Rhenium(III) and rhenium(V) complexes stabilized by the potentially tetradentate ligand tris(2-diphenylphosphinoethyl)amine

Article abstract of DOI:10.1016/S0020-1693(01)00696-X

The reaction of the rhenium(V) nitrido complex [Re(N)Cl₂(PPh₃)₂] with the tripodal ligand N(CH₂CH₂PPh₂)₃ (NP₃) in THF gave [Re(N)Cl₂(η²-P,P-NP₃)] (1) in which NP₃ acts as a tridentate ligand using the nitrogen and two phosphorus donors for coordination. Refluxing 1 in a polar solvent such as ethanol produced [(η⁴-NP₃)Re(N)Cl]Cl (2) in which NP₃ acts as a tetradentate ligand. Treatment of complex [Re(O)Cl₃(AsPh₃)₂] containing the [Re=O]³⁺ core with NP₃ in THF yielded [ReCl₃{η³-N,P,P-(N{CH₂CH₂Ph ₂}₂{CH₂CH₂P(O)Ph₂})}] (3). Complexes 1 and 3 have been characterized by single-crystal X-ray analyses.

Full text of DOI:10.1016/S0020-1693(01)00696-X

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Inorganica Chimica Acta 327 (2002) 140–146
Rhenium(III) and rhenium(V) complexes stabilized by the
potentially tetradentate ligand tris(2-diphenylphosphinoethyl)amine
Valerio Bertolasi a, Andrea Marchi a, Lorenza Marvelli a, Roberto Rossi a,*,
Claudio Bianchini b,*, Isaac de los Rios b, Maurizio Peruzzini b,*
a Dipartimento di Chimica, Uni6ersita` di Ferrara, Via Borsari 46, 44100 Ferrara, Italy
b Istituto per lo Studio della Stereochimica ed Energetica dei Composti di Coordinazione, ISSECC-CNR, Via J. Nardi 39,
I-50132 Florence, Italy
Received 15 June 2001; accepted 14 September 2001
Dedicated to Professor Kees Vrieze in recognition of his outstanding contribution to inorganic chemistry
Abstract
The reaction of the rhenium(V) nitrido complex [Re(N)Cl2(PPh3)2] with the tripodal ligand N(CH2CH2PPh2)3 (NP3) in THF
gave [Re(N)Cl2(h2-P,P-NP3)] (1) in which NP3 acts as a tridentate ligand using the nitrogen and two phosphorus donors for
coordination. Refluxing 1 in a polar solvent such as ethanol produced [(h4-NP3)Re(N)Cl]Cl (2) in which NP3 acts as a tetradentate
ligand. Treatment of complex [Re(O)Cl3(AsPh3)2] containing the [ReꢀO]3+ core with NP3 in THF yielded [ReCl3{h3-N,P,P-
(N{CH2CH2Ph2}2{CH2CH2P(O)Ph2})}] (3). Complexes 1 and 3 have been characterized by single-crystal X-ray analyses. © 2002
Elsevier Science B.V. All rights reserved.
Keywords: Rhenium; Tripodal phosphines; P/N ligands; X-ray crystallography
the coordination chemistry of rhenium with tripodal
polyphosphine ligands is still largely unexplored. In
particular, no example of rhenium complex with the
potentially tetradentate aminotriphosphine N(CH2CH2-
PPh2)3 (NP3) has ever been reported, which is quite
surprising as NP3 metal complexes are known for most
late-transition metals [13–16] including technetium [17].
Indeed, the presence of the amine nitrogen and of two
CH2 spacers separating the phosphorus donors from
the bridgehead atom make NP3 more sterically and
coordinatively flexible than triphos and PP3. In particu-
lar, the diversity of accessible bonding modes (h4-NP3,
h3-P,P,P, h3-N,P,P and h2-P,P) allows NP3 to form
mononuclear and polynuclear complexes in an rich
variety of coordination geometries (trigonal, tetrahe-
dral, square-planar, square-pyramidal, trigonal-bipyra-
midal, octahedral, pentagonal-bipyramidal, dodeca-
hedral) [2,13–17].
