Dirhenium complexes that contain the ligand 1,1-bis(diphenylphosphino)ethene (dppE). Synthesis, characterization and reactivity of Re2Cl4(μ-dppE)2

Article abstract of DOI:10.1016/S0020-1693(99)00545-9

The dirhenium(II) compound Re₂Cl₄(μ-dppE)₂ (1), where dppE = (Ph₂P)₂C=CH₂, which contains an electron-rich triple bond, has been prepared by the reaction of (n-Bu₄N)₂Re₂Cl₈ with CH₃CO₂Na and dppE in refluxing ethanol. Its reactivity towards CO alone, and CO in combination with XylNC and 2,5-Me₂-C₆H₃CN has been explored. The complexes Re₂Cl₄(μ-dppE)₂(CO)₂ (2) and [Re₂Cl₃(μ-dppE)₂(CO)₂(L)]O₃SCF₃, where L = CO (3), XylNC (4) or 2,5-Me₂-C₆H₃CN (5) have been isolated and characterized by IR and NMR spectroscopy, cyclic voltammetry and X-ray crystallography. The complex trans-Re₂(μ-O₂CCH₃)₂Cl₂(μdppE)₂ (6) has been obtained by the reaction of Re₂(μ-O₂CCH₃)₄Cl₂ with dppE. Crystal structure determinations on 1, 2, 4 and 6 reveal that the Re-Re distances are 2.2448(5), 2.5748(5), 2.5767(5) and 2.2861(6) A, which are in accordance with Re-Re bond orders of 3, 2, 2 and 3, respectively. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(99)00545-9

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Inorganica Chimica Acta 300–302 (2000) 434–441
Dirhenium complexes that contain the ligand
1,1-bis(diphenylphosphino)ethene (dppE). Synthesis,
characterization and reactivity of Re2Cl4(m-dppE)2
Shan-Ming Kuang, Phillip E. Fanwick, Richard A. Walton *
Department of Chemistry, Purdue Uni6ersity, 1393 Brown Building, West Lafayette, IN 47907-1393, USA
Received 23 September 1999; accepted 18 November 1999
Abstract
The dirhenium(II) compound Re2Cl4(m-dppE)2 (1), where dppE=(Ph2P)2CꢀCH2, which contains an electron-rich triple bond,
has been prepared by the reaction of (n-Bu4N)2Re2Cl8 with CH3CO2Na and dppE in refluxing ethanol. Its reactivity towards CO
alone, and CO in combination with XylNC and 2,5-Me2ꢁC6H3CN has been explored. The complexes Re2Cl4(m-dppE)2(CO)2 (2)
and [Re2Cl3(m-dppE)2(CO)2(L)]O3SCF3, where L=CO (3), XylNC (4) or 2,5-Me2ꢁC6H3CN (5) have been isolated and character-
ized by IR and NMR spectroscopy, cyclic voltammetry and X-ray crystallography. The complex trans-Re2(m-O2CCH3)2Cl2(m-
dppE)2 (6) has been obtained by the reaction of Re2(m-O2CCH3)4Cl2 with dppE. Crystal structure determinations on 1, 2, 4 and
,
6 reveal that the ReꢁRe distances are 2.2448(5), 2.5748(5), 2.5767(5) and 2.2861(6) A, which are in accordance with ReꢁRe bond
orders of 3, 2, 2 and 3, respectively. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Crystal structures; Dirhenium(II) complexes; Bidentate phosphines; 1,1-Bis(diphenylphosphino)ethene; Metal–metal multiple bonds
1. Introduction
nes R2PXPR2 (where X represents CH2 in the case
of dppm) upon the reactivity of compounds of the
type Re2Cl4(m-R2PXPR2)2, we have been developing
procedures for the synthesis of dirhenium(II) com-
pounds with phosphines other than Ph2PCH2PPh2.
We have previously prepared and structurally
characterized the compound Re2Cl4(m-dppa)2, where
dppa=Ph2PNHPPh2, and examined a few aspects
of its reactivity [11–13]. More recently, we isolated
and characterized the compound Re2Cl4(m-dcpm)2,
where dcpm=Cy2PCH2PCy2 [14]. In the present re-
port we describe the synthesis and structural character-
ization of another compound of the type Re2-
Cl4(m-R2PXPR2)2, viz., Re2Cl4(m-dppE)2, where dppE
=1,1-(Ph2P)2CꢀCH2, and examine its reactivity to-
wards carbon monoxide in combination with xylyl
isocyanide (XylNC) and 2,5-dimethylbenzonitrile
(Me2C6H3CN). The isolation and structural characteri-
zation of trans-Re2(m-O2CCH3)2Cl2(m-dppE)2 is also de-
scribed.
The complex Re2Cl4(m-dppm)2, where dppm=
Ph2PCH2PPh2, is the prototypical dirhenium(II) com-
pound with an electron-rich triple bond [1–3]. The
exploration of its reactivity towards reagents as varied
as O2 [4], H2S [5], CS2 [6], organic nitriles [7] and
carboxylates [8] has provided valuable insight into the
nature of the s2p4d2d*2 ground state electronic configu-
ration. Of additional interest is the large number of
structural isomers of mixed carbonyl–isocyanide spe-
cies of the types [Re2Cl3(m-dppm)2(CO)(CNXyl)2]+ and
[Re2Cl2(m-dppm)2(CO)(CNXyl)3]2+ that have been pre-
pared by various synthetic strategies starting from
Re2Cl4(m-dppm)2 [9,10].
