Polymeric dirhenium(III) complexes of the type [cis-Re2(O2CCH3)2Cl4(LL)](n) involving the symmetrical linker ligands pyrazine, 4,4'-bipyridine, and methylenebis(diphenylphosphine oxide)

Article abstract of DOI:10.1016/S0020-1693(99)00585-X

The reactions of the dirhenium(III) complex cis-Re₂(μ-O₂CCH₃)₂Cl₄(H₂O)₂ with the linker ligands pyrazine (pyz), 4,4'-bipyridine (4,4'-bpy) and methylenebis(diphenylphosphine oxide) (dppmO₂) in acetone solution have been used to prepare the polymeric complexes [cis-Re₂(μ-O₂CCH₃)₂Cl₄(μ-pyz)](n) (1), [cis-Re₂(μ-O₂CCH₃)₂Cl₄(pyz)]₂(μ-pyz) (2), [cis-Re₂(μ-O₂CCH₃)₂Cl₄(μ-4,4'-bpy)](n) (3) and [cis-Re₂(μ-O₂CCH₃)₂Cl₄(μ-dppmO₂)](n) (4). The structures of all four complexes (1-4) have been determined and show that the Re-Re distances are 2.2358(8), 2.240(2), 2.2512(4) and 2.2438(4) A, respectively. The structure of 2 shows the presence of terminal and bridging pyrazine ligands, while the polymeric complex 3 possesses both planar and twisted bridging 4,4'-bipyridine ligands. (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0020-1693(99)00585-X

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Inorganica Chimica Acta 300–302 (2000) 505–511
Polymeric dirhenium(III) complexes of the type
[cis-Re2(O2CCH3)2Cl4(LL)]n involving the symmetrical linker
ligands pyrazine, 4,4%-bipyridine, and
methylenebis(diphenylphosphine oxide)
Yan Ding, Sophia S. Lau, Phillip E. Fanwick, Richard A. Walton *
Department of Chemistry, Purdue Uni6ersity, 1393 Brown Building, West Lafayette, IN 47907-1393, USA
Received 28 October 1999; accepted 29 November 1999
Abstract
The reactions of the dirhenium(III) complex cis-Re2(m-O2CCH3)2Cl4(H2O)2 with the linker ligands pyrazine (pyz), 4,4%-
bipyridine (4,4%-bpy) and methylenebis(diphenylphosphine oxide) (dppmO2) in acetone solution have been used to prepare the
polymeric complexes [cis-Re2(m-O2CCH3)2Cl4(m-pyz)]n (1), [cis-Re2(m-O2CCH3)2Cl4(pyz)]2(m-pyz) (2), [cis-Re2(m-O2CCH3)2Cl4(m-
4,4%-bpy)]n (3) and [cis-Re2(m-O2CCH3)2Cl4(m-dppmO2)]n (4). The structures of all four complexes (1–4) have been determined and
,
show that the ReꢀRe distances are 2.2358(8), 2.240(2), 2.2512(4) and 2.2438(4) A, respectively. The structure of 2 shows the
presence of terminal and bridging pyrazine ligands, while the polymeric complex 3 possesses both planar and twisted bridging
4,4%-bipyridine ligands. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Crystal structures; Dirhenium(III) carboxylates; Bridging ligands; Polymeric complexes; Metal–metal multiple bonds
in which M2(m-O2CR)4 units, where M=Cr [4], Mo
[5,6], Ru [7–10] or Rh [11,12], are linked by the binding
of bridging ligands in the axial sites, such examples are
rare with multiply bonded dirhenium systems. The
quadruply bonded complex cis-Re2(m-O2CCH3)2Cl4-
(H2O)2 has two weakly bound water molecules coor-
dinated at the axial positions, which can be replaced
by stronger neutral donors to form compounds of the
type cis-Re2(m-O2CCH3)2Cl4L2, where L=pyridine, 4-
methylpyridine, dimethylacetamide, DMF, DMSO, and
Ph3PO [13–15]. This tendency to coordinate ligands at
the axial positions makes cis-Re2(m-O2CCH3)2Cl4-
(H2O)2 an ideal dirhenium ‘building block’ for long
chain polymers. Surprisingly, there is only one prior
example in the literature that involves the linkage of the
cis-Re2(O2CR)2X4 unit by axially bridging ligands to
form polymeric chains [16]. In the present report, we
describe the reactions between cis-Re2(m-O2CCH3)2-
Cl4(H2O)2 and linker ligands that contain delocalized p
orbitals.
