Synthesis, structure, and reaction chemistry of samarium(ii), europium(ii), and ytterbium(ii) complexes of the unsymmetrical benzamidinate ligand [PhC(NSiMe3)(NC6H3Prl2-2,6)] -

Article abstract of DOI:10.1021/ic901327m

Neutral mononuclear lanthanide(II) bis(amidinate) complexes [LnL ₂(THF)_x] [L = PhC(NSiMe₃)(NC₆H ₃Pr^′₂-2,6)^-; Ln = Sm, x = 2 (3); Ln = Eu, x = 2, (4); Ln = Yb, x = 1 (5)] were synthesized by the reaction of the appropriate Lnl2(THF)₂ with potassium amidinate [KL] _n (2). The reduction chemistry of 3-5 was also examined. The reaction of the Sm(II) and Eu(II) amidinates 3 and 4 with diphenyl dichalcogenides PhEEPh (E = Se, Te) led to the binuclear lanthanide(III) amidinate- chalcogenolatecomplexes [LnL₂(μ-EPh)]₂ [Ln = Sm, E = Se (6); Ln = Eu, E = Se (7); Ln = Sm, E = Te (9)], whereas reacting the Yb(II) bis(amidinate) 5 with PhSeSePh yielded the mononuclear [YbL₂(SePh) (THF)] (8). The reaction of 5 with iodine led to the Yb(III) bis(amidinate) iodide complex [YbL₂(I)(THF)] (10). Treatment of 3 with N,N′-dicyclohexylcarbodiimide afforded the mixed-ligand Sm(III) tris(amidinate) [SmL₂{CyNC(H)NCy}] (11) (Cy = cyclohexyl). The molecular structures of complexes 2-5 and 7-11 were elucidated by X-ray diffraction analyses.

Full text of DOI:10.1021/ic901327m

9936 Inorg. Chem. 2009, 48, 9936–9946
DOI: 10.1021/ic901327m
Synthesis, Structure, and Reaction Chemistry of Samarium(II), Europium(II), and
Ytterbium(II) Complexes of the Unsymmetrical Benzamidinate Ligand
[PhC(NSiMe3)(NC6H3Pri2-2,6)]-
Shuang Yao,† Hoi-Shan Chan,† Chi-Keung Lam,‡ and Hung Kay Lee*,†
†Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories,
Hong Kong SAR, P.R. China, and ‡School of Chemistry and Chemical Engineering,
Sun Yat-Sen University, Guangzhou 510275, P.R. China
Received July 9, 2009
Neutral mononuclear lanthanide(II) bis(amidinate) complexes [LnL2(THF)x] [L = PhC(NSiMe3)(NC6H3Pri2-2,6)-;
Ln = Sm, x = 2 (3); Ln = Eu, x = 2, (4); Ln = Yb, x = 1 (5)] were synthesized by the reaction of the appropriate
LnI2(THF)2 with potassium amidinate [KL]n (2). The reduction chemistry of 3-5 was also examined. The reaction
of the Sm(II) and Eu(II) amidinates 3 and 4 with diphenyl dichalcogenides PhEEPh (E = Se, Te) led to the binu-
clear lanthanide(III) amidinate-chalcogenolate complexes [LnL2(μ-EPh)]2 [Ln = Sm, E = Se (6); Ln = Eu, E = Se (7);
Ln = Sm, E = Te (9)], whereas reacting the Yb(II) bis(amidinate) 5 with PhSeSePh yielded the mononuclear
[YbL2(SePh)(THF)] (8). The reaction of 5 with iodine led to the Yb(III) bis(amidinate) iodide complex [YbL2(I)(THF)]
(10). Treatment of 3 with N,N0-dicyclohexylcarbodiimide afforded the mixed-ligand Sm(III) tris(amidinate)
[SmL2{CyNC(H)NCy}] (11) (Cy = cyclohexyl). The molecular structures of complexes 2-5 and 7-11 were
elucidated by X-ray diffraction analyses.
Introduction
and electronic properties can be readily modified by intro-
duction of various R1 and R2 substituents. Amidinates are
useful ligands in organolanthanide chemistry,5 and a number
of trivalent lanthanide amidinates have been reported.1,5-12
In contrast, the chemistry of their divalent counterparts
remains an underdeveloped area. Edelmann and co-work-
ers13 have reported a series of mononuclear Yb(II) benzami-
dinate complexes [Yb{(RC6H4)C(NSiMe3)2}2(THF)2] (R =
H, OMe, Ph). The reactivity of some of these complexes
toward reduction of diaryl dichalcogenides REER (R = Ph,
Mes; E = Se, Te) was also studied.13b Recently, Junk and co-
workers14 have reported the sterically hindered complex
Over the past decades, tremendous research efforts have
been devoted to the development of various types of ancil-
lary ligands as alternatives for cyclopentadienyl ligands.1,2
Among those cyclopentadienyl alternatives, amidinate li-
gands [R1NC(R2)NR1]- have proved to be versatile, forming
stable complexes with a wide range of metals.3,4 Their steric
*To whom correspondence should be addressed. E-mail: hklee@cuhk.
edu.hk.
(1) (a) Edelmann, F. T. In Comprehensive Organometallic Chemistry II ;
Abel, E. W., Stone, F. G. A., Wilkinson, G., Eds.; Elsevier Science Ltd.: Oxford,
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102, 1851–1896.
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A. G.; Rheingold, A. L. Inorg. Chem. 2008, 47, 11376–11381.
(3) Edelmann, F. T. Coord. Chem. Rev. 1994, 137, 403–481.
(4) Junk, P. C.; Cole, M. L. Chem. Commun. 2007, 1579–1590.
(5) Edelmann, F. T. Chem. Soc. Rev. 2009, 38, 2253–2268.
(6) (a) Duchateau, R.; van Wee, C. T.; Meetsma, A.; Teuben,
J. H. J. Am. Chem. Soc. 1993, 115, 4931–4932. (b) Duchateau, R.; Meetsma,
A.; Teuben, J. H. Organometallics 1996, 15, 1656–1661. (c) Duchateau, R.; van
Wee, C. T.; Teuben, J. H. Organometallics 1996, 15, 2291–2302. (d) Duchateau,
R.; van Wee, C. T.; Meetsma, A.; van Duijnen, P. T.; Teuben, J. H. Organome-
tallics 1996, 15, 2279–2290.
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Soc., Dalton Trans. 2000, 4093–4097.
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Hessen, B. J. Am. Chem. Soc. 2004, 126, 9182–9183.
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Pang, X.; Zhang, Y.; Shen, Q. J. Mol. Struct. 2005, 743, 229–235. (c) Li, C.;
Wang, Y.; Zhou, L.; Sun, H.; Shen, Q. J. Appl. Polym. Sci. 2006, 102, 22–28.
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4624–4632.
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Amberger, H. D.; Edelmann, F. T.; Pegelow, U.; Shalimoff, G. V. J. Organomet.
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2005, 1581–1583.
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r
pubs.acs.org/IC
Published on Web 09/16/2009
2009 American Chemical Society

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9937
Scheme 1. Synthesis of Complexes 1 and 2
Chart 1
N0-tetramethylethylenediamine) was readily prepared by
the reaction of the lithium anilide [Li{N(SiMe3)(C6H3-
Pri2-2,6)}(TMEDA)]17 with benzonitrile (Scheme 1). The
reaction involves nucleophilic attack of the [N(SiMe3)-
(C6H3Pri2-2,6)]- anion to the CtN functional group of
benzonitrile, followed by 1,3-silyl migration. Complex
[Sm{HC(NC6H3Pri2-2,6)2}2(THF)2], which represents the
first example of a Sm(II) bis(amidinate) to be synthesized
and structurally characterized. This Sm(II) complex can be
readily converted to its homoleptic Sm(III) counterpart.