In order to examine the effects of varying the bridg-
ing group X and the R groups in the bidentate phosphi-
* Corresponding author. Tel.: +1-765-494 5464; fax: +1-765-494
0239.
E-mail address: rawalton@purdue.edu (R.A. Walton)
0020-1693/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00545-9

S.-M. Kuang et al. / Inorganica Chimica Acta 300–302 (2000) 434–441
435
2. Experimental
(25 ml) was added to afford a red–brown precipitate, 3,
which was filtered off, washed with 20 ml of diethyl
ether and dried under a vacuum; yield 75 mg (50%).
Anal. Calc. for C56H44Cl3F3O6P4Re2S: C, 44.70; H,
2.95. Found: C, 44.79; H, 2.97%.
2.1. Starting materials and reaction procedures
Standard literature procedures were used to prepare
(n-Bu4N)2Re2Cl8 [15], cis-Re2(O2CCH3)2Cl4(H2O)2 [16]
and Re2(O2CCH3)4Cl2 [17]. The ligand 1,1-bis(-
diphenylphosphino)ethene (abbreviated dppE) was syn-
thesized through the method described by Colquhoun
and McFarlane [18]. All other reagents and organic
solvents were purchased from commercial sources. Sol-
vents were deoxygenated by purging with N2(g) prior to
use and all reactions were carried out under an atmo-
sphere of N2. Infrared spectra, NMR spectra and cyclic
voltammetric measurements were determined as previ-
ously described [19]. Elemental microanalyses were per-
formed by Dr Lee of the Purdue University
Microanalytical Laboratory.
2.5. Synthesis of [Re2Cl3(v-dppE)2(CO)2(CNXyl)]-
SO3CF3 (4)
A mixture of 2 (136 mg, 0.10 mmol), TlO3SCF3 (35.3
mg, 0.10 mmol) and XylNC (13 mg, 0.10 mmol) in 30
ml of dichloromethane was stirred at room temperature
for 20 h. The yellow–brown mixture was filtered to
remove insoluble materials, and the volume of the
filtrate was reduced to about 3 ml. Diethyl ether (15 ml)
was added to precipitate the yellow–brown complex 4
which was filtered off, washed with 20 ml of diethyl
ether and dried under a vacuum; yield 102 mg (64%).
Anal. Calc. for C65H55Cl5F3NO5P4Re2S (i.e. [Re2Cl3(m-
dppE)2(CO)2(CNXyl)]O3SCF3·CH2Cl2): C, 46.12; H,
3.27. Found: C, 45.85; H, 3.18%.
2.2. Synthesis of Re2Cl4(v-dppE)2 (1)
A mixture of (n-Bu4N)2Re2Cl8 (1000 mg, 0.88 mmol),
CH3CO2Na (144 mg, 1.76 mmol), and dppE (770 mg,
1.94 mmol) in 40 ml of ethanol was refluxed for 48 h.
The brown precipitate that formed was filtered off,
washed with 15 ml of ethanol and dried under a
vacuum. The complex was recrystallized from
dichloromethane–diethyl ether to afford brown micro-
crystals; yield 720 mg (63%). Anal. Calc. for
C53H46Cl6P4Re2 (i.e. Re2Cl4(m-dppE)2·CH2Cl2): C,
45.73; H, 3.33. Found: C, 46.12; H, 3.16%.
2.6. Synthesis of [Re2Cl3(v-dppE)2(CO)2(NCC6H3-
2,5-Me2)]O3SCF3 (5)
The reaction between 2 (200 mg, 0.15 mmol),
TlO3SCF3 (52.0 mg, 0.15 mmol) and 2,5-dimethylben-
zonitrile (24 mg, 0.185 mmol) in 30 ml of
dichloromethane was carried out as described in Sec-
tion 2.5 to afford the yellow–brown product 5; yield
123 mg (51%). Anal. Calc. for C64H53Cl3F3NO5P4Re2S:
C, 47.81; H, 3.32. Found: C, 47.39; H, 3.65%.
2.3. Synthesis of Re2Cl4(v-dppE)2(CO)2 (2)
A quantity of Re2Cl4(m-dppE)2 (131 mg, 0.10 mmol)
was dissolved in 30 ml of dichloromethane. Carbon
monoxide was bubbled into this solution for 2 h, and
the solution was then stirred under an atmosphere of
carbon monoxide for 24 h at room temperature. The
volume of the green–brown solution was reduced to
about 3 ml, then 15 ml of diethyl ether were added to
give a greenish-brown precipitate of 2 which was
filtered off, washed with 20 ml of diethyl ether and
dried under a vacuum; yield 118 mg (87%). Anal. Calc.
for C55H46Cl6O2P4Re2 (i.e. Re2Cl4(m-dppE)2(CO)2·
CH2Cl2): C, 45.56; H, 3.34. Found: C, 45.22; H, 3.18%.
2.7. The reaction of Re2(v-O2CCH3)4Cl2 with dppE
A mixture of Re2(m-O2CCH3)4Cl2 (100 mg, 0.15
mmol) and dppE (350 mg, 0.90 mmol) was refluxed in
25 ml of methanol for 3 days. The cooled reaction
mixture was filtered and the insoluble brown crystals of
trans-Re2(m-O2CCH3)2Cl2(m-dppE)2 (6) were washed
with methanol (10 ml) and diethyl ether (10 ml) and
dried under a vacuum; yield 53 mg (27%). Anal. Calc.
forC57H54Cl2O5P4Re2(i.e.Re2(m-O2CCH3)2Cl2(m-dppE)2·
MeOH): C, 49.39; H, 3.93. Found: C, 49.59; H, 3.88%.
