Selective formation and characterization of oxorhenium(V) complexes with 2-methylquinolin-8-ylamido (Hamq). Interconversion between [ReOX2(Hamq)(PPH3)] and [ReOX2(Hamq)(OPPH3)] (X = Cl, Br)

Article abstract of DOI:10.1246/bcsj.76.1199

The reactions of Re(V) precursors [ReOX₃(PPh₃)₂] (X = Cl, Br) with 8-amino-2-methylquinoline (H2amq) gave [ReOX₂(Hamq)(PPh3)] (X = Cl, 1; Br, 2) as major products and [ReOX₂(Hamq)(OPPh₃)] (X = Cl, 3; Br, 4) as minor products. 3 and 4 were also obtained from the reaction of 1 and 2 with an excess of free OPPh₃ ligand. The crystal structures of 1, 3, and 4 were determined by X-ray analyses. These complex molecules have a distorted octahedral geometry. The Re=O bond in 1 occupies the trans position to the amido N atom of the partially deprotonated H₂amq ligand. Its distance (1.724(4) A) is long due to the trans influence of the amido N atom. The Re=O bonds in 3 and 4 occupy the trans position to the O atom of the OPPh₃ ligand, indicating a geometrical conversion during the ligand substitution reaction. Some intramolecular and/or intermolecular stacking interactions are also observed in the crystalline state. All complexes were characterized in the solid state by IR, far-IR, diffuse reflectance, and ³¹P{¹H} CP-MAS NMR spectra. From UV-vis absorption and ³¹P{¹H} NMR spectra, it was indicated that the PPh₃ and OPPh₃ ligands in 1-4 are released in solution.

Full text of DOI:10.1246/bcsj.76.1199

ꢀ 2003 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 76, 1199–1205 (2003) 1199
Selective Formation and Characterization of Oxorhenium(e) Complexes
with 2-Methylquinolin-8-ylamido (Hamq). Interconversion between
[ReOX2(Hamq)(PPh3)] and [ReOX2(Hamq)(OPPh3)] (X = Cl, Br)
#
Tetuya Ohashi, Yoshitaro Miyashita, Yasunori Yamada, Kiyoshi Fujisawa, and Ken-ichi Okamoto
ꢀ
ꢀ
Department of Chemistry, University of Tsukuba, Tsukuba 305-8571
(Received December 17, 2002)
The reactions of Re(e) precursors [ReOX3(PPh3)2] (X = Cl, Br) with 8-amino-2-methylquinoline (H2amq) gave
[ReOX2(Hamq)(PPh3)] (X = Cl, 1; Br, 2) as major products and [ReOX2(Hamq)(OPPh3)] (X = Cl, 3; Br, 4) as minor
products. 3 and 4 were also obtained from the reaction of 1 and 2 with an excess of free OPPh3 ligand. The crystal
structures of 1, 3, and 4 were determined by X-ray analyses. These complex molecules have a distorted octahedral
geometry. The Re=O bond in 1 occupies the trans position to the amido N atom of the partially deprotonated H2amq
ꢀ
ligand. Its distance (1.724(4) A) is long due to the trans influence of the amido N atom. The Re=O bonds in 3 and 4
occupy the trans position to the O atom of the OPPh3 ligand, indicating a geometrical conversion during the ligand sub-
stitution reaction. Some intramolecular and/or intermolecular stacking interactions are also observed in the crystalline
state. All complexes were characterized in the solid state by IR, far-IR, diffuse reflectance, and 31P{1Hg CP-MAS NMR
spectra. From UV-vis absorption and 31P{1Hg NMR spectra, it was indicated that the PPh3 and OPPh3 ligands in 1–4 are
released in solution.
Rhenium compounds containing an oxorhenium(e) core
have been of interest in nuclear medical theraphy.1 In addi-
tion, the oxorhenium(e) core has many other attractive fea-
tures, such as its oxygen transfer properties, catalytic proces-
ses, spectroscopy, and coordination geometry.2{7 Therefore,
it is important to explore the stereoselective synthesis and
reactivity. In recent years, the nitrogen-containing Re(e) com-
plexes, which have monodentate-N ligands or didentate-N,N li-
gands, have been widely investigated.7{13 Many symmetrical
didentate-N,N ligands, such as bipyridine12;13 and bi-
imidazole,10;11 have received special attention. When the co-
ordinated nitrogen atom is part of an arylamino group, further-
more, the deprotonated monodentate imido ligand imitates the
features of a multiple Re–N bond between double and triple
bonds, depending on the Re–N–C bond angle.14{20 Therefore,
8-aminoquinoline (H2aq), which has two types of nitrogen
atoms in a heterocyclic ring and an aromatic amine, is favor-
able as the didentate-N,N ligand from the standpoint of fixing
the bond angle of the imido ligand. In 1995, Ahmet et al. re-
ported that two equivalents of H2aq reacted with an
oxorhenium(e) precursor [ReOCl3(PPh3)2] as a didentate qui-
nolinylamido (amino group is partially deprotonated) to form
[ReO(Haq)2(PPh3)]BPh4.14 On the other hand, we have re-
cently reported that one equivalent of H2aq reacted with the
oxorhenium(e) precursor as a didentate quinolinylimido (ami-
no group is fully deprotonated) deoxidized the oxorhenium(e)
core to form [ReCl3(aq)(PPh3)].20 It occurred to us that closer
exploration was necessary to describe these properties.
