Facile oxidative addition of C-Cl bonds to new neutral and cationic rhodium(I)-bipyridine complexes

Article abstract of DOI:10.1002/1099-0682(200207)2002:7<1827::AID-EJIC1827>3.0.CO;2-Q

Neutral and cationic Rh(dmbpy) systems (dmbpy = 4,4′-dimethyl-2,2′-bipyridine) were synthesized starting from different metal precursors. [RhCl(dmbpy)(DMSO)] (3) was obtained either from the ethylene precursor [RhCl(dmbpy)(C₂H₄)] (1)

Full text of DOI:10.1002/1099-0682(200207)2002:7<1827::AID-EJIC1827>3.0.CO;2-Q

FULL PAPER
Facile Oxidative Addition of C؊Cl Bonds to New Neutral and Cationic
Rhodium(I)-Bipyridine Complexes
Reto Dorta,[a] Linda J. W. Shimon,[b] Haim Rozenberg,[b] and David Milstein*[a]
Keywords: Rhodium / N ligands / Oxidative addition / Peroxo complexes
Neutral and cationic Rh(dmbpy) systems (dmbpy = 4,4Ј-di-
methyl-2,2Ј-bipyridine) were synthesized starting from ing RhIII complexes [RhCl2(CH2C6H5)(dmbpy)(DMSO)] (7),
different metal precursors. [RhCl(dmbpy)(DMSO)] (3) was [RhCl2(CH2C6H5)(dmbpy){CNC(CH3)3}] (9) [RhCl(CH2-
obtained either from the ethylene precursor
[RhCl(dmbpy)(C2H4)] (1) or directly from [Rh2Cl2(COE)4]
chloride leading to quantitative isolation of the correspond-
C6H5)(dmbpy)(DMSO)2]PF6 (10) and [RhCl(CH2C6H5)-
(dmbpy){CNC(CH3)3}2]BF4 (12). Oxidative addition of dichlo-
(COE = cyclooctene) in DMSO. The neutral isocyanide com- romethane by complexes 3 and 5 yielded the corresponding
plex [RhCl(dmbpy){CNC(CH3)3}] (4) was obtained by reac- chloromethyl complexes [RhCl2(CH2Cl)(dmbpy)(DMSO)] (8)
tion of 1 with tert-butyl isocyanide. Reaction of dmbpy with
[Rh(DMSO)4]PF6 gave the corresponding cationic complex
[Rh(dmbpy)(DMSO)2]PF6 (5), and the cationic system
[Rh(dmbpy){CNC(CH3)3}2]BF4 (6) was prepared starting from
[Rh(dmbpy)(HD)]BF4 (2) (HD = 1,5-hexadiene). All of these
complexes were found to activate the C−Cl bond in benzyl
and [RhCl(CH2Cl)(dmbpy)(DMSO)2]PF6 (11). The reactivity
of 3 towards oxygen led to the isolation of the peroxo RhIII
complex [RhCl(O2)(dmbpy)(DMSO)] (13). Complexes 6, 8, 9
and 12 were characterized by X-ray crystallography.
( Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany,
2002)
Introduction
tion of the relatively inert CϪCl bond, which is more chal-
lenging than that of the CϪBr and CϪI bonds. Oxidative
addition of CϪCl bonds, especially of dichloromethane, re-
quires an electron-rich rhodium center. Relatively few ex-
amples of simple oxidative addition of dichloromethane to
RhI complexes have been reported. These systems incorpor-
ate mono- or polydentate phosphorous ligands,[9Ϫ11] mono-
or polydentate nitrogen ligands,[12Ϫ14] sulfur macrocycles[15]
or phosphorous-nitrogen hybrid ligands,[16Ϫ18]and in sev-
eral cases the starting RhI species were not isol-
ated.[12,14,17,18]
Herein we report the synthesis, characterization and ox-
idative addition chemistry of new RhI complexes with the
bidentate ligand 4,4Ј-dimethyl-2,2Ј-bipyridine (dmbpy).[19]
The nucleophilicity of the RhI can be controlled by the cho-
ice of the additional ligands. We chose the loosely bound
DMSO ligand and the relatively strongly bound tert-butyl
isocyanide ligand for our study. The oxidative addition of
dichloromethane at room temperature takes place in the
complexes stabilized by additional DMSO ligands. Oxidat-
ive addition of the CϪCl bond of benzyl chloride is ob-
served in all of these complexes. Reaction of the neutral
RhI-(dmbpy)-DMSO complex with O2 leads to the isola-
tion of a stable peroxo-RhIII compound.
