Scandium SALEN complexes bearing chloro, aryloxo, and hydroxo ligands

Article abstract of DOI:10.1021/ic802082b

Heteroleptic amide complexes (SALEN)Sc[N(SiHMe₂)₂] (SALEN = Salen/^Bu/Bu, Salcyc^/Bu/Bu, or Salpren ^/Bu/Bu if not stated differently) were examined as synthesis precursors according to silylamine elimin

Full text of DOI:10.1021/ic802082b

Inorg. Chem. 2009, 48, 2561-2570
Scandium SALEN Complexes Bearing Chloro, Aryloxo, and Hydroxo
Ligands
Christian Meermann,† Karl W. To¨rnroos,† and Reiner Anwander*,†,‡
Department of Chemistry, UniVersity of Bergen, Alle´gaten 41, 5007 Bergen, Norway, and Institut
fu¨r Anorganische Chemie, UniVersita¨t Tu¨bingen, Auf der Morgenstelle 18,
72076 Tu¨bingen, Germany
Received October 31, 2008
Heteroleptic amide complexes (SALEN)Sc[N(SiHMe2)2] (SALEN ) SalentBu,tBu, SalcyctBu,tBu, or SalprentBu,tBu if not
stated differently) were examined as synthesis precursors according to silylamine elimination reactions. Treatment
of (SALEN)Sc[N(SiHMe2)2] with H2O or phenols (HOArR,R; R ) tBu, iPr) afforded complexes [(SALEN)Sc(µ-OH)]2
and (SALEN)Sc(OArR,R), while chloro exchange products were formed from the respective reactions with NH4Cl or
AlMe2Cl. Such complexes [(SALEN)Sc(µ-Cl)]2 and (SALEN)ScCl(thf) were also obtained by utilizing alternative
synthesis protocols, allowing for controlled donor absence and presence. Heteroleptic amide precursors [Sc(NiPr2)2(µ-
Cl)(thf)]2 and [Sc[N(SiHMe2)2]2(µ-Cl)(thf)]2 readily undergo amine elimination reactions with H2SALEN derivatives to
form the corresponding chloride complexes. Spectroscopic and X-ray structural data of the heteroleptic scandium
complexes revealed an exclusive intramolecular tetradentate coordination mode of the SALEN ligands independent
of the SALEN ligand bite angle and the nature of the “second” ligand (chloro, amido, aryloxo, hydroxo). The
coordination of the SALEN ligands is rationalized on the basis of (a) the displacement d of the metal center from
the [N2O2] least-squares plane, (b) the dihedral angle R between the phenyl rings of the salicylidene moieties, and
(c) the angle ꢀ ) Ct-Ln-Ct (Ct ) centroid of the phenyl rings) in the case of strongly twisted ligands.
Introduction
yield complexes [(SALEN)Ln(Cl)]n.5-8 Deprotonation of H2-
SALEN is conveniently achieved by applying KN(SiMe3)2,
sodium or potassium hydride, or lithium bases such as MeLi
or BuLi. The remaining chloro ligand in [(SALEN)-
Ln(Cl)]n can then easily be exchanged in a subsequent salt
metathesis by various actor ligands.9 Alcoholysis, that is,
treatment of Ln(OR)3 (R ) alkyl, aryl) with H2SALEN to
give (SALEN)Ln(OR), is an alternative synthesis route,
which has also been exploited in d-transition metal SALEN
chemistry.9-12 Similarly, rare-earth metal amide complexes
engage in protonolysis reactions displaying versatile synthesis
precursors for complexes with noncyclopentadienyl ancillary
ligands. The routinely used amide precursor compound
Ln[N(SiMe3)2]3, however, does not afford monomeric com-
Complexes of the general formula (SALEN)Ln(III)-X,
where Ln is a rare-earth metal, that is, Sc, Y, and the
lanthanides, and SALEN is a N,N′-bis(salicylidene)ethyl-
enediamine, are successfully employed in homogeneous
catalysis, particularly for enantioselective organic transfor-
mations.1-3 These heteroleptic rare-earth metal SALEN
complexes can be synthesized by different approaches
featuring alk(aryl)oxo, hydroxo, and amido groups as actor
ligands X.4 Most common are, indeed, salt metathesis
synthesis protocols utilizing LnCl3(thf)n and alkali metal salts
of the corresponding SALEN ligand as starting materials to
* To whom correspondence should be addressed. E-mail: reiner.anwander@
uni-tuebingen.de.
(5) Evans, W. J.; Fujimoto, C. H.; Ziller, J. W. Chem. Commun. 1999,
†
University of Bergen.
Universita¨t Tu¨bingen.
311–312.
‡
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10.1021/ic802082b CCC: $40.75  2009 American Chemical Society
Inorganic Chemistry, Vol. 48, No. 6, 2009 2561
Published on Web 02/11/2009

Meermann et al.
Figure 1. Coordination features of SALEN ligands.
Chart 1. Coordination Modes in Structurally Characterized Ln(III)/(IV)-SALEN Complexes (hfac ) hexafluoroacetylacetonate)
plexes (SALEN)Ln(NR2) due to steric constraints imparted
by the bulky bis(trimethylsilyl)amido ligands.13 This problem
can be dealt with by utilization of Ln[N(SiHMe2)2]3(thf)n
according to the extended silylamide route.13,14 Contrary to
aluminum SALEN chemistry, where AlR3 and R2AlCl
feature repeatedly exploited starting materials, rare-earth
metal alkyls have, to our knowledge, not yet been used as
precursors for SALEN complexes.15,16 It is noteworthy that
Piers et al. succeeded in synthesizing related scandium and
yttrium salicylaldiminato complexes from Ln(CH2SiMe2-
Ph)3(thf)2.17
ligand backbone.18 Preferably, this dianionic tetradentate
[ONNO] ligand chelates transition metals in an equatorial
fashion, comparable to porphyrinato ligands. For the
structurally characterized Ln(III)-SALEN complexes, the
ancillary ligand coordination environment can be char-
acterized by (i) the displacement d of the metal center
from the [N2O2] least-squares plane, (ii) the dihedral angle
R between the phenyl rings of the salicylidene moieties,
and (iii) the angle ꢀ (Ct-Ln-Ct) (Ct ) centroid of the
phenyl rings) in the case of strongly twisted ligands
(Figure 1).
The large rare-earth metal(III) centers uniquely dem-
onstrate the coordination flexibility of the dianionic
SALEN ligand, which is strongly affected by the diimino
In rare-earth metal chemistry, the SALEN ligand adopts
a variety of different coordination geometries (Chart 1). Cis
coordination mode I has been found repeatedly, for example,
in (SALEN)Y[N(SiHMe2)2](thf)1,13 or (Salen)Y(OArtBu,tBu)-
(thf),9 and seems to be favored over the octahedral trans
arrangement featured by cationic complex [(Salen)Sc-
(thf)2][BPh4]19 (III, Chart 1, cis and trans referring to the
position of donor and actor ligands). Cationic complexes of
the larger rare-earth metal centers [(Salpren)Ln(thf)3][BPh4]
(Ln ) Y, La) are seven-coordinate, and coordination of an
additional donor molecule implies geometry V.19 A sim-
ilar coordination geometry was detected in (Salen)Y-
(OSiPh3)(thf)(CH3CN).14
(9) Evans, W. J.; Fujimoto, C. H.; Ziller, J. W. Polyhedron 2002, 21,
1683–1688.
(10) Ovitt, T. M.; Coates, G. W. J. Am. Chem. Soc. 1999, 121, 4072–
4073.
(11) Fukuzawa, S.; Komuro, Y.; Nakano, N.; Obara, S. Tetrahedron Lett.
2003, 44, 3671–3674.
(12) Mascarenhas, C. M.; Miller, S. P.; White, P. S.; Morken, J. P. Angew.
Chem., Int. Ed. 2001, 40, 601–603.
(13) Runte, O.; Priermeier, T.; Anwander, R. Chem. Commun. 1996, 1385–
1386.
(14) Anwander, R.; Go¨rlitzer, H. W.; Gerstberger, G.; Palm, C.; Runte,
O.; Spiegler, M. J. Chem. Soc., Dalton Trans. 1999, 3611–3615.
