Samarium(III) compounds supported by the hydrotris(3,5-dimethyl-pyrazolyl)borate ligand: Synthetic utility of the putative, reduction prone Sm(III)-hydrocarbyls, ' (TpMe2)2SmR '

Article abstract of DOI:10.1016/S0022-328X(01)00855-5

Addition of a stoichiometric amount of KR (R=CH₂C₆H₄-o-NMe₂, C₆H₄-o-CH₂NMe₂, CH₂C₆H₅) to a solution of Sm(Tp^Me2)₂Cl in toluene or THF led to the immediate formation of the insoluble, purple Sm(Tp^Me2)₂ compound. However, when these reactions are carried out in the presence of protic substrates such as HOPh, HCp, HCCPh, HOC₆H₂-2,4,6-^tBu₃, HNPh₂ and 3,5-Me₂pzH, the corresponding Sm(Tp^Me2)₂(Y) compounds (Y=OPh (1), CCPh (2), Cp (3), OC₆H₂-2,4,6-^tBu₃ (4), NPh₂ (5), 3,5-Me₂pz (6)) readily form and in good yields. The structures of 4-6 have been established by X-ray crystallography.

Full text of DOI:10.1016/S0022-328X(01)00855-5

Journal of Organometallic Chemistry 632 (2001) 119–125
www.elsevier.com/locate/jorganchem
Samarium(III) compounds supported by the
hydrotris(3,5-dimethyl-pyrazolyl)borate ligand: synthetic utility of
Me
2
the putative, reduction prone Sm(III)-hydrocarbyls, ‘(Tp )2SmR’
a
a
b
a
.
Irene Lopes , Bernardo Monteiro , Guanyang Lin , Angela Domingos ,
Noe´mia Marques a,*, Josef Takats b
a Departamento de Qu´ımica, ITN, Estrada Nacional 10, P-2686 Saca6e´m Codex, Portugal
b Department of Chemistry, Uni6ersity of Alberta, Edmonton, Alta, Canada T6G 2G2
Received 21 February 2001; accepted 18 April 2001
Dedicated with affection to Professor Alberto Roma˜o Dias on the occasion of his 60th birthday
Abstract
Addition of a stoichiometric amount of KR (R=CH2C6H4-o-NMe2, C6H4-o-CH2NMe2, CH2C6H5) to a solution of
Sm(TpMe2)2Cl in toluene or THF led to the immediate formation of the insoluble, purple Sm(TpMe2)2 compound. However, when
these reactions are carried out in the presence of protic substrates such as HOPh, HCp, HCCPh, HOC6H2-2,4,6-tBu3, HNPh2 and
3,5-Me2pzH, the corresponding Sm(TpMe2)2(Y) compounds (Y=OPh (1), CCPh (2), Cp (3), OC6H2-2,4,6-tBu3 (4), NPh2 (5),
3,5-Me2pz (6)) readily form and in good yields. The structures of 4–6 have been established by X-ray crystallography. © 2001
Elsevier Science B.V. All rights reserved.
Keywords: Samarium complexes; Hydrotris(pyrazolyl)borate ligands; Crystal structures
t
2
1. Introduction
alkoxide derivatives, Sm(TpMe )2OR (R=Ph, Phꢀ4- Bu,
C5H5N) [6,7], were obtained by salt metathesis of
Sm(TpMe )2Cl with NaOR, whereas Sm(Tp )2(CCPh)
Me
2
2
The exploration of the molecular chemistry of
organolanthanides and the spectacular advances made
in this area owe much to the pentamethylcyclopentadi-
enyl ligand [1,2]. However, in the past few years there
has been increased interest in other alternative ligand
systems [3].
and Sm(TpMe )2(Cp) are available by reacting
2
Sm(TpMe
) with Hg(CCPh)2 [8] or TlCp [9], respec-
2
2
tively. The hydrocarbyl derivatives Sm(TpMe )2R are
not known.
2
Here we describe our attempts to obtain
Sm(TpMe )2R compounds by metathesis of Sm(Tp )2-
Me
We have focussed our attention on the study of
hydrotris(pyrazolyl)borate anchored lanthanide com-
pounds, in particular, on the reaction chemistry of
2
2
Cl with the potassium salts of several hydrocarbyls.
