Substitution reactions of rhenium-chloride bonds in [Re2(DMAA)4Cl2], (DMAA = 2′,6′-dimethylacetanilido); synthesis and characterisation of [Re2(DMAA)4X2] (X = NCO, NCS, N3) and [Re2(DMAA)4Ln][SbF6]2 (n = 2, L = pyridine; n = 1, L = 4,4′-bipyridine)

Article abstract of DOI:10.1016/S0277-5387(03)00072-X

Substitution of chloride ligands in [Re₂(DMAA)₄Cl₂] (1), (DMAA = 2′,6′-dimethylacetanilido) in a mixture of dichloromethane - methanol affords [Re₂(DMAA)₄X₂] complexes with X = [N₃]^-, 2·CH₂Cl₂, [SCN]^-, 3, or [NCO]^-, 4·CH₂Cl₂ in yields of 84, 72 and 76%, respectively. The reaction of 1 and Ag[SbF₆] in air affords [Re₂(DMAA)₄(H₂O)₂] [SbF₆]₂·H₂O, 5·H₂O (71%). The aquo ligands in 5 can be displaced by pyridine or 4,4′-bipyridine to produce [Re₂(DMAA)₄(pyridine)₂][SbF₆] ₂ (6) (68%), and [Re₂(DMAA)₄(4,4′-bipyridine)][SbF₆] ₂·CH₂Cl₂ (7) (42%). All new compounds were characterised with C, H and N chemical analysis, FTIR and, except for 7, ¹H and ¹³C NMR spectroscopies. Additionally, single crystal X-ray crystallography was used to establish the molecular structures of 2·CH₂Cl₂ and 3·0.83CHCl₃. Principal distances and angles are: rhenium-rhenium distances in 2 and 3 of 2.2477(3) and 2.2324(5) A?, respectively; rhenium to azido nitrogen distances in 2 of 2.158(5) and 2.166(6) A?, and rhenium to isothiocyanato nitrogen distances in 3 of 2.208(8) and 2.210(6) A?; essentially linear azido and isothiocyanato ligands with N-N-N angles of 178.4(10) and 179.1(9)° and N-C-S angles of 177.9(10) and 179.7(9)°, and Re-N-X angles (X = N for 2 and C for 3) of the rhenium pseudo-halide bonds of 139.8(6) and 128.6(5)° in 2 and 151.9(7) and 169.1(9)° in 3, respectively.

Full text of DOI:10.1016/S0277-5387(03)00072-X

Polyhedron 22 (2003) 1281ꢀ1287
/
www.elsevier.com/locate/poly
Substitution reactions of rheniumꢀ
[Re2(DMAA)4Cl2], (DMAAꢁ2?,6?-dimethylacetanilido); synthesis
and characterisation of [Re2(DMAA)4X2] (XꢁNCO, NCS, N3) and
[Re2(DMAA)4Ln][SbF6]2 (nꢁ2, Lꢁpyridine; nꢁ1, Lꢁ4,4?-
bipyridine)
/
chloride bonds in
/
/
/
/
/
/
Donocadh P. Lydon a,*, Trevor R. Spalding a, John F. Gallagher b
a Department of Chemistry, University College Cork, National University of Ireland, Cork, Ireland
b School of Chemical Sciences, Dublin City University, Dublin 9, Ireland
Received 4 December 2002; accepted 6 February 2003
Abstract
Substitution of chloride ligands in [Re2(DMAA)4Cl2] (1), (DMAAꢁ
methanol affords [Re2(DMAA)4X2] complexes with Xꢁ
[N3]ꢂ, 2×CH2Cl2, [SCN]ꢂ, 3, or [NCO]ꢂ, 4×
76%, respectively. The reaction of 1 and Ag[SbF6] in air affords [Re2(DMAA)4(H2O)2][SbF6]2×H2O, 5×
in 5 can be displaced by pyridine or 4,4?-bipyridine to produce [Re2(DMAA)4(pyridine)2][SbF6]2 (6) (68%), and [Re2(DMAA)4(4,4?-
bipyridine)][SbF6]2×CH2Cl2 (7) (42%). All new compounds were characterised with C, H and N chemical analysis, FTIR and, except
for 7, 1H and 13C NMR spectroscopies. Additionally, single crystal X-ray crystallography was used to establish the molecular
structures of 2×CH2Cl2 and 3×0.83CHCl3. Principal distances and angles are: rheniumꢀrhenium distances in 2 and 3 of 2.2477(3)
and 2.2324(5) A, respectively; rhenium to azido nitrogen distances in 2 of 2.158(5) and 2.166(6) A, and rhenium to isothiocyanato
/
2?,6?-dimethylacetanilido) in a mixture of dichloromethaneꢀ
CH2Cl2 in yields of 84, 72 and
H2O (71%). The aquo ligands
/
/
/
/
/
/
/
/
/
/
˚
˚
˚
nitrogen distances in 3 of 2.208(8) and 2.210(6) A; essentially linear azido and isothiocyanato ligands with NÃ
/
NÃ
/N angles of
178.4(10) and 179.1(9)8 and NÃCÃS angles of 177.9(10) and 179.7(9)8, and ReÃNÃX angles (XꢁN for 2 and C for 3) of the
/
/
/
/
/
rhenium pseudo-halide bonds of 139.8(6) and 128.6(5)8 in 2 and 151.9(7) and 169.1(9)8 in 3, respectively.
# 2003 Elsevier Science Ltd. All rights reserved.
Keywords: Synthesis; Dirhenium; Pseudo-halides; Crystal structures; Di-cation; Amidato
1. Introduction
such systems with dirhodium [1] and diruthenium [2]
cores have been prepared and polymers of the general
formula [Re2(RCOO)2Cl4(L)]n, where RꢁMe or Et,
Lꢁ4,4?-bipyridine or pyrazine have also been reported
[3].
