N-substituted guanidinate anions as ancillary ligands in organolanthanide chemistry. Synthesis and characterization of {CyNC[N(SiMe3)2]NCy}2SmCH(SiMe 3)2

Article abstract of DOI:10.1021/om980480r

Addition of N(SiMe₃)₂ anion equivalents to CyN=C=NCy provided entry to a series of N-substituted guanidinate complexes of Sm(III) and Yb(III) with the general formula M{CyNC[N(SiMe₃)₂]NCy}₂(μ-Cl) ₂Li(S)₂ (M = Sm, Yb; Cy = cyclohexyl; S = Et₂O, 1/2 TMEDA). Substitution of the chloro ligands of these complexes using LiCH(SiMe₃)₂ or LiN(SiMe₃)₂ yields solvent-free, monomeric alkyl and amido compounds, respectively. Definitive evidence for the molecular structures of these products is provided through single-crystal X-ray analysis, and in particular, the results for Sm{CyNC[N(SiMe₃)₂]NCy}₂CH(SiMe ₃)₂ (7) and Yb{CyNC[N(SiMe₃)₂]NCy}₂N(SiMe₃) ₂ (8) are presented. These results provide the first reported example of an organolanthanide complex supported by a guanidinate ligand.

Full text of DOI:10.1021/om980480r

Organometallics 1998, 17, 4387-4391
4387
N-Su bstitu ted Gu a n id in a te An ion s a s An cilla r y Liga n d s
in Or ga n ola n th a n id e Ch em istr y. Syn th esis a n d
Ch a r a cter iza tion of
{CyNC[N(SiMe3)2]NCy}2Sm CH(SiMe3)2
Yuanlin Zhou, Glenn P. A. Yap, and Darrin S. Richeson*
Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5
Received J une 10, 1998
Addition of N(SiMe3)2 anion equivalents to CyNdCdNCy provided entry to a series of
N-substituted guanidinate complexes of Sm(III) and Yb(III) with the general formula
M{CyNC[N(SiMe3)2]NCy}2(µ-Cl)2Li(S)2 (M ) Sm, Yb; Cy ) cyclohexyl; S ) Et2O, 1/2 TMEDA).
Substitution of the chloro ligands of these complexes using LiCH(SiMe3)2 or LiN(SiMe3)2
yields solvent-free, monomeric alkyl and amido compounds, respectively. Definitive evidence
for the molecular structures of these products is provided through single-crystal X-ray
analysis, and in particular, the results for Sm{CyNC[N(SiMe3)2]NCy}2CH(SiMe3)2 (7) and
Yb{CyNC[N(SiMe3)2]NCy}2N(SiMe3)2 (8) are presented. These results provide the first
reported example of an organolanthanide complex supported by a guanidinate ligand.
Organolanthanide chemistry is an area of vigorous
research due largely to the marvelous catalytic abilities
exhibited by many of these species.1-7 The most suc-
cessful ancillary ligands in this field have been deriva-
tives of the cyclopentadienyl anion whose dominant
presence in the organometallic chemistry of the lan-
thanides began with the preparation of the tris(cyclo-
pentadienyl) compounds.8 Among the most versatile
materials for the preparation of catalytically active
species have been complexes with the formula (C5Me5)2-
LnX, where X is hydride or hydrocarbyl.
In an effort to develop alternatives to cyclopentadi-
enyl-based ligands, we were attracted to N-substituted
guanidinate anions, [RNC(NR′2)NR′′]-, as potential
bulky supporting ligands for organolanthanide com-
plexes. These ligands, which have not been previously
used in lanthanide chemistry, fall into a family of
bidentate, three-atom bridging ligands with the general
formula RNXNR- (X ) CNR′2,9 CR′,10 or N11). One
member of this family, N,N′-bis(trimethylsilyl)benz-
amidinate-based ligands [Me3SiNC(C6H5-nRn)NSiMe3]-,
has recently been employed for preparation of inorganic
complexes of the lanthanide elements12-14 and organo-
metallic complexes of yttrium.15 Steric analysis of this
ligand system places it intermediate between the Cp
(1) For general organolanthanide reviews, see: (a) Schumann, H.;
Meese-Marktschffel, J . A.; Esser, L. Chem. Rev. 1995, 95, 865 and
references therein. (b) Edelmann, F. T. In Comprehensive Organome-
tallic Chemistry II; Abel, E. W., Stone, F. G. S., Wilkinson, G., Eds.;
Pergamon Press: Oxford, U.K., 1995; Vol. 4, Chapter 2 and references
therein. (b) Schaverien, C. J . Adv. Organomet. Chem. 1994, 36, 283
and references therein. (c) Evans, W. J . Adv. Organomet. Chem. 1985,
24, 131 and references therein. (d) Kagan, H. B.; Namy, J . L. In
Handbook on the Physics and Chemistry of Rare Earths; Gschneider,
K. A., Eyring, L., Eds.; Elsevier: Amsterdam, 1984; Chapter 50. (e)
Marks, T. J .; Ernst, R. D. In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. S., Abel, E. W., Eds.; Pergamon Press:
Oxford, U.K., 1982; Chapter 21 and references therein.
