Exploring alternative synthetic routes for the preparation of five-coordinate diamidoamine group 4 metal complexes

Article abstract of DOI:10.1021/om0580349

Efficient synthetic routes for the preparation of electrophilic titanium and zirconium complexes featuring a tridentate diamidoamine ligand have been developed. The five-coordinate titanium dichloride complexes [(MesNCH ₂CH₂)₂NR]TiCl₂ (R = H (3), SiMe ₃ (4)) are conveniently prepared from the amine elimination reactions of the triamines (MesNHCH₂CH₂)₂NR (R = H (1), SiMe₃ (2)) with Ti(NEt₂)₂Cl₂. Treatment of Ti(NEt₂)₄ with 2 equiv of SiMe₃Cl offers an effective method for the preparation of Ti(NEt₂) ₂Cl₂. The corresponding five-coordinate zirconium homologues [(MesNCH₂CH₂)₂NR]ZrCl₂ (R = H (5), SiMe₃ (6)) are synthesized via the toluene elimination reactions of Zr(benzyl)₂Cl₂(Et₂O)₂ with 1 and 2, respectively. The thermally unstable and photosensitive Zr(benzvl)₂Cl₂(Et₂O)₂ species may be prepared in situ from the reaction of Zr(benzyl)₄ with 2 equiv of [NEt₃H]Cl in diethyl ether at 0°C in the dark. The toluene elimination reaction of Hf(benzyl)₄ with 1 affords the dibenzyl Hf complex [(MesNCH₂CH₂)₂NH]Hf(benzyl) ₂, 7. The X-ray structural and solution NMR data for 4, 5, 6, and 7 reveal that these electrophilic group 4 metal complexes adopt the facial structure with either a chloride or a η²-benzyl ligand trans to the central amino N atom of the tridentate diamidoamine ligand.

Full text of DOI:10.1021/om0580349

Organometallics 2005, 24, 5383-5392
5383
Exploring Alternative Synthetic Routes for the
Preparation of Five-Coordinate Diamidoamine Group 4
Metal Complexes
Alicia R. Morgan,1a Michael Kloskowski,1b Felix Kalischewski,1b
Aaron H. Phillips,1a and Jeffrey L. Petersen*,1a
C. Eugene Bennett Department of Chemistry, West Virginia University,
Morgantown, West Virginia 26506-6045
Received June 16, 2005
Efficient synthetic routes for the preparation of electrophilic titanium and zirconium
complexes featuring a tridentate diamidoamine ligand have been developed. The five-
coordinate titanium dichloride complexes [(MesNCH2CH2)2NR]TiCl2 (R ) H (3), SiMe3
(4)) are conveniently prepared from the amine elimination reactions of the triamines
(MesNHCH2CH2)2NR (R ) H (1), SiMe3 (2)) with Ti(NEt2)2Cl2. Treatment of Ti(NEt2)4 with
2 equiv of SiMe3Cl offers an effective method for the preparation of Ti(NEt2)2Cl2. The
corresponding five-coordinate zirconium homologues [(MesNCH2CH2)2NR]ZrCl2 (R ) H (5),
SiMe3 (6)) are synthesized via the toluene elimination reactions of Zr(benzyl)2Cl2(Et2O)2 with
1 and 2, respectively. The thermally unstable and photosensitive Zr(benzyl)2Cl2(Et2O)2 species
may be prepared in situ from the reaction of Zr(benzyl)4 with 2 equiv of [NEt3H]Cl in diethyl
ether at 0 °C in the dark. The toluene elimination reaction of Hf(benzyl)4 with 1 affords the
dibenzyl Hf complex [(MesNCH2CH2)2NH]Hf(benzyl)2, 7. The X-ray structural and solution
NMR data for 4, 5, 6, and 7 reveal that these electrophilic group 4 metal complexes adopt
the facial structure with either a chloride or a η2-benzyl ligand trans to the central amino
N atom of the tridentate diamidoamine ligand.
Introduction
amine9-12), O (diaryl ether13-16 or dialkyl ether17-19), or
S (diaryl thioether20 or dialkyl thioether18) donor to pre-
pare a myriad of five-coordinate metal complexes as cat-
alyst precursors. They observed that [(MesNCH2CH2)2-
NMe]ZrMe2,9,10 when activated with [Ph3C][B(C6F5)4],
promotes the polymerization of 1-hexene at 0-20 °C.
Although this catalyst system was nearly living in terms
of â-hydrogen elimination, the activity decreases at a
moderate rate due to intramolecular cyclometalation
Electrophilic early transition metal complexes featur-
ing multifunctional ligands have provided a new gen-
eration of “non-metallocene” catalysts for olefin polym-
erization.2 The use of a chelating diamido ligand has
led to the preparation of four- and five-coordinate
precursors capable of promoting the living polymeriza-
tion of R-olefins. McConville and co-workers3,4 observed
that four-coordinate titanium dialkyl complexes derived
from [ArN(CH2)3NAr]TiCl2, where Ar ) 2,6-iPr2C6H3
and 2,6-Me2C6H3, when activated with MAO, B(C6F5)3,
or [Ph3C][B(C6F5)4], catalyze the polymerization of
1-hexene. The [ArN(CH2)3NAr]TiCl2 complexes were
prepared by the elimination of 2 equiv of SiMe3Cl from
the reactions of the corresponding silylated diamines
Ar(SiMe3)N(CH2)3N(SiMe3)Ar with TiCl4.
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* To whom correspondence should be addressed. E-mail: jpeterse@
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10.1021/om0580349 CCC: $30.25 © 2005 American Chemical Society
Publication on Web 09/17/2005

5384 Organometallics, Vol. 24, No. 22, 2005
Morgan et al.
that leads to dimerization10-12 and deactivation. When
the ortho-methyl groups of the aryl substituents were
replaced with chlorine atoms, the resultant system
performed as a living catalyst for 1-hexene polymeri-
zation with no evidence of catalyst decomposition at
bidentate and multifunctional ligands. The related
amine elimination and toluene elimination reactions of
H2Ln with M(NR2)2Cl2 or a M(benzyl)2Cl2 equivalent
offer two potentially attractive routes to the correspond-
ing metal dichloride complexes, LnMCl2 (eq 1 and 2). In
0
°C.11 The triamines (MesNHCH2CH2)2NH and
M(NR2)2Cl2 + H2Ln f 2 NR2H + LnMCl2 (1)
(ArClNHCH2CH2)2NMe, where ArCl ) 2,6-Cl2C6H3, were
attached to Zr by an amine elimination reaction with
Zr(NMe2)4, affording [(MesNCH2CH2)2NH]Zr(NMe2)2
and [(ArClNCH2CH2)2NMe]Zr(NMe2)2, respectively. Treat-
ment of these Zr dimethylamide species with SiMe3Cl
affords the corresponding chloride derivatives, which
upon alkylation with MeMgI or MeMgBr yields
[(MesNCH2CH2)2NMe]ZrMe2 and [(ArClNCH2CH2)2NMe]-
ZrMe2.
Amine elimination and toluene elimination strategies
based upon M(NR2)4 and M(benzyl)4, where R ) Me,
Et; M ) Ti, Zr, Hf, often provide suitable alternatives
to conventional metathesis reactions for the prepara-
tion of electrophilic metal diamide5,7-47 and diben-
zyl17,18,24,37,38,44,45,48-61 complexes featuring a variety of
M(benzyl)2Cl2(Et2O)2 + H2Ln f
2 toluene + LnMCl2 + 2 Et2O (2)
their patent application, researchers62 at Peroxid-Che-
mie G.m.b.H. in Germany reported that heating sto-
ichiometric amounts of Ti(NMe2)2Cl2 and (C5Me4H)Si-
(NH-t-Bu) directly affords [(C5Me4)SiMe2(N-t-Bu)]TiCl2.