Although the compounds proved to be unstable, de-
Sm(TpMe )2 [4]. This compound undergoes facile one-
2
composing spontaneously to the reduced Sm(TpMe
)
2
2
electron transfer reactions leading to Sm(TpMe )2X
2
species, we present circumstantial evidence to show that
they have lifetime long enough to undergo protonolysis
with several protic substrates. This procedure allows the
compounds where X is the mono-anionic form of O2,
PhNNPh, OCPh2 and quinones [5]. However, the com-
pound fails to react with protic substrates such as
alcohols, amines, CpH or terminal alkynes. The known
preparation of the previously reported Sm(TpMe )2-
2
(OPh) (1) [6], Sm(TpMe )2(CCPh) (2) [8], and Sm-
2
(TpMe )2(Cp) (3) [9] compounds, and of the new
2
* Corresponding author. Tel.: +351-21-994-6200; fax: +351-21-
994-1455.
E-mail address: nmarques@itn1.itn.pt (N. Marques).
complexes Sm(TpMe )2Y (Y=OC6H2ꢀ2,4,6- Bu3 (4),
NPh2 (5), 3,5-Me2pz (6)).
t
2
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00855-5

120
I. Lopes et al. / Journal of Organometallic Chemistry 632 (2001) 119–125
toluene
Me
Sm(TpMe )2Cl+HOPh ꢀꢀꢀꢁ Sm(Tp )2(OPh)+KCl
2
2
2. Results and discussion
KR
1
+RH
(2)
2.1. Reaction of Sm(TpMe )2 with KR reagents:
2
reduction to Sm(TpMe
)
2
The C6H5CH2NMe2 by-product could be identified by
recording the H-NMR spectrum of the obtained solid
2
1
prior to washing with n-hexane.
Addition of one equivalent of KR (R=CH2C6H4-o-
NMe2, C6H4-o-CH2NMe2, CH2C6H5) to a solution of
The same procedure was used for the synthesis of
known Sm(TpMe )2(CCPh) (2) and Sm(Tp )2(Cp) (3)
Me
2
2
Sm(TpMe )2Cl in toluene or THF led to immediate
2
and for the new compounds Sm(TpMe )2(OC6H2−2,4,6-
2
formation of a purple precipitate and a pale purple
solution. The precipitate is a mixture of the insoluble,
Me
2
Me
2
tBu3) (4), Sm(Tp )2(NPh2) (5), and Sm(Tp )2(3,5-
Me2pz) (6). When the reactions were conducted in THF
excess of the protic substrates had to be used for the
preparation of 2, 3, 5 and 6, otherwise the reactions did
not go to completion and appreciable amounts of
purple, Sm(TpMe )2 compound and KCl. The solution,
2
after simple work-up, revealed the presence of a small
amount of Sm(TpMe )2 and unidentified organic prod-
2
ucts, Eq. (1):
Sm(TpMe )2Cl remained in the reaction mixture. In the
2
KR
Sm(TpMe )2ClꢀꢀꢀꢀꢀꢀꢀꢀꢀꢁSm(Tp
)2(s)+KCl(s)
Me
2
2
case of Sm(TpMe )2(Cp) (3), reduction was also ob-
2
toluene or THF
served in the absence of excess CpH both in toluene
and THF.
+unidentified organic products
(1)
Admittedly, the reactions outlined above could pro-
ceed via initial deprotonation of the protic substrates
HY by KR, resulting in the formation of KY, followed
No reaction was observed when KMe was added to a
toluene solution of Sm(TpMe )2Cl. Stirring the mixture
2
for more than 24 h ultimately led to decomposition.
A plausible explanation for the facile reduction of
by metathesis with Sm(TpMe )2Cl. Indeed Sm(Tp )2Cl
undergoes metathesis with a variety of anionic reagents
[6,7] and we have verified that it reacts with
K(OC6H2ꢀ2,4,6-tBu3), KNPh2 and K(3,5-Me2pz) to
give compounds 4–6, respectively. However, the fol-
lowing observations indicate that the former reactions
involve protonolysis of a transient SmꢀC bond, at least
in parallel with the deprotonation/metathesis pathway.