(2) For examples of catalytic activity of organolanthanides in a
variety of alkene and alkyne transformations including hydrogenation
see: (a) Molander, G. A.; Hoberg, J . O. J . Org. Chem. 1992, 57, 3266.
(b) J eske, G.; Lauke, H.; Mauermann, H.; Schumann, H.; Marks, T. J .
J . Am. Chem. Soc. 1985, 107, 8111. (c) Evans, W. J .; Bloom, I.; Hunter,
W. E.; Atwood, J . L. J . Am. Chem. Soc. 1983, 105, 1401.
(3) For examples of catalytic activity of organolanthanides in
hydroamination see: (a) Li, Y.; Marks, T. J . J . Am. Chem. Soc. 1996,
118, 9295. (b) Li, Y.; Marks, T. J . Organometallics 1996, 15, 3770. (c)
Li, Y.; Marks, T. J . J . Am. Chem. Soc. 1996, 118, 707. (d) Gagne´, M.
R.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc. 1992, 114, 275. (e)
Gagne´, M. R.; Nolan, S. P.; Marks, T. J . Organometallics 1990, 9, 1716.
(f) Gagne´, M. R.; Marks, T. J . J . Am. Chem. Soc. 1989, 111, 4108.
(4) For examples of catalytic activity of organolanthanides in
hydrosilylation see: (a) Fu, P.-F.; Brard, L.; Li, Y.; Marks, T. J . J . Am.
Chem. Soc. 1995, 117, 7157. (b) Molander, G. A.; J ulius, M. J . Org.
Chem. 1992, 57, 6347. (c) Sakakura, T.; Lautenschlager, H.; Tanaka,
M. J . Chem. Soc., Chem. Commun. 1991, 40. (d) Takahashi, T.;
Hasegawa, M.; Suzuki, N.; Saburi, M.; Rousset, C. J .; Fanwick, P. E.;
Negishi, E. J . J . Am. Chem. Soc. 1991, 113, 8564.
(7) For examples of catalytic activity of organolanthanides in
reductive cyclizations see: (a) Molander, G. A.; Nichols, P. J . J . Am.
Chem. Soc. 1995, 117, 4415. (b) Molander, G. A.; Hoberg, J . O. J . Am.
Chem. Soc. 1992, 114, 3123.
(8) Wilkinson, G.; Birmingham, J . M. J . Am. Chem. Soc. 1954, 76,
6210.
(9) Mehrotra, R. C. In Comprehensive Coordination Chemistry;
Wilkinson, G., Gillard, R. D.; McCleverty, J . A., Eds.; Pergamon
Press: Oxford, U.K., 1987; Chapter 13.8.
(10) Kilner, M.; Baker, J . Coord. Chem. Rev. 1994, 133, 219.
(11) Moore, D. S.; Robinson, S. D. Adv. Inorg. Chem. Radiochem.
1986, 30, 1.
(12) (a) Hagen, C.; Reddmann, H.; Amberger, H.-D.; Edelmann, F.
T.; Pegelow, U.; Shalimoff, G. V.; Edelstein, N. M. J . Organomet. Chem.
1993, 462, 69. (b) Wedler, M.; Knosel, F.; Pieper, U.; Stalke, D.;
Edelmann, F. T.; Amberger, H.-D. Chem. Ber. 1992, 125, 2171.
(13) Recknagel, A.; Knosel, F.; Gornitzka, H.; Noltemeyer, M.;
Edelmann, F. T.; Behrens, U. J . Organomet. Chem. 1991, 417, 363.
(14) (a) Wedler, M.; Noltemeyer, M.; Pieper, U.; Schmidt, H.-G.;
Stalke, D.; Edelmann, F. T. Angew. Chem., Int. Ed. Engl. 1990, 29,
894. (b) Wedler, M.; Recknagel, A.; Gilje, J . W.; Noltemeyer, M.;
Edelmann, F. T. J . Organomet. Chem. 1992, 426, 295.
(5) For examples of catalytic activity of organolanthanides in
hydroboration see: (a) Bijpost, E. A.; Duchateau, R.; Teuben, J . H. J .
