New bromo-, triflato-, and hydridotricarbonylrhenium(I) complexes with diphosphinite ligands: Structural, spectral and protonation studies of various hydrides

Article abstract of DOI:10.1016/j.jorganchem.2005.08.014

Bromotricarbonylrhenium(I) complexes [ReBr(CO)₃L] [L = Ph ₂PO(CH₂)₃OPPh₂ (L¹), ⁱPr₂PO(CH₂)₂OPⁱPr ₂ (L²), Cy

Full text of DOI:10.1016/j.jorganchem.2005.08.014

Journal of Organometallic Chemistry 690 (2005) 4945–4958
www.elsevier.com/locate/jorganchem
New bromo-, triflato-, and hydridotricarbonylrhenium(I)
complexes with diphosphinite ligands: Structural, spectral
and protonation studies of various hydrides
a
*
*
´
´
´
Sandra Bolano, Jorge Bravo , Jesu´s Castro, Soledad Garcıa-Fontan , M Carmen Marın,
˜
´
Pilar Rodrıguez-Seoane
Departamento de Quı´mica Inorga´nica, Universidade de Vigo, Lagoas-Marcosende, E-36310 Vigo, Spain
Received 23 May 2005; received in revised form 29 July 2005; accepted 4 August 2005
Available online 22 September 2005
Abstract
Bromotricarbonylrhenium(I) complexes [ReBr(CO)3L] [L = Ph2PO(CH2)3OPPh2 (L1), iPr2PO(CH2)2OPiPr2 (L2), Cy2PO-
(CH2)2OPCy2 (L3)] were prepared by reaction of [ReBr(CO)5] with L. X-ray crystallography showed them all to be mononuclear,
with the CO ligands fac. Subsequent reaction with AgOTf gave fac-[Re(OTf)(CO)3L], as shown by IR and NMR spectra. By con-
trast, reaction of [ReH(CO)5] with L1–3 gave hydrido complexes, the nuclearity and stereochemistry of which depended on the iden-
tity of L, as was confirmed by X-ray crystallography of mer-[ReH(CO)3L1], fac-[ReH(CO)3L2] and [{ReH(CO)4}2(l-L3)].
Protonation of the hydrido compounds at 183 K with HBF4 Æ OMe2 gave the corresponding non-classical cationic dihydrogen com-
plexes (T1(min) ꢀ 15 ms at 400 MHz), which released H2 at temperatures above critical temperatures (243–263 K) that depended on
the co-ligands.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Rhenium; Carbonyl; Triflato; Hydrido compounds; Dihydrogen compounds; Phosphinites
1. Introduction
rhenium hydrido complexes bearing phosphines as co-li-
gands are known. However, few that bear phosphinites
have been used [5]. The weaker r-donor and stronger p-
acceptor nature of phosphinites [6] may be expected to
influence the properties of the metal centre, and hence
those of the complex.
We have previously investigated the properties and flux-
ional behaviour of a number of halide and hydrido rhe-
nium complexes bearing mono- and bidentate
phosphinites, phosphonites or phosphites, finding signifi-
cant dependence on the nature of the phosphorus-bearing
ligands [7]. In this paper, we report the synthesis and prop-
erties of hydrido-, bromo- and triflatorhenium(I) carbonyl
complexes with three diphosphinite ligands differing in the
nature of the R groups bound to the P atom and in the
length (two or three carbons) of the alkyl chain linking
the two R2PO groups.
Transition metal hydrido compounds can be used as effi-
cient catalysts for homogeneous processes [1] and as new
materials for storage of hydrogen [2]. Phosphines can be
readily employed in such complexes as supporting ligands
due to their easily modified electronic and steric effects al-
low modulation of catalytic behaviour. Moreover, the use
of potential chelating ligands offers extra control over the
selectivity of many catalytic reactions [3].
The field of organorhenium chemistry has progressed
significantly in recent decades [4], and a large number of
*
Corresponding authors. 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.2005.08.014

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S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
i
i
(CH )
Cy
Cy
(CH )
Ph
Ph
Cy
Cy
Ph
Ph
(CH )
2 2
Pr
2 2
2 3
Pr
O
P
O
P
P
P O
O
P
O
P
O
i
i
Pr
Pr
1
2
3
L
L
L
Scheme 1. Diphosphinite ligands L1–3
.
2. Results and discussion
2.1. Diphosphinite ligands
tiplet (d ꢀ 188 ppm) corresponding to the other two CO
ligands.
2.2.2. Description of the structures
The new diphosphinite ligand 1,3-bis(diphenyl-
phosphinoxy)propane (L1) and the known ligands
1,2-bis(diisopropylphosphinoxy)ethane (L2) and 1,2-bis-
(dicyclohexylphosphinoxy)ethane (L3) (Scheme 1) were
prepared following a previously published method [8]
by reaction of the corresponding diol with a chlorophos-
phine in the presence of triethylamine. As expected, their
31P{1H} NMR spectra in CDCl3 show just a single signal
for the two phosphorus atoms (L1, d 112.6; L2, d 154.9;
L3, d 150.1 ppm).
Perspective views of the molecular structures of com-
pounds 1a–c with atom numbering scheme are shown in
Figs. 1–3, respectively. Selected bond lengths and bond an-
gles are listed in Table 1, while the crystallographic data
and the details of the structure determination are given in
Table 4.
X-ray crystallography showed that 1a–c all consist of
discrete molecules with no significant hydrogen bonds be-
tween neighbours. In each complex, the central rhenium
atom is surrounded by three facially arranged carbonyl li-
gands, one bromine atom, and the two phosphorus atoms
of the bidentate ligand L (Figs. 1–3). The Re–C distances
of the carbonyl ligands trans to the phosphorus atoms
2.2. Bromotricarbonylrhenium(I) complexes
˚
2.2.1. Synthesis and spectroscopic characterization
range from 1.931(7) to 1.967(8) A, while that of the CO
Reaction of ligands L1–3 with [ReBr(CO)5] in 1:1 mole
ratio in refluxing toluene replaced two CO ligands with
the corresponding bidentate ligand, affording the new
bromotricarbonyl complexes fac-[ReBr(CO)3L] (1a–c;
Scheme 2).
trans to the bromine atom is significantly shorter due to
the p-donor character of the Br which increases the Re–
CO backbonding. However, all the Re–X bond lengths
(X = C, Br, P) are in the ranges found among similar com-
plexes [7d,10]. The angles around the metal are close to
those of a regular octahedron; the greatest distortion is
present in compound 1b, in which, probably due to the ste-
ric hindrance of the isopropyl groups, the cis angles range
from 85.7(2)ꢁ to 94.89(5)ꢁ and the narrowest axial angle is
172.43(17)ꢁ.
The new complexes are stable in the solid state and in
solution at room temperature, and were characterized by
the usual spectroscopic techniques. In their IR spectra,
three strong m(CO) bands characteristic of the fac-ReI(CO)3
moiety are observed at 2031, 1948 and 1922 cmꢁ1 for 1a,
2029, 1951 and 1897 cmꢁ1 for 1b, and 2022, 1954 and
1888 cmꢁ1 for 1c [9]. The 31P{1H} NMR spectra of com-
plexes 1a–c show single resonances (showing the magnetic
equivalence of the two phosphorus nuclei), with negative
coordination shifts in all cases. In keeping with the fac
arrangement of the CO ligands, the 13C{1H} NMR spectra
show two low-field signals assignable to the CO groups: a
triplet corresponding to the CO group located cis to both
phosphorus nuclei (d ꢀ 189 ppm; 2JCP ꢀ 7 Hz), and a mul-
In compound 1a the conformation of the eight-mem-
bered chelate ring can be described as a chair [11], the
planes defined by {Re, P(1), P(2), O(51), O(52)} and
{C(51), C(52), C(53)} being almost parallel [dihedral angle
2.8(3)ꢁ]. The seven-membered chelate rings of compounds
1b and 1c are both best described as a boat with an intra-
molecular interaction between the bromine atom and a
methylene proton belonging to the bidentate ligand (H–
˚
˚
Br = 2.84 A in 1b and 2.59 A in 1c).
Br
Br
R2
(CH2)n
OC
OC
P
O
O
OC
OC
CO
CO
- 2CO
Re
(CH2)n
+
Re
O
PR2
R2P
O
Toluene, reflux
P
R2
CO
CO
1a: R= Ph ; n = 3
1b: R= iPr ; n = 2
1c: R= Cy ; n = 2
Scheme 2. Synthesis of the complexes 1a–c.

