Migratory insertion reactions in asymmetrical guanidinate-supported zirconium complexes

Article abstract of DOI:10.1021/om300942p

The new diguanidinate-supported dibenzylzirconium complexes [Zr{κ²N,N'-(N-i-Pr)(NAr)CNH(i-Pr)}₂(CH ₂Ph)₂] (Ar = 4-t-BuC₆H₄ (1), 4-BrC₆H₄ (2)) and [Zr{κ²N,N'

Full text of DOI:10.1021/om300942p

Article
pubs.acs.org/Organometallics
Migratory Insertion Reactions in Asymmetrical Guanidinate-
Supported Zirconium Complexes
Rafael Fernandez-Galan,* Antonio Antinolo,* Fernando Carrillo-Hermosilla, Isabel Lopez-Solera,
́
́
́
̃
Antonio Otero, Amparo Serrano-Laguna, and Elena Villasenor
̃
́
́
́
Departamento de Quımica Inorganica, Organica y Bioquımica, Facultad de Ciencias y Tecnologías Quımicas, Universidad de
́
́
Castilla-La Mancha, Campus Universitario de Ciudad Real, 13071-Ciudad Real, Spain
S
* Supporting Information
ABSTRACT: The new diguanidinate-supported dibenzylzirconium com-
plexes [Zr{κ2N,N′-(N-i-Pr)(NAr)CNH(i-Pr)}2(CH2Ph)2] (Ar = 4-t-
BuC6H4 (1), 4-BrC6H4 (2)) and [Zr{κ2N,N′-(NEt)(N-t-Bu)-
CNMe2}2(CH2Ph)2] (3) have been prepared. Complexes 1 and 2 were
synthesized by protonolysis of [Zr(CH2Ph)4] with the guanidine
derivatives and complex 3 by treating [Zr{κ2N,N′-(NEt)(N-t-Bu)-
CNMe2}2Cl2] (4) with MgCl(CH2Ph). The treatment of 1−3 with 2,6-
dimethylphenyl isocyanide (XyNC) results in migratory insertion and
formation of the terminal imido species [Zr{κ2N,N′-(N-i-Pr)(N(Ar))-
CNH(i-Pr)}2{N(2,6-Me2C6H3)}] (Ar = 4-t-BuC6H4 (7), 4-BrC6H4 (8))
with 1 and 2, respectively, whereas the analogous reaction with 3 leads to
the enediamido complex [Zr{κ2N,N′-(NEt)(N-tBu)CNMe2)}2{N(2,6-
Me2C6H3)(CH2Ph)CC(CH2Ph)N(2,6-Me2C6H3)}] (9). All the inter-
mediate iminoacyl complexes have been characterized, and the molecular
structures of 2, 4, and 9 have been determined by single-crystal X-ray diffraction.
on the guanidinate ligand concerned and the reaction
conditions.
INTRODUCTION
■
Monoanionic chelating guanidinate anions are often used as
ancillary ligands, due to their ability to stabilize non-
cyclopentadienyl coordination and organometallic compounds
of early and late transition metals.1 Furthermore, the steric and
electronic features of these ligands, as well as their coordination
to the metal center, can be modified by varying the substituents
on the nitrogen atoms (Scheme 1).
Guanidines have been synthesized using a variety of
methods, although the catalytic hydroamination of carbodii-
mides tends to be the most common method due to its 100%
atom economy.2 Indeed, several examples of this type of
reaction have been developed over the past few years,3 and we
have recently reported the synthesis of aromatic guanidine
derivatives with ZnEt2 as a catalytic precursor.4
To the best of our knowledge, the majority of group 4 metal
diguanidinate complexes reported to date have the same
substituents on the N-donor atoms bonded to the metal center
and therefore coordinate symmetrically.5 The only non-
symmetric guanidinate complexes described to date are the
zirconium and hafnium complexes [M{PhNC(R)NSiMe3}3Cl]
(R = dimethylamido, 1-piperidino).6
As a continuation of our research into group 4 and 5
complexes with guanidinate ligands,7 herein we report the
synthesis and characterization of new asymmetric guaninidi-
nate-supported zirconium complexes and migratory insertion
reactions of isocyanide into the resulting M−C bonds to give
terminal imido, iminoacyl, or enediamido complexes depending
RESULTS AND DISCUSSION
■
We have recently prepared the aromatic guanidine derivatives
(HN-i-Pr)2CNAr (Ar = 4-t-BuC6H4, 4-BrC6H4) in good
yields by a catalytic process involving ZnEt2 as a catalytic
precursor for the addition of aromatic amines to carbodii-
mides.4,8
Although guanidinate-supported complexes are traditionally
synthesized by treatment of metal dialkylamide complexes
[M(NR2)n] with the corresponding guanidines,9 the insertion
of carbodiimide derivatives into a metal−amido5e,10 or metal−
imido bond,11 or the metathesis reaction of halide metal
complexes with lithium guanidinate derivatives,5a,12 a proto-
nolysis reaction between a guanidine compound and an alkyl
metal complex is a clean and easy method to obtain the target
complexes.5b,d,13,14 In addition, to the best of our knowledge, all
the dialkyl guanidinate supported zirconium complexes
reported to date involve symmetrical coordination of the
chelating guanidinate ligands.5a−e
The reaction of Zr(CH2Ph)4 with 2 equiv of the
corresponding guanidine derivatives in toluene at room
temperature leads to the dibenzyl complexes [Zr{κ2N,N′-(N-
i-Pr)(NAr)CNH(i-Pr)}2(CH2Ph)2] (Ar = 4-t-BuC6H4 (1), 4-
Received: October 8, 2012
Published: November 29, 2012
© 2012 American Chemical Society
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Scheme 1. Resonance Structures for Monoanionic Guanidinate Ligands
BrC6H4 (2)), which contain asymmetrically coordinated
guanidinate ligands, in high yields (see Scheme 2). These
complexes are stable for several days in solution under an inert
atmosphere at room temperature.
activation parameters of the exchange have been calculated by
an Eyring plot giving similar values for the methyl group, ΔH⧧
= 1.54 kcal mol−1 and ΔS⧧ = −65.36 eu, and for the benzyl
groups, ΔH⧧ = 1.67 kcal mol−1 and ΔS⧧ = −68.81 eu. This
fluxional process has also been observed in hexacoordinated
complexes with amidinate or β-diketinimate ligands; moreover,
the small differences between the ΔH⧧ and the negative ΔS⧧
values can be explained by a Bailar twist mechanism.17
Scheme 2. Synthesis of Complexes 1 and 2
The room-temperature 13C{1H} NMR spectra of 1 and 2
contain signals consistent with the proposed structures,
including a signal at ca. 164 ppm corresponding to the central
CN3 carbon of the guanidinate ligands and a resonance at ca.
75.1 ppm for the two benzylic carbon atoms (CH2). The 1JC−H
value of the −CH2 groups (ca. 123.0 Hz) in the room-
temperature 13C NMR spectra indicates that the benzylic
groups do not exhibit η2 hapticity in solution.14c
The formation of complexes 1 and 2 gives rise to the
possibility of different isomers depending on the coordination
mode of the guanidinate ligands and the cis or trans
coordination of L ligands to the Zr center in a pseudooctahe-
dral geometry; however, the spectroscopic data of 1 and 2 show
the existence of only one of these isomers. In this sense, three
isomers with L ligands in cis positions are possible (Figure 1).
