Synthesis and structural characterization of scandium SALEN complexes

Article abstract of DOI:10.1039/b513370j

A series of heteroleptic scandium SALEN complexes, [(SALEN)Sc(-Cl)] ₂ and (SALEN)Sc[N(SiHMe₂)₂] is obtained via amine elimination reactions using [Sc(NⁱPr₂) ₂(-Cl)(THF)]₂ and Sc[N(SiHMe₂) ₂]₃(THF) as metal precursors, respectively. H ₂SALEN ligand precursors comprising H₂Salen [(1,2-ethandiyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol], H ₂Salpren [(2,2-dimethylpropanediyl)bis(nitrilomethylidyne)bis(2,4-di- tert-butyl)phenol], H₂Salcyc [(1R,2R)-(-)-1,2-cyclohexanediyl) bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol] and H₂Salphen [((1S,2S)-(-)-1,2-diphenylethandiyl)bis(nitrilomethylidyne)bis(2, 4-di-tert-butyl)phenol] are selected according to solubility and ligand backbone variation ("N-(R)-N" bite angle) criteria. Consideration is given to the feasibility of [Cl → NR₂] and [N(SiHMe₂) ₂ → OSiR₃] secondary ligand exchange reactions. X-ray crystal structure analyses of donor-free (Salpren)Sc(NⁱPr ₂), (R,R)-(Salcyc)Sc[N(SiHMe₂)₂], (Salen)Sc(OSi^tBuPh₂) and (Salphen)Sc(OSiH ^tBu₂) reveal (i) a very short Sc-N bond distance of 2.000(3), (ii) weak β(Si-H)_amido-Sc agostic interactions and (iii) an exclusive intramolecularly tetradentate and intrinsically bent coordination mode of the SALEN ligands with ∠(Ph,Ph) dihedral angles and Sc-[N₂O₂] distances in the 124.27(9)-127.7(3)° and 0.638(1)-0.688(1) range, respectively. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b513370j

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www.rsc.org/dalton | Dalton Transactions
Synthesis and structural characterization of scandium SALEN complexes
Christian Meermann,a Peter Sirsch,b Karl W. To¨rnroosa and Reiner Anwander*a
Received 20th September 2005, Accepted 9th November 2005
First published as an Advance Article on the web 14th December 2005
DOI: 10.1039/b513370j
A series of heteroleptic scandium SALEN complexes, [(SALEN)Sc(l-Cl)]2 and (SALEN)Sc-
[N(SiHMe2)2] is obtained via amine elimination reactions using [Sc(NiPr2)2(l-Cl)(THF)]2 and
Sc[N(SiHMe2)2]3(THF) as metal precursors, respectively. H2SALEN ligand precursors comprising
H2Salen [(1,2-ethandiyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol], H2Salpren [(2,2-dimethyl-
propanediyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol], H2Salcyc [(1R,2R)-(−)-1,2-cyclo-
hexanediyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol] and H2Salphen [((1S,2S)-(−)-1,2-
diphenylethandiyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol] are selected according to
=
=
solubility and ligand backbone variation (“ N–(R)–N ” bite angle) criteria. Consideration is given
to the feasibility of [Cl → NR2] and [N(SiHMe2)2 → OSiR3] secondary ligand exchange reactions.
X-ray crystal structure analyses of donor-free (Salpren)Sc(NiPr2), (R,R)-(Salcyc)Sc[N(SiHMe2)2],
(Salen)Sc(OSitBuPh2) and (Salphen)Sc(OSiHtBu2) reveal (i) a very short Sc–N bond distance of
˚
2.000(3) A, (ii) weak b(Si–H)amido–Sc agostic interactions and (iii) an exclusive intramolecularly
tetradentate and intrinsically bent coordination mode of the SALEN ligands with ∠(Ph,Ph)
◦
˚
dihedral angles and Sc–[N2O2] distances in the 124.27(9)–127.7(3) and 0.638(1)–0.688(1) A range,
respectively.
derived from 2,2ꢀ-diamino-6,6ꢀ-dimethylbiphenyl) for the intra-
molecular hydroamination of aminoalkenes.11
Introduction
Non-cyclopentadienyl ancillary ligands launched the design of
a new generation of highly active polymerization catalyst pre-
cursors, so called postmetallocenes, with structurally defined
reaction centres.1 This is also emphasised by a rapidly growing
library of mono- and dianionic alkoxide (aryloxide) and amido
ligands employed for the synthesis of novel postlanthanidocene
complexes.2–6 Chelating anionic Schiff-base ligands have been
extensively employed as ancillary ligands in d-transition metal-
mediated homogeneous catalysis.7 Particularly, SALEN-type
Recently, the smallest rare-earth element scandium attracted
considerable attention in organolanthanide catalysis†12–14 due to
distinct reactivity features arising from its rare-earth metal “pole
position” with respect to smallest LnIII size, highest Lewis acidity,
highest electronegativity, and pronounced d-element character.15
This motivated us to systematically study Sc–SALEN chemistry
and organoscandium catalysis. Herein we present a comprehensive
account on synthetic aspects by addressing issues such as efficient
scandium precursors, SALEN ligand variation, and modeling
silica surface chemistry.
ligands8 which feature
a conformationally rigid dianionic
[ONNO]2− ancillary ligand set, are efficiently applied in chiral
reagents for enantioselective organic transformation as well as
in postmetallocene complexes (Salen, N,Nꢀ-bis(3,5-di-tert-butyl-
salicylidene)ethylenediamine).8 We have previously reported
the synthesis, derivatization and structural characterization of
a discrete, mononuclear SALEN complex of the medium-
sized rare-earth metal centre yttrium, (H2Salen)Y[N(SiHMe2)2]-
(THF), according to the extended silylamide route, i.e., use
of Y[N(SiHMe2)2]3(THF)2 as a synthetic precursor.9 Meanwhile
several research groups examined such complexes (SALEN)Ln-
[N(SiHMe2)2] as catalyst precursors. Lin and RajanBabu showed
that complexes (Salcyc)Y[N(SiHMe2)2](THF) are more efficient
catalyst precursors for enantioselective acyl transfer reactions
than commercially available yttrium isopropoxide [Y5(OiPr)13O].10
Scott and co-workers employed chiral non-racemic SALEN-
type complexes (L)Y[N(SiHMe2)2](THF) (H2L = salicylaldimine
Results and discussion
SALEN ligand selection
Crucial criteria for ligand selection were enhanced complex
solubility and ligand backbone variation. The former is routinely
achieved via 3,5-bis(tBu)-substitution of the two phenyl rings. Vari-
=
=
ation of the “ N–(R)–N ” ligand backbone and concomitantly
of the ligand bite angle is known to be a delicate issue for such
multidentate ligands with respect to “intramolecular chelating”
vs. “intermolecular bridging” coordination modes.16 Fig. 1 shows
the various SALEN ligand precursors used in this study.
[Sc(NiPr2)2(l-Cl)(THF)]2 as a precursor. Previously, Evans
et al. showed that dinculear chloro-bridged derivatives
[(Salen)Y(l-Cl)(THF)]2, obtained via salt metathesis using
aUniversity of Bergen, Alle´gaten 41, 5007, Bergen, Norway. E-mail:
reiner.anwander@kj.uib.no; Fax: +47 55589490; Tel: +47 55589491
† The efficiency of Sc(OTf)3 promoted Lewis acid catalysis is well
documented by the work of Kobayashi.13 Note that Fukuzawa et al.
used mixtures of Sc(OTf)3 and chiral H2SALEN as promising catalyst
precursors in asymmetric Diels–Alder reactions.14
bDepartment of Chemistry, University of New Brunswick, Fredericton, NB,
E3B 6E2, Canada
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1. Upon reaction of 1 with H2Salen or H2Salcyc in a hexane–THF
mixture, [(Salen)Sc(l-Cl)]2 2 and [(R,R)-(Salcyc)Sc(l-Cl)]2 3, pre-
cipitated as white solids in high yield from initially clear solutions.
Complexes 2 and 3 were characterised by 1H, 13C NMR
and IR spectroscopy as well as by a derivatisation reaction.
A rigid coordination of the tetradentate SALEN ligand to the
scandium centre is unequivocally indicated by the 1H NMR
spectra. In accordance with other Salen metal complexes the
protons of the ethylene bridge are no longer magnetically equal
as in the H2Salen ligand precursor, forming a AAꢀXXꢀ spin
system. Actually, two broad signals at 3.73 and 2.72 ppm were
observed for 2. In chiral complex 3, the rigidity of the Salcyc
ligand causes a similar signal splitting of the a-protons of the
cyclohexylene fragment. Two signals at 4.26 and 2.12 with ddd
multiplicity are observed indicating an interconversion of the
isomeric chair conformations is infeasible. This is also confirmed
by the different coupling constants of the magnetically unequal
3
CHa groups (3Jaa = 9.9/11.4 Hz; Jae = 4.7/4.8 Hz). Drying in
vacuo was sufficient to completely remove any coordinated THF,
however, it is reasonable to assume that the scandium centres
achieve a final coordination number of six by forming bis(chloro)-
bridged dimers.17 A successful amine elimination and formation
of [(SALEN)Sc(l-Cl)]2 was further proven by a subsequent salt
metathetic [Cl → N(SiMe3)2] ligand exchange. The preparation
of bis(trimethylsilyl)amido complex (R,R)-(Salcyc)Sc[N(SiMe3)2]
5 was accomplished in high yield.
We experienced some problems during the synthesis of putative
[(Salpren)Sc(l-Cl)]2 4, which gave several hexane-insoluble non-
separable products including 4. The only hexane-soluble com-
pound obtained from this reaction was (Salpren)Sc(NiPr2) 6. This
can be explained by the use of a Sc(NiPr2)3(THF) contaminated
precursor [Sc(NiPr2)2(l-Cl)(THF)]2 or a non-negligible dispropor-
tionation of the latter into ScCl3(THF)3 and Sc(NiPr2)3(THF).
Nevertheless, due to its high solubility in hexane product 6 could
be easily separated from 4 and obtained in form of single crystals
suitable for an X-ray structure analysis. The molecular structure
of 6 is shown in Fig. 2, selected bond lengths and angles are listed
in Table 1 and 2.