S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
4947
O1
O2
O3
C15
C2
C1
C3
C16
C12
Re
C11
P1
Br
P2
O51
O52
C53
C51
C52
Fig. 1. Molecular structure of 1a.
O1
O2
O3
C1
C2
C3
Re
P1
P2
O51
O52
C51
C52
Fig. 2. Molecular structure of 1b.
2.3. Triflatotricarbonylrhenium(I) complexes
IR spectra all showed three strong bands in the region
1914–2042 cmꢁ1 that can be assigned to the CO stretching
vibrations. These bands are blue-shifted by about 17 cmꢁ1
with respect to those of complexes 1a–c, which is attribut-
able to OTf having greater electron-withdrawing power
than Br. 31P{1H} and 13C{1H} NMR spectra of complexes
2a–c showed that the fac arrangement of the CO groups is
inherited from the Br compounds: the 31P{1H} NMR
When compounds 1a–c were reacted with Ag(SO3CF3)
in 1:1 mole ratio in refluxing CH2Cl2, the corresponding
triflato derivatives were obtained through replacement of
the bromo ligand by OTf (Scheme 3).
Complexes 2a–c were stable in the solid state and in
methylene chloride solution at room temperature, and their

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S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
O1
O2
C1
O3
C2
C3
Re
P1
P2
Br
C22
C21
O51
O52
C24
C26
C51
C52
C25
Fig. 3. Molecular structure of 1c.
spectra all showed a single singlet, and the 13C{1H} spectra
two low-field signals of structure and multiplicity similar to
those observed for the bromo derivatives.
Table 1
˚
Selected bond lengths (A) and angles (ꢁ) in the bromo complexes
Complex 1a 1b 1c
˚
Bond lengths (A)
Re–C(1)
Re–C(2)
Re–C(3)
Re–P(1)
1.919(7)
1.967(8)
1.931(7)
2.474(2)
2.462(2)
2.621(1)
1.889(6)
1.938(7)
1.956(6)
2.495(2)
2.467(1)
2.632(1)
1.931(8)
1.950(7)
1.958(7)
2.474(2)
2.479(2)
2.654(1)
2.4. Hydridotricarbonylrhenium(I) complexes
2.4.1. Synthesis and spectroscopic characterization of
mer-[ReH(CO)3L1] (3a)
Re–P(2)
Re–Br
Reaction of [ReH(CO)5] with L1 afforded mer-[Re-
H(CO)3L1] (3a) in 39% yield (Scheme 4). The crude reac-
tion product was contaminated with about 1% of what,
on the basis of 1H and 31P NMR data, was tentatively iden-
tified as the fac isomer 3a0 [1H (CD2Cl2): d ꢁ4.76 ppm (t,
JPH = 27 Hz, ReH); 31P{1H} (CD2Cl2): d 122.8 ppm (s)].
Washing with THF and subsequent recrystallization from
2:10 (v/v) CH2Cl2/EtOH solution afforded pure 3a.
The IR spectrum of 3a shows the CO vibrations as two
strong bands at 1917 and 1954 cmꢁ1 and a medium-strength
band at 2035 cmꢁ1. The 31P{1H} NMR spectrum of 3a
shows the two doublets that are expected for two non-
equivalent phosphorus nuclei (at 120.8 and 124.4 ppm;
JPP = 23 Hz), but its 1H NMR spectrum surprisingly
shows, at high field, only a single doublet for the hydrido
Bond angles (ꢁ)
C(1)–Re–C(2)
C(1)–Re–C(3)
C(1)–Re–P(1)
C(1)–Re–P(2)
C(2)–Re–C(3)
C(2)–Re–P(2)
C(3)–Re–P(1)
P(1)–Re–P(2)
C(2)–Re–Br
C(3)–Re–Br
P(1)–Re–Br
P(2)–Re–Br
C(3)–Re–P(2)
C(1)–Re–Br
88.4(3)
89.3(3)
88.3(2)
90.5(2)
90.6(3)
88.6(2)
87.3(2)
93.4(1)
90.4(2)
89.6(2)
92.9(1)
90.5(1)
179.2(2)
178.4(2)
176.1(2)
86.3(3)
92.7(2)
90.2(2)
93.0(2)
85.7(2)
89.8(2)
90.0(2)
94.9(1)
92.7(2)
86.2(2)
90.8(1)
88.0(1)
172.4(2)
178.6(2)
174.3(2)
88.5(3)
86.9(3)
92.2(2)
90.8(2)
89.1(3)
90.7(2)
92.6(2)
87.7(1)
86.9(2)
88.1(2)
92.5(1)
94.2(1)
177.7(2)
173.3(2)
178.2(2)
C(2)–Re–P(1)
R2
P
Br
R2
P
OTf
Re
OC
OC
O
O
- AgBr
OC
OC
O
O
Re
CO
(CH2)n
+ AgOTf
(CH2)n
CH2Cl2, reflux
P
P
R2
CO R2
2a: R = Ph; n = 3
2b: R =iPr; n = 2
2c: R = Cy; n = 2
Scheme 3. Synthesis of the complexes 2a–c.

S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
4949
CO
Ph2
P
OC
Re
H
O
O
(CH2)3
P
Ph2
CO
mer (99%)
H
(CH2)3
OC
OC
CO
CO
- 2CO
Re
+
Ph2P
O
O
PPh2
+
THF-Toluene, r.t.
H
CO
Ph2
P
OC
OC
O
O
Re
(CH2)3
P
Ph2
CO
fac (1%)
Scheme 4. Synthesis of the complex 3a.
nucleus (d ꢁ6.09 ppm; JPH = 36 Hz), which suggests that
coupling between the hydrido and one of the phosphorus
nuclei must be almost zero. Two multiplets located at
2.02 ppm (2H) and 3.91 ppm (4H) may be assigned to the
methylene protons of the diphosphinite ligand.
Lowering the temperature from 293 to 183 K just
slightly broadens the 31P{1H} signals. In the 1H NMR
spectrum the hydrido doublet and the multiplet at
2.02 ppm are broadened more markedly, and the multiplet
at 3.91 ppm decoalesces into three new broad signals, two
of which integrate to 1 proton and one to 2. These changes
appear to reflect the initial stages of the freezing of an equi-
librium between conformers of the chelate ring, as has been
observed in similar systems [7a]. Determination of the min-
imum spin-lattice relaxation time [T1(min)] for the hydrido
nucleus at 400 MHz by the standard inversion-recovery
method gave a value of 296 ms at 215 K.
the methylene protons of the chelate ring. The 31P{1H}
NMR spectrum of 3b shows a singlet at 149.5 ppm, indicat-
ing the magnetic equivalence of the two phosphorus nuclei
at room temperature.
When the temperature was lowered from 293 to 173 K,
the triplet observed at ꢁ5.69 ppm in the room-temperature
1H NMR spectrum became a single broad signal, and the
two multiplets corresponding to the methylene protons col-
lapsed into a single broad hump (Fig. 4). In the 31P{1H}
NMR spectrum of 3b (Fig. 5) the signal observed at
293 K broadened progressively, disappeared into the base-
line at 193 K, and re-emerged at 173 K as two broad sig-
nals at 132.6 and 167.1 ppm, indicating the magnetic
non-equivalence of the two phosphorus nuclei at this tem-
perature. DGꢀ was calculated as 31.35 0.2 kJ molꢁ1 at the
coalescence temperature, 193 K [13]. The fluxional process
responsible for this behaviour is probably interconversion
between two conformers of the seven-membered chelate
ring [14]. Determination of T1(min) for the hydrido nucleus
at 400 MHz by the standard inversion-recovery method
gave a value of 234 ms at 190 K.
2.4.2. Synthesis and spectroscopic characterization of
fac-[ReH(CO)3L2] (3b)
When [ReH(CO)5] was reacted with L2 in 1:3 mole ratio
in THF, chromatography of the crude product afforded
fac-[ReH(CO)3L2] (3b; Scheme 5) [12].
2.4.3. Synthesis and spectroscopic characterization of fac-
[ReH(CO)3L3] (3c) and [{ReH(CO)4}2(l-L3)] (3c0)
Reaction of [ReH(CO)5] with ligand L3 in 1:3 mole
ratio gave a 3:7 mixture of two products that were subse-
quently separated by column chromatography. The minor
component was identified as the mononuclear compound
1
The room-temperature H NMR spectrum of 3b dis-
plays a triplet at ꢁ5.69 ppm (JHP = 27 Hz) that integrates
to one proton corresponding to the hydrido ligand. The
two multiplets at 2.16 and 2.32 ppm can be assigned to
iPr methine protons, and those at 4.03 and 4.23 ppm to
H
iPr2
H
(CH2)2
OC
OC
P
O
O
OC
OC
CO
CO
- 2CO
iPr2P
PiPr2
Re
(CH2)2
+
Re
O
O
THF-Toluene
60˚C
P
iPr2
CO
CO
3b
Scheme 5. Synthesis of the complex 3b.

