Four-coordinate erbium organometallic and coordination complexes: Synthesis and structure

Article abstract of DOI:10.1016/j.jorganchem.2010.07.033

The synthesis and reactivity of several erbium organometallic and coordination complexes supported by a β-diketiminato ancillary ligand are described. The reaction of ErCl₃(THF)_3.5 with LiL (L = ArNC(Me)CHC(Me)NAr; Ar = 2,6-ⁱPr₂-C₆H ₃) afforded the dimeric complex Er(L)Cl(μ-Cl)₃Er(L) (THF), 1. Reaction of complex 1 with four equiv of the bulky silylamide LiN(SiMe₃)₂ generated the unexpected four-coordinate adduct dimer [Er(L)N(SiMe₃)₂Cl(μ-(LiN(SiMe ₃)₂))]₂, 2. Conversely, reaction of 1 with two or four equiv of LiCH₂SiMe₃ led to the base-free mixed chloro/alkyl species [Er(L)(CH₂SiMe₃)(μ-Cl)] ₂, 3, and the four-coordinate dialkyl Er(L)(CH₂SiMe ₃)₂, 4, respectively. The protonolysis reactivity of 4 was demonstrated by reaction with [Et₃NH]I to generate Er(L)I ₂, 5. By contrast, reaction of complex 1 with trimethylsilyliodide resulted in the formation of ErI₃(THF)₃, 6, through a ligand redistribution process. Compounds 1-6 were characterized by single crystal X-ray diffraction, multinuclear NMR spectroscopy, FT-IR spectroscopy, solution magnetic susceptibility measurements and CHN combustion analysis.

Full text of DOI:10.1016/j.jorganchem.2010.07.033

Journal of Organometallic Chemistry 695 (2010) 2747e2755
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Four-coordinate erbium organometallic and coordination complexes: Synthesis
and structure
,
Kevin R.D. Johnson a, Adrien P. Côté b, Paul G. Hayes a
*
a Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, AB, Canada T1K 3M4
b Xerox Research Centre of Canada, 2660 Speakman Drive, Mississauga, ON, Canada L5K 2L1
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and reactivity of several erbium organometallic and coordination complexes supported by
Received 30 April 2010
Received in revised form
25 July 2010
Accepted 30 July 2010
Available online 13 August 2010
a
b
-diketiminato ancillary ligand are described. The reaction of ErCl3(THF)3.5 with LiL (L ¼ ArNC(Me)CHC
(Me)NAr; Ar ¼ 2,6-iPr2-C6H3) afforded the dimeric complex Er(L)Cl(
m-Cl)3Er(L)(THF), 1. Reaction of
complex 1 with four equiv of the bulky silylamide LiN(SiMe3)2 generated the unexpected four-coordinate
adduct dimer [Er(L)N(SiMe3)2Cl(
LiCH2SiMe3 led to the base-free mixed chloro/alkyl species [Er(L)(CH2SiMe3)(
m
-(LiN(SiMe3)2))]2, 2. Conversely, reaction of 1 with two or four equiv of
-Cl)]2, 3, and the four-
m
coordinate dialkyl Er(L)(CH2SiMe3)2, 4, respectively. The protonolysis reactivity of 4 was demonstrated by
reaction with [Et3NH]I to generate Er(L)I2, 5. By contrast, reaction of complex 1 with trimethylsilyliodide
resulted in the formation of ErI3(THF)3, 6, through a ligand redistribution process. Compounds 1e6 were
characterized by single crystal X-ray diffraction, multinuclear NMR spectroscopy, FT-IR spectroscopy,
solution magnetic susceptibility measurements and CHN combustion analysis.
In memory of Professor Herbert Schumann.
Keywords:
Erbium
Lanthanide
b
-Diketiminato
Ó 2010 Elsevier B.V. All rights reserved.
Iodide
X-ray crystallography
Low-coordinate
1. Introduction
the preparation of isolable low-coordinate species; many of which
may not have been accessible with alternative ligands [5,8].
Although the cyclopentadienyl ligand (Cp) has been extremely
influential in the development of organolanthanide chemistry [1],
it is limited in the extent to which it can be electronically or
sterically tuned [2]. Consequently, significant attention has recently
been devoted to the exploration of non-Cp ancillaries for sup-
Of the smallest rare earth metals, well-defined organometallic
and coordination complexes of scandium [9], lutetium [9r,s,10], and
ytterbium(III) [11] supported by the nacnac ligand have been
prepared over the past decade. Similarly, several groups have
reported nacnac complexes of the larger yttrium ion and unique
reactivity thereof [9r,s,10,11j,12]. While a large degree of attention
has been focused on suchyttrium complexes, presumably due to the
fact that yttrium is diamagnetic, only limited investigations have
involved late lanthanide congeners, such as erbium. This is
surprising considering that size-based differences in reactivity are
well-established [1a,c,13]. For example, a recent study comparing
the ethylene polymerization ability of aminopyridinate-stabilized
organolanthanide cations (Sc, Lu, Er and Y) reported that the highest
activity, by a substantial margin, was exhibited by the erbium
complex [14]. An investigation of erbium species, rather than those
of yttrium, might be viewed as a disadvantage because the para-
magnetic nature of the heavier f-element limits the usefulness of
NMR spectroscopy. However, the technology of alternative charac-
terization techniques, such as X-ray crystallography, easily allows
for rapid and unambiguous structural determination of para-
magnetic species [15]. In light of this, we believe that rich
porting rare earth metals [3]. In particular, the monoanionic
b-
diketiminato or “nacnac” ancillary ligand [R0NC(R)CHC(R)NR0]e has
proven extremely useful in synthetic organometallic and coordi-
nation chemistry [4,5].
The nacnac ligand is an attractive scaffold for supporting
lanthanide metal complexes of generic form LLnR2. The modular
nature of the ligand at the nitrogen atoms and carbon backbone
allows facile incorporation of various substituents for fine-tuning of
electronic properties and adjustment of the steric environment
[5,6]. In particular, bulky N-aryl groups, such as 2,6-diisopropyl-
phenyl (Dipp) can be readily installed in high yield [7]. The
steric stabilization imparted by such bulky groups often allows for
* Corresponding author. Tel.: þ1 403 329 2313; fax: þ1 403 329 2057.
E-mail address: p.hayes@uleth.ca (P.G. Hayes).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.07.033

2748
K.R.D. Johnson et al. / Journal of Organometallic Chemistry 695 (2010) 2747e2755
organometallic and coordination chemistry can be harvested from
the development of erbium complexes supported by nacnac ancil-
laries. Such complexes may prove valuable as catalysts for olefin
polymerization [16], hydroamination [17], or lactone polymeriza-
tion [18], to mention just a few possibilities. Furthermore, these
species are likely to provide fundamental insight into rare bonding
and structural motifs.