The use of transition metal catalysts that employ nitro-
gen-donor ligands is expanding rapidly.[1] The most widely
used nitrogen ligand is the bidentate 2,2Ј-bipyridine unit.[2]
RhI-bipyridine systems and closely related derivatives have
been extensively investigated as catalysts in the hydrogena-
tion and hydrogen-transfer reactions of olefins and ke-
tones.[3] In this context, the cationic complex
[Rh(bpy)(L)2]X (X ϭ PF6؊, BF4؊, ClO4؊; bpy ϭ 2,2Ј-bi-
pyridine, L ϭ acetone) is believed to be the active species in
the hydrogenation of olefins.[4] Such complexes with labile
additional ligands have never been isolated, the only known
complexes of this type being with L ϭ CO,[5] or with chelat-
ing ligands such as dienes[6] or bipyridine.[7] Furthermore,
oxidative addition to neutral or cationic precursors of this
type has never been studied in detail, the only example re-
ported involving oxidative addition of methyl iodide to
[Rh(bpy)(CO)X] (X ϭ Cl, Br, I; bpy ϭ 2,2Ј-bipyridine).[8]
The oxidative addition of carbon halides to low-valent
metal complexes is involved in numerous industrially im-
portant catalytic cycles and has therefore attracted consid-
erable academic interest. Of particular interest is the activa-
[a]
Department of Organic Chemistry, The Weizmann Institute of
Science,
Results and Discussion
Synthesis of the RhI-dmbpy Complexes
The new complexes 1Ϫ6 were prepared from different
precursors. The preparation of 1 was achieved following a
Rehovot, 76100, Israel
E-mail: david.milstein@weizmann.ac.il
[b]
Department of Chemical Services, The Weizmann Institute of
Science,
Rehovot, 76100, Israel
Eur. J. Inorg. Chem. 2002, 1827Ϫ1834  WILEY-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002 1434Ϫ1948/02/0707Ϫ1827 $ 20.00ϩ.50/0
1827

R. Dorta, L. J. W. Shimon, H. Rozenberg, D. Milstein
FULL PAPER
literature method published for the corresponding 2,2Ј-bi-
The corresponding cationic complexes, 5 and 6, respect-
pyridine complex.[20] Complex 1 was found to be moder- ively, were also synthesized (Scheme 2). Compound 5 was
ately stable in a dichloromethane solution but decomposed obtained as a red solid after addition of dmbpy to a DMSO
immediately when dissolved in either acetonitrile, pyridine solution containing [Rh(DMSO)4]PF6.[21] As expected, the
or methanol. Surprisingly, dissolution of 1 in DMSO re- 1H NMR spectrum in [D6]DMSO showed only three peaks
sulted in quantitative formation of 3, which was isolated by in the aromatic region for the ligand and one singlet for the
pouring the concentrated DMSO solution into a large ex- two methyl groups of dmbpy. Complex 6 was obtained by
cess of diethyl ether. Direct synthesis of 3 was achieved by treating a THF slurry of [Rh(dmbpy)(HD)]BF4 (2) (HD ϭ
treating
a DMSO solution of the rhodium dimer 1,5-hexadiene) with 2 equiv. of tert-butyl isocyanide. After
[Rh2Cl2(COE)4] (COE ϭ cyclooctene) with an equimolar precipitation from pentane, 6 was obtained as a deep-red
1
amount of 4,4Ј-dimethyl-2,2Ј-bipyridine. Subsequent pre- solid. FT-IR spectroscopy, H NMR spectroscopy and ele-
cipitation from diethyl ether gave 3 as a brick-red solid in mental analysis support its formulation, and the molecular
high yield (Scheme 1).
structure of 6 was confirmed by an X-ray diffraction study
of red single crystals obtained by slow evaporation of an
acetone solution. An ORTEP drawing is shown in Figure 1
and the averages of selected bond lengths and angles are
given in Table 1. The rhodium atom of complex 6 is located
in the center of a square planar arrangement with the two
Scheme 1. Synthesis of the neutral RhI complexes 3 and 4
1
The H NMR spectrum of 3 showed six resonances in
the aromatic region attributable to the nonequivalent parts
of the ligand unit, one singlet at δ ϭ 3.19 ppm for the co-
ordinated DMSO (bound through the sulfur atom) and two
singlets for the methyl groups of dmbpy at δ ϭ 2.31 and
2.51 ppm . The corresponding neutral isocyanide complex
4 was synthesized in high yield by treating a suspension of
1 in THF with 1 equiv. of tert-butyl isocyanide as shown in
Scheme 1. Starting with 3 and treating it with 1 equiv. of
tert-butyl isocyanide led to a mixture of products. One of
the by-products was isolated by precipitation from the solu-
Scheme 2. Synthesis of the cationic RhI complexes 5 and 6
1
tion mixture and identified by H NMR spectroscopy to
be the symmetrical species [Rh(dmbpy){CNC(CH3)3}2]Cl.
