Synthesis and reactivity of silyl iron, cobalt, and nickel complexes bearing a [PSiP]-pincer ligand via Si-H bond activation

Article abstract of DOI:10.1021/om400047j

The synthesis and characterization of a series of Ni, Co, and Fe complexes bearing a tridentate bis(phosphino)silyl ligand (κ³-(2-Ph ₂PC₆H₄)₂SiMeH, [PSiP]-H, 1) are reported. 1 reacted with Ni(PMe₃)₄ to afford the mononuclear nickel(0) complex [η²(Si-H)-PSiP]Ni(PMe₃) (2). The halogeno nickel complexes [PSiP]Ni(X)(PMe₃) (X = Cl (3), Br (4), I (5)) were synthesized in the reactions of 2 with Me₃SiCl or MeHSiCl₂, EtBr, and MeI. Complex 2 underwent ligand substitution of PMe₃ by CO to give [η²(Si-H)-PSiP]Ni(CO) (6). Complex 3 reacted with NaOMe to deliver [PSiP]Ni(OMe)(PMe₃) (7) through anionic ligand substitution, while the neutral ligand replacement of PMe ₃ by CO in 3 afforded the rare hexacoordinate 20-electron nickel(II) complex [PSiP]Ni(Cl)(CO)₂ (8). Unexpectedly, reaction of 1 with NiMe₂(PMe₃)₃ produced the tetracoordinate nickel(0) complex [Me₂PSiP]₂Ni (9). The complex [Me ₂PSiP]Ni(CO)₂ (10) was acquired from 9 after the substitution of one [PSiP] ligand by two carbonyl ligands. 1 reacted with Co(PMe₃)₄ or CoCl(PMe₃)₃ to afford the hydrido cobalt(II) complex [PSiP]CoH(PMe₃) (11) or hydrido cobalt(III) complex [PSiP]Co(H)(Cl)(PMe₃) (13). Complex 12, [PSiP]Co(H)(I)(PMe₃), could be obtained from the reaction of MeI with 11 or 13. Treatment of 13 with 1 equiv of MeLi or n-BuMgBr in THF resulted in the clean formation of cobalt(I) complex [PSiP]Co(PMe₃)₂ (14) via reductive elimination. The simple anhydrous inorganic salt NiCl ₂ or CoCl₂ could also react with 1 in the presence of PMe₃ to form the corresponding silyl complexes 3 and [PSiP]Co(Cl)(PMe₃) (15) via Si-H bond cleavage. 1 reacted with Fe(PMe₃)₄ to form the hexacoordinate octahedral hydrido iron(II) complex [PSiP]Fe(H)(PMe₃)₂ (16). The molecular structures of complexes 2-5, 10, 12, 13, 15, and 16 were determined by X-ray single crystal diffraction. 16 has excellent catalytic reactivity for the reduction of aldehydes and ketones.

Full text of DOI:10.1021/om400047j

Article
pubs.acs.org/Organometallics
Synthesis and Reactivity of Silyl Iron, Cobalt, and Nickel Complexes
Bearing a [PSiP]-Pincer Ligand via Si−H Bond Activation
Siquan Wu, Xiaoyan Li, Zichang Xiong, Wengang Xu, Yunqiang Lu, and Hongjian Sun*
School of Chemistry and Chemical Engineering, Key Laboratory of Special Functional Aggregated Materials, Ministry of Education,
Shandong University, Shanda Nanlu 27, 250100 Jinan, People’s Republic of China
S
* Supporting Information
ABSTRACT: The synthesis and characterization of a series of Ni, Co, and Fe
complexes bearing a tridentate bis(phosphino)silyl ligand (κ3-(2-
Ph2PC6H4)2SiMeH, [PSiP]-H, 1) are reported. 1 reacted with Ni(PMe3)4 to
afford the mononuclear nickel(0) complex [η2(Si−H)-PSiP]Ni(PMe3) (2). The
halogeno nickel complexes [PSiP]Ni(X)(PMe3) (X = Cl (3), Br (4), I (5)) were
synthesized in the reactions of 2 with Me3SiCl or MeHSiCl2, EtBr, and MeI.
Complex 2 underwent ligand substitution of PMe3 by CO to give [η2(Si−H)-
PSiP]Ni(CO) (6). Complex 3 reacted with NaOMe to deliver [PSiP]Ni-
(OMe)(PMe3) (7) through anionic ligand substitution, while the neutral ligand
replacement of PMe3 by CO in 3 afforded the rare hexacoordinate 20-electron
nickel(II) complex [PSiP]Ni(Cl)(CO)2 (8). Unexpectedly, reaction of 1 with
NiMe2(PMe3)3 produced the tetracoordinate nickel(0) complex [Me2PSiP]2Ni (9). The complex [Me2PSiP]Ni(CO)2 (10) was
acquired from 9 after the substitution of one [PSiP] ligand by two carbonyl ligands. 1 reacted with Co(PMe3)4 or CoCl(PMe3)3
to afford the hydrido cobalt(II) complex [PSiP]CoH(PMe3) (11) or hydrido cobalt(III) complex [PSiP]Co(H)(Cl)(PMe3)
(13). Complex 12, [PSiP]Co(H)(I)(PMe3), could be obtained from the reaction of MeI with 11 or 13. Treatment of 13 with 1
equiv of MeLi or n-BuMgBr in THF resulted in the clean formation of cobalt(I) complex [PSiP]Co(PMe3)2 (14) via reductive
elimination. The simple anhydrous inorganic salt NiCl2 or CoCl2 could also react with 1 in the presence of PMe3 to form the
corresponding silyl complexes 3 and [PSiP]Co(Cl)(PMe3) (15) via Si−H bond cleavage. 1 reacted with Fe(PMe3)4 to form the
hexacoordinate octahedral hydrido iron(II) complex [PSiP]Fe(H)(PMe3)2 (16). The molecular structures of complexes 2−5, 10,
12, 13, 15, and 16 were determined by X-ray single crystal diffraction. 16 has excellent catalytic reactivity for the reduction of
aldehydes and ketones.
TM chemistry.3 Silyl pincer ligands have a great advantage in
Si−H bond activation because they make an electron-rich metal
center and coordinatively unsaturated species stable by their
INTRODUCTION
■
The preparation and reaction of silyl transition-metal (TM)
complexes have attracted significant interest, since they are
invoked as key intermediates in numerous TM-catalyzed
reactions of silicon compounds such as hydrosilylation,
strong trans-labilizing effects and rigid framework of the
multidentate ligand. Recently, the chemistry of the reactions
of the pincer ligand κ3-(2-R2PC6H4)2SiMeH (R = Ph, i-Pr, Cy,
dehydrogenative coupling, dehydrogenative borylation, hydro-
carboxylation of allenes, and transfer hydrogenation.1 The
t-Bu) with various metal precursors (M = Ru, Rh, Ir, Pd, Pt, Ni)
has been investigated by the groups of Milstein, Turculet,
reaction of hydrosilanes with low-valent TM complexes via Si−
H bond activation is one of the most important methods for
Iwasawa, and Li.4−7 The resulting PSiP-pincer complexes
exhibit remarkable reactivity in inert bond activation and TM-
preparing silyl TM complexes. Usually, oxidative addition of the
catalyzed transformations.
Si−H bond at the metal center gives rise to silyl metal hydride
In comparison to the poisonous noble metals (Ru, Rh, Ir, Pd,
Pt), Fe-, Co- and Ni-based catalysts are low cost and eco-
friendly. In this paper we describe a systematic investigation of
the synthesis and unique properties of silyl iron, cobalt, and
complexes (Si−M−H) by the cleavage of the Si−H σ-bond.
Occasionally, the reaction stops at the stage of Si−H σ-bond
coordination to the metal to form a η2(Si−H) metal complex,
which can be considered as a “frozen intermediate”.2 Research
nickel complexes bearing a [PSiP]-pincer ligand. These
on silyl metal complexes may provide deeper insight into TM-
complexes were prepared by the reaction of electron-rich
catalyzed silylation reaction mechanisms.
low-valent iron, cobalt, and nickel complexes supported by
A pincer ligand as the tridentate ligand could stabilize a
trimethylphosphine with a [PSiP]-pincer ligand. The frozen
variety of high-oxidation-state metal complexes through the bis-
chelate effect. This has inspired widespread attention to the
synthesis, reaction, and catalytic reactivity of pincer metal
complexes. The silyl ligand shows strong σ-donating character
and displays a stronger trans influence than common ligands in
intermediate η2(Si−H)Ni0 complexes and silyl metal hydrides
Received: February 21, 2013
Published: May 28, 2013
© 2013 American Chemical Society
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(CoII−H, CoIII−H and FeII−H) were synthesized and
characterized. Their reactivity was also investigated. Further-
more, several corresponding halogenated Ni and Co complexes
could be obtained directly from the reactions of simple
inorganic salts NiCl2 and CoCl2 with ligand 1 in the presence of
trimethylphosphine via Si−H bond activation.
constant is ca. 82.0 Hz by non-1H-decoupled 29Si NMR. This is
much larger than typical values found for H−M−Si complexes
and implies the elongation of the Si−H bond by the η2(Si−H)
1
coordination to the nickel center. The JSiH coupling constant
1
of complex 2 is relatively smaller than JSiH = 89 Hz of η2(Si−
H)Ni(PPh3) reported by the Iwasawa group6f and larger than
those (40−70 Hz) for previously reported η2(Si−H) metal
complexes.9
RESULTS AND DISCUSSION
■
X-ray crystallography confirmed the molecular configuration
of 2 (Figure 1). Two five-membered chelate rings with
1. Synthesis and Reactivity of Silyl Nickel Complexes.
In the beginning, we investigated the reaction of Ni(PMe3)4
with bis(o-(diphenylphosphino)phenyl)methylsilane (1). When
a solution of 1 in THF was treated with Ni(PMe3)4 at room
temperature, a small amount of yellow powder deposited after
14 h. After the volatiles were removed, the residue was
extracted with pentane and diethyl ether. Complex 2 was
isolated at 0 °C from diethyl ether as yellow crystals in a yield
of 75% (Scheme 1).
