Synthesis and structures of zirconium and hafnium alkyl complexes that contain [H3CC(2-C5H4N)(CH2NAr)2] 2- ([ArNpy]2-; Ar = Mesityl, triisopropylphenyl) ligands

Article abstract of DOI:10.1021/om0207055

We report the synthesis of the arylated diamidopyridine ligands [H₃CC(2-C₅H₄N)(CH₂NAr)₂] ^2- ([ArNpy]^2-; Ar = 2,4,6-Me₃C₆H₂ (Mes), 2,4,6-(i-Pr)₃C₆H₂ (Trip)). [ArNpy]M(NMe₂)₂ (M = Zr, Hf) complexes were prepared by treating M(NMe₂)₄ with H₂[ArNpy], while [ArNpy]MCl₂ was prepared in a reaction between [ArNpy] M(NMe₂)₂ and Me₃SiCl. Zirconium dialkyl complexes that were prepared include [MesNpy]ZrR₂ (R = methyl, benzyl, neopentyl, isobutyl), [MesNpylZr(THF)Me₂, [Li(Et₂O)]{[MesNpy]ZrMe₃}-, and [TripNpy]Zr(i-Bu)₂. Hafnium [MesNpy]HfR₂ complexes are relatively stable, even when β-protons are present in R (R = Me, Et, n-Pr, n-Bu, i-Bu, i-Pr). Monoalkyl monochloro hafnium complexes that were prepared include [MesNpy]Hf(i-Pr)Cl and [MesNpy]Hf(t-Bu)Cl. X-ray studies were carried out for [MesNpy]ZrMe₂, [MesNpy]Zr(THF)Me₂, [Li(Et₂O)]{[MesNpy]ZrMe₃}, [TripNpy]Zr(i-Bu)₂, [MesNpy]Hf(i-Pr)Cl, and [MesNpy]Hf(i-Pr)₂.

Full text of DOI:10.1021/om0207055

Organometallics 2002, 21, 5785-5798
5785
Syn th esis a n d Str u ctu r es of Zir con iu m a n d Ha fn iu m
Alk yl Com p lexes Th a t Con ta in [H3CC(2-C5H4N)(CH2NAr )2]2-
([Ar Np y]2-; Ar ) Mesityl, Tr iisop r op ylp h en yl) Liga n d s
Parisa Mehrkhodavandi, Richard R. Schrock,* and Peter J . Bonitatebus, J r.
Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue,
Cambridge, Massachusetts 02139
Received August 28, 2002
We report the synthesis of the arylated diamidopyridine ligands [H3CC(2-C5H4N)-
(CH2NAr)2]2- ([ArNpy]2-; Ar ) 2,4,6-Me3C6H2 (Mes), 2,4,6-(i-Pr)3C6H2 (Trip)). [ArNpy]-
M(NMe2)2 (M ) Zr, Hf) complexes were prepared by treating M(NMe2)4 with H2[ArNpy],
while [ArNpy]MCl2 was prepared in a reaction between [ArNpy]M(NMe2)2 and Me3SiCl.
Zirconium dialkyl complexes that were prepared include [MesNpy]ZrR2 (R ) methyl, benzyl,
neopentyl, isobutyl), [MesNpy]Zr(THF)Me2, [Li(Et2O)]{[MesNpy]ZrMe3}, and [TripNpy]Zr-
(i-Bu)2. Hafnium [MesNpy]HfR2 complexes are relatively stable, even when â-protons are
present in R (R ) Me, Et, n-Pr, n-Bu, i-Bu, i-Pr). Monoalkyl monochloro hafnium complexes
that were prepared include [MesNpy]Hf(i-Pr)Cl and [MesNpy]Hf(t-Bu)Cl. X-ray studies
were carried out for [MesNpy]ZrMe2, [MesNpy]Zr(THF)Me2, [Li(Et2O)]{[MesNpy]ZrMe3},
[TripNpy]Zr(i-Bu)2, [MesNpy]Hf(i-Pr)Cl, and [MesNpy]Hf(i-Pr)2.
Ch a r t 1
In tr od u ction
In the past decade, a great deal of metal chemistry
has appeared in which two or three amido ligands
have “supported” chemistry at the metal center.1 Poly-
dentate multiamido ligands have the advantage of not
being lost from the metal as readily as monodentate
amido ligands and the potential to sterically and
electronically define the remaining coordination sites.2
Diamido/donor ligands, in which the donor occupies a
position between the two amido functionalities, have
emerged as a relatively useful class of polydentate
multiamido ligands.2 Five-coordinate and six-coordinate
species are usually encountered. In the most common
version of a diamido/donor ligand the two “arms” contain
two atoms (usually two carbon atoms or one carbon and
one silicon atom) and both arms are connected directly
to the donor in the middle. These ligands adopt either
a “mer” arrangement of the two amido nitrogens and
the donor atom or a “fac” arrangement, as illustrated
in Chart 1 for two generic five-coordinate [(RNCH2-
CH2)2D]MX2 species (where D ) donor, e.g., O, S, or
NR′). An exception is the diamido/donor ligand [H3CC-
(2-C5H4N)(CH2NAr)2]2- ([RNpy]2-) developed by Gade,
in which a pyridyl is the donor functionality, the arms
are not directly attached to the donor atom, and R )
trimethylsilyl.2-5 In this case the geometry is restricted
to fac if the pyridyl donor remains bound to the metal.
contain diamido/donor ligands6 with the goal of develop-
ing new olefin polymerization catalysts7 and, in par-
ticular, living polymerization catalysts.8,9 Although our
first successful living polymerization systems involved
ligands of the type [(t-BuN-o-C6H5)2O]2- bound to
In the past 5 years we have been interested in
exploring the chemistry of group 4 complexes that
(3) Gade, L. H.; Mountford, P. Coord. Chem. Rev. 2001, 216, 65-
97.
(4) Friedrich, S.; Schubart, M.; Gade, L. H.; Scowen, I. J .; Edwards,
A. J .; McPartlin, M. Chem. Ber./ Recl. 1997, 130, 1751-1759.
(5) Blake, A. J .; Collier, P. E.; Gade, L. H.; McPartlin, M.; Mountford,
P.; Schubart, M.; Scowen, I. J . Chem. Commun. 1997, 1555.
(1) Kempe, R. Angew. Chem., Int. Ed. 2000, 39, 468-493.
(2) Gade, L. H. Chem. Commun. 2000, 173-181.
10.1021/om0207055 CCC: $22.00 © 2002 American Chemical Society
Publication on Web 11/21/2002

5786 Organometallics, Vol. 21, No. 26, 2002
Mehrkhodavandi et al.
zirconium,6b,c,e we have become interested most recently
in the potential advantage of a ligand that can coordi-
nate to a metal in only a fac manner, namely the
[RNpy]2- ligand. However, in our opinion silated amido
ligands, with rare exceptions, are not likely to be stable
toward side reactions in the cationic complexes that are
employed for olefin polymerization.10 Therefore, we have
largely employed aryl substituents on the amido nitro-
gens in diamido/donor ligands that contain saturated
arms and, in particular, 2,6-disubstituted aryl groups.
We have hoped that this approach will allow us to probe
in detail the characteristics of catalyst systems for the
living polymerization of ordinary olefins.
In two preliminary communications we have reported
zirconium11 and hafnium12 complexes that contain a
[ArNpy]2- ligand, where Ar ) 2,4,6-trimethylphenyl
(Mes), and their use for the polymerization of 1-hexene.
It turns out that {[MesNpy]Hf(alkyl)}[B(C6F5)4] com-
plexes are readily prepared in wide variety and are well-
behaved catalysts for the living polymerization of 1-hex-
ene below 10 °C in chlorobenzene.12 Systems of this type
are believed to be deactivated once â-hydride elimina-
tion takes place, thereby limiting the number of polymer
chains to one per metal. Most importantly, however,
because of the living characteristics of these catalysts
under the conditions we have employed, and because
we believe that no polymer chain is regenerated after
â-elimination under the conditions employed, we have
had the opportunity to carry out NMR and direct kinetic
studies on a variety of cationic alkyl complexes. In
contrast, the many questions that have been posed in
other single-site olefin polymerization systems in the
past, activated metallocenes in particular,13 could only
be addressed “indirectly” through polymer analysis.
(See, however, recent quantitative work by Landis on
an ionic metallocene system.14,15) We also have come to
believe that the {[MesNpy]Hf(alkyl)}+ systems are
relatively “open”, a characteristic that may accentuate
the role played by a weakly coordinating anion such as
[B(C6F5)4]-.
In this paper we report the preparation of zirconium
and hafnium alkyl complexes that we will employ in
polymerization studies to be reported in subsequent
papers. Stable dialkyl complexes are required for the
synthesis of alkyl monocations. As we will show here,
hafnium dialkyl complexes are especially stable and
isolable, even when the alkyl is a secondary alkyl such
as isopropyl.
Resu lts
Syn th esis of Zir con iu m Dia lk yl Com p lexes. The
parent diamine H3CC(2-C5H4N)(CH2NH2)2 was synthe-
sized in four steps from 2-ethylpyridine in the manner
reported by Gade et al.4 The aryl groups subsequently
were attached to the amine nitrogens using a coupling
reaction developed by Buchwald (eq 1).16,17 A 1% catalyst
loading (Pd2(dibenzylideneacetone)3 plus BINAP) was
used for the preparation of both H2[MesNpy] and H2-
[TripNpy]. The synthesis of H2[MesNpy] was complete
after 1-2 days at 100 °C, whereas synthesis of H2-
[TripNpy] required at least 8 days in refluxing toluene
to go to completion. H2[MesNpy] can be recrystallized
readily from pentane, while H2[TripNpy] could be
obtained only as a waxy solid.
(6) (a) Aizenberg, M.; Turculet, L.; Schattenmann, F.; Davis, W. M.;
Schrock, R. R. Organometallics 1998, 17, 4795. (b) Baumann, R.;
Schrock, R. R. J . Organomet. Chem 1998, 557, 69. (c) Baumann, R.;
Stumpf, R.; Davis, W. M.; Liang, L.-C.; Schrock, R. R. J . Am. Chem.
Soc. 1999, 121, 7822. (d) Flores, M. A.; Manzoni, M. R.; Baumann, R.;
Davis, W. M.; Schrock, R. R. Organometallics 1999, 18, 3220. (e)
Goodman, J . T.; Schrock, R. R. Organometallics 2001, 20, 5205. (f)
Liang, L.-C.; Schrock, R. R.; Davis, W. M.; McConville, D. H. J . Am.
Chem. Soc. 1999, 121, 5797. (g) Schrock, R. R.; Schattenmann, F.;
Aizenberg, M.; Davis, W. M. Chem. Commun. 1998, 199. (h) Schrock,
R. R.; Baumann, R.; Reid, S. M.; Goodman, J . T.; Stumpf, R.; Davis,
W. M. Organometallics 1999, 18, 3649. (i) Schrock, R. R.; Seidel, S.
W.; Schrodi, Y.; Davis, W. M. Organometallics 1999, 18, 428. (j)
Schrock, R. R.; Casado, A. L.; Goodman, J . T.; Liang, L.-C.; Bonitatebus,
P. J ., J r.; Davis, W. M. Organometallics 2000, 19, 5325. (k) Schrock,
R. R.; Bonitatebus, P. J ., J r.; Schrodi, Y. Organometallics 2001, 20,
1056. (l) Schrodi, Y.; Schrock, R. R.; Bonitatebus, P. J ., J r. Organo-
metallics 2001, 20, 3560.
We have found that the most reproducible approach
to zirconium or hafnium dialkyl complexes which con-
tain a [ArNpy]2- ligand is that shown in Scheme 1.
Complexes [MesNpy]Zr(NMe2)2 and [MesNpy]ZrCl2 could
be prepared in ∼90% yield. The [MesNpy]ZrMe2 com-
plex has a pronounced tendency to coordinate THF and
also to form an “ate” complex with the methylating
agent. However, [MesNpy]ZrMe2 can be synthesized in
moderate yields if the reaction conditions are strictly
controlled: i.e., no THF is present in the drybox
atmosphere and the Grignard reagent has been care-
fully titrated. Exposure of [MesNpy]ZrMe2 to even small
quantities of THF yields the THF adduct [MesNpy]Zr-
(THF)Me2, while addition of methyllithium to [MesNpy]-
ZrMe2 leads to a complex with the formula [Li(Et2O)]-
{[MesNpy]ZrMe3} (eq 2). The preferred preparation of
the THF adduct is a “direct” method in which ZrCl4 in
ether is treated with H2[MesNpy] followed by 4 equiv
of MeMgCl in THF. In systems such as [(MesNCH2-
CH2)2NMe]ZrMe26j and [(t-BuN-o-C6H5)2O]ZrMe2,6c ether
(7) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 428-447.
(8) Coates, G. W. J . Chem. Soc., Dalton Trans. 2002, 467-475.
(9) Coates, G. W.; Hustad, P. D.; Reinartz, S. Angew. Chem., Int.
Ed. 2002, 41, 2236-2257.
(10) Schrock, R. R.; Liang, L.-C.; Baumann, R.; Davis, W. M. J .
Organomet. Chem. 1999, 591, 163.
(11) Mehrkhodavandi, P.; Bonitatebus, P. J .; Schrock, R. R. J . Am.
Chem. Soc. 2000, 122, 7841-7842.
(12) Mehrkhodavandi, P.; Schrock, R. R. J . Am. Chem. Soc. 2001,
123, 10746-10747.
(13) Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143.
(14) Liu, Z.; Somsook, E.; Landis, C. R. J . Am. Chem. Soc. 2001,
123, 2915-2916.
(15) Liu, Z.; Somsook, E.; White, C. B.; Rosaaen, K. A.; Landis, C.
R. J . Am. Chem. Soc. 2001, 123, 11193-11207.
(16) Wolfe, J . P.; Wagaw, S.; Buchwald, S. L. J . Am. Chem. Soc.
1996, 118, 7215-7216.
(17) Wolfe, J . P.; Wagaw, S.; Marcoux, J .-F.; Buchwald, S. L. Acc.
Chem. Res. 1998, 31, 805-818.

