Closely Related Benzylene-Linked Diamidophosphine Scaffolds and Their Zirconium and Hafnium Complexes: How Small Changes of the Ligand Result in Different Complex Stabilities and Reactivities

Article abstract of DOI:10.1021/acs.organomet.6b00384

The closely related benzylene-linked diaminophosphines PhP(CH₂C₆H₄-o-NHPh)₂ ([^PhA]H₂) and PhP(C₆H₄-o-CH₂NHXyl)₂ ([B]H₂) were prepared

Full text of DOI:10.1021/acs.organomet.6b00384

Article
pubs.acs.org/Organometallics
Closely Related Benzylene-Linked Diamidophosphine Scaffolds and
Their Zirconium and Hafnium Complexes: How Small Changes of the
Ligand Result in Different Complex Stabilities and Reactivities
Sonja Batke, Malte Sietzen, Lukas Merz, Hubert Wadepohl, and Joachim Ballmann*
Anorganisch-Chemisches Institut, Ruprecht-Karls-Universitat Heidelberg, Im Neuenheimer Feld 276, 69120 Heidelberg, Germany
̈
S
* Supporting Information
ABSTRACT: The closely related benzylene-linked diamino-
phosphines PhP(CH2C6H4-o-NHPh)2 ([PhA]H2) and PhP-
(C6H4-o-CH2NHXyl)2 ([B]H2) were prepared as robust
alternatives to the previously reported N,N′-bis(trimethylsilyl)-
substituted derivative PhP(CH2C6H4-o-NHSiMe3)2 ([SiA]H2).
Upon reaction of [PhA]H2 and [B]H2 with M(NMe2)4 (M = Zr,
Hf), the respective dimethylamido complexes [PhA]M(NMe2)2
and [B]M(NMe2)2 ([PhA]-1-M and [B]-1-M, M = Zr, Hf) were
isolated in high yields and converted to the corresponding
diiodo derivatives [PhA]MI2 and [B]MI2 ([PhA]-2-M and [B]-2-
M, M = Zr, Hf). In contrast to [SiA]ZrI2, these thermally robust
diiodo complexes were found to react cleanly with Bn2MgL2 (L = THF or Et2O), resulting in the corresponding dibenzyl species
[PhA]MBn2 and [B]MBn2 ([PhA]-4-M and [B]-4-M, M = Zr, Hf). Upon addition of [B]H2 to [B]ZrBn2, the related homoleptic
species [B]2Zr ([B]-5-Zr) was generated. Similar 2:1 complexes have not been observed for the hafnium homologue bearing the
latter ligand or for [SiA]- or [PhA]-coordinated complexes. The former dibenzyl complexes were reacted with 2,6-xylylisonitrile,
and clean conversions to the bis-η2-iminoacyl complexes [B]-6-Hf and [PhA]-6-M were observed for [B]-4-Hf and [PhA]-4-M
(M = Zr, Hf). For [SiA]HfBn2 ([SiA]-4-Hf) only one equivalent of the former isonitrile was inserted into one of the hafnium
carbon bonds, which is in line with the steric differences between [SiA] and [PhA].
Chart 1. Strategies to Improve the Thermal Stability of
[SiA]MI2 (M = Zr, Hf) via Replacement of the N-
Trimethylsilyl Substituents (a) or via Inversion of the
Benzylene Linker (b)
INTRODUCTION
■
Over the past decades, reduced zirconocene and hafnocene
fragments (i.e., “Cp2Zr” and “Cp2Hf”) and their tetra- and
pentamethyl-cyclopentadienyl variants have been investigated
in detail, especially in view of their reactivities toward alkynes
and dinitrogen.1 In both of these research fields, unanticipated
dissimilarities between zirconium and hafnium were uncovered
and ascribed to hafnium’s propensity to form stronger σ-bonds,
which in turn leads to an increased π-back-bonding.2 That the
formal substitution of pentamethyl-cyclopentadiene for tetra-
methyl-cyclopentadiene led to the discovery of even more
astonishing differences with respect to the reactivity of the
resulting zircono- and hafnocenes clearly demonstrated that
seemingly minor changes at the ligand require a careful
evaluation.3 While these effects are nowadays well accepted in
cyclopentadienyl chemistry,4 little is known on the impact of
small changes at Cp-free capping ligands. In the case of
amidophosphines, which are frequently seen as adequate
replacements for cyclopentadienyl moieties,5 divergent reac-
tivities have been found for homologous zirconium and
hafnium complexes as well,6 but systematic studies using
comparable ligand backbone architectures are scare.6b,c
stability.7 On the basis of this finding, we decided to
systematically probe for differences between [NPN]-coordi-
nated hafnium and zirconium derivatives8 and the depend-
In a previous report, we have noted that the simple
zirconium diiodo complex [SiA]ZrI2 shown in Chart 1 is fairly
unstable at room temperature, while the hafnium homologue
[SiA]HfI2 was found to exhibit a significantly enhanced thermal
Received: May 11, 2016
© XXXX American Chemical Society
A
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Scheme 1. Synthesis of the Protioligand [PhA]H2
encies of these differences on subtle ligand alterations. To
exclude that the dissimilar thermal stabilities of [SiA]ZrI2 and
[SiA]HfI2 are solely due to a more or less pronounced ligand
degradation reaction, robust analogues of the former benzylene-
linked [NPN] ligand were required. At first glance, a formal
exchange of the trimethylsilyl groups for N-phenyl substituents
(see Chart 1) seemed reasonable in order to exclude possible
decomposition pathways via silyl amide bond cleavage.9 An
inversion of the benzylene linker, however, was recognized as a
plausible strategy as well, as this modification would result in a
more robust triphenylphosphine-based ligand core (see Chart
1),10 which might hamper decomposition pathways via
phosphine-centered redox processes. In the latter case, N-
xylyl substituents were chosen to circumvent solubility issues,
which have been noted for related [PN3] ligands.11
Anticipating that either one or even both of these strategies
would lead to thermally stable group 4 diiodo complexes, which
tolerate consecutive transformations and reactivity studies, a
simultaneous exploration of [PhA]- and [B]-coordinated
systems was pursued (see Chart 1). As detailed in the
following, we have found that dibenzyl complexes incorporating
these ligands can be accessed via their thermally stable diiodo
derivatives. As an alternative route for the preparation of
[SiA]MBn2 was discovered as well, a comparative analysis of all
these dibenzyl derivatives was conducted, which revealed
different complex stabilities and reactivities12 toward isonitriles
(mono- vs bis-insertion).
chloride, protioligand [PhA]H2 was obtained as a thick oil in
1
high purity as judged by H and 31P{1H} NMR spectroscopy
(δ(31P) = −24.3 ppm). Upon standing at room temperature,
this oil solidified over a period of several days, but the
preparation of stock solutions was more convenient, as it
allowed for the direct use of [PhA]H2.
For the preparation of the protioligand [B]H2, reductive
amination of the bis-formyl-substituted triphenylphosphine
derivative 5 was attempted in a first approach (see Scheme 2,
Scheme 2. Synthesis of Protioligand [B]H2 (Xyl = 3,5-Xylyl)
RESULTS AND DISCUSSION
■
Ligand Synthesis. For the synthesis of [PhA]H2, a retro-
synthetic strategy that relied on the presence of the N-phenyl
substituent prior to the introduction of the phosphine had to be
developed, as numerous attempts to access the target molecule
via Pd- or Cu-catalyzed coupling13,8a of the unsubstituted ligand
backbone7 (PhP(CH2C6H4-o-NH2)2) were unsuccessful. Em-
ploying N-phenyl-substituted 2-aminobenzyl halides14 or
anthranilic chlorides15 was found to be problematic as well,
mainly due to the ease of 9,10-dihydroacridine and acridone
formation via intramolecular electrophilic alkylation of the N-
phenyl substituent.16 To circumvent the former acridine
formation process, the benzylic leaving group was modified in
a trial and error approach and in one attempt replaced by a
trimethylammonium group. Gratifyingly, this approach ham-
pered intramolecular cyclization, but still allowed for
nucleophilic substitution at the benzylic positon and thus for
the introduction of the phenyl phosphine subunit in the last
step.17 Based on these observation, a large-scale synthesis for
the trimethylammonium-substituted N-phenyl benzylamine 3
was developed starting from 118 (see Scheme 1). After
reduction of 1 with lithium aluminum hydride, the dimethyl-
amine derivative 2 was obtained in high yields and directly
converted to 3 via treatment with excess methyl iodide. An N-
SiMe3 protection of the NH group is possible, but not required,
as no signs of methylation at that nitrogen atom were noticed.
Upon addition of n-butyllithium to a cold 1:2 mixture of phenyl
phosphine and 3 in DME, the dilithium salt of the target
molecule was generated (see Scheme 1). After acidic workup
with NEt3HCl and separation of the iodide and chloride salts,
the crude protioligand was obtained as a thick yellow oil.
Further purification was achieved by protonation of the
diaminophosphine with hydrogen chloride and recrystallization
of the resulting bis-hydrochloride salt. After deprotonation with
triethylamine and separation of triethylammonium hydro-
method A).19 The required bis-aldehyde 5 was easily generated
via deprotection of 420 and directly reacted with 3,5-
xylylamine.11a The resulting bis-imine was reduced in situ
with sodium borohydride, and the target molecule then purified
by column chromatography. Although pure [B]H2 was
obtained, poorly reproducible yields in the range 10−35%
rendered this route rather unreliable. In the presence of water,
bis-aldehyde 5 is known to undergo complex redox reactions
that involve formyl coupling with concurrent transfer of an
oxygen atom to the phosphine.21 In the above-described
reaction of 5 with 3,5-xylylamine, these formyl-coupled
phosphine oxides were detected by 31P{1H} NMR spectrosco-
py. However, attempts to trap both equivalents of water, which
are generated in the condensation reaction via addition of
molecular sieves or sodium sulfate, did not result in higher
yields or in an improved reproducibility.
Therefore, a second method (method B, see Scheme 2)
starting from N-xylyl-ortho-bromobenzylamine (6) was devel-
oped. Addition of two equivalents of n-butyllithium to a cold
B
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solution of 6 in diethyl ether resulted in amine deprotonation
and bromine−lithium exchange. In a one-pot procedure, the
dilithiated intermediate 7 was quenched with PhPCl2 and pure
[B]H2 isolated after recrystallization from ethanol. Using this
method, the desired protioligand was obtained as an off-white
powder in reproducible yields of approximately 50% (δ(31P) =
−26.3 ppm), and its molecular structure was ascertained by
single-crystal X-ray diffraction (see Supporting Information).
Due to its robust triphenylphosphine core, protioligand [B]H2
was found to be stable in air for weeks, while oxidative
decomposition was observed for [PhA]H2 within a few hours
after exposure to air.
Synthesis of [PhA]MI2 and [B]MI2 (M = Zr, Hf). With
gram quantities of [PhA]H2 and [B]H2 available, the synthesis
of the desired group 4 diiodo complexes was pursued via the
corresponding dimethylamido complexes. Thus, [PhA]H2 and
[B]H2 were reacted with M(NMe2)4 (M = Zr, Hf), and the
resulting complexes [PhA]M(NMe2)2 ([PhA]-1-M) and [B]M-
(NMe2)2 ([B]-1-M) isolated in both cases (see Scheme 3).
Scheme 3. Synthesis of Complexes [PhA]-1-M, [B]-1-M,
a
[PhA]-2-M, and [B]-2-M (M = Zr, Hf)
Figure 1. ORTEP diagrams of [B]-1-Zr (top) and [B]-1-Hf (bottom).
Hydrogen atoms and cocrystallized solvent molecules are omitted for
clarity; thermal ellipsoids are set at 50% probability. Selected bond
lengths and angles are summarized in Table 1 together with the
corresponding values for [PhA]-1-Zr.
were found in the refined C1-symmetric molecular structures. In
the case of [B]-1-Zr, the main axis through P−Zr−N4 deviates
significantly from 180° (P−Zr−N4 = 150.96(5)°) and allows
for an alternative interpretation of the complex geometry as a
tetrahedral zirconium ion with a loosely bound phosphine. This
is corroborated by a rather long metal phosphorus distance of
2.8976(5) Å, which points to a relatively weak Zr···P
interaction.22 This observation is in line with the phosphine
donor in [B] being less electron donating than the one in
[PhA], which renders the zirconium phosphine interaction in
[B]-1-Zr weaker than in [PhA]-1-Zr. For [B]-1-Hf, the
deviation from the expected trigonal bipyramidal geometry is
by far less pronounced and interpreted as a consequence of
hafnium’s stronger σ-bond to the phosphine anchor (cf. Figure
1).2c
Complexes [PhA]-1-M and [B]-1-M (M = Zr, Hf) were
found to react cleanly with Me3SiI, affording the expected
a
Arabic numbers printed in red are used in the Experimental Section
Table 1. Selected Metrical Parameters and 31P NMR Shifts
(C6D6) of Complexes [PhA]-1-Zr, [B]-1-Zr, and [B]-1-Hf
for NMR signal assignments.