1. Introduction
Over the past decade, research into the design of new
materials has steadily increased, particularly in the area
of inorganic polymers [1], organic and inorganic conduc-
tors [2], and microelectronic devices [3]. The present
study focuses on the synthesis and electronic properties
of new, one-dimensional polymeric materials containing
metal–metal multiple bonds, specifically those in which
rhenium–rhenium quadruple bonds are linked by ligands
that contain delocalized p orbitals, such as pyrazine and
4,4%-bipyridine. This type of ligand can potentially inter-
act with the d orbitals of the dimetal unit and form a
delocalized ‘molecular wire’ type structure.
While several examples of polymeric complexes con-
taining metal–metal multiple bonds have been reported
* 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)005 85-X

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Y. Ding et al. / Inorganica Chimica Acta 300–302 (2000) 505–511
2. Experimental
C, 21.78; H, 2.02; N, 3.36%. Far IR spectrum (Nujol
mull): 362(s), 358(s), 345(m) and 332(m-w) cm−1
.
2.1. Starting materials and reaction procedures
Single crystals of 3 were obtained by use of the same
procedure as described for 1.
The standard literature procedure was used to pre-
pare cis-Re2(O2CCH3)2Cl4(H2O)2 [14]. The ligand 4,4%-
bipyridine (4,4%-bpy) was provided by Dr D.R.
McMillin of Purdue University, while samples of
Ph2P(O)CH2P(O)Ph2 (dppmO2) were synthesized as de-
scribed in the literature [17]. All other reagents and the
organic solvents were purchased from commercial
sources. IR spectra, NMR spectra and cyclic voltam-
metric measurements were determined as described pre-
viously [18]. Solid-state microwave conductivity
measurements were carried out by Dr Kathleen Hoek-
stra of Purdue University. Elemental microanalyses
were performed by Dr H.D. Lee of the Purdue Univer-
sity Microanalytical Laboratory.
2.4. Synthesis of [cis-Re2(v-O2CCH3)2Cl4(v-dppmO2)]n
(4)
A quantity of cis-Re2(m-O2CCH3)2Cl4(H2O)2 (0.146
g, 0.22 mmol) was mixed with acetone (10 ml) and
acetic acid (5 ml) and the mixture was heated and
stirred for 2 h, then allowed to cool to r.t. and approx-
imately 2 equiv. of Ph2P(O)CH2P(O)Ph2 (0.183 g, 0.44
mmol) added. This mixture was heated to reflux
overnight, and the resulting blue crystals collected by
filtration, washed with acetone, and dried in air; yield
0.16 g (68%). Anal. Calc for C29H28Cl4O6P2Re2: C,
33.21; H, 2.69. Found: C, 32.94; H, 2.81%.
Crystals of 4, which were suitable for a single-crystal
X-ray structure determination, were obtained from the
bulk crystalline samples.
2.2. Synthesis of [cis-Re2(v-O2CCH3)2Cl4(v-pyz)]n (1)
and [cis-Re2(v-O2CCH3)2Cl4(pyz)]2(v-pyz) (2)
A solution of pyrazine (0.20 g, 2.5 mmol) in 20 ml of
acetone was added slowly to a solution of cis-Re2(m-
O2CCH3)2Cl4(H2O)2 (0.20 g, 0.30 mmol) in 20 ml of
acetone and the mixture stirred for 1 h at room temper-
ature (r.t.). The blue powder was filtered off and
washed with acetone and diethyl ether; yield 0.20 g
(93%). Water can also be used as a reaction solvent in
place of acetone. Anal. Calc for C8H10Cl4N2O4Re2: C,
13.49; H, 1.41; N, 3.93. Found: C, 13.69; H, 1.56; N,
3.67%. Far IR spectrum (Nujol mull): 385(m), 374(m-
2.5. Doping with bromine
A quantity of polymer 1 or 3 was ground to a fine
powder and spread as a thin layer on the bottom of a
glass dish equipped with a cover. A smaller dish con-
taining several drops of bromine was then placed inside
this glass dish. The glass dish was covered, allowing the
bromine vapor to come in contact with the polymeric
powder. After 1 h, the cover was removed and the
excess bromine was allowed to evaporate.
s), 362(s), 351(m-s) and 336(m) cm−1
.
