Rare-earth metal hydroxylamide complexes

Article abstract of DOI:10.1039/b810234a

The rare-earth metal hydroxylamide compound Y[N(SiHMe₂) ₂]₂[ONBn₂][THF] (1) was prepared by the silylamide elimination pathway from the reaction of N,N-dibenzylhydroxylamine, Bn₂NOH (Bn = CH₂

Full text of DOI:10.1039/b810234a

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PAPER
www.rsc.org/dalton | Dalton Transactions
Rare-earth metal hydroxylamide complexes†
Ajay Venugopal,a,b Alexander Hepp,b Tania Pape,b Andreas Mixa and Norbert W. Mitzel*a
Received 17th June 2008, Accepted 13th August 2008
First published as an Advance Article on the web 14th October 2008
DOI: 10.1039/b810234a
The rare-earth metal hydroxylamide compound Y[N(SiHMe2)2]2[ONBn2][THF] (1) was prepared by the
silylamide elimination pathway from the reaction of N,N-dibenzylhydroxylamine, Bn2NOH (Bn =
CH2C6H5), with Y[N(SiHMe2)2]3[THF]2 and was characterised by multinuclear NMR spectroscopy
and elemental analysis. The compounds [Cp2Y(ONBn2)]2 (2a) [Cp2Sm(ONBn2)]2 (2b) were
obtained by the reactions of MCp3 (M = Y, Sm) with Bn2NOH. The trinuclear compound
Cp5Y3[ON(Me)CH2CH2(Me)NO]2 (3) was obtained by the reaction of YCp3 and the bishydroxylamine
HON(Me)CH2CH2(Me)NOH. 2a, 2b and 3 were characterised by NMR spectroscopy, single-crystal
X-ray diffraction and elemental analysis. In all these complexes side-on-coordination of the
hydroxylamide units was observed. The compounds are of dynamic nature in solution.
compounds. These reaction schemes of silylamine elimination6,7
Introduction
and protonolysis reactions7,8 of cyclopentadienyl compounds
of the rare-earth metals have been successfully employed for
the synthesis of alkoxides in the past, but not used with OH
functional hydroxylamines. Here we used the mono-functional
hydroxylamine HONBn2 and the bi-functional hydroxylamine
HON(Me)CH2CH2(Me)NOH as ligand precursors for obtaining
the rare-earth metal hydroxylamide complexes.
Hydroxylamines belong to a unique class of ligands possessing
adjacent donor atoms. This makes them ideal ligand precursors
for saturating the coordination spheres of the rare-earth metal
ions with a minimum of steric shielding and the additional
advantage of being hemilabile. The adjacent O and N donors in
the hydroxylamines can bind to the metal centre resulting in the
formation of three-membered rings, i.e., the hydroxylamide unit
binds in a side-on mode. This binding mode and hemilability
is already well established in the coordination chemistry of
Group 4 metal ions.1 Also, there is now a wealth of structural
information available for the hydroxylamide complexes of Group
122 and 13,3 which points out the flexibility of the binding modes
(including hemilability) of the anionic hydroxylamide ligands in
these complexes.
Till recently, there was only one report on a rare-earth hydrox-
ylamide complex, namely [(C5H6Me4NO)2Sm(m-ONC5H6Me4)]2.
In this compound, the O,N-ligand was introduced by a redox
process starting with the TEMPO radical.4 We then reported the
first systematic approach of synthesising hydroxylamide rare-earth
metal complexes by salt-metathesis reactions of the hydroxylamide
salts KONR2 with the anhydrous metal trichlorides, but the
resulting products were found to be anionic ‘ate’-complexes
Results
Initial studies in this work involved the reaction of the commonly
used precursor, Y[N(SiHMe2)2]3[THF]2 with N,N-dibenzyl-
hydroxylamine (Scheme 1). This reaction yielded compound 1,
which was characterised by multinuclear NMR spectroscopy (1H,
13C, 29Si and 89Y) and elemental analysis. The composition of
1
1 follows from the integrals of the resonances in the H NMR
spectrum, proving the presence of the two amide groups beneath
one Bn2NO ligand and one THF molecule. This 1H NMR
spectrum does not change upon cooling the sample to 210 K.
i
with a formula K[M(ONR2)4] (M = Y, Sm, R = Pr). They
form polymeric aggregates in the solid state.5 Thus it seemed
desirable to find a generally applicable preparative pathway
to neutral organo rare-earth metal hydroxylamide compounds.