Fig. 1 H2SALEN Ligand precursors used in this study. H2Salen [(1,2-
ethandiyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol], H2Salpren
[(2,2-dimethylpropandiyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)-
phenol], H2Salcyc [((1R,2R)-(−)-1,2-cyclohexanediyl)bis(nitrilomethyl-
idyne)bis(2,4-di-tert-butyl)phenol], H2Salphen [((1S,2S)-(−)-1,2-diphenyl
ethandiyl)bis(nitrilomethylidyne)bis(2,4-di-tert-butyl)phenol].
K2Salen, are versatile precursors for heteroleptic amido, hexa-
fluoroacetylacetonate and cyclopentadienyl complexes.‡17–19 We
found that heteroleptic amido chloro complexes [Ln(NiPr2)2(l-
Cl)(THF)]2 (Ln = Sc, Y) can be efficient precursors according to
an amine elimination/salt metathesis reaction sequence.20 Initially,
we used this reaction path for the synthesis of postyttrocene
complexes with chelating diamido ligands.21 Herein we studied
the applicability of the scandium derivative for the synthesis
of scandium SALEN complexes (Scheme 1). Accordingly, two
equivalents of LDA were reacted with ScCl3(THF)3 to give
exclusively the l-chloro bridged species [Sc(NiPr2)2(l-Cl)(THF)]2
The scandium centre is five-coordinated in a square pyramidal
fashion by the ONNO and N heteroatom sites of the Salpren
and diisopropylamido ligands. For comparison, the yttrium centre
in (Salen)Y[N(SiHMe2)2](THF)9 adopts a distorted trigonal-
prismatic geometry due to additional THF coordination. The
intrinsically bent coordination of the Salpren ligand in complex
˚
Table 1 Ln displacement from the [N2O2] least-squares plane (A) and
dihedral angle, a (◦), between the two phenyl groups
a/◦
Ref.
˚
Compound
Ln–[N2O2]/A
a
a
a
(Salpren)Sc(NiPr2), 6
0.638(1)
124.27(9)
Scheme 1 Synthesis of scandium SALEN complexes 1–5. Reagents and
conditions: (i) 2 LDA, hexane, rt; (ii) H2Salen or H2Salcyc, hexane–THF,
rt; (iii) KN(SiMe3)2, hexane, rt.
(R,R)-(Salcyc)Sc[N(SiHMe2)2], 9
(Salen)Sc(OSitBuPh2), 11
(Salen)Y[N(SiHMe2)2](THF)
(Salcyc)Y[N(SiHMe2)2](THF)
0.688(1)/0.694(1)b 127.7(2)
0.656(1)
0.95
0.95
0.93
0.86
177.4(2)
108
92.3
119.8
136
163
161
9
10
17
17
17
30
t
(Salen)Y(OC6H3 Bu2-2,6)(THF)
‡ The synthesis of heteroleptic Schiff base lanthanum chloro complexes
utilizing a salt metathetic reaction was first reported by Floriani and
co-workers.18 Rutherford and Atwood employed heteroleptic R2AlCl
(R = Me, Et) for the synthesis of (SALEN)AlCl which can be
converted via salt metathetic [Cl → N(SiMe3)2] ligand exchange into
(SALEN)Al[N(SiMe3)2].19
(Salen)Y(C5Me5)
(Salen)Y(hfac)(THF)2
(Salen)Y(OSiPh3)(THF)(CH3CN) 0.23
0.01
a This work. b Two independent molecules in the unit cell.
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◦
˚
˚
Table 2 Selected bond lengths (A), intramolecular distances (A) and angles ( ) for 6, 9 and 11
9
6
Molecule 1
Molecule 2
11
Sc–O(1)
Sc–O(2)
Sc–N(1)
Sc–N(2)
Sc–N(3)
1.994(2)
2.016(2)
2.277(2)
2.283(3)
2.000(3)
Sc(1)–O(1)
Sc(1)–O(2)
Sc(1)–N(1)
Sc(1)–N(2)
Sc(1)–N(3)
Sc(1) · · · Si(1)
Sc(1) · · · Si(2)
1.985(3)
1.976(3)
2.254(3)
2.227(3)
2.048(3)
3.144(2)
3.363(2)
Sc(2)–O(3)
Sc(2)–O(4)
Sc(2)–N(4)
Sc(2)–N(5)
Sc(2)–N(6)
Sc(2) · · · Si(4)
Sc(2) · · · Si(3)
1.981(3)
1.977(3)
2.268(3)
2.215(3)
2.050(3)
3.190(2)
3.318(2)
Sc–O(1)
Sc–O(2)
Sc–N(1)
Sc–N(2)a
1.973(2)
1.970(2)
2.222(2)
2.234(4)
2.252(6)
1.901(2)
Sc–O(3)
O(1)–Sc–O(2)
O(1)–Sc–N(1)
O(1)–Sc–N(2)
O(2)–Sc–N(1)
O(2)–Sc–N(2)
O(1)–Sc–N(3)
O(2)–Sc–N(3)
N(1)–Sc–N(2)
N(1)–Sc–N(3)
N(2)–Sc–N(3)
97.23(9)
81.10(9)
133.70(10)
153.61(9)
80.88(9)
113.55(9)
109.58(9)
81.51(9)
94.93(10)
110.44(10)
O(1)–Sc(1)–O(2)
O(1)–Sc(1)–N(1)
O(1)–Sc(1)–N(2)
O(2)–Sc(1)–N(1)
O(2)–Sc(1)–N(2)
O(1)–Sc(1)–N(3)
O(2)–Sc(1)–N(3)
N(1)–Sc(1)–N(2)
N(1)–Sc(1)–N(3)
N(2)–Sc(1)–N(3)
Sc(1)–N(3)–Si(1)
Sc(1)–N(3)–Si(2)
100.6(2)
81.64(10)
140.03(10)
136.66(10)
80.10(10)
113.9(2)
110.0(2)
72.17(10)
108.2(2)
102.9(2)
112.7(2)
126.8(2)
O(3)–Sc(2)–O(4)
O(3)–Sc(2)–N(4)
O(3)–Sc(2)–N(5)
O(4)–Sc(2)–N(4)
O(4)–Sc(2)–N(5)
O(3)–Sc(2)–N(6)
O(4)–Sc(2)–N(6)
N(4)–Sc(2)–N(5)
N(4)–Sc(2)–N(6)
N(5)–Sc(2)–N(6)
Sc(2)–N(6)–Si(4)
Sc(2)–N(6)–Si(3)
100.6(2)
80.70(10)
141.8(2)
133.93(10)
81.20(10)
114.2(2)
111.1(2)
71.83(10)
109.9(2)
100.1(2)
114.5(2)
124.2(2)
O(1)–Sc–O(2)
O(1)–Sc–O(3)
O(2)–Sc–O(3)
O(1)–Sc–N(1)
O(2)–Sc–N(1)
O(3)–Sc–N(1)
Sc–O(2)–C(9)
Sc–O(1)–C(24)
Sc–O(3)–Si
101.24(8)
114.27(8)
110.55(8)
80.94(8)
142.86(8)
101.73(8)
137.9(2)
133.9(2)
172.9(2)
a N(2) is disordered over two positions.
˚
˚
˚
O2 2.016(2) A, Sc–N1 2.277(2) A, Sc–N2 2.283(3) A) match those
found in a scandium Schiff base alkyl complex [L2Sc(CH2SiMe3)]
˚
˚
described by Piers et al. (Sc–O1 2.001(1) A, Sc–O2 2.001(1) A,
Sc–N1 2.245(2) A, Sc–N2 2.306(2) A).
4
˚
˚
Application of the extended silylamide route
We have previously shown that (Salen)Y[N(SiHMe2)2](THF) can
be synthesised in high yield via the “extended silylamide route”,
i.e., use of five-coordinate Y[N(SiHMe2)2]3(THF)2 as a syn-
thetic precursor.9,24,26 Accordingly, coordinatively less flexible four-
coordinate Sc[N(SiHMe2)2]3(THF) was examined in protonolysis
reactions with H2Salen, H2Salpren, H2Salcyc and H2Salphen
(Scheme 2).
Fig. 2 The molecular structure of complex (Salpren)Sc(NiPr2) 6. Atomic
displacement ellipsoids are drawn at the 50% level. Hydrogen atoms are
omitted for clarity.
6 is in accordance with previously reported molecular struc-
tures of monoyttrium Salen complexes (Table 1).9,10,22 Given
the smaller size of the ScIII centre its displacement from the
[N2O2] least-squares plane is less pronounced. The Sc–N(amido)
˚
bond distance of 2.000(3) A is the shortest Sc–N bond length
23–25
reported so far involving a deprotonated secondary amine.§
For comparison, the Sc–N(silylamido) bond lengths in a five-
coordinate bis(dimethylsilyl)amidocalix[4]arene complex23 and in
four-coordinate precursor Sc[N(SiHMe2)2]3(THF) are 2.060(2)
24
˚
and 2.069 A (av.), respectively. The Sc–O and Sc–N bond
˚
distances involving the Salpren ligand (Sc–O1 1.994(2) A, Sc–
Scheme 2 Synthesis of scandium SALEN bis(dimethylsilyl)amido com-
plexes 7–10, [R = ethan-1,2-diyl (Salen), 2,2-dimethylpropandiyl (Sal-
pren), (R,R)-1,2-cyclohexylenediyl (Salcyc), (S,S)-1,2-diphenylethanediyl
(Salphen). Reagents and conditions: (i) H2SALEN, hexane–THF, rt.
§ A Cambridge Crystallographic Data search52 gave the following short-
est Sc–N bond distances: four-coordinate scandium complexes de-
rived from primary amine H2NtBu: [ArNCtBuCHCtBuNAr]ScCl(NHtBu)
t
t
t
˚
˚
[1.986(2) A], [ArNC BuCHC BuNAr]ScCH3(NH Bu) [2.000(2) A] (Ar =
i
C6H3 Pr2-2,6);25b endohedral metallofullerene derivatives: Sc3N@C80[CoII-
Hexane-soluble scandium SALEN bis(dimethylsilyl)amido
complexes 7–10 could be isolated as yellow solids in high yield
and were fully characterised. The NMR and IR spectra were
(OEP)]·1.5CHCl3·0.5C6H6 [1.993(1)–2.053(1) A], Sc3N@C78[CoII(OEP)]·
25c
˚
0.3CHCl3·1.5C6H6 [1.983(5)–2.125(5) A], Sc3N@C68[NiII(OEP)]·2C6H6
25d
˚
25e
˚
[1.961(4)–2.022(3) A] (OEP = 2,3,7,8,12,13,17,18-octaethylporphinate).
