Hydrido-oxo complexes of rhenium(V): Synthesis, structure, spectroscopic properties, and reactions with acids and bases

Article abstract of DOI:10.1016/S0020-1693(03)00153-1

The reaction of [ReH₄(η²-H₂)(Cyttp)]X (X=SbF₆ (1(SbF₆)), OTf (1OTf)); Cyttp=PhP(CH₂CH₂CH₂PCy₂) ₂, OTf=O₃SCF₃) with neat acetone at reflux temperature affords the dihydrido-oxo complex [ReH₂(O)(Cyttp)]X (X=SbF₆ (2(SbF₆)), OTf (2(OTf))). The isotopomers [ReH₂(¹⁸O)(Cyttp)]SbF₆ (2-¹⁸O(SbF₆)), [ReD₂(O)(Cyttp)]SbF₆ (2-d₂(SbF₆)), and [ReD₂(¹⁸O)(Cyttp)]SbF₆ (2-d₂,¹⁸O(SbF₆)) were prepared, respectively, by treatment of 2(SbF₆) with H₂¹⁸O, D₂ under photolysis, and D₂ followed by H₂¹⁸O. The structure of 2 (as 2(SbF₆)·3/4MeOH) was determined by single-crystal X-ray diffraction analysis and shown to contain a meridionally-coordinated Cyttp and an oxo ligand approximately cis to each of the three phosphorus donor atoms (Re-O=1.732(7) A?). The hydrido ligands were not located; however, their presence in the positions essentially cis and trans to the oxide in a severely distorted coordination octahedron of the metal is suggested by the elucidated molecular structure. The ¹H NMR signals at δ -1.04 (tt) and -12.62 (dtd) and the IR ν(ReH) absorptions at 2030 and 1716 cm^-1 provide strong evidence for this assignment. The IR ν(Re¹⁶O) band of 2(SbF₆) at 923 cm^-1 surprisingly shifts to 897 cm^-1 in 2-d₂(SbF₆). Similarly, the ν(Re¹⁸O) of 2-¹⁸O(SbF₆) at 887 cm^-1 moves to 854 cm^-1 in 2-d₂,¹⁸O(SbF₆). Changes are also observed for one of the δ(ReH) absorptions of 2(SbF₆) at 817 cm^-1, which appears at 810 cm^-1 in 2-¹⁸O(SbF₆). A simple analysis of the ν(ReO) and δ(ReH or ReD) vibrational frequencies suggests that a resonance interaction occurs between the ν(ReO) and one of the δ(ReH) modes. Complex 2(OTf) reacts at low temperature with KOH-pyridine to form [Re(O)₂(py)(Cyttp)]OTf, and with Li[BEt₃H] in excess to give ReH₅(Cyttp). Treatment of 2(OTf) with aqueous HCl in benzene yields a green solid which is formulated as [ReH₂(OH)Cl(Cyttp)]OTf from spectroscopic evidence.

Full text of DOI:10.1016/S0020-1693(03)00153-1

Inorganica Chimica Acta 352 (2003) 171ꢁ178
/
www.elsevier.com/locate/ica
Hydrido-oxo complexes of rhenium(V): synthesis, structure,
spectroscopic properties, and reactions with acids and bases
Youhyuk Kim 1, Dean E. Rende 2, Judith C. Gallucci 3, Andrew Wojcicki *
Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210-1185, USA
Received 27 August 2002; accepted 30 October 2002
Dedicated to Professor Martin A. Bennett in recognition his many contributions to inorganic chemistry
Abstract
The reaction of [ReH4(h2-H2)(Cyttp)]X (Xꢀ
SbF6 (2(SbF6)), OTf (2(OTf))).
The isotopomers [ReH2(18O)(Cyttp)]SbF6 (2-18O(SbF6)), [ReD2(O)(Cyttp)]SbF6 (2-d2(SbF6)), and [ReD2(18O)(Cyttp)]SbF6 (2-
d2,18O(SbF6)) were prepared, respectively, by treatment of 2(SbF6) with H128O, D2 under photolysis, and D2 followed by H128O. The
/
SbF6 (1(SbF6)), OTf (1OTf)); Cyttpꢀ
/
PhP(CH2CH2CH2PCy2)2, OTfꢀ
/O3SCF3)
with neat acetone at reflux temperature affords the dihydrido-oxo complex [ReH2(O)(Cyttp)]X (Xꢀ
/
structure of 2 (as 2(SbF6)×
/
3/4MeOH) was determined by single-crystal X-ray diffraction analysis and shown to contain a
meridionally-coordinated Cyttp and an oxo ligand approximately cis to each of the three phosphorus donor atoms (Reꢁ
/
Oꢀ
/
˚
1.732(7) A). The hydrido ligands were not located; however, their presence in the positions essentially cis and trans to the oxide in a
severely distorted coordination octahedron of the metal is suggested by the elucidated molecular structure. The 1H NMR signals at
d ꢂ
/
1.04 (tt) and ꢂ
12.62 (dtd) and the IR n(ReH) absorptions at 2030 and 1716 cmꢂ1 provide strong evidence for this assignment.
/
The IR n(Re16O) band of 2(SbF6) at 923 cmꢂ1 surprisingly shifts to 897 cmꢂ1 in 2-d2(SbF6). Similarly, the n(Re18O) of 2-18O(SbF6)
at 887 cmꢂ1 moves to 854 cmꢂ1 in 2-d2,18O(SbF6). Changes are also observed for one of the d(ReH) absorptions of 2(SbF6) at 817
cmꢂ1, which appears at 810 cmꢂ1 in 2-18O(SbF6). A simple analysis of the n(ReO) and d(ReH or ReD) vibrational frequencies
suggests that a resonance interaction occurs between the n(ReO) and one of the d(ReH) modes. Complex 2(OTf) reacts at low
temperature with KOHꢁpyridine to form [Re(O)2(py)(Cyttp)]OTf, and with Li[BEt3H] in excess to give ReH5(Cyttp). Treatment of
/
2(OTf) with aqueous HCl in benzene yields a green solid which is formulated as [ReH2(OH)Cl(Cyttp)]OTf from spectroscopic
evidence.
