Organo-rare-earth complexes supported by chelating diamide ligands

Article abstract of DOI:10.1021/om020783s

The synthesis of a series of heteroleptic ate-complex-free rare-earth(III) diamide complexes by alkane and amine elimination reactions, starting from Ln(CH₂SiMe₃)₃(THF)₂ and Ln-(NiPr₂)₃(THF)_x (x = 1, Ln = Sc, Lu; x = 2, Ln = Y), respectively, is described. 2,6-Bis(((2,6-diisopropylphenyl)amino)methyl)pyridine (H₂BDPPpyr) formed monomeric complexes of the types (BDPPpyr)Ln(CH₂SiMe₃)(THF)_x (x = 1, Ln = Sc, Lu; x = 2, Ln = Y) and (BDPPpyr)-Ln(NiPr₂)(THF) (Ln = Sc, Lu), which display enhanced stability for the smaller metal center scandium, for diisopropylamide coordination, and in donor solvents such as THF. Conversion of the silylalkyl complexes into their amide derivatives via secondary alkane elimination, i.e., reaction with HNEt₂ and HN(SiHMe₂)₂, increased the complex stability. The mono-THF adduct complexes (BDPPpyr)Sc(L)(THF) show a nonfluxional structure in solution, which contrasts the dynamic behavior of the corresponding bis-THF adduct complexes of the larger elements lutetium and yttrium. Sterically less encumbered 2,6-bis((mesitylamino)-methyl)pyridine (H₂BMespyr) gave the less stable complexes (BMespyr)Ln(CH₂SiMe₃)(THF)_x (x = 1, Ln = Sc; x = 2, Ln = Lu; the Y derivative could not be isolated). Again, subsequent silylalkyl/silylamide ligand exchange gave the complexes (BMespyr)Ln[N(SiHMe₂)₂](THF), exhibiting considerably increased stability. The complexes (BDPPoxyl)Ln(CH₂SiMe₃)(THF) (Ln = Sc, Lu, Y), derived from a nonfunctionalized diamide ligand (H₂BDPPoxyl = 1,2-bis-(((2,6-diisopropylphenyl)amino)methyl)benzene), were isolated in high yields. The 4- and 5-coordinate complexes (BDPPoxyl)Sc(CH₂SiMe₃)(THF) and (BDPPpyr)Sc(CH₂SiMe₃)(THF), respectively, were also characterized by X-ray diffraction structure determinations. All of the 5-coordinate scandium complexes derived from the BDPPpyr ligand effectively polymerize methyl methacrylate in a living manner (M_w/M_n < 1.5), affording mainly atactic polymer at ambient temperature.

Full text of DOI:10.1021/om020783s

1212
Organometallics 2003, 22, 1212-1222
Or ga n o-Ra r e-Ea r th Com p lexes Su p p or ted by Ch ela tin g
Dia m id e Liga n d s
Frank Estler, Georg Eickerling, Eberhardt Herdtweck, and Reiner Anwander*
Anorganisch-chemisches Institut, Technische Universita¨t Mu¨nchen, Lichtenbergstrasse 4,
D-85747 Garching, Germany
Received September 18, 2002
The synthesis of a series of heteroleptic ate-complex-free rare-earth(III) diamide complexes
by alkane and amine elimination reactions, starting from Ln(CH2SiMe3)3(THF)2 and Ln-
(NiPr2)3(THF)x (x ) 1, Ln ) Sc, Lu; x ) 2, Ln ) Y), respectively, is described. 2,6-Bis(((2,6-
diisopropylphenyl)amino)methyl)pyridine (H2BDPPpyr) formed monomeric complexes of the
types (BDPPpyr)Ln(CH2SiMe3)(THF)x (x ) 1, Ln ) Sc, Lu; x ) 2, Ln ) Y) and (BDPPpyr)-
Ln(NiPr2)(THF) (Ln ) Sc, Lu), which display enhanced stability for the smaller metal center
scandium, for diisopropylamide coordination, and in donor solvents such as THF. Conversion
of the silylalkyl complexes into their amide derivatives via secondary alkane elimination,
i.e., reaction with HNEt2 and HN(SiHMe2)2, increased the complex stability. The mono-
THF adduct complexes (BDPPpyr)Sc(L)(THF) show a nonfluxional structure in solution,
which contrasts the dynamic behavior of the corresponding bis-THF adduct complexes of
the larger elements lutetium and yttrium. Sterically less encumbered 2,6-bis((mesitylamino)-
methyl)pyridine (H2BMespyr) gave the less stable complexes (BMespyr)Ln(CH2SiMe3)(THF)x
(x ) 1, Ln ) Sc; x ) 2, Ln ) Lu; the Y derivative could not be isolated). Again, subsequent
silylalkyl/silylamide ligand exchange gave the complexes (BMespyr)Ln[N(SiHMe2)2](THF),
exhibiting considerably increased stability. The complexes (BDPPoxyl)Ln(CH2SiMe3)(THF)
(Ln ) Sc, Lu, Y), derived from a nonfunctionalized diamide ligand (H2BDPPoxyl ) 1,2-bis-
(((2,6-diisopropylphenyl)amino)methyl)benzene), were isolated in high yields. The 4- and
5-coordinate complexes (BDPPoxyl)Sc(CH2SiMe3)(THF) and (BDPPpyr)Sc(CH2SiMe3)(THF),
respectively, were also characterized by X-ray diffraction structure determinations. All of
the 5-coordinate scandium complexes derived from the BDPPpyr ligand effectively polymerize
methyl methacrylate in a living manner (Mw/Mn < 1.5), affording mainly atactic polymer at
ambient temperature.
In tr od u ction
ceived considerably less attention.4-12 Moreover, the
polymerization efficiency of previously reported rare-
earth complexes based on chelating diamide ligands
seems to be limited,13 which is in contrast to the case
for amidinate14 complexes as well as that for function-
alized monoanionic amide complexes such as cationic
triazacyclononane alkyls15,16 and amidodiphosphine
alkyls.17
In the past decade “nonmetallocene” or “postmetal-
locene” complexes have attracted considerable attention
in R-olefin polymerization chemistry.1 Particularly,
functionalized chelating diamide ligands have been
extensively studied as a rigid supporting environment2
giving highly active precatalysts comparable to the well-
established group 4 metallocenes.3 The stereoelectronic
demands of amide ligands can be effectively tuned by
single or double functionalization of the coordinating
nitrogen. For comparison, dialkoxide systems, which
also implicate more electron-deficient metal centers, are
sterically more difficult to control. Given the intrinsic
interrelation between group 3/lanthanide and group 4
metal polymerization chemistry, corresponding “true”
diamide complexes of the rare-earth metals have re-
(4) Gountchev, T. I.; Tilley, T. D. Organometallics 1999, 18, 2896.
(5) Cloke, F. G. N.; Elvidge, B. R.; Hitchcock, P. B. Lamarche, V.
M. E. J . Chem. Soc., Dalton Trans. 2002, 2413.
(6) Shah, A. A. S.; Dorn, H.; Roesky, H. W.; Lubini, P.; Schmidt,
H.-G. Inorg. Chem. 1997, 36, 1102.
(7) (a) Skinner, M. E. G.; Tyrrell, B. R.; Ward, B. D.; Mountford, P.
J . Organomet. Chem. 2002, 647, 145. (b) Skinner, M. E. G.; Mountford,
P. J . Chem. Soc., Dalton Trans. 2002, 1694.
(8) Graf, D. D.; Davis, W. M.; Schrock, R. R. Organometallics 1998,
17, 5820.
(9) Fryzuk, M. D.; Yu, P.; Patrick, B. O. Can. J . Chem. 2001, 79,
1194.
(10) Lee, L.; Berg, D. J .; Bushnell, G. W. Inorg. Chem. 1994, 33,
5302.
(11) (a) Fryzuk, M. D.; Love, J . B.; Rettig, S. J . J . Am. Chem. Soc.
1997, 119, 9071. (b) Fryzuk, M. D.; J afapour, L.; Kerton, F. M.; Love,
J . B.; Patrick, B. O.; Rettig, S. J . Organometallics 2001, 20, 1387.
(12) Scholz, J .; Go¨rls, H.; Schumann, H.; Weimann, R. Organome-
tallics 2001, 20, 4394.
(13) Hou, Z.; Wakatsuki, Y. Coord. Chem. Rev. 2002, 231, 1.
(14) Duchateau, R.; van Wee, C. T.; Meetsma, A.; Teuben, J . H. J .
Am. Chem. Soc. 1993, 115, 4931.
(15) Hajela, S.; Schaefer, W. P.; Bercaw, J . E. J . Organomet. Chem.
1997, 532, 45.
* To whom correspondence should be addressed. Fax: +49 89 289
13473. E-mail: reiner.anwander@ch.tum.de.
(1) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 428.
(2) (a) Schrock, R. R. Acc. Chem. Res. 1997, 30, 9. (b) Kempe, R.
Angew. Chem., Int. Ed. 2000, 39, 468. (c) Gade, L. H. Acc. Chem. Res.
2002, 35, 575.
(3) For examples, see: (a) Gue´rin, F.; McConville, D. H.; Vittal, J .
J . Organometallics 1996, 15, 5586. (b) Gibson, V. C.; Kimberley, B. S.;
White, A. J . P.; Williams, D. J .; Howard, P. Chem. Commun. 1998,
313.
10.1021/om020783s CCC: $25.00 © 2003 American Chemical Society
Publication on Web 02/12/2003

Organo-Rare-Earth Complexes
Organometallics, Vol. 22, No. 6, 2003 1213
Ch a r t 1
In their timely review article, Piers and Emslie
presented a most useful classification of non-cyclopen-
tadienyl ancillaries in organo-group 3 metal chemistry
covering bi-, tri, tetra-, and polydentate amide and
alkoxide ligands.18 It is clearly seen that a rich chem-
istry has evolved from N-heteroallylic/electron-delocal-
ized systems such as amidinates, guanidinates, and
aminotroponiminates as well as â-diketiminates, while
true dianionic chelating diamide ligands seem to be
underrepresented. For example, the C2-symmetric dia-
mide complexes [DADMB]YR(THF)x (A: DADMB )
2,2′-bis((tert-butyldimethylsilyl)amido)-6,6′-dimethyl-
biphenyl; R ) H, Me, Et) (Chart 1) show no polymeri-
zation activity toward ethylene; however, rapid insertion
of ethylene occurred for the hydride derivative to afford
an yttrium ethyl complex.4 The B-type monoalkyl
complex Y[ArN(CH2)3NAr]R (R ) CH(SiMe3)2; Ar )
C6H3iPr2-2,6) failed to undergo any 1-hexene insertion
at elevated temperatures,5 while further “activation” of
chloride and trifluoroacetate compounds of type C into
hydride or alkyl derivatives has not yet been reported.6
Yttrium complexes of the types D,7 E,8 F ,9 G,10 and H11
carrying hard and soft donor substituted diamide ligands
and an additional alkyl ligand were reported to be often
unstable at ambient temperature or upon removal of
coordinating solvent molecules such as THF. Remark-
ably, monoalkyl rare-earth-metal complexes of type H
are capable of a nonradical/nonredox phenyl coupling.11
In this paper, we wish to present the synthesis, struc-
tural characterization, and reactivity of various mono-
alkyl rare-earth complexes supported by bidentate and
conformationally rigid tridentate diamide ligands. Their
performance as initiators for acrylate polymerization
reveals a remarkable structure-reactivity relationship.
prepared according to literature procedures (Chart 2).19
As the BDPPpyr ligand (1-2H; H2BDPPpyr ) 2,6-bis-
(((2,6-diisopropylphenyl)amino)methyl)pyridine) has been
most successfully applied in group 4 and group 5 metal
polymerization initiators,3a we first set out to synthesize
analogous rare-earth-metal complexes. This tridentate
pincer ligand features two amide functions and a
pyridine donor acting as a rigid backbone in derived
metal complexes. The dianionic [NNN]2- ligand has
been shown to effectively stabilize five-coordinate com-
plexes ligating exclusively in a meridional fashion.20 The
BMespyr ligand (2-2H; H2BMespyr ) 2,6-Bis((mesityl-
amino)methyl)pyridine) was selected for reasons of
decreased steric demand compared to ligand 1-2H. The
methyl group at the 4-position was introduced to
enhance its solubility in organic solvents. Furthermore,
in contrast to its oily 2,6-bis(((2,6-dimethylphenyl)-
amino)methyl)pyridine (H2BDMPpyr) analogue,20 H2-
BMespyr is easily obtained and purified as a solid. The
previously unreported ligand BDPPmxyl (3-2H; H2-
BDPPmxyl ) 1,3-bis(((2,6-diisopropylphenyl)amino)-
methyl)benzene) was synthesized from R,R′-dibromo-m-
xylene and lithium 2,6-diisopropylanilide. This “donor-
free” analogue of BDPPpyr was anticipated to unravel
the influence of the nitrogen donor on the structure,
stability, and reactivity of the putative complexes.
