Absence of dichroism in dinuclear rhenium complexes with sterically hindered μ2-(η2-N,O)-nitrosobenze ligands

Article abstract of DOI:10.1002/ejic.200500772

The substitution reactions of [Re(CO)₅X] (X = Cl, Br) with 2,6-dihalo-substituted nitrosobenzene derivatives C₆H ₂YZ₂NO (Y = H, Cl, Br; Z = Cl, Br) leads to the formation of dinuclear μ₂-η²-N,O-nitrosobenzene-bridged complexes of the type [{(CO)₃Re(μ-X)}₂ONC ₆H₂YZ₂] (6a,b, 7a,b, 8a,b, 9a). The turquoise coloured solutions of the complexes in CH₂Cl₂ show only one UV/Vis absorption of medium intensity in the region 670-710 nm, depending on the halogen bridges X and substituents Z. Single crystals of the complexes do not exhibit any dichroic properties. This may be due to the almost perpendicular orientation of the phenyl ring towards the Re-O-N-Re plane. The molecular structures of six compounds, as determined by single-crystal X-ray analyses, show two face-joined octahedra with Re centres that are bridged by two halogens X and one NO group. NO coordinates in a nonsymmetrical η²-like fashion with N- or O-linkage to each Re centre. The phenyl rings do not lie within the symmetry plane containing the atoms Re, N and O, but are almost perpendicular to this (torsion angle O-N-C-C = 83.5-85.4°) because of the 2,6-dihalogen substituents Z. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200500772

FULL PAPER
DOI: 10.1002/ejic.200500772
Absence of Dichroism in Dinuclear Rhenium Complexes with Sterically
Hindered µ2-(η2-N,O)-Nitrosobenzene Ligands
Christoph Krinninger,[a] Stefan Wirth,[a] Peter Klüfers,[a] Peter Mayer,[a] and
Ingo Peter Lorenz*[a]
Keywords: Dichroism / Dinuclear complexes / N ligands / Rhenium / Structure elucidation
The substitution reactions of [Re(CO)5X] (X = Cl, Br) with
2,6-dihalo-substituted nitrosobenzene derivatives
N–Re plane. The molecular structures of six compounds, as
determined by single-crystal X-ray analyses, show two face-
joined octahedra with Re centres that are bridged by two hal-
ogens X and one NO group. NO coordinates in a nonsym-
metrical η2-like fashion with N- or O-linkage to each Re cen-
tre. The phenyl rings do not lie within the symmetry plane
containing the atoms Re, N and O, but are almost perpendic-
ular to this (torsion angle O–N–C–C = 83.5–85.4°) because of
the 2,6-dihalogen substituents Z.
C6H2YZ2NO (Y = H, Cl, Br; Z = Cl, Br) leads to the formation
of dinuclear µ2-η2-N,O-nitrosobenzene-bridged complexes of
the type [{(CO)3Re(µ-X)}2ONC6H2YZ2] (6a,b, 7a,b, 8a,b, 9a).
The turquoise coloured solutions of the complexes in CH2Cl2
show only one UV/Vis absorption of medium intensity in the
region 670–710 nm, depending on the halogen bridges X and
substituents Z. Single crystals of the complexes do not exhibit
any dichroic properties. This may be due to the almost per-
pendicular orientation of the phenyl ring towards the Re–O–
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
Introduction
The coordination chemistry of organic RNO nitroso
compounds has been extensively investigated,[1] and their
many different coordination modes have been summarised
in schemes in previous accounts of our work, as well as by
others.[2,3] The dominant bonding mode bridging two metal
centres is of the type µ-η1-N, µ-η1:η2-N,O, µ-η1:η1-N,O or
µ-η2:η2-N,O (Scheme 1), although the unassisted ligand
function µ-η1:η1-N,O (type I) with a simple bridging coor-
dination mode is less common. Co-assisted ligand func-
tions, that is those with additional coordination by a further
donor system (e.g. amido or carbonyl groups), have been
verified in most examples and form additional five-
(type Ia)[4] or six-membered rings (type Ib).[5] Furthermore,
type I has been only observed in a unique neutral complex
of platinum[6] and in a dinuclear rhodium cation with thiol-
ato bridges.[7]
Scheme 1. Bonding modes of C-nitroso compounds bridging two
metals (µ-η2-N,O).
vochromic ligand-to-metal CT band ([NO–ReI]). Light re-
flected from microcrystalline powders of the substances
shines with different colours (like shells). Visual inspection
of suitable crystals with polarized light under a microscope
clearly showed a polarisation-dependent absorption. In the
case of [{(CO)3Re(µ-Br)}2ONC6H4NEt2] sufficiently large
single crystals showed a pronounced linear dichroism.[3] We
were able to correlate this dichroism with the arrangement
of the molecules in the unit cells, which show alignment of
the RNO units along a crystal plane. It is worthwhile to
note that the dihedral angles Re–O–N–Re and O–N–C–C
(phenyl ring) are less than 5° and 3°, respectively. This me-
ans that the NO group and the phenyl ring (together with
the NR2 substituent)[2,3] lie almost within the symmetry
plane of the dinuclear complexes. To prove this correlation,
we decided to synthesise analogous complexes with ni-
trosobenzene ligands that are sterically hindered in both or-
tho positions. Our aim was, therefore, to twist the phenyl
We have recently published a series of complexes[2,3] that
are the first simple, neutral and dinuclear C-nitroso com-
plexes to exhibit this rare, unassisted µ-η1:η1-N,O ligand
function (type I), and contain only single atoms, X, as ad-
ditional bridges (X = Cl, Br, I). All of these complexes show
dichroic properties and form deep-blue solutions. In the
UV/Vis spectra, one very intense broad absorption is found
at λ = 600–650 nm (log ε Ͼ 30000), which is due to a sol-
[a] Ludwig Maximilian University Munich, Department of Chem-
istry and Biochemistry,
Butenandtstr. 5–13, 81377 Munich, Germany
Fax: +49-89-2180-77867
E-mail: ipl@cup.uni-muenchen.de
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Absence of Dichroism in Dinuclear Rhenium Complexes
FULL PAPER
ring out of the plane and to observe the effect this had nuclear complexes. In spite of the frequency range of λ2,
on the dichroism. We undertook the reaction of 2,6-dihalo- there is no dependence of its spectral position on either the
substituted nitrosobenzenes with [Re(CO)5X] (X = Cl, Br), halogen bridges or substituents.
