Synthesis and thermal reactivity of organoscandium and yttrium complexes of sterically less bulky salicylaldiminato ligands

Article abstract of DOI:10.1039/b303097k

Scandium and yttrium bis(ligand) mono(alkyl) complexes, of N-phenyl (L ¹) N-2-isopropylphenyl (L²) and N-mesityl (L³) substituted ortho-tert-butylsalicylaldiminato ligands were prepared by alkane elimination from [M(CH

Full text of DOI:10.1039/b303097k

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Synthesis and thermal reactivity of organoscandium and yttrium
complexes of sterically less bulky salicylaldiminato ligands†
David J. H. Emslie, Warren E. Piers* and Masood Parvez
Department of Chemistry, University of Calgary, 2500 University Drive, N. W, Calgary,
Alberta, Canada, T2N 1N4. E-mail: wpiers@ucalgary.ca; Fax: 403 289 9488;
Tel: 403 220 5746
Received 18th March 2003, Accepted 30th April 2003
First published as an Advance Article on the web 14th May 2003
Scandium and yttrium bis(ligand) mono(alkyl) complexes, of N-phenyl (L1) N-2-isopropylphenyl (L2) and N-mesityl
(L3) substituted ortho-tert-butylsalicylaldiminato ligands were prepared by alkane elimination from [M(CH2SiMe2R)3-
(THF)2] (R = Me, Ph) and two equivalents of proteo ligand (HL). The resulting [L2M(THF)n(CH2SiMe2R)] (n = 0–2,
L = L1 (1), L2 (2), L3 (3)) complexes are thermally unstable, decomposing rapidly between Ϫ20 and 20 ЊC. In order
to gain insight in to ligand features necessary to impart thermal stability in early transition metal organometallic
chemistry, the decomposition pathways of 1–3 have been investigated and compared with more sterically congested
N-2,6-diisopropylphenyl substituted analogues. Compounds 1 and 2 decompose rapidly and cleanly at room
temperature by 1,3-migration of the entire CH2SiMe2R group to the aldimine carbon. By contrast, L3 mono(alkyls) 3
decompose cleanly by metallation of an ortho-C6H2Me3 group. In the case of yttrium, the metallated alkyl undergoes
subsequent 1,3-migration to the aldimine carbon, forming a five-membered C4N-ring.
of which are remarkably thermally robust, decomposing
Introduction
cleanly (130 ЊC, 3 days) by metallation of an isopropyl group,
Organoscandium and yttrium chemistry has been dominated
followed by rapid 1,3-migration of the newly formed alkyl
by the bent metallocene or Cp-amido ligand environments,1 but
to the aldimine carbon.8 Bochmann and co-workers have
recent years have seen a surge of interest in alternative ancil-
employed the mesityl substituted ligand L3, among others, to
laries.2 While there is a huge variety of ligands to choose from,
prepare similar bis and mono ligand alkyl compounds of Sc
steric tunability, resistance to ligand redistribution or metal-
and Y.9
lation and stability in the presence of reactive M–C or M–H
It is clear from both our and Bochmann’s work that the
bonds are among the requirements for an effective ancillary for
supporting organogroup 3 metal chemistry. Therefore, despite
the efforts of many groups, truly effective non-cyclopentadienyl
nature of the N substitutent of the salicylaldiminato ligand has
a profound effect on the behaviour of the resulting organo-
scandium and yttrium complexes of general formula LMR2-
(THF)n and L2MR(THF)n. Although these derivatives are not
ligand environments for the development of the organometallic
chemistry of group 3 metals and the lanthanides are still rare.3
particularly useful as single-site olefin polymerization catalysts,
The salicylaldiminato ligand framework has a long history as
an ancillary ligand in coordination and organometallic chem-
they do have potential in the polymerization of ε-caprolactone9
and as catalyst precursors for the hydroamination of C᎐C and
᎐
istry. Recently, bulky derivatives have been employed in the
preparation of nickel(),4 chromium(),5 titanium()6 and
zirconium()7 olefin polymerization catalysts and these ligands
are therefore promising candidates for supporting organogroup
3 metal derivatives. Using a bulky N-2,6-diisopropylphenyl
substituted salicylaldiminato ligand (L4, Chart 1) we prepared a
range of both di(alkyl) and mono(alkyl) complexes, the latter
10
᎐
C᎐C bonds. The mono-ligand LMR2(THF)n family is prone
᎐
to ligand redistribution reactions and therefore we have
focussed on the bis-ligand derivatives L2MR(THF)n. While the
complexes employing bulky ligand L4 are quite thermally stable,
less sterically imposing ligands would be expected to lead to
more reactive compounds; here we report the preparation and
thermal stability of the bis-ligand Sc and Y complexes of the
ligands L1, L2 and L3. Along with metallation/migration
deactivation pathways, we identify direct migration of the metal
alkyl function to the imine carbon as being a significant thermal
reactivity mode.
Results and discussion
Synthesis and characterization of [(Ln)2M(CH2SiMe2R)(THF)n]
complexes
The method of choice for preparing these compounds is alkane
elimination using M(CH2SiMe2R)3(THF)2 (R = CH3, Ph) and
HLn. The cleanest reactions occur when R = Ph due to the
superior stability and easier purification of this tris-alkyl start-
ing material; however, in some instances the alkane by-product
Me3SiPh is difficult to remove from the product during work-
up. In this case, use of the R = CH3 tris-alkyl is preferred, since
Me4Si is easily dealt with due to its volatility.