# 2003 Elsevier Science B.V. All rights reserved.
Keywords: Rhenium complexes; Hydrido complexes; Oxo complexes; Isotopomers; IR spectra; Crystal structure
1. Introduction
since 1976. Most of them have dealt with binuclear and
polynuclear metal hydrido-oxo compounds, which are
known for both homometallic and heterometallic sys-
Reports of new transition-metal hydrido-oxo com-
plexes have been gradually appearing in the literature
tems, including Ta2 [1], W2 [2], Re3 [3], Ru3 [4ꢁ6], Re4
/
[7], WRe [8], WRe2 [9], W2Re2 [8a], MnFe3 [10], MoOs3
[11], and WOs3 [12]. In practically all of these com-
pounds, one or more hydride and a single oxide serve as
bridging ligands (m2 for H; m2, m3 or m4 for O), and at
least one metal center bonds to both hydride and oxide.
Compared to the foregoing, the number of known
mononuclear transition-metal hydrido-oxo complexes is
still very modest. In 1986 Bercaw and coworkers
ꢃ
* Corresponding author. Tel.: ꢄ
1685.
E-mail
wojcicki@chemistry.ohio-state.edu (A. Wojcicki).
/
1-614-292 4750; fax: ꢄ
/
1-614-292
addresses:
gallucci.1@osu.edu
(J.C.
Gallucci),
1
Present address: Department of Chemistry, School of
Fundamental Sciences, Dankook University, Cheonan, Chungnam
330-714, South Korea.
2
Present address: UOP, 50 East Algonquin Road, PO Box 5016,
Des Plaines, IL 60017-5016, USA.
reported the synthesis of Cp2 Ta(O)H (Cp*ꢀ
h5-
/
ꢃ
3
C5Me5) by reaction of Cp2Ta(CH2)H with H2O [13],
To whom inquiries concerning the X-ray crystallographic study
?
and later Moıse et al. prepared the related Cp Ta(O)H
¨
2
should be addressed. Fax: ꢄ
/
1-614-292-1685.
0020-1693/03/$ - see front matter # 2003 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0020-1693(03)00153-1

172
Y. Kim et al. / Inorganica Chimica Acta 352 (2003) 171ꢁ
/178
h5-C5H4Bu-t) from Cp2TaCl2H [14a] or
[Cp2TaH2] [14b] and hydroxide. The first hydrido-
2.3. Preparation of [ReH2(O)(Cyttp)]SbF6 (2(SbF6))
?
(Cp?ꢀ
/
ꢄ
?
oxo complexes of rhenium, Re(RCÅ
or Et), were obtained in 1989 by Mayer and coworkers
via thermolysis of Re(RCÅCR)2(O)(O2CH) [15a]. The
analogous Re(PhCÅCPh)2(O)H resulted on treatment of
Re(PhCÅCPh)2(O)I with (n-Bu)3SnH [15b]. Subse-
quently, it was demonstrated that Re(EtCÅCEt)3(OH)
rearranges with loss of one EtCÅCEt ligand also to yield
Re(EtCÅCEt)2(O)H [16]. Other reported Re complexes
/
CR)2(O)H (Rꢀ
/
Me
A colorless solution of 1(SbF6) (1.0 g, 0.98 mmol) in
150 ml of acetone was maintained at reflux temperature
/
(ca. 60 8C) for 12ꢁ15 h during which time it turned
/
/
brown. The solution was allowed to cool to room
temperature (r.t.) and was concentrated to approxi-
mately 5 ml under reduced pressure. Addition of 30 ml
of Et2O resulted in the formation of a light tan
precipitate. The solid was collected on a filter frit,
washed with a small amount of Et2O, and dried under
vacuum overnight. The yield of 2(SbF6) was 0.90 g
/
/
/
/
are those of rhenium(V) and include TpRe(O)(H)Cl,
Tp*Re(O)H2, Tp*Re(O)(H)Cl, and Tp*Re(O)(H)OTf
(Tpꢀ
(3,5-dimethyl-1-pyrazolyl)borate, OTfꢀ
as well as [ReH2(O)(Cyttp)]ꢄ and [ReH(O)(F)(Cyttp)]ꢄ
(CyttpꢀPhP(CH2CH2CH2PCy2)2) [18,19].
/
hydridotris(pyrazolyl)borate, Tp*ꢀ/hydridotris-
(90%). IR (Nujol): n(ReH) 2030 (w), 1716 (m) cmꢂ1
n(ReO) 923 (m) cmꢂ1, d(ReH) 845 (m), 817 (m) cmꢂ1
,
,
/O3SCF3) [17],
n(SbF6) 650 (s) cmꢂ1. 1H NMR (CD2Cl2, Cyttp signals
2
/
not given): d ꢂ
/
1.04 (tt, JHHꢀ2
/
JP H
ꢀ
/
5.0 Hz (PCꢀ
/
C
2
Interest attaches to metal complexes with hydrido and
oxo ligands because of their potential to transfer both of
these atoms to various unsaturated substrates. In
addition, the coupling of H and O ligands to generate
OH is a transformation of current research interest and
activity [16,17,20].
central P), JP Hꢀ
/
25.0 Hz (PWꢀ
/wing P), 1 H, ReH),
W
2
2
2
ꢂ
/
12.62 (dtd, JHH
35.0 Hz, 1 H, ReH). 31P{1H} NMR (CD2Cl2): d 22.56
(d, 2JP P 18.3 Hz, PW), 6.77 (t, 2JP P
18.3 Hz, PC).
ꢀ
/
5.0 Hz, JP H
ꢀ
/
57.5 Hz, JP Hꢀ
/
C
W
ꢀ
/
ꢀ
/
C
W
C W
Anal. Found: C, 42.19; H, 5.91. Calc. for C36H63F6O-
P3ReSb: C, 42.11; H, 6.18%.
