Synthesis and characterization of mono β-diketiminatosamarium amides and hydrocarbyls

Article abstract of DOI:10.1039/b501437a

Reaction of SmCl₃ with 1 eq of KL (L = [DippNC(Me)CHC(Me)NDipp]; Dipp = 2,6-i-Pr₂C₆H₃) in THF afforded the dimeric samarium dichloride LSmCl₂(THF)Cl₂SmL (1) in high yield. Reactions of 1 wi

Full text of DOI:10.1039/b501437a

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F U L L P A P E R
Synthesis and characterization of mono b-diketiminatosamarium
amides and hydrocarbyls†
Chunming Cui,a,b Alexandr Shafir,a,b Joseph A. R. Schmidt,‡a,b Allen G. Olivera,b and
John Arnold*a,b
a Department of Chemistry, University of California, Berkeley, CA, 94720-1460, USA
b Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA,
94720-1460, USA
Received 8th July 2004, Accepted 24th February 2005
First published as an Advance Article on the web 10th March 2005
Reaction of SmCl3 with 1 eq of KL (L = [DippNC(Me)CHC(Me)NDipp]; Dipp = 2,6-i-Pr2C6H3) in THF afforded
the dimeric samarium dichloride LSmCl2(THF)Cl2SmL (1) in high yield. Reactions of 1 with NaN(SiMe3)2, KNHAr
(Ar = 2,4,6-t-Bu3C6H2), KBHEt3, and KCp* (Cp* = C5Me5) yielded various new complexes: LSmClN(SiMe3)2 (2),
LSm[N(SiMe3)2]2 (3), LSmNHAr(HBEt3) (4), LSm(NHAr)2 (5), and LSmCp*Cl (6). Reaction of 1 with one eq of
NaN(SiMe3)2 followed by treatment with excess AlMe3 afforded a unique bimetallic samarium tetramer
Cl3L2Sm2(AlMe4)2Sm2L2Cl3 (7). Reaction of 6 with LiMe or LiCH2SiMe3 afforded LSmCp*Me (8) and
LSmCp*CH2SiMe3 (9) in excellent yield. Methyl abstraction from 8 with B(C6F5)3 in toluene yielded the cationic
borate species (LSmCp*)[MeB(C6F5)3] (10). Molecular structures of 1–7 and 9 were determined by X-ray single
crystal analysis.
Introduction
Recent efforts in the design and synthesis of new ligand systems
for lanthanide chemistry have been aimed to a large degree
at extending organolanthanide chemistry beyond the realm of
lanthanocene species. A major impetus for such studies can be
traced to the well known applications of lanthanide complexes
in homogeneous catalysis.1,2 Our recent efforts in this area have
been to apply bulky, kinetically-stabilizing monoanionic ligand
systems to the lanthanide metals3,4 in the hope that they will
allow the isolation of low-coordinate metal complexes showing
unique bonding or patterns of reactivity.
In this paper we are concerned with the chemistry of samarium
compounds containing the monoanionic b-diketiminato (or
nacnac) ligand L {L = [DippNC(Me)CHC(Me)NDipp], Dipp =
2,6-i-Pr2C6H3}.5 This general class of ligands has been the
subject of intense interest in recent years,6 especially the more
Scheme 1
bulky variants which seem unique in stabilizing some unusual
complexes of main group7–9 and transition metals.10–13 Piers
and co-workers14–16 have extensively investigated the scandium
chemistry with such bulky ligands, and recent reports continue
to extend the less-developed chemistry of other lanthanide
metals.17–26 Herein, we describe some new chemistry of samar-
ium with b-diketiminato ligands6,17,25–27 including amide and
alkyl complexes, several X-ray structures and some reaction
chemistry.28
one of the two dimeric molecules of 1 is shown in Fig. 1.
The compound adopts a dimeric structure with three chlorine
atoms bridging the two samarium centers while one chlorine
atom resides in a terminal position on one samarium atom; the
coordination sphere of the other samarium atom is completed by
a coordinated THF molecule. Each diketiminate ligand binds to
a samarium atom in the typical chelating fashion, with acute
Results and discussion
The potassium salt of the ligand L {L = [DippNC(Me)CHC-
(Me)NDipp] (Dipp = 2,6-i-Pr2C6H3) employed in this study was
obtained by reaction of the free ligand LH5 with KN(SiMe3)2.
Reaction of KL with SmCl3 in THF was conducted at room
temperature (Scheme 1) to yield the dimeric samarium species
LSmCl2(THF)Cl2SmL (1) in high yield.
Crystals of 1 were obtained from toluene at −40 ◦C. The
crystallographic model features two molecules of 1, as well
as 4.5 eq of incorporated toluene solvent. The structure of
† Dedicated to the memory of Professor Ian Rothwell.
‡ Present address: Department of Chemistry, University of Toledo,
Toledo, OH 43606 USA.
Fig. 1 Ortep drawing of complex 1 (50% probability). Hydrogen atoms
and the two Dipp groups on the nitrogen atoms have been omitted for
clarity.
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
D a l t o n T r a n s . , 2 0 0 5 , 1 3 8 7 – 1 3 9 3
1 3 8 7
©

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N–Sm–N angles (N101–Sm11–N102 = 75.9(2)◦ and N103–
Sm12–N104 = 77.9(3)◦). The chloride ligands bridge asymmet-
rically across the two Sm atoms, such that the bonds to the Sm
proposed connectivity; however, the data is of relatively poor
quality and will not be discussed further.
Reaction of 1 with a 1 : 1 ratio of KNHAr and KN(SiMe3)2
in toluene at 80 ◦C did not yield mixed amide or deprotonated
imide species, but instead gave a 1 : 1 mixture of 3 and 5. When
the reaction was carried out stepwise (first, addition of KNHAr
and stirred overnight, then KN(SiMe3)2), the same 1 : 1 mixture
of 3 and 5 was still obtained.