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similar to those of 6 and (Salen)Y[N(SiHMe2)2](THF)9 indicating
double deprotonation of the SALEN ligand precursors and their
rigid coordination. Compared to the chloro complexes 2 and 3
of organometallic complexes according to a surface organo-
metallic chemistry.27,28 Our previous investigations revealed that
HOSiPh3 and HOSi(OtBu)3 are suitable models for isolated
silanol sites of thermally activated periodic mesoporous silica.29–31
In the course of these studies the X-ray structure analyses of
monolanthanide complexes (Salen)Y(OSiPh3)(THF)(CH3CN)30
=
=
the proton resonances of the “ N–(R)–N ” ligand backbone
of (Salen)Sc[N(SiHMe2)2] 7 and (R,R)-(Salcyc)Sc[N(SiHMe2)2]
1
9 appeared well-resolved. Also, the H NMR spectrum of the
and La[OSi(OtBu)3](AlMe3)(AlMe4)2 were reported. Particu-
31
Salpren derivative 8 shows two doublets for the N-bonded
methylene protons and separate signals for exo/endo arranged
methyl groups. In complex (Salphen)Sc[N(SiHMe2)2] 10, both
protons of the 1,2-diphenylethane bridge resolve as a doublet.
larly, the former model complex revealed that tailor-made het-
eroleptic molecular precursors can be attached to the silica surface
via a mild surface reaction and formation of a thermodynami-
cally stable lanthanide siloxide bond. We have also shown that
Sc[N(SiHMe2)2]3(THF) can be efficiently grafted onto MCM-41
silica to afford the first hybrid materials with catalytically relevant
Sc methyl surface species.32
In the following, the moderate basicity of the bis(dimethylsilyl)-
amido ligand (pKa (HN(SiHMe2)2) in THF = 22.8)24 was exploited
for the feasibility of [N(SiHMe2)2 → OSiR3] ligand exchange
reactions in heteroleptic complexes (SALEN)Sc[N(SiHMe2)2]
(Scheme 3). The modeling reactions for complexes 7–9 (SALEN =
Salen, Salpren, Salcyc) were performed with silanol HOSitBuPh2.
For the reaction of (Salphen)Sc[N(SiHMe2)2] 10 we selected
HOSiHtBu2 in order to exclude extensive NMR signal over-
lapping in the aromatic region. Furthermore, the SiH(silanol)
functionality provides an efficient FTIR spectroscopic probe. All
of the protonolysis reactions were quantitative and the resulting
complexes (SALEN)Sc(OSiR3) 11–14 could be obtained as light
yellow crystals from saturated hexane solutions.
=
Additionally, the IR spectra of complexes 7–10 show intense N C
stretching vibrations at 1611–1615 cm−1 characteristic of SALEN-
to-Ln coordination (cf., mC=N(H2SALEN): 1626–1631 cm−1).
(R,R)-(Salcyc)Sc[N(SiHMe2)2] 9 could be crystallised at −35 ◦C
from a saturated hexane solution. An X-ray crystallographic
analysis confirmed the mononuclear molecular structure (Fig. 3).
Table 1 and 3 give selected bond lengths and angles. Like in
(Salpren)Sc(NiPr2) 6, the scandium centre of complex 9 is five-
coordinated in a square pyramidal fashion by the Salcyc and
bis(dimethylsilyl)amido ligands. The bis(dimethylsilyl)amido lig-
and coordinates asymmetrically with one of the bis(dimethylsilyl)
fragments showing an intramolecular Sc · · · SiH interaction. This
bending towards the scandium centre is reflected in significantly
different angles Sc–N3–Si1 (112.7(2)◦) and Sc–N3–Si1 (126.8(2)◦)
˚
as well as in different Sc–Si distances of 3.144(2) and 3.363(2) A.
This is also in accordance with IR spectroscopic investigations in-
dicating a broad shoulder in the “agostic range” (mSiH = 2031 cm−1).
We previously reported a similar asymmetric coordination for
a five-coordinated scandium bis(dimethylsilyl)amidocalix[4]arene
complex (Sc–N–Si1 113.9(2)◦, Sc–N–Si2 124.4(2)◦).23 The Sc–
˚
N3(amido) bond distance of 2.048(3) A is also similar to the
˚
2.060(2) A in this Sc calix[4]arene complex, however, signifi-
˚
cantly shorter than the average Sc–N bond distance of 2.069 A
in four-coordinated Sc[N(SiHMe2)2]3(THF).24 The Sc–[ONNO]-
Scheme 3 Synthesis of scandium SALEN siloxide complexes 11–14.
Reagents and conditions: (i) HOSitBuPh2, toluene, rt; (ii) HOSiHtBu2,
toluene, rt.
˚
˚
(Salcyc) bond distances (Sc–O1 1.985(3) A, Sc–O2 1.976(3) A,
˚
˚
Sc–N1 2.254(3) A, Sc–N2 2.227(3) A) agree with the Sc–[ONNO]-
(Salpren) bond lengths in complex 6.
1H NMR and FTIR experiments revealed complete silylamide/
siloxide ligand exchange. Contrary to the silylamido derivatives
(SALEN)Sc[N(SiHMe2)2], complex (Salphen)Sc(OSiHtBu2) 14
features a non-agostic SiH(siloxide) moiety (dSiH = 4.61 ppm,
mSiH = 2096 cm−1). For comparison, homoleptic [Nd(OSiHtBu2)2-
(l-OSiHtBu2)]2 shows a pronounced b(Si–H)–Nd agostic inter-
action in the solid state.33 X-Ray crystallographic analyses of
(Salen)Sc(OSitBuPh2) 11 and (Salphen)Sc(OSiHtBu2) 14 con-
firmed their monomeric molecular structures (Fig. 4 and 5).
Selected bond lengths and angles for complex 11 are listed in
Tables 1 and 2.¶
In both complexes the ONNO and O coordinating atoms
of the SALEN and siloxide ligands adopt a square pyrami-
dal coordination comparable to the five-coordinate aluminium
Fig.
3
The molecular structure of complex (R,R)-(Salcyc)Sc-
[N(SiHMe2)2] 9. Atomic displacement ellipsoids are drawn at the 50%
level. Hydrogen atoms are omitted for clarity.
¶ The crystals obtained for (Salphen)Sc(OSiHtBu2) 14 showed weak
scattering power; thus no satisfactory structure model could be obtained.
Nevertheless, the connectivity for the non-hydrogen atoms could be
unequivocally established. For this reason we have not reported any bond
distances or angles. Experimental data for the X-ray diffraction study of 14:
C52H73N2O3SiSc, 765.18 g mol−1, triclinic, a = 15.9527(1), b = 16.1989(1),
SALEN siloxide complexes
◦
Silanols HOSiR3 bearing sterically demanding substituents R are
routinely employed for modeling the silica surface attachment
˚
c = 22.8353(3) A, a = 102.9278(4), b = 94.1641(4), c = 112.0086(6) , V =
3
−1
˚
5251.78(9) A , Z = 4, T = 123 K, l = 0.202 mm
.
1044 | Dalton Trans., 2006, 1041–1050
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©

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tions with a variety of H2SALEN derivatives. Thus formed discrete
heteroleptic complexes (SALEN)Sc[N(SiHMe2)2] can be easily
converted into siloxide complexes (SALEN)Sc(OSiR3) which
proves the feasibility of bulky ligand exchange reactions and
hence the availability of an additional scandium coordination
site. Moreover, such donor-free SALEN siloxide complexes can
provide useful information about the surface attachment of cat-
alytically relevant scandium SALEN complexes on silica materials.
Spectroscopic and X-ray structural data of all of the heteroleptic
complexes reveal an exclusive intramolecular tetradentate coordi-
nation mode of the SALEN ligand independent of the SALEN
ligand bite angle and the nature of the “second” ligand (chloro,
(silyl)amido, siloxide). Preliminary studies directed toward the
formation of complexes (SALEN)Sc(alkyl), e.g., via reaction
of (SALEN)Sc(NR2) with AlMe3, and complexes (SALEN)Sc+,
e.g. ‘cationization’ with borate ligands, are promising.
Fig. 4 The molecular structure of complex (Salen)Sc(OSitBuPh2) 11.
Atomic displacement ellipsoids are drawn at the 50% level. Hydrogen
atoms and one part of the disordered ethylene bridge are omitted for
clarity.
Experimental
General considerations: techniques and reagents
All of the manipulations of metal complexes were performed
under 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 Deutero GmbH, degassed, dried over Na/K alloy
for 24 h, filtered, and stored in a glovebox. LDA was prepared by
reacting diisopropylamine (Aldrich) with n-butyllithium (Aldrich)
in hexane. KN(SiMe3)2 was purchased from Aldrich and sub-
limed prior to use. Sc[N(SiHMe2)2]3(THF),24 HOSiHtBu2 and
38
HOSitBuPh2 were synthesised according to literature proce-
38
dures. ScCl3(THF)3 was obtained from anhydrous ScCl3 (Strem)
via Soxhlet extraction.39 The SALEN ligand precursors were
synthesised according to slightly modified literature procedures
by condensation reaction of salicylaldehyde derivative 3,5-di-
tert-butyl-2-hydroxybenzaldehyde (Aldrich) with the correspond-
ing diamines 1,2-ethylenediamine (Aldrich), 1,3-diamino-2,2-
dimethylpropane (Aldrich), (1R,2R)-(−)-1,2-diaminocyclohexane
(Fluka) and (1S,2S)-(−)-1,2-diphenylethylenediamine (Fluka).
NMR data were obtained in C6D6 solution at 25 ◦C from a
FT-JEOL-JNM-GX-400 (1H: 399.80 MHz; 13C: 100.51 MHz), a
Bruker DMX-400 Avance (1H: 400.13 MHz; 13C: 100.61 MHz)
and a FT-JEOL-JNM-GX-270 (1H: 270 MHz; 13C: 67.5 MHz)
spectrometer. 1H and 13C shifts are referenced to internal solvent
resonances and reported relative to TMS. IR spectra were recorded
on a Perkin Elmer FTIR spectrometer 1760X or a Jasco FT/IR-
460 Plus spectrometer using Nujol mulls sandwiched between CsI
plates. Elemental analyses were performed on an Elementar Vario
EL III.