Previously, an erbium diiodide complex supported by a unique
tetradentate nacnac ligand ErL0I2 ([L0]e ¼ [Et2NCH2CH2NC(Me)CHC
(Me)NCH2CH2NEt2]e) was prepared [19], but only limited investi-
gations into reactivity have since been published [20]. More
recently, a complex of form ErL00Cl2(THF)2([L00]e ¼ [(2,6-Me2-C6H3)
NC(Me)CHC(Me)N(2,6-Me2-C6H3)]e) was reported as a pre-catalyst
for isoprene polymerization [21]. Herein, we present the synthesis
and characterization of a novel erbium dichloride dimer of the
Dipp-substituted nacnac ligand, [ArNC(Me)CHC(Me)NAr]e ([L]e,
Ar ¼ 2,6-iPr2-C6H3), and the rare four-coordinate and base-free
products which result from reaction with lithium bis(trimethylsilyl)
amide and trimethylsilylmethyllithium. Further derivatization at
the metal center was accomplished by reaction of the organo-
erbium complexes with [Et3NH]I. Additionally, the synthesis of the
potentially useful starting material, ErI3(THF)3, is described. In
summary, this work highlights many of the similarities and differ-
ences in reactivity patterns that exist between erbium and other
rare earth metals.
Fig. 1. ORTEP diagram (50% probability) of Er(L)Cl(m-Cl)3Er(L)(THF) (1) with hydrogen
atoms, iPr groups and the solvent moꢁlecule of crystallization omitted for clarity.
ꢀ
Selected bond distances (A) and angles ( ): Er(1)eN(1) ¼ 2.294(4), Er(1)eN(2) ¼ 2.296
(4), Er(1)eCl(1) ¼ 2.525(1), Er(1)eCl(2) ¼ 2.720(1), Er(1)eCl(3) ¼ 2.747(1), Er(1)eCl
(4) ¼ 2.767(1), Er(2)eN(3) ¼ 2.312(4), Er(2)eN(4) ¼ 2.302(4), Er(2)eCl(2) ¼ 2.665(1), Er
(2)eCl(3) ¼ 2.660(1), Er(2)eCl(4) ¼ 2.646(1), Er(2)eO(1) ¼ 2.295(3), N(1)eEr(1)eN
(2) ¼ 83.2(1), Cl(1)eEr(1)eCl(2) ¼ 165.82(4), Cl(3)eEr(1)eN(2) ¼ 167.8(1), Cl(4)eEr
(1)eN(1) ¼ 160.5(1), N(3)eEr(2)eN(4) ¼ 81.2(1), Cl(3)eEr(2)eN(4) ¼ 174.5(1), Cl(2)eEr
(2)eN(3) ¼ 170.7(1), Cl(4)eEr(2)eO(1) ¼ 157.20(9).
2. Results and discussion
distance between the bridging chlorides and Er(2) is shorter than
that to Er(1), with average distances of 2.657 A and 2.744 A,
Complexation of the ancillary ligand L was achieved through the
salt metathesis reaction of ErCl3(THF)3.5 with LiL (Scheme 1).
Following reflux of the reagents in THF for 6.5 h, and subsequent
ꢀ
ꢀ
respectively. As expected, the terminal Er(1)eCl(1) distance (2.525
ꢀ
(1) A) is significantly less than that to the bridging chlorides. The
recrystallization from toluene, the dimeric complex Er(L)Cl(m-
solid-state structure for 1 is essentially isostructural with the anal-
ogous samarium [22], ytterbium [11a] and yttrium [12d] complexes.
Reaction of complex 1 with four equiv of LiN(SiMe3)2 led to the
formation of a unique mixed chloride/silylamido species, 2 (Scheme
2). Intriguingly, complex 2 contains LiN(SiMe3)2 as a bridging
adduct. In the solid-state, the LiN(SiMe3)2 moiety coordinates to the
chloride of the complex via the lithium atom, and bridges through
the nitrogen atoms of each silylamido group, giving a dimeric
Cl)3Er(L)(THF) (1) was isolated on a multigram scale in 79.5% yield
as analytically pure, pale pink needles.
Single crystals of 1 suitable for X-ray diffraction were readily
obtained from a concentrated toluene solution at ꢀ35 ꢁC. The
molecular structure of 1 is illustrated in Fig. 1 as a thermal ellipsoid
plot. This complex adopts an asymmetric dimeric geometry with
three chlorides bridging the two erbium(III) centers. Each erbium
metal exhibits distorted octahedral geometry, with three sites
occupied by the facially arranged bridging chlorides. Two of the six
coordination sites of each erbium center are defined by the nacnac
species of formula [Er(L)N(SiMe3)2Cl(m-(LiN(SiMe3)2))]2, 2. It would
appear that the dimeric structure of 2 stems from the propensity of
group 1 metals, such as lithium, to dimerize and oligomerize in
order to saturate their coordination spheres [23]. While lanthanide
metals exhibit the same tendency, the bulky nacnac and silylamide
substituents sterically saturate the erbium center, thus resulting in
a reduced coordination number. The molecular structure of complex
2, as determined from an X-ray diffraction experiment, is depicted in
Fig. 2 as a thermal ellipsoid plot.
ligand coordinated in a
The metal centers sit above the plane of the NCCCN backbone by
k
2 fashion through its two nitrogen donors.
ꢀ
ꢀ
0.928 A for Er(1) and 0.710 A for Er(2). The sixth site of the octahe-
dron is occupied by a chloride for one erbium center (Er(1)) and
a neutral THF donor for the other (Er(2)). It is noteworthy that the
Compound 2 represents a rare example of a bimetallic erbium
coordination complex where each metal center is only four-coor-
dinate. The complex exhibits distorted tetrahedral geometry at
both erbium atoms. Each tetrahedron is defined by coordination of
one chloride ligand, one silylamido group and the k2 nacnac
ancillary bound through the two nitrogen atoms. In the case of this
complex, the metal sits significantly further above the plane
ꢀ
ꢀ
defined by the NCCCN backbone (1.448 A for Er(1) and 1.459 A for
ꢀ
ꢀ
Er(2) c.f. 0.928 A for Er(1) and 0.710 A for Er(2) in 1). Situation of the
metal out of plane from the ancillary can be attributed to the
extremely sterically congested environment in which it resides.
Bonding of this nature is typical of four-coordinate rare earth metal
complexes of L [5,9i,12a].
As a further consequence of the bulk of L, it is speculated that
steric hindrance from the Dipp groups inhibits the bridging silyla-
mido moieties (N(4) and N(5)) from directly coordinating to each
Scheme 1. Synthesis of 1 from ErCl3(THF)3.5 and LiL.

K.R.D. Johnson et al. / Journal of Organometallic Chemistry 695 (2010) 2747e2755
2749
Scheme 2. Reactivity of 1.
erbium center. It is interesting to note that the samarium analog of
1 reacts with 4 equiv of NaN(SiMe3)2 to generate the expected
complex, Sm(L)(N(SiMe3)2)2 [22]. It is likely that the difference in
reactivity between erbium and samarium is due to the larger ionic
radius of samarium, thus permitting coordination of two bulky
silylamide ligands, rather than only one.
ꢀ
ꢀ
At 2.5382(9) A (Er(1)eCl(1)) and 2.533(1) A (Er(2)eCl(2)) the
EreCl bond lengths in complex 2 are relatively short. These
ꢀ
distances are comparable to the EreCl bond of 2.593(9) A in Er{N[Si
(CH3)2CH2CH2Si(CH3)2]}3(m-Cl)Li(Et2O)3 [24], which is the only
other structurally characterized four-coordinate chloride-contain-
ing erbium complex.