This indicates that displacement of the DMSO molecule in
3 is much slower than that of ethylene leading to the dis-
placement of the chloride and the formation of the more
1
stable bis-isocyanide species. The H NMR spectrum of 4
showed the expected peaks for the nonsymmetrical dmbpy
ligand and a singlet at δ ϭ 1.53 ppm for the coordinated
tert-butyl isocyanide.
Figure 1. ORTEP drawing of a molecule of 6 (50% of probability);
hydrogen atoms are omitted for clarity
1828
Eur. J. Inorg. Chem. 2002, 1827Ϫ1834

Addition of CϪCl Bonds to Rhodium(I)-Bipyridine Complexes
FULL PAPER
˚
Table 1. Selected bond lengths (A) and bond angles (°) for 6
Rh(2)ϪC(70)
Rh(2)ϪC(60)
1.909(7) Rh(2)ϪN(3)
1.910(8) Rh(2)ϪN(4)
2.060(7)
2.077(6)
C(70)ϪRh(2)ϪC(60) 87.5(4)
C(70)ϪRh(2)ϪN(4) 95.6(3)
C(70)ϪRh(2)ϪN(3)
C(60)ϪRh(2)ϪN(3)
174.5(3) C(60)ϪRh(2)ϪN(4) 176.9(3)
97.9(3) N(3)ϪRh(2)ϪN(4) 79.0(3)
isocyanide ligands trans to the corresponding pyridine moi-
eties of dmbpy.
Oxidative Addition of C؊Cl Bonds
When an acetone or DMSO solution of 3 was treated
with benzyl chloride, an immediate color change from deep
1
red to yellow took place. The H NMR spectrum showed
clean oxidative addition of the CϪCl bond, and subsequent
workup of the yellow solution gave complex 7 in high yield
(Scheme 3). The benzylic CH2 group is seen as two non-
equivalent proton signals showing couplings with each
other (6.8 Hz) and with the rhodium metal center (3.1 Hz).
In the case of dichloromethane, oxidative addition was, as
expected, much slower and took 15 h for completion, giving
Scheme 3. Reaction of the RhI complexes 3؊6 with RϪCl to yield
the RhIII complexes 7؊12
complex 8 in quantitative yield. Following the process by (Ͻ10% by integration) of an isomeric species were also pre-
1H NMR spectroscopy showed the appearance of two sig- sent. In this case, the ligand seems to be symmetrical with
nals at δ ϭ 4.31 ppm (dd, J ϭ 5.7, 3.0 Hz) and δ ϭ 4.75 three signals in the aromatic region and one singlet for the
ppm (dd, J ϭ 5.7, 3.0 Hz) for the CH2Cl unit (Figure 2) methyl group of dmbpy. The chloromethyl moiety gives rise
together with a new set of peaks for the dmbpy unit. When to one doublet at δ ϭ 5.05 ppm (d, J ϭ 3.1 Hz). These data
the reaction was performed in [D6]DMSO, minor amounts indicate a species with the two chloride ligands trans to the
1
Figure 2. H NMR follow-up experiment of the reaction between 3 and dichloromethane in [D6]DMSO
Eur. J. Inorg. Chem. 2002, 1827Ϫ1834
1829

R. Dorta, L. J. W. Shimon, H. Rozenberg, D. Milstein
FULL PAPER
bipyridine moiety and with the chloromethyl group and the icity of the metal center. Treating a deep-red acetone solu-
DMSO ligand axially arranged. This compound could be tion of 4 with benzyl chloride for 12 h at room temperature
1
removed during workup due to its higher solubility in di- led to a color change to yellow. The H NMR spectrum
ethyl ether. It was not observed when the reaction was per- showed that clean oxidative addition took place also in this
formed in acetone. Trying to obtain this compound in pure case, leading to quantitative isolation of complex 9. In con-
form, an NMR tube sample of 8 in [D6]DMSO was heated trast, oxidative addition of dichloromethane to complex 4
1
at 80 °C for 2 h. Indeed, the H NMR spectrum showed did not occur at room temperature. Even after stirring a
30% of this compound compared to 8 was formed.[22] Col- solution of 4 with excess CH2Cl2 for several days the start-
orless single crystals of 8 suitable for X-ray diffraction were ing complex was recovered unchanged. The crystal struc-
obtained by slow diffusion of diethyl ether into a concen- ture of [RhCl2(CH2C6H5)(dmbpy){CNC(CH3)3}] (9) has
trated DMSO solution. The geometry around the rhodium been determined (Figure 4) and found to adopt an octahed-
atom in this complex is distorted octahedral (Figure 3). In ral geometry. In the equatorial plane, the rhodium center is
the equatorial plane, a chloride atom, the two N atoms of bound to the dmbpy, the tert-butyl isocyanide and to one
dmbpy and the S atom of DMSO are coordinated to the of the chloride atoms. The benzylic moiety together with
rhodium atom. The chloromethyl ligand and the second the second chloride atom adopt the apical positions. As in
chloride atom occupy the axial positions. As expected, the the case of 8, the RhϪCl bond length of the chloride trans
two chloride atoms show quite different bond lengths to to the pyridine of dmbpy is significantly shorter than the
rhodium, the one trans to the N atom being significantly one trans to the benzyl moiety [Rh(1)ϪCl(3) ϭ 2.3573(10)
shorter than the chloride trans to the chloromethyl moiety and Rh(1)ϪCl(2) ϭ 2.5391(9), respectively] (Table 3).
