Construction of rhodium(I) and gold(I) macrocycles by transferring a phosphine-functionalized 4,5-diazafluorenide ligand from its copper(I) N-heterocyclic carbene complex

Article abstract of DOI:10.1021/om200994b

We report the synthesis and characterization of a phosphine-functionalized 4,5-diazafluorene ligand, 9-(2-(diphenylphosphino)ethyl)-4,5-diazafluorene (L_pH), and its Cu(IPr) complex (IPr = N,N′-bis(2,6- diisopropylphenyl)imidazol-2-ylidene) [Cu(IPr)L_p] (2a), which exhibits a monomeric structure in solution but dimerizes in the solid state. Compound 2a reacts with Rh(PPh₃)₃Cl, [Rh(COD)Cl] ₂, Au(SMe₂)Cl, and Au(IPr)Cl to form the macrocyclic complexes [Rh(PPh₃)L_p]₂ (2b), [Rh(COD)L _p]₂ (2c), and [AuL_p]₂ (2d) and the mononuclear complex [Au(IPr)L_p] (2f), respectively, via ligand transfer. Although 2b-d,f could also be synthesized from the deprotonated ligand L_p^- and the corresponding metal starting materials directly, the reactions require longer time and give lower yields. The reaction between L_pH and Au(SMe₂)Cl gives Au(L_pH) ₂Cl (2e) exclusively.

Full text of DOI:10.1021/om200994b

Article
pubs.acs.org/Organometallics
Construction of Rhodium(I) and Gold(I) Macrocycles by Transferring
a Phosphine-Functionalized 4,5-Diazafluorenide Ligand from Its
Copper(I) N-Heterocyclic Carbene Complex
Runyu Tan, Frederick Sin Nang Chiu, Alen Hadzovic, and Datong Song*
Davenport Chemical Research Laboratories, Department of Chemistry, University of Toronto, 80 St. George Street, Toronto,
Ontario, Canada M5S 3H6
S
* Supporting Information
ABSTRACT: We report the synthesis and characterization of
a phosphine-functionalized 4,5-diazafluorene ligand, 9-(2-
(diphenylphosphino)ethyl)-4,5-diazafluorene (LpH), and its
Cu(IPr) complex (IPr = N,N′-bis(2,6-diisopropylphenyl)-
imidazol-2-ylidene) [Cu(IPr)Lp] (2a), which exhibits a
monomeric structure in solution but dimerizes in the solid
state. Compound 2a reacts with Rh(PPh3)3Cl, [Rh(COD)-
Cl]2, Au(SMe2)Cl, and Au(IPr)Cl to form the macrocyclic
complexes [Rh(PPh3)Lp]2 (2b), [Rh(COD)Lp]2 (2c), and
[AuLp]2 (2d) and the mononuclear complex [Au(IPr)Lp] (2f),
respectively, via ligand transfer. Although 2b−d,f could also be
−
synthesized from the deprotonated ligand Lp and the
corresponding metal starting materials directly, the reactions
require longer time and give lower yields. The reaction between LpH and Au(SMe2)Cl gives Au(LpH)2Cl (2e) exclusively.
coordinating groups tethered on C9 of the diazafluorene
could compete with the chelation of the two nitrogen donor
atoms upon binding to metal species and allow for stepwise
construction of multimetallic macrocycles.13,14 In our ligand
design, we reasoned that functionalization of the LH ligand
with a phosphine group might create competitive binding sites
and lead to the syntheses of multinuclear macrocyclic
complexes. Herein we report the synthesis of such a ligand,
9-(2-(diphenylphosphino)ethyl)-4,5-diazafluorene (LpH), and
INTRODUCTION
■
Ligands with multiple coordination sites have been frequently
used to synthesize metallamacrocyclic complexes, which have
found use in sensing applications and size-selective catalysis.1−4
Transformation of one metallamacrocycle to another via ligand
redistribution reactions is extremely rare but represents a useful
strategy for building new macrocyclic complexes.5,6 In this
scenario, d10 metal complexes seem to be suitable precursors,
due to the lack of ligand field stabilization and hence weak
ligand-to-metal interactions, which could facilitate the ligand
transfer reaction.7 For example, it is well documented that
NHC-Ag(I) (NHC = N-heterocyclic carbene) species could be
used as NHC ligand transfer reagents to synthesize other metal-
NHC complexes and recently NHC-Cu(I) species has been
found able to transfer the NHC ligand as well.8 However,
transferring a chelating ligand from its NHC-Cu(I) derivative
to another metal species has not been documented to date.
Our laboratory has recently studied the coordination
chemistry of 4,5-diazafluorene (LH),9−12 the structure of
which can be viewed as two pyridine rings fused onto a
cyclopentadiene (CpH) ring in a syn fashion (Scheme 1).