2.4. Synthesis of [Re2Cl3(v-dppE)2(CO)3]SO3CF3 (3)
2.8. The reaction of cis-Re2(v-O2CCH3)2Cl4(H2O)2
with dppE
A solution that contained the dicarbonyl complex 2
(136 mg, 0.10 mmol) and TlO3SCF3 (35.3 mg, 0.10
mmol) in 30 ml of dichloromethane was stirred under
an atmosphere of CO at room temperature for 24 h.
The resulting red–brown mixture was filtered to re-
move insoluble materials and the volume of the filtrate
was reduced to about 3 ml. An excess of diethyl ether
A mixture of Re2(m-O2CCH3)2Cl4(H2O)2 (100 mg,
0.15 mmol) and dppE (131 mg, 0.33 mmol) was
refluxed in 25 ml of ethanol for 3 h. The brown
crystalline product, Re2Cl4(m-dppE)2 (1) was filtered
off, washed with fresh ethanol (10 ml), and dried under
vacuum; yield 87 mg (45%). The identity of this product

436
S.-M. Kuang et al. / Inorganica Chimica Acta 300–302 (2000) 434–441
was confirmed by comparison of its spectroscopic and
electrochemical properties with those of an authentic
sample (see Section 2.2).
vents was found crystallized with the dirhenium
molecule in the asymmetric unit. It was included in the
analysis and refined satisfactorily with anisotropic ther-
mal parameters. The largest remaining peak in the final
−3
2.9. X-ray crystallography
,
difference Fourier was 3.79 e A
.
In the case of 2, the dirhenium unit lies on a crystal-
lographic inversion center. Consequently, the bridging
carbonyl group atoms C(11) and O(11) were disordered
with the bridging chlorine Cl(11), while the terminal
carbonyl group atoms C(2) and O(2) were found to be
disordered with the terminal chlorine Cl(2). In the final
refinement, the bridging group atoms C(11), O(11) and
Cl(11), and the terminal group atoms C(2), O(2) and
Cl(2) were each given fixed site-occupancy factors of
0.5. A common isotropic thermal parameter was refined
for atoms C(11), O(11), C(2), and O(2). Two dichloro-
methane molecules from the crystallization solvents
were found crystallized with 2 in the asymmetric unit.
These were included in the analysis and refined satisfac-
torily with anisotropic thermal parameters. The largest
Single crystals of 1 and 4 were grown by the vapor
diffusion of diethyl ether into dichloromethane solu-
tions of the complexes, while crystals of 2 were grown
at room temperature by the slow evaporation of a
solution of the complex in dichloromethane. In the case
of 6, crystals were harvested directly from the reaction
mixture.
The data collections were performed at 19391 K on
a Nonius KappaCCD diffractometer. Lorentz and po-
larization corrections were applied to the data sets. The
crystallographic data for the compounds are given in
Table 1.
The structures were solved using the structure solu-
tion program PATTY in DIRDIF-92 [20]. The remaining
atoms were located in succeeding difference Fourier
syntheses. Hydrogen atoms were placed in calculated
positions according to idealized geometries with
remaining peak in the final difference Fourier was 1.44
−3
,
e A
.
The crystal of compound 4 had two sites of partial
dichloromethane molecules from the crystallization sol-
vents in the asymmetric unit; their C and Cl atoms were
located and refined satisfactorily with anisotropic ther-
mal parameters. Refinement of these two solvent
molecules gave occupancies of 0.797 and 0.736. The
,
CꢁH=0.95 A and U(H)=1.3Ueq(C). They were in-
cluded in the refinement but constrained to ride on the
atom to which they are bonded. An empirical absorp-
tion correction using SCALEPACK [21] was applied. The
final refinements were performed by the use of the
program SHELXL-97 [22].
largest remaining peak in the final difference Fourier
During the course of the structure analysis of 1, one
dichloromethane molecule from the crystallization sol-
−3
,
was 1.09 e A
.
Table 1
Crystallographic data for Re2Cl4(m-dppE)2·CH2Cl2 (1), Re2Cl4(m-dppE)2(CO)2·2CH2Cl2 (2), [Re2Cl3(m-dppE)2(CO)2(CNXyl)]O3SCF3·1.533
CH2Cl2 (4) and trans-Re2(m-O2CCH3)2Cl2(m-dppE)2·MeOH (6)
1
2
4
6
Chemical formula
Formula weight
Space group
C53H46Cl6P4Re2
1391.97
P21/c (no. 14)
C56H48Cl8O2P4Re2 C65.53H56.07Cl6.07F3NO5P4Re2S
C57H54Cl2O5P4Re2
1386.27
C2/c (no. 15)
1532.93
1738.06
P21/c (no. 14)
P212121 (no. 19)
Unit cell dimensions
,
a (A)
12.7450(4)
18.4561(6)
21.7440(7)
90
96.6764(18)
90
5080.0(5)
4
1.820
5.306
0.40, 0.88
0.049
0.109
1.019
8.8964(2)
22.3308(6)
14.1592(3)
90
96.0002(15)
90
2797.5(2)
2
1.820
4.922
0.50, 0.61
0.049
0.135
1.084
12.2601(2)
15.2336(3)
35.6102(9)
90
90
90
6650.8(4)
4
1.736
4.114
0.42, 0.66
0.057
15.0451(9)
22.1142(14)
16.2959(7)
90
107.701(4)
90
5165.1(10)
4
1.783
5.022
0.44, 0.69
0.044
0.083
0.957
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (g cm−3
)
v (Mo Ka) (mm−1
)
Transmission factors (min./max.)