[Rh(1)ϪCl(3) ϭ 2.3528(7) and Rh(1)ϪCl(3) ϭ 2.4891(7)]
˚
(Table 2). The Rh(1)ϪC(4) distance of 2.046(2) A is very
close to the value reported recently for [RhCl2(CH2Cl){2,6-
(CHϭNiPr)2-C5H3N}].[13] The C(4)ϪCl(4) bond length of
˚
1.811(3) A is longer than those found for other metal chloro-
methyl complexes, indicating a slightly higher carbene
character of 8 (RhϭCH2ϩClϪ).
Figure 4. ORTEP drawing of a molecule of 9 (50% of probability);
hydrogen atoms (except RhϪCh2R) are omitted for clarity
˚
Table 3. Selected bond lengths (A) and bond angles (°) for 9
Rh(1)ϪC(31)
Rh(1)ϪN(1)
Rh(1)ϪN(2)
1.943(4)
2.023(3)
2.070(3)
Rh(1)ϪC(20)
Rh(1)ϪCl(3)
Rh(1)ϪCl(2)
2.100(4)
2.3573(10)
2.5391(9)
Figure 3. ORTEP drawing of a molecule of 8 (50% of probability);
hydrogen atoms (except RhϪCh2Cl) are omitted for clarity
C(31)ϪRh(1)ϪN(1) 98.11(13) N(2)ϪRh(1)ϪCl(3) 95.57(8)
C(31)ϪRh(1)ϪN(2) 176.73(13) C(20)ϪRh(1)ϪCl(3) 86.42(11)
N(1)ϪRh(1)ϪN(2) 79.50(11) C(31)ϪRh(1)ϪCl(2) 94.09(11)
C(31)ϪRh(1)ϪC(20) 88.59(16) N(1)ϪRh(1)ϪCl(2) 84.55(8)
N(1)ϪRh(1)ϪC(20) 94.04(13) N(2)ϪRh(1)ϪCl(2) 87.93(8)
N(2)ϪRh(1)ϪC(20) 89.35(14) C(20)ϪRh(1)ϪCl(2) 177.12(12)
C(31)ϪRh(1)ϪCl(3) 86.84(11) Cl(3)ϪRh(1)ϪCl(2) 94.76(3)
N(1)ϪRh(1)ϪCl(3) 175.04(8)
˚
Table 2. Selected bond lengths (A) and bond angles (°) for 8
Rh(1)ϪC(4)
Rh(1)ϪN(20)
Rh(1)ϪN(10)
2.046(2)
Rh(1)ϪS(5)
2.2870(7)
2.3528(7)
2.4891(7)
2.0526(19) Rh(1)ϪCl(2)
2.0678(19) Rh(1)ϪCl(3)
C(4)ϪRh(1)ϪN(20) 89.92(9)
C(4)ϪRh(1)ϪN(10) 89.78(9)
N(20)ϪRh(1)ϪN(10) 79.19(7)
N(10)ϪRh(1)ϪCl(2) 93.79(5)
S(5)ϪRh(1)ϪCl(2)
86.46(2)
The cationic complexes 5 and 6 also undergo oxidative
addition of the CϪCl bond of benzyl chloride (Scheme 3).