1. Introduction
Much current interest in the coordination chemistry
of rhenium is motivated by the perspective of replacing
technetium-99m with rhenium-186/188 for use as a
diagnostic or radiotherapeutic agent [1]. Like tech-
netium compounds, the rhenium ones must exhibit high
thermodynamic stability, particularly to metal leaching
under thermal and hydrolytic conditions, to be success-
fully employed in nuclear medicine. For this purpose,
polyphosphine ligands should be particularly well
suited as they are known to form very stable metal
complexes in a variety of coordination numbers and
metal oxidation states [2]. However, with the exception
of some compounds with the triphosphine
MeC(CH2PPh2)3 (triphos) [3–11], and of a few others
with the tetraphosphine P(CH2CH2PPh2)3 (PP3) [12],
Aimed at filling this gap by the synthesis of stable
rhenium complexes with diverse oxidation states and
structures, we decided to carry out a systematic study
of the coordination chemistry of this metal with NP3.
* Corresponding authors. Tel.: +39-055-24 5990; fax: +39-055-
247 8366.
E-mail addresses: mg2@dns.unife.it (R. Rossi), bianchin@fi.cnr.it
(C. Bianchini), peruz@fi.cnr.it (M. Peruzzini).
0020-1693/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00696-X

V. Bertolasi et al. / Inorganica Chimica Acta 327 (2002) 140–146
141
In this article we describe the synthesis, structure and
spectroscopic characterization of the first rhenium(III)
and rhenium(V) complexes stabilized by NP3 acting as
h2-P,P, h3-N,P,P and h4-NP3 ligand.
sample of 1 was obtained by slow diffusion of diethyl
ether into a diluted acetonitrile solution. Elemental
analysis: Anal. Found: C, 53.7; H, 4.4; N, 3.1. Calc. for
C42H42N2Cl2P3Re: C, 54.6; H, 4.6; N, 3.0%. IR (KBr,
cm−1) w(ReꢁN) 1067.
2. Experimental
2.3. Preparation of [ReNCl(p4-NP3)]Cl (2Cl)
2.1. General procedures
A suspension of [Re(N)Cl2(PPh3)2] (0.30 g, 0.37
mmol) and NP3 (0.30 g, 0.46 mmol) in ethanol (60 ml)
was refluxed under nitrogen for approximately 4 h
during which time the brick-red color faded to give a
clear yellow solution. Evaporation of the solvent to
approximately 16 ml and addition of diethyl ether (30
ml) gave yellow microcrystals of 2Cl. Yield: 90%. Ele-
mental analysis: Anal. Found: C, 54.2; H, 4.6; N, 2.8.
Calc. for C42H42N2Cl2P3Re: C, 54.6; H, 4.6; N, 3.0%.
IR (KBr, cm−1): w(ReꢁN) 1060.
Tetrahydrofuran (THF) and diethyl ether were
purified by distillation under nitrogen over LiAlH4,
dichloromethane was refluxed overnight onto P2O5 and
distilled just prior to use. All the other reagents and
chemicals were of reagent grade and, unless otherwise
stated, were used as received from commercial suppli-
ers. All reactions and manipulations were routinely
performed under a dry nitrogen atmosphere by using
standard Schlenk-tube techniques. The solid complexes
were collected on a sintered glass-frit and washed as
indicated, before being dried in a stream of nitrogen.
The ligand N(CH2CH2PPh2)3 (NP3) [18] and the com-
plexes [Re(N)Cl2(PPh3)2] [19], and [Re(O)Cl3(AsPh3)2]
[20] were prepared as described in the literature.