Our current research interest focuses on the chemistry of
metal complexes supported by anionic nitrogen-based li-
gands.15 Earlier, we have reported on the coordination che-
mistry of the chelating 2-pyridyl amido ligand [N(SiButMe2)-
(2-C5H3N-6-Me)]- toward trivalent lanthanides.15d Besides,
we have also reported a series of divalent transition metal
(Mn-Ni) complexes derived from the unsymmetrical benza-
midinate ligand [PhC(NSiMe3)(NC6H3Me2-2,6)]-.15e One
common feature of the 2-pyridyl amido system and the
amidinato system is the presence of a NCN ligand backbone.
This results in the formation of four-membered MNCN
metallacyclic rings when these ligands coordinate to metal cen-
ters in a chelating fashion (Chart 1). Continuing our work on
the unsymmetrical amidinato ligand system,15e we have ex-
tended our studies to the lanthanide series using a sterically
more bulky 2,6-diisopropylphenyl substituted [PhC(NSi-
Me3)(NC6H3Pri2-2,6)]- (L) ligand.16 Herein, we report on
the synthesis and structural characterization of lanthanide(II)
bis(amidinate) complexes [LnL2(THF)x] (Ln=Sm and Eu, x=
2; Ln=Yb, x=1). To the best of our knowledge, complex
[EuL2(THF)2] is the first structurally authenticated Eu(II)
amidinate. The reaction chemistry of the present lanthanide(II)
amidinates toward reduction of diphenyl dichalcogenides
PhEEPh (E = Se, Te), iodine, and N,N0-dicyclohexylcarbodii-
mide was also examined in our studies.
1
1 gave satisfactory elemental analysis. The H and 13C
NMR spectra of 1 showed one set of resonance signals
due to the L ligand and TMEDA. It is noteworthy that the
methyl protons of the isopropyl substituents of the L
ligand occurred as two doublets at 1.22 and 1.25 ppm,
respectively, indicating that the isopropyl methyl groups
are diastereotopic. This may be attributed to hindered
rotation about the N-Cipso bond.18
X-ray diffraction analysis revealed that 1 is mo-
nonuclear with the Li atom coordinated by a κ2-bound
L- anion and a chelating TMEDA ligand (Figure 1).19
The coordination geometry around the lithium atom can
be described as distorted tetrahedral. The almost identical
˚
˚
C(13)-N(1) (1.319(1) A) and C(13)-N(2) (1.330(2) A)
distances indicate delocalization of the anionic charge
over the amidinato NCN moiety. The Li(1)-N(1) and
˚
Li(1)-N(2) distances of 2.041(3) and 2.052(4) A, respec-
tively, are only marginally longer than the corresponding
bond lengths of 2.009(3) and 2.032(3) A in the closely rela-
˚
ted [Li{PhC(NSiMe3)(NC6H3Me2-2,6)}(TMEDA)].15e
The potassium salt of the L ligand was prepared by a
transmetalation reaction of [LiL(TMEDA)] (1) with KO-
But. Addition of 1 to a slurry of KOBut in diethyl ether at
room temperature yielded potassium benzamidinate 2,
which was isolated as very air-sensitive, colorless crystals.
Compound 2 is soluble in THF, but only sparingly soluble
in toluene, diethyl ether, and hexane. Its 1H and 13C NMR
spectra showed one set of resonance signals, which were
assignable to the L ligand. The methyl groups of the
isopropyl substituents of the L ligand in 2 are also diaster-
eotopic, as revealed by the occurrence of two doublets at
1.10 and 1.17 ppm, respectively, in its 1H NMR spectrum.
The solid-state structure of 2 was determined by X-ray
crystallography. Compound 2 crystallizes as a one-di-
mensional polymer made up of linked binuclear K2L2
subunits (Figure 2). Each potassium atom in 2 is bound by
Results and Discussion
Synthesis of Lithium and Potassium Salts of [PhC-
(NSiMe3)(NC6H3Pri2-2,6)]- (L). The lithium benzami-
dinate complex [LiL(TMEDA)] (1) (TMEDA=N,N,N0,
(15) (a) Lee, H. K.; Wong, Y.-L.; Zhou, Z.-Y.; Zhang, Z.-Y.; Ng, D. K. P.;
Mak, T. C. W. J. Chem. Soc., Dalton Trans. 2000, 539–544. (b) Lee, H. K.; Peng,
Y.; Kui, S. C. F.; Zhang, Z.-Y.; Zhou, Z.-Y.; Mak, T. C. W. Eur. J. Inorg. Chem.
2000, 2159–2161. (c) Lee, H. K.; Lam, C. H.; Li, S.-L.; Zhang, Z.-Y.; Mak, T. C. W.
Inorg. Chem. 2001, 40, 4691–4695. (d) Kui, S. C. F.; Li, H.-W.; Lee, H. K. Inorg.
Chem. 2003, 42, 2824–2826. (e)Lee, H. K.;Lam, T. S.; Lam, C.-K.;Li, H.-W.;Fung,
S. M. New J. Chem. 2003, 27, 1310–1318. (f) Au-Yeung, H. Y.; Lam, C. H.; Lam,
C.-K.; Wong, W.-Y.; Lee, H. K. Inorg. Chem. 2007, 46, 7695–7697.
(17) (a) Schumann, H.; Winterfeld, J.; Rosenthal, E. C. E.; Hemling, H.;
Esser, L. Z. Anorg. Allg. Chem. 1995, 621, 122–130. (b) Schumann, H.;
Gottfriedsen, J.; Dechert, S.; Girgsdies, F. Z. Anorg. Allg. Chem. 2000, 626, 747–
758.
(18) (a) Scollard, J. D.; McConville, D. H.; Vittal, J. J. Organometallics
1997, 16, 4415–4420. (b) Hill, M. S.; Hitchcock, P. B. Organometallics 2002, 21,
3258–3262.
(16) As compared to the less hindered [PhC(NSiMe3)(NC6H3Me2-2,6)]-
ligand reported previously by our group (ref 15e), the sterically more bulky L
ligand was anticipated to be a potential candidate, providing sufficient steric
shielding, for the preparation of neutral, mononuclear lanthanide(II) complexes.
˚
(19) Selected bond distances (A) and angles (deg) for complexes 1-5, 7, 8,
9 C7H8, 10, and 11 are provided in Tables S1-10, respectively. See
3
Supporting Information.

9938 Inorganic Chemistry, Vol. 48, No. 20, 2009
Yao et al.
Scheme 2. Synthesis of Complexes 3-5
Figure 1. Molecular structure of [LiL(TMEDA)] (1) (30% thermal
ellipsoids) with atom labeling.
addition of two molar equivalents of 2 to a solution of
SmI2(THF)2 in THF at room temperature yielded the
Sm(II) bis(amidinate) [SmL2(THF)2] (3) as deep greenish
blue crystals in a moderate yield. A 1:1 reaction of SmI2-
(THF)2 and 2 was also examined. In our hands, treatment
of SmI2(THF)2 with one molar equivalent of 2 led to 3 as
the only isolable product. Analogous reactions of EuI2-
(THF)2 and YbI2(THF)2 with two molar equivalents of 2
in THF led to [EuL2(THF)2] (4) (orange crystals) and
[YbL2(THF)] (5) (dark red crystals), respectively. All of
the complexes 3-5 are extremely sensitive to air and
moisture. They are readily soluble in common organic
solvents. Their formulations were confirmed by elemental
analysis and NMR spectroscopy (for the diamagnetic
1
Yb(II) complex 5). The H and 13C NMR spectra of 5
Figure 2. Polymeric structure of [KL]n (2) (30% thermal ellipsoids) with
atom labeling.