Compound 1 was obtained as green crystals suitable
for X-ray structure determination using the following
procedure. A small volume of acetone was carefully
layered above an aqueous solution of cis-Re2(m-
O2CCH3)2Cl4(H2O)2 in a test tube; the use of this
acetone layer helped to prevent immediate mixing of
the reactants. An acetone solution of pyrazine (1:1 mole
ratio of pyrazine to the dirhenium complex) was then
carefully layered above the acetone layer in the test
tube. Crystals of 1 were obtained after 4 weeks. When
more than 1 equiv. of pyrazine was used crystals of the
oligomer [cis-Re2(m-O2CCH3)2Cl4(pyz)]2(m-pyz) (2) were
obtained instead. The identity of 2 was established by
single-crystal X-ray structure analysis.
2.6. X-ray crystallography
Single crystals of 1–4 were obtained as described in
Sections 2.2–2.4. The data collections for 1–4 were
recorded at 293(91), 296(91), 203(91) and 193(91)
K, respectively, on a Nonius Kappa CCD diffractome-
ter. Lorentz and polarization 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 DIRDIF92 [19]. The remaining
atoms were located in succeeding difference Fourier
syntheses. Hydrogen atoms were placed in calculated
positions according to idealized geometries with
,
CꢀH=0.95 A and U(H)=1.3 Ueq(C). They were in-
2.3. Synthesis of [cis-Re2(v-O2CCH3)2Cl4(v-4,4%-bpy)]n
(3)
cluded in the refinement but constrained to ride on the
atom to which they are bonded. An empirical absorp-
tion correction using SCALEPACK [20] was applied in
the case of 1, 3 and 4, while a correction based on the
method of Blessing [21] was used for 2. The final
refinements were performed by the use of the program
SHELXL-97 [22]. The crystal of 3 contained a badly
disordered solvent molecule, which was removed using
A procedure similar to the one described in Section
2.2 was employed with the use of 0.11 g (0.16 mmol) of
cis-Re2(m-O2CCH3)2Cl4(H2O)2 and 0.16 g (1.0 mmol) of
4,4%-bipyridine; yield 0.08 g (65%). Anal. Calc for
C14H14Cl4N2O4Re2: C, 21.33; H, 1.79; N, 3.55. Found:

Y. Ding et al. / Inorganica Chimica Acta 300–302 (2000) 505–511
507
Table 1
Crystallographic data for [cis-Re2(m-O2CCH3)2Cl4(m-pyz)]n (1), [cis-Re2(m-O2CCH3)2Cl4(pyz)]2(m-pyz) (2), [cis-Re2(m-O2CCH3)2Cl4(m-4,4%-bpy)]n
(3) and [cis-Re2(m-O2CCH3)2Cl4(m-dppmO2)]n (4)
1
2
3
4
Chemical formula
Formula weight
Space group
C8H10Cl4N2O4Re2
712.39
C20H24Cl8N6O8Re4
1504.87
P21/n (no. 14)
8.5204(2)
12.2411(4)
17.6383(6)
90
91.58(11)
90
1839.0(3)
2
2.718
13.941
0.08/0.19
0.051
0.136
C14H14Cl4N2O4Re2
788.49
C32H34Cl4O7P2Re2
1106.78
P21/n (no. 14)
12.0504(4)
17.3029(7)
18.3985(5)
90
94.879(2)
90
3882.3(4)
4
1.923
6.822
0.47/0.71
0.055
0.147
Pnma (no. 62)
16.6786(5)
9.8491(8)
11.8916(9)
90
90
90
1953.4(3)
4
2.422
13.116
0.31/0.37
0.043
0.109
1.095
C2/c (no. 15)
21.4581(9)
12.8902(6)
19.1995(7)
90
105.500(2)
90
5117.4(7)
8
2.047
10.023
0.42/0.47
0.039
0.080
,
a (A)
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
zcalc (g cm−3
)
v(Mo Ka) (mm−1
)
Transmission factors (min./max.)