BDPPoxyl (4-2H; H2BDPPoxyl ) 1,2-bis(((2,6-diisopro-
pylphenyl)amino)methyl)benzene) represents the bulki-
est diamide ligand employed in this study. Its increased
steric bulk obtained by aryl backbone 1,2-substitution
should preferentially stabilize low-coordinate rare-earth
alkyl complexes. Titanium(IV) complexes supported by
this ligand were successfully used in isotactic propylene
polymerization.21
Syn th esis of Ra r e-Ea r th -Meta l P r ecu r sor s. Due
to the low acidity of the diamine ligands under study, a
transamination reaction according to our extended
silylamide route was not feasible.22 Thus, we had to
Resu lts a n d Discu ssion
Syn th esis a n d Descr ip tion of Dia m in e Liga n d
P r ecu r sor s. Diamines 1-4 employed in this work were
(19) Scollard, J . D.; McConville, D. H.; Vittal, J . J . Organometallics
1995, 14, 5478.
(20) (a) Gue´rin, F.; McConville, D. H.; Payne, N. C. Organometallics
1996, 15, 5085. (b) Gue´rin, F.; McConville, D. H.; Vittal, J . J .
Organometallics 1997, 16, 1491.
(16) Bambirra, S.; van Leusen, D.; Meetsma, A.; Hessen, B.; Teuben,
J . H. Chem. Commun. 2001, 637.
(17) Fryzuk, M. D.; Giesbrecht, G.; Rettig, S. J . Organometallics
1996, 15, 3329.
(18) Piers, W. E.; Emslie, D. J . H. Coord. Chem. Rev. 2002, 233-
234, 131.
(21) Tsubaki, S.; J in, J .; Ahn, C.-H.; Sano, T.; Uozumi, T.; Soga, K.
Macromol. Chem. Phys. 2001, 202, 482.

1214 Organometallics, Vol. 22, No. 6, 2003
Estler et al.
Ch a r t 2
Sch em e 1
Sch em e 2
focus on alternative lanthanide precursors exhibiting
increased ligand basicity. To cover a reasonable reactiv-
ity scale, we decided to use lanthanide alkyls of the type
23
Ln(CH2SiMe3)3(THF)2 and diisopropylamides of the
type Ln(NiPr2)3(THF)x.24 The former silylalkyl com-
plexes appeared in the literature as early as 1973 and
have recently been used successfully in alkane elimina-
tion reactions.25 The latter rare-earth diisopropylamides
were first described by Ghotra and Hart.24 However,
their original synthesis according to a “conventional”
salt metathesis reaction involving lithium diisopropyl-
amide (LDA) and rare-earth halides as well as varia-
tions therefrom led exclusively to mixtures of Ln-
(NiPr2)3(THF)x and their corresponding ate complexes
MLn(NiPr2)4(THF)x (M ) Li, Na),26 impeding their use
as valuable synthetic precursors. Here we describe the
synthesis of the first ate-complex-free lanthanide tris-
(diisopropylamide) complexes utilizing the lanthanide
alkyls described above (Scheme 1). Reaction of Ln(CH2-
SiMe3)3(THF)2 (5) with 3 equiv of diisopropylamine in
hexane at room temperature for 18 h produced Ln-
(NiPr2)3(THF)x (6) in high yields (x ) 1; Ln ) Sc, Lu; x
) 2, Ln ) Y). The solid-state connectivity structure of
yttrium derivative 6c revealed a mononuclear bis-THF
adduct with severely disordered amide and THF
ligands.27 Such rare-earth amide precursors should be
basic enough to deprotonate the aryl-substituted di-
amine ligands 1-4. The resulting heteroleptic com-
plexes LLn(NiPr2) could display enhanced stability
compared to the corresponding heteroleptic silylalkyl
complexes due to the increased steric bulk of the
diisopropylamide ligand.
Syn th esis of Dia m id e Com p lexes Der ived fr om
BDP P p yr . Reaction of H2BDPPpyr (1, Chart 2) with
Ln(CH2SiMe3)3(THF)2 in THF at ambient temperature
for 1 h yielded the monoalkyl complexes 7a -c. Spec-
troscopic and microanalytical data are consistent with
a molecular composition as shown in Scheme 2: that
is, a five-coordinate mono-THF adduct for the scandium
derivative 7a and a six-coordinate bis-THF adduct for
the larger metal centers lutetium (7b) and yttrium (7c).
The stability of the complexes decreases with increasing
size of the metal center. While scandium complex 7a is
stable in noncoordinating solvents such as hexane,
compounds 7b,c undergo slow (within 1 day) and rapid
(22) Anwander, R. Top. Organomet. Chem. 1999, 2, 1.
(23) (a) Lappert, M. F.; Pearce, R. J . Chem. Soc., Chem. Commun.
1973, 126. (b) Arndt, S.; Voth, P.; Spaniol, T. P.; Okuda, J . Organo-
metallics 2000, 19, 4690.
(24) Bradley, D. C.; Ghotra, J . S.; Hart, F. A. Inorg. Nucl. Chem.
Lett. 1976, 12, 735.
(25) (a) Mu, Y.; Piers, W. E.; MacQuarrie, D. C.; Zawarotko, M. J .;
Young, U. G., J r. Organometallics 1996, 15, 2720. (b) Hultzsch, K. C.;
Spaniol, T. P.; Okuda, J . Angew. Chem., Int. Ed. 1999, 38, 227. (c)
Hultzsch, K. C. Ph.D. Thesis, J ohannes Gutenberg-Universita¨t Mainz,
1999. (d) Hultzsch, K. C.; Okuda, J .; Voth, P.; Beckerle, K.; Spaniol,
T. P. Organometallics 2000, 19, 228. (e) Evans, W. J .; Brady, J . C.;
Ziller, J . W. J . Am. Chem. Soc. 2001, 123, 7711. (f) Emslie, D. J . H.;
Piers, W. E.; Parvez, M.; McDonald, R. Organometallics 2002, 21, 4226.
(26) (a) Aspinall, H. C.; Tillotson, M. R. Polyhedron 1994, 13, 3229.
(b) Evans, W. J .; Anwander, R.; Ziller, J . W.; Khan, S. I. Inorg. Chem.
1995, 34, 5927.
(27) Due to strong ligand disordering in the solid state at 143 K
only the atomic connectivity of the compound could be unambiguously
determined. 6c crystallized from hexane in the orthorhombic space
group Cmc21 (No. 36) with a ) 12.9407(4) Å, b ) 14.862(1) Å, c )
16.1536(7) Å, V ) 3106.7(3) Å3, and Dcalcd ) 1.141 g cm-3 for Z ) 4.

Organo-Rare-Earth Complexes
Organometallics, Vol. 22, No. 6, 2003 1215
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p lex 7a
Sc-N1
Sc-N2
Sc-N3
2.101(2)
2.092(1)
2.219(1)
Sc-O
Sc-C32
2.182(1)
2.248(2)
N1-Sc-N2
N1-Sc-N3
N2-Sc-N3
O-Sc-C32
O-Sc-N1
O-Sc-N2
137.04(6)
72.22(5)
72.75(5)
96.21(6)
101.97(5)
99.96(5)
O-Sc-N3
156.01(5)
109.35(6)
104.39(6)
107.71(6)
123.63(9)
C32-Sc-N1
C32-Sc-N2
C32-Sc-N3
Sc-C32-Si
The Sc-N1/N2 bond lengths of 2.097 Å (average) are
considerably longer than those in four-coordinate
Sc[N(SiHMe2)2]3(THF) (2.069 Å (average)).28 For com-
parison, the Sc-N distances in five-coordinate di-
alkylscandium complexes supported by a â-diketiminato
ligand are 2.190(7) and 2.201(6) Å.29 The Sc-O(THF)
and Sc-N(lutidine) donor bond lengths of 2.182(1) and
2.219(1) Å lie in the expected range. The Sc-C(alkyl)
bond distance, 2.248(2) Å, is comparable to those of the
formerly mentioned â-diketiminato complex, 2.210(9)
and 2.245(9) Å.29 Sc-C bond lengths for other neutral
monoalkyl complexes range from 2.243(8) to 2.346(2)
Å.30-33
F igu r e 1. PLATON46 drawing of the complex (BDPPpyr)-
ScCH2SiMe3(THF) (7a ) in the solid state. Thermal el-
lipsoids are drawn at the 50% probability level. The unit
cell contains one molecule of toluene, which is omitted for
clarity.
1
The H NMR spectrum of 7b in C6D6 shows a set of
resonances comparable to those for 7a , except for the
lutidine ring and the alkyl ligand, whose broad signals
indicate rapid structural fluctuation. For example, the
N-methylene groups display two broad singlets at 5.42
and 4.57 ppm. We ascribe the observed fluxional solu-
tion structure to (i) a weak metal-THF interaction and
facile THF dissociation, which is corroborated by the
slight shift of the THF signal compared to noncoordi-
nated THF, and (ii) to a poor coordinative fit of the
[NNN]2- ligand with larger metal centers, involving
labile Ln-N bonds and probably intermolecular Ln-N
association. Since both this fluctuation and complex
decomposition increase with increasing size of the metal
decomposition (within 1 h), respectively. A pronounced
instability of diamide complexes in the absence of
coordinating solvent molecules such as THF has been
pointed out previously.8,10,18
The 1H NMR spectrum of 7a in C6D6 revealed a
nonfluxional coordination at ambient tempeature. The
diastereotopic N-methylene groups exhibit two doublets
at 5.41 and 4.46 ppm, which are considerably downfield
shifted compared to those of 1 (δ 4.26 ppm). The
isopropyl groups of the conformationally rigid [NNN]2-
ligand also exhibit one significantly downfield shifted
multiplet for the methine groups at 4.54 ppm and one
slightly upfield shifted multiplet at 3.43 ppm (cf., H2-
BDPPpyr, δ ) 3.54 ppm) as well as four doublets for
the methyl groups at 1.53, 1.45, 1.15, and 1.14 ppm,
respectively. This indicates a large rotational barrier for
the isopropyl groups, making them diastereotopic. The
signals of the lutidine ring appear upfield shifted at 6.94
and 6.60 ppm, respectively, indicating an interaction
between the lutidine and the metal center (cf. H2-
BDPPpyr, δ 7.05 and 6.85 ppm). Moreover, the signifi-
cantly upfield shifted multiplets of the THF ligand at
3.01 and 0.78 ppm are in agreement with a strongly
bonded THF molecule.