The analogous approach was employed by Steinhuebel
and Lippard to prepare (Me2ATI)2TiCl2, where Me2ATI
is N,N′-dimethylaminotroponimate.63 Ti(NMe2)2Cl2 is
normally obtained by the comproportionation reaction
of Ti(NMe2)4 and TiCl4.64 However, we have found that
the Ti(NR2)2Cl2 complexes, where R ) Me, Et, are also
accessible by the stoichiometric treatment of Ti(NR2)4
with 2 equiv of SiMe3Cl. The Zr and Hf dibenzyl
dichloride complexes, M(benzyl)2Cl2(Et2O)2, were orig-
inally prepared by treatment of an ether solution of
M(benzyl)4 with 2 equiv of HCl gas.65 Because of their
thermal instability and photosensitivity, these species
must be made and handled in the dark at temperatures
at or below 0 °C. Zr(benzyl)2Cl2(Et2O)2 may also be
generated by deprotonation of Zr(benzyl)4 with 2 equiv
of [NEt3H]Cl (vide infra) under similar conditions.
In this paper we report the results of our efforts to
develop alternative synthetic routes based upon modi-
fied amine elimination and toluene elimination strate-
gies for the efficient preparation of five-coordinate group
4 metal complexes featuring a tridentate diamidoamine
ligand. For this purpose we employed the triamines,
(MesNHCH2CH2)2NR, R ) H, SiMe3. The latter tri-
amine provided the opportunity to evaluate the stereo-
electronic influence of the bulky SiMe3 group on the
M-N(amine) bond and the molecular structure. Where-
as the amine elimination reactions of these triamines
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Diamidoamine Group 4 Metal Complexes
Organometallics, Vol. 24, No. 22, 2005 5385
with Ti(NEt2)2Cl2 afford [(MesNCH2CH2)2NR]TiCl2,
the corresponding toluene elimination reactions of
these triamines with Zr(benzyl)2Cl2(Et2O)2 yield
[(MesNCH2CH2)2NR]ZrCl2. Specific details regarding
the synthesis and structural characterization of
these five-coordinate group 4 metal complexes and
[(MesNCH2CH2)2NH]Hf(benzyl)2 are described.
The 1H NMR resonances of 4 are compatible with the
chemical shifts observed for the proton resonances
displayed by 3. The two meta-protons and methyl
protons of the three methyl groups of the mesityl rings
are inequivalent, the methylene protons are observed
as two doublets of triplets and a pseudoquartet, and the
nine protons of the trimethylsilyl group give a singlet.
The molecular structure of 4 was determined by an
X-ray crystallographic analysis.
Results and Discussion
Preparation
and
Characterization
of
Preparation
of
the
Triamines
[(MesNCH2CH2)2NR]ZrCl2, R ) H, SiMe3. The five-
coordinate zirconium complexes [(MesNCH2CH2)2NR]-
ZrCl2 (R ) H (5), SiMe3 (6)) were conveniently pre-
pared by the reactions of Zr(benzyl)2Cl2(Et2O)2 with 1
and 2, respectively (eq 6). The dibenzyl Zr complex,
(MesNHCH2CH2)2NR, R ) H, SiMe3. The preparation
of (MesNHCH2CH2)2NH, 1, was accomplished by the
arylamination of diethylenetriamine with 2 equiv of
bromomesitylene with Buchwald’s Pd2(dba)3/BINAP
catalyst.66 Treatment of an ether solution of 1 with
SiMe3Cl in the presence of 1,8-diazabicyclo[5.4.0]undec-
7-ene (DBU) provided a selective route for the silylation
of the central amine N to afford (MesNHCH2CH2)2-
NSiMe3, 2 (eq 3). Cloke and co-workers67 used a similar
(MesNHCH2CH2)2NR + Zr(benzyl)2Cl2(Et2O)2 f
[(MesNCH2CH2)2NR]ZrCl2 + 2 toluene + 2 Et2O
(6)
Zr(benzyl)2Cl2(Et2O)2, was prepared by protonolysis of
Zr(benzyl)4 with 2 equiv of [NEt3H]Cl in diethyl ether
(eq 7). Because of the thermal instability and light
Zr(benzyl)4 + 2 [NEt3H]Cl + excess Et2O f
Zr(benzyl)2Cl2(Et2O)2 + 2 toluene + 2 NEt3 (7)
approach to prepare (Me3SiNHCH2CH2)2NSiMe3 from
triethylenediamine. The solution 1H and 13C NMR
spectra of 2 exhibit the expected number of resonances
with the protons and carbon of the trimethylsilyl sub-
stituent appearing at δ 0.11 and 0.14, respectively.
sensitivity of Zr(benzyl)2Cl2(Et2O)2, this reaction must
be performed in a darkened room while maintaining the
reaction temperature at 0 °C. Following replacement of
diethyl ether with toluene, the corresponding triamine
was added directly to the same reaction flask. Both of
these toluene elimination reactions proceeded cleanly
Preparation
and
Characterization
of
[(MesNCH2CH2)2NR]TiCl2, R ) H, SiMe3. The five-
coordinate titanium complexes [(MesNCH2CH2)2NR]-
TiCl2 (R ) H (3), SiMe3 (4)) were prepared in good yields
by the thermally induced amine elimination reactions
of 1 and 2 with Ti(NEt2)2Cl2 (eq 4). Ti(NEt2)2Cl2 was
1
with the formation of 5 and 6. The H NMR chemical
shifts of 5 are consistent with those reported by Schrock
and co-workers9,10 for this complex. The solution 1H and
13C NMR data for 6 reflect the presence of mirror
symmetry. The two meta-protons and the three in-
equivalent methyl substituents of the mesityl group
display distinct singlets, and the four methylene protons
afford multiplets. A singlet at δ 0.27 corresponds to the
protons of the trimethylsilyl substituent. A total of 12
resonances were observed in the 13C APT NMR spec-
trum of 6. Four of the six aromatic resonances cor-
respond to the four quaternary carbons of each mesityl
ring with the ipso-carbon at δ 148.6, and the ortho- and
para-carbons at δ 134.7, 133.3, and 132.8. In the gated
nondecoupled 13C NMR spectrum, the meta-carbons
exhibit separate doublets δ 130.3 and 129.8 with 1JC-H
) 160. The methylene carbons appear as triplets at δ
Ti(NEt2)2Cl2 + (MesNHCH2CH2)2NR f
[(MesNCH2CH2)2NR]TiCl2 + 2 NEt2H (4)
prepared by the stoichiometric reaction of Ti(NEt2)4 with
2 equiv of SiMe3Cl (eq 5). Both compounds were isolated
Ti(NEt2)4 + 2 SiMe3Cl f Ti(NEt2)2Cl2 +
2 SiMe3NEt2 (5)
as reddish-orange solids that are moderately soluble in
chloroform. The solution 1H NMR spectrum of 3 in
CDCl3 is consistent with the presence of mirror sym-
metry. The meta-protons and the protons of the methyl
substituents of the mesityl groups appear as separate
singlets. The methylene protons exhibit two doublets
of triplets centered at δ 3.55 and 4.19 and a more
intense pseudoquartet centered at δ 3.75. The 13C NMR
spectrum of 3 displays the expected nine resonances for
the mesityl group; the signals for the methylene carbons
adjacent to the central amine nitrogen and to the amido
nitrogens are observed at δ 49.2 and 60.7, respectively.
1
56.8 and 52.3 with JC-H ) 137 and 135 Hz, respec-
tively. The three methyl substituents within the mesityl
groups give separate 1:3:3:1 quartets at δ 20.9, 20.1, and
1
19.4 with JC-H ) 125-126 Hz. The carbon resonance
of the trimethylsilyl substituent appears as a quartet
at δ 0.0 with 1JC-H ) 119 Hz. The molecular structures
of 5 and 6 were confirmed by X-ray crystallographic
analyses.
Preparation of [(MesNCH2CH2)2NH]Hf(benzyl)2,
7. The reaction of Hf(benzyl)4 with one equivalent of
1 proceeds cleanly with the loss of 2 equiv of tol-
uene and the formation of the Hf dibenzyl complex,
[(MesNCH2CH2)2NH]Hf(benzyl)2, 7 (eq 8).
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5386 Organometallics, Vol. 24, No. 22, 2005
Morgan et al.