The new benzyl guanidinate complexes 1 and 2 were isolated
as yellow crystalline solids and characterized by 1H and
1
13C{1H} NMR spectroscopy. The room-temperature H NMR
spectra for both complexes are similar, exhibiting signals for
only one compound. The following common characteristics
were found: (i) two groups of signals corresponding to two
nonequivalent isopropyl substituents, thus indicating an
asymmetrical coordination of the guanidinate ligands to the
metal center, (ii) a doublet assigned to the proton of the
disubstitued amine group HN-i-Pr, and (iii) a broad signal for
the benzylic protons (see the Experimental Section). These
features suggest a fluxional behavior in solution in which the
methyl protons of the iPr groups and the benzylic protons
exchange on the NMR time scale, whereas the HN(i-Pr)
moiety does not.
1
A variable-temperature H NMR experiment (toluene-d8)
with complex 1 revealed the presence of four doublet signals for
the isopropyl methyl groups at −25 °C (ΔG⧧ = 13.23 kcal/
c
mol at a coalescence temperature of 5 °C)15 and two doublets
for the diastereotopic CH2Ph protons of the benzyl ligands
Figure 1. Possible conformations for the asymmetric bis(guanidinate)-
supported zirconium complexes with the L ligands in cis positions.
(ΔG⧧ = 11.06 kcal/mol at a coalescence temperature of −5
c
°C). Similar results have been reported for the symmetric
guanidinate-supported complex [Zr{κ2N,N′-(N-i-
Pr)2CNMe2}2(CH2Ph)2].5e The rate constants of this inter-
conversion of 1 at various temperatures were calculated from eq
1 (where Δν and Δνο are frequency differences (Hz) between
The isomers II and III should be heavily disfavored due to
steric effects as in the trans isomers, while the isomer I, which
contains the two aryl amide groups in an apical position, is the
most favored.
These spectroscopic data were supported by X-ray diffraction
studies. Suitable crystals of complex 2 were grown from toluene
solution at −30 °C. The molecular structure and atomic
numbering scheme of 2 are shown in Figure 2. Selected bond
lengths and angles for 2 are given in Table 1.
2
k = π 2(ν0 − v2)
(1)
exchange-broadened sites at temperature T and between the
two sites at the slow exchange limit, respectively).16 The
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coordination mode and the two benzyl groups completing the
coordination sphere.
The N1−C1, N2−C1, N4−C8, and N5−C8 bond lengths
(ca. 1.33(1) Å) are intermediate between a single and double
bond and are similar to the N3−C1 and N6−C8 bond lengths
(ca. 1.35(1) Å), thus indicating charge delocalization via the
guanidinate atoms and the π-conjugated NCN chelate. The
planarity of the “CN3” core is shown by the sum of the angles
around C1 and C8 (360°). The dihedral angles between the
two guanidinate ligands (Zr−N1−C1−N2 and Zr−N4−C8−
N5) are 87.7 and 86.8° for molecules A and B, respectively.
The dihedral angles between the C1−N3−C5 and Zr1−N1−
C1−N2 planes (31.7 and 27.8° for molecules A and B,
respectively) and between the C8−N6−C12 and Zr1−N4−
C8−N5 planes (33.7 and 35.0° for molecules 1 and 2,
respectively) indicate a significant contribution from the
zwitterionic resonance structure for the guanidinate ligand in
this complex (Scheme 1).
Figure 2. ORTEP drawing of complex 2. Hydrogen atoms have been
omitted for clarity, and thermal ellipsoids are shown at 30%
probability. Selected bond lengths (Å) and angles (deg): N1−C1,
1.35(1); N2−C1, 1.31(1); N3−C1, 1.35(1); N4−C8, 1.32(1); N5−
C8, 1.35(1); N6−C8, 1.35(1); Zr−N1, 2.20(1); Zr−N2, 2.33(1); Zr−
N4, 2.20(1); Zr−N5, 2.23(1); Zr−C41, 2.28(1); Zr−C51, 2.25(1);
N1−Zr−N2, 58.0(3); N1−N4−Zr−N5, 59.4(2); N1−C1−N2,
111.5(6); N1−C1−N3, 123.1(7); N2−C1−N3, 125.3(7).
Complexes 1 and 2 contain guanidinate ligands with a HNAr
group (Ar = 4-t-BuC6H4 or 4-BrC6H4) that does not coordinate
to the metal center. As such, we decided to complete our study
by synthesizing analogous complexes containing asymmetric
guanidinate ligands with an NR2 group in the noncoordinating
position. Thus, we synthesized the dibenzyl complex [Zr-
{κ2N,N′-(NEt)(N-t-Bu)CNMe2}2(CH2Ph)2] (3) from the new
complex [Zr{κ2N,N′-(NEt)(N-t-Bu)CNMe2}2Cl2] (4), which
we obtained by an insertion reaction of the carbodiimide
EtNCN-t-Bu into the metal−amide bonds of the complex
[ZrCl2(NMe2)2(THF)2]18 in very good yields, as described
Table 1. Selected Bond Lengths (Å) and Angles (deg) for
Complex 2
molecule A
molecule B
Bond Lengths
2.20(1)
previously13g 19 (Scheme 3). Complex 4 is stable in solution
,
Zr−N1
Zr−N2
Zr−N4
Zr−N5
Zr−C41
Zr−C51
N1−C1
N2−C1
N3−C1
N4−C8
N5−C8
N6−C8
2.20(1)
2.30(1)
2.23(1)
2.28(1)
2.30(1)
2.26(1)
1.33(1)
1.35(1)
1.38(1)
1.35(1)
1.32(1)
1.36(1)
under an inert atmosphere at room temperature. To the best of
our knowledge, only the complex [Ta{κ2N,N′-(NEt)(N-t-
Bu)CNMe2}2(NMe2)4]20 with this guanidinate ligand has
2.33(1)
2.20(1)
2.23(1)
1
been reported. The H NMR spectrum of complex 4 contains
2.28(1)
a single set of resonances for the guanidinate ligand, with
resonances for the tert-butyl and NMe2 protons appearing at
1.37 and 2.27 ppm, respectively, alongside triplet and quartet
signals at 1.26 and 3.29 ppm (3JHH = 6.9 Hz) corresponding to
the ethyl fragments.
These spectroscopic data were confirmed by X-ray diffraction
studies. Suitable crystals of complex 4 were grown from a
toluene solution at −30 °C. The molecular structure and
atomic numbering scheme of 4 are shown in Figure 3; selected
bond lengths and angles for 4 are given in Table 2.
Complex 4 crystallizes in the P21/n space group and is the
first structurally characterized dichloro complex of a group 4
metal with the guanidinate ligand (NEt)(N-t-Bu)CNMe2,
which coordinates to the pseudotetrahedral Zr center in an
asymmetrical mode in a manner similar to that for complex 2
above. The coordination sphere of the metal center consists of
two chloride ligands and two bidentate guanidinate ligands,
each of which occupies one coordination site in a κ2N,N′-
(NEt)(N-t-Bu) coordination mode.