In this paper we report the synthesis, structure,
spectroscopic properties, and reactions with acids and
bases of the rhenium(V) complex [ReH2(O)(Cyttp)]ꢄ
(2). Later, related publications will deal with mechanism
of formation of 2 from [ReH4(h2-H2)(Cyttp)]ꢄ (1) and
ketones [21] and with the transfer of the hydrido and
oxo ligands of 2 to several unsaturated substrates [22]. A
related study on [ReH(O)(F)(Cyttp)]ꢄ (3) and prelimin-
ary results on 2 have appeared in print [18,19].
2.4. Preparation of [ReH2(O)(Cyttp)]OTf (2(OTf))
The reaction between 1(OTf) and acetone was carried
out under the same conditions as that between 1(SbF6)
and acetone, with essentially identical results. Spectro-
scopic properties of 2(OTf) matched those given for
2(SbF6), except for the data characteristic of the anions.
2.5. Preparation of isotopomers of
[ReH2(O)(Cyttp)]SbF6 (2(SbF6)
2. Experimental
2.5.1. Preparation of [ReD2(O)(Cyttp)]SbF6 (2-
d2(SbF6))
2.1. General procedures and measurements
A deoxygenated benzene solution (30 ml) of [Re-
H2(O)(Cyttp)]SbF6 (2(SbF6)) (0.30 g, 0.29 mmol) in a
Pyrex Schlenk flask was irradiated with a 450-W
Hanovia medium-pressure Hg lamp at a distance of
approximately 20 cm under a slow, continuous purge of
D2. After 30 min solvent was removed, and Et2O (15 ml)
was added to the light tan residue. The solid was filtered
off, washed with Et2O, and dried under vacuum over-
night. Yield, 0.25 g (83%). IR (Nujol): n(ReO) 897 (s)
Reactions and manipulations of air-sensitive com-
pounds were conducted under an atmosphere of dry
argon by use of standard procedures [23]. Solvents were
dried [24], distilled under argon, and degassed before
use. Elemental analyses were performed by M-H-W
2
Laboratories, Phoenix, AZ. IR and NMR (1H, H, 19F,
and 31P) spectra were obtained as described previously
[25,26].
2
cmꢂ1, d(ReD) 582 (w) cmꢂ1. H NMR (acetone-d6): d
2
12.6 (dt, JP D
2
ꢂ
/
1.0 (t, ReD), ꢂ
/
ꢀ
/
8.5 Hz, JP Dꢀ5.6
/
C
W
2.2. Materials
Hz, ReD). 31P NMR (CD2Cl2): d 23.0 (br s, PW), 7.3 (br
s, PC).
Reagents were procured from commercial sources and
used as received, except as noted below. The complex
2.5.2. Preparation of [ReH2(18O)(Cyttp)]SbF6
(2-18O(SbF6))
A solution of [ReH2(O)(Cyttp)]SbF6 (2(SbF6)) (0.20
g, 0.19 mmol) and excess H128O (0.25 ml, 13 mmol) in 30
ml of benzene was stirred for 10 h at r.t. The work-up
was identical with that in Section 2.5.1. Yield, 0.18 g
[ReH4(h2-H2)Cyttp)]SbF6 (1(SbF6), Cyttpꢀ
CH2CH2PCy2)2) was prepared according to the litera-
/PhP(CH2-
ture [27]. [ReH4(h2-H2)(Cytttp)]OTf (1(OTf), OTfꢀ
O3SCF3) was synthesized analogously from Re-
H5(Cyttp) [28] by using HOTf in place of HSbF6.
/

Y. Kim et al. / Inorganica Chimica Acta 352 (2003) 171ꢁ
/178
173
(90%). IR (Nujol): n(ReH) 2028 (w), 1737 (w), 1687 (w)
cmꢂ1, n(Re18O) 887 (m) cmꢂ1, d(ReH) 845 (m), 810
2.8. Crystallographic analysis of
[ReH2(O)(Cyttp)]SbF6×3/4MeOH (2(SbF6)×
4MeOH)
/
/3/
(m) cmꢂ1
.
The crystal used for data collection was orangeꢁ
/
red in
2.5.3. Preparation of [ReD2(18O)(Cyttp)]SbF6 (2-
d2,18O(SbF6))
color, clear, and multifaceted. Examination of the
diffraction pattern at 223 K on a Rigaku AFC5S
diffractometer revealed a monoclinic crystal system
The preparation was identical with that of [Re-
H2(18O)(Cyttp)]SbF6 (2-18O(SbF6)) (Section 2.5.2), ex-
cept that [ReD2(O)(Cyttp)]SbF6 (2-d2(SbF6)) was used
in place of [ReH2(O)(Cyttp)]SbF6 (2(SbF6)). IR (Nujol):
with systematic absences h0l, hꢄ
/
lꢀ
/
2nꢄ1, and 0k0,
/
kꢀ2nꢄ1, which uniquely determine the space group as
/
/
P21/n. The cell constants were obtained by a symmetry-
restricted least-squares fit of the diffractometer setting
n(Re18O) 854 (s) cmꢂ1, d(ReD) 582 (w) cmꢂ1
NMR (CD2Cl2): d 23.0 (br s, PW), 7.3 (br s, PC).