Zirconium and Hafnium Alkyl Complexes
Organometallics, Vol. 21, No. 26, 2002 5787
Sch em e 1. Syn th esis of Dia lk yl Com p lexes
adducts do not form readily, presumably because such
species are sterically more crowded than [MesNpy]-
ZrMe2.
in a mer fashion. The planes of the mesityl rings are
virtually perpendicular to the plane of the amido
ligands: e.g., the C(13)-N(2)-C plane. This will be true
in all complexes whose structures are reported here. An
orientation of the aryl plane perpendicular to the amido
ligand plane is most reasonable sterically; also, π-bond-
ing to the metal is likely to be more significant than
any conjugation with the phenyl π-system.
The X-ray crystal structures of [MesNpy]Zr(THF)Me2
(Figure 2, Tables 1 and 4) and [Li(Et2O)]{[MesNpy]-
ZrMe3} (Figure 3, Tables 1 and 4) showed them to be
pseudo-octahedral complexes, with one molecule of THF
in the former coordinated trans to an amido nitrogen
(N(2)) and a lithium cation (to which one ether is bound)
interacting approximately equally with the methyl
groups (Li-C ) 2.206, 2.217, and 2.272 Å) in the latter.
The differences between these structures and [MesNpy]-
ZrMe2 is readily understood in terms of the higher
coordination geometry. The main difference is that the
Namido-Zr-Namido bond angle in each is ∼10° less than
what it is in [MesNpy]ZrMe2. In [Li(Et2O)]{[MesNpy]-
A single-crystal X-ray study of [MesNpy]ZrMe2 re-
veals a trigonal-bipyramidal structure with pseudo-Cs
symmetry (Figure 1 and Tables 1 and 3). The ligand is
coordinated with a fac geometry, as expected. The angle
between the two methyl groups (C(28) and C(29)) is
89.1(2)°, and the respective Zr-C bond lengths are
2.294(5) and 2.284(6) Å. The N(1)-Zr(1)-N(2) angle in
[MesNpy]ZrMe2 is 102.24(12)°, which is significantly
smaller than the angle in analogous complexes where
the ligand is coordinated with a mer geometry: i.e.,
6j
140.5(2) and 139.6(2)° for [(MesNCH2CH2)2NMe]ZrMe2
or [2,6-(2,6-Et2C6H3NCH2)2NC5H3]ZrMe2,18 respectively.
The Zr-Ndonor bond is only slightly longer than those
reported for [(MesNCH2CH2)2NMe]ZrMe26j (2.387(7) Å)
or [2,6-(2,6-Et2C6H3NCH2)2NC5H3]ZrMe2 (2.325(4) Å),18
in which the diamido/donor ligands bind to the metal
F igu r e 1. Thermal ellipsoid plot (35% probability level)
of the structure of [MesNpy]ZrMe2.
(18) Guerin, F.; McConville, D. H.; Vittal, J . J . Organometallics
1996, 15, 5586-5590.

5788 Organometallics, Vol. 21, No. 26, 2002
Mehrkhodavandi et al.
Ta ble 1. Cr ysta l Da ta a n d Str u ctu r e Refin em en t Deta ils for [MesNp y]Zr Me2, [MesNp y]Zr (THF )Me2, a n d
[Li(Et2O)]{[MesNp y]Zr Me3}a
[MesNpy]ZrMe2
[MesNpy]Zr(THF)Me2
[Li(Et2O)]{[MesNpy]ZrMe3}
empirical formula
fw
C
33H49N3OZr
C33H47N3OZr
592.96
C34H52LiON3Zr
617.15
594.97
temp, K
183(2)
180(2)
183
cryst syst
space group
orthorhombic
P212121
monoclinic
C2/c
orthorhombic
P212121
unit cell dimens
a, Å
b, Å
c, Å
11.4721(2)
16.3643(3)
17.5024(2)
32.739(2)
14.540(6)
15.451(6)
15.504(5)
12.6838(7)
15.1138(9)
92.890(2)
â, deg
V, Å3
3285.78(9)
6268.0(6)
3483(2)
Z
4
8
3
density (calcd), g/cm3
abs coeff, mm-1
F(000)
1.203
0.362
1264
1.257
0.379
2512
1.176
0.343
1312
cryst size, mm3
θ range for data collecn, deg
index ranges
0.5 × 0.5 × 0.5
2.12-23.25
-12 e h e 8
-18 e k e 18
-19 e l e 19
13 544
4674 (R(int) ) 0.0361)
99.9 (23.25)
empirical
0.32 × 0.25 × 0.18
1.25-23.28
-36 e h e 36
-14 e k e 9
-15 e l e 16
12 617
4502 (R(int) ) 0.0528)
99.9 (23.28)
none
0.3 × 0.3 × 0.3
2.33-23.39
-16 e h e 11
-17 e k e 12
-12 e l e 13
6715
4175 (R(int) ) 0.0478)
85.5 (23.39)
empirical
no. of rflns collected
no. of indep rflns
completeness, % (to θ, deg)
abs cor
max, min transmission
no. of data/restraints/params
goodness of fit on F2
final R indices (I >2σ(I))
R indices (all data)
extinction coeff
0.2617, 0.2347
4674/0/344
1.129
R1 ) 0.0410, wR2 ) 0.0990
R1 ) 0.0462, wR2 ) 0.1030
0.0028(5)
0.9349, 0.8883
4502/0/363
1.263
R1 ) 0.0616, wR2 ) 0.1346
R1 ) 0.0718, wR2 ) 0.1395
0.00008(8)
0.461, -0.444
0.2731, 0.2158
4175/0/361
0.941
R1 ) 0.0426, wR2 ) 0.0842
R1 ) 0.0745, wR2 ) 0.0924
-0.04(6)
largest diff peak, hole, e Å-3
0.462, -0.436
0.248, -0.298
a
In all cases the wavelength was 0.710 73 Å (Mo KR) and the refinement method was full-matrix least squares on F2.
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t for [Tr ip Np y]Zr (i-Bu )2, [MesNp y]Hf(i-P r )Cl, a n d
a
[MesNp y]Hf(i-P r )2
[TripNpy]Zr(i-Bu)2
[MesNpy]Hf(i-Pr)Cl
[MesNpy]Hf(i-Pr)2
C33H47N3Hf
empirical formula
C47H75N3Zr
C30H40ClN3Hf
fw
temp, K
cryst syst
space group
773.32
293(2)
triclinic
P1h
656.59
183(2)
orthorhombic
Pbca
664.23
293(2)
orthorhombic
Pbca
unit cell dimens
a, Å
b, Å
c, Å
12.592(4)
12.601(4)
17.403(6)
15.4981(9)
18.3136(11)
21.0590(13)
15.926(4)
18.600(5)
20.937(6)
R, deg
69.662(5)
86.747(5)
64.631(5)
2325.6(13)
2
1.104
0.268
836
0.2 × 0.2 × 0.1
2.54-11.65
-8 e h e 13
-13 e k e 10
-19 e l e 13
4637
4249 (R(int) ) 0.0330)
63.4 (23.31)
empirical
â, deg
γ, deg
v, Å3
5977.1(6)
6202(3)
Z
8
8
density (calcd), g/cm3
abs coeff, mm-1
F(000)
1.459
1.423
3.601
3.388
2640
2704
cryst size, mm3
θ range for data collecn, deg
index ranges
0.26 × 0.20 × 0.10
0.16 0.14 × 0.10
1.94-23.27
-17 e h e 17
-20 e k e 15
-23 e l e 21
24 072
2.34-23.27
-16 e h e 17
-18 e k e 20
-23 e l e 21
22 824
no. of rflns collected
no. of indep rflns
completeness, % (to θ, deg)
abs cor
4288 (R(int) ) 0.0499)
99.8 (23.27)
empirical
4450 (R(int) ) 0.0468)
99.9 (23.27)
empirical
max, min transmission
no. of data/restraints/params
goodness of fit on F2
final R indices (I >2σ(I))
R indices (all data)
extinction coeff
0.9291 and 0.6462
4249/0/460
1.020
R1 ) 0.0452, wR2 ) 0.1125
R1 ) 0.0608, wR2 ) 0.1217
0.7147 and 0.4545
4288/0/453
1.125
R1 ) 0.0375, wR2 ) 0.0727
R1 ) 0.0461, wR2 ) 0.0758
0.000000(13)
0.652, -0.983
0.9848 and 0.6827
4450/0/346
1.082
R1 ) 0.0292, wR2 ) 0.0603
R1 ) 0.0380, wR2 ) 0.0634
0.000024(16)
0.825, -0.667
largest diff peak, hole, e Å-3
0.421, -0.309
a
In all cases the wavelength was 0.71073 Å (MoKR) and the refinement method was full-matrix least-squares on F2.
ZrMe3} the equatorial Zr-C bonds are now ∼0.1 Å
longer than the axial Zr-C bond. A similar interaction
between (two) methyl groups and a solvated lithium ion
is found in [Li(tmeda)][ZrMe6].19

Zirconium and Hafnium Alkyl Complexes
Organometallics, Vol. 21, No. 26, 2002 5789
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles (d eg) in th e F ive-Coor d in a te Com p lexes
[MesNpy]ZrMe2
[TripNpy]Zr(i-Bu)2
[MesNpy]Hf(i-Pr)Cl
[MesNpy]Hf(i-Pr)2
M-Namido(1)
M-Namido(2)
M-N(py)
M-Cax
2.027(3)
2.034(3)
2.444(4)
2.284(6)
2.294(5)
102.24(12)
102.2(2)
101.2(2)
125.55(19)
127.74(19)
89.1(2)
2.047(4)
2.047(4)
2.483(4)
2.253(5)
2.258(7)
98.46(16)
102.31(17)
104.35(18)
130.2(3)
125.0(3)
90.4(2)
1.997(5)
2.031(5)
2.339(5)
2.252(7)
2.445(2)
97.35(18)
108.0(2)
97.4(2)
118.49(14)
139.98(15)
87.98(19)
83.78(18)
82.08(18)
168.1(2)
84.96(13)
2.032(3)
2.035(3)
2.412(3)
2.297(4)
a
M-Leq
2.268(5)
N
N
N
N
N
amido(1)-M-Namido(2)
amido(1)-M-Cax
amido(2)-M-Cax
amido(1)-M-Leq
amido(2)-M-Leq
98.94(14)
105.57(15)
97.72(15)
122.75(17)
134.62(17)
88.24(18)
81.14(12)
81.34(13)
173.28(14)
87.73(16)
Cax-M-Leq
N
N
amido(1)-M-N(py)
amido(2)-M-N(py)
80.81(14)
80.58(14)
175.96(19)
86.9(2)
80.03(13)
81.18(14)
173.46(18)
83.5(2)
Cax-M-N(py)
Leq-M-N(py)
a
Leq is an alkyl or (for [MesNpy]Hf(i-Pr)Cl) a chloride ligand.
Ta ble 4. Selected Bon d Dista n ces (Å) a n d
An gles (d eg) in th e Six-Coor d in a te Com p lexes
[MesNpy]-
[Li(OEt2)]-
Zr(THF)Me2
{[MesNpy]ZrMe3}
M-Namido(1)
M-Namido(2)
M-N(py)
M-Cax
2.063(4)
2.115(4)
2.471(4)
2.288(6)
2.361(5)
2.387(4)
90.73(16)
79.93(15)
173.81(14)
99.4(2)
100.70(18)
76.66(15)
84.23(14)
111.3(2)
154.26(19)
95.35(13)
172.1(2)
82.69(18)
85.84(18)
82.56(16)
89.7(2)
2.113(5)
2.101(5)
2.399(5)
2.319(6)
2.461(6)
2.421(7)
91.48(18)
80.44(17)
165.7(2)
105.5(2)
87.39(19)
79.74(18)
94.3(2)
105.6(2)
167.1(2)
87.8(2)
171.62(18)
87.40(18)
85.4(2)
M-Ceq
a
M-Leq
Namido(1)-M-Namido(2)
N
amido(1)-M-N(py)
Namido(1)-M-Leq
Namido(1)-M-Cax
F igu r e 2. Thermal ellipsoid plot (35% probability level)
of the structure of [MesNpy]Zr(THF)Me2.
N
amido(1)-M-Ceq
Namido(2)-M-N(py)
amido(2)-M-Leq
Namido(2)-M-Cax
amido(2)-M-Ceq
N
N
N(py)-M-Leq
N(py)-M-Cax
N(py)-M-Ceq
Leq-M-Cax
Leq-M-Ceq
Cax-M-Ceq
84.1(2)
87.0(2)
a
Leq is an alkyl or (for [MesNpy]Zr(THF)Me2) a THF ligand.
NMR Stu d ies of Zir con iu m Meth yl Com p lexes.
The 1H and 13C{1H} NMR spectra of [MesNpy]ZrMe2
show significant solvent and temperature dependence.
1
In C6D6 at 20 °C, the H NMR spectrum of [MesNpy]-
ZrMe2 shows a singlet at 0.56 ppm corresponding to six
Zr-CH3 protons, while the 13C{1H} NMR spectrum
shows one broad resonance at 36.5 ppm for the Zr-CH3
carbons. In C6D5Br at 20 °C and a concentration of 0.01
M in [MesNpy]ZrMe2, the 1H NMR spectrum shows two
broad singlets at 0.22 and 0.32 ppm (Figure 4), while
the 13C{1H} NMR spectrum shows two resonances at
35.46 and 36.65 ppm. At -25 °C two relatively sharp
resonances are observed, corresponding to the axial and
equatorial methyl groups (Figure 4). As the temperature
is raised, the peaks broaden and finally coalesce to a
broad singlet at 90 °C, indicating an exchange of methyl
groups. At temperatures above 70 °C [MesNpy]ZrMe2
starts to decompose to yield methane (0.15 ppm in the
1H NMR spectrum) as well as unidentified zirconium
products. At a concentration of 0.1 M the 20 °C spectrum
shows a single resonance for the two methyl groups at
0.26 ppm. All data are consistent with a significant
intermolecular component to the methyl exchange pro-
cess. Since two alkyl groups are observed at 22 °C and
F igu r e 3. Thermal ellipsoid plot (35% probability level)
of the structure of [Li(Et2O)]{[MesNpy]ZrMe3}.
Dimethyl complexes of the bulkier [TripNpy]2- ligand
could also be prepared by similar methods. [TripNpy]-
ZrMe2 is easier to synthesize and isolate than [MesNpy]-
ZrMe2, since complications due to solvent coordination
or zirconate formation are minimized, presumably
because of the greater steric demand of the [TripNpy]2-
ligand versus the [MesNpy]2- ligand.
Dimethyl complexes that contain a 13C label in the
methyl groups also have been prepared in good yield
and were used in many labeling and NMR studies to
be discussed below and in future papers.
(19) Morse, P. M.; Girolami, G. S. J . Am. Chem. Soc. 1989, 111,
4114-4116.