Herein, we describe a method based on bis(dimethylsilyl)amine
and hydrocarbon elimination reactions for the synthesis of such
Scheme 1
The 89Y NMR spectrum shows a single resonance at 314 ppm
(see ESI†). For Y[N(SiHMe2)2]3[THF]2, a single peak is reported at
444 ppm.9 Thus, there is an upfield shift of the 89Y resonance upon
replacement of a bis[(dimethyl)silylamide] group by a hydroxy-
lamide group. The 29Si NMR spectrum of compound 1 shows a
resonance at -22.0 ppm, while that of the Y[N(SiHMe2)2]3[THF]2
is observed at -19.6 ppm. Compound 1 could not be crystallised
and hence information about its structure in the solid state could
not be obtained. Although it is likely that the Bn2NO ligand is
bound side on, this cannot be unequivocally proven by the NMR
data.
aInstitut fu¨r Anorganische und Analytische Chemie, Westfa¨lische Wilhelms-
Universita¨t Mu¨nster, Corrensstr. 30, 48149, Mu¨nster, Germany
bLehrstuhl fu¨r Anorganische Chemie und Strukturchemie, Universita¨t Biele-
feld, Universita¨tsstrasse 25, 33615, Bielefeld, Germany. E-mail: mitzel@uni-
bielefeld.de; Fax: +49 (0)521 106-6026
† Electronic supplementary information (ESI) available: 1H and 89Y NMR
spectra of compound 1, 1H NMR spectrum of compound 2a. CCDC
reference numbers 687816 (2a), 687817 (2b) and 687818 (3). For ESI
and crystallographic data in CIF or other electronic format see DOI:
10.1039/b810234a
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Compounds [Cp2MON(CH2C6H5)2]2 (M = Y 2a and Sm 2b)
were prepared by the reactions of one equivalent of M(C5H5)3
and one equivalent of N,N-dibenzylhydroxylamine in THF
(Scheme 2). The resulting compounds are extremely air and
moisture sensitive, but are stable in THF even under reflux con-
dition. They were characterised by NMR spectroscopy, elemental
analyses and single-crystal X-ray diffraction studies.
Scheme 2
Fig. 1 1H NMR spectrum of compound 3 in THF-d8. The asterisk
denotes a resonance of the solvent.
Due to the paramagnetic nature of compound 2b, the protons at
the ortho-positions of the aromatic rings at the hydroxylamide unit
appear at 3.05 ppm in the H NMR spectrum. The signals for
1
and two triplets at 3.47 ppm (3JH = 13.6 Hz) and 2.96 ppm (3JH
=
the CH2 protons are observed at -0.53 and 1.98 ppm in 2b as
compared to the 2a, where only one broad peak at 4.40 ppm is
found. Each of these signals is further split into doublets, which
are not well resolved at ambient temperature (the spectrum is
displayed in ESI†). This indicates that the nitrogen atom of the
hydroxylamide unit in compound 2b is bonded to the samarium
atom and is therefore not capable of inverting its configuration,
which leads to two chemically differrent H atoms in each CH2 unit.
Thus, a geminal coupling between these protons results in a
doublet splitting.
14.5 Hz). This implies that the four protons of the ethylene unit are
not equivalent. The doublet splitting is due to the coupling of the
nuclear spin of one of the protons with one vicinal proton. The
pseudo triplet splitting results from the coupling of the nuclear
spins of one of the protons with two vicinal protons.