(MesNHCH2CH2)2NH + Hf(benzyl)4 f
[(MesNCH2CH2)2NH]Hf(benzyl)2 + 2 toluene (8)
The solution 1H and 13C NMR spectra are consistent
with a mirror plane passing through the Hf, amino N,
and the two benzyl methylene C atoms. The four
inequivalent methylene protons within the (CH2)2NH-
(CH2)2 linkage appear as multiplets and the three
inequivalent methyl groups and the two inequivalent
meta-protons are observed as singlets. The inequiva-
lency of the meta protons of the mesityl substituents
was confirmed by the observation of a cross-peak in the
2D COSY NMR spectrum. The two benzyl ligands
produce two distinct sets of ortho-, meta-, and para-
proton resonances. The solution NMR spectra for the
related Hf dimethyl complex, [(MesNCH2CH2)2NH]-
HfMe2, also exhibit a pair of proton and carbon reso-
nances indicative of two inequivalent methyl ligands.9
The observation of the two singlets at δ 1.26 and 1.61
for the protons of the methylenes attached to Hf is
further indication that the benzyl groups are inequiva-
lent. Nine distinct carbon resonances are exhibited by
the mesityl substituents, two methylene carbon reso-
nances are displayed by the (CH2)2NH(CH2)2 linkage,
and the two benzyl ligands provide an additional 10
resonances. The downfield resonance at δ 148.0 for the
two equivalent ipso-C atoms of the mesityl substituents
is identified by its higher intensity. The three remaining
quaternary carbons of the mesityl groups are observed
at δ 134.0, 134.90, and 134.93 with the three methyl
carbons located at δ 19.1, 19.9, and 21.0. The two carbon
resonances at δ 128.5 and 129.4 are assigned to the two
inequivalent meta-carbons on the basis of the cross-
peaks observed in the 2D COSY and HETCOR spectra.
The two inequivalent methylene carbons appear as
Figure 1. Structural representations of the meridonal and
facial stereoisomers.
1
triplets centered at δ 49.1 and 57.0 with JC-H ) 135
Figure 2. Perspective view of the molecular structure and
the atom-labeling scheme for [(MesNCH2CH2)2NSiMe3]-
TiCl2, 4. The thermal ellipsoids are scaled to enclose 30%
probability.
Hz in the gated nondecoupled 13C NMR spectrum.
Finally, the 10 resonances for the two benzyl ligands
were found at δ 66.0 and 74.0 with 1JC-H ) 128 Hz for
the two methylene carbons bound to Hf, at δ 141.0 and
153.7 for the two ipso-C atoms, at δ 120.8 and 125.5 for
the para-C atoms, and at δ 123.7, 128.6, 130.3, 130.4
for the remaining ortho- and meta-C atoms.
In contrast, in the Cs-symmetric fac structure, the
two amido nitrogen donors occupy two equatorial posi-
tions and the central donor atom (X) resides in an
axial position. This alternative ligand arrangement
was observed for [(Me3SiNCH2CH2)2NSiMe3]ZrCl(CH-
Discussion of the Molecular Structures. X-ray
structural analyses performed on five-coordinate group
4 metal complexes featuring a dianionic tridentate
diamido ligand indicate that these compounds adopt
either a meridonal (mer) or a facial (fac) configuration
(Figure 1) within a trigonal bipyramidal framework. In
the mer structure, the two terminal amido nitrogen
donors occupy the two axial sites and the central donor
atom (X) lies in the equatorial plane. The three donor
atoms of the tridentate ligand in this C2v-symmetric
structure define a plane that bisects the L-M-L bond
angle. This arrangement was reported by Schrock and
co-workers for [(ArNCH2CH2)2O]MR2-type complexes,17,18
where M ) Zr or Hf, R ) alkyl, Ar ) 2,6-dimethylphenyl
or 2,6-di-isopropylphenyl; [(t-BuN-o-C6H4)2O]MMe2,
where M ) Ti13,14 or Zr;14 and [(MesNCH2CH2)2NMe]-
ZrMe2.9,10 The corresponding [(Ar)NCH2(NC5H3)CH2N-
(Ar)]ZrCl2 complexes31,68 that feature a planar pyridyl
nitrogen donor also conform to the mer configuration.
(SiMe3)2)69 as well as [(ArNCH2CH2)2O]Ti(benzyl)2
17,18
and [(ArNCH2CH2)2S]ZrMe2,18 where Ar ) 2,6-dimeth-
ylphenyl.
Perspective views of the molecular structures of
[(MesNCH2CH2)2NSiMe3]TiCl2 (4), [(MesNCH2CH2)2-
NR]ZrCl2 (R ) H (5), SiMe3 (6)), and [(MesNCH2CH2)2-
NH]Hf(benzyl)2 (7) are depicted in Figures 2, 3, 4, and
5, respectively. The structural parameters about the
central metal of 4, 5, and 6 indicate that these three
five-coordinate complexes adopt geometries consistent
with the fac structure. The equatorial positions of the
distorted trigonal bipyramid are defined by the two
amide nitrogen donor atoms and Cl(1). The respective
Cl(2)-M-N(2) and Cl(1)-M-N(2) bond angles (170.23-
(6)° and 91.99(6)° for 4, 169.5(2)° and 87.4(2)° for 5,
166.41(7)° and 93.06(7)° for 6) are consistent with Cl(2)
(69) Cloke, F. G. N.; Hitchcock, P. B.; Love, J. B. J. Chem. Soc.,
Dalton Trans. 1995, 25-30.
(68) Merkel, M.; Petersen, J. L., unpublished results.

Diamidoamine Group 4 Metal Complexes
Organometallics, Vol. 24, No. 22, 2005 5387
Figure 3. Perspective view of the molecular structure and
the atom-labeling scheme for [(MesNCH2CH2)2NH]ZrCl2,
5. The thermal ellipsoids are scaled to enclose 30% prob-
ability.
Figure 5. Perspective view of the molecular structure and
the atom-labeling scheme for [(MesNCH2CH2)2NH]Hf-
(benzyl)2, 7. The thermal ellipsoids are scaled to enclose
30% probability.
similar to the 120° dihedral angle expected for the fac
structure. Chelation of the diamidoamine ligand in these
complexes produces two puckered five-membered rings
with an S-shaped backbone. To reduce steric conges-
tion about the metal atom, the two mesityl substitu-
ents of the amido nitrogen donors of 4, 5, and 6 are
directed toward the side opposite from the equatorial
chloride ligand, Cl(1), and away from the hydrogen or
trimethylsilyl group at N(2). This feature is readily seen
in Figure 3, which offers a view parallel to the Zr(1),
Cl(1), and Cl(2) plane in 5.
The Zr-N(amido) distances of 2.055(5) and 2.048(6)
Å in 5 and 2.038(3) and 2.042(3) Å in 6 are shorter than
the Zr-N(amido) distances in five-coordinate meridonal
d0 Zr(IV) complexes (2.101(4) and 2.104(5) Å in [(Ar)-
NCH2(NC5H3)CH2N(Ar)]ZrMe2, where Ar ) 2,6-di-iso-
propylphenyl;31 2.070(4) and 2.077(4) Å in [(Ar)NCH2-
(NC5H3)CH2N(Ar)]ZrCl2, where Ar ) 2,6-dimethyl-
9,10
phenyl;68 2.095(4) Å in [(MesNCH2CH2)2NMe]ZrMe2
)
that also feature appreciable N(pπ)-Zr(dπ) π-bond-
ing.70 The shorter Zr-N(amido) bond distances ob-
served for 5 and 6 are a consequence of the relative
positions of the two amido π-donors. The N(amido)-
Zr-N(amido) bond angles in 5 and 6 are ca. 120°,
whereas those in [(Ar)NCH2(NC5H3)CH2N(Ar)]ZrCl2
and [(MesNCH2CH2)2NMe]ZrMe2 are ca. 140°, indicat-
ing that the amido nitrogen atoms are positioned more
nearly trans to each other in the mer structures. This
arrangement places each filled nitrogen pπ-orbital in
direct competition because their respective electron
pairs are interacting with the same zirconium dπ-orbital.