Dimers of the form [Re2(m-lig)4X2] (Scheme 1(a)
/
where ligꢁ
/
a bidentate bridging ligand, Xꢁ
/
terminal
/
ligand) which contain rheniumꢀ
/
rhenium multiply
bonded cores are of interest as precursors to the
formation of conducting molecular wires provided that
Dirhenium complexes with several types of bridging
ligands are known including those with bridging car-
boxylato ligands, [Re2(RCOO)4Cl2] [4,5]. The carbox-
ylato compounds have been studied extensively since the
the linear XÃ
/
ReÃ
/
ReÃ/X sequence can be incorporated
into a conjugated system, Scheme 1(b). Examples of
series of compounds with RꢁMe, Et, n-Bu, iso-Bu, n-
/
C7H15 was first described [5]. Complexes with other
organic-based bidentate bridging ligands such as ami-
dato, [6] 2-oxypyridinato, [7] amidinato [8] and adenato
* Corresponding author. Tel.: ꢃ
427-4797.
E-mail address: d.lydon@ucc.ie (D.P. Lydon).
/
353-21-490-2911; fax: ꢃ353-21-
/
0277-5387/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0277-5387(03)00072-X

1282
D.P. Lydon et al. / Polyhedron 22 (2003) 1281ꢀ1287
/
Scheme 1. (a) Dirhenium supported by bidentate bridging ligands; (b) dirhenium units joined by linkage groups.
[9] have also been reported but, in general, there has
been less work on these species.
2. Results and discussion
Neutral pseudo-halide complexes [Re2(DMAA)4X2]
where Xꢁ
[N3]ꢂ (2), [SCN]ꢂ (3) or [NCO]ꢂ (4) were
prepared from the reactions between [Re2(DMAA)4Cl2]
and the pseudo-halide salts Na[N3], [NH4]SCN or
K[NCO], respectively. The reactions were carried out
Some studies of [Re2(m-lig)4Cl2] dimers concerning the
reactivity of the rhenium chloride bonds have been
published. Substitutions of the chloride by iodide,
thiocyanate and aquo ligands in [Re2(RCOO)4Cl2]
have been reported [5,10]. Furthermore, the reaction
/
between [Re2Cl8]2ꢂ and mixtures of H2SO4ꢀ[SO4]2ꢂ
/
in mixtures of dichloromethaneꢀ
heated at reflux temperature for 16 h. The products
isolated were 2×CH2Cl2, 3 and 4×CH2Cl2 in yields of 77,
/methanol and were
affords [11] the species [Re2(SO4)4]2ꢂ while the octa-
methyl complex [Re2(Me)8]2ꢂ is formed from
[Re2(PhCOO)4Cl2] by reaction with methyllithium [12].
/
/
72 and 71%, respectively, Table 1. Complexes 2 and 4
Kuhn et al. have replaced the chloride ligands in
¨
were red and 3 was orange.
[Re2(ButCOO)4Cl2] by the moiety [(CO)5M(CN)]ꢂ
The IR spectrum of the diazido complex, [Re2-
(DMAA)4(N3)2] (2) shows very strong bands at 2064
and 2042 cmꢂ1 which are assigned to the n(N3)
stretches. The spectrum of complex 3 shows a very
strong n(CN) band at 2015 cmꢂ1 which, since it is closer
to 2000 than 2100 cmꢂ1, is indicative of an isothiocya-
(where Mꢁ
that the chloride ligands in the amidinato complex
[Re2(DFM)4Cl2] (where HDFMꢁdi-p-toylformami-
/Cr, Mo, W) [13]. It has also been reported
/
dine) have been replaced by methoxy groups [14].
We have used the complex [Re2(DMAA)4Cl2] (1)
(where HDMAAꢁ
/
2?,6?-dimethylacetanilide) to prepare
nato ReÃ
/
NCS bonded species [15]. The band at 801
a number of compounds by substituting chloride ligands
with the pseudo-halide species [N3]ꢂ, [SCN]ꢂ and
[NCO]ꢂ. In addition, we report the synthesis of the
dicationic dirhenium complexes [Re2(DMAA)4-
(H2O)2][SbF6]2, [Re2(DMAA)4(pyridine)2][SbF6]2 and
cmꢂ1 in the spectrum of 3 can be assigned as the n(CS)
vibration. Complex 4 shows very strong bands of almost
equal intensity at 2183 and 2168 cmꢂ1 which are
assigned to the n(CN) stretches of rhenium-bonded
Ã
/
NCO or Ã
/OCN groups.
1
{[Re2(DMAA)4L?][SbF6]2}n where L?ꢁ
/
4,4?-bipyridine.
The general features of the H NMR spectra of 2ꢀ4
/
The [Re2(DMAA)4Cl2] complex was chosen for this
work partly because Cotton et al. [6] reported it to be a
single isomer with virtual D2d symmetry in the central
are similar to those reported for the chloride complex
[Re2(DMAA)4Cl2] (1) suggesting that the complexes
have similar structures in solution, Table 2. However,
whereas compounds 2 and 3 are present as single
[Re2(NÃ
/
CÃ
/
O)4] part of the molecule.