5790 Organometallics, Vol. 21, No. 26, 2002
Mehrkhodavandi et al.
1
F igu r e 4. Variable-temperature H NMR spectra (500 MHz, C6D5Br, ZrCH3) of [MesNpy]ZrMe2 (0.010 M).
to the two methyl groups in (partially) 13C-labeled
[TripNpy]ZrMe2, along with a broad singlet at 36.9 ppm
that corresponds to (partially) 13C-labeled [MesNpy]-
ZrMe2. We propose that the intermediates in such
intermolecular exchanges contain two bridging methyl
groups, as shown in Scheme 2, on the basis of ready
formation of six-coordinate species, especially [Li(Et2O)]-
{[MesNpy]ZrMe3}. There is always a possibility that the
pyridyl group can dissociate from the metal at some
point during an exchange process, since a dissociated
pyridyl donor has been observed in certain imido
complexes that contain the [TMSNpy]2- ligand that
have been reported in the literature.3
1
The H NMR spectrum (20 °C, C6D6) of [MesNpy]Zr-
(THF)Me2 shows a singlet at 0.54 ppm which corre-
sponds to six Zr-CH3 protons, along with resonances
for 1 equiv of THF, while the 13C{1H} spectrum shows
a broad signal at 35.8 ppm. The 1H NMR spectrum
(C6D6, 20 °C) of [Li(Et2O)]{[MesNpy]ZrMe3} shows a
singlet at -0.06 ppm corresponding to nine Zr-CH3
protons along with resonances that correspond to 1
equiv of diethyl ether. Two resonances are observed for
the ortho methyl groups on the mesityl rings, consistent
with restricted rotation of the aryl groups. Zirconium-
methyl group exchange may be more complex in [MesN-
py]Zr(THF)Me2 and [Li(Et2O)]{[MesNpy]ZrMe3} than in
[MesNpy]ZrMe2. However, we presume that [MesNpy]-
ZrMe2 is readily accessible in each of the octahedral
systems and that methyl groups exchange intermolecu-
larly.
Oth er Zir con iu m Dia lk yl Com p lexes. Several
other zirconium dialkyl compounds could be prepared
by alkylation of dichloride complexes. The dibenzyl
compound [MesNpy]ZrBz2 was isolated easily in 83%
yield and was found to be quite robust, as is typically
the case for benzyl complexes (e.g., ZrBz4) compared to
methyl or other alkyl analogues, in which the alkyl
contains a â-proton. The 1H NMR spectrum (21 °C,
C6D6) showed one broad resonance at 2.5 ppm corre-
F igu r e 5. Exchange of methyl groups between [TripNpy]-
Zr13Me2 (B) and [MesNpy]ZrMe2 (A) (20 °C, C6D6, 0.018
M) to give partially labeled B and A.
concentrations of ∼0.01 M in compounds of zirconium
and hafnium in which the alkyl groups are large relative
to methyl, we believe that exchange of two alkyl groups
may be exclusively intermolecular and, therefore, fast
only for methyl.
Exchange of the methyl groups is slower in [TripNpy]-
ZrMe2, as shown by the presence of two resonances for
the two zirconium methyl groups at room temperature
in benzene at 0.53 and 0.61 ppm, consistent with the
greater steric demand of the [TripNpy]2- ligand. The
13C{1H} NMR spectrum of [TripNpy]Zr13Me2 shows two
resonances for Zr-CH3 carbons at 34.2 and 38.3 ppm.
The pattern observed for the isopropyl group resonances
are also consistent with slow rotation about the Trip-N
bond in the sterically more crowded environment.
A double-labeling study revealed that methyl groups
transfer rapidly on the chemical time scale between
[MesNpy]ZrMe2 and [TripNpy]Zr13Me2. For example, as
shown in Figure 5, 13C{1H} NMR spectra (20 °C, C6D6)
of mixtures of [MesNpy]ZrMe2 and [TripNpy]Zr(13Me)2
show resonances at 39.8 and 34.9 ppm corresponding

Zirconium and Hafnium Alkyl Complexes
Organometallics, Vol. 21, No. 26, 2002 5791
Sch em e 2. P r op osed Mech a n ism for Meth yl Exch a n ge betw een betw een [Tr ip Np y]Zr 13Me2 a n d
[MesNp y]Zr Me2
sponding to the four Zr-CH2 protons of the two benzyl
groups. At -40 °C in C6D5CD3, the peak at 2.5 ppm
splits into two separate resonances for two distinct sets
of Zr-CH2 protons at 2.92 and 3.44 ppm, respectively.
The dineopentyl complex [MesNpy]ZrNp2 could also be
isolated readily from the reaction between [MesNpy]-
ZrCl2 and 2 equiv of neopentyllithium. (Similar reac-
tions with neopentylmagnesium chloride were unsuc-
cessful.) The 1H NMR spectrum (20 °C, C6D6) of
[MesNpy]ZrNp2 showed two resonances for the tert-
butyl protons at 1.10 and 1.36 ppm and another set of
signals for the Zr-CH2 groups at 1.27 and 1.46 ppm.
Presumably intermolecular alkyl exchange is slow in
[MesNpy]ZrNp2, at least on the NMR time scale.
Dialkylzirconium complexes in which â-protons are
present in the alkyl group have limited stability.
[MesNpy]Zr(i-Bu)2 can be prepared, although light must
be avoided in order to realize good yields (>90%).
Different isobutyl resonances are observed, but a single
broad resonance is observed for the ortho methyl groups
in the proton NMR spectrum at 2.29 ppm at room
temperature, consistent with rotation of the mesityl
rings on the NMR time scale. Although [MesNpy]ZrEt2
appeared to form as a product of the reaction between
[MesNpy]ZrCl2 and EtMgBr in diethyl ether, it was not
stable enough to be isolated readily in pure form. Proton
NMR spectra at 22 °C were consistent with the proposed
composition, although decomposition was rapid at room
temperature (minutes).
is bound in a fac manner with the alkyl groups in axial
and equatorial positions, as found for other dialkyl
complexes in this category mentioned so far. The
structural features are similar to those of [MesNpy]-
ZrMe2. The Zr-C(5)-C(6) and Zr-C(1)-C(2) bond
angles are 130.3 and 135.5°, respectively.
Syn th esis of Ha fn iu m Dia lk yl Com p lexes. Hafni-
um complexes, [MesNpy]Hf(NMe2)2 and [MesNpy]HfCl2,
can be prepared readily by a procedure analogous to
that shown in Scheme 1. Alkylation of [MesNpy]HfCl2
leads to relatively stable [MesNpy]HfR2 species, even
when â protons are present in R. Dialkyl complexes have
been isolated for R ) Me, Et, n-Pr, i-Pr, n-Bu, and i-Bu.
NMR spectra of [MesNpy]HfMe2 and its 13C-labeled
analogue are entirely analogous to those for [MesNpy]-
ZrMe2. NMR spectra of other dialkyls are straightfor-
ward, with different resonances for axial and equatorial
alkyl groups and broad resonances for the ortho methyl
Synthesis and isolation of [TripNpy]Zr(i-Bu)2 was
more straightforward than that of [MesNpy]Zr(i-Bu)2.
Two isobutyl groups were observed in the NMR spec-
trum, and rotation about the Trip-N bonds was slow
on the NMR time scale at room temperature. An X-ray
study of [TripNpy]Zr(i-Bu)2 revealed the structure
shown in Figure 6. (See also Tables 2 and 3.) The ligand
F igu r e 6. Thermal ellipsoid plot (35% probability level)
of [TripNpy]Zr(i-Bu)2.

5792 Organometallics, Vol. 21, No. 26, 2002
Mehrkhodavandi et al.
F igu r e 8. Thermal ellipsoid plot (35% probability level)
of the structure of [MesNpy]Hf(i-Pr)2.
F igu r e 7. Thermal ellipsoid plot (35% probability level)
of the structure of [MesNpy]Hf(i-Pr)Cl.
Discu ssion
The complexes reported here further establish that
groups in the mesityl rings being observed. (All data
can be found in the Experimental Section.) The prepa-
ration and isolation of relatively stable [TripNpy]Hf-
(i-Bu)2 is also straightforward.
[ArNpy]2- ligands (Ar ) Mes, Trip, 3,5-Cl2C6H3
)
20
enforce formation of complexes in which the ligand is
bound in a fac manner to the metal, as has been
observed in several group 4 complexes that contain the
[TMSNpy]2- ligand.3,4 Since the plane of an amido
ligand approximately bisects the Cax-M-Ceq angle in
five-coordinate dialkyl complexes, it is not apparent, in
the absence of calculations, whether one or two metal-
nitrogen (amido) π-bonds can form efficiently and,
therefore, whether a five-coordinate species has a 12-
or a 14-electron count. In a variety of other amido
complexes of early metals1 the σ- and π-electron-
donating ability of nitrogen in nitrogen-based ligands
in general almost certainly decreases the electrophilicity
of the metal and consequently the polarity of metal-
carbon bonds in general, thereby leading to electron-
deficient dialkyl complexes that are relatively stable
toward intermolecular or intramolecular â-hydride ab-
straction reactions. The ability of nitrogen in amido
complexes to delocalize positive charge from the metal
out onto the amido nitrogens clearly also will be even
more important in cationic complexes.
Addition of only 1 equiv of i-PrMgCl to [MesNpy]HfCl2
led to isolation of [MesNpy]Hf(i-Pr)Cl. Only one isomer
was observed, according to NMR spectra of this com-
pound. Treatment of [MesNpy]Hf(i-Pr)Cl with 1.2 equiv
of MeMgBr led to two major products, which we
presume to be isomers that contain the isopropyl group
either in an axial or in an equatorial position, i.e.,
[MesNpy]Hf(i-Pr)eqMeax and [MesNpy]HfMeeq(i-Pr)ax.
Minor amounts of [MesNpy]HfMe2 and [MesNpy]Hf(i-
Pr)2 are also present in solution, presumably as a
consequence of some alkyl exchange between hafnium
and magnesium compounds. Treatment of [MesNpy]-
HfCl2 with 2 equiv of (t-Bu)MgCl resulted in the
1
formation of [MesNpy]Hf(t-Bu)Cl in 48% yield. The H
NMR spectrum (22 °C, C6D6) showed a resonance at 0.98
ppm corresponding to nine Hf-C(CH3)3 protons. The
13C{1H} NMR spectrum showed only one signal for the
Hf-C(CH3)2 carbon at 70.6 ppm.
The X-ray crystal structure of [MesNpy]Hf(i-Pr)Cl
(Figure 7, Tables 2 and 3) reveals that the isopropyl
group is located in the axial position of a trigonal-
bipyramidal structure that overall is similar to the
structure of other five-coordinate species discussed here.
However, the Cl-Hf-Namido angles (118.49(14) and
139.98(15)°) are significantly different, and this struc-
ture therefore is distorted significantly compared to
other five-coordinate species reported here. On the basis
of this structure we assume that the tert-butyl group
in [MesNpy]Hf(t-Bu)Cl is also located in the axial
position.
An X-ray study of [MesNpy]Hf(i-Pr)2 (Figure 8, Tables
2 and 3) revealed, as expected, that the structure of
[MesNpy]Hf(i-Pr)2 is similar to that of the other dialkyl
complexes. The TBP geometry is slightly distorted with
N(1)-Hf-C(1) ) 122.75(17)° and N(2)-Hf-C(1) )
134.62(17)°. The Hf-C(1)-C(2) angle is 135.1(4)°, but
the Hf-C(1)-C(3) angle is only 107.9(3)°. (The Hf-
C(4)-C(5) and Hf-C(4)-C(6) angles are 118.6(3) and
111.7(3)°, respectively.) We could find no evidence (e.g.,
an agostic interaction) that would lead to an explanation
of the difference between the Hf-C(1)-C(2) and Hf-
C(1)-C(3) angles.
The increased stability of hafnium dialkyls versus
zirconium dialkyls toward â-hydride processes is rela-
tively well documented in the literature.21-23 For ex-
ample, Cp2MEt2 is relatively stable only when M ) Hf.
Even Cp2Hf(t-Bu)Cl is known, and it reacts with butyl-
lithium to give isolable Cp2Hf(t-Bu)(n-Bu).24 However,
several dialkylzirconocenes in which the alkyl contains
a â-hydrogen are also known.22,25 Amido ligands appear
to produce more stable dialkyl complexes, as demon-
strated by Andersen some time ago.26,27 In our research
on diamido/donor complexes we have found many
examples of relatively stable dialkyls in which the alkyl
contains a â-hydrogen, e.g., diisobutyl complexes that
(20) Araujo, J . P.; Wicht, D. K.; Bonitatebus, P. J ., J r.; Schrock, R.
R. Organometallics 2001, 20, 5682.
(21) Negishi, E.; Takahashi, T. Acc. Chem. Res. 1994, 27, 124-130.
(22) Guo, Z. Y.; Swenson, D. C.; J ordan, R. F. Organometallics 1994,
13, 1424-1432.
(23) Erker, G.; Schlund, R.; Kru¨ger, C. Organometallics 1989, 8,
2349.
(24) Buchwald, S. L.; Kreutzer, K. A.; Fisher, R. A. J . Am. Chem.
Soc. 1990, 112, 4600.
(25) Wendt, O. F.; Bercaw, J . E. Organometallics 2001, 20, 3891.
(26) Planalp, R. P.; Andersen, R. A.; Zalkin, A. Organometallics
1983, 2, 16.
(27) Andersen, R. A. Inorg. Chem. 1979, 18, 2928.