.
31P
angles for 25 reflections in the 2u range 21ꢁ
/
308 with Mo
Ka radiation.
Data were collected by the v scan method at 223 K.
Six standard reflections were measured after every 150
reflections during data collection and indicated that a
very small amount of crystal decomposition had
occurred. On the average the intensities of the standards
decreased by 3.4%. The data were corrected for Lorentz
and polarization effects and for decay. A correction for
absorption was made by the empirical c-scan method
[29]. All calculations were done by the TEXSAN package
of crystallographic programs [30].
The position of the Re atom was found from a
Patterson map and used as a phasing model in the
DIRDIF direct methods procedure [31]. Much of the Re
complex and the SbF6 anion were then located on the
resulting electron density map. The remaining non-
hydrogen atoms were subsequently located by standard
Fourier methods. Full-matrix least-squares refinements
based on F were performed in TEXSAN [30]. It eventually
became apparent that there are three additional peaks
near an inversion center and that they are not associated
with the Re complex or the SbF6 anion. These peaks are
assumed to be part of a disordered solvent molecule.
2.6. Reaction of [ReH2(O)(Cyttp)]OTf (2(OTf)) with
KOH and pyridine
A solution of 2(OTf) (0.062 g, 0.066 mmol) and
pyridine (0.100 ml, 1.24 mmol) in 10 ml of CH2Cl2 was
cooled to ꢂ78 8C and treated with KOH (0.010 g, 0.17
/
mmol). The contents were allowed to warm to r.t. with
stirring over a 5-h period and then were concentrated to
2 ml under reduced pressure. Addition of Et2O resulted
in the formation of a yellow precipitate which was
washed with 4 ml of H2O and 5 ml of Et2O and dried
overnight. The yield of [Re(O)2(py)(Cyttp)]OTf was
0.067 g (85%). Selected spectroscopic data. IR (Nujol):
n(ReO) 817 (s) cmꢂ1
.
31P{1H} NMR (CD2Cl2): d
2
2
ꢂ
/
21.9 (t, JP P
ꢀ
/
17.3 Hz, PC), ꢂ
/
26.1 (d, JP P
ꢀ
/
C
W
C
17.3 Hz, PW). 19F{1H} NMR (CD2Cl2): d ꢂW
(referenced to internal CFCl3, s, OTfꢂ). Anal. Found:
C, 49.40; H, 6.28; N, 1.23. Calc. for
/
77.3
C42H66F3NO5P3ReS: C, 48.83; H, 6.44; N, 1.36%.
Crystals suitable for X-ray diffraction analysis were
grown from a CH2Cl2ꢁhexane solution.
/
Since the crystals were grown from CH2Cl2ꢁ
/MeOH,
and since the heights of these peaks are within a small
/
3.3 e Aꢂ3), it is assumed that the disordered
˚
range (2.3ꢁ
2.7. Reaction of [ReH2(O)(Cyttp)]OTf (2(OTf)) with
aqueous HCl
solvent molecule is methanol. All three peaks are labeled
as carbon atoms (C(37), C(38), and C(39)) and given
occupancy factors of 0.5. The interpretation of this
model is as follows: 50% of the time a methanol
molecule is located on an inversion center (C(39) and
C(39)? [related by the inversion center] for a total of two
MeOH molecules in the unit cell), and 50% of the time a
methanol molecule is located in a general position
(C(38)) for a total of four MeOH’s in the unit cell).
The molecular formula is then an average of these two
A solution of 2(OTf) (0.050 g, 0.053 mmol) in 5 ml of
benzene was treated with 0.50 ml of 1.20 M aqueous
HCl, and the contents were vigorously stirred for 30 min
resulting in the formation of a yellow precipitate. The
solid was filtered off, washed with benzene, and dried
overnight. It turned from yellow to fluorescent green
upon drying for 4 h under reduced pressure. The yield of
[ReH2(OH)Cl(Cyttp)]OTf was 0.035 g (67%). Selected
models and is given as [ReH2(O)(Cyttp)]SbF6×
/3/
spectroscopic data. IR (Nujol): n(OH) ꢀ
/
3280 (br)
4MeOH. The atoms involved in the disorder model
are kept at the isotropic level of refinement. After
anisotropic refinement the hydrogen atoms were in-
cmꢂ1, n(ReH) 1617 (m) cmꢂ1. H NMR (CD2Cl2): d
1
ꢂ
/
3.3 (br, 1 H, ReH), ꢂ
/
7.9 (br m, 1 H, ReH). 31P{1H}
2
NMR (CD2Cl2): d 29.3 (br, PW), ꢂ
Hz, PC). 19F{1H} NMR (CD2Cl2): d ꢂ
to internal CFCl3, s, OTfꢂ).