Scheme 1. Preparation of Silyl Nickel Complexes 2−6
Figure 1. ORTEP plot of complex 2 at the 50% probability level
(hydrogen atoms except for Ni−H are omitted for clarity).
considerable ring bending are formed through two P atoms
of the PPh2 groups and a metalated Si atom. The Ni atom is
centered in a distorted tetrahedron. The Ni1−H100 distance
(1.26(9) Å) is obviously shorter than typical values of Ni−H
bonds (1.30−1.70 Å),8 while the Ni1−Si1 distance (2.235(2)
Å) is relatively long among known NiII−SiR3 bonds (2.14−2.30
Å)10 but shorter than that of a η2(Si−H)NiII complex (2.348 Å)
reported by Shimada10a and a η2(Si−H)Ni0 complex
(2.2782(4) Å) reported by Iwasawa.6f The Si1−Ni1−H100
angle is 52(4)°. The Si1−H100 distance (1.77(9) Å) is much
longer than that (∼1.5 Å) in the parent silane and (1.62(3) Å)
in the η2(Si−H)Ni0 complex reported by Iwasawa.6f In
addition, this distance is also among the typical values of
previously reported η2(Si−H) metal complexes (1.6−1.9 Å).10
Ni1−P3 (2.163(2) Å) is longer than Ni1−P1 (2.147(2) Å) and
Ni1−P2 (2.137(2) Å) due to the trans influence of the silyl
group, while the difference between Ni1−P1 and Ni1−P2 may
be caused by the packing effects in the crystal cell.
Inspired by the work on Si−H or Si−Cl bond activation via
[R-PSiP]Pt complexes with hydridochlorosilanes by Turculet,5e
we found that it is difficult for complex 2 to cleave the Si−H
bond by reaction with Et3SiH or PhMe2SiH because the
hydrogen atoms in both reactants are more electronegative. In
fact, complex 2 did react with 1 equiv of Me3SiCl or MeHSiCl2
to form the nickel(II) complex [PSiP]Ni(Cl)(PMe3) (3) in a
yield of 40% (Scheme 1). In like manner, other pincer nickel
halide complexes, [PSiP]Ni(Br)(PMe3) (4) and [PSiP]Ni(I)-
(PMe3) (5), could be obtained bt the reactions of 2 with EtBr
and MeI in THF.
Similar to the research reported by the Iwasawa group,6 we
obtained a η2(Si−H)Ni0 complex. Unlike the traditional metal
hydride complex, the resonance of the H atom of the
coordinated Si−H bond linked to the Ni atom was shifted
downfield (δ −3.71 ppm), which is coupled with three
phosphorus atoms (td, JHP = 31.4, 14.3 Hz) and with the
methyl protons (q, JHH = 2.0 Hz), while the related resonance
of η2(Si−H)Ni(PPh3) reported by the Iwasawa group6f is at δ
−2.90 ppm with both 31P−1H coupling (td, JHP = 29.9, 15.8
1
Hz) and H−1H coupling with SiCH3 (q, JHH = 1.3 Hz). The
reason for this difference may be due to the smaller steric
effects and strong coordination ability of PMe3. Moreover, a
strong absorption at 1721 cm−1 can be observed in the IR
spectrum. This can be identified as a typical vibration
absorption peak of a Ni−H bond, which is close to the value
for the Ni−H bond in similar [PCP]NiH complexes.8a
Furthermore, the signals of the Si−H bond of 1 disappeared
on monitoring by the 1H NMR spectrum (δ 6.11 ppm) and IR
spectrum (ν(Si−H) 2143 cm−1). This change indicated that the
Si−H bond was activated. In addition, the 29Si resonance of
complex 2 appears at δ 13.77 ppm (dt, JSiP = 82.0 and 3.3 Hz)
Complex 4 or 5 was isolated as red blocklike crystals from
diethyl ether at −30 °C. The mechanism likely begins with
1
in C6D6 at 296 K by 29Si{1H} NMR. The JSiH coupling
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cleavage of the C−X (X = Br, I) bond of EtBr or MeI and
oxidative addition of the Si−H bond at the Ni(0) center to
afford an intermediate Ni(IV) complex.11 This Ni(IV) species
is not stable and delivers complex 4 or 5 with the escape of a
molecule of ethane or methane, detected by in situ 1H NMR via
reductive elimination. Similar reactions were reported by
Tanaka.10a,b
X-ray crystallography confirmed that complexes 3−5 have a
trigonal-bipyramidal coordination geometry (Figures 2−4)
Figure 4. ORTEP plot of complex 5 at the 50% probability level
(hydrogen atoms are omitted for clarity).
Table 1. Selected Bond Distances (Å) and Angles (deg) of
Complexes 2−5
bond distance or
angle
2 (X = H) 3 (X = Cl) 4 (X = Br) 5 (X = I)
Ni1−X1
Ni1−Si1
Ni1−P1
Ni1−P2
1.26(9)
2.235(2)
2.147(2)
2.137(2)
2.163(2)
115.79(9)
147.23(9)
52(4)
2.379(2)
2.283(2)
2.165(2)
2.219(2)
2.257(2)
123.29(7)
170.26(7)
84.15(6)
87.81(7)
2.525(1)
2.298(2)
2.229(2)
2.180(2)
2.264(2)
122.77(7)
170.22(8)
83.62(6)
88.30(7)
2.628(1)
2.292(2)
2.169(2)
2.207(2)
2.254(2)
123.48(6)
172.48(7)
83.87(5)
89.96(5)
Figure 2. ORTEP plot of complex 3 at the 50% probability level
(hydrogen atoms are omitted for clarity).
Ni1−P3
P1−Ni1−P2
Si1−Ni1−P3
Si1−Ni1−X1
P3−Ni1−X1
95(4)
spectrum (δ −2.13 ppm for the H atom of Si−H group) and IR
spectrum (ν 1725 cm−1 for the Ni−H vibration) with a tiny
shift in comparison with those of 2. It could be concluded that
the trimethylphosphine ligand was replaced by a carbonyl
ligand because the characteristic absorption peak (ν 946 cm−1)
of PMe3 in 2 disappeared in the IR spectrum. In addition, the
phosphorus resonance (δ −15.46 ppm) of PMe3 in the 31P
NMR spectrum was absent. Furthermore, the coupling splitting
1
of the η2(Si−H) peak in the H NMR spectrum turned out to
be tq coupling (Figure 5b for 6) instead of tdq coupling (Figure
Figure 3. ORTEP plot of complex 4 at the 50% probability level
(hydrogen atoms are omitted for clarity).
formed by [P1P2X1] as the equatorial plane with Si1−Ni1−
P3 in the axial position. Table 1 suggests that the Ni−X bond
length becomes longer with an increase of the X atomic radius.
The trigonal-bipyramidal structure becomes much more
distorted on going from 3 to 5 because of steric effects and
trans influence.
The carbonyl complex 6 is readily formed by placing a THF
solution of 2 under an atmosphere of CO at room temperature
(Scheme 1). Light yellow crystals of 6 were obtained from
diethyl ether at −30 °C. The η2(Si−H)Ni structural moiety
remained in this transformation, as monitored by the 1H NMR
Figure 5. Hydrido resonances of complexes 2 (a) and 6 (b).
5a for 2) owing to the loss of the P−H coupling with the P
2
atom of PMe3. This shows that the couplings J(Pmethyl,H) =
14.3, 2J(Pphenyl,H) = 34.1, and 3J(Simethyl,H) = 2.0 Hz in
complex 2 shifted to 2J(Pphenyl,H) = 25.1 and 3J(Simethyl,H) = 1.9
Hz in complex 6. In comparison to PMe3, CO has a strong
coordination capability due to the smaller steric hindrance and
π-back-bonding formation. It is considered that the weaker
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electron-donating ability of CO and the decrease in the electron
cloud density of the nickel center make the coupling constants
smaller. The 29Si{1H} NMR exhibited the Si atom resonance at
δ 7.40 ppm with 29Si−1H coupling (d, 1JSiH = 104.8 Hz), which
was shifted upfield in comparison to that of complex 2 (δ 13.71
Scheme 3. Preparation of Silyl Nickel Complexes 9 and 10
1
ppm). This difference in JSiH might be due to the strong
1
coordination of the carbonyl ligand. The relatively larger JSiH
value suggests that back-donation from the metal center to the
σ* orbital of the Si−H bond in this complex is weak.
Complex 3 could also be synthesized as red crystals in over
50% yield by reaction of the simple inorganic salt NiCl2 with
ligand 1 in the presence of PMe3 via Si−H bond activation
from diethyl ether at −30 °C (Scheme 2). In addition, complex
3 was the major product of the reactions of 1 with
NiCl2(PMe3)2 and NiMeCl(PMe3)2 in THF.
Scheme 2. Preparation of Silyl Nickel Complexes 7 and 8
Scheme 4. Proposed Formation Mechanism of Complex 9
pentane extract solution and confirmed by IR.13 The related
reactions for Pd and Pt were discussed by Shiro and Schubert.14
To collect accurate structural information on complex 9, CO
was imported into the solution of 9. The solution turned light
yellow quickly. Complex 10 as pale yellow crystals was obtained
from diethyl ether at −30 °C (Scheme 3).
To explore the reactivity of complex 3, 3 was treated with
NaOMe in THF to give the methoxy complex 7. Complex 7
was isolated as red crystals in a yield of 65% from pentane.
Unfortunately, no single crystals of 7 suitable for XRD were
obtained. However, the NMR spectra of 7 clearly exhibited the
resonance of the hydrogen of the methoxy group at 3.45 ppm
and the resonance of the carbon of the methoxy group at 49.6
ppm.