˚
ligated by THF are ca. 0.05 A shorter than those to the Sm
with the terminal chloride. As expected, the Sm–Cl (terminal)
˚
distance (2.605(3) A) is quite short compared to the Sm–Cl
˚
(bridging) (2.72–2.83 A).
Compound 1 serves as a good starting synthon for LSm
derivatives via simple metathesis chemistry. For example, 1
reacted with the sodium amide NaN(SiMe3)2 in 1 : 2 and 1 :
4 ratios at room temperature to afford LSmN(SiMe3)2(Cl) (2)
and LSm[N(SiMe3)2]2 (3), respectively. Reaction of 1 with the
amide KNHAr followed by addition of KHBEt3 generated
LSm(NHAr)(HBEt3) (4, Ar = 2,4,6-t-Bu3C6H2). Compound 1
also reacts with two eq of KNHAr at elevated temperature to
afford LSm(NHAr)2 (5). A single chloride ligand can also be
replaced by Cp* via treatment of 1 with Cp*K, which affords
LSmCp*Cl (6) in high yield (Scheme 2).
Attempts to prepare mono- or di-alkyl complexes by reacting
1 with various alkyl reagents have been unsuccessful to date.
The 1H NMR spectrum of 2 is resolvable (although the reso-
nances are broad and shifted due to its paramagnetic nature),
while that of 3 appears very broad. The latter is thermally
stable in refluxing toluene over several days. In contrast, 4 is
thermally unstable and very air- and moisture-sensitive at room
temperature in solution; nonetheless it can be stored as a solid
for one week without noticeable decomposition.
The molecular structures of 2, 3, 5, and 6 are shown in
Figs. 2–5, respectively. All of these complexes have a monomeric
structure in the solid state with the b-diketiminato ligand
coordinated to the samarium atom in a chelating mode with
a relatively acute angle. Single crystals of 2 suitable for X-
ray diffraction were obtained from toluene at −40 ◦C. The
compound crystallizes in monoclinic space group P21/c. The
structure is pseudo-tetrahedral (Fig. 2), with three nitrogen
atoms and one chlorine atom coordinated to the central atom.
˚
The Sm–Cl distance (2.615(1) A) is in line with that found
˚
in 1. The Sm1–N1 (amide) bond is shorter (2.276(3) A) than
Sm–N bonds to the diketiminato ligand (Sm1–N2 (2.334(3)
˚
˚
A) and Sm1–N3 (2.354(3)A). The typical ‘enveloping’ of the
The 1H NMR spectrum of 4 shows a high field, broad singlet
(d −20.15 ppm in C7D8; −18.95 ppm in C6D6) assigned to the
proton in the HBEt3, indicating a Sm–H–B interaction in this
molecule. Similar high field resonances have been reported for
the metallocenes [C5H4(CMe3)]2SmHBEt3(THF)x (d −23 ppm)
and [C5H4(CH2)2OCH3]2SmHBEt3 (d −23.4 ppm).29,30 A strong
band for the B–H stretch occurs at 1880 cm−1 (KBr) in the
IR spectrum, in the region associated with l-HB bonds (cf.
m(BH) in M(HBEt3) salts at 1870, 1835, and 1950 cm−1 for M =
Li, Na, K, respectively).31 Addition of PMe3, pyridine or
triethylamine to 4 in THF or toluene led to unidentified products
rather than the anticipated terminal hydride. There are few
examples of structurally characterized metal triethylborohydride
complexes,32 although several lanthanide complexes of this
type have been spectroscopically characterized.29,30,33 An X-ray
dataset was obtained on 4, solution of which established the
Fig. 2 Ortep drawing of complex 2 (50% probability). Hydrogen atoms
have been omitted for clarity.
Scheme 2
1 3 8 8
D a l t o n T r a n s . , 2 0 0 5 , 1 3 8 7 – 1 3 9 3

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˚
and 2.324(3) A) than does the diketiminato ligand (2.503(3),
˚
2.427(3) A). All four Sm–N bonds are longer than the cor-
responding metrics found in 2 due no doubt to the more
crowded coordination environment. Correspondingly, the N–
Sm–N angle to the diketiminato ligand (79.100(2)◦) is smaller
than that (81.6(1)◦) in 2.
Compound 5 crystallizes in monoclinic space group P21/c
with two molecules of 5 and 1.5 eq of pentane in the asymmet-
ric unit (Fig. 4). One of the molecules is shown in Fig. 4. The
overall structure is very similar to that of 3 with four nitrogen
atoms coordinated to the samarium atom. Again, the two Sm–N
˚
(amide) distances (2.311(5) and 2.260(5) A) are similar and are
close to those seen in 4. The N13–Sm–N14 angle (133.6(2)◦) is
large due to the bulkiness of the Ar group while the N12–Sm–
N11 (79.6(2)◦) of the chelating ring is still acute, similar to those
in compounds 2 and 3.
The X-ray structure of 6 (Fig. 5) shows it to be a solvent-free
“half-metallocene” complex. Samarium compounds involving
Cp ligands are well-known, with the work of Evans and co-
workers dominating the literature in this area.34–37 By far the
vast majority of complexes entail bis-Cp* ligand sets, although
in recent years a number of mono-Cp* derivatives have been
prepared.38–40 The b-diketiminato ligand is coordinated to the
central atom in a chelating fashion and Cp* is bound in the nor-
Fig. 3 Ortep drawing of complex 3 (50% probability). Hydrogen atoms
have been omitted for clarity.