2.25(1)
1.35(1)
1.31(1)
1.35(1)
1.32(1)
1.35(1)
1.35(1)
Bond Angles
58.0(3)
N1−Zr−N2
N2−Zr−N5
N2−Zr−N4
N2−Zr−C51
C41−Zr−C51
N1−C1−N2
N1−C1−N3
N2−C1−N3
N4−C8−N5
N4−C8−N6
N5−C8−N6
59.1(2)
164.8(4)
105.9(4)
112.2(3)
94.7(3)
163.0(2)
104.8(3)
113.8(3)
96.5(3)
111.5(6)
123.1(7)
125.3(7)
110.6(6)
125.6(6)
123.8(7)
111.6(6)
124.8(6)
123.5(7)
112.5(8)
122.0(9)
125.5(8)
The bond lengths of the “CN3” moieties (N1−C1 =
1.340(5), N2−C1 = 1.347(5), N3−C1 = 1.359(5), N4−C11
= 1.350(5), N5−C11 = 1.329(6), and N6−C11 = 1.369(5) Å)
are consistent with a partial double-bond character and a π-
conjugated chelate coordination, thus implying that the
guanidinate ligand behaves as a strong donor system toward
the electron-poor zirconium center. The Zr−N bond distances
(2.19−2.20 Å) also support this proposal. Moreover, the
guanidinate bite angles of 60.5(1) and 60.0(1)° and the angles
between the planes of the NMe2 moiety and the metal chelate
Complex 2 crystallizes in the P1 space group, with two
̅
molecules per asymmetric unit (A and B), corresponding to the
two possible enantiomers. In contrast to the diguanidinate
zirconium complexes reported previously, the geometry of 2
shows the Zr atom in a highly distorted octahedral environment
that is perhaps better considered as a pseudotetrahedral
environment, with the two bidentate guanidinate ligands
using one coordination site each in a κ2N,N′-(N-i-Pr)(NAr)
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Scheme 3. Synthetic Route to Complexes 3 and 4
benzylic CH2Ph protons as well as a broad signal for the
methylene protons of the ethyl substituents, indicating a
fluxional process in solution. The 13C{1H} NMR spectrum of 3
shows only one set of resonances for the guanidinate ligands
and two signals for the metal-bonded benzylic carbon atoms,
thus confirming the dialkylation process.
In order to study these fluxional processes, we have carried
1
out variable-temperature H NMR studies in toluene-d8. When
the temperature was decreased to −50 °C, the spectra showed
two doublets at 2.39 and 2.79 ppm for the benzylic protons,
2
with a JHH coupling constant of 11 Hz, and two multiplets at
2.96 and 3.09 ppm corresponding to the nonequivalent
methylene protons of each ethyl substituent. The signals for
the benzylic protons coalesced at 25 °C (ΔG⧧ = 15.57 kcal/
c
mol),15 whereas those for the methylene protons of the ethyl
groups coalesced at 40 °C (ΔG⧧ = 16.85 kcal/mol). Raising
c
the temperature to 110 °C led to a single multiplet for the
methylene protons of the ethyl substituents. The rate constants
of the interconversion in 3 at various temperatures were
calculated from eq 1, and the Eyring plot gives similar values for
the activation parameters of the exchange for the benzyl
protons, ΔH⧧ = 3.95 kcal mol−1 and ΔS⧧ = −54.94 eu, and for
the methylene protons, ΔH⧧ = 3.78 kcal mol−1 and ΔS⧧ =
−56.97 eu. This fluxional process and small ΔH⧧ and negative
ΔS⧧ values can be explained by a Bailar twist mechanism
analogous to that described above for complexes 1 and 2.
The migratory insertion of alkyl groups toward isocyanide
ligands allows the formation of iminoacyl groups, which can
coordinate in different modes. Thus, the κ2C,N coordination of
iminoacyl ligands is common for high-valent oxophilic early-
transition-metal complexes.21 Furthermore, their ability to
undergo a range of carbon−carbon bond forming reactions
has been shown to be particularly interesting in organometallic
synthesis,22 with insertion and intramolecular rearrangement
processes leading to the formation of different products and
intermediates, The type of ligand present is known to influence
the reactivity of the metal center during subsequent insertion
and intramolecular C−C coupling.23 The products and
intermediates found in such migratory insertion processes are
shown in Scheme 4.
In fact, when two alkyl groups are bonded to the metal
center, the addition of 1 equiv of isocyanide ligand produces
the migratory insertion of one alkyl group to form iminoacyl
complexes which evolve to give the vinylamido derivative
(route a) or the imido complexes and the corresponding olefin
(route b). If 2 equiv of isocyanide is used, the two alkyl groups
undergo insertion (route c) to form the bis(iminoacyl)
derivatives, which evolve to the enediamido complexes.
The treatment of 1 and 2 with 2,6-dimethylphenyl isocyanide
(XyNC) in a 1:1 stoichiometric ratio in toluene at room
temperature gave the monoinsertion reaction products 5 and 6,
Figure 3. ORTEP drawing of complex 4. Hydrogen atoms have been
omitted for clarity, and thermal ellipsoids are shown at 30%
probability. Selected bond lengths (Å) and angles (deg): N1−C1,
1.340(5); N2−C1, 1.347(5); N3−C1, 1.359(5); N4−C11, 1.350(5);
N5−C11, 1.329(6); N1−Zr1−N2, 60.5(1); N4−Zr1−N5, 60.0(1).
Table 2. Selected Bond Lengths (Å) and Angles (deg) for
Complex 4
Bond Lengths
Zr1−Cl1
Zr1−Cl2
Zr1−N1
Zr1−N2
Zr1−N4
Zr1−N5
2.55(4)
N1−C1
N2−C1
N3−C1
N4−C11
N5−C11
1.340(5)
1.347(5)
1.359(5)
1.350(5)
1.329(6)
2.428(1)
2.186(3)
2.193(3)
2.197(4)
2.204(3)
Bond Angles
Cl1−Zr1−Cl2
N1−Zr1−N2
N4−Zr1−N5
N1−C1−N2
N1−C1−N3
96.3(8)
60.5(1)
60.0(1)
110.3(3)
124.1(4)
N2−C1−N3
N4−C11−N5
N4−C11−N6
N5−C11−N6
125.5(4)
110.5(4)
122.6(4)
126.9(4)
ring of 48.2(3) and 50.3(4)° for Zr1−N1−C1−N2 and Zr1−
N4−C11−N5, respectively, indicate a slight overlap between
the nitrogen p orbital and the π-conjugated chelate system.5e
The planarity of the “CN3” core is also shown by the sum of the
bond angles around C1 and C11 (360°). The dihedral angle
between the two NCN guanidinate chelate rings is 89.2°.
