Synthesis and X-ray crystal structures of the samarium mono(pentamethylcyclopentadienyl) aryloxide complexes (η-C5Me5)Sm(O-2,6-t-Bu2C6H 3)2(THF) and [(η-C5Me5)Sm(O-2,6-i-Pr2C6H 3)3Li(THF)]. Differences in metathesis chemistry of 2,6-di-iso-propylphenoxide.

Article abstract of DOI:10.1016/S0022-328X(98)01046-8

The reaction of SmCl₃ with three equivalents of KO-2,6-t-Bu₂C₆H₃ in THF produces the tris(aryloxide) complex Sm(OAr)₃(THF) (Ar=2,6-t-Bu₂C₆H₃, 1). Complex 1 undergoes clean metathesis reaction with one equivalent of LiC₅Me₅ to form the mono(pentamethylcyclopentadienyl) aryloxide derivative (η-C₅Me₅)Sm(OAr)₂(THF) (2). In contrast, an analogous reaction of LiC₅Me₅ with the 2,6-di-iso-propylphenoxide complex Sm(OAr*)₃(THF)₂ (Ar=2,6-i-Pr₂C₆H₃, 3) leads to overall addition of the alkali metal reagent, and isolation of the lithium-containing 'ate' complex [(η-C₅Me₅)Sm(OAr*)(μ-OAr*) ₂Li(THF)] (4). Compounds 2 and 4 have been subjected to single-crystal X-ray diffraction studies. Complex 2 features a three-legged piano-stool geometry, with Sm-O distances to the aryloxide ligands of 2.133(6) and 2.188(6) A, and a Sm-O(THF) distance of 2.435(7) A. Complex 4 also exhibits a three-legged piano-stool geometry, with two of the aryloxide oxygen atoms coordinated to a lithium metal center. A THF ligand completes the coordination sphere of the lithium. The Sm-O bond lengths to the lithium-coordinated aryloxide oxygens (2.250(6) and 2.247(5) A) are longer than the distance to the terminal aryloxide (Sm-O=2.144(6) A). The Li-O distances range from 1.876(17) to 1.945(18) A.

Full text of DOI:10.1016/S0022-328X(98)01046-8

Journal of Organometallic Chemistry 577 (1999) 228–237
Synthesis and X-ray crystal structures of the samarium
mono(pentamethylcyclopentadienyl) aryloxide complexes
(p-C5Me5)Sm(O-2,6-t-Bu2C6H3)2(THF) and
[(p-C5Me5)Sm(O-2,6-i-Pr2C6H3)3Li(THF)]. Differences in metathesis
chemistry of 2,6-di-iso-propylphenoxide and 2,6-di-tert-butylphenoxide
ligands
Raymond J. Butcher a,1, David L. Clark b, John C. Gordon a, John G. Watkin a,*
a Chemical Science and Technology Di6ision, Los Alamos National Laboratory, CST-18, Mail Stop J514, Los Alamos, NM 87545, USA
b Los Alamos National Laboratory, NMT-DO, Mail Stop E500, Los Alamos, NM 87545, USA
Received 12 June 1998; received in revised form 30 September 1998
Abstract
The reaction of SmCl3 with three equivalents of KO-2,6-t-Bu2C6H3 in THF produces the tris(aryloxide) complex
Sm(OAr)3(THF) (Ar=2,6-t-Bu2C6H3, 1). Complex 1 undergoes clean metathesis reaction with one equivalent of LiC5Me5 to form
the mono(pentamethylcyclopentadienyl) aryloxide derivative (p-C5Me5)Sm(OAr)2(THF) (2). In contrast, an analogous reaction of
LiC5Me5 with the 2,6-di-iso-propylphenoxide complex Sm(OAr*)3(THF)2 (Ar*=2,6-i-Pr2C6H3, 3) leads to overall addition of the
alkali metal reagent, and isolation of the lithium-containing ‘ate’ complex [(p-C5Me5)Sm(OAr*)(v-OAr*)2Li(THF)] (4). Com-
pounds 2 and 4 have been subjected to single-crystal X-ray diffraction studies. Complex 2 features a three-legged piano-stool
˚
˚
geometry, with Sm–O distances to the aryloxide ligands of 2.133(6) and 2.188(6) A, and a Sm–O(THF) distance of 2.435(7) A.
Complex 4 also exhibits a three-legged piano-stool geometry, with two of the aryloxide oxygen atoms coordinated to a lithium
metal center. A THF ligand completes the coordination sphere of the lithium. The Sm–O bond lengths to the lithium-coordinated
˚
˚
aryloxide oxygens (2.250(6) and 2.247(5) A) are longer than the distance to the terminal aryloxide (Sm–O=2.144(6) A). The
Li–O distances range from 1.876(17) to 1.945(18) A. © 1999 Elsevier Science S.A. All rights reserved.
˚
Keywords: Samarium; Aryloxide; Metathesis; Pentamethylcyclopentadienyl
1. Introduction
drogenation and hydroamination, as well as in alkyne
coupling reactions [3]. The most extensively investigated
organolanthanide systems are those containing bis(pen-
tamethylcyclopentadienyl) ligation [2]. The presence of
these two bulky ligands can have dramatic conse-
quences for the reactivity of the complexes toward
potential substrates. One example of this behavior has
been demonstrated by Marks and co-workers in the
reaction of olefins with a series of complexes containing
‘open’ (C5Me5)2Ln and ‘bridged’ Me2Si(C5Me4)2Ln
fragments (Ln=Nd, Sm, Lu) [3c]. The bridged analogs
were found to exhibit significant reactivity increases
In recent years, there has been a great deal of interest
in the structure and reactivity of organometallic com-
plexes of the f-elements [1,2]. Lanthanide complexes, in
particular, have been shown to be extremely active
catalysts and have found application in areas such as
organic syntheses, olefin polymerization, catalytic hy-
* Corresponding author.