Multiple attempts to force elimination of LiCl from complex 2, in
order to generate Er(L)(N(SiMe3)2)2, were unsuccessful. For
example, extending the reaction period from 1.25 h to 18 h resulted
in isolation of Er[N(SiMe3)2]3 [25], as the sole product (identified by
combustion analysis and single crystal X-ray diffraction unit cell
determination). This homoleptic compound likely arose via ligand
scrambling to give a final product with reduced steric crowding at
the erbium center. Conversely, addition of 18-crown-6 to complex 2
afforded two equiv of (18-crown-6)LiN(TMS)2 (identified by 7Li
NMR spectroscopy) and presumably two equiv of Er(L)ClN(TMS)2.
Unfortunately the latter species could not be unambiguously
identified due to the presence of additional intractable reaction
products.
The salt metathesis reaction of complex 1 with two equiv of
LiCH2SiMe3 afforded the mixed alkyl/chloro complex [Er(L)
(CH2SiMe3)(m-Cl)]2, 3 (Scheme 2). Single crystals of 3 suitable for an
X-ray diffraction experiment were readily obtained from a toluene
solution at ꢀ35 ꢁC. Complex 3 crystallized as a centrosymmetric
dimer in the space group P21/n with bridging chloride ligands. The
molecular structure of 3 is depicted in Fig. 3 as a thermal ellipsoid
plot. Each Er center is five-coordinate with two sites occupied by
the k2 bound nacnac, and the other three sites defined by one tri-
methylsilylmethyl group and two bridging chlorides. To the best of
our knowledge, complex 3 is the first structurally characterized
erbium complex containing only one trimethylsilylmethyl ligand.
Metrical parameters of interest in complex 3 include the Er(1)eC
Fig. 2. ORTEP diagram (50% probability) of [Er(L)N(SiMe3)2Cl(m-(LiN(SiMe3)2))]2 (2).
The dimeric structure (with hydrogen atoms and iPr groups omitted for clarity) is
shown in (A), while a monomeric moiety (with hydrogenꢁatoms omitted for clarity) is
ꢀ
depicted in (B). Selected bond distances (A) and angles ( ): Er(1)eN(1) ¼ 2.259(3), Er
(1)eN(2) ¼ 2.256(3), Er(1)eN(3) ¼ 2.193(3), Er(1)eCl(1) ¼ 2.5382(9), Er(2)eN(6) ¼
2.198(3), Er(2)eN(7) ¼ 2.261(3), Er(2)eN(8) ¼ 2.248(3), Er(2)eCl(2) ¼ 2.533(1), Li(1)e
Cl(1) ¼ 2.499(6), Li(2)eCl(2) ¼ 2.492(6), Li(1)eN(5) ¼ 2.005(7), Li(2)eN(5) ¼ 2.013(7),
Li(1)eN(4) ¼ 2.034(7), Li(2)eN(4) ¼ 2.024(7), N(1)eEr(1)eN(2) ¼ 84.3(1), N(1)eEr(1)e
Cl(1) ¼ 105.71(7), N(1)eEr(1)eN(3) ¼ 124.8(1), N(2)eEr(1)eCl(1) ¼ 106.91(8), N(2)eEr
(1)eN(3) ¼ 116.3(1), N(3)eEr(1)eCl(1) ¼ 114.31(8), N(8)eEr(2)eN(7) ¼ 87.1(1), N(7)e
Er(2)eCl(2) ¼ 104.35(8), N(7)eEr(2)eN(6) ¼ 125.5(1), N(8)eEr(2)eCl(2) ¼ 107.86(8), N
(8)eEr(2)eN(6) ¼ 114.4(1), N(6)eEr(2)eCl(2) ¼ 113.93(8), Li(1)eN(5)eLi(2) ¼ 75.7(3),
Li(1)eN(4)eLi(2) ¼ 74.9(3), N(5)eLi(1)eN(4) ¼ 104.7(3), N(5)eLi(2)eN(4) ¼ 104.8(3).
ꢀ
ꢀ
(30) bond length of 2.343(7) A and EreCl distances of 2.653(2) A (Cl
ꢀ
(1)) and 2.638(2) A (Cl(1)_1). The similarity of the EreCl bond

2750
K.R.D. Johnson et al. / Journal of Organometallic Chemistry 695 (2010) 2747e2755
Fig. 4. ORTEP diagram (50% probability) of Er(L)(CH2SiMe3)2 (4) with hydrogen atoms
and the solvent molecule of crystallization omitted for clarity. Selected bond distances
ꢁ
ꢀ
(A) and angles ( ): Er(1)eN(2) ¼ 2.234(2), Er(1)eN(1) ¼ 2.258(2), Er(1)eC(30) ¼ 2.342
(3), Er(1)eC(34) ¼ 2.380(2), Si(1)eC(30)eEr(1) ¼ 127.0(1), Si(2)eC(34)eEr(1) ¼ 129.8
(1), N(1)eEr(1)eN(2) ¼ 86.8(1), C(30)eEr(1)eC(34) ¼ 117.7(1), C(30)eEr(1)eN(1) ¼
110.0(1), C(30)eEr(1)eN(2) ¼ 108.7(1), C(34)eEr(1)eN(1) ¼ 111.9(1), C(34)eEr(1)eN
(2) ¼ 117.5(1).
agostic interactions. The observed EreC bond lengths in 4 are 2.342
ꢀ
ꢀ
(3) A (Er(1)eC(30)) and 2.380(2) A (Er(1)eC(34)).
Significantly, complex 4 represents the first example of a struc-
turally characterized neutral four-coordinate organoerbium
complex. In comparison, there have only been five other four-
coordinate erbium compounds previously characterized by X-ray
crystallography, including a neutral erbium coordination complex
[26], three anionic coordination complexes [24,27], and one anionic
organometallic species [28].
ꢀ
Remarkably, the Er(1)eC(30) bond in 3 at 2.343(7) A and the Er
ꢀ
(1)eC(30) bond in 4 at 2.342(3) A are not significantly different, and
Fig. 3. ORTEP diagram (50% probability) of [Er(L)(CH2SiMe3)(m-Cl)]2 (3). The dimeric
as such, represent the shortest EreR (R ¼ CH2SiMe3) bond lengths
to date. There are only three other structurally characterized
complexes containing an EreCH2SiMe3 bond: Er(CH2SiMe3)3(THF)2
structure (with hydrogen atoms and iPr groups omitted for clarity) is shown in (A),
while the asymmetric unit (with hydrogen atoms omitted for clarity) is depicted in (B).
ꢁ
ꢀ
Selected bond distances (A) and angles ( ): Er(1)eN(1) ¼ 2.284(5), Er(1)eN(2) ¼ 2.270
(5), Er(1)eCl(1) ¼ 2.653(2), Er(1)eCl(1)_1 ¼ 2.638(2), Er(1)eC(30) ¼ 2.343(7), N(1)eEr
(1)eN(2) ¼ 85.4(2), Cl(1)eEr(1)eCl(1)_1 ¼77.4(1), Cl(1)eEr(1)eN(2) ¼ 142.2(2), Cl(1)e
Er(1)eN(1) ¼ 86.3(2), Cl(1)_1eEr(1)eN(2) ¼ 87.9(1), Cl(1)_1eEr(1)eN(1) ¼ 143.5(1), C
(30)eEr(1)eN(1) ¼ 107.9(2), C(30)eEr(1)eN(2) ¼ 109.5(2), C(30)eEr(1)eCl(1) ¼ 108.2
(2), C(30)eEr(1)eCl(1)_1 ¼108.2(2). Note: Cl(1)_1 was generated by the symmetry
operator ꢀx þ 2, ꢀy þ 1, ꢀz þ 2.
i
[29], Er(CH2SiMe3)3(THF)(ImMe2 Pr2) [30], and Er(CH2SiMe3)3(iPr-
trisox) [31], all of which are composed of three alkyl ligands and
either one or two neutral donors. In comparison to the bond
lengths in 3 and 4, these tris(alkyl) erbium complexes exhibit
ꢀ
considerably elongated EreC distances ranging from 2.392(3) A e
ꢀ
2.428(3) A.