Alkylation of 4 with 2 equiv of MgCl(CH2Ph) produces the
dibenzyl complex [Zr{κ2 N, N′-(NEt)(N-t-Bu)-
CNMe2}2(CH2Ph)2] (3) in good yield (Scheme 3). This
complex is stable at room temperature under an inert
1
atmosphere. The H NMR spectrum at room temperature
shows the presence of a broad signal corresponding to the
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Scheme 4. Reaction Products and Intermediates in the Migratory Insertion of XyCN into Zr−C Bonds
Scheme 5. Possible Isomers for Complexes 5 and 6 (Coplanar and Perpendicular Benzyl and η2-Iminoacyl Ligands)
with full conversion being reached after 2 days, whereas
complexes 5 and 6 were obtained in almost quantitative yield in
16 h when the reaction was carried out at 50 °C. Complexes 5
and 6 were characterized by NMR and FT-IR spectroscopy.
formations, it has been demonstrated that the N-outside isomer
is the initial kinetic iminoacyl-containing product of the
insertion reaction; most group 4 metal derivatives appear as
the N-inside isomer, which results from thermodynamic
control.24 As such, we tentatively propose that this complex
is the only product resulting from thermodynamic control and
that it adopts the N-inside conformation (Scheme 5).
However, heating a solution of this reaction mixture in
toluene at reflux for 1 h resulted in a color change from yellow
to purple and formation of the imido complex [Zr{κ2N,N′-(N-
i-Pr)(N(Ar)CNH(i-Pr)}2{N(2,6-Me2C6H3)}] (Ar = 4-t-
BuC6H4 (7), 4-BrC6H4 (8)) in very good yield (Scheme 6).
Surprisingly, these imido complexes were also obtained when a
solution of 1 equiv of 1 or 2 and 2 equiv of XyNC was heated at
70 °C for 4 h, with approximately 1 equiv of XyNC remaining
unreacted. This implies that imido formation is favored by the
addition of an excess of isocyanide. Moreover, the presence of
2-benzylstyrene was detected when these reactions were carried
out in an NMR tube (a doublet at 3.49 ppm for the CH2Ph
1
The benzyl methylene protons are diastereotopic; thus, the H
NMR spectrum shows a broad doublet at ca. 2.38 ppm as well
as a broad singlet at ca. 3.79 ppm for the inserted benzylic
protons. A singlet is also observed at ca. 1.97 ppm for the
methyl protons of the 2,6-dimethylphenyl moiety, and the two
guanidinate ligands become nonequivalent, with each present-
ing a set of signals. The κ2 coordination mode of the iminoacyl
group is suggested by 13C{1H} NMR and IR data, with a signal
at ca. 252.3 ppm and an absorption at ca. 1561 cm−1 being
assigned to the iminoacyl quaternary carbon atom and the
ν(CN) stretching vibration, respectively. Moreover, the
iminoacyl group can position itself in a perpendicular or
coplanar (“proximal” or “N-outside” and “distal” or “N-inside”)
geometry with the benzyl ligand (Scheme 5). Although the
spectroscopic data do not distinguish between those con-
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Scheme 6. Reaction of Complexes 1 and 2 with XyNC To
Give the Imido Complexes 7 and 8, Respectively
Figure 4. ORTEP drawing of complex 9. Hydrogen atoms have been
omitted for clarity, and thermal ellipsoids are shown at 30%
probability. Selected bond lengths (Å) and angles (deg): Zr1−N1,
2.248(2); Zr1−N2, 2.270(2); Zr1−N4, 2.283(2); Zr1−N5, 2.231(2);
Zr1−N7, 2.152(2); Zr1−N8, 2.140(2); C11−C31, 1.347(4); N1−C1,
1.327(3); N2−C1, 1.336(3); N3−C1, 1.394(4); N4−C1A, 1.330(4);
N5−C1A, 1.346(4); N6−C1A, 1.382(4); N1−Zr1−N2, 58.88(8);
N4−Zr1−N5, 58.72(9); N1−C1−N2, 113.0(2); N1−C1−N3,
123.2(3); N2−C1−N3, 123.8(3).
protons and a multiplet at ca. 6.30 ppm for the olefin −CH
CH− protons), thus indicating that the reaction proceeds via a
mechanism similar to that proposed for alkyl complexes with
symmetrical guanidinate ligands.5b
Complexes 7 and 8 were characterized spectroscopically. The
1H NMR spectra show an absence of resonances corresponding
to the benzylic groups and the presence of four doublets for the
i-Pr methyl groups, as well as two singlets for the two methyl
groups of the arylimido ligand, thus indicating that the
previously described rotation process is strongly hindered in
Table 3. Selected Bond Lengths (Å) and Angles (deg) for
Complex 9
1
Bond Lengths
this complex at room temperature. Variable-temperature H
Zr1−N1
Zr1−N2
Zr1−N4
Zr1−N5
Zr1−N7
Zr1−N8
N1−C1
N2−C1
2.248(2)
2.270(2)
2.283(2)
2.231(2)
2.152(2)
2.140(2)
1.327(3)
1.336(3)
N3−C1
1.394(4)
1.330(4)
1.346(4)
1.382(4)
1.435(3)
1.426(3)
1.347(4)
NMR studies of 7 in toluene-d8 showed two broad signals for
the methyl protons of the i-Pr substituents at 80 °C, with the
two singlet resonances corresponding to the methyl groups of
the aryl isocyanide being observed as a broad signal. The
coalescence temperature was 70 °C, and the calculated free
energy of activation was 16.6 kcal/mol. The two guanidinate
ligands are equivalent at this temperature, due to the existence
of a C2 axis and a plane containing the ZrN bond.
N4−C1A
N5−C1A
N6−C1A
N7−C11
N8−C31
C11−C31
Bond Angles
58.88(8)
Complexes 7 and 8 are imido guanidinate complexes
containing asymmetric guanidinate ligands with the Zr atom
in a distorted-trigonal-bipyramidal geometry at room temper-
ature similar to that exhibited by the few known examples of
terminal imido complexes of group 4 metals with symmetrically
coordinated guanidinate ligands.5b,c Additionally, the geometry
around the Zr atom changed from trigonal bipyramidal to
square pyramidal, in agreement with the variable-temperature
NMR data at 80 °C.
N1−Zr1−N2
N4−Zr1−N5
N7−Zr1−N8
N1−C1−N2
N1−C1−N3
N2−C1−N3
N4−C1A−N5
N4−C1A−N6
N5−C1A−N6
C1−N3−C2
122.9(3)
125.5(3)
121.1(3)
120.3(3)
123.3(3)
121.1(3)
58.72(9)
75.44(8)
113.0(2)
123.2(3)
123.8(3)
111.6(2)
C1−N3−C3
C1A−N6−C2A
C1A−N6−C3A
In contrast to the reactivity outlined above, complex 3
reacted with 2 equiv of XyNC in toluene at reflux over 6 h to
yield the enediamido complex [Zr{κ2N,N′-(N-t-Bu)(NEt)-
CNMe2}2}{κ2N,N′-N(2,6-Me2C6H3)(CH2Ph)CC(CH2Ph)-
N(2,6-Me2C6H3)}] (9). Formation of the new enediamido
ligand is supported on the basis of the IR spectrum, which
shows a characteristic stretching vibration at 1539 cm−1, and a
single-crystal X-ray diffraction study. Suitable crystals of
complex 9 were grown from toluene solution at −30 °C. An
ORTEP diagram of 9 is shown in Figure 4. Selected bond
lengths and angles for 9 are given in Table 3.