showed one set of resonance signals which were assign-
able to a pair of L ligands and one THF molecule. Similar
to the lithium and potassium derivatives 1 and 2, the
methyl groups of the isopropyl substituents in 5 are also
diastereotopic. This is indicated by the occurrence of two
doublet signals at 1.27-1.40 ppm in its 1H NMR, as well
as two resonance signals at 22.9 and 25.9 ppm in its 13C
NMR spectrum.
a L ligand in an unusual η1-amide:η6-arene fashion. A
similar η1:η6-binding mode of amidinate ligands has been
observed in the potassium formamidinate complexes
- 20
[K(FMes)(HFMes)] [FMes = HC(NC6H2Me3-2,4,6)2
]
and [{K(DippForm)2K(THF)2}n] xTHF (DippForm =
3
HC(NC6H3Pri2-2,6)2-).21 The potassium-nitrogen distances
˚
˚
of 2.846(6) A [K(1)-N(2)] and 2.824(7) A [K(2)-N(4)]
in 2 are longer than the corresponding distance in [K-
Single crystals of complexes 3-5 suitable for X-ray dif-
fraction analysis were obtained from n-hexane. The Sm(II)
bis(amidinate) 3 crystallizes in the monoclinic space group
Cc. Figure 3 shows the crystal structure of complex 3, with
selected bond distances and angles provided in Supporting
Information, Table S3.22 The asymmetric unit of3 consists of
four independent molecules of nearly the same structure.
Each Sm atom is bound by a pair of κ2-bound L ligands and
two THF molecules. The complex exhibits a cisoid structure
with a crystallographic C2 axis passing through the Sm(II)
center. The Sm-N distances in 3, which fall within the range
(FMes)(HFMes)] (2.719(1) A),20 but comparable to that of
˚
21
2.863(4) A in [{K(DippForm)2K(THF)2}n] xTHF. The
˚
3
K(1)-C(centroid) and K(2)-C(centroid) distances in com-
plex 2are 2.908 A and 2.864 A, respectively. They are similar to
˚
˚
˚
the corresponding distance of 2.887(7) A in [K(FMes)-
(HFMes)],20 but slightly shorter than that (3.034(9) A) in
˚
[{K(DippForm)2K(THF)2}n] xTHF.21 Each potassium
3
atom in 2 is further coordinated to the CdN bond of the
NCN moiety of a neighboring L ligand, completing the one-
dimensional polymeric structure of the compound [K(1)-
˚
of 2.49(1)-2.67(1) A, are comparable to those reported for
˚
˚
N(3)#1 2.760(6) A, K(1)-C(38)#1 3.505(9) A, K(2)-N(1)
[Sm{HC(NC6H3Pri2-2,6)2}2(THF)2] (2.529(3) and 2.617(3)
˚
˚
2.807(6) A, and K(2)-C(13) 3.488(8) A].
14
A) and the four-coordinate Sm(II) bis(guanidinate)
˚
Synthesis and Structures of Lanthanide(II) Bis(ami-
dinate) Complexes. The potassium benzamidinate [KL]n
(2) was used as a ligand-transfer reagent in subsequent
studies. Divalent samarium, europium, and ytterbium
complexes with the L ligand were readily prepared by
metathesis reactions of the appropriate LnI2(THF)2
(Ln = Sm, Eu and Yb) with 2. As outlined in Scheme 2,
i
23
˚
[Sm{(2,6-Pr2C6H3N)2C(NCy2)}2] (2.529(2)-2.570(2) A).
˚
The Sm-O(THF) bond lengths of 2.61(1)-2.64(1) A in 3are
similar to the corresponding distances in [Sm{HC(NC6-
i 14
H3Pr 2-2,6)2}2(THF)2] (2.599(3) and 2.560(3) A). The acute
˚
N-C-N bite angles of the L ligands in 3 (51.3(3)-53.7(4)°)
(22) The carbon atoms of the coordinated THF molecules in complex 3
exhibit large thermal motion. They were refined with isotropic thermal
parameters and subjected to atom-atom distance restraints.
(23) Heitmann, D.; Jones, C.; Junk, P. C.; Lippert, K.-A.; Stasch, A.
Dalton Trans. 2007, 187–189.
(20) Baldamus, J.; Berghof, C.; Cole, M. L.; Evans, D. J.; Hey-Hawkins,
E.; Junk, P. C. Dalton Trans. 2002, 2802–2804.
(21) Cole, M. L.; Junk, P. C. J. Organomet. Chem. 2003, 666, 55–62.

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9939
Figure 5. Molecular structure of the transoid isomer in the crystal
structure of complex 4. The Eu atom is located at an inversion center.
Thermal ellipsoids were plotted at 30% probability level. Symmetry
transformation: 1-x, 1-y, 1-z.
Figure 3. Molecular structure of [SmL2(THF)2] (3) (30% thermal
ellipsoids) withatom labeling. Only one ofthe fourindependentmolecules
in the asymmetric unit is shown.
Figure 4. Molecularstructure ofthe cisoid isomerin the crystal structure
of[EuL2(THF)2] (4). Eachasymmetric unit consists ofone moleculeofthe
cisoid isomer. Thermal ellipsoids were plotted at 30% probability level.
Figure 6. Molecular structure of [YbL2(THF)] (5) (30% thermal
ellipsoids) with atom labeling.
˚
Me3)2}2(DME)2] (Eu-N=2.530(4) A, DME=1,2-dime-
are similar to that of 52.9(1)° reported for [Sm{HC-
(NC6H3Pri2-2,6)2}2(THF)2],14 and those of 52.55(7)° and
52.18(7)° in [Sm{(2,6-Pri2C6H3N)2C(NCy2)}2].23
thoxyethane).24a However, they are slightly longer than
˚
the terminal Eu-N distance of 2.448(4) A in [Na-
Eu{N(SiMe3)2}3].24b The Eu-O(THF) bond distance of
the transoid isomer (2.604(4) A) is slightly longer than
Complex 4 crystallizes in the monoclinic space group
P21/c. Interestingly, the asymmetric unit consists of one
molecule of a cisoid isomer and a “half” molecule of a
transoid isomer. The molecular structures of the cisoid
and transoid isomers of 4 are depicted in Figures 4 and 5,
respectively. Selected bond lengths and angles for the
complex are listed in Supporting Information, Table S4.
The cisoid isomer exhibits non-crystallographic C2 sym-
metry with two κ2-bound L ligands and two “cis” THF
molecules [O(1)-Eu(1)-O(2)=109.0(1)°]. The coordina-
tion geometry around the Eu(II) center in this isomer can
be described as distorted octahedral. On the other hand,
the transoid isomer is located at an inversion center and
conforms closely to C2h symmetry. Four amidinato nitro-
gen atoms form an equatorial plane, while two “trans”
THF molecules occupy the axial positions [O(10)-
Eu(10)-O(10)#1=180.0(2)°]. The Eu-N distances of the
two isomeric forms of 4 are similar, covering the range of
˚
˚
those of the cisoid form (2.527(4) and 2.570(4) A). The
N-C-N bite angles of the L ligands in 4 are acute, falling
within the range of 50.9(1) to 52.4(1)°.
The Yb(II) bis(amidinate) 5 is present as a mono-THF
adduct. The molecular structure of 5 is illustrated in Fig-
ure 6, with selected bond distances and angles provided in
Supporting Information, Table S5. The complex has a five-
coordinate ligand environment, which consists of four
amidinato nitrogen atoms from a pair of κ2-bound L ligands
and one oxygen atom of a coordinated THF molecule. It is
believed that the smaller ionic radius of Yb2+ in 5 (as
compared with those of Sm2+ and Eu2+ in 3 and 4,
respectively) can allow the coordination of only one THF
˚
ligand. The Yb-N distances of 2.399(3)-2.453(4) A in 5are
marginally shorter than the corresponding distances in the
six-coordinate [Yb{PhC(NSiMe3)2}2(THF)2] (2.468(2) and
13
2.478(2) A). However, they are comparable to those
˚
˚
2.526(4)-2.768(4) A. They are comparable to the corre-
˚
sponding distances of 2.525(2)-2.563(2) A reported for
the related Eu(II) bis(guanidinate) complex [Eu{(2,6-
Pri2C6H3N)2C(NCy2)}2].23 Similar Eu(II)-N distances
were also reported for the Eu(II) diamide [Eu{N(Si-
(24) (a) Tilley, T. D.; Zalkin, A.; Andersen, R. A.; Templeton, D. H.