1
Each H and 13C NMR spectrum of these dimethylamido
[
PhA]-1-Zr
[B]-1-Zr
[B]-1-Hf
complexes exhibited only one set of signals for the two ligand
side arms of the respective amidophosphine and two geminally
coupled doublets for the methylene protons indicative of Cs-
symmetric species in solution. However, NMR spectra
measured at −80 °C showed a desymmetrization to C1,
indicative of an antiparallel alignment of both ligand side arms
upon cooling.7 Single crystals of [PhA]-1-Zr (see Supporting
Information for an ORTEP diagram) and [B]-1-Hf (see Figure
1) were subjected to X-ray diffraction, and the expected trigonal
bipyramidal coordination geometries around the central metals
M−P (Å)
M−N (Å)
2.8305(9)
2.1601(11)
2.1442(10)
2.0430(11)
2.0488(13)
163.85(3)
95.03(3)
2.8976(5)
2.1293(15)
2.1502(16)
2.0606(16)
2.0510(16)
150.96(5)
97.34(5)
2.8114(8)
2.1223(15)
2.0739(16)
2.0469(16)
2.0426(16)
169.89(4)
91.33(5)
M−(NMe2) (Å)
P−M−(NMe2) (deg)
N−M−N (deg)
125.31(4)
10.2
125.14(6)
−28.0
113.86(6)
−23.8
δ
31P (ppm)
C
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diiodo complexes [PhA]MI2 ([PhA]-2-M) and [B]MI2 ([B]-2-
M). In contrast to [SiA]MI2 ([SiA]-2-M, M = Zr, Hf), these
complexes were found to be thermally stable at room
temperature and even at +70 °C. That the titanium derivatives
could be prepared seems noteworthy as well, as this was not the
case for [SiA]H27 (see Supporting Information for experimental
procedures and the ORTEP plots of the molecular structures of
[PhA]Ti(NMe)2, [PhA]TiI2, [B]Ti(NMe2)2, and [B]TiI2).23 In
the 31P{1H} NMR spectra of complexes [PhA]-2-M and [B]-2-
M (M = Zr, Hf), the expected singlet resonances were found in
each case. On the NMR time scale, these species were found to
Table 2. Selected Metrical Parameters and 31P NMR Shifts
(C6D6) of Complexes [SiA]-2-Zr, [PhA]-2-Zr, and [B]-2-Zr
[SiA]-2-Zr
[
PhA]-2-Zr
[B]-2-Zr
M−P (Å)
M−N (Å)
2.7875(7)
2.019(2)
2.051(2)
2.8595(3)
2.8356(3)
175.861
2.7671(7)
2.046(2)
2.059(2)
2.8407(3)
2.7765(3)
168.842(15)
94.379(14)
121.06(8)
0.7
2.7646(11)
2.044(2)
2.035(2)
M−I (Å)
2.8350(11)
2.8116(12)
174.443(15)
84.59(3)
P−M−I (deg)
N−M−N (deg)
82.774(15)
109.68(9)
8.5
1
111.32(8)
−10.0
exhibit averaged Cs-symmetries in solution as judged by H
δ
31P (ppm)
NMR spectroscopy. On the basis of single-crystal X-ray
diffraction analysis, the zirconium diiodo derivatives [PhA]-2-
Zr and [B]-2-Zr were found to be C1-symmetric in the solid
state (see Figure 2), which is also the case for [SiA]-2-Zr (see
indicating that the sterically demanding N-trimethylsilyl groups
effectively interfere with this equilibration process.24
Synthesis of Dibenzyl Complexes. In order to exploit
hafnium’s tendency to form stronger metal−carbon σ-bonds,
the synthesis of dialkyl complexes was pursued. Therefore, the
reactions of LiCH2SiMe3 and Bn2MgL2 (L = THF, Et2O)25
with [PhA]-2-M and [B]-2-M were examined. Upon reaction of
[PhA]-2-M with LiCH2SiMe3, the expected alkyls [PhA]-3-M
were isolated for both metals (see Scheme 4, see Supporting
Information for the ORTEP plots of the corresponding
molecular structures), which was not the case for complexes
[SiA]-2-M.7
Disappointingly, only mixtures of products were obtained
upon reaction of [B]-2-M with LiCH2SiMe3. As a systematic
Scheme 4. Synthesis of [PhA]-3-M, [PhA]-4-M, [B]-4-M, and
[B]-5-Zr (M = Zr, Hf) Starting from [PhA]-2-M and [B]-2-M
Figure 2. ORTEP diagrams of [PhA]-2-Zr (top) and [B]-2-Zr
(bottom). Hydrogen atoms and cocrystallized solvent molecules are
omitted for clarity; thermal ellipsoids are set at 50% probability.
Selected bond lengths and angles are summarized in Table 2 together
with the corresponding values for [SiA]-2-Zr.
Supporting Information for an ORTEP plot). For all three
systems, similar slightly distorted trigonal bipyramidal coordi-
nation environments were found in the respective solid-state
structures (see Table 2 for selected metrical parameters). That
averaged Cs-symmetric solution structures were observed for
complexes [PhA]-1-M, [PhA]-2-M, [B]-1-M, and [B]-2M was
interpreted as a consequence of a twist-type rotational
equilibration of both ligand side arms in solution, which agrees
well with our previous study on group 4 complexes bearing the
related propylene-linked ligand [PhP(CH2CH2CH2NPh)2]2−.7
For [SiA]-1-M and [SiA]-2-M, however, C1-symmetries were
observed not only in the solid state but also in solution,
D
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comparison between analogous dialkyl complexes was desired,
the dibenzyl derivatives were targeted, hoping that these species
were accessible for both ligands. Gratifyingly, clean reactions
between Bn2MgL2 and [PhA]-2-Hf (L = THF) and [B]-2-Hf (L
= Et2O) were observed, and the corresponding hafnium
dibenzyl complexes [PhA]-4-Hf and [B]-4-Hf were isolated in
good yields (see Scheme 4). For zirconium, [PhA]ZrBn2
([PhA]-4-Zr) was isolated readily as well, but its [B]ZrBn2
counterpart ([B]-4-Zr) was found to be exceedingly heat and
light sensitive. Nevertheless, an in situ characterization of [B]-4-
Zr by NMR spectroscopy undoubtedly showed that this
product was formed cleanly. For both of the zirconium
complexes, [PhA]-4-Zr and [B]-4-Zr, similar averaged Cs-
symmetric structures were found in solution, which is also the
case for the hafnium derivatives. Although solid samples of [B]-
4-Zr could not be obtained due to decomposition upon solvent
removal, solutions of the four derivatives [NPN]MBn2 (M =
Zr, Hf; [NPN] = [PhA], [B]) were made available, which
brought a comparative analysis within reach. Single crystals of
[PhA]-4-Zr, [PhA]-4-Hf, and [B]-4-Hf were subjected to X-ray
diffraction, and C1-symmetric structures similar to [PhA]-2-Zr
and [B]-2-Zr were found to be present in the solid state (see
Figure 3 and Supporting Information, cf. Table 3). In all three
cases, trigonal bipyramidal coordination polyhedra around the
respective central metals were found with the axial positions in
each case occupied by the phosphine and one of the benzyl
ligands. For [B]-4-Hf, an additional agostic interaction between
the central metal and H7B with d(Hf···H7B) = 2.49(4) Å
seems to be present (see Figure 3),26 although doubts remain
due to the (refined) positional disorder of one benzyl and one
N-xylyl group. In agreement with these molecular structures,
inequivalent benzyl ligands (cis and trans to P) were detected in
the respective proton NMR spectra, which is also the case for
their zirconium counterparts. Given that three steps were
required to prepare each dibenzyl complex starting from the
respective protioligands, alternative synthetic routes employing
ZrBn427 (vide infra) and HfBn428 were pursued and found to be
effective in the case of hafnium (see Scheme 4). Using a simple
protonolysis approach, both hafnium dibenzyl complexes
[PhA]-4-Hf and [B]-4-Hf were obtained from the correspond-
ing protioligands in 78% and 81% yield, respectively. This
procedure was also successful for the N-trimethylsilyl-
substituted protioligand [SiA]H2, which led to the isolation of
[SiA]HfBn2 ([SiA]-4-Hf) in 71% yield (see Scheme 5).
According to NMR and X-ray diffraction analysis, [SiA]-4-Hf
was found to adopt a C1-symmetric structure in solution and in
1
the solid state. Two H NMR signals for two inequivalent
trimethylsilyl groups were detected for [SiA]-4-Hf, and the
complex was judged to be configurationally stable at room
temperature by EXSY NMR spectroscopy. At 80 °C (i.e., under
the conditions of complex formation; cf. Scheme 5) a minor
species (approximately 7%) with δ(31P{1H}) = −4.6 ppm was
detected in addition to [SiA]-4-Hf (δ(31P{1H}) = 8.2 ppm) and
identified as the corresponding Cs-symmetric isomer (an
ORTEP plot of the corresponding molecular structure is
provided in the Supporting Information). Prolonged heating,
however, resulted in decomposition prior to an enrichment of
this Cs-symmetric product. These observations exposed
significant differences between [SiA]-4-Hf and [PhA]-4-Hf
despite their similar metrical parameters in the solid state (cf.
Table 3).
Figure 3. ORTEP diagrams of [PhA]-4-Hf (top), [B]-4-Hf (middle),
and [SiA]-4-Hf (C1-symmetric isomer, bottom). Hydrogen atoms are
omitted for clarity; thermal ellipsoids are set at 50% probability;
disordered Bn and N-Xyl positions in [B]-4-Hf are omitted for clarity.
Selected metrical parameters are summarized in Table 3.
Bn2Mg(L)2 (L = THF, Et2O),25 but was readily prepared via
salt metathesis. After deprotonation of [SiA]H2 with n-BuLi at
−40 °C, the dilithium salt of the ligand was reacted with
Bn2ZrCl2(OEt2),29 affording the desired dibenzyl complex
[SiA]-4-Zr in 41% yield (see Scheme 5). In contrast to [SiA]H2
and [PhA]H2, [B]H2 was found to react cleanly with ZrBn4,
resulting in the formation of a new zirconium complex. In
contrast to the expected dibenzyl species [B]-4-Zr, which
exhibits a single 31P{1H} NMR signal at −15.6 ppm, two broad
and equally intense 31P{1H} NMR resonances at −18.7 and
Interestingly, the zirconium derivative [SiA]ZrBn2 could not
be obtained from [SiA]H2 and ZrBn4 or from [SiA]ZrI2 and
E
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28
Table 3. Selected Metrical Parameters and 31P NMR Shifts
nor via direct protonolysis of HfBn4 with two equivalents of
[B]H2. To confirm the molecular structure of [B]-5-Zr, single
crystals were grown from a concentrated n-pentane/Et2O
solution at −40 °C and subjected to X-ray diffraction analysis
(C6D6) of Complexes [SiA]-4-Hf (C1), [PhA]-4-Hf, and [B]-4-
Hf
a
[SiA]-4-Hf (C1)
[
PhA]-4-Hf
[B]-4-Hf
(see Figure 5). In agreement with the 31P{1H} and H NMR
1
M−P (Å)
M−N (Å)
2.8676(9)
2.058(3)
2.070(3)
2.281(3)
2.264(3)
172.42(9)
88.66(9)
119.01(10)
8.2
2.7858(12)
2.070(4)
2.076(4)
2.276(5)
2.270(5)
171.04(13)
81.76(12)
117.13(14)
4.6
2.8412(13)
2.056(3)
2.031(3)
2.274(4)
2.272(4)
163.07(10)
84.32(11)
112.21(12)
−19.3
M−C (Å)
P−M−C (deg)
N−M−N (deg)
δ
31P (ppm)
a
Metrical parameters for a second fairly similar independent molecule
in the unit cell are provided in the Supporting Information together
with the corresponding values for the Cs-symmetric isomer of [SiA]-4-
Hf.
Scheme 5. Synthesis of [SiA]-4-M (M = Zr, Hf)
Figure 5. ORTEP diagram of [B]-5-Zr. Hydrogen atoms are omitted
for clarity; thermal ellipsoids are set at 50% probability. Selected bond
lengths (Å) and angles (deg): Zr−P1 2.8580(11), Zr−P2 2.9456(11),
Zr−N1 2.120(3), Zr−N2 2.157(3), Zr−N3 2.161(3), Zr−N4
2.139(3), Zr−C7 2.745(4), Zr···H7A 2.39(4), P1−Zr−P2 129.90(3),
P1−Zr−H7A 72.1(10), P2−Zr−H7A 141.9(11), N1−Zr−P1
68.47(9), N1−Zr−N2 95.48(13), N2−Zr−P1 79.32(9), N3−Zr−P2
77.92(9), N4−Zr−P2 77.95(9), N4−Zr−N3 92.54(13), H7A−Zr−C7
20.2(11).
−21.3 ppm were found for this new complex (the 31P{1H}
NMR spectrum recorded at room temperature is shown on the
left-hand side in Figure 4).
data, inequivalent ligands were found upon inspection of the
solid-state molecular structure of [B]-5-Zr. As indicated by the
short Zr···H7A contact (2.39(4) Å) and the narrow Zr−N1−
C7 angle of 98.4(2)°,26 an agostic interaction between the
metal center and one methylene group of one of the ligands
seems to be present. Whether crystal-packing effects or the
metal’s compact coordination environment plays a role in this
The latter product was then isolated and identified as the
homoleptic 2:1 complex [B]2Zr ([B]-5-Zr), which was formed
27
exclusively even when [B]H2 and ZrBn4
(or Zr-
(CH2SiMe3)4)30 were employed in equimolar amounts (half
of the ZrBn4 or Zr(CH2SiMe3)4 precursors remained unreacted
in these cases). Addition of [B]H2 to [B]-4-Zr led to the
isolation of [B]-5-Zr as well (see Scheme 4). For hafnium,
however, the formation of a similar homoleptic 2:1 complex
was neither observed upon reaction of [B]-4-Hf with [B]H2
1
agostic contact cannot be excluded, as broad H NMR signals
at or below room temperature (−60 to 25 °C) interfered with
the NMR signal assignment at these temperatures (vide infra).
Despite the presence of six donors around zirconium, the
Figure 4. 31P{1H} NMR spectra (162 MHz, toluene-d8) of [B]-5-Zr recorded at room temperature (left) and at +100 °C (right).
F
DOI: 10.1021/acs.organomet.6b00384
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Article
t
metal’s coordination polyhedron is derived neither from a
regular octahedral nor from a trigonal prismatic geometry.
Instead, it is best described as a tetrahedral assembly, which is
distorted by two zirconium−phosphine interactions and the
agostic contact. The zirconium−nitrogen bond lengths are
found within the expected range for zirconium amides, but the
Zr−P1 (2.8580(11) Å) and Zr−P2 (2.9456(11) Å) distances
are at the upper end of similar zirconium amidophosphine
complexes, suggesting these interactions to be rather weak.22
At +100 °C only one 31P{1H} NMR signal was detected for
[B]-5-Zr (see Figure 4), and reasonably sharp signals were
observed in the 1H NMR spectrum (see Supporting
Information), which is in line with a highly symmetric species
bearing two equivalent diamidophosphine ligands, assumingly
with no agostic interactions present at this temperature. So far,
similar homoleptic 2:1 complexes bearing [PhA] remained
elusive, although all of the possible routes shown in Scheme 4
have been probed carefully. Therefore, the three-step routes
starting from the diiodo complexes were required for the
preparation of both zirconium dibenzyl complexes [PhA]-4-Zr
and [B]-4-Zr.