coordinated in an asymmetrical mode. It crystallizes in the P1
space group. The zirconium atom exhibits a distorted-
pseudotetrahedral geometry, with two bidentate guanidinate
ligands bonded via two nitrogen atoms in a κ2 coordination
mode and the enediamido group also bonded via two nitrogen
atoms. The enediamido group has a bite angle of 75.45(8)°,
which is smaller than that typically observed in other
compounds (approximately 85°);5b,25 the guanidinate bite
angles are ca. 58.8°. The Zr1−N7 and Zr1−N8 bond distances
(2.152(2) and 2.140(2) Å, respectively) corresponding to the
Zr−amido linkages are shorter than the average Zr−N
guanidinate bond lengths of ca. 2.26(2) Å. The planarity of
the “CN3” core, which is seen by the sum of bond angles
̅
Complex 9 is the first structurally characterized enediamido
complex of a group 4 metal with guanidinate ligands
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Organometallics
Article
around C1 and C1A (360°), is in contrast with the three
different distances found for the N−C bonds. These findings
imply a different charge delocalization in this complex, with a
less electron donating guanidinate ligand, probably due to the
presence of other strong donors, such as enediamido, in the
coordination sphere of the metal atom. The C11−C31 distance
of 1.347(4) Å corresponds to a CC bond, whereas the N7−
C11 and N8−C31 distances of 1.435(3) and 1.426(3) Å,
respectively, are consistent with single bonds between sp2-
hybridized C and N atoms. The dihedral angle of 13.6°
between the N7−Zr1−N8 and N7−C11C31−N8 planes
indicates a practically planar chelate ring.
via an intramolecular coupling of the two iminoacyl groups in
the syn isomer, as carbon−carbon coupling would be strongly
hindered in the anti isomer.23,26 However, this situation is in
contrast with the synthesis of the previously described imido
complexes 7 and 8, where the presence of two aryl groups in
apical positions can block formation of the bis(κ2-iminoacyl)
derivative and favor formation of the less sterically hindered
imido complex.
CONCLUSIONS
■
The current work describes new dibenzylzirconium(IV)
complexes containing asymmetric guanidinate ligands and
their different behaviors with regard to the insertion of aryl
isocyanides. Thus, the more hindered complexes 1 and 2 only
allow a single insertion reaction to give the imido complexes 7
and 8, respectively, whereas the enediamido derivative 9 is
obtained by an intramolecular coupling reaction of the two
iminoacyl ligands in complex 10. These results show that steric
effects resulting from the coordination mode of the guanidinate
ligands play a decisive role in the migratory insertion reaction
of the aryl isocyanide and the stability of κ2C,N-iminoacyl
intermediates. In addition, we have isolated and identified the
monoacyl intermediates 5 and 6, the bis(iminoacyl) complex
10, and 2-benzylstyrene as a reaction byproduct.
The treatment of 3 with 2 equiv of XyNC at room
temperature for 16 h led to formation of the bis(κ2C,N-
iminoacyl) complex [Zr{κ2N,N′-(N-t-Bu)(NEt)CNMe2}2}-
{κ2C,N-(2,6-Me2C6H3)NC(CH2Ph)}2] (10) (Scheme 7).
Scheme 7. Migratory Insertion Processes and Evolution to
the Enediamido Complex 9 from 10
EXPERIMENTAL SECTION
■
General Procedures. All manipulations were performed using
standard Schlenk and glovebox techniques under an atmosphere of dry
nitrogen. Solvents were purified by passage through a column of
activated alumina (Innovative Technologies) and degassed under
nitrogen before use. Microanalyses were carried out using a Perkin-
Elmer 2400 CHN analyzer. NMR spectra were recorded using a
Varian Inova FT-500 spectrometer and referenced to the residual
deuterated solvent using standard VARIANT-FT software. FT-IR
spectra were recorded using a Bruker Tensor 27 spectrophotometer.
27
Zr(CH2Ph)4 and [Zr(NMe2)2Cl2(THF)2]21 were prepared accord-
ing to literature procedures. ZrCl4, ZnEt2, amines, 2,6-dimethylphenyl
isocyanide, MgCl(CH2Ph), and the carbodiimide derivatives were
purchased from Sigma Aldrich.
Synthesis of [Zr{κ2N,N′-(N-i-Pr)(N4-t-BuC6H4)CNH(i-
Pr)}2(CH2Ph)2] (1). (HN-i-Pr)2CN(4-t-BuC6H4) (0.60 g, 2.20
mmol) was added to a solution of Zr(CH2Ph)4 (0.50 g, 1.10 mmol)
in toluene (15 mL), and the resulting yellow solution was stirred at
room temperature for 30 min. The solvent was then evaporated to
dryness to afford a yellow solid, which was redissolved in toluene and
cooled to −20 °C to obtain yellow crystals of 1. Yield: 0.83 g (93%).
1H NMR (C6D6, 25 °C): δ 0.63 (d, 12H, HNCH(CH3)2, 3JH−H = 6.3
The formation of 10 was supported by IR and 13C{1H} NMR
spectroscopy, with the IR spectrum showing a characteristic
stretching vibration at 1560 cm−1 and the 13C{1H} NMR
spectrum a signal at 251.9 ppm for the CN group. In
1
addition, the H NMR spectrum shows an AB system that can
be assigned to the diasterotopic methylene protons of the
iminoacyl ligands formed by a migratory insertion process.
Although the formation of two isomers (anti/syn) of the
pseudooctahedral metal complex 10 would be expected
(Scheme 8), the NMR spectra of complex 10 show only one
set of signals, corresponding to a single species.
Hz), 1.17 (d, 12H, NCH(CH3)2, 3JH−H = 6.6 Hz), 1.20 (s, 18H, t-Bu),
2.39 (br s, 4H, CH2Ph), 3.21 (m, 4H, HNCH(CH3)2 and
3
NCH(CH3)2), 3.59 (d, 2H, HNCH(CH3)2, JH−H = 9.15 Hz),
6.77−7.27 (m, 18H, 4-t-BuC6H4 and CH2Ph). 13C{1H} NMR (C6D6,
25 °C): δ 23.9 (HNCH(CH3)2), 24.1 (NCH(CH3)2), 31.9, (C-
(CH3)3), 34.1 (C(CH3)3), 43.8 (HNCH(CH3)2, 44.8 (NCH(CH3)2),
75.1 (CH2Ph), 118.9−149.7 (4-t-BuC6H4 and CH2Ph), 165.9 (CN3).
Anal. Calcd for C48H70ZrN6: C, 70.20; H, 8.53; N, 10.24. Found: C,
70.46; H, 8.49; N, 10.33.