and obtained the corresponding dinuclear complexes
The X-ray structure analyses of 6a,b–8a,b show that the
[{(CO)3Re(µ-X)}2ONC6H2YZ2], which exhibit the same ni- phenyl ring with both halo substituents in the ortho posi-
troso ligand function µ2-η1:η1-O, but with a perpendicular tions is orientated perpendicular to the symmetry plane. As
orientation of the phenyl ring towards the plane formed by is therefore expected, the light reflected from crystalline
the atoms Re, O, N and Re. As a consequence of this, the powders of these complexes does not shine in different col-
dichroism is lost.
ours and neither does it show any polarisation-dependent
absorption of the type mentioned above.[2,3] Therefore, they
do not exhibit any significant dichroic properties.
The IR spectra of 6a,b–8a,b and 9a show five ν(CO) ab-
sorptions. As the NO group is bonded by N and O to dif-
ferent Re centres, the electronic situation at both Re centres
is different. This normally results in two different fac-
Re(CO)3 fragments, each with local C3v symmetry. How-
ever, because of the bulky substituents in the ortho position
of the nitrosobenzenes, the local symmetry of the Re(CO)3
fragment at N is reduced to Cs. Therefore, three bands of
the type 2AЈ + AЈЈ are detected. Due to electronic reasons
the N-bonded Re(CO)3 moiety should be more electron rich
and act as a better π-donor for the CO ligands than the O-
bonded one. Therefore, the absorptions at higher wave-
numbers with varying intensities have been assigned to the
Results and Discussion
The reaction of [Re(CO)5X] (X = Cl, Br) (1a,b) with the
sterically hindered C-nitroso compounds 4-Y-2,6-
Z2C6H2NO [Y = H, Z = Cl (2), Br (3); Y = Cl, Z = Br (4);
Y = Br, Z = Cl (5)] leads to the dinuclear complexes 6a,b–
8a,b and 9a (Scheme 2). All reactions were carried out in
boiling CH2Cl2. Whereas 9a was obtained in good yield
(65%), 9b could not be isolated under the same reaction
conditions. It is interesting to note that using boiling tolu-
ene as solvent resulted in the dimeric halo complexes
[(CO)4ReX]2 (X = Cl, Br); no reaction occurred when
[Re(CO)5I] was used as the starting material.
{(CO)3Re–O} fragment [ν
= 2086–2091 (A1), 2006–
˜
2012 cm–1 (E)] and the three absorptions at lower wave-
numbers and similar intensities to the {(CO)3Re–N} frag-
ment [ν = 2024–2058 (AЈ), 1961–1970 (AЈ), 1913–1949 cm–1
˜
(AЈЈ)]. Because several bands lie very close together it is
not possible to draw any conclusions about the halogens as
substituents or bridges. The ν(NO) band of the complexes
is found at 1329–1350 cm–1, which is a shift to lower fre-
quency of about 115 cm–1 with respect to the free C-nitroso
ligand and of about 50 cm–1 compared with other com-
plexes.[2,3]
The 1H NMR spectrum of 6a shows three separate doub-
lets at δ = 7.40, 7.42 and 7.44 ppm. In the case of 6b, only
a multiplet between δ = 7.38–7.44 ppm can be detected. In
the spectra of 7a two doublets for the ring protons in the
3,5-positions are detected at δ = 7.26 and 7.37 ppm, and
one triplet for the proton in the 4-position at δ = 7.67 ppm.
Scheme 2. Synthesis of sterically hindered µ2-(η2-N,O)-nitrosoben-
zene complexes 6–9.
Compounds 6a,b–8a,b and 9a were obtained as dark- Complex 7b exhibits a triplet at δ = 7.27 ppm, a doublet at
green crystals that are stable in air for some days. The com- δ = 7.38 ppm and a multiplet at δ = 7.61–7.64 ppm, whereas
plexes are soluble in THF, acetone, CHCl3, CH2Cl2, and 8a only shows one broad signal at δ = 7.66 ppm, and 8b and
even in toluene, but nearly insoluble in pentane or hexane. 9a exhibit singlets at δ = 7.64 and 7.60 ppm, respectively. It
The turquoise solutions formed in these solvents can be is noteworthy that in spite of the mirror symmetry in the
kept in air for several days without decomposition. In the Re2NO plane compounds 6a,b and 7a,b with the benzene
UV/Vis spectra (CH2Cl2) two broad absorptions are ob- ring substituted in 2,6-positions exhibit different signals for
served, one lies consistently at about λ1 = 375–380 nm, the three protons in the 3,4- and 5-positions. Compounds
whereas the second, which originates from a ligand-to-me- 8a,b, and 9a, however, show only one resonance for the 3,5-
tal CT (NO–ReI), is observed over a larger range at λ2 = protons.
670–710 nm. It is shifted to lower frequency with respect to
In the 13C NMR spectra of 6a,b–8a,b and 9a the signals
the corresponding π–π*-NO electronic transition of the free for the phenyl groups are detected at δ = 124.1–140.9 ppm.
ligands. It is noteworthy that they are also observed at lower Here, we observe three signals for the three different types
frequencies and with smaller intensities than those of the of C-atoms in the 2,6-, 3,5- and 4-positions. The N-bonded
corresponding nitrosoaniline complexes published pre- quaternary carbon is observed at δ = 160.2–164.5 ppm and
viously,[2,3] where the NO group, phenyl ring and the NR2 the signals corresponding to the CO ligands at the Re
substituent lie exactly within the symmetry plane of the di- centres appear at δ = 181–192 ppm.
Eur. J. Inorg. Chem. 2006, 1060–1066
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FULL PAPER
The parent peaks as well as peaks corresponding to frag-
ments resulting from the successive loss of up to six CO
ligands are observed in the mass spectra (DEI-MS) of 6a,b–
8a,b and 9a.
The compositions and structures of complexes 6a,b–8a,b
were confirmed by X-ray structure analysis (see Table 2).