Bis-ligand mono-alkyl scandium and yttrium complexes of
the small N-phenyl substituted ligand (L1) were thus generated
cleanly in situ from [M(CH2SiMe2Ph)3(THF)2] and 2 HL1 in
d8-toluene at Ϫ20 ЊC (Scheme 1). The scandium complex
Chart 1
† Electronic supplementary information (ESI) available: Further
experimental details. See http://www.rsc.org/suppdata/dt/b3/b303097k/
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
D a l t o n T r a n s . , 2 0 0 3 , 2 6 1 5 – 2 6 2 0
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Scheme 3
was isolated in 68% yield and characterised by elemental analy-
sis and NMR spectroscopy. As with the N-2,6-diisopropyl-
phenyl substituted analogue, [(L4)2Sc(CH2SiMe3)],8 only a
single isomer of 3-ScMe, in which both salicylaldiminato ligands
are equivalent, could be observed by NMR spectroscopy
(Ϫ80 to 20 ЊC). The O-donors likely occupy axial positions of a
trigonal bipyramid, which is the preferred arrangement on the
basis of steric and electronic factors.8
Scheme 1
[(L1)2Sc(CH2SiMe2Ph)(THF)] (1-ScPh; the subscripted “Ph” in
compound designations refers to the alkyl group substitutent)
shows inequivalent ligand environments by 1H and 13C NMR at
Ϫ30 ЊC, and is likely octahedral with trans-disposed phenoxy
groups, and cis imines. This arrangement is also adopted by
related trigonal bipyramidal complexes in order to minimise
steric interactions between salicylaldiminato ligands.8 For the
larger yttrium metal, the resulting complex [(L1)2Y(CH2-
SiMe2Ph)(THF)2] (1-YPh) is seven coordinate with two THF
The yttrium complexes [(L3)2Y(CH2SiMe2R)(THF)] (3-YR; R
= Me, Ph) were prepared similarly but at Ϫ20 ЊC due to lower
thermal stability. The larger metal yttrium retains one molecule
of THF, and d8-toluene solutions of 3-YR clearly show the
presence of three isomers at Ϫ40 ЊC; one major and two minor
(96 : 2 : 2% for 3-YMe, 92 : 6 : 2% for 3-YPh), which were investi-
gated by 1H NMR, 2D-COSY and 2D-EXSY spectroscopy. All
three isomers display a pair of resonances between Ϫ0.5 and
1
ligands flanking the alkyl group. H NMR spectra of 1-YPh
(Ϫ40 to Ϫ80 ЊC) show a single set of ligand and THF reson-
ances, but diastereotopic YCH2 and SiMe2Ph groups. These
data are consistent with a single isomer, most likely of pen-
tagonal bipyramidal geometry with the phenoxy groups
occupying axial sites. Due to the thermal sensitivity of these
compounds (vide infra), they were not isolated.
2
Ϫ1.5 ppm for diastereotopic YCH2 protons (dd, JH,H 12 Hz,
2JH,Y 2 Hz). The predominant species shows two CH᎐NMs and
᎐
six C6H2Me3 signals due to inequivalent ligands which lack
top–bottom symmetry, and is likely isostructural with 1-ScPh.
Less information is available for the two minor isomers of 3-YR
since resonances other than the YCH2 protons are obscured by
those of the major isomer. We speculate that they are six-
coordinate geometric isomers accessible via a transient five-
coordinate intermediate. 2D-EXSY experiments show that the
three isomers are in dynamic equilibrium, and since addition of
100 equivalents of d8-THF to solutions of 3-YMe or 3-YPh did
not change the ratio of isomers, none of the three solution
species may be attributed to the five-coordinate, THF free
complex.
Reaction of [M(CH2SiMe2Ph)3(THF)2] with two equivalents
of the moderately more sterically encumbered HL2, incorpor-
ating an ortho isopropyl group, in n-hexane at or below 0 ЊC
gave solutions of [(L2)2M(CH2SiMe2Ph)(THF)] (2-ScPh, 2-YPh,
Scheme 2). While somewhat more thermally stable than the
N-phenyl alkyls described above, concentration gave bright
yellow oils for both compounds 2, precluding satisfactory
analytical data. However, their identity as mono-THF adducts
of similar structure to 1-ScPh could be unambiguously assigned
1
by H NMR in d8-toluene at 10 ЊC. Thus, in the yttrium com-
plexes, addition of each N-aryl isopropyl substituent prevents
THF coordination, since the complexes of L4 are THF free even
for yttrium.
Thermal reactivity of [(Ln)2M(CH2SiMe2R)(THF)n] complexes
The alkyl compounds incorporating the less bulky ligands
L1 and L2 decompose rapidly and cleanly at or below room
temperature by 1,3-migration of the entire CH2SiMe2Ph
group to the aldimine carbon (Scheme 4). For the least
sterically protected N–Ph compounds, five-coordinate [(L1)-
Sc{(tBuC6H3O)CH(CH2SiMe2Ph)NPh}(THF)] (4-ScPh) and
octahedral [(L1)Y{(tBuC6H3O)CH(CH2SiMe2Ph)NPh}(THF)2]
(4-YPh) were obtained as analytically pure, brick-red solids from
in situ generated toluene solutions of 1-MPh. Both compounds
are formed as a single diastereomer. The complexes were
characterised by elemental analysis, NMR spectroscopy and in
the case of 4-YPh, by X-ray crystallography. Additionally, the
analogous scandium compound 4-ScMe, formed by migration
of a CH2SiMe3 group from in situ generated 1-ScMe, was charac-
terized crystallographically to show the structural features of
compounds 4-ScR.