Table 1
Characterisation of compounds 2ꢀ
/7
Complex (ligꢁ
/
DMAA)
M.p. (8C)
Yield (%)
IR
Analysis (theoretical values)
C
H
N
Re2(lig)4{N3}2×
Re2(lig)4{SCN}2
Re2(lig)4{NCO}2×
[Re2(lig)4(H2O)2][SbF6]2×
[Re2(lig)4(py2)][SbF6]2
/
CH2Cl2
288 a
320 a
196 a
255 a
264 a
270 a
77
72
71
71
68
42
2064 s, 2042 vs, 1326 m
2016 vs, 801 m
2183 vs, 2168 vs
659 vs
41.5 (41.4)
44.7 (44.4)
43.6 (43.4)
30.5 (31.1)
36.3 (36.4)
34.6 (34.3)
4.3 (4.2)
4.6 (4.3)
4.5 (4.2)
3.5 (3.5)
3.8 (3.4)
3.3 (3.3)
11.6 (11.8)
7.0 (7.4)
6.8 (7.1)
3.5 (3.6)
4.9 (4.9)
4.7 (4.6)
/
CH2Cl2
/
H2Ob
1604 m, 659 vs
659 vs
[Re2(lig)4bipy][SbF6]2×
/
CH2Cl2
a
Melting with decomposition.
b
The compound [Re2(lig)4(H2O)2][SbF6]2×H2O analysed 0% for chlorine.
/

D.P. Lydon et al. / Polyhedron 22 (2003) 1281ꢀ
/1287
1283
compared with the sulfur atom. Whereas, for complex 4,
there is less to choose between the N and O donor sites
of NCO on both electronic and size grounds.
The yellow dicationic dirhenium complex [Re2-
(DMAA)4(H2O)2][SbF6]2×
/
H2O, 5×
/
H2O was formed by
the addition in air of silver hexafluoroantimonate to a
dichloromethane solution of [Re2(DMAA)4Cl2] at room
temperature and subsequent work-up in air. The yellow
product was isolated in 71% yield, Table 1. The IR
spectrum of 5 confirmed the presence of the hexafluor-
oantimonate anion with a single very strong band at 659
Scheme 2. dirhenium complexes labelling 1H and 13C NMR nuclei.
isomers, complex 4 shows three sets of resonances due to
three isomers in solution. One set of resonances is twice
the intensity of the other two. This may be rationalised
on the basis that complex 4 exists as a mixture of three
isomers in solution i.e. the (OCNRe)2, (OCN)Re-
Re(OCN) and (NCORe)2 bonded species with a statis-
tical distribution of 1:2:1, respectively. This suggestion is
supported by the 13C NMR spectrum of 4, Table 2, but,
since there appears to be accidental overlap of the
resonances for the C(3)/OCN sites in the isomer
mixture, the signals at 145.9 and 145.3 ppm can only
be assigned tentatively. The 13C NMR spectrum of 3
shows a resonance at 151.2 ppm, which is attributed to
the carbon atom in the SCN ligand. The observation of
a single isomer for complex 3 is in contrast to the three
isomers observed for complex 4 and this may be a
consequence of both the preference of rhenium for the
distinctly ‘harder’ donor properties of N compared with
S in 4 and the smaller size of the nitrogen donor atom
1
cmꢂ1. H and 13C NMR spectra were similar to those
observed for complexes 1ꢀ3, Table 2. Unfortunately
/
crystals of 5 suitable for an X-ray structural determina-
tion, could not be obtained.
Two other yellow dicationic dirhenium complexes
were prepared from complex 5, i.e. [Re2(DMAA)4(pyr-
idine)2][SbF6]2 (6) and {[Re2(DMAA)4L?][SbF6]2}n, (7)
(L?ꢁ4,4?-bipyridine). Reaction in dichloromethane so-
/
lution at room temperature between 5 and 2 equiv. of
pyridine afforded the bispyridine dicationic complex
[Re2(DMAA)4(pyridine)2][SbF6]2 (6) in 68% yield. The
IR spectrum of 6 confirms the presence of the hexa-
fluoroantimonate anion with a very strong band at 659
1
cmꢂ1. The H NMR spectrum exhibits three multiplet
signals between 8.08 and 6.98 ppm that can be attributed
to the pyridine ligand. The aromatic protons on the
bridging DMAA ligand occur at 6.78 ppm, and the
aliphatic protons at 3.36 and 2.32 ppm. A similar
Table 2
1H and 13C NMR spectroscopic data for compounds 1ꢀ
6
/
Nucleus
Signal intensity
Compound
1
2
3
4 a
5 b
6 c
H(5,6) d
H(1)
H(7)
C(2)
1H
1H
2H
7.04
2.86
2.22
185.2
7.05
2.85
2.23
184.3
7.04
2.92
7.04
2.86
7.16
3.01
2.21
187.6
6.78
3.37
2.32
188.8
2.23
184.7
151.2
2.21
184.7
145.3 f
C(8) e
C(9)
C(3)
147.7
142.5
141.2
133.1
130.5
129.4
126.6
21.1
147.4
145.8
144.8
145.9 f
140.8
C(11)
C(4)
C(5)
132.5
129.1
127.3
131.8
129.3
127.0
131.8
129.3
127.6
131.9
129.1
127.2
132.9
130.5
129.4
C(6)
C(10)
C(1)
C(7)
21.8
18.9
21.0
18.4
21.1
18.4
21.2
18.4
21.6
18.4
18.8
a
Less abundant isomers of NCO had the following 13C NMR signals C2 185.3, 185.0; C4 131.9, 131.7; C5 130.0, 129.3; C6 128.1, 127.6; C1 21.4,
21.0; C7 18.6, 18.4.
b
In CD3CN; broad signal centred at 2.27 ppm due to H2O.