Inorg. Chem. 1981, 20, 551–554. (b) Tilley, T. D.; Andersen, R. A.; Zalkin, A.
Inorg. Chem. 1984, 23, 2271–2276.

9940 Inorganic Chemistry, Vol. 48, No. 20, 2009
Yao et al.
˚
(2.378(2)-2.430(2) A) reported for the mononuclear Yb(II)
bis(guanidinate) [Yb{(2,6-Pri2C6H3N)2C(NCy2)}2], and
˚
2.373(3) and 2.426(3) A for the binuclear [Yb{(2,6-
Pri2C6H3N)2C(NCy2)}(THF)(μ-I)]2.23
Reduction Chemistry of Complexes 3-5. Divalent
lanthanide complexes are strong reducing agents. The re-
duction potentials of the Eu3+/Eu2+, Yb3+/Yb2+, and
Sm3+/Sm2+ couples were reported to be -0.35, -1.15,
and -1.55 V (versus NHE), respectively.25 Their reducing
properties have been well documented,26,27 particularly the
use of SmI2 as a coupling or reducing agent in synthetic
chemistry.28 Early work on the redox chemistry of
organolanthanide(II) compounds was focused on divalent
metallocene complexes. Evans and co-workers have stu-
died the redox chemistry of samarocene complexes in
detail.27,29 Recently, the reduction of N,N0-dicyclohexyl-
carbodiimide by [Sm(MeC5H4)2(THF)] has also been
reported.30 Andersen and co-workers31 have studied the
reduction of dichalcogenides by divalent ytterbocene com-
plexes. Beside cyclopentadienyl complexes, there were also
a few reports on the reduction chemistry of organol-
anthanide(II) complexes supported by non-cyclopentadie-
nyl ligands. Edelmann and co-workers13 have studied the
reactivity of [Yb{RC6H4C(NSiMe3) 2}2(THF)2] (R = H,
OMe) toward reduction of diaryl dichalcogenides. The
reduction of carbodiimides by Sm(II) amido complexes
of the [N(SiMe3)2]- ligand has been examined by Junk and
co-workers as well.32 In the present work, we have exam-
ined the reduction chemistry of complexes 3- 5 toward
diphenyl dichalcogenides PhEEPh (E = Se, Te), iodine
and N,N0-dicyclohexylcarbodiimide.
Figure 7. Molecular structure of [EuL2(μ-SePh)]2 (7) (30% thermal
ellipsoids) with atom labeling. The [PhC(NSiMe3)(NC6H3Pri2-2,6)]- (L)
ligand is 2-fold disordered and only one of the two possible orientations is
shown for clarity.
is coordinated by two κ2-bound benzamidinate ligands
and two bridging phenylselenolate ligands. The coordi-
nation geometry around the Eu(III) center can be de-
scribed as distorted octahedral. The L ligands bind to the
Eu atom in a slightly unsymmetrical manner, as revealed
by the slightly different Eu(1)-N(1) and Eu(1)-N(2)
˚
˚
bond distances of 2.362(5) A and 2.442(5) A, respectively.
Thismaybeascribedtoa differenceinthe sizeof the C6H 3-
Pri2-2,6 and SiMe3 substituents attached to N(1) and
N(2), respectively. The observed Eu(1)-Se(1) bond length
˚
in 7 is 3.0813(6) A.
On the other hand, treatment of [YbL2(THF)] (5) with
PhSeSePh under a similar reaction condition yielded the
mononuclear [YbL2(SePh)(THF)] (8) (Scheme 3). The
molecular structure of 8 is shown in Figure 8, with selected
bond distances and angles listed in Supporting Informa-
tion, Table S7. The Yb(III) center in 8 exhibits hexacoor-
dinate geometry surrounded by two chelating L ligands,
one terminal PhSe- ligand and one THF molecule. The
difference in the molecular structures of 7 and 8 (binuclear
versus mononuclear) may be attributed to a smaller ionic
1. Reactions of Complexes 3-5 with PhEEPh (E = Se,
Te). Treatment of two molar equivalents of [SmL2-
(THF)2] (3) with PhSeSePh in hexane resulted in a
gradual color change of the reaction mixture from deep
greenish blue to yellow, from which Sm(III) benzamidi-
nate-selenolate complex 6 was isolated as yellow crystals.
The Eu(II) bis(amidinate) 4 reacted smoothly with PhSe-
SePh under similar reaction condition yielding the dark
red, crystalline Eu(III) derivative 7 (Scheme 3). Results of
elemental analyses were in good agreement with the
formulation of 6 and 7 as shown in Scheme 3. The mole-
cular structure of complex 7 was determined by X-ray
diffraction.33 As depicted in Figure 7, complex 7 crystal-
lizes as a dimer with a planar Eu2Se2 core. The complex
conforms closely to C2h symmetry with a crystallographic
2-fold axis passing through both Eu atoms. Each Eu atom
3+
34
radius of Yb3+ (0.868 A) than that of Eu (0.947 A).
˚
˚
The L ligands also coordinate in a slightly unsymmetrical
fashion to the Yb(II) center in 8: the observed Yb-N-
i
˚
(C6H3Pr 2-2,6) bond lengths are 2.385(4) A [Yb(1)-N(1)]
˚
and 2.406(4) A [Yb(1)-N(3)], whereas the corresponding
˚
Yb-N(SiMe3) distances are 2.313(4) A [Yb(1)-N(2)] and
˚
2.277(4) A [Yb(1)-N(4)]. The Yb-N distances in 8 are
˚
comparable to those of 2.265(7)-2.366(7) A reported
(25) Morss, L. R. Chem. Rev. 1976, 76, 827-842 and references therein.
(26) Bochkarev, M. N. Coord. Chem. Rev. 2004, 248, 835–851.
(27) (a) Evans, W. J. Coord. Chem. Rev. 2000, 206-207, 263–283.
(b) Evans, W. J. J. Organomet. Chem. 2002, 647, 2–11. (c) Evans, W. J.
J. Organomet. Chem. 2002, 652, 61–68.
(28) Namy, J. L.; Girard, P.; Kagan, H. B. Nouv. J. Chim. 1977, 1, 5–7.
(29) Evans, W. J.; Keyer, R. A.; Ziller, J. W. J. Organomet. Chem. 1990,
394, 87-97 and references therein.
(30) Deng, M.; Yao, Y.; Zhang, Y.; Shen, Q. Chem. Commun. 2004, 2742–
2743.
(31) Berg, D. J.; Andersen, R. A.; Zalkin, A. Organometallics 1988, 7,
1858–1863.
(32) Deacon, G. B.; Forsyth, C. M.; Junk, P. C.; Wang, J. Inorg. Chem.
2007, 46, 10022–10030.
for the related [Yb{PhC(NSiMe3)2}(SePh)(THF)].13
The observed Yb(1)-Se(1) distance in complex 8 is
2.7604(7) A, which is slightly shorter than the correspond-
˚
13
˚
ing distance of 2.805(1) A in the latter complex.