amino-2-methylquinoline (H2amq), as the unsymmetrical bi-
dentate-N,N ligand and attempted to synthesize the corre-
sponding two types of Re(e) complexes; [Re-
O(Hamq)2(PPh3)]þ and [ReCl3(amq)(PPh3)]. In practice,
however, new types of complexes were obtained. Moreover,
they showed a very interesting replacement reaction that lead
to changing coordination geometry. We describe here the sys-
tematical synthesis, characterization, and coordination geome-
trical change around the oxorhenium(e) core. The intercon-
version between [ReOX2(Hamq)(PPh3)] and [ReOX2(Hamq)-
(OPPh3)] (X = Cl, Br) is also discussed on the basis of X-
ray crystal structures and some spectroscopic analyses (Chart
1).
Results and Discussion
Syntheses and Reactivity.
The reactions of the
oxorhenium(e) precursors [ReOX3(PPh3)2] (X = Cl, Br) with
8-amino-2-methylquinoline (H2amq) as a 1:2 molar ratio in the
CH2Cl2/C6H5CH3 mixed solvent gave selectively the dark
In the present work, we introduced a 2-methyl derivative, 8-
# Present Address: Department of Chemistry, Faculty of Science
and Engineering, Saga University, Saga 840-8502
Chart 1.

1200 Bull. Chem. Soc. Jpn., 76, No. 6 (2003)
Oxorhenium(e) Complexes with Quinolinylamido
brown precipitate [ReOX2(Hamq)(PPh3)] (X = Cl, 1; Br, 2)
(Eq. 1). In spite of the addition of two equivalents of
H2amq, no complexes containing two amq ligands, such as
[ReO(Hamq)2(PPh3)]þ, could be obtained. Since the bis type
complex [ReO(Haq)2(PPh3)]þ was obtained from the reaction
with an excess of H2aq,14 H2amq and H2aq seem to extract the
halide ions from the oxorhenium(e) precursors.
ð1Þ
The recrystallization of the dark brown precipitate gave two
types of crystals. Although most of them were the dark brown
prismatic-shaped crystals, the small amounts of dark brown
octahedral-shaped crystals were also formed. From X-ray ana-
lyses and IR spectra, the major crystals were the PPh3 com-
plexes [ReOX2(Hamq)(PPh3)] (X = Cl, 1; Br, 2), whereas
the minor crystals were the OPPh3 complexes [Re-
OX2(Hamq)(OPPh3)] (X = Cl, 3; Br, 4). Specifically, it seems
that oxidation and ligand substitution reactions of PPh3 with
OPPh3 occurred during the recrystallization. The OPPh3 com-
plexes 3 and 4 can also be synthesized by the reaction of 1 and
2 with an excess of free OPPh3. These reactions can be re-
versed from 3 and 4 to 1 and 2 by adding an excess of free
PPh3 (Eq. 2).
Fig. 1. An ORTEP view of [ReOCl2(Hamq)(PPh3)] (1)
with numbering scheme. Hydrogen atoms have been
omitted for clarity.
ð2Þ
Although 1–4 are stable in the solid state even under aerobic
atmosphere, it is suspected that they release PPh3 or OPPh3 in
solution from the UV-vis absorption and 31P{1Hg NMR
spectra. In the present case, therefore, it is conceivable that
the PPh3 complexes (1 and 2) and/or the OPPh3 complexes
(3 and 4) precipitate depending on the amount of free PPh3
or OPPh3 in solution. Namely, these complexes showed the
easy substitution reaction of PPh3 by OPPh3. Additionally,
it is suggested that 3 and 4 were produced as the minor pro-
ducts from the reactions of 1 and 2 with a small amount of
OPPh3, which was formed by the oxidation of free PPh3, dur-
ing the recrystallization. Since the corresponding 2-methyl-8-
quinolinolato (hmq) complex [ReOCl2(hmq)(PPh3)], which
was synthesized by the same method to 1 using Hhmq instead
of H2amq, is stable in solution and shows no reaction with
OPPh3,21 it can be said that the present easy substitution prop-
erty is very interesting. Indeed, many reported Re(e) com-
plexes with OPPh3 ligands were synthesized from the precur-
sors containing a coordinated OPPh3 ligand like [ReOCl3-
(Me2S)(OPPh3)].4;10;22;23
Fig. 2. An ORTEP view of [ReOCl2(Hamq)(OPPh3)] (3)
with numbering scheme. Hydrogen atoms have been
omitted for clarity. The numbering scheme of [Re-
OBr2(Hamq)(OPPh3)] (4) is the same as that of 3.