Reactivities of [NPN]MBn2 (M = Zr, Hf) toward
Isonitriles. To further elucidate the different stabilities of the
dibenzyl zirconium and hafnium complexes, reactivity studies
seemed to be required and insertion reactions were targeted in
this study. Upon treatment of [PhA]-4-M (M = Zr, Hf) with
2,6-xylylisonitrile, clean insertion reactions31 affording the
bis(η2-iminoacyl) complexes [PhA]-6-M were observed, as
judged by NMR spectroscopy (see Scheme 6).
Both products were isolated without difficulties and found to
be stable at room temperature. Gentle heating led to
decomposition rather than C−C coupling, which was found
to occur cleanly for tropocoronand-,32 guanidinate-,33 amidi-
nate-,34 aryloxide-35 and Cp-coordinated36 bis(η2-iminoacyl)
group 4 complexes. This thermal degradation is even more
pronounced for the corresponding BuNC insertion products,
which were found to be unstable even below room temper-
ature, thus impeding their purification and isolation. In the
proton NMR spectra of both complexes [PhA]-6-M, two sets of
signals were detected for the η2-iminoacyl ligands, indicating
that these groups are situated in cis- and trans-position to the
phosphine. In the case of [B]-4-Hf, a similar insertion of 2,6-
xylylisonitrile into both Hf−C bonds affording [B]-6-Hf was
observed, but only mixtures of products were obtained for [B]-
4-Zr (see Scheme 6). To further elucidate this observations,
single crystals for X-ray diffraction were grown for [PhA]-6-Zr
and [B]-6-Hf by cooling saturated solutions of the complexes
in Et2O to −40 °C (see Figure 6). In both cases, the η2-
iminoacyl ligands were found in the expected positions, i.e., cis
and trans to the phosphine, with the two NC vectors of the
η2-iminoacyl groups aligned nearly collinear (see Figure 6, cf.
Table 4). Interestingly, these NC vectors are pointing in
opposite directions (anti) in the case of [PhA]-6-Zr, but in the
same direction (syn) in the case of [B]-6-Hf, which has been
observed in other bis(η2-iminoacyl) complexes as well.37,33b For
the latter complex, an agostic interaction between H22B and
the central hafnium ion seems to be present, as judged by the
narrow H22A−C22−H22B angle (100.1(17)°).26 The question
why a clean reaction of 2,6-xylylisonitrile with [B]-4-M was
only observed for M = Hf cannot be answered with certainty, as
this observation might not solely depend on the stability of the
anticipated zirconium complex [B]-6-Zr, but also on the
stability of the starting material [B]-4-Zr, whose thermal
decomposition might be accelerated in the presence of isonitrile
ligands. Nevertheless, the finding agrees well with previous
reports on zirconium’s higher reactivity,2c for example in
zirconocen-catalyzed silane dehydrocoupling reactions.38 In the
case of complexes [SiA]-4-M (M = Zr, Hf), a clean conversion
with respect to insertion of 2,6-xylylisonitrile was found for the
hafnium derivative only, while at least four different species
were observed in the corresponding reaction of [SiA]-4-Zr.
Upon addition of two equivalents of 2,6-xylylisonitrile to [SiA]-
4-Hf, a new species ([SiA]-6-Hf) was formed cleanly according
to 31P{1H} NMR spectroscopy. Inspection of the correspond-
Scheme 6. Reactions of [PhA]-4-M, [B]-4-M, and [SiA]-4-M
with Ar−NC (M = Zr, Hf; Ar = 2,6-Me2C6H3)
1
ing H NMR revealed that only half of the isonitrile was
consumed and that one hafnium benzyl moiety was left
unreacted. A comparison of the benzylic methylene resonances
in the starting material (δ(cis-CH2Bn) = 2.18 and 2.25 ppm with
3JH,P = 8.0 and 6.8 Hz, δ(trans-CH2Bn) = 2.58 and 2.62 ppm
with 3JH,P = 2.5 and 2.2 Hz) and the product (δ(CH2Bn) = 2.44
3
and 2.75 ppm, unresolved JH,P) revealed that the trans-
positioned benzyl group remained in place, while the cis-
positioned one underwent insertion.24 To confirm this finding,
the molecular structure of [SiA]-6-Hf was acquired by single-
crystal X-ray diffraction and found to exhibit the expected
stereochemistry (see Figure 6).
Upon heating [SiA]-6-Hf with 2,6-xylylisonitrile, extensive
decomposition was observed instead of a second insertion into
the remaining hafnium benzyl unit. Assuming that the
electronic structures of [PhA]-4-Hf and [SiA]-4-Hf are fairly
similar, the preference for monoinsertion in the case of [SiA]-4-
Hf is thought to be a consequence of the sterically more
demanding N-trimethylsilyl substituents. That the benzyl−
hafnium bond in [SiA]-6-Hf is indeed shielded by both flanking
trimethylsilyl groups is not obvious from the ORTEP plot of
the molecular structure shown in Figure 6, but seen in the
corresponding space-filling representation (see Supporting
Information). Thus, the different insertion chemistry of [SiA]-
G
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Article
Figure 6. ORTEP diagrams of [PhA]-6-Zr (left), [B]-6-Hf (middle), and [SiA]-6-Hf (right). Hydrogen atoms are omitted for clarity; thermal
ellipsoids are set at 50% probability. Carbon atoms of the diamidophosphine ligands (except C22 in the case of [B]-6-Hf) are omitted in the
truncated views depicted in the second row. Selected bond lengths and angles are summarized in Table 4. In addition to the shown molecule of
[SiA]-6-Hf, a second independent molecule with fairly similar metrical parameters is present in the unit cell (for details see Supporting Information).
Table 4. Selected Metrical Parameters and 31P NMR Shifts
between zirconium and hafnium have been found for ligand
[B] (e.g., formation of the 2:1 complex [B]-5-Zr), which might
(C6D6) of Complexes [PhA]-6-Zr, [B]-6-Hf, and [SiA]-6-Hf
in part stem from the ligand’s propensity to support agostic
a
[
PhA]-6-Zr
[B]-6-Hf
[SiA]-6-Hf
interactions with the central metals. While the latter point
certainly requires further clarification, it was clearly shown that
the silyl-free ligand [PhA] is superior to [SiA] and that both
these ligands are distinct from [B], although it is just an
inverted benzylene linker differentiating [PhA] and [SiA] from
[B].
M−P (Å)
M−N (Å)
2.9422(10)
2.193(3)
2.186(3)
2.274(3)
2.212(3)
2.253(4)
2.271(4)
155.98(8)
89.54(8)
122.54(13)
104.00(12)
103.38(11)
1.289(4)
1.274(5)
7.4
2.8184(4)
2.1313(14)
2.1130(14)
2.2302(15)
2.3019(14)
2.2237(18)
2.2548(17)
165.38(4)
97.66(4)
2.8674(7)
2.110(2)
2.078(2)
2.227(2)
M−N(ArNCBn) (Å)
M−C (Å)
b
2.242(3)
c
2.313(3)
CONCLUSIONS
■
P−M−N(ArNCBn) (deg)
P−M−C (deg)
99.21(6)
To this end, the conclusion to be drawn from this study is that
the diamidophosphine-coordinated zirconium complexes pre-
pared herein are less robust (i.e., more reactive) than their
hafnium counterparts, which is in line with the observations
made for zirconocenes.2c Accordingly, the dibenzyl hafnium
complexes [SiA]-4-Hf, [PhA]-4-Hf, and [B]-4-Hf could be
prepared via direct reaction of the respective protioligands with
HfBn4, while decomposition or formation of the homoleptic
species [B]-5-Zr was observed with ZrBn4. In the case of ligand
[B], the dibenzyl zirconium species [B]-4-Zr was found to be
exceedingly sensitive, which disallowed for an isolation of solid
samples. The related dibenzyl zirconium complexes of [PhA]
and [SiA], however, were isolated without difficulties, although
significantly different synthetic routes had to be chosen.
Despite the latter dissimilarity between [PhA] and [SiA], the
b
148.38(5)
82.23(4)
78.72(7)
c
172.37(8)
112.87(9)
1.294(4)
N−M−N (deg)
CN(ArNCBn)
103.94(6)
1.294(2)
1.298(2)
δ
31P (ppm)
−13.7
6.8
a
Metrical parameters for a second fairly similar independent molecule
b
in the unit cell are provided in the Supporting Information. η2-
c
Iminoacyl carbon (C27). Benzylic carbon (C43).
4-Hf and [PhA]-4-Hf seems to originate from the different
spatial demands of both these ligands. However, the most
pronounced and therefore most unpredictable differences
H
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Article
1
compound as a white solid (0.95 g, 1.74 mmol, 80%). H NMR (600
differences between zirconium and hafnium seem to be most
pronounced for ligand [B]. This was supported by probing the
reactivities of the six dibenzyl complexes [PhA]-4-M, [B]-4-M,
and [SiA]-4-M (M = Zr, Hf) with respect to insertion of 2,6-
xylylisonitrile. Stable η2-iminoacyl products were isolated for
both metals in the case of ligand [PhA], but only the hafnium
bis(η2-iminoacyl) complex [B]-6-Hf was obtained for ligand
[B]. For [SiA]-4-Hf, the mono-(η2-iminoacyl) complex [SiA]-6-
Hf was isolated, indicating that the metal−carbon bonds are
less accessible for this sterically more demanding ligand.
Whether the benzylic positions within these complexes, in
particular within the [B]-coordinated derivatives, are prone to
cyclometalations39 and whether such processes induce a more
pronounced discrimination of one metal over the other is
currently being explored in our laboratory.
MHz, THF-d8): δ [ppm] = 8.02−7.47 (m, 4 H, R2NH2Cl), 7.68−7.61
(m, 2 H, o-PPh), 7.41 (t, JH,H = 7.3 Hz, 1 H, p-PPh), 7.29 (t, JH,H
3
3
=
3
6.9 Hz, 2 H, m-PPh), 7.18 (d, JH,H = 8.0 Hz, 2 H, 6-ArH), 7.09 (t,
3JH,H = 7.8 Hz, 4 H, m-NPh), 6.98 (d, JH,H = 7.7 Hz, 6 H, o-NPh),
3
3
3
6.93 (d, JH,H = 7.7 Hz, 2 H, 3-ArH), 6.75 (t, JH,H = 7.4 Hz, 2 H, p-
3
NPh), 6.64 (t, JH,H = 7.4 Hz, 2 H, 4-ArH), 4.31−4.21 (m, 2 H,
PCH2), 4.01−3.91 (m, 2 H, PCH2). 13C{1H} NMR (151 MHz, THF-
3
d8): δ [ppm] = 145.4 (s, ipso-NPh), 143.4 (d, JP,C = 4.3 Hz, 1-ArC),
2
3
134.5 (d, JP,C = 13.8 Hz, o-PPh), 132.7 (s, p-PPh), 132.4 (d, JP,C
7.1 Hz, 3-ArC), 129.6 (s, m-NPh), (s, ipso-PPh), 129.4 (s, m-PPh),
128.5 (s, 5-ArC), 124.9 (s, 2-ArC), 122.2 (s, 4-ArC), 120.6 (s, p-NPh),
=
1
120.3 (s, 6-ArC), 118.4 (s, m-NPh), 29.5 (d, JP,,C = 17.9 Hz, PCH2).
31P{1H} NMR (243 MHz, THF-d8): δ [ppm] = 4.06 (s). HR-MS
(FAB+): observed m/z = 473.2148, calcd m/z for C32H30N2P ([M − 2
Cl − H]+) = 473.2141. To a stirred suspension of the bis-
(hydrochloride) salt (0.95 g, 1.74 mmol) in dichloromethane (30
mL) at 0 °C was added neat NEt3 (1.00 mL, 7.18 mmol, 4.13 equiv
with respect to the bis(hydrochloride) salt) over the course of 15 min.
The resulting reaction mixture was stirred for 15 min at 0 °C and then
allowed to warm to room temperature. The solvent was removed
under reduced pressure, and Et2O (30 mL) was added to the residue.
The precipitate (NEt3HCl) was removed via filtration over Celite, and
the Celite pad was washed carefully with Et2O (3 × 10 mL). The
combined extracts and washings were condensed under reduced
pressure, and the title compound was obtained as a pale yellow,
EXPERIMENTAL SECTION
■
All manipulations were performed under an atmosphere of dry and
oxygen-free argon by means of standard Schlenk or glovebox
techniques. Toluene, THF, pentanes, hexanes, diethyl ether, and
dimethoxyethane (DME) were purified by passing the solvents
through activated alumina columns (MBraun solvent purification
system). Toluene-d8, THF-d8, benzene-d6, and 1,4-dioxane were
refluxed over sodium and purified by distillation. DMSO-d6, CD2Cl2-
d2, Me3SiOSiMe3, NEt3, and dichloromethane were dried over CaH2
and distilled prior to use. NMR spectra were recorded on a Bruker
Avance II 400 MHz or a Bruker Avance III 600 MHz spectrometer at
room temperature unless noted otherwise. 1H and 13C{1H} NMR
spectra were referenced to residual proton signals of the lock solvent.
31P{1H} NMR spectra were referenced to external P(OMe)3 (141.0
ppm with respect to 85% H3PO4 at 0.0 ppm). Microanalyses (C, H,
N) were performed at the Department of Chemistry at the University
of Heidelberg. Solutions of n-butyllithium (2.5 M in hexanes),
solutions of HCl (1.0 M in Et2O), M(NMe2)4 (M = Zr, Hf), Me3SiX
(X = Cl, OTf, I), methyl iodide, phenyl phosphine, NEt3HCl, LiAlH4,
and 2,6-(dimethylphenyl)isonitrile were purchased from commercial
suppliers and used as received. A purchased solution of (trimethylsi-
lylmethyl)lithium (1.0 m solution in pentane) was condensed to half
of its volume, and LiCH2SiMe3 crystallized at −40 °C and was isolated
as a white powder. Commercially available solutions of BnMgCl (1.0
M in Et2O) were used for the preparation of MBn4 (M = Zr, Hf),27,28
Bn2ZrCl2(OEt2),29 and Bn2Mg(L)2 (L = THF, Et2O).25 Compounds
1,18 4,20 5,20 [SiA]H2,7 [SiA]-1-M,7 and [SiA]-2-M (M = Zr, Hf)7 were
synthesized according to the literature. Experimental procedures for
the preparation of compounds 2, 3, and 6 are provided in the
Supporting Information.