The carbonyl complex 8 was formed by placing a THF
solution of 3 under an atmosphere of CO at room temperature
for 14 h. Two strong stretching absorptions at 2007 and 1938
cm−1 could be observed in the IR spectrum of 8, which were
identified as the signals of two terminal carbonyl ligands in
asymmetric positions. The NMR spectra also confirmed the
formation of complex 8. Complex 8 is a hex-coordinate
nickel(II) complex with 20 valence electrons.12
The reaction of 1 with 1 equiv of NiMe2(PMe3)3 in THF
afforded the unexpected tetracoordinate bis-chelate nickel(0)
complex 9 (Scheme 3). The mechanism (Scheme 4) may begin
with Si−H bond cleavage. The oxidative addition of the Si−H
bond at the Ni(II) center affords a Ni(IV) intermediate. This
Ni(IV) intermediate is not stable and releases a molecule of
methane via reductive elimination to form intermediate 9A.
The migration of the Ni−methyl of 9A from nickel to the Si
atom by reductive elimination causes the reduction of nickel(II)
to nickel(0) species 9B. The ligand exchange between two
molecules of 9B delivers the formation of complex 9.
Ni(PMe3)4 as the second product was isolated from the
The molecular configuration of complex 10 was confirmed
by X-ray single crystal diffraction (Figure 6). The nickel(0)
center is coordinated with two phosphorus atoms of the [PSiP]
ligands and two carbon monoxide molecules. The nickel has a
tetrahedral geometry. The C7−Ni1−C8 (106.6(3)°), C7−
Ni1−P1 (114.9(2)°), C8−Ni1−P1 (108.8(2)°), C7−Ni1−P2
(115.4(2)°), C8−Ni1−P2 (101.4(2)°), and P1−Ni1−P2
angles (108.64(6)°) are typical (109.5°) for a distorted
tetrahedron. Two methyl groups are linked to the Si atom.
The Ni1−Si1 distance (3.82(2) Å) is much longer than those
of the known Ni−Si bonds (2.14−2.30 Å).6f,10 This means that
there is no bond interaction between these two atoms. The
result indicates that CO as a strong σ,π ligand substitutes one
[PSiP] ligand of complex 9 to form complex 10. This can be
regarded as collateral evidence of the existence of 9B in the
mechanism of formation of 9. In other words, there is an
equilibrium between 9B and 9.
In order to prepare hydrido nickel complex 2A, NaBH4 was
used to reduce complex 3. However, instead of complex 2A,
complex 2 was isolated (Scheme 5). The reaction mechanism
probably goes through intermediate 2A. 2A transforms to the
η2(Si−H)Ni0 complex 2 via reductive elimination, as 2A may be
thermodynamically unstable.
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Si−Ni−H angle of 172.95°. The three P atoms form a triangle
with angles of 122.54, 117.98, and 119.19°. The optimized
structure of 2DFT is almost the same as the crystal structure of 2,
although the Ni−H bond distance (1.5969 Å) is longer and the
Si−Ni−H angle (43.86°) is smaller. The result indicates that
2
DFT is more stable than 2A by 5.20 kcal/mol. This is consistent
with the experimental results.
2. Synthesis and Reactivity of Silyl Cobalt Complexes.
Encouraged by the results of silyl nickel complexes, the reaction
of Co(PMe3)4 with 1 was studied and delivered hydrido
cobalt(II) complex 11 as a yellow powder from diethyl ether at
0 °C (Scheme 6). Complex 11 was produced via Si−H
Scheme 6. Preparation of Silyl Cobalt Complexes 11 and 12
Figure 6. ORTEP plot of complex 10 at the 50% probability level
(hydrogen atoms are omitted for clarity). Selected bond lengths (Å)
and angles (deg): Ni1−Si1 = 3.82(2), Ni1−C7 = 1.753(7), Ni1−C8 =
1.770(7), Ni1−P1 = 2.242(2), Ni1−P2 = 2.254(2); C7−Ni1−C8 =
106.8(3), C7−Ni1−P1 = 114.9(2), C8−Ni1−P1 = 108.8(2), C7−
Ni1−P2 = 115.4(2), C8−Ni1−P2 = 101.4(2), P1−Ni1−P2 =
108.64(6).
oxidative addition and has a typical ν(Co−H) stretching band
1
at 1916 cm−1 in the IR spectrum. The H NMR spectrum
exhibits the resonance of the hydrido ligand at −14.04 ppm as a
quartet with an H−P coupling constant of 61.5 Hz.
Unfortunately, no single crystals of 11 suitable for X-ray
crystallography could be obtained by recrystallization from
pentane, diethyl ether, or toluene solution. The 31P NMR data
of 11 clearly show one signal (δ 68.2 ppm) for the two trans-
diphenylphosphinyl groups and a multiplet (δ −8.5 ppm) for
trimethylphosphine. Complex 11 probably has a trigonal-
bipyramidal geometry, and the cobalt atom is coordinated with
two five-membered metallacycles, one H atom, and one
trimethylphosphine ligand.
Scheme 5. Reduction of Complex 6 with NaBH4
Furthermore, to compare the structures and relative stability
of complexes 2A and 2, theoretical calculations were carried out
using DFT with the B3LYP functional. The optimized
structures of 2A and 2 are shown in Table 2. 2ADFT exhibits
a trigonal-bipyramidal configuration with P1−P2−P3 as the
equatorial plane and Si1−Ni1−H in the axial direction. The H
atom is almost in a trans position opposite the Si atom with a
Complex 11 was treated with CH3I in THF. After workup
complex 12 was isolated as orange crystals from diethyl ether at
−30 °C (Scheme 6). In this transformation hydrido cobalt(II)
complex 11 turns out to be the hydrido cobalt(III) complex 12,
which is a very stable cobalt(III) species and does not
spontaneously eliminate HI to form a cobalt(I) complex. The
ν(Co−H) stretching band of complex 12 was observed at 1927
1
cm−1 in the IR spectra. The H NMR spectrum of 12 in
Table 2. Optimized Structures of 2A and 2 using DFT with
benzene-d6 confirmed the presence of the hydride ligand at
−14.67 ppm. The reaction mechanism from 11 to 12 probably
goes through a radical reaction process. The homolytic cleavage
of iodomethane produces iodine radical and methyl radical.
The iodine radical addition to the cobalt(II) center of complex
11 produces complex 12 with a cobalt(III) center. Two methyl
radicals combine to form one molecule of ethane. In this
process the pentacoordinate 17-electron cobalt(II) complex 11
transforms to the hexacoordinate 18-electron cobalt(III)
species 12. The formation of ethane was confirmed by an in
the B3LYP Functional [6-31G*]
15
1
situ H NMR spectrum with a chemical shift of 0.88 ppm.
The molecular configuration of complex 12 was confirmed
by single-crystal XRD as an octahedral structure (Figure 7) with
a Co center and [P1P2P3H100] in the equatorial plane and
Si1−Co1−I1 in the axial direction. The cobalt atom is
coordinated with two five-membered metallacycles, one
trimethylphosphine, and one iodide atom as well as one H
atom in a distorted-octahedral geometry. Owing to the trans
influence the iodine atom is situated in the position trans to the
Si atom while the PMe3 ligand occupies the location opposite
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Figure 7. ORTEP plot of complex 12 at the 50% probability level
(hydrogen atoms except for Co−H are omitted for clarity).
Figure 8. ORTEP plot of complex 13 at the 50% probability level
(hydrogen atoms except for Co−H are omitted for clarity).
the H atom. The Co1−H100 distance (1.40(4) Å) is very close
to those of the known Co−H bonds (1.40−1.50 Å).16 The
Si1−H100 distance (2.406 Å) is much longer than that (∼1.5
Å) in the parent silane and that (1.89(1) Å) in the η2(Si−
H)Ni0 complex 2. This means that there is no bonding
interaction between Si1 and H100. Complex 12 is a classic
metal hydride complex.
The hydrido cobalt(III) chloride 13, a derivative of hydrido
cobalt(III) iodide 12, could be obtained through the reaction of
1 with CoCl(PMe3)3 in THF (Scheme 7). Complex 13 could
Table 3. Selected Bond Distances (Å) and Angles (deg) of
Complexes 12, 13, and 15
bond distance or angle
12 (X = I)
13 (X = Cl)
15 (X= Cl)
Co1−H100
Co1−X1
Co1−Si1
Co1−P1
Co1−P2
1.40(4)
1.52(2)
2.6749(7)
2.256(1)
2.183(1)
2.193(1)
2.247(1)
141.01(5)
91.43(4)
174.10(4)
94.47(4)
2.410(1)
2.252(2)
2.188(1)
2.188(1)
2.259(2)
147.09(7)
93.76(7)
173.38(7)
92.85(6)
2.275(1)
2.259(1)
2.160(1)
2.200(1)
2.230(1)
111.24(5)
173.89(5)
86.22(5)
89.52(5)
Co1−P3
P1−Co1−P2
Si1−Co1−P3
Si1−Co1−X1
P3−Co1−X1
Scheme 7. Preparation of Silyl Cobalt Complexes 12−15
of complexes 12 and 13. This indicates that the Co−H bond in
complex 12 is stronger than that in complex 13.
A substitution of a chlorine by an iodine ligand was observed
through the reaction of complex 13 with CH3I in THF
(Scheme 7). We tried to prepare alkyl pincer cobalt complexes
via the reaction of complex 13 with alkylating agents. The
treatments of 13 with 1 equiv of MeLi or n-BuMgBr resulted in
the clean formation of the new silyl Co(I) complex 14. The
expected alkyl pincer cobalt complex was not isolated. This may
be caused by the instability of the expected hydrido alkyl pincer
1
cobalt complex. The PMe3 signals of complex 14 in the H
NMR (δ 0.79 and 1.19 ppm) and 31P NMR spectra (δ −17.48
and 4.00 ppm) clearly indicate that the two trimethylphosphine
ligands are not in the same chemical environment. The
molecular structure could be a trigonal-bipyramidal geometry,
in which the two PMe3 ligands are in asymmetric positions.
One is in the position opposite to the Si atom (axial position),
and the other is coplanar with the two P atoms of the [PSiP]
ligand.