1 Present address: Department of Chemistry, Howard University,
Washington, DC 20059, USA.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01046-8

R.J. Butcher et al. / Journal of Organometallic Chemistry 577 (1999) 228–237
229
over the non-bridged analogs in reactions which pro-
ceed via sterically sensitive processes, such as olefin
insertion into the (p-C5Me5)2LnR and Me2Si(C5Me4)2-
LnR metal–carbon | bond. The conclusion of this
study was that the bridging ring system allowed for an
increase in the available coordination space around the
metal center. As a consequence of these and other
observations, it has been envisioned that the even
greater steric and electronic unsaturation of mono(cy-
clopentadienyl) lanthanide systems, relative to their bis-
ring counterparts, should make them desirable synthetic
goals as potentially active catalysts [1,4].
Our recent research efforts have focused upon the
chemistry of lanthanide metals containing primarily
aryloxide ligation. We, and other groups, have noted
that a significant degree of control over the coordina-
tion number and degree of oligomerization of the lan-
thanide complexes is available via the use of bulky
substituents on the aryloxide ligand [5–11]. Owing to
the relatively scarce nature of monomeric mono(pen-
tamethylcyclopentadienyl) complexes containing ary-
loxide ligands, we set out to explore the possibility of
preparing examples of this class via metathesis of an
aryloxide ligand from tris(aryloxide) precursors using
LiC5Me5. Lithium aryloxide formation (i.e. precipita-
tion) has been used previously as a synthetic tool to
replace a number of aryloxides with other ligand types,
including alkyls and amides (Eqs. (1a) and (1b)) [1a].
addition to 2,6-di-tert-butylphenoxide. The isolation
and characterization of the products from reactions of
the tris(aryloxide) complexes Sm(O-2,6-t-Bu2C6H3)3-
(THF) and Sm(O-2,6-i-Pr2C6H3)3(THF)2 with one
equivalent of LiC5Me5 are the subject of the present
paper.
2. Results and discussion
2.1. Synthesis and reacti6ity
The reaction of anhydrous samarium trichloride with
three equivalents of KO-2,6-t-Bu2C6H3 in THF leads to
formation of the mono-THF adduct Sm(O-2,6-t-
Bu2C6H3)3(THF) (1) in 28% yield (Eq. (3)). Similar
tris-aryloxide complexes have been reported previously
as both the solvent-free homoleptic species, and also as
Lewis base adducts with coordinated acetonitrile and
THF [6e,8a,16].
SmCl3+3 KOArTꢀHꢀFꢁSm(OAr)3(THF)+3 KCl
(3)
Ar=2,6-t-Bu2C6H3
Metathesis reaction of 1 with one equivalent of
LiC5Me5 proceeds smoothly to yield the mono(pen-
tamethylcyclopentadienyl) samarium complex (p-
C5Me5)Sm(O-2,6-t-Bu2C6H3)2(THF) (2) (Fig. 1) in
good yield:
Ln(OAr)3+3LiR“LnR3+3LiOAr
(1a)
Ln=La, Sm; Ar=2,6-t-Bu2C6H3; R=CH(SiMe3)2;
Ref. [12]
Ln(OAr)3+MC5Me5“(p-C5Me5)Ln(OAr)2+MOAr
(1b)
M=Li, Ln=La [13], Ce [14]; M=K, Ln=Y [15]
Ar=2,6-t-Bu2C6H3
(4)
A similar synthetic route, employing Ln(O-2,6-t-
Bu2C6H3)3 (Ln=Y, La, Ce) and one equivalent of
KC5Me5 (Ln=Y) or LiC5Me5 (Ln=La, Ce), has
been used previously to prepare the analogous base-
free yttrium, lanthanum and cerium complexes (p-
C5Me5)Ln(O-2,6-t-Bu2C6H3)2 (Ln=Y [15], La [13],
Ce [14]). The fact that the lanthanum compound has
been reported to react with THF to form a bis-THF
adduct, (p-C5Me5)Ln(O-2,6-t-Bu2C6H3)2(THF)2, rather
than a mono-THF adduct analogous to 2, presumably
reflects the larger ionic radius of lanthanum compared
We have previously reported, however, that the reac-
tion of Sm(O-2,6-i-Pr2C6H3)3(THF)2 with three equiva-
lents of LiCH2SiMe3 did not lead to the desired
metathesis reaction, but rather resulted in the addition
of two equivalents of lithium alkyl to produce the
mixed alkyl–aryloxide complex [Li(THF)]2[Sm(O-2,6-i-
Pr2C6H3)3(CH2SiMe3)2] [7a]:
Ln(OAr)3(THF)2+3 LiRTꢀHꢀFꢁ[Li(THF)]2[Ln(OAr)3R2]
+LiR
(2)
1
to samarium. The ambient temperature H-NMR spec-
Ln=Sm; Ar=2,6-i-Pr2C6H3; R=CH2SiMe3
trum of 2 in benzene-d6 reveals a 2:1 ratio of aryloxide
and Cp* ligands, and also upfield shifted resonances
typical of a THF ligand bound to a samarium metal
center. It has been reported that solutions of the lan-
thanum compound (p-C5Me5)La(O-2,6-t-Bu2C6H3)2
and the bis-THF adduct (p-C5Me5)Ln(O-2,6-t-
Bu2C6H3)2(THF)2 are both susceptible to ligand redis-
Thus we set out to investigate whether lithium ary-
loxide metathesis could be used as a rational synthetic
route to prepare mono(pentamethylcyclopentadienyl)
samarium(III) complexes containing other bulky ary-
loxide ligands such as 2,6-di-iso-propylphenoxide, in

230
R.J. Butcher et al. / Journal of Organometallic Chemistry 577 (1999) 228–237
Fig. 1. ORTEP plot (40% probability ellipsoids) showing the molecular structure of (p-C5Me5)Sm(O-2,6-t-Bu2C6H3)2(THF) (2) giving the labeling
scheme used in the Tables.
1
tribution to form
a
mixture of Cp*La(OAr),
analytical results (elemental analysis, H-NMR integra-
tion) which show the presence of less than one solvent
2
Cp*La(OAr)2 and La(OAr)3 [13]. No evidence of simi-
lar solution behavior for 2 was observed. Complex 2
was found to crystallize from hexane with one molecule
of lattice solvent per unit cell, and does not appear to
be prone to solvent loss upon standing in the drybox
atmosphere.
The synthesis of the Lewis base adduct Sm(O-2,6-i-
Pr2C6H3)3(THF)2 (3) has been described elsewhere [7a].