Figure 4. Perspective view of the molecular structure and
the atom-labeling scheme for [(MesNCH2CH2)2NSiMe3]-
ZrCl2, 6. The thermal ellipsoids are scaled to enclose 30%
probability.
lying trans to N(2) and Cl(1) occupying an equatorial
position of a distorted trigonal bipyramid. The obtuse
dihedral angles between the corresponding planes con-
taining N(1), M, N(2) and N(2), M, N(3) of 128.0°, 131.4°,
and 129.6° in 4, 5, and 6, respectively, deviate substan-
tially from the corresponding idealized dihedral angle
of 180° expected for the mer structure but are more
(70) Hagen, K.; Holwill, C. J.; Rice, D. A.; Runnacles, J. D. Inorg.
Chem. 1988, 27, 2032-2035.

5388 Organometallics, Vol. 24, No. 22, 2005
Table 1. Crystallographic Data for 4, 5, 6, and 7
Morgan et al.
empirical formula
fw
temperature, K
cryst syst
C25H39Cl2N3SiTi, 4
528.48
C22H31Cl2N3Zr, 5
499.62
C25H39Cl2N3SiZr, 6
571.80
C36H45N3Hf, 7
698.24
295(2)
223(2)
223(2)
223(2)
monoclinic
P21/c
16.3146(8)
14.6825(8)
14.4946(8)
113.001(1)
3196.0(3), 4
1.451
orthorhombic
P212121
7.6772(3)
14.3292(6)
25.8800(11)
monoclinic
P21/c
orthorhombic
P212121
8.9109(6)
16.1975(12)
19.4837(13)
space group
a, Å
15.537(3)
11.263(2)
14.829(2)
109.589(3)
2444.8(7), 4
1.357
b, Å
c, Å
â, deg
volume, Å3; Z
density (calc), g/cm3
abs coeff, cm-1
F(0 0 0)
2847.0(2), 4
1.233
5.47
1120
2812.2(3), 4
1.351
6.41
1192
6.80
1032
32.92
1416
cryst dimens, mm
θ range for data collection, deg
limiting indices
0.09 × 0.20 × 0.41
1.57 to 27.54
-9 e h e 9
-18 e k e 18
-33 e l e 33
20 337
6493 (Rint ) 0.0465)
99.4
0.0506, 0.000
298
1.020
0.10 × 0.16 × 0.36
2.28 to 27.52
-20 e h e 20
-14 e k e 13
-19 e l e 18
16 863
5563 (Rint ) 0.1156)
98.9
0.0728, 0.000
262
0.968
0.12 × 0.14 × 0.20
1.63-27.55
-10 e h e 11
-21 e k e 19
-24 e l e 25
20 341
6393 (Rint ) 0.0621)
99.4
0.0279, 0.000
298
1.010
0.17 × 0.22 × 0.32
1.94-27.52
-21 e h e 19
-17 e k e 18
-18 e l e 17
22 412
7312 (Rint ) 0.0335)
99.4
0.0267, 0.4876
367
1.022
no. of reflns collected
no. of indep reflns
completeness, %
a, b
refined params
GOF on F2
R indices [I > 2σ(I)]
R1 ) 0.0420
wR2 ) 0.0960
0.227, -0.195
R1 ) 0.0664
wR2 ) 0.1371
0.724, -0.636
R1 ) 0.0438
wR2 ) 0.0757
0.379, -0.327
R1 ) 0.0254
wR2 ) 0.0600
0.593, -0.397
largest diff peak and hole, e/Å3
Table 2. Selected Interatomic Distances (Å) and
Bond Angles (deg) of 4, 5, and 6
Consequently, the longer Zr-N(amido) distances ob-
served for the meridonal structures reflect a decrease
in the N(pπ)-Zr(dπ) contribution to these bonds.
4
5
6
A. Interatomic Distances
The corresponding Ti-N(amido) distances of 1.892-
(2) and 1.905(2) Å for 4 are appreciably shorter than
the two Ti-N(amido) distances of 1.977(6) and 1.979-
(5) Å in the meridonal structure of [(Ar)NCH2(NC5H3)-
CH2N(Ar)]Ti(CH2CMe2Ph)Br, where Ar ) 2,6-dimeth-
ylphenyl,71 but are comparable to the Ti-N(amido)
distances of 1.905(2) and 1.910(2) Å in the pseudo-facial
complex, [(SiMe3NCH2CH2)2NSiMe3]TiMe2.67 The ob-
served variation for these Ti-N(amido) bonds can also
be attributed to the relative positions of the amido
π-donors. The N(amido)-Ti-N(amido) bond angles in
4 and [(SiMe3NCH2CH2)2NSiMe3]TiMe2 of 121.45(9)°
and 124.67(9)°, respectively, are, as expected, apprecia-
bly smaller than the corresponding angle of 142.1(2)°
in [(Ar)NCH2(NC5H3)CH2N(Ar)]Ti(CH2CMe2Ph)Br.
Whereas the amido nitrogen donors have two lone
pairs for π-bonding to the electron deficient group 4
metal, the central amine nitrogen donor of the triden-
tate diamidoamine ligand has only one lone pair to form
a dative NfZr or NfTi bond. As a consequence, the
central M-N(amino) distances of 2.438(2), 2.361(6), and
2.475(3) Å for 4, 5, and 6, respectively, are significantly
longer than the corresponding M-N(amido) distances.
The 0.11 Å increase in the Zr-N(amine) bond distance
upon replacement of the hydrogen on the central
nitrogen of 5 with the trimethylsilyl substituent in 6
reflects a decrease in the nitrogen donor strength due
to the greater electron-withdrawing character of the
trimethylsilyl substituent relative to hydrogen. An even
more substantial elongation of the central Zr-N(amino)
distance was observed for [(SiMe3NCH2CH2)2NSiMe3]-
ZrCl(CH(SiMe3)2).69 In this case, the corresponding Zr-
N(amino) interatomic separation of 2.770(5) Å is 0.73
Å longer than the two Zr-N(amido) distances of 2.035-
(5) and 2.041(5) Å.
M-Cl(1)
2.2885(9)
2.2563(10)
1.892(2)
2.438(2)
1.905(2)
1.473(3)
1.450(3)
1.498(3)
1.491(3)
1.473(3)
2.417(2)
2.411(2)
2.055(5)
2.361(6)
2.048(6)
1.472(8)
1.456(9)
1.475(9)
1.469(9)
1.470(8)
1.449(8)
2.415(1)
2.402(1)
2.038(3)
2.475(3)
2.042(3)
1.463(5)
1.449(5)
1.514(4)
1.503(4)
1.463(4)
M-Cl(2)
M-N(1)
M-N(2)
M-N(3)
N(1)-C(1)
N(1)-C(5)
N(2)-C(2)
N(2)-C(3)
N(3)-C(4)
N(3)-C(14)
N(3)-C(17)
N(2)-Si(1)
1.448(3)
1.823(2)
1.449(4)
1.820(3)
B. Bond Angles
Cl(1)-M-Cl(2)
Cl(1)-M-N(1)
Cl(1)-M-N(2)
Cl(1)-M-N(3)
Cl(2)-M-N(1)
Cl(2)-M-N(2)
Cl(2)-M-N(3)
N(1)-M-N(2)
N(1)-M-N(3)
N(2)-M-N(3)
97.79(4)
116.41(7)
91.99(6)
115.03(7)
99.20(7)
170.23(6)
99.73(7)
76.24(8)
121.45(9)
75.96(8)
103.1(1)
100.52(4)
114.82(9)
93.06(7)
115.24(9)
100.61(10)
166.41(7)
99.56(9)
72.95(11)
120.67(14)
74.64(11)
110.0(2)
87.4(2)
114.3(2)
104.2(2)
169.5(2)
102.8(2)
71.7(2)
120.1(2)
72.3(2)
The covalent radius of zirconium (1.45 Å) and the
ionic radius of Zr4+ (0.80 Å) are ca. 0.12-0.13 Å larger
than those of titanium (1.32 Å) and Ti4+ (0.68 Å).72 Thus,
the larger size of zirconium is expected to produce longer
M-Cl and M-N bonds than titanium in similar ligand
environments. A comparison of the structural data in
Table 2 shows that the observed differences between the
M-Cl and M-N(amido) distances for 4 and 6 are
consistent with this expectation. However, the corre-
sponding M-N(amino) bonds are more similar in mag-
nitude. Although these long M-N(amino) bonds reflect
the weaker amine nitrogen donor strength due to the
trimethylsilyl substituent, an additional lengthening of
(71) Gue´rin, F.; McConville, D. H.; Payne, N. C. Organometallics
1996, 15, 5085-5089.