Single crystals of complexes 6a,b–8a,b were obtained by the
diffusion of pentane into solutions of the complexes in
CHCl3. The molecular structures and selected bond lengths
and angles are given in Figures 1 (6a), 2 (6b), 3 (7a), 4 (7b),
5 (8a) and 6 (8b). They show two face-joined octahedra
with two halogens and the NO group as bridging ligands.
The N–O distances are approximately 1.299 Å, similar to
the values for analogous complexes,[1–3] but significantly
longer than the average N–O distances of free C-nitroso
compounds (1.21 Å).[8] There is no significant dependence
of the NO lengths upon varying the halo bridges. In all
cases, and in contrast to the recently published analogous
complexes,[2,3] the Re–O bonds (approx. 2.10 Å) are signifi-
cantly longer than the Re–N bonds (approx. 1.99 Å),
whereas all the bridging Re–X bonds in the complexes are
similar in length. For better comparison, the most impor-
tant structural parameters of all complexes are summarised
in Table 1.
Figure 2. Molecular structure of 6b. Selected bond lengths [Å] and
angles [°]:Re(1)–N(1) 1.990(6), Re(2)–O(7) 2.116(5), Re(1)–Br(1)
2.6115(13), Re(1)–Br(2) 2.5965(11), Re(2)–Br(1) 2.6199(10), Re(2)–
Br(2) 2.6305(12), O(7)–N(1) 1.299(8), N(1)–C(7) 1.451(9), Re(1)–
C(1) 1.923(9), Re(1)–C(2) 1.936(9), Re(1)–C(3) 2.020(9), Re(2)–
C(4) 1.902(8), Re(2)–C(5) 1.891(9), Re(2)–C(6) 1.907(9); N(1)–
O(7)–Re(2) 121.8(4), O(7)–N(1)–Re(1) 126.5(5), O(7)–Re(2)–Br(2)
84.25(14), O(7)–Re(2)–Br(1) 83.58(4), N(1)–Re(1)–Br(1) 85.84(17),
N(1)–Re(1)–Br(2) 86.73(17), Br(2)–Re(1)–Br(1) 82.89(4), Br(1)–
Re(2)–Br(2) 82.07(4), O(7)–N(1)–C(7) 109.7(5), O(7)–N(1)–C(7)–
C(12) 85.44.
The dihedral angles Re–O–N–CPh of all complexes are
smaller than 1.4°. The main difference between these com-
plexes compared to those recently published[2,3] is that the
dihedral angles O(7)–N(1)–C(7)–C(8/12) lie between 83.5–
85.4°. This means that there is a near perpendicular orienta-
tion of the phenyl ring towards the plane formed by the
atoms Re, O, N and Re. The consequence of this is the loss
of dichroism. No Re–Re interaction is observed in any of
the compounds, although the Re–Re distance varies with
the size of the halogen bridges [Re(1)–Re(2) Ϸ 3.47 (6a, 7a,
8a) and 3.54 Å (6b, 7b, 8b)].
It is worthwhile to emphasise that the orientation of the
molecules described in this paper within the lattice is similar
to that reported earlier[3] for the dichroic molecules. The
triclinic crystal system is observed in both cases, although
the packing of the dichroic molecules is closer, in particular
with respect to the parallel phenyl rings of adjacent mole-
cules, and the π-delocalisation is more widespread. Both ef-
fects lead to the significant anisotropy that is necessary for
dichroism. Such close contact between the phenyl rings of
the present molecules is not possible and the π-delocalis-
ation is less. Therefore, it can be concluded that the absence
of dichroism in 6a,b–8a,b and 9a is a result of the non-
planar arrangement of the phenyl rings with respect to the
Figure 1. Molecular structure of 6a. Selected bond lengths [Å] and
angles [°]: Re(1)–N(1) 1.994(4), Re(2)–O(7) 2.124(4), Re(1)–Cl(1)
2.4914(14), Re(1)–Cl(2) 2.4726(14), Re(2)–Cl(1) 2.5024(14), Re(2)–
Cl(2) 2.5056(14), O(7)–N(1) 1.282(6), N(1)–C(7) 1.457(6), Re(1)–
C(1) 2.031(6), Re(1)–C(2) 1.952(6), Re(1)–C(3) 1.917(7), Re(2)–
C(4) 1.928(6), Re(2)–C(5) 1.902(6), Re(2)–C(6) 1.908(6); N(1)–
O(7)–Re(2) 120.2(3), O(7)–N(1)–Re(1) 123.9(3), O(7)–Re(2)–Cl(2)
82.82, O(7)–Re(2)–Cl(1) 82.82(11), N(1)–Re(1)–Cl(1) 84.52(13),
N(1)–Re(1)–Cl(2) 85.96(13), Cl(2)–Re(1)–Cl(1) 80.83(5), Cl(1)–
Re(2)–Cl(2) 79.98(5), O(7)–N(1)–C(7) 110.3(4), O(7)–N(1)–C(7)–
C(8) 84.74.
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Absence of Dichroism in Dinuclear Rhenium Complexes
FULL PAPER
Figure 4. Molecular structure of 7b. Selected bond lengths [Å] and
angles [°]: Re(2)–N(1) 2.012(8), Re(1)–O(7) 2.123(7), Re(1)–Br(1)
2.6364(10), Re(1)–Br(2) 2.6292(10), Re(2)–Br(1) 2.6057(10), Re(2)–
Br(2) 2.6182(10), O(7)–N(1) 1.279(9), N(1)–C(7) 1.453(12), Re(1)–
C(1) 1.874(11), Re(1)–C(2) 1.902(10), Re(1)–C(3) 1.936(12), Re(2)–
C(4) 2.043(12), Re(2)–C(5) 1.920(11), Re(2)–C(6) 1.908(11); N(1)–
O(7)–Re(1) 122.7(6), O(7)–N(1)–Re(2) 123.4(6), O(7)–Re(1)–Br(2)
83.53(16), O(7)–Re(1)–Br(1) 84.39(16), N(1)–Re(2)–Br(1) 87.1(2),
N(1)–Re(2)–Br(2) 85.6(2), Br(1)–Re(1)–Br(2) 82.51(3), Br(2)–
Re(2)–Br(1) 81.72(3), O(7)–N(1)–C(7) 110.9(7), O(7)–N(1)–C(7)–
C(12) 84.91.