In acetone-d6; resonances for pyridine ligands: 8.08 2H m (J3 4.8 Hz, J4 2.3 Hz) ortho, 7.53 1H m (J3 7.5 Hz, J4 1.5 Hz) para, 6.98 2H m (J3 6.3
c
Hz, J4 1.3 Hz) meta. Relative intensities of proton signals for two pyridine: four DMAA was 10:48. C(9), C(10) and C(11) refer to carbon atoms
ortho, meta and para to the heteroatom on pyridine, respectively.
d
See Scheme 2 above for positions of nuclei.
C(8), carbon nucleus on pseudo-halide group.
Tentative assignments see text.
e
f

1284
D.P. Lydon et al. / Polyhedron 22 (2003) 1281ꢀ1287
/
reaction to that affording 6, i.e. reaction between 5 and
either one or two equiv. of 4,4?-bipyridine, produced the
insoluble, possibly polymeric, complex {[Re2-
(DMAA)4L?][SbF6]2}n (7). The IR spectrum of 7 was
very similar to that of 6 and was characterised by bands
due to the organic ligand and the hexafluoroantimonate
anion.
3. X-ray crystallographic studies of the structures of 2
and 3
In order to establish the structural details of these
compounds, single crystal structure studies were under-
taken. Suitable crystals were obtained by evaporation of
dichloromethaneꢀether solution of compound 2 and a
/
Fig. 2. View of [Re2(DMAA)4(SCN)2], with numbering scheme.
chloroform solution of 3. Data collection and structure
refinement details are given in the Section 4 below. The
molecular structures of 2 and 3 are depicted in Figs. 1
and 2 and important distance and angle data are given
in Tables 3 and 4, respectively.
Table 3
Selected bond distances (A) and angles (8) in [Re2(DMAA)4(N3)2] (2)
˚
Atom labels
Atom labels
Compound 2 appears to be the first dirhenium(III)
azide-containing structure to be studied and compound
3 is the first dirhenium(III) isothiocyanate with a linear
Bond distances
Re(1)Ã
Re(1)Ã
Re(1)Ã
Re(1)Ã
Re(1)Ã
Re(1)Ã
N(1A)Ã
N(1B)ÃN(2B)
/
Re(2)
O(1A)
O(1C)
N(41)
N(21)
N(1A)
2.2477(3) Re(2)Ã
/
O(1D)
O(1B)
N(31)
N(11)
N(1B)
1.987(4)
2.037(4)
2.098(5)
2.104(5)
2.166(6)
1.145(9)
1.136(10)
/
2.001(4)
2.025(4)
2.111(4)
2.070(5)
2.158(5)
1.185(8)
1.214(9)
Re(2)Ã
Re(2)Ã
Re(2)Ã
Re(2)Ã
N(2A)Ã
N(2B)ÃN(3B)
/
NÃ
/
ReÃ
/
ReÃ
/
N grouping. In general, each rhenium atom
/
/
is octahedrally coordinated being bonded to two trans-
located nitrogen and two trans-located oxygen atoms
from the bridging DMAA ligands, a nitrogen atom from
the pseudo-halide and the other rhenium atom.
Although the mean values of the rhenium to nitrogen
distances in 2 and 3 for nitrogen in the bridging DMAA
/
/
/
/
/
/N(3A)
/N(2A)
/
/
Bond angles
O(1A)ÃRe(1)Ã
O(1C)ÃRe(1)Ã
N(21)ÃRe(1)Ã
N(41)ÃRe(1)Ã
O(1A)ÃRe(1)Ã
O(1C)ÃRe(1)Ã
N(21)ÃRe(1)Ã
N(41)ÃRe(1)Ã
N(1A)ÃRe(1)Ã
N(2A)ÃN(1A)Ã
N(3A)ÃN(2A)Ã
O(1A)ÃC(1A)ÃN(11) 119.6(5)
O(1C)ÃC(1C)ÃN(31) 120.6(6)
/
/
N(1A)
90.7(2)
87.1(2)
92.2(2)
89.0(2)
O(1D)Ã
O(1B)ÃRe(2)Ã
N(31)ÃRe(2)Ã
N(11)ÃRe(2)Ã
Re(2)Ã
89.39(12) O(1D)ÃRe(2)Ã
90.92(13) N(31)ÃRe(2)Ã
87.83(13) N(11)ÃRe(2)Ã
175.31(16) N(1B)ÃRe(2)Ã
Re(1) 139.8(6) N(1B)Ã
N(2B)Ã
N(1A) 178.4(10) N(3B)ÃN(2B)Ã
O(1B)ÃC(1B)Ã
O(1D)ÃC(1D)Ã
/
Re(2)Ã
/
N(1B) 96.95(19)
˚
ligands are similar at 2.096(5) and 2.096(6) A, respec-
tively, there are significant differences within each set of
/
/
N(1A)
/
/
N(1B)
81.86(19)
91.2(2)
/
/N(1A)
/
/
N(1B)
N(1B)
/
/N(1A)
/
/
90.1(2)
/
/Re(2)
92.70(11) O(1B)Ã
/
/
Re(1)
Re(1)
89.18(11)
92.04(11)
90.77(14)
87.81(13)
/
/
Re(2)
/
/
/
/Re(2)
/
/
Re(1)
Re(1)
/
/Re(2)
/
/
/
/
Re(2)
/
/
Re(1) 170.79(16)
/
/
/
/
Re(2) 128.6(5)
/
/
/
/
N(1B) 179.1(9)
/
/
/
/
N(21) 119.7(5)
/
/
/
/
N(41) 119.9
ReÃ
Re(2)Ã
N(41) distance is 2.130(6) A. Significant differences also
exist in the ReÃO(amidato) distances in 2 but this is not
/N(amidato) distances in each molecule, e.g. in 3 the
˚
/
N(21) distance is 2.079(6) A whereas the Re(2)Ã
/
˚
/
observed in the molecular structure of 3. The mean ReÃ
/
˚
O values are 2.012(4) and 2.013(5) A for 2 and 3,
respectively.