/3.4 (t, JP P
ꢀ
/
15.4
cluded in the model as fixed contributions in their
˚
Hꢀ0.98 A
C
W
/77.3 (referenced
calculated positions with the assumptions Cꢁ
/
/
and B(H)ꢀ
/
1.2×
/
B(Ceq). The two hydride ligands

174
Y. Kim et al. / Inorganica Chimica Acta 352 (2003) 171ꢁ178
/
bonded to the Re atom are omitted from the model as
they could not be located on a difference electron
density map. The final refinement cycle yielded agree-
[ReH4(h2-H2)(Cyttp)]SbF6 (1(SbF6)) with dry acetone
at reflux temperature affords the dihydrido-oxo complex
2(SbF6) in 90% yield (Eq. (1)). Longer reaction times
result in the formation of [ReH(O)(F)(Cyttp)]SbF6
(3(SbF6)) as well,
ment indices of Rꢀ
reflections with Fo2ꢁ
maximum and minimum peaks of the final difference
/
0.046 and Rwꢀ
/
0.049 for the 4979
/
3s(Fo2) and the 445 variables. The
/
1.06 e Aꢂ3, with the
˚
electron density map are 1.26 and ꢂ
˚
maximum peak 0.92 A from the Re atom. The next
largest peaks in the map, from 0.91 to 1.20 e Aꢂ3, are in
˚
ð1Þ
the vicinity of the disordered solvent molecule. Scatter-
ing factors for the non-hydrogen atoms, including terms
for anomalous dispersion [32], and the scattering factors
for the hydrogen atom [33], are from the literature. A
summary of the crystal data and the details of the
intensity data collection and refinement are provided in
Table 1.
whereas use of acetone/benzene or acetone/toluene leads
to the isolation of 3(SbF6) only [18,19]. To circumvent
this substitution of fluoride for hydride, the counterion
SbF6ꢂ was replaced with OTfꢂ later in our studies. The
synthesis of 2(OTf) was effected in two steps, viz.
reaction of ReH5(Cyttp) with HOTf and treatment of
the product 1(OTf) with acetone as described above for
1(SbF6).
Complex 2 was also obtained by using neat cyclohex-
anone or one of several other ketones in place of
acetone. The apparent abstraction of oxygen from
ketones by the metal center is precedented by similar
behavior of WCl2(PMePh2)4 [34]. These and related
reactions of 1 will be considered in some detail in
another paper dealing with mechanism of formation of 2
by use of organic carbonyl compounds [21].
3. Results and discussion
3.1. Synthesis of [ReH2(O)(Cyttp)]ꢄ (2) and its
isotopomers
In the course of studies of reactions of rhenium(V)
phosphine complexes with ketones, we
15 h) of
polyhydridoꢁ
/
observed that prolonged treatment (12ꢁ
/
Table 1
Summary of crystal data, data collection, and structure refinement
parameters for [ReH2(O)(Cyttp)]SbF6×3/4MeOH (2(SbF6)×3/4MeOH)
The product 2(SbF6) was isolated as a light tan solid
that is stable to air in solution at ambient temperature
for several days. It is soluble in CH2Cl2, acetone, THF,
and benzene but essentially insoluble in Et2O and
MeOH. The triflate salt 2(OTf) has similar solubility
properties except that it dissolves in MeOH.
/
/
Empirical formula
Formula weight
Crystal system
C
36H63F6OP3ReSb×3/4CH4O
/
1050.80
monoclinic
P21/n
Space group
Unit cell dimensions
˚
a (A)
13.517(2)
17.742(2)
18.162(2)
102.95(1)
4244.6(9)
4
To aid in the studies of spectroscopic properties and
reaction chemistry of 2, the isotopomers [ReH2(18O)-
(Cyttp)]SbF6 (2-18O(SbF6)), [ReD2(O)(Cyttp)]SbF6 (2-
d2(SbF6)) and [ReD2(18O)(Cyttp)]SbF6 (2-d2,18O(SbF6))
were prepared from the unlabeled complex. The 18O-
containing isotopomer resulted on treatment of 2(SbF6)
with a large excess of H128O (Eq. (2)).
˚
b (A)
˚
c (A)
b (8)
3
˚
V (A )
Z
Dcalc (g cmꢂ3
)
1.64
223
Temperature (K)
Crystal size (mm3)
Radiation
0.12ꢅ
/
0.19ꢅ0.23
/
Mo Ka, graphite (lꢀ
/0.71069
˚
A)
m (cmꢂ1
)
38.2
2u range (8)
4ꢁ
0.849ꢁ
h, ꢄ
10063
4979
445
/
55
Transmission factors
Data collected
Unique data
/
1.000
ꢄ
/
/
k, 9l
/
Unique data with Fo2ꢁ
Final no. of variables
R(F) a
/
3s(Fo2)
ð2Þ
0.046
0.049
Error in observation of unit weight 1.23
Rw(F) b
This reaction probably proceeds by nucleophilic attack
of H128O at the Re center and formation of a [Re-
H2(16OH)(18OH)(Cyttp)]ꢄ intermediate. A similar me-
(e)
a
chanism has been proposed for the oxygen exchange in
ꢃ
R(F)ꢀ
Rw(F)ꢀ
/
[SjFojꢂ
/
jFcj/SjFoj].
18
Cp2 WO and Cp2 Ta(O)H using H2 O [20,35]. Interest-
b
jFcj)2/S wjFoj ] with wꢀ
2 1/2
/
1/s2(Fo).
ꢃ
/
[S w(jFojꢂ
/

Y. Kim et al. / Inorganica Chimica Acta 352 (2003) 171ꢁ
/178
175
ingly, use of D2O in conjunction with 2(SbF6) does not
lead to the formation of 2-d2(SbF6). Again, this ob-
servation is similar to that of the absence of isotopic
Table 2
Selected bond lengths (A) and bond angles (8) for
[ReH2(O)(Cyttp)]SbF6×3/4MeOH (2(SbF6)×3/4MeOH)
˚
/
/
ꢃ
ꢃ
exchange for Cp2 WO and Cp2 Ta(O)H on treatment
with D2O [20,35]. The deuterium-labeled isotopomer 2-
d2(SbF6) was, however, obtained by photolysis of a
benzene solution of 2(SbF6) under an atmosphere of D2
(Eq. (3)).