Figure 3. Molecular structure of 7a. Selected bond lengths [Å] and
angles [°]: Re(1)–N(1) 1.991(4), Re(2)–O(7) 2.126(4), Re(1)–Cl(1)
2.4801(12), Re(1)–Cl(2) 2.5000(12), Re(2)–Cl(1) 2.5117(12), Re(2)–
Cl(2) 2.5144(11), O(7)–N(1) 1.282(5), N(1)–C(7) 1.460(7), Re(1)–
C(1) 2.030(6), Re(1)–C(2) 1.923(6), Re(1)–C(3) 1.930(6), Re(2)–
C(4) 1.903(5), Re(2)–C(5) 1.914(6), Re(2)–C(6) 1.920(6); N(1)–
O(7)–Re(2) 120.3(3), O(7)–N(1)–Re(1) 126.2(3), O(7)–Re(2)–Cl(2)
82.82(9), O(7)–Re(2)–Cl(1) 83.78(11), N(1)–Re(1)–Cl(1) 86.47(12),
N(1)–Re(1)–Cl(2) 84.65(12), Cl(2)–Re(1)–Cl(1) 80.87(4), Cl(1)–
Re(2)–Cl(2) 79.98(5), O(7)–N(1)–C(7) 109.9(4), O(7)–N(1)–C(7)–
C(12) 85.28.
dichloronitrosobenzene, 2,6-dibromo-4-chloronitrosobenzene and,
4-bromo-2,6-dichloronitrosobenzene were prepared according to a
literature procedure.[12] NMR spectra were recorded with a Jeol Ex
400 (1H: 399.78 MHz; 13C: 100.54 MHz) or a Jeol Eclipse 270 MHz
spectrometer (1H: 270.17 MHz; 13C: 67.94 MHz) in CDCl3. Mass
spectra were obtained with a Jeol Mstation JMS 700. IR and UV/
Vis spectra were measured with a Perkin–Elmer Spectrum One FT-
IR or Perkin–Elmer Lambda 16 spectrometer. Elemental analyses
were performed with a Heraeus Elementar Vario EL. For X-ray
data see Table 2.
Re2NO plane. In addition, it is interesting to note that this
is the only structural parameter that changes in comparison
with the dichroic complexes.[3]
In summary, we have synthesised a novel series of analo-
gous[2,3] neutral and dinuclear Re complexes with C-nitroso
ligands. They also contain an unassisted µ2-η1:η1-N,O
bridge (type I, Scheme 1) and only single atoms (X = Cl,
Br) as additional bridges. However, the complexes do not
possess any dichroic properties. This is a result of the dif-
ferent orientation of the C-nitroso ligand, which is almost
perpendicular to the Re–O–N–Re symmetry plane. This is
Synthesis of 6–9 from 1a,b. General Procedure: [Re(CO)5X] (X =
Cl, Br) (1a,b) and 4-Y-2,6-Z2C6H2NO [Y = H, Z = Cl (2), Z = Br
(3); Y = Cl, Z = Br (4); Y = Br, Z = Cl (5)] were dissolved in 20 mL
of dichloromethane and heated for 40 h under reflux, whereby the
caused by the two substituents (Z) in the two ortho posi- solution turned green. The solvent was then evaporated and the
green residue was purified by column chromatography (CH2Cl2).
µ2-(η2-N,O-2,6-Dichloronitrosobenzene)bis[µ-chlorotricarbonylrhen-
ium(I)] (6a): Synthesised from 116 mg (0.321 mmol) of 1a and
tions of the phenyl ring. A considerably different reaction
pathway has been found for the reaction of [Re(CO)5X] (X
= Cl, Br, I) with more sterically demanding C-nitroso li-
gands (e.g. 1-nitroso-2-naphthol), whereby HX or CO2 eli- 42.4 mg (0.240 mmol) of 3. Yield: 51.7 mg (0.066 mmol, 41 %)
green crystals, m.p. 145 °C (dec.). 1H NMR (399.78 MHz, CDCl3):
mination has been observed, and quite different mononu-
3
4
clear products have been obtained.[9]
δ = 7.40 (d, J = 6.54 Hz, 1 H, CHarom.), 7.42 (d, J = 0.66 Hz, 1
4
H, CHarom.), 7.44 (d, J = 2.04 Hz, 1 H, CHarom.) ppm. 13C NMR
(100.53 MHz, CDCl3): δ = 124.1 (CHarom.), 129.2 (CHarom.), 131.5
(CHarom.), 161.3 (ON-Cq), 185.1 (CO), 192.2 (CO) ppm. IR (KBr):
˜
Experimental Section
All operations were carried out under argon in dry solvents.[10]
ν = 2965 cm–1 (w), 2405 (w), 2338 (w) 2098 (m), 2037 (vs), 2012
(vs), 1970 (s), 1949 (s), 1931 (vs), 1618 (m), 1566 (m), 1437 (m),
[Re(CO)5X] (X = Cl, Br),[11] 2,6-dibromonitrosobenzene, 2,6- 1350 (m), 1319 (m), 1293 (w), 1263 (w), 1207 (w), 1192 (s), 1154
Eur. J. Inorg. Chem. 2006, 1060–1066
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C. Krinninger, S. Wirth, P. Klüfers, P. Mayer, I. P. Lorenz
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Figure 5. Molecular structure of 8a. Selected bond lengths [Å] and
angles [°]: Re(2)–N(1) 2.007(8), Re(1)–O(7) 2.099(6), Re(1)–Cl(2)
2.497(3), Re(1)–Cl(1) 2.500(2), Re(2)–Cl(2) 2.474(2), Re(2)–Cl(1)
2.482(2), O(7)–N(1) 1.297(10), N(1)–C(7) 1.440(11), Re(1)–C(1)
1.920(11), Re(1)–C(2) 1.927(10), Re(1)–C(3) 1.899(11), Re(2)–C(4)
2.018(10), Re(2)–C(5) 1.934(12), Re(2)–C(6) 1.941(11); N(1)–O(7)–
Re(1) 120.8(5), O(7)–N(1)–Re(2) 123.3(6), O(7)–Re(1)–Cl(1)
83.50(18), O(7)–Re(1)–Cl(2) 83.67(18), N(1)–Re(2)–Cl(2) 85.4(2),
N(1)–Re(2)–Cl(1) 85.0(2), Cl(2)–Re(1)–Cl(1) 79.27(8), Cl(2)–Re(2)–
Cl(1) 80.06(8), O(7)–N(1)–C(7) 110.9(7), O(7)–N(1)–C(7)–C(12)
84.84.