Fig. 5 Molecular structure of (Salphen)Sc(OSiHtBu2) 14.¶
SALEN complex (Salen)Al(OSiPh3).34 The distance of the scan-
dium atom from the N2O2 least-squares plane is almost identical
˚
˚
in 11 (0.656(1) A) and 9 (0.688(1) A) (Table 1) whereas the
corresponding displacement of the smaller AlIII is 0.52 A. The
˚
Sc–O(Salen) and Sc–N(Salen) bond distances in complex 11 of
˚
1.973(2)/1.970(2) and 2.222(2) A, respectively, lie within the range
observed for those in complexes 6 and 9. The Sc–O(siloxide) bond
˚
length of 1.901(2) A is significantly shorter. To our knowledge,
other five-coordinate scandium siloxide complexes have not yet
been described and four-coordinate Sc(OSitBu3)3(THF)35 was not
structurally characterised. Edelmann and co-workers discussed
six-coordinate silsesquioxane and disiloxanediolate complexes
as structural models for surface-grafted scandium. Complexes
36
37
[Sc(acac)2(l-Cy7Si8O12O)]2 and {[(Ph2SiO)2O]2Sc3(acac)5} dis-
play a variety of bridging siloxide moieties with considerably
longer Sc–l-O(siloxide) bond distances of 2.081(3)–2.113(3) and
Tetrahydrofuran(chloro)bis(diisopropylamido)scandium(III)
[Sc(NiPr2)2(l-Cl)(THF)]2 (1)
˚
2.130(2) A, respectively.
ScCl3(THF)3 (1001 mg, 2.27 mmol) and LDA (577 mg, 5.39 mmol)
were suspended in 15 ml hexane. After stirring for 20 h, the white
slurry was centrifuged and filtered. The hexane was removed in
vacuo yielding a beige powder. Colourless crystals of [Sc(NiPr2)2(l-
Cl)(THF)]2 1 were grown from a hexane solution at −45 ◦C (yield
Conclusions
Scandium amido complexes [Sc(NiPr2)2(l-Cl)(THF)]2 and
Sc[N(SiHMe2)2]3(THF) readily undergo amine elimination reac-
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Dalton Trans., 2006, 1041–1050 | 1045
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854 mg, 88%). Anal. Calc. for C32H72Cl2N4O2Sc2: C, 54.5; H, 10.3;
[N,Nꢀ-Bis(3,5-di-tert-butylsalicylidene)-trans-1,2-
cyclohexylenediamino][bis(trimethylsilyl)amido]-
scandium(III) (R,R)-(Salcyc)Sc[N(SiMe3)2] (5)
1
N, 7.9, Cl, 10.0. Found: C, 53.7; H, 10.1; N, 7.8, Cl, 11.0%. H
◦
NMR (C6D6, 25 C, 270 MHz): d 3.79 (m, 8H, THF), 3.57 (sp,
3
3
8H, JHH = 6.4 Hz, CH), 1.38 (d, 48H, JHH = 6.4 Hz, CH3).
[(Salcyc)Sc(l-Cl)]2 3 (114 mg, 0.18 mmol) was mixed with
KN(SiMe3)2 (36 mg, 0.18 mmol) and suspended in 5 ml hexane.
After stirring the orange–red suspension for 24 h at ambient
temperature, KCl was removed via centrifugation. Evaporation
of the solvent yielded (Salcyc)ScN(SiMe3)2 5 as a dark orange
powder (115 mg). The 1H NMR spectrum indicated the presence
of non-reacted and non-separable KN(SiMe3)2 (15%). Therefore,
13C{ H} NMR (C6D6, 25 ◦C, 100.5 MHz): d 71.7 (THF), 47.2
1
(CH), 26.4 (CH3), 25.1 (THF).
General procedure for the synthesis of scandium SALEN chloro
complexes 2 and 3
To a stirred solution of 1 equivalent [Sc(NiPr2)2(l-Cl)(THF)]2 1,
in hexane were added 2 equivalents of H2SALEN dissolved in
THF. The yellow solution was stirred over night and then the
solvent and volatile products evaporated in vacuo. Trituration with
hexane (2 × 10 ml) and solvent removal in vacuo left 2 and 3 as
yellowish white solids.
an elemental analysis was not performed. 1H NMR (C6D6, 25 ◦C,
4
=
270 MHz) d 7.96 (s, 1H, CH N), 7.78 (d, 1H, JHH = 2.5 Hz,
4
=
CHar.), 7.74 (s, 1H, CH N), 7.40 (d, 1H, JHH = 2.7 Hz, CHar.),
4
4
7.31 (d, 1H, JHH = 2.7 Hz, CHar.), 7.07 (d, 1H, JHH = 2.5 Hz,
CHar.), 4.30 (ddd, 1H, 3JHaHa = 11.2 Hz, 3JHaHe = 4.9 Hz, N(CHa)),
3
3
2.33 (ddd, 1H, JHaHa = 12.3 Hz, JHaHe = 4.6 Hz, N(CHa)),
1.84 (s, 9H, C(CH3)3), 1.70 (s, 9H, C(CH3)3), 1.60–1.39 (m, 4H,
CH2,b), 1.34 (s, 18H, C(CH3)3), 1.30–1.18 (m, 4H, CH2,c), 0.28
Chloro[N,Nꢀ-bis(3,5-di-tert-butylsalicylidene)ethylenediamino]-
scandium(III) [(Salen)Sc(l-Cl)]2 (2)
(s, 18H, Si(CH3)3). 13C{ H} NMR (C6D6, 25 ◦C, 67.9 MHz): d
1
ꢀ
=
=
170.0 (CH N), 163.3 (C-2), 162.2 (CH N), 161.6 (C-2 ), 139.4
(Car.), 138.3 (Car.), 137.8 (Car.), 130.5 (CHar.), 130.1 (CHar.), 128.6
(CHar.), 128.1 (CHar.), 122.5 (C-1), 71.5 (N(CHa), 65.6 (N(CHa)),
35.7 (C(CH3)3), 35.6 (C(CH3)2), 34.0 (CH2,b), 31.4 (C(CH3)3), 30.2
(C(CH3)3), 26.5 (CH2,b), 25.1 (CH2c), 24.8 (CH2,c), 5.2 (Si(CH3)3).
Following the procedure described above, [Sc(NiPr2)2(l-Cl)-
(THF)]2 1 (141 mg, 0.20 mmol) and H2Salen (197 mg, 0.40 mmol)
yielded 2 (225 mg, 98%). Anal. Calc. for C64H92Cl2N4O4Sc2: C,
67.30; H, 8.12; N, 4.90. Found: C, 64.2; H, 8.7; N, 4.7%. 1H NMR
◦
mmax/cm−1 1615vs (C N), 1550m, 1535m, 1411m, 1361m, 1320s,
1274m, 1255s, 1200w, 1171m, 1035w, 974w, 931m, 874w, 840w,
787w, 748w, 722w, 666w, 537m, 484w, 466w, 418w.
=
(C6D6, 25 C, 270 MHz) d 7.71 (s, 2H, CH N), 7.51 (s, 2H,
=
CHar.), 6.99 (s, 2H, CHar.), 3.72 (s, br, 2H, N(CHH)2N), 2.70 (s, br,
2H, N(CHH)2N), 1.74 (s, 18H, C(CH3)3), 1.37 (s, 18H, C(CH3)3).
◦
13C{ H} NMR (C6D6, 25 C, 67.9 MHz): d 167.9 (CH N),
1
=
162.8 (C-2), 139.1 (Car.), 137.9 (Car.), 129.7 (CHar.), 128.5 (CHar.),
122.5 (C-1), 58.9 (N(CH2)2N); 35.6 (C(CH3)3), 33.9 (C(CH3)3),
[N,Nꢀ-bis(3,5-di-tert-butylsalicylidene)-2,2-
dimethylpropylenediamino][diisopropylamido]scandium(III)
(Salpren)Sc(NiPr2) (6)
31.5 (C(CH3)3), 30.0 (C(CH3)3). mmax/cm−1 1616vs (C N), 1553m,
=
1538m, 1414m, 1308m, 1274m, 1256m, 1200w, 1172m, 1064w,
969w, 857w, 835w, 812w, 783m, 749m, 722m, 546m, 476w,
419w.
Following the procedure described above, reaction of
[Sc(NiPr2)2(l-Cl)(THF)]2 1 (141 mg, 0.20 mmol) and H2Salpren
(197 mg, 0.40 mmol) gave several hexane-insoluble products which
were not separated. The hexane phase was dried in vacuo yielding
Chloro[N,Nꢀ-bis(3,5-di-tert-butylsalicylidene)-trans-1,2-
cyclohexylenediamino]scandium(III) [(Salcyc)Sc(l-Cl)]2 (3)
6 (52 mg). A satisfactory elemental analysis could not be obtained.
◦
1H NMR (C6D6, 25 C, 270 MHz) d 7.78 (s, 2H, CH N), 7.76
=
(d, 2H, 4JHH = 2.4 Hz, CHar.), 7.14 (d, 2H, 4JHH = 2.0 Hz, CHar.),
Following the procedure described above, [Sc(NiPr2)2(l-Cl)-
(THF)]2 1 (353 mg, 0.50 mmol) and H2Salcyc (547 mg, 1.00 mmol)
yielded 3 (621 mg, 99%). Anal. Calc. for C72H52Cl2N4O4Sc2: C,
2
3
4.15 (d, 2H, JHH = 12.0 Hz, N(CHH)), 3.45 (sp, 2H; JHH
=
2
6.4 Hz, NCH(CH3)2), 2.70 (d, 2H, JHH = 12.0 Hz, N(CHH)),
1.80 (s, 18H, C(CH3)3), 1.35 (s, 18H, C(CH3)3), 1.21 (d, 12H,
3JHH = 6.4 Hz, NCH(CH3)2), 0.68 (s, 3H, C(CH3)(CH3)), 0.25 (s,
69.16; H, 8.38; N, 4.48. Found: C, 69.4; H, 8.6; N, 3.8%. 1H
◦
=
NMR (C6D6, 25 C, 270 MHz) d 7.84 (s, 1H, CH N), 7.76 (s,
◦
1
3H, C(CH3)(CH3)). 13C{ H} NMR (C6D6, 25 C, 100.5 MHz): d
4
=
1H, CH N), 7.75 (d, 2H, JHH = 2.5 Hz, CHar.), 7.25 (d, 1H,
4JHH = 2.2 Hz, CHar.), 7.10 (d, 1H, JHH = 2.2 Hz, CHar.), 4.26
4
=
172.1 (CH N), 165.1 (C-2), 140.0 (Car.), 137.8 (Car.), 130.9 (CHar.),
129.7 (CHar.), 122.3 (C-1), 76.2 ( NCH2–), 48.0 (NCH(CH3)2),
36.4 (C(CH3)3), 36.0 (C(CH3)2), 34.5 (C(CH3)3), 32.1 (C(CH3)3),
(ddd, 1H, 3JHaHa = 11.4 Hz, 3JHaHe = 4.7 Hz, N(CHa)), 2.37 (ddd,
=
3
3
1H, JHaHa = 9.9 Hz, JHaHe = 4.8 Hz, N(CHa)), 1.75 (s, 9H,
31.1 (C(CH3)3), 27.5 (C(CH3)(CH3)), 27.2 (NCH(CH3)2), 21.4
C(CH3)3), 1.74 (s, 9H, C(CH3)3), 1.48–1.39 (m, 4H, CH2,b), 1.45
(C(CH3)(CH3)). mmax/cm−1 1610s (C N), 1537m, 1410s, 1384s,
=
(s, 9H, C(CH3)3), 1.38 (s, 9H, C(CH3)3), 1.27–1.23 (m, 4H, CH2,c).