Mol. Catal. 1995, 95, 121. (b) Harrison, K. N.; Marks, T. J . J . Am.
Chem. Soc. 1992, 114, 9220.
(6) For examples of catalytic activity of organolanthanides in
polymerization see: (a) Heeres, H. J .; Renkema, J .; Booij, M.; Meetsma,
A.; Teuben, J . H. Organometallics 1988, 7, 2495. (b) J eske, G.; Schock,
L. E.; Swepston, P. N.; Schumann, H.; Marks, T. J . J . Am. Chem. Soc.
1985, 107, 8103. (c) Evans, W. J .; DeCoster, P. M.; Greaves, J .
Macromolecules 1995, 28, 7929. (d) Ihara, E.; Nodono, M.; Yasuda, H.;
Kanehisa, N.; Kai, Y. Macromol. Chem. Phys. 1996, 197, 1909. (e) Boff,
L. S.; Novak, B. M. Macromolecules 1997, 30, 3494.
S0276-7333(98)00480-4 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 09/04/1998

4388 Organometallics, Vol. 17, No. 20, 1998
Zhou et al.
Sch em e 1
and Cp* ligands.12,15 Substituted guanidinate ligands
(X ) NR′2, R * H) present an ideal system for exploring
the effects of making rational modifications to both the
steric bulk and electronic properties of the supporting
ligands through changes to the organic substituents on
the nitrogen atoms.
Herein we report the synthesis and characterization
of a novel series of guanidinate complexes of Sm and
Yb including the first reported alkyl and amido lan-
thanide complexes with this family of ancillary ligands.
We also provide a preliminary account of the use of
these ligands in the preparation of Yb(II) complexes.
These efforts complement work with alkylamidinates
ligands and the main group and transition metals.16,17
These paramagnetic compounds represent a novel
class of precursors for soluble organolanthanide species
free of cyclopentadienyl ligands. Furthermore, these
disubstituted complexes are important for the design
of new complexes with potential in catalysis as they
represent potential analogues of the well-known species
(C5Me5)2Ln(µ-Cl)2Li(solvent)2, which are important start-
ing materials for the synthesis of alkyl and hydride
complexes.
The metathesis reaction of 2 and 3 with LiCH(SiMe3)2
or LiN(SiMe3)2 allowed for the replacement of chloride
and the production of the solvent-free complexes 6-9
in excellent yields (73-87%). Although 1H NMR pro-
vided evidence for the presence of the substituents, the
paramagnetic nature of these complexes hindered full
interpretation of the spectra.
Resu lts a n d Discu ssion
Definitive formulation of the structural features of 7
and 8 was provided by single-crystal X-ray diffraction
analysis (Figures 1 and 2).18,19 These studies establish
the coordination geometry of the metal center and the
connectivity of the ligand for these compounds and
provide the first reported structural characterization of
alkyl or amido lanthanide complexes with guanidinate
or amidinate ligands.
Consistent with our proposals, the structural analysis
of 7 (Figure 1)20 revealed a monomeric species with the
coordination sphere of the Sm(III) center composed of
the four nitrogen atoms of two chelating guanidinate
anions and the bulky alkyl. The coordination geometry
of 7 is best described as trigonal planar with the bisector
of the guanidinate ligands (Sm-C(13) and Sm-C(32)
vectors) defining two vertexes and the alkyl carbon
(C(39)) the third. The angles defined by these vectors
sum to 360°. This analysis emphasizes that fact that
the molecular structure of 7 resembles that of the bent
metallocene derivatives containing (C5Me5)2Ln units.
The bonding parameters within the two guanidinate
ligands are not dramatically different, and the two
nitrogens and bridging carbon atoms for each lie in a
plane which includes the Sm atom. This results in an
Guanidinate anion 1 was generated by the direct
reaction of 1,3-dicyclohexylcarbodiimide with 1 equiv of
LiN(SiMe3)2 in diethyl ether. Although the lithium salt
could be isolated in pure form by simple removal of the
solvent, in most cases metathesis reactions with lan-
thanide halide salts can be carried out with freshly
prepared solutions of lithium guanidinate. Thus, reac-
tion of a 2:1 ratio of lithium salt of N,N′-dicylohexyl-
N′′-bis(trimethylsilyl)guanidinate with either YbCl3 or
SmCl3 produced, after crystallization from diethyl ether,
the new “ate” complexes M{CyNC[N(SiMe3)2]NCy}2(µ-
Cl)2Li(Et2O)2 (M ) Sm (2), Yb (3)) (Scheme 1) in 79%
and 88% yield, respectively. We propose the structures
in Scheme 1 on the basis of the results of crystal-
lographic characterization described below and analogy
with the reported complex [(CF3)3C6H2C(NSiMe3)2]Nd(µ-
Cl)2LiTHF2.13 Compounds 2 and 3 are monochloro bis-
(guanidinate) complexes in which 1 equiv of LiCl is
retained in the coordination sphere of the lanthanide
center. Diethyl ether completes the coordination sphere
of the Li cation. The ether molecules in 2 and 3 can be
displaced easily by reaction with other coordinating
species such as N,N′-tetramethylethylenediamine to
yield 4 and 5.