Crystal structure discussion
[Cp2Y(ONBn2)]2 (2a)
In an attempt to obtain Cp2Y[ON(Me)CH2CH2(Me)NO]YCp2,
two equivalents of YCp3 were treated with one equivalent of the
bis-hydroxylamine HON(Me)CH2CH2(Me)NOH in THF. How-
ever, this reaction afforded a compound of the composition
Cp5Y3[ON(Me)CH2CH2(Me)NO]2 (3) (Scheme 3). Also, unre-
acted YCp3 remained in the mixture after the reaction. In a further
stoichiometrically optimised experiment, the reagent ratio was
changed to suit the metal to ligand ratio of 3 leading to a yield of
88%. Compound 3 was characterised by elemental analysis, NMR
spectroscopy and a single-crystal X-ray diffraction experiment.
¯
Compound 2a crystallises in the triclinic space group P1 as a
dimer with one monomer in the asymmetric unit. The N,N-
dibenzylhydroxylamide ligand is bound to the metal centre in
h -manner, which results in the formation of a three-membered
YON ring (Fig. 2). The O atoms of the hydroxylamide ligands are
bridging the two metal centres in a m2-fashion. Two cyclopenta-
dienyl anions saturate the rest of the coordination sphere about
each yttrium atom. The average distance between the centroids
of the cyclopentadienyl rings and each of the yttrium atoms is
2
˚
2.394 A. The two distinguishable Y–O distances are quite similar
˚
at 2.248(3) and 2.255(2) A (Table 1). They fall in the same range
as that found for the h -bound ONiPr2 ligand in K[Y(ONiPr2)4].5
The Y–N distances are 2.503(3) A, which is similar to the Y–N
distances in K[Y(ONiPr2)4].5
2
˚
Scheme 3
The NMR spectra of THF-d8 solutions of 3 are strongly
temperature dependent. The signals for the methyl protons of the
bis-hydroxylamide appear as a single broad peak at 2.77 ppm in
1
the H NMR spectrum at 303 K and those for the ethylene unit
appear as broad peaks at 3.44, 3.04, 2.84 and 2.49 ppm (Fig. 1).
At 243 K, the methyl protons appear as two singlets at 2.77 and
2.73 ppm. The signals for the ethylene protons are found as two
doublets at 2.86 ppm (3JH = 15.2 Hz) and 2.46 ppm (3JH = 13.9 Hz)
Fig. 2 Molecular structure of compound 2a. H atoms are omitted for
clarity. Thermal ellipsoids are drawn at 50% probability level.
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◦
˚
Table 1 Selected bond lengths [A] and bond angles [ ] in compounds 2a
and 2b
Y1–O1(A)
Y1–O1
2.255(2)
2.248(3)
2.503(3)
1.438(2)
Sm1–O1
Sm2–O2
Sm1–O2
Sm2–O1
Sm1–N1
Sm2–N2
N1–O1
2.332(2)
2.344(2)
2.296(2)
2.290(2)
2.569(3)
2.550(3)
1.431(3)
1.432(3)
Y1–N1
N1–O1(A)
N2–O2
N1–Y1–O1(A)
N1–Y1–O1
34.7(1)
106.9(1)
72.3(1)
63.2(1)
82.1(1)
N1–Sm1–O1
N2–Sm2–O2
N1–Sm1–O2
N2–Sm2–O1
O1–Sm1–O2
O1–Sm2–O2
Sm1–N1–O1
Sm2–N2–O2
Sm1–O1–N1
Sm2–O2–N2
33.5(2)
33.7(1)
103.3(2)
102.5(2)
70.3(2)
70.2(1)
64.1(3)
65.2(2)
82.4(2)
81.1(2)
Fig. 4 Structures of the molecular cores of 2a and 2b showing the different
interplanar angles between the MON groups in the dimers.