ꢀ
Similar to that of 2, at 1.237 A the erbium center in 4 sits
significantly above the NCCCN backbone. While this out-of-plane
bonding is not as dramatic as that observed in 2, it is more evident
than that in five-coordinate 3 and six-coordinate 1. As expected,
implementation of the sterically demanding eCH2SiMe3 and eN
(SiMe3)2 ligands resulted in steric saturation of the erbium coor-
dination sphere, thus giving rise to monomeric four-coordinate
erbium complexes.
Complex 4 is slightly thermally sensitive. In the solid-state, 4
decomposes at temperatures above 107 ꢁC as evidenced by change
from a pale pink solid to an oily brown residue and visible effer-
vescence (presumably SiMe4). The complex is, however, indefi-
nitely stable if stored as a solid at ꢀ35 ꢁC. Although lack of
crystallinity of the decomposition product prevented unambiguous
identification, it is speculated that intramolecular ligand metalation
with concomitant loss of tetramethylsilane, as documented for
other rare earth complexes, is probable [9a,12a,32]. When the
thermal stability of complex 4 was monitored in solution (benzene-
d6) by 1H NMR spectroscopy, slight decomposition was observed
lengths, which are close to the average Er(2)eCl distance in 1
ꢀ
(2.657 A), indicates a nearly symmetric bridging interaction. The
ꢀ
metal center in complex 3 sits above the NCCCN plane by 1.043 A,
which is also comparable to that of 1.
Reaction of complex 1 with four equiv of LiCH2SiMe3 generated
the monomeric dialkyl species Er(L)(CH2SiMe3)2, 4 in 62.6% yield
(Scheme 2). High quality single crystals of 4 were grown from
a saturated toluene solution at ꢀ35 ꢁC. Under these conditions,
complex 4 crystallized in the centrosymmetric space group C2/c
with half of a molecule of toluene in the asymmetric unit. In the
solid-state, this complex adopts a distorted tetrahedral geometry
defined by the coordination of two alkyl groups and the k2 bound
nacnac ligand (Fig. 4). The closest contacts between the erbium
ꢀ
ꢀ
center and the nacnac backbone are 2.973(2) A, 3.169(2) A and
ꢀ
3.030(2) A for C(2), C(3) and C(4), respectively. These elongated
distances suggest little to no bonding interaction with the ligand
backbone, and thus, complex 4 is best described as four-coordinate.
Similarly, the erbium center does not appear to be supported by any

K.R.D. Johnson et al. / Journal of Organometallic Chemistry 695 (2010) 2747e2755
2751
after 24 h at 295 K. Under these conditions, approximately 15%
product loss was observed with the concomitant generation of
tetramethylsilane. Unfortunately, due to the paramagnetic nature
of complex 4, the relative amount of decomposition versus tetra-
methylsilane formation could not be accurately established by NMR
spectroscopy; therefore, no kinetic details about this process can be
presented at this time.
In the context of the potentially reactive EreC bonds in 3 and 4,
it was expected that these species would serve as useful precursors
for further derivatization at the metal center. Specifically, it was
anticipated that access to an erbium iodide derivative could be
achieved through the acid-base reaction of 4 with the iodide
delivery reagent [Et3NH]I. As expected, treatment of 4 with two
equiv of [Et3NH]I cleanly afforded the diiodide complex, Er(L)I2 (5),
with simultaneous production of tetramethylsilane and triethyl-
amine (Scheme 3).
Recrystallization of complex 5 from a toluene/THF solution
at ꢀ35 ꢁC generated pale pink plates of 5$THF suitable for an X-ray
diffraction experiment. Under these conditions, complex 5$THF
crystallized in the monoclinic space group P21/c and is depicted in
Fig. 5 as a thermal ellipsoid plot. In the solid-state, 5$THF is defined
by coordination of two iodide ligands, one THF donor and the
nacnac ancillary. The five-coordinate erbium center exhibits dis-
torted trigonal bipyramidal geometry with the iodide ligands and
one nitrogen atom of the nacnac in the equatorial positions. The
apical sites of the complex are occupied by a molecule of THF and
the second nitrogen of the nacnac ligand. Complex 5$THF exhibits
Fig. 5. ORTEP diagram (30% probability) of Er(L)I2(THF) (5ꢂTHF) with hydrogen atoms
and the solvent molecule of crystallization omitted for clarity. Selected bond distances
ꢁ
ꢀ
(A) and angles ( ): Er(1)eN(1) ¼ 2.244(3), Er(1)eN(2) ¼ 2.290(3), Er(1)eI(1) ¼ 2.9077
(5), Er(1)eI(2) ¼ 2.9278(4), Er(1)eO(1) ¼ 2.361(3), N(1)eEr(1)eN(2) ¼ 83.4(1), I(1)eEr
(1)eI(2) ¼ 132.24(1), I(1)eEr(1)eN(1) ¼ 101.30(7), I(2)eEr(1)eN(1) ¼ 126.14(7), O(1)e
Er(1)eN(2) ¼ 168.4(1).
reported rare earth complexes of the generic form LnCl3(THF)3 [35].
Distinct differences were noted, however, between the IR spectra of
6 and that of the ion pair, ErI3(THF)3.5 [34]. The Er(1)eI(2) and Er
ꢀ
ꢀ
(1)eI(1) bond lengths of 2.9276(6) A and 2.9504(4) A, respectively,
are quite similar to the values reported for 5$THF and agree well
with other previously reported EreI bonds [19,33].
ꢀ
ꢀ
relatively short EreI contacts of 2.9077(5) A and 2.9278(4) A, which
are slightly less than values previously reported for EreI containing
ꢀ
ꢀ
compounds (2.931(1) A e 3.0874(9) A) [19,33]. Thus, the low-end of
In the attempted synthesis of 5 via reaction of complex 1 with
trimethylsilyliodide, significant reactivity issues were observed.
Specifically, a ligand redistribution process led to the formation of 6
rather than 5. Comparably, the ease in which complex 5 was
synthesized by reaction of 4 with [Et3NH]I supports the value of
protonolysis reactivity in lanthanide chemistry as a means for
accessing certain structural motifs.
While erbium chloride complex 1 has been demonstrated
herein as a useful precursor for salt metathesis reactions with
various amido- and organo-lithium reagents, the iodide complexes,
5 and 6, are of interest to us due to their potential for reactivity with
ꢀ
the range for a typical EreI bond should be extended to 2.9077(5) A.
