 1-7 show a characteristic
IR absorption band at 1630-1650 cm-1 attributable to
the -N.C.N- stretching model.18 Although the crys-
tal structure analysis indicates that the guanidinate
ligands of compounds 3-5 and 7 are bonded to the
lanthanide ions by an asymmetric mode in the solid
state, it should be noted that complex 6 did not exhibit
i
1
two doublets for the Pr groups in the H NMR, which
may suggest that compounds 3-7 are fluxional in
solution. The structures of 1-5 and 7 were also deter-
mined by X-ray single-crystal diffraction analysis.
Cr ysta l Str u ctu r es of Com p lexes 1-5 a n d 7. The
X-ray structural analysis results show that the overall
structure of 2 (Figure 1, Table 2) is similar to that of
the complex (C5H5)2Ln[iPrNC(NiPr2) NiPr] (Ln ) Yb,
Dy).10 The Y3+ ion is bonded to two η5-C5H5 groups and
one η2-guanidinate ligand. The YNCN unit is coplanar.
The coordination number of the Y atom is 8. The
complex has no unusual distances or angles in the
(C5H5)2Y unit. The Y-C(C5H5) distances range from
2.624(9) to 2.667(9) Å. The average value of 2.653(2) Å
is similar to those found in other trivalent lanthanide
complexes, such as [(C5H5)2Y(µ-CH3)]2 (2.66(2) Å)19a and
All of these complexes are air- and moisture-sensitive.
They dissolve readily in THF and toluene but are
sparingly soluble in n-hexane. They have been charac-
(17) Shapiro, P. J .; Heiling, L. M.; Marsh, R. E.; Bercaw, J . E. Inorg.
Chem., 1990, 29, 4560.
(18) Wilkins, J . D. J . Organomet. Chem. 1974, 80, 349.

Organolanthanides Containing Guanidinate Ligands
Organometallics, Vol. 23, No. 13, 2004 3307
F igu r e 3. ORTEP diagrams of 3 (Ln ) Yb), 4 (Ln ) Er),
and 5 (Ln ) Dy) with the probability ellipsoids drawn at
the 30% level. Hydrogen atoms are omitted for clarity.
Ta ble 3. Bon d Len gth s (Å) a n d An gles (d eg) for
3-5
F igu r e 2. ORTEP diagram of 1 with the probability
ellipsoids drawn at the 30% level. Hydrogen atoms are
omitted for clarity.
3 (Ln ) Yb)
4 (Ln ) Er)
5 (Ln ) Dy)
Ln(1)-N(2)
Ln(1)-N(1)
Ln(1)-C(9)
Ln(1)-C(3)
Ln(1)-C(5)
Ln(1)-C(10)
Ln(1)-C(7)
Ln(1)-C(8)
Ln(1)-C(1)
Ln(1)-C(4)
Ln(1)-C(6)
Ln(1)-C(2)
N(1)-C(11)
N(2)-C(11)
N(3)-C(11)
2.252(3)
2.256(3)
2.590(5)
2.601(5)
2.603(5)
2.603(6)
2.611(5)
2.613(5)
2.616(5)
2.617(5)
2.617(5)
2.617(5)
1.333(5)
1.344(5)
1.378(5)
2.252(5)
2.254(5)
2.586(8)
2.604(8)
2.604(8)
2.605(8)
2.609(8)
2.610(8)
2.612(8)
2.610(8)
2.616(8)
2.638(7)
1.342(7)
1.337(7)
1.379(7)
2.295(4)
2.304(4)
2.639(6)
2.648(6)
2.648(6)
2.650(6)
2.654(5)
2.656(6)
2.661(6)
2.663(6)
2.666(6)
2.667(6)
1.337(5)
1.326(5)
1.378(6)
[(C5H5)2Y(µ-Me)2AlMe2] (2.62(4) Å).19b The Y-N dis-
tances of 2.280(4) and 2.282(5) Å are in the range
expected for a Y-N bond interaction with partial single-
and donor-bond character.20 The average Y-N distance
of 2.281(5) Å is comparable to the corresponding dis-
tance in organolanthanide guanidinates (C5H5)2Ln-
[iPrNC(NiPr2)NiPr] (Ln ) Yb, Dy), when the difference
in the metal ionic radii is considered.21
Unfortunately, the quality of the crystallographic data
for 1 is poor, with the value of R being on the high side
(R1 ) 0.1252, wR2 ) 0.3201). The bond distances and
bond angles for 1 cannot be discussed, therefore. How-
ever, the overall structure of 1 was clearly determined,
as shown in Figure 2. Complex 1 is a solvent-free
monomer with the ytterbium atom bonded to three
chelating guanidinate ligands to form a distorted-
octahedral geometry, which is similar to those of Nd-
[iPrNC(NiPr2)NiPr]3 6e and Ru[η2-(NPh)2CNHPh]3.22 The
coordination number of Y3+ is 6.