The reaction of 3 with one equivalent of LiC5Me5 does
not produce the expected Cp*Sm(O-2,6-i-Pr2C6H3)2
species, but rather leads to overall addition of the
lithium reagent to form the lithium ‘ate’ complex
[(p-C5Me5)Sm(O-2,6-i-Pr2C6H3)(v-O-2,6-i-Pr2C6H3)2-
Li(THF)] (4) as illustrated in Eq. (5).
1
molecule per samarium moiety. H-NMR spectra of 4
in benzene-d6 show only one aryloxide ligand environ-
ment, indicative of rapid lithium exchange between
pairs of ‘legs’ of the piano stool geometry. Rapid
exchange of alkali metal cations between multiple
alkoxide ligands has been a characteristic feature of
previously-isolated f-element ‘ate’ complexes [7a,c,d].
Reaction of a hexane solution of 4 with an excess of
TMEDA (tetramethylethylenediamine, Me2NCH2CH2-
NMe2) leads to formation of a compound formulated
as the salt complex 5 as shown in Eq. (6).
(6)
Microanalytical data and 1H-NMR integration are
consistent with the presence of two equivalents of
TMEDA per formula unit. The formulation of 5 as a
charge-separated salt complex is based upon the signifi-
cant reduction in solubility in non-polar solvents of 5 as
compared to 4 (5 is found to be insoluble in hexane and
toluene, soluble in THF and methylene chloride), and
also the known ability of a bis-TMEDA coordination
(5)
Compound 4 (Fig. 2) is obtained as a yellow solid in
good yield and is soluble in hydrocarbon solvents such
as hexane and toluene. Compound 4 is found to crystal-
lize from toluene with one lattice solvent molecule per
formula unit. Removal of the mother liquor from a
crystalline sample of 4 leads to rapid powdering and to

R.J. Butcher et al. / Journal of Organometallic Chemistry 577 (1999) 228–237
231
Fig. 2. ORTEP representation (40% probability ellipsoids) of the molecular structure of [(p-C5Me5)Sm(O-2,6-i-Pr2C6H3)3Li(THF)] (4) giving the
labeling scheme used in the Tables. Methyl carbon atoms of the iso-propyl groups have been omitted for clarity.
environment to effectively separate a lithium cation
from an anionic complex [17]. Attempts to grow single
crystals of 5 for X-ray diffraction analysis were
unsuccessful.
The Sm–C bond distances to the cyclopentadienyl
ligand average 2.762(10) A, which is comparable to
˚
those observed in other samarium pentamethylcy-
clopentadienyl complexes [18,19]. The Sm–O(aryloxide)
˚
bond lengths of 2.133(6) and 2.188(6) A are in the
range previously observed for Sm(III)–O(aryloxide) in-
teractions [7b,18,19a,20], while the Sm–O(THF) dis-
tance of 2.435(7) A is also typical of those observed
2.2. Solid state and molecular structures
˚
The mono(pentamethylcyclopentadienyl) aryloxide
complexes 2 and 4 have been examined by single crystal
X-ray diffraction techniques. Data collection parame-
ters are given in Table 1.
previously. The Sm–O–C(aryloxide) bond angles of
165.3(6) and 175.7(5)° differ considerably from those
found in the base-free cerium analog (p-C5Me5)Ce(O-
2,6-t-Bu2C6H3)2 [14]. In the cerium complex, Ce–O–C
angles of 158.6(2) and 105.0(2)° were found, and a
significant C–H···Ce interaction was observed with a
methyl group on the aryloxide possessing the acute
Ce–O–C angle. In the case of 2, it is proposed that the
presence of the coordinated THF ligand leads to
greater steric saturation and decreased electrophilicity
of the metal center, resulting in the absence of Sm–
methyl contacts and the typically obtuse Sm–O–C(ary-
loxide) angles.
The two aryloxide ring planes differ markedly in
their orientation with respect to the Cp* ligand. While
the aryloxide containing O(1) is oriented with its ring
plane roughly parallel to the Cp* plane, the aryloxide
containing O(2) is twisted until almost perpendicular to
the cyclopentadienyl ligand. As a result, the THF lig-
2.2.1. (p-C5Me5)Sm(O-2,6-t-Bu2C6H3)2(THF) · C6H14
(2)
Single crystals of 2 suitable for an X-ray diffraction
study were grown by slow evaporation of a hexane
solution in the drybox atmosphere. Diffraction data
were collected at −70°C. Fractional atomic coordi-
nates and isotropic thermal parameters for 2 are pre-
sented in Table 2, while selected bond lengths and
angles are listed in Table 3. The monomeric complex 2
crystallizes in the orthorhombic space group P212121
with one molecule of lattice hexane per formula unit.
The geometry about the samarium metal center approx-
imates a three-legged piano stool with two aryloxide
ligands and a THF molecule constituting the ‘legs’ of
the molecule.

232
R.J. Butcher et al. / Journal of Organometallic Chemistry 577 (1999) 228–237
Table 2
and is found to be situated significantly closer to the
O(2) aryloxide (O(2)–Sm(1)–O(3)=84.6(2)°) than the
O(1) aryloxide (O(1)–Sm(1)–O(3)=111.4(2)°), which
has one of its tert-butyl groups directed toward the
THF ligand.