R(Fo) a
Rw(Fo2) b
GOF
0.087
1.019
a R=SꢀFoꢁ−ꢁFcꢀ/SꢁFoꢁ with Fo2\2|(Fo2).
b Rw=[Sw(ꢁFo2ꢁ−ꢁFc2ꢁ)2/SwꢁFo2ꢁ2]1/2
.

S.-M. Kuang et al. / Inorganica Chimica Acta 300–302 (2000) 434–441
437
Table 2
which has E1/2(ox)= +0.87 and +0.29 V versus Ag/
AgCl, and Re2Cl4(m-dppa)2, with E1/2(ox)= +0.94 and
+0.40 V [12]. The 1H NMR spectrum of 1 (recorded in
CD2Cl2) shows a pentet at l +6.17 due to the bridge-
head ꢂCꢀCH2 group, while the 31P{1H} NMR spec-
trum consists of a singlet at l +14.6.
The crystal structure of Re2Cl4(m-dppE)2 confirms its
close structural relationship to Re2Cl4(m-dppm)2 [3] and
Re2Cl4(m-dppa)2 [12]. An ORTEP representation [23] of
the structure is given in Fig. 1 and key structural
parameters are listed in Table 2. The ReꢁRe distance of
,
Important bond distances (A) and angles (°) for the complex
Re2Cl4(m-dppE)2·CH2Cl2 (1) a
Re(1)ꢁRe(2)
Re(1)ꢁCl(12)
Re(1)ꢁCl(11)
Re(1)ꢁP(3)
Re(1)ꢁP(1)
Re(2)ꢁCl(21)
2.2448(5) Re(2)ꢁCl(22)
2.367(2)
2.443(2)
2.460(2)
1.334(13)
1.305(12)
2.360(2)
2.369(2)
2.417(2)
2.450(2)
2.356(2)
Re(2)ꢁP(2)
Re(2)ꢁP(4)
C(11)ꢁC(12)
C(21)ꢁC(22)
Re(2)ꢁRe(1)ꢁCl(12) 118.59(6) Re(1)ꢁRe(2)ꢁCl(21) 115.90(6)
Re(2)ꢁRe(1)ꢁCl(11) 116.34(6) Re(1)ꢁRe(2)ꢁCl(22) 120.06(6)
Cl(12)ꢁRe(1)ꢁCl(11) 124.99(8) Cl(21)ꢁRe(2)ꢁCl(22) 124.02(8)
Re(2)ꢁRe(1)ꢁP(3)
Cl(12)ꢁRe(1)ꢁP(3)
Cl(11)ꢁRe(1)ꢁP(3)
Re(2)ꢁRe(1)ꢁP(1)
Cl(12)ꢁRe(1)ꢁP(1)
Cl(11)ꢁRe(1)ꢁP(1)
P(3)ꢁRe(1)ꢁP(1)
,
2.2448(5) A is close to the values reported for Re2Cl4(m-
90.90(6) Re(1)ꢁRe(2)ꢁP(2)
88.32(8) Cl(21)ꢁRe(2)ꢁP(2)
88.08(8) Cl(22)ꢁRe(2)ꢁP(2)
94.44(6) Re(1)ꢁRe(2)ꢁP(4)
88.53(8) Cl(21)ꢁRe(2)ꢁP(4)
90.15(8) Cl(22)ꢁRe(2)ꢁP(4)
174.61(8) P(2)ꢁRe(2)ꢁP(4)
89.18(5)
88.70(8)
90.68(8)
93.77(6)
91.47(8)
86.43(8)
176.62(8)
,
,
dppm)2 (2.234(3) A) and Re2Cl4(m-dppa)2 (2.2417(5) A),
and the expected fully staggered rotational geometry is
confirmed by values for the torsion angles
Cl(11)ꢁRe(1)ꢁRe(2)ꢁCl(21), Cl(12)ꢁRe(1)ꢁRe(2)ꢁCl(22),
P(1)ꢁRe(1)ꢁRe(2)ꢁP(2) and P(3)ꢁRe(1)ꢁRe(2)ꢁP(4) of
48.5, 43.8, 44.3 and 43.3°, respectively.
a Numbers in parentheses are estimated S.D.s in the least signifi-
cant digits.
3.2. Reactions of Re2Cl4(v-dppE)2 (1)
The atoms Re(1), Re(2), Cl(1) and Cl(2) of the
dirhenium unit in compound 6 are located on a twofold
crystallographic rotational axis. One molecule of
methanol from the crystallization solvents was found in
the asymmetric unit during the course of the structure
determination. It was included in the analysis and
refined satisfactorily with anisotropic thermal parame-
Several reactions of the title complex 1 were carried
out in order to compare its reactivity patterns with
those of Re2Cl4(m-dppm)2. The results are summarized
in Eqs. (1)–(4).
CO
Re2Cl4(m-dppE)2“Re2Cl4(m-dppE)2(CO)
CO
“Re2Cl4(m-dppE)2(CO)2 (1)
ters. The largest remaining peak in the final difference
−3
,
Fourier was 0.80 e A
.
Re2Cl4(m-dppE)2(CO)2
TlO SCF
The important intramolecular bond distances and
angles for the structures of 1, 2, 4 and 6 are given in
Tables 2–5.