Scheme 2
Similar alkane elimination protocols lead to the N-mesityl
substituted complexes [(L3)2M(CH2SiMe2R)(THF)n] (M = Sc,
R = Me, n = 0, 3-ScMe; M = Y, R = Me, Ph, n = 1 3-YR)
which were isolated in good yield as yellow (M = Sc) or white
(M = Y) solids (Scheme 3). Related mono(ligand), bis(alkyl)
[(L3)M(CH2SiMe3)2(THF)] (M = Sc, Y) complexes as well as
[(L3)3Y] were recently reported by Bochmann and co-workers.9
The scandium complex [(L3)2Sc(CH2SiMe3)] (3-ScMe), which is
stable for short periods of time in solution at room temperature,
In the solid state, the structure of 4-ScMe (which contains
three near identical molecules in the unit cell) is distorted
trigonal bipyramidal, with the phenoxy group of the new
amidoaryloxide ligand and the imine group of the intact
D a l t o n T r a n s . , 2 0 0 3 , 2 6 1 5 – 2 6 2 0
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angle between the axial and equatorial phenoxy groups
(O11–Sc1–O12 110.92(7)Њ) arises in order to minimise steric
interactions between tert-butyl groups.
1H- and 13C NMR spectra of the six-coordinate yttrium
complex, 4-YPh, show only one set of resonances for co-
ordinated THF at room temperature. However, unlike 4-ScR
which exists as a single isomer in solution (Ϫ80 to 20 ЊC), low-
1
temperature H NMR spectra of 4-YPh are complicated by the
presence of several isomers. Addition of d8-THF to solutions
of 4-YPh in d8-toluene leads to the disappearance of signals for
coordinated THF, indicating that the coordinated THF in 4-YPh
is labile in solution. In the solid state, 4-YPh, adopts a distorted
octahedral geometry with the phenoxide groups trans to one
another, and cis-disposed THF donors (Fig. 2).
Scheme 4
salicylaldimine ligand in the axial sites (Fig. 1). In related
[(L4)2ScR] complexes,8 the axial positions are occupied by
phenoxy groups, and the switch to an axial imine group in
4-ScMe is most likely a result of the increased steric bulk and
decreased planarity of the amidoaryloxide ligand relative to
that of an intact salicylaldiminate. In an effort to minimise
steric interactions, the trigonal bipyramidal geometry of 4-ScMe
is quite distorted, with an angle of 165.20(8)Њ between the two
axial atoms (O12–Sc1–N11), and wedges as large as 142.49(7)Њ
(O13–Sc1–N12 between THF and the amido group) or as small
as 101.33(7)Њ (O11–Sc1–O13 between the phenoxy group of L1
and THF) in the equatorial plane. Similarly, the considerable
Fig. 2 Molecular structure of 4-YPh (hydrogen atoms omitted for
clarity; thermal elipsoids drawn to 50% probability level). Selected
bond distances (Å) and angles (Њ): Y–O(1) 2.185(3), Y–O(2) 2.150(3),
Y–O(3) 2.375(3), Y–O(4) 2.419(3), Y–N(1) 2.475(3), Y–N(2)2.288(3),
C(10)–N(1) 1.302(5), C(30)–N(2) 1.483(5); O(1)–Y–O(2) 167.91(11),
O(3)–Y–N(1) 157.71(11), O(4)–Y–N(2) 164.16(11), O(1)–Y–N(1)
73.78(10), O(1)–Y–N(2) 109.99(11), O(1)–Y–O(3) 86.55(10), O(1)–Y–
O(4) 85.64(10), O(2)–Y–N(1) 101.81(11), O(2)–Y–N(2) 81.70(11),
O(2)–Y–O(3) 95.32(10), O(2)–Y–O(4) 82.86(10), N(1)–Y–N(2)
99.73(11), N(2)–Y–O(3) 96.75(11), O(3)–Y–O(4) 81.18(10), O(4)–Y–
N(1) 86.86(11).
In an analogous fashion, the L2 complexes 2-ScPh and 2-YPh
decompose cleanly by nucleophilic attack of the entire CH2-
SiMe2Ph group on the aldimine carbon, albeit at a qualitatively
slower rate than the L1 derivatives (Scheme 4). The orange
i
products, [(L2)M{(tBuC6H3O)CH(CH2SiMe2Ph)NC6H4 Pr-2}-
(THF)n] (M = Sc, 5-ScPh, n = 1 and Y, 5-YPh, n = 2) are formed as
a single diastereomer from in situ generated 2-MPh, and were
characterised by a range of 1D and 2D NMR spectroscopy. As
with their precursors, the high solubility and tendency to form
oils and retain solvent prevented isolation of 5-ScPh and 5-YPh
as solids. The thermal instability of the 2-MPh complexes lies in
stark contrast to [(L4)2M(CH2SiMe2Ph)] complexes8 which are
indefinitely stable in toluene at 90 ЊC, and decompose only after
3 days at 130 ЊC via metallation of one of the aryl isopropyl
groups followed by 1,3-migration of the metallated carbon to
the aldimine function. The superior thermal stability of the L4
complexes highlight the importance of the ‘N-2,6-dialkylaryl’
motif in order to protect the aldimine carbon from intra-
molecular nucleophilic attack. Interestingly, during the course
of this work, Bochmann and co-workers have reported [(LCy)2-
Fig. 1 Molecular structure of one of three very similar molecules of
4-ScMe in the asymmetric unit (hydrogen atoms omitted for clarity;
thermal elipsoids drawn to 50% probability level). Selected bond
distances (Å) and angles (Њ) for the molecule shown: Sc(1)–O(11)
1.9549(16), Sc(1)–O(12) 1.9631(16), Sc(1)–N(12) 2.0798(19), Sc(1)–
O(13) 2.2067(17), Sc(1)–N(11) 2.2880(19); O(12)–Sc(1)–N(11)
165.20(8), N(11)–Sc(1)–O(11) 82.28(7), N(11)–Sc(1)–N(12) 92.62(7),
N(11)–Sc(1)–O(13) 83.24(7), O(12)–Sc(1)–O(11) 110.92(7), O(12)–
Sc(1)–N(12) 87.78(7), O(12)–Sc(1)–O(13) 87.45(7), O(11)–Sc(1)–N(12)
115.08(7), N(12)–Sc(1)–O(13) 142.49(7), O(13)–Sc(1)–O(11) 101.33(7).