(15) (a) Duchateau, R.; van Wee, C. T.; Meetsma, A.; van Duijnen,
P. T.; Teuben, J . H. Organometallics 1996, 15, 2279. (b) Duchateau,
R.; van Wee, C. T.; Meetsma, A.; Teuben, J . H. J . Am. Chem. Soc. 1993,
115, 4931.
(16) (a) Foley, S. R.; Bensimon, C.; Richeson, D. S. J . Am. Chem.
Soc. 1997, 119, 10359 and references therein. (b) Littke, A.; Sleiman,
N.; Bensimon, C.; Richeson, D.; Yap, G. P. A.; Brown, S. Organome-
tallics 1998, 17, 446 and references therein.
(18) C45H99N6Si6Sm‚0.33O(SiC3H9)2, space group ) P1h, a ) 14.157-
(3) Å, b ) 24.952(5) Å, c ) 28.115(6) Å, R ) 74.78(3)°, â ) 76.74(3)°, γ
) 82.14(3)°, V ) 9297(3) Å3, Z ) 6, T ) 293 K; R for 46 631 reflections
[I > 2σ(I)], R(F) ) 0.0616, wR(F2) ) 0.1046, GOF on F2 ) 1.061.
(19) C44H98N7Si6Yb‚THF, space group ) P21/c, a ) 13.303(5) Å, b )
19.602(4) Å, c ) 2.932(5) Å, â ) 91.741(2)°, V ) 7019.77(2) Å3, Z ) 4;
R for 6224 reflections [I > 2.5σ(I)], R(F) ) 0.066, wR(F2) ) 0.102.
(20) For conciseness, the discussion of the structural parameters of
7 and the ORTEP shown in Figure 1 are confined to one of the three
molecules that constitute the asymmetric unit in the crystal structure.
Full data are provided in the Supporting Information.
(17) (a) Coles, M. P.; J ordan R. F. J . Am. Chem. Soc. 1997, 119,
8125. (b) Coles, M. P.; Swenson, D. C.; J ordan, R. F.; Young, V. G.
Organometallics 1997, 16, 5183.

Guanidinate Anions as Ancillary Ligands
Organometallics, Vol. 17, No. 20, 1998 4389
ecules 82.5°) militates against π-overlap between these
two moieties. The nearly perpendicular disposition is
likely the result of steric interactions between the
cyclohexyl functions and the bulky trimethylsilyl groups.
This orientation of the bulky N(SiMe3)2 group effectively
adds a third dimension to the steric bulk of the
otherwise essentially planar guanidinate ligand.
The structural analysis of 8 (Figure 2) revealed a
monomeric species with general features similar to 7
with CH(SiMe3)2 replaced by N(SiMe3)2. Again, the
coordination geometry of Yb in this species is best
described as trigonal planar with the bisector of the
guanidinate ligands (Yb-C(7)) and Yb-C(20) vectors)
defining two vertexes subtending an angle of 130.5°. The
metal-amido linkage defines the third vertex. These
three vectors lie in a plane. As was observed for 7, the
two coordinated nitrogen atoms and bridging carbon
atoms of the guanidinate ligands are planar. The amido
nitrogen atom, N(7), is also planar as are the N(SiMe3)2
groups of the guanidinate ligands. The possibility of a
π interaction between these N(SiMe3)2 functions and the
bidentate NCN fragments can be ruled out on the basis
of the observed dihedral angles of 100.8 and 100.1°.