N(2)-Ln(1)-N(1)
C(11)-N(1)-Ln(1)
C(11)-N(2)-Ln(1)
N(1)-C(11)-N(2)
N(1)-C(11)-N(3)
N(2)-C(11)-N(3)
N(1)-C(11)-Ln(1)
N(2)-C(11)-Ln(1)
N(3)-C(11)-Ln(1)
58.98(11)
94.5(2)
94.4(2)
112.0(3)
124.2(4)
123.8(4)
56.1(2)
55.99(19)
178.3(3)
59.18(17)
94.0(3)
57.70(12)
94.3(3)
94.3(3)
95.0(3)
112.3(5)
125.0(5)
122.7(5)
56.3(3)
112.9(4)
124.2(4)
122.9(4)
56.7(2)
56.2(3)
56.3(2)
177.2(4)
176.9(3)
The molecular structure of 3 is shown in Figure 3.
Selected bond lengths and angles of 3 are listed in Table
3. The X-ray crystal analysis results show that the
primary amino group in 3 has combined with N,N′-
diisopropylcarbodiimide, forming a four-membered het-
erometallacycle. In contrast to the behavior observed
for the guanidinate rearrangement of {[Me2NC(Ni-
Pr)2]2TiO}2,7a where the asymmetric guanidinate ligand
shows a localized bonding situation, 3 exhibits delocal-
ized bonding throughout the N3C guanidinate core. The
planarity of the YbN2C ring and nearly equivalent
C(11)-N(1) and C(11)-N(2) (1.333(5) and 1.343(5) Å,
respectively) and Yb(1)-N(1) and Yb(1)-N(2) (2.256(3)
and 2.252(3) Å, respectively) bond lengths suggest the
existence of a resonance stabilization in the YbN2C ring
and no hydrogen atom at the coordinated nitrogen
atom.10 This guanidinate isomerization can also be
confirmed by a comparison with the structural param-
eters of other known guanidinate complexes.23
Characteristically, the distance between the central
carbon and noncoordinated nitrogen (C(11)-N(3) )
1.378(5) Å) is shorter than that expected for C(sp2)-
N(sp3) single bonds (C-Nav ) 1.416 Å)24 and is also
significantly shorter than the value observed in (C5H5)2-
Yb[(iPrN)2CNiPr2] (1.427(7) Å).10 This may be attributed
to less steric repulsion between the substituents, which
leads to a stronger p-π conjugation between the lone-
pair electron on noncoordinated nitrogen and the N2C-
unit. Consistently, the average Yb-N distance (2.254-
(3) Å) is slightly shorter than the corresponding distance
in (C5H5)2Yb[(iPrN)2CNiPr2] (2.288(5) Å), indicating a
(19) (a) Holton, J .; Lappert, M. F.; Ballard, D. R.; Pearce, R.; Atwood,
J . L.; Hunter, W. E. J . Chem. Soc., Dalton Trans. 1979, 54. (b) Holton,
J .; Lappert, M. F.; Ballard, D. G. H.; Pearce, R.; Atwood, J . L.; Hunter,
W. E. J . Chem. Soc., Chem. Commun. 1976, 31, 425. Scollary, G. R.
Aust. J . Chem. 1985, 31, 411.
(20) (a) Evans, W. J .; Drummond, D. K.; Chamberlain, L. A.; Doeden,
R. J .; Bott, S. G.; Zhang, H.; Atwood, J . L. J . Am. Chem. Soc., 1988,
110, 4983. (b) 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.
(21) Shannon, R. D. Acta Crystallogr. 1976, A32, 751.
(23) (a) Bailey, P. J .; Gould, R. O.; Harmer, C. N.; Pace, S.; Steiner,
A.; Wright, D. S. Chem. Commun. 1997, 1161. (b) Bailey, P. J .; Mitchell,
L. A.; Parsons, S. J . Chem. Soc., Dalton Trans. 1996, 2389.
(24) Lide, D. R., Ed. Handbook of Chemistry and Physics; CRC
Press: Boca Raton, FL, 1996.
(22) Bailey, P. J .; Grant, K. J .; Mitchell, L. A.; Pace, S.; Parkin, A.;
Parsons, S. Dalton 2000, 1887.

3308 Organometallics, Vol. 23, No. 13, 2004
Zhang et al.