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S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
At 298 K, the 31P{1H} NMR spectrum of 3c displays a
singlet at 143.5 ppm and the 1H NMR spectrum a triplet at
ꢁ5.68 ppm (JPH = 27 Hz). As in the case of similar systems
[7], the signals corresponding to the methylene protons of
the bidentate ligand appear as two multiplets (at 3.93 and
4.13 ppm), indicating their diastereotopic nature. The
13C{1H} spectrum shows, at low field, a triplet (d =
196.0 ppm, JCP = 8 Hz) and a multiplet (d = 194.9 ppm),
the integrals of which are in an approximate ratio of 1:2.
These results support the formulation of compound 3c as
the fac isomer of [ReH(CO)3L3]. Upon lowering the tem-
perature to 173 K, the singlet at 143.5 ppm in the room-
temperature 31P{1H} NMR spectrum broadens gradually
until, at 203 K, it disappears into the baseline. The collapse
of the methylene signals into a single broad signal at 193 K
may be interpreted in the same way as for compound 3b,
i.e., as indicating the initial freezing of the interconversion
between two conformers of the seven-membered chelate
ring. The value of T1(min) found for the hydrido signal,
224 ms at 400 MHz.
The room-temperature 31P{1H} NMR spectrum of the
major component of the mixture, 3c0, shows a single singlet
at 145.9 ppm, indicating the magnetic equivalence of the
Fig. 4. 1H NMR spectra of compound 3b at various temperatures.
1
two phosphorus nuclei. In the H NMR spectrum there
is a doublet at high field (d = ꢁ6.17 ppm, JHP = 23 Hz),
and the appearance of the methylene proton signal as a sin-
gle narrow multiplet (at 3.93 ppm) shows that in 3c0, with
its bridging ligand, the environment of these nuclei is more
uniform than in 3c, with its more restrictive chelating li-
gand. In agreement with these results, the 13C{1H} NMR
spectrum shows, at low field, three doublets attributable
to the CO groups: one at 190.5 ppm (JCP = 43 Hz) corre-
sponding to the CO trans to the P atom, one at
192.0 ppm (JCP = 10 Hz) that is assignable to the mutually
trans CO groups (this signal integrates to approximately
double the previous one), and one at 192.2 ppm
(JCP = 7 Hz) corresponding to the CO trans to the H atom.
When the temperature is lowered from 293 to 173 K, the
signals of the 1H and 31P{1H} spectra broaden just slightly,
in keeping with the proposed formulation. The value of
T1(min) for the hydrido signal at 400 MHz is 320 ms; this
Fig. 5. 31P{1H} NMR spectra of compound 3b at various temperatures.
fac-[ReH(CO)3L3] (3c), and the major component as the
binuclear compound [{ReH(CO)4}2(l-L3)] (3c0); see
Scheme 6.
H
CO
P Cy2
OC
OC
Re
H
H
Cy2
P
O
O
Cy2P
Cy2P
CO
OC
OC
O
O
- 2CO
OC
OC
O
CO
CO
(CH2)2
Re
(CH2)2
+
+
(CH2)2
Re
THF-Toluene, r.t.
P
Cy2
O
CO
Re
CO
CO
P Cy2
OC
OC
CO
H
3c' (70%)
3c (30%)
Scheme 6. Synthesis of the complexes 3c and 3c0.

S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
4951
value is significantly higher than that obtained for com-
pound 3c, possibly due to their having different numbers
of P nuclei in the vicinity of the hydrido ligand [15].
and bond angles are listed in Table 2, while the crystallo-
graphic data and the details of the structure determination
are given in Table 5.
X-ray crystallography confirmed the structures pro-
posed for complexes 3a, 3b and 3c0 on the basis of their
spectra, and showed them to consist of discrete molecules
with no significant H-bonds between neighbours (Figs. 6–
8). The apparent Re–H distances range from 1.60(5) to
2.4.4. Description of the structures
Perspective views of the molecular structures of com-
pounds 3a, 3b and 3c0 with atom numbering scheme are
shown in Figs. 6–8, respectively. Selected bond lengths
C35
C23
C24
C34
O1
O2
C36
C31
C22
C1
C33
C2
C25
H1
C21
C26
C32
Re
P2
P1
C16
C3
O3
C41
O52
C15
C14
C51
O51
C12
C53
C52
C13
Fig. 6. Molecular structure of 3a.
O2
O3
C2
C3
H1
C22
C43
C23
Re
C1
C42
P2
C41
C21
C31
P1
O1
C12
O51
C33
O52
C32
C11
C13
C51
C52
Fig. 7. Molecular structure of 3b.