In both cases, oxidative addition occurred somewhat slower
than for the corresponding neutral complexes, leading to
the cationic RhIII complexes 10 and 12, respectively. Sur-
prisingly, the benzyl methylene group in 10 shows formation
of the asymmetrical species with one DMSO molecule trans
C(4)ϪRh(1)ϪCl(3) 175.50(8)
N(20)ϪRh(1)ϪCl(3) 89.58(6)
C(4)ϪRh(1)ϪS(5)
N(20)ϪRh(1)ϪS(5)
N(10)ϪRh(1)ϪS(5)
C(4)ϪRh(1)ϪCl(2)
92.71(8)
100.68(6) N(10)ϪRh(1)ϪCl(3) 85.74(5)
177.51(5) S(5)ϪRh(1)ϪCl(3) 91.78(2)
87.08(8) Cl(2)ϪRh(1)ϪCl(3) 92.88(4)
N(20)ϪRh(1)ϪCl(2) 172.38(5)
The reactivity of the corresponding tert-butyl isocyanide to the benzyl methylene, giving rise to two doublets of
complex 4 towards CϪCl bonds was checked next. As ex- doublets for the methylene group. Oxidative addition to
pected, complex 4 is much less reactive due to significantly complex 6 does lead to the expected symmetrical species
higher backbonding from the rhodium center to the tert- with the methylene group appearing as one doublet at δ ϭ
butyl isocyanide ligand and the resulting lower nucleophil- 3.12 ppm, the doublet signal arising from coupling to the
1830
Eur. J. Inorg. Chem. 2002, 1827Ϫ1834

Addition of CϪCl Bonds to Rhodium(I)-Bipyridine Complexes
FULL PAPER
rhodium center. Slow diffusion of diethyl ether into an acet- chloride occupy the position trans to the second oxygen
one solution of 12 led to colorless crystals suitable for X- atom. With respect to the properties of 13, we should note
ray diffraction. As shown in Figure 5, compound 12 adopts that O2 is bonded strongly and did not dissociate under
the expected octahedral arrangement around the metal vacuum or by bubbling N2 through a solution of 13.[23]
center. The bond lengths between the rhodium atom and Complexes 4 and 5 also add oxygen and a detailed investi-
the tert-butyl isocyanide and dmbpy ligands are very close gation of the reactivity of these complexes will be published
to the values observed in the starting complex 6 with mar- in due course.
ginally longer Rh(1)ϪC(40) and Rh(1)ϪC(30) bond lengths
(Table 4). As observed in the neutral systems, also in the
cationic case the DMSO stabilized complex 5 oxidatively
added dichloromethane due to its higher nucleophilicity.
Reaction of 5 with excess CH2Cl2 resulted in a gradual
color change from deep-red to yellow when left standing at
room temperature for two days and gave the symmetrical
complex 11 in high yield (Scheme 3).
Scheme 4. Reaction of complex 3 with O2 giving the peroxo com-
plex 13
Figure 5. ORTEP drawing of a molecule of 12 (50% of probability);
hydrogen atoms (except RhϪCh2R) are omitted for clarity
Summary
New neutral and cationic rhodium complexes bearing the
chelating 4,4Ј-dimethyl-2,2Ј-bipyridine (dmbpy) ligand and
additional DMSO or tert-butyl isocyanide ligands were syn-
˚
Table 4. Selected bond lengths (A) and bond angles (°) for 12
Rh(1)ϪC(40)
Rh(1)ϪC(30)
Rh(1)ϪN(1)
1.939(4)
1.939(4)
2.065(3)
Rh(1)ϪN(2)
Rh(1)ϪC(20)
Rh(1)ϪCl(2)
2.066(3)
2.098(3)
2.4928(10)
thesized in high yield starting from various RhI precursors.
These complexes underwent oxidative addition of the CϪCl
bond of benzyl chloride at room temperature. The com-
plexes bearing the additional DMSO ligands were shown to
be more nucleophilic at the rhodium center and underwent
CϪCl oxidative addition of dichloromethane. In addition,
the oxidative addition of O2 to one of the RhI complexes
led to the quantitative isolation of a stable RhIII peroxo spe-
cies.
C(40)ϪRh(1)ϪC(30) 84.80(15) N(1)ϪRh(1)ϪC(20) 90.36(13)
C(40)ϪRh(1)ϪN(1) 175.67(13) N(2)ϪRh(1)ϪC(20) 84.42(13)
C(30)ϪRh(1)ϪN(1) 97.93(13) C(40)ϪRh(1)ϪCl(2) 86.09(11)
C(40)ϪRh(1)ϪN(2) 97.87(13) C(30)ϪRh(1)ϪCl(2) 88.75(11)
C(30)ϪRh(1)ϪN(2) 176.95(12) N(1)ϪRh(1)ϪCl(2) 90.60(8)
N(1)ϪRh(1)ϪN(2) 79.49(11) N(2)ϪRh(1)ϪCl(2) 92.89(8)
C(40)ϪRh(1)ϪC(20) 92.81(15) C(20)ϪRh(1)ϪCl(2) 176.93(11)
C(30)ϪRh(1)ϪC(20) 94.01(15)
Oxidative Addition of Oxygen to 3
Experimental Section
When a deep-red DMSO or acetone solution of 3 was
treated with 1 equiv. or excess O2, an immediate color
change to yellow occurred. The product was identified as
being the peroxo complex [RhCl2(O2)(dmbpy)(DMSO)]
(13) based on elemental analysis and the appearance of an
General Procedures: All experiments were carried out under an at-
mosphere of purified nitrogen in a Vacuum Atmospheres glove box
equipped with a MO 40-2 inert gas purifier. All solvents were re-
agent grade or better. All non-deuterated solvents were refluxed
over sodium/benzophenone ketyl and distilled under argon atmo-
sphere. Deuterated solvents were used as received. All the solvents
IR band at ν˜ ϭ 870 cmϪ1 for the peroxo ligand (Scheme 4).
