Preparation and characterization of chloro- and polyhydride complexes of rhenium: Variable-temperature NMR spectroscopy and protonation studies

Article abstract of DOI:10.1016/j.jorganchem.2005.07.103

The rhenium complex fac-[ReOCl₃L] [1; L = 1,3- bis(diphenylphosphanyloxy)propane] was prepared by reacting L with [ReOCl ₃(AsPh₃)₂]. Refluxing complex 1 in ethanol gave [ReOCl₂(OEt)L] (2), which X-ray

Full text of DOI:10.1016/j.jorganchem.2005.07.103

Journal of Organometallic Chemistry 690 (2005) 4899–4907
www.elsevier.com/locate/jorganchem
Preparation and characterization of chloro- and
polyhydride complexes of rhenium: Variable-temperature
NMR spectroscopy and protonation studies
*
*
´
´
Jorge Bravo , Jesu´s Castro, Soledad Garcıa-Fontan ,
´
Manuel Iglesias, Pilar Rodrıguez-Seoane
Departamento de Quı´mica Inorga´nica, Universidade de Vigo, Lagoas-Marcosende, E-36310 Vigo, Pontevedra, Spain
Received 10 June 2005; received in revised form 26 July 2005; accepted 26 July 2005
Available online 31 August 2005
Abstract
The rhenium complex fac-[ReOCl3L] [1; L = 1,3-bis(diphenylphosphanyloxy)propane] was prepared by reacting L with [ReO-
Cl3(AsPh3)2]. Refluxing complex 1 in ethanol gave [ReOCl2(OEt)L] (2), which X-ray crystallography showed to have an octahedral
rhenium environment and an Re–O–Et fragment of unusual linearity. The paramagnetic chlorocomplexes mer-[ReCl3LL0] [3;
L0 = P(OEt)3 in 3a, PPh(OEt)2 in 3b, PPh2(OEt) in 3c] were obtained by treating compound 1 with L0. Reaction of complexes 1
and 3a–c with excess NaBH4 gave the polyhydrides [ReH7L] (4) and [ReH5LL0] (5a–c), respectively, all of which were characterized
by variable-temperature (VT) NMR spectroscopy as highly fluxional classical hydrides. Complete protonation of these polyhydrides
with HBF4 Æ OMe2 required 3 equiv. of acid, and the cationic polyhydride complexes so obtained were characterized as non-classical
species by VT NMR spectroscopy and T1 measurements.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Rhenium; Polyhydride compounds; Phosphinites; Phosphonites; Phosphites; Variable-temperature NMR
1. Introduction
corresponding phosphine-containing species, must influ-
ence the properties of their polyhydride complexes [5].
We have previously described the synthesis and
properties of several families of rhenium polyhydride
complexes containing the bidentate chelating ligands
1,2-bis(diphenylphosphanyloxy)ethane [6] and 1,2-
bis(dicyclohexylphosphanyloxy)ethane [7]. We found
that the nature of the hydrocarbyl groups of the chelat-
ing ligand had significant effects on, inter alia, the stabil-
ity of non-classical dihydrogen complexes obtained by
protonation of the complexes initially synthesized.
Here, we describe the synthesis, characterization and
protonation reactions of a new family of rhenium poly-
hydride complexes featuring the bidentate phosphorus
ligand 1,3-bis(diphenylphosphanyloxy)propane (L),
which were prepared in order to investigate whether
their larger chelate ring would significantly alter their
Rhenium polyhydride complexes are of interest for
activation of C–H bonds [1], for studies of the mecha-
nisms of hydrogenases and nitrogenases [2], and because
of the possibility of their use for hydrogen storage [3].
Their properties are very much influenced by co-ligands
of the hydride ligands. Ligands containing phosphine
moieties have been extensively investigated in this re-
spect, but less attention has been paid to phosphorus li-
gands containing fragments of the form PðRnÞðOR03ꢀnÞ
(n = 0–2) [4]. The stronger p-acceptor and weaker r-do-
nor capabilities of these ligands, as compared with the
*
Corresponding author. Tel.: +34 986812275; fax: +34 986813798.
E-mail addresses: jbravo@uvigo.es (J. Bravo), sgarcia@uvigo.es
´
´
(S. Garcıa-Fontan).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.07.103

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J. Bravo et al. / Journal of Organometallic Chemistry 690 (2005) 4899–4907
properties with respect to those of their ethane
homologues.
stretching, and the 31P{1H} NMR spectrum in CDCl3
shows a singlet at 102.0 ppm that indicates the magnetic
equivalence of the two P nuclei, and that the ethoxo
group is trans to the oxo group. The appearance of
1
2. Results and discussion
new H NMR signals at 0.05 ppm (t) and 2.26 ppm (q)
(3JHH = 7 Hz) is also in keeping with coordination of
2.1. Chlorocomplexes
the ethoxo ligand.
2.1.1. fac-[ReOCl3L] (1)
2.1.3. Description of the structure of 2
Reaction of [ReOCl3(AsPh3)2] with the diphosphinite
ligand 1,3-bis(diphenylphosphanyloxy)propane (L) gave
the new oxochloro complex fac-[ReOCl3L] (1) in high
yield as a violet solid that was stable to air. Its IR spec-
trum shows the strong band characteristic of Re@O
stretching at 982 cmꢀ1 [8]; its 31P{1H} NMR spectrum
in CDCl3, with a singlet at 78 ppm, indicates the mag-
netic equivalence of the two phosphorus atoms of the
diphosphinite ligand; and its 1H NMR spectrum has
multiplets at 7–8 ppm corresponding to the phenyl
groups, and three two-proton multiplets at 2.23, 4.18
and 4.50 ppm that are due to the methylene protons of
the diphosphinite ligand.