3
3
ꢁꢁꢁꢁꢁꢁꢁꢃ [Re2Cl3(m-dppE)2(CO)3]O3SCF3 (2)
CO
Table 3
,
Important bond distances (A) and angles (°) for the complex
3. Results and discussion
Re2Cl4(m-dppE)2(CO)2·2CH2Cl2 (2) a
Re(1)ꢁRe(1)%
Re(1)ꢁC(2)
Re(1)%ꢁC(11)
Re(1)ꢁC(11)
Re(1)ꢁCl(1)
Re(1)ꢁCl(11)
Re(1)ꢁP(2)
2.5748(5) Re(1)%ꢁCl(11)
1.864(17) Re(1)%ꢁCl(2)
2.462(5)
2.466(4)
2.4713(18)
1.22(3)
1.15(2)
1.308(11)
3.1. The synthesis and characterization of
Re2Cl4(v-dppE)2
1.83(3)
Re(1)ꢁP(1)
O(11)ꢁC(11)
O(2)ꢁC(2)
2.38(2)
2.399(2)
2.425(4)
2.4560(18)
The synthesis of Re2Cl4(m-dppE)2 utilized the reac-
tion between (n-Bu4N)2Re2Cl8, NaO2CCH3 and dppE
in refluxing ethanol and is similar to the procedure we
used to obtain Re2Cl4(m-dppm)2 [2]. This reaction al-
most certainly proceeds through the intermediacy of the
paramagnetic [Re2]5+ complex Re2(m-O2CCH3)Cl4(m-
dppE)2. This procedure is a convenient alternative to
the one whereby a bisphosphine ligand is reacted with
cis-Re2(O2CCH3)2Cl4(H2O)2 [2a,11a]. The cyclic volta-
mmetric (CV) properties of 1, recorded on solutions in
0.1 M n-Bu4NPF6–CH2Cl2 with the use of a Pt-bead
electrode, consist of two reversible one-electron oxida-
tions with E1/2(ox)= +0.92 and +0.37 V versus Ag/
AgCl and Ep values of 60 mV. These data can be
contrasted with data reported for Re2Cl4(m-dppm)2,
C(311)ꢁC(312)
C(2)ꢁRe(1)ꢁC(11)
C(2)ꢁRe(1)ꢁCl(1)
C(11)ꢁRe(1)ꢁCl(1)
C(2)ꢁRe(1)ꢁCl(11)
C(11)ꢁRe(1)ꢁCl(11) 100.7(6)
Cl(1)ꢁRe(1)ꢁCl(11)
73.9(8)
97.6(5)
170.4(6)
173.5(5)
C(2)ꢁRe(1)ꢁRe(1)%
C(11)ꢁRe(1)ꢁRe(1)%
Cl(1)ꢁRe(1)ꢁRe(1)
Cl(11)ꢁRe(1)ꢁRe(1)%
P(2)ꢁRe(1)ꢁRe(1)%
117.1(5)
43.3(6)
145.06(8)
58.91(11)
95.00(4)
57.51(9)
141.41(11)
95.13(5)
63.58(11)
74.2(7)
88.08(12) Cl(11)ꢁRe(1)%ꢁRe(1)
C(11)ꢁRe(1)%ꢁCl(11) 121.4(6)
Cl(2)ꢁRe(1)%ꢁRe(1)
P(1)ꢁRe(1)ꢁRe(1)%
Re(1)ꢁCl(11)ꢁRe(1)%
C(11)ꢁRe(1)ꢁCl(1)
C(11)ꢁRe(1)%ꢁCl(2)
Cl(1)ꢁRe(1)%ꢁCl(2)
Cl(11)ꢁRe(1)%ꢁCl(2)
P(2)ꢁRe(1)ꢁP(1)
82.7(7)
155.4(7)
73.53(14) Re(1)ꢁC(11)ꢁRe(1)%
83.03(16) O(2)ꢁC(2)ꢁRe(1)
169.10(6) O(11)ꢁC(11)ꢁRe(1)% 159.8(18)
62.6(7) O(11)ꢁC(11)ꢁRe(1) 125.0(17)
179.4(17)
C(11)ꢁRe(1)%ꢁRe(1)
a Numbers in parentheses are e.s.d.s in the least significant digits.

438
S.-M. Kuang et al. / Inorganica Chimica Acta 300–302 (2000) 434–441
1
Table 4
the bridgehead ꢂCꢀCH2 group in the H NMR spec-
trum (spectra recorded in CD2Cl2 at 25°C) accords with
this molecule being fluxional, as is the case for
Re2Cl4(m-dppm)2(CO)2 [24]. Further confirmation of
,
Important bond distances (A) and angles (°) for the complex
[Re2Cl3(m-dppE)2(CO)2(CNXyl)]O3SCF3·1.533CH2Cl2 (4) a
Re(1)ꢁRe(2)
Re(1)ꢁC(100)
Re(1)ꢁC(12)
Re(1)ꢁCl(1)
Re(1)ꢁP(3)
2.5767(5) Re(2)ꢁCl(2)
2.013(11) Re(2)ꢁCl(12)
2.033(11) Re(2)ꢁP(4)
2.417(3)
2.465(2)
2.488(3)
2.496(3)
1.176(11)
1.135(11)
1.151(12)
1.314(13)
1.331(13)
the close relationship between
2 and Re2Cl4(m-
dppm)2(CO)2 is the similarity between their CV proper-
ties, which for solutions of 2 in 0.1 M n-Bu4NPF6–
CH2Cl2 consists of a one-electron oxidation at E1/2
+1.01 V (Ep=60 mV) and a one-electron reduction at
1/2= −0.58V (Ep=65 mV) versus Ag/AgCl.