Therefore, if LH is deprotonated at the 9-position, the resulting
4,5-diazafluorenide (L−) should have two types of metal
binding sites, the pyridine nitrogen donors and the Cp− carbon
donors, which can potentially accommodate multiple metal
centers. It appeared that most metal ions prefer to bind with
the nitrogen donors, and only Pd(II) binds with both
coordination sites of the L− ligand to form a cyclic dipalladium
complex.12 However, it has been shown that strongly
−
Lp ligand transfer reactions from the complex [Cu(IPr)Lp]
(IPr = N,N′-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) to
Rh(I) and Au(I) metal centers, resulting in the formation of
macrocyclic complexes.
RESULTS AND DISCUSSION
■
Synthesis of the Ligand LpH. The ligand LpH can be
synthesized from spiro compound 1, which can be prepared by
a cyclopropanation reaction of L− with an excess amount of 1,2-
dibromoethane (Scheme 2).15 The subsequent nucleophilic
attack by lithium diphenylphosphide results in the formation of
LpLi. Compound LpLi is a dark solid, and its 31P NMR
spectrum in THF shows a singlet at −16.4 ppm. Due to
difficulty in the purification and characterization of LpLi, it is
protonated to the neutral ligand LpH. The 31P NMR spectrum
of LpH shows a singlet at −16.1 ppm, very close to that of LpLi.
Received: October 16, 2011
Published: March 15, 2012
© 2012 American Chemical Society
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Scheme 1
Scheme 2. Synthesis of LpH
Figure 1. POV-Ray plot of the molecular structures of 1 (left) and LpH (right).
Scheme 3. Synthesis of 2a
1
The solid-state structures of 1 and LpH have been confirmed by
X-ray crystallography and are shown in Figure 1.
lost its C2v symmetry. Both 31P and H NMR spectra suggest
the formation of a copper complex with at least the IPr ligand
and two nitrogen donor atoms of Lp occupying its coordination
‑
Synthesis and Structure of 2a. When LpH is treated with
1 equiv of KOtBu in THF, a deep purple solution is formed.
The subsequent addition of 1 equiv of Cu(IPr)Cl16 in THF
results in a change of the solution from deep purple to green,
and the 31P NMR spectrum of the reaction mixture indicates
the formation of the new species 2a with a chemical shift of
−14.2 ppm, only slightly shifted from that of Lp− (−16.4 ppm).
sites (Scheme 3). The phosphine arm appears to be dangling,
as evidenced by the similar 31P NMR resonances displayed by
17
2a and Lp . Variable-temperature 31P NMR studies, however,
suggested the presence of a dynamic behavior of 2a in solution,
as evidenced by initial broadening and then sharpening of the
phosphorus resonance along with downfield shift upon cooling
the sample of 2a in toluene (see the Supporting Information).
The solid-state structure of 2a has been revealed by X-ray
crystallography. To our surprise, 2a is a dimeric, head-to-tail
−
1
The H NMR spectrum shows one set of pyridine proton
resonances and two distinct isopropyl groups, indicating that
the ligand Lp− retains its symmetry but the Cu(IPr) moiety has
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macrocyclic species in the solid state (Figure 2). Each molecule
Scheme 4. Synthesis of 2b
of 2a has a crystallographically imposed inversion center. Each
inversion center (Figure 3). Each Rh center adopts a square-
planar geometry with the carbon and phosphorus donor atoms
−
of one Lp in a chelating fashion, one nitrogen donor atom
from the other Lp , and a phosphorus donor from a
Figure 2. POV-Ray plot of the molecular structure of 2a. The 2,6-
diisopropylphenyl groups, hydrogen atoms, and the cocrystallized
THF solvents are omitted for clarity.
−
triphenylphosphine occupying the four coordination sites.
The two diazafluorenyl moieties are antiparallel with an
interplane distance of ∼2.9 Å. The Rh1−P1 bond length
(2.1996(9) Å) is shorter than that of Rh1−P2 (2.2397(10) Å),
due to the stronger trans influence of the carbon donor. The
31P NMR spectrum (vide supra) is consistent with the solid-
state structure, suggesting that the dimeric structure is retained
in solution. The 1H NMR spectrum shows two sets of pyridine
proton signals, consistent with the solid-state structure in which
only one nitrogen donor of each diazafluorenyl moiety is bound
to the metal center.