1
The H NMR spectrum showed shifts for all the protons were degassed with argon and kept in the glove box over molecular
sieves. Commercially available reagents were used as received.
The complexes [Rh2Cl2(COE)4],[24] [Rh2Cl2(C2H4)4],[25] and
[Rh(DMSO)4]PF6 [21] were prepared according to literature proced-
ures.
relative to the peaks observed for the starting complex 3.
As expected, the biggest difference is seen in one of the
protons in the α-position to the nitrogen of the dmbpy li-
gand, the pyridine moiety being substantially more shielded
by the presence of the oxygen atom trans to it. However,
1H NMR spectra were recorded at 250 MHz on a Bruker AMX-
we could not determine whether the DMSO ligand or the 250 NMR spectrometer or on a Bruker AMX-400 NMR spectro-
Eur. J. Inorg. Chem. 2002, 1827Ϫ1834 1831

R. Dorta, L. J. W. Shimon, H. Rozenberg, D. Milstein
FULL PAPER
meter. Chemical shifts are reported in ppm downfield from tetra-
298 K): δ ϭ 1.53 (s, 9 H), 2.23 (s, 3 H), 2.49 (s, 3 H), 7.10 (d, J ϭ
methylsilane and are referenced to the residual hydrogen signal of 5.9 Hz, 1 H), 7.46 (d, J ϭ 5.7 Hz, 1 H), 7.98 (s, 1 H), 8.14 (s, 1 H),
the deuterated solvents (δ ϭ 2.04 ppm, acetone; δ ϭ 2.49 ppm,
DMSO; δ ϭ 5.32 ppm, dichloromethane). Abbreviations used in
the description of NMR spectroscopic data are as follows: br.,
broad; s, singlet; d, doublet; t, triplet; m, multiplet. Elemental ana-
lyses were performed by H. Kolbe, Mikroanalytisches Laborator-
ium, 45470 Mülheim, Germany.
8.85 (d, J ϭ 5.6 Hz, 1 H), 9.37 (d, J ϭ 5.7 Hz, 1 H) ppm.
C17H21ClN3Rh (405.7): C 50.32, H 5.22, N 10.36; found C 50.21,
H 5.29, N 10.26.
Synthesis of [Rh(dmbpy)(DMSO)2]PF6 (5): [Rh(DMSO)4]PF6
(65 mg, 0.115 mmol) and dmbpy (21 mg, 0.115 mmol) were dis-
solved in 4 mL DMSO and the resulting deep-red solution was
stirred at room temperature for 2 h. The solution was then poured
into diethyl ether (150 mL) and the brick-red precipitate was de-
canted, washed with additional diethyl ether and dried in vacuo.
Synthesis of [RhCl(dmbpy)(C2H4)] (1): [Rh2Cl2(C2H4)4] (241 mg,
0.620 mmol) was dissolved in toluene (35 mL) and filtered, af-
fording an orange solution. 4,4Ј-dimethyl-2,2Ј-bipyridine (205 mg,
1.115 mmol) was dissolved in toluene (8 mL) and added dropwise.
The color of the solution turned from orange to violet. Stirring
at room temperature for 2 h resulted in the formation of a violet
precipitate which was filtered off, washed with toluene and dried
in vacuo. Yield: 346 mg, 89%. 1H NMR (250 MHz, CD2Cl2,
298 K): δ ϭ 2.27 (s, 3 H), 2.53 (s, 3 H), 3.62 (s, 4 H), 7.00 (d, J ϭ
5.1 Hz, 1 H), 7.21 (d, J ϭ 5.9 Hz, 1 H), 7.39 (d, J ϭ 5.6 Hz, 1 H),
7.63 (s, 1 H), 7.84 (s, 1 H), 9.06 (d, J ϭ 5.6 Hz, 1 H) ppm.
C14H16ClN2Rh (350.7): C 47.95, H 4.60, N 7.99; found C 47.99, H
4.78, N 7.78.
1
Yield: 61 mg, 90%. H NMR (250 MHz, [D6]DMSO, 298 K): δ ϭ
2.52 (s, 6 H), 7.52 (d, J ϭ 5.9 Hz, 2 H), 8.41 (s, 2 H), 8.70 (d, J ϭ
5.8 Hz, 2 H) ppm. C16H24F6N2O2PRhS2 (588.4): C 32.66, H 4.11,
N 4.76; found C 32.78, H 4.18, N 4.71.