The crystal structure of 2 was solved using a disorder
2.417(2)
2.475(3)
2.477(3)
2.484(2)
Re(2)ꢁP(2)
O(12)ꢁC(12)
O(202)ꢁC(201)
N(100)ꢁC(100)
=
Re(1)ꢁP(1)
Re(1)ꢁCl(12)
Re(2)ꢁC(201)
Re(2)ꢁC(12)
E
1.910(10) C(1)ꢁC(2)
2.114(10) C(3)ꢁC(4)
model in which the bridging and terminal CO ligands
are disordered with two of the Cl ligands through a
crystallographic inversion center. In this model the
terminal CO ligand (C(2)O(2)) is disordered only with
atom Cl(2) and not Cl(1), while the bridging CO ligand
(C(11)O(11)) is disordered with Cl(11). A disorder was
also encountered in solving the structure of Re2Cl4(m-
dppm)2(CO)2, but in this case it involved all four equa-
torial terminal metal–ligand sites as well as a disorder
between the two bridging ligands [24]. The ORTEP rep-
resentation [23] of the structure of 2 in Fig. 2 shows one
half of the disorder, in which we assume the CO ligands
are cis to one another. This is substantiated by the
structure of the xylyl isocyanide complex 4 (vide infra),
which is a derivative of 2. Important structural parame-
ters are given in Table 3. The structure of 2 shows that
the bridging CO ligand is unsymmetrically bound to the
two Re centers in the solid state, the ReꢁC distances
C(100)ꢁRe(1)ꢁC(12)
C(100)ꢁRe(1)ꢁCl(1)
C(12)ꢁRe(1)ꢁCl(1)
C(100)ꢁRe(1)ꢁP(3)
C(12)ꢁRe(1)ꢁP(3)
Cl(1)ꢁRe(1)ꢁP(3)
C(100)ꢁRe(1)ꢁP(1)
C(12)ꢁRe(1)ꢁP(1)
Cl(1)ꢁRe(1)ꢁP(1)
P(3)ꢁRe(1)ꢁP(1)
C(100)ꢁRe(1)ꢁCl(12) 172.7(3)
C(12)ꢁRe(1)ꢁCl(12) 111.2(3)
Cl(1)ꢁRe(1)ꢁCl(12)
P(3)ꢁRe(1)ꢁCl(12)
P(1)ꢁRe(1)ꢁCl(12)
76.1(4)
82.1(3)
158.2(3)
87.6(3)
93.0(3)
85.29(9) Cl(12)ꢁRe(2)ꢁP(4)
85.2(3)
95.7(3)
C(12)ꢁRe(2)ꢁCl(12)
109.1(3)
93.39(9)
89.6(3)
Cl(2)ꢁRe(2)ꢁCl(12)
C(201)ꢁRe(2)ꢁP(4)
C(12)ꢁRe(2)ꢁP(4)
Cl(2)ꢁRe(2)ꢁP(4)
94.7(3)
84.40(9)
88.82(8)
90.5(3)
C(201)ꢁRe(2)ꢁP(2)
C(12)ꢁRe(2)ꢁP(2)
96.1(3)
83.07(9) Cl(2)ꢁRe(2)ꢁP(2)
167.06(9) Cl(12)ꢁRe(2)ꢁP(2)
84.32(9)
90.91(9)
168.68(9)
122.1(3)
50.2(3)
152.36(7)
58.98(6)
95.01(6)
94.55(6)
62.75(6)
76.8(4)
P(4)ꢁRe(2)ꢁP(2)
C(201)ꢁRe(2)ꢁRe(1)
90.54(8) C(12)ꢁRe(2)ꢁRe(1)
92.19(8) Cl(2)ꢁRe(2)ꢁRe(1)
93.57(9) Cl(12)ꢁRe(2)ꢁRe(1)
C(100)ꢁRe(1)ꢁRe(2) 129.0(3)
P(4)ꢁRe(2)ꢁRe(1)
P(2)ꢁRe(2)ꢁRe(1)
C(12)ꢁRe(1)ꢁRe(2)
Cl(1)ꢁRe(1)ꢁRe(2)
P(3)ꢁRe(1)ꢁRe(2)
P(1)ꢁRe(1)ꢁRe(2)
Cl(12)ꢁRe(1)ꢁRe(2)
C(201)ꢁRe(2)ꢁC(12)
C(201)ꢁRe(2)ꢁCl(2)
C(12)ꢁRe(2)ꢁCl(2)
53.0(3)
148.77(7) Re(2)ꢁCl(12)ꢁRe(1)
96.44(6) Re(1)ꢁC(12)ꢁRe(2)
96.45(6) O(12)ꢁC(12)ꢁRe(1)
58.27(5) O(12)ꢁC(12)ꢁRe(2)
71.9(4)
85.5(3)
143.1(8)
140.0(9)
,
being 1.83(3) and 2.38(2) A (see Table 3). The ReꢁRe
O(202)ꢁC(201)ꢁRe(2) 178.6(9)
N(100)ꢁC(10)ꢁRe(1) 179.5(10)
C(100)ꢁN(100)ꢁC(101) 169.9(10)
,
bond distance of 2.5748(5) A is close to that reported
157.4(3)
,
for Re2Cl4(m-dppm)2(CO)2 (2.584(1) A) [24]. The eight-
C(201)ꢁRe(2)ꢁCl(12) 178.1(3)
membered [Re(m-PꢁCꢁP)2Re] ring exists in a chair con-
formation in accordance with the crystallographically
imposed center of symmetry.
a Numbers in parentheses are estimated S.D.s in the least signifi-
cant digits.