In 2, the rhenium to azido nitrogen distances ReÃ
/
N(1), Table 3, are slightly longer at 2.158(5) and
˚
Fig. 1. View of [Re2(DMAA)4(N3)2], with numbering scheme.
2.166(6) A than the longest ReÃ
/
N(amidato) distance

D.P. Lydon et al. / Polyhedron 22 (2003) 1281ꢀ
/1287
1285
Table 4
Selected bond distances (A) and angles (8) in [Re2(DMAA)4(NCS)2] (3)
oxidation state. Of these, the only quadruply bonded
rhenium dimers are [Re2(NCS)8L2]2ꢂ with Lꢁ
acetone
8a or pyridine 8b ligands [18]. In both 8a and 8b there is
a linear XÃReÃReÃX sequence with X being either the
O atom of acetone or the N atom of pyridine and the
isothiocyanate ligands occupying the positions taken by
the amidato ligands in 3 [18]. Other rhenium compounds
of relevance in the Cambridge Crystallographic Data-
base were cis- and trans-[Re(NCS)(Cl2)(PMe2Ph)3] (9a)
˚
/
Atom labels
Atom labels
/
/
/
Bond distances
Re(1)Ã
Re(2)Ã
Re(2)Ã
Re(2)Ã
Re(2)Ã
Re(2)Ã
S(2)Ã
C(2)Ã
/
Re(2)
O(1A)
O(1C)
N(21)
N(41)
(N1)
2.2324(5) Re(1)Ã
/
O(1D)
O(1B)
N(31)
N(11)
N(2)
1.997(5)
2.021(5)
2.079(6)
2.094(6
/
2.008(5)
2.027(5)
2.079(6
Re(1)Ã
Re(1)Ã
Re(1)Ã
Re(1)Ã
S(1)Ã
C(1)Ã
/
/
/
/
/
/
2.130(6)
2.208(8)
1.623(9)
1.146(10)
/
2.210(6)
1.617(11)
1.095(12)
/
/
C(1)
N(1)
and
[Re(NCS)3(PEt2Ph)(Ph2PCH2CH2PPh2)]
Comparison of the ReÃNÃCÃ
those in the other compounds shows in general that (i)
the ReÃN bonds in 3 are significantly longer (mean
(9b),
respectively
[19]
and
mer-
/
C(2)
N(2)
/
(10)
[20].
/
/
/
/S distances in 3 with
Bond angles
O(1D)ÃRe(1)Ã
O(1B)ÃRe(1)ÃN(2)
N(31)ÃRe(1)Ã
N(11)ÃRe(1)Ã
O(1D)ÃRe(1)Ã
O(1B)ÃRe(1)ÃRe(2)
N(31)ÃRe(1)Ã
N(11)ÃRe(1)Ã
N(2)ÃRe(1)Ã
N(1)Ã
C(1)ÃN(1)Ã
O(1A)Ã
O(1B)ÃC(1B)Ã
/
/
N(2)
94.9(2)
82.7(2)
91.8(2)
88.9(2)
O(1A)Ã
O(1C)Ã
N(21)ÃRe(2)Ã
N(41)ÃRe(2)Ã
Re(2)Ã
Re(2)Ã
Re(2)Ã
Re(2)Ã
Re(2)Ã
/
Re(2)Ã
/
N(1)
N(1)
91.4(3)
87.1(3)
92.6(3)
/
/
/
/
Re(2)Ã
/
˚
˚
˚
2.209(8) A compared with a range of 1.992(8) A in 10ꢀ
/
/
/
N(2)
/
/N(1)
2.071(4) A in 9b), (ii) the NÃ
/
C distances are shorter
/
/
N(2)
/
/N(1)
88.3(3)
˚
(mean 1.121(12) A in 3, compared with a range of
/
/Re(2)
92.78(15) O(1A)Ã
89.60(14) O(1C)Ã
90.35(17) N(21)Ã
88.75(16) N(41)Ã
171.95(19) N(1)Ã
/
/
Re(1)
Re(1)
91.57(14)
90.01(14)
91.16(17)
87.98(17)
175.2(2)
179.7(9)
151.9(7)
/
/
/
/
˚
˚
1.09(1) A in 9aꢀ
/
1.18(2) A in 8a), and (iii) the CÃ
/
S
distances are longer (mean 1.620(11) A in 3, compared
/
/
Re(2)
/
/Re(1)
˚
/
/
Re(2)
/
/Re(1)
˚
˚
1.64(2) A in 9a).
with a range of 1.560(13) A in 8aꢀ
Overall this suggests that the bonding in 3 may be
Sdꢂ with the possibility
/
/
/
Re(2)
/
/Re(1)
/
C(1)Ã
/
S(1)
177.9(10) N(2)Ã
169.1(9)
/
C(2)Ã
N(2)Ã
O(1C)Ã
O(1D)Ã
/
S(2)
represented as ReÃ
/N
dꢃ Å
/
CÃ
/
/
/
Re(2)
C(2)Ã
/
/
Re(1)
/
C(1A)Ã
/N(11) 118.6(7)
/
C(1C)Ã
C(1D)Ã
/
N(31) 119.2(7)
N(41) 120.6(7)
that the sulfur atom is available for bonding to another
metal centre.
/
/
N(21) 119.8(7)
/
/
It is noteworthy that the ReÃ
quite different from 1208 and also different within the
molecule being 139.8(6) and 128.6(5)8. The ReÃNÃ
/
NÃ
/
N angles in 2 are
˚
of 2.111(4) A. The rheniumꢀ
/
azide moieties in 2 are
azide groups with the N(1)ÃN(2)
bonds slightly, but not significantly, shorter than the
N(2)ÃN(3) bonds.