(15) Evans, D. A.; Janey, J. M.; Magomedov, N.; Tedrow, J. S. Angew.
Chem., Int. Ed. 2001, 40, 1884–1888.
(16) Atwood, D. A.; Harvey, M. J. Chem. ReV. 2001, 101, 37–52.
(17) Emslie, D. J. H.; Piers, W. E.; MacDonald, R. J. Chem. Soc., Dalton
Trans. 2002, 293–294.
(18) Katsuki, T. Chem. Soc. ReV. 2004, 33, 437–444.
(19) Liu, Q.; Meermann, C.; Go¨rlitzer, H. W.; Herdtweck, E.; Sirsch, P.;
To¨rnroos, K. W.; Anwander, R. Dalton Trans. 2008, 6170-6178.
2562 Inorganic Chemistry, Vol. 48, No. 6, 2009

Scandium SALEN Complexes
Scheme 1. Synthesis of Sc-SALEN Bis(dimethylsilyl)amide Complexes 1a-c and Homoleptic Sc-Salpren Complex 2
Heteroleptic Sc(III)-SALEN complexes appear sterically
saturated in the absence of donor molecules favoring a
square-pyramidal coordination, as in (Salcyc)Sc[N(SiHMe2)2]
and (Salpren)Sc(NiPr2) (II).20 The same structural motif was
found in (Salen)Y(Cp*).9 For small monoanionic actor
ligands such as Cl- or OH-, the coordination number at the
yttrium metal center is increased to seven by dimerization,
trans and H2Salpren/H2Salcyc a cis configuration (Scheme
1, inset).25,26 It is noteworthy that the highly flexible Salen
ligand backbone or a mismatch of the chelate conformation
and Ln3+ size can impede this silylamine elimination, as
found for the system H2Salen-La[N(SiHMe2)2]3(thf)2.19
H2Salpren, on the other hand, featuring a substituted
propylene link between the rigid cis-oriented salicylidene
moieties, offers an ideal scaffold for the chelating coordina-
tion of Ln(III) centers, as shown for the synthesis of heter-
oleptic complex (Salpren)Sc[N(SiHMe2)2] (1b) (Scheme
1).20,27 However, recrystallization of complex 1b at -35 °C
from hexane caused ligand scrambling and formation of the
homoleptic complex Sc2(Salpren)3 (2) in almost quantitative
yield. The latter compound, 2, can be also prepared by a
protonolysis reaction according to the extended silylamide
route when the proligand and Sc[N(SiHMe2)2]3(thf) are used
in a 3:2 ratio (Scheme 1). The composition of 2 could be
confirmed by elemental analysis and IR spectroscopy. The
IR spectrum revealed Salpren as the only coordinating ligand
with a characteristic NdC stretching vibration at 1612 cm-1
(νCdN H2Salpren ) 1626-1631 cm-1). The 1H NMR
spectrum of 2 was difficult to interpret due to two sets of
magnetically different protons in the ligand backbones. A
salt metathesis approach utilizing ScCl3(thf)3 and in situ
generated K2Salpren in a 2:3 ratio led to product mixtures
which were not further investigated.
5
as found in [(Salen)Y(µ-Cl)(thf)]2 and [(Salcyc)Y(µ-
OH)(acetone)]2 (IV).12 Tetravalent cerium can bind two
SALEN ligands forming neutral complexes (SALENR,R)2Ce
(SALENR,R ) SalentBu,tBu, SalenH,Cl, SalcycH,H, SalcycCl,Cl
;
VI).8,21,22 The same geometry was also found for the anionic
species in [(SalenH,H)2Er]-[NH2C4H10]+ and for (SalenH,H)Eu
(HSalenH,H).23,24
In this article, we report on the versatility of scandium
amide complexes for the synthesis of SALEN derivatives
with additional chloro, aryloxo, and hydroxo ligands.
Results and Discussion
Synthesis of Sc-SALEN Amido Derivatives. The ex-
tended silylamide route gives easy access to heteroleptic
complexes (SALEN)Ln[N(SiHMe2)2](thf)x, as reported pre-
viously for Ln ) Sc (1a-c, x ) 0; Scheme 1), Y, and La (x
) 1), with SALEN ) SalentBu,tBu, SalcyctBu,tBu, and
SalprentBu,tBu 19,20 The conformational mobility of the SALEN
.
ligands is already expressed in the solid-state structures of
their proligands, where ethylene-bridged H2Salen adopts a
The solid-state structure of homoleptic 2 corroborates the
high conformational flexibility of such ligand systems (Figure
2). Salpren not only adopts the common η4(O2N2) tetradentate
coordination but can also act as a bridging ligand in a
(20) Meermann, C.; Sirsch, P.; To¨rnroos, K. W.; Anwander, R. Dalton
Trans. 2006, 1041–1050.
(21) Kubono, K.; Hirayama, N.; Kokusen, H.; Yokoi, K. Anal. Sci. 2001,
17, 193–197.
(22) Szlyk, E.; Wojtczak, A.; Dobrzanska, L.; Barwiolek, M. Polyhedron
2008, 27, 765–776.
(23) Mangani, S.; Takeuchi, A.; Yamada, S.; Orioli, P. Inorg. Chim. Acta
1989, 155, 149–152.
(25) Mucha, F.; Haberecht, J.; Bohme, U.; Roewer, G. Monatsh. Chem.
1999, 130, 117–132.
(26) Darensbourg, D. J.; Mackiewicz, R. M.; Rodgers, J. L.; Fang, C. C.;
Billodeaux, D. R.; Reibenspies, J. H. Inorg. Chem. 2004, 43, 6024–
6034.
(24) Huang, L.; Huang, C.-H.; Xu, G.-X.; Han, Y.-Z.; Li, G.-P. Chin. J.
Struc. Chem. 1990, 9, 100–104.
(27) Artus, G. R. J.; Rauch, M. U.; Herrmann, W. A. Z. Kristallogr., New
Cryst. Struct. 1997, 212, 227–228.
Inorganic Chemistry, Vol. 48, No. 6, 2009 2563

Meermann et al.
(Table 1; 3a, av. Sc-O, 2.0054 Å; av. Sc-N, 2.2956 Å;
3b, Sc-O1, 2.008(2) Å; Sc-O2, 2.009(2) Å; Sc-N1, 2.275
(2) Å; Sc-N2, 2.277(2) Å; 3c, av. Sc-O, 2.001 Å; av.
Sc-N, 2.283 Å).
Because of the same core moiety [Sc(µ-OH)2Sc], com-
plexes 3a-c allow for direct comparison of the intrinsic
SALEN ancillary ligand coordination following the criteria
introduced in Figure 1. The smallest angle ꢀ (Ct-Sc-Ct;
largest bending) was found for the Salpren ligand in 3b
(94.6°), differing markedly from that of the Salcyc ligand
(3c: 125.6° and 128.5°; Table 1). Closest to planarity are
the Salen ligands in compound 3a, with angles of 136.5°
and 137.0°. The only other structurally characterized SALEN
lanthanide hydroxy complex [(Salcyc)Y(OCMe2)(µ-OH)]2
was obtained from Y5O(OiPr)13 and H2Salcyc in dichlo-
romethane and subsequent crystallization by allowing acetone
to diffuse into the reaction mixture.12 The presence of the
hydroxo groups was explained by adventitious moisture. In
the latter complex, the yttrium metal center is seven-
coordinated and shows a geometry closer to 3b than to the
respective Salcyc complex 3c. Clearly, the additional donor
coordination and the larger metal ion size enforce this larger
bending of the Salcyc ligand (ꢀ ) 112°). Partial hydrolysis
of rare-earth metal alkyl complexes (SalantBu,R)Lu(CH2-
Figure 2. Solid-state structure of complex Sc2(Salpren)3 (2). Heavy atoms
are represented by atomic displacement ellipsoids at the 50% level.
Hydrogen atoms and tBu-substitution in the 3- and 5- positions are omitted
for clarity.
µ2-[η2(ON)]2 fashion between two scandium centers. Com-
pound 2 crystallizes in the monoclinic space group C2/c.