(72) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: Ithaca, NY, 1960.

Diamidoamine Group 4 Metal Complexes
Organometallics, Vol. 24, No. 22, 2005 5389
the Ti-N(2) bond in 4 arises from the more sterically
crowded coordination environment about the smaller
titanium metal center. A substantially weaker dative
NfTi interaction is indicated by the significantly
disposition of the methylene protons of C(30) for the
η1-benzyl ligand sterically hinders C(24) of the η2-benzyl
ligand from interacting more strongly with the electro-
philic d0 Hf atom. To further reduce the steric congestion
about the Hf atom, the two mesityl substituents are
directed toward the same side of the molecule away from
the benzyl ligands.
longer Ti-N(amine) separation of 2.732(2)
Å in
[(SiMe3NCH2CH2)2NSiMe3]TiMe2.67 The M-Cl(2) bond
trans to the M-N(2) bond in 4 and in 6 is consistently
shorter than the M-Cl(1) bond that lies perpendicular
to the M-N(2) bond. The weaker dative bonding inter-
action of the neutral amino nitrogen donor in 4 and in
6 is compensated by enhanced π-donation from Cl(2) to
the electrophilic metal. The noticeably larger difference,
The orientation of the two benzyl ligands of 7 is
dramatically different than observed for [(C10H6CH2)2-
NMe]Zr(benzyl)2,77 which was obtained by the addi-
tion of the dilithium salt Li2[(C10H6CH2)2NMe] to
Zr(benzyl)2Cl2(Et2O)2. The tridentate bis(σ-aryl)amine
ligand in this five-coordinate complex adopts a meri-
donal structure with the bent wings of the two benzyl
ligands pointed away from each other. In contrast, the
phenyl ring of the η2-benzyl ligand of 7 is directed
toward the η1-benzyl ligand. The two Zr-C(CH2)-
C(ipso) bond angles of 97.7(4)° and 110.1(4)° and
Zr‚‚‚C(ipso) distances of 2.82(1) and 3.10(1) Å in
[(C10H6CH2)2NMe]Zr(benzyl)2 suggest that of one of its
benzyl ligands exhibits weak η2-character. Mountford
and co-workers61 recently reported the molecular struc-
ture of [(SiMe3NCH2CH2CH2)2NMe]Zr(benzyl)2, which
was prepared by the toluene elimination reaction of
(SiMe3NHCH2CH2CH2)2NMe with Zr(benzyl)4. Although
the diamidoamine ligand is facial in this case, both
benzyl ligands exhibit η1-bonding, which may be a
consequence of the steric bulk of the SiMe3 sub-
stituents and the additional CH2 link within each
chelate ring.
The results of our X-ray structural analyses of 4, 5,
6, and 7 reveal that these complexes adopt analogous
facial structures. Their solution NMR data are consis-
tent with the presence of Cs symmetry in solution. The
S-shaped backbone of the N(CH2)2N(CH2)2N unit intro-
duces an element of chirality in the solid-state struc-
tures of 4, 5, and 6. However, the appearance of two
rather than four distinct methylene carbon resonances
indicates that the chemical environments of the R- and
the â-methylene carbons (relative to the central amino
nitrogen) are equivalent on the NMR time scale for
these three compounds.
∆
M-Cl, between the two M-Cl distances of 0.032 Å in 4
compared to 0.013 Å in 6 provides another indication
of a weaker N(2)fM dative interaction in 4 compared
to 6.
The coordination sphere about the Hf atom in 7
consists of the two sp2 amido N-donors and the central
sp3 amine N-donor of the tridentate diamidoamine
ligand and the two benzyl ligands. The Hf-N(amido)
distances of 2.050(2) and 2.074(2) Å are comparable to
the Hf-N distances in d0 Hf-amido complexes, where
there exists appreciable N(pπ)fHf(dπ) π-bonding.32,36,73
The lack of a π-bonding capability for the central sp3
amine N-donor results in a substantially longer
Hf-N(2) distance of 2.350(3) Å. Two different coordina-
tion modes are observed for the two benzyl ligands, as
indicated by the Hf-C(CH2)-C(ipso) bond angles and
the Hf‚‚‚C(ipso) distances. The Hf-C(23)-C(24) bond
angle and Hf‚‚‚C(24) distance of 91.6(2)° and 2.741(3)
Å, respectively, indicate a η2-benzyl interaction, whereas
the Hf-C(30)-C(31) bond angle and nonbonding
Hf‚‚‚C(31) distance of 118.7(2)° and 3.283(4) Å, respec-
tively, are consistent with a normal η1-benzyl bonding
mode.24,48,74-76
The three C atoms, C(23), C(24), and C(30), of the two
benzyl ligands define a plane that essentially passes
through the central Hf atom and the N(2) atom. The
N(2)-Hf(1)-C(23) and N(2)-Hf(1)-C(30) bond angles
of 152.2(1)° and 89.8(1)° indicate a highly unsym-
metrical disposition of the two benzyl ligands within this
plane. The N(2)-Hf(1)-C(24) angle of 175.6(1)° places
the ipso-C of the η2-benzyl ligand trans to N(2), consis-
tent with a fac structure for this compound. Chelation
of the tridentate diamidoamine ligand produces two
puckered five-membered chelate rings. The obtuse
dihedral angle between the planes containing N(1),
Hf(1), N(2) and N(2), Hf(1), N(3) of 136.9° provides
further evidence of the fac geometry, whereby the
Hf and three N atoms do not lie in the same plane.
The corresponding dihedral angle between the two N,
Ti, O planes in the related Ti dibenzyl complex,
[(ArNCH2CH2)2O]Ti(benzyl)2, Ar ) 2,6-dimethylphen-
yl,17,18 is also 137°. However, in this Ti complex both
benzyl ligands are bonded in a η1-fashion with the
Ti-C(CH2)-C(ipso) angles being 121.0(6)° and
122.9(6)°. This difference is likely a consequence of the
smaller size of Ti compared to Hf. Finally, the spatial
Concluding Comment. The results from this ex-
ploratory study demonstrate that Ti(NEt2)2Cl2 and
Zr(benzyl)2Cl2(Et2O)2 offer potentially attractive re-
agents for the efficient preparation of electrophilic group
4 metal dichloride complexes. The former avoids the
possibility of metal reduction that sometimes occurs
during conventional metathesis reactions of Ti halides
and organolithio salts. These two reagents may further
prove useful whenever the conversion of an intermediate
organometal diamide species with SiMe3Cl to the cor-
responding dichloride derivative is incomplete or proves
to be problematic.
Experimental Section
Reagents. Reagent grade hydrocarbon and ethereal sol-
vents were purified using standard methods.78 Pentane,
toluene, and THF were refluxed under nitrogen over Na/K and
then transferred to storage flasks containing [(C5H5)2Ti(µ-
(73) Hillhouse, G. L.; Bulls, A. R.; Santarsiero, B. D.; Bercaw, J. E.
Organometallics 1988, 7, 1309-1312.
(74) Girolami, G. S.; Wilkinson, G.; Thornton-Pett, M.; Hursthouse,
M. B. J. Chem. Soc., Dalton Trans. 1984, 2789-2794.
(75) Latesky, S. L.; McMullen, A. K.; Niccolai, G. P.; Rothwell, I.
P.; Huffman, J. C. Organometallics 1985, 4, 902-908.
(76) Pellecchia, C.; Immirzi, A.; Grassi, A.; Zambelli, A. Organome-
tallics 1993, 12, 4473-4478.
(77) Bouwkamp, M.; van Leusen, D.; Meetsma, A.; Hessen, B.
Organometallics 1998, 17, 3645-3647.
(78) Gordon, A. J.; Ford, R. A. The Chemist’s Companion; Wiley-
Interscience: New York, 1972.