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S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
O3
C3
O8
O4
O7
O1
C1
C4
Re1
C8
C7
H1
O5
C2
C5
C52
O2
H2
Re2
C51
P1
O52
O51
C6
P2
C36
O6
C31
C32
C35
C34
C33
Fig. 8. Molecular structure of 3c0.
˚
1.90(4) A, but these figures may be misleading due to the
well-known limitations of X-ray diffractometry for hydrido
ligands coordinated to third-row transition metals.
phos)] [17]. The eight-membered ring has a twisted boat
conformation with six atoms virtually coplanar (rms devi-
˚
˚
ation of 0.063 A), C(53) 0.816(6) A above the plane, and
˚
C(51) 0.832(6) A below it (Fig. 9).
2.4.4.1. Compound 3a. Complex 3a is, to the best of our
knowledge, the first mononuclear monohydrido complex
with an ReHP2(CO)3 core to have been found by X-ray
crystallography to have its hydrido ligand trans to the
phosphorus atom. Among the different factors that could
favour the formation of the mer stereoisomer, the large bite
angle of L1 ligand could be a likely one. The coordination
polyhedron is a distorted octahedron, the sources of the
distortion being the small size of the hydrogen atom and
the steric requirements of the bidentate ligand. Thus, the
2.4.4.2. Compound 3b. In 3b the Re–C(2) and Re–C(3)
bond lengths are slightly shorter than Re–C(1) (Table 2),
as expected from the p-donor capacity of the P atom that
increases the Re–CO backbonding. The Re–P distances
are both longer than those reported in the literature for
mononuclear complexes [16,7d]. The angles around the me-
tal are more distorted than in the bromo analogue, with cis
angles ranging from 82.0(3) to 95.6(2)ꢁ and axial angles
from 167.9 (2)ꢁ to 174.9(1)ꢁ (the latter for C–Re–H). The
Re–ligand bonds in the equatorial plane are all bent to-
wards the hydrido, so that the rhenium atom lies
˚
chelate angle is 107.3(5)ꢁ, and P(2) lies 0.81(1) A from the
plane defined by the three carbonyl ligands. The Re–P
˚
˚
bond lengths are 2.385(2) and 2.405(1) A, the shorter corre-
0.182(2) A from the best equatorial plane, on the opposite
sponding to the phosphorus atom trans to the hydrido li-
gand, which exerts less trans influence than the carbonyl
ligand [16]. Both these distances are slightly shorter than
those found in the similar complex fac-[ReH(CO)3P],
[P = 1,2-bis(diphenylphosphinoxy)ethane] [7d], in which
the chelate ring is seven-membered, but they are slightly
longer than those found in a trans-mer complex with
monodentate phosphorus-donor ligands [16]. The three
Re–C distances are in keeping with the expected trans influ-
side from the hydrido atom. As in 1b, the conformation of
the seven-membered chelate ring of 3b is best described as a
˚
boat, with O(51) 0.112 (4) A below the best plane and the
˚
other C and O atoms above it [O(52) by 0.678 (4) A,
˚
˚
C(51) by 0.964 (6) A, and C(52) by 1.595(5) A].
2.4.4.3. Compound 3c0. Low-temperature X-ray diffrac-
tometry of compound 3c0 confirmed that this complex is
a binuclear compound in which both rhenium(I) atoms
are surrounded by four carbonyl ligands, a hydrido ligand,
and one of the phosphorus atoms of the bis-monodentate
ligand that bridges between them. The coordination poly-
hedra are slightly distorted octahedra with similar bond
lengths, except that all the distances around Re(1) are
˚
ences: an average 1.926(7) A for the mutually trans car-
bonyl ligands, and 1.901(6) for the carbonyl trans to a
phosphorus atom. These distances are significantly shorter
than those found in the related complexes mentioned above
[16,7d], but are close to those found in [ReH(CO)2(tri-

S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
4953
Table 2
Selected bond lengths (A) and angles (ꢁ) in the hydrido complexes
C53
O51
P1
˚
Re
Complex
3a
3b
3c0
C52
(Re1)
(Re2)
1.86(5)
˚
Bond lengths (A)
Re–H(1)
Re–C(1)
Re–C(2)
Re–C(3)
1.75(4)
1.90(4)
1.60(5)
1.925(7)
1.901(6)
1.927(7)
2.385(2)
2.405(2)
1.967(6)
1.943(5)
1.929(6)
2.439(1)
2.438(2)
1.967(6)
1.973(6)
1.951(5)
2.440(1)
1.983(6)
1.990(6)
1.954(6)
2.443(1)
P2
C51
O52
Fig. 9. Eight-membered ring in 3a.
Re–P(1)
Re–P(2)
Re–C(4)
1.987(6)
1.987(5)
Bond angles (ꢁ)
H(1)–Re–C(1)
H(1)–Re–C(2)
H(1)–Re–C(3)
C(1)–Re–C(2)
C(2)–Re–C(3)
C(1)–Re–C(3)
H(1)–Re–P(1)
H(1)–Re–P(2)
C(1)–Re–P(1)
C(2)–Re–P(1)
C(3)–Re–P(1)
C(1)–Re–P(2)
C(2)–Re–P(2)
C(3)–Re–P(2)
P(1)–Re–P(2)
H(1)–Re–C(4)
P(1)–Re–C(4)
C(1)–Re–C(4)
C(2)–Re–C(4)
C(3)–Re–C(4)
from their ideal values are the axial angles P–Re–C,
163.5(2)ꢁ and 166.0(2)ꢁ, probably due to the greater steric
demands of the cyclohexyl substituents. If angles involving
the hydrido ligand are ignored because of the unreliability
of X-ray measurements of these angles, the most distorted
cis angles are those between the phosphorus atom and the
carbon trans to the hydrido ligand, with values of 98.7(1)ꢁ
and 99.9(2)ꢁ around Re(1) and Re(2), respectively. The
octahedra can thus be considered as fairly regular except
for the position of the phosphorus atom, which has swung
towards the hydrido ligand; as a result, the phosphorus
atoms, instead of being in the same plane as three carbonyl
94.2(1)
82.7(1)
85.7(1)
90.5(3)
91.2(3)
178.2(3)
172.1(1)
77.5(1)
92.4(2)
92.9(2)
87.9(2)
86.6(2)
159.7(2)
91.6(2)
107.3(5)
174.9(1)
87.8(1)
82.0(1)
95.9(2)
86.0(2)
94.7(3)
83.1(1)
88.0(1)
93.2(1)
170.8(2)
91.5(1)
95.6(2)
86.8(1)
167.9(2)
94.1(4)
173.2(2)
176(2)
91(2)
88.5(1)
76.9(2)
91.8(2)
87.6(2)
96.3(3)
79.8(2)
86.4(2)
92.5(2)
89.7(2)
95.2(2)
86.9(2)
98.7(1)
88.4(1)
166.0(2)
99.9(2)
88.7(2)
163.5(2)
˚
carbon atoms, are 0.42(1) and 0.58(1) A from the plane de-
84(2)
88.5(1)
92.7(2)
91.0(2)
176.6(2)
90.2(2)
fined by those carbons, with the rhenium atoms on the
other side of this plane and, respectively, 0.075(4) and
89.2(1)
91.8(3)
175.4(2)
91.7(2)
˚
0.045(4) A from it.
2.4.5. Protonation studies
(Re1) Values corresponding to the environment of the rhenium atom
labelled Re(1).
(Re2) Values corresponding to the environment of the rhenium atom
labelled Re(2), with P(2) represented by P(1), H(2) by H(1), C(5) by C(1),
C(6) by C(2), C(7) by C(3), and C(8) by C(4).
Protonation of 3a, 3b, 3c and 3c0 with HBF4 Æ Me2O in
CD2Cl2 at 183 K gave the corresponding cationic dihydro-
gen complexes mer-[Re(g2-H2)(CO)3L1]+(3a*), fac-[Re(g2-
H2)(CO)3L2]+(3b*), fac-[Re(g2-H2)(CO)3L3]+ (3c*) and
[{Re(g2-H2)(CO)4}2(l-L3)]+ (3c0*), as was shown by the
replacement of the sharp high-field signals in the 1H
NMR spectra of the hydrides by broad signals (about
ꢁ4 ppm) downfield of them that had T1(min) values typical
of non-classical dihydrogen compounds [18] (Table 3).
slightly longer than those around Re(2). Unlike those of
the related mononuclear complex [ReH(CO)4{P-
Ph2(OMe)}] [16], in 3c0 the angles showing most deviation
Table 3
Selected NMR data (at 183 K) for the cationic compounds originated by protonation of complexes 3a–c and 3c0
Compounda
1H NMR;b d (ppm)
Assignment
T1(min) [ms]
31P{1H} NMR; d (ppm)
Td (K)
mer-[Re(g2-H2)(CO)3L1]+ (3a*)
ꢁ4.81 (br)
2.13 (br)
3.67–4.12 (br)
ꢁ4.47 (br)
1.16 (br)
g2-H2
–CH2–
–OCH2–
g2-H2
14 3 at 197 K
110.0 (br)
111.0 (br)
263
fac-[Re(g2-H2)(CO)3L2]+ (3b*)
14 3 at 215 K
–
253
c
–CH3
2.47 (br)
4.05 (br)
ꢁ4.43 (br)
3.80–4.10 (m, br)
ꢁ4.16 (br)
4.03 (br)
–CH—
–OCH2–
g2-H2
c
fac-[Re(g2-H2)(CO)3L3]+ (3c*)
15 2 at 213 K
16 3 at 206 K
–
253
243
–OCH2–
g2-H2
–OCH2–
[{Re(g2-H2)(CO)4}2(l-L3)]+ (3c0*)
140.2 (br)
a
In CD2Cl2 at 400 MHz.
b
Cyclohexyl and phenyl proton resonances are omitted.
Signal buried in the baseline.
Limit of thermal stability.
c
d