The successful isolation of complexes 7 and 8 prompted
us to extend our studies on the reactivity of 3-5 toward
the heavier diphenyl ditelluride. Addition of PhTeTePh
to [SmL2(THF)2] (3) in toluene resulted in a color change
of the solution from deep greenish blue to orange. Work-
up of the resultant solution yielded the Sm(III) benzami-
dinate-tellurate complex [SmL2(μ-TePh)]2 (9) as orange
crystals. Attempts to prepare the analogous Eu(III) and
(33) Unfortunately, attempts to obtain X-ray quality crystals of the
Sm(III) derivative 6 were unsuccessful. On the basis of results of elemental
3þ
analysis and the fact that Sm3þ (0.958 A) and Eu (0.947 A) have similar
ionic radii, it is expected that complex 6 may have a similar molecular
structure as that of the Eu(III) counterpart 7.
˚
˚
(34) Shannon, R. D. Acta Crystallogr. 1976, A32, 751–767.

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9941
Scheme 3. Synthesis of Complexes 6-9
Figure 9. Molecular structure of [SmL2(μ-TePh)]2 C7H8 (9 C7H8)
3
3
Figure 8. Molecular structure of [YbL2(SePh)(THF)] (8) (30% thermal
ellipsoids) with atom labeling.
(30% thermal ellipsoids) withatomlabeling. The toluene solvatemolecule
is omitted for clarity.
˚
of 2.367(5)-2.453(5) A, and the Sm-Te distances are
Yb(III) tellurate complexes by reacting 4 and 5, respec-
tively, with PhTeTePh were unsuccessful, as only an
intractable oil was obtained. Figure 9 shows the solid-
˚
3.2463(6)-3.3360(6) A. The Sm-Te distances are com-
parable to corresponding distances of 3.2627(4) A in
˚
dimeric [(C5Me5)2Sm(μ-TePh)]2,35 but slightly longer
state structure of the solvated complex 9 C7H8, and
3
˚
than the terminal Sm-Te bond length of 3.1279(3) A in
selected bond distances and angles are listed in Support-
ing Information, Table S8. Complex 9 conforms closely
to D2 symmetry with a planar [Sm2Te2] core. Each Sm
atom exhibits hexacoordinate geometry, with its coordi-
nation sphere consisting of two chelating L ligands and
two bridging PhTe- anions. In fact, the coordination
geometry around each Sm atom in 9 is similar to that
observed in the Eu(II) selenolate counterpart [EuL2(μ-
SePh)]2 (7). The Sm-N distances in 9 fall within the range
monomeric [(C5Me5)2Sm(TePh)(THF)].35
2. Reaction of Complex 5 with Iodine. Direct reaction
of [YbL2(THF)] (5) with iodine resulted in formation
of the mononuclear Yb(III) bis(amidinate) iodide com-
plex [YbL2(I)(THF)] (10), which was isolated as yellow
(35) Evans, W. J.; Miller, K. A.; Lee, D. S.; Ziller, J. W. Inorg. Chem.
2005, 44, 4326–4332.

9942 Inorganic Chemistry, Vol. 48, No. 20, 2009
Scheme 4. Synthesis of Complex 10
Yao et al.
a color change of the reaction mixture from deep greenish
blue to yellow, indicative of the oxidation of Sm(II) to
Sm(III) (Scheme 5). Workup of the resulting solution
yielded the mononuclear, mixed-ligand tris(amidinate)
[SmL2{CyNC(H)NCy}] (11) as the only isolable product
in moderate yield.
Crystals of complex 11 suitable for X-ray diffraction
were obtained from hexane. The solid-state structure of
11 is depicted in Figure 11, with selected bond distances
and angles provided in Supporting Information, Table
S10. The Sm atom is coordinated by two benzamidinate L
ligands and one formamidinate anion [CyNC(H)NCy]-,
all of which being bound in a κ2-fashion. The coordina-
tion geometry around the Sm atom can be described as
highly distorted octahedral. Unsymmetrical binding of
the L ligands to the Sm atom is revealed by the different
Figure 10. Molecular structure of [YbL2(I)(THF)] (10) (30% thermal
ellipsoids) with atom labeling.
˚
Sm(1)-N(1) and Sm(1)-N(2) distances of 2.517(2) A and
˚
2.398(2) A, respectively. The Sm-N(formamidinate)
crystals in 68% yield (Scheme 4). Attempts to prepare the
analogous Sm(III) and Eu(III) derivatives by reacting 3
and 4 with iodine under a similar reaction condition were
unsuccessful, yielding only an intractable oil. The mole-
cular structure of 10 is illustrated in Figure 10, with
selected bond lengths and angles provided in Supporting
Information, Table S9. The Yb(III) center in 10 exhibits
six-coordinate geometry with the Yb-N distances
˚
distance [Sm(1)-N(3)] is 2.394(2) A, which is similar to
that of Sm(1)-N(2) but slightly shorter than the corres-
ponding distances reported for the homoleptic Sm(III)
formamidinate [Sm{HC(NC6H3Pri2-2,6)2}3] (2.448(6)-
2.467(6) A).14 The N-C-N bite angles of the amidinate
˚
ligands in 11 are acute, falling within the range of 54.82-
(8)-56.6(1)°.
Carbodiimides are important substrates for metal-
based reactivity studies. Reactions of carbodiimides with
organosamarium(II) complexes have been reported. Re-
duction of RNdCdNR (R = Cy, Pri) by the divalent
samarocene [Sm(MeC5H4)2(THF)] led to the coupled
oxalamidinate products [{(MeC5H4)2Sm(HMPA)}2(μ-
C2N4R4)].30 More interestingly, reactions of RNdCd
NR (R = Cy, C6H3Pri2-2,6) with the non-metallocene
complexes [Sm{N(SiMe3)2}2(THF)2] and [NaSm{N(Si-
Me3)2}3] gave unexpected results.32 Direct reactions of
[Sm{N(SiMe3)2}2(THF)2] and [NaSm{N(SiMe3)2}3] with
CyNdCdNCy afforded the binuclear Sm(III) oxalami-
dinate [{Sm[N(SiMe3)2]2}2(μ-C2N4Cy4)]. An analogous
reaction of [Sm{N(SiMe3)2}2(THF)2] with the more
bulky (2,6-Pri2C6H3)NdCdN(C6H3Pri2-2,6) led to an
unusual binuclear complex, in which a C-C coupling of
two isopropyl methine carbon atoms was observed. A
similar reaction of [NaSm{N(SiMe3)2}3] with (2,6-Pri2-
C6H3)NdCdN(C6H3Pri2-2,6) resulted in a γ C-H acti-
˚
falling within the range of 2.290(3)-2.367(3) A, which
˚
are comparable to those of 2.277(4)-2.406(4) A found
in the selenolate counterpart [YbL2(SePh)(THF)] (8).
Similar Yb(III)-N distances were also reported for
the Yb(III) benzamidinate complex [Yb{PhC(NCy)2}3]
36
˚
(2.321(5)-2.333(5) A),
and the guanidinate com-
plex [Yb{(Me3Si)2NC(NCy)2}2{N(SiMe3)2}] (2.30(1)-
2.33(1) A). Comparison of the structural parameters
37
˚
of complexes 8 and 10 revealed the different steric proper-
ties of the PhSe- and I- ligands in these two complexes.
It is noteworthy that the C(13)-Yb(1)-C(35) angle of
134.7(1)° formed by the two L ligands in 10 is similar
to corresponding angle of 134.0(1)° in 8. On the other
hand, the O(1)-Yb(1)-I(1) angle of 85.66(7)° in 10 is
much smaller than the O(1)-Yb(1)-Se(1) angle of
101.7(1)° in 8.
3. Reaction of Complex 3 with N,N0-dicyclohexylcar-
bodiimide. Addition of N,N0-dicyclohexylcarbodiimide
(DCC) to an equimolar amount of 3 in THF resulted in
-
vation of a N(SiMe3)2 ligand to give a C-substituted
amidinate complex.
(36) Luo, Y.; Yao, Y.; Shen, Q.; Sun, J.; Weng, L. J. Organomet. Chem.
2002, 662, 144–149.