The scandium centers are six-coordinated, which is in
contrast to previously investigated monomeric scandium
SALEN complexes showing a square-pyramidal coordination
geometry (coordination number ) 5; II, Chart 1).20
The η4(O2N2) coordinated Salpren ligand is bent about the
scandium metal center with a dihedral angle R of 85.9° and
an angle ꢀ (Ct-Sc-Ct) of 102.7° between the two phenyl
rings (Table 1). This is a larger deviation than in monomeric
(Salpren)Sc(NiPr2) (R ) 124.27(9)°).20 The scandium oxygen
and nitrogen distances (η4(O2N2): Sc-O2, 2.029(3) Å;
Sc-O3, 1.980(3) Å; Sc-N2, 2.251(3) Å; Sc-N3, 2.278(3)
Å. µ2-[η2(ON)]2: Sc-O1, 2.025(2) Å; Sc-N1, 2.301(3) Å)
match those found in (Salpren)Sc(NiPr2) (Sc-O1, 1.994(2)
Å; Sc-O2, 2.016(2) Å; Sc-N1, 2.277(2) Å; Sc-N2,
2.283(3) Å).20
SiMe3)(thf) (SalantBu,R
)
[2-O-3-tBu-5-R-C6H2CH2-
N(CH3)CH2]2, R ) H, tBu) by treatment with water-enriched
N2 gave mixed hydroxy/siloxy complexes (SalantBu,R)Lu(µ-
OSiMe3)(µ-OH)Lu(SalantBu,R).28 X-ray structure analysis of
this Lu-SalantBu,tBu complex revealed an asymmetric dimer
with a geometry comparable to that of 3a.28
The feasibility of bulky ligand exchange reactions of rare-
earth metal-SALEN amide complexes has been proven
previously. Recently, we reported on the synthesis of
(SALEN)Sc(OSiR3) from complex 1 by protonolysis with
the corresponding silanols and secondary ligand exchange
Synthesis of [(SALEN)Sc(OR)] Derivatives (R ) H,
OAr). It has been shown previously that (SALEN)Sc[N(Si-
HMe2)2] (1a-c) can easily be converted into siloxide
complexes, for example, (Salen)Sc(OSitBuPh2), and donor-
stabilized monocationic species [(SALEN)Sc(thf)2][BPh4] by
protonolysis reactions.19,20 As expected for rare-earth metal
amide complexes, compounds 1a-c are moisture-sensitive.
However, hydrolysis comes to a halt at air-stable complexes
[(SALEN)Sc(OH)] (3a-c) with the strongly chelating SALEN
ligands counteracting extensive hydrolysis to Sc(OH)3 and
H2SALEN (Scheme 2).
13,20
of (Salen)Y[N(SiHMe2)2](thf) with HOArtBu,tBu
.
Evans
et al. investigated the accessibility of the latter aryloxide
derivatives (Salen)Y(OArtBu,tBu)(thf) through different syn-
thesis approaches.9 A salt metathesis approach utilizing
[(Salen)Y(µ-Cl)(thf)]2 and LiOArtBu,tBu did not give a pure
product; instead, the reaction of Y(OArtBu,tBu)3 or (Salen)-
Y[N(SiMe3)2](thf) with the corresponding phenol formed the
thf adduct (Salen)Y(OArtBu,tBu)(thf).9 According to a similar
silylamine elimination reaction, 1a and 1c could be trans-
formed quantitatively to (Salen)Sc(OArtBu,tBu) (4a), (Salcyc)-
Sc(OArtBu,tBu) (4b), and (Salcyc)Sc(OAriPr,iPr) (4c), with
HOArtBu,tBu and HOAriPr,iPr (Scheme 2). Additional donor
coordination, as found for the yttrium complex, was not
observed. The reactions were performed in hexane, the
products crystallized from toluene solutions, and their
composition confirmed by NMR and IR spectroscopy.
Moreover, an X-ray crystallographic analysis of compound
4b confirmed its mononuclear structure (Figure 6). The
scandium center is five-coordinated in a square-pyramidal
fashion (geometry II, Chart 1) by the ONNO+O coordinating
atoms of the Salcyc and aryloxo ligands, reminiscent of the
X-ray crystal structure analyses of compounds 3a-c
revealed dimeric complexes of the composition [(SALEN)-
Sc(µ-OH)]2, with six-coordinated scandium metal centers
(Figures 3-5; c.f., similar yttrium complexes are seven-
coordinated and exhibit geometry IV, Chart 1). Complexes
3a and 3c crystallize in the orthorhombic space groups Pba2
and P212121; however, 3b crystallizes in the triclinic space
j
group P1.
For all three compounds, the hydrogen atoms on the
µ-bridging O atoms could be located in the difference Fourier
maps. The Sc-(µ-OH) bond lengths are similar and lie in
the range of 2.0836(9)-2.1166(9) Å. Also, the Sc-O(SALEN)
and Sc-N(SALEN) distances are consistent with each other
(28) Liu, X.; Cui, D. Dalton Trans. 2008, 3747–3752.
2564 Inorganic Chemistry, Vol. 48, No. 6, 2009

Scandium SALEN Complexes
Table 1. Selected Bond Distances (Å) and Bonding Features (deg/Å; according to Figure 1) for Compounds 2, 3a-c, 4b, and 5ba
5b
2b
3a
3bb
3c
4b
molecule 1
molecule 2
SALEN Ligand η4(O2N2)
R [deg]
ꢀ [deg]
85.9
29.1
36.6
136.5
74.1
94.6
53.0
52.2
125.6
35.8
7.75
14.4
102.7
134.0
162.8
161.6
137.0
128.5
d [Å]
n.d.c
n.d.c
n.d.c
n.d.c
0.73
0.20
0.20
Sc-O [Å]
2.029(3)
1.980(3)
1.9943(9)
2.0160(9)
1.9838(9)d
2.0275(9)d
2.315(1)
2.286(1)
2.321(1)d
2.260(1)d
2.008(2)
2.009(2)
1.998(2)
2.007(2)
1.977(2)d
2.022(2)d
2.286(3)
2.297(3)
2.248(3)d
2.301(3)d
1.963(2)
1.993(2)
1.973(5)
1.981(5)
1.970(5)
1.976(5)
Sc-N [Å]
2.251(3)
2.278(3)
2.275(2)
2.277(2)
2.227(2)
2.235(2)
2.237(6)
2.245(6)
2.235(6)
2.219(6)
Actor Ligand E
Sc1-E1 [Å]
Sc1-E2 [Å]
2.1166(9)
2.0836(9)
2.089(2)
2.093(2)
2.088(2)
2.102(2)
1.946(2)
2.438(2)
2.440(2)
a Actor ligand E ) µ-OH (3a-c), OArtBu,tBu (4b), Cl (5b). R ) dihedral angle between the phenyl rings; ꢀ ) angle Ct-Sc-Ct between the phenyl rings;
d ) displacement from the [N2O2] least-squares plane (geometry I, Chart 1). b Intramolecular symmetry. c Not determined. d Second SALEN ligand.
Scheme 2. High-Yield Protonolysis Reactions of (SALEN)Sc[N(SiHMe2)2] (1a-c) with HOArtBu,tBu, HOAriPr,iPr, and H2O
ONNO+N coordination environment in precursor (Salcyc)
Sc[N(SiHMe2)2] (1c).20 The distance of the scandium atom
from the N2O2 least-squares plane (0.73 Å, Table 1) is
comparable to the respective displacement in 1c (molecule
1, 0.68 Å; molecule 2, 0.69 Å). The Sc-O(Salcyc) and
Sc-N(Salcyc) bond distances are almost identical in 4b
(Sc-O1, 1.963(2) Å; Sc-O2, 1.993(2) Å; Sc-N1, 2.227(2)
Å; Sc-N2, 2.235(2) Å) and 1c (molecule 1, Sc1-O1,
1.985(3) Å; Sc1-O2, 1.976(3) Å; Sc1-N1, 2.254(3) Å;
Sc1-N2, 2.227(3) Å; molecule 2, Sc2-O3, 1.981(3) Å;
Sc2-O4, 1.977(3) Å; Sc2-N4, 2.268(3) Å; Sc2-N5,
2.215(3) Å). However, less steric crowding in 4b is indicated
by a larger angle ꢀ (Ct-Sc-Ct) of 134.0° compared to that
for 1c (molecule 1, 127.8°; molecule 2, 127.3°). The
Sc-OArtBu,tBu bond length of 1.946(2) Å is comparable to
the Sc-O(siloxide) distance of 1.901(2) Å in five-coor-
dinated complex (Salen)Sc(OSitBuPh2).20 The longer
Y-OArtBu,tBu distance in (Salen)Y(OArtBu,tBu)(thf) (2.128(2)
Å) follows the trend in ionic radii and the higher coordi-
nation number.9 Attempted further ligand exchange with
LiCH2SiMe3 toward putative (Salen)Sc(CH2SiMe3) was not
successful, and the orange decomposition products were not
further characterized. Furthermore, attempted synthesis of
such alkyl complexes from homoleptic Sc(CH2SiMe3)3(thf)2
was also unsuccessful.