Figure 6. Molecular structure of 8b. Selected bond lengths [Å] and
angles [°]: Re(1)–N(1) 2.001(12), Re(2)–O(7) 2.127(11), Re(1)–Br(3)
2.578(2), Re(1)–Br(4) 2.611(2), Re(2)–Br(3) 2.589(2), Re(2)–Br(4)
2.637(2), O(7)–N(1) 1.257(15), N(1)–C(7) 1.458(19), Re(2)–C(1)
1.963(19), Re(2)–C(2) 1.95(2), Re(2)–C(3) 1.903(17), Re(1)–C(4)
2.08(2), Re(1)–C(5) 1.908(19), Re(1)–C(6) 1.99(2); N(1)–O(7)–Re(2)
123.7(9), O(7)–N(1)–Re(1) 123.3(10), O(7)–Re(2)–Br(3) 83.5(3),
O(7)–Re(2)–Br(4) 83.5(3), N(1)–Re(1)–Br(3) 86.6(3), N(1)–Re(1)–
Br(4) 86.4(4), Br(3)–Re(1)–Br(4) 81.10(7), Br(3)–Re(2)–Br(4)
80.40(7), O(7)–N(1)–C(7) 109.9(11), O(7)–N(1)–C(7)–C(12) 83.49.
Table 1. Comparison of bond lengths [Å] and angles [°] of com-
pounds 6a,b–8a,b.
(w), 1101 (w), 1067 (w), 946 (w), 929 (w), 895 (w), 929 (w), 895
(w), 854 (w), 799 (m), 786 (s), 743 (w), 726 (w), 681 (w), 643 (w),
6a
6b
7a
7b
8a
8b
617 (m), 529 (w). IR (CH Cl ): ν = 2090 cm–1 (m), 2033 (s), 2011
˜
2
2
Re–Xav
Re–O
Re–N
N–O
N–CPh
Re–X–Reav
Re–N–O
Re–O–N
Re–O–N–CPh
2.488 2.608 2.496 2.633 2.499 2.595
2.124 2.116 2.126 2.123 2.099 2.127
1.994 1.990 1.991 2.012 2.007 2.001
1.282 1.299 1.282 1.279 1.297 1.257
1.457 1.451 1.460 1.453 1.440 1.458
80.41 82.48 80.43 82.12 79.67 80.75
123.9 126.5 126.2 123.4 123.3 123.3
120.2 121.8 120.3 122.7 120.8 123.7
(vs), 1962 (s), 1941 (s). UV/Vis (CH2Cl2): λmax (log ε) = 376 nm
(4685), 670 (7892). C12H3Cl4NO7Re2 (787.30): calcd. C 18.30, H
0.38, N 1.78; found C 18.39, H 0.41, N 1.76. MS (DEI): m/z (%)
= 786.3 (50) [M+], 702.4 (38) [M+ – 3 CO], 674.4 (36) [M+ – 4 CO],
646.5 (92) [M+ – 5 CO], 618.5 (100) [M+ – 6 CO].
µ2-(η2-N,O-2,6-Dichloronitrosobenzene)bis[µ-bromotricarbonylrhen-
ium(I)] (6b): Synthesised from 152 mg (0.419 mmol) of 1b and
1.03
0.53
1.34
0.78
0.27
0.82
43.4 mg (0.247 mmol) of 2. Yield: 112 mg (0.128 mmol, 60%) green
O–N–C–C(8/12) 84.74 85.44 85.28 84.91 84.84 83.49
1
crystals; m.p. 147 °C (dec.). H NMR (399.78 MHz, CDCl3): δ =
7.38–7.44 (m, 3 H, CHarom.) ppm. 13C NMR (100.53 MHz,
CDCl3): δ = 126.3 (CHarom.), 129.2 (CHarom.), 130.8 (CHarom.), µ2-(η2-N,O-2,6-Dibromonitrosobenzene)bis[µ-chlorotricarbonylrhen-
161.8 (ON-C ), 184.8 (CO), 191.5 (CO) ppm. IR (KBr): ν = ium(
75.5 mg (0.285 mmol) of 3. Yield: 106 mg (0.121 mmol, 57%) green
1930 (vs),1614 (m), 1577 (s), 1475 (s), 1438 (vs), 1333 (s), 1290 (m), crystals; m.p. 140 °C (dec.). H NMR (399.78 MHz, CDCl3): δ =
I
)] (7a): Synthesised from 154 mg (0.427 mmol) of 1a and
˜
q
3080 cm–1 (m), 2997 (w), 2094 (m), 2024 (vs),2007 (vs), 1970 (s),
1
3
3
1206 (s), 1161 (w), 1132 (w), 1100 (m), 1069 (w), 970 (w), 904 (m),
896 (w), 853 (w), 804 (m), 794 (s), 782 (vs), 732 (m), 640 (w), 617 CHarom.), 7.67 (t, 3J = 8.13 Hz, 1 H, CHarom.) ppm. 13C NMR
(w), 581 (w), 550 (w), 522 (w). IR (CH Cl ): ν = 2086 cm–1 (m),
(100.53 MHz, CDCl3): δ = 131.8 (CHarom.), 132.3 (CHarom.), 133.1
7.26 (d, J = 8.35 Hz, 1 H, CHarom.), 7.37 (d, J = 7.91 Hz, 1 H,
˜
2
2
2031 (s), 2011 (vs), 1962 (s), 1941 (s). UV/Vis (CH2Cl2): λmax (log (CHarom.), 163.7 (ON-Cq), 185.6 (CO), 192.1 (CO) ppm. IR (KBr):
ε) = 371 nm (4405), 702 (6409). C12H3Br2Cl2NO7Re2 (876.27):
calcd. C 16.43, H 0.34, N 1.60; found C 16.34, H 0.39, N 1.62. MS
(DEI): m/z (%) = 876.2 (18) [M+], 848.2 (5) [M+ – CO], 792.3 (13)
ν = 2953 cm–1 (m), 2924 (s), 2854 (m), 2337 (w), 2097 (m), 2059
˜
(s), 2029 (vs), 2007 (s), 1966 (s), 1913 (vs), 1624 (m), 1566 (w), 1466
(w), 1432 (m), 1416 (m), 1376 (w), 1341 (w) 1316 (w), 1262 (w),
[M+ – 3 CO], 764.3 (10) [M+ – 4 CO], 736.4 (21) [M+ – 5 CO], 1199 (w), 1149 (w), 1100 (w), 923 (w), 893 (w), 861 (w), 774 (w),
708.3 (24) [M+ – 6 CO].