(37) Zhou, Y.; Yap, G. P. A.; Richeson, D. S. Organometallics 1998, 17,
4387–4391.
In our hands, the reduction of CyNdCdNCy by 3
afforded the mononuclear, mixed-ligand [SmL2{CyN-
C(H)NCy}] (11) as the only isolable product. It is believed

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9943
Scheme 5. Synthesis of Complex 11
(toluene) or calcium hydride (hexane), and degassed twice by
freeze-thaw cycles prior to use. LnI2(THF)2 (Ln = Sm, Eu, Yb)
were synthesized according to published procedures.38 The
lithium anilide [Li{N(SiMe3)(C6H3Pri2-2,6)}(TMEDA)] was
prepared as described previously.17 Benzonitrile was distilled
over calcium hydride before use. All other reagents were used as
received. Melting-points were recorded on an Electrothermal
melting-point apparatus and were uncorrected. 1H and 13C
NMR spectra were recorded on a Bruker DPX300 NMR
1
spectrometer (at 300.13 MHz for H and 75.47 MHz for 13C
NMR), or a Bruker Advance III 400 NMR spectrometer (at
400.13 MHz for 1H NMR). Elemental analyses (C, H, N) were
performed by MEDAC Ltd., Brunel University, U.K.
Synthesis of [Li{PhC(NSiMe3)(NC6H3Pri2-2,6)}(TMEDA)]
(1). To a yellow solution of [Li{N(SiMe3)(C6H3Pri2-2,6)}(TM-
EDA)] (5.86 g, 15.8 mmol) in diethyl ether (40 mL) at 0 °C was
slowly added C6H5CN (1.6 mL, 15.8 mmol) via a syringe. The
reaction mixture was stirred at room temperature for 12 h, and
concentrated under reduced pressure to about 20 mL to yield 1 as
colorless crystals. Yield: 6.89 g, 14.6 mmol, 92%. Mp 155-158 °C.
1H NMR (300.13 MHz, C6D6): δ 7.32-7.29 (m, 2H, ArH), 7.05 (t,
J = 1.5 Hz, 1H, ArH), 7.03 (s, 2H, C6H5), 7.01-6.98 (m, 1H,
C6H5), 6.96-6.89 (m, 2H, C6H5), 3.61 (septet, J = 6.9 Hz, 2H,
CHMe2), 2.06 (s, 12H, NMe2), 1.83(s, 4H, NCH2), 1.25(d, J=6.9
Hz, 6H, CHMe2), 1.22 (d, J = 6.9 Hz, 6H, CHMe2), 0.14 (s, 9H,
SiMe3). 13C NMR (75.47 MHz, C6D6):δ173.9, 148.3, 143.4, 141.5,
128.0, 127.2, 126.6, 122.8, 122.0, 56.7, 45.8, 28.1, 26.0, 23.5, 4.14.
Anal. Calcd for C28H47N4SiLi: C, 70.84; H, 9.98; N, 11.80%.
Found: C, 70.90; H, 10.13; N, 11.77%.
Figure 11. Molecular structure of [SmL2{CyNC(H)NCy}] (11) (30%
thermal ellipsoids) with atom labeling.
that the present reaction may involve a one-electron
reduction of CyNdCdNCy by Sm(II) which generates
the corresponding “C(NCy)2•-” radical anionic species.
Apparently, the latter species undergoes subsequent hy-
drogen abstraction from the reaction solvent (THF) and/
or the coordinated THF molecules in 3 to give complex
11. In a further investigation, the reaction of 3 with DCC
was repeated with toluene as the reaction solvent. In the
latter case, complex 11 was still obtained as the only
isolable product. Conceivably, the coordinated THF
molecules in 3 may also provide a source of the hydride
yielding complex 11, even though the reaction was carried
out in a solvent other than THF.
Synthesis of [K{PhC(NSiMe3)(NC6H3Pri2-2,6)}]n (2). To a
stirring suspension of KOBut (1.52 g, 13.6 mmol) in diethyl ether
(10 mL) was slowly added a solution of 1 (6.42 g, 13.5 mmol) in
the same solvent (30 mL) at room temperature. The reaction
mixture was stirred under ambient conditions for 12 h, where-
upon a white solid precipitated out. The precipitate was col-
lected and redissolved in THF. The resulting solution was
filtered and concentrated under reduced pressure to about 20
mL to give 2 as colorless crystals. Yield: 3.95 g, 10.1 mmol, 75%.
Summary
Utilization of the bulky unsymmetrical benzamidinate
ligand [PhC(NSiMe3)(NC6H3Pri2-2,6)]- (L) has led to the
synthesis of neutral, mononuclear lanthanide(II) bis(amidi-
nate) complexes [LnL2(THF)x] [Ln=Sm, x=2 (3); Ln=
Eu, x=2, (4); Ln= Yb, x=1 (5)]. Complexes 3-5 act as one-
electron reductants, which react readily with diphenyl dichal-
cogenides, iodine and N,N0-dicyclohexylcarbodiimide to give
the corresponding lanthanide(III) chalcogenides (6 - 9),
iodide (10), and a mixed-ligand tris(amidinate) complex
(11), respectively.
1
Mp 90-93 °C. H NMR (300.13 MHz, THF-d8): δ 7.26 (br,
2H, ArH), 7.09 (t, J = 6.9 Hz, 2H, C6H5), 7.01, (t, J = 6.9 Hz,
1H, C6H5), 6.96-6.90 (m, 2H, C6H5), 6.68 (br, 1H, ArH), 3.49
(septet, J = 6.9 Hz, 2H, CHMe2), 1.17 (d, J = 6.9 Hz, 6H,
CHMe2), 1.10 (d, J = 6.9 Hz, 6H, CHMe2), -0.36 (s, 9H,
SiMe3). 13C NMR (75.47 MHz, THF-d8): δ 168.2, 142.5, 141.7,
128.5, 128.1, 127.5, 125.8, 122.6, 119.5, 28.8, 24.3, 23.5, 3.76.
Anal. Calcd for C22H31N2SiK: C, 67.64; H, 8.00; N, 7.17%.
Found: C, 67.00; H, 8.26; N, 6.80%.
Synthesis of [Sm{PhC(NSiMe3)(NC6H3Pri2-2,6)}2(THF)2]
(3). A solution of 2 (1.64 g, 4.2 mmol) in THF (30 mL) was
added dropwise to a deep blue solution of SmI2(THF)2 (1.19 g,
2.2 mmol) in THF (20 mL) at room temperature. The resulting
Experimental Section
General Methods. All manipulations were carried out under a
purified nitrogen atmosphere using modified Schlenk techni-
ques. Solvents were dried over and distilled from sodium
benzophenone (diethyl ether and tetrahydrofuran), Na/K alloy
(38) Watson, P. L.; Tulip, T. H.; Williams, I. Organometallics 1990, 9,
1999–2009.

9944 Inorganic Chemistry, Vol. 48, No. 20, 2009
Yao et al.