1
center, we could not obtain an interpretable H NMR
spectrum of yttrium derivative 7c in C6D6. The dynamic
behavior of complexes 7b,c is supported by their 1H
NMR spectra in THF-d8. In those spectra, the N-
methylene groups display significantly downfield shifted
singlets at 4.95 (7b) and 4.87 (7c) ppm (cf., δ(1, THF-
d8) 4.19 ppm), suggesting a C2-symmetric ligand sphere
for a bis-THF adduct. The signals of the aryl-bonded
isopropyl groups, which are multiplets at 3.84 (7b) and
3.80 (7c) ppm (cf. δ(1, THF-d8) 3.49 ppm) and two
doublets at 1.16/1.14 (7b) and 1.17/1.15 ppm (7c) (cf.
δ(1, THF-d8) 1.21 ppm), indicate enhanced steric satu-
ration via a large rotational barrier for the isopropyl
groups, making them diastereotopic.
An X-ray structure analysis of complex 7a confirmed
its mononuclear nature and composition, as shown in
Scheme 2. A view of the molecular structure and
relevant bond distances and angles can be found in
Figure 1 and Table 1.
Complexes 7a -c feature one remaining alkyl ligand
accessible to secondary ligand exchange reactions. We
The coordination geometry at the five-coordinate
scandium metal center is best described as distorted
trigonal bipyramidal. The anilide nitrogen atoms (N1,
N2) and the alkyl ligand (C32) form the equatorial
plane, while the THF oxygen atom and the pyridine
nitrogen atom (N3) occupy the apical positions (O-Sc-
N3 ) 156.01(5)°). The [NNN]2- ligand coordinates in a
meridional fashion with a bite angle of 137.04(6)°, which
is a typical coordination mode for this pincer ligand, as
previouslyshown for Ti(IV),Zr(IV),andTa(V)complexes.3a,19,20
(28) Anwander, R.; Runte, O.; Eppinger, J .; Gerstberger, G.;
Herdtweck, E.; Spiegler, M. J . Chem. Soc., Dalton Trans. 1998, 847.
(29) Hayes, P. G.; Piers, W. E.; Lee, L. W. M.; Knight, L, K.; Parvez,
M.; Elsegood, M. R. J .; Clegg, W. Organometallics 2001, 20, 2533.
(30) Thompson, M. E.; Baxter, S. M.; Bulls, A. R.; Burger, B. J .;
Nolan, M. C.; Santarsiero, B. D.; Schaefer, W. P.; Bercaw, J . E. J . Am.
Chem. Soc. 1987, 109, 203.
(31) Schaefer, W. P.; Ko¨hn, R. D.; Bercaw, J . E. Acta Crystallogr.
1992, C48, 251.
(32) Arnold, J .; Hoffmann, C. G.; Dawson, D. Y.; Hollander, F. J .
Organometallics 1993, 12, 3645.
(33) Schumann, H.; Erbstein, F.; Herrmann, K.; Demtschuk, J .;
Weimann, R. J . Organomet. Chem. 1998, 562, 255.

1216 Organometallics, Vol. 22, No. 6, 2003
Estler et al.
Sch em e 3
examined the reactivity of 7a -c toward tetramethyl-
disilazane (HN(SiHMe2)2), diethylamine, and diisopro-
pylamine, as shown in Scheme 2. Such envisaged
heteroleptic triamido complexes should be more stable
than complexes 7 but still reactive enough for further
derivatization involving the terminally bonded amide
ligand.
Reaction of 7a -c with HN(SiHMe2)2 in hexane at
ambient temperature for 18 h gave the silylamide
derivatives 8b (Lu) and 8c (Y). The scandium analogue
8a did not form even after a 48 h reaction period,
probably due to steric reasons. Spectroscopic and mi-
croanalytical data are consistent with five- (8b) or six-
coordinate complexes (8c). For the mono-THF adduct
8b, a nonfluxional structure is found in C6D6 with both
diasterotopic N-methylene and aryl-bonded isopropyl
groups groups as well as a strong N(lutidine) and
O(THF) donor bonding. The spectroscopic features of the
N(SiHMe2)2 ligand are Si-H stretching vibrations at ν
2103 and 2042 cm-1 and a SiH proton resonance at 4.64
ppm (septet). Because of rapid THF fluctuation in the
yttrium bis-THF adduct 8c (cf. 7b,c) its NMR spectra
were recorded in THF-d8. The singlet resonance of the
N-methylene groups at 4.78 ppm indicates a symmetric
ligand sphere, while the signals of the aryl-bonded
isopropyl methyl groups, displaying a multiplet at 3.67
ppm and two doublets at 1.18/1.12 ppm, are diastero-
topic as a consequence of restricted rotation about the
N-Cipso bond. The presence of a N(SiHMe2)2 ligand in
8c is clearly indicated by the Si-H stretching vibration
at ν 2097 and 2010 cm-1 and a SiH proton displaying a
septet at δ 4.46 ppm.
The HNEt2 reaction (Scheme 2), which was conducted
for 7a -c in hexane at ambient temperature for 18 h,
gave ligand exchange for all complexes. Spectroscopic
data and elemental analyses are consistent with the
formation of a mono-THF adduct for scandium (9a ) and
lutetium (9b) and a six-coordinate bis-THF adduct for
yttrium (9c). The handling of complexes 9a -c revealed
an increased stability compared to those of complexes
7a -c.34 1H NMR spectroscopy of diethylamido com-
plexes 9a ,b showed the absence of any dynamic behav-
ior in C6D6. Again, the familiar signal pattern for both
diasterotopic N-methylene groups and isopropyl methyl
groups was observed. Donor moieties strongly interact-
ing with the metal centers are indicated by the upfield
shifted lutidine ring signals and upfield shifted THF
multiplets. For reasons of facile donor (THF) dissocia-
tion, the 1H NMR spectrum of the yttrium bis-THF
adduct 9c was measured in THF-d8. The C2 symmetry
of complex 9c is evidenced by a sharp resonance for the
N-methylene groups at 4.77 ppm. Again, inequivalent
isopropyl groups are consistent with a hindered rotation
about the N-Cipso bond.
Sch em e 4
temperature after 7 h (Scheme 3). Complexes 10a ,b are
stable in noncoordinating solvents such as hexane.
The 1H NMR spectrum of 10a recorded in C6D6
revealed a signal set comparable to that of 7a ; however,
as for complex 7b broad signals were observed, which
is in agreement with a weakly coordinated THF ligand.
For example, the N-methylene groups of 10a show two
very broad singlets at approximately 5.4 and 4.5 ppm.
An interpretable NMR spectrum of 10b in C6D6 was not
obtained. The NMR spectra of 10a ,b simplified remark-
ably when recorded in a donor solvent such as THF-d8.
Now, the N-methylene groups feature a significantly
downfield shifted singlet at 4.74 (10a ) and 4.85 ppm
(10b), implicating a higher complex symmetry.
Syn th esis of Dia m id e Com p lexes Der ived fr om
BMesp yr . Reaction of the complexes Ln(CH2SiMe3)3-
(THF)2 with 1 equiv of H2BMespyr (2; Chart 2) in THF
at ambient temperature for 15 min gave complexes
11a ,b (Scheme 4). Remarkably, the putative complex
11c derived from the larger yttrium metal could not be
isolated, which we interpret as a consequence of a very
fast decomposition. Spectroscopic data and elemental
analyses of 11a ,b are consistent with a mono-THF and
a bis-THF adduct, respectively. The complexes are
stable in donor solvents only, and again, the stability
of the complexes decreases with increasing size of the
metal center. 1H NMR spectroscopy in THF-d8 revealed
a symmetric ligand environment. The N-methylene
groups were found as significantly downfield shifted
singlets at 4.72 (11a ) and 4.85 ppm (11b) (cf. δ(H2-
BMespyr, THF-d8) 4.22 ppm). The aryl-bonded methyl
groups exhibit two singlets at 2.24 and 2.16 ppm (11a )
and 2.26 and 2.15 ppm (11b), respectively. These
findings are in good agreement with those obtained for
the BDPPpyr complexes. The sterically less encumbered
BMespyr ligand implies shorter reaction times and
increased steric unsaturation at the metal centers.
While the yttrium derivative 7c of the bulkier BDPPpyr
With HNiPr2 no ligand exchange reactions could be
observed in hexane at ambient temperature after a
period of 18 h. We interpret this as a consequence of
the relatively lower Brønsted acidity of HNiPr2 vs HN-
(SiHMe2)2 combined with the increased steric demand
(HNiPr2 vs HNEt2). However, the diisopropylamide
derivatives 10a ,b were obtained from Ln(NiPr2)3(THF)x
(6) and 1 equiv of H2BDPPpyr in hexane at ambient
(34) Complex 9a was also synthesized from hexane-soluble [Sc-
(NEt2)3] and 1.

Organo-Rare-Earth Complexes
Sch em e 5
Organometallics, Vol. 22, No. 6, 2003 1217
Sch em e 6
ligand is isolable, the corresponding BMespyr complex
is unstable at ambient temperature.
F igu r e 2. PLATON46 drawing of the complex (BDPPoxyl)-
ScCH2SiMe3(THF) (14a ) in the solid state. Thermal el-
lipsoids are drawn at the 50% probability level.
On the other hand, BMespyr complexes 11a ,b can be
further stabilized via alkane elimination and formation
of complexes (BMespyr)LnN(SiHMe2)2(THF) (Ln ) Sc
(12a ), Ln ) Lu (12b); Scheme 4). Complexes 12 are even
stable in noncoordinating solvents, wherein the scan-
dium mono(THF) adduct 12a shows a nonfluxional
structure featuring a relatively strong interaction be-
tween the lutidine and the metal center. The N(Si-
HMe2)2 ligand is characterized by Si-H stretching
vibrations at ν 2075 and 1920 cm-1 and a SiH proton
displaying a septet at δ 4.83 ppm. Because of rapid THF
fluctuations in C6D6 at ambient temperature, conclusive
NMR spectra of 12b were obtained only in THF-d8. The
spectroscopic features of the N(SiHMe2)2 ligand are a
Si-H stretching vibration at ν 2062 cm-1 and a SiH
proton displaying a septet at δ 4.34 ppm.
Ta ble 2. Selected Bon d Len gth s (Å) a n d An gles
(d eg) for Com p lex 14a
Sc-N1
Sc-N2
2.017(1)
2.037(1)
Sc-O1
Sc-C33
2.161(1)
2.218(2)
N1-Sc-N2
N1-Sc-C33
N2-Sc-C33
O1-Sc-C33
105.79(5)
106.73(7)
118.30(7)
107.37(6)
O1-Sc-N1
O1-Sc-N2
Sc-C33-Si
109.74(6)
108.73(5)
137.4(1)
hexane at ambient temperature for 16 h gave the
diamide complexes 14a-c in quantitative yields (Scheme
6). Apparently, the ortho-substituted ligand backbone
provides a sterically preferred environment, giving
seven-membered metallacycles of increased stability
compared to putative 3-derived complexes featuring the
meta-substituted ligand backbone. Spectroscopic and
microanalytical data are consistent with the formation
of monoalkyl complexes carrying an additional THF
ligand. Such four-coordinate heteroleptic complexes are
stable in nondonor solvents.