731 (w), 688 (w), 660 (w), 662 (w). IR (CH Cl ): ν = 2089 cm–1
˜
2 2
1064
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 1060–1066

Absence of Dichroism in Dinuclear Rhenium Complexes
FULL PAPER
Table 2. Summary of crystallographic data for complexes 6a,b–8a,b.[13,14]
6a
6b
7a
Empirical formula
C12H3Cl4NO7Re2
787.30
C12H3Br2Cl2NO7Re2
876.27
C12H3Br2Cl2NO7Re2
876.27
Formula weight [gmol–1]
Crystal size [mm]
0.38×0.10×0.009
black block
triclinic
0.02×0.10×0.20
black plate
0.02×0.10×0.20
black plate
Crystal colour, habit
Crystal system
triclinic
triclinic
¯
¯
¯
Space group
P1
P1
P1
a [Å]
8.7459(2)
10.2474(2)
11.6216(3)
81.0843(11)
84.2984(11)
65.4287(12)
935.09(4)
2
8.8974(18)
10.310(2)
11.722(2)
80.82(3)
8.8423(2)
10.2035(2)
11.8154(3)
81.5702(10)
83.8498(10)
65.5635(8)
958.76(4)
2
b [Å]
c [Å]
α [°]
β [°]
84.79(3)
γ [°]
66.31(3)
Volume [Å3]
971.7(3)
Z
2
Density calcd. [gcm–3]
Absorption coefficient [mm–1]
F(000)
2.740
2.995
3.035
13.532
16.865
17.094
696
784
784
Index ranges
–11 Յ h Յ 11
–13 Յ k Յ 13
–15 Յ l Յ 15
3.17–27.48
13095
–10 Յ h Յ 9
–11 Յ k Յ 0
–13 Յ l Յ 13
2.18–23.97
3238
–11 Յ h Յ 11
–13 Յ k Յ 13
–15 Յ l Յ 15
3.15–27.49
13564
θ Range [°]
Reflections collected
Independent reflections
Observed reflections
Parameter/restrains
R1/wR2 (all data)
R1/wR2 (final)
4208
3043
4342
3753
2757
3715
236/0
235/0
235/0
0.0404/0.886
0.0341/0.0847
1.076
0.0316/0.0736
0.0268/0.0712
1.156
0.0387/0.0658
0.0295/0.0623
1.061
Goodness of fit
Min./max. ρe [eÅ3]
Temperature [K]
Diffractometer used
Scan type
Solution
Refinement
–2.597/1.573
200(2)
Nonius Kappa CCD
area detection
SHELXS-97
SHELXL-97
–1.450/0.591
293(2)
Nonius Mach 3
area detection
SHELXS-97
SHELXS-97
–2.113/1.154
200(2)
Nonius Kappa CCD
area detection
SHELXS-97
SHELXS-97
7b
8a
8b
Empirical formula
C12H3Br4NO7Re2
965.18
C12H2Br2Cl3NO7Re2
910.72
C12H2Br4ClNO7Re2
999.64
0.10×0.08×0.06
black plate
monoclinic
C2/c
15.473(3)
39.231(8)
14.732(3)
90
Formula weight [gmol–1]
Crystal size [mm]
0.02×0.11×0.20
black plate
triclinic
0.18×0.11×0.07
black block
triclinic
Crystal colour, habit
Crystal system
¯
¯
Space group
P1
P1
a [Å]
8.9736(2)
10.2985(3)
11.9402(5)
81.6543(19)
84.3852(19)
66.3718(17)
999.28(6)
2
8.6204(17)
9.1558(18)
15.059(3)
75.97(3)
b [Å]
c [Å]
α [°]
β [°]
74.55(3)
64.54(3)
111.52(3)
90
γ [°]
Volume [Å3]
1023.1(4)
2
8319(3)
Z
8
Density calcd. [gcm–3]
Absorption coefficient [mm–1]
F(000)
3.208
2.956
3.192
20.132
16.150
19.476
856
816
7104
Index ranges
–10 Յ h Յ 10
–12 Յ k Յ 12
–14 Յ l Յ 14
3.30–25.03
11093
–10 Յ h Յ 10
–10 Յ k Յ 10
–17 Յ l Յ 17
3.24–25.05
10395
–18 Յ h Յ 18
–46 Յ k Յ 45
–17 Յ l Յ 11
3.15–25.09
49979
θ Range [°]
Reflections collected
Independent reflections
Observed reflections
Parameter/restrains
R1/wR2 (all data)
R1/wR2 (final)
3513
3559
7365
2767
3218
5029
235/0
245/0
487/0
0.0562/0.0924
0.0385/0.0837
1.023
0.0654/0.1584
0.0613/0.1535
1.048
0.0936/0.1590
0.0543/0.1397
1.060
Goodness of fit
Min./max. ρe [eÅ3]
Temperature [K]
Diffractometer used
Scan type
Solution
Refinement
–1.583/1.351
200(2)
Nonius Kappa CCD
area detection
SHELXS-97
SHELXL-97
–4.346/3.900
200(2)
Nonius Kappa CCD
area detection
SHELXS-97
SHELXS-97
–2.971/1.404
200(2)
Nonius Kappa CCD
area detection
SHELXS-97
SHELXS-97
Eur. J. Inorg. Chem. 2006, 1060–1066
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
1065

C. Krinninger, S. Wirth, P. Klüfers, P. Mayer, I. P. Lorenz
FULL PAPER
(m), 2033 (s), 2010 (vs), 1962 (m), 1940 (m). UV/Vis (CH2Cl2): λmax
µ2-(η2-N,O-2,6-Dichloro-4-bromonitrosobenzene)bis[µ-chlorotricar-
( l o g ε ) = 2 6 0 n m ( 6 2 6 6 ) , 3 7 6 ( 2 5 5 1 ) , 6 9 9 ( 3 9 7 3 ) . bonylrhenium(I)] (9a): Synthesised from 139 mg (0.384 mmol) of 1a
C12H3Br2Cl2NO7Re2 (876.28): calcd. C 16.43, H 0.34, N 1.60;
found C 16.26, H 0.37, N 1.54. MS (DEI): m/z (%) = 876.2 (62)
[M+], 848.2 (17) [M+ – CO], 820.2 (4) [M+ – 2 CO], 792.3 (45)
[M+ – 4 CO], 764.3 (23) [M+ – 5 CO], 736.3 (23) [M+ – 6 CO].