Me
2
2
Sm(TpMe )2Cl, with concomitant formation of Sm-
2
(TpMe )2 and KCl, is homolytic cleavage of the SmꢀC
2
bond of the putative Sm(TpMe )2R compounds. Al-
2
though early reports on reduction of lanthanide(III)
organometallics by alkali metal hydrocarbyls were re-
stricted to Yb and Eu compounds [10,11], recently
Gambarotta reported homolytic cleavage of a SmꢀC
bond of a Sm(III)–vinyl derivative supported by a
calix-tetrapyrrole ligand [12]. The ease of decomposi-
Thus, although Sm(TpMe )2Cl reacts with KCp or
2
NaCp in toluene to give Sm(TpMe )2(Cp) (3), the reac-
2
tion of ‘Sm(TpMe )2R’ is perhaps not surprising in view
tion in THF leads to substantial amounts of
SmCp3·THF [13]. Formation of the latter is not ob-
2
of the anticipated congested nature of the complexes
2
and the attendant long and weak Sm(III)ꢀR bond.
served when a mixture of Sm(TpMe )2Cl and CpH is
Indeed, during our investigations on Sm(TpMe
)
2
we
treated with KR in THF. In addition we have observed
that whereas deprotonation of HNPh2 by KR in tolu-
ene is slow, formation of 5 when KR is added to
2
observed that the compound reacts preferentially with
flat or narrow, cylindrical ligands which can fit into the
cleft created by the ‘Sm(TpMe
)
2
fragment of the so
Sm(TpMe )2Cl and HNPh2 in the same solvent is rapid.
2
2
obtained Sm(TpMe )2Y compounds.
2
Finally, the yields of compounds 4–6 are substantially
The instability of the putative ‘Sm(TpMe )2R’ com-
pounds led us to explore alternative means to ascertain,
albeit indirectly, their existence. Protonolysis of the
presumed Sm(III)ꢀR bond offered one such possibility.
higher by the ‘KR to mixture of Sm(TpMe )2Cl/HY’
2
2
protocol than by metathesis with preformed KY.
The Sm(TpMe )2(Y) compounds are soluble in aro-
2
matic and ether type solvents, but are poorly soluble in
aliphatic hydrocarbons, except for 4 which is moder-
ately soluble in n-hexane.
2.2. Reaction of Sm(TpMe )2 with KR in the presence
2
of protic reagents: synthesis and characterization of
Compounds 1–3 were identified by comparison of
their 1H-NMR spectra with those reported in the
literature.
Sm(TpMe )2Y compounds
2
The IR spectra of 4–6 showed the typical w(BꢀH)
Slow addition of an equiv of KC6H4CH2NMe2 in
toluene to stoichiometric amounts of Sm(TpMe )2Cl and
stretching vibration at about 2500 cm−1, characteristic
2
of a k3-coordination mode of the TpMe ligands [14].
2
HOPh in the same solvent led, after stirring for 2 h, to
a turbid solution. The KCl precipitate was filtered off
and the solvent removed under reduced pressure. The
remaining white solid was washed with n-hexane to
remove the organic products. Compound 1, Sm-
1
The room temperature H-NMR spectra of 4 and 5
exhibited six TpMe methyls and three 4-H singlets,
2
consistent with C2-symmetric structures for both com-
pounds. In addition the spectra displayed resonances
associated with the aryloxide and diphenylamide pro-
tons with the expected intensities and multiplicities.
(TpMe )2(OPh), was obtained in almost quantitative
2
yield (Eq. (2)):

I. Lopes et al. / Journal of Organometallic Chemistry 632 (2001) 119–125
121
1
Table 1. The solid-state structure consists of well-sepa-
rated monomeric units with no significant intermolecu-
lar contacts. The metal centre is seven-coordinate by
way of two tridentate pyrazolylborates and the arylox-
ide ligand. The coordination geometry is best described
as distorted pentagonal bipyramidal with N(3) and
N(5) occupying the apical sites, the N(3)ꢀSmꢀN(5) an-
gle is 146.1(2)°. Although the solid-state structure has
only C1 symmetry, small angle deformations coupled
with oscillation of the aryloxide ligand between pyra-
zolyl groups N(1) and N(4) are all that is necessary to
result in a time-averaged C2 molecular symmetry as
found in solution.
The room temperature H-NMR spectrum of 6 ex-
hibited three broad resonances in a 3:3:1 ratio assigned
to the TpMe ligands, with the resonance due to the
2
3-Me protons almost collapsed into the baseline. Two
resonances with an intensity ratio 1:6 were assigned to
proton H-4 and methyl protons of the 3,5-dimethyl-
pyrazolide ligand. Cooling the toluene-d8 solution re-
sulted in progressive broadening and shifting of the
proton resonances associated with the pyrazolylborate
ligands. The low temperature limiting spectrum of 6
was obtained at −50°C and is consistent with a C2-
symmetric structure.