Addition of 1 equiv of H2Mespyr to Sc(NiPr2)3(THF)
in hexane at ambient temperature afforded complex 13a
after 1 h (Scheme 5). Like its silylamide analogue 12a ,
1
complex 13a is stable in noncoordinating solvents. H
NMR spectroscopy of 13a in THF-d8 revealed a signifi-
cantly downfield shifted singlet at 4.63 ppm for the
N-methylene groups consistent with a symmetric ligand
sphere.
1H NMR spectroscopy of 14a in C6D6 revealed dias-
tereotopic N-methylene groups appearing as two con-
siderably downfield shifted doublets at 5.52 and 3.64
ppm. A marked rotational barrier about the N-Cipso
bond is evidenced by two downfield shifted multiplets
at 4.26 and 3.55 ppm for the isopropyl methine groups
and by four doublets at 1.62, 1.55, 1.34, and 1.16 ppm
for the isopropyl methyl groups. Two significantly
upshifted multiplets at 3.28 and 1.15 ppm indicate a
strongly bonded THF molecule.
The solid-state structure of complex 14a could be
unequivocally established by an X-ray structure analysis
(Figure 2). The scandium center adopts a distorted-
tetrahedral geometry. Selected bond distances and
angles are given in Table 2. The BDPPoxyl ligand shows
a bite angle of 105.79(5)°. The Sc-N bond lengths
average 2.027 Å and, as expected, are markedly shorter
than those in the five-coordinate complex 7a ; however,
they are also considerably shorter than those in four-
coordinate dialkylscandium complexes supported by a
At t em p t ed Syn t h esis of Dia m id e Com p lexes
Der ived fr om BDP P m xyl. Under the reaction condi-
tions, which have been successfully applied for the
synthesis of BDPPpyr and BMespyr rare-earth com-
plexes, the N-donor-free analogue H2BDPPmxyl (3;
Chart 2) did not form any tractable product. For
example, when 3 was reacted with Ln(CH2SiMe3)3-
(THF)2 in hexane or THF at ambient temperature, the
formation of the putative complexes (BDPPmxyl)Ln-
(CH2SiMe3)(THF)x did not occur after 2 h. Also, pro-
longed reaction times led to decomposition or oligomer-
ization products only. This observation can be explained
by a strongly stabilizing effect of the central lutidine
donor atom on the eight-membered metallacycles in
BDPPpyr- and BMespyr-derived complexes.
Syn th esis of Dia m id e Com p lexes Der ived fr om
BDP P oxyl. Reaction of the o-xylene-derived diamine
H2BDPPoxyl (4; Chart 2) with Ln(CH2SiMe3)3(THF)2 in

1218 Organometallics, Vol. 22, No. 6, 2003
Estler et al.
â-diketiminato ligand (2.091(5)-2.145(1) Å).29 The Sc-C
bond length of 2.218(2) Å is similar to those in the
aforementioned â-diketiminato complex (2.118(5)-2.265-
(6) Å)29 and that in (N2NN′)Sc(CH2SiMe3) (2.289(2) Å;
H2N2NN′ ) (2-C5H4N)CH2N{CH2CH2N(H)SiMe3}2).7
Ta ble 3. P olym er iza tion of Meth yl Meth a cr yla te
Ca ta lyzed by Ra r e-Ea r th Alk yl a n d Am id o
Com p lexesa
d
pre- conversn 10-3Mw 10-3Mn Mw/
tacticityc
mr/mm/rr (°C)
Tg
entry cat.
(%)
(g/mol) (g/mol)b Mn
The 1H NMR spectra of 14b,c were measured in THF-
d8 because of THF fluctuations occurring in C6D6. The
singlet for the N-methylene groups, which appears
significantly downfield shifted at 4.65 (14b) and 4.69
ppm (14c) (cf. δ(4, THF-d8) 4.15 ppm), indicates a
symmetric ligand sphere. The xylene ring exhibits
significantly upfield shifted multiplets at 7.1-6.9 ppm
(14b) and 7.1-6.8 ppm (14c) (cf. δ(4, THF-d8) 7.55/7.25
ppm) indicative of an interaction between the aromatic
system and the metal center. It is interesting to note
that the accessibility and stability of five- and four-
coordinate complexes derived from BDPPpyr and BD-
PPoxyl ligands, respectively, are very similar. Appar-
ently, the increased steric bulk of the latter ligand can
approximately compensate for the strong coordinating
capability of the N(lutidine) donor atom of the BDPPpyr
ligand. We attribute the enhanced steric shielding of the
BDPPoxyl ligand also to its backbone conformation, with
the xylene ring bending toward the metal center and
hence sterically blocking one side of the complex.
Meth yl Meth a cr yla te P olym er iza tion . Achiral
and chiral lanthanidocene(III) complexes of type “Cp2-
Ln-R” are highly efficient precatalysts for the stereo-
regular polymerization of methyl methacrylate (MMA).35
The steric bulk and basicity/nucleophilicity of the
operational Ln-R functionality, adding to MMA via 1,4-
addition (enolate formation), is of utmost importance for
controlling stereoregulation, molecular weight, and
polydispersity. Hydrido,36 hydrocarbyl,37 amido,38 and
sulfido moieties39 were shown to display efficient groups
R for polymerization initiation. All of the monoalkyl and
heteroleptic amide complexes 7-14 reported in this
paper were examined in MMA polymerization. The
polymerizations were carried out in toluene at 40 °C.
After the mixture was stirred for 48 h, the reaction was
quenched with methanol and the precipitated polymer
was collected by filtration and dried under reduced
pressure.
1
2
3
4
5
6
7a
7b
7c
9a
95
11
12
87
129
5149
1720
83
105
1837
81
60
58
65
67
1.60 44/6.5/49.5
77
86.5 27/20/53
29.9 25/37/38
1.28 49.5/9/41.5
1.56 47.5/8/44.5
17.5 21/19.5/59.5
84
99
10a >99
10b trace
105
a
Conditions: in toluene; precat./MMA (mol/mol) ) 1/500; MMA/
solvent (v/v) ) 1/10; polymerization time 48 h; polymerization
b
temperature 40 °C. Measured by GPC calibrated with standard
polystyrene samples. c mr, mm, and rr are hetero-, iso-, and
d
syndiotactic triads, respectively. Glass temperature.
row polydispersity indicative of a living polymerization
(Mw/Mn ) 1.28 for 9a ; for an ideal living polymerization
Mn ) 50 × 103 g/mol). In contrast, corresponding
complexes of the larger metal centers lutetium and
yttrium showed negligible monomer conversion, giving
polymers of very broad polydispersities (entries 2, 3, and
6). Apparently, the BDPPpyr ligand optimally matches
the stereoelectronic demands of the Sc(III) center as a
true ancillary ligand, its chelating Sc-N bonds behaving
passively in the initiation and propagation process. The
polymer microstructure as judged by 13C NMR spec-
troscopy is predominantly syndio- (ca. 50%) and het-
erotactic (ca. 50%). The initiator behavior of complexes
7 and 8 bearing the BDPPpyr ligand shows that steric
unsaturation, when it implies enhanced complex insta-
bility (larger metal centers!), counteracts catalytic activ-
ity. Also, the nonactive BMespyr-derived complexes 11
and 12 point toward the importance of steric shielding
of the metal center and/or steric shielding of the Ln-
N(diamide) bonds. Furthermore, complex symmetry
and/or the presence of additional donor atoms, expressed
in a formally increased coordination number, seem to
be crucial, as shown for the lack of polymerization
capability of four-coordinate BDPPoxyl-derived com-
plexes 14. Note that the influence of the initiating
ligand, alkyl vs amide, seems to be marginal.
Con clu sion s
Interestingly, only the BDPPpyr (1)-derived com-
plexes were found to catalyze the polymerization of
MMA. The analytical data of the PMMA obtained are
summarized in Table 3. The scandium complexes 7a ,
9a , and 10a showed very promising polymerization
behavior (entries 1, 4, and 5). Both initiating alkyl and
amide groups gave polymethyl methacrylate with nar-
Functionalized [NNN]2- diamide ligands such as
2,6-bis(((2,6-diisopropylphenyl)amido)methyl)pyridine
(BDPPpyr) provide versatile ancillary ligand sets for
rare-earth-based post-metallocene complexes. The use
of a series of structurally related ligands showed that
the formation of the diamide complexes via alkane and
amine elimination routes, their stability, and catalytic
reactivity are sensitively balanced by stereoelectronic
factors. An optimal coordinative fit of the n-chelating
ligand (bite angle) and metal size are crucial. The steric
shielding of the metal center by the ancillary ligand
periphery and by additional donor solvent molecules has
also a marked effect on complex stability and reactivity.
Moreover, the catalytic performance of such heteroleptic
diamide-supported complexes in methyl methacrylate
polymerization revealed the coordination geometry to
be an important factor as well. Accordingly, low coor-
dination numbers (steric unsaturation) do not seem to
be the prevalent steric criterion for enhanced catalytic
activity of organo-rare-earth complexes.
(35) (a) Yasuda, H.; Tamai, H. Prog. Polym. Sci. 1993, 18, 1097. (b)
Yasuda, H.; Ihara, E. Macromol. Chem. Phys. 1995, 196, 2417. (c)
Yasuda, H.; Ihara, E.; Hayakawa, T.; Kakehi, T. J . Macromol. Symp.-
Pure Appl. Chem. 1997, A34, 1929.
(36) (a) Yasuda, H.; Yakamoto, H.; Yokota, K.; Miyake, S.; Naka-
mura, A. J . Am. Chem. Soc. 1992, 114, 4908. (b) Yasuda, H.; Yakamoto,
H.; Yamashita, M.; Yokota, K.; Nakamura, A.; Miyake, S.; Kai, Y.;
Kanehisa, N. Macromolecules 1993, 26, 7134.
(37) Giardello, M. A.; Yamamoto, Y.; Brard, L.; Marks, T. J . J . Am.
Chem. Soc. 1995, 117, 3276.
(38) (a) Mao, L.; Shen, Q.; Sun, J . J . Organomet. Chem. 1998, 566,
9. (b) Mao, L.; Shen, Q. J . Polym. Sci., Part A: Polym. Chem. 1998,
36, 1593. (c) Lee, M. H.; Hwang, K.-W.; Kim, Y.; Kim, J .; Han, Y.; Do,
Y. Organometallics 1999, 18, 5124. (d) Qian, C.; Nie, W.; Sun, J .
Organometallics 2000, 19, 4134. (e) Qian, C.; Zou, G.; Chen, Y.; Sun,
J . Organometallics 2001, 20, 3106.
(39) Nakayama, Y.; Shibahara, T.; Fukumoto, H.; Nakamura, A.;
Mashima, K. Macromolecules 1996, 29, 8014.

Organo-Rare-Earth Complexes
Exp er im en ta l Section
Organometallics, Vol. 22, No. 6, 2003 1219
C6D6): δ 7.59 (s br, 1H, ar), 7.33 (m, 2H, ar), 7.26-7.13 (m,
3
3
6H, ar), 4.08 (d, J ) 7.0 Hz 4H, N-CH2), 3.37 (sp, J ) 6.9
3
3
Gen er a l P r oced u r es. Unless otherwise indicated, all
reactions and manipulations with air-sensitive compounds
were performed under dry argon, using standard Schlenk and
glovebox techniques. Reagents were obtained from commercial
suppliers and used without further purification, unless other-
wise noted. Hexane and toluene were degassed and then dried
using a method described by Grubbs et al.40 THF was distilled
from Na/K alloy benzophenone ketyl. Solvents were stored in
a glovebox. Deuterated solvents were distilled from Na/K alloy
and stored in a glovebox over activated 4 Å molecular sieves.