µ2-(η2-N,O-2,6-Dibromonitrosobenzene)bis[µ-bromotricarbonylrhen-
ium(I)] (7b): Synthesised from 425 mg (1.050 mmol) of 1b and
and 65.3 mg (0.256 mmol) of 5. Yield: 65.5 mg (0.076 mmol, 37%)
green powder; m.p. 123 °C (dec.). 1H NMR (270.16 MHz, CDCl3):
δ = 7.60 (s, 2 H, CHarom.) ppm. 13C NMR (100.53 MHz, CDCl3):
δ = 124.8 (CHarom.), 130.3 (CHarom.), 131.6 (CHarom.), 160.2
(ON-Cq), 187.6 (CO), 191.9 (CO) ppm. IR (KBr): ν˜ = 3116 cm–1
(m), 3082 (m), 2088 (vs), 2022 (vs), 1950 (vs), 1925 (vs), 1726 (w),
1615 (s), 1560 (s), 1548 (s), 1469 (s), 1429 (w),1390 (w), 1378 (m),
1365 (w), 1333 (w), 1297 (m), 1280 (w), 1263 (w), 1182 (s), 1077
(m), 927 (m), 898 (w), 858 (s), 812 (m), 787 (m), 752 (w), 659 (w),
615 (m), 590 (w), 534 (w), 540 (w). IR (CH2Cl2): ν˜ = 2091 cm–1 (s),
2034 (vs), 2011 (vs), 1963 (vs), 1941 (vs). UV/Vis (CH2Cl2): λmax
(log ε) = 385 nm (2952), 491 (1906). C12H2BrCl4NO7Re2 (866.28):
calcd. C 16.63, H 0.23, N 1.62; found C 17.28, H 1.38, N 1.55. MS
(DEI): m/z (%) = 866.6 (52) [M+], 782.6 (49) [M+ – 3 CO], 754.6
(48) [M+ – 4 CO], 726.7 (100) [M+ – 5 CO], 698.6 (98) [M+ – 6
CO].
139 mg (0.524 mmol) of 3. Yield: 70.0 mg (0.073 mmol, 14%) green
1
crystals; m.p. 144 °C (dec.). H NMR (399.78 MHz, CDCl3): δ =
7.27 (t, 3J = 8.13 Hz, 1 H, CHarom.), 7.38 (d, 3J = 8.13 Hz, 1 H,
CHa r o m . ), 7.61–7.64 (m, 1 H, CHa r o m . ) ppm. 1 3 C NMR
(67.93 MHz, CDCl3): δ = 132.9 (CHarom.), 133.0 (CHarom.), 133.6
(CHarom.), 164.5 (ON-Cq), 185.2 (CO), 191.4 (CO) ppm. IR (KBr):
ν = 3070 cm–1 (w), 2963 (m), 2925 (m), 2096 (m), 2058 (m), 2006
˜
(vs), 1966 (s), 1929 (vs), 1611 (w), 1563 (s), 1571 (m), 1458 (m),
1437 (vs), 1420 (s), 1372 (w), 1343 (w), 1283 (vs), 1263 (vs), 1200
(s), 1154 (w), 1097 (s), 1060 (s), 1023 (s), 923 (w), 862 (m), 847 (s),
803 (vs), 803 (vs), 733 (s), 633 (m), 577 (w). IR (CH Cl ): ν =
˜
2
2
2088 cm–1 (m), 2032 (s), 2010 (vs), 1961 (m), 1943 (m). UV/Vis
(CH2Cl2): λmax (log ε) = 260 nm (12896), 376 (5319), 699 (8244).
C12H3Br4NO7Re2 (965.18): calcd. C 14.93, H 0.31, N 1.45; found
C 16.03, H 0.89, N 1.47. MS (DEI): m/z (%) = 964.1 (56) [M+],
936.1 (28) [M+ – CO], 880.1 (40) [M+ – 3 CO], 852.2 (18) [M+ – 4
CO], 824.2 (72) [M+ – 5 CO], 796.2 (89) [M+ – 6 CO].
[1] M. Cameron, B. G. Gowenlock, G. Vasapollo, Chem. Soc. Rev.
1990, 19, 355–379.
[2] R. Wilberger, C. Krinninger, H. Piotrowksi, P. Mayer, I.-P. Lo-
renz, Eur. J. Inorg. Chem. 2004, 12, 2488–2492.
[3] C. Krinninger, C. Högg, H. Nöth, J. C. Gálvez Ruiz, P. Mayer,
O. Burkacky, A. Zumbusch, I.-P. Lorenz, Chem. Eur. J. 2005,
11, 7228–7236.
µ2-(η2-N,O-2,6-Dibromo-4-chloronitrosobenzene)bis[µ-chlorotricar-
[4] a) E. Colacio, J. M. Dominguez-Vera, A. Escuer, R. Kivekas,
A. Romerosa, Inorg. Chem. 1994, 33, 3914–3924; b) E. Colacio,
J. M. Dominguez-Vera, E. Escuer, M. Klinga, R. Kivekas, A.
Romerosa, J. Chem. Soc., Dalton Trans. 1995, 343–348; c) E.