copper center adopts a highly distorted tetrahedral geometry,
with the carbon donor from IPr, two nitrogen donor atoms
−
from one Lp , and the phosphorus donor atom from the other
−
Lp occupying the four coordination sites. Within each five-
membered chelate ring, the two Cu−N bond lengths are quite
different (2.324(3) vs 2.185(3) Å), which has been observed in
other metal complexes of diazafluorene derivatives.13,18 The
carbon atom at the 9-position of the diazafluorenide moiety
retains its sp2 hybridization and adopts a typical trigonal-planar
geometry. The two diazafluorenide moieties are parallel to each
other with a distance of ∼4.54 Å. The macrocycle is formed
−
with two bridging Lp groups interconnected by two Cu−P
bonds and four Cu−N bonds. Similar d8−d10 heteronuclear
metallamacrocycles with diazafluorene derivatives have been
reported, where small ligands such as halides and dithiolate are
bound to the metal centers. It is startling that the Cu(I) center
in complex 2a can bear a fourth ligand in the presence of a
highly sterically demanding IPr ligand. To minimize the steric
repulsion and accommodate such a coordination environment,
the IPr group is tilted away from the phosphine moiety with a
large C−Cu−P bond angle of 117.64(11)°, and a dihedral angle
of ∼49° is observed between the middle ring of IPr and the
diazafluorenide plane. To the best of our knowledge, the
structure of 2a in the solid state represents the first four-coordinate
Cu(I) complex bearing an IPr ligand.
Figure 3. POV-Ray plot of the molecular structure of 2b. Hydrogen
atoms are omitted for clarity.
Synthesis and Structure of 2b. Since the NMR spectra of
2a indicate that, in solution, the phosphorus donor is dangling
rather than bound to copper, we set out to explore the
reactivity of 2a with other metals, hoping to install a second
metal center onto the phosphine-C9 chelating site of the ligand
The stoichiometry of the reaction requires the formation of
1
Cu(IPr)Cl and free PPh3 as byproduct. Indeed, H and 31P
NMR analyses of the reaction mixture revealed the formation of
Cu(IPr)Cl and PPh3 in solution. Considering that 2a is
−
−
synthesized from Lp and Cu(IPr)Cl, it served as a ligand
Lp . When 2a is treated with 1 equiv of Rh(PPh3)3Cl in
transfer reagent in the synthesis of 2b and regenerates
Cu(IPr)Cl. It is worth noting that 2b can also be synthesized
from LpH and Rh(PPh3)3Cl directly (top route in Scheme 4),
although the reaction requires a much longer time and gives a
lower yield.
Synthesis and Structure of 2c. The observation of the
ligand transfer reaction between 2a and Rh(PPh3)3Cl prompted
us to investigate the generality of this type of reactivity. When
benzene, a bright orange precipitate of 2b (bottom route in
Scheme 4) is formed. The 31P NMR spectrum of 2b shows two
doublet of doublets resonances (90.58, 64.92 ppm) with both
2
Rh−P and P−P couplings (1JRh−P = 181.4 Hz, JP−P = 38.41
Hz), indicating coordination of the tethered phosphine group.
The solid-state structure of 2b has been unambiguously
confirmed by X-ray crystallography. Interestingly, 2b is a
dinuclear Rh complex with a crystallographically imposed
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[Rh(COD)Cl]2 was added to a benzene solution of 2a, the 1H
NMR spectrum of the reaction mixture indicated the formation
of Cu(IPr)Cl and the 31P NMR spectrum showed the clean
which is presumably due to rapid interconversion of conforma-
tional isomers in solution.
Syntheses and Structures of 2d,e. To explore the
reactivity of 2a with metals having other geometric preferences,
we chose Au(I), since it generally prefers a two-coordinate
linear geometry,19 which is distinct from the case for most other
metals. The reaction of 2a with 1 equiv of Au(SMe2)Cl20 in
benzene (bottom route in Scheme 6) results in the formation
formation of a doublet with Rh−P coupling (27.4 ppm, JRh−P
=
149 Hz). The same 31P NMR signal could be observed for the
−
reaction mixture of Lp and [Rh(COD)Cl]2, suggesting that
the same product 2c (Scheme 5) is formed in both reactions.
Scheme 5. Synthesis of 2c
Scheme 6. Synthesis of 2d
The solid-state structure of 2c has been confirmed crystallo-
graphically. As shown in Figure 4, 2c is again a dimeric
of an appreciable amount of red precipitate and the
concomitant disappearance of the 31P NMR signal of 2a. The
1H NMR spectrum of the reaction mixture again indicated the
formation of Cu(IPr)Cl in solution. X-ray-quality crystals of 2d
were obtained by letting a THF solution of an equimolar
mixture of 2a and Au(SMe2)Cl stand undisturbed. Complex 2d
is insoluble in THF, Et2O, and C6H6 and unstable in
chlorinated solvents. As shown in Figure 5, 2d also self-
Figure 4. POV-Ray plot of the molecular structure of 2c. Hydrogen
atoms are omitted for clarity.
macrocyclic rhodium complex with a crystallographically
imposed inversion center. Interestingly, the coordination
−
mode of the Lp ligands in 2c is similar to that in 2a and
Figure 5. POV-Ray plot of the molecular structure of 2d. Hydrogen
atoms are omitted for clarity.