It is well known that the presence of a guanidinate ligand
influences the reactivity of a metal center as a result of its steric
and electronic effects on the iminoacyl complex.5a,15 23 This
b,
Synthesis of [Zr{κ2N,N′-(N-i-Pr)(N4-BrC6H4)CNH(i-
Pr)}2(CH2Ph)2] (2). Complex 2 was prepared in a manner identical
with that for 1 from Zr(CH2Ph)4 (0.16 g, 0.35 mmol) and (HN-i-
Pr)2CN(4-BrC6H4) (0.21 g, 0.70 mmol). Yield: 0.29 g (95%).1 H
NMR (C6D6, 25 °C): δ 0.58 (d, 12H, HNCH(CH3)2, 3JHH = 6.2 Hz),
factor will lead to formation of the final enediamido complex 9
Scheme 8. Possible Isomers (anti/syn) of the Iminoacyl
Complex
3
1.11 (d, 12H, NCH(CH3)2, JHH = 6.2 Hz), 2.18 (br s, 4H, CH2Ph),
3.05 (m, 2H, NCH(CH3)2), 3.09 (m, 2H, HNCH(CH3)2), 3.49 (d,
3
2H, HNCH(CH3)2, JHH = 9.2 Hz), 6.35−7.40 (m, 18H, 4-BrC6H4
and CH2Ph). 13C{1H} NMR (C6D6, 25 °C): δ 21.4 (HNCH(CH3)2),
23.0 (NCH(CH3)2), 44.4 (HNCH(CH3)2, 45.8 (NCH(CH3)2), 75.2
(CH2Ph), 118.0−150.1 (4-BrC6H4 and CH2Ph), 163.0 (CN3). Anal.
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Calcd for C40H52ZrN6Br2: C, 55.54; H, 6.02; N, 9.72. Found: C, 55.71;
H, 5.98; N, 9.68.
(15 mL), and the reaction mixture was stirred at reflux for 1 h. The
resulting purple solution was dried in vacuo to afford complex 7 as a
dark red solid. Yield: 0.16 g (86%). 1H NMR (C6D6, 25 °C): δ 0.44 (d,
6H, HNCH(CH3)2, 3JHH = 6.4 Hz), 0.56 (d, 6H, HNCH(CH3)2, 3JHH
Synthesis of [Zr{κ2N,N′-(N-t-Bu)(NEt)CNMe2}2Cl2}] (4). t-
BuNCNEt (0.82 g, 5.27 mmol) was added to a solution of
[ZrCl2(NMe2)2(THF)2] (0.90 g, 2.29 mmol) in toluene (50 mL) at
−78 °C, and the mixture was stirred at room temperature for 6 h. The
resulting pale yellow solution was then dried in vacuo to afford a
yellow solid, which was redissolved in THF and cooled to −20 °C to
obtain colorless crystals of 4. Yield: 1.10 g (96%). 1 H NMR (C6D6, 25
3
= 6.4 Hz), 0.91 (d, 6H, NCH(CH3)2, JHH = 6.4 Hz), 1.08 (d, 6H,
3
NCH(CH3)2, JHH = 6.4 Hz), 1.27 (s, 18H, t-Bu), 2.08, 2.22 (2s, 6H,
2,6-(CH3)2C6H3), 3.08 (m, 2H, HNCH(CH3)2), 3.51 (m, 4H,
NCH(CH3)2 and HNCH(CH3)2), 6.87−7.20 (m, t-BuC6H4 and 2,6-
(CH3)2C6H3). 13C{1H} NMR (C6D6, 25 °C): δ 18.7 (2,6-
(CH3)2C6H3), 23.7, 23.9, 24.2, 24.7 (HNCH(CH3)2, NCH(CH3)2),
31.8 (C(CH3)3), 34.2 (C(CH3)3), 44.9 (HNCH(CH3)2, 46.7 (NCH-
(CH3)2), 123.7 - 149.9 (2,6-(CH3)2C6H3 and t-BuC6H4), 164.0 (CN3).
Anal. Calcd for C42H65ZrN7: C, 66.47; H, 8.57; N, 12.93. Found: C,
66.76; H, 8.88; N, 12.85.
3
°C): δ 1.26 (t, 6H, NCH2CH3, JHH = 6.9 Hz), 1.37 (s, 18H, t-Bu),
2.27 (s, 12H, NMe2), 3.29 (q, 4H, NCH2CH3, 3JHH = 6.9 Hz).13C{1H}
NMR (C6D6, 25 °C): δ 17.3 (NCH2CH3), 31.4 (NCH2CH3),
40.3(C(CH3)3), 42.7 (C(CH3)3), 53.9 (NMe2), 173.8 (CN3). Anal.
Calcd for C18H40ZrN6Cl2: C, 43.02; H, 7.97; N, 16.73. Found: C,
43.64; H, 8.26; N, 16.99.
Synthesis of [Zr{κ2N,N′-(N-i-Pr)(N4-BrC6H4)CNH(i-Pr)}2{N(2,6-
Me2C6H3)}] (8). Complex 8 was prepared in a manner identical with
that for 7 from 2 (0.09 g, 0.11 mmol) and 2,6-dimethylphenyl
isocyanide (0.10 g, 0.11 mmol). Yield: 0.08 g (98%). 1H NMR (C6D6,
Synthesis of [Zr{κ2N,N′-(N-t-Bu)(NEt)CNMe2}2(CH2Ph)2] (3).
MgCl(CH2Ph) (2.00 mL, 3.98 mmol, 2 M in THF) was added to a
solution of 4 (1.00 g, 1.99 mmol) in THF (50 mL) at −78 °C, and the
mixture was stirred at room temperature for 16 h. The resulting yellow
solution was dried in vacuo, the residue extracted with n-hexane, and
the solvent partially removed under vacuum to afford yellow crystals of
3
25 °C): δ 0.39 (d, 6H, HNCH(CH3)2, JHH = 6.1 Hz), 0.47 (d, 6H,
3
3
HNCH(CH3)2, JHH = 6.1 Hz), 0.75 (d, 6H, NCH(CH3)2, JHH = 6.1
Hz), 0.99 (d, 6H, NCH(CH3)2, 3JHH = 6.1 Hz), 2.04, 2.16 (2s, 6H, 2,6-
(CH3)2C6H3), 2.87 (m, 2H, HNCH(CH3)2), 3.37 (m, 4H,
NCH(CH3)2 and HNCH(CH3)2), 6.60−7.22 (m, BrC6H4 and 2,6-
(CH3)2C6H3). 13C{1H} NMR (C6D6, 25 °C): δ 20.2 (2,6-
(CH3)2C6H3), 23.2, 23.5, 24.0, 24.6 (HNCH(CH3)2 and NCH-
(CH3)2), 45.1 (HNCH(CH3)2), 46.7 (NCH(CH3)2), 121.2−149.9
(2,6-(CH3)2C6H3 and BrC6H4), 163.9 (CN3). Anal. Calcd for
C34H47ZrN7Br2: C, 50.93; H, 5.87; N, 12.23. Found: C, 51.23; H,
6.14; N, 12.44.