◦
13
1
1322s, 1278m, 1259m, 1171s, 1107m, 1073m, 1010m, 929m, 844m,
807w, 783w, 746w, 600w, 539m, 476m, 441m.
=
C{ H} NMR (C6D6, 25 C, 67.9 MHz): d 166.7 (CH N), 162.4
ꢀ
=
(C-2), 162.0 (C-2 ), 161.7 (CH N), 139.9 (Car.), 139.0 (Car.), 138.1
(Car.), 130.1 (CHar.), 129.8 (CHar.), 129.0 (CHar.), 128.7 (CHar.),
122.7 (C-1), 122.4 (C-1ꢀ), 70.7 (N(CHa)); 64.8 (N(CHa)), 35.7
(C(CH3)3), 35.6 (C(CH3)3), 34.0 (CH2,b), 31.6 (C(CH3)3), 30.0
(C(CH3)3), 27.9 (CH2,b), 24.8 (CH2c), 24.3 (CH2,c). mmax/cm−1 1613s
General procedure for the synthesis of scandium SALEN
bis(dimethylsilyl)amido complexes 7–10
=
(C N), 1553m, 1538m, 1411m, 1315m, 1273m, 1256m, 1200w,
1171m, 969w, 878w, 863w, 841w, 816w, 785m, 751m, 722m, 556m,
484w.
To a stirred solution of Sc[N(SiHMe2)2]3(THF) in hexane was
added an equimolar amount of H2SALEN in THF. In order to
ensure complete reaction the yellow mixture was stirred for 5 d.
1046 | Dalton Trans., 2006, 1041–1050
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3
1
0.24 (d, 12H, JHH = 3.0 Hz, Si(CH3)2H). 13C{ H} NMR (C6D6,
Then the solvent was removed in vacuo. The yellow residues were
crystallised from saturated hexane solutions and analysed as 7–10.
◦
ꢀ
=
25 C, 100.5 MHz): d 169.0 (CH N), 163.7 (C-2), 163.3 (C-2 ),
162.7 (CH N), 139.5 (Car.), 138.3 (Car.), 137.7 (Car.), 130.5 (CHar.),
130.1 (CHar.), 128.9 (CHar.), 128.7 (CHar.), 122.7 (C-1), 70.2
[N(CHa)]; 65.9 [N(CHa)], 35.7 [C(CH3)3], 35.6 [C(CH3)2–], 34.0
(CH2,b), 31.5 [C(CH3)3], 30.0 [C(CH3)3], 26.9 (CH2,b), 24.9 (CH2c),
24.5 (CH2,c), 2.8 [Si(CH3)2H], 2.6 [Si(CH3)2H]. mmax/cm−1 2118m
(Si–H), 1615vs (C N), 1550m, 1536m, 1411m, 1361m, 1320m,
1274w, 1256m, 1234w, 1200w, 1170m, 876w, 838w, 815w, 787w,
748w, 721w, 665w, 538m, 485w, 467w.
=
[N,Nꢀ-Bis(3,5-di-tert-butylsalicylidene)ethylenediamino]-
[bis(dimethylsilyl)amido]scandium(III) (Salen)Sc[N(SiHMe2)2] (7)
Following the procedure described above, Sc[N(SiHMe2)2]3(THF)
(206 mg, 0.41 mmol) and H2Salen (197 mg, 0.41 mmol) yielded
7 (214 mg, 80%). Anal. Calc. for C36H60N3O2ScSi2: C, 64.73; H,
=
1
9.05; N, 6.29. Found: C, 65.3; H, 9.4; N, 5.3%. H NMR (C6D6,
◦
4
=
25 C, 400 MHz) d 7.77 (s, 2H, CH N), 7.60 (d, 2H, JHH
=
4
2.6 Hz, CHar.), 7.07 (d, 2H, JHH = 2.6 Hz, CHar.), 4.80 (sp, 2H,
[N,Nꢀ-Bis(3,5-di-tert-butylsalicylidene)-1,2-diphenylethylene-
diamino][bis(dimethylsilyl)amido]scandium(III)
(Salphen)Sc[N(SiHMe2)2] (10)
3JHH = 3.2 Hz, Si(CH3)2H), 3.68 (dd, 2H, 2JHH = 12.8 Hz, 3JHH
=
6.4 Hz, N(CHH)2N), 2.80 (dd, 2H, 2JHH = 12.8 Hz, 3JHH = 6.4 Hz,
N(CHH)2N), 1.80 (s, 18H, C(CH3)3), 1.34 (s, 18H, C(CH3)3), 0.21
◦
(d, 12H, 3JHH = 3.2 Hz, Si(CH3)2H). 13C{ H} NMR (C6D6, 25 C,
1
Following the procedure described above, Sc[N(SiHMe2)2]3(THF)
(206 mg, 0.41 mmol) and H2Salphen (258 mg, 0.41 mmol) yielded
10 (314 mg, 96%). Anal. Calc. for C48H68N3O2ScSi2: C, 70.29; H,
=
100.5 MHz): d 169.4 (CH N), 163.7 (C-2), 139.3 (Car.), 138.0
(Car.), 130.4 (CHar.), 128.5 (CHar.), 122.6 (C-1), 57.7 (N(CH2)2N),
35.6 (C(CH3)3), 33.9 (C(CH3)3), 31.4 (C(CH3)3), 29.9 (C(CH3)3),
2.7 (Si(CH3)2H). mmax/cm−1 2101s (Si–H), 1615vs (C N), 1538s,
1388m, 1311m, 1255m, 1171m, 1052w, 1023w, 985m, 927m, 897s,
836s, 785m, 750m, 707w, 640w, 544m, 475m, 425w.
1
8.3◦6; N, 5.12. Found: C, 69.9; H, 8.9; N, 4.7%. H NMR (C6D6,
=
=
=
25 C, 400 MHz) d 8.12 (s, 1H, CH N), 8.08 (s, 1H, CH N), 7.78
(d, 2H, 4JHH = 2.4 Hz, CHar.), 7.18 (d, 2H, 4JHH = 2.4 Hz, CHar.),
6.96 (m, 10H, CHar.), 5.80 (d, 1H, 3JHH = 11.6 Hz, N(CHPh)), 5.10
(sp, 1H, 3JHH = 3.2 Hz, Si(CH3)2H), 5.00 (sp, 1H, 3JHH = 3.2 Hz,
Si(CH3)2H), 4.46 (d, 1H, 3JHH = 11.6 Hz, N(CHPh)), 1.88 (s, 18H,
[N,Nꢀ-Bis(3,5-di-tert-butylsalicylidene)-2,2-dimethylpropylene-
diamino][bis(dimethylsilyl)amido]scandium(III)
(Salpren)Sc[N(SiHMe2)2] (8)
3
C(CH3)3), 1.14 (s, 18H, C(CH3)3), 0.35 (d, 12H, JHH = 3.2 Hz,
Si(CH3)2H). 13C{ H} NMR (C6D6, 25 ◦C, 100.5 MHz): d 172.8
1
=
(CH N), 166.7 (C-2), 139.2 (Car.), 138.4 (Car.), 138.1 (Car.), 133.8
Following the procedure described above, Sc[N(SiHMe2)2]3(THF)
(191 mg, 0.37 mmol) and H2Salpren (198 mg, 0.37 mmol) yielded
8 (235 mg, 89%). Anal. Calc. for C39H66N3O2ScSi2: C, 65.97;
(CHar.), 131.1 (CHar.), 130.7 (CHar.), 130.2 (CHar.), 123.0 (C-1), 76.8
( NCHPh–), 75.1 ( NCHPh–), 35.7 (C(CH3)3), 33.8 (C(CH3)3),
31.2 (C(CH3)3), 30.1 (C(CH3)3), 2.8 (Si(CH3)2H). mmax/cm−1 2119m
(Si–H), 1611vs (C N), 1550m, 1536m, 1411m, 1317m, 1255m,
1201m, 1170m, 1026w, 1003w, 909w, 849w, 788w, 746w, 721w,
698w, 572w, 543w, 473w.
=
=
H, 9.37; N, 5.92. Found: C, 65.7; H, 9.6; N, 4.9%. 1H NMR
=
◦
=
(C6D6, 25 C, 270 MHz) d 7.75 (s, 2H, CH N), 7.72 (d, 2H,
4JHH = 1.7 Hz, CHar.), 7.12 (d, 2H, JHH = 1.8 Hz, CHar.),
4
3
2
4.89 (sp, 2H; JHH = 3.2 Hz, Si(CH3)2H), 4.00 (d, 2H, JHH
=
2
12.3 Hz, N(CHH)), 2.70 (d, 2H, JHH = 12.3 Hz, N(CHH)),
1.77 (s, 18H, C(CH3)3), 1.39 (s, 3H, C(CH3)(CH3)), 1.33 (s, 18H,
C(CH3)3), 0.70 (s, 3H, C(CH3)(CH3)), 0.29 (d, 12H, 3JHH = 3.2 Hz,
General procedure for the synthesis of scandium SALEN siloxide
complexes 11–14
Si(CH3)2H). 13C{ H} NMR (C6D6, 25 ◦C, 100.5 MHz): d 171.4
Diphenyl-tert-butylsilanol or di-tert-butylsilanol was added
to a stirred solution of the respective scandium SALEN
bis(dimethylsilyl)amido complex (SALEN)Sc[N(SiHMe2)2] in
toluene. After the yellow solution was stirred overnight, the solvent
was removed in vacuo. The yellowish powders were crystallised
from saturated hexane solutions and identified as 11–14.