different from that in 2b. Each Rh(I) center is five-coordinate
and adopts a distorted-trigonal-bipyramidal geometry, with
both nitrogen donor atoms from one ligand Lp , two CC
double bonds from the COD ligand, and a phosphorus donor
atom from the other Lp occupying the five sites. The carbon
donor from the Cp ring of Lp does not participate in the
coordination. The distance between the two diazafluorenide
planes is ∼4.7 Å, comparable to that of 2a, but much longer
than that of 2b, presumably due to the absence of Rh−Cp
bonds. The Rh1−N2 bond length (2.4582(19) Å) is much
longer than that of Rh1−N1 (2.0962(18) Å). The DFT
optimized geometry of 2c in the gas phase also features uneven
Rh−N bond lengths (see the Supporting Information),
suggesting that such an unsymmetrical binding mode of the
diazafluorenide is not due to crystal-packing effects. However,
−
assembles into a head-to-tail macrocyclic dimer with a
crystallographically imposed central symmetry. Each gold
center adopts a quasi-linear geometry (P1−Au1−N1 =
170.9(3)°) and is coordinated with one nitrogen donor atom
from one Lp− ligand and one phosphorus donor atom from the
other. The two diazafluorenide moieties are again antiparallel
with a separation distance of ∼3.39 Å. Complex 2d can also be
−
−
−
directly synthesized from the reaction of Lp and Au(SMe2)Cl
(top route in Scheme 6); however, this synthetic route requires
a longer reaction time and tedious purification procedures.
While searching for an alternative route to the dimeric gold
complex 2d, we attempted to produce the neutral complex
Au(LpH)Cl first, followed by the removal of HCl with a strong
base, which might trigger the dimerization and the formation of
1
the solution H NMR shows only one set of pyridine signals,
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Scheme 7. Synthesis of 2e
2d. Interestingly, when LpH reacted with Au(SMe2)Cl, the
three-coordinate gold complex Au(LpH)2Cl (2e) was the
exclusive product (Scheme 7), regardless of the amount of
ligand LpH added. As shown in Figure 6, each gold center
Scheme 8. Synthesis of 2f
Figure 6. POV-Ray plot of the molecular structure of 2e. Hydrogen
atoms, except for those on the C5 rings, are omitted for clarity.
adopts a trigonal-planar geometry and is coordinated with two
phosphorus donor atoms from two LpH ligands and one
chloride atom. All the bond lengths and angles are within the
normal ranges. Three-coordinate Au(I) complexes with
phosphine ligands are well documented in the presence of
small phosphines such as PMe3 and PEt3 and are often in
equilibrium with the two-coordinate and four-coordinate Au(I)
species, depending on the stoichiometry of the phosphine
ligand present in solution.19 The preferential formation of 2e is
tentatively attributed to the relatively low solubility of 2e.
Synthesis and Structure of 2f. When Au(SMe2)Cl is used
in the synthesis of 2d, the dimer formation can be viewed as the
replacement of Me2S at the Au(I) center by a nitrogen donor
from an adjacent molecule, due to the labile nature of Me2S.
We now ask the question whether we can disrupt the
dimerization by using a less labile ligand such as IPr, instead
of Me2S, and still use 2a to transfer an Lp− ligand to the Au(I)
center. The reaction of 2a and 1 equiv of Au(IPr)Cl21 resulted
in the production of a red precipitate (top route in Scheme 8).
The solid-state structure was confirmed by X-ray crystallog-
raphy and is shown in Figure 7. 2f is indeed a monomeric
gold(I) complex, as the IPr ligand could not be replaced by the
Figure 7. POV-Ray plot of the molecular structure of 2f. Isopropyl
groups, hydrogen atoms, and cocrystallized THF solvent are omitted
for clarity.
requires a much longer time and gives impure product due to
the coprecipitation of 2f and the inorganic salt; due to the poor
solubility of 2f in organic solvents and instability toward protic
solvents, it is difficult to isolate 2f from the inorganic salt. Using
−
2a to transfer the Lp ligand is once again a better synthetic
route.
CONCLUSION
■
In conclusion, we have prepared the Cu(I) complex 2a, which
is a monomer in solution and a dimer in the solid state.