In the presence of PMe3 the reaction of anhydrous CoCl2
with 1 in THF afforded complex 15 as red blocklike crystals.
The IR spectrum of 15 indicated that the Si−H bond vibration
absorption (ν 2143 cm−1) of 1 disappeared. A strong
absorption at 934 cm−1 was identified as the characteristic
absorption peak of PMe3. Complex 15, as a cobalt(II) species,
is paramagnetic and no reasonable spectra were available,
despite the attempts made. The structure of complex 15 was
crystallize from diethyl ether at −30 °C. In the IR spectrum of
13 a typical ν(Co−H) absorption at 1910 cm−1, less than that
1
of 12, was found. Meanwhile, the H NMR spectrum of 13
revealed the resonance of the hydrogen of the Co−H bond at
−13.68 ppm. This signal is shifted downfield in comparison
with that (−14.67 ppm) in 12. This difference is probably
caused by the larger inductive effect of the Cl atom in
comparison with that of the I atom. Single-crystal X-ray
diffraction analysis confirmed that 13 has an octahedral
coordination geometry (Figure 8). In comparison with that of
12, the Co−H bond distance is longer (Table 3). This result is
consistent with inference from the data of the infrared spectra
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confirmed by X-ray diffraction analysis. The cobalt atom is
coordinated with two five-membered metallacycles, one
trimethylphosphine, and one chloride atom in a distorted-
trigonal-bipyramidal geometry (Figure 9). The chelate rings are
Figure 10. ORTEP plot of complexes 16 at the 50% probability level
(hydrogen atoms except for Fe−H are omitted for clarity). Selected
bond lengths (Å) and angles (deg): Fe1−H1 = 1.55(4), Fe1−Si1 =
2.331(1), Fe1−P1 = 2.214(1), Fe1−P2 = 2.222(1), Fe1−P3 =
2.276(1), Fe1−P4 = 2.263(2); P4−Fe1−H1 = 168(1), P3−Fe1−Si1 =
169.16(5), P1−Fe1−P2 = 148.67(6), Si1−Fe1−H1 = 76(1), Si1−
Fe1−P4 = 92.57(5), P1−Fe1−P3 = 95.53(5), P2−Fe1−P3 =
95.01(5), P4−Fe1−P3 = 98.26(6).
Figure 9. ORTEP plot of complex 15 at the 50% probability level
(hydrogen atoms are omitted for clarity).
plane. The Fe1−H1 distance (1.55(4) Å) is slightly longer than
a normal Fe−H bond (∼1.42 Å).17 The Fe−P3 distance
(2.276(1) Å) is longer than the Fe−P4 distance (2.263(2) Å),
presumably due to the trans influence of the Si atom being
greater than that of the H atom, while both distances are longer
than the normal Fe1−P1 (2.214(1) Å) and Fe1−P2 distances
(2.222(1) Å), owing to the weaker trans influence of the
phosphorus atom.
almost perpendicular to each other. The axial angle of P3−
Co1−Si1 is 173.89(5)°, deviating from 180°. The methyl
groups of the phosphine ligand are oriented in a staggered
conformation with respect to the three coordinated atoms in
the triangular plane [P1P2Cl1], to decrease the repulsion
among them, while the staggered conformation between the
silyl group and the three coordinated atoms (P1P2Cl1) is
strongly distorted because of the formation of the pincer
geometry and the six crowded phenyl groups. Co1−P3
(2.230(1) Å) is longer than Co1−P1 (2.160(1) Å) and
Co1−P2 (2.200(1) Å) due to the trans influence of the silyl
group, while the difference between Co1−P1 and Co1−P2 may
be caused by the packing effects in the crystal cell.
4. Catalytic Activity of the Hydrido Iron Complex 16.
The metal hydride complexes are fundamentally important for
their crucial roles in a wide variety of TM catalytic systems.18
Recently, there has been considerable interest in developing
iron-catalyzed hydrosilylation of aldehydes and ketones.17,19 At
the beginning of this catalytic exploration, complex 16 was used
as the catalyst to reduce the five selected aldehydes and ketones
(Table 4). It was found that complex 16 could catalytically
reduce aldehydes and ketones efficiently with triethoxysilane as
a hydrogen source under mild conditions (Scheme 9).
The catalytic result suggests that benzaldehyde and furfural
exhibit good activity. With benzaldehyde as substrate benzyl
alcohol could be obtained in a yield of 100% after 1h (entry 1,
Table 4) while furfuryl alcohol was produced in the yield of
92% during the same time (entry 3, Table 4). 4-
Methoxybenzaldehyde with an electron-donating group on
the phenyl ring required a longer reaction time until complete
conversion (entry 2, Table 4). Entries 4 and 5 show that
complex 16 also has good catalytic activity in the reduction of
aryl ketone and aliphatic ketone. Expansion of the scope of
substrates and reaction mechanism studies will be reported in
follow-up work from our laboratory.
3. Synthesis and Reactivity of Silyl Iron Complexes.
When 1 was treated with 1 equiv of Fe(PMe3)4 in toluene, the
solution turned dark red-brown after 14 h (Scheme 8).
Scheme 8. Preparation of Silyl Iron Complex 16
Complex 16 was isolated as orange crystals from diethyl
ether. The typical ν(Fe−H) stretching band was found at 1870
cm−1 in the IR spectrum. The characteristic hydride signal as a
td peak was found at −17.09 ppm with both 31P−1H coupling
constants (JHP = 71.4, 18.1 Hz) in the 1H NMR spectrum of 16.
Two signals (δ 0.53 and 0.98 ppm) for the PMe3 ligands in the
1H NMR spectrum clearly indicate that the trimethylphosphine
ligands are not chemically identical. X-ray crystallography
confirmed a distorted hexacoordinate octahedral structure of 16
(Figure 10). The axial angle P1−Fe1−P2 is 148.67(6)°, greatly
deviating from 180°. [Si1Fe1P3P4H1] are in the equatorial
CONCLUSION
■
A study of the reactions of the tridentate pincer-type ligand
bis(o-(diphenylphosphino)phenyl)methylsilane with electron-
rich low-valent iron, cobalt, and nickel complexes supported by
trimethylphosphine ligands has been carried out. The synthesis
and characterization of a series of nickel, cobalt, and iron
complexes bearing tridentate bis(phosphino)silyl ligands (κ3-
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Table 4. Catalytic Reduction on Unsaturated Bonds with 16
a
Reaction conditions: substrate (1.0 mmol), (EtO)3SiH (1.5 mmol), complex 16 (0.010 mmol) in 2.5 mL of THF and n-dodecane as internal
standard.
Bubbles from the solution could be seen clearly, and the solution
Scheme 9. Catalytic Reduction of Aldehydes
turned brown. After removal of the solvents the residue was extracted
with diethyl ether. Complex 2 (0.27 g, 0.39 mmol) was isolated as
yellow powder in 46% yield at −30 °C. Mp: > 177 °C dec. Anal. Calcd
for C40H41NiP3Si (701.42 g/mol): C, 68.49; H, 5.84. Found: C, 68.75;
H, 6.01. IR (Nujol, KBr): 3038 (ArH), 1721 (η2(Ni−H)), 1583
1
(ArCC), 947 (PMe3) cm−1. H NMR (300 MHz, benzene-d6, 300
(2-Ph2PC6H4)2SiMeH, [PSiP]-H, 1) have been reported via the
K, ppm): δ −3.71 (tdq, J = 31.4, 14.3, 2.0 Hz, NiH, 1H), 0.99 (d, J =
activation of Si−H bonds. The preparation and isolation of
5.9 Hz, PMe3, 9H), 1.37 (d, J = 1.9 Hz, SiMe, 3H), 6.88 (t, J = 7.4 Hz,
η2(Si−H)M and [Si−M−H] complexes were achieved. The
Ar, 4H), 6.95−7.10 (m, Ar, 10H), 7.15 (td, J = 7.2, 4.5 Hz, Ar, 6H),
properties of these hydrido metal complexes were investigated.
At the same time, several corresponding halogenated nickel and
cobalt complexes were obtained in a survey of reactivity.
Further studies showed that the metal hydride complexes could
be used as catalysts in the reduction of aldehydes and ketones.
7.39 (d, J = 7.6 Hz, Ar, 2H), 7.78 (dt, J = 10.6, 4.0 Hz, Ar, 4H), 8.05
(d, J = 7.3 Hz, Ar, 2H) ppm. 31P{1H} NMR (121 MHz, benzene-d6,
300 K, δ): −15.5 (s, PMe3, 1P), 48.5 (s, PPh2, 2P) ppm. 13C NMR (75
MHz, benzene-d6, 300 K, δ): 5.0 (m, SiCH3), 21.3 (m, PMe3), 126.6
(s, Ar), 127.0−127.6 (m, Ar), 128.0 (s, Ar), 130.8 (s, Ar), 131.5 (m,
Ar) 131.7 (m, Ar) 131.8 (s, Ar) ppm. 29Si NMR (79.5 MHz, benzene-
d6, 296 K, δ): 13.71 (dt, J = 82.0, 3.3 Hz, 1H-decoupled); (tt, J = 82.0,
82.0, 3.3 Hz, non-1H-decoupled) ppm.
EXPERIMENTAL SECTION
■
General Procedures and Materials. Standard vacuum techni-
ques were used in the manipulations of volatile and air-sensitive
materials. Solvents were dried by known procedures and distilled
under nitrogen before use. The compounds (2-Ph2PC6H4)2SiH-Me,5a
Ni(PMe3)4,20a NiCl2(PMe3)2,20b NiMeCl(PMe3)2,20c Ni-
Me2(PMe3)3,20c Co(PMe3)4,20d CoCl(PMe3)3,20e Fe(PMe3)4,20f and
(EtO)3SiH20g were prepared according to literature procedures.