R(Fo) a
Rw(Fo2) b
GOF
1.061
1.047
1.074
a R=ꢀꢁFoꢂ−ꢂFcꢁ/ꢀꢂFoꢂ with Fo2\2|(Fo2).
b Rw=[ꢀw(ꢂFo2ꢂ−ꢂFc2ꢂ)2/ꢀwꢂFo2ꢂ2]1/2
.
the squeeze option in PLATON [23]. An acetone
molecule from the reaction solvent was found co-crys-
tallized with 4 in the asymmetric unit during the course
of the structure analysis. It was included in the analysis
and refined satisfactorily. The largest remaining peaks
in the final difference Fouriers of 1–4 were 2.42, 2.36,
The preparation of [cis-Re2(m-O2CCH3)2Cl4(m-pyz)]n
(1) by the slow diffusion of the reagents in acetone was
also found to afford crystalline [cis-Re2(m-O2CCH3)2-
Cl4(pyz)]2(m-pyz) (2) when an excess of pyrazine was
used. The identities of these two complexes and [cis-
Re2(m-O2CCH3)2Cl4(m-LL)]n, where LL=4,4%-bpy (3)
or dppmO2 (4), were confirmed by X-ray crystallogra-
phy.
1.97 and 3.52 e A−3, respectively.
,
The important intramolecular bond distances and
angles for the structures of 1–4 are given in Tables
2–5.
The insolubility of these complexes in non-coordinat-
ing solvents limited their spectroscopic characteriza-
tions to the solid-state. The low frequency IR spectra
(Nujol mulls) of 1 and 3 (see Sections 2.2 and 2.3)
resembled closely that of the parent complex cis-Re2(m-
O2CCH3)2Cl4(H2O)2, which possessed bands at 365(m-
3. Results and discussion
s,sh), 356(s) and 337(m-w) cm−1
. The band at
3.1. The synthesis of complexes of the type
[cis-Re2(v-O2CCH3)2Cl4(v-LL)]n (LL=pyz, 4,4%-bpy
or dppmO2)
approximately 350 cm−1 in these spectra is assigned to
Table 2
,
Important bond distances (A) and angles (°) for the complex [cis-
Re2(m-O2CCH3)2Cl4(m-pyz)]n (1) a
The substitutional lability of the axial water ligands
in the quadruply bonded complex cis-Re2(O2CCH3)2-
Cl4(H2O)2 was utilized to synthesize new, one-dimen-
sional polymers containing isolated metal–metal mul-
tiple bonds. Three bidentate ligands, pyrazine,
4,4%-bipyridine and methylenebis(diphenylphosphine
oxide), were used to displace the weakly bound axial
ligands to form long-range linkage of dirhenium units
as shown in Eq. (1).
ReꢀRe%
ReꢀCl(1)
ReꢀCl(2)
2.2358(8)
2.304(3)
2.314(3)
ReꢀN(51)
ReꢀO(3)
ReꢀO(4)
2.528(10)
2.049(7)
2.026(8)
O(4)ꢀReꢀO(3)
O(4)ꢀReꢀRe%
O(3)ꢀReꢀRe%
O(4)ꢀReꢀCl(1)
O(3)ꢀReꢀCl(1)
Re%ꢀReꢀCl(1)
O(4)ꢀReꢀCl(2)
O(3)ꢀReꢀCl(2)
89.2(3)
89.7(2)
89.8(2)
Re%ꢀReꢀCl(2)
104.15(8)
91.52(12)
78.4(3)
78.9(3)
163.6(2)
87.4(2)
Cl(1)ꢀReꢀCl(2)
O(4)ꢀReꢀN(51)
O(3)ꢀReꢀN(51)
Re%ꢀReꢀN(51)
Cl(1)ꢀReꢀN(51)
Cl(2)ꢀReꢀN(51)
87.7(3)
166.3(2)
103.51(8)
165.9(2)
88.2(3)
87.5(2)
cis-Re2(m-O2CCH3)2Cl4(H2O)2+LL
“[cis-Re2(m-O2CCH3)2Cl4(m-LL)]n+2H2O
(LL=pyz, 4,4%-bpy, dppmO2)
(1)
a Numbers in parentheses are e.s.d.s in the least significant digits.
The unlabeled Re atom in Fig. 1 is denoted as Re% in this table.