ꢁ
ꢀ
Table 1. Selected Bond Distances (A) and Angles ( ) for
[ReOCl2(Hamq)(PPh3)] (1)
Re1–Cl1
Re1–P1
Re1–N1
2.337(1)
2.455(1)
2.165(4)
Re1–Cl2
Re1–O1
Re1–N2
2.452(1)
1.724(4)
1.999(4)
Cl1–Re1–Cl2
Cl1–Re1–O1
Cl1–Re1–N2
Cl2–Re1–O1
Cl2–Re1–N2
P1–Re1–N1
O1–Re1–N1
N1–Re1–N2
87.46(5)
103.9(1)
86.9(1)
96.0(1)
95.0(1)
92.9(1)
94.8(2)
75.3(2)
Cl1–Re1–P1
Cl1–Re1–N1
Cl2–Re1–P1
Cl2–Re1–N1
P1–Re1–O1
P1–Re1–N2
O1–Re1–N2
92.43(5)
161.0(1)
178.34(5)
87.7(1)
82.4(1)
86.6(1)
164.9(2)
X-Ray Crystal Structures.
X-ray crystal analyses re-
vealed the presence of a complex molecule and a CH2Cl2 mo-
lecule (1) and only a complex molecule (3 and 4) in an asym-
metric unit. Perspective drawings of the complex molecules 1
and 3 are shown in Figs. 1 and 2. Selected bond distances and
angles for 1, 3, and 4 are listed in Tables 1 and 2. The coor-
dination geometry around the Re atom in 1 is a distorted octa-
hedron with the oxo ligand, the unsymmetrical didentate-N,N
ligand, two chloro ligands, and the PPh3 ligand. The oxo li-
gand and the aromatic amido N2 atom lie along the axial direc-
tion, and the heterocyclic N1 atom, the P atom, and two cis Cl
atoms occupy the equatorial plane. On the other hand, the
OPPh3 ligand in 3 and 4 occupies the trans position to the

T. Ohashi et al.
Bull. Chem. Soc. Jpn., 76, No. 6 (2003) 1201
ꢁ
ꢀ
Table 2. Selected Bond Distances (A) and Angles ( ) for [ReOX2(Hamq)(OPPh3)] (X =
Cl, 3; Br, 4)
3
4
3
4
Re1–X1
Re1–O1
Re1–N1
2.363(2)
1.670(5)
2.156(6)
2.509(1)
1.665(7)
2.170(10)
Re1–X2
Re1–O2
Re1–N2
2.447(2)
2.116(4)
1.952(7)
2.600(1)
2.125(7)
1.938(9)
X1–Re1–X2
X1–Re1–O2
X1–Re1–N2
X2–Re1–O2
X2–Re1–N2
O1–Re1–N1
O2–Re1–N1
N1–Re1–N2
85.77(9)
87.7(1)
87.5(2)
80.9(1)
163.8(2)
91.6(2)
79.7(2)
79.2(3)
86.54(5)
87.5(2)
86.6(3)
81.3(2)
164.3(3)
92.9(4)
80.0(3)
78.5(4)
X1–Re1–O1
X1–Re1–N1
X2–Re1–O1
X2–Re1–N1
O1–Re1–O2
O1–Re1–N2
O2–Re1–N2
Re1–O2–P1
102.6(2)
162.5(2)
92.6(2)
103.9(2)
167.4(2)
103.3(3)
84.2(2)
101.7(3)
161.3(3)
91.2(3)
105.0(3)
167.9(4)
104.0(4)
84.3(3)
167.6(3)
166.7(5)
ꢀ
oxo ligand, although the PPh3 ligand in 1 occupies the cis
position. This means that the coordination geometrical con-
version occurred during the ligand substitution reaction of
PPh3 with OPPh3. A similar tendency, in which the trans po-
sition of the oxo ligand prefers coordination of the oxygen
atom, as observed in 3 and 4, was generally observed for ana-
logous OPPh3 complexes.9;22;23
A, respectively. In addition, the C11–C16 phenyl ring position
is not just above the amq ring (torsion angle; N1–Re1–P1–C11
= ꢂ29:7(2)ꢁ in 1), but it is over between the methyl group C10
and the edge of the quinoline ring C1. Consequently, it is sug-
gested that intramolecular p–p and/or CH–p stacking interac-
tions exist between these two planes.22 This behavior is differ-
ent from the mono aq complex [ReCl3(aq)(PPh3)], where the
phenyl ring is just above the quinoline ring.20 This difference
can be attributed to the presence of a substitution group. The
intermolecular interactions are also considered to be a factor in
the crystal packings of the representative complexes 1 and 3
(Fig. 3). In the crystal packing of 1, quinoline rings of adja-
cent molecules are overlapping in the axial direction, and the
complex molecules assume a dimeric structure. The interplane
Although the Re–N1 distances in 1, 3, and 4 are within re-
ported Re–N(heterocyclic) distances in oxorhenium(e) com-
ꢀ
plexes (2.11–2.17 A), the Re–N2 distances are signifi-
cantly shorter than the Re–N1 distances. Since the Re–
6{10;24
ꢀ
N(amido) distances are in the range of 1.93 to 2.05 A, it is sug-
gested that the N2 amino group is partially deprotonated and
the Re–N2 bond has a multi bond character between single
and double bonds.14{16 The Re=O distance in 1, which occu-
pies the trans position to the Re–N2(amido) bond, lies at the
ꢀ
distances (average 3.46(8) A) between the two planes of the
neighboring amq moieties are within the range of intermolecu-
lar p–p stacking.30;31 Although the CH2Cl2 molecule is also
incorporated in the crystal packing, it does not participate in
any intermolecular interactions. On the other hand, in the
crystal packing of 3, the molecules align according to the
Re=O axis and no intermolecular p-p interaction is
observed. The crystal packing of 4 is almost the same as that
of 3. Consequently, this seems to indicate that the differences
in coordination geometry influence the crystal packing.