5
mal g fashion. The overall geometry can be described as tetra-
˚
hedral. The Sm–Cl bond length (2.610(1) A) is very close to that
41
in 2 and Sm(TpMe2)2Cl (2.637(3) A), and is noticeably shorter
˚
42
˚
than that found in (C5Me5)2SmCl(THF) (ave 2.73(1) A).
Upon treatment of yellow compound 1 with one eq of
NaN(SiMe3)2, followed by an excess of AlMe3 in toluene,
a deep red color was developed in 2 h, and an interesting
samarium aluminate tetramer Cl3L2Sm2(AlMe4)2Sm2L2Cl3 (7)
could be crystallized in low yield (ca. 20%) after careful work-
up. We note that direct reaction of 1 with AlMe3 did not yield
identified products. One possible mechanism for the formation
of 7 proceeds via substitution of the terminal chlorine atom
in 1 by an [N(SiMe3)2]− group, followed by exchange of the
[N(SiMe3)2]− with [AlMe4]− and displacement of THF.
The structure of 7 is shown in Fig. 6, the geometry of the
Sm atoms being distorted octahedral while that of aluminium
is tetrahedral. The most interesting feature of this molecule
is the distorted square geometry formed by Al1–C5–Sm2–
Cl1–Sm1–C1–Al2–C2–Sm4–Cl4–Sm3–C6 atoms, with methyl
groups bridging the Al and Sm atoms and Cl and Al atoms
at the corners. The Sm1–Cl1–Sm2 angle is 89.43◦ whereas the
C5–Al1–C6 angle is rather more obtuse (107.1(2)◦). The angle
at Sm (i.e. Cl1–Sm2–C5) is far from linear (159.1(1)◦) while that
seen at the bridging methyl groups is much closer (Sm2–C5–Al1
Fig. 4 Ortep drawing of complex 5 (50% probability). Hydrogen atoms
have been omitted for clarity.
Fig. 5 Ortep drawing of complex 6 (50% probability). Hydrogen atoms
have been omitted for clarity.
diketiminato ligand is observed in which the carbon atoms are
folded down ca. 43◦ from the N–Sm–N plane.
The structure of closely related 3 is also four-coordinate
(Fig. 3). The two amides display shorter bonds to Sm (2.299(3)
Fig. 6 Ortep drawing of complex 7 (50% probability). Hydrogen atoms
and the two Dipp groups have been omitted for clarity.
D a l t o n T r a n s . , 2 0 0 5 , 1 3 8 7 – 1 3 9 3
1 3 8 9

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(177.5(3)◦)). The N–Sm–N angles are all acute (77.8–78.7◦) and
˚
the Sm–Cl bond lengths (2.750(2)–2.783(2) A) are comparable to
˚
those found in 1 (2.720–2.835A). The Sm–N distances (2.354(4)–
˚
2.397(5) A) are also in the range found in all compounds in this
˚
paper. The Sm–C bond lengths (2.720(6)–2.759(6) A) and the
˚
Al–C (bridging) distances (2.034–2.037 A) are very close to those
42
˚
˚
found in [Cp*2Sm(AlMe4)]2 (2.743–2.750 A, 2.003–2.051 A).
The overall structural features of the AlMe4 units are similar
−
to normal AlMe4 anions.43
Compound 6 cleanly reacted with lithium alkyl reagents LiR
to give mono-alkyls LSmCp*R (R = Me (8), CH2SiMe3 (9);
Scheme 3) in excellent yield.
Fig. 7 Ortep drawing of complex 9 (50% probability). Hydrogen atoms
have been omitted for clarity.
trogen atoms, one carbon atom from the alkyl ligand and the Cp*
˚
ring. The Sm–C distances (C5Me5 ring) (2.695–2.776 A) are simi-
lar to those in the bis-metallocene compounds Cp*2SmCl(THF)
˚
˚
(2.72(3) A), Cp*2SmMe(THF) (2.711(6) A), and Cp*2SmCH2-
42
˚
C6H5(THF) (2.755(2) A). The Sm–C (CH2SiMe3) distance
(2.458(9) A) is similar to related bonds in Cp*2SmMe(THF)
(2.48(1) A), Cp*2SmCH2C6H5(THF) (2.498(5) A), and
Cp*2C6H5(THF) (2.511(5) A), and [2-(CH NC6H3-2,6-iPr2)-
˚
˚
˚
˚
=
˚
5-tBuC4N]2SmCH2SiMe3(THF) (2.455(4) A). The Sm–N dis-
˚
˚
tances (2.399(4) A) are close to those seen in 6 (2.381(3) A),
whereas the N–Sm–N angle (79.7(2)◦) is more acute (by ca.
2.4◦) due presumably to the bulk of CH2SiMe3 relative to the
chloride in 6.
Nitriles and isocyanides insert into the Sm–C bond in alkyls
8 and 9 to afford mono-insertion products (Scheme 4). Under
ambient conditions, they display no further tendency toward
reaction with excess substrate.
Scheme 3
1
Formation of the Sm–C bond is indicated by the H NMR
spectra of paramagnetic compounds 8 and 9, which showed the
low field alkyl resonances at 10.20 (Sm–Me) and 11.98 ppm (Sm–
CH2SiMe3), respectively. A singlet (d 1.15 for 8 and 1.30 ppm for
9) in the 1H NMR spectra could be assigned to the Cp*methyl
groups.
Compounds 8 and 9 are not active catalysts for ethylene
or methyl methacrylate (MMA) polymerization. Attempts to
prepare hydrides by the reaction of 8 and 9 with H2 or PhSiH3
led to the formation of complicated mixtures according to NMR
analysis, and no pure products have yet been isolated from
preparative scale reactions.