5390 Organometallics, Vol. 24, No. 22, 2005
Morgan et al.
Cl)2]2Zn79 or (C5H5)5ZrMe2.80,81 The deuterated solvents C6D6
(Aldrich, 99.5%) and CDCl3 (Aldrich, 99.8%) were dried over
activated 4 Å molecular sieves prior to use, as were diethyl-
enetriamine (Aldrich) and Et2NH (Aldrich). TiCl4(THF)2,82
(26.0 mmol) of Na-O-t-Bu, 0.0211 g (0.0204 mmol) of
Pd2(dba)3‚CHCl3, and 0.0379 g (0.0608 mmol) of rac-BINAP.
Toluene (40 mL) was added via vacuum distillation. The
reaction mixture was placed under a nitrogen atmosphere and
heated to 100-120 °C for 40 h. The reaction mixture was
cooled to room temperature and filtered. The product was
extracted and the toluene removed, leaving a dark reddish
solid. Pentane (30 mL) was added via vacuum distillation. The
solution was filtered and the solvent removed, leaving a dark
oily product. The oil was frozen by submersion of the reaction
flask in liquid nitrogen. The product remained as a reddish
solid after the liquid nitrogen was removed, and the flask was
warmed to ambient temperature. The product (3.11 g, 91.7%
Zr(benzyl)4,83 and Hf(benzyl)4 were prepared by literature
83
procedures. The workup procedure used for (MesNHCH2CH2)2-
NH was modified from the large-scale preparation originally
described by Schrock and co-workers.9 [NEt3H]Cl was prepared
by the stoichiometric addition of HCl to a pentane solution of
NEt3. LiNEt2 was prepared by treatment of a pentane solution
of NEt2H with 1 equiv of n-BuLi. TiCl4 (Aldrich), ZrCl4
(Aldrich), HfCl4 (Aldrich), n-BuLi (Aldrich, 1.6 M in hexanes),
HCl (Matheson), NEt2H (Aldrich), NEt3 (Aldrich), SiMe3Cl
(Aldrich), 2-bromomesitylene (Aldrich), Na-O-t-Bu (Acros),
Pd2(dba)3‚CHCl3 (Strem Chemicals), rac-BINAP (Strem Chemi-
cals), and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU, Aldrich)
were used without further purification.
1
yield) was dried under vacuum. H NMR (CDCl3): δ 6.81 (s,
meta-H, 4H), 3.39 (t, NH, 2H), 3.03 (m, CH2, 4H), 2.83 (m, CH2,
4H), 2.26 (s, ortho-Me, 12H), 2.21 (s, para-Me, 6H). Gated
1
nondecoupled 13C NMR (CDCl3) (mult, JC-H in Hz): δ 143.6
(s, ipso-C), 131.2 (s, para-C), 129.7 (s, ortho-C), 129.4 (d, meta-
CH, 158), 50.0 (t, CH2, 133), 48.4 (t, CH2, 136), 20.5 (q, para-
Me, 125), 18.3 (q, ortho-Me, 126).
General Considerations. All syntheses and manipulations
were carried out on a double-manifold, high-vacuum line or
in a Vacuum Atmospheres glovebox equipped with an HE-493
Dri-Train. Reactions were typically carried out in pressure-
equalizing filter-frits equipped with high-vacuum Teflon stop-
cocks and Solv-seal joints. Nitrogen was purified by passage
over reduced BTS catalysts and activated 4 Å molecular sieves.
All glassware was thoroughly oven-dried and/or flame-dried
under vacuum prior to use. NMR sample tubes were sealed
Preparation of (MesNHCH2CH2)2NSiMe3, 2. To a 100
mL Solv-seal flask equipped with a sidearm was added 1.236
g (8.12 mmol) of DBU. To the sidearm was added 2.769 g (8.16
mmol) of 1. Diethyl ether (35 mL) and 1.1 mL (8.67 mmol) of
SiMe3Cl were added via vacuum distillation. The DBU/
SiMe3Cl/Et2O solution was placed under a nitrogen atmo-
sphere and stirred at room temperature for 1 h, immediately
forming a white solid. The triamine was added in small
increments. The reaction mixture was stirred overnight at
room temperature. The solution was filtered, the product
extracted with pentane, and the solvent removed. The oily
product (3.11 g, 92.6%) was dried under vacuum to remove
any volatiles. The NMR spectra indicated the isolated product
was sufficiently pure to use. 1H NMR (CDCl3): δ 6.79 (s, meta-
H, 4H), 2.97 (m, CH2, 8H), 2.22 (s, ortho-Me, 12H), 2.21 (s,
para-Me, 6H), 0.11 (s, SiMe3, 9H). 13C{1H} NMR (CDCl3): δ
143.6 (ipso-C), 130.9 (para-C), 129.4 (meta-CH), 129.1 (ortho-
C), 47.1, 46.5 (CH2), 20.5 (para-Me), 18.4 (ortho-Me), 0.14
(SiMe3).
1
under approximately 500 Torr of nitrogen. H and 13C NMR
spectra were measured on a JEOL GX-270 or Eclipse 270
FT-NMR spectrometer. The 1H chemical shifts are referenced
to the residual proton peak of benzene-d6 (δ 7.15) or chloroform-
d1 (δ 7.24); the 13C resonances are referenced to the central
carbon peak of benzene-d6 (δ 128.0) or chloroform-d1 (δ 77.0).
Elemental analyses were performed by Complete Analysis
Laboratories Inc., Parsippany, NJ.
Preparation of Ti(NEt2)4. To a 100 mL Solv-seal flask
equipped with a sidearm was added 1.470 g (18.6 mmol) of
freshly prepared LiNEt2. A 1.515 g (4.54 mmol) sample of
TiCl4(THF)2 was added to the sidearm. After the addition of
dry toluene (35 mL), the TiCl4(THF)2 was added in small
increments. The reaction mixture was stirred overnight at
room temperature and then heated at 100 °C for several hours.
The toluene was replaced by 40 mL of pentane. The yellow
solution was filtered and the product extracted before the
solvent was removed. The brownish-red oily product (1.42 g,
92.6% yield) was dried under vacuum. The 1H NMR spectrum
[(MesNCH2CH2)2NH]TiCl2, 3. To a 100 mL Solv-seal flask
were added 2.175 g (8.26 mmol) of Ti(NEt2)2Cl2, 2.804 g (8.26
mmol) of 1, and 45 mL of toluene. The reaction mixture was
heated at 100 °C overnight under a nitrogen flush for 48 h.
The toluene was removed and the product residue was washed
with pentane (3 × 25 mL) to extract any soluble impurities.
Removal of the volatiles left 3.464 g (91.8% yield) of a reddish
1
indicated the product was clean. H NMR (C6D6): δ 3.57 (q,
1
CH2), 1.10 (t, CH3). 13C{1H} NMR (C6D6): δ 45.3 (CH2), 15.6
orange powder. H NMR (CDCl3) (mult., JH-H in Hz): δ 6.85,
6.83 (s, meta-H, 4H), 4.19 (dt, CH2, 13.8, 6.0, 2H), 3.75 (pseudo-
q, CH2, 6.0, 6.1, 4H), 3.55 (dt, CH2, 13.8, 6.1, 2H), 2.36, 2.27,
2.21 (s, ortho- and para-Me, 18H). 13C{1H} NMR (CDCl3): δ
135.7 (ipso-C), 131.9 (para-C), 129.7, 129.3 (ortho-C), 129.25,
129.2 (meta-CH), 60.7, 49.2 (CH2), 20.8 (para-Me), 18.9, 18.8
(ortho-Me). Anal. Calcd for C22H31N3Cl2Ti: C, 57.91; H, 6.85;
N, 9.21. Found: C, 56.98; H, 6.96; N, 8.92. The low carbon
percentage may reflect Ti carbide formation during the
combustion analysis.
(CH3).