The distances are 1.185(8) and 1.214(9) A, and
/
/N
typical of metalꢀ
/
/
angles in the Re(I) complex trans-[Re(N3)(N2)Ã
/
(Ph2PCH2CH2PPh2)2] [16] and the Re(V) complex
[ReN(N3)(Me2PhP)2(Et2tcb)], [17] are notably larger at
/
˚
150.3(5) and 151.6(7)8, respectively. The ReÃ
/
NÃ
/
C
˚
1.145(9) and 1.136(10) A, respectively. Both azido
angles in 3 are 151.9(7) and 169.1(9)8 which are more
typical of those observed in previously studied
ligands are essentially linear with NÃNÃN angles of
/
/
178.4(10) and 179.1(9)8. These data can be compared
with those from the only other rhenium azide complexes
reported in the Cambridge Crystallographic Database.
These compounds contain single rhenium centres and
rheniumꢀisothiocyanate complexes where a range of
/
values from 162(1)8 in 8b to 174.3(9)8 in 10 have been
reported. Both the ReN3 sections in 2 are almost co-
planar with planes containing the adjacent set of
(O)2ReRe? atoms, see Fig. 1, with torsional angles
neither contains rhenium in oxidation state ꢃ
compounds are the Re(I) complex trans-[Re(N3)(N2)Ã
(Ph2PCH2CH2PPh2)2] [16] and the Re(V) complex
[ReN(N3)(Me2PhP)2(Et2tcb)], [17] where Et2tcbꢁN-
(N,N-diethylthiocarbonylbenzamidine). These mole-
cules contain ReÃN(1), N(1)ÃN(2), N(2)ÃN(3) dis-
tances of 2.058(3), 1.199(10) and 1.200(13) A and
/III. The
/
O(1A)Ã
N(1A)Ã
Re(2)ÃN(1B)Ã
/
Re(1)Ã
N(2A) of 172.2(8) and 8.7(8)8 and O(1D)Ã
N(2B) and O(1B)ÃRe(2)ÃN(1B)ÃN(2B)
/
N(1A)Ã
/
N(2A)
and
O(1C)Ã
/
Re(1)Ã
/
/
/
/
/
/
/
/
/
of 179.1(6) and 0.2(6)8. However, co-planarity of the
related sections in molecule 3 only occurs in one part of
the molecule, see Fig. 2, i.e. in the sections containing
/
/
/
˚
˚
2.323(9), 1.23(1) and 1.08(1) A, respectively, and the
Re(1)Ã
Re(2) where the relevant torsional angles O(1D)Ã
Re(1)ÃN(2)ÃC(2) and O(1B)ÃRe(1)ÃN(2)ÃC(2) are
173.5(14) and 6.5(14)8.
The rheniumꢀrhenium distances in 2 and 3 of
/
N(2)Ã
/
C(2)Ã
/
S(2) and Re(1), O(1B), O(1D) and
azide groups are linear.
The rhenium to isothiocyanato nitrogen distances in 3
˚
are much longer at 2.208(8) and 2.210(6) A than the
/
/
/
/
/
/
˚
N(amidato) distance in 3 of 2.130(6) A. The
longest ReÃ
/
/
˚
isothiocyanate groups in 3 have NÃ
/
C distances of
S distances of
2.2477(3) and 2.2324(5) A, respectively, are typical of
quadruply bonded rhenium atoms and may be com-
˚
1.095(12) and 1.146(10) A and CÃ
/
˚
˚
1.617(11) and 1.623(9) A, respectively. The NÃ
/
CÃ/S
pared with 2.2364(5) A reported in the dichloro
derivative [Re2(DMAA)4Cl2]6 or values of 2.270(1) and
groups are essentially linear as expected with angles of
177.9(10) and 179.7(9)8. Of the 32 reported compounds
˚
2.296(1) A in compounds 8a and 8b, respectively. The
with ReÃ
/
NCS bonds in the Cambridge Crystallographic
ReÃ
/
Re distances in the four DMAA complexes reported
Database, only five of these contain rhenium in the ꢃ
/III
by Cotton et al. [6] were in the range 2.2181(6)ꢀ
/

1286
D.P. Lydon et al. / Polyhedron 22 (2003) 1281ꢀ1287
/
˚
2.2364(5) A. There are no unusual distances or angles
within the bridging amidato ligands.
4.4. Structure determination
For both 2 and 3 accurate cell dimensions and the
crystal orientation matrix were determined by a least-
squares treatment of the setting angles of 67 and 38
reflections, respectively, for 2 and 3. Data were collected
on a Bruker P-4 diffractometer using graphite-mono-
chromatised (Mo Ka) radiation. Intensities of four
reflections measured every 296 reflections showed no
significant decay for 2 but a 3% decay was detected in
the intensity controls for 3. Data were corrected for
Lorentz, polarisation and absorption effects (C-scans).
The coordinates of the heavy atoms and remaining non-
hydrogen atoms were located via the heavy-atom
method in SHELXS-97 [21]. Refinement was by full-
matrix least-squares calculations with the SHELXL-97
[21], initially, with isotropic and later with anisotropic
displacement parameters for all of the non-hydrogen
atoms [22]. Hydrogen atoms were visible in difference
maps and were allowed for as riding atoms in the final
refinement cycles.