Y(CH2SiMe3)(THF)] (LCy
= N-cyclohexyl-ortho-tert-butyl-
salicylaldiminato), which is stable in solution for several days
at 60 ЊC.9 The lack of alkyl group transfer in this compound
may stem from the fact that this compound adopts a different
geometry than the six- and seven-coordinate compounds 1 and
2; the LCy complex contains equivalent ligand environments,
D a l t o n T r a n s . , 2 0 0 3 , 2 6 1 5 – 2 6 2 0
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suggesting that the axial sites consist of the alkyl and THF
ligands as indicated in the Bochmann paper.9
group to the aldimine carbon; both 4-ScMe and 4-YPh have been
studied by X-ray crystallography. By contrast, N-mesityl substi-
tuted compounds 3 decompose by metallation of an ortho-
C6H2Me3 group. In the case of yttrium, further chemistry
ensues at room temperature; the newly formed alkyl group
undergoes 1,3-migration to the aldimine carbon, forming a five-
membered C4N-ring. Similar reactivity is observed for the bulky
N-2,6-diisopropylphenyl substituted analogue, which at 130 ЊC
partakes in a related sequence of metallation followed by 1,3-
migration, although in this case a six-membered C5N ring is
formed.8 The above study of thermal reactivity will aid in the
design of future ligands for use in early transition metal organo-
metallic chemistry.
Thermal reactivity of [(L3)2M(CH2SiMe2R)(THF)]
In contrast to the L1 and L2 complexes, the L3 mono(alkyls)
3-MR decompose cleanly by metallation of an ortho-C6H2Me3,
rather than by a 1,3-migration of the alkyl group (CH2SiMe2R)
to the aldimine carbon (Scheme 5). The products formed are
Me SiR and bright-red [(L3)M{(tBuC H O)CH᎐NC H Me -
᎐
3
6
3
6
2
2
CH2}(THF)] (6-M). The scandium compound was prepared
from 3-ScPh at 25 ЊC in n-hexane (1 day), while 6-Y was best
prepared at 0 ЊC from in situ generated 3-YMe in n-hexane
(1 week). Both complexes give rise to five C6H2Me3 or C6H2Me2-
CH2 signals, two MCH2 resonances and a single MCH2
1
resonance in the H and 13C NMR spectra at 25 ЊC. While
Experimental
decomposition of 3-YR to 6-Y is facile at 25 ЊC in hydrocarbon
solution, this process is noticeably slower in the presence of
excess THF, implying the intermediacy of five-coordinate,
THF-free [(L3)2Y(CH2SiMe2R)]. Such a compound could not
be detected in the NMR spectra of 3-YR, but its existence is
suggested by the equilibrium which exists between the three
isomers of octahedral 3-YR (vide supra).
General procedures
These procedures have been described in detail elsewhere.8b
ScCl3(H2O)3,11 YCl3(THF)3.5
,
LiCH2SiMe2Ph,8b [M(CH2-
12
SiMe2Ph)3(THF)2] (M = Sc, Y)8b and ortho-tert-butylsalicyl-
aldehyde13 were prepared by published methods. Anhydrous
ScCl3(THF)3 was prepared from ScCl3(H2O)3 and SOCl2 in
THF. Ligands HL1 and HL2 were prepared as described by
Fujita and co-workers,7 while the preparation of HL3 is
described in the ESI.† Solutions of [M(CH2SiMe3)3(THF)2]
(M = Sc, Y) which are unstable above 0 ЊC, were prepared by a
modification of the literature procedure (see experimental).14
Note: solid [MCl3(THF)n] (M = Sc, Y) and LiCH2SiMe2R (R =
Me, Ph) start to react at room temperature (noticeable after
∼30 s), so should be cooled to Ϫ78 ЊC very shortly after mixing.
Elemental analyses were performed by Mrs Dorothy Fox or Ms
Roxanna Simank of this department. A Fischer Scientific
Ultrasonic FS-14 bath was used to sonicate reaction mixtures
where indicated.
X-Ray crystallographic analyses were performed on suitable
crystals coated in Paratone oil and mounted on either a Rigaku
AFC6S (University of Calgary) diffractometer.
CCDC reference numbers 206284 and 206285.
See http://www.rsc.org/suppdata/dt/b3/b303097k/ for crystal-
lographic data in CIF or other electronic format.
[(L1)2Sc(CH2SiMe2Ph)(THF)] (1-ScPh)
Scheme 5
Generated in situ: A solution of HL1 (16 mg, 62.8 µmol) in d8-
toluene (0.4 ml) was added to a solution of [Sc(CH2SiMe2Ph)3-
(THF)2] (20 mg, 31.4 µmol) in d8-toluene (0.2 ml) at Ϫ78 ЊC.