Hz, 4H, ar-CH), 3.17 (t, J ) 7.0 Hz, 2H, N-H), 1.22 (d, J )
6.9 Hz, 24H, CH3). 13C NMR (100 MHz, C6D6): δ 143.4, 143.1,
141.1, 129.1, 127.4, 127.0, 124.7, 124.0 (Car), 56.4 (N-CH2),
28.1 (ar-CH), 24.4 (CH3). IR: ν 3374 (m, N-H), 1609 (w), 1589
(w), 1461 (vs, Nujol), 1378 (s, Nujol), 1362 (s), 1332 (m), 1310
(m), 1255 (s), 1244 (s), 1192 (s), 1159 (w), 1110 (m), 1055 (s),
995 (w), 967 (w), 932 (m), 899 (w), 888 (w), 863 (w), 847 (w),
800 (m), 786 (m), 770 (m), 756 (s), 745 (s), 721 (m), 710 (s),
701 (s), 663 (w), 652 (w), 625 (w), 611 (w), 567 (w), 553 (w),
526 (m), 518 (w), 493 (w), 477 (w), 452 (w), 433 (m), 408 (w)
cm-1. Anal. Calcd for C32H44N2: C, 84.2; H, 9.7; N, 6.1.
Found: C, 82.5; H, 9.6; N, 5.8.
22
LnCl3(THF)x and LiCH2SiMe325c were prepared according to
literature procedures. A slightly modified procedure was used
for the preparation of the complexes Ln(CH2SiMe3)3(THF)2
(5).23 2,6-Bis(((2,6-diisopropylphenyl)amino)methyl)pyridine
(H2BDPPpyr, 1) was prepared by using a method described
by McConville.20 Organolithiations were carried out according
to standard literature methods. Methyl methacrylate was dried
using a method described previously.41 NMR spectra were
recorded on a Bruker DPX-400 (FT, 400 MHz 1H; 100 MHz
13C) spectrometer. Chemical shifts are reported in ppm relative
to TMS (1H, 13C, and 29Si) at room temperature; J values are
given in Hz. IR spectra were recorded on a Perkin-Elmer 1650
FT-IR spectrometer as Nujol mulls. Elemental analyses were
performed in the microanalytical laboratory of the institute.
Some carbon analyses were found outside journal guidelines,
which could be due to the presence of fractional amounts of
solvent (2, 3 ()oil)) and an instability at ambient temperature
due to the presence of intrinsically labile alkyl and isopropy-
lamide moieties (5b, 6a , 6b, 7a , 7b, 9a ). Incomplete combus-
tion of the samples, particularly for the element combination
Ln/N/Si (8b, 12a ), has also been discussed to explain the
mismatch of the elemental analyses of organolanthanide
compounds.47
1,2-Bis(((2,6-d iisop r op ylp h e n yl)a m in o)m e t h yl)b e n -
zen e (H2BDP P oxyl, 4). To a stirred solution of 494 mg of
R,R′-dibromo-o-xylene (1.87 mmol) in 5 mL of THF was added
a solution of 721 mg of lithium 2,6-diisopropylanilide (3.93
mmol) in 5 mL of THF at ambient temperature. The solution
was stirred for 18 h, and the solvent was removed in vacuo.
The resulting yellow oil was dissolved in 15 mL of hexane,
and a white precipitate formed, which was separated by
filtration and extracted with hexane. The remaining hexane
phases were combined, and the solvent was removed under
reduced pressure to yield 769 mg (90%) of an orange powder.
1H NMR (400 MHz, C6D6): δ 7.55 (m, 2H, ar), 7.2-7.1 (m, 8H,
3
ar), 4.23 (d, 4H, N-CH2), 3.37 (sp, J ) 6.9 Hz, 4H, ar-CH),
1.21 (d, 3J ) 6.9 Hz, 24H, CH3). 13C NMR (100 MHz, C6D6): δ
143.7, 143.0, 138.6, 128.9, 127.9, 124.7, 124.0 (Car), 54.0 (N-
CH2), 28.2 (ar-CH), 24.4 (CH3). IR: ν 3355 (m N-H), 2722 (m),
2677 (w), 1914 (w), 1853 (w), 1792 (w), 1588 (m), 1458 (vs
Nujol), 1377 (vs Nujol), 1362 (s), 1338 (s), 1310 (s), 1254 (s),
1220 (m), 1192 (s), 1110 (m), 1053 (s), 964 (w), 932 (s), 889
(w), 804 (s), 743 (vs), 677 (w), 605 (w), 576 (w), 528 (w) cm-1
.
Anal. Calcd for C32H44N2: C, 84.2; H, 9.7; N, 6.1. Found: C,
84.4; H, 9.3; N, 5.8.
2,6-Bis((m esit yla m in o)m et h yl)p yr id in e (H 2BMesp yr ,
2). A THF solution of 1.13 g of lithium 2,4,6-trimethylanilide
(8 mmol, 35 mL) was added slowly to a stirred solution of 1.06
g of 2,6-bis(bromomethyl)pyridine (4 mmol) in THF (15 mL)
at -78 °C. The mixture was warmed to ambient temperature
and stirred for 16 h. The solution was quenched with a
saturated NaHCO3 solution (50 mL) and extracted with ether
(50 mL). The solvent was removed in vacuo, and the resulting
solid was dissolved in 50 mL of hexane and filtered. Solvent
removal and drying under reduced pressure yielded 852 mg
Gen er a l P r oced u r e for Syn th esizin g Ln (CH2SiMe3)3-
(THF )2 (5). To a suspension of LnCl3(THF)x in 5 mL of hexane
was added dropwise a solution of LiCH2SiMe3 in 13 mL of
hexane at ambient temperature. The mixture was stirred for
3 h and then filtered. The solid residue was extracted with 10
mL of hexane, and the volatiles were removed in vacuo, giving
a white solid. The product was recrystallized from a minimum
amount of hexane at -30 °C, yielding the pure product as
colorless crystals. 5a : 620 mg of ScCl3(THF)3 (1.69 mmol); 468
mg of LiCH2SiMe3 (4.97 mmol); yield 505 mg (71%). Anal.
Calcd for C20H49O2ScSi3: C, 53.3; H, 11.0. Found: C, 53.7; H,
10.8. 5b: 851 mg of LuCl3(THF)3 (1.71 mmol); 474 mg of
LiCH2SiMe3 (5.04 mmol); yield 646 mg (65%). Anal. Calcd for
1
(57%) of a white solid. H NMR (400 MHz, C6D6): δ 7.35 (dd,
1H, pyr), 7.2-7.1 (m, 4H, ar), 7.04 (d, 2H, pyr), 4.75 (s br, 2H,
N-H), 4.53 (s, 4H, N-CH2), 2.63 (s, 12H, ar-CH3), 2.53 (s, 6H,
ar-CH3). 13C NMR (100 MHz, C6D6): δ 159.2, 144.1, 136.7,
131.2, 129.9, 120.3 (Car), 54.3 (N-CH2), 20.7 (ar-CH3), 18.7 (ar-
CH3). IR: ν 3355 (m, N-H), 2741 (m), 1590 (s), 1575 (m), 1538
(w), 1481 (s), 1458 (vs, Nujol), 1374 (s, Nujol), 1303 (m), 1258
(m), 1229 (w), 1154 (m), 1083 (m), 1031 (m), 852 (s), 799 (w),
720 (m), 561 (w), 539 (w), 505 (w), 488 (w), 466 (w), 452 (w),
434 (w), 427 (w), 417 (w) cm-1. Anal. Calcd for C25H31N3: C,
80.4; H, 8.4; N, 11.2. Found: C, 79.4; H, 8.3; N, 10.8.
1,3-Bis(((2,6-d iisop r op ylp h e n yl)a m in o)m e t h yl)b e n -
zen e (H2BDP P m xyl, 3). To a stirred solution of 486 mg of
R,R′-dibromo-m-xylene (1.84 mmol) in 5 mL of THF at ambient
temperature was added a solution of 709 mg of lithium 2,6-
diisopropylanilide (3.93 mmol) in 5 mL of THF. The solution
was stirred for 18 h, and the solvent was removed in vacuo.
The resulting yellow oil was dissolved in 15 mL of hexane. A
white precipitate formed, which was separated by filtration
and extracted with hexane. The remaining hexane phases were
combined and the solvent was removed under reduced pressure
to yield 773 mg (92%) of a colorless oil. 1H NMR (400 MHz,
C
20H49O2LuSi3: C, 41.4; H, 8.5. Found: C, 42.0; H, 8.9. 5c:
752 mg of YCl3(THF)3.5 (1.68 mmol); 466 mg of LiCH2SiMe3
(4.96 mmol); yield 574 mg (69%). Anal. Calcd for C20H49O2-
YSi3: C, 48.6; H, 10.0. Found: C, 48.7; H, 10.8. The spectro-
scopic data of complexes 5 correspond to those reported
previously.23
Gen er a l P r oced u r e for Syn th esizin g Ln (NiP r 2)3(THF )x
(6). HNiPr2 was added to a stirred solution of Ln(CH2SiMe3)3-
(THF)2 in 5 mL of hexane at ambient temperature and reacted
for 18 h. Then the solution was filtered and the volatiles were
removed in vacuo. The resulting yellow solid was recrystallized
from hexane to yield the pure product as colorless crystals.
Sc(NiP r 2)3(THF ) (6a ): 240 mg of Sc(CH2SiMe3)3(THF)2
(0.53 mmol); 164 mg of HNiPr2 (1.62 mmol); yield 155 mg
1
(70%). H NMR (400 MHz, C6D6): δ 3.82 (m, 4H, THF), 3.66
3
3
(sp, J ) 6.4 Hz, 6H, N-CH), 1.37 (d, J ) 6.4 Hz, 36H, CH3),
1.17 (m, 4H, THF). 13C NMR (100 MHz, C6D6): δ 72.4 (THF),
47.1 (N-CH), 27.0 (CH3) 24.9 (THF). Anal. Calcd for C22H50
-
ON3Sc: C, 63.3; H, 12.1; N, 10.1. Found: C, 62.6; H, 11.7; N,
9.9.
Lu (NiP r 2)3(THF ) (6b). 295 mg Lu(CH2SiMe3)3(THF)2 (0.51
mmol); 157 mg HNiPr2 (1.56 mmol); yield 212 mg (76%). 1H
(40) Grubbs, R. H.; Pangborn, A. B.; Giardello, M. A.; Rosen, R. K.;
Timmers, F. J . Organometallics 1996, 15, 1518.
(41) Allen, R. D.; Long, T. E.; McGrath, J . E. Polym. Bull. 1986, 15,
127.

1220 Organometallics, Vol. 22, No. 6, 2003
Estler et al.
NMR (400 MHz, C6D6): δ 3.72 (m, 4H, THF), 3.63 (sp, 3J )
(BDP P p yr )Lu N(SiHMe2)2(THF ) (8b): 190 mg of 7b (0.26
mmol); 46.8 µL of bis(dimethylsilyl)amine (0.26 mmol); yield
180 mg (83%). H NMR (400 MHz, C6D6): δ 7.25 (dd, 2H, ar),
3
6.3 Hz, 6H, N-CH), 1.39 (d, J ) 6.3 Hz, 36H, CH3), 1.13 (m,
4H, THF). 13C NMR (100 MHz, C6D6): δ 72.3 (THF), 47.3 (N-
CH), 27.0 (CH3) 24.8 (THF). Anal. Calcd for C22H50LuON3: C,
48.3; H, 9.2; N, 7.7. Found: C, 48.9; H, 9.1; N, 7.3.