In an effort to prepare complex 5 via an alternative route,
complex 1 was reacted with 4 equiv of trimethylsilyliodide in
toluene solution over 21 h at ambient temperature. Following
removal of solvent and recrystallization, the unexpected complex
ErI3(THF)3 (6) was isolated as a sparingly soluble pale pink solid in
89.8% yield (Scheme 2). By this route, formation of complex 6 is
accompanied by elimination of trimethylsilylchloride, and gener-
ation of one equiv of “ErL2I”. The formulation of “ErL2I” as a reaction
by-product is tentative as we have been unable to isolate or char-
acterize such a species; it is possible that it is unstable and prone to
ligand redistribution.
Recrystallization of 6 from methylene chloride gave rise to pale
pink prisms that were suitable for X-ray diffraction. Complex 6
crystallized in centrosymmetric space in the orthorhombic space
group Pbcn (#60). In the unit cell of the crystal structure, each
erbium center sits on a 2-fold rotation axis. This symmetry is
exhibited in the molecular structure along the O(1)eEr(1)eI(2)
vector. In the solid-state, complex 6 displays a distorted meridional
octahedral geometry comprised of three iodide ligands and three
THF donors (Fig. 6). Contrary to the previously reported erbium
iodide ion pair, ErI3(THF)3.5 [34], which was only characterized by
IR spectroscopy and combustion analysis, 6 is a neutral erbium
triiodide THF adduct. Inspection of the IR spectrum of complex 6
revealed many similar absorption bands to other previously
ꢀ
Fig. 6. ORTEP diagram (50% probability) of ErI3(THF)3 (6). Selected bond distances (A)
and angles (ꢁ): Er(1)eI(2): 2.9276(6), Er(1)eI(1): 2.9504(4), Er(1)eO(1): 2.327(5), Er
(1)eO(2): 2.273(3), I(2)eEr(1)eI(1) ¼ 91.99(1), I(1)eEr(1)eO(1) ¼ 88.01(1), I(2)eEr
(1)eO(2) ¼ 97.03(9), I(1)eEr(1)eO(2) ¼ 90.18(9), O(2)eEr(1)eO(1) ¼ 82.97(9). Note: I
(1)_1 and O(2)_1 were generated by the symmetry operator ꢀx þ 1, y, ꢀz þ 0.5.
Scheme 3. Synthesis of 5.

2752
K.R.D. Johnson et al. / Journal of Organometallic Chemistry 695 (2010) 2747e2755
organo-potassium reagents. It has previously been shown that an
iodide ligand can be more labile than chloride when allowed to
react with potassium compounds [12b,34]. Therefore, it is expected
that diiodide ErLI2 (5) may facilitate access to the dibenzyl analog of
complex 4 (Er(L)(CH2Ph)2) upon reaction with benzyl potassium.
We are currently in the process of investigating the viability of this
synthetic pathway.
4.2. Synthesis of complexes
4.2.1. Er(L)Cl( -Cl)3Er(L)(THF) (1)
m
To a 100 mL bomb charged with LiL (5.12 g, 12.0 mmol) and
ErCl3(THF)3.5 (6.35 g, 12.1 mmol) THF (70 mL) was added to give
a brown suspension. The reaction mixture was heated to 85 ꢁC for
6.5 h resulting in a clear red solution. The solvent was removed in
vacuo leaving a yellow-beige residue that was taken into a glove box.
Toluene (20 mL) was added to reconstitute the solid, and the
resulting suspension was filtered through a fine frit to remove LiCl.
The frit was washed with toluene (2 ꢃ1 mL) and the dark red filtrate
was concentrated under vacuum. Upon cooling the solution to
ꢀ35 ꢁC for 48 h, pink needles of 1 developed, and were collected by
filtration, washed with pentane, and dried in vacuo. Yield: 6.63 g
3. Conclusions
The compound Er(L)Cl(m-Cl)3Er(L)(THF) (1) was readily
prepared via the reaction of erbium chloride and LiL. Salt metath-
esis of 1 with four equiv of LiN(SiMe3)2 generated the mixed chloro/
silylamido dimer adduct [Er(L)N(SiMe3)2Cl(m-(LiN(SiMe3)2))]2 (2)
as an unusual example of a four-coordinate erbium coordination
(79.5%). Magnetic moment (chloroform-d, 295 K): meff 11.8 mB
.
1H
Dn1/2 ¼ 864 Hz), 56.64
complex. Reaction of 1 with either two or four equiv of LiCH2SiMe3
NMR (benzene-d6, 295 K): 121.39
d
(
generated the mixed chloro/alkyl dimer [Er(L)(CH2SiMe3)(
m-Cl)]2
(
(
(
(
(
Dn1/2 ¼ 97 Hz), 55.01 (Dn1/2 ¼ 301 Hz), 39.51 (Dn1/2 ¼ 89 Hz), 37.35
Dn1/2 ¼ 177 Hz), 36.59 (Dn1/2 ¼ 80 Hz), 34.71 (Dn1/2 ¼ 115 Hz), 28.99
Dn1/2 ¼ 62 Hz), 27.70 (Dn1/2 ¼ 80 Hz), 20.38 (Dn1/2 ¼ 89 Hz), 17.49
Dn1/2 ¼ 159 Hz), 15.31 (Dn1/2 ¼ 97 Hz), ꢀ1.41 (Dn1/2 ¼ 132 Hz), ꢀ2.59
Dn1/2 ¼ 192.4 Hz), ꢀ6.80 (Dn1/2 ¼ 180 Hz), ꢀ11.90 (Dn1/2 ¼ 96 Hz),
(3) or the dialkyl monomer Er(L)(CH2SiMe3)2 (4), respectively. As
complex 4 represents a rare example of a relatively stable four-
coordinate dialkyl lanthanide complex, we are currently investi-
gating its small molecule reactivity in an effort to further obtain
unique structures and bonding modes. As a preliminary investi-
gation into the reactivity of 4, the erbium diiodide complex Er(L)I2
(5) was prepared via reaction of 4 with [Et3NH]I. Complex 5, in
addition to the iodide complex ErI3(THF)3 (6) (obtained by reaction
of 1 with trimethylsilyliodide), will likely serve as useful precursors
for salt metathesis reactions with organo-potassium reagents and
we are currently exploring the full range of their utility.
ꢀ17.51
(
Dn1/2 ¼175 Hz), ꢀ21.01
(
Dn1/2 ¼144 Hz), ꢀ26.07
(Dn1/
¼ 437 Hz), ꢀ29.63 (Dn1/2 ¼ 618 Hz), ꢀ36.62 (Dn1/2 ¼ 89 Hz), ꢀ42.96
2
(
Dn1/2 ¼ 263 Hz), ꢀ61.77 (Dn1/2 ¼ 201 Hz), ꢀ166.27 (Dn1/2 ¼ 874 Hz).
Anal. Calcd. (%)forC62H90Cl4Er2N4O: C, 53.82;H, 6.56; N, 4.05. Found:
C, 54.32; H, 6.92; N, 3.81. Complex 1 can be alternatively prepared in
approximately the same yield through an analogous procedure
utilizing anhydrous ErCl3 in place of ErCl3(THF)3.5
.