Synthesis of [(SALEN)Sc(Cl)] Derivatives. We have
previously introduced heteroleptic amide/chloride complexes
[Ln(NiPr2)2(µ-Cl)(thf)]2 (Ln ) Sc, Y) as efficient precursors
according to an amine elimination/salt metathesis reaction
sequence.20 According to synthesis protocol A (Scheme 3),
the reaction of [Sc(NiPr2)2(µ-Cl)(thf)]2 with H2Salen or
H2Salcyc gave the dinuclear chloro-bridged derivatives
[(Salen)Sc(µ-Cl)]2 and [(Salcyc)Sc(µ-Cl)]2.20 We also ex-
amined the reaction of [Sc(NiPr2)2(µ-Cl)(thf)]2 with
H2Salpren, producing several nonseparable products (B,
Scheme 3). To further investigate the feasibility of amido/
chloro ligand exchange under mild conditions, (SALEN)-
Sc[N(SiHMe2)2] (1a, 1b) were treated with NH4Cl and stirred
until clear solutions formed (C, E, Scheme 3). While the
only side productssNH3 and HN(SiHMe2)2scould be re-
Inorganic Chemistry, Vol. 48, No. 6, 2009 2565

Meermann et al.
Figure 3. Solid-state structure of complex [(Salen)Sc(µ-OH)]2 (3a). Heavy
atoms are represented by atomic displacement ellipsoids at the 50% level.
Hydrogen atoms, except for H1O and H2O, and cocrystallized toluene are
omitted for clarity.
Figure 5. Solid-state structure of complex [(Salcyc)Sc(µ-OH)]2, 3c. Heavy
atoms are represented by atomic displacement ellipsoids at the 50% level.
Hydrogen atoms, except for H5O and H6O, tBu-substitution in the 3- and
5- positions, and cocrystallized toluene are omitted for clarity.
Figure 6. Solid-state structure of complex (Salcyc)Sc(OArtBu,tBu) (4b).
Heavy atoms are represented by atomic displacement ellipsoids at the 50%
level. Hydrogen atoms are omitted for clarity.
Figure 4. Solid-state structure of complex [(Salpren)Sc(µ-OH)]2, 3b. Heavy
atoms are represented by atomic displacement ellipsoids at the 50% level.
Hydrogen atoms, except for H1OH and H1OH′, and cocrystallized C6D6
are omitted for clarity.
also be obtained according to approaches D and F, by
reacting complexes 1a and 1b with Me2AlCl, which also
forms byproduct {Me2Al[µ-N(SiHMe2)2]}2. Protocol F is less
straightforward due to presence of thf and the formation of
Me2AlCl(thf); however, complete consumption of the [N(Si-
HMe2)2] moieties was indicated by NMR spectroscopy.
Synthesis approach G is certainly the fastest and easiest route
toward 5a,b and was exploited previously by Evans et al.
and Gambarotta et al. for the synthesis of [(Salen)Y(µ-
Cl)(thf)]2 from YCl3 and K2Salen and (Salophen)SmCl(OEt)
(H2Salophen ) N,N′-phenylenebis(3,5-di-tert-butyl-sali-
cylideneimine)) from SmCl3(thf)3 and the corresponding
sodium salt, respectively.5,6 Unlike what was reported for
yttrium, we used the thf adduct ScCl3(thf)3 rather than the
less soluble/reactive ScCl3. Such salt metathesis reactions
potentially involve ate complexation. Deacon et al. reported
on the reaction of anhydrous NdCl3 with Na2(Salpn)(thf)
(H2Salpn ) N,N′-propylenebis(salicylideneimine)) yielding
an insoluble precipitate of unknown composition. The same
reaction with NdCl3 × 2(LiCl) gave complex {[Nd(salpn)-
(thf)Cl][LiCl(thf)]2}2, which was structurally characterized.7
Contrary to [Sc(NiPr2)2(µ-Cl)(thf)]2, the analogous bis-
(dimethylsilyl)amide complexes can only be obtained as
mixtures of [Sc[N(SiHMe2)2]2(µ-Cl)(thf)]2 and Sc[N(Si-
moved under reduced pressure, total consumption of the
silylamido group was indicated by the complete disappear-
ance of the Si-H band in the IR product spectra. If the
reactions were performed in thf compounds, (Salen)ScCl(thf)
(5a) and (Salcyc)ScCl(thf) (5b) could be isolated instead of
[(SALEN)Sc(µ-Cl)]2 (E, Scheme 3).
Metal-coordinated thf was clearly revealed in the 1H NMR
spectrum of 5a (δ ) 1.29 and 3.52 ppm; cf., noncoordinated
thf in C6D6, 1.40 and 3.57 ppm).29 As reported previously,
drying of the chloro exchange products under a vacuum was
sufficient to completely remove any coordinated thf.20
Removal of the coordinated donor solvent does, however,
not markedly affect the magnetic environment of the SALEN
ligand, resulting in almost identical 1H NMR chemical shifts
for the spectator ligands in 5 and [(SALEN)Sc(µ-Cl)]2.
Formation of dimeric six-coordinate molecules after the
removal of thf is plausible given the similar size of chloro
and hydroxo ligands (cf., complexes 3a-c). Complex 5 could
(29) Gottlieb, H. E.; Kotlyar, V.; Nudelman, A. J. Org. Chem. 1997, 62,
7512–7515.
2566 Inorganic Chemistry, Vol. 48, No. 6, 2009

Scandium SALEN Complexes
Scheme 3. Different Synthesis Protocols for Dimeric and Monomeric Sc-SALEN Chloride Complexesa
a Products [(Salen)Sc(µ-Cl)]2 and (Salen)ScCl(thf) (5a) represent likely coordination geometries. Approaches C-H were only carried out for SALEN )
Salen, Salcyc.
0.20 Å from the N2O2 least-squares plane. However, the
salicylidene groups are not coplanar, showing an angle ꢀ
(Ct-Sc-Ct) of 162.8° (molecule 2: 161.6°), which compares
to the aforementioned cationic complex (Sc-N2O2 ) 0.02
Å, ꢀ (Ct-Sc-Ct) ) 169.1°).19 Despite the different ligand
imino backbone, the Sc-N and Sc-O distances in 5b
(molecule 1, Sc1-O1, 1.973(5) Å; Sc1-O2, 1.981(5) Å;
Sc1-N1, 2.237(6) Å; Sc1-N2, 2.245(6) Å; molecule 2,
Sc2-O4, 1.970(5) Å; Sc2-O5, 1.976(5) Å; Sc2-N3,
2.235(6) Å; Sc2-N4, 2.219(6) Å) match those in
[(Salen)Sc(thf)2][BPh4] (Sc1-O1, 1.973(2) Å; Sc1-O2,
1.967(2) Å; Sc1-N1, 2.233(2) Å; Sc1-N2, 2.222(2) Å). It
is noteworthy that the Sc-O(thf) distances (Sc-O3, 2.177(2)
Å; Sc-O4, 2.154(2) Å) in the latter cationic complex are
shorter than in 5b (molecule 1, Sc-O3, 2.287(5) Å; molecule
2, Sc-O6, 2.284(4) Å). The Sc-Cl bond distance of 2.438(2)
Å (molecule 2, 2.440(2) Å) is comparable to the termi-
nal Sc-Cl distance in monomeric complexes such as
Figure 7. Solid-state structure of complex (Salcyc)ScCl(thf) (5b, molecule
one out of two). Heavy atoms are represented by atomic displacement
ellipsoids at the 50% level. Hydrogen atoms and cocrystallized thf are
omitted for clarity.