1
viscous oil (544 mg, 1.15 mmol, 53% with respect to PhPH2). H
NMR (600 MHz, C6D6): δ [ppm] = 7.32−7.26 (m, 2 H, ArH), 7.24−
4
7.19 (m, 2 H, ArH), 7.13−7.05 (m, 5 H, ArH), 7.01 (td, JH,H = 1.1
Hz, 3JH,H = 8.4 Hz, 3 H, ArH), 6.97−6.90 (m, 3 H, ArH), 6.79 (t, 3JH,H
= 7.5 Hz, 4 H, ArH), 6.75 (d, 3JH,H = 7.6 Hz, 4 H, ArH), 5.46 (d, 3JH,H
= 3.7 Hz, 2 H, NH), 2.97 (s, 4 H, PCH2). 13C{1H} NMR (151 MHz,
C6D6): δ [ppm] = 144.9 (s, ArC), 141.7 (d, JP,C = 3.0 Hz, ArC), 137.3
(d, JP,C = 17.6 Hz, ArC), 133.2 (d, JP,C = 19.1 Hz, ArC), 131.4 (d, JP,C
= 5.9 Hz, ArC), 129.8 (s, ArC), 129.6 (d, JP,C = 2.6 Hz, ArC), 128.8 (d,
JP,C = 7.1 Hz, ArC), 127.5 (d, JP,C = 2.5 Hz, ArC), 123.0 (d, JP,C = 1.8
Hz, ArC), 121.5 (d, JP,C = 1.0 Hz, ArC), 120.4 (s, ArC), 117.6 (s,
ArC), 117.3 (s, ArC), 32.31 (d, JP,,C = 15.1 Hz, PCH2). 31P{1H}
1
NMR (243 MHz, C6D6): δ [ppm] = −24.3 (s). Anal. Calcd for
C32H29N2P: C 81.33 H 6.19, N 5.93. Found: C 81.59, H 6.34, N 6.16.
[B]H2. Method A. To a solution of 5 (7.50 g, 23.6 mmol, 1.00
equiv) in trifluoroethanol (150 mL) was added 3,5-dimethylaniline
(5.90 mL, 5.72 g, 47.2 mmol, 2.00 equiv), and the stirred reaction
mixture was heated to 60 °C for 1 h. Sodium borohydride (2.14 g, 56.6
mmol, 2.40 equiv) was added, and the mixture was stirred for 1 h at
that temperature. After removal of the solvent under reduced pressure,
the residue was dried thoroughly under vacuum, and dichloromethane
(100 mL) was added. After filtration, the solution was condensed to
dryness and the crude product subjected to column chromatography
(petroleum ether/ethyl acetate = 10:1, Rf = 0.38). The title compound
was obtained as a colorless solid in varying yields (1.25−4.38 g, 2.37−
8.29 mmol, 10−35%). 1H NMR (600 MHz, C6D6): δ [ppm] = 7.44−
7.48 (m, 2 H, 3-ArH), 7.32−7.39 (m, 5 Hoverlapping, 4-ArH, PPh-H),
[PhA]H2. Neat phenylphosphine (240 μL, 2.18 mmol, 1.00 equiv)
was added in one portion to a stirred suspension of 3 (1.80 g, 4.89
mmol, 2.24 equiv) in DME (100 mL) at −78 °C. After 5 min, n-BuLi
(2.50 M in hexanes, 4.00 mL, 9.60 mmol, 4.40 equiv) was added
dropwise at this temperature. Stirring was continued for 1 h at −78 °C,
and the reaction flask then placed in an ice bath. After stirring for 30
min at 0 °C, the reaction mixture was allowed to warm to room
temperature and stirred for another 2 h. Subsequently, all volatiles
were removed under vacuum, and the residue was extracted with
toluene (40 mL). Solid HNEt3Cl (1.22 g, 3.60 mmol, 3.50 equiv) was
added to the toluene extract, and the resulting suspension was stirred
for 2 h. The liberated NEt3 was removed in part by concentrating the
reaction mixture to a volume of approximately 30 mL. Lithium iodide
was then precipitated by addition of 1,4-dioxane (5 mL), and the
yellow suspension was filtered over Celite. The Celite pad was washed
with toluene (2 × 5 mL), and the combined filtrate was concentrated
to approximately 5 mL, diluted with Et2O (20 mL), and then cooled to
0 °C. A solution of HCl (2.0 M in Et2O, 5.40 mL, 10.8 mmol, 2.20
equiv) was added dropwise, resulting in the formation of a white
precipitate. Stirring was continued for 30 min at 0 °C. The solids were
collected on a sinter glass frit, washed with Et2O (2 × 10 mL), and
dried under vacuum to afford the bis(hydrochloride) salt of the title
3
7.20−7.26 (m, 4 Hoverlapping, 5-ArH, PPh-H), 6.94 (dd, JH,H = 7.5 Hz,
3JP,H = 4.3 Hz, 2 H, 6-ArH), 6.38 (s, 2 H, p-Xyl), 5.99 (s, 4 H, o-Xyl),
4.53 (dd, 2JH,H = 13.8 Hz, 4JP,H = 4.0 Hz, 2 H, CH2), 4.39 (dd, 2JH,H
=
13.8 Hz, 4JP,H = 5.3 Hz, 2 H, CH2), 3.49 (bs, 2 H, NH), 2.13 (s, 12 H,
Xyl-CH3). 13C{1H} NMR (101 MHz, C6D6): δ [ppm] = 148.3 (s, ipso-
Xyl), 144.3 (d, 2JP,C = 24.5 Hz, 2-ArC), 139.0 (s, m-Xyl), 136.5 (d, JP,C
2
1
= 9.7 Hz, PPh-C), 136.0 (d, JP,C = 14.2 Hz, 6-ArC), 134.6 (d, JP,C
20.2 Hz, 1-ArC), 134.4 (s, 4-ArC), 129.6 (s, 5-ArC), 129.4 (s, PPh-C),
=
129.1−129.2 (overlapping signals, 3-ArC, PPh-C), 128.0 (s, Ph-C),
3
119.9 (s, p- Xyl), 111.2 (s, o-Xyl, PPh−C), 47.4 (d, JP,C = 23.1 Hz,
CH2), 21.6 (s, Xyl-CH3). 31P{1H} NMR (243 MHz, C6D6): δ [ppm]
= −26.3 (s). Anal. Calcd for C36H37N2P: C 81.79, H 7.05, N 5.30.
Found: C 81.79, H 7.21, N 5.06. HR-MS (FAB): m/z = 529.2799,
calcd m/z for C36H38N2P ([M]+) = 529.2773 (Δ = 4.9 ppm).
Method B. A solution of 6 (10.0 g, 34.4 mmol, 0.50 equiv) in dry
diethyl ether (350 mL) was cooled to −78 °C, and n-BuLi (28.0 mL,
2.5 M in hexanes, 70.0 mmol, 2.00 equiv) was added dropwise. The
I
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Article
reaction mixture was briefly warmed to 0 °C and recooled to −78 °C.
A solution of PhPCl2 (2.30 mL, 17.2 mmol, 1.00 equiv) in diethyl
ether (350 mL) was then added over the course of 2 h. The reaction
mixture was allowed to warm to room temperature, and stirring was
continued overnight. The reaction was quenched by addition of
distilled H2O (200 mL), and the phases were separated. The organic
phase was washed with distilled H2O (2 × 100 mL), dried over sodium
sulfate, and concentrated under reduced pressure. The pale yellow
residue was recrystallized from ethanol, and the product obtained as a
colorless solid (4.60 g, 8.69 mmol, 51%). Analytical data were found to
be identical to those obtained for the product prepared via method A.
[PhA]Zr(NMe2)2 ([PhA]-1-Zr). A solution of Zr(NMe2)4 (154 mg,
583 μmol, 1.10 equiv) in toluene (10 mL) was added slowly to a
stirred solution of [PhA]H2 (250 mg, 530 μmol, 1.00 equiv) in toluene
(10 mL). An immediately color change to yellow was observed, and
the solution was stirred 3 h at room temperature. Subsequently, all
volatiles were removed under vacuum, and the residue was washed
with Et2O (2 × 5 mL). The product was obtained as a pale yellow
solid (254 mg, 391 μmol, 67%). 1H NMR (600 MHz, C6D6): δ [ppm]
= 7.36 (d, 3JH,H = 7.3 Hz, 2 H, 4-ArH), 7.26 (t, 3JH,H = 7.7 Hz, 2 H, o-
PPh), 7.14−7.09 (m, 6 Hoverlapping, 5-ArH, m-NPh), 6.97 (ddd, J = 1.4
Hz, J = 5.2 Hz, J = 8.8 Hz, 2 H, m-PPh), 6.95−6.91 (m, 1 H, p-PPh),
6.86−6.83 (m, 2 H, 3-ArH), 6.83−6.80 (m, 2 H, 6-ArH), 6.72 (t, 3JH,H
= 7.2 Hz, 2 H, p-NPh), 6.59 (d, 3JH,H = 7.8 Hz, 4 H, o-NPh), 3.32 (s, 6
H, NMe2), 2.83 (dd, J = 7.1 Hz, J = 13.4 Hz, 2 H, PCH2), 2.74 (s, 6 H,
NMe2), 2.51 (dd, J = 8.7 Hz, J = 13.4 Hz, 2 H, PCH2). 13C{1H} NMR
(151 MHz, C6D6): δ [ppm] = 153.3 (s, ipso-NPh), 144.1 (s, 1-ArC),
136.9 (s, 2-ArC), 133.3 (s, 4-ArC), 132.7 (s, ipso-PPh), 131.4 (d, 3JP,C
1 H, p-PPh), 6.86 (t, J = 7.3 Hz, 2 H, 6-ArH), 6.78 (t, J = 7.5 Hz, 2 H,
5-ArH), 6.61 (s, 4 H, o-Xyl), 6.45 (s, 2 H, p-Xyl), 5.01 (d, J = 15.5 Hz,
2 H, CH2), 4.70 (d, J = 15.5 Hz, 2 H, CH2), 3.18 (s, 6 H, NMe2), 2.97
(s, 6 H, NMe2), 2.25 (s, 12 H, Xyl-CH3). 13C{1H} NMR (151 MHz,
C6D6): δ [ppm] = 153.4 (s, ipso-Xyl), 147.4 (d, J = 18.8 Hz, 1-ArC),
138.0 (s, m-Xyl), 135.6 (d, J = 1.3 Hz, 6-ArC), 134.2 (d, J = 13.8 Hz, 2-
ArC), 133.3 (d, J = 14.3 Hz, PPh-C), 130.6 (d, J = 8.4 Hz, PPh-C),
130.5 (d, J = 15.9 Hz, 3-ArC), 130.0 (d, J = 1.2 Hz, 5-ArC), 129.2 (s,
PPh-C), 128.7 (d, J = 7.5 Hz, 4-ArC), 128.4 (s, PPh-C), 119.9 (s, p-
Xyl), 114.4 (s, o-Xyl), 52.2 (d, J = 11.1 Hz, CH2), 43.7 (s, NMe2), 42.9
(d, J = 1.9 Hz, NMe2), 22.2 (s, Xyl-CH3). 31P{1H} NMR (243 MHz,
C6D6): δ [ppm] = −28.0 (s). Anal. Calcd for C40H47N4PZr: C 68.05,
H 6.71, N 7.94. Found: C 67.77, H 6.70, N 7.55.
[B]Hf(NMe2)2 ([B]-1-Hf). Following the procedure provided for the
zirconium derivative [B]-1-Zr, the title compound was prepared
starting from Hf(NMe2)4 (369 mg, 10.4 mmol, 1.10 equiv) and [B]H2
(500 mg, 9.46 mmol, 1.00 equiv) in toluene (15 mL). The resulting
reaction mixture was heated to 80 °C for 30 min, and the product
isolated as a pale yellow powder (623 mg, 7.85 mmol, 83%). 1H NMR
(600 MHz, C6D6): δ [ppm] = 7.25 (t, J = 5.7 Hz, 2 H, 3-ArH), 7.00−
7.07 (m, 4 Hoverlapping, 4-ArH, o-PPh), 6.97 (t, J = 7.5 Hz, 2 H, m-PPh),
6.91 (t, J = 6.8 Hz, 1 H, p-PPh), 6.85 (t, J = 7.6 Hz, 2 H, 6-ArH), 6.78
(t, J = 7.5 Hz, 2 H, 5-ArH), 6.71 (s, 4 H, o-Xyl), 6.45 (s, 2 H, p-Xyl),
4.95 (d, J = 15.5 Hz, 2 H, CH2), 4.71 (d, J = 15.5 Hz, 2 H, CH2), 3.20
(s, 6 H, NMe2), 3.02 (s, 6 H, NMe2), 2.27 (s, 12 H, Xyl-CH3).
13C{1H} NMR (151 MHz, C6D6): δ [ppm] = 151.1 (s, ipso-Xyl),
145.3 (d, J = 17.8 Hz, 1-ArC), 140.1 (s, m-Xyl), 135.4 (d, J = 1.5 Hz, 6-
ArC), 132.9 (d, J = 13.8 Hz, 2-ArC), 130.2 (d, J = 8.4 Hz, PPh-C),
129.7 (d, J = 1.3 Hz, PPh-C), 129.0 (s, PPh-C), 128.8 (d, J = 14.9 Hz,
3-ArC), 128.3 (s, PPh-C), 128.2 (s, 5-ArC), 127.5 (d, J = 3.7 Hz, 4-
ArC), 119.7 (s, p-Xyl), 114.8 (s, o-Xyl), 50.6 (d, J = 11.8 Hz, CH2),
23.2 (s, NMe2), 21.4 (s, NMe2), 21.8 (s, Xyl-CH3). 31P{1H} NMR
(243 MHz, C6D6): δ [ppm] = −23.8 (s). Anal. Calcd for
C40H47HfN4P: C 60.56, H 5.97, N 7.06. Found: C 60.93, H 6.32, N
6.85.