The temperature was then raised to Ϫ20 ЊC for 1 h, which
resulted in complete conversion to the product. 1H NMR
(Ϫ30 ЊC, d8-toluene): δ 7.85 (d, 2H, J 7 Hz, Ph), 7.74, 7.63
{s, 2 × 1H, CH(NPh)}, 7.42–7.35 (m, 2H, Ph), 7.28–7.18 (m,
3H, Ph), 6.90–6.79 (m, 10H, Ph), 6.67–6.79 (m, 4H, Ph), 3.96,
3.79 (m, 2 × 2H, coord. THF), 3.56 (m, 4H, free THF), 1.52,
1.35 (s, 2 × 9H, CMe3), 1.38 (br s, 4H, free THF), 1.18 (m,
4H, coord. THF), 0.37 (d, 1H, J 11 Hz, ScCH2), 0.37, 0.34
(s, 2 × 3H, SiMe2Ph), 0.14 (d, 1H, J 11 Hz, ScCH2). 13C{1H}
NMR (Ϫ30 ЊC, d8-toluene): δ 170.88, 170.14 {s, CH(NPh)},
166.37, 164.76, 154.46, 152.62, 147.99, 140.31, 138.28, 123.97,
122.86 (s, 9 quaternary aromatic), 135.25, 134.37, 134.08,
133.34, 132.76, 128.79, 128.60, 127.51, 127.48, 126.14, 125.66,
123.33, 122.61, 115.79, 115.67 (s, 15 Ph), 71.51 (s, coord. THF),
67.86 (s, free THF), 35.35, 35.13 (s, 2 CMe3), 29.63, 29.53 (s, 2
CMe3), 29.53 (ScCH2), 25.78 (s, free THF), 24.95 (coord. THF),
3.02, 2.73 (s, 2 SiMe2Ph). Complexes [(L1)2Y(CH2SiMe2Ph)-
(THF)] (1-YPh), [(L2)2Sc(CH2SiMe2Ph)(THF)] (2-ScPh) and
[(L2)2Y(CH2SiMe2Ph)(THF)] (2-YPh) were prepared similarly
(see ESI†).
While 6-Sc does not react further at room temperature, the
newly formed alkyl group in 6-Y undergoes 1,3-migration to the
aldimine carbon, forming a C4N-ring; brick-red [(L3)Y{(tBuC6-
H3O)CH–N–C6H2Me2–CH2}(THF)2] (7-Y) was isolated in
reasonable yield as an approximate 3 : 1 mixture of diastereo-
mers. This two-step process is related to the high-temperature
decomposition of the L4 scandium and yttrium compounds as
described previously.8 The preference of L3 for metallative
rather than alkyl migratory decomposition pathways most
likely stems from favourable formation of a five-membered
metallacycle coupled with a more sterically protected aldimine
carbon. Again, the presence of two ortho-substituents on
the N-aryl moiety appears important in order to disfavor 1,3
transfer of the M–R group to the aldimine carbon prior to
metallation.
Conclusions
Mono(alkyl) bis(ligand) complexes of scandium and yttrium
have been prepared using three salicylaldiminato ligands of low
to intermediate steric bulk. In contrast to previously reported
N-2,6-diisopropylphenyl substituted analogues8 which are
THF-free and indefinitely stable at 90 ЊC, compounds 1–3
retain 0–2 molecules of THF, and decompose at 0–25 ЊC. The
N-phenyl and N-2-isopropylphenyl substituted compounds 1
and 2 decompose by 1,3-migration of the entire CH2SiMe2R
[(L3)2Sc(CH2SiMe2Ph)] (3-ScPh)
A solution of HL3 (276 mg, 0.94 mmol) in n-hexane (4 ml) was
added to [Sc(CH2SiMe2Ph)3(THF)2] (300 mg, 0.47 mmol) in
D a l t o n T r a n s . , 2 0 0 3 , 2 6 1 5 – 2 6 2 0
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n-hexane (20 ml) at Ϫ78 ЊC. The mixture was then warmed to
0 ЊC for 1 h, and the resulting orange solution evaporated to
lower volume in vacuo. The slurry was sonicated, cooled to Ϫ78
ЊC and filtered to collect a yellow solid. Yield 250 mg (68%). 1H
NMR (Ϫ20 ЊC, d8-toluene): δ 7.67–7.64 (m, 2H, Ph), 7.62 {s,
2H, CH(NAr)}, 7.40 (dd, 2H, J 7, 2 Hz, Ph), 7.16–7.14 (m, 3H,
Ph), 6.74 (s, 2H, Ph), 6.66 (dd, 2H, J 8, 2 Hz, Ph), 6.59 (t, 2H,
J 8 Hz, Ph), 6.53 (s, 2H, Ph), 2.15 (s, 6H, o-C6H2Me3), 2.14 (s,
6H, o-C6H2Me3), 1.87 (s, 6H, p-C6H2Me3), 1.18 (s, 18H, CMe3),
1.07, 0.41 (d, 2 × 1H, 2JH,H 10 Hz, ScCH2), 0.41, 0.25 (s, 2 × 3H,
SiMe2Ph). 13C{1H} NMR (Ϫ20 ЊC, d8-toluene): δ 176.15 {s,
CH(NAr)}, 167.30, 150.48, 146.48, 140.39, 135.79, 130.85,
130.55, 123.62 (s, 8 quaternary aromatic), 135.12, 134.98,
134.23, 130.67, 130.00, 128.12, 127.91, 117.08 (s, 8 Ph),
40.27 (weak s, ScCH2) 35.53 (s, CMe3), 30.23 (s, CMe3), 21.18,