Colacio, J. M. Dominguez-Vera, A. Escuer, R. Kivekas, M.
Klinga, J.-M. Moreno, A. Romerosa, J. Chem. Soc., Dalton
Trans. 1997, 1685–1689; d) K. K.-H. Lee, W.-T. Wong, J. Chem.
Soc., Dalton Trans. 1997, 2987–2995.
[5] a) E. Colacio, J. M. Dominguez-Vera, A. Romerosa, R. Ki-
vekas, M. Klinga, A. Escuer, Inorg. Chim. Acta 1995, 234, 61–
65; b) E. Colacio, C. Lopez-Magana, V. McKee, A. Romerosa,
J. Chem. Soc., Dalton Trans. 1999, 2923–2926.
[6] D. L. Packett, W. C. Trogler, A. L. Rheingold, Inorg. Chem.
1987, 26, 4308–4309.
bonylrhenium(I)] (8a): Synthesised from 132 mg (0.366 mmol) of 1a
and 73.0 mg (0.244 mmol) of 4. Yield: 112 mg (0.123 mmol, 67%)
green crystals; m.p. 129 °C (dec.). 1H NMR (399.78 MHz, CDCl3):
δ = 7.66 (s, 2 H, CHarom.) ppm. 13C NMR (100.53 MHz, CDCl3):
δ = 131.2 (CHarom.), 132.7 (CHarom.), 133.9 (CHarom.), 162.3
(ON-C ), 187.5 (CO), 191.8 (CO) ppm. IR (KBr): ν = 3074 cm–1
˜
q
(w), 2963 (w), 2089 (vs), 2031 (vs), 2000 (vs), 1949 (vs), 1922 (vs),
1614 (m), 1562 (m), 1538 (w), 1506 (w), 1407 (w), 1447 (w), 1419
(m), 1371 (m), 1337 (m), 1294 (w), 1195 (m), 1127 (m), 1059 (w),
925 (w), 897 (m), 862 (m), 806 (w), 747 (w), 735 (w), 642 (w), 580
(w), 562 (w). IR (CH Cl ): ν = 2090 cm–1 (vs), 2034 (vs), 2010 (vs),
˜
2
2
1962 (vs), 1941 (vs). UV/Vis (CH2Cl2): λmax (log ε) = 375 nm
(4615), 707 (6304). C12H2Br2Cl3NO7Re2 (910.72): calcd. C 15.81,
H 0.20, N 1.72; found C 16.21, H 0.21, N 1.63. MS (DEI): m/z (%)
= 910.7 (15) [M+], 826.7 (13) [M+ – 3 CO], 798.7 (7) [M+ – 4 CO],
770.7 (28) [M+ – 5 CO], 742.8 (26) [M+ – 6 CO].
µ2-(η2-N,O-2,6-Dibromo-4-chloronitrosobenzene)-bis[µ-bromotricar-
bonylrhenium(I)] (8b): Synthesised from 137 mg (0.339 mmol) of 1b
[7] T. Iwasa, H. Shimada, A. Takami, H. Matsuzaka, Y. Ishii, M.
Hidai, Inorg. Chem. 1999, 38, 2851–2859.
[8] C. Romming, H. J. Talberg, Acta Chem. Scand. 1973, 27, 2246–
2248.
[9] C. Krinninger, S. Wirth, J. C. Galvez Ruiz, P. Klüfers, H. Nöth,
I.-P. Lorenz, Eur. J. Inorg. Chem. 2005, 20, 4094–4098.
[10] Trocknen im Labor, brochure from the series “Reagenzien”,
Merck, Darmstadt.
[11] G. Brauer, Handbuch der Präparativen Anorganischen Chemie,
Ferdinand Enke Verlag, Stuttgart, vol. III, 3rd. ed., 1981,
1951–1952.
and 73.0 mg (0.203 mmol) of 4. Yield: 45.0 mg (0.045 mmol, 26%)
green crystals; m.p. 135 °C (dec.). 1H NMR (399.78 MHz, CDCl3):
δ = 7.64 (s, 2 H, CHarom.) ppm. 13C NMR (100.53 MHz, CDCl3):
δ = 131.2 (CHarom.), 132.5 (CHarom.), 133.9 (CHarom.), 164.3
(ON-C ), 186.3 (CO) ppm. IR (KBr): ν = 3073 cm–1 (w), 2963 (w),
˜
[12] R. R. Holmes, R. P. Bayer, J. Am. Chem. Soc. 1960, 82, 3454–
q
2086 (s), 2034 (vs), 1999 (vs), 1954 (vs), 1923 (vs), 1615 (w), 1563
(m), 1507 (w), 1481 (w), 1461 (w), 1420 (w), 1373 (w), 1353 (w),
1329 (w), 1297 (w), 1126 (w), 1105 (w), 1054 (w), 1030 (w), 924
(m), 862 (m), 807 (m), 807 (m), 747 (m), 687 (w), 637 (w), 609 (w),
3456.
[13] CCDC-285191 (for 6a), -283167 (for 6b), -285190 (for 7a), -
285189 (for 7b), -283168 (for 8a) and -283169 (for 8b) contain
the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crys-
tallographic Data Centre via www.ccdc.cam.ac.uk/data_requ-
est/cif.
[14] G. M. Sheldrick, SHELXL 97, Program for Crystal Structure
Refinement, University of Göttingen, Germany, 1997.
Received: September 1, 2005
576 (w), 539 (w). IR (CH Cl ): ν = 2086 cm–1 (vs), 2034 (vs), 2010
˜
2
2
(vs), 1962 (vs), 1941 (vs). UV/Vis (CH2Cl2): λmax (log ε) = 373 nm
(3476), 704 (3117). C12H2Br4ClNO7Re2 (999.63): calcd. C 14.43, H
0.20, N 1.40; found C 15.87, H 0.39, N 1.66. MS (DEI): m/z (%)
= 998.1 (1) [M+], 914.2 (1) [M+ – 3 CO], 858.1 (1) [M+ – 5 CO],
830.3 (28) [M+ – 6 CO].
Published Online: January 9, 2006
1066
www.eurjic.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 1060–1066