Reaction of 8 with B(C6F5)3 in an attempt to effect methyl
abstraction afforded the species (LSmCp*)[MeB(C6F5)3] (10)
as judged by NMR spectroscopy and elemental analysis. The
1H NMR spectrum showed a broad singlet (d −15.47 ppm)
attributable to the methyl group, indicating its proximity to the
paramagnetic samarium center in solution. A singlet attributable
to the Cp* methyl groups at d 0.13 ppm in 10 is shifted upfield by
1 ppm compared to that (d 1.15 ppm) of the parent compound
8. Compound 10 is remarkably stable under CO atmosphere
in toluene and does not react with ethylene or MMA at room
temperature. It is air and moisture sensitive, but appears to be
quite thermally stable in aromatic solvents. The relatively low
solubility in toluene compared to parent compound 8 lends
further support to its ionic formulation. X-Ray quality crystals
have not been obtained thus far.
Scheme 4
=
The products LSmCp*[N C(Me)(C6H4-4-Me)] (11), LSm-
=
Cp*[C(Me) N–C6H3-2,6-Me2] (12), and LSmCp*[C(CH2-
1
=
SiMe3) N–C6H3-2,6-Me2] (13) have been characterized by H
NMR, IR spectroscopy, and elemental analysis.
Orange complex 11 is soluble in toluene and benzene, but is
1
sparingly soluble in hexane. Its H NMR spectrum showed a
resonance attributable to NCMe at d 6.19 ppm, while a strong
absorption at 1640 cm−1 can be attributed to the C N stretch.
=
The molecular structure of compound 9 was determined by
X-ray single crystal analysis, as shown in Fig. 7. The overall
structure of 9 may be viewed as being typical of a distorted tetra-
hedron, with the central samarium atom coordinated to two ni-
Compounds 12 and 13 were obtained as yellow crystals from
toluene/pentane. Their H NMR spectra are similar, showing
alkyl resonances (Me and CH2SiMe3) in SmC(R)N at d 4.51 and
1
1 3 9 0
D a l t o n T r a n s . , 2 0 0 5 , 1 3 8 7 – 1 3 9 3

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5.12 ppm, respectively. A singlet for the C5Me5 methyl groups
appears at d 1.04 for 12 and 0.96 ppm for 13.
68.43; H, 9.79; N, 4.47%. 1H NMR (C6D6): d −18.95 (br s, 1H,
HBEt3), −5.08 (br, 2H, CHMe2), −1.45 (m, 6H, B(CH2CH3)3),
−0.80 (d, 6H, CHMe2), −0.28 (s, 6H, CHMe2), 0.36 (br, 9H,
B(CH2CH3)3), 0.84 (s, 6H, Me), 1.65 (d, 6H, CHMe2), 1.71 (s,
9H, CMe3), 1.74 (s, 9H, CMe3), 2.70 (d, 6H, CHMe2), 3.08 (s,
9H, CMe3), 4.42 (s, 1H, NH), 5.67 (d, 2H, Ar–H), 6.65 (m, 2H,
Ar–H), 6.92 (sept, 2H, CHMe2), 7.85 (s, 1H, Ar–H), 8.52 (s,
1H, Ar–H), 16.95 (s, 1H, CH). IR (Nujol, KBr): 3283 (w), 3059
(w), 2765 (w), 2363 (m), 2027 (m), 1880 (s), 1766 (w), 1622 (w),
1583 (m), 1505 (w), 1293 (w), 1253 (w), 1230 (m), 1197 (m),
1167 (m), 1108 (s), 1046 (s), 1016 (m), 926 (m), 888 (s), 827 (m),
797 (m), 757 (s), 740 (m), 599 (s), 524 (m).
Experimental
General
Standard Schlenk-line and glovebox techniques were used unless
stated otherwise. Toluene and pentane were purified by passage
through a column of activated alumina and degassed with
˚
argon. THF was dried by passage through a column of 4 A
molecular sieves and degassed under vacuum. C6D6 was vacuum
transferred from sodium/benzophenone. Melting points were
determined in sealed capillary tubes under nitrogen and are
uncorrected. 1H and 13C NMR spectra were recorded at ambient
temperature on a Bruker AM-300 spectrometer. 1H NMR
chemical shifts are given relative to C6D5H (7.15 ppm) or C7D7H
(2.09 ppm). 13C NMR spectra are relative to C6D6 (128.39 ppm).
IR samples were prepared as Nujol mulls and taken between
KBr plates. Elemental analyses were determined at the College
of Chemistry, University of California, Berkeley. Single-crystal
X-ray structure determinations were performed at CHEXRAY,
University of California, Berkeley.
LSm(NHAr)2 (5, Ar = 2,4,6-t-Bu3C6H2). Toluene (30 mmol)
was added to a mixture of 1 (0.67 g, 0.5 mmol) and KNHAr
(0.60 g, 2 mmol). The mixture was heated to 80 ◦C and was
stirred for 4 h before being allowed to cool to room temperature.
The solution was filtered, the filtrate was reduced to 5 mL then
stored at −40 ◦C for one week. Red crystals of 5 were obtained
in 80% yield (0.87 g). Mp: 225 ◦C. Anal. calcd for C65H101N4Sm:
C, 71.70; H, 9.35; N, 5.14. Found: C, 71.43; H, 9.02; N, 4.96%.
1H NMR (C6D6): d −4.05 (sept, 2H, CHMe2), −3.20 (d, 6H,
CHMe2), −1.23 (s, 18H, CMe3), −0.16 (d, 6H, CHMe2), 1.39
(d, 9H, CMe3), 1.66 (s, 2H, NH), 1.73 (d, 9H, CMe3), 1.78 (d,
6H, CHMe2), 1.89 (s, 6H, Me), 2.12 (s, 9H, CMe3), 3.11 (d, 6H,
CHMe2), 3.62 (s, 9H, CMe3), 4.34 (d, 2H, Ar–H), 5.82 (m, 2H,
Ar–H), 6.50 (d, 2H, Ar–H), 7.15 (s, 1H, Ar–H), 7.31 (s, 2H, Ar–
H), 7.55 (s, 1H, Ar–H), 7.69 (sept, 2H, CHMe2), 8.00 (s, 1H,
CH). IR (Nujol, KBr): 3693 (w), 3504 (w), 2364 (w), 1720 (w),
1312 (m), 1235 (s), 1199 (m), 1165 (m), 1091 (m), 1020 (s), 926
(m), 867 (m), 829 (m), 794 (s), 776 (s), 729 (m), 594 (m), 565 (m).