4954
S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
These cations, which all had quite similar NMR charac-
teristics (Table 3), released H2 when the temperature
was raised, as was indicated by the appearance of a sharp
singlet at 4.6 ppm corresponding to free H2 [19]. This oc-
curred at lowest temperature for 3c0*, and at highest for
3a* (Table 3), which may be explained in terms of the
number of CO ligands [16] and the nature of the R groups
of the phosphinite ligand, as follows. Diphosphinite li-
gands have lesser p-acceptor properties than carbonyl li-
gands making the metal centre more electron-rich thus
favouring the p back-donation to the H2 r* orbital.
The amount of p back-donation is crucial: too little
backbonding makes the complex unstable towards H2 re-
lease, while too much back-donation converts dihydrogen
complexes into classical dihydrido compounds. In the case
of dihydrogen complexes 3(a–c)* and 3c0* the back-dona-
tion is not enough to produce the homolytic cleavage of
the H2 ligand. Besides, their different stabilities towards
H2 release could be rationalised as a function of the
amount of backbonding between the metal centre and
the H2 ligand, being the least stable compound, 3c0*,
the only one with four carbonyl groups around the rhe-
nium atom. That compounds 3b* and 3c* have similar
thermal stabilities may be attributed to their having the
same number of carbonyls and similar R groups (isopro-
pyl and cyclohexyl). Compound 3a* is more stable than
3b*, 3c* and the similar compound [Re(g2-H2)(CO)3L]
[L = 1,2-bis(diphenylphosphinoxy)ethane] [7d], which like
3b* and 3c* has fac stereochemistry and releases hydro-
gen at about 230 K. The greater stability of 3a* may be
attributed to its dihydrogen ligand being trans to a P
atom, whereas in the fac complexes it is necessarily lo-
cated trans to a CO with greater p-accepting capacity
than P.
3.1. Synthesis of Ph2PO(CH2)3OPPh2 (L1)
Ph2PCl (13 mL, 72.4 mmol), Et3N (10 mL, 72.1 mmol)
and toluene (60 mL) were placed into a 250 mL Schlenk
flask equipped with an addition funnel in which a solution
of 2 mL (36 mmol) of 1,3-propanediol and 35 mL of tolu-
ene was placed. This solution was added dropwise at
ꢁ80 ꢁC and was stirred over 1.5 h. at 0 ꢁC. The solid
formed was filtered off, and the solvent and most impuri-
ties were removed by distillation under reduced pressure.
This gave a viscous oil that was pure enough for NMR
analysis but decomposed within 24 h, for which reason
this product was kept, and used in subsequent steps, in
toluene solution under argon. Yield: 80%. 1H NMR
(400 MHz, CDCl3): d 2.91 (m, 2H, –CH2–), d 3.95 (m,
4H, –OCH2–). 31P{1H} NMR (161 MHz, CDCl3): d
112.6 (s).
3.2. Preparation of fac-[ReBr(CO)3L] (1) [L = L1 (1a),
L2 (1b), L3 (1c)]
[ReBr(CO)5] (0.1 g, 0.25 mmol) was suspended in 10 mL
of toluene and an equimolar amount of L was added
(1.2 mL of a 0.22 M solution of L1; 0.9 mL of a 0.29 M
solution of L2; 2.1 mL of a 0.12 M solution of L3). The
mixture was refluxed for 3–4 h, allowed to cool to room
temperature, and stirred for a further 3 h. The solvent
was removed under vacuum, and the residue was treated
with ethanol (2 mL), affording a white product that was fil-
tered out, washed with ethanol, dried under vacuum, and
recrystallized from 2:10 (v/v) CH2Cl2/EtOH by slow
evaporation.
Compound 1a. Yield: 56% (0.19 g). Anal. Calc. for
C30H26BrO5P2Re: C, 46.0; H, 3.20%. Found: C, 45.35; H,
3.30%. MS (m/z, referred to the most abundant isotopes):
794, [M]; 766, [M ꢁ CO]; 738, [M ꢁ 2CO]; 715, [M ꢁ Br].
3. Experimental
IR(mCO): 2031, 1948, 1922 cmꢁ1 1H NMR (400 MHz,
.
All experimental manipulations were carried out under
an atmosphere of argon using Schlenk techniques. All the
solvents were purified by conventional procedures [20]
and distilled prior to use. The ligands 1,2-bis(diisopropyl-
phosphinoxy)ethane (L2) and 1,2-bis(dicyclohexylphos-
phinoxy)ethane (L3), and the hydrido precursor
[ReH(CO)5], were prepared by published methods [8,21].
1H, 31P, 13C and 19F NMR spectra were obtained on a
Bruker ARX-400 spectrometer operating at frequencies
of 400, 161, 100 and 376 MHz, respectively; the spectra
were recorded in CDCl3 or CD2Cl2 solutions, as indi-
cated, using the solvent as internal lock. 1H and
13C{1H} signals are referred to internal TMS, those of
19F{1H} to CFCl3, and those of 31P{1H} to 85%
H3PO4; downfield shifts (d in ppm) are considered posi-
tive. IR spectra (KBr discs) were recorded on a Bruker
VECTOR IFS 28 FT apparatus, and mass spectra on a
Micromass Autospec M LSIMS (FAB+) system. Microa-
nalyses were carried out on a Fisons Model EA 1108 ele-
mental analyzer.
CDCl3): d 1.71–2.32 (m, 2H, –CH2CH2–), d 3.59–4.54 (m,
4H, –OCH2–), d 7.32–7.98 (m, 20H, Ph). 31P{1H} NMR
(161 MHz, CDCl3): d 97.7 (s). 13C{1H} NMR (100 MHz,
CDCl3): d 31.8 (s, –CH2–), d 66.4 (s, –OCH2–), d 128.7–
137.2 (m, Ph), d 188.0 (m, CO cis to Br), d 189.0 (t,
2JCP = 7 Hz, CO trans to Br).
Compound 1b. Yield: 19% (0.07 g). Anal. Calc. for
C17H32BrO5P2Re: C, 31.68; H, 5.0%. Found: C, 32.11; H,
5.4%. MS (m/z, referred to the most abundant isotopes):
644, [M]; 616, [M ꢁ CO]; 588, [M ꢁ 2CO]; 560,
[M ꢁ 3CO]. IR(mCO): 2029, 1951, 1897 cmꢁ1
.
1H NMR
(400 MHz, CDCl3): d 1.21–1.38 (m, 24H, –CH3), d 2.52–
2.95 (m, 4H, ˜CH–), d 3.83–4.53 (m, 4H, –CH2CH2–).
31P{1H} NMR (161 MHz, CDCl3): d 135.6 (s). 13C{1H}
NMR (100 MHz, CDCl3): d 18.8 (m, –CH3), d 29.7 (m,
˜CH–), d 64.2 (m, –OCH2CH2O–), d 187.9 (t, 2JCP = 8 Hz,
CO trans to Br), d 188.2 (m, CO cis to Br).
Compound 1c. Yield: 50% (0.15 g). Anal. Calc. for
C29H48BrO5P2Re: C, 43.90; H, 6.40%. Found: C, 43.28;
H, 6.01%. MS (m/z, referred to the most abundant