Spectroscopic Characterization. The IR spectral patterns
of 1 and 2 are very similar to each other, and those of 3 and 4,
which gave the same geometrical structure in the X-ray analy-
sis, are also similar to each other (Fig. 4). The band at ca.
3300 cmꢂ1 due to the N–H bond supports the idea of a partial-
ly deprotonated amido group. The strong IR bands of the
Re=O bond in 3 and 4 are observed at ca. 970 cmꢂ1, which
are in the normal region (1000–940 cmꢂ1) for the analogous
oxorhenium(e) complexes.32 On the other hand, 1 and 2 ex-
hibit the same IR bands at ca. 910 cmꢂ1 on the lower wave-
number side. Since the lower wavenumber shift supports the
long Re=O bond observed in the X-ray crystal analysis, it
can be inferred that the structure of 2 should be similar to that
of 1. The large differences between the PPh3 complexes and
the OPPh3 complexes are also observed at ca. 1150, 1120,
and 725 cmꢂ1. These bands, which were only observed in 3
and 4, seem to have arisen from the OPPh3 ligand, since the
free OPPh3 ligand exhibits bands at 1190, 1120, and 722
cmꢂ1. In the far-IR spectra, the Re–Cl stretching bands in 1
long end of the range found for the Re=O double bond in
6;7;14;24{27
ꢀ
oxorhenium(e) complexes (1.63–1.71 A).
On the
other hand, the Re=O distances in 3 and 4, which occupy
the trans position to the OPPh3 ligand, are normal for
oxorhenium(e) complexes. Refosco et al. reported that the
oxorhenium(e) complex [ReO{PPh2(C6H4NH-2)g2Cl] has a
ꢀ
surprisingly long Re=O bond (1.767(7) A), which also occu-
pies the trans position to the partially deprtotonated aromatic
amido.15 It is suggested, therefore, that the reason for the long
Re=O bond in 1 is the result of the trans influence of the Re–
N2(amido) bond. These characteristics are similar to those in
the bis Haq complex [ReO(Haq)2(PPh3)]þ.14 In addition, the
ꢀ
Re–Cl2 distance in 3 is 0.084 A longer than the Re–Cl1 dis-
tance because of the trans influence of the Re–N2(amido)
bond. The trans influence of the P atom is also observed in
1. The Re–Cl2 distance, which occupies the trans position
ꢀ
to the P atom, is 0.115 A longer than the Re–Cl1 distance,
which occupies the cis position to the P atom. Similar beha-
vior was also observed for the Re(e) complexes with phos-
phine ligands.7;24;28;29 The bond distances and angles in 4
are approximately the same as those of 3, except that the
ꢀ
Re–Br distances are ca. 0.15 A longer than the Re–Cl distances
(Table 2), depending on the covalent bond radii.
In the cases of both 1 and 3, the C11–C16 phenyl rings of
the phosphine ligand are approximately parallel to the quino-
line rings (dihedral angle = 22.7(2)ꢁ in 1 and 10.8(3)ꢁ in 3)
and the inter-ring average distances are 3.67(1) and 3.75(2)

1202 Bull. Chem. Soc. Jpn., 76, No. 6 (2003)
Oxorhenium(e) Complexes with Quinolinylamido
Fig. 4. IR spectra of (a) [ReOCl2(Hamq)(PPh3)] (1), (b)
[ReOBr2(Hamq)(PPh3)] (2), (c) [ReOCl2(Hamq)(OPPh3)]
(3), and (d) [ReOBr2(Hamq)(OPPh3)] (4).
Fig. 3. Projection of crystal packings for (a) [ReOCl2-
(Hamq)(PPh3)] CH2Cl2 (1 CH2Cl2) and (b) [ReOCl2-
(Hamq)(OPPh3)] (3) viewed along c axis.
ꢄ
ꢄ
Fig. 5. Diffuse reflectance spectra of (a) [ReOCl2-
(Hamq)(PPh3)] (1), (b) [ReOBr2(Hamq)(PPh3)] (2), (c)
[ReOCl2(Hamq)(OPPh3)] (3), and (d) [ReOBr2(Hamq)-
(OPPh3)] (4).
and 3 are observed at ca. 320 and 280 cmꢂ1 as two strong
bands. Although no strong bands are observed in 2 and 4 be-
low 400 cmꢂ1, it is reasonable to assume that two relatively
weak bands at ca. 230 and 210 cmꢂ1 for 2 and 4 are due to
the Re–Br stretching vibration mode by considering the re-
duced mass. Thus, 1–4 can be distinguished by the IR and
far-IR spectra.