Complex 2 crystallizes in the chiral space group P21.
It consists of discrete molecules with no significant inter-
molecular hydrogen bonds. Its molecular structure and
numbering scheme are shown in Fig. 1, and Table 1 lists
the parameters of the environment of the metal atom.
The central rhenium (V) atom has a slightly distorted
octahedral environment defined by two mutually cis
chlorine atoms, the mutually trans oxo and ethoxo
ligands, and the two phosphorus atoms of the bidentate
ligand. The Re–Cl, Re–P and Re–O distances are similar
to those of other compounds with an ReCl2O2P2 kernel,
regardless of whether the arrangement of the donor
atoms is the same as in 2 [9,10] or not [11]. In particular,
the competition for the p-bond between the mutually
trans oxo and ethoxo ligands leads to Re–O(1) and
Re–O(2) distances that indicate some triple bond char-
acter for the former and some double bond character
for the latter. The P–Re–P angle, 105.3(1)ꢁ, is slightly
wider than in similar complexes, presumably due to
the spatial requirements of the –O(CH2)3O– group.
The eight-membered chelate ring has a conformation
similar to that found in other complexes of this ligand:
the Re, P1, P2, O11 and O12 atoms are almost coplanar
2.1.2. [ReOCl2(OEt)L] (2)
When the mother liquor from which complex 1 was
obtained was left standing for several days, pink crystals
of [ReOCl2(OEt)L] (2) were obtained. This compound
was also obtained when a suspension of 1 in ethanol
was refluxed for 2 h. The replacement of chloro by al-
koxo groups has also been observed in similar com-
pounds [9]. The spectral features of compound 2 are
very similar to those of compound 1: its IR spectrum
shows strong absorption at 980 cmꢀ1 due to Re@O
˚
˚
(rms deviation 0.072 A), C52 is only 0.28(1) A from the
C52
C53
O12
P1
C51
O11
O1
P2
Re
Cl2
Cl1
O2
C1
C2
Fig. 1. Molecular structure of compound 2.

J. Bravo et al. / Journal of Organometallic Chemistry 690 (2005) 4899–4907
4901
Table 1
OEt in the CCDC data base [12], only three have an
Re–O–C angle wider than 160ꢁ.
˚
Bond lengths (A) and angles (ꢁ) in 2
˚
Bond lengths (A)
2.1.4. mer-[ReCl3LL0] [3a, L0 = P(OEt)3; 3b,
Re–O(1)
Re–Cl(1)
Re–P(1)
P(2)–O(11)
Re–O(2)
Re–Cl(2)
Re–P(2)
1.695(6)
2.434(2)
2.451(2)
1.607(8)
1.844(6)
2.449(2)
2.455(2)
1.598(7)
L0 = PPh(OEt)2; 3c, L0 = PPh2(OEt)]
Refluxing a THF solution of 1 with a threefold excess
of L0 for 1 h under argon afforded yellow solutions from
which the complexes mer-[ReCl3LL0] (3) were obtained
as yellow paramagnetic solids by concentration under
reduced pressure. The absence of any band in the 900–
1000 cmꢀ1 region of their IR spectra confirms the
P(1)–O(12)
Bond angles (ꢁ)
O(1)–Re–O(2)
O(2)–Re–Cl(1)
O(2)–Re–Cl(2)
O(1)–Re–P(1)
Cl(1)–Re–P(1)
O(1)–Re–P(2)
Cl(1)–Re–P(2)
P(1)–Re–P(2)
C(2)–O(2)–Re
O(1)–Re–Cl(1)
O(1)–Re–Cl(2)
Cl(1)–Re–Cl(2)
O(2)–Re–P(1)
Cl(2)–Re–P(1)
O(2)–Re–P(2)
Cl(2)–Re–P(2)
O(11)–P(2)–C(31)
1
173.8(3)
removal of the oxo ligand of 1. Their H NMR spectra
90.5(2)
90.1(2)
90.2(2)
82.2(1)
86.0(2)
172.4(1)
105.3(1)
178.3(7)
94.8(2)
93.4(2)
86.4(1)
87.4(2)
168.4(1)
89.1(2)
85.9(1)
94.4(4)
in CDCl3 (Fig. 2 shows that of 3a) show the paramag-
netically shifted resonances expected for mononuclear
d4 systems in a low-spin octahedral environment [13];
their signals have been assigned on the basis of signal
intensity and previous work [8a,14].
2.2. Polyhydride complexes
2.2.1. [ReH7L] (4)
The rhenium heptahydride [ReH7L] (4) was obtained
as a diamagnetic solid that is stable in air by reaction of
the oxochloro compound 1 with a 20-fold excess of
NaBH4 in absolute ethanol. Its IR spectrum shows
two medium-strong bands at 1915 and 1971 cmꢀ1 that
are attributable to Re–H stretching vibrations [15]. Like
the homologous complexes of 1,2-bis(diphenylphospha-
nyloxy)ethane [6] and 1,2-bis(dicyclohexylphosphanyl-
oxy)ethane [7] (hereinafter L[6] and L[7], respectively),
compound 4 is converted into a dinuclear compound,
[Re2H8L2], when dissolved in CHCl3, CH2Cl2, benzene
plane they define, and C53 and C51 are respectively
˚
˚
0.99(1) A below and 0.70(1) A above this plane. The
C(2)–O(2)–Re angle, 178.3(7)ꢁ, indicates that the ethoxo
oxygen has a certain degree of sp character. Of the 36
previously known Re compounds with monodentate
Fig. 2. 1H NMR spectrum of compound 3a in CDCl3.