Synthesis of [Rh(dmbpy){CNC(CH3)3}2]BF4 (6): A THF (3 mL) so-
lution of tert-butyl isocyanide (33 mg, 0.401 mmol) was added
dropwise to a red suspension of 2 (87 mg, 0.191 mmol) in THF (6
mL). The suspension was left stirring at room temperature for 2 h
during which time the color turned deep-red with precipitation of
a deep-red solid. Concentration to 3 mL, addition of pentane and
subsequent washings with additional pentane afforded a deep-red
solid which was dried in vacuo. Yield: 91 mg, 88%. 1H NMR
(250 MHz, [D6]acetone, 298 K): δ ϭ 1.62 (s, 18 H), 2.55 (s, 6 H),
7.56 (d, J ϭ 5.6 Hz, 2 H), 8.39 (s, 2 H), 8.67 (d, J ϭ 5.5 Hz, 2 H)
ppm. C22H30BF4N4Rh (540.2): C 48.91, H 5.60, N 10.37; found C
48.76, H 5.52, N 10.27.
Synthesis of [Rh(dmbpy)(HD)]BF4 (2):
A
suspension of
[Rh2Cl2(COE)4] (140 mg, 0.196 mmol) in MeOH (7 mL) was
treated with excess 1,5-hexadiene (1.1 mL) and the yellow suspen-
sion was stirred at room temperature for 1.5 h. Addition of a solu-
tion of 4,4Ј-dimethyl-2,2Ј-bipyridine (72 mg, 0.392 mmol) in
dichloromethane (4 mL) resulted in a color change to deep red.
After stirring the solution at room temperature for 1 h, a solution
of AgBF4 (76 mg, 0.392 mmol) in dichloromethane (4 mL) was ad-
ded dropwise and the solution was stirred at room temperature
for another hour. Filtration, followed by concentration of the red
solution to 6 mL and addition of diethyl ether led to the precipita-
tion of a red solid which was filtered, washed with additional di-
ethyl ether and dried in vacuo. Yield: 173 mg, 97%. 1H NMR
(250 MHz, CD2Cl2, 298 K): δ ϭ 1.94 (m, 2 H), 2.54 (m, 2 H), 2.61
(s, 6 H), 3.00 (d, J ϭ 13.9 Hz, 2 H), 3.59 (d, J ϭ 7.7 Hz, 2 H), 4.78
(m, 2 H), 7.47 (d, J ϭ 5.7 Hz, 2 H), 7.66 (d, J ϭ 5.8 Hz, 2 H), 8.15
(s, 2 H) ppm. C18H22BF4N2Rh (456.1): C 47.40, H 4.87, N 6.14;
found C 47.36, H 4.79, N 6.08.
Reaction of
3 with Benzyl Chloride. Formation of [RhCl2-
(CH2C6H5)(dmbpy)(DMSO)] (7): Complex 3 (70 mg, 0.175 mmol)
was dissolved in an acetone/DMSO (3:1 mL) mixture and stirred
at room temperature for 30 min giving a deep-red solution. Addi-
tion of benzyl chloride (44 mg, 0.348 mmol) led to an immediate
color change to yellow. Leaving the solution at room temperature
for 1 h resulted in the formation of a yellow precipitate which was
carefully decanted, washed with diethyl ether and dried in vacuo.
1
Yield: 77 mg, 84%. H NMR (250 MHz, [D6]DMSO, 298 K): δ ϭ
2.39 (s, 3 H), 2.48 (s, 3 H), 3.51 (dd, J ϭ 6.8 Hz and 3.0 Hz, 1 H),
4.02 (dd, J ϭ 6.8 Hz and 3.1 Hz, 1 H), 6.17 (d, J ϭ 6.9 Hz, 2 H),
6.50 (dd, J ϭ 7.5 Hz, 2 H), 6.70 (dd, J ϭ 7.3 Hz, 1 H), 7.42 (d,
J ϭ 5.0 Hz, 1 H), 7.52 (d, J ϭ 5.0 Hz, 1 H), 8.01 (s, 1 H), 8.18 (s,
1 H), 9.12 (d, J ϭ 5.9 Hz, 1 H), 9.41 (d, J ϭ 5.7 Hz, 1 H) ppm.
C21H25Cl2N2ORhS (527.3): C 47.83, H 4.78, N 5.31; found C
47.35, H 4.76, N 5.22.