1
7.13 (d, 2H, ar), 6.95 (dd, 1H, pyr), 6.57 (d, 2H, pyr), 5.44 (d,
2
2J ) 19.0 Hz, 2H, N-CH2), 4.64 (m, 2H, Si-H), 4.49 (d, J )
Y(NiP r 2)3(THF )2 (6c): 283 mg of Y(CH2SiMe3)3(THF)2 (0.57
mmol); 176 mg of HNiPr2 (1.77 mmol); yield 246 mg (81%). 1H
NMR (400 MHz, C6D6): δ 3.62 (m, 8H, THF), 3.56 (sp, 3J )
19.0 Hz, 2H, N-CH2), 4.35 (m, 2H, ar-CH), 3.54 (m, 2H, ar-
CH), 3.07 (m, 4H, THF), 1.52 (d, 6H, CH3), 1.44 (d, 6H, CH3),
1.20 (d, 6H, CH3), 1.13 (d, 6H, CH3), 0.84 (m, 4H, THF), 0.29
(d, 12H, Si-CH3). 13C NMR (100 MHz, C6D6): δ 165.5, 155.4,
147.7, 146.5, 137.1, 124.0, 123.4, 122.9, 117.1 (Car), 70.9 (THF),
65.1 (N-CH2), 28.5, 27.5, 26.2, 25.3, 24.9, 24.6 (ar-CH, CH3,
THF), 4.3 (Si-CH3). 29Si NMR (79.43 MHz, C6D6): δ -22.7.
IR: ν 2759 (m), 2672 (w), 2103 (m, Si-H), 2042 (m, Si-H),
1601 (m), 1574 (m), 1462 (vs, Nujol), 1377 (s, Nujol), 1308 (m),
1240 (s), 1202 (m), 1186 (w), 1157 (m), 1100 (w), 1052 (m),
1036 (m), 1004 (w), 940 (m), 893 (s), 858 (m), 836 (m), 773
(m), 721 (m), 678 (m), 624 (w), 543 (w), 515 (m), 483 (w), 472
(w), 452 (w), 444 (w), 436 (w), 430 (w), 408 (w) cm-1. Anal.
Calcd for C39H63LuN4OSi2: C, 56.1; H, 7.6; N, 6.7. Found: C,
57.1; H, 7.6; N, 6.0.
3
6.4 Hz, 6H, N-CH), 1.38 (d, J ) 6.4 Hz, 36H, CH3), 1.25 (m,
8H, THF). 13C NMR (100 MHz, C6D6): δ 70.2 (THF), 47.6 (N-
CH), 26.8 (CH3) 25.2 (THF). Anal. Calcd for C26H58O2N3Y: C,
58.5; H, 11.0; N, 7.9. Found: C, 58.4; H, 10.8; N, 7.2.
(BDP P p yr )ScCH2SiMe3(THF ) (7a ). To a stirred solution
of 296 mg of 1 (0.66 mmol) in 10 mL of THF was added
dropwise a solution of 300 mg of 5a (0.66 mmol) in 5 mL of
THF at ambient temperature. The mixture was stirred for 1
h and filtered, and the volatiles were removed in vacuo,
yielding 436 mg (>99%) of a yellow powder. Recrystallization
from a mixture of hexane and toluene at -30 °C afforded
colorless crystals suitable for an X-ray analysis. 1H NMR (400
MHz, C6D6): δ 7.22 (dd, 2H, ar), 7.12 (d, 4H, ar), 6.94 (dd, 1H,
pyr), 6.60 (d, 2H, pyr), 5.41 (d, 2J ) 20.1 Hz, 2H, N-CH2),
(BDP P p yr )YN(SiHMe2)2(THF )2 (8c): 144 mg of 7c (0.22
mmol); 42.6 µL of bis(dimethylsilyl)amine (0.24 mmol); yield
2
4.54 (m, 2H, ar-CH), 4.46 (d, J ) 20.1 Hz, 2H, N-CH2), 3.43
1
134 mg (90%). H NMR (400 MHz, THF-d8): δ 7.74 (dd, 1H,
(m, 2H, ar-CH), 3.01 (m, 4H, THF), 1.53 (d, 6H, CH3), 1.45 (d,
6H, CH3), 1.15 (d, 6H, CH3) 1.14 (d, 6H, CH3), 0.78 (m, 4H,
THF), 0.16 (s, 9H, Si-CH3), 0.05 (s, 2H, Sc-CH2). 13C NMR
(100 MHz, C6D6): δ 163.8, 152.7, 147.4, 145.9, 137.2, 124.1,
123.7, 123.4 117.4 (Car), 71.2 (THF), 64.5 (N-CH2), 28.2, 27.2,
26.2, 25.7, 25.2, 24.7 (ar-CH, CH3, THF, Sc-CH2), 3.7 (Si-
CH3). 29Si NMR (79,43 MHz, C6D6): δ -4.3. Anal. Calcd for
pyr), 7.19 (d, 2H, pyr), 7.00 (d, 4H, ar), 6.88 (m, 2H, ar), 4.78
(s, 4H, N-CH2), 4.46 (m, 2H, Si-H), 3.67 (m, 4H, ar-CH), 1.18
(d, 12H, CH3), 1.12 (d, 12H, CH3), -0.08 (d, 12H, Si-CH3).
13C NMR (100 MHz, THF-d8): δ 166.0, 154.7, 147.1, 138.0,
123.9, 122.9, 117.9 (Car), 65.8 (N-CH2), 28.5, 26.9, 25.1 (ar-
CH, CH3), 4.0 (Si-CH3). 29Si NMR (79,43 MHz, THF-d8): δ
-22.9. IR: ν 2760 (m), 2672 (w), 2097 (H-Si, m), 2010 (H-Si,
m), 1600 (w), 1574 (m), 1461 (vs, Nujol), 1421 (s), 1377 (vs),
1307 (s), 1239 (vs), 1201 (s), 1185 (m), 1157 (m), 1101 (m), 1052
(s), 1005 (m), 942 (s), 893 (vs), 855 (s), 836 (s), 804 (m), 773
(s), 722 (m), 688 (w), 624 (w), 542 (w), 474 (w), 421 (w), 409
(w) cm-1. Anal. Calcd for C43H71N4O2Si2Y: C, 62.9; H, 8.7; N,
6.8. Found: C, 63.2; H, 8.5; N, 6.7.
C
39H60N3OScSi: C, 71.0; H, 9.2; N, 6.4. Found: C, 70.2; H,
9.7; N, 5.7.
(BDP P p yr )Lu CH2SiMe3(THF )2 (7b). A solution of 272 mg
of 5b (0.47 mmol) in 5 mL of THF was added dropwise to a
stirred solution of 214 mg of 1 (0.47 mmol) in 8 mL of THF at
ambient temperature. The mixture was stirred for 1 h and then
filtered, and the volatiles were removed in vacuo, resulting in
a yellow powder. Recrystallization from a mixture of hexane
and toluene at -30 °C yielded 282 mg (76%) of the pure
product. 1H NMR (400 MHz, THF-d8): δ 7.80 (dd, 1H, pyr),
7.29 (d, 2H, pyr), 7.03 (d, 4H, ar), 6.91 (dd, 2H, ar), 4.95 (s,
4H, N-CH2), 3.84 (m, 4H, ar-CH), 1.16 (d, 12H, CH3), 1.14 (d,
12H, CH3), -0.27 (s, 9H, Si-CH3), -0.82 (s, 2H, Lu-CH2).
13C NMR (100 MHz, THF-d8): δ 165.7, 152.9, 147.8, 138.2,
123.9, 123.4, 118.5 (Car), 65.8 (N-CH2), 27.9, 26.9, 26.4, 25.5
(ar-CH, CH3, Lu-CH2), 4.1 (Si-CH3). 29Si NMR (79,43 MHz,
THF-d8): δ -1.1. Anal. Calcd for C43H68LuN3O2Si: C, 59.9;
H, 8.0; N, 4.9. Found: C, 59.9; H, 7.9; N, 4.9.
(BDP P p yr )ScNEt2(THF ) (9a ): 206 mg of 7a (0.31 mmol);
1
32.2 µL of HNEt2 (0.31 mmol); yield 162 mg (81%). H NMR
(400 MHz, C6D6): δ 7.27 (dd, 2H, ar), 7.19 (d, 2H, ar), 6.93
(dd, 1H, pyr), 6.55 (d, 2H, pyr), 5.00 (d, 2J ) 19.4 Hz, 2H,
2
N-CH2), 4.63 (d, J ) 19.4 Hz, 2H, N-CH2), 4.05 (m, 2H, ar-
CH), 3.59 (sp, 2H, ar-CH), 3.34 (m, 4H, THF), 2.23 (q, 4H,
N-CH2Me), 1.44 (d, 6H, CH3), 1.40 (d, 6H, CH3), 1.27 (d, 6H,
CH3), 1.13 (d, 6H, CH3), 0.98 (m, 4H, THF), 0.80 (t, 6H, NCH2-
CH3). 13C NMR (100 MHz, C6D6): δ 164.1, 155.0, 146.7, 145.6,
136.7, 123.9, 123.3, 123.0, 116.8 (Car), 71.1 (THF), 64.8 (N-
CH2), 41.9 (N-CH2-Me), 27.5, 26.2, 25.3, 24.9, 24.6, 15.1 (ar-
CH, CH3, N-CH2-CH3, THF). Anal. Calcd for C39H59N4OSc:
C, 72.6; H, 9.2; N, 8.7. Found: C, 71.9; H, 9.0; N, 8.5.
(BDP P p yr )YCH2SiMe3(THF )2 (7c). To a stirred solution
of 221 mg of 1 (0.48 mmol) in 8 mL of THF was added dropwise
a solution of 239 mg of 5c (0.48 mmol) in 7 mL of THF at
ambient temperature. The mixture was stirred for 1 h and
filtered, and the volatiles were removed in vacuo, resulting in
a brown powder. Recrystallization from a mixture of hexane
and toluene at -30 °C yielded 64 mg (21%) of the pure product.
1H NMR (400 MHz, THF-d8): δ 7.78 (dd, 1H, pyr), 7.27 (d,
2H, pyr), 7.03 (d, 4H, ar), 6.94 (dd, 2H, ar), 4.87 (s, 4H,
N-CH2), 3.80 (m, 4H, ar-CH), 1.17 (d, 12H, CH3), 1.15 (d, 12H,
CH3), -0.27 (s, 9H, Si-CH3), -0.73 (d, 2J ) 5.3 Hz, 2H,
Y-CH2). 13C NMR (100 MHz, THF-d8): δ 165.8, 151.9, 147.9,
138.1, 123.9, 123.4, 118.4 (Car), 65.7 (N-CH2), 28.0, 26.9, 26.4,
25.9 (ar-CH, CH3, Y-CH2), 4.1 (Si-CH3). Anal. Calcd for
(BDP P p yr )Lu NEt2(THF ) (9b): 182 mg of 7b (0.23 mmol);
1
23.7 µL of HNEt2 (0.23 mmol); yield 155 mg (87%). H NMR
(400 MHz, C6D6): δ 7.35-7.05 (m, 6H, ar), 6.93 (dd, 1H, pyr),
2
6.57 (d, 2H, pyr), 5.29 (d, J ) 19.6 Hz, 2H, N-CH2), 5.00 (d,
2J ) 19.6 Hz, 2H, N-CH2), 4.24 (m, 2H, ar-CH), 3.59 (m, 2H,
ar-CH), 3.22 (q, 4H, N-CH2Me), 3.11 (s, 4H, THF), 1.47 (m,
12H, CH3), 1.23 (m, 12H, CH3), 1.02 (t, 6H, NCH2-CH3), 0.91
(m, 4H, THF). 13C NMR (100 MHz, C6D6): δ 165.2, 154.8,
147.6, 146.4, 136.8, 123.5, 123.3, 122.7, 117.1 (CAr), 70.8 (THF),
65.5 (N-CH2), 44.2 (N-CH2Me), 28.3, 27.8, 27.1, 26.2, 25.4,
24.9 (ar-CH, CH3, N-CH2-CH3, THF). Anal. Calcd for C39H59
-
LuN4O: C, 60.5; H, 7.7; N, 7.2. Found: C, 60.2; H, 7.6; N, 6.5.