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J. Bravo et al. / Journal of Organometallic Chemistry 690 (2005) 4899–4907
or toluene. The conversion rate is faster in the halo-
genated solvents than in the others, and in these halo-
genated solvents increases at room temperature in the
order [ReH7L[7]] (5 days [7]) < compound 4 (2 days) <
[ReH7L[6]] (12–18 h [6]).
In the 1H NMR spectrum of 4 in CD2Cl2, the hydride
nuclei appear as a seven-proton triplet at d = ꢀ6.06 ppm
due to coupling to the two phosphorus atoms
(2JHP = 16 Hz). The 31P{1H} NMR spectrum in the same
solvent displays a singlet at d = 127.0 ppm that becomes
an octuplet [JPH(residual) = 15 Hz] when an off-resonance
experiment is performed, confirming the number of hy-
dride ligands directly bound to the rhenium atom.
Lowering the temperature from 293 to 174 K did not
significantly alter the 31P{1H} NMR spectrum of 4, but
1
in its H NMR spectrum the high-field triplet began to
Fig. 4. 31P{1H} NMR spectra of [ReH7L] (4) in CD2Cl2 at 183 K
when protonated with HBF4 Æ OMe2 in various mole ratios.
undergo decoalescence at 193 K, and by 174 K had split
into two broad peaks with an approximate intensity ra-
tio of 2:5 (Fig. 3). Thus 4 appears to be significantly
more rigid than analogous heptahydride diphosphinite
complexes in which seven-membered chelate rings are
formed by L[6] [6a] or L[7] [7], since the 1H NMR spectra
of both these latter complexes show just a slight broad-
ening of the high-field triplet, even at 174 K. Like these
latter complexes, however, 4 is a classical hydride [16],
the value of T1(min) measured for the high-field signal
by the standard inversion-recovery method at
400 MHz being 98 ms at 218 K.
nals recorded at this temperature to 112.2 and
ꢀ4.3 ppm, respectively (Figs. 4 and 5). As Fig. 4 shows,
total protonation required the use of 3 equiv. of acid in-
stead of the 2 equiv. required by analogues with seven-
membered chelate rings [6a,7]. Similar acidity has been
shown by the monohydride [ReH(CO)3L] [18] and, in
this study, by the pentahydrides [ReH5LL0] [L0 =
PPhn(OR)3ꢀn; see next paragraph], and may be due to
increased steric hindrance associated with the increase
in the size of the chelate ring [17].
Protonation of compound 4 with HBF4 Æ Me2O at
183 K as described previously for other compounds
The value of T1(min) measured at 400 MHz and 203 K
1
[6a,7] shifted the 31P{1H} and high-field H NMR sig-
1
for the H NMR signal of the protonated compound at
ꢀ4.3 ppm is 18 ms, showing that this is a non-classical hy-
dride that can tentatively be formulated as [Re(g2-
H2)H6L]BF4. Upon raising the temperature to 243 K,
new signals appear at 120.6 ppm in the 31P{1H} NMR
Fig. 5. High-field 1H and 31P{1H} NMR spectra obtained at various
temperatures following protonation of [ReH7L] (4) with 3 equiv. of
HBF4 Æ OMe2 in CD2Cl2. Signals with an asterisk correspond to the
putative derivative [Re2H9L2]BF4.
Fig. 3. High-field 1H NMR spectra of [ReH7L] (4) in CD2Cl2 at
various temperatures.

J. Bravo et al. / Journal of Organometallic Chemistry 690 (2005) 4899–4907
4903
-3H2
-
-
2[ReH8L]+BF4
[Re2H9L2]+BF4
-HBF4
Scheme 1.
1
spectrum and at ꢀ4.18 ppm in the H NMR spectrum,
coinciding with the release of H2(g) (shown by the appear-
ance of a singlet at 4.6 ppm in the 1H NMR spectrum). At
293 K the 31P{1H} NMR spectrum shows only the
120.6 ppm signal (a singlet), and the 1H NMR spectrum
shows only the signal at ꢀ4.18 ppm (a quintuplet;
2JPH = 7.5 Hz). Similar behaviour by related heptahy-
drides has been ascribed to formation of a cationic dinu-
clear compound as in Scheme 1, and the temperatures at
which the putative non-classical mononuclear precursors
[Re(g2-H2)H6K]BF4 begin to decompose (K = L, L[6],
L[7]) increase in the order L (243 K) < L[7] (273 K
[7]) < L[6] (288 K [6a]). The value of T1 for the 1H NMR
quintuplet at ꢀ4.18 ppm at 273 K, 153 ms, shows that
the final product, presumably [Re2H9L2]BF4, is classical
in nature.