508
Y. Ding et al. / Inorganica Chimica Acta 300–302 (2000) 505–511
Table 3
Table 4
,
,
Important bond distances (A) and angles (°) for the complex [cis-
Important bond distances (A) and angles (°) for the complex [cis-
Re2(m-O2CCH3)2Cl4(pyz)]2(m-pyz) (2) a
Re2(m-O2CCH3)2Cl4(m-4,4%-bpy)]n (3) a
Re(1)ꢀRe(2)
Re(1)ꢀCl(11)
Re(1)ꢀCl(12)
Re(1)ꢀO(11)
Re(1)ꢀO(12)
Re(1)ꢀN(101)
2.240(2)
2.315(4)
2.314(4)
2.035(9)
2.055(9)
2.541(12)
Re(2)ꢀCl(21)
Re(2)ꢀCl(22)
Re(2)ꢀO(21)
Re(2)ꢀO(22)
Re(2)ꢀN(201)
2.307(4)
2.314(4)
2.027(9)
2.035(9)
2.436(12)
Re(1)ꢀRe(2)
Re(1)ꢀCl(11)
Re(1)ꢀCl(12)
Re(1)ꢀO(1)
Re(1)ꢀO(3)
Re(1)ꢀN(11)
2.2512(4) Re(2)ꢀCl(21)
2.311(2)
2.316(2)
2.045(6)
2.046(6)
2.456(7)
2.309(2)
2.315(2)
2.037(6)
2.053(5)
2.464(6)
Re(2)ꢀCl(22)
Re(2)ꢀO(2)
Re(2)ꢀO(4)
Re(2)ꢀN(21)
O(11)ꢀRe(fl1)ꢀO(12) 88.1(4)
O(21)ꢀRe(2)ꢀO(22)
O(21)ꢀRe(2)ꢀRe(1)
O(22)ꢀRe(2)ꢀRe(1)
O(21)ꢀRe(2)ꢀCl(21)
O(22)ꢀRe(2)ꢀCl(21)
88.6(4)
89.9(3)
90.3(3)
O(1)ꢀRe(1)ꢀO(3)
O(1)ꢀRe(1)ꢀRe(2)
O(3)ꢀRe(1)ꢀRe(2)
O(1)ꢀRe(1)ꢀCl(11)
O(3)ꢀRe(1)ꢀCl(11)
Re(2)ꢀRe(1)ꢀCl(11) 102.78(5) Re(1)ꢀRe(2)ꢀCl(21)
O(1)ꢀRe(1)ꢀCl(12)
O(3)ꢀRe(1)ꢀCl(12)
87.5(2)
O(2)ꢀRe(2)ꢀO(4)
88.4(2)
88.91(14)
89.55(14)
89.37(18)
166.46(15)
103.77(6)
167.23(15)
88.86(17)
103.54(5)
90.38(8)
78.6(2)
O(11)ꢀRe(1)ꢀRe(2)
O(12)ꢀRe(1)ꢀRe(2)
89.1(3)
89.0(3)
90.07(14) O(2)ꢀRe(2)ꢀRe(1)
89.40(13) O(4)ꢀRe(2)ꢀRe(1)
90.14(16) O(2)ꢀRe(2)ꢀCl(21)
167.60(15) O(4)ꢀRe(2)ꢀCl(21)
O(11)ꢀRe(1)ꢀCl(12) 166.7(3)
O(12)ꢀRe(1)ꢀCl(12) 89.4(3)
Re(2)ꢀRe(1)ꢀCl(12) 103.92(11) Re(1)ꢀRe(2)ꢀCl(21)
86.8(3)
164.4(3)
104.60(10)
165.0(3)
88.9(3)
104.84(10)
91.73(15)
75.8(4)
O(11)ꢀRe(1)ꢀCl(11)
88.3(3)
O(21)ꢀRe(2)ꢀCl(22)
O(22)ꢀRe(2)ꢀCl(22)
165.29(15) O(2)ꢀRe(2)ꢀCl(22)
86.86(17) O(4)ꢀRe(2)ꢀCl(22)
O(12)ꢀRe(1)ꢀCl(11) 166.5(3)
Re(2)ꢀRe(1)ꢀCl(11) 103.93(10) Re(1)ꢀRe(2)ꢀCl(22)
Cl(12)ꢀRe(1)ꢀCl(11) 91.20(16) Cl(21)ꢀRe(2)ꢀCl(22)
O(11)ꢀRe(1)ꢀN(101) 78.6(4)
O(12)ꢀRe(1)ꢀN(101) 78.0(4)
Re(2)ꢀRe(1)ꢀN(101) 162.3(3)
Cl(12)ꢀRe(1)ꢀN(101) 88.1(3)
Cl(11)ꢀRe(1)ꢀN(101) 88.5(3)
Re(2)ꢀRe(1)ꢀCl(12) 103.44(5) Re(1)ꢀRe(2)ꢀCl(22)
Cl(11)ꢀRe(1)ꢀCl(12)
O(1)ꢀRe(1)ꢀN(11)
O(3)ꢀRe(1)ꢀN(11)
Re(2)ꢀRe(1)ꢀN(11)
Cl(11)ꢀRe(1)ꢀN(11)
Cl(12)ꢀRe(1)ꢀN(11)
92.47(8) Cl(21)ꢀRe(2)ꢀCl(22)
80.4(2)
80.3(2)
166.21(17) Re(1)ꢀRe(2)ꢀN(21)
87.27(16) Cl(21)ꢀRe(2)ꢀN(21)
85.29(17) Cl(22)ꢀRe(2)ꢀN(21)
O(21)ꢀRe(2)ꢀN(201)
O(22)ꢀRe(2)ꢀN(201)
Re(1)ꢀRe(2)ꢀN(201) 160.9(3)
Cl(21)ꢀRe(2)ꢀN(201) 87.5(3)
Cl(22)ꢀRe(2)ꢀN(201) 89.2(3)
O(2)ꢀRe(2)ꢀN(21)
O(4)ꢀRe(2)ꢀN(21)
77.0(4)
79.0(2)
163.2(2)
87.47(19)
88.68(18)
a Numbers in parenthesis are e.s.d.s in the least significant digits.