Complex 2a can transfer an Lp− ligand to metals having various
geometric preferences. The advantages of using 2a instead of
Lp directly include faster reactions and cleaner products. The
simple group 1 salts of Lp in general have poor solubility in
−
nitrogen donor from Lp . Each Au(I) adopts a linear geometry,
−
with the C26−Au1−P1 angle being 176.30(9)°, and is
−
coordinated with the carbon donor atom from the IPr ligand
−
and the phosphorus donor atom from Lp , leaving the nitrogen
nonpolar organic solvents (e.g., benzene). Introducing [Cu-
−
(IPr)]+ to Lp improves the solubility and therefore makes the
−
and carbon donors of Lp all dangling. Although the synthesis
−
of 2f could be realized through a reaction between Lp and
reactions faster. The resulting byproduct Cu(IPr)Cl remains
Au(IPr)Cl directly (bottom route in Scheme 8), the reaction
soluble in nonpolar organic solvents, while the products (2b−f)
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́
stored over 4 Å molecular sieves in the glovebox. Unless otherwise
stated, all reagents were purchased from commercial sources and used
without further purifications. LiPPh2 was prepared from equimolar
HPPh2 and n-BuLi. 4,5-Diazafluorene,22 Cu(IPr)Cl,16 Au(IPr)Cl,21
and Au(SMe2)Cl20 were synthesized according to literature
are much less soluble. The solubility difference allows the
cleaner isolation of products. A series of dimeric metallamacro-
cycles and monomeric complexes have been synthesized from
2a and the appropriate metal starting materials. The properties
of these macrocycles and monomeric complexes and the
application of 2a in the construction of more complex
molecular architectures are being studied in our laboratory.
procedures. H, 13C{1H}, and 31P{1H} NMR spectra were recorded
1
on a Varian 300, Varian 400, or Bruker Avance 400 spectrometer.
Chemical shifts were referenced relative to the solvent’s residual
signals but are reported relative to Me4Si. Elemental analyses were
performed on a PE 2400 C/H/N/S analyzer at the Analest of our
Chemistry Department.
Synthesis of 1. To a mixture of 4,5-diazafluorene (168 mg, 1.0
mmol) and 1,2-dibromoethane (564 mg, 3.0 mmol) in 10 mL of THF
was added NaH (60 mg, 2.2 mmol) slowly. All the volatiles were
removed under reduced pressure, and the residue was partitioned
between DCM and water. The organic layer was dried over Mg2SO4.
The solvent was then removed, and the residue was washed with
EXPERIMENTAL DETAILS
■
General Considerations. All preparations and manipulations
were performed under argon or dinitrogen using standard Schlenk
techniques or in a nitrogen atmosphere glovebox from MBraun. All the
solvents were dried and degassed using standard procedures and
a
Table 2. Selected Bond Lengths (Å) and Angles (deg)
1
pentane to yield the product as a brown solid (82% yield). H NMR
Compound 2a
(CDCl3, 400 MHz, 25 °C): δ 8.58 (dd, J = 4.8, 1.2 Hz, 2H), 7.27 (dd,
J = 7.6, 1.2 Hz, 2H), 7.16 (dd, J = 7.6, 4.8 Hz, 2H), 1.65 (s, 4H).
13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ 157.5, 148.7, 142.7,
C(26)−Cu(1)
P(1)−Cu(1)
1.956(3)
N(1)−Cu(1)
N(2)−Cu(1)
2.324(3)
2.185(3)
2.2855(10)
126.6, 122.6, 25.99, 17.36. Anal. Calcd for C13H10N2: C, 80.39; H,
5.19; N, 14.42. Found: C, 80.00; H, 5.51; N, 14.52.
C(26)−Cu(1)−N(2) 116.38(11) C(26)−Cu(1)−N(1) 117.64(11)
C(26)−Cu(1)−P(1)
N(2)−Cu(1)−P(1)
138.24(9)
N(2)−Cu(1)−N(1)
P(1)−Cu(1)−N(1)
82.49(10)
Synthesis of 9-(2-(Diphenylphosphino)ethyl)-4,5-diazafluor-
ene (LpH). To a solution of LiPPh2 (192 mg, 1.0 mmol) in 10 mL of
THF was added 2 (168 mg, 1.0 g) at 0 °C. The reaction mixture was
refluxed for 5 h and cooled to room temperature. The solvent was
removed in vacuo, and the residue was washed with pentane and dried
in vacuo. The residue was dissolved in 5 mL of Et2O, washed with
saturated NH4Cl solution, and dried over Na2SO4. After the removal
of Et2O the residue was recrystallized in pentane/THF to afford LpH
92.56(7)
94.27(7)
Compound 2b
Rh(1)−N(1)
Rh(1)−P(1)
Rh(1)−P(2)
Rh(1)−C(11)
N(1)−Rh(1)−P(1)
2.123(3)
C(4)−C(11)#1
C(11)−C(7)#1
C(11)−C(4)#1
C(11)−C(12)
1.478(5)
1.470(5)
1.478(5)
1.534(4)
103.0(3)
2.1996(9)
2.2397(10)
2.282(3)
169.98(8)
C(7)#1−C(11)−C(4)
1
#1
as a pale yellow crystalline solid (40% yield). H NMR (CDCl3, 400
MHz, 25 °C): δ 8.72 (d, J = 4.8 Hz, 2H), 7.69 (d, J = 7.6 Hz, 2H),
7.32−7.22 (m, 12H), 4.08 (t, J = 5.2 Hz, 1H), 2.24−2.17 (m, 2H),
1.64−1.59 (m, 2H). 13C{1H} NMR (CDCl3, 100 MHz, 25 °C): δ
158.9, 149.9, 140.5, 137.9 (d, JP−C = 12.0 Hz), 132.7 (d, JP−C = 18.0
N(1)−Rh(1)−P(2)
P(1)−Rh(1)−P(2)
N(1)−Rh(1)−C(11)
P(1)−Rh(1)−C(11)
P(2)−Rh(1)−C(11)
90.64(8)
97.12(3)
C(7)#1−C(11)−C(12)
C(4)#1−C(11)−C(12)
116.9(3)
116.5(3)
104.0(2)
102.7(2)
111.9(2)
90.41(11) C(7)#1−C(11)−Rh(1)
81.98(8)
C(4)#1−C(11)−Rh(1)
C(12)−C(11)−Rh(1)
Hz), 132.0, 128.8, 128.5 (d, JP−C = 7.0 Hz), 122.8, 43.60 (d, JP−C
=
178.31(9)