The two TpMe ligands are bent back from each other
2
at an angle of 136.6(2)°. This value is lower than the
BꢀSmꢀB angles found in previously reported
3. Solid state structures
Sm(TpMe )2X compounds and is understandable on the
2
3.1. Sm(TpMe )2(OC6H2—2,4,6- Bu3 (4)
t
2
basis of the steric demands of the aryloxide ligand. This
is also reflected in a longer SmꢀO(1) bond length
The aryloxide 4 crystallized from n-hexane in the
space group P21/a with a molecule of solvent in the
lattice. The molecular structure is shown in Fig. 1 and
selected bond lengths and bond angles are given in
,
(2.188(5) A) than the corresponding distance in
Sm(TpMe )2(OPh−4- Bu) (2.159(2) A) [6], but compares
t
2
,
with those in Sm(TpMe )2(OCPh2) and Sm(Tp )2-
Me
2
2
,
(OC13H8) [5c] (2.201(3) and 2.186(4) A, respectively).
The geometrical requirements of the TpMe ligands also
2
result in a longer SmꢀO(1) bond length in comparison
,
with the corresponding distance of 2.13(1) A in the
metallocene derivative (C5Me5)2Sm(OC6Hꢀ2,3,5,6-Me4)
[15].
Accordingly, the average SmꢀN(pz) bond length of
,
,
2.61(12) A (range 2.772–2.468 A) is longer than the
corresponding distance in the seven-coordinate Sm-
(TpMe )2(OPh−4- Bu) [6] (2.572(5) A), being only com-
t
2
,
parable with those in the eight-coordinate Sm(TpMe )2-
2
,
(OC5H4N) [7] (2.60(7) A). The axial SmꢀN(3) (2.488(6)
,
,
A) and SmꢀN(5) (2.468(6) A) bond lengths are shorter
,
than those in the equatorial girdle (average 2.673(7) A).
The boron atoms are tetrahedral and the twisting of
the pyrazolyl groups are not exceptional (range 8–21°),
although a higher distortion of the pyrazolyl rings
closer to the large aryloxide ligand might have been
anticipated.
Fig. 1. ORTEP diagram of [Sm(TpMe )2(OC6H2−2,4,6-tBu3)]·C6H14
using 35% probability ellipsoids.
2
Table 1
,
Selected bond lengths (A) and bond angles (°) for 4·C6H14, 5·C7H8
3.2. Sm(TpMe )2(NPh2) (5)
and 6
2
4·C6H14
5·C7H8
6
The diphenylamide complex 5 crystallized from tolu-
ene in the space group C2/c with a molecule of toluene
in the lattice. The molecular structure of 5 is shown in
Fig. 2.
Bond lengths
Av. (SmꢀN)Tp 2.61(12)
2.56(7)
2.478(7)
2.59(7)
2.486(5)
Range
(SmꢀN)Tp
2.468(6)
-2.772(6)
2.188(5)
-2.627(8)
2.435(11)
-2.687(5)
Selected bond lengths and angles are given in Table
1. The molecule has a crystallographic imposed two-
fold rotation axis, passing through the Sm and N(4)
atoms. The geometry around the Sm centre may be
regarded as pentagonal bipyramidal, with N(2) and
N(2%) occupying the axial sites, the N(2)ꢀSmꢀN(2%) an-
gle is 151.7(4)°. This symmetry is retained in solution as
SmꢀO
SmꢀN
2.386(5),
2.363(5)
Bond angles
BꢀSmꢀB
SmꢀOꢀC
136.6(2)
173.2(5)
152.0(4)
146.0(2)
33.3(2)
N(7)ꢀSmꢀN(8)
1
was inferred from the H-NMR spectrum.

122
I. Lopes et al. / Journal of Organometallic Chemistry 632 (2001) 119–125
3.3. Sm(TpMe )2(3,5-Me2pz) (6)
2
Crystals of the dimethylpyrazolide complex 6 were
obtained by slow sublimation in vacuum at 210°C. The
molecular structure is shown in Fig. 3 and selected
bond lengths and angles are given in Table 1. The Sm
atom is eight-coordinate being bonded to the six nitro-
gen atoms of the two tridentate TpMe ligands and to
2
the two nitrogen atoms of the dimethylpyrazolide lig-
and. The coordination geometry can be described as
dodecahedral. Alternatively, due to the small bite of the
,
dimethylpyrazolide ligand (0.57 A), the mid-point of
the NꢀN bond of the pyrazolide group can be consid-
ered as occupying the seventh coordination site of a
pentagonal bipyramid, with N(3) and N(6) in the axial
positions (N(3)ꢀSmꢀN(6) equals 153.7(2)°) and the
equatorial plane being defined by N(1), N(2), N(5),
N(4) and the mean position between N(7) and N(8).