a Numbers in parentheses are e.s.d.s in the least significant digits.
w(ReꢀCl). In the case of the crystalline samples of 4, the
w(PꢁO) mode is at 1171(vs) cm−1, lower than that of the
free ligand [24].
are much larger (range 102.8–104.8°). This ‘bending
back’ of the chloro ligands away from the ReꢀRe bond
and towards the axial sites leads to a marked non-linear-
ity of the ReꢀReꢀL(axial) units; the angles are 163.6(2)°
for (1), 162.3(3) and 160.9(3)° for 2, 166.21(17) and
3.2. The structural characterization of complexes 1–4
The four new complexes isolated in the present study
have all been characterized by X-ray crystallography.
The ORTEP representations [25] of these structures are
shown in Figs. 1–4, while the most important structural
parameters are given in Tables 2–5. Compounds 1, 3 and
4 are infinite polymers, while 2 consists of two cis-
Re2(O2CCH3)2Cl4(pyz) units, each containing a termi-
nally bound 1,4-pyrazine ligand, which are linked by a
bridging pyrazine ligand. The basic structures of these
four complexes resemble those of cis-Re2(m-O2CCH3)2-
Cl4(H2O)2 and other complexes with monodentate lig-
ands [15], so the substitution of the two water molecules
proceeds with retention of stereochemistry. Note that
loss of the axial ligands is known to proceed with a
change in structure to trans-Re2(m-O2CCH3)2Cl4 [26,27],
and no adducts of [Re2(m-O2CCH3)2Cl4] are yet known
with a trans arrangement of m-O2CR ligands.
Table 5
,
Important bond distances (A) and angles (°) for the complex [cis-
Re2(m-O2CCH3)2Cl4(m-dppmO2)]n (4) a
Re(1)ꢀRe(2)
Re(1)ꢀCl(11)
Re(1)ꢀCl(12)
Re(1)ꢀO(11)
Re(1)ꢀO(12)
Re(1)ꢀO(1)
2.2438(4)
2.318(2)
2.307(2)
2.061(6)
2.060(7)
2.331(6)
2.307(2)
Re(2)ꢀCl(22)
Re(2)ꢀO(21)
Re(2)ꢀO(22)
Re(2)ꢀO(2)
P(1)ꢀO(1)
2.311(2)
2.063(6)
2.045(7)
2.257(6)
1.488(6)
1.486(6)
P(2)ꢀO(2)
Re(2)ꢀCl(21)
O(12)ꢀRe(1)ꢀO(11)
O(12)ꢀRe(1)ꢀRe(2)
O(11)ꢀRe(1)ꢀRe(2)
O(12)ꢀRe(1)ꢀCl(12)
O(11)ꢀRe(1)ꢀCl(12) 167.21(17) Re(1)ꢀRe(2)ꢀO(2)
Re(2)ꢀRe(1)ꢀCl(12) 102.67(5)
O(12)ꢀRe(1)ꢀCl(11) 165.34(17) O(21)ꢀRe(2)ꢀCl(21) 89.2(2)
O(11)ꢀRe(1)ꢀCl(11) 89.2(2) Re(1)ꢀRe(2)ꢀCl(21) 103.44(6)
Re(2)ꢀRe(1)ꢀCl(11) 104.51(6) O(2)ꢀRe(2)ꢀCl(21) 87.04(19)
Cl(12)ꢀRe(1)ꢀCl(11)
O(12)ꢀRe(1)ꢀO(1)
O(11)ꢀRe(1)ꢀO(1)
Re(2)ꢀRe(1)ꢀO(1)
Cl(12)ꢀRe(1)ꢀO(1)
Cl(11)ꢀRe(1)ꢀO(1)
O(22)ꢀRe(2)ꢀO(21)
86.7(3)
O(22)ꢀRe(2)ꢀRe(1)
89.93(16)
89.85(15)
79.0(2)
77.4(2)
163.52(19)
89.54(15) O(21)ꢀRe(2)ꢀRe(1)
89.44(15) O(22)ꢀRe(2)ꢀO(2)
89.20(19) O(21)ꢀRe(2)ꢀO(2)
O(22)ꢀRe(2)ꢀCl(21) 165.97(17)
The ReꢀRe distances in compounds 1–4 occur in the
91.72(9)
77.1(2)
78.9(2)
O(22)ꢀRe(2)ꢀCl(22) 88.8(2)
O(21)ꢀRe(2)ꢀCl(22) 166.12(17)