13.0 Hz), 27.38 (d, JP−C = 19.0 Hz), 22.78 (d, JP−C = 12.0 Hz).
31P{1H} NMR (CDCl3, 162 MHz, 25 °C): δ −16.10. Anal. Calcd for
C25H21N2P·1/2THF: C, 77.87; H, 6.05; N, 6.73. Found: C, 77.96; H,
5.85; N, 7.23.
Compound 2c
C(26)−Rh(1)
C(27)−Rh(1)
C(30)−Rh(1)
C(31)−Rh(1)
2.133(2)
2.177(2)
2.108(2)
2.137(2)
N(1)−Rh(1)
N(2)−Rh(1)
P(1)−Rh(1)#2
2.0962(18)
2.4582(19)
2.3744(9)
Synthesis of [Cu(IPr)Lp] (2a). KOtBu (6.0 mg, 0.054 mmol) and
LpH (20.0 mg, 0.053 mmol) were dissolved in THF (2 mL), and the
mixture was stirred for 0.5 h. A solution of Cu(IPr)Cl (26.1 mg, 0.054
mmol) in 2 mL of THF was then added dropwise. A change in color
from purple to navy blue was observed. The reaction mixture was
further stirred for 3 h, and the solvent was removed in vacuo. The
residue was recrystallized from THF/pentane to afford 2a as a dark
N(1)−Rh(1)−C(30)
N(1)−Rh(1)−C(26)
C(30)−Rh(1)−C(26)
N(1)−Rh(1)−C(31)
C(30)−Rh(1)−C(31)
C(26)−Rh(1)−C(31)
N(1)−Rh(1)−C(27)
C(30)−Rh(1)−C(27)
C(26)−Rh(1)−C(27)
C(31)−Rh(1)−C(27)
N(1)−Rh(1)−P(1)#2
88.69(8) C(30)−Rh(1)−P(1)#2 121.79(7)
160.53(8) C(26)−Rh(1)−P(1)#2 106.10(6)
97.80(9) C(31)−Rh(1)−P(1)#2 160.75(7)
92.03(8) C(27)−Rh(1)−P(1)#2
38.98(9) N(1)−Rh(1)−N(2)
81.90(9) C(30)−Rh(1)−N(2)
161.50(8) C(26)−Rh(1)−N(2)
80.86(9) C(31)−Rh(1)−N(2)
37.65(8) C(27)−Rh(1)−N(2)
89.39(9) P(1)#2−Rh(1)−N(2)
85.56(5)
87.04(7)
80.51(7)
141.02(8)
82.97(7)
103.69(8)
117.03(7)
94.76(5)
1
green crystalline solid (90% yield). H NMR (C6D6, 400 MHz, 25
°C): δ 7.87 (d, J = 7.8 Hz, 2H), 7.51−7.43 (m, 4H), 7.37−7.33 (m,
2H), 7.22−7.17 (m, 4H), 7.10−6.94 (m, 8H), 6.84 (d, J = 3.9 Hz,
2H), 6.38 (s, 2H), 3.54−3.43 (m, 2H), 2.76−2.66 (m, 4H), 2.51 (t, J =
7.0 Hz, 2H), 1.18 (d, J = 6.7 Hz, 12H), 1.08 (d, J = 6.7 Hz, 12H). 31P
NMR (C6D6, 121.5 MHz, 25 °C): δ −15.6 ppm. Anal. Calcd for
C104H112N8Cu2P2.2THF): C, 74.43; H, 7.14; N, 6.20. Found: C, 74.37;
H, 7.29; N, 6.43.