Fig. 2. ORTEP diagram of [Sm(TpMe2)2(NPh2)]·C7H8 using 35% prob-
ability ellipsoids.
The two TpMe ligands are bent back from each other
2
at an angle of 146.0(2)° being intermediate between 4
,
and 5. The average SmꢀN(pz) bond length is 2.59(7) A
,
(range 2.687–2.486 A), also in between 4 and 5, and in
the range found for the corresponding distance in other
seven-coordinate Sm(TpMe )2X compounds [5c,5d,6].
2
,
,
The SmꢀN(7) (2.386(5) A) and SmꢀN(8) (2.363(5) A)
bond lengths are similar to the corresponding distances
in the eight-coordinate [Yb(Ph2Pz)2(DME)2] (2.424(7)
,
A) [20], after correction for the difference in the ionic
,
,
radii of Yb(II) (1.14 A) and Sm(III) (1.079 A) [21].
In accord with the congested nature of the complex,
the pyrazolyl rings N1N11 and N4N41 (those next to
the pyrazolide ligand) are considerably twisted about
their BꢀN bonds, with BꢀNꢀNꢀSm torsion angles of
51(1) and 31(1)°, respectively.
Fig. 3. ORTEP diagram of and [Sm(TpMe2)2(3,5-Me2pz)] using 30%
probability ellipsoids.
4. Experimental
4.1. General procedures
The two TpMe ligands are bent back from each other
2
All operations were performed using standard
Schlenk line and dry box techniques under an inert
atmosphere of nitrogen. THF, toluene, and n-hexane
were dried by standard methods and degassed prior to
use. Deuterated solvents, benzene-d6 and toluene-d8,
at an angle of 152.0(4)°. The average SmꢀN(pz) dis-
,
,
tance of 2.56(7) A (range 2.627–2.478 A) is shorter
than that of 4 but compares with those in other seven-
coordinate Sm(TpMe )2X compounds [5c,5d,6]. The
2
were dried over Na and distilled. Sm(TpMe )2 [4] and
2
,
SmꢀN(4) distance (2.435(11) A) is longer than the
Sm(TpMe )2Cl [22] were synthesized by reported meth-
2
corresponding distance in the eight-coordinate Sm-
ods. LiCH2C6H4NMe2 [23], LiC6H4CH2NMe2 [23] and
LiCH2C6H5 [24] were prepared as previously reported
and converted into their potassium salts as described
before [25]. The protic reagents, HOPh, HOC6H2ꢀ2,4,6-
tBu3, HNPh2 and 3,5-Me2pzH were sublimed prior to
use and the corresponding potassium salts were ob-
tained by reacting a stoichiometric amount of KH with
(TpMe )2(h -N2Ph2) [4] (2.386(8) and 2.418(8) A) and in
2
2
,
amido derivatives of the metallocenes Sm(C5Me5)2[N-
(SiMe3)2] [16] (2.301(3) A), Sm(C5Me5)2(NHPh)(THF)
,
2
,
[17] (2.331(3) A), Sm(C5Me5)2(h -PhNHNPh)(THF)
5
5
,
[17] (2.330(5) A), and [Na(THF)2(m-h :h -MeC5H4)2-
,
Sm(NPh2)2]n [18] (2.376(3) A) but much shorter than
1
the Sm(III)ꢀN dative bonds in Sm(C5Me5)2(N-MeIm)2
(2.618(10) and 2.673(11) A) [19] and in Sm(C5Me5)2(h -
PhNHNPh)(THF) (2.610(5) A) [17].
the appropriate reagent in THF. H-NMR spectra were
2
,
recorded on Varian VXR 300 spectrometer and refer-
enced internally using the residual solvent resonances
,

I. Lopes et al. / Journal of Organometallic Chemistry 632 (2001) 119–125
123
relative to Me4Si. IR spectra were recorded on a
Perkin–Elmer 2000 FT-IR spectrometer. Carbon, hy-
drogen and nitrogen analyses were performed in-house
using a Perkin–Elmer automatic analyser.
zene-d6, 21°C, l ppm): 8.66 (2H, s, Hm); 6.63 (2H, s,
4-H); 5.33 (2H, s, 4-H); 3.84 (2H, s, 4-H); 3.16 (6H, s,
CH3); 3.14 (6H, s, CH3); 2.87 (6H, s, CH3); 2.83 (6H, s,
CH3); 2.45 (18H, s, C(CH3)3); 1.96 (9H, s, C(CH3)3);
0.35 (6H, s, CH3); −8.70 (6H, s, CH3).