19.95 (s, 2 o-C6H2Me3), 19.66 (s, p-C6H2Me3), 3.28, 2.94 (s, 2
SiMe2Ph). Anal. Calc. for C49H61N2O2SiSc: C, 75.16; H, 7.85;
N, 3.58. Found: C, 75.20; H, 8.15; N, 3.54%. [(L3)2Y(CH2-
SiMe3)(THF)] (3-YMe) and [(L3)2Y(CH2SiMe2Ph)(THF)] (3-
YPh) were prepared similarly from HL3 and [Y(CH2SiMe2R)3-
(THF)2] in n-hexane at Ϫ20 ЊC. Yields 69 and 75%, respectively
(see ESI†).15
[(L2)Sc{(tBuC6H3O)CH(CH2SiMe2Ph)NC6H4iPr-2}(THF)],
5-ScPh
A solution of bright yellow [(L2)2Sc(CH2SiMe2Ph)(THF)]
(2-ScPh) in d8-toluene (0.6 ml) was generated as described above,
and allowed to stand at room temperature for 5 days. The
resulting orange solution of 5-ScPh was evaporated to dryness
in vacuo to give a red–orange oil. The product was not isolated
as a solid. 1H NMR (C6D6): δ 7.83 {s, 1H, CH(NAr)}, 7.39 (m,
3H, Ph), 7.3–7.1 (m, 6H, Ph), 7.1–7.0 (m, 4H, Ph), 6.92 (d, 2H,
J 7 Hz, Ph), 6.89 (td, 2H, J 8, 2 Hz, Ph), 6.63 (td, 2H, J 8, 2 Hz,
Ph), 4.08 (dd, 1H, 3JH,H 12, 2 Hz, CHCH2), 3.58 (s, 4H, THF),
2
3.14 (br septet, 2H, CHMe2), 1.86 (dd, 1H, JH,H 13,
3JH,H 12 Hz, CHCH2), 1.47, 1.26 (s, 2 × 9H, CMe3), 1.32, 1.27,
1.16, 0.97 (d, 4 × 3H, J 7 Hz, CHMe2), 1.38 (dd, 1H, 2JH,H 13,
3JH,H 2 Hz, CHCH2), 1.04 (m, 4H, THF), Ϫ0.02, Ϫ0.07 (s,
2 × 3H, SiMe2Ph). 13C{1H} NMR (C6D6): δ 174.33 {s,
CH(NAr)}, 166.92, 162.16, 153.80, 152.32, 141.01, 140.65,
140.04, 137.51, 137.09, 123.26, 121.15 (s, 11 quaternary
aromatic), 134.88, 134.67, 134.01, 128.92, 128.69, 128.11,
127.70, 127.21, 127.09, 126.80, 126.75, 126.71, 125.96, 125.25,
116.95, 116.53 (s, 16 Ph), 71.79 (s, THF), 69.13 (s, CHCH2),
35.80, 35.46 (s, 2 CMe3), 30.79, 29.91 (s, 2 CMe3), 29.11, 25.67,
25.62 (s, 3 CHMe2), 25.17 (s, THF), 24.71 (s, CHCH2), Ϫ1.27,
Ϫ3.25 (s, 2 SiMe2Ph). [(L2)Y{(tBuC6H3O)CH(CH2SiMe2Ph)-
[(L1)Sc{(tBuC6H3O)CH(CH2SiMe3)NPh}(THF)] 4-ScMe
i
NC6H4 Pr-2}(THF)2], 5-YPh was prepared similarly (see ESI†).
A mixture of [ScCl3(THF)3] (300 mg, 0.82 mmol) and LiCH2-
SiMe3 (231 mg, 2.45 mmol) in n-hexane (20 ml) was stirred for
2 h at 0 ЊC and then filtered to give a colourless solution of
[Sc(CH2SiMe3)3(THF)2]. After cooling to Ϫ78 ЊC, a solution of
HL1 (413 mg, 1.63 mmol) in n-hexane (4 ml) was added and the
temperature raised to 0 ЊC for 2 h and then RT for 16 h. The
resulting bright red solution was evaporated to dryness in vacuo
to give an oily red solid to which O(SiMe3)2 (10 ml) was added.
The mixture was then sonicated and filtered to collect a brick-
red solid which was washed with O(SiMe3)2 (× 2) and dried
in vacuo. Yield 303 mg (47%). Crystals of 4-ScMe were grown by
allowing a hot hexane solution of 4-ScMe to cool to room
[(L3)Sc{(tBuC H O)CH᎐NC H Me CH }(THF)], 6-Sc
᎐
6
3
6
2
2
2
A mixture of [ScCl3(THF)3] (300 mg, 0.82 mmol) and
LiCH2SiMe3 (231 mg, 2.45 mmol) in n-hexane (20 ml) was
stirred for 2 h at 0 ЊC and then filtered to give a colourless
solution of [Sc(CH2SiMe3)3(THF)2]. After cooling to Ϫ78 ЊC, a
solution of HL3 (482 mg, 1.63 mmol) in n-hexane (4 ml) was
added and the mixture stirred at room temperature for 14 h.
The mixture was then cooled to Ϫ78 ЊC and a flaky red solid
collected by filtration and washed with cold n-hexane (×1).
Yield 320 mg (56%). 1H NMR (C6D6): δ 7.99, 7.62 {s, 2 × 1H,
CH(NAr)}, 7.49 (dd, 1H, J 8, 2 Hz, Ph), 7.38 (dd, 1H, J 8, 2 Hz,
Ph), 7.03 (dd, 1H, J 8, 2 Hz, Ph), 6.84 (s, 1H, C6H2Me3), 6.82
(dd, 1H, J 8, 2 Hz, Ph), 6.71 (t, 1H, J 8 Hz, Ph), 6.64 (t, 1H,
J 8 Hz, Ph), 6.47, 6.38, 6.30 (s, 3 × 1H, C6H2Me3), 3.67 (m, 4H,
THF), 2.22 (s, 3H, C6H2Me3), 2.23, 2.17 (d, 2 × 1H, 2JH,H 12 Hz,
ScCH2), 2.07, 1.90 (s, 2 × 3H, C6H2Me3), 1.88 (br s, 6H,
C6H2Me3), 1.63, 1.39 (s, 2 × 9H, CMe3), 1.13 (m, 4H, THF).