S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
4955
isotopes): 804, [M]; 748, [M ꢁ 2CO]; 720, [M ꢁ 3CO];
3.4. Preparation of mer-[ReH(CO)3L1] (3a)
725, [M ꢁ Br]. IR(mCO): 2022, 1954, 1888 cmꢁ1
.
1H
NMR (400 MHz, CDCl3): d 1.15–2.55 (m, 44H, Cy), d
A solution of [ReH(CO)5] (0.1 mL, 0.7 mmol) in THF
(10 mL) was added to a solution of L1 in toluene (10 mL,
0.22 M), the mixture was stirred for 24 h, and the white so-
lid formed was filtered out. This product was a mixture of
mer and fac isomers. Washing with THF removed the more
soluble fac-isomer, leaving the mer-isomer, which was
washed with 2 mL of ethanol and recrystallized from 2:10
(v/v) CH2Cl2/EtOH by slow evaporation. Yield: 39%
(0.2 g). Anal. Calc. for C30H27O5P2Re: C, 50.72; H,
3.80%. Found: C, 50.35; H, 3.80%. MS (m/z, referred to
the most abundant isotopes): 716, [M]; 688, [M ꢁ CO].
3.84–4.46 (m, 4H, –OCH2CH2O–). 31P{1H} NMR
(161 MHz, CDCl3):
d
129.7 (s). 13C{1H} NMR
(100 MHz, CDCl3): d 23.8–28.9(m, C2–C6 of Cy), d
37.9–43.1 (m, C1 of Cy), d 64.6 (s, a, –OCH2), d 64.9
(s, a, –OCH2), d 188.1 (m, CO cis to Br), d 189.0 (t,
2JCP = 7 Hz, CO trans to Br).
3.3. Preparation of fac-[Re(O3SCF3)(CO)3L] (2) [L = L1
(2a), L2 (2b), L3 (2c)]
A mixture of the appropriate compound 1 (0.13 mmol)
and Ag(O3SCF3) (0.1 mmol) in CH2Cl2 (20 mL) was
heated under reflux for 1 h and filtered to remove AgBr.
The solvent was removed under vacuum, and the residue
was treated with ethanol (2 mL), affording a brown prod-
uct that was filtered out, washed with ethanol and dried un-
der vacuum.
IR(mCO): 2035, 1954, 1917 cmꢁ1 1H NMR (400 MHz,
.
CD2Cl2): d ꢁ6.09 (d, 1H, JPH = 36 Hz, ReH), d 2.02 (m,
2H, –CH2–), d 3.91 (m, 4H, –OCH2–), d 7.50–7.95 (m,
20H, Ph). 31P{1H} NMR (161 MHz, CD2Cl2): d 120.8 (d,
JPP = 23 Hz); 124.4 (d, JPP = 23 Hz). 13C{1H} NMR
3
(100 MHz, CDCl3): d 32.7 (t, JCP = 4 Hz, –CH2–), d
59.8 (s, –OCH2–), d 61.0 (s, –OCH2–), d 127.7–132.5 (m,
ortho-C, meta-C, para-C of Ph), d 141.8 (d, JCP = 55 Hz,
ipso-C of Ph), d 143.7 (d, JCP = 49 Hz, ipso-C of Ph), d
193.2 (t, JCP = 12 Hz, cis CO), d 196.9 (m, trans CO).
Compound 2a. Yield: 67% (0.02 g). Anal. Calc. for
C31H26F3O8P2ReS: C, 43.05; H, 3.03%. Found: C, 42.98;
H, 2.96%. MS (m/z, referred to the most abundant iso-
topes): 864, [M]. IR(mCO): 2042, 1960, 1940 cmꢁ1
.
1H
NMR (400 MHz, CDCl3):
d
1.72–2.16 (m, 2H,
3.5. Preparation of fac-[ReH(CO)3L2] (3b)
–CH2CH2–), d 3.66–3.86 (m, 4H, –OCH2–), d 7.19–7.70
(m, 20H, Ph). 31P{1H} NMR (161 MHz, CDCl3): d 112.7
(s). 13C{1H} NMR (100 MHz, CDCl3): d 30.2 (s, –CH2),
d 64.8 (s, –OCH2), d 118.8 (s, –CF3), d 128.2–134.9 (m,
A solution of [ReH(CO)5] (0.1 mL, 0.7 mmol) in THF
(10 mL) was added to a solution of [1,2-bis(diisopropyl-
phosphinoxy)ethane] (7.5 mL, 0.29 M) in toluene (Re:L
mole ratio 1:3), and the mixture was heated at 60 ꢁC for
6 h. After cooling to room temperature, the solvent was re-
moved under vacuum, and the residual oil was chromato-
graphed on a silica gel column (length 70 cm, diameter
4 cm) using a 10:1 mixture of light petroleum (40–60 ꢁC)
and diethyl ether as eluent. The first fraction eluted
(25 mL) was concentrated to dryness, leaving an oil that
was treated with ethanol (2 mL). Cooling the resulting
solution to –25 ꢁC afforded white crystals of complex 3b.
Yield: 24% (0.09 g). Anal. Calc. for C17H33O5P2Re: C,
36.10; H, 5.88%. Found: C, 36.40; H, 5.96%. MS (m/z, re-
ferred to the most abundant isotopes): 566, [M]; 538,
2
Ph), d 189.2 (t, JCP = 7 Hz, CO trans to OTf), d 189.5
(m, CO cis to OTf). 19F{1H} NMR (376 MHz, CDCl3): d
ꢁ76.9 (s).
Compound 2b. Yield: 50% (0.02 g). Anal. Calc. for
C18H32F3O8P2ReS: C, 30.25; H, 4.52%. Found: C, 30.22;
H, 4.56%. MS (m/z, referred to the most abundant iso-
topes): 714, [M]; 658, [M ꢁ 2CO]. IR(mCO): 2038, 1968,
1
1914 cmꢁ1. H NMR (400 MHz, CDCl3): d 1.16–1.51 (m,
24H, –CH3), d 2.49–2.59 (m, 4H, ˜CH–), d 3.98–4.08 (m,
4H, –CH2CH2–). 31P{1H} NMR (161 MHz, CDCl3): d
145.0 (s). 13C{1H} NMR (100 MHz, CDCl3): d 16.2 (m,
–CH3), d 28.1 (m, ˜CH–), d 62.1 (m, –OCH2CH2O–), d
2
118.2 (s, –CF3), d 188.9 (t, JCP = 8 Hz, CO trans to
[M ꢁ CO]. IR(mCO): 2077, 1964, 1914 cmꢁ1
.
1H NMR
OTf), d 187.2 (m, CO cis to OTf). 19F{1H} NMR
(376 MHz, CDCl3): d ꢁ77.1 (s).
(400 MHz, CD2Cl2): d ꢁ5.69 (t, 1H, JHP = 27 Hz, ReH),
d 1.04–1.20 (m, 24H, –CH3), d 2.16 (m, 2H, ˜CH–), d
2.32 (m, 2H, ˜CH–), d 4.03 (m, 2H, –OCH2–), d 4.23 (m,
2H, –OCH2–). 31P{1H} NMR (161 MHz, CD2Cl2): d
149.5 (s). 13C{1H} NMR (100 MHz, CDCl3): d 17.2,
17.4, 17.8 and 18.6 (all s, CH3), d 33.0 (t, JCP = 15 Hz,
˜CH–), d 33.4 (t, JCP = 14 Hz, ˜CH–), d 67.0 (m, –OCH2-
CH2O–), d 195.6 (m, CO cis to H), d 196.2 (t, 2JCP = 14 Hz,
CO trans to H).
2
Compound 2c. Yield: 56% (0.01 g). Anal. Calc. for
C30H48F3O8P2ReS: C, 41.18; H, 5.53%. Found: C,
41.12; H, 5.64%. MS (m/z, referred to the most abundant
isotopes): 874, [M]; 846, [M ꢁ CO]; 818, [M ꢁ 2CO]; 790,
[M ꢁ 3CO]. IR(mCO): 2040, 1972, 1918 cmꢁ1
.
1H NMR
(400 MHz, CDCl3): d 1.16–2.32 (m, 44H, Cy), d 3.63–
4.04 (m, 4H, –OCH2CH2O–). 31P{1H} NMR
(161 MHz, CDCl3):
d
138.8 (s). 13C{1H} NMR
(100 MHz, CDCl3): d 26.1–27.4(m, C2–C6 of Cy), d
40.4–43.2 (m, C1 of Cy), d 65.9 (s, a, –OCH2–), d
118.5 (s, –CF3), d 190.2 (m, CO cis to OTf), d 192.1
3.6. Preparation of fac-[ReH(CO)3L3] (3c) and
[Re2H2(CO)8-l-L3] (3c0)
2
(t, JCP = 7 Hz, CO trans to OTf). 19F{1H} NMR
A solution of [ReH(CO)5] (0.1 mL, 0.7 mmol) in THF
(10 mL) was added to a solution of [1,2-bis(dicyclohexyl-
(376 MHz, CDCl3): d ꢁ76.8 (s).