3
4
= 13.5 Hz, o-PPh), 131.2 (d, JP,C = 4.9 Hz, 6-ArC), 129.8 (d, JP,C
=
0.9 Hz, p-PPh), 129.6−129.5 (overlapping signals, m-NPh, 5-ArC),
3
129.0 (d, JP,C = 7.5 Hz, m-PPh), 126.7 (s, 3-ArC), 117.6 (s, p-NPh),
115.4 (s, m-NPh), 45.1 (d, 3JP,C = 3.9 Hz, NMe2), 43.0 (s, NMe2), 30.6
(s, PCH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] = 10.2 (s).
Anal. Calcd for C36H39N4PZr: C 66.53, H 6.05, N 8.62. Found: C
65.91, H 6.36, N 8.79. Note that low carbon values have been found,
despite numerous attempts using recrystallized and carefully dried,
finely ground samples.
[PhA]ZrI2 ([PhA]-2-Zr). A solution of trimethylsilyl iodide (105 mg,
527 μmol, 2.10 equiv) in toluene (5 mL) was added slowly to a stirred
solution of [PhA]-1-Zr (163 mg, 251 μmol, 1.00 equiv) in toluene (10
mL), and the reaction mixture was stirred for 2 h at room temperature.
Subsequently, all volatiles were removed under vacuum, and the
residue was washed with toluene (2 × 5 mL). The product was
obtained as an orange solid (248 mg, 149 μmol, 73%). 1H NMR (600
MHz, CD2Cl2): δ [ppm] = 7.49−7.43 (m, 3 H, ArH), 7.43−7.38 (m, 4
H, ArH), 7.38−7.33 (m, 2 H, ArH), 7.26−7.21 (m, 4 H, ArH), 7.16−
[PhA]Hf(NMe2)2 ([PhA]-1-Hf). A solution of Hf(NMe2)4 (197 mg,
555 μmol, 1.04 equiv) in toluene (10 mL) was added slowly to a
stirred solution of [PhA]H2 (250 mg, 530 μmol, 1.00 equiv) in toluene
(10 mL). An immediately color change to yellow was observed, and
the solution was stirred 6 h at 80 °C. Subsequently, all volatiles were
removed under vacuum, and the residue was washed with Et2O (2 × 5
mL). The product was obtained as a pale yellow solid (258 mg, 345
1
3
μmol, 63%). H NMR (600 MHz, C6D6): δ [ppm] = 7.41 (d, JH,H
=
7.12 (m, 4 H, m-NPh), 6.94−6.90 (m, 2 H, p-NPh,), 6.83 (dd, JH,H
=
3
5.4 Hz, 2 H, 4-ArH), 7.28 (t, JH,H = 7.6 Hz, 2 H, o-PPh), 7.16−7.12
(m, 6 Hoverlapping, 5-ArH,/m-NPh), 6.99−6.94 (m, 2 H, m-PPh), 6.94−
6.90 (m, 1 H, p-PPh), 6.88−6.85 (m, 2 H, 3-ArH), 6.85−6.82 (m, 2 H,
6-ArH), 6.72 (t, 3JH,H = 7.2 Hz, 2 H, p-NPh), 6.63 (d, 3JH,H = 5.4 Hz, 4
H, o-NPh), 3.39 (s, 6 H, NMe2), 2.87 (dd, J = 7.8 Hz, J = 13.4 Hz, 2
H, PCH2), 2.73 (s, 6 H, NMe2), 2.56 (dd, J = 8.8 Hz, J = 13.5 Hz, 2 H,
PCH2). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] = 153.5 (s, ipso-
NPh), 143.7 (s, 1-ArC), 136.8 (s, 2-ArC), 133.6 (s, 4-ArC), 132.3 (s,
ipso-PPh), 131.4 (d, JP,C = 13.3 Hz, o-PPh), 131.1 (d, JP,C = 4.7 Hz,
6-ArC), 129.9 (s, p-PPh) 129.7−129.6 (overlapping signals, 5-ArC, m-
NPh), 129.1 (d, 3JP,C = 7.6 Hz,, m-PPh), 126.7 (s, 3-ArC), 117.6 (s, p-
NPh), 115.7 (s, o-NPh), 44.9 (s, NMe2), 42.7 (s, NMe2), 30.4 (s,
PCH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] = 16.0 (s). Anal.
Calcd for C36H39N4PHf: C 58.65, H 5.33, N 7.60. Found: C 58.66, H
5.36, N 7.64.
[B]Zr(NMe2)2 ([B]-1-Zr). A solution of Zr(NMe2)4 (278 mg, 10.4
mmol, 1.10 equiv) in toluene (5 mL) was added to a stirred solution of
[B]H2 (500 mg, 9.46 mmol, 1.00 equiv) in toluene (10 mL), and the
reaction mixture was heated to 110 °C for 2 h. After cooling to room
temperature, all volatiles were removed under reduced pressure and
the residue was washed with n-pentane (2 × 2 mL). After drying under
vacuum, the product was obtained as a pale yellow powder (528 mg,
7.47 mmol, 79%). 1H NMR (600 MHz, C6D6): δ [ppm] = 7.24 (t, J =
6.2 Hz, 2 H, 3-ArH), 7.09 (t, J = 7.4 Hz, 2 H, o-PPh), 7.03 (t, J = 8.4
Hz, 2 H, 4-ArH), 6.99 (t, J = 7.5 Hz, 2 H, m-PPh), 6.91 (t, J = 7.6 Hz,
0.9 Hz, JH,H = 8.6 Hz, 4 H, o-NPh), 3.22 (dd, J = 9.1 Hz, J = 13.9 Hz, 2
H, PCH2), 3.09 (dd, J = 10.3 Hz, J = 13.9 Hz, PCH2, 2 H). 13C{1H}
NMR (151 MHz, CD2Cl2): δ [ppm] = 150.9 (s, ArC), 144.8 (s, ArC),
136.9 (s, ArC), 134.5 (d, JP,C = 3.0 Hz, ArC), 132.0 (d, JP,C = 9.6 Hz,
ArC), 131.6−131.4 (m, ArC), 131.0 (d, JP,C = 2.8 Hz, ArC), 129.7 (s,
ArC), 129.6 (d, JP,C = 1.6 Hz, ArC), 129.4 (d, JP,C = 8.7 Hz, m-NPh),
129.3 (s, ArC), 122.3 (s, p-NPh), 118.5 (s, m-NPh), 117.3 (s, ArC),
29.4 (d, J = 12.2 Hz, PCH2). 31P{1H} NMR (243 MHz, CD2Cl2): δ
[ppm] = 1.1 (s). Anal. Calcd for C32H27I2N2PZr: C 47.13, H 3.34, N
3.43. Found: C 47.35, H 3.34, N 3.54.
2
4
[PhA]HfI2 ([PhA]-2-Hf). A solution of trimethylsilyl iodide (91.0 mg,
456 μmol, 2.10 equiv) in toluene (5 mL) was added slowly to a stirred
solution of [PhA]1-Hf (160 mg, 217 μmol, 1.00 equiv) in toluene (10
mL), and the reaction mixture was stirred for 2 h at room temperature.
Following the workup procedure provided for the zirconium
derivative, the title compound was obtained as a yellow solid (248
mg, 149 μmol, 73%). 1H NMR (600 MHz, CD2Cl2): δ [ppm] = 7.48−
3
7.39 (m, 7 H, ArH), 7.32−7.32 (m, 2 H, ArH), 7.25 (dd, JH,H = 7.4
Hz, 3JH,H = 14.8 Hz, 4 H, ArH), 7.12 (t, 3JH,H = 7.9 Hz, 4 H, m-NPh),
3
3
6.85 (t, JH,H = 7.3 Hz, 2 H, p-NPh), 6.81 (t, JH,H = 6.6 Hz, 4 H, o-
NPh), 3.32 (dd, J = 9.4 Hz, J = 13.9 Hz, 2 H, PCH2), 3.20−3.14 (m, 2
H, PCH2). 13C{1H} NMR (151 MHz, CD2Cl2): δ [ppm] = 151.0 (s,
ArC), 144.8 (s, ArC), 134.5 (s, ArC), 133.5 (d, JP,C = 19.2 Hz, ArC),
132.0 (d, JP,C = 9.6 Hz, ArC), 131.5 (d, JP,C = 5.4 Hz, ArC), 131.0 (s,
ArC), 129.7 (s, ArC), 129.5 (d, JP,C = 3.4 Hz, ArC), 129.4 (d, JP,C = 8.8
J
DOI: 10.1021/acs.organomet.6b00384
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Hz, ArC), 129.3 (s, m-NPh), 122.3 (s, p-NPh), 118.5 (s, m-NPh),
CH2SiMe3), 2.6 (s, CH2SiMe3), 1.4 (s, SiMe3), 0.0 (s, SiMe3). 31P{1H}
NMR (243 MHz, C6D6): δ [ppm] = 1.0 (s). Anal. Calcd for
C40H49N2PSi2Zr: C 65.26, H 6.71, N 3.81. Found: C 65.63, H 6.60, N
4.06.
1
117.3 (s, ArC), 29.4 (d, JP,C = 12.3 Hz, PCH2). 31P{1H} NMR (243
MHz, CD2Cl2): δ [ppm] = 9.1 (s). Anal. Calcd for C32H27HfI2N2P: C
42.57, 3.01, N 3.10. Found: C 42.92, H 3.29, N 3.14.
[PhA]Hf(CH2SiMe3)2 ([PhA]-3-Hf). A precooled solution (−40 °C)
of LiCH2TMS (14.8 mg, 157 μmol, 2.22 equiv) in toluene (10 mL)
was slowly added to cold suspension (−40 °C) of [PhA]-2-Hf (64.0
mg, 70.9 μmol, 1.00 equiv) in toluene (10 mL). The reaction mixture
was allowed to warm to room temperature, and stirring was continued
for 2 h. Following the workup procedure provided for the zirconium
derivative, the title compound was obtained as a pale yellow solid
[B]ZrI2 ([B]-2-Zr). A solution of trimethylsilyl iodide (0.16 mL, 240
mg, 1.20 mmol, 2.10 equiv) in toluene (5 mL) was added dropwise to
a stirred solution of [B]-1-Zr (400 mg, 0.57 mmol, 1.00 equiv) in
toluene (15 mL), and the resulting reaction mixture was stirred for 30
min at room temperature. All volatiles were removed under vacuum,
and the residue was washed with a mixture (50 vol % each) of diethyl
ether and pentane (2 × 3 mL). After drying under vacuum, the title
compound was obtained as a yellow powder (402 mg, 0.46 mmol,
81%). 1H NMR (600 MHz, C6D6): δ [ppm] = 7.34−7.38 (m, 2 H, 3-
ArH), 6.88−6.96 (m, 7 Hoverlapping, 4-ArH, 6-ArH, PPh-H), 6.85 (t, J =
7.5 Hz, 2 H, 5-ArH), 6.80 (s, 4 H, o-Xyl), 6.36 (t, J = 7.5 Hz, 2 H, PPh-
H), 6.48 (s, 2 H, p-Xyl), 5.39 (d, J = 16.8 Hz, 2 H, CH2), 4.37 (d, J =
16.8 Hz, 2 H, CH2), 2.08 (s, 12 H, Xyl-CH3). 13C{1H} NMR (151
MHz, C6D6): δ [ppm] = 145.0 (s, ipso-Xyl), 145.1 (d, J = 16.5 Hz, 1-
ArC), 140.0 (s, m-Xyl), 135.2 (d, J = 10.7 Hz, 3-ArC), 134.0 (d, J =
10.7 Hz, PPh-C), 131.0 (s, 6-ArC), 130.3 (s, PPh-C), 129.8 (d, J = 8.9
Hz, 2-ArC), 128.7 (d, J = 8.7 Hz, PPh-C), 118.6 (s, 5-ArC), 128.3 (s,
4-ArC), 128.0 (d, J = 5.0 Hz, PPh-C), 126.2 (s, p-Xyl), 118.2 (s, o-
Xyl), 50.8 (d, J = 9.0 Hz, CH2), 21.6 (s, Xyl-CH3). 31P{1H} NMR
(243 MHz, C6D6): δ [ppm] = −10.0 (s). Anal. Calcd for
C36H35I2N2PZr: C 49.60, H 4.05, N 3.21. Found: C 49.60, H 4.34,
N 3.40.
1
(44.7 mg, 54.3 μmol, 77%). H NMR (600 MHz, C6D6): δ [ppm] =
3
7.38 (d, JH,H = 7.6 Hz, 2 H, ArH), 7.09−7.00 (m, 8 H, ArH), 6.96−
6.94 (m, 3 H, ArH), 6.84 (t, 3JH,H = 7.4 Hz, 2 H, ArH), 6.81−6.76 (m,
6 H, ArH), 6.71 (t, 3JH,H = 7.3 Hz, 2 H, ArH), 2.81 (dd, J = 7.0 Hz, J =
13.2 Hz, 2 H, PCH2), 2.59 (dd, J = 8.2 Hz, J = 13.3 Hz, 2 H, PCH2),
0.99 (d, 3JP,H = 2.4 Hz, 2 H, CH2SiMe3), 0.73 (d, 3JP,H = 7.4 Hz, 2 H,
CH2SiMe3), 0.44 (s, 9 H, SiMe3), −0.02 (s, 9 H, SiMe3). 13C{1H}
NMR (151 MHz, C6D6): δ [ppm] = 152.6 (s, ArC), 142.7 (s, ArC),
136.0 (s, ArC), 133.6 (d, JP,C = 2.1 Hz, ArC), 133.1 (s, ArC), 131.5 (d,
JP,C = 4.9 Hz, ArC), 131.1 (d, JP,C = 11.4 Hz, ArC), 129.9 (d, JP,C = 1.1
Hz, ArC), 129.8 (d, JP,C = 2.6 Hz, ArC), 129.3 (s, ArC), 128.4 (s,
ArC), 127.1 (d, JP,C = 1.4 Hz, ArC), 119.6 (s, ArC), 116.5 (s, ArC),
29.7 (s, PCH2), 22.7 (s, CH2SiMe3), 14.3 (s, CH2SiMe3), 4.2 (s,
SiMe3), 2.9 (s, SiMe3). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] =
5.5 (s). Anal. Calcd for C40H49HfN2PSi2: C 58.34, H 6.00, N 3.40.
Found: C 58.91, H 6.05, N 3.45. Note that low carbon values have
been found, despite numerous attempts using recrystallized and
carefully dried, finely ground samples.