4. Experimental
4.2.2. [Er(L)N(SiMe3)2Cl( -(LiN(SiMe3)2))]2 (2)
m
In a glove box, toluene (10 mL) was added at ambient temper-
ature to an intimate mixture of 1 (0.371 g, 0.268 mmol) and LiN
(SiMe3)2 (0.196 g, 1.17 mmol) in a 25 mL Erlenmeyer flask. As the
reaction mixture was stirred for 1.25 h, it rapidly took on a cloudy
peach-orange appearance. The solution was filtered through a fine
porosity frit and the clear orange filtrate was concentrated in vacuo
to 2 mL and left at ꢀ35 ꢁC to crystallize. Analytically pure pale pink
crystals of 2 were collected by filtration, washed with pentane, and
dried under reduced pressure. Yield: 0.302 g (59.4%). Magnetic
4.1. General
All reactions were carried out under an argon atmosphere with
the rigorous exclusion of oxygen and water using standard glove
box (MBraun) or high vacuum line techniques. The solvents THF,
pentane, toluene and methylene chloride were dried and purified
using a solvent purification system (MBraun) and distilled under
vacuum prior to use from sodium benzophenone ketyl (THF),
“titanocene” (pentane and toluene) or calcium hydride (methylene
chloride). Unless specified otherwise, solvents were introduced
directly into reaction flasks by vacuum transfer with condensation
at ꢀ78 ꢁC. Deuterated solvents were dried over sodium benzo-
phenone ketyl (benzene-d6) or calcium hydride (chloroform-d),
degassed via three freezeepumpethaw cycles, distilled under
vacuum and stored in glass bombs under argon. Samples for NMR
spectroscopy were recorded on a 300 MHz Bruker Avance II
(Ultrashield) spectrometer (1H 300.13 MHz, 7Li 116.64 MHz) and
referenced relative to either SiMe4 through the residual solvent
resonance(s) for 1H or external LiCl for 7Li. Peak width at half-
height is given for the paramagnetically broadened resonances.
Solution magnetic moments were determined by the Evans
method [36] with an appropriate diamagnetic correction [37] and
are the average value of at least two independent measurements.
FT-IR spectra were recorded on a Bruker ALPHA FT infrared spec-
trometer with Platinum ATR sampling. Elemental analyses were
performed using an Elementar Americas Vario MicroCube instru-
ment. The reagents [Et3NH]I [38], and LiL [39], were prepared
according to literature procedures. [Et3NH]I was further purified by
recrystallization from an acetone-methanol mixture (1:1) at ꢀ35 ꢁC
and dried thoroughly under vacuum. The synthesis of ErCl3(THF)3.5
was carried out by a modified literature procedure [40]. Anhydrous
ErCl3 was purchased from Strem Chemicals and used as received.
All other reagents were obtained from Aldrich Chemicals or Alfa
Aesar and used as received.
moment (benzene-d6, 295 K): meff 13.1 mB
.
1H NMR (benzene-d6,
116.79 (Dn1/2 ¼ 619 Hz), 99.84 (Dn1/2 ¼ 214 Hz), 79.05
Dn1/2 ¼ 128 Hz), 44.23 (Dn1/2 ¼ 48 Hz), 29.04 (Dn1/2 ¼ 80 Hz), 9.35
Dn1/2 ¼ 103 Hz), 4.71 Dn1/2 ¼ 44 Hz), ꢀ40.41 Dn1/2 ¼ 90 Hz),
295 K):
d
(
(
(
(
ꢀ59.66
(
Dn1/2 ¼ 167 Hz), ꢀ94.61
(
Dn1/2 ¼ 378 Hz), ꢀ238.83
(
Dn1/2 ¼ 322 Hz). 7Li NMR (benzene-d6, 295 K):
d 11.17. Anal. Calcd.
(%) for C82H154Cl2Er2Li2N8Si8: C, 51.94; H, 8.19; N, 5.91. Found: C,
52.16; H, 8.12; N, 5.91.
4.2.3. [Er(L)(CH2SiMe3)(m-Cl)]2 (3)
In a glove box, a 25 mL Erlenmeyer flask was charged with 1
(0.248 g, 0.179 mmol) and LiCH2SiMe3 (0.0340 g, 0.361 mmol) and
then cooled to ꢀ35 ꢁC. Cold toluene (5 mL) was added at ꢀ35 ꢁC
and the reaction mixture was left at this temperature for 1 h with
mixing. The cloudy orange solution was then allowed to warm to
ambient temperature where it was stirred for a further 0.5 h. The
reaction mixture was filtered through a fine porosity frit and the frit
was washed with 2 ꢃ1 mL of toluene. The clear yellow filtrate was
concentrated slightly under vacuum and left at ꢀ35 ꢁC to crystal-
lize. Small pale pink crystals of 3 were collected by filtration,
washed with cold pentane, and dried under reduced pressure.
Yield: 0.057 g (22.3%). Magnetic moment (chloroform-d, 295 K):
meff 10.5 mB
.
1H NMR (chloroform-d, 295 K):
d
179.16
(
Dn1/2 ¼ 1475 Hz), 48.86 (Dn1/2 ¼ 65 Hz), 41.23
(
Dn1/2 ¼ 300 Hz),
39.73 (Dn1/2 ¼ 76 Hz), 28.44 (Dn1/2 ¼ 38 Hz), 22.92 (Dn1/2 ¼ 130 Hz),
1.51 (132 Hz), ꢀ1.21 (Dn1/2 ¼ 59 Hz), ꢀ49.53 (Dn1/2 ¼ 55 Hz), ꢀ83.60

K.R.D. Johnson et al. / Journal of Organometallic Chemistry 695 (2010) 2747e2755
2753
(
Dn1/2 ¼171 Hz), ꢀ222.75 (Dn1/2 ¼ 849 Hz). Anal. Calcd. (%) for
then stirred for 1 h. All volatiles were removed from the reaction
mixture to afford a pink residue that was taken into a glove box. The
residue was reconstituted in toluene (5 mL), filtered to remove
excess [Et3NH]I, concentrated under reduced pressure to w2 mL
and left at ꢀ35 ꢁC to crystallize. Pink-orange crystals of 5 were
collected by filtration, washed with pentane, and dried in vacuo.
Yield: 0.0928 g (25.3%). Magnetic moment (5$THF, chloroform-d,
C66H104Cl2Er2N4Si2: C, 56.02; H, 7.41; N, 3.96. Found: C, 55.85; H,
7.18; N, 3.96.
4.2.4. Er(L)(CH2SiMe3)2 (4)
In a glove box, a 25 mL Erlenmeyer flask was charged with 1
(1.11 g, 0.802 mmol) and LiCH2SiMe3 (0.302 g, 3.21 mmol) and then
cooled to ꢀ35 ꢁC. Cold toluene (10 mL) was added at ꢀ35 ꢁC and the
reaction mixture was left at this temperature for 1 h with mixing.
The cloudy orange solution was then allowed to warm to ambient
temperature where it was stirred for a further 0.5 h. The reaction
mixture was filtered through a fine porosity frit and the frit was
washed with 2 ꢃ 1 mL of toluene. The clear orange filtrate was
concentrated to 5 mL under vacuum and then left at ꢀ35 ꢁC to
crystallize. Small pale pink crystals of 4 were collected by filtration,
washed with cold pentane, and dried under reduced pressure.