13C{1H} NMR (C6D6): δ 173.46, 164.66 {s, 2 CH(NAr)},
166.64, 163.69, 150.69, 148.75, 146.26, 139.85, 139.59, 135.62,
134.43, 130.85, 129.73, 126.60, 123.92, 123.80 (s, 14 quaternary
aromatic), 134.76, 133.50, 132.83, 131.58, 129.51, 129.27,
127.48, 125.15, 116.70, 116.34 (s, 10 Ph), 70.75 (s, THF), 48.60
(weak s, ScCH2), 35.74, 35.55 (s, 2 CMe3), 30.26, 30.15 (s, 2
CMe3), 25.40 (s, THF), 21.70, 21.26, 21.15 (s, 3 C6H2Me3),
19.37, 18.50 (br s, 2 C6H2Me3). Anal. Calc. for C44H55N2O3Sc:
C, 74.97; H, 7.86; N, 3.97. Found: C, 75.26; H, 7.78; N, 3.92%.
1
temperature. H NMR (C6D6): δ 7.90 {s, 1H, CH(NPh)}, 7.43
(dd, 1H, J 8, 2 Hz, Ph), 7.26 (dd, 1H, J 8, 2 Hz, Ph), 7.20–
7.14 (m, 2H, Ph), 7.11 (dd, 1H, J 7, 1 Hz, Ph), 7.05–6.90 (m,
6H, Ph), 6.83 (d, 2H J 8 Hz, Ph), 6.71 (t, 1H, J 8 Hz, Ph),
6.70 (t, 1H, J 8 Hz, Ph), 6.62 (t, 1H, J 7 Hz, Ph), 4.66 (dd, 1H,
3JH,H 13, 3 Hz, CHCH2), 3.58 (m, 4H, THF), 1.58 (s, 9H,
2
3
CMe3), 1.51 (dd, 1H, JH,H 12, JH,H 13 Hz, CHCH2), 1.43 (s,
2
3
9H, CMe3), 1.09 (dd, 1H, JH,H 12, JH,H 3 Hz, CHCH2), 1.02
(m, 4H, THF), Ϫ0.07 (s, 9H, SiMe3). 13C{1H} NMR (C6D6):
δ 171.03 {s, CH(NPh)}, 165.31, 161.72, 155.72, 151.58, 140.64,
137.39, 135.64, 124.10 (s, 8 quaternary aromatic), 134.84,
134.00, 129.97, 129.79, 127.82, 127.11, 125.64, 123.12, 117.94,
117.28, 114.90, 114.25 (s, 12 Ph), 71.68 (s, THF), 62.46 (s,
CHCH2), 35.68, 35.61 (s, 2 CMe3), 30.94, 29.94 (s, 2 CMe3),
26.01 (s, CHCH2), 25.33 (s, THF), Ϫ0.65 (s, SiMe3). Anal.
Calc. for C42H55N2O3SiScؒC3H9O0.5Si: C, 68.40; H, 8.16; N,
3.54. Found: C, 68.06; H, 7.54; N, 3.79%. Crystal data:
C42H55N2O3ScSi, M = 708.93, monoclinic, space group P21/a,
a = 16.67660(10), b = 20.5525(2), c = 35.7789(4) Å, U =
[(L3)Y{(tBuC H O)CH᎐NC H Me CH }(THF)], 6-Y
᎐
6
3
6
2
2
2
12240.2(2) Å3, T = 170(2) K, Z = 12, µ(Mo-Kα) = 0.25 mmϪ1
,
A yellow slurry of [(L3)2Y(CH2SiMe3)(THF)] (3-YMe) (160 mg,
0.19 mmol) in n-hexane (10 ml) was stirred for 1 week at 0 ЊC.
The resulting brick-red solution was evaporated to dryness
in vacuo, dissolved in O(SiMe3)2 (10 ml), sonicated for 10–
20 min until precipitation of a red solid, cooled to Ϫ45 ЊC, and
filtered to collect orange–red 6-Y. Yield 71 mg (51%). 1H NMR
(d8-toluene): δ 8.02, 7.61 {s, 2 × 1H, CH(NAr)}, 7.44, 7.39, 7.05
(dd, 3 × 1H, J 8, 2 Hz, Ph), 6.79 (s, 1H, C6H2Me3), 6.78 (dd, 1H,
J 8, 2 Hz, Ph), 6.70, 6.58 (t, 2 × 1H, J 8 Hz, Ph), 6.43 (s, 2H,
C6H2Me3), 6.23 (s, 1H, C6H2Me3), 3.62 (m, 4H, THF), 2.26 (s,
3H, C6H2Me3), 2.13, 1.90 (s, 2 × 3H, C6H2Me3), 1.86 (s, 6H,
C6H2Me3), 1.59, 1.45 (s, 2 × 9H, CMe3), 1.18 (m, 4H, THF).
YCH2 signals not located. 13C{1H} NMR (d8-toluene): δ 173.80,
165.54 {s, 2 CH(NAr)}, 166.85, 163.85, 150.19, 148.03, 144.73,
38126 reflections measured, 21153 unique (Rint = 0.034) which
were used in calculations. The final wR(F 2) was 0.119 (all
data). [(L1)Sc{(tBuC6H3O)CH(CH2SiMe2Ph)NPh}(THF)], 4-
ScPh and [(L1)Y{(tBuC6H3O)CH(CH2SiMe2Ph)–NPh}(THF)2],
15
4-YPh were prepared similarly in 84 and 62% yield, respect-
ively (see ESI†). Crystals of 4-YPhؒ0.5C6H5Me were grown by
cooling a concentrated solution of 4-YPh in toluene to Ϫ35 ЊC.