[B]HfI2 ([B]-2-Hf). A solution of trimethylsilyl iodide (0.15 mL, 222
mg, 1.06 mmol, 2.10 equiv) in toluene (1 mL) was added dropwise to
a stirred solution of [B]-1-Hf (400 mg, 0.50 mmol, 1.00 equiv) in
toluene (15 mL), and the resulting pale yellow solution was heated at
60 °C for 45 min. The reaction mixture was allowed to cool to room
temperature and condensed to dryness. Following the workup
procedure provided for the zirconium derivative, the title compound
[PhA]ZrBn2 ([PhA]-4-Zr). A precooled solution (−40 °C) of
Bn2Mg(THF)2 (34.3 mg, 98.5 μmol, 1.10 equiv) in toluene (10
mL) was slowly added to a precooled suspension (−40 °C) of [PhA]-
2-Zr (73 mg, 89.5 μmol, 1.00 equiv) in toluene (10 mL). The
vigorously stirred reaction mixture was allowed to warm to room
temperature, and stirring then continued for 2 h. Subsequently, a few
drops of 1,4-dioxane were added to precipitate the magnesium salt
biproducts. The resulting suspension was filtered using a syringe filter,
and the solvent was removed under vacuum. The residue was washed
with pentane (2 × 5 mL) to afford the title compound as a pale yellow
1
was obtained as a yellow solid (422 g, 0.44 mmol, 88%). H NMR
(600 MHz, C6D6): δ [ppm] = 7.15−7.20 (m, 2 H, 3-ArH), 7.07 (t, J =
6.4 Hz, 2 H, 4-ArH), 6.99 (s, 4 H, o-Xyl), 6.88−6.93 (m, 5 Hoverlapping
,
6-ArH, PPh-H), 6.85 (t, J = 7.5 Hz, 2 H, 5-ArH), 6.67 (t, J = 7.5 Hz, 2
H, PPh-H), 6.48 (s, 2 H, p-Xyl), 5.37 (d, J = 16.8 Hz, 2 H, CH2), 4.43
(d, J = 16.8 Hz, 2 H, CH2), 2.11 (s, 12 H, Xyl-CH3). 13C{1H} NMR
(151 MHz, C6D6): δ [ppm] = 148.3 (s, ipso-Xyl), 146.0 (d, J = 16.1
Hz, 1-ArC), 139.0 (s, m-Xyl), 135.7 (s, 4-ArC), 133.9 (d, J = 10.7 Hz,
3-ArC), 131.8 (d, J = 21.6 Hz, PPh-C), 131.0 (d, J = 1.8 Hz, 5-ArC),
130.3 (d, J = 2.1 Hz, 6-ArC), 130.0 (d, J = 9.0 Hz, 2-ArC), 129.3 (s,
PPh-C), 128.7 (d, J = 9.0 Hz, PPh-C), 128.6 (s, PPh-C), 125.4 (s, p-
Xyl), 118.5 (s, o-Xyl), 49.4 (d, J = 8.7 Hz, CH2), 21.6 (s, Xyl-CH3).
31P{1H} NMR (243 MHz, C6D6): δ [ppm] = −6.0 (s). Anal. Calcd for
C36H35HfI2N2P: C 45.09, H 3.68, N 2.92. Found: C 44.55, H 3.69, N
3.07. Note that low carbon values have been found, despite numerous
attempts using recrystallized and carefully dried, finely ground samples.
[PhA]Zr(CH2SiMe3)2 ([PhA]-3-Zr). A precooled solution (−40 °C)
of LiCH2TMS (23.0 mg, 244 μmol, 2.22 equiv) in toluene (10 mL)
was slowly added to a cold suspension (−40 °C) of [PhA]-2-Zr (90.0
mg, 110 μmol, 1.00 equiv) in toluene (20 mL). The reaction mixture
was allowed to warm to room temperature and stirred for 2 h. A few
drops of 1,4-dioxane were added to precipitate MgI2 in the form of its
1,4-dioxane adduct. The resulting suspension was filtered using a
micropore syringe filter, and the solvent was removed under vacuum.
The residue was washed with pentane (2 × 5 mL) and then dried
under vacuum to afford the product as a pale yellow solid (51.8 mg,
1
solid (55.3 mg, 74.3 μmol, 83%). H NMR (600 MHz, C6D6): δ
[ppm] = 7.25 (d, 3JH,H = 7.4 Hz, 2 H, ArH), 7.16−7.15 (m, 2 H, ArH),
3
7.07 (d, JH,H = 7.2 Hz, 2 H, ArH), 7.03−6.94 (m, 9 H, ArH), 6.94−
6.86 (m, 4 H, ArH), 6.81 (t, 3JH,H = 7.4 Hz, 4 H, ArH), 6.77−6.70 (m,
5 H, ArH), 6.58 (d, 3JH,H = 7.4 Hz, 2 H, ArH), 6.52 (d, 3JH,H = 7.7 Hz,
4 H, ArH), 3.02 (s, 2 H, CH2Ar), 2.54−2.49 (m, 2 H, PCH2), 2.58−
2.47 (m, 4 H, PCH2/CH2Ar). 13C{1H} NMR (151 MHz, C6D6): δ
[ppm] = 151.3 (s, ArC), 147.4 (s, ArC), 147.3 (d, JP,C = 3.2 Hz, ArC),
141.4 (d, JP,C = 5.7 Hz, ArC), 136.3 (s, ArC), 133.4 (d, JP,C = 2.4 Hz,
ArC), 132.4 (d, JP,C = 4.2 Hz, ArC), 131.2 (d, JP,C = 5.1 Hz, ArC),
130.9 (s, ArC), 130.8 (s, ArC), 130.0 (d, JP,C = 2.6 Hz, ArC), 129.9 (s,
ArC), 129.6 (s, ArC), 129.3 (s, ArC), 129.1 (s, ArC), 129.0 (d, JP,C
=
1.9 Hz, ArC), 128.6 (s, ArC), 127.6 (s, ArC), 127.3 (s, ArC), 126.5 (s,
ArC), 122.0 (s, ArC), 121.5 (s, ArC), 120.4 (s, ArC), 116.9 (s, ArC),
80.9 (s, CH2Ar), 73.4 (d, 2JP,C = 25.5 Hz, CH2Ar), 30.1 (d, 1JP,C = 3.5
Hz, PCH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] = 1.4 (s).
Anal. Calcd for C46H41N2PZr: C 74.26, H 5.55, N 3.77. Found: C
73.42, H 5.93, N 3.23. Note that low carbon values have been found,
despite numerous attempts using recrystallized and carefully dried,
finely ground samples.
1
[PhA]HfBn2 ([PhA]-4-Hf). Method A. A precooled solution (−40
°C) of Bn2Mg(THF)2 (28.9 mg, 82.8 μmol, 1.10 equiv) in toluene (10
mL) was slowly added to a precooled suspension (−40 °C) of [PhA]-
2-Hf (68 mg, 75.3 μmol, 1.00 equiv) in toluene (10 mL). The reaction
mixture was allowed to warm to room temperature and stirred for 2 h.
Following the workup procedure provided for the zirconium
derivative, the title compound was obtained as a pale yellow solid
(51.9 mg, 62.5 μmol, 83%). Analytical data were found to be identical
to those obtained for the product prepared via method B.
70.4 μmol, 64%). H NMR (600 MHz, C6D6): δ [ppm] = 7.36 (d,
3JH,H = 7.1 Hz, 2 H, ArH), 7.08−6.99 (m, 8 H, ArH), 6.98−6.92 (m, 3
H, ArH), 6.80−6.70 (m, 10 H, ArH), 2.77 (dd, JH,H = 6.6 Hz, JH,H
=
13.2 Hz, 2 H, PCH2), 2.53 (dd, JH,H = 8.1 Hz, JH,H = 13.3 Hz, 2 H,
3
3
PCH2), 1.44 (d, JH,H = 2.5 Hz, 2 H, CH2SiMe3), 1.35 (d, JH,H = 7.1
Hz, 2 H, CH2SiMe3), 0.45 (s, 9 H, SiMe3), −0.01 (s, 9 H, SiMe3).
13C{1H} NMR (151 MHz, C6D6): δ [ppm] = 152.4 (s, ArC), 142.7 (s,
ArC), 136.0 (s, ArC), 133.2 (s, ArC), 131.4 (d, J = 4.9 Hz, ArC), 131.1
(d, J,P,C = 11.8 Hz, ArC), 130.7 (s, ArC), 129.7 (d, J = 2.6 Hz, ArC),
129.4 (s, ArC), 129.3 (s, ArC), 128.9 (d, J,P,C = 7.0 Hz, ArC), 125.7 (s,
ArC), 120.0 (s, ArC), 116.2 (s, ArC), 29.8 (s, PCH2), 3.9 (s,
Method B. A solution of HfBn4 (302 mg, 556 μmol, 1.05 equiv) in
toluene (2 mL) was added to a stirred solution of [PhA]H2 (250 mg,
K
DOI: 10.1021/acs.organomet.6b00384
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
530 μmol, 1.00 equiv) in toluene (5 mL), and the resulting pale yellow
solution was heated to 70 °C overnight. The reaction mixture was
allowed to cool to room temperature and condensed to dryness under
reduced pressure. The residue was washed with n-pentane (2 × 2 mL)
and dried under vacuum to afford the title compound as a pale yellow
solid (340 mg, 406 μmol, 78%). 1H NMR (600 MHz, C6D6): δ [ppm]
7.5 Hz, 2 H, Bn-H/PPh-H), 6.57 (s, 4 H, o-Xyl), 6.47 (s, 2 H, p-Xyl),
4.93 (d, J = 15.8 Hz, 2 H, CH2), 4.22 (d, J = 15.7 Hz, 2 H, CH2), 2.76
(d, J = 8.2 Hz, 2 H, CH2-Ph), 2.39 (d, J = 2.2 Hz, 2 H, CH2-Ph), 2.16
(s, 12 H, Xyl-CH3). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] =
146.1 (s, ipso-Xyl), 143.5 (d, J = 18.3 Hz, 1-ArC), 135.4 (s, m-Xyl),
132.7 (d, J = 12.7 Hz, 3-ArC), 130.0 (d, J = 1.3 Hz, PPh-C), 129.8 (d, J
= 8.4 Hz, 2-ArC), 129.3 (s, Bn-C/PPh-C), 129.0 (s, Bn-C/PPh-C),
128.7 (d, J = 7.5 Hz, 6-ArC), 128.2 (s, Bn-C/ArC), 128.0 (s, Bn-C/
ArC), 127.8 (s, 4-ArC), 127.6 (d, J = 3.9 Hz, 5-ArC), 127.2 (s, Bn-C/
PPh-C), 127.1 (s, Bn-C/PPh-C), 126.8 (s, Bn-C/PPh-C), 122.9 (s, p-
Xyl), 121.9 (s, Bn-C), 120.7 (s, Bn-C), 117.3 (s, o-Xyl), 80.2 (d, J =
22.2 Hz, CH2-Ph), 73.3 (d, J = 7.4 Hz, CH2-Ph), 49.5 (d, J = 12.5 Hz,
CH2), 21.1 (s, Xyl-CH3). 31P{1H} NMR (243 MHz, C6D6): δ [ppm]
= −19.3 (s). Anal. Calcd for C50H49HfN2P: C 67.67, H 5.57, N 3.16.
Found: C 67.44, H 5.34, N 3.33.
3
= 7.25 (d, JH,H = 7.1 Hz, 2 H, ArH), 7.21−7.17 (m, 3 H, ArH), 7.11
3
(d, JH,H = 7.6 Hz, 3 H, ArH), 7.02−6.93 (m, 9 H, ArH), 6.92−6.85
(m, 4 H, ArH), 6.82 (t, 3JH,H = 7.5 Hz, 2 H, ArH), 6.78−6.70 (m, 4 H,
ArH), 6.67 (t, 3JH,H = 7.4 Hz, 1 H, ArH), 6.58 (d, 3JH,H = 7.8 Hz, 4 H,
ArH), 6.52 (d, 3JH,H = 7.2 Hz, 2 H, ArH), 2.80−2.74 (m, 4 Hoverlapping
,
PCH2, CH2Ar), 2.57 (dd, J = 8.7 Hz, J = 13.7 Hz, 2 H, PCH2), 2.24 (d,
J = 6.2 Hz, 2 H, CH2Ar). 13C{1H} NMR (151 MHz, C6D6): δ [ppm]
= 151.3 (s, ArC), 148.4 (s, ArC), 146.9 (s, ArC), 144.7 (s, ArC), 142.3
(s, ArC), 140.9 (s, ArC), 136.4 (s, ArC), 134.0 (s, ArC), 131.1 (d, JP,C
= 5.2 Hz, ArC), 130.9 (s, ArC), 130.8 (s, ArC), 130.2 (d, JP,C = 2.3 Hz,
[B]2Zr ([B]-5-Zr). A solution of ZrBn4 (43.1 mg, 0.09 mmol, 0.50
equiv) in toluene (2 mL) was added to a stirred solution of [B]H2
(100 mg, 0.19 mmol, 1.00 equiv) in toluene (5 mL), and the resulting
yellow solution was heated to 80 °C for 30 min. The reaction mixture
was allowed to cool to room temperature, and all volatiles were
removed under reduced pressure. The crude product was washed with
n-pentane (2 × 3 mL) and subsequently dried under vacuum to afford
ArC), 129.9 (s, ArC), 129.5 (s, ArC), 129.3 (s, ArC), 129.1 (d, JP,C
=
7.5 Hz, ArC), 128.4 (s, ArC) 127.5 (d, JP,C = 1.2 Hz, ArC), 127.5 (s,
ArC), 127.1 (s, ArC), 122.3 (s, ArC), 121.6 (s, ArC), 120.2 (s, ArC),
117.0 (s, ArC), 89.3 (d, 2JP,C = 7.8 Hz, CH2Ar), 80.5 (s, CH2Ar), 29.9
(s PCH2). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] = 4.6 (s). Anal.
Calcd for C46H41HfN2P: C 66.46, H 4.97, N 3.37. Found: C 66.17, H
5.03, N 3.16.