The derivatization of 2 in the presence of TlO3SCF3
and CO, XylNC or 2,5-Me2ꢁC6H3CN (see Eqs. (2)–(4))
affords complexes of the type [Re2Cl3(m-dppE)2-
(CO)2(L)]O3SCF3, where L=CO (3), XylNC (4) or
2,5-Me2ꢁC6H3CN (5). On the basis of the similarity of
their spectroscopic and cyclic voltammetric properties,
and a crystal structure determination of 4, these com-
plexes are assigned an all-cis structure of the type
[(CO)ClRe(m-Cl)(m-CO)(m-dppE)2ReCl(L)]+, with the
two CO ligands and ligand L being cis to one another
on one side of the molecule. The ORTEP representation
[23] of 4 is given in Fig. 3 and important structural
parameters are listed in Table 4. The ReꢁRe distance of
Re2Cl4(m-dppE)2(CO)2
TlO SCF
3
ꢁꢁꢁꢁꢁꢁ3ꢃ [Re2Cl3(m-dppE)2(CO)2(CNXyl)]O3SCF3 (3)
XylNC
Re2Cl4(m-dppE)2(CO)2
TlO SCF
3
ꢁꢁꢁꢁꢁꢁꢁꢁ3ꢁꢁꢃ [Re2Cl3(m-dppE)2(CO)2(NCC6H3-2,5-Me2)]
2,5-Me C H CN
2 6 3
O3SCF3
(4)
The reaction of Re2Cl4(m-dppE)2 with CO proceeds
through the intermediacy of Re2Cl4(m-dppE)2(CO) to
afford the edge-sharing bioctahedral complex Re2Cl4(m-
dppE)2(CO)2 (2), which shows a close structural rela-
tionship to Re2Cl4(m-dppm)2(CO)2 [24]. The IR
spectrum of 2 (KBr pellet) shows w(CO)t and w(CO)b
modes at 1953(vs) and 1736(m) cm−1, respectively,
while the presence of a singlet at l +9.0 in the 31P{1H}
NMR spectrum and an apparent pentet at l +6.21 for
,
2.5767(5) A is essentially identical to that of 2
,
(2.5748(5) A). While the dppm complex, which is
analogous to 4, has been isolated [25], it has not yet
been crystallographically characterized. However, struc-
ture determinations on [Re2Cl3(m-dppm)2(CO)2-
(NCEt)]PF6 [26] and [Re2Cl3(m-dppm)2(CO)3]PF6 [27]
reveal the same type of structure as that for 4 (Fig. 3),
,
with ReꢁRe distances of 2.586(1) and 2.582(1) A, re-
spectively.

S.-M. Kuang et al. / Inorganica Chimica Acta 300–302 (2000) 434–441
439
Complexes 3–5 show an intense band for the triflate
anion at ca. 1270 cm−1 in their IR spectra (KBr
pellets), along with characteristic w(CO) and w(CN)
modes for the CO, XylNC and 2,5-Me2ꢁC6H3CN lig-
ands; for 3 at 2014(vs), 1897(m), and 1717(m-s) cm−1
,
for 4 at 2156(vs), 2005(vs) and 1719(m) cm−1, and for
5 at 2258(w), 1995(vs), ꢀ1940sh, and 1719(m) cm−1
.
The bands at 2156 and 2258 cm−1 in the IR spectra of
4 and 5, respectively, are assigned to w(CN) modes,
while the w(CO)b mode for each of the three complexes
is at approximately 1720 cm−1
.
The symmetrical nature of 3 is shown by a singlet at
l +9.9 in the 31P{1H} NMR spectrum (recorded in
CD2Cl2), while the related spectra of 4 and 5 are
Fig. 2. ORTEP [23] representation of the structure of the molecule of
Re2Cl4(m-dppE)2(CO)2 as present in 2. This representation shows half
of the disorder involving the CO and Cl ligands which are related by
a center of symmetry at the mid-point of the Re-Re bond. The
unlabeled atoms are related to the labeled ones by the center of
symmetry. The unlabeled Re atom is designated as Re(1)% in Table 3.
The thermal ellipsoids are drawn at the 50% probability level except
for the phenyl group atoms of the dppE ligands which are circles of
arbitrary radius.