Table 1. Selected Crystallographic Dataa for Complexes 1-4
1
2
3
4
molecular formula
molecular weight
crystal size, mm3
crystal system
C
474.73
28H47LiN4Si
C44H62K2N4Si2
731.36
0.30 ꢁ 0.20 ꢁ 0.10
orthorhombic
Pbca
18.520(2)
20.284(3)
25.347(3)
90
90
90
8
9522(2)
1.090
0.281
293(2)
49739
8386 (Rint = 0.2482)
2770
C52H78N4O2Si2Sm
997.71
0.40 ꢁ 0.30 ꢁ 0.20
monoclinic
Cc
26.150(4)
25.969(4)
32.829(5)
90
95.941(4)
90
16
22175(6)
1.195
1.141
293(2)
59373
28036 (Rint = 0.0876)
16280
R1 = 0.0566
wR2 = 0.1105
R1 = 0.1263
wR2 = 0.1468
C52H78N4O2Si2Eu
999.33
0.40 ꢁ 0.30 ꢁ 0.20
monoclinic
P21/c
11.3897(11)
20.474(2)
35.475(3)
90
98.248(2)
90
0.40 ꢁ 0.40 ꢁ 0.30
triclinic
P1
space group
˚
a, A
9.6479(3)
10.5509(3)
15.3111(5)
92.0060(10)
90.0550(10)
97.8830(10)
2
1542.88(8)
1.022
0.096
293(2)
21808
7271 (Rint = 0.0298)
4374
R1 = 0.0534
wR2 = 0.1357
R1 = 0.0993
wR2 = 0.1588
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
Z
6
3
˚
V, A
8186.9(14)
1.216
1.232
293(2)
55492
19706 (Rint = 0.0770)
8847
R1 = 0.0502
wR2 = 0.1077
R1 = 0.1499
wR2 = 0.1523
density, g cm-3
abs coeff., mm-1
temperature, K
reflections collected
independent reflections
obs. data with I g 2σ(I)
final R indices [I g 2σ(I)]b
R1 = 0.0967
wR2 = 0.2103
R1 = 0.2676
wR2 = 0.3681
R indices (all data)b
a Data collected on a Bruker SMART CCD diffractometer or a Bruker KAPPA APEX II diffractometer with graphite-monochromatized Mo KR
P
P
P
P
radiation (λ = 0.71073 A) using ω scan. b R1 = ||Fo| - |Fc||/ |Fo|; wR2 = { w(Fo2 - Fc2)2/ w(Fo2)2}1/2
.
˚
Table 2. Selected Crystallographic Dataa for Complexes 5, 7, and 8
5
7
8
molecular formula
molecular weight
crystal size, mm3
crystal system
C
948.30
48H70N4OSi2Yb
C100H134N8Se2Si4Eu2
2022.35
0.50 ꢁ 0.40 ꢁ 0.30
orthorhombic
Cmca
32.583(6)
18.221(3)
18.365(3)
90
90
90
C54H75N4OSeSi2Yb
1104.36
0.50 ꢁ 0.40 ꢁ 0.30
0.40 ꢁ 0.30 ꢁ 0.20
triclinic
P1
triclinic
P1
Space group
˚
a, A
11.5584(14)
13.1786(16)
17.986(2)
87.540(2)
78.050(2)
72.646(2)
2
2557.8(5)
1.231
1.910
293(2)
13866
8980 (Rint = 0.0255)
7336
R1 = 0.0347
wR2 = 0.0811
R1 = 0.0494
wR2 = 0.0953
10.404(2)
11.636(2)
25.142(5)
85.181(3)
86.664(3)
64.703(3)
2
2741.2(9)
1.338
2.452
293(2)
14837
9599 (Rint = 0.0338)
8206
R1 = 0.0389
wR2 = 0.0933
R1 = 0.0492
wR2 = 0.1040
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
Z
4
3
˚
V, A
10903(3)
1.232
1.895
173(2)
27305
4893 (Rint = 0.0528)
3393
R1 = 0.0468
wR2 = 0.1389
R1 = 0.0663
wR2 = 0.1541
density, g cm-3
abs coeff., mm-1
temperature, K
reflections collected
independent reflections
obs. data with I g 2σ(I)
final R indices [I g 2σ(I)]b
R indices (all data)b
a Data collected on a Bruker SMART CCD diffractometer or a Bruker KAPPA APEX II diffractometer with graphite-monochromatized Mo KR
P
P
P
P
radiation (λ = 0.71073 A) using ω scan. b R1 = ||Fo| - |Fc||/ |Fo|; wR2 = { w(Fo2 - Fc2)2/ w(Fo2)2}1/2
.
˚
deep green reaction mixture was stirred for 12 h, after which all
the volatiles were removed in vacuo. The residue was extracted
with hexane (40 mL). Filtration and concentration of the
solution to about 5 mL, followed by standing the solution at
room temperature for 1 day yielded complex 3 as deep greenish
blue crystals. Yield: 1.05 g, 1.05 mmol, 48%. Mp 164-167 °C
(dec.). Anal. Calcd for C52H78N4O2Si2Sm: C, 62.60; H, 7.88; N,
5.61%. Found: C, 62.28; H, 7.88; N, 6.08%.
C52H78N4O2Si2Eu: C, 62.50; H, 7.87; N, 5.60%. Found: C,
62.32; H, 8.09; N, 5.87%.
Synthesis of [Yb{PhC(NSiMe3)(NC6H3Pri2-2,6)}2(THF)] (5).
Complex 5 was prepared by a procedure similar to that of 3.
Treatment of YbI2(THF)2 (1.16 g, 2.0 mmol) in THF (20 mL)
with a solution of 2 (1.52 g, 3.9 mmol) in the same solvent (30
mL) afforded the title compound as dark red crystals. Yield:
1.03 g, 1.09 mmol, 56%. Mp 193-196 °C (dec.). 1H NMR
(400.13 MHz, C6D6): δ 7.25 (d, J = 7.2 Hz, 4H, ArH), 7.02 (d,
J = 7.2 Hz, 4H, C6H5), 6.97 (t, J = 7.2 Hz, 6H, C6H5), 6.85 (t,
J = 7.2 Hz, 2H, ArH), 3.77 (br, 4H, CHMe2), 3.60 (br, 4H,
THF), 1.40-1.27 (2d, J = 6.0 Hz, 28H, CHMe2 and THF),
-0.01 (s, 18H, SiMe3). 13C NMR (75.47 MHz, C6D6): δ 174.9,
Synthesis of [Eu{PhC(NSiMe3)(NC6H3Pri2-2,6)}2(THF)2]
(4). Complex 4 was synthesized by a procedure similar to that
of 3. Reaction of EuI2(THF)2 (1.06 g, 1.9 mmol) with 2 (1.44 g,
3.7 mmol) in THF (30 mL) gave 4 as orange crystals. Yield: 0.78
g, 0.77 mmol, 41%. Mp 188-191 °C (dec.). Anal. Calcd for

Article
Inorganic Chemistry, Vol. 48, No. 20, 2009 9945
Table 3. Selected Crystallographic Dataa for Complexes 9 C7H8, 10, and 11
3
9 C7H8
3
10
11
molecular formula
molecular weight
crystal size, mm3
crystal system
C107H142N8Te2Si4Sm2
2208.55
C48H70IN4OSi2Yb
1075.20
0.40 ꢁ 0.30 ꢁ 0.20
monoclinic
P21/c
14.241(2)
14.095(2)
25.946(4)
90
95.391(2)
90
C57H85N6Si2Sm
1060.84
0.40 ꢁ 0.30 ꢁ 0.20
monoclinic
C2/c
14.513(3)
18.376(3)
22.516(4)
90
102.796(3)
90
0.40 ꢁ 0.30 ꢁ 0.20
triclinic
P1
Space group
˚
a, A
13.7791(17)
19.970(2)
22.393(3)
114.055(2)
103.082(2)
92.451(2)
2
5417(1)
1.354
1.692
293(2)
29381
18944 (Rint = 0.0334)
13719
R1 = 0.0592
wR2 = 0.1690
R1 = 0.0830
wR2 = 0.1832
˚
b, A
˚
c, A
R, deg
β, deg
γ, deg
Z
4
4
3
˚
V, A
5185.1(13)
1.377
2.481
293(2)
27640
9125 (Rint = 0.0452)
7315
R1 = 0.0315
wR2 = 0.0750
R1 = 0.0466
wR2 = 0.0840
5855.7(18)
1.203
1.082
293(2)
19827
7111 (Rint = 0.0461)
5892
R1 = 0.0377
wR2 = 0.0909
R1 = 0.0520
wR2 = 0.0993
density, g cm-3
abs coeff., mm-1
temperature, K
reflections collected
independent reflections
obs. data with I g 2σ(I)
final R indices [I g 2σ(I)]b
R indices (all data)b
a Data collected on a Bruker SMART CCD diffractometer or a Bruker KAPPA APEX II diffractometer with graphite-monochromatized Mo KR
P
P
P
P
radiation (λ = 0.71073 A) using ω scan. b R1 = ||Fo| - |Fc||/ |Fo|; wR2 = { w(Fo2 - Fc2)2/ w(Fo2)2}1/2
.