Syntheses
LSmCl2(THF)Cl2SmL (1). THF (50 mL) was condensed
onto a mixture of SmCl3 (1.28 g, 5.0 mmol) and KL (2.28 g,
5.0 mmol) at −78 ◦C. The suspension was allowed to warm
to room temperature and stirred overnight. The solvent was
removed under vacuum and the remaining solid was extracted
with toluene (50 mL). Af◦ter filtration, the filtrate was concen-
trated and stored at −40 C overnight to afford orange yellow
crystals of 1 (2.93 g, 87%). Mp: 147 ◦C (decomp.). Anal. calcd for
C62H90Cl4N4OSm2: C, 55.17; H, 6.72; N, 4.15. Found: C, 55.66;
H, 7.01; N, 3.90%. IR (Nujol, KBr): 3057 (m), 2724 (w), 2669
(w), 1841 (w), 1623 (m), 1317 (s), 1261 (s), 1166 (s), 1097 (m),
1074 (m), 1020 (s), 965 (w), 926 (s), 862 (m), 839 (m), 791 (s),
757 (m), 722 (w), 667 (m), 633 (m), 585 (w), 555 (m), 509 (m).
LSmCp*Cl (6). Toluene (20 mL) was transferred to a solid
mixture of 1 (1.35 g, 1 mmol) and Cp*K (0.35 g, 2 mmol).
After the mixture was stirred at room temperature for 15 h, it
was filtered. The orange filtrate was concentrated and stored at
◦
−40 C overnight to afford orange crystals of 7 (1.12 g, 76%).
Mp: 186 ◦C (decomp.). Anal calcd for C39H56ClN2Sm (738.73):
C, 63.41; H, 7.64; N, 3.79. Found: C, 63.29; H, 7.78; N, 3.69%.
1H NMR (C6D6): d −9.51 (sept, 2H, CHMe2), 3.92 (d, 6H,
CHMe2), −0.87 (d, 6H, CHMe2), 0.98 (s, 15H, C5Me5), 1.62 (d,
6H, CHMe2), 2.38 (d, 6H, CHMe2), 2.98 (s, 6H, Me), 4.35 (d,
2H, Ar–H), 5.77 (t, 2H, Ar–H), 6.19 (d, 2H, Ar–H), 6.57 (sept,
2H, CHMe2), 10.82 (s, 1H, CH). IR (Nujol, KBr): 2726 (m),
1925 (w), 1863 (w), 1579 (w), 1513 (s), 1313 (s), 1271 (m), 1253
(m), 1232 (s), 1170 (s), 1108 (m), 1020 (s), 926 (s), 859 (s), 787
(s), 742 (m), 711 (m), 668 (m), 635 (w), 507 (m).
LSmClN(SiMe3)2 (2). To a solution of 1 (0.67 g, 0.5 mmol)
in toluene (25 mL) was added a solution of NaN(SiMe3)2 (0.18 g,
1 mmol) in toluene (10 mL) at room temperature. The mixture
was stirred for 12 h and filtered. The filtrate was concentrated
and stored at −40 ◦C for 2 d to give yellow crystals of 2 (0.57 g,
75%). Mp: 234 ◦C. Anal. calcd for C35H59ClN3Si2Sm: C, 55.05;
H, 7.79; N, 5.50. Found: C, 54.95; H, 7.87; N, 5.22%. 1H NMR
(C6D6): d −2.30 (br, 6H, CHMe2), −1.32 (br, 6H, CHMe2), 0.80
(s, 18H, SiMe3), 1.21 (d, 6H, CHMe2), 2.23 (d, 6H, CHMe2),
3.21 (s, 6H, Me), 5.09 (d, 2H, Ar–H), 5.96 (br m, 2H, CHMe2),
6.27 (m, 2H, Ar–H), 6.53 (d, 2H, Ar–H), 11.78 (s, 1H, CH).
Cl3L2Sm2(AlMe4)2Sm2L2Cl3 (7). To a solution of 2 (0.76 g
1.0 mmol) in toluene was added AlMe3 (1 mL, 2 M in
heptane, 2.0 mmol) at room temperature. The yellow solution
immediately turned to red. The mixture was stirred for 12 h,
and it was filtered to give a clear solution. The solution was
LSm[N(SiMe3)2]2 (3). The compound was prepared simi-
larly to 2 except 4 mole eq of NaN(SiMe3)2 (0.36 g, 2.0 mmol)
was employed. The product was crystallized from pentane to
give yellow crystals of 3 (0.67 g, 52%). Mp: 275 ◦C. Anal. calcd
for C41H77N4Si4Sm: C, 55.43; H, 8.74; N, 6.30. Found: C, 55.27;
H, 9.03; N, 5.96%. IR (Nujol, KBr): 3060 (w), 2361 (m), 2339
(m), 1623 (w), 1578 (w), 1306 (s), 1251 (s), 1165 (m), 1093 (m),
1020 (s), 948 (s), 924 (s), 877 (m), 831 (s), 791 (m), 771 (m), 731
(m), 667 (s), 605 (m).