Fractional atomic coordinates (×105) and equivalent isotropic dis-
placement coefficientsa (A2×104) for (p-C5Me5)Sm(O-2,6-t-
Bu2C6H3)2(THF) (2)
x
y
z
Ueq
Sm(1)
O(1)
O(2)
O(3)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10)
C(11)
C(12)
C(121)
C(122)
C(123)
C(124)
C(13)
C(14)
C(15)
C(16)
C(161)
C(162)
C(163)
C(164)
C(21)
C(22)
18311(3)
27049(47)
4654(40)
17336(3)
7033(40)
84021(2)
177(1)
2.2.2. [(p-C5Me5)Sm(O-2,6-i-Pr2C6H3)3Li(THF)] · C7H8
(4)
80875(36)
78967(30)
77009(33)
91735(46)
94837(46)
97132(50)
95351(49)
92131(48)
89296(61)
95825(60)
240(20)
163(18)
222(20)
236(27)
274(28)
312(31)
249(29)
213(30)
371(38)
348(36)
405(38)
347(35)
382(39)
262(29)
391(40)
320(32)
265(30)
479(42)
518(46)
598(54)
891(80)
589(55)
344(36)
418(40)
651(56)
703(60)
609(55)
157(25)
163(28)
304(33)
425(41)
278(32)
284(32)
280(32)
295(32)
265(29)
201(27)
249(28)
402(38)
291(32)
321(30)
234(30)
303(34)
350(37)
370(35)
15716(35)
29642(40)
24884(61)
17101(68)
18102(74)
26387(60)
30447(57)
27138(75)
9560(71)
12130(78)
30432(71)
39477(68)
−716(55)
−8057(68)
−9022(56)
−857(60)
Single crystals of 4 suitable for X-ray diffraction
analysis were grown by slow evaporation of a toluene
solution in the drybox atmosphere. Diffraction data
were collected at −100°C. Fractional atomic coordi-
nates and isotropic thermal parameters for 4 are pre-
sented in Table 4, while selected bond lengths and
angles are listed in Table 5. Compound 4 crystallizes in
the monoclinic space group P21/c. The coordination
geometry about the lanthanide metal center approxi-
mates a three-legged piano stool, the samarium atom
being directly bound to three aryloxide ligands and a
pentamethylcyclopentadienyl group. The overall molec-
ular geometry is thus similar to that observed in the
mono-pentamethylcyclopentadienyl lutetium tris(tert-
butoxide) complex [(p-C5Me5)Lu(O-t-Bu)3Li(TME-
DA)] [21].
20218(42)
32401(73)
29897(66)
20121(66)
16945(73)
24450(71)
42118(78)
36008(73)
15199(78)
8072(76)
24971(89)
30689(66)
26638(74)
17934(78)
12806(67)
10256(77)
21488(92)
30346(85)
101855(58)
97948(53)
90300(62)
79435(54)
81917(67)
86680(59)
88480(52)
83739(72)
93086(68)
79862(86)
75675(103)
73353(86)
75073(61)
72366(65)
67968(71)
77881(77)
67955(72)
75745(48)
78950(51)
85916(56)
88349(57)
90706(51)
86183(51)
75520(58)
69007(54)
65990(59)
69277(51)
65502(54)
58571(55)
68934(52)
64959(50)
75786(52)
70737(61)
71756(60)
73156(61)
−14945(64)
−12904(78)
−15956(65)
37913(102) −16323(81)
42006(93)
38626(67)
43612(82)
36774(92)
47297(110)
52248(83)
−9131(80)
−1125(73)
6659(79)
11528(100)
12071(94)
4655(98)
14080(52)
15488(50)
18730(66)
18556(97)
13170(69)
27893(61)
13937(62)
11153(65)
9947(57)
Table 1
Summary of crystal data
Compounda
2
4
−3673(59)
−12656(63)
Empirical formula C48H79O3Sm
C57H74LiO4Sm
Monoclinic
P21/c
Crystal system
Space group
Unit cell
Orthorhombic
P212121
C(221) −13551(71)
C(222) −24006(73)
C(223)
−8085(70)
dimension
˚
C(224) −10067(73)
a (A)
13.962(3)
15.779(3)
20.621(4)
90
10.878(5)
13.869(10)
35.94(2)
93.06
˚
C(23)
C(24)
C(25)
C(26)
C(261)
C(262)
C(263)
C(264)
C(30)
C(31)
C(32)
C(33)
−21066(64)
−20869(74)
−12151(65)
−3665(64)
5914(63)
b (A)
˚
c (A)
i (°)
Crystal size (mm) 0.57×0.35×0.35
Temperature (°C) −70
0.53×0.34×0.32
−100
11205(57)
9283(58)
6107(81)
Z (mol/unit cell)
4
4
5415
1.111
0.71073
3953(84)
3
˚
V (A )
4543.3
1.249
0.71073
854.5
05h516, 05k5
18, −55l524
13.29
11391(78)
11978(65)
11807(68)
14774(68)
25580(77)
28219(65)
2077(66)
Dcalc. (g cm−3
u(Mo–Kh) (A)
Formula weight
Index ranges
)
17347(72)
35031(57)
41405(65)
41934(70)
32642(77)
˚
905.9
05h512, 05k516,
−425l542
11.22
Absorption
coefficient
a Equivalent isotropic U defined as one third of the trace of the
orthogonalized Uij tensor.
(cm−1
)
Independent
reflections
Observed reflec-
tions
5542
9326
4534 (F\4.0|(F)) 6503 (F\3.0|(F))
The samarium-ring carbon distances in 4 average
2.701(8) A, comparable to those seen in 2. The lithium
cation displays a planar, three-coordinate geometry,
b
˚
R1
0.0491
0.0626
0.0800
0.0869
b
wR2
being bound to two aryloxide oxygens (Li–O=
a 2=(p-C5Me5)Sm(O-2,6-t-Bu2C6H3)2(THF) · C6H14
Me5)Sm(O-2,6-i-Pr2C6H3)3Li(THF)]·C7H8].
;
4=[(p-C5-
˚
1.892(15) and 1.945(18) A) and one THF ligand (Li–
b R1=ꢀ ꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀ ꢁFoꢁ; wR2=[S[w(F2o–Fc2)2]/S[w(Fo2)2]]1/2
.