O1–Y1–O1(A)
Y1–N1–O1(A)
Y1–O1(A)–N1
Even though compounds 2a and 2b crystallise from THF–
pentane, the metal centres do not take up any THF molecule
for further coordination. This underlines the efficiency of the
multidonor ability of the hydroxylamide ligands in saturating the
coordination sphere of the large rare-earth metal ions.
[Cp2Sm(ONBn2)]2 (2b)
These compounds were found to bind the hydroxylamine
Compound 2b crystallises in the monoclinic space group C2/c
with one dimer in the asymmetric unit. The ONBn2 ligand binds
to the metal centre similar (in coordination) to 2a (Fig. 3).
2
ligands in an h -binding mode such as found earlier in
4
[(C5H6Me4NO)2Sm(m-ONC5H6Me4)]2 and also in dicyanononi-
trosomethanide complexes of La, Ce, Nd and Gd.10
˚
The four Sm–O distances are between 2.290(2) and 2.344(2) A
2
(Table 1). This resembles those of the h -bound TEMPO- lig-
Cp5Y3[ON(Me)CH2CH2(Me)NO]2 3
4
2
and in [(C5H6Me4NO)2Sm(m-ONC5H6Me4)]2 and the h -bound
ONiPr2 ligand in K[Sm(ONiPr2)4].5 The Sm–N distances are
Compound 3 crystallises in the orthorhombic space group P212121.
Two yttrium atoms bear two cyclopentadienyl ligands each while
the third central yttrium atom binds to only one cyclopentadienyl
ligand (Fig. 5). Two bis-hydroxylamide ligands are shared between
these three yttrium atoms forming four three-membered YON
rings, two four-membered Y2O2 rings and two six-membered
YO2N2C2 rings. There is also one THF molecule in the asym-
metric unit, but is not coordinated to any metal atoms.
˚
2.569(3) and 2.550(3) A and are thus comparable to those
4
˚
in the complex [(C5H6Me4NO)2Sm(m-ONC5H6Me4)]2 (2.537 A)
and K[Sm(ON Pr2)4] (between 2.512(14) and 2.589(11) A). The
i
5
˚
average distance from the centroid of the cyclopentadienyl rings
˚
coordinating to the corresponding samarium atoms is 2.470 A.
Fig. 5 Molecular structure of compound 3. A solvent THF molecule and
the H atoms are omitted for clarity. Thermal ellipsoids are drawn at 50%
probability level.
Fig. 3 Molecular structure representing the dimeric unit of compound
2b. H atoms are omitted for clarity. Thermal ellipsoids are drawn at 50%
probability level.
In an alternative way, 3 can be described as a CpY moiety,
“crowned” by a 14-membered macrocycle consisting of two
yttrium atoms, four oxygen atoms, four nitrogen atoms and four
carbon atoms (Fig. 6). Four oxygen atoms and three nitrogen
atoms of this 14-membered crown are coordinating to the central
The only marked difference between the structures of 2a and
2b are the conformations of the M2N2O2 cores (Fig. 4). Whereas
the MON rings in 2a are almost coplanar with the M2O2 unit, the
dihedral angle between these units is 22.6◦ in 2b.
6630 | Dalton Trans., 2008, 6628–6633
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The reaction of YCp3 with HON(Me)CH2CH2(Me)NOH re-
sembles that of AlMe3 with HON(Me)CH2(Me)NOH. Both reac-
tions proceed independently of the initially chosen stoichiometry
of reactants to give trinuclear complexes. The aluminium and
yttrium complexes exhibit some parallels in their aggregation
modes (Scheme 5). Compound 6 has a five-coordinate Al atom
in the centre, which is in rapid dynamic equilibrium with other
structures as indicated in Scheme 5. Compared to the aggregation
mode of the aluminium complex, the yttrium complex only differs
from the former by additional side-on coordination of all four N
atoms to the yttrium atoms. This difference arises, because Y3+
3+
11
˚
˚
(1.04 A) has a much larger ionic radius than Al (0.535 A) and
thus has a greater demand for the saturation of its coordination
sphere by further contacts to donor sites. As in the aluminium
compound 6, the yttrium compound 3 is also highly dynamic and
the central Y atom can be seen as bound to all eight N,O-donor
atoms on time average.