Fig. 6. Hydride region of the 1H NMR spectrum of compound 5a at
various temperatures. Italic numbers indicate the relative values of the
integrated signals.
the doublet that at 293 K corresponds to these latter nu-
clei becoming first two broad signals and then, in the
case of complex 5a (the most rigid of the series; rigidity
increases with the number of OEt groups), a broad dou-
ble doublet and a broad singlet (Fig. 7). The mecha-
nisms responsible for this behaviour may be the same
as those we have proposed for similar rhenium pentahy-
drides [6b,7]. The T1(min) values of compounds 5 show
that all three are classical in nature (Table 2).
Protonation of compounds 5 at 174 K with 3 equiv.
of HBF4 Æ OMe2 in CD2Cl2 yielded the complexes
[ReH6LL0](BF4) (5*), all of which had T1(min) values
indicative of a non-classical nature (Table 2). At 174 K
2.2.2. Synthesis, properties and protonation reactions of
[ReH5LL0] [5a, L0 = P(OEt)3; 5b, L0 = PPh(OEt)2;
5c, L0 = PPh2(OEt)]
Reaction of compounds 3a–c with a 50-fold mol excess
of NaBH4 in ethanol yielded the pentahydrides [Re-
H5LL0] (5a–c), which were isolated as whitish diamag-
netic solids that were stable in air. Their IR spectra
show two or three bands between 1900 and 1950 cmꢀ1
that can be assigned to the m(Re–H) vibrations, and their
room-temperature 1H and 31P{1H} NMR spectra in
CD2Cl2 are similar to those of [ReH5L[6]L0] [6b] and [Re-
H5L[7]L0] [7], the 1H NMR spectra displaying a five-pro-
ton double triplet at high field and the 31P{1H} NMR
spectra a doublet and a triplet in 2:1 intensity ratio corre-
sponding to the L and L0 ligands, respectively. As the elec-
tron-withdrawing character of L0 increases with the
number of OEt groups it contains, the hydride signal
shifts upfield.
Lowering the temperature slowed the fast fluxional
processes responsible for the magnetic equivalence of
the hydrido ligands at room temperature. For example,
1
at 183 K the H NMR spectrum of complex 5a shows
four different signals that, from low to high field, inte-
grate in the ratios 1:2:1:1 (Fig. 6). The various decoales-
cence events observed as the temperature falls are
similar to those reported for [ReH5L[6]L0] [6b], but take
place at temperatures 10–20ꢁ higher as a result of the in-
creased size of the chelate ring diminishing fluxional
behaviour. In the 31P{1H} NMR spectra, lowering the
temperature results in the triplet corresponding to the
phosphorus nucleus of L0 becoming a broad double
doublet due to coupling with the phosphorus nuclei of
L, which at low temperature are not equivalent; and to
Fig. 7. 31P{1H} NMR spectrum of compound 5a at various temper-
atures in CD2Cl2.

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J. Bravo et al. / Journal of Organometallic Chemistry 690 (2005) 4899–4907
Table 2
T1(min) values at 400 MHz for compounds 5 and 5*
Compound
T/K
T1(min)/ms
5a
5b
[ReH5L{P(OEt)3}]
[ReH5L{PPh(OEt)2}]
[ReH5L{PPh2(OEt)}]
[ReH4(g2-H2)L{P(OEt)3}]+
[ReH4(g2-H2)L{PPh(OEt)2}]+
[ReH4(g2-H2)L{PPh2(OEt)}]+
234
231
231
230
233
234
124
131
117
23
22
23
5c
5*a
5*b
5*c
1
their H NMR spectra show a broad hump at about
ꢀ4 ppm indicating the initial freezing of the exchange
of the hydride ligands (Table 3), which shows them to
be significantly less fluxional than the corresponding
complexes of L[6] [6b]. The 31P{1H} NMR spectra of
compounds 5* behave similarly. In particular, at
174 K that of 5a* displays a broad doublet at
113.7 ppm corresponding to the monodentate ligand
P(OEt)3, and a broad singlet at 127.1 ppm and a broad
doublet at 112.1 ppm that correspond to the bidentate
ligand L (Fig. 8). By contrast, in the case of the L[6] ana-
logue [6b], these signals still show fluxional behaviour at
174 K, resembling those obtained from 5a* at 193 K
(Fig. 8). The similarity between the substructures of
the two broad doublets observed at 174 K suggests that
the P(OEt)3 phosphorus, P1, is located in a pseudo-trans
position with respect to one of those of the bidentate
ligand (P2), making the coupling constant JP1–P2 signifi-
cantly larger than JP1–P3 or JP2–P3 (Scheme 2).
Fig. 8. 31P{1H} NMR spectra of [ReH4(g2-H2)L{P(OEt)3}] (5*a+) in
CD2Cl2 at various temperatures.
CH2
CH2
O
H2C
Ph
Ph
O
P2
Ph
P3
Ph
Re
At about ꢀ4 ppm in the room temperature 1H NMR
spectra of compounds 5* (Table 3), a broad quadruplet
reflects coupling between the hydride and phosphorus
nuclei (JPH ꢁ 14 Hz). At this temperature compounds
5* decay within a few hours, with loss of H2(g) reflected
OEt
OEt
P1
EtO
Scheme 2.
1
by the appearance of a H NMR singlet at 4.6 ppm.
Their stabilities in CD2Cl2 at room temperature are thus
similar to those of the homologous compounds of L[6]
[6b] and significantly less that those of the L[7] homo-
logues [7], which remain unaltered for more than 24 h.
The room temperature 31P{1H} NMR spectra display
the doublet and triplet expected for an AX2 system
(Table 3).