Table 5
,
Important bond distances (A) and angles (°) for the complex ‘trans-
Re2(m-O2CCH3)2Cl2(m-dppE)2·MeOH (6) a
Re(1)ꢁRe(2)
Re(1)ꢁO(1)
Re(1)ꢁP(2)
Re(1)ꢁCl(1)
Re(2)ꢁO(2)
Re(2)ꢁP(1)
2.2861(6)
2.122(5)
2.439(2)
2.608(3)
2.128(5)
2.431(2)
Re(2)ꢁCl(2)
O(1)ꢁC(1)
O(2)ꢁC(1)
C(1)ꢁC(2)
C(11)ꢁC(12)
2.634(3)
1.287(8)
1.253(8)
1.481(10)
1.356(10)
AA%BB% patterns with the centers of the two complex
multiplets being at l +12.7 and l +3.6 (for 4), and l
+13.5 and l +1.2 (for 5). The CVs of 3–5 (recorded
in 0.1 M n-Bu4NPF6–CH2Cl2) are very similar, each
showing two reversible one-electron reductions, with
E1/2 values of +0.22/−0.80, −0.01/−0.96 and
−0.13/−1.11 V versus Ag/AgCl for 3, 4 and 5, respec-
tively; the values of Ep (i.e. Ep,a−Ep,c) for each of the
O(1)ꢁRe(1)ꢁO(1)%
O(1)ꢁRe(1)ꢁRe(2)
O(1)ꢁRe(1)ꢁP(2)
O(1)%ꢁRe(1)ꢁP(2)
Re(2)ꢁRe(1)ꢁP(2)
P(2)ꢁRe(1)ꢁP(2)%
O(1)ꢁRe(1)ꢁCl(1)
179.4(3)
O(2)ꢁRe(2)ꢁO(2)%
176.4(3)
89.70(14) O(2)ꢁRe(2)ꢁRe(1)
87.30(15) O(2)ꢁRe(2)ꢁP(1)
92.76(15) Re(1)ꢁRe(2)ꢁP(1)
95.65(5)
168.71(10) P(1)ꢁRe(2)ꢁP(1)%
90.30(14) O(2)ꢁRe(2)ꢁCl(2)
88.20(13)
89.53(16)
101.67(5)
91.20(16)
156.66(10)
91.80(13)
O(2)%ꢁRe(2)ꢁP(1)
Re(2)ꢁRe(1)ꢁCl(1) 180.00(14) Re(1)ꢁRe(2)ꢁCl(2) 180.00(13)
P(2)ꢁRe(1)ꢁCl(1) 84.35(5) P(1)ꢁRe(2)ꢁCl(2) 78.33(5)
a Numbers in parentheses are estimated standard deviations in the
least significant digits. Primed atoms are related to the unprimed ones
by a twofold rotation axis Cl(1)ꢁRe(1)ꢁRe(2)ꢁCl(2).
Fig. 3. ORTEP [23] representation of the structure of the dirhenium
cation [Re2Cl3(m-dppE)2(CO)2(CNXyl)]+ present in the structure of
4. The thermal ellipsoids are drawn at the 50% probability level
except for the phenyl group atoms of the dppE ligands and the xylyl
group atoms of the XylNC ligand which are circles of arbitrary
radius.
Fig. 1. ORTEP [23] representation of the structure of the molecule of
Re2Cl4(m-dppE)2 as present in 1. The thermal ellipsoids are drawn at
the 50% probability level except for the phenyl group atoms of the
dppE ligands which are circles of arbitrary radius.

440
S.-M. Kuang et al. / Inorganica Chimica Acta 300–302 (2000) 434–441
,
dppm)2 [28] and shorter by approximately 0.02 A than
the ReꢁRe distances for the cis isomers of both the
dppm and dppa complexes [11].
4. Concluding remarks
In contrast to the behavior of the phosphine ligands
Me2PCH2PMe2 (dmpm) and Ph2Ppy, which form the
tris(bidentate phosphine) dirhenium(II) complexes
Re2Cl4(m-dmpm)3 [29] and Re2Cl4(m-Ph2Ppy)3 [30], the
ligand (Ph2P)2CꢀCH2 (dppE) gives the bis-complex
Re2Cl4(m-dppE)2. This compound most closely resem-
bles Re2Cl4(m-dppm)2 (dppm=Ph2PCH2PPh2) [1–
3,7,8] and Re2Cl4(m-dppa)2 (dppa=Ph2PNHPPh2)
[11–13] in terms of its structure and chemical reactivity.
The present report serves as a prelude to a detailed
comparison of the reactions of Re2Cl4(m-dppE)2,
Re2Cl4(m-dppm)2 and Re2Cl4(m-dcpm)2 (dcpm=
Cy2PCH2PCy2) with the isocyanide ligands t-BuNC and
XylNC, the details of which will be communicated
shortly.
Fig. 4. ORTEP [23] representation of the structure of the molecule of
trans-Re2(m-O2CCH3)2Cl2(m-dppE)2 as present in 6. The thermal el-
lipsoids are drawn at the 50% probability level except for the phenyl
group atoms of the dppE ligands which are circles of arbitrary radius.
The unlabeled atoms are related to the labeled ones by a twofold
rotational axis which contains atoms Re(1), Re(2), Cl(1) and Cl(2). In
Table 5 they are labeled with a prime.
processes are in the range 60–70 mV. These data
resemble those reported previously for dppm complexes
of these types [25–27].
5. Supplementary material
Tables giving full details for the crystal data and data
collection parameters, atomic positional parameters,
anisotropic thermal parameters, bond distances and
bond angles for compounds 1, 2, 4 and 6 are available
on request from the author (R.A.W.).
3.3. Isolation and characterization of trans-Re2(v-
O2CCH3)2Cl2(v-dppE)2
We have previously shown that the cis and trans iso-
mers of the dirhenium(II) complexes Re2(m-O2CCH3)2-
Cl2(m-dppm)2 and Re2(m-O2CCH3)2Cl2(m-dppa)2 can be
prepared through the reactions of Re2Cl4(m-dppm)2
with [(Ph3P)2N]O2CCH3, and of cis-Re2(O2CCH3)2-
Cl4(H2O)2 or Re2(O2CCH3)4Cl2 with dppm or dppa
[11,28]. In the present study we have used the reaction
between Re2(O2CCH3)4Cl2 and dppE in refluxing
methanol to form trans-Re(m-O2CCH3)2Cl2(m-dppE)2
(6) and thereby further demonstrate the close relation-
ship between dppm and dppE in their reactivity to-
wards dirhenium complexes. Compound 6 shows a
singlet at l +22.1 in its 31P{1H} NMR spectrum
(recorded in CD2Cl2), while its CV in 0.1 M n-
Bu4NPF6–CH2Cl2 possesses a one-electron oxidation at
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