˚
145.6, 141.7, 141.2, 127.6, 127.4, 127.1, 123.6, 122.9, 69.2, 28.6,
25.9, 25.4, 22.9, 3.03. Anal. Calcd for C48H70N4OSi2Yb: C,
60.79; H, 7.44; N, 5.91%. Found: C, 60.51; H, 7.76; N, 6.19%.
was slowly added a solution of iodine (0.26 g, 1.0 mmol) in Et2O
(20 mL) at room temperature. The resulting solution was stirred
at room temperature for 8 h, whereupon its color changed from
dark red to orange red and finally to yellow. All the volatiles
were removed in vacuo, and the residue was extracted with
hexane (40 mL). Filtration and concentration of the solution to
about 10 mL yielded 10 as yellow crystals. X-ray quality crystals
of 10 were obtained by recrystallization from a hexane/toluene
solvent mixture. Yield: 1.46 g, 1.36 mmol, 68%. Mp 233-
236 °C. Anal. Calcd for C48H70N4IOSi2Yb: C, 53.62; H, 6.56;
N, 5.21%. Found: C, 54.10; H, 7.02; N, 5.48%.
Synthesis of [Sm{PhC(NSiMe3)(NC6H3Pri2-2,6)}2(μ-SePh)]2
(6). A solution of PhSeSePh (0.298 g, 0.96 mmol) in hexane (25
mL) was slowly added to a solution of 3 (1.92 g, 1.92 mmol) in
the same solvent (35 mL) at room temperature. The reaction
mixture turned gradually from deep greenish blue to yellow.
Stirring was continued for 8 h at room temperature. The
solution was filtered and concentrated to about 10 mL to give
6 as yellow crystals. Yield: 0.93 g, 0.46 mmol, 48%. Mp 156-
159 °C. Anal. Calcd for C100H134N8Se2Si4Sm2: C, 59.48; H,
6.69; N, 5.55%. Found: C, 59.66; H, 6.92; N, 5.53%.
Synthesis of [Eu{PhC(NSiMe3)(NC6H3Pri2-2,6)}2(μ-SePh)]2
(7). Complex 7 was prepared by a procedure similar to that of 6.
A solution of PhSeSePh (0.38 g, 1.2 mmol) in hexane (35 mL)
was slowly added to a solution of 4 (2.42 g, 2.4 mmol) in the same
solvent (25 mL). The reaction mixture turned gradually from
orange to dark red, from which complex 7 was isolated as dark
red crystals. Yield: 1.31 g, 0.65 mmol, 54%. Mp 128-131 °C
(dec.). Anal. Calcd for C100H134N8Se2Si4Eu2: C, 59.39; H, 6.68;
N, 5.54%. Found: C, 59.55; H, 7.02; N, 5.32%.
Synthesis of [Sm{PhC(NSiMe3)(NC6H3Pri2-2,6)}2{HC-
(NCy)2}] (11). To a solution of 3 (1.21 g, 1.2 mmol) in THF
(30 mL) was slowly added a solution of N,N0-dicyclohexylcar-
bodiimide (1.8 M, 0.8 mL, 1.4 mmol) in Et2O (20 mL). The
resulting solution turned from deep greenish blue to yellow.
After stirring at room temperature for 8 h, the solution was
pumped to dryness and the residue was extracted with hexane
(40 mL). Filtration and concentration of the solution to about
5 mL afforded the title compound as pale yellow crystals. Yield:
0.53 g, 0.50 mmol, 42%. Mp 215-218 °C. Anal. Calcd for
C57H85N6Si2Sm: C, 64.53; H, 8.08; N, 7.92%. Found: C, 64.47;
H, 8.29; N, 7.82%.
Synthesis of [Yb{PhC(NSiMe3)(NC6H3Pri2-2,6)}2(SePh)-
(THF)] (8). Complex 8 was synthesized by a procedure similar
to that of 6. Treatment of 5 (2.44 g, 2.2 mmol) with PhSeSePh
(0.34 g, 1.1 mmol) in hexane yielded 8 as orange crystals. Yield:
1.62 g, 1.47 mmol, 67%. Mp 180-183 °C. Anal. Calcd for
C54H75N4OSi2SeYb: C, 58.73; H, 6.84; N, 5.07%. Found: C,
59.02; H, 6.99; N, 5.28%.
X-ray Crystallographic Analysis. Single crystals of com-
pounds 1-5, 7, 8, 9 C7H8, 10, and 11 suitable for X-ray
diffraction studies were mounted in glass capillaries and sealed
under nitrogen. Data were collected on a Bruker SMART CCD
diffractometer or a Bruker KAPPA APEX II diffractome-
ter with graphite-monochromatized Mo-KR radiation (λ =
0.71073 A) at 293 K (for 1-5, 8, 9 C7H8, 10, and 11) and 173
K (for 7). An empirical absorption correction was applied using
the SADABS program.39 The structures were solved by direct
phase determination using the computer program SHELX-97
and refined by full-matrix least-squares with anisotropic ther-
mal parameters for the non-hydrogen atoms.40 Hydrogen atoms
3
˚
Synthesis of [Sm{PhC(NSiMe3)(NC6H3Pri2-2,6)}2(μ-TePh)]2
C7H8 (9 C7H8). A solution of PhTeTePh (0.37 g, 0.9 mmol) in
3
3
3
toluene (25 mL) was added dropwise to a solution of 3 (1.79 g,
1.8 mmol) in the same solvent (30 mL) at room temperature. The
reaction mixture was stirred for 8 h whereupon its color changed
from deep greenish blue to orange. The solution was filtered and
concentrated to about 10 mL to yield the title compound as
orange crystals. Yield: 0.90 g, 0.41 mmol, 46%. Mp 145-148 °C.
(39) Sheldrick, G. M. SADABS: Program for Empirical Absorption Cor-
rection of Area Detector Data. University of Gottingen: Gottingen, Germany,
1996.
(40) Sheldrick, G. M.; SHELXTL 5.10 for Windows NT, Structure
Determination Software Programs. Bruker Analytical X-Ray Systems, Inc.:
Madison, WI, 1997.
::
::
Anal. Calcd for C100H134N8Si4Sm2Te2 C7H8: C, 58.19; H, 6.48;
3
N, 5.07%. Found: C, 58.14; H, 6.52; N, 5.03%.
Synthesis of [Yb{PhC(NSiMe3)(NC6H3Pri2-2,6)}2(I)(THF)]
(10). To a solution of 5 (1.91 g, 2.0 mmol) in hexane (20 mL)

9946 Inorganic Chemistry, Vol. 48, No. 20, 2009
Yao et al.
were introduced in their idealized positions and included in
structure factor calculations with assigned isotropic tempera-
ture factors. Details of the data collection and crystallographic
data are given in Tables 1, 2, and 3.
indebted to Professor Thomas C. W. Mak for helpful discus-
sions on the X-ray structural analyses. We thank The Chinese
University of Hong Kong for a postgraduate studentship to S.Y.
Supporting Information Available: Crystallographic informa-
˚
tion files (CIF), and selected bond distances (A) and angles (deg)
Acknowledgment. This work was supported by the Re-
search Grants Council of The Hong Kong Special Adminis-
trative Region, China (Project No. CUHK 401405). We are
of complexes 1-5, 7, 8, 9 C7H8, 10, and 11. This material is
3
available free of charge via the Internet at http://pubs.acs.org.