HMe2)2]3(thf).30 The protonolysis reaction with H2SALEN
will therefore give a mixture of 1 and (SALEN)ScCl, and
we were fortunate to isolate the first monomeric scandium
SALEN chloride complex, 5b, from the reaction products.
Admittedly, separation of 5b from 1c is only possible by
fractional crystallization due to the high solubility of both
complexes in noncoordinating solvents such as hexane.
Compound 5b could be fully characterized by NMR/IR
spectroscopy and elemental analysis and crystallizes in the
monoclinic space group P21 with two independent molecules
in the unit cell (Figure 7). The scandium center in 5b is
octahedrally coordinated by one chloro ligand, one thf, and
the Salcyc ligand (geometry III, Chart 1), reminiscent of
the cationic fragment in [(Salen)Sc(thf)2][BPh4].19 The
scandium center in 5b is well-embedded into the Salcyc
ligand, as revealed by a metal center displacement of
TMS
TMS
Sc(N2 Npy)Cl(thf) (2.4426(7) Å; N2
N
py
) MeC(2-
C5H4N)(CH2NSiMe3)2) but, as expected, is shorter than in
the dimeric precursor compound [Sc[N(SiHMe2)2]2(µ-
Cl)(thf)]2 (av. Sc-Cl, 2.56 Å).30
Conclusions
Heteroleptic scandium SALEN amide complexes (SALEN)-
Sc[N(SiHMe2)2] can be easily converted into hydroxy,
aryloxide, and chloride derivatives. In particular, protonolysis
via treatment of (SALEN)Sc[N(SiHMe2)2] with NH4Cl
proved to be a viable route for the high-yield synthesis of
discrete (SALEN)ScCl(thf)x complexes. The X-ray structural
analyses of hydrolyzed complexes [(SALEN)Sc(µ-OH)]2
revealed a strong bonding of the chelating dianionic [ONNO]
ligands, which has important implications for their use as
(30) Meermann, C.; To¨rnroos, K. W.; Nerdal, W.; Anwander, R. Angew.
Chem., Int. Ed. 2007, 46, 6508–6513.
Inorganic Chemistry, Vol. 48, No. 6, 2009 2567

Meermann et al.
1074w, 841w, 748w, 659w, 540w, 480w. Anal. calcd for
versatile homogeneous Lewis acid catalysts. Moreover,
distinct coordination features of the SALEN ligands are
indicated in the solid state: the intrinsic SALEN bending
increases (decreasing ∠ꢀ) in the order Salen < Salcyc <
Salpren, depending on the nature of the ligand backbone.
The formation of the homoleptic species Sc2(Salpren)3
emphasizes ligand backbone conformational flexibility of the
Salpren ligand, encouraging alternative ancillary ligand
coordination such as intermolecular bridging and multiple
coordination.
C
105H156N6O6Sc2: C, 74.70; H, 9.31; N, 4.98. Found: C, 74.6; H,
9.3; N, 4.7.
[(Salen)Sc(µ-OH)]2 (3a). (Salen)Sc[N(SiHMe2)2] (30 mg, 0.04
mmol) was loaded into a Schlenk flask and dissolved in 2 mL of
hexane. Outside the glovebox, excess H2O was added to the yellow
solution. Evaporation of the solvent under a vacuum gave a yellow
powder, which was dissolved in toluene. Storage of the solution at
ambient temperature produced single-crystalline complex 3a as
yellow cubes (7 mg, 0.006 mmol, 32%). 1H NMR (600 MHz, C6D6):
7.65 (s, 4H, CHdN), 7.56 (s, 4H, CHAr), 6.99 (s, 4H, CHAr), 3.47
(dd, 4H, 2JHH ) 12.6 Hz, 3JHH ) 6.6 Hz, N(CHH)2N), 3.29 (s, 2H,
2
3
OH), 2.71 (dd, 4H, JHH ) 12.6 Hz, JHH ) 6.0 Hz, N(CHH)2N),
1.68 (s, 36H, tBu), 1.34 (s, 36H, tBu). 13C NMR (100.6 MHz,
C6D6): 167.6 (CHdN), 163.7 (C-2), 139.1 (CAr), 136.4 (CAr), 129.0
(CHAr), 122.1 (C-1), 58.3 (N(CH2)2N); 35.6 (tBu), 33.9 (tBu), 31.6
(tBu), 29.9 (tBu). IR (Nujol; cm-1): 3690m (OH), 1621s (CdN),
1551m, 1533m, 1412m, 1336m, 1269vs, 1197m, 1057w, 866w,
Experimental Section
General Considerations: Techniques and Reagents. All of the
manipulations of metal complexes were performed under the
rigorous exclusion of air and moisture in an argon-filled glovebox
(MB Braun MB150B-G-II; <1 ppm O2, <1 ppm H2O). Solvent
pretreatment/purification was performed with Grubbs columns
(MBraun SPS, solvent purification system). C6D6 was obtained from
Aldrich, degassed, dried over Na for 24 h, filtered, and stored in a
glovebox. Li[N(SiHMe2)2] was prepared from HN(SiHMe2)2 (Al-
drich) and n-butyllithium (Aldrich). Me2AlCl, KH, 2,6-di-tert-
butylphenol, and 2,6-diisopropylphenol were ordered from Aldrich
and used as received. NH4Cl (Aldrich) was sublimed before use.
Sc[N(SiHMe2)2]3(thf)31 and (SALEN)Sc[N(SiHMe2)2]20 were syn-
thesized according to literature procedures. The SALEN ligand
precursors were synthesized according to slightly modified literature
procedures through a condensation reaction of salicylaldehyde
derivative 3,5-di-tert-butyl-2-hydroxybenzaldehyde (Aldrich) with
the corresponding diamines 1,2-ethylenediamine (Aldrich), 1,3-
diamino-2,2-dimethylpropane (Aldrich), and (1R,2R)-(-)-1,2-diami-
nocyclohexane (Fluka).
793w, 744m, 550m, 483w. Anal. calcd for C64H94N4O6Sc2
×
C18H24: C, 73.18; H, 8.84; N, 4.16. Found: C, 73.2; H, 8.5; N, 3.8.
[(Salpren)Sc(µ-OH)]2 (3b). A NMR sample of (Salpren)Sc[N-
(SiHMe2)2] (10 mg, 0.01 mmol) in 0.5 mL of C6D6 was stored
outside the glovebox. After several days, single crystals could be
harvested and identified as 3b. 1H NMR (400 MHz, CDCl3): 7.92
4
4
(s, 4H), 7.34 (d, 4H, JHH ) 2.8 Hz, CHAr), 6.92 (d, 4H, JHH
)
2
2.8 Hz, CHAr), 4.30 (d, 4H, JHH ) 12.0 Hz, N(CHH)), 3.52 (s,
2H, OH), 3.08 (d, 4H, JHH ) 12.0 Hz, N(CHH)), 1.38 (s, 36H,
2
tBu), 1.24 (s, 36H, tBu), 1.04 (s, 6H, C(CH3)2), 0.80 (s, 6H,
C(CH3)2). 13C NMR (100.6 MHz, CDCl3): 168.7 (CHdN), 163.0
(C-2), 138.3 (CAr), 136.3 (CAr), 129.0 (CHAr), 128.2 (CHAr), 125.3,
121.0 (C-1), 74.3 (N(CHH)), 36.7 (tBu), 35.4 (tBu), 31.4 (tBu),
29.8 (tBu), 29.4 (tBu), 27.1 (C(CH3)2), 22.8 (C(CH3)2). IR (Nujol;
cm-1): 3700w (OH), 1612vs (CdN), 1536m, 1412m, 1330m,
1317m, 1256s, 1201s, 1072m, 915w, 876w, 841m, 812w, 786m,
657s, 542s, 482s, 467s. Anal. calcd for C70H106N4O6Sc2 × (C7H8):
C, 72.16; H, 8.97; N, 4.37. Found: C, 72.5; H, 9.1; N, 4.2.