Table 3
Selected NMR dataa of complexes 5*a–c at 174 and 293 K
Compound
1H NMRb (d, Hz)
31P{1H} NMR (d, Hz)
174 K
293 K
174 K
293 K
5*a [ReH4(g2-H2)L{P(OEt)3}]+
ꢀ4.37 (br)
ꢀ4.54 (q) JPH = 14
112.1 (br,d)
113.7 (br,d)
127.1 (br,s)
111.2 (t)
116.5 (d)
J = 40
5*b [ReH4(g2-H2)L{PPh(OEt)2}]+
5*c [ReH4(g2-H2)L{PPh2(OEt)}]+
ꢀ4.20 (br)
ꢀ4.00 (br)
ꢀ4.29 (q) JPH = 14
ꢀ3.96 (q) JPH = 14
114.8 (br)
125.1 (br)
127.4 (br)
117.1 (d)
128.7 (t)
J = 29
102.6 (br)
114.0 (br)
130.3 (br)
105.4 (t)
117.7 (d)
J = 20
a
In CD2Cl2 at 400 MHz.
Hydride region.
b

J. Bravo et al. / Journal of Organometallic Chemistry 690 (2005) 4899–4907
4905
3. Conclusions
on a Micromass Autospec M LSIMS (FAB+) system
with 3-nitrobenzyl alcohol as matrix. Microanalyses
were carried out on a Fisons EA-1108 apparatus.
New chloro- and polyhydride rhenium complexes
containing 1,3-bis(diphenylphosphanyloxy)propane (L)
as supporting ligand have been prepared and character-
ized. X-ray crystallography of [ReOCl2(OEt)L] showed
an octahedral coordination polyhedron and unusual lin-
earity of the Re–O–Et group. The classical nature of the
heptahydride [ReH7L] (4) and the pentahydrides [Re-
H5LL0] [5; L0 = PPhn(OEt)3ꢀn; n = 0–2] is shown by
T1(min) values of 98–131 ms at 400 MHz. All are flux-
ional compounds, but significantly less so than analo-
gous compounds in which the size of the chelate ring
is reduced from 8 to 7 members by replacement of 1,3-
bis(diphenylphosphanyloxy)propane by 1,2-bis(diphe-
nylphosphanyloxy)ethane [6].
For their complete protonation, polyhydrides 4 and 5
need more HBF4.Me2O than do their 1,2-bis(diphenyl-
phosphanyloxy)ethane analogues, 3 equiv. instead of 2.
This increase in acidity may be due to a greater degree
of steric hindrance by their larger chelate ring. The
protonated complexes have T1(min) values of about
20 ms at 400 MHz, showing the presence of at least one
dihydrogen ligand. These protonated compounds are
unstable at room temperature in CD2Cl2, decomposing
in a few hours by loss of H2(g). [Re(g2-H2)H6L]BF4 is less
stable than its 1,2-bis(diphenylphosphanyloxy)ethane
and 1,2-bis(dicyclohexylphosphanyloxy)ethane homolo-
gues, while the compounds [Re(g2-H2)H4LL0]BF4
[L0 = PPhn(OEt)3ꢀn; n = 0–2] are similar in stability
to their 1,2-bis(diphenylphosphanyloxy)ethane homo-
logues but significantly less stable than their 1,2-bis(di-
cyclohexylphosphanyloxy)ethane homologues.
4.2. Synthesis of fac-[ReOCl3L] [L = 1,3-
bis(diphenylphosphanyloxy)propane] (1)
To a solution of [ReOCl3(AsPh3)2] (1.0 g, 1.09 mmol)
in tetrahydrofuran (50 mL) was added 3.8 mL of a
0.27 M solution of L in toluene. The resulting mixture
was stirred and refluxed for 1 h, and stirring was main-
tained at room temperature for a further 3 h. Concentra-
tion under reduced pressure then afforded an oil that was
taken into ethanol, forming a violet precipitate that was
filtered out, washed with ethanol and dried under reduced
pressure. Yield 0.56 g, 73%. Anal. calc. for C27H26Cl3O3-
P2Re, C 43.07, H 3.48%; Found: C, 43.26; H, 3.50%. IR
1
(cmꢀ1): 982 (s) m(Re@O). H NMR (CDCl3, 400 MHz):
d (ppm) = 2.23 (m, 2H, CH2), 4.18 (m, 2H, OCH2), 4.50
(m, 2H, OCH2), 7.22–7.90 (m, 20H, Ph). 31P{1H} NMR
(CDCl3, 161 MHz): d (ppm) = 78 (s). FAB MS: m/z (re-
ferred to the most abundant isotopes) 752.5, [M]; 717.0,
[M ꢀ Cl]; 681.5 [M ꢀ 2Cl]; 308.5 [M ꢀ L].
4.3. Synthesis of [ReOCl2(OEt)L] (2)
A suspension of 1 (0.10 g, 0.13 mmol) in 20 mL of
ethanol was refluxed for 3 h. The resulting pink solid
was filtered out and dried in vacuo. Single crystals suit-
able for X-ray diffractometry were obtained by recrys-
tallization from 10:2 (v/v) CH2Cl2/EtOH. Yield 0.65 g,
80%. Anal. calc. for C29H31Cl2O4P2Re, C, 45.67; H,
4.10%; Found: C, 45.85; H, 4.17%. IR (cmꢀ1): 980 (s)
m(Re@O). 1H NMR (CDCl3, 400 MHz):
d
3
(ppm) = 0.05 (t, JHH = 7 Hz, 3H, CH3), 2.10 (m, 1H,
3
4. Experimental
CH2), 2.26 (q, JHH = 7 Hz, 2H, CH2), 2.51 (m, 1H,
CH2), 4.11 (m, 4H, OCH2), 7.59–8.33 (m, 20H, Ph).