◦
concentrated and stored at −40 C for 3 d to give red crystals
of 7 (0.17 g, 20%). Mp: 127 ◦C (decomp.). Anal. calcd for
C124H188Al2Cl6N8Sm4: C, 56.02; H, 7.13; N, 4.21. Found: 55.71;
H, 7.24; N, 4.60%. IR (Nujol, KBr): 3057 (m), 2729 (m), 1929
(w), 1867 (w), 1604 (m), 1516 (s), 1310 (m), 1259 (m), 1165 (m),
1097 (s), 1021 (s), 928 (m), 893 (w), 842 (m), 791 (s), 755 (m),
727 (s), 694 (s), 638 (m), 616 (m), 564 (w), 543 (m), 512 (m).
LSmCp*Me (8). To a solution of 6 (0.74 g, 1 mmol) in
toluene (15 mL) was added MeLi (0.72 mL, 1.4 M in ether,
1 mmol) at room temperature. After stirring overnight, the
solution was filtered. The solvent was evaporated and the
remaining solid was washed with a small amount of cold pentane
to afford pure 8 as an orange microcrystalline solid (0.65 g, 90%).
Mp: 132 ◦C (decomp.). Anal. calcd for C40H59N2Sm (718.32): C,
66.88; H, 8.28; N, 3.90. Found: C, 66.59; H, 8.34; N, 3.96%.
1H NMR (C6D6): d −10.65 (br, 2H, CHMe2), −5.40 (d, 6H,
CHMe2), −1.15 (d, 6H, CHMe2), 1.15 (s, 15H, C5Me5), 2.32 (d,
6H, CHMe2), 2.60 (s, 6H, Me), 2.76 (d, 6H, CHMe2), 3.32 (d, 2H,
LSm(NHAr)(BHEt3) (4, Ar = 2,4,6-t-Bu3C6H2). Toluene
was added to a mixture of 1 (0.67 g, 0.5 mmol) and KNHAr
(0.30 g, 1.0 mmol) at room temperature. The mixture was
stirred overnight, then a solution of KHBEt3 in THF was
added. The solution was stirred for an additional 12 h, the
solvent was then removed under vacuum, and the remaining
red residue was extracted with pentane. It was filtered, and the
filtrate was concentrated and stored at −40 ◦C for 2 d to afford
red crystals of 4 (0.73 g, 79%). Mp: 120 ◦C (decomp.). Anal
calcd for C53H87BN3Sm: C, 68.64; H, 9.45; N, 4.53. Found: C,
D a l t o n T r a n s . , 2 0 0 5 , 1 3 8 7 – 1 3 9 3
1 3 9 1

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Ar–H), 5.17 (m, 2H, Ar–H), 5.94 (d, 2H, Ar–H), 9.13 (br, 2H,
CHMe2), 10.2 (br s, 3H, Sm–Me), 10.51 (s, 1H, CH). IR (Nujol,
KBr): 3057 (w), 2720 (w), 1721 (w), 1515 (s), 1309 (s), 1269 (m),
1236 (w), 1167 (m), 1108 (m), 1090 (m), 1019 (s), 928 (m), 835
(m), 783 (s), 742 (m), 504 (m).
LSmCp*CH2SiMe3 (9). To a solid mixture of 6 (0.74 g,
1 mmol) and LiCH2SiMe3 (0.094 g, 1 mmol) was added toluene
(15 mL) at room temperature. The mixture was stirred at room
temperature for 15 h. All volatiles were removed under vacuum,
and the residue was extracted wi◦th pentane. It was filtered,
and the filtrate was stored at −40 C overnight to give orange
◦
crystals of 9 (0.70 g, 89%). Mp: 142 C (decomp.). Anal calcd
for C43H67N2SiSm: C, 65.33; H, 8.54; N, 3.54. Found: C, 65.03;
H, 8.88; N, 3.29%. 1H NMR (C6D6): d −8.75 (br, 2H, CHMe2),
−5.48 (d, 6H, CHMe2), −0.98 (d, 6H, CHMe2), 1.25 (s, 9H,
SiMe3), 1.30 (s, 15H, C5Me5), 2.26 (s, 6H, Me), 2.37 (d, 6H,
CHMe2), 2.62 (d, 6H, CHMe2), 3.93 (d, 2H, Ar–H), 5.62 (m,
2H, Ar–H), 6.40 (d, 2H, Ar–H), 8.96 (br, 2H, CHMe2), 9.90 (s,
1H, CH), 11.98 (s, 2H, SmCH2). IR (Nujol, KBr): 3059 (m),
2726 (m), 1924 (w), 1863 (w), 1579 (w), 1313 (s), 1271 (s), 1252
(s), 1232 (s), 1170 (s), 1108 (s), 1020 (s), 926 (s), 859 (s), 786 (m),
742 (s), 710 (m), 668 (m), 636 (m), 507 (m).
(LSmCp*)[MeB(C6F5)3] (10). Toluene (20 mL) was added
to a mixture of 8 (0.30 g, 0.42 mmol) and B(C6F5)3 (0.21 g,
◦
0.42 mmol) at 0 C. The mixture immediately turned red. The
ice bath was removed, and the mixture was stirred at room
temperature for 4 h. After removal of solvent in vacuo, the red
solid was washed twice with pentane and dried under vacuum
to give 10 as a deep red powder (0.42 g, 81%). Mp: 340 ◦C
(decomp.). Anal. calcd for C58H59BF15N2Sm (1230.18): C, 56.63;
H, 4.83; N, 2.28. Found: C, 56.87; H, 5.18, N, 2.40%. 1H NMR
(C7D8): d −15.78 (br s, 3H, MeB), −2.08 (br, 2H, CHMe2),
−0.82 (br, 6H, CHMe2), −0.18 (br, 6H, CHMe2), 0.13 (s, 15H,
C5Me5), 0.18 (br, 6H, CHMe2), 0.73 (br, 2H, CHMe2), 1.49 (br,
6H, CHMe2), 4.17 (s, 6H, Me), 6.24 (d, 4H, Ar–H), 6.68 (m, 2H,
Ar–H), 12.50 (s, 1H, CH).