2.4. Preparation of [Re(N)Cl(p4-NP3)]BPh4 (2BPh4)
The tetraphenylborate salt 2BPh4 was obtained in
quantitative yield by metathesis of the chloride 2Cl,
dissolved in ethanol, using a slight excess of sodium
tetraphenylborate. Elemental analysis: Anal. Found: C,
64.9; H, 5.1; N, 3.3. Calc. for C66H62N2BClP3Re: C,
65.6; H, 5.2; N, 3.2%. IR (KBr, cm−1): w(ReꢁN) 1060,
Deuterated solvents for NMR measurements (Merck
and Aldrich) were dried over molecular sieves (4 A). H
1
,
NMR spectra were recorded in Varian VXR 300 or
Bruker AC200 spectrometers operating at 299.94 or
200.13 MHz (1H), respectively. Peak positions are rela-
tive to tetramethylsilane and were calibrated against the
residual solvent resonance. 31P{1H} NMR spectra were
recorded in either the Varian VXR 300 or Bruker
AC200 instruments operating at 121.42 and 81.01
MHz, respectively. Chemical shifts were measured rela-
tive to external 86% H3PO4 with downfield values taken
as positive. Infrared spectra were recorded as Nujol
mulls in a Perkin–Elmer 1600 series FT-IR spectrome-
ter between KBr plates. Molar Conductivities were
measured with an AMEL model 134 conductance cell
connected with a model 101 conductivity meter. The
conductivity data on 2BPh4 were obtained at sample
concentrations of 10−3 M in methanol solutions at
room temperature (r.t., 298 K). Elemental analyses (C,
H, N) were performed using a Carlo Erba model 1106
elemental analyzer.
w(BPh4) 1678, 611.
\
(298 K, MeOH)=106
M
V
−1 cm2 mol−1
.
2.5. Con6ersion of [Re(N)Cl2(p2-P,P-NP3)]] (1) into
[Re(N)Cl(p4-NP3)]Cl (2Cl)
A suspension of 1 (0.30 g, 0.32 mmol) in 10 ml of
EtOH was refluxed for 3 h. Work-up as above gave 2Cl
in quantitative yield.
2.6. Preparation of [ReCl3(p3-N,P,P-
N{(CH2CH2PPh2)2(CH2CH2P(O)Ph2)})] (3)
Addition of 1 equiv. of NP3 (0.22 g, 0.33 mmol) to a
stirred THF solution (60 ml) of [Re(O)Cl3(AsPh3)2]
(0.30 g, 0.33 mmol) kept at approximately 40 °C
caused the separation of 3 as a yellow precipitate in 1 h.
The yellow solid was separated from the hot mother
liquor and the solid product was washed with ethanol
and diethyl ether before being dried under nitrogen.
Yield: 80%. Yellow crystals of 3·CH3NO2 suitable for
an X-ray study were obtained by slow evaporation of
the solvent from a diluted CH3NO2/EtOH solution (1:1
v/v). Elemental analysis: Anal. Found: C, 51.6; H, 4.2;
N, 1.3. Calc. for C42H42NCl3OP3Re: C, 52.4; H, 4.4; N,
1.5%. IR (KBr, cm−1): w(PꢀO) 1184.
2.2. Preparation of [Re(N)Cl2(p2-P,P-NP3)] (1)
A suspension of [Re(N)Cl2(PPh3)2] (0.20 g, 0.26
mmol) and NP3 (0.16 g, 0.26 mmol) in THF (30 ml)
was refluxed under nitrogen for approximately 30 min
during which time the brick-red suspension turned yel-
low. The reaction mixture was cooled to r.t. A yellow
solid precipitated which was filtered off and then
washed with a 1:1 (v/v) mixture of acetone/diethyl ether
and dried under nitrogen. Yield: 84%. A crystalline

142
V. Bertolasi et al. / Inorganica Chimica Acta 327 (2002) 140–146
Table 2
2.7. X-ray crystallography
,
Selected bond distances (A) and angles (°) with e.s.d.s in parentheses
for compounds 1 and 3·CH3NO2
Single crystals of 1 and 3·CH3NO2 suitable for X-ray
diffraction analyses were obtained as described above.
Crystals of the compounds were mounted on glass
fibers, on a CAD4 diffractometer, which was used for
the space group determination and for the data collec-
tion, that was carried out at r.t. for compounds 1 and
3·CH3NO2. Unit cell dimensions were obtained by
least-squares fit of the 2q values of 25 high order
reflections. Crystallographic and other relevant data are
listed in Table 1. Data were measured with variable
scan speed to ensure constant statistical precision on
the collected intensities. Three standard reflections were
used to check the stability of the crystals and of the
experimental conditions, and measured every hour. The
collected intensities were corrected for Lorentz and
polarization factors and empirically (c scans) for ab-
sorption [21]. The standard deviations on intensities
were calculated in terms of statistics alone.