Zirconium and Hafnium Alkyl Complexes
Organometallics, Vol. 21, No. 26, 2002 5793
prepared from 13CH3I and (CH3)2CH13CH2Br, respectively, and
Mg turnings in diethyl ether according to standard procedures.
All others were purchased from Aldrich. All Grignard reagents
were carefully titrated with 2-butanol in the presence of 1,10-
phenanthroline prior to use. H2[H3CC(2-C5H4N)(CH2NAr)2],4
contain [(t-BuN-o-C6H5)2O]2- or [(i-PrN-o-C6H5)2O]2-
ligands.6b,c,h In one case even a titanium diisobutyl
complex ([(i-PrN-o-C6H4)2O]Ti(i-Bu)2) was stable at room
temperature.6c Recently Sita28-33 published several
examples of stable acetamidinate complexes of the type
Cp*Zr(acetamidinate)R(Cl) and Cp*Zr(acetamidinate)-
R2, including an example of a Cp*Zr(acetamidinate)-
(t-Bu)(Cl) species. Therefore, nitrogen-based ligands in
general appear to stabilize group 4 monoalkyl and
dialkyl complexes against facile â-hydride elimination
or abstraction. If a stable dialkyl complex is to be
prepared, then clearly the supporting ligand must be
large enough to prevent any intermolecular decomposi-
tion of a monoalkyl intermediate or the dialkyl product,
but not so large as to prevent formation of a dialkyl
complex or to induce a â-hydride abstraction reaction
in a dialkyl complex to give an olefin complex. Therefore,
the fact that [MesNpy]Hf(i-Pr)2 is stable toward â-hy-
dride abstraction is not especially surprising, nor is the
stability of [MesNpy]Hf(t-Bu)Cl. (We could find no
example of a diisopropyl complex that contains a group
4 metal.)
In future publications we will employ many of the Zr
or Hf dialkyl complexes reported here as precursors to
monoalkyl monocations. We have shown that {[MesNpy]-
HfR}[B(C6F5)4] species are stable below 10 °C in chloro-
benzene or bromobenzene and will serve as catalysts
for the living polymerization of up to 600 equiv of
1-hexene without any detectable â-hydride elimina-
tion.12 The rigidity of the [ArNpy]2- ligand and the
ability to vary the size of the substituent on the amido
nitrogen will both help define the degree of steric
crowding in the resulting ion pair more definitively than
has been possible in other diamido/donor ligand systems
that we have employed in past studies.6
Zr(NMe2)4,35 and Hf(NMe2)4 were prepared according to
35
previously reported methods.
The reaction between 13CO2 and i-PrMgBr in diethyl ether
followed by in situ reduction with LiAlH4 and quenching of
the reaction mixture with water yielded (CH3)2CH13CH2OH.
The alcohol was separated from diethyl ether by careful and
repeated distillations. The alcohol was treated with PBr3 at
0 °C, followed by refluxing at 90 °C for 2 h, to yield
(CH3)2CH13CH2Br, which was distilled (80-84 °C, 30 mTorr)
and dried over MgSO4.
H2[MesNp y]. A Schlenk flask was charged with H3CC(2-
C5H4N)(CH2NH2)2 (5.00 g, 30 mmol), mesityl bromide (11.74
g, 59 mmol), tris(dibenzylideneacetone)dipalladium(0) (0.419
g, 0.45 mmol), rac-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl
(0.717 g, 1.15 mmol), sodium tert-butoxide (8.75 g, 91 mmol),
and toluene (200 mL). The reaction mixture was stirred and
heated to 110 °C under a stream of N2. The reaction was
complete after 1 day, with H2[MesNpy] being the only signifi-
cant product in the reaction mixture. The hot solution was
filtered through Celite to remove NaBr and washed with
pentane. The solvent was removed in vacuo, and the red
residue was dissolved in refluxing pentane (200 mL) and
filtered while hot. Clear, colorless crystals of H2[MesNpy] were
obtained from pentane: yield 7.5 g (63%); 1H NMR (500 MHz,
CDCl3/C6D6, 295 K) δ 1.71/1.59 (s, 3H, CH3), 2.16/2.21 (s, 12H,
o-CH3), 2.21/2.19 (s, 6H, p-CH3), 3.17/3.25 (d, 2H, CH2), 3.45/
3.49 (d, 2H, CH2), 3.45/3.70 (s, 2H, NH), 6.79/6.79 (s, 4H, CH),
7.22/6.63 (m, 1H, py CH), 7.49/7.06 (m, 1H, py CH), 7.71/7.07
(m, 1H, py CH), 8.69/8.41 (m, 1H, py o-CH); 13C{1H} NMR (125
MHz, C6D6, 295 K) δ 18.86 (s, o-CH3), 21.17 (s, p-CH3), 23.31
(s, CH3), 46.97 (s, CR4), 57.97 (s, CH2), 121.76 (s, Ar C), 122.00
(s, Ar C), 130.25 (s, Ar C), 130.83 (s, Ar C), 131.59 (s, Ar C),
136.65 (s, Ar C), 144.99 (s, Ar C), 149.25 (s, Ar C), 165.77 (s,
Ar C); HRMS (EI, 70 eV) m/z calcd for C27H35N3 401.283 098,
found 401.2840 (12).
Exp er im en ta l Section
H2[Tr ip Np y]. A Schlenk flask was charged with H3CC(2-
C5H4N)(CH2NH2)2 (5.16 g, 31.2 mmol), triisopropylphenyl
bromide (17.25 g, 60.9 mmol), tris(dibenzylideneacetone)-
dipalladium(0) (0.429 g, 0.468 mmol), rac-2,2′-bis(diphenylphos-
phino)-1,1′-binaphthyl (0.603 g, 0.968 mmol), sodium tert-
butoxide (9.06 g, 94.3 mmol), and toluene (400 mL). The
reaction mixture was refluxed under a stream of dinitrogen.
The reaction was complete after 8 days, with H2[TripNpy]
being the only significant product in the reaction mixture. The
solvent was removed in vacuo and the purple residue taken
up in diethyl ether (100 mL). The solution was washed with
H2O (4 × 100 mL) and saturated NaCl (3 × 100 mL). The
organic phase was dried over MgSO4. Evaporation of the
solvent gave a red solid which was used without further
Gen er a l P r oced u r es. All manipulations, with the excep-
tion of the synthesis of ligand precursors, were performed
under N2 in a glovebox or using standard Schlenk procedures.
Solvents were dried using conventional procedures.34 Chloro-
benzene (HPLC grade) and deuterated solvents were degassed
and stored over and distilled from CaH2. Commercial reagents
were used without further purification. NMR spectra were
recorded on a Varian INOVA 500 spectrometer. 1H NMR
chemical shifts are given in ppm versus residual protons in
the deuterated solvents as follows: δ 7.16, C6D6; δ 2.09,
toluene-d8 (methyl); δ 7.29, C6D5Br (most downfield resonance).
13C{1H} NMR chemical shifts are given in ppm versus residual
13C in the solvents as follows: δ 128.39, C6D6; δ 20.4, toluene-
d8 (methyl); δ 122.25, C6D5Br (most upfield resonance). Some
aryl resonances in 1H and 13C{1H} spectra are not given.
Elemental analyses were performed by H. Kolbe, Mikroana-
lytisches Laboratorium, Mu¨lheim an der Ruhr, Germany. The
Grignard reagents 13CH3MgI and (CH3)2CH13CH2MgBr were
1
purification: yield 14.4 g (81%); H NMR (500 MHz, CDCl3/
C6D6, 295 K) δ 1.13/1.23 (d, 12H, CH3), 1.90/1.25 (d, 12H, CH3),
1.23/1.30 (d, 12H, CH3), 1.77/1.76 (s, 3H, CH3), 2.83/2.84 (m,
2H, CH), 3.03/3.27 (d/m, 2H, CH2), 3.14/3.42 (m, 4H, CH), 3.43/
3.63 (d/m, 2H, CH2), 3.26/3.67 (s/m, 2H, NH), 6.91/7.10 (s, 4H,
CH), 7.22/6.68 (m, 1H, py CH), 7.51/7.10 (m, 1H, py CH), 7.70/
7.10 (m, 1H, py CH), 8.68/8.50 (m, 1H, py o-CH); 13C{1H} NMR
(125 MHz, C6D6, 295 K) δ 23.08 (s, CH3), 24.80 (s, CH3), 24.94
(s, CH3), 28.18 (s, CH3), 34.96 (s, CH), 35.15 (s, CH), 47.15 (s,
CR4), 61.55 (s, CH2), 121.77 (s, Ar C), 122.00 (s, Ar C), 122.91
(s, Ar C), 122.77 (s, Ar C), 128.68 (s, Ar C), 136.63 (s, Ar C),
142.47 (s, Ar C), 143.56 (s, Ar C), 144.55 (s, Ar C), 149.27 (s,
Ar C), 165.89 (s, Ar C); HRMS (EI, 70 eV) m/z calcd for
C39H59N3 569.4704, found 569.4708.
(28) J ayaratne, K. C.; Sita, L. R. J . Am. Chem. Soc. 2000, 122, 958-
959.
(29) J ayaratne, K. C.; Keaton, R. J .; Henningsen, D. A.; Sita, L. R.
J . Am. Chem. Soc. 2000, 122, 10490-10491.
(30) J ayaratne, K. C.; Sita, L. R. J . Am. Chem. Soc. 2001, 123,
10754-10755.
(31) Keaton, R. J .; J ayaratne, K. C.; Fettinger, J . C.; Sita, L. R. J .
Am. Chem. Soc. 2000, 122, 12909-12910.
(32) Keaton, R. J .; J ayaratne, K. C.; Henningsen, D. A.; Koterwas,
L. A.; Sita, L. R. J . Am. Chem. Soc. 2001, 123, 6197-6198.
(33) Keaton, R. J .; Koterwas, L. A.; Fettinger, J . C.; Sita, L. R. J .
Am. Chem. Soc. 2002, 124, 5932.
(34) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Tinners, F. J . Organometallics 1996, 15, 1518.
(35) Diamond, G. M.; J ordan, R. F. Organometallics 1996, 15, 4030-
4037.