We have some evidence that the reported guandinate
anions were also able to function as supporting ligands
for soluble Yb(II) complexes (Scheme 2). Entry to
{CyNC[N(SiMe3)2]NCy}2Yb(TMEDA) (10) is provided by
either reduction of 4 with Na/K alloy or by direct
reaction of YbI2 with the {CyNC[N(SiMe3)2]NCy}-
anion. In the first case the solvated complex, 10, is
generated directly due to the presence of TMEDA in the
starting material. Both preparations proceed in excel-
lent yield. The diamagnetic nature of divalent Yb
allowed definitive characterization of these materials
by NMR spectroscopy. Equivalence of the Cy groups
in the NMR spectra, as exemplified by the single
resonance (3.47 ppm) for the cyclohexyl protons R to
nitrogen and corresponding carbon (57.5 ppm), indicates
a symmetrical and/or fluxional structure for 10 and is
a point of future investigation. These compounds are
analogues of the reported Yb(II) benzamidinates (e.g.
p-PhC6H4C(NSiMe3)2]2Yb), which were prepared from
YbI2.14
F igu r e 1. ORTEP diagram for one of the three symmetry
unique molecules of 7. Thermal ellipsoids are drawn at 30%
probability. Selected bond distances (Å) and angles (deg):
Sm(1)-N(4) 2.395(4), Sm(1)-N(1) 2.424(4), Sm(1)-N(2)
2.424(4), Sm(1)-N(5); 2.426(4), Sm(1)-C(39) 2.472(5);
N(1)-Sm(1)-N(2) 55.06(13), N(4)-Sm(1)-N(5) 55.59(13),
N(1)-Sm(1)-C(39) 104.7(2), N(2)-Sm(1)-C(39) 124.2(2),
N(5)-Sm(1)-C(39) 106.9(2), N(4)-Sm(1)-C(39) 119.3(2),
C(13)-N(1)-Sm(1) 95.3(3), C(13)-N(2)-Sm(1) 95.4(3),
C(13)-N(3)-Si(1) 119.9(3), C(13)-N(3)-Si(2) 117.6(3), Si-
(1)-N(3)-Si(2) 122.5(2), C(32)-N(4)-Sm(1) 96.1(3), C(32)-
N(5)-Sm(1) 94.6(3), N(3)-C(13)-Sm(1) 174.2(3).
Through a combination of X-ray crystallographic and
spectroscopic studies, we have confirmed that substi-
tuted guanidinate anions can function as ligands for the
preparation of a novel family of lanthanide complexes.
These results contribute to revealing the steric and
electronic features that influence the reactivity of metal
guanidinate compounds. The alkyl complexes 6 and 7
are certainly interesting species; they are readily soluble
nonpolar solvents and reactive with a variety of sub-
strates. Their use as precursors to catalytically active
species, and the reactivity of the reported Yb(II) com-
plexes is currently under investigation.
F igu r e 2. ORTEP diagram for 8. Thermal ellipsoids are
drawn at 30% probability. Selected bond distances (Å) and
angles (deg): Yb-N(1) 2.329(13), Yb-N(2) 2.301(15), Yb-
N(3) 2.311(13), Yb-N(4) 2.328(12), Yb-N(7) 2.343(19),
N(1)-Yb-N(2) 58.0(5), N(3)-Yb-N(4) 57.9(4), N(1)-Yb-
N(7) 100.6(6), N(2)-Yb-N(7) 119.4(6), N(3)-Yb-N(7) 124.6-
(6), N(4)-Yb-N(7) 104.6(6), C(7)-N(1)-Yb 94.5(10), C(7)-
N(2)-Yb 93.7(11), C(7)-N(5)-Si(1) 118.7(11), C(7)-N(5)-
Si(2) 118.5(11), Si(1)-N(5)-Si(2) 122.7(8), C(20)-N(3)-Yb
92.7(10), C(20)-N(3)-Yb 92.7(10).
approximately C2 symmetric molecular geometry in
which the pseudo-2-fold axis lies along the Sm-C(39)
bond.
(21) (a) Schumann, H.; Rosenthal, E. C. E.; Kociok-Kohn, G.;
Molander, G. A.; Winterfeld, J . J . Organomet. Chem. 1995, 496, 233.
(b) Clark, D. L.; Gordon, J . C.; Huffman, J . C.; Watkin, J . G.; Zwick,
B. D. Organometallics 1994, 13, 4266. (c) Giardello, M. A.; Conticello,
V. P.; Brard, L.; Sabat, M.; Rheingold, A. L.; Stern, C. L.; Marks, T. J .
J . Am. Chem. Soc. 1994, 116, 10212. (d) Conticello, V. P.; Brard, L.;
Giardello, M. A.; Tsuji, Y.; Sabat, M.; Stern, C. L.; Marks T. J . J . Am.
Chem. Soc. 1992, 114, 2761. (e) Hitchcock, P. B.; Lappert, M. F.; Smith,
R. G. J . Chem. Soc., Chem. Commun. 1989, 369. (f) Hitchcock, P. B.;
Lappert, M. F.; Smith, R. G.; Bartlett, R. A.; Power, P. P. J . Chem.