The solid state diffuse reflectance (DR) spectral patterns of
1 and 2 are similar to each other, and those of 3 and 4 are also
similar to each other (Fig. 5). These reflect the structural simi-
larities of the complexes. The representative UV-vis absorp-
tion spectra of the chloro complexes 1 and 3, which were mea-
sured in a CH2Cl2 solution at various concentrations, are
shown in Fig. 6. In the energy region lower than 27 ꢃ 103
cmꢂ1, the absorption spectra exhibit a concentration depen-
dence, especially in 1. The absorption spectrum of 1 in con-
centrated solution is relatively similar to its DR spectrum,
whereas that in dilute solution is similar to the corresponding
absorption spectrum of 3 rather than the DR spectrum of 1. In
3, the absorption spectra of the concentrated solution and the
dilute one are similar to each other, and differ from the DR
spectrum of 3. Accordingly, 1 in dilute solution and 3 in con-
centrated and dilute solutions do not retain the structure ob-
served in the X-ray analysis. Moreover, it is believed that they
have an analogous structure which releases the PPh3 or OPPh3
ligand from each other. This is supported by the spectra of so-
lutions containing 1 or 3 (ca. 10ꢂ5 mol dmꢂ3) and a large ex-
cess of PPh3 (ca. 10ꢂ3 mol dmꢂ3) being similar to that of 1 in
concentrated solution. In all cases, Fig. 6 shows characteristic
bands at ca. 30 ꢃ 103 cmꢂ1. Although these bands appear in

T. Ohashi et al.
Bull. Chem. Soc. Jpn., 76, No. 6 (2003) 1203
Fig. 7. 31P{1Hg CP-MAS NMR spectra (spinning rate; 8000
rotation sꢂ1) of (a) [ReOCl2(Hamq)(PPh3)] (1), (b) [Re-
OBr2(Hamq)(PPh3)] (2), (c) [ReOCl2(Hamq)(OPPh3)]
(3), and (d) [ReOBr2(Hamq)(OPPh3)] (4): 6000 times of
integration for 1 and 2, 64 times integration for 3 and 4.
Fig. 6. UV-vis absorption spectra in CH2Cl2 of 1 in con-
centrated solution (2:99 ꢃ 10ꢂ3 mol dmꢂ3; —), 1 in dilute
solution (5:63 ꢃ 10ꢂ5 mol dmꢂ3; – - –), 3 in concentrated
solution (2:54 ꢃ 10ꢂ3 mol dmꢂ3; – – –), and 3 in dilute so-
lution (1:69 ꢃ 10ꢂ5 mol dmꢂ3; - - - - -).
structures of 1–4 are not retained in solution.
Conclusion
the region where the CT transition of the coordinated phos-
phine or quinoline ligands is normally observed,15 these bands
can be attributed to the coordinated amq ligand, considering
the release of the phosphine. Similar results were observed
for the bromo complexes 2 and 4.
In this work, two types of new oxorhenium(e) complexes
with 2-methylquinolin-8-ylamido, which show interconversion
with a coordination geometrical change, were prepared. They
were characterized by X-ray crystallography, IR, UV-vis, and
31P{1Hg NMR spectroscopic methods. It turned out that the
present oxorhenium(e) complexes have much higher PPh3 or
OPPh3 replacement ability than many reported oxorhenium
(e) complexes. Because of this property, free coordination
sites can be obtained easily. Further investigation of the repla-
cement reactions using many neutral monodentate ligands is
now in progress.