4. Experimental
4.1. General
All preparative experiments and crystallisation were
carried out in an inert atmosphere except in the case of
the preparation of 5. Compounds 2?,6?-dimethylacetani-
lide, 4,4?-bipyridine, pyridine, silver hexafluoroantimo-
nate, ammonium thiocyanate, potassium cyanate, and
sodium azide were obtained from Aldrich Chem. Co.
and used without further purification. Potassium per-
rhenate was obtained from Alfa Aesar. Synthesis of
[Re2(DMAA)4Cl2] was carried out as described in the
literature [6]. IR spectra of compounds 2ꢀ
recorded from a KBr disc on a PerkinꢀElmer Paragon
FT spectrometer. Carbon, hydrogen, nitrogen and
chlorine analyses were performed at University College
Cork. NMR spectra were recorded on a Bruker AM 300
spectrometer. Solvents for NMR spectra were CDCl3
/
7 were
/
4.5. Preparation of [dirhenium-tetra(2,6-
dimethylacetanilide){diazide}] (2)
for 1ꢀ4, CD3CN for 5, and acetone-d6 for 6. Chemical
/
shifts (d) are expressed in parts per million (ppm) and
are relative to internal SiMe4 (1H) and 13C, positive
values represent shifts to high frequency (‘low-field’) of
the standards.
To [Re2(2?,6?-dimethylacetanilide)4Cl2] [6] (0.100 g,
0.092
dichloromethaneꢀ
mmol)
dissolved
in
a
methanol (4/1) (50 ml), was added
mixture
of
/
sodium azide (0.026 g, 0.400 mmol). The reaction
mixture was heated at reflux temperature (16 h). A
colour change from orange to red was observed. The
reaction mixture was allowed to cool to room tempera-
ture (r.t.) and the solvent was removed under reduced
pressure. The crude product was re-dissolved in dichlo-
romethane, filtered and layered with ether. Crystallisa-
tion from dichloromethane afforded dark red crystals of
4.2. Crystal structure analysis for compound 2
A
suitable crystal was obtained from CH2Cl2
solution*Crystal data C41H50Cl2N10O4Re2, Mꢁ
1190.21, monoclinic, P21/n, Zꢁ
/
/
˚
/
4, aꢁ
/
11.7316(10) A,
96.743(6)8, Uꢁ
1.762 g cmꢂ3, F(000)ꢁ
2328,
293(1)
2s(I), Rw(F2)ꢁ
˚
˚
bꢁ
/
13.9957(11) A, cꢁ
/
27.513(3) A, bꢁ
/
/
2 as the mono CH2Cl2 solvate, [Re2(C10H12NO)4(N3)2]×
/
3
4486.2(7) A , Dcalc
˚
ꢁ
/
/
CH2Cl2, (0.085 g, 0.077 mmol, 84%), 2×
/CH2Cl2.
˚
l(Mo Ka)ꢁ
/
0.71073 A, mꢁ
/
5.562 mmꢂ1, Tꢁ
K, Rꢁ0.0384 for 7585 data with I ꢀ
/
The isothiocyanate, [Re2(C10H12NO)4(NCS)2] (3),
(yield 0.104 g, 0.092 mmol, 72%) and dicyanate,
/
/
/
0.0970 for all 8792 measured data. A disordered
dichloromethane solvent molecule of crystallisation is
located in the lattice.
[Re2(C10H12NO)4(NCO)2]×
/
CH2Cl2, 4×
/
CH2Cl2, (yield
0.120 g, 0.109 mmol 76%) complexes were similarly
prepared from reactions between Re2[(2?,6?-dimethyla-
cetanilide)4]Cl2 and ammonium thiocyanate and potas-
sium cyanate, respectively.
4.3. Crystal structure analysis for compound 3
Carbon, H and N analyses, 1H and 13C NMR
spectroscopic data for 2, 3 and 4 are listed in Tables 1
and 2, respectively.
A
suitable crystal was obtained from CHCl3
solution*Crystal data C42.83H48.83Cl2.48N6O4 Re2S2,
Mꢁ1235.95, monoclinic, P21/c, Zꢁ4, aꢁ20.099(3)
22.461(4) A, bꢁ110.233(12)8,
1.672 g cmꢂ3, F(000)ꢁ
2416,
5.191 mmꢂ1, Tꢁ
293 K,
0.0464 for 7485 data with I ꢀ
2s(I), Rw(F2)ꢁ
/
/
/
/
˚
˚
˚
A, bꢁ
Uꢁ
l(Mo Ka)ꢁ
Rꢁ
/
11.5911(17) A, cꢁ
/
/
4.6. Preparation of [dirhenium-tetra(2?,6?-
dimethylacetanilide)(diaquo)]
bis{hexafluoroantimonate} (5)
3
˚
/
4909.9(12) A , Dcalc
ꢁ
/
/
˚
/
0.71073 A, mꢁ
/
/
/
/
/
0.1088 for all 9568 measured data. A disordered partial
occupancy (0.83) chloroform solvent molecule of crys-
tallisation is located in the lattice.
To [Re2(2?,6?-dimethylacetanilide)4Cl2] (0.100 g, 0.092
mmol) dissolved in dichloromethane (50 ml), was added
a solution of silver hexafluoroantimonate (0.063 g, 0.182

D.P. Lydon et al. / Polyhedron 22 (2003) 1281ꢀ
/1287
1287
mmol) in dichloromethane (10 ml). The reaction mixture
was stirred in air for 30 min at r.t. and the reaction
solution changed colour from orange to yellow. A white
precipitate was filtered from the reaction mixture.
(fax: ꢃ44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk
or www: http://www.ccdc.cam.ac.uk); on request quot-
ing the deposition numbers 169082 and 169083.