5794 Organometallics, Vol. 21, No. 26, 2002
Mehrkhodavandi et al.
[MesNp y]Zr (NMe2)2. Zr(NMe2)4 (2.00 g, 7.48 mmol) and
H2[MesNpy] (3.16 g, 7.86 mmol) were dissolved in pentane (60
mL). The reaction mixture was stirred at room temperature
for 16 h. The mixture was filtered, and the solvent was
evaporated from the filtrate to yield an orange solid: yield 3.90
g (86%). [MesNpy]Zr(NMe2)2 can be recrystallized from pen-
tane at -30 °C to yield yellow-orange crystals: 1H NMR (500
MHz, C6D6, 295 K) δ 1.07 (s, 3H, CH3), 2.20 (s, 6H, p-CH3),
2.30 (s, 12H, o-CH3), 2.83 (d, 2H, CH2), 2.99 (s, 6H, N(CH3)2),
3.00 (s, 6H, N(CH3)2), 4.12 (d, 2H, CH2), 6.68 (m, 1H, py CH),
6.87 (m, 1H, py CH), 6.89 (s, 4H, CH), 7.09 (m, 1H, py CH),
8.69 (m, 1H, py o-CH); 13C{1H} NMR (125 MHz, C6D6, 295 K)
δ 19.68 (s, o-CH3), 21.28 (s, p-CH3), 25.29 (s, CH3), 42.53 (s,
N(CH3)2), 45.14 (s, N(CH3)2), 47.01 (s, CR4), 67.03 (s, CH2),
120.65 (s, Ar C), 122.18 (s, Ar C), 130.07 (s, Ar C), 132.12 (s,
Ar C), 134.14 (s, Ar C), 138.92 (s, Ar C), 148.63 (s, Ar C), 149.96
(s, Ar C), 163.94 (s, Ar C). Anal. Calcd for C31H45N5Zr: C, 64.31;
H, 7.83; N, 12.10. Found: C, 64.39; H, 7.76; N, 11.94.
To the cold solution was added PhCH2MgCl (1.0 M in diethyl
ether, 0.73 mL, 0.73 mmol), and the resulting mixture was
stirred at room temperature for 15 min until the cloudy
suspension became clear. Dioxane (0.06 mL, 0.73 mmol) was
added to the solution, and the mixture was filtered through
Celite. The filtrate was reduced to ∼5 mL and stored at -30
°C for 1 day to give [MesNpy]ZrBz2 as yellow crystals: yield
1
0.21 g (83%); H NMR (500 MHz, C6D6, 295 K) δ 0.87 (s, 3H,
CH3), ∼2 (v broad s, 12H, o-CH3), 2.26 (s, 6H, p-CH3), ∼2.5
(broad s, 2H, CH2Ph), 2.65 (d, 2H, CH2), 4.01 (d, 2H, CH2),
6.53 (m, 1H, py CH), 6.68 (m, 1H, py CH), 6.78 (m, 1H, py
CH), ∼6.8 (broad s, 4H, CH), 6.91 (broad s, 4H, Bn-CH), 6.93
(m, 2H, Bn-CH), 7.04 (m, 4H, Bn-CH), 8.65 (m, 1H, py o-CH).
Anal. Calcd for C41H47N3Zr: C, 73.17; H, 7.04; N, 6.24.
Found: C, 73.25; H, 7.07; N, 6.19.
[MesNp y]Zr Np 2. A suspension of [MesNpy]ZrCl2 (1.01 g,
1.80 mmol) in diethyl ether (30 mL) was cooled to -30 °C. To
the cold solution was added a solution of NpLi (0.280 g, 3.60
mmol) in diethyl ether at -30 °C, and the resulting mixture
was stirred at room temperature for 45 min until the cloudy
suspension became clear orange. The mixture was filtered
through Celite, and the filtrate was reduced to ∼15 mL and
stored at -30 °C for 1 day to give [MesNpy]ZrNp2 as a white
powder: yield 0.59 g (52%); 1H NMR (500 MHz, C6D6, 295 K)
δ 0.95 (s, 3H, CH3), 1.10 (s, 9H, Zr-CH2C(CH3)3), 1.27 (s, 2H,
Zr-CH2C(CH3)3), 1.36 (s, 9H, Zr-CH2C(CH3)3), 1.46 (s, 2H,
Zr-CH2C(CH3)3), 2.14 (s, 6H, p-CH3), ∼2.3 (v broad s, 12H,
o-CH3), 2.75 (d, 2H, CH2), 4.03 (d, 2H, CH2), 6.67 (m, 1H, py
CH), 6.78 (m, 1H, py CH), 6.88 (s, 4H, CH), 7.05 (m, 1H, py
CH), 9.17 (m, 1H, py o-CH); 13C{1H} NMR (125 MHz, C6D6,
295 K) δ 19.76 (s, o-CH3), 21.25 (s, o-CH3), 23.07 (s, p-CH3),
25.46 (s, CH3), 34.40 (s, Zr-CH2C(CH3)3), 35.47 (s, Zr-CH2C-
(CH3)3), 36.26 (s, Zr-CH2C(CH3)3), 36.32 (s, Zr-CH2C(CH3)3),
46.28 (s, CR4), 67.07 (s, CH2), 79.61 (s, Zr-CH2C(CH3)3), 82.07
(s, Zr-CH2C(CH3)3), 120.54 (s, Ar C), 122.02 (s, Ar C), 128.68
(s, Ar C), 134.02 (s, Ar C), 139.07 (s, Ar C), 147.48 (s, Ar C),
148.38 (s, Ar C), 163.47 (s, Ar C). Anal. Calcd for C37H55N3Zr:
C, 70.20; H, 8.76; N, 6.64. Found: C, 70.08; H, 8.65; N, 6.86.
[MesNp y]Zr Cl2. To a solution of [MesNpy]Zr(NMe2)2 (7.74
g, 13.4 mmol) in diethyl ether (200 mL) was added TMSCl
(5.09 mL, 40.0 mmol), and the reaction mixture was stirred
at room temperature for 1 h. The resulting white solid was
filtered, washed with pentane (3 × 10 mL), and dried in vacuo
for 4 h: yield 6.50 g (86%). [MesNpy]ZrCl2 can be recrystallized
from toluene at room temperature to yield clear, colorless
crystals: 1H NMR (500 MHz, C6D6, 295 K) δ 0.86 (s, 3H, CH3),
1.51 (s, 6H, o-CH3), 2.16 (s, 6H, p-CH3), 2.76 (d, 2H, CH2), 2.90
(s, 6H, o-CH3), 3.83 (d, 2H, CH2), 6.65 (m, 1H, py CH), 6.70 (s,
2H, CH), 6.89 (m, 1H, py CH), 6.90 (s, 2H, CH), 6.98 (m, 1H,
py CH), 10.41 (m, 1H, py o-CH); 13C{1H} NMR (125 MHz, C6D6,
295 K) δ 18.63 (s, o-CH3), 19.08 (s, o-CH3), 19.85 (s, p-CH3),
21.30 (s, CH3), 46.89 (s, CR4), 65.82 (s, CH2), some aryl peaks
are omitted. Anal. Calcd for C27H33N3Cl2Zr: C, 57.73; H, 5.92;
N, 7.48; Cl, 12.62. Found: C, 57.61; H, 6.11; N, 7.42; Cl, 12.47.
[MesNp y]Zr Me2. A suspension of [MesNpy]ZrCl2 (0.606 g,
1.079 mmol) in diethyl ether (30 mL) was cooled to -30 °C.
To the cold solution was added MeMgBr (3.4 M in diethyl
ether, 0.666 mL, 2.266 mmol), and the resulting mixture was
stirred at room temperature for 15 min until the cloudy
suspension became clear. (Note: correct stoichiometry is very
important to the success of the reaction.) Dioxane (0.216 mL,
2.535 mmol) was added to the solution, and the mixture was
filtered through Celite. The filtrate was reduced to ∼5 mL and
stored at -30 °C for 1 day to give [MesNpy]ZrMe2 as clear,
colorless crystals; yield 0.33 g (59%). The 13C-labeled complex
[MesNpy]Zr(13Me)2 was prepared in a similar manner using
13MeMgI. White crystals suitable for a single-crystal X-ray
diffraction study were grown by slow crystallization from
[MesNp y]Zr (i-Bu )2. Note: all of the following manipula-
tions were carried out in the absence of light. A suspension of
[MesNpy]ZrCl2 (0.212 g, 0.377 mmol) in diethyl ether (10 mL)
was cooled to -30 °C. To the cold solution was added (i-Bu)-
MgBr (2.0 M in diethyl ether, 0.377 mL, 0.755 mmol), and the
resulting mixture was stirred at room temperature for 10 min
until the cloudy suspension became clear. Dioxane (0.080 mL,
0.944 mmol) was added to the solution, and the mixture was
filtered through Celite. The solvent was removed in vacuo to
give a white powder; yield 0.21 g (92%). [MesNpy]Zr(i-Bu)2 can
be recrystallized from diethyl ether at -30 °C to yield clear,
colorless crystals: 1H NMR (500 MHz, C6D6, 295 K) δ 0.94 (s,
3H, CH3), 0.97 (d, 6H, Zr-CH2CH(CH3)2), 1.04 (m, 4H, Zr-
CH2CH(CH3)2), 1.27 (d, 6H, Zr-CH2CH(CH3)2), 2.16 (s, 6H,
p-CH3), 2.29 (broad s, 12H, o-CH3), 2.35 (m, 1H, Zr-
CH2CH(CH3)2), 2.52 (m, 1H, Zr-CH2CH(CH3)2), 2.72 (d, 2H,
CH2), 4.00 (d, 2H, CH2), 6.62 (m, 1H, py CH), 6.78 (m, 1H, py
CH), 6.89 (s, 4H, CH), 7.02 (m, 1H, py CH), 8.87 (m, 1H, py
o-CH); 1H NMR (500 MHz, C6D5Br, 295 K) δ 0.74 (d, 6H, Zr-
CH2CH(CH3)2), 0.81 (d, 2H, Zr-CH2CH(CH3)2), 0.88 (d, 2H,
Zr-CH2CH(CH3)2), 1.11 (d, 6H, Zr-CH2CH(CH3)2), 1.22 (s, 3H,
CH3), 2.14 (s, 6H, p-CH3), 2.19 (broad s, 13H, o-CH3, Zr-
CH2CH(CH3)2), 2.39 (m, 1H, Zr-CH2CH(CH3)2), 2.73 (d, 2H,
CH2), 4.02 (d, 2H, CH2), 6.82 (s, 4H, CH), 7.02 (m, 1H, py CH),
7.17 (m, 1H, py CH), 7.48 (m, 1H, py CH), 8.89 (m, 1H, py
o-CH); 13C{1H} NMR (125 MHz, C6D6, 295 K) δ 19.25 (s,
o-CH3), 21.31 (s, p-CH3), 25.67 (s, CH3), 29.03 (s, Zr-CH2CH-
(CH3)2), 29.63 (s, Zr-CH2CH(CH3)2), 30.51 (s, Zr-CH2CH-
(CH3)2), 32.72 (s, Zr-CH2CH(CH3)2), 46.18 (s, CR4), 66.52 (s,
CH2), 72.59 (s, Zr-CH2CH(CH3)2), 74.21 (s, Zr-CH2CH(CH3)2),
120.93 (s, Ar C), 122.60 (s, Ar C), 130.18 (s, Ar C), 134.19 (s,
Ar C), 135.18 (s, Ar C), 139.19 (s, Ar C), 146.79 (s, Ar C), 147.42
1
diethyl ether at -30 °C: H NMR (500 MHz, C6D6, 295 K) δ
0.56 (s, 6H, Zr-CH3), 0.95 (s, 3H, CH3), 2.18 (s, 6H, p-CH3),
2.27 (s, 12H, o-CH3), 2.73 (d, 2H, CH2), 4.04 (d, 2H, CH2), 6.56
(m, 1H, py CH), 6.77 (m, 1H, py CH), 6.87 (s, 4H, CH), 7.02
1
(m, 1H, py CH), 8.77 (m, 1H, py o-CH); H NMR (500 MHz,
C6D5Br, 295 K) δ 0.22 (s, 3H, Zr-CH3), 0.32 (s, 3H, Zr-CH3),
1.24 (s, 3H, CH3), 2.16 (s, 12H, o-CH3), 2.18 (s, 6H, p-CH3),
2.74 (d, 2H, CH2), 4.05 (d, 2H, CH2), 6.80 (s, 4H, CH), 6.97 (m,
1H, py CH), 7.18 (m, 1H, py CH), 7.47 (m, 1H, py CH), 8.83
(m, 1H, py o-CH); 13C{1H} NMR (125 MHz, C6D6, 295 K) δ
19.28 (s, o-CH3), 21.31 (s, p-CH3), 25.47 (s, CH3), 36.5 (broad
s, Zr-CH3), 46.31 (s, CR4), 66.13 (s, CH2), 120.89 (s, Ar C),
122.61 (s, Ar C), 130.28 (s, Ar C), 134.18 (s, Ar C), 135.08 (s,
Ar C), 139.33 (s, Ar C), 145.97 (s, Ar C), 147.41 (s, Ar C), 162.75
(s, Ar C); 13C{1H} NMR (125 MHz, C6D5Br, 295 K) δ 19.92 (s,
o-CH3), 21.08 (s, p-CH3), 25.33 (s, CH3), 35.46 (s, Zr-CH3),
36.65 (s, Zr-CH3), 45.85 (s, CR4), 65.42 (s, CH2), 120.65 (s, Ar
C), 122.14 (s, Ar C), 131.44 (s, Ar C), 133.43 (s, Ar C), 134.46
(s, Ar C), 139.26 (s, Ar C), 145.36 (s, Ar C), 146.78 (s, Ar C),
162.13 (s, Ar C). Anal. Calcd for C29H39N3Zr: C, 66.87; H, 7.55;
N, 8.07. Found: C, 67.02; H, 7.46; N, 7.94.
[MesNp y]Zr Bz2. A suspension of [MesNpy]ZrCl2 (0.206 g,
0.367 mmol) in diethyl ether (30 mL) was cooled to -30 °C.