In CDCl3 solution, a single 31P{1Hg NMR signal was ob-
served at ꢀ ꢂ7:6 (1), ꢂ7:5 (2), 27.8 (3), and 27.7 (4). These
are close to the values of the free PPh3 (ꢀ ꢂ7:4) and OPPh3 (ꢀ
27.4) ligands, implying the release of the ligand. Moreover, no
signals due to the complex could be observed, even in a solu-
tion containing a large excess of PPh3 or OPPh3. The 1H NMR
spectra in solution could not be deciphered due to the dissocia-
tion of the ligand. For comparison, the measurements of the
31P{1Hg CP-MAS NMR spectra in the solid state were carried
out. The 31P{1Hg CP-MAS NMR spectra for 3 and 4 exhibit
many sharp signals with relatively low integration values
(Fig. 7). Changing the spin rate establishes the distinction be-
tween many spinning-sidebands and one main signal at ca. 39
ppm for 3 and 4. On the other hand, those for 1 and 2 show
very broad signals, in spite of 6000 scans for integration,
and could not be resolved. This broadening probably comes
from some quadrupole interaction of Re (I ¼ 5=2). In 1 and
2, the P atom bonds to the Re atom directly, whereas the O
atom exists between the P and Re atoms in 3 and 4. Therefore,
the OPPh3 complexes do not undergo the corresponding inter-
action, as in 1 and 2, and show sharp signals. A similar ten-
dency was also observed for their precursors; [ReOX3(PPh3)2]
(X = Cl or Br) showed broad signals, although the free PPh3
and OPPh3 ligands showed sharp signals. The sharp signal at
ca. 40 ppm in 1 is expected to come from 3, which is slightly
introduced as an impurity. Consequently, it was elucidated
that the 31P{1Hg CP-MAS NMR spectra can be used for discri-
minating the presence of a direct Re–P bond or not. Addition-
ally, the 31P{1Hg spectra also supported the fact that the crystal
Experimental
Materials. Rhenium, 8-amino-2-methylquinoline (H2amq),
and triphenylphosphine oxide (OPPh3) were purchased from Soe-
kawa Chemical Co., Ltd., Tokyo Kasei Kogyo Co., Ltd., and Al-
drich Chemical Co., Inc., respectively. The other materials were
purchased from Wako Pure Chemical Ind., Ltd. All the chemicals
were used without further purification. The starting materials [Re-
OCl3(PPh3)2] and [ReOBr3(PPh3)2] were prepared by the general
procedure from perrhenate and triphenylphosphine (PPh3).33
Preparation of Complexes. [ReOCl2(Hamq)(PPh3)] (1):
To a suspension containing [ReOCl3(PPh3)2] (515 mg, 0.618
mmol) in CH2Cl2 (35 cm3) was added a solution containing
H2amq (190 mg, 1.20 mmol) in C6H5CH3 (15 cm3). The light
green mixture was stirred for 1 h, whereupon the suspension
turned to dark brown. After removing yellow insoluble materials
(mainly H3amqCl) by filtration, the filtrate was concentrated to 10
cm3 under vacuum. The resulting dark brown precipitate was col-
lected by filtration and washed with H2O and Et2O. Yield: 314 mg
(73.3%). The precipitate was recrystallized from CH2Cl2/
C6H5CH3 to yield dark brown prismatic crystals (1, major pro-
duct) and dark brown octahedral crystals (3, minor product).
3

1204 Bull. Chem. Soc. Jpn., 76, No. 6 (2003)
Oxorhenium(e) Complexes with Quinolinylamido
can be removed to a certain extent by washing with EtOH. Anal.
Found: C, 48.54; H, 3.32; N, 4.15%. Calcd for [Re-
OCl2(C10H9N2)P(C6H5)3]: C, 48.56; H, 3.49; N, 4.04%. IR
mg (62.5%). Anal. Found: C, 47.51; H, 3.47; N, 3.85%. Calcd for
[ReOCl2(C10H9N2)OP(C6H5)3]: C, 47.46; H, 3.41; N, 3.95%. IR
3316m (N–H) and 973s (Re=O) cmꢂ1
. Far IR 316s and 280s
31P{1Hg CP-
3292m (N–H) and 908s (Re=O) cmꢂ1
.
Far IR 334s and 270s
(Re–Cl) cmꢂ1
MAS NMR ꢀ 38.4.
.
DR 13.6, 19.9, 22:7 ꢃ 103 cmꢂ1
.
(Re–Cl) cmꢂ1. DR 16.5sh, 19.1sh, 22:2 ꢃ 103 cmꢂ1. The sh label
denotes a shoulder. H3amqCl was also obtained by the treatment
of H2amq with HCl. This was confirmed by elemental analysis
and IR spectra.
[ReOBr2(Hamq)(OPPh3)] (4): The bromo complex 4 was
synthesized by a similar method to the chloro complex 3. After
2 (98.2 mg, 0.126 mmol) was reacted with OPPh3 (360 mg,
1.29 mmol) in the mixed solvent of CH2Cl2 and C6H5CH3, the re-
action mixture was concentrated under vacuum. The resulting
brown precipitate was redissolved in the mixed solvent and reac-
ted with OPPh3 again. After the solution was concentrated, a red-
dish brown precipitate appeared. Yield: 42.3 mg (42.1%). Anal.
Found: C, 42.14; H, 2.87; N, 3.65%. Calcd for [Re-
OBr2(C10H9N2)OP(C6H5)3]: C, 42.17; H, 3.03; N, 3.51%. IR
3311m (N–H) and 972s (Re=O) cmꢂ1. Far IR 231w and 210w
[ReOBr2(Hamq)(PPh3)] (2): The bromo complex 2 was syn-
thesized by a similar method to the chloro complex 1. To a sus-
pension containing [ReOBr3(PPh3)2] (500 mg, 0.517 mmol) in
CH2Cl2 (130 cm3) was added a solution containing H2amq (160
mg, 1.01 mmol) in C6H5CH3 (20 cm3). The yellow mixture
was stirred for 1 h, whereupon the suspension turned to dark
brown. After removing insoluble materials, the filtrate was con-
centrated to 10 cm3 under vacuum. A dark brown precipitate
appeared. Yield: 331 mg (81.9%). The precipitate was recrystal-
lized from CH2Cl2/C6H5CH3 to yield dark brown microcrystals
(2, major product) and dark brown octahedral crystals (4, minor
product). Anal. Found: C, 42.52; H, 2.93; N, 3.83%. Calcd for
[ReOBr2(C10H9N2)P(C6H5)3]: C, 43.03; H, 3.10; N, 3.58%. IR
3254m (N–H) and 915s (Re=O) cmꢂ1. Far IR 224w and 202w
(Re–Br) cmꢂ1. DR 16.6, 19.1sh, 21:7 ꢃ 103 cmꢂ1. 1 and 2 are so-
luble in CH2Cl2 and CHCl3, slightly soluble in EtOH, and insolu-
ble in H2O and Et2O.