C
43H68N3O2SiY: C, 66.6; H, 8.8; N, 5.4. Found: C, 66.5; H,
(BDP P p yr )YNEt2(THF )2 (9c): 162 mg of 7c (0.26 mmol);
29.1 µL of HNEt2 (0.28 mmol); yield 168 mg (85%). H NMR
8.7; N, 5.2.
1
Gen er a l P r oced u r e for Syn th esizin g LLn (THF )xNR2
(8, 9, 12). To a stirred solution of the diamide-supported rare-
earth alkyl complex in 5 mL of hexane was added HNR2 at
ambient temperature. The solution was stirred at ambient
temperature for 18 h. Then the solution was filtered, and the
volatiles were removed in vacuo. The resulting yellow solid
was recrystallized from hexane to yield the pure product.
(400 MHz, THF-d8): δ 7.72 (dd, 1H, pyr), 7.20 (d, 2H, pyr),
7.00 (d, 4H, ar), 6.87 (dd, 2H, ar), 4.77 (s, 4H, N-CH2), 3.58
(m, 4H, ar-CH), 2.60 (q, 4H, N-CH2Me), 1.18 (d, 12H, CH3),
1.16 (d, 12H, CH3), 0.48 (t, 6H, NCH2-CH3). 13C NMR (100
MHz, THF-d8): δ 165.9, 154.3, 147.0, 137.6, 123.7, 122.7, 118.0
(Car), 66.4 (N-CH2), 43.3 (N-CH2Me), 30.6, 28.3, 26.7, 26.4,

Organo-Rare-Earth Complexes
Organometallics, Vol. 22, No. 6, 2003 1221
16.3 (ar-CH, CH3, N-CH2-CH3, THF). Anal. Calcd for
130.9, 129.3, 116.8 (Car), 71.9 (THF), 62.4 (N-CH2), 27.2, 21.2,
19.8 (ar-CH3, THF), 3.5 (Si-CH3). 29Si NMR (79,43 MHz,
C6D6): δ -20.7. IR: ν 2729 (s), 2662 (m), 2075 (m, Si-H), 1920
(w, Si-H), 1601 (w), 1573 (m), 1458 (vs, Nujol), 1376 (s, Nujol),
1340 (m), 1298 (m), 1242 (s), 1225 (s), 1182 (m), 1157 (m), 1028
(s), 935 (m), 898 (s), 845 (s), 796 (m), 763 (m), 726 (m), 695
(w), 626 (m), 590 (w), 523 (m), 505 (w), 490 (w), 472 (w), 454
(w), 437 (w), 424 (m), 413 (w), 403 (w) cm-1. Anal. Calcd for
C
43H67N4O2Y: C, 67.9; H, 8.9; N, 7.4. Found: C, 68.0; H, 8.6;
N, 7.7.
(BDP P p yr )ScNiP r 2(THF ) (10a ). To a stirred solution of
209 mg of 1 (0.46 mmol) in 5 mL of hexane was added dropwise
a solution of 191 mg of 6a (0.46 mmol) in 10 mL of hexane at
ambient temperature. The mixture was stirred for 7 h and
filtered, and the volatiles were removed in vacuo, resulting in
a yellow powder. Recrystallization from a mixture of hexane
and toluene at -30 °C yielded 256 mg (79%) of the pure
product. 1H NMR (400 MHz, THF-d8): δ 7.74 (dd, 1H, pyr),
7.19 (d, 2H, pyr), 6.97 (d, 4H, ar), 6.83 (dd, 2H, ar), 4.74 (m,
4H, N-CH2), 3.81 (sp, 4H, N-CH), 1.14 (d, 12H, CH3), 1.07
(d, 12H, CH3), 1.00 (d, 12H, CH3). 13C NMR (100 MHz, THF-
d8): δ 165.1, 156.6, 146.4, 138.0, 123.7, 122.5, 117.5 (Car), 64.6
(N-CH2), 49.3 (N-CH), 30.5, 28.1, 27.0, 26.3 (ar-CH, CH3).
Anal. Calcd for C41H63N4OSc: C, 73.2; H, 9.4; N, 8.3. Found:
C, 73.1; H, 9.5; N, 7.9.
C
33H51N4OScSi2: C, 63.8; H, 8.3; N, 9.0. Found: C, 63.0; H,
8.4; N, 8.5.
(BMesp yr )Lu N(SiHMe2)2(THF ) (12b): 150 mg of 8b (0.24
mmol); 44.1 µL of bis(dimethylsilyl)amine (33 mg 0.25 mmol);
1
yield 141 mg (78%). H NMR (400 MHz, THF-d8): δ 7.73 (dd,
1H, pyr), 7.20 (d, 2H, pyr), 6.75 (s, 4H, ar), 4.77 (s, 4H,
N-CH2), 4.34 (m, 2H, Si-H), 2.25 (s, 12H, ar-CH3), 2.15 (s,
6H, ar-CH3), -0.16 (d, 12H, Si-CH3). 13C NMR (100 MHz,
C6D6): δ 165.7, 153.8, 136.7, 135.6, 130.2, 129.3, 117.1 (Car),
71.1 (THF), 62.7 (N-CH2), 24.8, 21.0, 19.7 (ar-CH3, THF), 3.7
(Si-CH3). 29Si NMR (79,43 MHz, C6D6): δ -22.2. IR: ν 2727
(m), 2667 (m), 2062 (m, Si-H), 1601 (w), 1574 (w), 1462 (vs,
Nujol), 1376 (s, Nujol), 1297 (m), 1241 (s), 1204 (w), 1185 (w),
1157 (m), 1058 (m), 1027 (m), 942 (m), 895 (s), 852 (m), 838
(m), 789 (w), 768 (w), 721 (m), 680 (w), 621 (w), 596 (w), 562
(w), 530 (w), 515 (w), 482 (w), 472 (w), 455 (w), 439 (w), 415
(w) cm-1. Anal. Calcd for C33H51LuN4OScSi2: C, 52.8; H, 6.9;
N, 7.5. Found: C, 52.3; H, 7.0; N, 6.9.
(BDP P p yr )Lu NiP r 2(THF ) (10b). A solution of 167 mg of
6b (0.30 mmol) in 5 mL of hexane was added slowly to a stirred
solution of 140 mg of 1 (0.30 mmol) in 5 mL of hexane at
ambient temperature. After the mixture was stirred for 7 h,
the solution was filtered and the volatiles were removed in
vacuo, giving a yellow powder. Recrystallization from
a
mixture of hexane and toluene at -30 °C yielded 166 mg (71%)
1
of the pure product. H NMR (400 MHz, THF-d8): δ 7.73 (dd,
1H, pyr), 7.18 (d, 2H, pyr), 6.98 (d, 4H, ar), 6.83 (dd, 2H, ar),
4.85 (s, 4H, N-CH2), 3.78 (sp, 4H, ar-CH), 3.40 (sp, 2H,
N-CH),1.15 (d, 12H, CH3), 1.10 (d, 12H, CH3), 0.98 (d, 12H,
CH3). 13C NMR (100 MHz, THF-d8): δ 166.0, 156.9, 147.0,
137.9, 123.7, 122.3, 117.7 (Car), 65.5 (N-CH2), 48.2 (N-CH),
(BMesp yr )ScNiP r 2(THF ) (13a ). To a stirred solution of
110 mg of 2 (0.30 mmol) in 5 mL of hexane was added dropwise
a solution of 123 mg of 6a (0.30 mmol) in 5 mL of hexane at
ambient temperature. The mixture was stirred for 1 h and
filtered, and the volatiles were removed in vacuo, giving a gray
28.2, 27.5, 26.8, 26.3 (ar-CH, CH3). Anal. Calcd for C41H63
-
powder. Recrystallization from
a mixture of hexane and
LuN4O: C, 61.3; H, 7.9; N, 7.0. Found: C, 60.9; H, 8.0; N, 6.6.
(BMesp yr )ScCH2SiMe3(THF ) (11a ). To a stirred solution
of 314 mg of 2 (0.84 mmol) in 8 mL of THF was slowly added
a solution of 379 mg of 5a (0.84 mmol) in 7 mL of THF at
ambient temperature. The mixture was stirred for 15 min and
then filtered, and the volatiles were removed in vacuo, result-
ing in a yellow powder. Recrystallization from a mixture of
hexane and toluene at -30 °C yielded 208 mg (43%) of the
pure product. 1H NMR (400 MHz, THF-d8): δ 7.79 (dd, 1H,
pyr), 7.28 (d, 2H, pyr), 6.78 (s, 4H, ar), 4.72 (s, 4H, N-CH2),
2.24 (s, 12H, ar-CH3), 2.16 (s, 6H, ar-CH3), -0.32 (s, 9H, Si-
CH3), -0.33 (s, 2H, Sc-CH2). 13C NMR (100 MHz, THF-d8):
δ 165.2, 152.9, 138.2, 135.7, 131.1, 129.3, 118.2 (Car), 62.0 (N-
CH2), 26.4 (Sc-CH2), 20.9, 19.4 (ar-CH3), 3.7 (Si-CH3). 29Si
NMR (79.43 MHz, THF-d8): δ 3.7. Anal. Calcd for C33H48N3-
OScSi: C, 68.8; H, 8.4; N, 7.3. Found: C, 68.5; H, 8.3; N, 6.9.
(BMesp yr )Lu CH2SiMe3(THF )2 (11b). A solution of 233
mg of 5b (0.40 mmol) in 5 mL of THF was slowly added to a
stirred solution of 15 mg of 2 (0.40 mmol) in 5 mL of THF at
ambient temperature. After the mixture was stirred for 15
min, the solution was filtered and the volatiles were removed
in vacuo. The resulting brown powder was recrystallized from
a mixture of hexane and toluene at -30 °C yielding 53 mg
(21%) of the pure product. 1H NMR (400 MHz, THF-d8): δ 7.73
(dd, 1H, pyr), 7.22 (d, 2H, pyr), 6.76 (s, 4H, ar), 4.85 (s, 4H,
N-CH2), 2.26 (s, 12H, ar-CH3), 2.15 (s, 6H, ar-CH3), -0.34 (s,
9H, Si-CH3), -1.15 (s, 2H, Lu-CH2). 13C NMR (100 MHz,
THF-d8): δ 166.7, 153.5, 137.7, 135.7, 130.1, 129.5, 118.1 (Car),
63.2 (N-CH2), 26.4 (Lu-CH2), 20.9, 19.7 (ar-CH3), 4.3 (Si-
CH3). 29Si NMR (79,43 MHz, THF-d8): δ 0.4. Anal. Calcd for
toluene at -30 °C yielded 83 mg (47%) of the pure product.