1
the product as a pale yellow powder (98.5 mg, 0.14 mmol, 72%). H
[B]ZrBn2 ([B]-4-Zr). To a stirred solution of [B]-2-Zr (200 mg,
0.25 mmol, 1.00 equiv) in toluene (10 mL) was added Bn2Mg(OEt2)2
(98 mg, 0.28 mmol, 1.10 equiv), and the resulting suspension was
stirred for 15 min at room temperature. After filtration, the title
compound was detected in the filtrate and used immediately for
further reactions. All attempts to isolate the pure compound were
hampered due to decomposition upon removal of the solvent. NMR
data were recorded after reaction of 20 mg of [B]-2-Zr with 9.8 mg of
Bn2Mg(OEt2)2 in deuterated benzene (0.7 mL). The resulting
suspension in C6D6 was filtered into an NMR tube using a micropore
syringe filter, and the spectra were acquired immediately after
NMR (600 MHz, tol-d8, 383 K): δ [ppm] = 7.36−728 (m, 3 H, ArH),
6.20−7.12 (m, 3 H, ArH), 7.10−6.94 (m, >14 H due to overlapping
residual proton signals of tol-d8, ArH), 6.91−6.87 (m, 2 H, ArH), 6.86
(s, 4 H, o-Xyl), 6.85−6.70 (m, 4 H, ArH), 6.33 and 6.32 (two
overlapping s, 6 H, o-Xyl and p-Xyl), 6.24 (s, 2 H, p-Xyl), 5.41 (d, J =
15.4 Hz, 2 H, CH2), 5.19 (d, J = 15.4 Hz, 2 H, CH2), 5.73 (d, J = 15.0
Hz, 2 H, CH2), 4.58 (d, J = 14.4 Hz, 2 H, CH2), 1.93 (s, 24 H, Xyl-
CH3). 13C{1H} NMR (151 MHz, tol-d8, 383 K): δ [ppm] = 144.1 (s,
ArC), 144.0 (s, ArC), 147.3 (d, J = 19.0 Hz, ArC), 146.8 (d, J = 20.9
Hz, ArC), 138.1 (d, J = 12.0 Hz, ArC), 136.9 (s, ArC), 135.5 (s, ArC),
135.1 (s, ArC), 133.4 (d, J = 12.8 Hz, ArC), 129.8 (s, ArC), 129.8 (s,
ArC), 129.7 (s, ArC), 129.6 (s, ArC), 129.4 (s, ArC), 128.6 (s, ArC),
128.6 (s, ArC), 127.1 (d, J = 3.2 Hz, ArC), 125.8 (s, ArC), 121.9 (s,
ArC), 120.9 (s, ArC), 120.0 (s, ArC), 117.5 (s, ArC), 21.8 (s, Ar-CH3),
21.4 (s, Ar-CH3). 31P{1H} NMR (243 MHz, tol-d8, 383 K): δ [ppm] =
−23.4 (s). Anal. Calcd for C72H70N4P2Zr: C 75.56, H 6.16, N 4.90.
Found: C 75.46, H 6.24, N 4.80.
1
filtration. H NMR (600 MHz, C6D6): δ [ppm] = 7.21 (t, J = 7.7
Hz, 2 H, 3-ArH), 6.96−7.09 (m, 5 Hoverlapping, Bn-H, PPh-H), 6.89−
6.95 (m, 8 Hoverlapping, Bn-H, PPh-H), 6.84 (t, J = 7.2 Hz, 2 H, 5-ArH),
6.76 (t, J = 7.5 Hz, 4 Hoverlapping, Bn-H, PPh-H), 6.63 (t, J = 7.5 Hz, 2
H, Bn-H), 6.41 (s, 2 H, p-Xyl), 6.27 (s, 4 H, o-Xyl), 5.08 (d, J = 15.7
Hz, 2 H, CH2), 4.09 (d, J = 15.7 Hz, 2 H, CH2), 3.08 (d, J = 9.0 Hz, 2
H, Zr-CH2), 2.56 (s, 2 H, Zr-CH2), 2.12 (s, 12 H, Xyl-CH3). 13C{1H}
NMR (151 MHz, C6D6): δ [ppm] = 141.7 (s, ipso-Xyl), 137.1 (d, J =
16.9 Hz, 1-ArC), 135.0 (d, J = 1.6 Hz, PPh-C), 134.3 (s, m-Xyl), 132.2
(d, J = 10.3 Hz, 3-ArC), 131.8 (s, Bn-C/PPh-C), 129.2 (s, 6-ArC),
128.8 (d, J = 2.9 Hz, PPh-C), 128.1 (s, Bn-C/PPh-C), 127.8 (d, J = 3.3
Hz, PPh-C), 127.4 (s, Bn-C/PPh-C), 126.6 (s, Bn-C/PPh-C), 125.5
(s, Bn-C/PPh-C), 124.5 (s, Bn-C/PPh-C), 122.1 (s, p-Xyl), 121.0 (s,
Bn-C), 119.3 (s, Bn-C), 115.0 (s, o-Xyl), 68.5 (d, J = 20.3 Hz, Zr-
CH2), 62.0 (d, J = 4.8 Hz, Zr-CH2), 49.2 (sbr, CH2), 20.6 (s, Xyl-CH3).
31P{1H} NMR (243 MHz, C6D6): δ [ppm] = −15.6 (s).
[B]HfBn2 ([B]-4-Hf). Method A. To a stirred solution of [B]-2-Hf
(200 mg, 0.30 mmol, 1.00 equiv) in toluene (10 mL) was added
Bn2Mg(OEt2)2 (118 mg, 0.33 mmol, 1.10 equiv) in one portion, and
the resulting suspension was stirred for 15 min at room temperature.
The reaction mixture was filtered and condensed to dryness under
reduced pressure. The residue was washed with n-pentane (2 × 2 mL)
and dried under vacuum to afford the product as a white powder (200
mg, 0.23 mmol, 75%). Analytical data were found to be identical to
those obtained for the product prepared via method B.
[SiA]ZrBn2 ([SiA]-4-Zr). A solution of [SiA]H2 (583 mg, 1.25 mmol,
1.00 equiv) in pentane (40 mL) was cooled to −40 °C, and n-BuLi
(1.05 mL, 2.5 M solution in hexane, 2.63 mmol, 2.10 equiv) was added
dropwise within 10 min. The pale yellow reaction mixture was stirred
at −40 °C for 2 h, and dioxane (859 μL, 10.0 mmol, 8.00 equiv) was
added, resulting in the formation of a yellowish precipitate. After
filtration at 0 °C, the solids collected on the frit were washed with n-
pentane (30 mL) and dried under vacuum. The dilithium salt
[SiA]Li2(diox)2 was obtained as a pale beige solid (459 mg, 813 μmol)
and used directly for the preparation of the title compound. A solution
of Bn2ZrCl2(OEt2) (340 mg, 813 μmol, 1.00 equiv) in toluene (20
mL) was slowly added to a solution of [SiA]Li2(diox)2 (459 mg, 813
μmol, 1.00 equiv) in toluene at −40 °C. The resulting reaction mixture
was allowed to warm to room temperature and stirred for 2 h. The
yellow suspension was filtered through Celite, and the filtrate
condensed to dryness. The residue was washed with hexamethyldisi-
loxane and recrystallized from n-pentane (10 mL) at −40 °C to afford
the product as a pale yellow solid (245 mg, 333 μmol, 41%). 1H NMR
(600 MHz, C6D6): δ [ppm] = 7.35−7.29 (m, 6 H, ArH), 7.14−7.11
(m, 1 H, ArH), 7.10−7.07 (m, 1 H, ArH), 7.06−7.03 (m, 2 H, ArH),
7.03−7.00 (m, 1 H, ArH), 6.98 (d, JH,H = 7.9 Hz, 2 H, ArH), 6.93−
6.87 (m, 4 H, ArH), 6.87−6.83 (m, 2 H, ArH), 6.76 (t, JH,H = 7.4 Hz, 1
H, ArH), 6.66 (t, JH,H = 7.3 Hz, 1 H, ArH), 6.37 (d, JH,H = 7.1 Hz, 2 H,
Method B. A solution of HfBn4 (205 mg, 0.38 mmol, 1.00 equiv) in
toluene (2 mL) was added to a stirred solution of [B]H2 (200 mg,
0.38 mmol, 1.00 equiv) in toluene (5 mL), and the resulting pale
yellow solution was heated to 80 °C for 30 min. The reaction mixture
was allowed to cool to room temperature and condensed to dryness
under reduced pressure. The residue was washed with n-pentane (2 ×
2 mL) and dried under vacuum to afford the title compound as a white
2
2
ArH), 3.16 (dd, JH,H/3JP,H = 2.9 Hz, JH,H/3JP,H = 13.6 Hz, 1 H,
PhCH2), 2.91 (dd, JH,H/3JP,H = 2.4 Hz, JH,H/3JP,H = 11.2 Hz, 1 H,
2
2
PhCH2), 2.83 (dd, JH,H/3JP,H = 2.5 Hz, JH,H/3JP,H = 11.2 Hz, 1 H,
2
2
1
2
2
powder (272 mg, 0.31 mmol, 81%). H NMR (600 MHz, C6D6): δ
PhCH2), 2.79 (dd, JH,H/3JP,H = 3.9 Hz, JH,H/3JP,H = 13.2 Hz, 1 H,
[ppm] = 7.19 (t, J = 7.5 Hz, 4 Hoverlapping, 3-ArH, PPh-H), 6.92−7.08
(m, 11 Hoverlapping, 4-ArH, 6-ArH, Bn-H, PPh-H), 6.90 (t, J = 7.6 Hz, 4
Hoverlapping, Bn-H, PPh-H), 6.86 (t, J = 7.3 Hz, 2 H, 5-ArH), 6.67 (t, J =
PCH2), 2.65−2.59 (m, 2 Hoverlapping, PCH2, PhCH2), 2.57 (dd, 2JH,H/P,H
2
2
= 8.3 Hz, JH,H/P,H = 10.5 Hz, 1 H, PCH2) 2.50 (dd, JH,H/P,H = 10.8
Hz, 2JH,H/P,H = 13.2 Hz, 1 H, PCH2), 0.28 (s, 9 H, SiMe3), −0.14 (s, 9
L
DOI: 10.1021/acs.organomet.6b00384
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1
H, SiMe3). H{31P} NMR (600 MHz, C6D6, selected peaks only): δ
3.84 (s, 2 H, CH2Ph), 3.70 (s, 2 H, CH2Ph), 2.95 (sbr, 2 H, PCH2),
2.67−2.50 (m, 2 H, PCH2), 2.01 (s, 6 H, CH3-Xyl), 1.04 (sbr, 6 H,
CH3-Xyl). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] = 155.3 (s,
ArC), 149.0 (s, ArC), 145.3 (s, ArC), 137.3 (s, ArC), 136.6 (s, ArC),
136.2 (s, ArC), 134.3 (s, ArC), 132.6 (d, JC,P = 3.4 Hz, ArC), 131.0 (s,
ArC), 130.9 (s, ArC), 130.8 (s, ArC), 130.4 (s, ArC), 130.2 (s, ArC),
129.8 (s, ArC), 129.3 (s, ArC), 129.2 (s, ArC), 129.1 (s, ArC), 128.7
(s, ArC), 128.6 (s, ArC), 128.6 (s, ArC), 128.4 (s, ArC), 128.4 (s,
ArC), 128.2 (s, ArC), 127.7 (s, ArC), 126.6 (s, ArC), 125.7 (s, ArC),
125.1 (s, ArC), 124.7 (s, ArC), 117.6 (s, ArC), 117.3 (s, ArC), 46.6 (s,
CH2Ph), 45.4 (s, CH2Ph), 34.4 (s, BnCN), 22.7 (s, BnCN), 19.5
(s, CH3-Xyl), 19.4 (s, CH3-Xyl), 14.3 (s, PCH2). 31P{1H} NMR (162
MHz, C6D6): δ [ppm] = 7.4 (s). Anal. Calcd for C64H61N4PZr: C
76.23, H 6.10 N 5.56. Found: C 75.68, H 6.26, N 5.55. Note that low
carbon values have been found, despite numerous attempts using
recrystallized and carefully dried, finely ground samples.
[ppm] = 3.16 (d, 2JH,H = 13.6 Hz, 1 H, PhCH2), 2.91 (d, 2JH,H = 11.2
2
Hz, 1 H, PhCH2), 2.83 (d, JH,H = 11.2 Hz, 1 H, PhCH2), 2.79 (d,
2JH,H = 13.2 Hz, 1 H, PCH2), 2.65−2.59 (m, 2 Hoverlapping, PCH2,
2
2
PhCH2), 2.57 (d, JH,H = 11.5 Hz, 2 H, PCH2), 2.50 (d, JH,H = 13.3
Hz, 1 H, PCH2). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] = 150.2
(d, JC,P = 0.7 Hz, ArC), 148.6 (d, JC,P = 3.0 Hz, ArC), 146.8 (d, JC,P
=
2.7 Hz, ArC), 145.9 (d, JC,P = 9.6 Hz, ArC), 134.7 (d, JC,P = 1.8 Hz,
ArC), 133.4 (d, JC,P = 2.4 Hz, ArC), 132.8 (d, JC,P = 2.9 Hz, ArC),
131.7 (d, JC,P = 4.6 Hz, ArC), 131.1 (d, JC,P = 1.1 Hz, ArC), 131.1 (s,
ArC), 131.0 (s, ArC), 130.8 (d, JC,P = 1.8 Hz, ArC), 129.9 (d, JC,P = 5.3
Hz, ArC), 129.9 (d, JC,P = 1.3 Hz, ArC), 129.2 (d, JC,P = 7.0 Hz, ArC),
129.0 (d, JC,P = 3.1 Hz, ArC), 128.81 (s, ArC), 128.5 (d, JC,P = 2.0 Hz,
ArC), 126.7 (s, ArC), 126.4 (s, ArC), 124.6 (d, JC,P = 1.9 Hz, ArC),
124.2 (s, ArC), 121.6 (s, ArC), 120.9 (s, ArC), 77.9 (d, 2JC,P = 4.5 Hz,
2
2
PCH2), 70.9 (d, JC,P = 28.7 Hz, PCH2), 35.1 (d, JC,P = 2.8 Hz,
[PhA]Hf(C(NXyl)Bn)2 ([PhA]-6-Hf). This compound was pre-
pared in analogy to the zirconium derivative. After reaction of 2,6-
(dimethylphenyl)isonitrile (33.5 mg, 255 μmol, 2.10 equiv) with
[PhA]-4-Hf (100 mg, 122 μmol, 1.00 equiv) in toluene, the title
compound was obtained as a pale yellow solid (82.0 mg, 74.4 μmol,
2
PhCH2), 27.7 (d, JC,P = 4.9 Hz, PhCH2), 2.1 (s, SiMe3), 1.6 (s,
SiMe3). 31P{1H} NMR (243 MHz, C6D6): δ [ppm] = 4.3 (s). Anal.