31P{1H} NMR (CDCl3, 161 MHz): d (ppm) = 102.0 (s).
4.1. General
All experimental manipulations were carried out un-
der argon using Schlenk techniques. All solvents were
purified by conventional procedures [19] and distilled
prior to use. The ligand 1,3-bis(diphenylphosphanyl-
oxy)propane (L) was prepared using a published method
[9]. 1H and 31P NMR spectra (d, ppm) were recorded in
CDCl3 or CD2Cl2 (as indicated) on a Bruker ARX-400
spectrometer, respectively, using the solvent as internal
lock; 1H signals were recorded at 400 MHz and referred
to internal TMS, and 31P{1H} were run at 161 MHz and
referred to 85% H3PO4. Spin-lattice relaxation times T1
were determined at various temperatures in deuterated
dichloromethane by the inversion-recovery method
using a standard 180ꢁ–s–90ꢁ pulse sequence and 16 dif-
ferent values of s at each temperature. IR spectra of
samples in KBr pellets were obtained on a Bruker Vec-
tor IFS28 FT spectrometer. Mass spectra were recorded
4.4. Synthesis of mer-[ReCl3LL0] [3a, L0 = P(OEt)3;
3b, L0 = PPh(OEt)2; 3c, L0 = PPh2(OEt)]
L0 was added in 3:1 mole ratio to a solution of 1
(0.30 g, 0.40 mmol) in tetrahydrofuran (30 mL), the
mixture was refluxed for 1 h and stirred at room temper-
ature for 3 h more, and the resulting yellow solution was
concentrated under reduced pressure, giving an oil that
when taken into ethanol afforded a yellow paramagnetic
solid that was filtered out, washed with ethanol and
dried under reduced pressure.
3a. Yield 0.12 g, 33%. Anal. calc. for C33H41Cl3O5-
P3Re, C 43.89, H 4.58%; Found: C, 43.11; H, 4.43%. 1H
NMR (CDCl3, 400 MHz; all signals are paramagnetically
shifted): d (ppm) = 2.81 (9H, CH3), 4.87 (2H, Ph), 5.50
(2H, Ph), 7.58 (2H, OCH2), 7.74 (2H, OCH2), 8.11 (2H,
CH2), 8.40 (4H, Ph), 8.73 (4H, Ph), 10.83 (6H,

4906
J. Bravo et al. / Journal of Organometallic Chemistry 690 (2005) 4899–4907
OCH2CH3), 16.15 (4H, Ph), 16.37 (4H, Ph). FAB MS: m/
z (referred to the most abundant isotopes) 902.7, [M];
867.2, [M ꢀ Cl]; 736.7, [M ꢀ L0]; 629.5, [M ꢀ L0 ꢀ 3Cl];
458.7 [M ꢀ L].
5a. Yield, 0.26 g, 29%. Anal. calc. for C33H46O5P3Re,
C, 49.43; H, 5.78%; Found: C, 49.02; H, 5.80%. IR
(cmꢀ1): 1889 (m), 1932 (w), 1970 (w) m(Re–H). 1H
NMR (CD2Cl2, 400 MHz):
d
(ppm) = ꢀ6.77 (dt,
2
3b. Yield 0.23 g, 61%. Anal. calc. for
C37H41Cl3O4P3Re, C, 47.52; H, 4.42%; Found: C, 46.90;
2JP(A)H = 16 Hz, JP(B)H = 20 Hz, 5H, Re–H), 1.03 (t,
3JHH = 7 Hz, 9H, CH3), 1.80 (m, 2H, CH2), 3.63 (q,
3JHH = 7 Hz, 6H, OCH2CH3), 3.81 (m, 4H, OCH2),
7.28 (m, 12H, Ph), 7.72 (m, 8H, Ph). 31P{1H} NMR
(CD2Cl2, 161 MHz): d (ppm) = 140.6 (t, PA), 134.0 (d,
PB), JP(A)P(B) = 33 Hz.
1
H, 4.38%. H NMR (CDCl3, 400 MHz; all signals are
paramagnetically shifted): d (ppm) = 3.45 (6H, CH3),
5.58 (1H, Ph), 6.77 (2H, Ph), 7.72 (2H, Ph), 8.22 (4H,
Ph), 8.59 (2H, CH2), 8.79 (2H, OCH2), 9.48 (2H,
OCH2), 11.60 (2H, OCH2CH3), 12.25 (2H, OCH2CH3),
16.09 (2H, Ph), 16.60 (4H, Ph), 17.68 (4H, Ph). FAB
MS: m/z (referred to the most abundant isotopes)
934.7, [M]; 899.2, [M ꢀ Cl]; 736.7, [M ꢀ 2L0]; 701.2,
[M ꢀ L0 ꢀ Cl]; 665.7, [M ꢀ 2L0 ꢀ 2Cl]; 490.7 [M ꢀ L].