1
complex 3. Yield: 1.17 g (97%). H NMR (C6D6, 25 °C): δ 0.96 (t,
3
6H, NCH2CH3, JHH = 6.9 Hz), 1.20 (s, 18H, t-Bu), 2.27 (s, 12H,
NMe2), 2.72 (br s, 4H, CH2Ph), 3.01 (br s, 4H, NCH2CH3), 6.84−
7.20 (m, 10H, CH2Ph). 13C{1H} NMR (C6D6, 25 °C): δ 16.7
(NCH2CH3), 31.6 (NCH2CH3), 40.6 (C(CH3)3), 40.7 (C(CH3)3),
52.7 (NMe2), 71.2 (CH2Ph), 120.3−149.9 (CH2Ph), 176.2 (CN3).
Anal. Calcd for C32H54ZrN6: C, 62.62; H, 8.81; N, 13.70. Found: C,
62.74; H, 8.92.01; N, 13.72.
Synthesis of [Zr{κ2N,N′-(N-t-Bu)(NEt)CNMe2}2}{κ2N,N′-N(2,6-
Me2C6H3)(CH2Ph)CC(CH2Ph)N(2,6-Me2C6H3)}] (9). 2,6-Dime-
thylphenyl isocyanide (0.09 g, 0.66 mmol) was added to a solution
of 3 (0.20 g, 0.33 mmol) in toluene (10 mL), and the mixture was
stirred at reflux temperature for 6 h to give an orange solution. All
volatiles were then removed in vacuo to provide a dark orange solid,
Synthesis of [Zr{κ2N,N′-(N-i-Pr)(N(4-t-BuC6H4))CNH(i-Pr)}2}-
{κ2C,N-(2,6-Me2C6H3)NC(CH2Ph)}(CH2Ph)] (5). 2,6-Dimethyl-
phenyl isocyanide (0.01 g, 0.11 mmol) was added to a solution of 1
(0.09 g, 0.11 mmol) in toluene (15 mL), and the reaction mixture was
stirred at 50 °C for 16 h. The resulting orange solution was dried in
vacuo to afford complex 5 as an orange solid. Yield: 0.09 g (89%). 1H
3
1
NMR (C6D6, 25 °C): δ 0.66 (d, 6H, HNCH(CH3)2, JHH = 5.9 Hz),
which was recrystallized from toluene. Yield: 0.21 g (72%). H NMR
3
0.69 (d, 6H, HNCH(CH3)2, JHH = 6.7 Hz), 1.20 (d, 6H,
(C6D6, 25 °C): δ 0.72 (br s, 6H, CH2CH3)), 1.04 (s, 18H, t-Bu), 2.08
(s, 12H, 2,6-(CH3)2C6H3), 2.27 (s, 12H, NMe2), 3.24 (br s, 4H,
CH2Ph), 3.03 (br s, 4H, CH2CH3), 6.87−7.20 (m, (2,6-CH3)2C6H3
and CH2Ph). 13C{1H} NMR (CD2Cl2, 25 °C): δ 16.1 (2,6-
(CH3)C6H3), 18.1 (CH2CH3), 32.1 (CH2CH3), 40.9 (C(CH3)3),
41.5 (C(CH3)3),53.2 (NMe2), 68.2 (CH2Ph), 121.8−153.4 (2,6-
(CH3)2C6H3 and C6H5) 168.4 (CN3). The signal corresponding to the
CC group is not observed. Anal. Calc. for C50H72ZrN8: C, 68.55; H,
8.22; N, 12.79. Found: C 68.72; H, 8.56; N, 12.89.
3
3
NCH(CH3)2, JHH = 5.9 Hz), 1.22 (d, 6H, NCH(CH3)2, JHH = 6.7
Hz), 1.23, 1.27 (2s, 18H, t-Bu), 1.97 (s, 6H, 2,6-(CH3)2C6H3), 2.39 (d,
2
2H, ZrCH2Ph, JHH = 20.0 Hz), 3.22 (m, 2H, HNCH(CH3)2), 3.42
(m, 2H, NCH(CH3)2), 3.57 (d, 1H, HNCH(CH3)2, JHH = 9.5 Hz),
3.62 (d, 1H, HNCH(CH3)2, JHH = 9.5 Hz), 3.79 (br s, 2H, CH2Ph),
3
3
6.60−7.20 (m, 21H, t-BuC6H4, 2,6-(CH3)2C6H3 and CH2Ph).
13C{1H} NMR (C6D6, 25 °C): δ 19.5 (2,6-(CH3)2C6H3), 23.4, 23.5,
24.4, 24.5 (HNCH(CH3)2 and (NCH(CH3)2), 31.8, (C(CH3)3), 34.2
(C(CH3)3), 46.2 (HNCH(CH3)2, 45.9 (NCH(CH3)2), 75.1 (Zr-
(CH2Ph)), 118.0−140.9 (CH2Ph, PhCH2CN, 2,6-(CH3)2C6H3, and
t-BuC6H4), 166.2 (CN3), 252.7 (CN). Anal. Calcd for C57H79ZrN7:
C, 71.83; H, 8.30; N, 10.29. Found: C, 72.01; H, 8.39; N, 10.22.
Synthesis of [Zr{κ2N,N′-(N-i-Pr)(N(4-BrC6H4))CNH(i-Pr)}2}-
{κ2C,N-(2,6-Me2C6H3)NC(CH2Ph)}(CH2Ph)] (6). Complex 6 was
prepared in a manner identical with that for 5 from 2 (0.09 g, 0.11
mmol) and 2,6-dimethylphenyl isocyanide (0.01 g, 0.11 mmol). Yield:
Synthesis of [Zr{κ2N,N′-(N-t-Bu)(NEt)CNMe2}2}{κ2C,N-(2,6-
Me2C6H3)NC(CH2Ph)}2] (10). 2,6-Dimethylphenyl isocyanide
(0.07 g, 0.55 mmol) was added to a solution of 3 (0.17 g, 0.27
mmol) in toluene (10 mL) and the mixture allowed to stir at room
temperature for 16 h. The resulting orange solution was dried in vacuo
1
to provide orange oil. Yield (0.23 g, 95%). H NMR (C6D6, 25 °C):
3
1.06 (t, 6H, NCH2CH3, JHH = 6.1 Hz), 1.37 (s, 18H, t-Bu), 2.01 (s,
12H, NMe2), 2.05 (s, 12H, 2,6-(CH3)2C6H3), 3.01 (br s, 8H,
2
1
1
NCH2CH3). 3.96, 4.17 (2d, 4H, CH2Ph, JHH = 13.2 Hz), 6.63−7.24
0.10 g (91%). H NMR (C6D6, 25 °C): δ H NMR (toluene-d8, 25
°C): δ 0.41 (br s, 6H, HNCH(CH3)2), 0.61 (d, 6H, HNCH(CH3)2,
3JHH = 6.4 Hz), 1.07 (br s, 6H, NCH(CH3)2), 1.48 (d, 6H,
NCH(CH3)2, 3JHH = 6.4 Hz), 2.39 (br s, 4H, CH2Ph), 2.14 (s, 6H, 2,6-
(CH3)2C6H3), 3.26 (m, 2H, NCH(CH3)2), 3.28 (m, 2H,
(2,6-(CH3)2C6H3 and CH2Ph). 13C{1H} NMR (C6D6, 25 °C): 17.4
(NCH2CH3), 17.8, 18.8 (2,6-(CH3)2C6H3), 33.1 (NCH2CH3), 40.1
(C(CH3)), 41.3 (C(CH3)), 53.1 (NMe2), 110.5−150.2 (PhCH2CN,
2,6-(CH3)2C6H3, and CH2Ph), 176.2 (CN3), 251.9 (CN). Anal.