Bond lengths
Reꢁ
/
P(1)
P(2)
2.412 (3)
2.380(3)
Reꢁ
/
P(3)
O
2.392(3)
1.732(7)
Reꢁ
/
Reꢁ
/
Bond angles
P(1)ꢁ
P(1)ꢁ
P(2)ꢁ
/
Reꢁ
Reꢁ
Reꢁ
/
P(2)
P(3)
P(3)
92.0(1)
137.1(1)
92.1(1)
P(1)ꢁ
P(2)ꢁ
P(3)ꢁ
/
Reꢁ
Reꢁ
Reꢁ
/
O
O
O
110.8(2)
111.1(3)
107.3(2)
/
/
/
/
/
/
/
/
hydrido ligands, implicated by the spectroscopic data
(cf. Section 3.3), were not located. The meridional
arrangement of the triphosphine around the metal is
ð3Þ
severely distorted, with the angles P(1)ꢁ
/
Reꢁ
/
P(2), P(2)ꢁ
/
ReꢁP(3), and P(1)ꢁReꢁP(3) being 92.0(1), 92.1(1), and
/
/
/
A monodeuterium product, 2-d1(SbF6), could not be
detected spectroscopically in that reaction. The double-
labeled 2-d2,18O(SbF6) resulted from 2-d2(SbF6) and
H128O.
137.1(1)8, respectively. These bond angles may be
contrasted with the much more octahedral ones found
in another Cyttp complex, cis, mer-Ru(OTf)2-
(CO)(Cyttp), where P(1)ꢁ
/
Ruꢁ
/
P(2), P(2)ꢁ
/
RuꢁP(3), and
/
P(1)ꢁRuꢁP(3) are, respectively, 89.95(4), 92.09(4) and
/
/
3.2. Structural characterization of [ReH2(O)(Cyttp)]-
SbF6 (2(SbF6))
177.87(4)8 [36]. The distortion in the meridional ar-
rangement of the Cyttp in 2 is most likely caused by the
small size of the hydrido ligands, which appear to be
positioned approximately cis and trans to the oxide. As
expected, the phosphorus donors are displaced in these
The structure of 2(SbF6) (as 2(SbF6)3/4MeOH),
determined by X-ray diffraction techniques, consists of
the complex cations 2 and the anions SbF6ꢂ. An ORTEP
drawing of 2 is presented in Fig. 1, and selected bond
distances and angles are given in Table 2.
The observed coordination environment around the
Re center is comprised of the meridionally attached
triphosphine Cyttp and one oxo ligand. The two
˚
directions. The rhenium atom is located 0.795 A out of
the P3 plane toward the oxo ligand. Such a displacement
of the metal atom has been noted for octahedral
rhenium Tp-oxo complexes [37]. This distortion in 2 is
also reflected in the magnitude of the Pꢁ
angles, 107.3(2)ꢁ111.1(3)8.
The bond distances Reꢁ
2.380(3), and ReꢁP(3)ꢀ2.392(3) A (2.395 A mean)
are somewhat longer than the ReꢁP distances in
ReH5(Cyttp) (2.380 A mean) but shorter than those in
/
Reꢁ
/
O bond
/
/
P(1)ꢀ
/
2.412(3), Reꢁ
/
P(2)ꢀ
/
˚
˚
/
/
/
˚
˚
1(SbF6) (2.435 A mean) [27]. The ReꢁO bond distance
/
˚
of 1.732(7) A is quite long for a monooxo complex of
rhenium(V), with most of the reported bond lengths
˚
being less than 1.7 A [37,38]. However, molecular orbital
considerations suggest a ReꢂO triple bond rather than
a ReÄ
O double bond for such a d2 octahedral monooxo
complex [38].
/
/
3.3. Spectroscopic properties of [ReH2(O)(Cyttp)]-
SbF6 (2(SbF6)) and its isotopomers
1
2
Selected H, H, and 31P{1H} NMR and IR data for
2(SbF6) and its isotopomers 2-d2(SbF6), 2-18O(SbF6),
and 2-d2,18O(SbF6) are provided in Sections 2.3 and 2.5.
1
The H NMR spectrum of 2(SbF6) clearly reveals the
presence of two inequivalent hydrido ligands with equal
intensity resonances at d ꢂ
/
1.04 and ꢂ12.62. The signal
/
Fig. 1. Molecular structure of [ReH2(O)(Cyttp)]ꢄ (2). Non-hydrogen
atoms are drawn with 50% probability displacement ellipsoids. The
two hydrogen atoms bonded to rhenium were not located. The other
hydrogen atoms are omitted for clarity.
at d ꢂ1.04, assigned to the hydride approximately trans
/
to the oxo ligand, occurs as a triplet of triplets by virtue
of coupling with two equivalent wing-phosphorus (PW)

176
Y. Kim et al. / Inorganica Chimica Acta 352 (2003) 171ꢁ178
/
nuclei (2JP Hꢀ
/
25.0 Hz) and because of equal coupling
W
constants 2JHHꢀ2
of the hydride ‘cis’ to the oxide appears as a doublet of
/
JP H 5.0 Hz. The higher-field signal
ꢀ
/
C
triplets of doublets, with splitting by the other hydride,
two equivalent PW nuclei (2JP Hꢀ
35.0 Hz), and the
/
W
central-phosphorus (PC) nucleus (2JP H
ꢀ57.5 Hz). The
/
C
2
relatively small value of this JP H [39] suggests that the
C
structure of 2 is distorted from a regular octahedron, as
demonstrated by the X-ray diffraction analysis. The
31P{1H} NMR spectrum consists of a doublet at d 22.56
2
and a triplet at d 6.77 with JP P
ꢀ18.3 Hz.