Infrared spectra (4000−400 cm−1), as obtained from Nujol mulls
between KBr disks, were recorded on a Bruker ALPHA FT-IR
instrument. NMR spectra were recorded using Bruker Avance 300 and
400 MHz spectrometers. GC-MS was recorded on a TRACE-DSQ
instrument, and GC was recorded on a Fuli 9790 instrument. X-ray
crystallography was performed with a Bruker Smart 1000 diffrac-
tometer. Melting points were measured in capillaries sealed under N2
and were uncorrected. Elemental analyses were carried out on an
Elementar Vario ELIII instrument.
Synthesis of [PSiP]Ni(Cl)(PMe3) (3). (a) One equivalent of
Me3SiCl or MeHSiCl2 was added to a solution of complex 2 (0.55 g,
0.78 mmol) in 50 mL of THF at 0 °C, and the mixture was then
stirred at room temperature for 6 h. After removal of the solvent under
reduced pressure, the residue was extracted with pentane and diethyl
ether. Compound 3 was isolated as red blocklike crystals in 40% yield
from diethyl ether at −30 °C.
(b) (2-Ph2PC6H4)2SiH-Me (1; 1.20 g, 2.12 mmol) in 30 mL of
THF was combined with NiMeCl(PMe3)2 (0.60 g, 2.31 mmol) in 20
mL of THF with stirring at room temperature for 14 h. After workup
compound 3 (1.08 g, 1.47 mmol) was isolated as red crystals in 69%
yield from diethyl ether at 0 °C.
(c) Compound 1 (0.83 g, 1.45 mmol) in 30 mL of THF was
combined with NiCl2(PMe3)2 (0.41 g, 1.45 mmol) in 20 mL of THF
with stirring at room temperature for 14 h. After workup complex 3
(0.66 g, 0.90 mmol) was isolated as a red powder in 62% yield from
diethyl ether at 0 °C.
Caution! (EtO)3SiH is flammable and highly toxic by inhalation and
may cause skin irritation and blindness.
Synthesis of η2(Si−H)[PSiP]Ni(PMe3) (2). (a) (κ3-(2-
Ph2PC6H4)2SiMeH (1; 1.20 g, 2.12 mmol) in 30 mL of THF was
combined with Ni(PMe3)4 (0.81 g, 2.23 mmol) in 20 mL of THF with
stirring at room temperature for 14 h. The reaction mixture turned
yellow, and a small amount of yellow powder precipitated. After
removal of the volatiles under reduced pressure the residue was
extracted with pentane and diethyl ether. Compound 2 (1.13 g, 1.61
mmol) was isolated as yellow crystals in 76% yield from diethyl ether
at 0 °C.
(d) Compound 1 (0.82 g, 1.45 mmol) in 30 mL of THF was treated
with anhydrous NiCl2 (0.19 g, 1.45 mmol) in 20 mL of THF. The
reaction mixture turned yellow, and a yellow powder precipitated. The
solution turned red after addition of PMe3 (0.15 g, 2.00 mmol).
Complex 3 (0.62 g, 0.84 mmol) could be obtained as a red powder in
58% yield. Mp: > 163 °C dec. Anal. Calcd for C40H40ClNiP3Si (735.88
g/mol): C, 65.28; H, 5.48. Found: C, 65.61; H, 5.61. IR (Nujol, KBr):
3046 (ArH), 1584 (ArCC), 949 (PMe3) cm−1. 1H NMR (300 MHz,
benzene-d6, 300 K, δ): 0.81 (d, J = 6.0 Hz, PCH3, 9H), 1.29 (d, J = 1.2
Hz, SiCH3, 3H), 6.93−7.21 (m, Ar, 24H), 7.61 (m, Ar, 2H), 8.42 (dd,
J = 9.0 and 27.0 Hz, Ar, 2H) ppm. 31P{1H} NMR (121 MHz, benzene-
d6, 300 K, δ): −16.9 (t, J = 28.6 Hz, PMe3, 1P), 34.6 (d, J = 28.7 Hz,
(b) NaBH4 (0.08 g, 2.11 mmol) was added to a solution of complex
3 (0.62 g, 0.84 mmol) in 50 mL of THF with stirring at room
temperature. A few drops of methanol were added to this mixture.
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PPh2, 2P) ppm. 13C NMR (75 MHz, benzene-d6, 300 K, δ): 3.7 (s,
SiCH3), 29.9 (s, PCH3), 128.5 (m, Ar), 128.8 (m, Ar), 129.6 (m, Ar),
130.9 (s, Ar), 131.7−132.1 (m, Ar), 132.3 (dd, J = 10.6, 5.4 Hz, Ar),
132.9 (m, Ar), 133.3 (m, Ar), 134.5 (t, J = 7.2 Hz, Ar), 137.1−137.6
(m, Ar), 139.4 (s, Ar) ppm.
SiCH3, 3H), 1.00 (d, J = 4.8 Hz, PCH3, 9H), 3.45 (s, OCH3, 3H),
6.90−7.24 (m, Ar, 22H), 7.80 (m, 4H), 8.46 (d, J = 7.2 Hz, Ar, 2H)
ppm. 31P{1H} NMR (121 MHz, benzene-d6, 300 K, δ): −29.8 (t, J =
23.3 Hz, PMe3, 1P), 26.3 (d, J = 23.3 Hz, PPh2, 2P) ppm. 13C NMR
(75 MHz, benzene-d6, 300 K, δ): 14.0 (s, SiCH3), 20.1 (dt, J = 16.6,
5.0 Hz, PCH3), 49.6 (s, OCH3), 127.2 (s, Ar), 127.3−128.4 (m, Ar),
131.7 (s, Ar), 132.7 (t, J = 6.6 Hz, Ar), 133.2 (t, J = 7.8 Hz, Ar), 135.7
(t, J = 9.8 Hz, Ar), 138.3−137.7 (m, Ar), 141.7 (t, J = 18.2 Hz, Ar),
147.6−145.9 (m, Ar) ppm.
Synthesis of [PSiP]Ni(Cl)(CO)2 (8). A sample of complex 3 (0.62
g, 0.84 mmol) in 50 mL of THF was stirred under 1 bar of CO at
room temperature for 14 h. Complex 8 (0.37 g, 0.53 mmol) was
isolated as a yellow powder from diethyl ether in a yield of 63%. Mp: >
215 °C dec. Anal. Calcd for C39H31ClNiO2P2Si (715.88 g/mol): C,
65.43; H, 4.36. Found: C, 65.72; H, 4.21. IR (Nujol, KBr): 3045
(ArH), 2007 (CO), 1938 (CO), 1584 (ArCC) cm−1. 1H NMR (300
MHz, benzene-d6, 300 K, δ): 0.57 (s, SiCH3, 3H), 6.65 (d, J = 7.8 Hz,
Ar, 2H), 6.80−7.10 (m, Ar, 16H), 7.29 (m, Ar, 4H), 7.48 (d, J = 7.2
Hz, Ar, 2H), 7.65 (m, Ar, 4H) ppm. 31P{1H} NMR (121 MHz,
benzene-d6, 300 K, δ): 31.8 (s, PPh2) ppm. 13C NMR (75 MHz,
benzene-d6, 300 K, δ): 1.8 (s, SiCH3), 128.4−128.6 (m, Ar), 129.2 (s,
Ar), 133.0 −133.6 (m, Ar), 136.3−136.7 (m, Ar), 143.2 (s, Ar), 188.0
(s, CO), 203.5 (s, CO) ppm.
Synthesis of [PSiP]Ni(Br)(PMe3) (4). EtBr (0.11 g, 1.0 mmol) was
added to a solution of complex 2 (0.55 g, 0.78 mmol) in 50 mL of
THF at 0 °C The mixture was stirred and refluxed for 3 h. After
removal of the solvent under reduced pressure, the residue was
extracted with pentane and diethyl ether. Compound 4 (0.23 g, 0.29
mmol) was isolated as red blocklike crystals in 37% yield from diethyl
ether at −30 °C. Mp: > 186 °C dec. Anal. Calcd for C40H40BrNiP3Si
(780.34 g/mol): C, 61.56; H, 5.17. Found: C, 61.31; H, 5.09. IR
1
(Nujol, KBr): 3045 (ArH), 1583 (ArCC), 948 (PMe3) cm−1. H
NMR (300 MHz, benzene-d6, 300 K, δ): 0.83 (d, J = 7.4 Hz, PMe3,
9H), 1.31 (d, J = 1.3 Hz, SiCH3, 3H), 6.95−7.23 (m, Ar, 22H), 7.64
(d, J = 7.2 Hz, Ar, 2H), 8.43 (dd, J = 5.1 and 12.0 Hz, Ar, 4H) ppm.
31P{1H} NMR (121 MHz, benzene-d6, 300 K, δ): −16.9 (t, J = 28.2
Hz, PMe3, 1P), 34.6 (d, J = 28.7 Hz, PPh2, 2P) ppm. 13C NMR (75
MHz, benzene-d6, 300 K, δ): 5.8 (s, SiCH3), 26.6 (s, P CH3), 126.9 (s,
Ar), 128.6−128.8 (m, Ar), 129.1 (s, Ar), 129.6 (s, Ar), 130.5 (s, Ar),
131.0 (s, Ar), 131.9 (s, Ar),132.5 (s, Ar), 132.6 (t, J = 5.6 Hz, Ar),
132.7 (s, Ar), 132.6 (s, Ar), 133.2 (s, Ar), 134.3 (s, Ar), 134.4 (t, J =
7.0 Hz, Ar), 134.5 (s, Ar) ppm.
Synthesis of [Me2PSiP]2Ni (9). Compound 1 (0.82, 1.45 mmol)
in 30 mL of THF was combined with Me2Ni(PMe3)3 (0.46 g, 1.45
mmol) in 20 mL of THF with stirring at room temperature for 14 h.
Compound 9 (0.48 g, 0.40 mmol) was isolated as an orange powder in
55% yield from pentane. Mp: > 145 °C dec. Anal. Calcd for
C76H68NiP4Si2 (1219.59 g/mol): C, 74.85; H, 5.62. Found: C, 75.02;
Synthesis of [PSiP]Ni(I)(PMe3) (5). MeI (0.22 g, 1.51 mmol) was
added to a solution of complex 2 (0.75 g, 1.06 mmol) in 50 mL of
THF at 0 °C. The mixture was stirred for 14 h at room temperature.