Yield: 0.763 g (62.6%). Magnetic moment (benzene-d6, 295 K): meff
295 K): meff 9.0 mB. d 32.87
1H NMR (5$THF, benzene-d6, 295 K):
(
Dn1/2 ¼1122 Hz), 30.34 (Dn1/2 ¼ 597 Hz), 25.90 (Dn1/2 ¼ 670 Hz),
21.50
(
Dn1/2 ¼ 47 Hz),
ꢀ13.91
(
Dn1/2 ¼ 529 Hz),
ꢀ19.07
(
Dn1/2 ¼103 Hz), ꢀ30.22 (Dn1/2 ¼1104 Hz), ꢀ62.62 (Dn1/2 ¼ 195 Hz).
Anal. Calcd. (%) for C36H49ErI2N2 (5$Toluene): C, 46.45; H, 5.31; N,
3.01. Found: C, 46.15; H, 5.73; N, 2.97.
4.2.6. ErI3(THF)3 (6)
Addition of toluene (40 mL) to a 100 mL round bottom flask
charged with 1 (0.924 g, 0.668 mmol) generated a clear pink
solution. Trimethylsilyliodide (0.40 mL, 2.8 mmol) was added via
syringe at ambient temperature giving a clear pale yellow solution.
The reaction mixture was stirred for 21 h, over which time the
product precipitated as an off-white solid. The volatiles were
removed in vacuo leaving a pale yellow residue. In a glove box, the
residue was reconstituted in toluene and a hot filtration was per-
formed to remove remaining solids. Upon cooling the toluene
solution to ambient temperature the product separated as an oil.
Addition of THF (1 mL) liberated a sparingly soluble off-white solid.
The supernatant was decanted, and the solid was washed with
pentane (5 ꢃ1 mL) and dried under vacuum to give 6 as a very pale
pink amorphous solid. Additional product was obtained by
removing all volatiles from the toluene/THF supernatant. The
7.2 mB
104.09 (Dn1/2 ¼ 1252 Hz), 87.04 (Dn1/2 ¼ 1252 Hz), 70.21 (Dn1/2
123 Hz), 32.29 (Dn1/2 ¼1802 Hz), 15.81 (Dn1/2 ¼ 183 Hz), ꢀ40.29
.
1H NMR (benzene-d6, 295 K):
d
217.74 (Dn1/2 ¼ 1973 Hz),
¼
(
Dn1/2 ¼189 Hz), ꢀ51.03 (Dn1/2 ¼ 241 Hz), ꢀ134.05 (Dn1/2 ¼ 639 Hz),
ꢀ265.36 (Dn1/2 ¼ 2447 Hz), ꢀ519.18 (Dn1/2 ¼ 6164 Hz). Anal. Calcd.
(%) for C37H63ErN2Si2: C, 58.52; H, 8.36; N, 3.69. Found: C, 58.41; H,
8.37; N, 3.54.
4.2.5. Er(L)I2 (5)
To a 100 mL round-bottomed flask charged with 4 (0.333 g,
0.438 mmol) and [Et3NH]I (0.203 g, 0.886 mmol) methylene chlo-
ride was added (20 mL) to give a clear pale orange solution. The
reaction mixture was allowed to warm to ambient temperature and
Table 1
Summary of crystallography data collection and structure refinement for compounds 1e6.
1a
2
3b
4c
5c
6
Formulad
C69H98Cl4Er2N4O
1475.83
Monoclinic
P21/n
19.083(2)
17.800(2)
20.451(2)
90
92.183(1)
90
6942(1)
4
C82H154Cl2Er2Li2N8Si8
1896.15
Monoclinic
P21/c
23.753(2)
20.775(1)
22.594(1)
90
115.107(1)
90
10095(1)
4
C80H120Cl2Er2N4Si2
1599.40
Monoclinic
P21/n
14.329(2)
16.093(3)
16.910(3)
90
102.420(2)
90
C40.5H66.5ErN2Si2
804.90
Monoclinic
C2/c
21.262(3)
10.489(1)
38.192(5)
90
94.946(1)
90
C36.5H52.5ErI2N2O
956.37
Monoclinic
P21/c
14.989(2)
12.321(2)
21.174(3)
90
102.311(2)
90
C12H24ErI3O3
764.27
Orthorhombic
Pbcn
9.328(1)
14.669(2)
14.417(2)
90
90
90
1972.7(4)
4
2.573
FWd/g molꢀ1
Crystal system
Space group
ꢀ
a/A
ꢀ
b/A
ꢀ
c/A
ꢁ
ꢁ
a
/
b
/
ꢁ
g
/
3
ꢀ
Volume/A
3808(1)
2
1.395
2.334
8486(2)
8
1.260
3820.5(11)
4
1.663
Z
Dcalcd/mg mꢀ3
1.412
2.598
1.248
1.840
m
d/mmꢀ1
2.061
3.841
8.950
Crystal size/mm
Crystal color
Crystal habit
0.43 ꢃ 0.07 ꢃ 0.06
Pale pink
Needle
1.56e24.71
63,004
11,842
99.9%
11,842/4/713
1.009
0.0351
0.0648
0.0609
0.0736
0.743 and ꢀ0.537
0.30 ꢃ 0.14 ꢃ 0.11
Pale pink
Prism
1.81e27.10
112,217
22,180
99.5%
22,180/0/981
1.002
0.0351
0.0663
0.0667
0.0775
0.19 ꢃ 0.11 ꢃ 0.04
Pale pink
Plate
1.69e27.10
52,373
0.37 ꢃ 0.19 ꢃ 0.06
Pale pink
Plate
1.92e27.10
46,724
9373
100%
9373/0/433
1.151
0.0261
0.0522
0.0306
0.0537
0.765 and ꢀ0.811
0.34 ꢃ 0.27 ꢃ 0.03
Pale pink
Plate
1.92e27.10
42,219
8428
100%
8428/7/388
1.017
0.0292
0.0675
0.0376
0.0721
2.627 and ꢀ2.162
0.24 ꢃ 0.09 ꢃ 0.07
Pale pink
Prism
2.59e26.72
20,122
2090
100%
2090/0/88
1.049
0.0237
0.0667
0.0291
0.0700
1.245 and ꢀ1.407
q
Range/ꢁ
N
Nind
8412
100%
Completeness to
q
¼ 27.10ꢁ
Data/restraints/parameters
8412/0/356
1.076 [0.910]
0.0631 [0.0540]
0.1658 [0.0975]
0.1515 [0.1168]
0.2047 [0.1126]
[0.698 and ꢀ0.900]
GoF on F2
R1 (I > 2
s
(I))e
s
wR2 (I > 2
(I))f
R1 (all data)e
wR2 (all data)f
ꢀꢀ3
Drmax and Drmin/e$A
1.415 and ꢀ0.893
a
Crystallized with one disordered molecule of toluene in the asymmetric unit.
A highly disordered solvent molecule was removed from the reflection file using the SQUEEZE subroutine of PLATON; statistics following treatment of data with SQUEEZE
b
are listed in square brackets.
c
Crystallized with half of one molecule of toluene in the asymmetric unit.
For non-SQUEEZED data.
d
e
R1 ¼ SkFoj ꢀ jFck/SjFoj.
f
wR2 ¼ {S[w(F2o ꢀ F2c)2]/S[w(Fo2)2]1/2
.