Compound 1
Bond distances
ReꢂN(1)
ReꢂP(1)
ReꢂP(3)
1.663(4)
2.386(1)
2.376(1)
ReꢂCl(1)
ReꢂCl(2)
Re..N(2)
2.414(1)
2.425(1)
2.640(4)
Bond angles
N(1)ꢂRe···N(2)
N(1)ꢂReꢂP(1)
N(1)ꢂReꢂP(3)
N(1)ꢂReꢂCl(1)
N(1)ꢂReꢂCl(2)
P(1)ꢂReꢂP(3)
165.6(6)
94.9(2)
92.3(2)
106.3(2)
105.8(2)
97.28(5)
P(1)ꢂReꢂCl(1)
P(1)ꢂReꢂCl(2)
P(3)ꢂReꢂCl(1)
P(3)ꢂReꢂCl(2)
Cl(1)ꢂReꢂCl(2)
158.26(6)
84.71(5)
86.54(5)
161.52(5)
86.14(5)
Compound 3.CH3NO2
Bond distances
ReꢂN
2.218(15)
ReꢂCl(2)
ReꢂCl(3)
P(2)ꢂO
2.389(6)
2.371(5)
1.508(17)
ReꢂP(1)
ReꢂP(3)
ReꢂCl(1)
2.430(6)
2.413(5)
2.376(5)
Bond angles
NꢂReꢂP(1)
NꢂReꢂP(3)
NꢂReꢂCl(1)
NꢂReꢂCl(2)
NꢂReꢂCl(3)
P(1)ꢂReꢂP(3)
P(1)ꢂReꢂCl(1)
P(1)ꢂReꢂCl(2)
The structures were solved by a combination of
Patterson and Fourier methods and refined by full-ma-
trix least-squares [22] (the function minimized being
ꢀ(ꢁFoꢁ−1/kꢁFcꢁ)2). All non-hydrogen atoms were treated
anisotropically in compound 1 while for compound
81.8(4)
82.1(4)
85.8(4)
176.1(4)
95.0(4)
163.5(2)
88.1(2)
96.6(2)
P(1)ꢂReꢂCl(3)
P(3)ꢂReꢂCl(1)
P(3)ꢂReꢂCl(2)
P(3)ꢂReꢂCl(3)
Cl(1)ꢂReꢂCl(2)
Cl(1)ꢂReꢂCl(3)
Cl(2)ꢂReꢂCl(3)
93.3(2)
87.5(2)
99.3(2)
91.3(2)
90.6(2)
178.4(2)
88.6(2)
Table 1
Crystal data and structure refinement parameters for compounds 1
and 3·CH3NO2
3·CH3NO2, the carbon atoms of the phenyl groups and
those of the clathrated nitromethane molecule were
treated isotropically.
No extinction correction was deemed necessary. The
scattering factors used, corrected for the real and imag-
inary parts of the anomalous dispersion, were taken
from the literature [23].
Compound
1
C
924.84
23
3·CH3NO2
42H42Cl2N2P3Re C43H45Cl3N2O3P3Re
Empirical formula
Molecular weight
Data collection
temperature (°C)
Crystal system
Space group
1023.33
23
monoclinic
P21/n
orthorhombic
Pna21
Unit cell dimensions
,
a (A)
15.615(2)
14.211(4)
18.115(2)
21.146(4)
12.200(2)
12.975(5)
The contribution of the hydrogen atoms in calculated
,
b (A)
,
positions, [CꢂH=0.95 (A), B(H)=1.3×B(Cbonded
)
,
c (A)
2
,
(A )] was taken into account but not refined. Upon
convergence no significant features were found in the
Fourier difference maps of both compounds. A selec-
tion of bond distances and angles is given in Table 2
(vide infra). All calculations were performed using the
MOLEN crystallographic package [22], and the struc-
tures drawn using the program ORTEP [24].
h (°)
i (°)
k (°)
92.81(1)
3
,
V (A )
Z
4015(1)
4
1.53
33.51
4297(2)
4
1.58
33.51
Dcalc (g cm−3
)
v (cm−1
)
Radiation
Mo Ka (graphite monochromator,
u=0.71069 A)
Additional materials including experimental data for
the X-ray diffraction studies with atom coordinates,
thermal parameters and remaining bond lengths and
angles for compounds 1 and 3·CH3NO2 are available
from the authors on request.