Calcd for C40H49N2PSi2Zr: C 65.26, H 6.71, N 3.81. Found: C 65.20
H 6.73 N 3.56.
[SiA]HfBn2 ([SiA]-4-Hf). A solution of Hf(Bn)4 (586 mg, 1.08
mmol, 1.00 equiv) in toluene (10 mL) was added to a stirred solution
of [SiA]H2 (500 mg, 1.08 mmol, 1.00 equiv) in toluene (20 mL) at
room temperature. The resulting pale yellow solution was heated to 80
°C for 48 h and then allowed to cool to room temperature. All
volatiles were removed under reduced pressure, and the residue was
washed with hexamethyldisiloxane (2 × 5 mL). After drying under
vacuum and recrystallization from n-pentane (10 mL) at −40 °C the
title compound was obtained as a pale yellow solid (632 mg, 767 μmol,
71%). 1H NMR (600 MHz, C6D6): δ [ppm] = 7.35 (t, 3JH,H = 7.6 Hz,
2 H, ArH), 7.30 (dd, JH,H = 7.2 Hz, JH,H = 14.4 Hz, 4 H, ArH), 7.11 (t,
1
61%). H NMR (400 MHz, C6D6): δ [ppm] = 7.32−7.26 (m, 2 H,
ArH), 7.10−7.01 (m, 8 H, ArH), 7.00−6.85 (m, 18 H, ArH), 6.82 (d,
3JH,H = 9.7 Hz, 5 H, ArH), 6.77 (dd, JH,H = 14.1 Hz, JH,H = 6.6 Hz, 2 H,
ArH), 6.63 (t, 3JH,H = 7.0 Hz, 2 H, ArH), 6.57 (d, 3JH,H = 7.4 Hz, 2 H,
ArH), 3.95 (s, 2 H, CH2Ph), 3.78 (s, 2 H, CH2Ph), 3.04 (sbr, 2 H,
PCH2), 2.67 (sbr, 2 H, PCH2), 2.02 (s, 6 H, CH3-Xyl), 1.04 (s, 6 H,
CH3-Xyl). 13C{1H} NMR (151 MHz, C6D6): δ [ppm] = 155.4 (s,
ArC), 148.6 (s, ArC), 144.9 (s, ArC), 137.5 (s, ArC), 136.8 (d, JC,P
=
1.6 Hz, ArC), 136.4 (s, ArC), 136.3 (s, ArC), 134.4 (s, ArC), 132.8 (s,
ArC), 130.9 (s, ArC), 130.8 (s, ArC), 130.8 (s, ArC), 130.3 (s, ArC),
130.1 (s, ArC), 129.8 (s, ArC), 129.7 (s, ArC), 129.1 (s, ArC), 128.6
(s, ArC), 128.5 (s, ArC), 128.5 (s, ArC), 128.5 (s, ArC), 127.7 (s,
ArC), 127.6 (s, ArC), 126.6 (s, ArC), 126.5 (s, ArC), 125.7 (s, ArC),
125.2 (s, ArC), 124.7 (s, ArC), 118.2 (s, ArC), 117.4 (s, ArC), 46.8 (s,
CH2Ph), 45.8 (s, CH2Ph), 34.4 (s, BnCN), 22.7 (s, BnCN), 19.4
(s, CH3-Xyl), 19.4 (s, CH3-Xyl), 14.3 (s, PCH2). 31P{1H} NMR (162
MHz, C6D6): δ [ppm] = 8.2 (s). Anal. Calcd for C64H61HfN4P: C
70.16, H 5.16, N 5.11. Found: C 69.19 H 5.53, N 5.06. Note that low
carbon values have been found, despite numerous attempts using
recrystallized and carefully dried, finely ground samples.
3JH,H = 7.4 Hz, 1 H, ArH), 7.06−6.99 (m, 3 H, ArH), 6.97 (d, 3JH,H
=
7.4 Hz, 2 H, ArH), 6.93−6.89 (m, 4 H, ArH), 6.87 (t, 3JH,H = 7.7 Hz, 2
H, ArH), 6.76 (t, 3JH,H = 7.4 Hz, 1 H, ArH), 6.60 (dd, JH,H = 13.9 Hz,
JH,H = 21.2 Hz, 1 H, ArH), 6.32 (d, JH,H = 7.5 Hz, 2 H, ArH), 3.25 (dd,
2JH,H/P,H = 3.5 Hz, 2JH,H/P,H = 13.6 Hz, 1 H, PCH2), 2.88 (dd, 2JH,H/P,H
= 4.0 Hz, 2JH,H/P,H = 13.2 Hz, 1 H, PCH2), 2.69−2.64 (m, 1 H, PCH2),
2.64−2.52 (m, 3 Hoverlapping, PCH2, PhCH2), 2.25 (dd, 2JH,H/3JP,H = 6.8
Hz, 2JH,H/3JP,H = 11.6 Hz, 1 H, PhCH2), 2.18 (dd, 2JH,H/3JP,H = 8.0 Hz,
2JH,H/3JP,H = 11.6 Hz, 1 H, PhCH2), 0.26 (s, 9 H, SiMe3), −0.13 (s, 9
1
H, SiMe3). H{31P} NMR (600 MHz, C6D6, selected peaks only): δ
[B]Hf(C(NXyl)Bn)2 ([B]-6-Hf).
A solution of 2,6-
2
2
[ppm] = 3.25 (d, JH,H = 13.6 Hz, 1 H, PCH2), 2.88 (d, JH,H = 13.2
(dimethylphenyl)isonitrile (70.4 mg, 536 μmol, 2.00 equiv) in toluene
(5 mL) was added to a stirred solution of [B]-4-Hf (238 mg, 268
μmol, 1.00 equiv) in toluene (5 mL) at room temperature. The
resulting reaction mixture was stirred for 2 h, and all volatiles were
removed under reduced pressure subsequently. The solid brown
residue was washed with n-pentane (2 mL) and dried under vacuum to
afford the title compound as a beige powder (213 mg, 185 μmol,
Hz, 1 H, PCH2), 2.66 (d, 2JH,H = 13.7 Hz, 1 H, PCH2), 2.64−2.52 (m,
2
3 Hoverlapping, PCH2, PhCH2), 2.25 (d, JH,H = 11.7 Hz, 1 H, PhCH2),
2.18 (d, JH,H = 11.7 Hz, 1 H, PhCH2). 13C{1H} NMR (151 MHz,
2
C6D6): δ [ppm] = 149.9 (s, ArC), 148.6 (d, JC,P = 3.4 Hz, ArC), 146.2
(d, JC,P = 2.7 Hz, ArC), 145.3 (d, JC,P = 9.7 Hz, ArC), 134.5 (s, ArC),
133.3 (d, JC,P = 3.8 Hz, ArC), 133.2 (d, JC,P = 2.8 Hz, ArC), 131.6 (d,
JC,P = 4.7 Hz, ArC), 131.5 (d, JC,P = 1.7 Hz, ArC), 131.4 (d, JC,P = 1.6
Hz, ArC), 131.1 (s, ArC), 131.0 (s, ArC), 123.0 (d, JC,P = 5.3 Hz,
ArC), 129.8 (d, JC,P = 1.2 Hz, ArC), 129.2 (d, JC,P = 7.1 Hz, ArC),
128.8 (d, JC,P = 3.2 Hz, ArC), 128.6 (s, ArC), 128.5 (d, JC,P = 2.0 Hz,
ArC), 127.3 (s, ArC), 126.9 (s, ArC), 124.4 (d, JC,P = 1.9 Hz, ArC),
124.2 (s, ArC), 121.8 (s, ArC), 121.4 (s, ArC), 85.2 (d, 2JC,P = 8.0 Hz,
69%). 1H NMR (600 MHz, C6D6): δ [ppm] = 7.29 (d, 3JH,H = 6.9 Hz,
3
2 H, 3-ArH), 7.22−7.18 (m, 4 H, 5-ArH and 6-ArH), 7.10 (d, JH,H
=
=
7.2 Hz, 2 H, ArH), 7.03 (d, 3JH,H = 7.3 Hz, 4 H, ArH), 6.99 (t, 3JH,H
7.2 Hz, 4 H, 4-ArH overlapping with ArH), 6.93 (dd, JH,H = 9.1 Hz,
JH,H = 5.7 Hz, 4 H, ArH), 6.86−6.83 (m, 3 H, ArH), 6.75 (dd, JH,H
=
7.0 Hz, JH,H = 4.8 Hz, 4 H, ArH), 6.70 (d, JH,H = 7.5 Hz, 2 H, ArH),
2
1
6.67 (s, 4 H, o-Xyl), 6.27 (s, 2 H, p-Xyl), 5.43 (d, 2JH,H = 15.5 Hz, 2 H,
PhCH2), 79.2 (d, JC,P = 28.5 Hz, PhCH2), 35.1 (d, JC,P = 4.4 Hz,
PCH2), 27.5 (d, 1JC,P = 6.4 Hz, PhCH2), 2.3 (s, SiMe3), 1.6 (s, SiMe3).
31P{1H} NMR (243 MHz, C6D6): δ [ppm] = 8.2 (s). Anal. Calcd for
C40H49HfN2PSi2: C 58.34, H 6.00, N 3.40. Found: C 58.30, H 5.93, N
3.44.
2
CH2), 4.51 (d, JH,H = 13.1 Hz, 2 H, CH2), 3.68 (s, 2 H, BnCN),
3.50 (s, 2 H, BnCN), 2.09 (s, 12 H, m-Xyl-CH3), 1.71 (s, 6 H, H3C-
XylNC), 1.66 (s, 6 H, H3C-XylNC). 13C{1H} NMR (151 MHz,
3
C6D6): δ [ppm] = 156.8 (sbr, XylCN) 148.2 (d, JC,P = 22.1 Hz,
[
PhA]Zr(C(NXyl)Bn)2 ([PhA]-6-Zr). A solution of 2,6-
ipso-Xyl), 148.0 (s, XylCN), 145.8 (s, XylCN), 138.6 (s, ArC),
138.4 (s, ArC), 136.9 (s, XylC), 135.5 (d, JC,P = 8.2 Hz, ArC), 133.2
(d, JC,P = 12.0 Hz, ArC), 130.5 (d, JC,P = 22.0 Hz, ArC), 130.2 (s,
ArC), 130.0 (s, ArC), 129.9 (s, 4-ArC), 129.7 (s, 3-ArC), 129.2 (d, JC,P
= 7.7 Hz, ArC), 128.8 (s, 5-ArC), 128.7 (s, ArC), 128.6 (s, ArC), 128.5
(d, JC,P = 5.3 Hz, ArC), 128.1−127.9 (signals overlapping with residual
proton signals of benzene-d6, ArC, XylCN), 127.2 (d, JC,P = 3.9 Hz,
XylCN), 126.4 (d, JC,P = 21.8 Hz, ArC), 125.0 (d, JC,P = 1.9 Hz, o-
Xyl), 119.9 (s, p-Xyl), 47.4 (d, 3JC,P = 23.6 Hz, CH2), 47.0 (s, PhCH2),
45.3 (s, PhCH2), 21.8 (s, m-Xyl-CH3), 19.4 (s, H3C-XylCN), 18.7
(dimethylphenyl)isonitrile (37.0 mg, 282 μmol, 2.10 equiv) in toluene
(5 mL) was added slowly to a stirred solution of [PhA]-4-Zr (100 mg,
134 μmol, 1.00 equiv) in toluene (10 mL), and the reaction mixture
was stirred for 20 min at room temperature. Subsequently, all volatiles
were removed under vacuum, and the residue was washed with
pentane (2 × 5 mL). The product was obtained as a yellow solid (85.0
1
mg, 84.3 μmol, 63%). H NMR (600 MHz, C6D6): δ [ppm] = 7.35−
7.28 (m, 3 H, ArH), 7.07−6.86 (m, 23 H, ArH), 6.84−6.76 (m, 9 H,
3
ArH), 6.68−6.61 (m, 2 H, ArH), 6.58 (d, JH,H = 6.1 Hz, 2 H, ArH),
M
DOI: 10.1021/acs.organomet.6b00384
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(s, H3C-XylCN). 31P{1H} NMR (243 MHz, C6D6): [ppm] = −13.7
(s). Anal. Calcd for C68H67N4PHf: C 71.04; H 5.87; N 4.87. Found: C
70.96, H 5.96, N 4.60.
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=
0.8 Hz, ArC), 150.1 (d, JC,P = 10.4 Hz, ArC), 149.2 (d, JC,P = 3.1 Hz,
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ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00384.
Additional ORTEP diagrams, selected NMR spectra and
details of the structure determinations for [B]H2, [PhA]-
1-Ti, [PhA]-1-Zr, [B]-1-Ti, [B]-1-Zr, [B]-1Hf, [PhA]-2-
Ti, [PhA]-2-Zr, [SiA]-2-Zr, [B]-2-Ti, [B]-2-Zr, [B]-2-Hf,
[PhA]-3-Zr, [PhA]-3-Hf, [PhA]-4-Zr, [PhA]-4-Hf, [SiA]-4-
Hf (C1), [SiA]-4-Hf (CS), [B]-4-Hf, [B]-5-Zr, [PhA]-6-
Zr, [SiA]-6-Hf, and [B]-6-Hf (PDF)
Crystallographic data (CIF)
AUTHOR INFORMATION
Corresponding Author
*E-mail: joachim.ballmann@uni-heidelberg.de. Tel: (+49)
6221-54-8596.
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Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
■
The authors thank the Fonds der Chemischen Industrie (FCI,
Li-187/02) and the Deutsche Forschungsgemeinschaft (DFG,
BA 4859/1-1) for funding of this work. We thank Prof. Dr. L.
H. Gade for generous support, fruitful discussions, and
continued interest in our work.
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