Fig. 6 Representation of the core structure of compound 3 with selected
˚
bond lengths shown [A]. Cp ligands and H atoms are omitted. Selected
bond angles [◦]: O3–Y1–O2 69.0(2), O3–Y1–N3 33.4(2), O4–Y1–N3
72.5(1), O1–Y1–O4 68.4(2), O1–Y1–N1 31.7(2), O2–Y1–N1 70.6(2),
O3–Y1–O1 116.3(2), O4–Y1–O2 144.2(2), O1–Y2–N4 98.2(2), O3–Y3–N2
97.7(1), O4–N4–C32 109.3(2), N3–C31–C32 114.5(3), C31N3–C30
109.3(2), C32–N42 119.2(2).
yttrium atom (Y1). The atoms Y2 and Y3 are coordinated to two
oxygen atoms and one nitrogen atom each and the rest of their
coordination sphere is saturated by the cyclopentadienyl rings.
The Y–O distances fall in a small range between 2.234 and
˚
2.277 A. The atoms O1 and O4 are m2-bridging between Y2 and
Y1 and O3 and O2 are m2-bridging between Y3 and Y1. The Y–
˚
N distances vary between 2.437 and 2.740 A. The longest Y–N
˚
distance in this molecule is the Y1–N1 bond length, at 2.740(3) A.
The average distance from the centroid of the cyclopentadienyl
Scheme 5
˚
rings coordinating to each of the yttrium atoms is 2.415 A.
Compounds 2a, 2b and 3 do not take up further solvent
THF molecules for coordination showing that the h -coordination
2
of the hydroxylamide ligands and the M–O contacts through
dimerisation is effective to saturate the coordination sphere. This
expresses the possibility of ligands with adjacent O,N-donors in
saturating the coordination sphere of the large rare-earth metal
ions with the formation of three-membered MON rings and a
small number of atoms in the ligand sphere.
Structural relationships
The structures of 2a and 2b are somewhat related to those of
aluminium and gallium compounds 4 and 5 (Scheme 4) In the
solid state, 4 shows dimerisation via the oxygen atoms of the
hydroxylamide ligand, whereas 5 dimerises via the nitrogen atoms,
but both Al and Ga atoms are not bound by the NO-ligands side-
on (Scheme 4). Compounds 2a and 2b with the larger rare-earth
Conclusion
2
metal atoms can accept such a h -binding mode and thus both the
aggregation types of 4 and 5 are combined into one with all four
atoms bound to the metal centres simultaneously.
The dibenzylhydroxylamide complexes [Cp2MONCH2C6H5)2]2
(M = Y 2a and Sm 2b) as well as a bishydroxylamide complex
Cp5Y3[ON(Me)CH2CH2(Me)NO]2 (3) were successfully prepared
in high yields and characterised. There are some relationships be-
tween the structural chemistry of the new compounds described in
this paper and hydroxylamine and bishydroxylamine compounds
of aluminium and gallium concerning the general aggregation,
but the difference is clearly the lower coordination number in
group 13 chemistry with the ligands bound through one atom
only (preferably oxygen), whereas the larger rare-earth compounds
2
Scheme 4
always accept the full h -binding capability of the NO ligands.