2754
K.R.D. Johnson et al. / Journal of Organometallic Chemistry 695 (2010) 2747e2755
(2003) 4372e4374;
residual oil was extracted with THF (5 mL) and the THF solution was
layered with pentane. The product precipitated and the superna-
tant was decanted. The solid was washed with pentane (5 ꢃ1 mL)
and dried under reduced pressure to yield a second crop of product.
Combined yield: 0.459 g (89.8%). Magnetic moment (chloroform-d,
(d) W.J. Evans, N.T. Allen, J.W. Ziller, J. Am. Chem. Soc. 123 (2001) 7927e7928;
(e) W.J. Evans, N.T. Allen, J.W. Ziller, Angew. Chem., Int. Ed. 41 (2002)
359e361;
(f) F. Jaroschik, F. Nief, X.-F. Le Goff, L. Ricard, Organometallics 26 (2007)
1123e1125;
(g) F. Jaroschik, F. Nief, X.-F. Le Goff, L. Ricard, Organometallics 26 (2007)
3552e3558;
295 K): meff 8.7 mB. IR:
n
(cmꢀ1) 1368 (w), 1342 (w), 1294 (w), 1247
(h) F. Jaroschik, A. Momin, F. Nief, X.-F. Le Goff, G.B. Deacon, P.C. Junk, Angew.
Chem., Int. Ed. 48 (2009) 1117e1121;
(w), 1178 (w), 1038 (m), 998 (m), 953 (w), 915 (w), 858 (sh, m), 828
(m), 572 (m), 476 (m). Anal. Calcd. (%) for C12H24ErI3O3: C, 18.86; H,
3.17. Found: C, 19.47; H, 3.29.
(i) G. Meyer, Angew. Chem., Int. Ed. 47 (2008) 4962e4964;
(j) G.B. Deacon, C.M. Forsyth, F. Jaroschik, P.C. Junk, D.L. Kay, T. Maschmeyer,
A.F. Masters, J. Wang, L.D. Field, Organometallics 27 (2008) 4772e4778;
(k) C. Ruspic, J.R. Moss, M. Schürmann, S. Harder, Angew. Chem., Int. Ed. 47
(2008) 2121e2126.
4.3. X-ray crystallography
[3] (a) F.T. Edelmann, D.M.M. Freckmann, H. Schumann, Chem. Rev. 102 (2002)
1851e1896;
Single crystals suitable for X-ray diffraction were obtained by
recrystallization of compounds 1e4 from concentrated toluene
solutions at ꢀ35 ꢁC, complex 5 from a concentrated toluene/THF
mixture at ꢀ35 ꢁC and complex 6 from a concentrated methylene
chloride solution at ꢀ35 ꢁC. Crystals were coated in dry Paratone oil
under an argon atmosphere and mounted onto a glass fiber. Data
(b) P. Mountford, B.D. Ward, Chem. Commun. (2003) 1797e1803;
(c) W.E. Piers, D.J.H. Emslie, Coord. Chem. Rev. 233e234 (2002) 131e155.
[4] (a) S.G. McGeachin, Can. J. Chem. 46 (1968) 1903e1912;
(b) J.E. Parks, R.H. Holm, Inorg. Chem. 7 (1968) 1408e1416.
[5] L. Bourget-Merle, M.F. Lappert, J.R. Severn, Chem. Rev. 102 (2002) 3031e3066.
[6] (a) S.D. Allen, D.R. Moore, E.B. Lobkovsky, G.W. Coates, J. Am. Chem. Soc. 124
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ꢀ
tometer (Mo K
a
radiation,
l
¼ 0.71073 A) outfitted with a CCD area-
detector and a KRYO-FLEX liquid nitrogen vapor cooling device. A
data collection strategy using
ꢀ 2
scans at 0.5ꢁ steps yielded full
u
q
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hemispherical data with excellent intensity statistics. Unit cell
parameters were determined and refined on all observed reflec-
tions using APEX2 software [41]. Data reduction and correction for
Lorentz polarization were performed using SAINT-Plus software
[42]. Absorption corrections were applied using SADABS [43]. The
structures were solved by direct methods and refined by the least
squares method on F2 using the SHELXTL software suite [44]. All
non-hydrogen atoms were refined anisotropically. Hydrogen atom
positions were calculated and isotropically refined as riding models
to their parent atoms. No decomposition was observed during data
collection. Table 1 provides a summary of selected data collection
and refinement parameters. Note: In the refinement of 3, a disor-
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the SQUEEZE subroutine of the PLATON program [45]. Information
regarding the crystal structure of 3 is given before and after treat-
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(l) L.K. Knight, W.E. Piers, R. Mcdonald, Organometallics 25 (2006)
3289e3292;
(m) A.L. Kenward, J.A. Ross, W.E. Piers, M. Parvez, Organometallics 28 (2009)
3625e3628;
(n) J.E. Bercaw, D.L. Davies, P.T. Wolczanski, Organometallics
443e450;
5 (1986)
Acknowledgements
(o) F. Basuli, J. Tomaszewski, J.C. Huffman, D.J. Mindiola, Organometallics 22
(2003) 4705e4714;
(p) A.M. Neculai, D. Neculai, H.W. Roesky, J. Magull, M. Baldus, O. Andronesi,
M. Jansen, Organometallics 21 (2002) 2590e2592;
(q) A.M. Neculai, H.W. Roesky, D. Neculai, J. Magull, Organometallics 20 (2001)
5501e5503;
(r) E. Lu, W. Gan, Y. Chen, Organometallics 28 (2009) 2318e2324;
(s) Z. Zhang, D. Cui, X. Liu, J. Polym. Sci., Part A: Polym. Chem. 46 (2008)
6810e6818.
P. G. H. acknowledges the Natural Sciences and Engineering
Research Council (NSERC) of Canada for a Discovery Grant, the
Canada Foundation for Innovation for a Leaders Opportunity Grant
and the University of Lethbridge for start-up funds. The authors
also wish to thank Mr. Craig Wheaton (University of Lethbridge) for
performing elemental analyses.
[10] X. Xu, X. Xu, Y. Chen, J. Sun, Organometallics 27 (2008) 758e763.
[11] (a) Y. Yao, Y. Zhang, Q. Shen, K. Yu, Organometallics 21 (2002) 819e824;
(b) Y. Yao, Y. Zhang, Z. Zhang, Q. Shen, K. Yu, Organometallics 22 (2003)
2876e2882;
Appendix A. Supplementary material
(c) Y. Yao, Z. Zhang, H. Peng, Y. Zhang, Q. Shen, J. Lin, Inorg. Chem. 45 (2006)
2175e2183;
(d) Z.-Q. Zhang, Y.-M. Yao, Y. Zhang, Q. Shen, W.-T. Wong, Inorg. Chim. Acta
357 (2004) 3173e3180;
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J. Sun, J. Organomet. Chem. 678 (2003) 108e116;
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(g) M. Xue, H. Sun, H. Zhou, Y. Yao, Q. Shen, Y. Zhang, J. Polym. Sci., Part A:
Polym. Chem. 44 (2006) 1147e1152;
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(j) A.M. Neculai, D. Neculai, H.W. Roesky, J. Magull, Polyhedron 23 (2004)
183e187.
CCDC 784848 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
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