4.2. Synthetic procedures
(b): Slow addition of a solution of KOC6H2-2,4,6-
Me
2
tBu3(106 mg, 0.35 mmol) in THF to Sm(Tp )2Cl (275
mg, 0.35 mmol) in the same solvent led to the forma-
tion of a pale-yellow solution from which 4 was isolated
as described in (a) in moderate yield (35%, 0.12 mmol).
Anal. Found: C, 56.02; H, 7.52; N, 16.08. Calc. for
C48H73N12B2SmO: C, 57.30; H, 7.31; N, 16.71%.
4.2.1. Sm(TpMe )2(OPh) (1)
2
To a solution of Sm(TpMe )2Cl (110 mg, 0.14 mmol)
2
and HOPh (14 mg, 0.14 mmol) in toluene was slowly
added 24 mg (0.14 mmol) of KC6H4CH2NMe2 in the
same solvent. After stirring for 2 h the precipitate of
KCl was filtered off and the solvent was removed under
vacuum. The white solid was washed with n-hexane
and vacuum dried.
4.2.5. Sm(TpMe )2(NPh2) (5)
2
(a): To a solution of Sm(TpMe )2Cl (108 mg, 0.14
2
1H-NMR (benzene-d6, 25°C, l ppm): 11.20 (2H, d,
Ho); 8.32 (2H, t, Hm); 7.81 (1H, t, Hp); 5.39 (6H, s,
4-H); 3.09 (18H, s, CH3(5)); −1.74 (18H, s, CH3(3)).
mmol) and HNPh2 (23 mg, 0.14 mmol) in toluene was
slowly added 24 mg (0.14 mmol) of KC6H4CH2NMe2
in the same solvent. There is immediate formation of an
orange-reddish solution. After stirring overnight, the
precipitate of KCl was separated and the solvent was
removed under vacuum. The orange solid was washed
with n-hexane and vacuum dried. Yield: 80% (102 mg,
0.11 mmol). Anal. Found: C, 56.73; H, 6.01; N, 19.46.
Calc. for C42H54N13B2Sm: C, 55.26; H, 5.96; N, 19.94%.
4.2.2. Sm(TpMe )2(CCPh) (2)
2
The compound was prepared as described for 1 by
using 105 mg (0.13 mmol) of Sm(TpMe )2Cl, excess of
2
HCCPh (30 ml, 0.27 mmol) and 24 mg (0.13 mmol) of
KC6H4CH2NMe2.
1H NMR (benzene-d6, 25°C, l ppm): 9.03 (2H, d,
Ho); 7.65 (2H, t, Hm); 7.35 (1H, m, Hp); 5.45 (6H, s,
4-H); 2.93 (18H, s, CH3(5)); −1.10 (18H, br, CH3(3)).
IR (Nujol, cm−1): 2540 (BꢀH). H-NMR (benzene-d6,
1
25°C, l ppm): 6.98 (2H, t, Hp); 6.81 (4H, t, Hm); 6.68
(2H, s, 4-H); 5.83 (4H, d, Ho); 5.33 (2H, s, 4-H); 3.87
(2H, s, 4-H); 3.66 (6H, s, CH3); 2.97 (6H, s, CH3); 2.24
(6H, s, CH3); 1.74 (6H, s, CH3); 1.33 (6H, s, CH3);
−0.59 (6H, s, CH3).
4.2.3. Sm(TpMe )2(Cp) (3)
2
The preparation was carried out as described for 1 by
adding a solution of KCH2C6H5 (15.2 mg, 0.12 mmol)
(b): Solid KNPh2 (53mg, 0.26mmol) was added to a
in THF to a solution of Sm(TpMe )2Cl (91 mg, 0.13
solution of Sm(TpMe )2Cl (200 mg, 0.26 mmol) in tolu-
2
2
mmol) in the same solvent, in the presence of excess of
CpH (20 ml, 0.24 mmol).
ene, at room temperature (r.t.). There was immediate
formation of a white precipitate and an orange-reddish
solution. After stirring for 2 h, the precipitate of KCl
was removed and the solution was evaporated to dry-
ness. Crystallization of the residue from a concentrated
1H NMR (benzene-d6, 20°C, l ppm): 9.85 (5H, s,
C5H5); 6.52 (1H, s, 4-H); 6.10 (1H, s, 4-H); 5.33 (2H, s,
4-H); 4.80 (3H, s, CH3); 4.73 (2H, s, 4-H); 2.65 (6H, s,
CH3); 2.48 (3H, s, CH3); 2.33 (3H, s, CH3); 2.21 (6H, s,
CH3); 1.41 (3H, s, CH3); −0.44 (6H, s, CH3); −2.20
(6H, s, CH3).
toluene solution yielded the orange–red Sm(TpMe )2-
2
(NPh2) compound in 65% yield (150 mg, 0.16 mmol).