Compound 2d
Syntheses of [Rh(PPh3)Lp]2 (2b), [Rh(COD)Lp]2 (2c), [AuLp]2
(2d), and [Au(IPr)Lp] (2f). General Method 1 (from 2a). To a
benzene solution (2 mL) of 2a (47.9 mg, 0.053 mmol) was
added dropwise a solution of the corresponding metal reagents
(for 2b, Rh(PPh3)3Cl (48.9 mg, 0.054 mmol); for 2c,
[Rh(COD)Cl]2 (13.3 mg, 0.027 mmol); for 2d, Au(SMe2)Cl
(15.9 mg, 0.054 mmol); for 2f, Au(IPr)Cl (33.5 mg, 0.054
mmol)) in benzene (2 mL), and the reaction mixture was
stirred for 3 h. The precipitate formed was collected by
decanting the supernatant, washed with benzene several times,
and dried in vacuo to afford the products.
N(1)−Au(1)
2.075(4)
P(1)−Au(1)
2.2293(14)
N(1)−Au(1)−P(1)
170.87(13)
Compound 2e
Cl(1)−Au(1)
P(1)−Au(1)
P(1)−Au(1)−P(2)
P(1)−Au(1)−Cl(1)
2.6647(15)
2.3021(14)
147.23(5)
111.04(5)
P(2)−Au(1)
2.3128(15)
100.60(5)
P(2)−Au(1)−Cl(1)
Compound 2f
C(26)−Au(1)
2.029(3)
P(1)−Au(1)
2.2828(8)
2b. Bright orange solid, 40% yield. 1H NMR (THF-d8, 400 MHz, 25
°C): δ 7.67−7.63 (m, 12H), 7.51 (d, J = 7.2 Hz, 4H), 7.24−7.17 (m,
24H), 6.79−6.75 (m, 6H), 6.63−6.59 (m, 12H), 6.30−6.25 (m, 4H),
C(26)−Au(1)−P(1)
176.30(9)
a
Symmetry codes: (#1) −x, −y + 2, −z; (#2) −x + 1, −y, −z.
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3.00−2.93 (m, 4H), 1.33−1.24 (m, 4H). 31P{1H} NMR (THF-d8, 162
MHz, 25 °C): δ 90.58 (dd, JRh−P = 181.4 Hz, JP−P = 38.41 Hz), 64.92
(dd, JRh−P = 171.9 Hz, JP−P = 38.41 Hz). Anal. Calcd for
C86H70N4P4Rh2: C, 69.36; H, 4.74; N, 3.76. Found: C, 68.79; H,
5.04; N, 3.60.
atoms were refined anisotropically, except for the disordered portions.
In all structures hydrogen atoms bonded to carbon atoms were
included in calculated positions and treated as riding atoms. The
crystallographic data are summarized in Table 1, while selected bond
lengths and angles are given in Table 2.
1
2c. Brown solid, 85% yield. H NMR (C6D6, 300 MHz, 25 °C): δ
8.41 (d, J = 8.4 Hz, 4H), 7.81−7.75 (m, 8H), 7.08−7.03 (m, 12H),
6.91 (d, J = 4.5 Hz, 4H), 6.82 (dd, J = 8.4 Hz, J = 4.5 Hz, 4H), 5.92
(br, 4H), 3.26 (br, 4H), 3.19−3.10 (m, 4H), 2.15 (br, 16H), 1.75−
1.67 (m, 4H). 31P NMR (C6D6, 121.5 MHz): δ 27.4 (d, JRh−P = 149
Hz). Anal. Calcd for C66H64N4P2Rh2: C, 67.12; H, 5.46; N, 4.74.
Found: C, 67.31; H, 6.06; N, 4.76.
2d. Deep red solid, 50% yield. Due to the low solubility of 2d, no
NMR data were collected. Anal. Calcd for C50H40N4Au2P2·2/3C6H6: C,
53.83; H, 3.68; N, 4.65. Found: C, 53.85; H, 3.96; N, 4.47.
2f. Deep red crystalline solid (60% yield). Anal. Calcd for
C52H56N4AuP·2THF: C, 64.97; H, 6.54; N, 5.05. Found: C, 65.53;
H, 6.94; N, 5.29.
ASSOCIATED CONTENT
■
S
* Supporting Information
A table giving results of DFT calculations, a figure giving VT-
NMR spectra for 2a, and CIF files giving crystallographic data
for 1, LpH, and 2a−f. This material is available free of charge via
the Internet at http://pubs.acs.org.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: dsong@chem.utoronto.ca.