Re(1)ꢀRe(2)ꢀCl(22) 103.21(6)
,
range 2.236–2.251 A and are characteristic of a ReꢀRe
quadruple bond [15]. By way of comparison, the distance
162.63(17) O(2)ꢀRe(2)ꢀCl(22)
88.36(17) Cl(21)ꢀRe(2)ꢀCl(22) 92.23(9)
88.32(18) P(1)ꢀO(1)ꢀRe(1)
86.6(3) P(2)ꢀO(2)ꢀRe(2)
88.84(18)
in the precursor complex cis-Re2(m-O2CCH3)2Cl4(H2O)2
,
is 2.224(5) A [28]. The ReꢀO and ReꢀCl distances are
166.3(4)
165.9(5)
similar for all four structures (Tables 2–5). While the
ReꢀReꢀO angles are close to 90° (range 88.9–90.3°), the
corresponding angles involving the terminal Cl ligands
a Numbers in parentheses are e.s.d.s in the least significant digits.

Y. Ding et al. / Inorganica Chimica Acta 300–302 (2000) 505–511
509
Fig. 1. ORTEP [25] representation of the structure of the polymeric complex [cis-Re2(m-O2CCH3)2Cl4(m-pyz)]n (1) showing the linkage of the
dirhenium units. The thermal ellipsoids are drawn at the 50% probability level. The unlabeled Re atom is labeled as Re% in Table 2.
Fig. 2. ORTEP [25] representation of the structure of the complex [cis-Re2(m-O2CCH3)2Cl4(pyz)]2(m-pyz) (2), which possesses both terminal and
bridging pyrazine ligands. The thermal ellipsoids are drawn at the 50% probability level.
Fig. 3. ORTEP [25] representation of the structure of the polymeric complex [cis-Re2(m-O2CCH3)2Cl4(m-4,4%-bpy)]n (3) showing the linkage of the
dirhenium units through two types of 4,4%-bipyridine ligands (planar and twisted). The thermal ellipsoids are drawn at the 50% probability level.
Fig. 4. ORTEP [25] representation of the structure of the polymeric complex [cis-Re2(m-O2CCH3)2Cl4(m-dppmO2)]n (4) showing the linkage of the
dirhenium units through bridging dppmO2 ligands. The thermal ellipsoids are drawn at the 50% probability level except for the phenyl group
atoms of the dppmO2 ligands, which are circles of arbitrary radius.

510
Y. Ding et al. / Inorganica Chimica Acta 300–302 (2000) 505–511
163.2(2)° for 3, and 162.63(17) and 163.52(19)° for 4. This
effect is presumably steric in origin.
isotropic thermal parameters bond distances and bond
angles for compounds 1–4 are available on request from
author R.A.W.
The axial ReꢀL distances are identical, or nearly so,
within each of the complexes, although the difference is
greatest in complex 2. This is not surprising given that
each dirhenium unit is bound to a bridging and a terminal
pyrazine ligand. Interestingly, it is the bridging pyrazine
ligand that gives the shortest ReꢀN bond (2.436(12) vs.
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4. Supplementary material
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