4956
S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
phosphinoxy)ethane] (17.5 mL, 0.12 M) in toluene, and the
reaction mixture was stirred for 5 h. The solvent was re-
moved under reduced pressure, and the residual oil was
chromatographed on a silica gel column (length 70 cm,
diameter 4 cm) using a 10:1 mixture of light petroleum
(40–60 ꢁC) and diethyl ether as eluent. The first fraction
eluted (20 mL) was concentrated to dryness, leaving an
oil that was treated with ethanol (2 mL). Cooling the
resulting solution to ꢁ25 ꢁC afforded white crystals of com-
plex 3c0. Yield of 3c0: 43% (0.14 g). Anal. Calc. for
C34H50O10P2Re2: C, 38.98; H, 4.88%. Found: C, 38.70;
H, 4.78%. MS (m/z, referred to the most abundant iso-
topes): 1054, [M]; 1052, [M ꢁ 2H]; 1025, [M ꢁ CO]; 1023,
[M ꢁ H ꢁ CO]; 998, [M ꢁ 2CO]; 997, [M ꢁ H ꢁ 2CO];
996, [M ꢁ 2H ꢁ 2CO]; 968, [M ꢁ 2H ꢁ 3CO]; 940,
From the second fraction eluted (10 mL), after evapora-
tion of the solvent and treatment with ethanol, a white so-
lid was obtained, complex 3c.
Yield of 3c: 10% (0.04 g). Anal. Calc. for C29H49O5P2Re:
C, 47.92; H, 6.80%. Found: C, 47.83; H, 6.52%. MS (m/z, re-
ferred to the most abundant isotopes): 726, [M]; 725,
[M ꢁ H]; 698, [M ꢁ CO]. IR(mCO): 1998, 1907, 1816 cmꢁ1
.
1H NMR (400 MHz, CD2Cl2): d ꢁ5.68 (t, 1H, JPH = 27 Hz,
ReH), d 2.05–1.27 (m, 44H, Cy), d 3.93 (m, 2H, –OCH2-
CH2O–), d 4.13 (m, 2H, –OCH2CH2O–). 31P{1H} NMR
(161 MHz, CD2Cl2):
d
143.5 (s). 13C{1H} NMR
(100 MHz, CDCl3): d 26.3–27.2 (Cy), d 42.6 (t, JCP = 14 Hz,
Cy), d 43.3 (t, JCP = 14 Hz, Cy), d 66.4 (s, –CH2CH2–), d
194.9 (m, cis CO–H), d 196.0 (t, JCP = 8 Hz, trans CO–H).
[M ꢁ 2H ꢁ 4CO]. IR(mCO): 2077, 1991, 1957 cmꢁ1
.
1H
3.7. Protonation reactions
NMR (400 MHz, CD2Cl2): d ꢁ6.17 (d, 2H, JPH = 23 Hz,
ReH), d 1.88–1.22 (m, 44H, Cy), d 3.93 (m, 4H, –OCH2-
CH2O–). 31P{1H} NMR (161 MHz, CD2Cl2): d 145.9 (s).
13C{1H} NMR (100 MHz, CDCl3): d 22.6–30.0(m, C2–
Hydrido compounds 3 were protonated following a pro-
cedure described in the literature for similar compounds [22].
1
C6 of Cy), d 44.5 (d, JCP = 30 Hz, C1 of Cy), d 72.6 (m,
3.8. X-ray crystallographic analysis
2
–OCH2CH2O–), d 190.5 (d, JCP = 43 Hz, trans CO–P), d
2
192.0 (d, JCP = 10 Hz, trans CO–CO), d 192.2 (d,
Compounds 1a–c, 3a, 3b and 3c0 were mounted on glass
fibres and studied on a SIEMENS Smart CCD area-
2JCP = 7 Hz, trans CO–H).
Table 4
Crystal and structure refinement data for the bromo complexes
Identification code
1a
1b
1c
Empirical formula
Formula weight
T (K)
k (A)
Crystal system
Space group
C
30H26 Br O5P2 Re
C17H32 Br O5P2 Re
644.48
293(2)
0.71073
Monoclinic
P21/n
C29H44 Br O5P2 Re
800.69
293(2)
0.71073
Triclinic
794.56
293(2)
0.71073
Monoclinic
P21/n
˚
ꢀ
P1
Unit cell dimensions
˚
a (A)
11.772(1)
15.418(1)
14.517(1)
9.911(1)
10.767(1)
11.156(1)
˚
b (A)
˚
c (A)
16.720(1)
16.563(1)
13.805(1)
a (ꢁ)
b (ꢁ)
c (ꢁ)
90
91.000(1)
90
3033.9(3)
90
89.158(1)
76.339(1)
86.639(1)
1608.6(2)
103.438(1)
90
2317.8(2)
3
˚
V (A )
Z
4
4
2
Dcalc (Mg/m3)
1.740
5.464
1544
1.847
7.127
1256
1.653
5.153
796
Absorption coefficient (mmꢁ1
F(000)
)
Crystal size (mm)
h Range for data collection (ꢁ)
Index ranges
0.21 · 0.20 · 0.20
1.80–28.00
0.47 · 0.44 · 0.17
1.68–28.02
0.40 · 0.30 · 0.11
1.52–28.02
ꢁ13 6 h 6 15, ꢁ19 6 k 6 20,
ꢁ19 6 h 6 18, ꢁ13 6 k 6 11,
ꢁ12 6 h 6 14, ꢁ14 6 k 6 10,
ꢁ15 6 l 6 22
ꢁ18 6 l 6 21
ꢁ14 6 l 6 18
Reflections collected
17765
13899
10153
Independent reflections (Rint
Reflections observed (>2r)
Data completeness (%)
Absorption correction
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
)
6922 (0.0439)
4442
94.5
Semi-empirical from equivalents
1.000 and 0.667
6922/0/352
5364 (0.0492)
4141
95.7
Semi-empirical from equivalents
1.0000 and 0.525267
5364/0/243
7073 (0.0329)
6057
90.9
Semi-empirical from equivalents
1.0000 and 0.468384
7073/0/343
0.901
0.970
1.027
Final R indices [I > 2r(I)]
R indices (all data)
Largest difference in peak and hole (e A
R1 = 0.0377, wR2 = 0.0816
R1 = 0.0751, wR2 = 0.0878
1.063 and ꢁ1.556
R1 = 0.0364, wR2 = 0.0842
R1 = 0.0528, wR2 = 0.0885
2.182 and ꢁ1.706
R1 = 0.0476, wR2 = 0.1285
R1 = 0.0551, wR2 = 0.1319
1.893 and ꢁ2.967
ꢁ3
˚
)