Soc., Chem. Commun.1988, 1007.
Characteristically, the alkyl carbon is nearly planar
and the Sm-C distance of 2.472(5) Å compares favor-
ably with the closely related yttrium species [C6H5C-
(NSiMe3)2]2YCH(SiMe3)2 (Y-C 2.431(5) Å)15 and falls
within the range reported for SmCH(SiMe3)2-containing
compounds.21
The dihedral angle formed by the planar N(SiMe3)2
function and the SmNCN plane (average for all mol-

4390 Organometallics, Vol. 17, No. 20, 1998
Zhou et al.
Sch em e 2
resulting pale yellow crystals were collected by filtration,
washed with hexane, and dried under vacuum (0.91 g, 0.84
mmol, 91%), mp (sealed) 200 °C dec. IR (Nujol, cm-1): 1635
(w), 1445 (s), 1350 (s), 1256 (s), 1182 (s), 1071 (s), 965 (s), 838
(s) 657 (m). 1H NMR (toluene-d8, ppm): 3.00 (br); 2.33 (br, s)
2.19 (br, s); 2.00-1.10 (br, m); -1.8 (br, m). Anal. Calcd for
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All manipulations were carried
out in either a nitrogen-filled drybox or under nitrogen using
standard Schlenk-line techniques. Solvents were distilled
under nitrogen from Na/K alloy. Deuterated benzene was
dried by vacuum transfer from potassium. Ytterbium, ICH2-
CH2I, and 1,3-dicyclohexylcarbodiimide were purchased from
Aldrich and used without further purification. 1H NMR
spectra were run on a Gemini 200 MHz spectrometer with
deuterated benzene or toluene as a solvent and internal
standard. All elemental analyses were run on a Perkin-Elmer
PE CHN 4000 elemental analysis system.
Li[C6H11NC(N(SiMe3)2)NC6H11] (1). A Schlenk flask was
charged with dicyclohexylcarbodiimide (1.00 g, 4.85 mmol),
lithium bis(trimethylsilyl)amide (0.77 g, 4.85 mmol), diethyl
ether (30 mL), and a stir bar. The mixture was stirred
overnight at room temperature. Removal of solvent under oil
C
44H96Cl2LiN8Si4Sm: C, 49.03; H, 8.98; N, 10.40. Found: C,
49.30; H, 9.09; N, 10.60.
[C6H11NC(N(SiMe3)2)NC6H11]2YbCH(SiMe3)2 (6). ASchlenk
flask was charged with 2 (2.00 g, 1.77 mmol) and toluene (50
mL). The solution was cooled to -78 °C, and LiCH(SiCH3)2
(0.29 g, 1.77 mmol) was added. The reaction mixture was
stirred overnight, during which time it slowly warmed to room
temperature. The solvent was removed under vacuum, and
the residue was extracted with hexane (50 mL). Concentration
to 15 mL and cooling to -30 °C yielded orange crystals of 6
(1.47 g, 1.38 mmol, 78%), mp (sealed) 95-97 °C. IR (Nujol,
cm-1): 1632 (w), 1443 (s), 1344 (s), 1253 (s), 1180 (s), 1131 (s),
1065(m), 1010 (s), 963 (s), 945 (s), 863 (s), 838 (s), 758 (m),
637 (m). 1H NMR (C6D6, ppm): 11.9 (br), 1.23 (s), 0.92 (s),
-2.24 (br), -7.1 (br), -11.5 (br), -22.7 (br), -23.5 (br). Anal.
Calcd for C45H99N6Si6Yb: C, 50.71; H, 9.36; N, 7.88. Found:
C, 50.66; H, 9.22; N, 7.63.
1
pump vacuum gave 1 as white solid in quantitative yield. H
NMR (C6D6, ppm): 3.38 (br, 2H, C6H11), 2.07-1.05 (m, 20H,
C6H11), 0.36 (s, 18H, SiMe3).
[C6H11NC(N(SiMe3)2)NC6H11]2Yb[Cl2Li(C2H5OC2H5)2] (2).