After removal of the solvent under reduced pressure, the residue was
extracted with pentane and diethyl ether. Compound 5 (0.53 g, 0.64
mmol) was isolated as red blocklike crystals in 60% yield from diethyl
ether at −30 °C. Mp: > 186 °C dec. Anal. Calcd for C40H40INiP3Si
(827.33 g/mol): C, 58.07; H, 4.87. Found: C, 57.91; H, 4.61. IR
1
H, 5.69. IR (Nujol, KBr): 3044 (ArH), 1583 (ArCC) cm−1. H
NMR (300 MHz, benzene-d6, 300 K, δ): 0.90 (t, J = 1.5 Hz, Si(CH3)2,
12H), 6.80−7.27 (m, Ar, 48H), 7.34 (m, Ar, 4H), 7.87 (d, J = 7.2 Hz,
Ar, 4H) ppm. 31P{1H} NMR (121 MHz, benzene-d6, 300 K, δ): −10.9
(s, PPh2) ppm. 13C NMR (75 MHz, benzene-d6, 300 K, δ): 2.8 (t, J =
10.0 Hz, Si(CH3)2), 128.8−126.9 (m, Ar), 129.2 (s, Ar), 133.5 (d, J =
18.9 Hz, Ar), 135.5 (s, Ar), 136.7 (d, J = 16.3 Hz, Ar), 138.8 (d, J =
13.1 Hz, Ar), 143.4 (d, J = 12.5 Hz, Ar), 148.3 (d, J = 47.5 Hz, Ar)
ppm.
1
(Nujol, KBr): 3050 (ArH), 1580 (ArCC), 943 (PMe3) cm−1. H
NMR (300 MHz, benzene-d6, 300 K, δ): 0.79 (d, J = 7.2 Hz, PCH3,
9H), 1.31 (d, J = 1.2 Hz, SiCH3, 3H), 6.85−7.11 (m, Ar, 22H), 7.49
(d, J = 7.2 Hz, Ar, 2H), 8.22 (dd, J = 5.1 and 11.7 Hz, Ar, 4H) ppm.
31P{1H} NMR (121 MHz, benzene-d6, 300 K, δ): −22.8 (t, J = 28.0
Hz, PMe3, 1P), 32.6 (d, J = 28.0 Hz, PPh2, 2P) ppm. 13C NMR (75
MHz, benzene-d6, 75 K, δ): 9.7 (s, SiCH3), 17.0−17.4 (m, PCH3),
126.9−127.2 (m, Ar), 128.5−128.6 (m, Ar), 129.1 (s, Ar), 129.5 (s,
Ar), 132.0 (d, J = 1.9 Hz, Ar), 133.0 (t, J = 5.6 Hz, Ar), 134.2 (t, J = 6.6
Hz, Ar), 136.8 (d, J = 3.9 Hz, Ar) ppm.
Synthesis of [Me2PSiP]Ni(CO)2 (10). A sample of complex 9
(0.50 g, 0.41 mmol) in 50 mL of THF was stirred under 1 bar of CO
at room temperature for 14 h. Complex 10 (0.33 g, 0.47 mmol) was
isolated as light yellow crystals from diethyl ether at −30 °C in a yield
of 58%. Mp: > 179 °C dec. Anal. Calcd for C40H34NiO2P2Si (695.41
g/mol): C, 69.08; H, 4.93. Found: C, 68.81; H, 5.01. IR (Nujol, KBr):
3058 (ArH), 2003 (CO), 1946 (CO), 1584 (ArCC) cm−1. 1H
NMR (300 MHz, benzene-d6, 300 K, δ): 0.44 (s, SiCH3, 6H), 6.65 (t, J
= 7.5 Hz, Ar, 2H), 6.71−6.81 (m, Ar, 2H), 6.87−7.06 (m, Ar, 14H),
7.40−7.47 (m, Ar, 2H), 7.47−7.59 (m, Ar, 8H) ppm. 31P{1H} NMR
(121 MHz, benzene-d6, 300 K, δ): 35.0 (s, PPh2) ppm. 13C NMR (75
MHz, benzene-d6, 300 K, δ): 5.9 (t, J = 10.0 Hz, SiCH3), 127.5−128.3
(m, Ar) 128.3 (s, Ar), 133.0 (d, J = 4.1 Hz, Ar), 133.4−133.8 (m, Ar),
137.5−137.9 (m, Ar), 138.3 (d, J = 2.8 Hz, Ar), 138.3 (d, J = 2.8 Hz,
Ar), 143.4 (s, Ar), 143.8 (s, Ar), 144.1 (s, Ar), 144.4 (s, Ar), 199.4 (t, J
= 4.1 Hz, CO) ppm.
Synthesis of η2(Si−H)[PSiP]Ni(CO) (6). A sample of 2 (0.65 g,
0.93 mmol) in 50 mL of THF was stirred under 1 bar of CO at room
temperature for 14 h. All volatiles were removed in vacuo. The residue
was extracted with pentane and diethyl ether. Compound 6 (0.35 g,
0.52 mmol) was isolated as pale yellow sticklike crystals in 55% yield
from diethyl ether at −30 °C. Mp: > 196 °C dec. Anal. Calcd for
C38H32NiOP2Si (653.39 g/mol): C, 69.85; H, 4.94. Found: C, 70.01;
H, 4.81. IR (Nujol, KBr): 3034 (ArH), 1990 (CO), 1726 (η2(Ni−H)),
1
1585 (ArCC) cm−1. H NMR (300 MHz, benzene-d6, 300 K, δ):
−2.13 (tq, J = 25.1, 1.9 Hz, NiH, 1H), 1.35 (d, J = 1.2 Hz, SiCH3, 3H),
6.63−7.15 (m, Ar, 20H), 7.34 (d, J = 7.8 Hz, Ar, 2H), 7.76 (d, J = 7.2
Hz, Ar, 2H), 7.86 (m, Ar, 4H) ppm. 31P{1H} NMR (121 MHz,
benzene-d6, 300 K, δ): 50.7 (s, PPh2, 2P) ppm. 13C NMR (75 MHz,
benzene-d6, 300 K, δ): 3.7 (m, SiCH3), 127.6 (s, Ar), 127.6 (s, Ar),
128.0 (s, Ar), 128.0 (s, Ar), 128.2 (s, Ar), 128.3 (s, Ar), 128.3 (s, Ar),
128.3 (s, Ar), 129.1 (s, Ar), 129.3 (s, Ar), 131.8 (t, J = 6.1 Hz, Ar),
133.0 (t, J = 8.1 Hz, Ar), 136.4−137.0 (m, Ar), 139.9−140.5 (m, Ar),
144.3−145.0 (m, Ar), 152.6−154.2 (m, Ar), 204.0 (CO, s) ppm. 29Si
NMR (79.5 MHz, benzene-d6, 297 K, δ): 7.40 (s, 1H-decoupled); (d, J
= 104.8 Hz, non-1H-decoupled) ppm.
Synthesis of [PSiP]Co(H)(PMe3) (11). Compound 1 (0.82 g, 1.45
mmol) in 30 mL of THF was combined with Co(PMe3)4 (0.52 g, 1.45
mmol) in 20 mL of THF at 0 °C. The mixture was stirred for 14 h at
room temperature. After workup, complex 11 (0.59 g, 0.84 mmol) was
isolated as a yellow powder from diethyl ether in a yield of 58%. Mp:
>142 °C dec. Anal. Calcd for C40H41CoP3Si (701.65 g/mol): C, 68.47;
H, 5.89. Found: C, 68.41; H, 5.71. IR (Nujol, KBr): 3050 (Ar−H),
1
1917 (Co−H), 1558 (ArCC), 952 (PMe3) cm−1. H NMR (300
Synthesis of [PSiP]Ni(OMe)(PMe3) (7). Complex 3 (0.62 g, 0.84
mmol) was treated with NaOMe (0.05 g, 0.92 mmol) in 50 mL of
THF with stirring at room temperature for 14 h. Compound 7 (0.39 g,
0.54 mmol) was isolated as red crystals by extraction with pentane and
diethyl ether in 65% yield. Mp: > 158 °C dec. Anal. Calcd for
C41H43NiOP3Si (731.49 g/mol): C, 67.32; H, 5.93. Found: C, 67.55;
H, 5.69. IR (Nujol, KBr): 3047 (ArH), 1584 (ArCC), 940 (PMe3)
cm−1. 1H NMR (300 MHz, benzene-d6, 300 K, δ): 0.82 (t, J = 4.5 Hz,
MHz, benzene-d6, 300 K, δ): −14.04 (q, J = 61.5 Hz, CoH, 1H), 0.64
(d, J = 7.6 Hz, PCH3, 9H), 0.82 (s, SiCH3, 3H), 7.10 (dd, J = 14.8, 7.4
Hz, Ar, 14H), 7.34 (t, J = 7.3 Hz, Ar, 2H), 7.40−7.54 (m, Ar, 2H),
7.68−7.89 (m, Ar, 4H), 8.21 (t, J = 7.3 Hz, Ar, 6H) ppm. 31P{1H}
NMR (121 MHz, benzene-d6, 300 K, δ): −8.5 (m, PMe3, 1P), 68.2
(m, PPh2, 2P) ppm. 13C NMR (75 MHz, benzene-d6, 300 K, δ): 8.2
(d, J = 4.6 Hz, SiCH3), 19.2 (d, J = 24.1 Hz, PCH3), 126.9−128.8 (m,
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Ar), 129.1−129.5 (m, Ar), 132.9 (t, J = 4.5 Hz, Ar), 133.7 (t, J = 5.0
Hz, Ar) ppm.
mmol) in 20 mL of toluene with stirring at room temperature for 24 h.