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further stirred for 18 h. The solvent was removed under vacuum
and the product was washed with n-pentane. It was crystallised
from a concentrated THF solution at room temperature. Yield:
Experimental
General remarks
1
0.729 g (88%). H NMR (THF-d8; 400 MHz): d 2.49 (br, 2H,
All manipulations were performed under a rigorously dry inert
atmosphere of argon using standard Schlenk techniques. THF,
toluene and pentane were dried with Na/benzophenone. They
were freshly condensed from LiAlH4 before being employed
in reactions. THF-d8 and toluene-d8 were dried over Na/K
alloy. NMR measurements were made with a Bruker Avance
400 spectrometer. Elemental analyses were carried out on a
Vario E1 III CHNS instrument. N,N-Dibenzylhydroxylamine was
purchased from Aldrich. Y[N(SiHMe2)2]3[THF]2, MCp3 (M = Y,
Sm) and HON(Me)CH2CH2(Me)NOH were prepared according
to literature procedures.12–14
CH2), 2.77 (br 12H, CH3), 2.84 (br, 2H, CH2), 3.04 (br, 2H, CH2),
3.44 (br, 2H, CH2), 6.02 (s, 10H, C5H5), 6.08 (s, 10H, C5H5), 6.19 (s,
5H, C5H5). Elemental analysis (%) for C33H45N4O4Y3: calculated
C 47.86, H 5.43, N 6.76, found C 47.60, H 5.85, N 6.15.
Single-crystal X-ray diffraction experiments. Single crystals
suitable for X-ray diffraction measurement were picked inside the
glove-box, suspended in paraffin oil and mounted on a glass fibre
and transferred onto the goniometer of the diffractometer. The
measurements were carried out on a Bruker APEX diffractometer
with Mo-Ka radiation. The structures were solved by direct
methods and refined by full-matrix least squares (SHELXTL
5.01).15 The structures in this article are represented using the
program ORTEP-III.16
Preparations
Compound 1. Toluene (10 mL) was condensed onto a
mixture of Y[N(SiHMe2)2]2[THF]2 (0.964 g, 1.53 mmol) and
HON(CH2C6H5)2 (0.326 g, 1.53 mmol) at -196 ◦C. Gradual
warming of the reaction mixture to room temperature resulted
in a clear solution. It was stirred overnight and the solvent was
removed under vacuum. The product was washed several times
with n-pentane to obtain a white powder. Yield: 0.752 g (87%).
Crystal data for 2a. C48H48N2O2Y2, Mr = 862.70, triclinic,
¯
˚
space group P1, a = 8.455(2), b = 10.888(2), c = 11.546(2) A,
◦
3
˚
a = 84.601(3), b = 76.727(3), g = 71.717(3) , V = 982.0(3) A ,
T = 153(2) K, Z = 1, 11324 scattering intensities collected and
5660 independent, Rint = 0.027, R1 [I > 2s(I)] = 0.035, wR2 [I >
2s(I)] = 0.074, R1 [all data] = 0.048, wR2 [all data] = 0.078.
1H NMR (toluene-d8; 400 MHz): d 0.29 (d, JHH = 2.8 Hz, 6H,
3
2
CH3), 1.46 (br, 2H, THF), 3.71 (br, 2H, THF), 4.54 (d, JHH
=
Crystal data for 2b. C48H48N2O2Sm2, Mr = 985.58, mon-
oclinic, space group C2/c, a = 42.893(9), b = 8.993(3), c =
2
14 Hz, 2H, CH2), 4.68 (d, JHH = 14 Hz, 2H, CH2), 5.23 (m,
3JHH = 2.8 Hz, 2H, SiH), 7.09 (t, J = 7.4 Hz, 2H, p-Ph,), 7.21 (m,
4H, m-Ph), 7.46 (d, J = 7.4 Hz, 4H, o-Ph). 13C NMR (toluene-d8;
100 MHz): d 3.7 (CH3), 25.5 (THF), 62.5 (CH2), 70 (THF), 128.4
(p-Ph), 128.6 (m-Ph), 131.0 (o-Ph), 134 (Ci). 29Si NMR (toluene-
d8; 79.5 MHz): d -22.0. 89Y NMR (toluene-d8; 19.6 MHz): d 314.
Elemental analysis (%) for C26H50NO2SiY: calculated C 49.52, H
9.52, N 2.66, found C 48.93, H 9.16, N 2.58.