General Method 2 (from LpK Directly). To a THF solution (5 mL)
of LpK (22.2 mg, 0.053 mmol) was added dropwise a solution of the
corresponding metal reagent (for 2b, Rh(PPh3)3Cl (48.9 mg, 0.054
mmol); for 2c, [Rh(COD)Cl]2 (13.3 mg, 0.027 mmol); for 2d,
Au(SMe2)Cl (15.9 mg, 0.054 mmol); for 2f, Au(IPr)Cl (33.5 mg,
0.054 mmol)) in THF (2 mL), and the reaction mixture was stirred for
24 h. The precipitate that formed was collected by decanting the
supernatant, washed with benzene several times, and dried in vacuo to
afford the products. Yield: 2b, 20%; 2c, 15%; 2d, 23%; 2f, 24%.
Synthesis of [Au(LpH)2Cl] (2e). The ligand LpH (10.0 mg, 0.026
mmol) and Au(SMe2)Cl (3.9 mg, 0.013 mmol) were dissolved in
benzene (0.5 mL). The reaction mixture was allowed to stand for 2 h
to give colorless crystals. The supernatant was decanted, and the
crystals were washed with benzene and dried in vacuo to afford
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This research was supported by grants to D.S. from the Natural
Science and Engineering Research Council (NSERC) of
Canada, the Canadian Foundation for Innovation, the Ontario
Research Fund, and the ERA program of Ontario. R.T. is
grateful for a postgraduate scholarship from the OGS program
of Ontario.
REFERENCES
1
■
analytically pure 2e (44% single-crystal yield). H NMR (C6D6, 300
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MHz, 25 °C): δ 8.67 (d, J = 4.8 Hz, 4H), 7.42 (d, J = 7.6 Hz, 4H),
7.31 (t, J = 8.2 Hz, 8H), 7.03−6.87 (m, 12H), 6.75 (dd, J = 7.6, 5.0 Hz,
4H), 3.62 (t, J = 5.0 Hz, 2H), 2.34−2.17 (m, 4H), 2.00−1.84 (m, 4H).
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C50H44N4AuClP2: C, 60.34; H, 4.46; N, 5.63. Found: C, 60.27; H,
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X-ray Diffraction Analyses. X-ray-quality crystals of 1 were
obtained by top-layering a CH2Cl2 solution of 1 with hexanes; those of
LpH and 2a were obtained by diffusing pentane vapor into THF
solutions of LpH and 2a, respectively; those of 2b were obtained by
diffusing Et2O vapor into a THF solution of 2b; those of 2c−e were
obtained by allowing THF solutions of the reaction mixture to stand;
those of 2f were obtained by allowing a benzene solution of the
reaction mixture to stand. All crystals were mounted on the tip of a
MiTeGen MicroMount, and the single-crystal X-ray diffraction data
were collected on a Bruker Kappa Apex II diffractometer. All data were
collected with graphite-monochromated Mo Kα radiation (λ = 0.710
73 Å) at 150 K controlled by an Oxford Cryostream 700 series low-
temperature system. The diffraction data were processed with the
Bruker Apex 2 software package.23 All structures were solved by direct
methods and refined using SHELXTL V7.00.24 Compound 1
crystallized in the monoclinic space group P21/n with one molecule
per asymmetric unit; LpH crystallized in the orthorhombic space group
Pbca with one molecule per asymmetric unit; 2a crystallized in the
monoclinic space group P21/n with half a molecule per asymmetric
unit along with one molecule of THF; 2b crystallized in the
monoclinic space group P21/n with half a molecule per asymmetric
unit along with one molecule of diethyl ether; 2c crystallized in the
monoclinic space group P21/n with half a molecule per asymmetric
unit; 2d crystallized in the monoclinic space group P21/c with half a
molecule per asymmetric unit; 2e crystallized in the monoclinic space
group C2/c with one molecule per asymmetric unit; 2f crystallized in
the monoclinic space group P21/c with one molecule per asymmetric
unit along with three molecules of THF. The residual diffuse electron
density of disordered solvent molecules in the lattices of 2d,e was
removed with the SQUEEZE function of PLATON,25 and their
contributions were not included in the formula. All non-hydrogen
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Stevens, E. D.; Slawin, A. M. Z.; Nolan, S. P. Dalton Trans. 2010, 7595.
(17) For a Cu(I)-bound phosphorus donor, the 31P signal should
shift downfield significantly (>6 ppm) in comparison to the free
ligand. For examples, see: Masar, M. S. III; Mirkin, C. A.; Stern, C. L.;
Zakharov, L. N.; Rheingold, A. L. Inorg. Chem. 2004, 43, 4693.
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2000, 4601.
(21) De Fremont, P.; Scott, N. M.; Stevens, E. D.; Nolan, S. P.
Organometallics 2005, 24, 2411.
(22) Plater, M. J.; Kemp, S.; Lattmann, E. J. Chem. Soc., Perkin Trans.
1 2000, 971.
(23) Apex 2 Software Package; Bruker AXS Inc., 2008.
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(24) Sheldrick, G. M. Acta Crystallogr., Sect. A: Found. Crystallogr.
2008, 64, 112.
(25) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7.
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