S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
4957
Table 5
Crystal and structure refinement data for the hydride complexes
Identification code
3a
3b
3c0
Empirical formula
Formula weight
T (K)
C30H27O5P2 Re
715.66
293(2)
C17H33O5P2 Re
565.57
293(2)
C34H46O10P2 Re2
1049.05
173(2)
˚
k (A)
0.71073
0.71073
0.71073
Crystal system
Space group
Monoclinic
P21/n
Monoclinic
P21/n
Triclinic
ꢀ
P1
Unit cell dimensions
˚
a (A)
12.084(1)
15.826(1)
15.191(1)
90
104.295(1)
90
2815.1(3)
4
14.969(1)
9.678(1)
16.317(1)A
10.029(1)
12.268(1)
16.859(1)
73.497(1)
83.842(1)
85.210(1)
1974.3(2)
2
˚
b (A)
˚
˚
c (A)
a (ꢁ)
b (ꢁ)
c (ꢁ)
90
109.707(1)
90
2225.2(2)
4
1.688
5.626
1120
3
˚
V (A )
Z
Dcalc (Mg/m3)
Absorption coefficient (mmꢁ1
F(000)
1.689
4.468
1408
1.765
6.257
1020
)
Crystal size (mm)
h Range for data collection (ꢁ)
0.17 · 0.16 · 0.11
1.89–28.04
0.43 · 0.33 · 0.15
1.60–28.03
0.40 · 0.30 · 0.06
1.73–28.03
Index ranges
ꢁ13 6 h 6 15, ꢁ17 6 k 6 20,
ꢁ19 6 l 6 20
16510
ꢁ15 6 h 6 19, ꢁ12 6 k 6 12,
ꢁ21 6 l 6 18
13383
ꢁ13 6 h 6 13, ꢁ15 6 k 6 14,
ꢁ21 6 l 6 13
Reflections collected
12330
Independent reflections (Rint
Reflections observed (>2r)
Data completeness
)
6457 (0.0663)
3751
0.946
5159 (0.0495)
4011
0.958
8586 (0.0281)
7142
0.897
Absorption correction
Semi-empirical from equivalents
1.0000 and 0.7278
6457/0/347
Semi-empirical from equivalents
1.0000 and 0.4500
5159/0/238
Semi-empirical from equivalents
1.0000 and 0.6239
8586/0/441
Maximum and minimum transmission
Data/restraints/parameters
Goodness-of-fit on F2
0.802
0.947
1.003
Final R indices [I > 2r(I)]
R indices (all data)
Largest difference in peak and hole (e A
R1 = 0.0416, wR2 = 0.0526
R1 = 0.0955, wR2 = 0.0591
1.626 and ꢁ1.427
R1 = 0.0347, wR2 = 0.0755
R1 = 0.0492, wR2 = 0.0789
2.076 and ꢁ1.849
R1 = 0.0346, wR2 = 0.0806
R1 = 0.0444, wR2 = 0.0845
1.850 and ꢁ1.882
ꢁ3
˚
)
detector diffractometer using graphite-monochromated Mo
Ka radiation (k = 0.71073 A). The crystal parameters and
L3 = 1,2-bis(dicyclohexylphosphinoxy)ethane], the triflato
complexes fac-[Re(OTf)(CO)3L1–3] (2a–c) and the hydrido
˚
experimental details of data collection are summarized in
Tables 4 and 5. ORTEP [23] drawings of the compounds,
along with the numbering schemes adopted, are shown in
Figs. 1, 2, 3 and 7, 8, 9. Absorption corrections were car-
ried out using SADABS [24]. All the structures were solved
by direct methods except 3c0, which was solved by the Patt-
erson method. All structures were refined by full-matrix
least-squares based on F2 [25]. All non-hydrogen atoms
were refined with anisotropic displacement parameters.
All hydrogen atoms were refined with isotropic displace-
ment parameters following location in a difference electron
density map (in the case of the hydride atoms) or inclusion
at idealized positions (all others). Atomic scattering factors
and anomalous dispersion corrections for all atoms were
taken from International Tables for X-ray Crystallography
[26].
complexes mer-[ReH(CO)3L1] (3a), fac-[ReH(CO)3L2,3
]
(3b,3c) and [{ReH(CO)4}2(l-L3)] (3c0) have been synthe-
sized and characterized. The bromo and triflato derivatives
are all mononuclear compounds with fac-CO groups. How-
ever, the nuclearity and stereochemistry of the hydrido
compounds depend on the diphosphinite ligand. Surpris-
ingly, no dinuclear complex of L1 was obtained, even
though its longer between-P spacer was expected to favour
its acting as a bridging ligand. The influence of the co-
ligands emerged mainly in their effects on the stability
of the cationic dihydrogen compounds obtained upon pro-
tonation of the hydride complexes: complexes 3(a–c)* and
3c0* are all thermally unstable towards H2 release and
homolytic cleavage of the H2 ligand was not observed;
compound 3a*, the only one in which the g2-H2 ligand is
trans to a diphosphinite P atom, is the most stable;
3b*,3c* and fac-[Re(g2-H2)(CO)3(L)] [L = 1,2-bis(diphe-
nylphosphinoxy)ethane] [7d], which all have similar geom-
etry, have thermal stabilities that correlate well with the
electronegativity of the R groups of the diphosphinite li-
gand; and compound 3c0* is the least stable, probably be-
cause of its 4:1 carbonyl:phosphorus ratio [16], reducing
4. Conclusions
A new diphosphinite ligand, 1,3-bis(diphenylphosphin-
oxy)propane (L1), the bromo complexes fac-[ReBr(CO)3-
L
1–3] [1a–c; L2 = 1,2-bis(diisopropylphosphinoxy)ethane,

4958
S. Bolan˜o et al. / Journal of Organometallic Chemistry 690 (2005) 4945–4958
(d) S. Bolano, J. Bravo, R. Carballo, S. Garcia-Fontan, U. Abram,
E.M. Vazquez-Lopez, Polyhedron 18 (1999) 1431.
[8] L.C. Baldwin, M.J. Fink, J. Organomet. Chem. 646 (2002)
˜
the backbonding between the metal centre and the H2
ligand.
230.
5. Supplementary material
[9] L.H. Staal, A. Oskam, K. Vrieze, J. Organomet. Chem. 170 (1979)
235.
[10] (a) See, for example: J. Zhang, J.J. Vittal, W. Henderson, J.R.
Wheaton, I.H. Hall, T.S.A. Hor, Y.K. Yan, J. Organomet. Chem.
650 (2002) 123;
Crystallographic data have been deposited with the
Cambridge Crystallographic Data Centre, CCDC Nos.
265545–265550. Copies of this information may be
obtained free of charge from the CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: +44 1223 336 003; e-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.
cam.ac.uk).
(b) M.S. Balakrishna, M.G. Walawalker, J. Organomet. Chem. 628
(2001) 76;
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40 (2001) 2358.
[11] D.H. Gibson, H. He, M.S. Mashuta, Organometallics 20 (2001)
1456.
[12] The reaction was carried out at 60 ꢁC because at room temperature
the yield was very low, as shown by NMR 31P{1H} spectrum of the
crude mixture.
Acknowledgements
Financial support from the Xunta de Galicia (Project
PGIDT04PXIC31401PN) and the Spanish Ministry of
Education (Project BQU2003-06783) is gratefully acknowl-
edged. We thank the University of Vigo CACTI services
for collecting X-ray data and recording NMR spectra.
[13] H. Gunther, in: NMR Spectroscopy: Basic Principles, Concepts, and
¨
Applications in Chemistry, Wiley, Chichester, 1995.
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N.L. Allinger, Molecular Mechanics, ACS Monograph 177, Amer-
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