[(Salcyc)Sc(µ-OH)]2 (3c). Single crystals of 3c were originally
obtained when storing a reaction mixture of [(Salcyc)ScCl] and
NaC5Me4H in toluene/thf outside the glovebox, of course aiming
NMR data were obtained in a C6D6 solution at 25 °C on a Bruker
DMX-400 Avance (1H, 400.13 MHz; 13C, 100.61 MHz) and a
Bruker-BIOSPIN-AV600 (5 mm cryo probe; 1H, 600.13 MHz; 13C,
1
150.91 MHz). H and 13C shifts are referenced to internal solvent
resonances and reported relative to TMS. IR spectra were recorded
on a Nicolet Impact 410 FTIR spectrometer using Nujol mulls
sandwiched between CsI plates. Elemental analyses were performed
on an Elementar Vario EL III.
1
at (Salcyc)Sc(C5Me4H). H NMR (600 MHz, C6D6): 7.81 (s, 2H,
4
CHdN), 7.71-7.72 (m, 4H, CHdN, CHAr), 7.64 (d, 2H, JHH
)
4
2.4 Hz, CHAr), 7.22 (d, 2H, JHH ) 2.4 Hz, CHAr), 7.11 (m, 4H,
CHAr), 3.77 (ddd, 2H, JHaHa ) 10.8 Hz, N(CHR)), 3.56 (s, 2H,
3
Sc2(Salpren)3 (2). Sc[N(SiHMe2)2]3(thf) (115 mg, 0.22 mmol)
was dissolved in 8 mL of hexane and 1.5 equiv of H2Salpren (179
mg, 0.34 mmol) in 3 mL of thf. The clear yellow solution was
stirred for 6 days and the solvent removed under vacuum to give
complex 2 as a dark yellow powder in almost quantitative yield
OH), 2.20 (ddd, 2H, 3JHaHa ) 10.8 Hz, N(CHR)), 1.78 (s, 18H, tBu),
1.69 (s, 18H, tBu), 1.53-1.32 (m, 8H, CH2,ꢀ), 1.43 (s, 18H, tBu),
1.39 (s, 18H, tBu), 0.83-0.61 (m, 8H, CH2,γ). 13C NMR (100.6
MHz, C6D6): 168.4 (CHdN), 164.1 (C-2), 163.4 (C-2′), 160.8
(CHdN), 140.1 (CAr), 139.4 (CAr), 137.0 (CAr), 136.2 (CAr), 129.6
(CHAr), 129.1 (CHAr), 128.9 (CHAr), 128.5 (CHAr), 122.5 (C-1),
70.6 [N(CHR)], 66.1 [N(CHR)], 36.0 (tBu), 35.8 (tBu), 34.2 (CH2,ꢀ),
32.4 (tBu), 31.9 (tBu), 30.2 (CH2,ꢀ), 27.6 (CH2γ), 25.3 (CH2,ꢀ). Anal.
calcd for C72H106N4O6Sc2: C, 71.26; H, 8.80; N, 4.62. Found: C,
70.0; H, 7.0; N, 3.9.
1
(370 mg, 0.22 mmol, 98%). H NMR (500 MHz, C6D6): 8.10 (s,
1H), 7.97 (s, 1H), 7.70 (m, 3H), 7.66 (m, 1H), 7.60 (s, 2H), 7.55
(m, 3H), 7.37 (s, 1H), 7.32 (s, 1H), 7.19 (d, 1H), 7.11 (s, 2H), 7.06
(s, 1H), 7.04 (s, 1H), 4.71 (d, 2H, 2JHH ) 10.5 Hz, N(CHH)), 4.13
2
2
(d, 1H, JHH ) 12.5 Hz, N(CHH)), 4.01 (d, 1H, JHH ) 12.5 Hz,
2
N(CHH)), 3.75 (d, 1H, JHH ) 10.5 Hz, N(CHH)), 3.58 (d, 1H,
2JHH ) 11.5 Hz, N(CHH)), 2.86 (d, 2H, 2JHH ) 12.5 Hz, N(CHH)),
General Procedure for the Synthesis of Scandium SALEN
Aryloxide Complexes 4. 2,6-Di-tert-butylphenol or 2,6-diisopro-
pylphenyl was added to a stirred solution of the respective scandium
SALEN bis(dimethylsilyl)amide complex (SALEN)Sc[N(SiHMe2)2]
in hexane. After the yellow solution had been stirred for 2 h, the
solvent was removed in vacuo. The obtained yellow powders were
crystallized from toluene and identified as monomeric complexes
4a, 4b, and 4c.
2
2
2.80 (d, 1H, JHH ) 12.5 Hz, N(CHH)), 2.65 (d, 1H, JHH ) 12.5
Hz, N(CHH)), 2.59 (d, 1H, JHH ) 11.5 Hz, N(CHH)), 2.28 (d,
1H, JHH ) 10.5 Hz, N(CHH)), 1.57 (s, 9H, tBu), 1.52 (s, 27H,
2
2
tBu), 1.46 (s, 9H, tBu), 1.45 (s, 9H, tBu), 1.41 (s, 27H, tBu), 1.34
(m, 9H, C(CH3)2), 1.31 (s, 18H, tBu), 0.88 (m, 9H, C(CH3)2). IR
(Nujol; cm-1): 1612s (CdN), 1536m, 1317m, 1257m, 1170m,
(Salen)Sc(OC6H3tBu2-2,6) (4a). Following the procedure de-
scribed above, (Salen)Sc[N(SiHMe2)2] (90 mg, 0.13 mmol) and
(31) Anwander, R.; Runte, O.; Eppinger, J.; Gerstberger, G.; Herdtweck,
E.; Spiegler, M. J. Chem. Soc., Dalton Trans. 1998, 847–858.
2568 Inorganic Chemistry, Vol. 48, No. 6, 2009

Scandium SALEN Complexes
Table 2. Crystallographic Parameters for Compounds 2, 3a-c, 4b, and
1.53-1.48 (m, 4H, CH2,ꢀ), 1.42 (s, 18H, tBu), 1.36 (d, 18H, 3 Hz,
tBu), 1.25-1.14 (m, 4H, CH2,γ). 13C NMR (100.6 MHz, C6D6):
169.0 (CHdN), 163.9 (C-2), 163.6 (C-2′), 163.5, 162.8 (OAr), 139.7
(CAr), 139.6 (CAr), 138.8 (CAr), 138.6 (OAr), 138.3 (CAr), 131.1
(CHAr), 130.6 (CHAr), 129.0 (CHAr), 128.9 (CHAr), 125.0 (OAr),
123.1, 122.8 (C-1), 117.7 (OAr), 70.8 [N(CHR)], 65.1 [N(CHR)],
38.6 (OAr), 36.0 (tBu), 35.9 (tBu), 34.9 (CH2,ꢀ), 34.2 (OAr), 31.7
(tBu), 31.0 (tBu), 30.5 (CH2,ꢀ), 30.4 (CH2γ), 30.2 (CH2,γ). Anal.
calcd for C50H73N2O3Sc: C, 75.53; H, 9.25; N, 3.52. Found: C, 75.6;
H, 9.1; N, 3.3.