Crystal data: C51H65N2O4SiYؒC10.5H12, M = 1025.25, mono-
clinic, space group P21/c, a = 12.5136(2), b = 24.7662(5), c =
17.9392(4) Å, U = 5556.23(19) Å3, T = 170(2) K,, Z = 4,
µ(Mo-Kα) = 1.12 mmϪ1, 18953 reflectons measured, 9653
unique (Rint = 0.053) which were used in calculations. The final
wR(F 2) was 0.153 (all data).
D a l t o n T r a n s . , 2 0 0 3 , 2 6 1 5 – 2 6 2 0
2619

View Article Online
139.71, 139.63, 134.78, 134.05, 129.60, 126.21, 123.40, 123.18
(s, 13 quaternary aromatic), 133.61, 133.19, 132.89, 130.84,
129.41, 125.95, 123.18, 116.03, 115.45 (s, 9 Ph), 70.25 (s, THF),
References
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1
47.85 (d, JC,Y 32 Hz, YCH2), 35.41, 35.37 (s, 2 CMe3), 29.97,
29.90 (s, 2 CMe3), 25.11 (s, THF), 21.45, 20.91, 20.70 (s, 3
C6H2Me3), 18.55 (br s, 2 × C6H2Me3). Anal. Calc. for C44H55-
N2O3Y: C, 70.57; H, 7.40; N, 3.74. Found: C, 64.46; H, 6.91; N,
3.51%.15
[(L3)Y{(tBuC6H3O)CH–N–C6H2Me2–CH2}(THF)2], 7-Y
A solution of HL3 (260 mg, 0.88 mmol) in n-hexane (4 ml) was
added to [Y(CH2SiMe2Ph)3(THF)2] (300 mg, 0.44 mmol) in
n-hexane (20 ml) at Ϫ78 ЊC. The solution was then stirred at
0 ЊC for 2 h, and 25 ЊC for 20 h before filtration and evacuation
to dryness. The resulting orange–red oil was sonicated in
O(SiMe3)2 (15 ml), cooled to Ϫ45 ЊC, filtered, and washed with
cold O(SiMe3)2 (×2) to leave an orange powder. Yield of 7-Y
(∼3 : 1 mixture of diastereomers) 190 mg (52%). 1H NMR
(C6D6): δ 7.96 {s, 1H, major CH(NAr)}, 7.74 {s, 0.5H, minor
CH(NAr)}, 7.50, 7.22, 7.08, 6.98 (d, 4 × 1H, J 8 Hz, major Ph),
7.48, 7.39, 7.18, 6.82 (d, 4 × 0.5H, J 8 Hz, minor Ph), 6.91 (s,
2H, major Ph), 6.91, 6.86 (t, 2 × 0.5H, J 8 Hz, minor Ph), 6.84,
6.60 (s, 2 × 0.5H, minor Ph), 6.83 (s, 1H, minor Ph), 6.83, 6.66
(t, 2 × 1H, J 8 Hz, major Ph), 6.72, 6.29 (s, 2 × 1H, major Ph),
4.37 (d, 1H, J 8 Hz, major CH), 4.21 (m, 1H, minor CH ϩ
minor CH2), 3.66 (d, 1H, J 13 Hz, major CH2), 3.59 (m, 12H,
THF), 3.16 (dd, 1H, J 13, 8 Hz, major CH2), 3.15 (0.5H, minor
CH2), 2.53 (br s, 6H, major o-C6H2Me3), 2.23 (s, 3H, Me), 2.17
(s, 3H, Me), 2.04 (s, 4.5H, Me), 1.99 (s, 4.5H, Me), 1.71, 1.68 (s,
2 × 4.5H, minor CMe3), 1.52 (s, 1.5H, minor Me), 1.52, 1.41 (s,
2 × 9H, major CMe3), 1.20 (m, 12H, THF). 13C{1H} NMR
(C6D6): δ 174.49 {s, minor CH(NAr)}, 171.82 {s, major
CH(NAr)}, 167.88, 163.67, 163.34, 155.69, 155.25, 151.64,
149.24, 139.85, 139.7, 137.96, 137.30, 136.84, 136.24, 135.35,
135.17, 135.09, 133.70, 127.53, 125.79, 123.82, 123.49 (s, 21
quaternary aromatic), 136.25 (minor), 136.16 (major), 133.56,
133.04 (major), 132.95 (minor), 130.64, 130.45, 129.5, 129.47
(major), 129.45 (minor), 128.00 (major), 126.60 (minor),
124.92 (minor), 124.21 (major), 115.89 (minor), 115.40 (major),
115.30 (minor), 115.24 (major) (s, 18 Ph), 75.21 (major CH),
74.58 (minor CH), 70.59 (s, THF), 48.69 (s, major CH2), 40.02
(s, minor CH2), 35.88, 35.81 (s, 2 minor CMe3), 35.78, 35.66
(s, 2 major CMe3), 30.95, 30.50 (s, 2 minor CMe3), 30.63, 30.43
(s, 2 major CMe3), 25.52 (s, THF), 23.38, 21.22, 21.21, 19.36 (s,
4 minor Me), 21.38, 21.05, 19.88(b), 19.22 (s, 4 major Me).
Anal. Calc. for C48H63N2O4Y: C, 70.23; H, 7.74; N, 3.41. Found:
C, 68.14; H, 7.68; N, 3.33%.15
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Acknowledgements
This work was supported by NSERC in the form of a Discovery
Grant and a Steacie Memorial Fellowship (2001-2003) to
WEP. D. J. H. E. thanks the Alberta Ingenuity Fund for a
Postdoctoral Associateship.
D a l t o n T r a n s . , 2 0 0 3 , 2 6 1 5 – 2 6 2 0
2620