1
=
(CH N), 163.9 (C-2), 139.2 (Car.), 137.9 (Car.), 130.5 (CHar.),
=
129.0 (CHar.), 122.2 (C-1), 74.4 ( NCH2–), 35.7 (C(CH3)3), 35.3
(C(CH3)2), 33.9 (C(CH3)3), 31.4 (C(CH3)3), 30.2 (C(CH3)3), 26.5
(C(CH3)(CH3)), 21.5 (C(CH3)(CH3)), 2.8 (Si(CH3)2H). mmax/cm−1
=
2119s (Si–H), 1612vs (C N), 1538m, 1384s, 1318m, 1256s, 1201w,
1170m, 1072w, 904m, 841m, 748w, 656w, 542m, 481m.
[N,Nꢀ-Bis(3,5-di-tert-butylsalicylidene)ethylenediamino](diphenyl-
tert-butylsiloxy)scandium(III) (Salen)Sc(OSitBuPh2) (11)
[N,Nꢀ-Bis(3,5-di-tert-butylsalicylidene)-trans-1,2-cyclohexyl-
enediamino][bis(dimethylsilyl)amido]scandium(III)
(R,R)-(Salcyc)Sc[N(SiHMe2)2] (9)
Following the procedure described above, (Salen)Sc[N(SiHMe2)2]
7 (130 mg, 0.18 mmol) and HOSitBuPh2 (46 mg, 0.18 mmol) gave
11 (143 mg, >99%). Anal. Calc. for C48H65N2O3ScSi: C, 72.88; H,
Following the procedure described above, Sc[N(SiHMe2)2]3(THF)
(300 mg, 0.58 mmol) and H2Salcyc (319 mg, 0.58 mmol) yielded
9 (409 mg, 97%). Anal. Calc. for C40H66N3O2ScSi2: C, 66.53; H,
1
8.2◦8; N, 3.54. Found: C, 72.5; H, 8.7; N, 3.4%. H NMR (C6D6,
t
25 C, 400 MHz) d 7.81 (d, 4H, 3JHH = 6.8 Hz, Si(C6H5)2 Bu), 7.77
1
=
9.21; N, 5.82. Found: C, 67.2; H, 9.3; N, 5.2%. H NMR (C6D6,
(d, 2H, 4JHH = 2.4 Hz, CHar.), 7.59 (s, 2H, CH N), 7.30 (m, 6H,
◦
t
4
=
=
25 C, 400 MHz) d 7.95 (s, 1H, CH N), 7.87 (s, 1H, CH N),
Si(C6H5)2 Bu), 7.03 (d, 2H, JHH = 2.4 Hz, CHar.), 3.37 (dd, 2H,
4
4
7.79 (d, 2H, JHH = 2.5 Hz, CHar.), 7.33 (d, 1H, JHH = 2.5 Hz,
2JHH = 8.8 Hz, 3JHH = 6.4 Hz, N(CHH)2N), 2.66 (dd, 2H, 2JHH
=
4
3
CHar.), 7.14 (d, 1H, JHH = 2.5 Hz, CHar.), 4.87 (sp, 2H; JHH
=
=
8.8 Hz, 3JHH = 6.4 Hz, N(CHH)2N), 1.78 (s, 18H, C(CH3)3), 1.39 (s,
3
3
t
1
3.0 Hz, Si(CH3)2H), 4.08 (ddd, 1H, JHaHa = 11.2 Hz, JHaHe
18H, C(CH3)3), 1.13 (s, 9H, Si(C6H5)2 Bu). 13C{ H} NMR (C6D6,
◦
4.9 Hz, N(CHa)), 2.37 (ddd, 1H, 3JHaHa = 12.3 Hz, 3JHaHe = 4.6 Hz,
N(CHa)), 1.84 (s, 9H, C(CH3)3), 1.81 (s, 9H, C(CH3)3), 1.48–1.39
(m, 4H, CH2,b), 1.36 (s, 18H, C(CH3)3), 1.27–1.23 (m, 4H, CH2,c),
25 C, 100.5 MHz) d 169.2 (CH N), 163.7 (C-2), 139.5 (Car.),
=
t
137.9 (Car.), 135.2 (Si(C6H5)2 Bu), 135.0 (CHar.), 130.4 (CHar.),
128.6 (Si(C6H5)2 Bu), 127.2 (Si(C6H5)2 Bu), 122.2 (C-1), 57.7
t
t
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(N(CH2)2N); 35.6 (C(CH3)3), 34.0 (C(CH3)3), 31.5 (C(CH3)3), 29.8
C52H73N2O3ScSi: C, 73.72; H, 8.68; N, 3.31. Found: C, 73.9; H,
8.8; N, 2.9%. H NMR (C6D6, 25 ◦C, 400 MHz) d 8.04 (s, 1H,
t
1
(C(CH3)3), 27.0 (Si(C6H5)2 Bu). mmax/cm−1 1619 s (C N), 1537m,
=
4
=
=
1257w, 1170w, 1113w, 856w, 722 w, 607w, 542w, 503w, 418w.
CH N), 8.02 (s, 1H, CH N), 7.75 (d, 2H, JHH = 2.5 Hz, CHar.),
7.19 (d, 2H, 4JHH = 2.5 Hz, CHar.), 6.96 (m, 8H, CHar.), 6.86 (d, 2H,
3JHH = 2.0 Hz, CHar.), 5.84 (d, 1H, JHH = 10.9 Hz, N(CHPh)),
3
[N,Nꢀ-Bis(3,5-di-tert-butylsalicylidene)-2,2-dimethylpropylene-
diamino](diphenyl-tert-butylsiloxy)scandium(III)
(Salpren)Sc(OSitBuPh2) (12)
4.61 (s, 1H, SiHtBu2) 4.46 (d, 1H, 3JHH = 10.4 Hz, N(CHPh)), 1.88
(s, 9H, C(CH3)3), 1.86 (s, 9H, C(CH3)3), 1.17 (s, 9H, C(CH3)3),
1.14 (s, 18H, SiHtBu2), 1.12 (s, 9H, C(CH3)3). 13C{ H} NMR
1
Following the procedure described above, (Salpren)Sc[N-
(SiHMe2)2] 8 (86 mg, 0.12 mmol) and HOSitBuPh2 (31 mg,
0.12 mmol) gave 12 (99 mg, >99%). Anal. Calc. for
C51H71N2O3ScSi: C, 73.52; H, 8.59; N, 3.36. Found: C, 72.7; H, 9.0;
◦
=
(C6D6, 25 C, 100.5 MHz) d 172.4 (CH N), 167.1 (C-2), 139.2
(Car.), 137.9 (Car.), 130.7 (CHar.), 130.2 (CHar.), 123.0 (C-1), 76.8
=
=
( NCHPh–), 75.3 ( NCHPh–), 35.7 (C(CH3)3), 33.8 (C(CH3)3),
31.2 (C(CH3)3), 30.0 (C(CH3)3), 27.5 (SiHtBu2). IR (Nujol):
N, 3.3%. 1H NMR (C6D6, 25 ◦C, 270 MHz) d 7.90 (d, 4H, 3JHH
=
mmax/cm−1 2096m (Si–H), 1610s (C N), 1536m, 1316m, 1255m,
1201w, 1170m, 981m, 837m, 721m, 699w, 572w, 545w, 473w.
=
t
4
8.1 Hz, Si(C6H5)2 Bu), 7.77 (d, 2H, JHH = 2.7 Hz, CHar.), 7.59
t
4
=
(s, 2H, CH N), 7.17 (m, 6H, Si(C6H5)2 Bu), 7.06 (d, 2H, JHH
=
2.7 Hz, CHar.), 3.70 (d, 2H, 2JHH = 11.8 Hz, N(CHH)), 2.45 (d, 2H,
2JHH = 11.8 Hz, N(CHH)), 1.79 (s, 18H, C(CH3)3), 1.55 (s, 3H,
Crystallography
t
C(CH3)(CH3)), 1.38 (s, 18H, C(CH3)3), 1.21 (s, 9H, Si(C6H5)2 Bu),
Crystals of 6, 9 and 11 were grown by standard techniques from
saturated solutions using n-hexane at −35 ◦C. Suitable single
crystals of dimensions (mm) 0.34 × 0.25 × 0.14 (6), 0.64 ×
0.44 × 0.28 (9) and 0.29 × 0.19 × 0.10 (11) were selected in a
glovebox, coated with paratone-N, fixed in a nylon loop, mounted
on a Bruker SMART 2 K CCD diffractometer (6), coated with
perfluorinated polyether, fixed in a glass capillary and mounted on
a Nonius KappaCCD diffractometer (MACH 3) equipped with
a rotating anode (Nonius FR591) (9, 11). X-Ray diffraction data
were collected at 123 K (6, 11) and 173 K (9) by using graphite-
0.53 (s, 3H, C(CH3)(CH3)). 13C{ H} NMR (C6D6, 25 ◦C, 100.5
1
=
MHz) d 171.6 (CH N), 164.0 (C-2), 139.3 (Car.), 137.9 (Car.), 135.3
t
t
(Si(C6H5)2 Bu), 135.0 (CHar.), 130.4 (CHar.), 129.6 (Si(C6H5)2 Bu),
129.1 (Si(C6H5)2 Bu), 128.1 (CHar.), 122.2 (C-1), 74.6 (N(CH2)2N),
t
35.7 (C(CH3)3), 35.3 (C(CH3)2), 33.9 (C(CH3)3), 31.5 (C(CH3)3),
t
30.2 (C(CH3)3), 27.1 (C(CH3)(CH3)), 26.6 (Si(C6H5)2 Bu), 21.5
(C(CH3)(CH3)). mmax/cm−1 1612 s (C N), 1539m, 1257w, 1170w,
=
1113w, 906w, 842w, 722w, 701w, 657w, 543w, 484w.