O=1.876(17) A). The two aryloxide oxygens bound to
˚

R.J. Butcher et al. / Journal of Organometallic Chemistry 577 (1999) 228–237
233
Table 4
the lithium cation exhibit somewhat longer Sm–O dis-
Fractional atomic coordinates (×105) and isotropic thermal parame-
ters (×104) for [(p-C5Me5)Sm(OAr*)(v-OAr*)2Li(THF)] (4) (Ar*=
2,6-i-Pr2C6H3)a
˚
tances (2.250(6) and 2.247(5) A) than the terminal
˚
aryloxide (Sm–O=2.144(6) A). These longer bonding
interactions are presumably due to a loss of electron
density at oxygen upon forming the Sm–O–Li bridges,
and can be compared to the average Sm–O distance of
x
y
z
Ueq
Sm(1)
Li(1)
O(1)
O(2)
O(3)
O(4)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
11389(3)
7132(4)
22856(133)
−6307(45)
21926(45)
10637(39)
30790(51)
13306(75)
4078(70)
−2730(68)
2386(75)
12287(71)
22661(73)
1627(84)
13888(1)
15395(41)
11814(13)
12036(13)
17798(13)
15720(17)
12981(21)
11386(21)
14275(22)
17700(20)
16883(20)
10895(24)
7382(22)
13719(28)
21554(22)
19810(22)
11636(20)
8255(22)
4925(22)
3045(26)
2101(28)
8030(26)
11104(27)
14382(25)
14745(22)
18240(20)
21457(23)
19613(26)
9978(20)
11432(22)
15169(26)
15147(34)
18141(28)
9400(25)
5941(28)
4446(24)
6400(20)
4798(25)
2181(32)
2918(40)
20072(21)
23809(22)
25386(22)
27793(60)
27421(54)
26025(22)
24599(25)
20961(25)
18640(22)
14677(26)
14298(33)
11987(27)
18204(49)
18383(30)
14419(54)
12905(26)
317(1)
˚
2.266(7) A found for the three lithium-coordinated
30890(132)
17958(42)
16941(47)
27580(43)
44872(54)
541(28)
364(16)
390(17)
335(16)
610(20)
389(21)
411(22)
347(21)
374(21)
323(20)
577(24)
635(24)
572(25)
520(23)
491(23)
344(21)
419(22)
567(24)
858(26)
792(26)
543(24)
587(25)
513(24)
406(22)
421(22)
595(24)
614(24)
375(21)
383(22)
568(25)
845(27)
972(27)
515(24)
667(25)
595(24)
382(21)
606(24)
1093(28)
1479(29)
344(21)
401(21)
608(24)
702(30)
833(30)
453(22)
537(23)
505(23)
383(22)
609(24)
864(26)
861(26)
440(29)
742(26)
496(30)
640(25)
aryloxide ligands in the complex [Li(THF)]2[Sm(O-2,6-
i-Pr2C6H3)3(CH2SiMe3)2] [7a]. The Sm–O distance for
the terminal ligand is directly comparable to the aver-
age Sm–O distances of 2.08(2), 2.099(9), and 2.101(6)
˚
−12331(66)
−12572(67)
−10186(67)
−8270(67)
−9810(65)
−15094(78)
−15561(82)
−10445(78)
−6185(76)
−9507(76)
23919(67)
29260(71)
27219(81)
14632(91)
37393(92)
35713(80)
37270(83)
31916(79)
25225(73)
19264(76)
28687(86)
11451(82)
17721(67)
14656(75)
9514(84)
−2238(93)
18785(104)
16818(81)
21592(89)
24231(84)
22416(71)
25013(79)
35528(112)
13493(114)
37865(64)
37960(71)
26744(83)
20177(146)
30672(173)
48705(77)
59121(73)
58873(73)
48355(68)
48028(76)
55405(84)
52565(90)
56616(158)
62329(94)
58725(173)
48488(89)
A found for the terminal aryloxide ligands in [(p-
C5Me5)2Sm]2(O2C16H10) [19a], [(p-C5Me5)2Sm(THF)]2-
(O2C16H10) [19a], and Sm2(O-2,6-i-Pr2C6H3)6 [7b].
Coordination of the lithium cation to O(2) and O(3)
is found to dramatically reduce the O(2)–Sm(1)–O(3)
angle from an expected tetrahedral value down to
76.9(2)°. Significant differences in orientation of the
aryloxide ring planes also result in the terminal arylox-
ide ligand being situated closer to the O(3) ligand
(O(1)–Sm(1)–O(3)=98.1(2)°) than the O(2) moiety
(O(1)–Sm(1)–O(2)=126.2(2)°), which has one of its
iso-propyl groups oriented directly toward the terminal
aryloxide. Angles about the lithium cation sum to
358.7°, indicating an almost perfect trigonal planar
coordination environment.
−13327(74)
−1851(75)
20175(70)
−14805(66)
−17302(71)
−10674(79)
−12664(97)
−11063(86)
−25785(73)
−31808(79)
−29646(73)
−21023(67)
−18575(68)
−15780(76)
−27030(75)
30191(71)
39115(66)
39793(77)
45975(83)
43761(98)
47296(77)
46846(88)
37803(87)
29203(68)
19513(83)
19336(101)
15914(111)
9162(61)
C(10)
C(11)
C(12)
C(121)
C(122)
C(123)
C(13)
C(14)
C(15)
C(16)
C(161)
C(162)
C(163)
C(21)
C(22)
C(221)
C(222)
C(223)
C(23)
C(24)
C(25)
C(26)
C(261)
C(262)
C(263)
C(31)
C(32)
C(321)
C(322)
C(323)
C(33)
C(34)
C(35)
C(36)
C(361)
C(362)
C(363)
C(40)
C(41)
C(42)
C(43)
3. Concluding remarks
We have described the results of attempted metathe-
sis reactions of samarium tris(aryloxide) complexes with
one equivalent of lithium pentamethylcyclopentadi-
enide. In the case where the aryloxide ligand is 2,6-di-
tert-butylphenoxide we observe a clean metathesis
reaction, with elimination of LiOAr, and the formation
of the desired neutral mono-pentamethylcyclopentadi-
enyl product. This result is consistent with the observa-
tions of other workers, in which the 2,6-di-
tert-butylphenoxide ligand was found to undergo suc-
cessful metathesis reactions with alkyllithium reagents
12088(68)
16784(83)
10856(139)
27015(147)
11031(66)
6988(75)
3826(70)
4730(61)
1130(83)
−8002(82)
8393(91)
Table 3
˚
Selected bond lengths (A) and angles (°) for (p-C5Me5)Sm(O-2,6-t-
Bu2C6H3)2(THF) (2)
˚
Bond lengths (A)
Sm(1)–O(1)
Sm(1)–O(3)
Sm(1)–C(2)
Sm(1)–C(4)
2.133(6) Sm(1)–O(2)
2.435(7) Sm(1)–C(1)
2.755(9) Sm(1)–C(3)
2.745(10) Sm(1)–C(5)
2.188(6)
2.796(10)
2.718(10)
2.795(9)
28650(145)
38790(87)
42756(166)
37372(80)
Bond angles (°)
O(1)–Sm(1)–O(2) 105.3(2)
O(1)–Sm(1)–O(3) 111.4(2)
Sm(1)–O(2)–C(21) 175.7(5)
O(2)–Sm(1)–O(3)
Sm(1)–O(1)–C(11)
84.6(2)
165.3(6)
a Equivalent isotropic U defined as one third of the trace of the
orthogonalized Uij tensor.