/
C
W
2
The isotopomer 2-d2(SbF6) shows two high-field H
2
2
signals: a triplet (2JP D; JDD and JP D not discerned)
W
C
2
at d ꢂ
/
1.0 and a doublet of triplets (2JP D and JP
,
WD
C
respectively) at d ꢂ12.6 with expected coupling con-
/
Fig. 2. Schematic representation of the interaction between n(ReO)
and d(ReH). (a) From the spectrum of 2-d2. (b) From the spectrum of
2-d2,18O.
stants (cf. Section 2.5.1). Its 31P{1H} NMR spectrum is
similar to that of 2(SbF6), but the signals are broad
owing to unresolved phosphorusꢁdeuterium coupling.
/
represents the interaction energy of n(Re16O) and
d(ReH), the energy of the ‘unperturbed’ state of
d(ReH) can be calculated for the observed frequency.
These calculated values are 871 and 843 cmꢂ1 for the
two bending modes observed for 2(SbF6) at 845 and 817
cmꢂ1, respectively. Although such an ‘unperturbed’
frequency of 871 cmꢂ1 is closer to 897 cmꢂ1 (i.e.,
‘unperturbed’ n(Re16O), observed for 2-d2(SbF6)), reso-
nance interaction apparently occurs with the other, 843
cmꢂ1 d(ReH) mode, presumably due to symmetry.
Similarly, the n(Re18O) band observed at 887 cmꢂ1
for 2-18O(SbF6) is shifted by 33 cmꢂ1 to the expected
(‘unperturbed’) value of 854 cmꢂ1 in the double-labeled
2-d2,18O. Thus, the energy of the ‘unperturbed’ state of
d(ReH) in 2-18O is calculated, using the interaction
energy of 33 cmꢂ1, to be 843 cmꢂ1. This turns out to be
identical with the d(ReH) calculated for 2. Finally, the
splitting into two components of the lower energy
n(ReH) band of 2-18O(SbF6) (vide supra) may be
rationalized by Fermi resonance involving the first
The presence of an oxo ligand in 2(SbF6), demon-
strated by X-ray diffraction, is also indicated by the IR
spectrum which shows a medium-intensity band at 923
cmꢂ1, assigned to n(ReO). In the labeled 2-18O(SbF6),
this absorption occurs at 887 cmꢂ1, whereas the
frequency predicted from the isotope mass effect is 877
cmꢂ1. Additionally, on going from 2 to 2-18O, the band
at 817 cmꢂ1, assigned to one of the d(ReH) modes,
shifts to 810 cmꢂ1, and that at 1716 cmꢂ1, attributed to
n(ReH), splits into two weaker-intensity components at
1737 and 1687 cmꢂ1. These spectroscopic changes
suggest occurrence of a resonance interaction between
the n(ReO) fundamental and one d(ReH) mode.
Additional evidence for such an interaction is pro-
vided by the IR spectrum of the dideuterio complex 2-
d2(SbF6). Significantly, the n(ReO) absorption of this
isotopomer occurs at 897 cmꢂ1. Furthermore, the
d(ReH) bands of 2(SbF6) at 845 and 817 cmꢂ1
disappear, and a new band replaces the former at 582
cmꢂ1, as calculated for d(ReD). The other d(ReD)
absorption, predicted to occur at approximately 600
cmꢂ1, is probably hidden under the strong peak of
n((SbF6) at 650 cmꢂ1. The two n(ReH) bands of
2(SbF6) at 2030 and 1716 cmꢂ1 are, as expected, absent
in this spectrum; however, the corresponding n(ReD)
absorptions could not be identified because of numerous
overtone of the ‘unperturbed’ n(Re18O) at 854 cmꢂ1
The above spectroscopic behavior has a precedent in
the IR n(CO) spectra of some metal hydridoꢁcarbonyl
complexes and their deuterioꢁcarbonyl structural ana-
.
/
/
logs. Vaska observed that on replacement of H with D
in IrH2(CO)Cl(PPh3)2 and mer-OsH2(CO)(PPh3)3, inter
alia, there was a shift in n(CO) for the carbonyl trans to
hydride, but not for that cis to hydride [40]. This shift
was attributed to a resonance interaction between the
vibrational states of n(CO) and n(MH) (but not n(MD)
because of a large energy difference) of the trans
hydride. It is possible that in the present study resonance
interaction, with the oxo ligand, also involves trans
hydride.
peaks in the 1450ꢁ
1200 cmꢂ1 region.
/
Finally, the isotopomer 2-d2,18O(SbF6) exhibits its
n(Re18O) absorption at 854 cmꢂ1. This is the expected
frequency for replacement of 16O in 2-d2 with 18O in 2-
d2,18O. Furthermore, the d(ReD) band at 582 cmꢂ1 for
2-d2(SbF6) remains unchanged in this spectrum. Thus,
there appears to be no resonance interaction between
the vibrational modes involving oxygen (16O or 18O) and
those involving deuterium.
The ‘unperturbed’ n(ReO) of 897 cmꢂ1 for 2(SbF6) is
substantially lower than the n(ReO) of 1006ꢁ
for [ReX(O)(F)(Cyttp)]ꢄ (Xꢀ
H (3), F, Cl, Br) [19]. It is
also lower than n(ReO) for rhenium(V) monooxo Tp*
/
1015 cmꢂ1
The foregoing interactions of the vibrational modes
are represented schematically in Fig. 2. Assuming that
the shift of 26 cmꢂ1 in n(Re16O) upon deuteriation of 2
/

Y. Kim et al. / Inorganica Chimica Acta 352 (2003) 171ꢁ
/178
177
and Tp complexes, which include Tp*Re(O)(Cl)X (Xꢀ
H, Cl, Br, I, OH, OTf, OMe, Et, Ph), TpRe(O)(X)Y
(XꢀCl, YꢀOTf, Me; XꢀBr, YꢀOTf, OEt; XꢀOTf,
YꢀOPh, Me), and a number of their close relatives.