[N,Nꢀ-Bis(3,5-di-tert-butylsalicylidene)-trans-1,2-cyclohexyl-
enediamino](diphenyl-tert-butylsiloxy)scandium(III)
(R,R)-(Salcyc)Sc(OSitBuPh2) (13)
˚
monochromated Mo-Ka radiation (k = 0.71073 A) and x-scans
(6), φ- and x-scans (9, 11).40,41 The unit cell parameters were
obtained by least-squares refinement of 15687, 10242 and 7219 (6,
9, 11) reflections and a total number of 49571, 70269 and 30449
reflections were measured, 7798, 18030 and 9285 of which were
unique (Rint = 0.100, 0.044 and 0.061, respectively). Raw data were
reduced and scaled with programs SAINT40 and DENZO42 and
corrections for absorption effects were applied using SHELXTL43
and SORTAV.44 The structures were solved by a combination of
direct methods (SHELXS45 and SIR9246) and difference-Fourier
syntheses (SHELXL-9747). For 9, two independent molecules in
the space group P21 were found. Refinement was not possible
using the centrosymmetric space group P21/c. The absolute
structure of the molecule actually chosen was determined by
the Flack parameter [x = 0.05(3)].48 All non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were included on
calculated positions, riding on their carrier atoms, while their
isotropic displacement parameters were linked to the equivalent
Following the procedure described above, (R,R)-(Salcyc)Sc-
[N(SiHMe2)2] 9 (242 mg, 0.34 mmol) and HOSitBuPh2 (86 mg,
0.34 mmol) gave 13 (283 mg, >99%). Anal. Calc. for
C52H71N2O3ScSi: C, 73.90; H,◦8.47; N, 3.31. Found: C, 73.5; H, 8.8;
1
=
N, 3.3%. H NMR (C6D6, 25 C, 400 MHz) d 7.85 (s, 1H, CH N)
3
t
=
7.83 [d, 4H, JHH = 12 Hz, Si(C6H5)2 Bu], 7.80 (s, 1H, CH N),
4
4
7.25 (d, 2H, JHH = 2.4 Hz, CHar.), 7.33 (d, 1H, JHH = 2.5 Hz,
t
4
CHar.), 7.10 [m, 6H, Si(C6H5)2 Bu], 7.00 (d, 1H, JHH = 2.4 Hz,
CHar.), 3.57 (ddd, 1H, 3JHaHa = 11.6 Hz, 3JHaHe = 4.1 Hz, N(CHa)),
3
3
2.30 (ddd, 1H, JHaHa = 10.8 Hz, JHaHe = 3.2 Hz, N(CHa)), 1.83
(s, 18H, C(CH3)3), 1.65 (m, 4H, CH2,b), 1.41 (s, 18H, C(CH3)3),
t
1
1.36 (m, 4H, CH2,c), 1.15 (s, 9H, Si(C6H5)2 Bu). 13C{ H} NMR
◦
=
(C6D6, 25 C, 100.5 MHz) d 168.4 (CH N), 164.1 (C-2), 163.4
ꢀ
=
(C-2 ), 160.8 (CH N), 139.4 (Car.), 137.8 (Car.), 137.0 (Car.), 135.2
(Si(C6H5)2 Bu), 129.7 (CHar.), 129.3 (CHar.), 129.1 (CHar.), 128.9
t
displacement parameter of their parent atom. A potentially
t
t
(CHar.), 128.5 (Si(C6H5)2 Bu), 128.0 (Si(C6H5)2 Bu), 122.5 (C-1),
70.6 (N(CHa)), 66.0 (N(CHa)), 35.8 (C(CH3)3), 34.1 (C(CH3)2),
32.3 (CH2,b), 31.8 (C(CH3)3), 30.2 (C(CH3)3), 26.7 (CH2,b), 26.7
(Si(C6H5)2 Bu), 25.4 (CH2c), 25.0 (CH2,c). mmax/cm 1614vs (C N),
1537m, 1536m, 1377s, 1256m, 1234w, 1200w, 1171m, 1110m,
982m, 840w, 819w, 722w, 702w, 544m, 485w.
3
˚
accessible area of 804 A has been calculated for 9. Due to severe
disorder no solvent molecule could be located. Thus the BYPASS
method49 (as implemented as the ‘SQUEEZE option’ in the
program PLATON50) was applied to account for the disordered
solvent contribution to the structure factors in the final refinement.
The number of refined parameters was 495, 865 and 494. The
maximum residual electron density was 0.32, 1.17 and 0.28 and
t
−1
=
[N,Nꢀ-Bis(3,5-di-tert-butylsalicylidene)-1,2-diphenyl-
ethylenediamino](di-tert-butylsiloxy)scandium(III)
(Salphen)Sc(OSiHtBu2) (14)
−3
˚
minimum −0.35, −0.70 and −0.30 e A , respectively. Further
details of the refinement and crystallographic data are listed in
Table 3. All plots were generated using the program ORTEP-3.51
CCDC reference numbers 284496–284498.
Following the procedure described above, (Salphen)Sc-
[N(SiHMe2)2] 10 (206 mg, 0.41 mmol) and HOSiHtBu2
(258 mg, 0.41 mmol) gave 14 (314 mg, 96%). Anal. Calc. for
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b513370j
1048 | Dalton Trans., 2006, 1041–1050
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©

View Article Online
Table 3 Crystallographic data for (Salpren)Sc(NiPr2) (6), (R,R)-(Salcyc)Sc[N(SiHMe2)2] (9) and (Salen)Sc(OSitBuPh2) (11)
6
9
11
Chemical formula
Mr
C44H73N3O2Sc
721.01
P21/c
15.9991(9)
11.0506(6)
25.1676(13)
90
97.203(1)
90
4414.5(4)
4
1580
123
1.085
C40H66N3O2Si2Sc
722.10
P21
14.5528(1)
12.6006(1)
26.9905(2)
90
103.7265(3)
90
4808.00(6)
4
1568
173
0.998
C48H65N2O3SiSc
791.07
P1
¯
Space group
˚
a/A
12.0560(2)
14.0187(2)
16.0392(3)
66.9842(6)
75.4467(6)
67.8923(6)
2294.25(7)
2
852
123
1.1451
0.227
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
V/A
Z
3
˚
F(000)
T/K
Dc/g cm−3
l/mm−1
0.203
0.0600, 0.1437
1.066
0.233
0.0584, 0.1647
1.056
a
b
R1 (obsd), wR2 (all)
0.0594, 0.1176
1.028
Sc
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
2
1/2
2
a R1 = (|Fo| − |Fc|)/ |Fo|. b wR2 = { [w(Fo − Fc2)2]/ [w(Fo2)2]}
.
c S = [ w(Fo − Fc2)2/(no–np)]1/2
.
Macromolecules, 1997, 30, 171; X.-G. Zhou, X.-Q. Yu, J.-S. Huang,
S.-G. Li, L.-S. Li and C.-M. Che, Chem. Commun., 1999, 1789; C. E.
Song, C. R. Oh, E. J. Roh and D. J. Choo, Chem. Commun., 2000, 1743;
K. Bernardo, S. Leppard, A. Robert, G. Commenges, F. Dahan and B.
Meunier, Inorg. Chem., 1996, 35, 381; T. Katsuki, Coord. Chem. Rev.,
1995, 140, 189; E. N. Jacobsen, W. Zhang, A. R. Muci, J. R. Ecker and
L. Deng, J. Am. Chem. Soc., 1991, 113, 7063.
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft (SPP 1166) and
the Fonds der Chemischen Industrie for generous support. C. M.
thanks Dr Andreas Fischbach for providing the silanol samples.
8 E. N. Jacobsen, Catalytic Asymmetric Synthesis, ed. I. Ojima, VCH,
Weinheim, 1993, p. 159; E. N. Jacobsen, Comprehensive Organometallic
Chemistry II, ed. G. Wilkinson, F. G. A. Stone, E. W. Abel and
L. S. Hegedus, Pergamon Press, New York, 1995, vol. 12, ch. 11.1;
J. F. Larrow and E. N. Jacobsen, Top. Organomet. Chem., 2004, 6, 123;
P. G. Cozzi, Chem. Soc. Rev., 2004, 33, 410; T. Katsuki, Chem. Soc.
Rev., 2004, 33, 437.
9 O. Runte, T. Priermeier and R. Anwander, Chem. Commun., 1996,
1385.
10 M.-H. Lin and T. V. RajanBabu, Org. Lett., 2002, 9, 1607.
11 P. N. O’Shaughnessy, P. D. Knight, C. Morton, K. M. Gillespie and
P. Scott, Chem. Commun., 2003, 1770.
12 For intrinsic organoscandium polymerization catalysis, see: F. Estler,
G. Eickerling, E. Herdtweck and R. Anwander, Organometallics, 2003,
22, 1212; Y. Luo, J. Baldamus and Z. Hou, J. Am. Chem. Soc., 2004,
126, 13910; X. Li, J. Baldamus and Z. Hou, Angew. Chem., Int.
Ed., 2005, 44, 962.
13 For reviews on Sc(OTf)3 promoted Lewis acid catalysis, see: S.
Kobayashi, Eur. J. Inorg. Chem., 1999, 15; S. Kobayashi and K. Manabe,
Acc. Chem. Res., 2002, 35, 209.
14 S. Fukuzawa, Y. Komuro, N. Nakano and S. Obara, Tetrahedron Lett.,
2003, 44, 3671.
15 R. Anwander, Top. Organomet. Chem., 1999, 2, 1.
16 For examples, see: H. Chen and R. D. Archer, Inorg. Chem., 1994, 33,
5195; R. D. Archer, H. Chen and L. C. Thompson, Inorg. Chem., 1998,
37, 2089; W. Xie, M. J. Heeg and P. G. Wang, Inorg. Chem., 1999, 38,
2541.
17 W. J. Evans, C. H. Fujimoto and J. W. Ziller, Chem. Commun., 1999,
311; W. J. Evans, C. H. Fujimoto and J. W. Ziller, Polyhedron, 2002,
1683.
References
1 For review articles, see: S. D. Ittel, L. K. Johnson and M. Brookhart,
Chem. Rev., 2000, 100, 1169; G. W. Coates, P. D. Hustad and S.
Reinartz, Angew. Chem., Int. Ed., 2002, 41, 2236; V. C. Gibson and
S. K. Spitzmesser, Chem. Rev., 2003, 103, 283.
2 For review articles, see: W. E. Piers and D. J. H. Emslie, Coord.
Chem. Rev., 2002, 233–234, 131; P. Mountford and B. D. Ward, Chem.