Preparation of Ti(NEt2)2Cl2. Toluene (30 mL) and 1.10
mL (8.67 mmol) of SiMe3Cl were vacuum transferred into a
100 mL Solv-seal flask containing 1.349 g (4.01 mmol) of
Ti(NEt2)4. The reaction mixture was placed under a nitrogen
atmosphere and then heated at 60 °C for 60 h. The toluene
was replaced by 40 mL of pentane. The solution was filtered
and the solvent was removed to afford a reddish oil (0.977 g,
92.6% yield) after removal of the volatile solvents under
1
Preparation of [(MesNCH2CH2)2NSiMe3]TiCl2, 4. Tolu-
ene (40 mL) was added to a 100 mL Solv-seal flask containing
1.736 g (6.60 mmol) of Ti(NEt2)2Cl2 and 2.716 g (6.60 mmol)
of 2. The reaction was stirred overnight while heating to 100
°C under a nitrogen flush. After removal of the volatiles, the
product was washed with pentane (3 × 30 mL), leaving 2.047
vacuum. The H NMR spectrum indicated clean formation of
1
the desired product. H NMR (C6D6): δ 3.55 (q, CH2), 0.87 (t,
CH3). 13C{1H} NMR (C6D6): δ 47.1 (CH2), 14.1 (CH3).
Preparation of (MesNHCH2CH2)2NH, 1. To a 100 mL
Solv-seal flask were added 1.03 g (9.98 mmol) of diethylen-
etriamine, 4.00 g (20.1 mmol) of 2-bromomesitylene, 2.50 g
1
g (58.7% yield) of a reddish-orange powder. H NMR (CDCl3)
(mult., JH-H in Hz): δ 6.85, 6.83 (s, meta-H, 4H), 4.19 (dt, CH2,
13.8, 5.8, 2H), 3.75 (pseudo-q, CH2, 6.0, 5.8, 4H), 3.57 (dt, CH2,
13.8, 6.0, 2H), 2.36, 2.27, 2.22 (s, ortho- and para-Me, 18H),
0.52 (s, SiMe3). 13C{1H} NMR (CDCl3): δ not obsd (ipso-, ortho-,
and para-C), 129.3, 129.2 (meta-CH), 61.3, 52.7 (CH2), 20.8
(para-Me), 19.5, 18.8 (ortho-Me), 0.5 (SiMe3). Anal. Calcd for
C25H39N3Cl2SiTi: C, 56.82; H, 7.44; N, 7.95. Found: C, 56.74;
H, 7.60; N, 8.16.
(79) Sekutowski, D. G.; Stucky, G. D. Inorg. Chem. 1975, 14, 2192-
2199.
(80) Samuel, E.; Rausch, M. D. J. Am. Chem. Soc. 1973, 95, 6263-
6267.
(81) Hunter, W. E.; Hrncir, D. C.; Vann Bynum, R.; Penttila, R. A.;
Atwood, J. L. Organometallics 1983, 2, 750-755.
(82) Manzer, L. E. Inorg. Synth. 1982, 21, 135-136.
(83) Zucchini, U.; Albizzati, E.; Giannini, U. J. Organomet. Chem.
1971, 26, 357-372.

Diamidoamine Group 4 Metal Complexes
Organometallics, Vol. 24, No. 22, 2005 5391
Table 3. Selected Interatomic Distances (Å) and
Bond Angles (deg) for
Preparation of [(MesNCH2CH2)2NH]ZrCl2, 5. To a 250
mL round-bottom flask equipped with two sidearms was added
3.887 g (8.53 mmol) of Zr(benzyl)4. To one sidearm was added
2.348 g (17.06 mmol) of [NEt3H]Cl. To the other sidearm was
added 2.896 g (8.53 mmol) of 1. Diethyl ether (ca. 60 mL) was
added via vacuum distillation. The reaction was stirred at 0
°C while the [NEt3H]Cl was added in small increments. After
the volatiles were removed, toluene (75 mL) was added. The
reaction mixture was stirred at 0 °C while 1 was added in
small increments. The reaction was then warmed to room
temperature and stirred overnight. The solution was filtered
and the product extracted before the toluene was removed. The
product residue was then washed with 45 mL of pentane to
remove any soluble impurities. The remaining light tan solid
(3.745 g, 87.9% yield) was dried in vacuo. The 1H NMR
spectrum confirmed the formation of 5 as the only product.
1H NMR (CDCl3): δ 6.87 (s, meta-H, 4H), 3.86, 3.55, 3.45 (m,
CH2, 8H), 2.37, 2.32, 2.22 (s, ortho- and para-Me). Gated
[(MesNCH2CH2)2NH]Hf(benzyl)2, 7
A. Interatomic Distances
Hf(1)-N(1)
Hf(1)-N(3)
Hf(1)-C(30)
N(1)-C(1)
N(2)-C(2)
N(3)-C(4)
C(1)-C(2)
C(23)-C(24)
2.074(2)
2.050(2)
2.301(3)
1.470(4)
1.466(3)
1.465(4)
1.509(4)
1.455(4)
Hf(1)-N(2)
Hf(1)-C(23)
Hf(1)-C(24)
N(1)-C(14)
N(2)-C(3)
N(3)-C(5)
C(3)-C(4)
2.350(3)
2.282(3)
2.741(3)
1.440(3)
1.473(4)
1.448(4)
1.514(4)
1.483(4)
C(30)-C(31)
B. Bond Angles
N(1)-Hf(1)-N(2)
N(2)-Hf(1)-N(3)
N(1)-Hf(1)-C(24)
N(2)-Hf(1)-C(23)
N(2)-Hf(1)-C(30)
N(3)-Hf(1)-C(24)
C(23)-Hf(1)-C(24)
C(1)-N(1)-Hf(1)
C(1)-N(1)-C(14)
C(14)-N(1)-Hf(1)
C(2)-N(2)-Hf(1)
C(2)-N(2)-C(3)
C(1)-C(2)-N(2)
C(3)-C(4)-N(3)
72.3(1) N(1)-Hf(1)-N(3)
71.6(1) N(1)-Hf(1)-C(23)
110.1(1) N(1)-Hf(1)-C(30)
152.2(1) N(2)-Hf(1)-C(24)
89.8(1) N(3)-Hf(1)-C(23)
109.1(1) N(3)-Hf(1)-C(30)
124.3(1)
97.0(1)
112.3(1)
175.6(1)
95.9(1)
108.5(1)
1
nondecoupled 13C NMR (CDCl3) (mult, JC-H in Hz): δ 145.0
32.1(1) C(23)-Hf(1)-C(30) 117.9(1)
(s, ipso-C), 135.3, 134.1, 133.7 (s, ortho- and para-C), 129.6,
129.5 (d, meta-CH, 161), 56.8 (t, CH2, 137), 49.2 (t, CH2, 134),
20.9 (q, para-Me, 126), 18.8, 18.7 (q, ortho-Me, 125). Anal.
Calcd for C22H31N3Cl2Zr: C, 52.89; H, 6.25; N, 8.41. Found:
C, 52.78; H, 6.52; N, 8.15.
122.3(2) C(5)-N(3)-Hf(1)
110.6(2) C(4)-N(3)-C(5)
127.1(2) C(4)-N(3)-Hf(1)
105.4(2) C(3)-N(2)-Hf(1)
114.4(2) N(1)-C(1)-C(2)
107.1(2) N(2)-C(3)-C(4)
108.6(2) C(24)-C(23)-Hf(1)
122.5(2)
111.0(2)
126.2(2)
112.0(2)
108.0(2)
107.6(2)
91.6(2)
Preparation of [(MesNCH2CH2)2NSiMe3]ZrCl2, 6. To a
250 mL round-bottom flask equipped with two sidearms was
added 3.652 g (8.01 mmol) of Zr(benzyl)4. To one sidearm was
added 2.206 g (16.03 mmol) of [NEt3H]Cl. To the other sidearm
was added 3.299 g (8.01 mmol) of 2. Diethyl ether (60 mL)
was added via vacuum distillation. The reaction was stirred
at 0 °C while the [NEt3H]Cl was added in small increments.