=
LSmCp*[N C(Me)(C6H4-4-Me)] (11). To a solution of 8
(0.50 g, 0.7 mmol) in toluene (10 mL) was added 4-MeC6H4CN
(0.082 g, 0.7 mmol). The orange solution was stirred at room
temperature for 2 h. All volatiles were removed under vacuum,
and the residue was crystallized from toluene to give orange
crystals of 11 (380 mg, 65%). Mp: 124 ◦C (decomp.). Anal. calcd
for C48H66N3Sm (835.45); C, 69.01; H, 7.96; N, 5.03. Found: C,
1
69.01; H, 8.12; N, 4.96%. H NMR (C6D6): d −12.01 (br, 2H,
CHMe2), −6.32 (br, 6H, CHMe2), −1.65 (br, 6H, CHMe2), 1.08
(s, 15H, C5Me5), 2.41 (s, 6H, Me), 2.56 (d, 6H, CHMe2), 2.62 (s,
3H, Ar–Me), 2.68 (d, 6H, CHMe2), 3.12 (d, 2H, Ar–H), 5.13 (m,
2H, Ar–H), 6.02 (d, 2H, Ar–H), 6.19 (s, 3H, NCMe), 7.98 (d,
2H, Ar–H), 9.02 (sept, 2H, CHMe2), 10.34 (s, 1H, CH), 11.43
(d, 2H, Ar–H). IR (Nujol, KBr): 3059 (w), 2720 (w), 1640 (s),
1602 (w), 1566 (w), 1518 (s), 1315 (s), 1261 (s), 1228 (m), 1173
(m), 1096 (m), 1020 (m), 956 (w), 926 (m), 815 (m), 787 (s), 755
(m), 722 (m), 579 (w).
=
LSmCp*[C(Me) N–C6H3-2,6-Me2] (12). To an orange so-
lution of 8 (0.50 g, 0.7 mmol) in toluene was added 2,6-
Me2C6H3NC (0.092 g, 0.7 mmol). The mixture was stirred at
room temperature for 4 h. After removal of solvent under
vacuum, the remaining orange solid was washed with cold
pentane to give yellow 12 (0.42 g, 71%). Mp: 131 ◦C (decomp.).
Anal. calcd for C49H68N3Sm: C, 69.28; H, 8.07; N, 4.94. Found:
1
C, 69.21, H, 8.23; N, 4.87%. H NMR (C6D6): d 0.45 (s, 6H,
Me), 0.52 (br, 6H, CHMe2), 0.58 (d, 6H, CHMe2), 1.04 (s, 15H,
C5Me5), 1.29 (d, 6H, CHMe2), 2.20 (s, 6H, Me), 2.40 (s, 1H,
CH), 2.59 (d, 6H, CHMe2), 4.51 (s, 3H, b-Me), 6.60 (sept, 2H,
CHMe2), 6.67 (d, 2H, Ar–H), 7.35 (m, 2H, Ar–H), 7.50 (d, 2H,
Ar–H). IR (Nujol, KBr): 3058 (m), 2725 (m), 1914 (w), 1845 (w),
1655 (w), 1621 (w), 1590 (w), 1510 (s), 1312 (s), 1274 (s), 1252
1 3 9 2
D a l t o n T r a n s . , 2 0 0 5 , 1 3 8 7 – 1 3 9 3

View Article Online
(s), 1228 (m), 1167 (s), 1109 (m), 1018 (s), 927 (m), 823 (m), 786
(s), 755 (m), 721 (m), 612 (m).
11 P. L. Holland and W. B. Tolman, J. Am. Chem. Soc., 1999, 121, 7270.
12 F. Basuli, B. C. Bailey, J. Tomaszewski, J. C. Huffman and D. J.
Mindiola, J. Am. Chem. Soc., 2003, 125, 6052.
13 F. Basuli, B. C. Bailey, J. C. Huffman and D. J. Mindiola, Chem.
Commun., 2003, 1554.
14 P. G. Hayes, W. E. Piers, L. W. M. Lee, L. K. Knight, M. Parvez,
M. R. J. Elsegood and W. Clegg, Organometallics, 2001, 20, 2533.
15 P. G. Hayes, W. E. Piers and R. McDonald, J. Am. Chem. Soc., 2002,
124, 2132.
16 P. G. Hayes, W. E. Piers and M. Parvez, J. Am. Chem. Soc., 2003,
125, 5622.
17 D. Drees and J. Magull, Z. Anorg. Allg. Chem., 1995, 621, 948.
18 M. F. Lappert and W. J. Evans, J. Organomet. Chem., 2002, 647, 1.
19 A. G. Avent, A. V. Khvostov, P. B. Hitchcock and M. F. Lappert,
Chem. Commun., 2002, 1410.
20 Y. M. Yao, Y. Zhang, Z. Q. Zhang, Q. Shen and K. B. Yu,
Organometallics, 2003, 22, 2876.
21 Y. Zhang, Y. M. Yao, Y. J. Luo, Q. Shen, Y. Cui and K. B. Yu,
Polyhedron, 2003, 22, 1241.