Anal. Found: C, 54.89; H, 6.08; N, 18.92. Calc. for
C42H54N13B2Sm: C, 55.26; H, 5.96; N, 19.94%.
4.2.4. Sm(TpMe )2(OC6H2–2,4,6- Bu3) (4)
t
2
(a): To a solution of Sm(TpMe )2Cl (202 mg, 0.26
4.2.6. Sm(TpMe )2(3,5-Me2pz) (6)
2
2
mmol) and HOC6H2ꢀ2,4,6-tBu3 (68 mg, 0.26 mmol) in
THF was slowly added 131 mg (0.26 mmol) of
KCH2Ph in the same solvent. There is immediate for-
mation of a yellow solution. After stirring overnight the
KCl precipitate was filtered off and the solvent re-
moved under vacuum. The resulting yellow residue was
extracted with n-hexane and the volume of the extract
reduced under vacuum. Yellow crystals of
(a): To a solution of Sm(TpMe )2Cl (100 mg, 0.13
2
mmol) and 3,5-Me2pzH (12 mg, 0.13 mmol) in toluene
was slowly added 22 mg (0.13 mmol) of
KC6H4CH2NMe2 in the same solvent. After stirring for
2 h, the precipitate was separated and the solvent was
removed under reduced pressure. The resultant white
residue was washed with hexane. Yield: 90% (100 mg,
0.12 mmol). Anal. Found: C, 49.62; H, 5.91; N, 20.94.
Calc. for C35H51N14B2Sm: C, 50.05; H, 6.12; N, 23.35%.
IR (Nujol, cm-1): 2540 (sh), 2500 (BꢀH). 1H-NMR
(toluene-d8, 27°C, l ppm): 7.89 (1H, s, 4-H(pz)); 5.37
(6H, br, 4-H); 4.04 (6H, s, CH3(pz)); 2.71 (18H, s,
Sm(TpMe )2(OC6H2−2,4,6- Bu3) were obtained from
this solution. Yield: 60% (150 mg, 0.15 mmol). Anal.
Found: C, 57.32; H, 7.41; N, 16.30. Calc. for
C48H73N12B2SmO: C, 57.30; H, 7.31; N, 16.71%. IR
t
2
1
1
(Nujol, cm−1): 2510 (sh), 2550 (BꢀH). H-NMR (ben-
CH3(5)); −1.20 (18H, br, CH3(3)). H-NMR (toluene-

124
I. Lopes et al. / Journal of Organometallic Chemistry 632 (2001) 119–125
d8, −50°C, l ppm): 8.74 (1H, s, 4-H(pz)); 6.56 (2H, s,
4-H); 5.37 (2H, s, 4-H); 4.96 (2H, s, 4-H); 4.24 (6H, s,
CH3(pz)); 3.95 (6H, s, CH3), 3.20 (6H, s, CH3), 2.89
(6H, s, CH3), 2.83 (6H, s, CH3), −0.72 (6H, s, CH3),
−8.37 (6H, s, CH3).
solved by Patterson methods [27] and developed by
alternating cycles of full-matrix least-squares refinement
on F2 and difference Fourier techniques, using SHELXL
-
93 [28]. For compound 4 a disordered hexane molecule
and for 5 a severely disordered toluene solvent molecule
near a centre of symmetry were localized in the asym-
metric unit. All the non-hydrogen atoms were refined
with anisotropic thermal motion parameters, except the
carbon atoms of the solvent in 4. The contributions of
the hydrogen atoms were included at calculated posi-
tions (except those of the solvent molecules). Atomic
scattering factors and anomalous dispersion terms were
taken from Ref. [28]. The illustrations were made with
ORTEPII [29] and all calculations were performed on a
Dec-alpha 3000 computer.
(b): A solution of K(3,5-Me2Pz) (51 mg, 0.38 mmol)
in THF was added to a solution of Sm(TpMe )2Cl (296
2
mg, 0.38 mmol) in the same solvent. After stirring
overnight the KCl was separated from the supernatant
solution. Removal of the solvent under vacuum fol-
lowed by extraction with CH2Cl2 gave the white com-
pound, Sm(TpMe )2(3,5-Me2pz) (6). Yield 47% (150 mg,
2
0.18 mmol). Anal. Found: C, 48.28; H, 6.23; N, 21.05.