A Schlenk flask was charged with 1 (2.65 g, 7.24 mmol), YbCl3
(1.00 g, 3.62 mmol), and THF (90 mL). The reaction mixture
was stirred overnight at room temperature. Solvent was
removed under vacuum, and the yellow residue was extracted
with diethyl ether and filtered to remove LiCl. The diethyl
ether solution was concentrated to 30 mL and cooled to -30
°C. Bright yellow crystals of 2 were collected in two crops by
filtration (3.61 g, 2.28 mmol, 88%). The product was subse-
quently recrystallized from diethyl ether, mp (sealed) 135 °C
dec. IR (Nujol, cm-1): 1635 (w), 1435 (s), 1344 (s), 1260 (s),
1183 (s), 1004 (s), 954 (s), 846 (s), 665 (m). Anal. Calcd for
[C6H11NC(N(SiMe3)2)NC6H11]2Sm CH(SiMe3)2 (7). Fol-
lowing a procedure similar to the synthesis of 6, 3 (2.00 g, 1.86
mmol) was dissolved in toluene (50 mL) and LiCH(SiCH3)2
(0.31 g, 1.86 mmol) was added at -78 °C. After stirring
overnight and workup, 7 was isolated as a crude material.
Crystals were obtained by dissolving the crude material in
hexamethyldisiloxane (approximately 30 mL) and cooling -30
°C. Bright yellow crystals were collected by filtration (1.64 g,
1.36 mmol, 73%). This compound can also be crystallized from
diethyl ether, mp (sealed) 64-65 °C. IR (Nujol, cm-1): 1635
(w), 1435 (s), 1344 (s), 1256 (s), 1177 (s), 1135 (s), 1065 (m),
C
46H100Cl2LiN6O2Si4Yb: C, 48.78; H, 8.90; N, 7.42. Found: C,
48.93; H, 8.67; N, 7.22.
1
1004 (s), 963 (s), 941 (s), 863 (s), 846 (s), 758 (m), 639 (m). H
[C6H11NC(N(SiMe3)2)NC6H11]2Sm [Cl2Li(C2H5OC2H5)2] (3).
Following a procedure similar to the synthesis of 2, using 2.85
g of 1 (7.79 mmol), 1.00 g of SmCl3 (3.90 mmol), and 90 mL of
THF followed by crystallization from diethyl ether yielded
bright yellow crystals of 3 (3.42 g, 2.22 mmol, 79%), mp (sealed)
157 °C dec. IR (Nujol, cm-1): 1637 (w), 1448 (s), 1355 (s), 1260
(s), 1177 (s), 1065 (s), 963 (s), 836 (s) 662 (m). 1H NMR
(toluene-d8, ppm): 1.43 (br); 3.30, 1.17 (br). Anal. Calcd for
NMR (C6D6, ppm): 15.83 (s), 3.20 (br, m), 1.87 (br), 0.88 (m),
0.585 (br) -1.32 (m), -2.19 (s) -5.36 (br s). Anal. Calcd for
C
45H99N6Si6Sm: C, 51.81; H, 9.57; N, 8.06. Found: C, 52.11;
H, 9.89; N, 8.11.
[C6H11NC(N(SiMe3)2)NC6H11]2YbN(SiMe3)2 (8). A Schlenk
flask was charged with 2 (1.00 g, 0.88 mmol), LiN(SiCH3)2 (0.14
g, 0.88 mmol), and diethyl ether (25 mL). The reaction mixture
was stirred overnight at room temperature. Filtration to
remove LiCl and removal of solvent gave a yellow solid (0.78
g, 0.73 mmol, 83%). The product was subsequently recrystal-
lized from diethyl ether at -30 °C, mp (sealed) 193 °C dec. IR
(Nujol, cm-1): 1633 (w), 1450 (s), 1350 (s), 1252 (s), 1184 (s),
1137 (s), 1071 (m), 1004 (s), 965 (s), 937 (s), 863 (s), 838 (s),
756 (m), 665 (m), 642 (m). Anal. Calcd for C44H98N7Si6Yb:
C, 49.54; H, 9.26; N, 9.19. Found: C, 49.23; H, 9.25; N, 8.87.
C
46H100Cl2LiN6O2Si4Sm: C, 49.78; H, 9.08; N, 7.57. Found:
C, 49.82; H, 9.06; N, 7.60.
[C6H 11NC(N(SiMe3)2)NC6H 11]2Yb [Cl2Li(Me2NCH 2CH 2-
NMe2] (4). Complex 2 (1.00 g, 0.88 mmol) was dissolved in
20 mL of diethyl ether, and excess of TMEDA was added. The
reaction mixture stood at room temperature for 1 day. The
resulting bright yellow crystals were collected by filtration,
washed with hexane, and dried under vacuum (0.94 g, 0.83
mmol, 94%), mp (sealed) 224 °C dec. IR (Nujol, cm-1): 1639
(w), 1448 (s), 1355 (s), 1257 (s), 1091 (s), 1016 (s), 952 (s), 835
(s) 642 (m). Anal. Calcd for C44H96Cl2LiN8Si4Yb: C, 48.02;
H, 8.79; N, 10.18. Found: C, 48.22; H, 9.00; N, 10.25.