1H NMR (400 MHz, THF-d8): δ 7.70 (dd, 1H, pyr), 7.19 (d,
2H, pyr), 6.68 (s, 4H, ar), 4.63 (s, 4H, N-CH2), 3.53 (sp, 4H,
N-CH), 2.14 (s, 12H, ar-CH3), 2.10 (s, 6H, ar-CH3), 0.95 (d,
12H, CH3). 13C NMR (100 MHz, THF-d8): δ 165.6, 156.0, 137.9,
134.9, 129.5, 129.3, 117.7 (Car), 62.0 (N-CH2), 48.0 (N-CH),
27.1, 20.7, 20.5 (ar-CH3, CH3). Anal. Calcd for C35H51N4OSc:
C, 71.4; H, 8.7; N, 9.5. Found: C, 70.9; H, 9.0; N, 9.2.
(BDP P oxyl)ScCH2SiMe3(THF ) (14a ). To a stirred solu-
tion of 248 mg of 4 (0.54 mmol) in 5 mL of hexane was added
dropwise a solution of 245 mg of 5a (0.54 mmol) in 5 mL of
hexane at ambient temperature. The mixture was stirred for
16 h and then filtered, and the volatiles were removed in
vacuo, yielding 355 mg (>99%) of a yellow powder. Recrystal-
lization from a mixture of hexane and toluene at -30 °C
afforded colorless crystals suitable for an X-ray analysis. 1H
NMR (400 MHz, C6D6): δ 7.30 (m, 2H, ar), 7.24-7.18 (m, 6H,
2
ar), 6.99 (m, 2H, ar), 5.52 (d, J ) 12.0 Hz, 2H, N-CH2), 4.26
2
(sp, 2H, ar-CH), 3.64 (d, J ) 12.0 Hz, 2H, N-CH2), 3.55 (sp,
2H, ar-CH), 3.28 (s br, 4H, THF), 1.62 (d, 6H, CH3), 1.55 (d,
6H, CH3), 1.34 (d, 6H, CH3), 1.16 (d, 6H, CH3) 1.15 (s br, 4H,
THF), -0.25 (s, 9H, Si-CH3), -0.30 (s, 2H, Sc-CH2). 13C NMR
(100 MHz, C6D6): δ 151.1, 145.9, 144.2, 142.1, 132.0, 124.7,
124.3, 123.5 (Car), 70.6 (THF), 60.8 (N-CH2), 29.5, 27.9, 27.1,
25.8, 25.0, 24.7, (ar-CH, CH3, THF, Sc-CH2), 3.3 (Si-CH3).
29Si NMR (79,43 MHz, C6D6): δ -3.5. Anal. Calcd for C40H61N2-
OScSi: C, 72.9; H, 9.3; N, 4.3. Found: C, 72.4; H, 9.3; N, 4.2.
(BDP P oxyl)Lu CH2SiMe3(THF ) (14b). A solution of 265
mg of 5b (0.46 mmol) in 5 mL of hexane was slowly added to
a stirred solution of 208.7 mg of 4 (0.46 mmol) in 5 mL of
hexane at ambient temperature. After the mixture was stirred
for 16 h, the solution was filtered and the volatiles were
removed in vacuo, yielding 362 mg (>99%) of a yellow powder.
1H NMR (400 MHz, THF-d8): δ 7.1-6.9 (m, 8H, ar), 6.88 (m,
2H, ar), 4.65 (s br, 4H, N-CH2), 3.85 (s br, 4H, ar-CH), 1.22
(d, 24H, CH3), -0.14 (s, 9H, Si-CH3), -1.10 (s, 2H, Lu-CH2).
13C NMR (100 MHz, THF-d8): δ 155.2, 146.4, 142.1, 131.7,
127.6, 124.0, 122.9 (Car), 59.0 (N-CH2), 28.7, 26.9, 26.4, (ar-
CH, CH3, Lu-CH2), 4.3 (Si-CH3). 29Si NMR (79,43 MHz, THF-
C
37H56LuN3O2Si: C, 57.1; H, 7.3; N, 5.4. Found: C, 57.0; H,
6.7; N, 5.6.
(BMesp yr )ScN(SiHMe2)2(THF ) (12a ): 150 mg of 11a (0.26
mmol); 55.5 µL of bis(dimethylsilyl)amine (41 mg, 0.32 mmol);
1
yield 119 mg (74%). H NMR (400 MHz, C6D6): δ 7.00-6.96
(m, 5H, ar + pyr), 6.57 (d, 2H, pyr), 4.83 (sp, 2H, Si-H), 4.59
(s br, 4H, N-CH2), 3.49 (s br, 4H, THF), 2.45 (s, 12H, ar-CH3),
2.26 (s, 6H, ar-CH3), 0.96 (s br, 4H, THF), 0.11 (d, 12H, Si-
CH3). 13C NMR (100 MHz, C6D6): δ 164.6, 154.1, 136.7, 135.4,

1222 Organometallics, Vol. 22, No. 6, 2003
Estler et al.
Ta ble 4. Cr ysta l Da ta a n d Da ta Collection
P a r a m eter s of Com p lexes 7a a n d 14a
analyzed by means of gel permeation chromatography, NMR
spectroscopy, and differential scanning calorimetry (cf. Table
3).
7a
14a
X-r a y Str u ctu r e Deter m in a tion s of Com p lexes 7a a n d
14a . Crystals suitable for diffraction experiments were selected
in a glovebox, coated with perfluorinated ether, and fixed in a
capillary. Preliminary examination of the crystal quality and
data collection were carried out on a Nonius KappaCCD
diffractometer in combination with a rotating-anode X-ray
generator and graphite-monochromated Mo KR radiation (λ
) 0.710 73 Å) employing the COLLECT software package.42
A total of 604 (419) collected images were processed using
Denzo.43 Data for compound 14a are given in parentheses.
Absorption and/or decay effects were corrected during the
scaling procedure.43 The structures were solved by direct
methods44 and refined with standard difference Fourier tech-
niques.45 All non-hydrogen atoms of the asymmetric unit were
refined with anisotropic thermal displacement parameters. In
14a all hydrogen atoms were found in the difference Fourier
maps and refined freely with individual isotropic thermal
displacement. For 7a all hydrogen atoms were placed in
calculated positions and included in the structure factor
calculation but not refined. Full-matrix least-squares refine-
chem formula
fw
C
39H60N3OScSi‚C7H8
C
40H61N2OScSi
752.08
658.96
color/shape
cryst size (mm)
cryst syst
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
colorless/fragment
0.53 × 0.28 × 0.20
triclinic
colorless/fragment
0.76 × 0.51 × 0.36
monoclinic
P21 (No. 4)
11.3658(1)
16.5331(2)
11.5392(1)
90
113.6789(5)
90
1985.80(4)
2
153
1.102
0.246
716
3.13-25.35
-13 to +13,
-19 to +19,
-13 to +13
38 508
P1h (No. 2)
11.4010(1)
13.1150(2)
15.7320(2)
78.1150(7)
79.5690(8)
76.8660(7)
2219.32(5)
2
193
1.125
0.228
816
Z
T (K)
Fcalcd (g cm-3
)
µ (mm-1
)
F000
θ range (deg)
data collected (h, k, l) -14 to +14,
-16 to +17,
2.13-27.50
-19 to +20
ments were carried out by minimizing ∑w(Fo - Fc2)2 employ-
2
no. of rflns collected
17 191
ing the SHELXL-97 weighting scheme and stopped at a
maximum shift/error of <0.001 (0.001). The right enantiomer
of 14a is proven by the Flack parameter ꢀ ) -0.01(2). For the
final model, 537 (650) parameters were refined to wR2 )
0.1115 (0.0656) on the basis of all 9706 (7256) data. For details
see Table 4.
no. of indep rflns/Rint 9706 (all)/0.023
7256 (all)/0.043
6868 (obsd)
no. of obsd rflns
7529 (obsd)
(I > 2σ(I))
no. of params refined 537
650
R1 (obsd/all)
0.0426/0.0662
0.0273/0.0308
0.0638/0.0656
1.033/1.033
+0.30/-0.15
wR2 (obsd/all)
GOF (obsd/all)
max/min ∆F (e Å-3
0.0973/0.1115
1.099/1.099
+0.27/-0.35
)
Ack n ow led gm en t. We thank Degussa AG for gen-
erous financial support and polymer analysis. Support
from the Deutsche Forschungsgemeinschaft, the Fonds
der Chemischen Industrie, and Prof. Wolfgang A. Herr-
mann is gratefully acknowledged. F.E. thanks the Fonds
der Chemischen Industrie for the award of a fellowship.
d8): δ 0.6. Anal. Calcd for C40H61LuN2OSi: C, 60.9; H, 7.8; N,
3.6. Found: C, 60.5; H, 7.8; N, 3.5.
(BDP P oxyl)YCH2SiMe3(THF ) (14c). To a stirred solution
of 186 mg of 4 (0.41 mmol) in 5 mL of hexane was added
dropwise a solution of 202 mg of 5c (0.41 mmol) in 5 mL of
hexane at ambient temperature. The mixture was stirred for
16 h and filtered, and the volatiles were removed in vacuo,
yielding 287 mg (>99%) of a yellow powder. 1H NMR (400
MHz, THF-d8): δ 7.1-6.8 (m, 10H, ar), 4.69 (s br, 4H, N-CH2),
3.78 (s br, 4H, ar-CH), 1.18 (d, 24H, CH3), -0.01 (s, 9H, Si-
CH3), -0.96 (d, 2J ) 3.6 Hz, 2H, Y-CH2). 13C NMR (100 MHz,
THF-d8): δ 155.7, 146.3, 141.8, 131.0, 126.9, 124.0, 122.5 (Car),
58.7 (N-CH2), 28.5, 26.9, 25.4, (ar-CH, CH3, Y-CH2), 4.5 (Si-
CH3). 29Si NMR (79,43 MHz, THF-d8): δ -1.7. Anal. Calcd
for C40H61N2OSiY: C, 68.3; H, 8.7; N, 4.0. Found: C, 67.8; H,
8.4; N, 3.6.
P olym er iza tion of Meth yl Meth a cr yla te (MMA). In a
typical reaction, to a solution of 0.2 mol % catalyst precursor
in toluene (1 mL/mmol of MMA) was added the desired amount
of MMA at ambient temperature. After the solution was stirred
for 48 h at ambient temperature, the polymerization was
terminated by the addition of 100 mL of methanol. The
resulting white polymer was collected by filtration and dried
under reduced pressure. The poly(methyl methacrylate) was
Su p p or tin g In for m a tion Ava ila ble: Tables of X-ray
crystallographic data for compounds 7a and 14a ; these data
are also given in CIF format. This material is available free
of charge via the Internet at http://pubs.acs.org.
OM020783S
(42) Hooft, R. COLLECT, Data Collection Software for Nonius
KappaCCD Devices; Nonius BV, Delft, The Netherlands, 1998.
(43) Otwinowski, Z.; Minor, W. In Processing of X-ray Diffraction
Data Collected in Oscillation Mode; Carter, C. W., J r., Sweet, R. M.,
Eds.; Academic Press: New York, 1997; Vol. 276, p 307.
(44) Altomare, A.; Cascarano, G.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr. 1994, 27,
435.
(45) Sheldrick, G. M. SHELXL-97; Universita¨t Go¨ttingen, Go¨ttingen,
Germany, 1998.
(46) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool;
Utrecht University: Utrecht, The Netherlands, 2001.
(47) Fryzuk, M. D.; J afarpour, L.; Kerton, F. M.; Love, J . B.; Patrick,
B. O.; Rettig, S. J . Organometallics 2001, 20, 1387.