After workup, complex 16 (0.72 g, 0.93 mmol) was isolated as orange
crystals from diethyl ether in a yield of 64%. Mp: > 141 °C dec. Anal.
Calcd for C43H50FeP4Si (774.65 g/mol): C, 66.67; H, 6.50. Found: C,
66.91; H, 6.62. IR (Nujol, KBr): 3047 (Ar−H), 1870 (Fe−H), 1584
Synthesis of [PSiP]Co(H)(I)(PMe3) (12). Complex 11 (0.52 g,
0.74 mmol) in 30 mL of THF was treated with MeI (0.12 g, 0.84
mmol) in 20 mL of THF at 0 °C. The mixture was stirred for 14 h at
room temperature. After workup, complex 12 (0.28 g, 0.34 mmol) was
obtained as orange crystals from diethyl ether in a yield of 46%. Mp: >
200 °C dec. Anal. Calcd for C40H41CoIP3Si (828.56 g/mol): C, 57.98;
H, 4.99. Found: C, 58.21; H, 4.83. IR (Nujol, KBr): 3048 (Ar−H),
1
(ArCC), 939 (PMe3) cm−1. H NMR (300 MHz, benzene-d6, 300
K, δ): −17.09 (td, J = 71.4, 18.1 Hz, FeH, 1H), 0.53 (d, J = 5.1 Hz,
PCH3, 9H), 0.98 (d, J = 5.4 Hz, PCH3, 9H), 1.06 (s, SiCH3, 3H),
7.07−6.82 (m, Ar, 16H), 7.34 (t, J = 7.1 Hz, Ar, 2H), 7.55 (m, Ar,
4H), 7.76 (t, J = 3.9 Hz, Ar, 4H), 8.50 (d, J = 7.3 Hz, Ar, 2H) ppm.
31P{1H} NMR (121 MHz, benzene-d6, 300 K, δ): 5.6 (t, J = 21.8 Hz,
PMe3, 2P), 88.9 (t, J = 19.7 Hz, PPh2, 2P) ppm. 13C NMR (75 MHz,
benzene-d6, 300 K, δ): 15.3 (s, SiCH3), 29.9 (s, PCH3), 126.5−126.7
(m, Ar), 126.9−127.0 (m, Ar), 128.5−128.6 (m, Ar), 130.8 (s, Ar),
131.5−131.6 (m, Ar), 133.6 (dt, J = 4.9, 6.9 Hz, Ar), 144.1−144.2 (m,
Ar) ppm.
General Procedure for Catalytic Reduction. In a 25 mL
Schlenk tube containing a solution of 16 (7.7 mg, 0.01 mmol) in 2.5
mL of THF were added the substrates (1.0 mmol) and (EtO)3SiH
(1.5 mmol). The reaction mixture was stirred at 60 °C until there were
no substrates left (monitored by GC). The reaction was then
quenched by MeOH (1 mL) and a 10% aqueous solution of NaOH (3
mL) with vigorous stirring at 60 °C for about 1 day. The organic
product was extracted with Et2O. All products were confirmed by GC-
MS, and the yields were determined by GC with n-dodecane (1.0
mmol) as internal standard.
X-ray Structure Determinations. Intensity data were collected
on a Bruker SMART diffractometer with graphite-monochromated Mo
Kα radiation (λ = 0.71073 Å). Crystallographic data for complexes 2−
5, 10, 12, 13, 15, and 16 are summarized in the Supporting
Information. The structures were solved by direct methods and refined
with full-matrix least squares on all F2 (SHELXL-97) with non-
hydrogen atoms anisotropic. Each hydride was located directly from
the difference map and the position refined. The remaining H atoms
were either located or calculated and subsequently treated with a
riding model. CCDC-914016 (2), CCDC-914017 (3), CCDC-914018
(4), CCDC-914019 (5), CCDC-914011 (10), CCDC-914012 (12),
CCDC-914013 (13), CCDC-914014 (15), and CCDC-914015 (16)
contain supplementary crystallographic data for this paper. Copies of
the data can be obtained free of charge on application to the CCDC,
12 Union Road, Cambridge CB2 1EZ, UK (fax, (+44)1223-336−-033;
e-mail, deposit@ccdc.cam.ac.uk).
Computational Methods. All calculations were performed with
the Gaussian03 package with the hybrid B3LYP functional.21 The basis
set was LANL2DZ for Ni and 6-31g(d)/6-31g* for all other atoms.
The LANL2DZ pseudopotential was used for Ni. Full optimization of
geometry was performed without any symmetry constraint, followed
by analytical computation of the Hessian matrix to identify the nature
of the located extrema as minima. The zero-point, thermal, and
entropy corrections were evaluated to compute enthalpies and Gibbs
free energies.
1
1927 (Co−H), 1584 (ArCC), 950 (PMe3) cm−1. H NMR (300
MHz, benzene-d6, 300 K, δ): −14.67 (q, J = 61.8 Hz, CoH, 1H), 0.70
(d, J = 7.5 Hz, PCH3, 9H), 1.45 (s, SiCH3, 3H), 7.10 (m, Ar, 14H),
7.30−7.43 (m, Ar, 4H), 7.71−7.82 (m, Ar, 4H), 8.25 (t, J = 7.4 Hz, Ar,
2H), 8.29−8.38 (m, Ar, 4H) ppm. 31P{1H} NMR (121 MHz, benzene-
d6, 300 K, δ): −14.8 (m, PMe3, 1P), 67.5 (m, PPh2, 2P) ppm. 13C
NMR (75 MHz, benzene-d6, 300 K, δ): 7.6 (d, J = 3.7 Hz, SiCH3),
18.1 (m, PCH3), 127.2−128.4 (m, Ar), 129.3 (d, J = 6.8 Hz, Ar),
131.6−132.0 (m, Ar), 132.6−132.8 (m, Ar), 133.8−134.0 (m, Ar),
137.3−137.7 (m, Ar), 138.6−139.0 (m, Ar), 146.3 (m, Ar), 157.8 (m,
Ar) ppm.
Synthesis of [PSiP]Co(H)(Cl)(PMe3) (13). Complex 1 (0.82 g,
1.45 mmol) in 30 mL of THF was combined with CoCl(PMe3)3 (0.47
g, 1.45 mmol) in 20 mL of THF at 0 °C. The mixture was stirred for
14 h at room temperature. After workup, complex 13 (0.82 g, 1.12
mmol) was obtained as yellow crystals at −30 °C from diethyl ether in
a yield of 77%. Mp: > 156 °C dec. Anal. Calcd for C40H41ClCoP3Si
(737.11 g/mol): C, 65.18; H, 5.61. Found: C, 65.31; H, 5.79. IR
(Nujol, KBr): 3047 (Ar−H), 1910 (Co−H), 1592 (ArCC), 952
(PMe3) cm−1. 1H NMR (300 MHz, benzene-d6, 300 K, δ): −13.68 (q,
J = 61.2 Hz, CoH, 1H), 0.63 (d, J = 7.30 Hz, PCH3, 9H), 0.78 (s,
SiCH3, 3H), 6.99−7.18 (m, Ar, 14H), 7.34 (t, J = 7.20 Hz, Ar, 2H),
7.41−7.52 (m, Ar, 2H), 7.83 (m, Ar, 4H), 8.10−8.27 (m, Ar, 6H)
ppm. 31P{1H} NMR (121 MHz, benzene-d6, 300 K, δ): −3.7 (m,
PMe3, 1P), 68.9 (m, PPh2, 2P) ppm. 13C NMR (75 MHz, benzene-d6,
300 K, δ): 7.6 (d, J = 4.4 Hz, SiCH3), 20.0 (d, J = 24.1 Hz, PCH3),
125.4 (s, Ar), 127.1−128.4 (m, Ar), 129.3 (d, J = 6.6 Hz, Ar), 130.5 (s,
Ar), 131.8 (t, J = 10.2 Hz, Ar), 132.7 (t, J = 4.7 Hz, Ar), 133.0 (s, Ar),
133.9 (t, J = 5.1 Hz, Ar), 135.1 (s, Ar) ppm.
Synthesis of [PSiP]Co(PMe3)2 (14). One equivalent of MeLi
(0.65 mL, 1.6 M) or n-BuMgBr (1.0 mL, 1.02 M) was added to a
solution of complex 13 (0.75 g, 1.02 mmol) in 50 mL of THF at 0 °C.
After the mixture was stirred for 14 h at room temperature, the
volatiles were removed under reduced pressure and the residue was
extracted with pentane and diethyl ether. Compound 14 (0.51 g, 0.66
mmol) was isolated as a red powder in 65% yield. Mp: > 174 °C dec.
Anal. Calcd for C43H49CoP4Si (776.73 g/mol): C, 66.49; H, 6.36.
Found: C, 66.76; H, 6.11. IR (Nujol, KBr): 3045 (Ar−H), 1579
1
(ArCC), 938 (PMe3) cm−1. H NMR (300 MHz, benzene-d6, 300
K, δ): 0.58 (s, SiCH3, 3H), 0.79 (d, J = 6.30 Hz, PCH3, 9H), 1.19 (d, J
= 5.30 Hz, PCH3, 9H), 6.93 (t, J = 7.10 Hz, Ar, 8H), 6.99−7.14 (m,
Ar, 14H), 7.72 (dd, J = 9.30, 5.90 Hz, Ar, 6H) ppm. 31P{1H} NMR
(121 MHz, benzene-d6, 300 K, δ): −17.5 (m, PMe3, 1P), 4.0 (m,
PMe3, 1P), 56.5 (PPh2, 2P) ppm. 13C NMR (75 MHz, benzene-d6, 300
K, δ): 4.4 (s, SiCH3), 24.2 (d, J = 5.8 Hz, PCH3), 24.4 (d, J = 5.5 Hz,
PCH3), 126.8 (s, Ar),127.0 (s, Ar), 127.3 (s, Ar), 127.5 (s, Ar), 127.7
(s, Ar), 127.8 (s, Ar), 128.1 (s, Ar), 130.5 (s, Ar), 130.9 (t, J = 11.1 Hz,
Ar), 132.8 (t, J = 5.3 Hz, Ar), 133.2 (t, J = 6.8 Hz, Ar), 142.6 (s, Ar)
ppm.