Commun., 2003, 1797.
3 For examples of dialkoxide(aryloxide) supported Ln complexes, see:
C. J. Schaverien, N. Meijboom and A. G. Orpen, J. Chem. Soc., Chem.
Commun., 1992, 124; P. L. Arnold, L. S. Natarajan, J. J. Hall, S. J.
Bird and C. Wilson, J. Organomet. Chem., 2002, 647, 205; C.-X. Cai,
L. Toupet, C. W. Lehmann and J.-F. Carpentier, J. Organomet. Chem.,
2003, 683, 131; D. V. Gribkov, K. C. Hultzsch and F. Hampel, Chem.
Eur. J., 2003, 9, 4796; C.-X. Cai, A. Amgoune, C. W. Lehmann and
J.-F. Carpentier, Chem. Commun., 2004, 330; D. V. Gribkov and K. C.
Hultzsch, Chem. Commun., 2004, 730; K. C. Hultzsch, F. Hampel
and T. Wagner, Organometallics, 2004, 23, 2601; F. M. Kerton, A. C.
Whitwood and C. E. Willans, Dalton Trans., 2004, 2237.
4 For Schiff base organolanthanide complexes, see: T. M. Ovitt and G. W.
Coates, J. Am. Chem. Soc., 1999, 121, 4072; C. M. Mascarenhas, S. P.
Miller, P. S. White and J. P. Morken, Angew. Chem., Int. Ed., 2001,
40, 601; D. J. H. Emslie, W. E. Piers and R. McDonald, J. Chem.
Soc., Dalton Trans., 2002, 293; D. J. H. Emslie, W. E. Piers, M. Parvez
and R. McDonald, Organometallics, 2002, 21, 4226; A. Lara-Sanchez,
A. Rodriguez, D. L. Hughes, M. Schormann and M. Bochmann,
J. Organomet. Chem., 2002, 663, 63; F. Lauterwasser, P. G. Hayes, S.
Bra¨se, W. E. Piers and L. L. Schafer, Organometallics, 2004, 23, 2234.
5 For applications in polymerisation catalysis, see: Z. Hou and Y. Wakat-
suki, Coord. Chem. Rev., 2002, 231, 1; J. Gromada, J.-F. Carpentier and
A. Mortreux, Coord. Chem. Rev., 2004, 248, 397.
18 P. Blech, C. Floriani, A. Chiesi-Villa and C. Guastino, J. Chem. Soc.,
Dalton Trans., 1990, 3557.
19 D. Rutherford and D. A. Atwood, Organometallics, 1996, 15, 4417.
20 For heteroleptic silylamido chloro complexes, see: M. Niemeyer,
Z. Anorg. Allg. Chem., 2002, 628, 647; H. C. Aspinall, D. C. Bradley,
M. B. Hursthouse, K. D. Sales, N. P. C. Walker and B. Hussain, J. Chem.
Soc., Dalton Trans., 1989, 623; D. J. Berg and R. A. L. Gendron,
Can. J. Chem., 2000, 78, 454; M. Karl, G. Seybert, W. Massa, S.
Agarwal, A. Greiner and K. Dehnicke, Z. Anorg. Allg. Chem., 1999,
625, 1405; J. Collin, N. Giuseppone, N. Jaber, A. Domingos, L. Maria
and I. Santos, J. Organomet. Chem., 2001, 628, 271.
6 For applications in fine chemical catalysis, see: H. C. Aspinall, Chem.
Rev., 2002, 102, 1807; K. Hultzsch, Adv. Synth. Catal., 2005, 347, 367.
7 For examples, see: J. M. McInnes, D. Swallow, A. J. Blake and P.
Mountford, Inorg. Chem., 1998, 37, 5970; V. I. Tararov, D. E. Hibbs,
M. B. Hursthouse, N. S. Ikonnikov, K. M. Abdul Malik, M. North, C.
Orizu and Y. N. Belekon, Chem. Commun., 1998, 387; X.-G. Zhou, J.-S.
Huang, P.-H. Ko, K.-K. Cheung and C.-M. Che, J. Chem. Soc., Dalton
Trans., 1999, 3303; T. Repo, M. Klinga, P. Pietika¨inen, M. Leskela¨,
A.-M. Uusitalo, T. Pakkanen, K. Hakala, P. Aaltonen and B. Lo¨fgren,
21 F. Estler, Dissertation, Technische Universita¨t Mu¨nchen, 2003.
This journal is
The Royal Society of Chemistry 2006
Dalton Trans., 2006, 1041–1050 | 1049
©

View Article Online
22 S. A. Fairhurst, D. L. Hughes, U. Kleinkes, G. J. Leigh, J. R. Sanders
and J. Weisner, J. Chem. Soc., Dalton Trans., 1995, 321.
23 F. Estler, E. Herdtweck and R. Anwander, J. Chem. Soc., Dalton Trans.,
2002, 3088.
33 A. Fischbach, G. Eickerling, W. Scherer, E. Herdtweck and
R. Anwander, Z. Naturforsch., Teil B, 2004, 59, 1353.
34 D. A. Atwood, M. S. Hill, J. A. Jegier and D. Rutherford,
Organometallics, 1997, 16, 2659.
24 R. Anwander, O. Runte, J. Eppinger, G. Gerstberger, E. Herdtweck and
M. Spiegler, J. Chem. Soc., Dalton Trans., 1998, 847.
35 K. J. Covert, D. R. Neithamer, M. C. Zonnevylle, R. E. LaPointe, C. P.
Schaller and P. T. Wolczanski, Inorg. Chem., 1991, 30, 2494.
36 V. Lorenz, A. Fischer and F. T. Edelmann, J. Organomet. Chem., 2002,
647, 245.
37 V. Lorenz, A. Fischer, K. Jacob, W. Bru¨ser and F. T. Edelmann, Chem.
Eur. J., 2001, 7, 848.
38 D. G. Mullen and G. Barany, J. Org. Chem., 1988, 53, 5240; T. J. Barton
and C. R. Tully, J. Organomet. Chem., 1979, 172, 11; R. Goikhman,
M. Aizenberg, H.-B. Kraatz and D. Milstein, J. Am. Chem. Soc., 1995,
117, 5865.
39 K. Rossmanith and C. Auer-Welsbach, Monatsh. Chem., 1965, 96, 602.
40 Bruker (1995); SMART, SAINT and XPREP. Area detector control
and data integration and reduction software. Bruker Analytical X-ray
Instruments Inc., Madison, WI, USA.
41 COLLECT, Data Collection Software, Nonius BV, 1998.
42 Z. Otwinowski and W. Minor, Processing of X-ray Diffraction Data
Collected in Oscillation Mode, Methods Enzymol., 1997, 276, 307.
43 G. M. Sheldrick, SHELXTL, University of Go¨ttingen, Germany, 2001.
44 R. H. Blessing, Acta Crystallogr., Sect. A, 1995, 51, 33.
45 G. M. Sheldrick, SHELXS, University of Go¨ttingen, Germany, 2001.
46 A. Altomare, G. Cascarano, C. Giacovazzo and A. Guagliardi, J. Appl.
Crystallogr., 1993, 26, 343.
47 G. M. Sheldrick, SHELXL-97, Program for Crystal Structure
Refinement, University of Go¨ttingen, Go¨ttingen, Germany, 1997.
48 H. D. Flack, Acta Crystallogr., Sect. A, 1983, 39, 876.
49 P. van der Sluis and A. L. Spek, Acta Crystallogr., Sect. A, 1990, 46,
194–201.
25 (a) For other Sc–N(amido) bond distances, see: K. Dehnicke and
A. Greiner, Angew. Chem., 2003, 115, 1378; (b) L. K. Knight,
W. E. Piers, P. Fleurat-Lessard, M. Parvez and R. McDonald,
Organometallics, 2004, 23, 2087; (c) M. M. Olmstead, A. de
Bettencourt-Dias, J. C. Duchamp, S. Stevenson, D. Marciu, H. C.
Dorn and A. L. Balch, Angew. Chem., Int. Ed., 2001, 40, 1223; (d) S.
Stevenson, G. Rice, T. Glass, K. Harich, F. Cromer, M. R. Jordan, J.
Craft, E. Hadju, R. Bible, M. M. Olmstead, M. Maitra, A. J. Fisher,
A. L. Balch and H. C. Dorn, Nature, 1999, 401, 55; (e) M. M. Olmstead,
H. Man Lee, J. C. Duchamp, S. Stevenson, D. Marciu, H. C. Dorn and
A. L. Balch, Angew. Chem., Int. Ed., 2003, 42, 900.
26 For the synthesis of Sn and Pb Salen complexes according to the
silylamide route, see: M. C. Kuchta, J. M. Hahn and G. Parkin, J. Chem.
Soc., Dalton Trans., 1999, 3559.
27 C. Cope´ret, M. Chabanas, R. P. Saint-Arroman and J.-M. Basset,
Angew. Chem., Int. Ed., 2003, 42, 156.
28 W. A. Herrmann, A. W. Stumpf, T. Priermeier, S. Bogdanovic, V.
Dufaud and J.-M. Basset, Angew. Chem., Int. Ed. Engl., 1996, 35, 2803;
J.-Y. Piquemal, S. Halut and J.-M. Bre´geault, Angew. Chem., Int. Ed.,
1998, 37, 1146.
29 R. Anwander, Chem. Mater., 2001, 13, 4419.
30 R. Anwander, H. W. Go¨rlitzer, G. Gerstberger, C. Palm, O. Runte and
M. Spiegler, J. Chem. Soc., Dalton Trans., 1999, 3611.
31 A. Fischbach, M. G. Klimpel, M. Widenmeyer, E. Herdtweck,
W. Scherer and R. Anwander, Angew. Chem., Int. Ed., 2004, 43,
2234.
50 A. L. Spek, J. Appl. Crystallogr., 2003, 36, 7.
32 I. Nagl, M. Widenmeyer, E. Herdtweck, G. Raudaschl-Sieber and
R. Anwander, Microporous Mesoporous Mater., 2001, 44–45, 311.
51 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565.
52 F. H. Allen, Acta Crystallogr., Sect. B, 2002, 58, 380.
1050 | Dalton Trans., 2006, 1041–1050
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