,
Number of independent 8736
4868
data collection
Number of observed
reflections (no)
Transmission coefficient 1.00–0.72
R
Rw
5946
(ꢁIoꢁ\3.0|(I))
2655 (ꢁIoꢁ\3.0|(I))
1.00–0.68
0.051
0.059
0.033
0.040
1.24
3. Results and discussion
Goodness-of-fit
1.22
2 1/2
R=ꢀ(ꢁFo−(1/k)Fcꢁ)/ꢀꢁFoꢁ; Rw=[ꢀw(Fo−(1/k)Fc)2/ꢀwꢁFoꢁ ]
where
The preparations and the principal reactions de-
scribed in this paper are reported in Scheme 1. Selected
w=[|2(Fo)]−1 and |(Fo)=[|2(Fo2)+f 4(Fo2)]1/2/2Fo.

V. Bertolasi et al. / Inorganica Chimica Acta 327 (2002) 140–146
143
Scheme 1.
spectroscopic data for the new complexes (IR and
31P{1H} NMR) are given in Section 2 together with
analytical and relevant chemical–physical properties.
of NP3. In keeping with the absence of any through-
the-metal electronic communication between the two
types of phosphorus atoms, the two resonances appear
as narrow singlets.
3.1. Synthesis and characterization of NP3 rhenium
complexes with the [ReꢁN]2+ core
The 31P{1H} NMR spectrum of 2 displays a well-re-
solved AM2 pattern [J(PP) of 9.0 Hz], which is consis-
tent with the coordination of all the phosphorus atoms
of the ligand and therefore with an octahedral coordi-
nation geometry [27].1 The doublet at 26.32 ppm and
the triplet at 9.26 ppm are assigned to the axial (2P)
and equatorial (1P) phosphorus nuclei, respectively.
Based on spectroscopic data alone, it is not possible
to discriminate between the two geometric isomers 2a
and 2b. However, if one considers that 1 transforms
selectively into 2Cl in refluxing ethanol, it is very likely
The reaction of the rhenium(V) complex [Re(N)Cl2-
(PPh3)2] with a stoichiometric amount of NP3 in reflux-
ing THF gave a yellow solution from which crystals of
the bischloride complex [Re(N)Cl2(h2-P,P-NP3)] (1)
precipitated in good yield by cooling the solution down
to room temperature. When the same reaction was
carried out in a more polar solvent like ethanol, the
ionic complex [h4-(NP3)Re(N)Cl]Cl (2Cl) was straight-
forwardly obtained by addition of diethyl ether. Alter-
natively, isolated 1 was refluxed in ethanol to give 2Cl.
The latter compound was quantitatively converted to
the tetraphenylborate salt 2BPh4 by metathetical reac-
tion with NaBPh4 in ethanol.
that the N(NP )ꢂReꢂN(nitrido) trans array, determined in
3
the parent compound, is maintained in 2.
Compounds 1 and 2 have been characterized by
elemental analysis, molar conductivity measurements
and NMR spectroscopy. Complex 1 was also authenti-
cated by a single-crystal X-ray analysis (vide infra).
The h4-N,P,P,P-coordination mode of NP3 in 2 was
indirectly confirmed by the absence in the IR spectrum
of the diagnostic band at approximately 2800 cm−1
that is observed whenever the nitrogen apical atom of
the NP3 ligand is not coordinated to the metal center
[25,26]. A typical absorption at 1067 cm−1 for 1 and at
1060 cm−1 for 2 is diagnostic for the presence of the
ReꢁN core in both compounds [25]. These stretching
frequencies are comparable to those found for other
nitrido–rhenium(V) [25] and technetium(V) complexes
[26].