Calcd for C50H72ZrN8: C, 68.55; H, 8.22; N, 12.79. Found: C, 68.83;
H, 8.36; N, 12.98.
3
HNCH(CH3)2), 3.42 (d, 1H, HNCH(CH3)2, JHH = 9.5 Hz), 3.62
(d, 1H, HNCH(CH3)2, 3JHH = 9.8 Hz), 3.92 (br s, 2H, CH2Ph), 6.40−
7.41 (m, CH2Ph, BrC6H4 and 2,6-(CH3)2C6H3). 13C{1H} NMR
(toluene-d8, 25 °C): δ 19.9 (2,6-(CH3)2C6H3), 23.2, 23.6, 24.3, 24.9
(HNCH(CH3)2) and (NCH(CH3)2), 45.0 (HNCH(CH3)2, 45.7
(NCH(CH3)2), 72.7 (ZrCH2Ph), 124.0−140.2 (CH2Ph, PhCH2C
N, and 2,6-(CH3)2C6H3), 164.6 (CN3), 251.9 (CN). Anal. Calcd for
C49H61ZrN7Br2: C, 59.90; H, 6.22; N, 9.99. Found: C, 60.32; H, 6.51;
N, 10.42.
X-ray Structure Analyses for Complexes 2, 4, and 9. Crystals
of complexes 2, 4, and 9 were obtained from toluene, THF, and
diethyl ether/toluene (1/1) solutions at −30 °C, respectively. Crystals
were mounted at low temperature in inert oil on a glass fiber. Data
were collected using a Bruker X8 APEX II CCD-based diffractometer,
equipped with a graphite-monochromated Mo Kα radiation source (λ
= 0.71073 Å).
The crystal data, data collection, structural solution, and refinement
parameters for all three complexes are summarized in the Supporting
Information. Data were integrated using SAINT,28 and an absorption
Synthesis of [Zr{κ2N,N′-(N-i-Pr)(N4-t-BuC6H4)CNH(i-Pr)}2{N-
(2,6-Me2C6H3)}] (7). 2,6-Dimethylphenyl isocyanide (0.03 g, 0.25
mmol) was added to a solution of 1 (0.21 g, 0.25 mmol) in toluene
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Organometallics
Article
correction was performed with the program SADABS.29 All structures
were solved by direct methods using SHELXTL30 and refined by full-
matrix least-squares methods based on F2. All non-hydrogen atoms
were refined with anisotropic thermal parameters. Hydrogen atoms
were placed using a “riding model” and included in the refinement at
calculated positions. Complexes 2 and 4 show some atoms in
disordered positions, and complexes 2 and 9 crystallize with toluene
molecules as solvates. The toluene molecule in complex 2 shows
unsolved disorder.
Richeson, D. S. Organometallics 2006, 25, 4728. (c) Zhang, W.-X.;
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2006, 25, 5515. (i) Montilla, F.; Pastor, A.; Galindo, A. J. Organomet.
Chem. 2004, 689, 993. (j) Zhang, W.-X.; Li, D.; Wang, Z.; Xi, Z.
Organometallics 2009, 28, 882. (k) Li, D.; Guang, J.; Zhang, W.-X.;
Wang, Y.; Xi, Z. Org. Biomol. Chem. 2010, 8, 1816. (l) Lachs, J. R.;
Barret, A. G. M.; Crimmin, M. R.; Kociock-Kohn, G.; Hill, M. S.;
Mahon, M. F.; Procopiou, P. A. Eur. J. Inorg. Chem. 2008, 4173.
(m) Shen, H.; Xie, Z. J. Organomet. Chem. 2009, 694, 1652. (n) Cao,
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50, 3729.
ASSOCIATED CONTENT
■
S
* Supporting Information
CIF files and a table giving full crystallographic data for 2, 4,
1
and 9 and figures giving H NMR spectra for 1−5. This
material is available free of charge via the Internet at http://
pubs.acs.org.
(4) Alonso-Moreno, C.; Carrillo-Hermosilla, F.; Garces
́
, A.; Otero,
AUTHOR INFORMATION
Corresponding Author
*E-mail: rafael.fgalan@uclm.es (R.F.-G.); antonio.antinolo@
uclm.es (A.A.).
Notes
■
́
A.; Lop
2010, 29, 2789.
́
ez-Solera, I.; Rodrıguez, A. M.; Antinolo, A. Organometallics
̃
(5) (a) Wood, D.; Yap, G. P. A.; Richeson, D. S. Inorg. Chem. 1999,
38, 5788. (b) Ong, T.-G.; Wood, D.; Yap, G. P. A.; Richeson, D. S.
Organometallics 2002, 21, 1. (c) Ong, T.-G.; Wood, D.; Yap, G. P. A.;
Richeson, D. S Organometallics 2002, 21, 2839. (d) Bazinet, P.; Wood,
D.; Yap, G. P. A.; Richeson, D. S. Inorg. Chem. 2003, 42, 6225.
(e) Duncan, A. P.; Mullins, S. M.; Arnold, J.; Bergman, R. G.
Organometallics 2001, 20, 1808. (f) Pang, X.-A.; Yao, Y.-M.; Wang, J.-
F.; Sheng, H.-T.; Zhang, Y.; Shen, Q. Chin. J. Chem. 2005, 23, 1193.
(g) Carmalt, C. J; Newport, A.; O’Neill, S. A.; Parkin, I. P.; White, A. J.
P.; Williams, D. J. Inorg. Chem. 2005, 44, 615. (h) Potts, S. E.; Carmalt,
C. J.; Blackman, C. S.; Abou-Chahine, F.; Pugh, D.; Davies, H. O.
Organometallics 2009, 28, 1838.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We are grateful for financial support from the Ministerio de
■
Ciencia e Innovacion
́
of Spain (Grants Nos. Consolider-
Ingenio 2010 ORFEOCSD2007-00006 and CTQ2009-09214)
and the Junta de Comunidades de Castilla-La Mancha, Spain
(Grant No. PCI08-0032). We also thank the Consejo Superior
́
(6) Zhou, M.; Tong, H.; Wei, X.; Liu, D. J. Organomet. Chem. 2007,
692, 5195.
de Investigaciones Cientificas (CSIC) of Spain for the award of
a user license for the Cambridge Crystallographic Data Base
(CSD).
(7) (a) Fernan
Lopez-Solera, I.; Otero, A.; Serrano-Laguna, A.; Villasenor, E. J.
Organomet. Chem. 2012, 711, 35. (b) Elorriaga, D.; Carrillo-
Hermosilla, F.; Antinolo, A.; Lopez-Solera, I.; Menot, B.; Fernandez-
, R.; Villasenor, E.; Otero, A. Organometallics 2012, 31, 1840.
́
dez-Galan, R.; Antinolo, A.; Carrillo-Hermosilla, F.;
́
̃
́
̃
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