[ReOCl2(Hamq)(OPPh3)] (3): To a solution containing 1
(90.2 mg, 0.130 mmol) in the mixed solvent of CH2Cl2 (60
cm3) and C6H5CH3 (10 cm3) was added OPPh3 (383 mg, 1.38
mmol) and stirred for 10 min. The dark brown solution was fil-
tered to remove insoluble materials and the filtrate was concentrat-
ed to 10 cm3 under vacuum. After the resulting brown precipitate
was collected by filtration and washed with Et2O, the precipitate
was redissolved in the mixed solvent of CH2Cl2 (60 cm3) and
C6H5CH3 (10 cm3). To this solution was added OPPh3 (370
mg, 1.33 mmol), filtered, and concentrated to 10 cm3 under va-
cuum again. The resulting reddish brown precipitate was filtered
and washed with a small amount of EtOH and Et2O. Yield: 57.6
(Re–Br) cmꢂ1
.
DR 13.8sh, 19.2sh, 22:5 ꢃ 103 cmꢂ1
.
31P{1Hg CP-MAS NMR ꢀ 39.7. 3 and 4 are soluble in CH2Cl2,
CHCl3, and EtOH, and insoluble in H2O and Et2O.
Reaction of [ReOX2(Hamq)(OPPh3)] with PPh3. To a solu-
tion containing 3 (20.6 mg, 0.0291 mmol) in the mixed solvent of
CH2Cl2 (20 cm3) and C6H5CH3 (5 cm3) was added PPh3 (76.4
mg, 0.291 mmol). The dark brown solution was stirred for 15
min and concentrated to 5 cm3 under vacuum. The resulting dark
brown precipitate of 1 was collected by filtration and washed with
Et2O. Yield: 9.7 mg (48%). 2 was also obtained by the same
method using 4 (20.4 mg, 0.0260 mmol) and PPh3 (68.4 mg,
0.261 mmol). Yield: 12.7 mg (63.6%). These were confirmed
by IR spectra.
Measurements. Elemental analyses (C, H, N) were performed
by the Chemical Analysis Center of the University of Tsukuba. IR
and far-IR spectra were recorded on a JASCO FT/IR-550 spectro-
meter as KBr pellets and Nujol mulls between polyethylene plates,
respectively. UV-vis absorption spectra were recorded on a JAS-
CO V-560 spectrophotometer. Diffuse reflectance spectra were
recorded on a JASCO V-570 spectrophotometer equipped with
an integrating sphere apparatus (JASCO ISN-470) using powder
Table 3. Crystal Data and Experimental Parameters for [ReOCl2(Hamq)(PPh3)] CH2Cl2 (1 CH2Cl2), [Re-
ꢄ
ꢄ
OCl2(Hamq)(OPPh3)] (3), and [ReOBr2(Hamq)(OPPh3)] (4)
1 CH2Cl2
ꢄ
3
4
Formula
C29H26Cl4N2OPRe
777.53
triclinic
C28H24Cl2N2O2PRe
708.60
monoclinic
P21=n (No. 14)
14.90(1)
C28H24Br2N2O2PRe
797.50
monoclinic
P21=n (No. 14)
15.127(3)
Formula weight
Crystal system
Space group
ꢁ
P1 (No. 2)
ꢀ
a/A
11.551(2)
14.105(2)
10.133(1)
91.258(9)
109.252(10)
75.30(1)
1504.2(3)
2
ꢀ
b/A
17.272(4)
10.485(2)
17.376(4)
10.569(2)
ꢀ
c/A
ꢁ/ꢁ
ꢂ/ꢁ
ꢃ/ꢁ
95.46(4)
96.56(2)
ꢀ 3
V/A
Z
2685(2)
4
1.75
48.1
6722, 6180, 0.037
2759.6(10)
4
1.92
74.0
6901, 6347, 0.038
Dcalcd/g cmꢂ3
ꢄ (Mo Kꢁ)/cmꢂ1
Reflections collected, unique, Rint 7390, 6902, 0.018
1.72
44.7
Reflections used (I > 1:5ꢅðIÞ)
Variable Parameters
Final RðF2Þ, RwðF2Þ
GOF
5824
343
0.053, 0.086
1.02
4862
325
0.068, 0.106
1.40
4058
325
0.074, 0.116
1.11

T. Ohashi et al.
Bull. Chem. Soc. Jpn., 76, No. 6 (2003) 1205
samples diluted by MgO. 1H and 31P{1Hg NMR spectra in CDCl3
were obtained on a BRUKER AVANCE 600 spectrometer with
SiMe4 as an internal reference and PPh3 as an external reference
(in CDCl3, PPh3 resonates at ꢀ ꢂ7:42 with respect to 85% H3PO4
in D2O),15 respectively. 31P{1Hg CP-MAS NMR spectra were ob-
tained at 243 MHz with the BRUKER AVANCE 600 spectrome-
11 S. Fortin and A. L. Beauchamp, Acta Crystallogr., Sect. C,
55, 517 (1999).