3c. Yield 0.27 g, 68%. Anal. calc. for C41H41Cl3-
O3P3Re, C, 50.91; H, 4.27%; Found: C, 51.31; H,
4.26%. 1H NMR (CDCl3, 400 MHz; all signals are para-
magnetically shifted): d (ppm) = 3.75 (3H, CH3), 4.40–
8.50 (18H, Ph), 9.00 (2H, CH2), 10.37 (2H, OCH2),
10.75 (2H, OCH2), 11.50 (2H, OCH2CH3), 14.11 (4H,
Ph), 16.05 (4H, Ph), 17.21 (4H, Ph). FAB MS: m/z (re-
ferred to the most abundant isotopes) 966.7, [M]; 931.2,
[M ꢀ Cl]; 736.7, [M ꢀ 2L0]; 701.2, [M ꢀ L0 ꢀ Cl]; 522.7
[M ꢀ L].
5b. Yield, 0.24 g, 25%. Anal. calc. for C37H46O4P3Re,
C, 53.29; H, 5.56%; Found: C, 52.87; H, 5.25%. IR
(cmꢀ1): 1884 (m), 1926 (w), 1963 (w) m(Re–H). 1H
NMR (CD2Cl2, 400 MHz):
d
(ppm) = ꢀ6.43 (dt,
2JP(A)H = 16 Hz, JP(B)H = 21 Hz, 5H, Re–H), 1.06 (t,
3JHH = 7 Hz, 6H, CH3), 1.80 (m, 2H, CH2), 3.80 (m,
8H, OCH2CH3 and OCH2), 7.27 (m, 16H, Ph), 7.65
(m, 9H, Ph). 31P{1H} NMR (CD2Cl2, 161 MHz): d
(ppm) = 148.5 (t, PA), 135.3 (d, PB), JP(A)P(B) = 38 Hz.
5c. Yield, 0.21 g, 24%. Anal. calc. for C41H46O3P3Re,
C, 56.87; H, 5.35%; Found: C, 56.50; H, 5.50%. IR
(cmꢀ1): 1888 (m), 1935 (m), 1958 (m) m(Re–H). 1H
2
Table 4
Crystal and structure refinement data for 2
4.5. Synthesis of [ReH7L] (4)
Identification code
Empirical formula
Formula weight
Temperature (K)
Wavelength (A)
Crystal system
Space group
2
C
762.58
293(2)
0.71073
Monoclinic
P21
29H31Cl2O4P2Re
A solution of NaBH4 (0.25 g, 6.64 mmol) in ethanol
(10 mL) was added to a suspension of 1 (0.10 g,
0.13 mmol) in the same solvent (10 mL). After 4 h of vig-
orous stirring, the solvent was removed under vacuum
and the residue was extracted with dichloromethane
(5 mL). This solution was concentrated in vacuo, giving
an oil that when taken into ethanol afforded a tan-col-
oured solid that was filtered out, washed with ethanol
and dried under vacuum. Yield 0.35 g, 41%. Anal. calc.
for C27H33O2P2Re, C, 50.85; H, 5.22%; Found: C,
50.20; H, 4.97%. IR (cmꢀ1): 1915 (m), 1971 (m) m(Re–
˚
Unit cell dimensions
˚
a (A)
9.9380(15)
14.914(2)
10.3853(15)
110.217(3)
1444.5(4)
2
1.753
4.536
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
Volume (A )
Z
Density (calculated) (Mg/m3)
Absorption coefficient (mmꢀ1
F(000)
1
)
H). H NMR (CD2Cl2, 400 MHz): d (ppm) = ꢀ6.06 (t,
2JPH = 16 Hz, 7H, Re–H), 2.00 (m, 2H, CH2), 3.98 (m,
4H, OCH2), 7.38 (m, 12H, Ph), 7.76 (m, 8H, Ph).
31P{1H} NMR (CD2Cl2, 161 MHz): d (ppm) = 127 (s).
752
Crystal size (mm)
h range for data collection (ꢁ)
Index ranges
0.35 · 0.21 · 0.07
2.18–28.01
ꢀ13 6 h 6 13;
ꢀ19 6 k 6 19; ꢀ13 6 l 6 7
9231
6204 [0.0446]
4514
0.976
4.6. Synthesis of [ReH5LL0] (5) [5a, L0 = P(OEt)3; 5b,
L0 = PPh(OEt)2; 5c, L0 = PPh2(OEt)]
Reflections collected
Independent reflections [Rint
Reflections observed (>2r)
Data completeness
]
A suspension of 3 (0.1 g) and NaBH4 1:50 (mol/mol)
in 20 mL of ethanol was stirred for 4 h, during which
time its colour changed from yellow to brown. The
solvent was removed under reduced pressure and the
residue was extracted with 10 mL of dichloromethane.
The resulting solution was concentrated in vacuo, giving
an oil that when treated with ethanol (2 mL) afforded a
whitish solid that was filtered out, washed with ethanol
and dried under vacuum.
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
Semi-empirical from equivalents
1.000000 and 0.614987
Full-matrix least-squares on F2
6204/1/344
0.805
R1 = 0.0434, wR2 = 0.0637
R1 = 0.0642, wR2 = 0.0677
0.008(8)
1.868 and ꢀ1.116
Absolute structure parameter
Largest difference peak and
ꢀ3
˚
hole (e A
)

J. Bravo et al. / Journal of Organometallic Chemistry 690 (2005) 4899–4907
4907
[2] R.A. Henderson, in: M. Peruzzini, R. Poli (Eds.), Recent
Advances in Hydride Chemistry, Elsevier, Amsterdam, 2001
(Chapter 16).