234
R.J. Butcher et al. / Journal of Organometallic Chemistry 577 (1999) 228–237
[12,13,15,22,23]. In the case of attempted metathesis
reaction involving the 2,6-di-iso-propylphenoxide lig-
and, however, the observation of an addition rather
than a metathesis reaction reinforces the mode of reac-
tivity previously observed [8a].
4. Experimental
4.1. General procedures and techniques
All manipulations were carried out under an inert
atmosphere of oxygen-free UHP grade argon using
standard Schlenk techniques, or under oxygen-free he-
lium in a Vacuum Atmospheres glovebox. The com-
pound 2,6-di-tert-butylphenol was purchased from
Aldrich and used as received. The compound KO-2,6-t-
Bu2C6H3 was prepared following the reaction of a slight
excess of potassium hydride (Aldrich) with 2,6-di-tert-
butylphenol in THF. The compound LiC5Me5 was
prepared from pentamethylcyclopentadiene and n-
butyllithium in hexane. The compounds Sm2(OAr*)6
and Sm(OAr*)3(THF)2 were prepared as described pre-
viously ([7]b). Solvents were degassed and distilled from
Na-benzophenone under nitrogen. Benzene-d6 and
toluene-d8 were degassed, dried over an Na–K alloy
and then trap-to-trap distilled before use. Methylene
chloride-d2 was trap-to-trap distilled from molecular
sieves.
NMR spectra were recorded at 22°C on Bru¨ker
WM300 or Varian Unity 300 spectrometers. All 1H-
NMR chemical shifts are reported in ppm relative to
the 1H impurity in benzene-d6, toluene-d8 and
methylene chloride-d2 set at l 7.15, 2.09 and 5.32 ppm,
respectively. NMR spectra of paramagnetic lanthanide
species are temperature dependent, thus it is important
to note that the temperatures quoted represent average
room temperatures (r.t.) and are approximate values.
IR spectra were recorded on a Digilab FTS-40 spec-
trometer. Solid-state IR spectra were taken as Nujol
mulls between KBr plates. Elemental analyses were
performed on a Perkin-Elmer 2400 CHN analyzer.
Elemental analysis samples were prepared and sealed in
tin capsules in the glovebox prior to combustion.
Previously [7a], we had interpreted the differences in
observed reactivity of alkyllithium reagents with lan-
thanide aryloxide complexes (compare Eqs. (1a) and
(2)) in terms of two contributing factors: (i) the reduced
steric requirement of the 2,6-di-iso-propylphenoxide lig-
and, compared with 2,6-di-t-butylphenoxide, allows
greater freedom for coordination of three aryloxide
ligands simultaneously to the lanthanide metal center,
and (ii) the solubility of lithium 2,6-di-iso-propylphe-
noxide in THF is considerably greater than that of
lithium 2,6-di-tert-butylphenoxide, thus the driving
force for precipitation of the lithium aryloxide is signifi-
cantly lower. The first of these factors appears to be
supported by very recent results, in which Evans et al.
reported that the reaction of the 2,6-dimethyl substi-
tuted aryloxide complex Y(O-2,6-Me2C6H3)3(THF)2
with one equivalent of NaC5Me5 led to the formation
of the discrete ion pair complex [Na(THF)6][(p-
C5Me5)Y(O-2,6-Me2C6H3)3] [24]. Thus the use of a less
sterically demanding aryloxide appears to favor the
formation of an addition, rather than a metathesis,
product. The extent to which the solubility of the
lithium aryloxide salt controls the reaction is still in
question. However, it appears that the use of a less
polar reaction solvent (e.g. toluene) favors metathesis
reaction (by encouraging precipitation of alkali metal
aryloxide), whereas use of a polar, coordinating solvent
such as THF encourages solvation of the alkali metal
cation and the formation of addition, or ‘ate’ com-
plexes. Further studies in this area are currently in
progress.
4.1.1. Sm(O-2,6-t-Bu2C6H3)3(THF) (1)
Table 5
Anhydrous SmCl3 (1.00 g, 3.89 mmol) was suspended
in THF (100 cm3). To the vigorously stirred suspension
was added solid KO-2,6-t-Bu2C6H3 (2.85 g, 11.66
mmol), resulting in an immediate change in color of the
reaction mixture from white to yellow. The reaction
mixture was allowed to stir overnight, and then all
solvent was removed in vacuo. The resulting pale yel-
low solid was extracted with hexane (150 cm3) and
filtered through a Celite pad to give a clear yellow
solution, which was then pumped to dryness to yield 1
˚
Selected bond distances (A) and angles (°) for [(p-
C5Me5)Sm(OAr*)(v-OAr*)2Li(THF)] (4) (Ar*=2,6-i-Pr2C6H3)
˚
Bond lengths (A)
Sm(1)–O(1)
Sm(1)–O(3)
Sm(1)–C(2)
Sm(1)–C(4)
O(2)–Li(1)
O(4)–Li(1)
2.144(6)
2.247(5)
2.744(8)
2.683(8)
1.892(15)
1.876(17)
Sm(1)–O(2)
Sm(1)–C(1)
Sm(1)–C(3)
Sm(1)–C(5)
O(3)–Li(1)
2.250(6)
2.722(8)
2.726(8)
2.693(8)
1.945(18)
Bond angles (°)
1
as a yellow solid. Yield 0.900 g (28%). H-NMR (300
O(1)–Sm(1)–O(2) 126.2(2)
O(2)–Sm(1)–O(3) 76.9(2)
Sm(1)–O(2)–C(21) 161.6(4)
C(21)–O(2)–Li(1) 102.5(7)
Sm(1)–O(3)–Li(1) 93.9(5)
O(1)–Sm(1)–O(3)
Sm(1)–O(1)–C(11)
Sm(1)–O(2)–Li(1)
Sm(1)–O(3)–C(31)
C(31)–O(3)–Li(1)
O(2)–Li(1)–O(4)
98.1(2)
161.2(4)
95.3(6)
158.7(5)
103.4(6)
134.4(10)
MHz, C6D6): l 8.24 (d, J=8 Hz, 6H, meta OAr), 7.92
(t, J=8 Hz, 3H, para OAr), 0.78 (s, 54H, C(CH3)3),
−1.25 (v br, 4H, THF), −1.32 (br, 4H, THF). IR
(Nujol, cm−1); 1582 (w), 1407 (s), 1378 (s), 1366 (sh,
m), 1352 (sh, m), 1316 (vw), 1260 (m), 1238 (s), 1213
(w), 1199 (m), 1151 (w), 1126 (w), 1120 (sh, w), 1103
O(2)–Li(1)–O(3)
O(3)–Li(1)–O(4)
93.6(7)
130.7(8)

R.J. Butcher et al. / Journal of Organometallic Chemistry 577 (1999) 228–237
235
(w), 1036 (vw), 1002 (m), 925 (vw), 915 (vw), 886, (w),
879 (w), 862 (s), 852 (sh, m), 831 (w), 820 (m), 799 (w),
752 (s), 667 (w), 654 (m), 590 (vw), 547 (w), 448 (w).