/
Removal of the solvent yielded a yellow solid
[Re2(C10H12NO)4(H2O)2][SbF6]2 (5) as the monohydrate
Acknowledgements
(0.102 g, 0.068 mmol 71%). Carbon, hydrogen and
1
nitrogen analyses, H and 13C NMR spectroscopic data
We thank the Higher Education Authority (Ireland)
for support to D.P.L., and J.F.G. thanks Dublin City
University for the purchase of a Bruker P-4 diffract-
ometer.
are listed in Tables 1 and 2, respectively. The 1H
spectrum showed a broad signal centred at 2.27 ppm
1
due to water. The intensity ratio of this signal to the H
signals from the 2?,6?-dimethylacetanilide ligand showed
that three water molecules were present in the rhenium
complex i.e. it was [Re2(C10H12NO)4(H2O)2][SbF6]2×
/
References
H2O.
[1] H. Miyasaka, C.S. Campos-Ferna´ndez, R. Cle´rac, K.R. Dunbar,
Angew. Chem., Int. Ed. 39 (2000) 3831.
4.7. Preparation of [dirhenium-tetra(2,6-
dimethylacetanilide)]bis-pyridine-
bis{hexafluoroantimonate} (6)
[2] K.T. Wong, J.M. Lehn, S.M. Peng, G.H. Lee, J. Chem. Soc.,
Chem. Commun. (2000) 2259.
[3] A.C. Price, S.T. Trzaska, R.E.L. Trout, Synth. React. Inorg. Met.
-Org. Chem. 28 (1998) 1595.
To [Re2(2,6-dimethylacetanide)4Cl2] (0.100 g, 0.092
mmol) dissolved in dichloromethane (50 ml), a solution
of silver hexafluoroantimonate (0.063 g, 0.182 mmol) in
dichloromethane (10 ml) was added. The reaction
mixture was stirred (30 min). A colour change from
orange to bright yellow solution was observed, together
with a white precipitate. To the filtered solution,
pyridine (0.016 g, 0.200 mmol) was added and the
yellow colour of the solution intensified. The solvent
[4] F.A. Cotton, R.A. Walton, Multiple Bonds Between Metal
Atoms, 2nd ed, Oxford University Press, 1993.
[5] F. Taha, G. Wilkinson, J. Chem. Soc. (1963) 5406.
[6] F.A. Cotton, J. Lu, T. Ren, Polyhedron 13 (1994) 807.
[7] F.A. Cotton, L.D. Gage, Inorg. Chem. 18 (1979) 1716.
[8] F.A. Cotton, W.H. Ilsley, W. Kaim, Inorg. Chem. 19 (1980) 2360.
[9] M.E. Prater, D.J. Mindiola, X. Ouyang, K.R. Dunbar, Inorg.
Chem. Commun. 1 (1998) 475.
[10] F.A. Cotton, C. Oldham, W.R. Robinson, Inorg. Chem. 5 (1968)
1798.
[11] F.A. Cotton, B.A. Frenz, L.W. Shive, Inorg. Chem. 14 (1975) 649.
[12] F.A. Cotton, L.D. Gage, K. Mertis, L.W. Shive, G. Wilkinson, J.
Am. Chem. Soc. 98 (1976) 6922.
was
removed
yielding
ne)2][SbF6]2 (6) as a yellow solid (0.103 g, 0.062 mmol
[Re2(C10H12NO)4(pyridi-
68%). Similarly, a 4,4?-bipyridine adduct, {[Re2(C10H12-
[13] F.E. Kuhn, I.S. Goncalves, A.D. Lopes, J.P. Lopes, C.C. Romao,
¸ ˜
¨
NO)4(4,4?-bipyridine)] [SbF6]2×
/
(CH2Cl2)}n (7) was pre-
W. Wachter, J. Mink, L. Hajba, A.J. Parola, F. Pina, J.
Sotomayor, Eur. J. Inorg. Chem. (1999) 295.
pared using the same procedure. Results of C, H, N
analyses, 1H and 13C NMR spectroscopic data are listed
in Tables 1 and 2, respectively. Results of C, H, N
analyses, 1H and 13C NMR spectroscopic data are listed
in Tables 1 and 2, respectively. Attempts to prepare the
bis 4,4?-bipyridine complex [Re2(C10H12NO)4(4,4?-bi-
pyridine)2][SbF6]2 from the reaction between [Re2(2,6-
dimethylacetanide)4Cl2] and 4,4?-bipyridine in a 1:2
stoichiometric ratio yielded 7.
[14] F.A. Cotton, T. Ren, J. Am. Chem. Soc. 114 (1992) 2495.
[15] K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, Part B, 5th ed, Wiley, New York,
1997.
[16] Y. Wang, J.J.R. Frau´sto Da Silva, A.J.L. Pombeiro, M.A.
Pellinghelli, A. Tiripicchio, J. Organomet. Chem. 454 (1993) 211.
[17] S. Ritter, U. Abram, Inorg. Chim. Acta 215 (1994) 159.
[18] F.A. Cotton, M. Matusz, Inorg. Chem. 26 (1987) 3468.
[19] R. Hubener, K. Ortner, J. Strahle, U. Abram, Inorg. Chim. Acta
244 (1996) 109.
[20] J.E. Hahn, T. Nimry, W.R. Robinson, D.J. Salmon, R.A.
Walton, J. Chem. Soc., Dalton Trans. (1978) 1232.
[21] G.M. Sheldrick, SHELXS-97 and SHELXL-97, Programs for the
Solution and Refinement of Crystal Structures, University of
Gottingen, Gottingen, Germany, 1997.
5. Supplementary material
¨
¨
Supplementary data are available from The Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK
[22] E.J. Gabe, Y. Le Page, J.-P. Charland, F.L. Lee, P.S. White, J.
Appl. Crystallogr. 22 (1989) 384.