The volatiles were then removed and toluene (65 mL) was
added. The reaction was stirred at 0 °C while 2 was added in
small increments. The reaction was then warmed to room
temperature and stirred overnight. The solution was filtered
and the toluene removed. The product was then washed with
40 mL of pentane. The off-white solid (3.394 g, 74.1% yield)
C(31)-C(30)-Hf(1) 118.7(2)
49.1 (NCH2), 2.55/19.9, 2.39/19.1, 2.19/21.0 (ortho- and para-
Me), 1.61/74.0 (HfCH2), 1.26/66.0 (HfCH2). Anal. Calcd for
C36H45N3Hf: C, 61.93; H, 6.50; N, 6.02. Found: C, 61.89; H,
6.52; N, 6.22.
Description of the X-ray Structural Analyses. The
X-ray structural analyses of 4, 5, 6, and 7 were performed by
using the same general procedures. Suitable crystals of 4-7
for the structural and elemental analyses were grown by slow
removal of diethyl ether from saturated solutions. Each crystal
was coated with the perfluoropolyether PFO-XR75 (Lancaster)
and sealed under nitrogen in a glass capillary. Each sample
was optically aligned on the four-circle of a Siemens P4
diffractometer equipped with a graphite monochromatic crys-
tal, a Mo KR radiation source (λ ) 0.71073 Å), and a SMART
CCD detector held at 5.054 cm from the crystal. The samples
of 5, 6, and 7 were cooled to -50 °C by the nitrogen cold stream
provided by a LT-2 low-temperature attachment. Four sets of
20 frames each were collected using the ω scan method with
a 10 s exposure time. Integration of these frames followed by
reflection indexing and least-squares refinement produced the
crystal orientation matrix and preliminary lattice parameters.
Data acquisition consisted of the measurement of a total of
1650 frames in five different runs covering a hemisphere of
data. The program SMART (version 5.6)84 was used for
diffractometer control, frame scans, indexing, orientation
matrix calculations, least-squares refinement of cell param-
eters, and the data collection. All 1650 crystallographic raw
data frames were read by the program SAINT (version 5/6.0)84
and integrated using 3D profiling algorithms. An absorption
correction was applied using the SADABS routine available
in SAINT. The data were corrected for Lorentz and polariza-
tion effects as well as any crystal decay. The linear absorption
coefficient, atomic scattering factors, and anomalous dispersion
corrections were calculated from values from the International
Tables for X-ray Crystallography.85
1
was dried under vacuum. The H NMR spectrum confirmed
the formation of 6 as the only product. 1H NMR (C6D6): δ 6.90,
6.80 (s, meta-H, 4H), 3.63, 3.03, 2.84, 2.68 (m, CH2, 8H), 2.57,
2.48, 2.12 (s, ortho- and para-Me, 18H), 0.27 (s, SiMe3, 9H).
1
Gated nondecoupled 13C NMR (C6D6) (mult., JC-H in Hz): δ
148.6 (s, ipso-C), 134.7, 133.3, 132.8 (s, ortho- and para-C),
130.3, 129.8 (d, meta-CH, 160), 56.8 (t, CH2, 137), 52.3 (t, CH2,
135), 20.9 (q, para-Me, 125), 20.1, 19.4 (q, ortho-Me, 126), 0.0
(q, SiMe3, 119). Anal. Calcd for C25H39N3Cl2SiZr: C, 52.51; H,
6.87; N, 7.35. Found: C, 52.29; H, 7.07; N, 7.27.
Preparation of [(MesNCH2CH2)2NH]Hf(benzyl)2, 7. To
a 100 mL Solv-seal flask was added 170 mg (0.5 mmol) of 1
and 272 mg (0.5 mmol) of Hf(benzyl)4. Approximately 20 mL
of pentane was added via vacuum distillation, and the solution
was allowed to stir overnight. The pentane was removed slowly
into a liquid N2 filled trap, leaving an off-white solid, which
was washed with cold pentane and dried under high vacuum.
Slow removal of solvent from a saturated diethyl ether solution
provided suitable crystals for X-ray crystallographic analysis.
The isolated yield was 286 mg (82% yield). 1H NMR (C6D6): δ
7.15 (m, aryl-H, 2H), 7.04 (t, para-H, 1H), 6.96 (d, meta-H,
2H), 6.92 (m, aryl-H, 2H), 6.90 (m, aryl-H, 2H), 6.85 (m, aryl-
H, 2H), 6.76 (t, para-H, 1H), 6.15 (d, meta-H, 2H), 3.39, 3.16,
2.36, 2.20 (m, NCH2, 8H), 2.55, 2.39, 2.19 (s, ortho- and para-
Me, 18H), 1.61, 1.26 (s, HfCH2, 4H). 13C NMR (C6D6) (mult.,
1JC-H in Hz): δ 148.0 (ipso-C, Mes), 153.7, 141.0 (ipso-C,
benzyl), 134.93, 134.90, 134.0 (ortho- and para-C), 130.4, 130.3,
129.4, 128.6, 128.5, 125.5, 123.7, 120.8, (d, aryl-CH, average
158), 74.0, 66.0, (t, HfCH2, 128), 57.0, 49.1 (t, NCH2, 135), 21.0
(q, para-Me, 125), 19.9, 19.1 (q, ortho-Me, 125). 2D HETCOR
NMR (C6D6): δ 7.15/128.6 (aryl-CH), 7.04/125.5 (para-CH,
benzyl), 6.96/129.4 (meta-CH, Mes), 6.92/130.4 (aryl-CH), 6.90/
130.3 (aryl-CH), 6.85/123.7 (aryl-CH), 6.76/120.8 (para-CH,
benzyl), 6.15/128.5 (meta-CH, Mes), 3.39, 3.16/57.0; 2.36, 2.20/
Initial coordinates for all of the non-hydrogen atoms were
determined by a combination of direct methods and difference
Fourier methods with the use of SHELXTL 6.1.86 Idealized
(84) SMART, SAINT, and XPREP programs are part of the Bruker
crystallographic software package for single-crystal data collection,
reduction, and preparation.
(85) International Tables for X-ray Crystallography; Kynoch Press:
Birmingham (Present distributor, D. Reidel, Dordrecht), 1974; Vol. IV,
p 55.

5392 Organometallics, Vol. 24, No. 22, 2005
Morgan et al.
positions for the hydrogen atoms were included as fixed
contributions using a riding model with isotropic temperature
factors set at 1.2 (aromatic and methylene protons) or 1.5
(methyl protons) times that of the adjacent carbon. The
positions of the methyl hydrogen atoms were optimized by a
rigid rotating group refinement with idealized tetrahedral
angles. Full-matrix least-squares refinement, based upon the
cal Society. J.L.P. gratefully acknowledges the financial
support provided by the Eberly College of Arts and
Sciences and the C. Eugene Bennett Department of
Chemistry and the unrestricted research funds provided
by Union Carbide Corporation and The Dow Chemical
Company to acquire a SMART CCD detector for the
Siemens P4 X-ray diffractometer at West Virginia
University.
minimization of ∑wi|Fo2 - Fc2|2, with wi-1 ) [σ2 (Fo ) + (aP)2 +
2
2
bP], where P ) (Max(Fo , 0) + 2Fc2)/3, converged to give final
discrepancy indices87 tabulated in Table 1. Pertinent inter-
atomic distances and bond angles for the molecular structures
of the dichloride complexes 4, 5, and 6 and the dibenzyl
complex 7 are provided in Tables 2 and 3, respectively.
Supporting Information Available: Complete tables of
the results from the X-ray structural analyses performed on
compounds 4-7. This material is available free of charge via
the Internet at http://pubs.acs.org.
OM0580349
Acknowledgment. Financial support for this re-
search was provided by the donors of the Petroleum
Research Fund, administered by the American Chemi-
(87) The equations for the R-factors are R1 ) ∑(||Fo| - |Fc||)/∑|Fo|
and wR2 ) [∑[w(Fo - Fc2)2]/∑w[Fo2]2]1/2. The expression for the
2
“goodness-of-fit” is GOF ) [∑[w(Fo - Fc2)2]/(n-p)]1/2, where n is the
2
(86) Sheldrick, G. M. SHELXTL6.1, Crystallographic software pack-
age; Bruker AXS, Inc.: Madison, WI, 2000.
number of reflections and p is the total number of parameters that
were varied during the last refinement cycle.