5b
2
3a
3b
chemical formula C105H156N6O6Sc2 C163H228N8O12Sc4 C106H142N4O6Sc2
Mr
1688.28
monoclinic
C2/c
20.5546(15)
22.3221(16)
28.192(2)
90.00
98.122(1)
90.00
12805.4(16)
4
2671.37
orthorhombic
Pba2
19.2322(4)
23.6954(6)
17.3634(3)
90.00
90.00
90.00
7912.8(3)
2
1658.16
triclinic
P1
cryst syst
space group
a/Å
b/Å
c/Å
R/deg
ꢀ/deg
γ/deg
V/Å3
j
11.5238(4)
12.6700(4)
17.5146(6)
79.829(1)
73.811(1)
83.451(1)
2411.56(14)
1
(Salcyc)Sc(OC6H3iPr2-2,6) (4c). Following the procedure de-
scribed above, (Salcyc)Sc[N(SiHMe2)2] (100 mg, 0.14 mmol) and
HOAriPr,iPr (25 mg, 0.14 mmol) gave 4c (40 mg, 0.05 mmol, 38%),
Z
1
F(000)
T/K
3672
123(2)
0.876
0.148
0.0805
0.2416
1.014
2884
183(2)
1.121
896
123(2)
1.142
0.195
0.0496
0.1255
1.039
upon extraction with toluene from the crude reaction mixture. H
NMR (600 MHz, C6D6): 8.00 (s, 1H, CHdN), 7.90 (s, 1H, CHdN),
F
calcd/g cm-3
4
4
7.79 (d, 1H, JHH ) 3.0 Hz, CHAr), 7.75 (d, 1H, JHH ) 3.0 Hz,
µ/mm-1
R1 (obsd)a
wR2 (all)b
Sc
0.223
CHAr), 7.30 (d, 1H, 4JHH ) 3.0 Hz, CHAr), 7.18 (d, 1H, 4JHH ) 3.0
Hz, CHAr), 7.06 (d, 2H, JHH ) 7.8 Hz, OAr), 6.87 (t, 1H, JHH
7.8 Hz, OAr), 3.66 (ddd, 2H, JHaHa ) 11.4 Hz, N(CHR)), 3.44 (s,
br, 2H, iPr), 2.36 (ddd, 2H, JHaHa ) 11.4 Hz, N(CHR)), 1.83 (s,
0.0407
0.0926
0.915
3
3
)
3
3
3c
4b
5b
9H, tBu), 1.76 (s, 9H, tBu), 1.47-1.41 (m, 4H, CH2,ꢀ), 1.38 (s,
18H, tBu), 1.28-1.20 (m, 4H, CH2,γ), 1.17 (d, 6H, 3JHH ) 7.8 Hz,
iPr), 1.06 (d, 6H, 3JHH ) 7.8 Hz, iPr). 13C NMR (100.6 MHz, C6D6):
168.2 (CHdN), 163.7 (C-2), 163.5 (C-2′), 163.4 (OAr), 139.7 (CAr),
139.8 (CAr), 139.7 (CAr), 138.5 (OAr), 138.3 (CAr), 130.8 (CHAr),
130.6 (CHAr), 129.0 (CHAr), 128.8 (CHAr), 123.0 (OAr), 122.6 (C-
1), 69.9 [N(CHR)], 66.0 [N(CHR)], 36.0 (tBu), 35.9 (tBu), 34.3
(CH2,ꢀ), 31.8 (tBu), 30.1 (CH2,ꢀ), 30.0 (CH2γ), 27.4 (CH2,γ) 24.8
(OAr), 23.5 (OAr). IR (Nujol; cm-1): 1634s (OAr), 1613vs (CdN),
1552m, 1534s, 1412w, 1272s, 1254s, 1202m, 1095w, 1028w, 922w,
897m, 876m, 842w, 784w, 744m, 592w, 540m. Anal. calcd for
C48H69N2O3Sc: C, 75.16; H, 9.07; N, 3.65. Found: C, 76.0; H, 8.7;
N, 3.5.
Synthesis of Scandium SALEN Chloride Complexes 5. The
chloride complexes 5a and 5b were synthesized by different
synthesis approaches (Scheme 3). Data reported for 5 were obtained
from complexes synthesized by approach E or G.
General Procedure for Route E (Scheme 3). The amide
complexes (SALEN)Sc[N(SiHMe2)2] (1a-c) were dissolved in 5
mL of thf and 1 equiv of NH4Cl was added. The reaction mixtures
were stirred until all NH4Cl had dissolved (3-5 days). After
evaporation of the volatiles under reduced pressure, 5a and 5b were
received as yellow powders.
chemical formula C107H146N4O6Sc2 C50H73N2O3Sc C52H84ClN2O6Sc
Mr
1674.20
orthorhombic
P212121
14.7536(9)
17.7288(11)
38.311(2)
90.00
90.00
90.00
10020.8(11)
4
795.06
913.62
cryst syst
space group
a/Å
b/Å
c/Å
R/deg
ꢀ/deg
γ/deg
V/Å3
orthorhombic monoclinic
P212121
10.9304(3)
17.4215(5)
25.1227(7)
90.00
90.00
90.00
4784.0(2)
4
P21
11.8966(6)
27.1729(13)
16.5478(8)
90.00
99.805(1)
90.00
5271.2(4)
4
Z
F(000)
T/K
3624
103(2)
1.110
0.188
0.0501
0.1434
1.078
1728
123(2)
1.104
1984
123(2)
1.151
F
calcd/g cm-3
µ/mm-1
R1 (obsd)a
wR2 (all)b
Sc
0.194
0.237
0.0340
0.0830
1.027
0.0660
0.1956
1.031
a R1 ) ∑(|Fo| - |Fc|)/∑|Fo|, Fo> 4σ(Fo). b wR2 ) {∑[w(Fo
-
2
c
2
2
Fc2)2]/∑[w(Fo )2]}1/2
.
S ) [∑w(Fo - Fc2)2/(no - np)]1/2
.
HOArtBu,tBu (28 mg, 0.13 mmol) gave 4a (97 mg, 0.13 mmol,
1
3
>99%). H NMR (600 MHz, C6D6): 7.75 (d, 2H, JHH ) 7.8 Hz,
4
OAr), 7.63 (s, 2H, CHdN), 7.50 (d, 2H, JHH ) 2.4 Hz, CHAr),
4
3
7.07 (d, 2H, JHH ) 2.4 Hz, CHAr), 6.81 (t, 1H, JHH ) 7.8 Hz,
OAr), 3.67 (dd, 2H, 2JHH ) 12.6 Hz, 3JHH ) 6.0 Hz, N(CHH)2N),
(Salen)Sc(Cl)(thf) (5a). When the procedure for route E was
followed, (Salen)Sc[N(SiHMe2)2] (85 mg, 0.13 mmol) and NH4Cl
2
3
2.77 (dd, 2H, JHH ) 12.6 Hz, JHH ) 6.0 Hz, N(CHH)2N), 1.74
(s, 18 H, tBu), 1.41 (s, 18H, tBu), 1.34 (s, 18H, OAr). 13C NMR
(100.6 MHz, C6D6): 169.9 (CHdN), 163.9 (C-2), 162.8 (OAr),
139.6 (CAr), 138.5 (CAr), 136.0 (OAr), 130.9 (CHAr), 128.5 (CHAr),
125.4 (OAr), 122.2 (C-1), 117.7 (OAr), 57.6 (N(CH2)2N), 35.9
(tBu), 34.9 (tBu), 34.3 (OAr), 31.7 (tBu), 30.7 (OAr), 30.4 (tBu).
IR (Nujol; cm-1): 1634 (OAr), 1618s (CdN), 1551m, 1536m,
1412s, 1309m, 1242vs, 1201m, 1051w, 984m, 876w, 744m, 542m.
Anal. calcd for C46H67N2O3Sc: C, 74.56; H, 9.11; N, 3.78. Found:
C, 72.2; H, 9.0; N, 3.8.
1
(7 mg, 0.13 mmol) gave 5a (80 mg, 0.12 mmol, 98%). H NMR
(600 MHz, C6D6): 7.72 (s, 2H, CHdN), 7.50 (s, 2H, CHAr), 7.00
3
(s, 2H, CHAr), 3.68 (d, 2H, JHH ) 6.0 Hz, N(CHH)2N), 3.52 (s,
4H, thf), 2.72 (d, 2H,3JHH ) 6.0 Hz, N(CHH)2N), 1.72 (s, 18 H,
tBu), 1.37 (s, 18H, tBu), 1.29 (s, 4H, thf). 13C NMR (100.6 MHz,
C6D6): 168.0 (CHdN), 163.0 (C-2), 139.3 (CAr), 138.1 (CAr), 130.1
(CHAr), 128.5 (CHAr), 122.7 (C-1), 68.5 (thf), 59.0 (N(CH2)2N),
35.8 (tBu), 34.2 (tBu), 31.8 (tBu), 30.1 (tBu), 25.6 (thf). IR (Nujol;
cm-1): 1621vs (CdN), 1553m, 1538m, 1415m, 1316m, 1279m,
1259m, 1202w, 1171s, 1047w, 969w, 912w, 886w, 866m, 840m,
809w, 783w, 752m, 550s, 478m. Anal. calcd for C36H54ClN2O3Sc:
C, 67.22; H, 8.46; N, 4.36. Found: C, 65.5; H, 8.4; N, 4.4.