Zirconium and Hafnium Alkyl Complexes
Organometallics, Vol. 21, No. 26, 2002 5795
(s, Ar C), 163.22 (s, Ar C). Anal. Calcd for C35H51N3Zr: C, 69.48;
H, 8.50; N, 6.95. Found: C, 69.37; H, 8.48; N, 6.86.
[Tr ip Np y]Zr Cl2. To a solution of [TripNpy]Zr(NMe2)2 (3.07
g, 4.11 mmol) in diethyl ether (80 mL) was added TMSCl (1.56
mL, 12.3 mmol), and the reaction mixture was stirred at room
temperature for 4 h. The resulting white solid was filtered off,
washed with pentane (3 × 10 mL) and dried in vacuo for 4 h:
[MesNp y]Zr (THF )Me2. ZrCl4 (0.89 g, 3.80 mmol) was
added to a cold (-30 °C) solution of H2[MesNpy] (2.00 g, 3.84
mmol) in diethyl ether (30 mL). The mixture was stirred at
room temperature for 1 h to yield a pink-orange solid. The
mixture was cooled to -30 °C, and MeMgCl (3.0 M in THF,
5.2 mL, 15.58 mmol) was added. The reaction mixture was
stirred for 20 min at room temperature. Dioxane (1.51 g, 17.11
mmol) was added to the mixture, the ensuing white solid
filtered through Celite, and the orange filtrate taken to dryness
in vacuo. After trituration with pentane (3 × 15 mL), [MesNpy]-
Zr(THF)Me2 was obtained as a yellow powder, which was
washed with cold pentane (3 × 10 mL) and dried in vacuo:
1
yield 2.8 g (93%); H NMR (500 MHz, C6D6, 295 K) δ 0.63 (d,
6H, CH3), 0.93 (s, 3H, CH3), 1.02 (br d, 6H, CH3), 1.29 (d, 6H,
CH3), 1.32 (d, 6H, CH3), 1.55 (d, 6H, CH3), 1.87 (d, 6H, CH3),
2.31 (br m, 2H, CH), 2.87 (m, 2H, CH), 3.06 (d, 2H, CH2), 4.03
(d, 2H, CH2), 4.33 (br m, 2H, CH), 6.68 (m, 1H, py CH), 6.73
(m, 1H, py CH), 6.93 (m, 1H, py CH), 6.95 (s, 2H, CH), 7.25
(d, 2H, CH), 10.24 (m, 1H, py o-CH).
[Tr ip Np y]Zr Me2. A suspension of [TripNpy]ZrCl2 (1.32 g,
1.81 mmol) in diethyl ether (20 mL) was cooled to -30 °C. To
the cold solution was added MeMgBr (3.6 M in diethyl ether,
1.00 mL, 3.62 mmol), and the resulting mixture was stirred
at room temperature for 30 min until the cloudy suspension
became clear. Dioxane (0.39 mL, 4.5 mmol) was added to the
solution, and the mixture was filtered through Celite. The
filtrate was reduced to ∼5 mL and stored at -30 °C for 1 day
to yield [TripNpy]ZrMe2 as clear, colorless crystals: yield 0.61
g (49%). The 13C-labeled complex, [TripNpy]Zr(13Me)2, was
1
yield 1.6 g (70%); H NMR (C6D6, 295 K) δ 0.45 (s, 6H, CH3),
0.98 (s, 3H, CH3), 1.21 (m, 4H, O(CH2CH2)2), 2.15 (s, 6H,
p-CH3), 2.23 (s, 12H, o-CH3), 2.76 (d, 2H, CH2), 3.48 (m, 4,
O(CH2CH2)2), 3.90 (d, 2H, CH2), 6.62 (m, 1H, py CH), 6.84 (s,
4H, CH), 6.86 (m, 1H, py CH), 7.05 (m, 1H, py CH), 8.85 (m,
1H, py CH); 13C{1H} NMR (125 MHz, C6D6, 295 K) δ 18.61 (s,
o-CH3), 20.83 (s, p-CH3), 24.85 (s, CH3), 35.04 (s, O(CH2CH2)2)
35.8 (broad s, Zr-CH3), 46.29 (s, CR4), 65.82 (s, CH2), 35.04
(s, O(CH2CH2)2), 120.67 (s, Ar C), 121.83 (s, Ar C), 129.63 (s,
Ar C), 133.09 (s, Ar C), 134.86 (s, Ar C), 138.51 (s, Ar C), 147.05
(s, Ar C), 147.98 (s, Ar C), 162.87 (s, Ar C). Anal. Calcd for
1
prepared in a similar manner using 13MeMgI: H NMR (500
MHz, C6D6, 295 K) δ 0.53 (s, 3H, Zr-CH3), 0.61 (s, 3H, Zr-
CH3), 0.73 (d, 6H, CH3), 0.95 (s, 3H, CH3), 1.25 (d, 12H, CH3),
1.40 (d, 6H, CH3), 1.55 (d, 6H, CH3), 1.65 (d, 6H, CH3), 2.88
(m, 4H, CH), 2.89 (d, 2H, CH2), 4.11 (d, 2H, CH2), 4.18 (m,
2H, CH), 6.61 (m, 1H, py CH), 6.75 (m, 1H, py CH), 7.05 (m,
1H, py CH), 7.12 (s, 2H, CH), 7.23 (s, 2H, CH), 8.90 (m, 1H,
C
29H39N3Zr: C, 66.84; H, 7.99; N, 7.09. Found: C, 66.69; H,
7.91; N, 6.99.
Yellow crystals suitable for a single-crystal X-ray diffraction
study were grown by slow crystallization from diethyl ether
at -30 °C.
1
py o-CH); H NMR (500 MHz, C6D5Br, 295 K) δ 0.21 (s, 3H,
Zr-CH3), 0.33 (s, 3H, Zr-CH3), 0.66 (d, 6H, CH3), 1.21 (s, 3H,
CH3), 1.20 (d, 12H, CH3), 1.26 (d, 6H, CH3), 1.45 (d, 6H, CH3),
1.50 (d, 6H, CH3), 2.77 (m, 2H, CH), 2.83 (m, 2H, CH), 2.86
(d, 2H, CH2), 4.00 (m, 2H, CH), 4.06 (d, 2H, CH2), 7.00 (s, 2H,
CH), 7.04 (m, 1H, py CH), 7.13 (m, 1H, py CH), 7.14 (s, 2H,
CH), 7.45 (m, 1H, py CH), 8.92 (m, 1H, py o-CH); 13C{1H} NMR
(125 MHz, C6D6, 295 K) δ 24.82 (s, CH3), 25.16 (s, CH3), 25.76
(s, CH3), 25.93 (s, CH3), 27.58 (s, CH3), 28.96 (s, CH), 29.05 (s,
CH), 34.86 (s, Zr-CH3), 34.96 (s, CH3), 39.71 (s, Zr-CH3),
46.44 (s, CR4), 69.67 (s, CH2), 120.82 (s, Ar C), 121.97 (s, Ar
C), 122.57 (s, Ar C), 123.08 (s, Ar C), 139.62 (s, Ar C), 144.84
(s, Ar C), 145.28 (s, Ar C), 146.03 (s, Ar C), 146.46 (s, Ar C),
147.62 (s, Ar C), 163.04 (s, Ar C). Anal. Calcd for C41H63N3Zr:
C, 71.45; H, 9.21; N, 6.10. Found: C, 71.33; H, 9.22; N, 6.18.
[Li(Et2O)]{[MesNp y]Zr Me3}. A suspension of [MesNpy]-
ZrMe2 (0.092 g, 1.079 mmol) in diethyl ether (5 mL) was cooled
to -30 °C. To the cold solution was added MeLi (4.4 M in
diethyl ether, 0.126 mL, 1.76 mmol), and the mixture was
stirred at room temperature for 10 min. The resulting solution
was filtered through Celite, and the filtrate was dried in vacuo
to give [Li‚OEt2][(MesNpy)ZrMe3] as a white powder: yield
1
0.109 g (100%); H NMR (500 MHz, C6D6, 295 K) δ -0.06 (s,
9H, Zr-CH3), 1.00 (t, 6H, O-CH2CH3), 1.12 (s, 3H, CH3), 1.78
(s, 6H, o-CH3), 2.21 (s, 6H, p-CH3), 2.94 (s, 6H, o-CH3), 3.02
(d, 2H, CH2), 3.16 (q, 4H, O-CH2CH3), 3.85 (d, 2H, CH2), 6.64
(m, 1H, py CH), 6.92 (s, 2H, CH), 7.02 (m, 1H, py CH), 7.07 (s,
2H, CH), 7.10 (m, 1H, py CH), 9.10 (m, 1H, py o-CH). Anal.
Calcd for C37H52N3LiOZr: C, 66.19; H, 8.50; N, 6.81. Found:
C, 66.26; H, 8.43; N, 6.89.
[Tr ip Np y]Zr (i-Bu )2. A suspension of [TripNpy]ZrCl2 (1.02
g, 1.40 mmol) in diethyl ether (50 mL) was cooled to -30 °C.
To the cold solution was added (i-Bu)MgBr (2.3 M in diethyl
ether, 1.40 mL, 3.21 mmol), and the resulting mixture was
stirred at room temperature for 10 min until the cloudy
suspension became clear. Dioxane (0.30 mL, 3.49 mmol) was
added to the solution, and the mixture was filtered through
Celite. The solvent was removed in vacuo to yield a white
powder. [TripNpy]Zr(i-Bu)2 was recrystallized from diethyl
ether at room temperature to yield clear, colorless crystals:
1H NMR (500 MHz, C6D5Br, 295 K) δ 0.54 (d, 6H, Zr-CH2-
CH(CH3)2), 0.62 (d, 6H, Zr-CH2CH(CH3)2), 0.75 (d, 2H, Zr-
CH2CH(CH3)2), 0.97 (d, 2H, Zr-CH2CH(CH3)2), 1.11 (d, 6H,
CH3), 1.21 (d, 6H, CH3), 1.22 (s, 3H, CH3), 1.33 (d, 6H, CH3),
1.46 (d, 6H, CH3), 1.60 (d, 6H, CH3), 2.12 (m, 1H, Zr-
CH2CH(CH3)2), 2.35 (m, 1H, Zr-CH2CH(CH3)2), 2.83 (m, 2H,
CH), 2.95 (d, 2H, CH2), 3.05 (m, 2H, CH), 3.87 (m, 2H, CH),
4.07 (d, 2H, CH2), 7.02 (s, 2H, CH), 7.09 (m, 1H, py CH), 7.12
(m, 1H, py CH), 7.14 (s, 2H, CH), 7.45 (m, 1H, py CH), 8.98
(m, 1H, py o-CH); 13C{1H} NMR (125 MHz, C6D5Br, 295 K) δ
23.67 (s, CH3), 24.32 (s, CH3), 24.35 (s, CH3), 24.96 (s, CH3),
25.70 (s, CH3), 27.47 (s, Zr-CH2CH(CH3)2), 27.52 (s, Zr-CH2-
CH(CH3)2), 28.69 (s, Zr-CH2CH(CH3)2), 29.28 (s, CH), 29.48
(s, CH), 32.13 (s, Zr-CH2CH(CH3)2), 34.18 (s, CH3), 45.85 (s,
CR4), 68.71 (s, CH2), 70.52 (s, Zr-CH2CH(CH3)2), 76.18 (s, Zr-
CH2CH(CH3)2), 120.41 (s, Ar C), 121.06 (s, Ar C), 121.97 (s,
Ar C), 122.48 (s, Ar C), 139.14 (s, Ar C), 144.32 (s, Ar C), 144.88
White crystals suitable for a single-crystal X-ray diffraction
study were grown by slow crystallization from diethyl ether
at -30 °C.
[Tr ip Np y]Zr (NMe2)2. Zr(NMe2)4 (2.53 g, 9.43 mmol) and
H2[TripNpy] (6.45 g, 11.3 mmol) were dissolved in pentane (80
mL). The reaction mixture was stirred at room temperature
for 16 h. The first batch of product was filtered off, and the
filtrate was stirred at room temperature for a further 16 h.
The solvent was reduced in volume in vacuo to yield more
product as a white precipitate. The products were combined
and washed with small amounts of cold pentane: yield 1.5 g
1
(60%); H NMR (500 MHz, C6D6, 295 K) δ 0.67 (d, 6H, CH3),
1.08 (s, 3H, CH3), 1.28 (d, 12H, CH3), 1.33 (d, 6H, CH3), 1.57
(d, 6H, CH3), 1.58 (d, 6H, CH3), 2.86 (m, 4H, CH), 2.89 (s, 6H,
N(CH3)2), 3.01 (d, 2H, CH2), 3.04 (s, 6H, N(CH3)2), 4.08 (m,
2H, CH), 4.19 (d, 2H, CH2), 6.69 (m, 1H, py CH), 6.79 (m, 1H,
py CH), 7.05 (m, 1H, py CH), 7.10 (d, 2H, CH), 7.25 (d, 2H,
CH), 8.71 (m, 1H, py o-CH); 13C{1H} NMR (125 MHz, C6D6,
295 K) δ 24.81 (s, CH3), 24.89 (s, CH3), 24.93 (s, CH3), 25.50
(s, CH3), 26.50 (s, CH3), 27.80 (s, CH), 29.01 (s, CH), 29.71 (s,
CH), 34.87 (s, CH3), 43.29 (s, N(CH3)2), 45.04 (s, N(CH3)2), 47.75
(s, CR4), 70.09 (s, CH2), 120.65 (s, Ar C), 121.55 (s, Ar C),
122.08 (s, Ar C), 122.75 (s, Ar C), 128.04 (s, Ar C), 139.00 (s,
Ar C), 144.28 (s, Ar C), 144.33 (s, Ar C), 146.00 (s, Ar C), 149.09
(s, Ar C). Anal. Calcd for C43H69N5Zr: C, 69.02; H, 9.31; N,
9.43. Found: C, 69.02; H, 9.30; N, 9.43.