[3] A.J. Maeland, in: M. Peruzzini, R. Poli (Eds.), Recent Advances
in Hydride Chemistry, Elsevier, Amsterdam, 2001 (Chapter 18).
[4] U. Abram, in: J.A. McCleverty, T.J. Meyer (Eds.), Comprehen-
sive Coordination Chemistry II, vol. 5, Elsevier, Amsterdam, 2004
(Chapter 3).
NMR (CD2Cl2, 400 MHz):
d
(ppm) = ꢀ6.10 (dt,
2JP(A)H = 17 Hz, JP(B)H = 20 Hz, 5H, Re–H), 1.04 (t,
3JHH = 7 Hz, 3H, CH3), 1.75 (m, 2H, CH2), 3.45 (m,
2H, OCH2CH3), 3.76 (m, 4H, OCH2), 7.27–7.65 (m,
30H, Ph). 31P{1H} NMR (CD2Cl2, 161 MHz): d
(ppm) = 124.5 (t, PA), 135.3 (d, PB), JP(A)P(B) = 34 Hz.
2
[5] C.A. Tolman, Chem. Rev. 77 (1977) 313.
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˜
4.7. Crystal structure determination
(2001) 81;
A single crystal of compound 2 was mounted on a
glass fibre and studied in a SIEMENS Smart CCD
area-detector diffractometer using graphite-monochro-
(b) S. Bolano, J. Bravo, S. Garcia-Fontan, J. Castro, J. Organo-
˜
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(2004) 4812.
˚
mated Mo Ka radiation (k = 0.71073 A). The crystal
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Antoniutti, G. Albertin, J. Chem. Soc., Dalton Trans. (1996)
2779;
parameters and experimental details of data collection
are summarized in Table 4. Fig. 1 was obtained using
ORTEP [20]. Absorption corrections were made using
SADABS [21]. The structure was solved by direct meth-
ods (with determination of absolute stereochemistry;
Flack parameter 0.006(8)), and was refined by full-ma-
trix least-squares on F2 [22]. All hydrogen atoms were
refined with isotropic displacement parameters, and all
non-hydrogen atoms with anisotropic displacement
parameters. Atomic scattering factors and anomalous
dispersion corrections for all atoms were taken from
International Tables for X-ray Crystallography [23].
(b) X.L.R. Fontaine, E.H. Fowles, T.P. Layzell, B.L. Shaw, M.
Thornton-Pett, J. Chem. Soc., Dalton Trans. (1991) 1519.
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´
P. Rodrıguez-Seoane, Polyhedron 22 (2003) 1711.
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´
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˜
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23.
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329 (2002) 1;
(b) Y.-P. Wang, C.-M. Che, K.-Y. Wong, S.-M. Peng, Inorg.
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(c) G.F. Ciani, G. DꢀAlfonso, P.F. Romiti, A. Sironi, M. Freni,
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5. Supplementary material
[13] J. Chatt, G.J. Leigh, D.M.P. Mingos, J. Chem. Soc. A (1969)
2867.
Crystallographic data for the structural analysis of
compound 2 have been deposited with the Cambridge
Crystallographic Data Centre (CDCC No. 272961).
Copies of this information may be obtained free of
charge from the CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: +44 1223 336003; e-mail: depos-
it@ccdc.cam.ac.uk; www: http://www.ccdc.cam.ac.uk.
[14] (a) F. Tisato, F. Refosco, C. Bolzati, A. Cagnolini, S. Gatto, G.
Bandoli, J. Chem. Soc., Dalton Trans. (1977) 1421;
(b) S. Bhattacharyya, S. Banerjee, B.K. Dirghangi, M. Menon,
A. Chakravorty, J. Chem. Soc., Dalton Trans. (1999) 155.
[15] J. Chatt, R.S. Coffey, J. Chem. Soc. A (1969) 1963.
[16] D. Michos, X.L. Luo, J.A.K. Howard, R.H. Crabtree, Inorg.
Chem. 31 (1992) 3914, and references cited therein.
[17] (a) J.R. Sowa Jr., V. Zanotti, G. Facchin, R.J. Angelici, J. Am.
Chem. Soc. 114 (1992) 160;
(b) J.R. Sowa Jr., J.B. Bonanno, V. Zanotti, R.J. Angelici, Inorg.
Chem. 31 (1992) 1370.
Acknowledgements
´
´
´
[18] S. Bolano, J. Bravo, J. Castro, S. Garcıa-Fontan, M.C. Marın, P.
˜
´
Rodrıguez-Seoane (in preparation).
Financial support from the Xunta de Galicia (Project
PGIDT04PXIC31401PN) and from the Spanish Minis-
try of Education and Science (Project BQU2003-
06783) is gratefully acknowledged. We thank the
University of Vigo CACTI services for collecting X-
ray data and recording NMR spectra.
[19] D.D. Perrin, W.L.F. Armarego, Purification of Laboratory
Chemicals, third ed., Butterworth and Heinemann, Oxford,
1988.
[20] M.N. Burnett, C.K. Johnson, ORTEPIII, Report ORNL-6895,
Oak Ridge National Laboratory, Oak Ridge, TN, 1996.
[21] G.M. Sheldrick, SADABS, An Empirical Absorption Correction
Program for Area Detector Data, University of Go¨ttingen,
Germany, 1996.
[22] G.M. Sheldrick, SHELX-97, Program for the Solution and Refine-
ment of Crystal Structures, University of Go¨ttingen, Germany,
1997.
References
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