Calc. for C35H51N14B2Sm: C, 50.05; H, 6.12; N, 23.35%.
4.3. X-ray crystallographic analysis
Pale yellow crystals of 4 were grown from a concen-
trated solution of n-hexane. Crystals of 5 (orange-red-
dish) were grown from a concentrated solution of
toluene. Vacuum sublimation at 210°C permitted the
isolation of 6 as transparent plates. The crystals were
mounted in thin-walled glass capillaries in a nitrogen-
filled glove-box. Data were collected at r.t. on an
Enraf–Nonius CAD4-diffractometer, with graphite-
monochromated Mo–Ka radiation, using the ꢀ–2q
scan technique. The data were corrected [26] for
Lorentz and polarization effects, for linear decay and
empirically for absorption by c scans. Table 2 summa-
rizes the crystallographic data. The structures were
5. Conclusions
Attempts to isolate Sm(TpMe )2R type compounds
have so far proven unsuccessful. The putative
2
Sm(III)ꢀR bond is unstable and undergoes spontaneous
reduction to Sm(TpMe )2 and uncharacterized organic
2
by-products. Neverthless, the protocol of treating mix-
tures of Sm(TpMe )2Cl/HY with KR is synthetically
2
useful and provides Sm(TpMe )2Y compounds in good
2
yields. Further studies, aimed at isolating and/or
providing more conclusive evidences for the existence of
Sm(TpMe )2R are underway.
2
Table 2
Crystal data and structure refinement parameters for complexes 4·C6H14, 5·C7H8 and 6
4·C6H14
5·C7H8
6
Empirical formula
Formula weight
Crystal system
C48H73B2N12OSm·C6H14
1092.33
Monoclinic
P21/a
C42H54B2N13Sm·C7H8
1005.09
Monoclinic
C2/c
C35H51B2N14Sm
839.87
Monoclinic
P21/c
Space group
Unit cell dimensions
,
a (A)
18.697(3)
14.638(2)
21.496(2)
96.986(11)
5839.5(13)
4
16.668(4)
16.996(3)
17.610(3)
98.61(2)
4933(2)
4
10.646(1)
22.397(1)
17.167(1)
95.884(7)
4071.7(5)
4
,
b (A)
,
c (A)
i (°)
V (A )
3
,
Z
Dcalc (g cm−3
)
1.242
1.052
1.353
1.238
1.370
1.486
v (Mo–Ka) (mm−1
)
Theta range for data collection (°)
Reflections collected
1.5–24.0
9424
1.5–25.0
4470
1.5–24.0
5584
Observed [I\2|(I)]
5779
2850
4101
Independent reflections (Rint
)
9153 (0.0499)
601
0.0610
0.1142
1.060
4313 (0.0451)
308
0.0763
0.1418
1.072
5277 (0.0515)
469
0.0395
0.0738
1.090
Parameters
a
R1
b
wR2
Goodness-of-fit on F2
a R1=ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀꢁFoꢁ.
b wR2=[ꢀ(w(Fo2−Fc2)2)/ꢀ(w(Fo2)2)]1/2; w=1/[|2(F2o)+(aP)2+bP], where P=(Fo2+2F2c)/3.

I. Lopes et al. / Journal of Organometallic Chemistry 632 (2001) 119–125
125
(c) I. Lopes, G.Y. Lin, A. Domingos, R. McDonald, N. Mar-
ques, J. Takats, in preparation;
6. Supplementary material
(d) A.C. Hiller, G.Y. Lin, S.-Y. Liu, I. Lopes, M.R.J. Elsegood,
A. Domingos, R. McDonald, A. Sella, N. Marques J. Takats, in
preparation.
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC nos. 158315, 158316 and 158317
for compounds 4–6, respectively. Copies of this infor-
mation may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
[6] A.C. Hiller, S.-Y. Liu, A. Sella, M.R.J. Elsegood, Inorg. Chem.
39 (2000) 2635.
[7] I. Lopes, A.C. Hiller, S.-Y. Liu, A. Domingos, J. Ascenso, A.
Sella, A. Galva˜o, N. Marques, Inorg. Chem. 40 (2001) 1116.
[8] G.Y. Lin, R. McDonald, J. Takats, Organometallics 19 (2000)
1814.
[9] I. Lopes, G.Y. Lin, A. Domingos, R. McDonald, N. Marques, J.
Takats, J. Am. Chem. Soc. 117 (1999) 7828.
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Acknowledgements
Financial support from PRAXIS XXI (2/2.1/QUI/
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