5796 Organometallics, Vol. 21, No. 26, 2002
Mehrkhodavandi et al.
(s, Ar C), 145.11 (s, Ar C), 145.28 (s, Ar C), 146.83 (s, Ar C),
162.65 (s, Ar C). Anal. Calcd for C47H75N3Zr: C, 73.00; H, 9.78;
N, 5.43. Found: C, 73.11; H, 9.71; N, 5.36.
[MesNp y]Hf(n -P r )2. A suspension of [MesNpy]HfCl2 (0.312
g, 0.481 mmol) in diethyl ether (50 mL) was cooled to -30 °C.
To the cold solution was added (n-Pr)MgCl (2.0 M in diethyl
ether, 0.53 mL, 1.06 mmol), and the resulting mixture was
stirred at room temperature for 10 min until the cloudy
suspension became clear. Dioxane (0.12 mL, 0.14 mmol) was
added to the solution, and the mixture was filtered through
Celite. The solvent was removed in vacuo to give a white
powder, which was redissolved in 5 mL of diethyl ether and
crystallized at -30 °C for 16 h and the product isolated as
white crystals: yield 0.175 g (55%); 1H NMR (500 MHz, C6D5-
Br, 295 K) δ 0.82 (m, 2H, Hf-CH2CH(CH3)2), 0.85 (m, 4H, Hf-
CH2CH(CH3)2), 0.92 (s, 3H, CH3), 0.95 (d, 6H, Hf-CH2CH-
(CH3)2), 1.27 (d, 6H, Hf-CH2CH(CH3)2), 2.17 (s, 6H, p-CH3),
2.3 (broad s, 12H, o-CH3), 2.41 (m, 1H, Hf-CH2CH(CH3)2), 2.54
(m, 1H, Hf-CH2CH(CH3)2), 2.84 (d, 2H, CH2), 4.12 (d, 2H,
CH2), 6.62 (m, 1H, py CH), 6.78 (m, 1H, py CH), 6.90 (s, 4H,
CH), 7.04 (m, 1H, py CH), 8.96 (m, 1H, py o-CH); 13C{1H} NMR
(125 MHz, C6D5Br, 295 K) δ 18.58 (s, o-CH3), 29.85 (s, Hf-
CH(CH3)2), 30.41 (s, Hf-CH(CH3)2), 21.29 (s, p-CH3), 25.12 (s,
CH3), 45.05 (s, CR4), 65.70 (s, CH2), 68.21 (s, Hf-CH(CH3)2),
65.85 (s, Hf-CH(CH3)2), 120.80 (s, Ar C), 122.83 (s, Ar C),
130.15 (s, Ar C), 134.13 (s, Ar C), 135.70 (s, Ar C), 139.27 (s,
Ar C), 146.92 (s, Ar C), 147.40 (s, Ar C), 163.40 (s, Ar C). Anal.
Calcd for C33H47N3Hf: C, 59.67; H, 7.13; N, 6.33. Found: C,
59.67; H, 7.13; N, 6.41.
[MesNp y]Hf(NMe2)2. Hf(NMe2)4 (4.00 g, 11.0 mmol) and
H2[MesNpy] (4.75 g, 12.0 mmol) were dissolved in pentane (80
mL). The reaction mixture was stirred at room temperature
for 16 h and filtered, and the solvent was evaporated to yield
the yellow product: yield 7.75 g (95%); 1H NMR (500 MHz,
C6D6, 295 K) δ 1.02 (s, 3H, CH3), 2.21 (s, 6H, p-CH3), 2.33 (s,
12H, o-CH3), 2.95 (d, 2H, CH2), 3.02 (s, 6H, N(CH3)2), 3.06 (s,
6H, N(CH3)2), 4.18 (d, 2H, CH2), 6.67 (m, 1H, py CH), 6.83 (m,
1H, py CH), 6.91 (s, 4H, CH), 7.04 (m, 1H, py CH), 8.77 (m,
1H, py o-CH). Anal. Calcd for C31H45N5Hf: C, 55.89; H, 6.81;
N, 10.51. Found: C, 55.96; H, 6.88; N, 10.40.
[MesNp y]HfCl2. To a solution of [MesNpy]Hf(NMe2)2 (7.75
g, 11.0 mmol) in diethyl ether (80 mL) was added TMSCl (4.35
mL, 34.0 mmol), and the reaction mixture was stirred at room
temperature for 1 h. The resulting white solid was filtered off,
washed with pentane (3 × 10 mL), and dried in vacuo for 4 h:
yield 6.82 g (95%); 1H NMR (500 MHz, C6D6, 295 K) δ 0.81 (s,
3H, CH3), 1.59 (s, 6H, o-CH3), 2.20 (s, 6H, p-CH3), 2.97 (d, 2H,
CH2), 2.97 (s, 6H, o-CH3), 4.10 (d, 2H, CH2), 6.65 (m, 1H, py
CH), 6.71 (s, 2H, CH), 6.89 (m, 1H, py CH), 6.89 (m, 1H, py
CH), 6.94 (s, 2H, CH), 10.41 (m, 1H, py o-CH). Anal. Calcd for
C
27H33N3Cl2Hf: C, 49.97; H, 5.13; N, 6.47; Cl, 10.93. Found:
C, 49.90; H, 5.08; N, 6.42; Cl, 11.06.
[MesNpy]Hf(i-P r )Cl. A suspension of [MesNpy]HfCl2 (0.744
g, 1.15 mmol) in diethyl ether (50 mL) was cooled to -20 °C.
To the cold solution was added (i-Pr)MgCl (2.0 M in diethyl
ether, 0.60 mL, 1.2 mmol), and the resulting mixture was
stirred at room temperature for 1 h until the cloudy suspension
became clear. Dioxane (0.15 mL, 1.7 mmol) was added to the
solution, and the mixture was filtered through Celite. The
solvent was removed in vacuo to yield a white powder, which
was redissolved in 5 mL of diethyl ether and crystallized at
-20 °C to give the product as white crystals: yield 0.35 g
[MesNp y]HfMe2. A suspension of [MesNpy]HfCl2 (1.17 g,
1.80 mmol) in diethyl ether (50 mL) was cooled to -30 °C. To
the cold solution was added MeMgBr (3.5 M in diethyl ether,
1.30 mL, 4.55 mmol), and the resulting mixture was stirred
at room temperature for 1 h until the cloudy suspension
became clear. Dioxane (0.50 mL, 5.87 mmol) was added to the
solution, and the mixture was filtered through Celite. The
filtrate was reduced to ∼5 mL and stored at -30 °C for 1 day
to give [MesNpy]HfMe2 as clear, colorless crystals: yield 1.09
g (64%); 1H NMR (500 MHz, C6D5Br, 295 K) δ 0.06 (s, 3H,
Hf-CH3), 0.14 (s, 3H, Hf-CH3), 1.22 (s, 3H, CH3), 2.16 (s, 6H,
p-CH3), 2.20 (s, 12H, o-CH3), 2.86 (d, 2H, CH2), 4.15 (d, 2H,
CH2), 6.81 (s, 4H, CH), 6.99 (m, 1H, py CH), 7.18 (m, 1H, py
CH), 7.48 (m, 1H, py CH), 8.91 (m, 1H, py o-CH). 13C{1H} NMR
(125 MHz, C6D5Br, 295 K) δ 18.72 (s, o-CH3), 20.88 (s, p-CH3),
24.91 (s, CH3), 45.21 (s, Hf-CH3), 45.85 (s, CR4), 49.36 (s, Hf-
CH3), 64.98 (s, CH2), 120.39 (s, Ar C), some aryl signal omitted
here, 134.81 (s, Ar C), 139.15 (s, Ar C). Anal. Calcd for
1
(47%); H NMR (500 MHz, C6D6, 295 K) δ 0.91 (s, 3H, CH3),
0.98 (m, 1H, Hf-CH(CH3)2), 1.48 (d, 6H, Hf-CH(CH3)2), 1.92
(s, 6H, o-CH3), 2.15 (s, 6H, p-CH3), 2.66 (s, 6H, o-CH3), 2.82
(d, 2H, CH2), 4.19 (d, 2H, CH2), 6.61 (m, 1H, py CH), 6.73 (m,
1H, py CH), 6.77 (s, 2H, CH), 6.95 (s, 2H, CH), 7.00 (m, 1H,
py CH), 9.67 (m, 1H, py o-CH); 13C{1H} NMR (125 MHz, C6D6,
295 K) δ 18.74 (s, o-CH3), 19.63 (s, o-CH3), 21.28 (s, p-CH3),
22.51 (s, Hf-CH(CH3)2), 25.22 (s, CH3), 46.28 (s, CR4), 65.47
(s, CH2), 68.27 (s, Hf-CH(CH3)2), 120.57 (s, Ar C), 123.04 (s,
Ar C), 130.14 (s, Ar C), 130.50 (s, Ar C), 134.89 (s, Ar C), 135.92
(s, Ar C), 139.70 (s, Ar C), 145.02 (s, Ar C), 149.20 (s, Ar C).
Anal. Calcd for C30H40N3ClHf: C, 54.88; H, 6.14; N, 6.40; Cl,
5.40. Found: C, 55.07; H, 6.22; N, 6.34; Cl, 5.32.
C
29H39N3Hf: C, 57.28; H, 6.46; N, 6.91. Found: C, 57.21; H,
6.55; N, 6.84.
The 13C-labeled complex [MesNpy]Hf(13Me)2 was prepared
in a similar manner with 13MeMgI.
[MesNp y]HfEt2. A suspension of [MesNpy]HfCl2 (0.210 g,
0.324 mmol) in diethyl ether (50 mL) was cooled to -30 °C.
To the cold solution was added EtMgBr (2.0 M in diethyl ether,
0.34 mL, 0.68 mmol), and the resulting mixture was stirred
at room temperature for 10 min until the cloudy suspension
became clear. Dioxane (0.07 mL, 0.81 mmol) was added to the
solution, and the mixture was filtered through Celite. The
solvent was removed in vacuo to give a white powder, which
was redissolved in 5 mL of diethyl ether and crystallized at
-30 °C for 16 h as white crystals: yield 0.098 g (48%); 1H NMR
(500 MHz, C6D5Br, 255 K) δ 0.53 (m, 4H, Hf-CH2CH3), 1.19
(s, 3H, CH3), 1.34 (t, 3H, Hf-CH2CH3), 1.57 (d, 3H, Hf-
CH2CH3), 2.17 (s, 6H, p-CH3), ∼2.2 (broad s, 12H, o-CH3), 2.83
(d, 2H, CH2), 4.13 (d, 2H, CH2), 6.83 (s, 4H, CH), 6.99 (m, 1H,
py CH), 7.12 (m, 1H, py CH), 7.45 (m, 1H, py CH), 8.81 (m,
1H, py o-CH); 13C{1H} NMR (125 MHz, C6D5Br, 255 K) δ 11.74
(s, Hf-CH2CH3), 13.63 (s, Hf-CH2CH3), 18.78 (s, o-CH3), 20.99
(s, p-CH3), 25.13 (s, CH3), 44.91 (s, CR4), 57.24 (s, Hf-CH2-
CH3), 59.39 (s, Hf-CH2CH3), 64.97 (s, CH2), 120.65 (s, Ar C),
121.97 (s, Ar C), 122.61 (s, Ar C), 131.16 (s, Ar C), 132.89 (s,
Ar C), 139.15 (s, Ar C), 146.07 (s, Ar C), 146.19 (s, Ar C), 162.05
(s, Ar C). Anal. Calcd for C3H43N3Hf: C, 58.53; H, 6.81; N,
6.60. Found: C, 58.40; H, 6.88; N, 6.53.
[MesNp y]Hf(i-P r )2. A suspension of [MesNpy]HfCl2 (1.70
g, 2.62 mmol) in diethyl ether (50 mL) was cooled to -30 °C.
To the cold solution was added (i-Bu)MgBr (2.0 M in diethyl
ether, 2.88 mL, 5.76 mmol), and the resulting mixture was
stirred at room temperature for 10 min until the cloudy
suspension became clear. Dioxane (0.670 mL, 0.786 mmol) was
added to the solution, and the mixture was filtered through
Celite. The solvent was removed in vacuo to give a white
powder, which was redissolved in 5 mL of diethyl ether and
crystallized at -30 °C for 16 h as white crystals: yield 0.098
1
g (53%); H NMR (500 MHz, C6D5Br, 295 K) δ 0.088 (m, 1H,
Hf-CH2(CH3)2), 0.51 (m, 1H, Hf-CH2(CH3)2), 1.19 (s, 3H,
CH3), 1.22 (d, 6H, Hf-CH2(CH3)2), 1.59 (d, 6H, Hf-CH2(CH3)2),
2.14 (s, 6H, p-CH3), 2.2 (broad s, 12H, o-CH3), 2.85 (d, 2H, CH2),
4.14 (d, 2H, CH2), 6.84 (s, 4H, CH), 7.03 (m, 1H, py CH), 7.17
(m, 1H, py CH), 7.47 (m, 1H, py CH), 8.77 (m, 1H, py o-CH);
13C{1H} NMR (125 MHz, C6D5Br, 295 K) δ 18.58 (s, o-CH3),
20.84 (s, Hf-CH(CH3)2), 21.32 (s, p-CH3), 21.99 (s, Hf-CH-
(CH3)2), 25.12 (s, CH3), 45.05 (s, CR4), 65.70 (s, CH2), 65.85 (s,
Hf-CH(CH3)2), 68.21 (s, Hf-CH(CH3)2), 120.53 (s, Ar C),
121.97 (s, Ar C), 132.96 (s, Ar C), 138.88 (s, Ar C), 146.46 (s,
Ar C), 147.00 (s, Ar C), 162.77 (s, Ar C). Anal. Calcd for