◦
3
˚
˚
25.253(5) A, b = 123.7(1) , V = 8102(3) A , T = 153(2) K, Z =
8, 45837 scattering intensities collected and 11847 independent,
Rint = 0.052, R1 [I > 2s(I)] = 0.037, wR2 [I > 2s(I)] = 0.075, R1
[all data] = 0.051, wR2 [all data] = 0.079.
Crystal data for 3. C37H53N4O4Y3, Mr = 900.56, orthorhom-
bic, space group P212121, a = 14.506(2), b = 15.930(2), c =
3
˚
˚
16.866(2) A, V = 3897.3(10) A , T = 153(2) K, Z = 4, 45322
Compounds 2a and 2b. THF (20 mL) was condensed onto a
mixture of MCp3 (1.00 mmol) and HON(CH2C6H5)2 (0.213 g,
scattering intensities collected and 11396 independent, Rint
=
14
0.070, R1 [I > 2s(I)] = 0.041, wR2 [I > 2s(I)] = 0.062, R1 [all
1.00 mmol) at -196 ◦C. The reaction mixture was gradually
warmed to room temperature to obtain a clear solution. It was
further stirred for 18 h. The solvent was removed under vacuum
and the product was washed with n-pentane. It was crystallised
by layering n-pentane onto a concentrated THF solution. Data
for 2a: Yield: 0.41 g (95%). 1H NMR (THF-d8; 400 MHz): d 4.40
(4H, CH2), 6.27 (10H, C5H5), 7.14 (4H, o-Ph), 7.32 (4H, p-Ph),
7.36 (2H, m-Ph). 13C NMR (THF-d8; 100 MHz): d 63.7 (CH2),
111.3 (C5H5), 128.5 (p-Ph), 128.8 (m-Ph), 130.4 (o-Ph), 137.5 (Ci).
Elemental analysis (%) for C48H48N2O2Y2: calculated C 66.89, H
5.57, N 3.25, found C 66.10, H 5.64, N 3.18. Data for 2b: Yield:
data] = 0.066, wR2 [all data] = 0.068.
Acknowledgements
We are grateful to the NRW International Graduate School of
Chemistry for support and a stipend for A. V. and to Deutsche
Forschungsgemeinschaft (SFB 424, project A16) for financial
support.
Notes and references
1
0.46 g (93%). H NMR (THF-d8; 400 MHz): d -0.53 (2H, CH2,
1 (a) A. P. Dove, X. Xie and R. M. Waymouth, Chem. Commun., 2005,
2152; (b) R. Wang, X. Zhang, S. Chen, X. Yu, C. Wang, D. B. Beach, Y.
Wu and Z. Xue, J. Am. Chem. Soc., 2005, 127, 5204; (c) N. W. Mitzel, S.
Parsons, A. J. Blake and D. W. H. Rankin, J. Chem. Soc., Dalton Trans.,
1996, 2098; (d) K. Wieghardt, I. Tolksdorf, J. Weiss and W. Swiridoff,
Z. Anorg. Allg. Chem., 1982, 490, 182.
2JHH = 8.5 Hz), 1.98 (2H, CH2, 2JHH = 8.5 Hz), 3.05 (4H, o-Ph),
6.58 (4H, m-Ph), 6.78 (2H, p-Ph), 9.77 (10H, C5H5). 13C NMR
(THF-d8; 100 MHz): d 62.8 (CH2), 106.0 (C5H5), 127.6 (m-Ph),
127.8 (p-Ph), 128.7 (o-Ph), 130.9 (Ci). Elemental analysis (%) for
C48H48N2O2Sm2: calculated C 58.54, H 4.87, N 2.84, found C
58.14, H 4.91, N 2.75.
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¨
Compound 3. THF (20 mL) was condensed onto a mixture
of YCp3 (0.852 g, 3.00 mmol) and HON(Me)CH2CH2(Me)NOH
(0.240 g, 2.00 mmol) at -196 ◦C. The reaction mixture was gradu-
ally warmed to room temperature to obtain a clear solution. It was
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