12 J. C. Bryan, R. E. Stenkamp, T. H. Tulip, and J. M. Mayer,
Inorg. Chem., 26, 2283 (1987).
13 J.-H. Jung, J.-S. Park, D. M. Hoffman, and T. R. Lee, Poly-
hedron, 20, 2129 (2001).
ter equipped with
NH4H2PO4 as an external reference (ꢀ 1.0).
Crystallography. Single crystals of 1 CH2Cl2, 3, and 4 were
used for data collection on a Rigaku AFC-7S four-circle diffract-
ometer with graphite-monochromatized Mo Kꢁ (0.71069 A)
radiation. The unit-cell dimensions were determined by a least-
squares refinement of 25 reflections. The intensity data were col-
lected by the !–2ꢆ scan technique up to 55ꢁ at 296 K. The inten-
sities were corrected for Lorentz and polarization. An empirical
absorption correction based on a series of ꢇ scans was applied.
The crystal data and experimental parameters are listed in Table 3.
The positions of most non-hydrogen atoms were determined by
a direct method (SIR 92)34 and some remaining atoms positions
were found by successive difference Fourier techniques.35 The
structures were refined by full-matrix least-squares techniques
using anisotropic thermal parameters for non-hydrogen atoms.
All the hydrogen atoms were included in the refinement but re-
a
PHMAS 4BL VTN instrument and
14 M. T. Ahmet, B. Coutinho, J. R. Dilworth, J. R. Miller, S.
J. Parrott, Y. Zheng, M. Harman, M. B. Hursthouse, and A. Malik,
J. Chem. Soc., Dalton Trans., 1995, 3041.
15 F. Refosco, F. Tisato, G. Bandoli, C. Bolzati, A. Moresco,
and M. Nicolini, J. Chem. Soc., Dalton Trans., 1993, 605.
16 G. Bandoli, A. Dolmella, T. I. A. Gerber, J. Perils, and J.
G. H. du Preez, Inorg. Chim. Acta, 303, 24 (2000).
17 H. Luo, I. Setyawati, S. J. Rettig, and C. Orvig, Inorg.
Chem., 34, 2287 (1995).
18 M. Hirsch-Kuchma, T. Nicholson, A. Davison, W. M.
Davis, and A. G. Jones, Inorg. Chem., 36, 3237 (1997).
19 G. Bandoli, T. I. A. Gerber, J. Perils, and J. G. H. du Preez,
Inorg. Chim. Acta, 278, 96 (1998).
20 Y. Miyashita, N. Mahboob, S. Tsuboi, Y. Yamada, K.
Fujisawa, and K. Okamoto, Acta Crystallogr., Sect. C, 57, 558
(2001).
ꢄ
ꢀ
21 Unpublished results.
ꢀ
strained to ride on the atoms (C–H = N–H = 0.95 A, U(H) =
22 L. Hansen, E. Alessio, M. Iwamoto, P. A. Marzilli, and L.
G. Marzilli, Inorg. Chim. Acta, 240, 413 (1995).
23 G. Battistuzzi, M. Cannio, M. Saladini, and R. Battistuzzi,
Inorg. Chim. Acta, 320, 178 (2001).
24 X. Chen, F. J. Femia, J. W. Babich, and J. Zubieta, Inorg.
Chim. Acta, 308, 80 (2000).
1.2U(C, N)). All of the calculations were performed using the
teXsan crystallographic software package.36 Crystallographic
data have been deposited at the CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK and copies can be obtained on request, free
of charge, by quoting the publication citation and the deposition
numbers 185380–185382.
25 J. M. Mayer, D. L. Thorn, and T. H. Tulip, J. Am. Chem.
Soc., 107, 7454 (1985).
26 T. I. A. Gerber, J. Bruwer, G. Bandoli, J. Perils, and J. G.
H. du Preez, J. Chem. Soc., Dalton Trans., 1995, 2189.
27 C. Bolzati, F. Tisato, F. Refosco, G Bandoli, and A.
Dolmella, Inorg. Chem., 35, 6221 (1996).
This work was supported by Grants-in-Aid for Scientific
Research and COE Research from the Ministry of Education,
Culture, Sports, Science and Technology.
28 X. Chen, F. J. Femia, J. W. Babich, and J. Zubieta, Inorg.
Chim. Acta, 306, 113 (2000).
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