Anal. Calc. for C46H71SmO4: C, 65.89; H, 8.54; Found:
C, 66.48; H, 8.01.
1031 (m), 975 (vw), 952 (vw), 941 (vw), 934 (vw), 918
(vw), 894 (sh, w), 885 (m), 863 (m), 849 (sh, s), 844 (s),
804 (w), 797 (w), 756 (s), 743 (s), 728 (m), 693 (m), 686
(m), 598 (w), 560 (m), 556 (m), 524 (w). Anal. Calc. for
C50H74LiO4Sm(C7H8)0.16: C, 67.38; H, 8.33. Found: C,
67.87; H 8.53.
4.1.2. (p-C5Me5)Sm(O-2,6-t-Bu2C6H3)2(THF) (2)
To a yellow solution of Sm(O-2,6-t-Bu2C6H3)3(THF)
(1) (0.364 g, 0.43 mmol) in THF (60 cm3) was added
solid LiC5Me5 (0.068 g, 0.48 mmol). The mixture was
allowed to stir overnight during which time the solution
appeared to deepen in color and a precipitate was
observed. All solvent was removed in vacuo, and the
pale yellow solid extracted into hexane (40 cm3). Filtra-
tion through a Celite pad yielded a clear yellow solu-
tion which was concentrated to ca. 30 cm3 and then
allowed to evaporate in the glovebox atmosphere. Once
the solvent had evaporated a yellow crystalline solid
remained. This was rinsed with 2×10 cm3 aliquots of
(Me3Si)2O and dried in vacuo. Yield 0.280 g (85%).
1H-NMR (300 MHz, C6D6): l 8.25 (d, J=8 Hz, 4H,
meta OAr), 7.93 (t, J=8 Hz, 2H, para OAr), 1.68 (s,
15H, C5Me5), 0.75 (s, 36H, C(CH3)3), −1.05 (v br, 4H,
THF), −2.65 (br, 4H, THF). Anal. Calc. for
C42H65O3Sm(C6H14) (hexane solvate): C, 67.47; H, 9.32;
Found: C, 67.97; H, 8.92.
4.1.3.2. Method 2. To a solution of Sm(O-2,6-i-
Pr2C6H3)3(THF)2 (1.28 g, 1.55 mmol) in THF (70 cm3)
was added LiC5Me5 (0.221 g, 1.55 mmol) as a solid.
The mixture was allowed to stir overnight, during
which time the solution had become orange in color.
The solvent was removed in vacuo to leave an orange/
yellow solid. The solid was extracted repeatedly with
hexane (total 200 cm3) and filtered through a Celite pad
to give a clear yellow solution. The solution was
pumped dry to yield a bright yellow solid. Yield 1.10 g
(79%).
4.2. [Li(TMEDA)2][(p-C5Me5)Sm(OAr*)3] (5)
To a solution of 4 (0.327 g, 0.36 mmol) in hexane (70
cm3) was added TMEDA (0.5 cm3) dropwise. The
initial yellow solution immediately decolorized and an
off-white solid precipitated. The solution was allowed
to stir for ca. 15 min, after which time the precipitate
was allowed to settle and the mother liquor decanted
off. The precipitate was washed with hexane (2×20
cm3) and dried under reduced pressure to yield an
4.1.3. [(p-C5Me5)Sm(OAr*)(v-OAr*)2Li(THF)] (4)
(Ar*=2,6-i-Pr2C6H3)
1
almost white solid. Yield 0.200 g (53%). H-NMR (300
4.1.3.1. Method 1. To a solution of Sm2(O-2,6-i-
Pr2C6H3)6 (0.400 g, 0.29 mmol) in 80 cm3 of THF was
added solid LiC5Me5 (0.083 g, 0.58 mmol). The reac-
tion mixture was allowed to stir at r.t. for 3 days,
during which time the solution darkened to a deep
yellow. Removal of solvent in vacuo left a yellow/or-
ange oil which was extracted into hexane (100 cm3) and
filtered through a Celite pad. The filtrate was concen-
trated to 20 ml and placed at −40°C leading to the
formation of a microcrystalline solid. The solid was
redissolved in toluene (20 cm3) and the solution allowed
to slowly evaporate in the glovebox atmosphere. Once
the solvent had evaporated, large yellow crystals with
an oily coating were present. The crystals were rinsed
with cold hexane and pumped dry. Yield 0.265 g (51%).