[C6H 11NC(N(SiMe3)2)NC6H 11]2Sm [Cl2Li(Me2NCH 2CH 2-
NMe2] (5). Complex 3 (1.00 g, 0.93 mmol) was dissolved in
15 mL of diethyl ether, and excess of TMEDA was added. The
reaction mixture stood at room temperature for 1 day. The
[C6H11NC(N(SiMe3)2)NC6H11]2Sm N(SiMe3)2 (9). A Schlenk
flask was charged with 3 (1.00 g, 0.93 mmol), LiN(SiCH3)2 (0.15
g, 0.93 mmol), and diethyl ether (20 mL). The reaction mixture
was stirred overnight at room temperature. Filtration to
remove LiCl and removal of solvent gave a colorless solid (0.85
g, 0.81 mmol, 87%). The product was subsequently recrystal-
lized from ether at -30 °C, mp (sealed) 200 °C dec. IR (Nujol,
cm-1): 1636 (w), 1444 (s), 1344 (s), 1298 (m), 1250 (s), 1174

Guanidinate Anions as Ancillary Ligands
Organometallics, Vol. 17, No. 20, 1998 4391
(s), 1137 (s), 1061(m), 1004 (s), 965 (s), 941 (s), 863 (s), 804
(s), 756 (m), 642 (m). 1H NMR (C6D6, ppm): 1.85 (s); -3.38
(s). Anal. Calcd for C44H98N7Si6Sm: C, 50.61; H, 9.46; N, 9.39.
Found: C, 50.80; H, 9.89; N, 9.65.
were refined with anisotropic displacement coefficients. Hy-
drogen atoms were treated as idealized contributions. All
computations used the SHELXTL (5.03) program library (G.
Sheldrick, Siemens XRD, Madison, WI).
[C6H 11NC(N(SiMe3)2)NC6H 11]2Yb [Me2NCH 2CH 2NMe2]
(10). In a drybox, a flask was charged with 4 (1.00 g, 0.91
mmol), excess NaK2.8, and benzene (15 mL). The reaction
mixture was stirred at room temperature for 5 days. The
solvent was removed under vacuum, and the residue was
extracted with hexane. Filtration and removal of solvent gave
deep red 10 (0.60 g, 0.58 mmol, 64%), mp (sealed) 50-53 °C
dec. IR (Nujol, cm-1): 1545 (s), 1477 (s), 1290 (s), 1249 (s),
1168 (s), 1122 (s), 1068 (s), 994 (s), 945 (s), 889 (s), 863 (s),
838 (s), 755 (m), 695 (m), 639 (m). 1H NMR (benzene-d6,
ppm): 3.58 (br, 4H, C6H11), 2.38 (s, 12H, NMe2), 2.10-1.20
(m, 44H, C6H11 and NCH2), 0.37 (s, 36H, SiMe3). 13C NMR
Cr ysta llogr a p h ic Stu d y of 8. Intensity data were col-
lected on a Rigaku diffractometer at -153 °C using the θ-2θ
scan technique for crystals mounted on glass fibers. The
structures were solved by direct methods. The non-hydrogen
atoms were refined anisotropically. The final cycle of full-
matrix least-squares refinement was based on the number of
observed reflections with I > 2.5σ(I). Anomalous dispersion
effects were included in the Fc. All calculations were per-
formed using the NRCVAX package. Full details of the data
collection, refinement, and final atomic coordinates are re-
ported in the Supporting Information.
(C6D6, ppm): 168.2 (s, CN3); 57.5, 39.0, 26.8, 26.7 (4s, C6H11
55.7 (NCH3), 45.6 (NCH2), 3.32 (SiCH3). Anal. Calcd for
)
Ack n ow led gm en t. This work was supported by the
Natural Sciences and Engineering Research Council of
Canada.
C
44H96N8Si4Yb: C, 51.68; H, 9.46; N, 10.96. Found: C, 51.60;
H, 9.35; N, 10.87. MS: m/z 1022 (M+).
Cr ysta llogr a p h ic Stu d y of 7. A suitable crystal of 7 was
mounted on a glass fiber. Systematic absences and the unit-
cell parameters are uniquely consistent for the reported space
group. No absorption correction was required. The structure
was solved by direct methods and refined by full-matrix least-
Su p p or tin g In for m a tion Ava ila ble: Listings providing
complete descriptions of the structural solutions and ORTEP
drawings for compounds
7 and 8 (44 pages). Ordering
information is given on any current masthead page.
2
squares procedures based on |F| . All non-hydrogen atoms
OM980480R