Zirconium and Hafnium Alkyl Complexes
Organometallics, Vol. 21, No. 26, 2002 5797
C33H47N3Hf: C, 59.67; H, 7.13; N, 6.33. Found: C, 59.76; H,
7.20; N, 6.35.
(s, 3H, CH3), 0.98 (s, 9H, Hf-C(CH3)3), 2.14 (s, 6H, CH3),
2.22 (s, 6H, CH3), 2.65 (s, 6H, o-CH3), 2.80 (d, 2H, CH2),
4.38 (d, 2H, CH2), 6.60 (m, 1H, py CH), 6.68 (m, 1H, py CH),
6.76 (s, 2H, CH), 6.90 (s, 2H, CH), 6.97 (m, 1H, py CH), 9.85
(m, 1H, py o-CH); 13C{1H} NMR (125 MHz, C6D6, 295 K) δ
20.41 (s, CH3), 20.92 (s, CH3), 21.41 (s, p-CH3), 25.79 (s, CH3),
32.10 (s, Hf-C(CH3)3), 46.35 (s, CR4), 65.58 (s, CH2), 70.59 (s,
Hf-C(CH3)2), 120.39 (s, Ar C), 122.99 (s, Ar C), 130.04 (s, Ar
C), 131.08 (s, Ar C), 133.71 (s, Ar C), 134.31 (s, Ar C), 134.38
(s, Ar C), 139.75 (s, Ar C), 145.79 (s, Ar C), 149.94 (s, Ar C),
163.08 (s, Ar C). Anal. Calcd for C31H42N3ClHf: C, 54.88; H,
6.14; N, 6.40; Cl, 5.40. Found: C, 55.07; H, 6.22; N, 6.34; Cl,
5.40.
[Tr ip Np y]Hf(NMe2)2. Hf(NMe2)4 (0.66 g, 1.85 mmol) and
H2[TripNpy] (1.06 g, 1.86 mmol) were dissolved in pentane (60
mL). The reaction mixture was stirred at room temperature
for 16 h, the residual insoluble precipitate was filtered, and
the solution was stirred at room temperature for a further 16
h. The solution was filtered to remove small amounts of solid
residue, and the solvent was removed partially in vacuo. The
red solution was cooled to -30 °C for 12 h to give a yellow
precipitate: yield 0.70 g (45%); 1H NMR (500 MHz, C6D6, 295
K) δ 0.66 (d, 6H, CH3), 1.03 (s, 3H, CH3), 1.28 (d, 12H, CH3),
1.33 (d, 6H, CH3), 1.58 (d, 6H, CH3), 1.59 (d, 6H, CH3), 2.86
(m, 2H, CH), 2.93 (s, 6H, N(CH3)2), 3.02 (m, 2H, CH), 3.07 (d,
2H, CH2), 3.10 (s, 6H, N(CH3)2), 4.12 (m, 2H, CH), 4.27 (d, 2H,
CH2), 6.69 (m, 1H, py CH), 6.78 (m, 1H, py CH), 7.05 (m, 1H,
py CH), 7.10 (d, 2H, CH), 7.27 (d, 2H, CH), 8.79 (m, 1H, py
o-CH). Anal. Calcd for C43H69N5Hf: C, 61.89; H, 8.33; N, 8.39.
Found: C, 62.01; H, 8.36; N, 8.31.
[MesNp y]Hf(n -Bu )2. A suspension of [MesNpy]HfCl2 (0.265
g, 0.408 mmol) in diethyl ether (10 mL) was cooled to -30 °C.
To the cold solution was added (n-Bu)MgBr (2.0 M in diethyl
ether, 0.43 mL, 0.81 mmol), and the resulting mixture was
stirred at room temperature for 10 min until the cloudy
suspension became clear. Dioxane (0.1 mL, 1 mmol) was added
to the solution, and the mixture was filtered through Celite.
The solvent was removed in vacuo to give a white powder,
which was redissolved in 2 mL of diethyl ether and crystallized
at -30 °C for 16 h and the product isolated as white crystals:
yield 0.14 g (50%); 1H NMR (500 MHz, C6D5Br, 295 K) δ 0.52
(m, 4H, Hf-CH2CH2CH2CH3), 0.73 (t, 3H, Hf-CH2CH2-
CH2CH3), 0.89 (t, 3H, Hf-CH2CH2CH2CH3), 1.11 (m, 2H, Hf-
CH2CH2CH2CH3), 1.21 (s, 3H, CH3), 1.40 (m, 2H, Hf-CH2-
CH2CH2CH3), 1.45 (m, 2H, Hf-CH2CH2CH2CH3), 1.83 (m, 2H,
Hf-CH2CH2CH2CH3), 2.16 (s, 6H, p-CH3), 2.2 (broad s, 12H,
o-CH3), 2.87 (d, 2H, CH2), 4.13 (d, 2H, CH2), 6.82 (s, 4H, CH),
7.02 (m, 1H, py CH), 7.18 (m, 1H, py CH), 7.49 (m, 1H, py
CH), 8.90 (m, 1H, py o-CH); 13C{1H} NMR (125 MHz, C6D5Br,
295 K) δ 14.13 (s, Hf-CH2CH2CH2CH3), 14.17 (s, Hf-CH2-
CH2CH2CH3), 18.70 (s, o-CH3), 20.85 (s, p-CH3), 25.06 (s, CH3),
30.33 (s, Hf-CH2(CH2)2CH3), 30.39 (s, Hf-CH2(CH2)2CH3),
30.58 (s, Hf-CH2(CH2)2CH3), 31.88 (s, Hf-CH2(CH2)2CH3),
45.26 (s, CR4), 65.22 (s, CH2), 66.85 (s, Hf-CH2(CH2)2CH3),
69.17 (s, Hf-CH2(CH2)2CH3), 120.44 (s, Ar C), 122.46 (s, Ar
C), 129.31 (s, Ar C), 129.69 (s, Ar C), 131.27 (s, Ar C), 134.86
(s, Ar C), 139.00 (s, Ar C), 146.06 (s, Ar C), 146.48 (s, Ar C).
Anal. Calcd for C35H51N3Hf: C, 60.72; H, 7.43; N, 6.07.
Found: C, 60.65; H, 7.37; N, 5.94.
[MesNp y]Hf(i-Bu )2. A suspension of [MesNpy]HfCl2 (1.70
g, 2.62 mmol) in diethyl ether (50 mL) was cooled to -30 °C.
To the cold solution was added (i-Bu)MgBr (2.0 M in diethyl
ether, 2.88 mL, 5.76 mmol), and the resulting mixture was
stirred at room temperature for 10 min until the cloudy
suspension became clear. Dioxane (0.670 mL, 0.786 mmol) was
added to the solution, and the mixture was filtered through
Celite. The solvent was removed in vacuo to yield a white
powder, which was redissolved in 5 mL of diethyl ether and
crystallized at -30 °C to give the product as white crystals:
yield 1.5 g (83%); 1H NMR (500 MHz, C6D6, 295 K) δ 0.82
(m, 2H, Hf-CH2CH(CH3)2), 0.85 (m, 4H, Hf-CH2CH(CH3)2),
0.92 (s, 3H, CH3), 0.95 (d, 6H, Hf-CH2CH(CH3)2), 1.27 (d, 6H,
Hf-CH2CH(CH3)2), 2.17 (s, 6H, p-CH3), 2.3 (broad s, 12H,
o-CH3), 2.41 (m, 1H, Hf-CH2CH(CH3)2), 2.54 (m, 1H, Hf-
CH2CH(CH3)2), 2.84 (d, 2H, CH2), 4.12 (d, 2H, CH2), 6.62 (m,
1H, py CH), 6.78 (m, 1H, py CH), 6.90 (s, 4H, CH), 7.04 (m,
1H, py CH), 8.96 (m, 1H, py o-CH); 13C{1H} NMR (125 MHz,
C6D6, 295 K) δ 19.23 (s, o-CH3), 21.29 (s, p-CH3), 25.38 (s, CH3),
29.85 (s, Hf-CH2CH(CH3)2), 30.41 (s, Hf-CH2CH(CH3)2), 30.77
(s, Hf-CH2CH(CH3)2), 32.80 (s, Hf-CH2CH(CH3)2), 45.84 (s,
CR4), 66.29 (s, CH2), 82.36 (s, Hf-CH2CH(CH3)2), 83.88 (s, Hf-
CH2CH(CH3)2), 120.80 (s, Ar C), 122.83 (s, Ar C), 130.15 (s,
Ar C), 134.13 (s, Ar C), 135.70 (s, Ar C), 139.27 (s, Ar C), 146.92
(s, Ar C), 147.40 (s, Ar C), 163.40 (s, Ar C). Anal. Calcd for
[Tr ip Np y]HfCl2. To a solution of [TripNpy]Hf(NMe2)2
(0.465 g, 0.567 mmol) in diethyl ether (15 mL) was added
TMSCl (0.2 mL, 1.67 mmol), and the reaction mixture was
stirred at room temperature for 4 h. The resulting white solid
was filtered, washed with pentane (3 × 10 mL), and dried in
1
vacuo for 4 h: yield 0.375 g (82%); H NMR (300 MHz, C6D6,
295 K) δ 0.67 (d, 6H, CH3), 0.91 (s, 3H, CH3), 1.12 (br d, 6H,
CH3), 1.30 (d, 6H, CH3), 1.32 (d, 6H, CH3), 1.59 (d, 6H, CH3),
1.86 (d, 6H, CH3), 2.43 (br m, 2H, CH), 2.88 (m, 2H, CH), 3.16
(d, 2H, CH2), 4.28 (d, 2H, CH2), 4.37 (br m, 2H, CH), 6.68 (m,
2H, py CH), 6.95 (m, 1H, py CH), 7.00 (s, 2H, CH), 7.28 (d,
2H, CH), 10.17 (m, 1H, py o-CH).
[Tr ip Np y]Hf(i-Bu )2. A suspension of [TripNpy]HfCl2 (0.600
g, 0.734 mmol) in diethyl ether (20 mL) was cooled to -30 °C.
To the cold solution was added (i-Bu)MgBr (2.0 M in diethyl
ether, 0.92 mL, 1.83 mmol), and the resulting mixture was
stirred at room temperature for 1 h until the cloudy suspension
became clear. Dioxane (0.20 mL, 2.2 mmol) was added to the
solution, and the mixture was filtered through Celite. The
solvent was removed in vacuo to yield a white powder, which
was redissolved in 5 mL of diethyl ether and crystallized at
-30 °C to yield the product as white crystals: yield 0.44 g
(70%); 1H NMR (500 MHz, C6D5Br, 295 K) δ 0.51 (d, 6H, Hf-
CH2CH(CH3)2), 0.55 (d, 2H, Hf-CH2CH(CH3)2), 0.60 (d, 6H,
Hf-CH2CH(CH3)2), 0.72 (d, 2H, Hf-CH2CH(CH3)2), 1.11 (d,
6H, o-CH3), 1.20 (s, 3H, CH3), 1.21 (d, 12H, p-CH3), 1.32 (d,
6H, o-CH3), 1.47 (d, 6H, o-CH3), 1.61 (d, 6H, o-CH3), 2.17 (m,
1H, Hf-CH2CH(CH3)2), 2.36 (m, 1H, Hf-CH2CH(CH3)2), 2.83
(m, 1H, CH), 3.05 (d, 2H, CH2), 3.09 (m, 1H, CH), 3.90 (d, 1H,
CH), 4.20 (d, 2H, CH2), 7.01 (s, 2H, CH), 7.11 (m, 1H, py CH),
7.12 (m, 1H, py CH), 7.16 (s, 2H, CH), 7.46 (m, 1H, py CH),
9.07 (m, 1H, py o-CH); 13C{1H} NMR (125 MHz, C6D5Br, 295
K) δ 23.47 (s, CH3), 24.38 (s, CH3), 24.08 (s, CH3), 25.42 (s,
CH), 25.82 (s, CH3), 27.47 (s, CH3), 27.90 (s, CH), 28.42 (s,
CH3), 28.72 (s, CH), 29.84 (s, CH), 29.46 (s, CH3), 32.21 (s,
CH), 34.15 (s, CH3), 45.50 (s, CR4), 68.44 (s, CH2), 81.68 (s,
Hf-CH2CH(CH3)2), 83.04 (s, Hf-CH2CH(CH3)2), some aryl
resonances are omitted. Anal. Calcd for C47H75N3Hf: C, 65.59;
H, 8.78; N, 4.88. Found: C, 65.43; H, 8.71; N, 4.95.
C
35H51N3Hf: C, 60.72; H, 7.43; N, 6.07. Found: C, 60.65; H,
7.51; N, 6.12.
[MesNpy]Hf(13CH2CHMe2)2 was prepared in a similar fash-
ion from Me2CH13CH2MgBr.
[MesNp y]Hf(t -Bu )Cl. A suspension of [MesNpy]HfCl2
(0.243 g, 0.374 mmol) in diethyl ether (15 mL) was cooled to
-20 °C. To the cold solution was added (t-Bu)MgCl (2.0 M in
diethyl ether, 0.45 mL, 0.90 mmol), and the resulting mixture
was stirred at room temperature for 15 min until the cloudy
suspension became clear. Dioxane (0.15 mL, 1.7 mmol) was
added to the solution, and the mixture was filtered through
Celite. The solvent was removed in vacuo to yield a white
powder, which was redissolved in 5 mL of diethyl ether and
crystallized at -20 °C to give the product as white crystals:
[TripNpy]Hf(13CH2CHMe2)2 was prepared in a similar fash-
ion from Me2CH13CH2MgBr.
1
yield 0.121 g (48%); H NMR (500 MHz, C6D6, 295 K) δ 0.93

5798 Organometallics, Vol. 21, No. 26, 2002
Mehrkhodavandi et al.
X-r a y Diffr a ction Exp er im en ts. All single-crystal X-ray
diffraction experiments were carried out using a Bruker three-
circle platform diffractometer equipped with a CCD detector.
A standard hemisphere of data was collected at 183 K. The
structures were solved using direct methods and difference
Fourier techniques utilizing the SHELXTL suite of programs.36
In each case, all non-hydrogen atoms were modeled anisotro-
pically, while hydrogen atoms were placed in calculated
positions. Absolute configurations were confirmed by analysis
of the Flack parameters37 following refinement. For [MesNpy]-
ZrMe2 the Flack parameter was -0.02(5), and for [Li(Et2O)]-
{[MesNpy]ZrMe3} it was -0.04(6).
porting this research and Dr. William M. Davis and
Paula Diaconescu for assistance with X-ray studies.
P.M. also thanks the NSERC of Canada for a postgradu-
ate scholarship (PGS B).
Su p p or tin g In for m a tion Ava ila ble: Fully labeled ther-
mal ellipsoid drawings and tables of crystal data and structure
refinement details, atomic coordinates, bond lengths and
angles, anisotropic displacement parameters, and hydrogen
coordinates for [MesNpy]Zr(THF)Me2, [Li‚OEt2]{[MesNpy]-
ZrMe3}, [TripNpy]Zr(i-Bu)2, [MesNpy]Hf(i-Pr)Cl, and [MesN-
py]Hf(i-Pr)2. This material is available free of charge via the
Internet at http://pubs.acs.org. Supporting data for the X-ray
structure of [MesNpy]ZrMe2 were provided in ref 11.
Ack n ow led gm en t. We thank the Department of
Energy (Contract No. DE-FG02-86ER13564) for sup-
(36) SHELXTL; Bruker Analytical X-ray Solutions, Madison, WI.
(37) Flack, H. D. Acta Crystallogr. 1983, A39, 876-881.
OM0207055