Ta ble 4. Bon d Len gth s (Å) a n d An gles (d eg) for 7
Yb(1)-N(1)
Yb(1)-N(2)
Yb(1)-C(7)
Yb(1)-C(6)
Yb(1)-C(4)
Yb(1)-C(1)
Yb(1)-C(3)
Yb(1)-C(8)
Yb(1)-C(2)
2.293(6)
2.297(7)
Yb(1)-C(9)
Yb(1)-C(5)
Yb(1)-C(10)
N(1)-C(11)
N(1)-C(12)
N(2)-C(11)
N(2)-C(18)
N(3)-C(11)
2.575(11)
2.582(10)
2.586(12)
1.364(14)
1.389(10)
1.304(13)
1.488(11)
1.368(8)
2.551(11)
2.560(10)
2.562(11)
2.567(12)
2.569(11)
2.572(11)
2.572(13)
N(1)-Yb(1)-N(2)
C(11)-N(1)-Yb(1)
C(11)-N(2)-Yb(1)
N(2)-C(11)-N(1)
N(2)-C(11)-N(3)
58.2(2)
93.3(5)
94.9(5)
113.6(6)
123.6(11)
N(1)-C(11)-N(3)
N(2)-C(11)-Yb(1)
N(1)-C(11)-Yb(1)
122.7(12)
56.8(4)
56.8(3)
N(3)-C(11)-Yb(1) 178.1(11)
hydrogen shift, is unambiguously identified by the
relative bond distances and bond angles (Table 4). 7 has
no unusual distances or angles in the (C5H5)2Yb unit.
The different C(11)-N(2) and C(11)-N(1) distances of
1.304(13) and 1.364(14) Å may be due to the additional
conjugation participated in by the phenyl ring.
F igu r e 4. ORTEP diagram of 7 with the probability
ellipsoids drawn at the 30% level. Hydrogen atoms are
omitted for clarity.
Con clu sion s
contribution from the increase of the nucleophilicity of
the guanidinate anion.25
The present results demonstrate that lanthanocene
amino derivatives exhibit high activity toward N,N′-
diisopropylcarbodiimide. N,N′-Diisopropylcarbodiimide
inserts readily into each of the Ln-N σ bonds of
Complexes 4 and 5 are isostructural with complex 3.
Their structural parameters (Table 3) also indicate that
the charge delocalization within the N3C core is evident
and the hydrogen linked to the nitrogen atom of the Nt-
Bu group has migrated to the noncoordinated nitrogen
atom. There is no unusual distance or angle in the
(C5H5)2Er or (C5H5)2Dy unit. The Er-C(C5H5) distances
range from 2.586(8) to 2.637(7) Å. The average value of
2.609(5) Å is similar to those found in other (C5H5)2Er-
containing complexes, such as (C5H5)2Er[(tBuN)2CnBu]
(2.653 Å)26a and (C5H5)ErCl2(THF)3 (2.667 Å).26b The
Dy-C(C5H5) distances of 2.622(6)-2.651(5) Å are in the
normal range.10,27 The Er-N (2.252(5), 2.254(5) Å) and
Dy-N (2.319(4), 2.321(4) Å) distances are similar to the
corresponding distances in complex 3, when the differ-
ence in the metal ionic radii is considered.21
(C5H5)Y(NiPr2)2 and [(C5H5)2LnNHR]2 (R ) Bu, Ln )
t
Yb, Er, Dy, Y; R ) Ph, Ln ) Yb) under mild conditions,
which provides a new way to synthesize lanthanide
guanidinate complexes. Interestingly, the insertion
product derived from N,N′-diisopropylcarbodiimide with
(C5H5)Y(NiPr2)2 is unstable at room temperature and
rearranges easily to Y[iPrNC(NiPr2)NiPr]3 (1) and
(C5H5)2Y[iPrNC(NiPr2)NiPr] (2). Moreover, the X-ray
analyses for complexes 3-5 and 7 show that the
t
resulting guanidinate ligands BuNC(NHiPr)NiPr and
PhNC(NHiPr)NiPr readily undergo a novel isomeriza-
tion via a 1,3-hydrogen shift, forming the asymmetrical
guanidinate complexes.
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.
Positive structural verification of 7 was also provided
by a single-crystal X-ray analysis. The solid-state struc-
ture of 7 (Figure 4) shows that the bonding mode of the
i
iPrNC(NHiPr)NPh group is similar to that of PrNC-
(NHiPr)NtBu observed in complexes 3-5. The corre-
sponding guanidinate isomerization, involving a 1,3-
Su p p or tin g In for m a tion Ava ila ble: Figures giving ad-
ditional views and CIF files giving atomic coordinates and
thermal parameters, all bond distances and angles, and
experimental data for all structurally characterized complexes.
This material is available free of charge via the Internet at
http://pubs.acs.org.
(25) Den Haan, K. H.; De Boer, J . L.; Teuben, J . H.; Spek, A. L.;
Kojic-Prodic, B.; Hays, G. R.; Huis, R. Organometallics 1986, 5, 1726.
(26) (a) Zhang, J .; Ruan, R. Y.; Shao, Z. H.; Cai, R. F.; Weng, L. H.;
Zhou, X. G. Organometallics 2002, 21, 1420. (b) Day, C. S.; Day, V.
W.; Ernst, R. D.; Vollmer, S. H. Organometallics 1982, 1, 998.
(27) Wu, Z. Z.; Xu, Z.; You, X. Z.; Zhou, X. G.; Huang, X. Y. J .
Organomet. Chem. 1994, 483, 107.
OM049866U