22 A. G. Avent, P. B. Hitchcock, A. V. Khvostov, M. F. Lappert and
A. V. Protchenko, Dalton Trans., 2003, 1070.
=
LSmCp*[C(CH2SiMe3) N–C6H3-2,6-Me2] (13). Compound
13 was obtained analogously to 12 above using 9. Yellow
◦
crystals (0.53 g, 82%). Mp: 197 C (decomp.). Anal. calcd for
C52H76N3SiSm: C, 67.76; H, 8.32; N, 4.56. Found: C, 67.23; H,
1
8.28, N, 4.27%. H NMR (C6D6): d 0.02 (s, 6H, Ar–Me), 0.36
(s, 9H, SiMe3), 0.96 (s, 15H, C5Me5), 1.16 (d, 6H, CHMe2), 1.23
(d, 6H, CHMe2), 2.04 (s, 6H, Me), 2.42 (d, 6H, CHMe2), 2.78
(d, 6H, CHMe2), 5.12 (br s, 2H, CH2SiMe3), 6.58 (d, 2H, Ar–
H), 6.86 (sept, 2H, CHMe2), 7.03 (m, 3H, Ar–H), 7.33 (m, 2H,
Ar–H), 7.43 (s, 1H, CH), 7.46 (sept, 2H, CHMe2), 7.72 (d, 2H,
Ar–H).
X-Ray structural determinations
Pertinent details for the individual compounds can be found in
Table 1. A suitable crystal was mounted on a glass capillary using
Paratone-N hydrocarbon oil. The crystal was transferred to a
Siemens SMART diffractometer/CCD area detector44 with Mo-
23 Y. M. Yao, Y. J. Luo, R. Jiao, Q. Shen, K. B. Yu and L. H. Weng,
Polyhedron, 2003, 22, 441.
24 Y. M. Yao, Y. Zhang, Q. Shen and K. B. Yu, Organometallics, 2002,
21, 819.
˚
Ka radiation (k = 0.71073 A), centered in the beam, and cooled
by a nitrogen flow low temperature apparatus. Preliminary
orientation matrix and cell constants were determined by
collection of 60 10-second frames, followed by spot integration
and least square refinement. An arbitrary hemisphere of data
was collected and the raw data were integrated using SAINT.45
Cell dimensions reported in Table 1 were calculated from all
reflections with I>10r(I). Data were analyzed for agreement and
possible absorption using XPREP.46 An empirical absorption
correction based on comparison of redundant and equivalent
reflections was applied using SADABS.47 The data were cor-
rected for Lorentz and polarization effects, but no correction
for crystal decay was applied. The structures were solved and
refined with the teXsan software package.48
25 P. B. Hitchcock, M. F. Lappert and S. Tian, J. Chem. Soc., Dalton
Trans., 1997, 1945.
26 D. Drees and J. Magull, Z. Anorg. Allg. Chem., 1994, 620, 814.
27 Y. M. Yao, Q. Shen, Y. Zhang, M. Q. Xue and J. Sun, Polyhedron,
2001, 20, 3201.
28 After submission of this manuscript, Shen and co-workers described
related work: Z. Q. Zhang, Y. M. Yao, Y. Zhang, Q. Shen and W. T.
Wong, Inorg. Chim. Acta, 2004, 357, 3173.
29 D. Baudry, A. Dormond, B. Lachot, M. Visseaux and G. Zucchi,
J. Organomet. Chem., 1997, 547, 157.
30 D. Barbier-Baudry, A. Dormond and M. Visseaux, J. Organomet.
Chem., 2000, 609, 21.
31 P. Binger, G. Benedikt, G. W. Rotermund and R. Koster, Liebigs Ann.
Chem., 1968, 717, 21.
32 M. J. Harvey, T. P. Hanusa and M. Pink, Chem. Commun., 2000, 489.
33 L. Hasinoff, J. Takats, X. W. Zhang, P. H. Bond and R. D. Rogers,
J. Am. Chem. Soc., 1994, 116, 8833.
34 W. J. Evans, T. A. Ulibarri and J. W. Ziller, J. Am. Chem. Soc., 1988,
110, 6877.
CCDC reference numbers 244217–244219, 244221–244223
and 245593 (there is no CCDC reference number for com-
pound 4).
See http://www.rsc.org/suppdata/dt/b5/b501437a/ for cry-
stallographic data in .cif or other electronic format.
35 W. J. Evans, K. J. Forrestal and J. W. Ziller, J. Am. Chem. Soc., 1998,
120, 9273.
36 W. J. Evans, B. L. Davis, G. W. Nyce, J. M. Perotti and J. W. Ziller,
J. Organomet. Chem., 2003, 677, 89.
37 W. J. Evans, J. M. Perotti, J. W. Ziller, D. F. Moser and R. West,
Organometallics, 2003, 22, 1160.
38 W. J. Evans, J. W. Grate, H. W. Choi, I. Bloom, W. E. Hunter and
J. L. Atwood, J. Am. Chem. Soc., 1985, 107, 941.
Acknowledgements
We are grateful to the NSF and DOE for the support of this
work and to the referees for their helpful comments.
39 R. J. Butcher, D. L. Clark, J. C. Gordon and J. G. Watkin,
J. Organomet. Chem., 1999, 577, 228.
40 Z. M. Hou, A. Fujita, Y. G. Zhang, T. Miyano, H. Yamazaki and Y.
Wakatsuki, J. Am. Chem. Soc., 1998, 120, 754.
41 A. C. Hillier, X. W. Zhang, G. H. Maunder, S. Y. Liu, T. A.
Eberspacher, M. V. Metz, R. McDonald, A. Domingos, N. Marques,
V. W. Day, A. Sella and J. Takats, Inorg. Chem., 2001, 40, 5106.
42 W. J. Evans, L. R. Chamberlain, T. A. Ulibarri and J. W. Ziller, J. Am.
Chem. Soc., 1988, 110, 6423.
43 J. L. Atwood and D. C. Hrncir, J. Organomet. Chem., 1973, 61, 43.
44 SMART Area-Detector Software package, Siemens Analytical X-ray
Instruments Inc., Madison, WI, 1995.
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D a l t o n T r a n s . , 2 0 0 5 , 1 3 8 7 – 1 3 9 3
1 3 9 3