(Salcyc)Sc(Cl)(thf) (5b). When the procedure for route E was
followed, (Salcyc)Sc[N(SiHMe2)2] (106 mg, 0.14 mmol) and NH4Cl
(8 mg, 0.15 mmol) gave 5b (104 mg, 0.15 mmol, >99%). 1H NMR
(600 MHz, C6D6): 7.83 (s, 1H, CHdN), 7.76 (m, 3H, CHdN,
(Salcyc)Sc(OC6H3tBu2-2,6) (4b). Following the procedure de-
scribed above, (Salcyc)Sc[N(SiHMe2)2] (40 mg, 0.05 mmol) and
HOArtBu,tBu (11 mg, 0.05 mmol) gave 4b (43 mg, 0.05 mmol,
>99%). 1H NMR (600 MHz, C6D6): 7.94 (s, 2H, CHdN), 7.81 (d,
1H, 4JHH ) 3.0 Hz, CHAr), 7.77 (d, 1H, 4JHH ) 3.0 Hz, CHAr), 7.34
4
3
(d, 1H, JHH ) 3.0 Hz, CHAr), 7.27 (d, 2H, JHH ) 7.8 Hz, OAr),
4
3
7.18 (d, 1H, JHH ) 3.0 Hz, CHAr), 6.80 (t, 1H, JHH ) 7.8 Hz,
3
4
OAr), 3.97 (ddd, 2H, JHaHa ) 11.4 Hz, N(CHR)), 2.34 (ddd, 2H,
CHAr), 7.25 (d, 1H, JHH ) 3 Hz, CHAr), 7.10 (s, 1H, CHAr), 4.22
3JHaHa ) 11.4 Hz, N(CHR)), 1.78 (s, 9H, tBu), 1.76 (s, 9H, tBu),
(ddd, 1H, 3JHRHR ) 10.2 Hz, N(CHR)), 3.56 (s, 4H, thf), 2.34 (ddd,
Inorganic Chemistry, Vol. 48, No. 6, 2009 2569

Meermann et al.
3
1H, JHRHR ) 10.2 Hz, N(CHR)), 1.75 (s, 9 H, tBu), 1.74 (s, 9 H,
saturated solutions using toluene at ambient temperature (3a, 3c),
toluene at -35 °C (4b), or hexane at -35 °C (2, 5b). Suitable
single crystals of 2, 4b, and 5b (selected in a glovebox) and 3b
and 3c (selected under air) were coated with Paratone-N (Hampton
Research), fixed in a nylon loop, and measured on a Bruker SMART
2K CCD diffractometer. A single crystal of 3a was mounted on a
glass fiber and measured on an Oxford Diffraction Xcalibur system
with a Ruby detector (Zurich Crystallography School, 2007). All
other data were collected using graphite monochromated Mo KR
radiation (λ ) 0.71073 Å) performing ω-scans in four ω positions.
The program suite CrysAlisPro was used for data collection,
semiempirical absorption correction, and data reduction (3a).32 Raw
data were collected using the SMART program33 and reduced and
scaled with the SAINT program.33 Corrections for absorption effects
were applied using SHELXTL.34 The structures were solved by a
combination of direct methods (SHELXS35 and SIR9236) and
difference-Fourier syntheses (SHELXL-9735). Final model refine-
ment was done using SHELXL-97. All plots were generated using
the ORTEP-3 program.37 Further details of the refinement and
crystallographic data are listed in Table 2 and in CIF files
(Supporting Information); CCDC reference numbers 706234-706239.
tBu), 1.55-1.47 (m, 4H, CH2,ꢀ), 1.45 (s, 9H, tBu), 1.39 (s, 9H,
tBu), 1.35 (m, 4H, thf), 0.94-0.69 (m, 4H, CH2,γ). Anal. calcd for
C40H60ClN2O3Sc: C, 68.90; H, 8.67; N, 4.02. Found: C, 67.6; H,
8.6; N, 4.0.
General Procedure for Route G (Scheme 3). According to a
slightly modified literature procedure, as described for [(Salen)Y(µ-
Cl)(thf)]2,5 the proligands H2SALEN were dissolved in thf, and 2
equiv of KH were added. After gas evolution had ceased, ScCl3(thf)3
was added to the clear yellow solutions. The reaction was stirred
overnight and, afterwards, the formed precipitate separated and
extracted with thf. Solvent removal from the combined thf fractions
gave complexes 5a and 5b as a yellow powder.
(Salen)Sc(Cl)(thf) (5a). When the procedure for route G was
followed, H2Salen (246 mg, 0.50 mmol), KH (40 mg, 1.00 mmol),
and ScCl3(thf)3 (184 mg, 0.50 mmol) gave complex 5a (246 mg,
1
0.38 mmol, 77%). H NMR (600 MHz, thf-d8, route G/Scheme
35): 8.33 (s, 2H, CHdN), 7.43 (s, 2H, CHAr), 7.14 (s, 2H, CHAr),
4.07 (m, 2H, N(CHH)2N), 3.72 (m, 2H, N(CHH)2N), 1.45 (s, 18
H, tBu), 1.27 (s, 18H, tBu).
(Salcyc)Sc(Cl)(thf) (5b). When the procedure for route G was
followed, H2Salcyc (300 mg, 0.55 mmol), KH (44 mg, 1.10 mmol),
and ScCl3(thf)3 (202 mg, 0.55 mmol) gave complex 5b (317 mg,
0.45 mmol, 83%). 1H NMR (500 MHz, thf-d8): 8.38 (s, 1H,
CHdN), 8.36 (s, 1H, CHdN), 7.46 (s, 2H, CHAr), 7.25 (s, 2H,
CHAr), 3.98 (m, 2H, 3JHRHR ) 10.4 Hz, N(CHH)2N), 3.22 (m, 2H,
3JHRHR ) 10.4 Hz, N(CHH)2N), 1.50 (s, 9 H, tBu), 1.47 (s, 9H,
tBu), 1.44-1.35 (m, 8H, CH2,γ, CH2,ꢀ), 1.31 (s, 18H, tBu). 13C NMR
(100.6 MHz, C6D6): 165.8 (CHdN), 164.9 (C-2), 163.7 (C-2′),
163.5 (CHdN), 139.2 (CAr), 139.0 (CAr), 137.9 (CAr), 137.8 (CHAr),
130.7 (CHAr), 130.6 (CHAr), 130.3 (CHAr), 123.8 (C-1), 123.7 (C-
1′), 70.0 (N(CHR)), 36.2 (tBu), 34.8 (tBu), 32.2 (CH2,ꢀ), 30.5 (tBu),
30.3 (tBu), 30.0 (CH2,ꢀ), 29.3 (CH2,γ), 26.6 (CH2,γ). IR (Nujol;
cm-1): 1611vs (CdN), 1554s, 1537s, 1408s, 1362m, 1349m, 1318s,
1272m, 1255s, 1236w, 1199w, 1168s, 1028m, 980w, 964w, 920w,
879m, 862m, 841s, 819m, 783m, 752s, 642m, 558vs, 484s, 468s,
405w. Anal. calcd for C40H60ClN2O3Sc: C, 68.90; H, 8.67; N, 4.02.
Found: C, 69.4; H, 8.6; N, 3.8.
Acknowledgment. C. M. thanks the Zurich Crystal-
lography School 2007, and Bernhard Spingler for X-ray
measuring time (3a).
Supporting Information Available: Crystallographic file in CIF
format. This material is available free of charge via the Internet at
http://pubs.acs.org.
IC802082B
(32) CrysAlisPro Software System, v.171.32; Oxford Diffraction Ltd.:
Oxford, U. K., 2007.
(33) SMART, v.5.054; SAINT, v.6.45a; Bruker Analytical X-ray Instruments
Inc.: Madison, WI, 2005.
(34) SHELXTL, v.6.12; Bruker Analytical X-ray Instruments Inc.: Madison,
WI, 2002.
(35) Sheldrick, G. M. Acta Crystallogr., Sect. A 2008, 64, 112–122.
(36) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A. J. Appl.
Crystallogr. 1993, 26, 343–350.
Crystallographic Data Collection and Refinement. Crystals
of 2, 3a-c, 4b, and 5b were grown by standard techniques from
(37) Farrugia, L. J. J. Appl. Crystallogr. 1997, 30, 565–566.
2570 Inorganic Chemistry, Vol. 48, No. 6, 2009