These complexes display n(ReO) in the range 938ꢁ1002
cmꢂ1 [17,37]. Four of them were shown by X-ray
diffraction to possess ReꢁO bond lengths of 1.665(5),
1.667(9), 1.675(4), and 1.705(5) A [17,37], all signifi-
/
bonding [37c]. The 31P{1H} NMR spectrum is consis-
tent with a meridional attachment of Cyttp to Re, and
1
the H NMR spectrum shows one coordinated pyridine
/
/
/
/
/
/
and the absence of hydrido ligands. The FAB mass
spectrum exhibits a peak at m/z 806 which corresponds
to the parent ion less one pyridine.
Treatment of 2(OTf) with an excess of either
Li[BEt3H] or NaH affords known ReH5(Cyttp) [28]
(Eq. (5)). When only 1 equiv. of Li[BEt3H] was
employed, a multitude of products resulted.
/
/
˚
˚
cantly shorter than that of 1.732(7) A for 2(SbF6). Thus,
both the IR and X-ray structural data indicate a lower
ReꢁO multiple bond order in 2 than in the foregoing
/
Tp* and Tp complexes. A possible reason for the
observed difference may be related to the presence of
five good electron-releasing phosphorus and hydrogen
donors in 2; this would enhance electron density at the
rhenium center and therefore promote relative impor-
ð5Þ
tance of ReÄ
/
O over ReꢂO through dispersal of
/
negative charge onto oxygen.
They underwent conversion to ReH5(Cyttp) upon addi-
tion of more Li[BEt3H]. A reaction similar to the
foregoing is the formation of Tp*ReH6 from
3.4. Reactions of [ReH2(O)(Cyttp)]SbF6 (2(SbF6))
with acids and bases
Tp*Re(O)(OR)2 (Rꢀ
/
Me or Et) and BH3×
/
THF [17b].
Complex 2(OTf) underwent reaction with aqueous
HCl in benzene to afford, after drying, a bright green
solid which is formulated as [ReH2(OH)Cl(Cyttp)]OTf
(5(OTf)) (Eq. (6)) on the basis of spectroscopic evidence.
Reactions of 2 with acids and bases were examined in
an attempt to learn about the nature of the hydrido and
oxo ligands in this complex. For these studies, 2(OTf)
rather than 2(SbF6) was used as the substrate complex in
order to circumvent possible participation of fluoride in
substitution at rhenium.
Attempted deprotonation of 2(OTf) with the strong
base NEt3 or Proton Sponge (C10H6(NMe2)2) in the
presence or absence of a potential ligand (MeCN,
pyridine) resulted in no detectable reaction. In contrast,
the small hydroxide ion reacted rapidly with 2(OTf) at
ambient temperature to afford a multitude of products,
observable by 31P{1H} NMR spectroscopy. By running
(6)
Accordingly, the 31P{1H} NMR spectrum shows signals
for the two equivalent wing-phosphorus atoms and the
1
central-phosphorus atom of Cyttp, and the H NMR
this reaction at ꢂ78 8C with warming to room tem-
/
spectrum reveals two hydrido ligands at d ꢂ
/
3.3 and
perature in the presence of pyridine, it was possible to
isolate [Re(O)2(py)(Cyttp)]OTf (4(OTf)) in very good
yield (Eq. (4)).
ꢂ
/
7.9. The OH proton was not observed in the NMR
spectrum; however, the IR spectrum shows a broad
n(OH) band centered around 3280 cmꢂ1. There are also
a n(ReH) absorption at 1617 cmꢂ1 and a strong band at
281 cmꢂ1, which may be due to n(ReCl) [41]. The
complex readily changes color to pale yellow upon
exposure to air and decomposes in solution. Satisfactory
chemical analysis or FAB mass spectrum was not
obtained.
ð4Þ
Based on the foregoing spectroscopic data, protona-
tion of 2(OTf) appears to have occurred at the oxo
ligand. Addition of proton to coordinated oxide is
The product was characterized by elemental analysis,
FAB mass spectrometry, and IR and NMR (31P{1H},
19F{1H}) spectroscopy. A complete X-ray diffraction
study of 4(OTf) was precluded by decomposition of the
crystal during data collection. Nevertheless, limited
acquired data support the trans arrangement of two
oxo ligands and the cis orientation of pyridine to each
oxygen. In the IR spectrum of 4(OTf), n(ReO) absorp-
known for Re(EtCÅ
/
CEt)2(O)H [15a].
4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
tion is observed at 817 cmꢂ1, in agreement with ReÄ
/O

178
Y. Kim et al. / Inorganica Chimica Acta 352 (2003) 171ꢁ178
/
(b) G. Parkin, A. van Asselt, D.J. Leahy, L. Whinnery, N.G. Hua,
R.W. Quan, L.M. Henling, W.P. Schaefer, B.D. Santasiero, J.E.
Bercaw, Inorg. Chem. 31 (1992) 82.
Data Centre, CCDC No. SIMCEW for 2(SbF6)×
4MeOH. Copies of this information may be obtained
free of charge from The Director, CCDC, 12 Union
/
3/
[14] (a) H. Brunner, M.M. Kubicki, J.-C. Leblanc, C. Moise, F.
¨
Road, Cambridge, CB2 1EZ, UK (fax: ꢄ44-1223-336-
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Volpato, J. Chem. Soc., Chem. Commun. (1993) 851.;
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Acknowledgements
Acknowledgement is made to the donors of The
Petroleum Research Fund, administered by the ACS,
for partial support of this research.
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