1H-NMR spectroscopy of the desolvated material re-
vealed the presence of a small amount of residual
toluene and indicated the approximate formula
MHz, CD2Cl2): l 7.06 (d, J=8 Hz, 6H, meta OAr),
6.85 (t, J=8 Hz, 3H, para OAr), 2.83 (br, 6H,
CHMe2), 2.50 (br, 8H, CH2CH2), 2.32 (br s, 24H,
NMe2), 1.52 (s, 15H, C5Me5), 0.64 (d, J=7 Hz, 36H,
CHMe2). IR (Nujol, cm−1): 1586 (m), 1429 (s), 1367
(m), 1358 (m), 1344 (sh, m), 1334 (s) 1282 (sh, m), 1270
(s), 1246 (m), 1208 (m), 1181 (vw), 1159 (w), 1141 (vw),
1127 (w), 1109 (w), 1098 (w), 1068 (w), 1058 (w), 1041
(m), 1030 (m), 1012 (w), 974 (vw), 946 (m), 936 (sh, w),
887 (m), 857 (s), 804 (w), 788 (m), 774 (vw), 750 (s), 690
(m), 595 (vw), 563 (m), 554 (m). Calc. for
C58H98LiN4O3Sm: C, 65.92; H, 9.35; N, 5.30. Found:
C, 65.95; H 9.69; N, 5.19.
5. Crystallographic studies
5.1. (p-C5Me5)Sm(O-2,6-t-Bu2C6H3)2(THF) · C6H14 (2)
[Cp*Sm(OAr*)3Li(THF)] · (C7H8)0.16
.
1H-NMR (300
MHz, C6D6): l 7.12 (t, J=7 Hz, 3H, para OAr), 6.98
(d, J=7 Hz, 6H, meta OAr), 4.14 (br, 4H, h-THF),
1.75 (br, 4H, i-THF), 1.12 (s, 15H, C5Me5), 0.45 (v br,
6H, CHMe2), −0.23 (br s, 36H, CHMe2). IR (Nujol,
cm−1); 1589 (m), 1431(s), 1366 (sh, s), 1360 (sh, s),
1325 (s), 1271 (s), 1256 (s), 1204 (s), 1199 (s), 1156 (vw),
1142 (vw), 1105 (w), 1096 (w), 1057 (vw), 1040 (m),
A yellow, rectangular block measuring 0.57×0.35×
0.35 mm was mounted on a thin glass fiber using
silicone grease. The crystal, which was mounted from a
pool of mineral oil bathed in argon, was then immedi-
ately placed under a nitrogen coldstream on an Enraf-
Nonius CAD4 diffractometer. The radiation used was
graphite monochromated Mo–Kh radiation (u=

236
R.J. Butcher et al. / Journal of Organometallic Chemistry 577 (1999) 228–237
˚
SHELXTL PLUS suite of computer programs (Siemens
Analytical X-ray Instr., Inc, 1990).
0.71073 A). Unit cell parameters were determined from
the least-squares refinement of (sin q/u)2 values for 24
accurately centered reflections. Three reflections were
chosen as intensity standards and were measured every
3600 s of X-ray exposure time, and three orientation
controls were measured every 250 reflections. The data
were reduced using the Structure Determination Pack-
age provided by Enraf-Nonius and corrected for ab-
sorption empirically using high chi psi-scans. The
intensities were corrected for Lorentz and polarization
effects, equivalent reflections were merged (Rint=0.041)
and systematically absent reflections were rejected. The
structure was solved by routine Patterson and Fourier
methods, using full-matrix least-squares refinement. Af-
ter inclusion of anisotropic thermal parameters for all
non-hydrogen atoms and geometrical generation of hy-
drogen atoms which were constrained to ‘ride’ upon the
appropriate carbon atoms, final refinement using 4534
unique observed [F\4|(F)] reflections converged at
R=0.049, Rw=0.063 (where w=[|2(F)+0.0024-
(F)2]−1). All data refinement calculations were per-
formed using the SHELXTL PLUS suite of computer
programs (Siemens Analytical X-ray Instr., Inc, 1990).
6. Supporting information
Listings of fractional atomic coordinates, bond
lengths and angles, anisotropic thermal parameters and
hydrogen atom coordinates for complexes 2 and 4 (20
pages) are available. Ordering information is given on
any current masthead page.
Acknowledgements
This work was performed under the auspices of the
Laboratory Directed Research and Development Pro-
gram. Los Alamos National Laboratory is operated by
the University of California for the US Department of
Energy under Contract W-7405-ENG-36.
References
5.2. [(p-C5Me5)Sm(O-2,6-i-Pr2C6H3)3Li(THF)] · C7H8
(4)
[1] (a) C.J. Schaverien, Adv. Organomet. Chem. 36 (1994) 283. (b)
F.T. Edelmann, Y.K. Gun’ko, Coord. Chem. Rev. 165 (1997)
163. (c) M. Ephritikhine, Chem. Rev. 97 (1997) 2193. (d) Y.
Gun’ko, F.T. Edelmann, Coord. Chem. Rev. 156 (1996) 1.
[2] H. Schumann, J.A. Meese-Marktscheffel, L. Esser, Chem. Rev.
95 (1995) 865 and references therein.
A yellow block measuring 0.53×0.34×0.32 mm was
mounted on a thin glass fiber using silicone grease. The
crystal, which was mounted from a pool of mineral oil
bathed in argon, was then immediately placed under a
nitrogen coldstream on a Siemens R3m/V diffractome-
ter. The radiation used was graphite monochromated
[3] See, for example: (a) G.A. Molander, Chem. Rev. 92 (1992) 29.
(b) G. Jeske, H. Lauke, H. Mauermann, P.N. Swepston, H.
Schumann, T.J. Marks, J. Am. Chem. Soc. 107 (1985) 8091. (c)
G. Jeske, L.E. Schock, H. Mauermann, P.N. Swepston, H.
Schumann, T.J. Marks, J. Am. Chem. Soc. 107 (1985) 8103. (d)
G. Jeske, H. Lauke, H. Mauermann, H. Schumann, T.J. Marks,
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Mo–Kh radiation (u=0.71073 A). The lattice parame-
ters were optimized from a least-squares calculation on
50 carefully centered reflections of high Bragg angle.
The data were collected using ꢀ scans with a 1.30° scan
range. Three reflections were chosen as intensity stan-
dards and were measured every 3600 s of X-ray expo-
sure time, and three orientation controls were measured
every 250 reflections.
The intensities were corrected for Lorentz and polar-
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based on azimuthal scans was applied. Equivalent
reflections were merged (Rint=0.019) and systemati-
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solved by routine Patterson and Fourier methods, using
full-matrix least-squares refinement. After inclusion of
anisotropic thermal parameters for all non-hydrogen
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Rw=0.087 (where w=[|2(F)+0.0002(F)2]−1). All
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