ASSOCIATED CONTENT
■
S
* Supporting Information
CIF files and a table giving crystallographic data for 2−5, 10,
12, 13, 15, and 16 and a figure giving the 1H NMR spectrum of
15. This material is available free of charge via the Internet at
http://pubs.acs.org.
Synthesis of [PSiP]Co(Cl)(PMe3) (15). Compound 1 (0.82 g, 1.45
mmol) was treated with anhydrous CoCl2 (0.19 g, 1.45 mmol) in
THF. The reaction mixture turned purple. The solution turned
reddish brown after PMe3 (0.15 g, 2.00 mmol) was added. After
workup compound 15 (0.43 g, 0.58 mmol) was isolated as red crystals
in 40% yield. Mp: > 183 °C dec. Anal. Calcd for C40H40ClCoP3Si
(736.10 g/mol): C, 65.27; H, 5.48. Found: C, 65.57; H, 5.39. IR
(Nujol, KBr): 3045 (Ar−H), 1582 (ArCC), 934 (PMe3) cm−1.
Complex 15 is paramagnetic, and its 1H NMR spectrum is given in the
Supporting Information.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail for H.S.: hjsun@sdu.edu.cn.
Notes
Synthesis of [PSiP]Fe(H)(PMe3)2 (16). Compound 1 (0.82 g, 1.45
mmol) in 30 mL of toluene was treated with Fe(PMe3)4 (0.55 g, 1.53
The authors declare no competing financial interest.
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(18) Kaesz, H. D.; Saillant, R. B. Chem. Rev. 1972, 72, 231−281.
(19) (a) Tondreau, A. M.; Atienza, C. C. H.; Weller, K. J.; Nye, S. A.;
Lewis, K. M.; Delis, J. G. P.; Chirik, P. J. Science 2012, 335, 567−570.
(b) Atienza, C. C. H.; Tondreau, A. M.; Weller, K. J.; Lewis, K. M.;
Cruse, R. W.; Nye, S. A.; Boyer, J. L.; Delis, J. P. G.; Chirik, P. J. ACS.
Catal. 2012, 2, 2169−2172. (c) Tondreau, A. M.; Atienza, C. C. H.;
Darmon, J. M.; Milsmann, C.; Hoyt, H. M.; Weller, K. J.; Nye, S. A.;
Lewis, K. M.; Boyer, J.; Delis, J. G. P.; Lobkovsky, E.; Chirik, P. J.
Organometallics 2012, 31, 4886−4893. (d) Tondreau, A. M.; Darmon,
J. M.; Wile, B. M.; Floyd, S. K.; Lobkovsky, E.; Chirik, P. J.
Organometallics 2009, 28, 3928−3940. (e) Tondreau, A. M.;
Lobkovsky, E.; Chirik, P. J. Org. Lett. 2008, 10, 2789−2792.
(f) Zhang, M.; Zhang, A. Appl. Organomet. Chem. 2010, 24, 751−757.
(20) (a) Klein, H.-F.; Karsch, H. H. Chem. Ber. 1976, 109, 2515−
2523. (b) Klein, H.-F.; Karsch, H. H. Chem. Ber. 1972, 105, 2628−
2636. (c) Klein, H.-F.; Karsch, H. H. Chem. Ber. 1973, 106, 1433−
1452. (d) Klein, H.-F.; Karsch, H. H. Chem. Ber. 1975, 108, 944−947.
(e) Klein, H.-F.; Karsch, H. H. Angew. Chem., Int. Ed. 1971, 10, 343−
344. (f) Klein, H.-F.; Karsch, H. H. Chem. Ber. 1977, 110, 2699−2711.
(g) Veda, N.; Gunji, T.; Abe, Y. J. Sol-Gel. Sci. Technol. 2008, 48, 163−
167.
ACKNOWLEDGMENTS
■
We gratefully acknowledge support by the NSF of China, No.
21072113/21272138. We also acknowledge the kind assistance
of Prof. Dieter Fenske (Karlsruhe Institute of Technology) in
the X-ray diffraction analysis.
REFERENCES
■
(1) (a) Corey, J. Y.; Wilking, J. B. Chem. Rev. 1999, 99, 175−292.
(b) Shimada, S.; Tanaka, M. Coord. Chem. Rev. 2006, 250, 991−1011.
(c) Corey, J. Y. Chem. Rev. 2011, 111, 863−1071.
(2) (a) Lin, Z. Y. Chem. Soc. Rev. 2002, 31, 239−245. (b) Nikonov,
G. I. Adv. Organomet. Chem. 2005, 53, 217−305.
(3) Zhu, J.; Lin, Z. Y.; Marder, T. B. Inorg. Chem. 2005, 44, 9384−
9390.
(4) Korshin, E. E.; Leitus, G.; Shimon, L. J. W.; Milstein, D. Inorg.
Chem. 2008, 47, 7177−7189.
(5) (a) MacInnis, M. C.; MacLean, D. F.; Lundgren, R. J.; McDonald,
R.; Turculet, L. Organometallics 2007, 26, 6522−6525. (b) MacLean,
D. F.; McDonald, R.; Ferguson, M. J.; Caddell, A. J.; Turculet, L.
Chem. Commun. 2008, 5146−5148. (c) Morgan, E.; MacLean, D. F.;
McDonald, R.; Turculet, L. J. Am. Chem. Soc. 2009, 131, 14234−
14236. (d) Mitton, S. J.; McDonald, R.; Turculet, L. Angew. Chem., Int.
Ed. 2009, 48, 8568−8571. (e) Mitton, S. J.; McDonald, R.; Turculet, L.
Organometallics 2009, 28, 5122−5136. (f) MacInnis, M. C.;
McDonald, R.; Ferguson, M. J.; Tobisch, S.; Turculet, L. J. Am.
Chem. Soc. 2011, 133, 13622−13633.
(21) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648−5652. (b) Lee,
C.; Parr, R. G.; Yang, W. Phys. Rev. 1998, 37, 785−789.
(6) (a) Takaya, J.; Iwasawa, N. J. Am. Chem. Soc. 2008, 130, 15254−
15255. (b) Korshin, E. E.; Leitus, G.; Shimon, L. J. W.;
Konstantinovski, L.; Milstein, D. Inorg. Chem. 2008, 47, 7177−7189.
(c) Takaya, J.; Iwasawa, N. Organometallics 2009, 28, 6636−6638.
(d) Takaya, J.; Kirai, N.; Iwasawa, N. J. Am. Chem. Soc. 2011, 133,
12980−12983. (e) Takaya, J.; Sasano, K.; Iwasawa, N. Org. Lett. 2011,
13, 1698−1701. (f) Takaya, J.; Iwasawa, N. Dalton Trans. 2011, 40,
8814−8821.
(7) (a) Fang, H. Y.; Choe, Y. K.; Li, Y. H.; Shimada, S. Chem. Asian J.
2011, 6, 2512−2521. (b) Li, Y. H.; Zhang, Y.; Ding, X. H. Inorg. Chem.
Commun. 2011, 14, 1306−1310. (c) Li, Y. H.; Ding, X. H.; Zhang, Y.;
He, W. R.; Huang, W. Inorg. Chem. Commun. 2012, 15, 194−197.
(8) (a) Boro, B. J.; Duesler, E. N.; Goldberg, K. I.; Kemp, R. A. Inorg.
Chem. 2009, 48, 5081−5087. (b) Liang, L. C.; Chien, P. S.; Lee, P. Y.
Organometallics 2008, 27, 3082−3093.
(9) Schubert, U.; Gilges, H. Organometallics 1996, 15, 2373−75.
(10) (a) Chen, W.; Shimada, S.; Tanaka, M.; Kobayashi, Y.; Saigo, K.
J. Am. Chem. Soc. 2004, 126, 8072−8073. (b) Shimada, S.; Rao, M. L.
N.; Tanaka, M. Organometallics 1999, 18, 291−293. (c) Shimada, S.;
Rao, M. L. N.; Hayashi, T.; Tanaka, M. Angew. Chem., Int. Ed. 2001,
40, 213−216.
(11) Klein, H.-F.; Bickelhaupt, A.; Lemke, M.; Sun, H.; Brand, A.;
Jung, T.; Rohr, C.; Florke, U.; Haupt, H.-J. Organometallics 1997, 16,
̈
̈
668−676.
(12) (a) Borah, M. J.; Singh, R. K.; Sinha, U. B.; Swu, T.; Borah, P. J.
J. Chem. Crystallogr. 2012, 42, 67−75. (b) Hopa, C.; Kurtaran, R.;
Mahir Alkan, M.; Hulya Kara, H.; Hughes, R. J. Chem. Crystallogr.
2010, 35, 1013−1018. (c) Braunstein, P.; Kermagoret, A.; Pattacini,
R.; Vasquez, P. C.; Rogez, G.; Welter, R. Angew. Chem., Int. Ed. 2007,
46, 6438−6441.
(13) Klein, H.-F.; Schmidbaur, H. Angew. Chem., Int. Ed. 1970, 9,
903−904.
(14) (a) Shimada, S.; Tanaka, M.; Shiro, M. Angew. Chem., Int. Ed.
Engl. 1996, 35, 1856−1858. (b) Pfeiffer, J.; Kickelbick, G.; Schubert,
U. Organometallics 2000, 19, 62−71.
(15) Hesse, M.; Meier, H.; Zeeh, B. Spektroskopische Methoden in der
organischen Chemie; Georg Thieme Verlag: Stuttgart, New York, 1991;
p 178.
(16) Anirban, B.; Murielle, C. K.; Eugen, S. A.; Marc, F.; Martin, J. F.;
Vincent, A. Inorg. Chem. 2012, 51, 7087−7093.
(17) Bhattacharya, P.; Krause, J. A.; Guan, H. Organometallics 2011,
30, 4720−4729.
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