Single crystals of 1 have been obtained by slow
evaporation of the solvent from a diluted solution in a
CH2Cl2/CH3CN mixture. An ORTEP drawing of the
complex cation is presented in Fig. 1 while selected
bond lengths and angles are given in Table 2.
The crystal structure consists of discrete
[Re(N)Cl2(h2-P,P-NP3)] molecules held together by van
der Waals forces. The coordination around the Re
atom is square-pyramidal; the metal atom is displaced
from the mean plane (defined by the Cl(1), Cl(2), P(1)
and P(3) atoms) towards the nitrogen atom N(1) by
,
,
0.398(1) A. The ReꢁN(1) distance of 1.663(4) A is
indicative of a strong Re–N triple bond in agreement
with other X-ray authenticated square-pyramidal or
The 31P{1H} NMR spectrum (CD2Cl2) of 1 exhibits
two phosphorus environments at 18.83 and −18.80
ppm in a 2:1 intensity ratio, respectively. The high-field
resonance falls in the usual range for free phosphines
and is therefore assigned to a dangling phosphine arm
1 The NMR properties of complex 2 are not affected by the nature
of the counteranion (Cl or BPh4).

144
V. Bertolasi et al. / Inorganica Chimica Acta 327 (2002) 140–146
The above-mentioned wrapping mode of NP3 about
a metal has no precedent within the rich database of
X-ray authenticated structures of this tripodal ligand
[16]. It is well documented a case in which appreciable
octahedral Re–nitrido complexes where genuine ReꢁN
,
distances fall in the range 1.61–1.66 A [28–33].
The tripodal aminophosphine ligand acts as a biden-
tate ligand with two phosphorus donors while the N(2)
amine atom trans to the ReꢂN(1) bond [N(1)ꢂRe···
N(2)=166.6(6)°] forms a short contact with the Re
elongation of the M···N(NP ) bond occurs (up to
3
,
3.486(8) A, i.e. in the centrosymmetric Co(I) dimer
[{(NP3)Co}2S]) [36], and there is also an example,
[(NP3)Ni{CHꢀCHC(O)OEt}]+, in which one of the
arms of NP3 remains uncoordinated [37]. In no case,
however, these two structural features were found to be
present in the same metal complex.
,
atom [Re···N(2)=2.640(4) A]. This arrangement can be
described as an elongated square-pyramidal coordina-
tion polyhedron which is on the brink of reaching an
octahedral geometry. A similar situation has been ob-
served in the Tc(V) complex: [(PNP)Tc(N)Cl2] [26],
[PNP=CH3CH2CH2N(CH2CH2PPh2)2] where the
3.2. Rhenium complexes with the [ReꢀO]3+ core.
Synthesis and characterization of [ReCl3(p3-N,P,P-
N{CH2CH2PPh2}2{CH2CH2P(O)Ph2})] (3)
,
Tc···N separation reduces to 2.491(4) A. Accordingly,
assuming a pseudo-octahedral coordination for the
complex cation, the lengthening of the Re···N(2) dis-
,
tance with respect to the value of 2.22(2) A determined
When the rhenium(V) oxo complex Re(O)Cl3-
(AsPh3)2 containing the [ReꢀO]3+ core, isoelectronic
with [ReꢁN]2+, was treated with NP3 in warm THF,
yellow microcrystals of 3 were obtained in excellent
yield.
in 3·CH3NO2 (vide infra), can be interpreted as a
consequence of the strong trans-influence exerted by the
ReꢁN multiple bond. For the same metal center, an
important factor which may cause a severe elongation
of the MꢂN bonds is the trans influence between the
amine and the axial coligand [34].2 Both the ReꢂCl and
ReꢂP bond distances are within the range found for
other rhenium complexes and do not deserve additional
comments [3–12,35].
Complex 3 is paramagnetic with a veff as low as 1.9
mB as a consequence of the large spin–orbit coupling
typical of the d4-rhenium(III) ion [4,38]. The compound
is air stable in both the solid state and solution of
common organic solvents where it behaves as a non-
electrolyte. The 31P{1H} NMR spectrum in CD3NO2
shows a sharp singlet at 62.17 ppm for the free PꢀO
group while the coordinated phosphorus nuclei do not
provide any observable resonance as a consequence of
the paramagnetism of the complex which causes their
fast relaxation [39]. In the IR spectrum a broad and
strong absorption at approximately 1184 cm−1 wit-
nesses the presence of the phosphine oxide group.
Slow recrystallization of 3 from a diluted EtOH/
CH3NO2 solution gave well-shaped crystals which al-
lowed us to determine the crystal structure of
3·CH3NO2. The structure consists of discrete complex
molecules and clathrated nitromethane solvent
molecules in a 1:1 ratio. Selected bond lengths and
angles are given in Table 2 while an ORTEP drawing of
the complex is shown in Fig. 2.
In keeping with the chemical–physical characteriza-
tion, the rhenium center shows a slightly distorted
octahedral geometry with NP3 acting as a tridentate
ligand through two phosphorus and the bridgehead
nitrogen. The other three coordination positions are
taken by three chlorine atoms. The tridentate NP3
ligand conforms to a meridional geometry with the two
mutually trans PPh2 groups considerably bent over the
plane defined by Re, and the chlorine atoms. The
P(1)ꢂReꢂP(3) angle is 163.6(2)°. The ReꢂN distance of
Fig. 1. ORTEP view of the compound [h2-P,P(NP3)Re(N)Cl2] (1)
,
2.22(2) A matches well the ReꢂN(amine) distances
showing thermal ellipsoids at 30% probability.
,
(2.16–2.22 A) [40–42]. The ReꢂP distances [2.430(6)
2 See for example, Ref. [34b]: [(NP3)NiCl]+, dNiꢂN=1.97(1) A
,
and 2.416(6) A] are longer than those determined in 1
,
,
,
[average 2.38 A] and reflect the mutual trans influence
[34a]; [(NP3)Ni(SO2)], dNiꢂN=2.31(1) A.

V. Bertolasi et al. / Inorganica Chimica Acta 327 (2002) 140–146
145
Fig. 2. ORTEP view of the compound [h3-N,P,P-(N{CH2CH2PPh2}2{CH2CH2P(O)Ph2})]ReCl3]·CH3NO2 (3·CH3NO2) showing thermal ellipsoids
at 30% probability.
exerted by the P atoms. The greater trans influence of
phosphorus with respect to chlorine is most likely re-
sponsible also for the lengthening of the ReꢂCl dis-
4. Supplementary Material
Supplementary material is available from Cambridge
Crystallographic Data Centre and comprises experi-
mental data for the X-ray diffraction studies including
atom coordinates, thermal parameters and remaining
,
tances in 1 [average 2.42 A] with respect to those in
.
,
3 CH3NO2 [average 2.38 A]. One arm of the tripodal
ligand is uncoordinated and the phosphorus(III) group
has been oxidized to phosphine oxide. A similar situa-
tion has been crystallographically ascertained in the
tetrahedral cobalt complex [{NP2(PO)}Co(NO)2]+
where NP3 acts as an h2-P,P ligand [43].
bond lengths and angles for compounds
1 and
3.CH3NO2. Copies of this information may be obtained
from The Director, CCDC, 12 Union Road, Cam-
bridge CB2 1IZ, UK (Fax: +44-1223-336033; e-mail:
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
Oxidation of one arm of a polyphosphine ligand by
the ReꢀO moiety has been previously observed. Once
formed, the PꢀO group may remain free, as in the
present case [44], or bound through the oxygen atom to
the metal [45].3 In the absence of a detailed mechanistic
study, we cannot state whether the oxidation mecha-
nism is intermolecular or intramolecular [46]. On the
other hand, the oxidation of a polyphosphine arm by
ReꢀO is not a general rule, for example, the tridentate
tripodal ligand triphos has been found to react with
[Re(O)Cl3(PPh3)2] in refluxing benzene yielding the oxo-
chloride complex [Re(O)Cl3(h2-P,P-triphos)] with a
free non-oxidized phosphine arm [4].
Acknowledgements
I. de los R´ıos thanks ‘Ministerio de Ciencia y Tec-
nologia’ (Spain) for a post-doctoral grant. R.R. thanks
MURST (Rome, Italy) for financial support.
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