Synthesis of [RhCl(dmbpy)(DMSO)] (3): [Rh2Cl2(COE)4] (494 mg,
0.692 mmol, COE ϭ cyclooctene) was dissolved in DMSO (16 mL)
and the deep-orange solution was stirred at room temperature for
30 min. 4,4Ј-Dimethyl-2,2Ј-bipyridine (255 mg, 1.384 mmol) was
then added as a solid in small portions resulting in a color change
to deep red. The solution was stirred for 3 h at room temperature
and then poured into diethyl ether (450 mL). The resulting brick-
red solid was carefully decanted, washed with diethyl ether and
pentane and dried in vacuo. Yield: 460 mg, 83%. 1H NMR
(250 MHz, [D6]acetone, 298 K): δ ϭ 2.31 (s, 3 H), 2.51 (s, 3 H),
3.19 (s, 6 H), 7.16 (d, J ϭ 6.0 Hz, 1 H), 7.45 (d, J ϭ 5.8 Hz, 1 H),
8.03 (s, 1 H), 8.18 (s, 1 H), 9.46 (d, J ϭ 5.7 Hz, 1 H), 9.83 (d, J ϭ
6.0 Hz, 1 H) ppm. C14H18ClN2ORhS (400.7): C 41.96, H 4.53, N
6.99; found C 41.78, H 4.46, N 7.06.
Reaction of
3 with Dichloromethane. Formation of [RhCl2-
(CH2Cl)(dmbpy)(DMSO)] (8): Complex 3 (80 mg, 0.200 mmol) was
dissolved in DMSO (2 mL) and five drops of CH2Cl2 were added.
Leaving the solution at room temperature for one day led to the
formation of pale yellow crystals. Addition of diethyl ether and
subsequent washing with additional diethyl ether gave an off-white
solid which was dried in vacuo. Yield: 82 mg, 85%. 1H NMR
(250 MHz, [D6]DMSO, 298 K): δ ϭ 2.53 (s, 3 H), 2.57 (s, 3 H),
4.31 (dd, J ϭ 5.7 Hz and 3.0 Hz, 1 H), 4.75 (dd, J ϭ 5.7 Hz and
3.0 Hz, 1 H), 7.60 (d, J ϭ 5.0 Hz, 1 H), 7.65 (d, J ϭ 5.0 Hz, 1 H),
8.51 (s, 1 H), 8.57 (s, 1 H), 9.17 (d, J ϭ 5.9 Hz, 1 H), 9.33 (d, J ϭ
6.0 Hz, 1 H) ppm. C15H20Cl3N2ORhS (485.7): C 37.10, H 4.15, N
5.77; found C 37.27, H 4.06, N 5.71.
Synthesis of [RhCl(dmbpy){CNC(CH3)3}] (4): A solution of tert-
butyl isocyanide (40 mg, 0.486 mmol) in THF (10 mL) was added
dropwise to a violet slurry of 1 (170 mg, 0.486 mmol) in THF (14
mL). The resulting green-brown solution was stirred at room tem-
perature for 2 h. Concentration of the THF solution to 10 mL and
addition of diethyl ether (40 mL) caused the precipitation of a
green-brown solid which was washed with diethyl ether and dried
in vacuo. Yield: 162 mg, 83%. 1H NMR (250 MHz, [D6]acetone,
Reaction of
4
with Benzyl Chloride. Formation of [RhCl2-
(28 mg,
(CH2C6H5)(dmbpy){CNC(CH3)3}] (9): Complex
4
0.069 mmol) was dissolved in acetone (3 mL) giving a green-black
solution. Addition of benzyl chloride (17 mg, 0.138 mmol) resulted
in a color change to pale yellow after one day at room temperature.
1832
Eur. J. Inorg. Chem. 2002, 1827Ϫ1834

Addition of CϪCl Bonds to Rhodium(I)-Bipyridine Complexes
Addition of diethyl ether led to the precipitation of an off-white frozen in a nitrogen stream at 120 K. Data were collected on a
FULL PAPER
solid which was washed with additional diethyl ether and dried in
vacuo. Yield: 33 mg, 89%. 1H NMR (250 MHz, [D6]acetone,
298 K): δ ϭ 1.61 (s, 9 H), 2.42 (s, 3 H), 2.48 (s, 3 H), 3.00 (dd, J ϭ
Nonius Kappa-CCD diffractometer mounted on a FR590 gener-
ator equipped with a sealed tube with Mo-Kα radiation (λ ϭ
˚
0.71073A) and a graphite monochromator. The four structures
7.8 Hz and 3.2 Hz, 1 H), 3.70 (dd, J ϭ 7.8 Hz and 3.0 Hz, 1 H), were solved by direct methods with SHELXS-97 and refined by
6.54 (m, 2 H), 6.73 (m, 3 H), 7.25 (d, J ϭ 5.8 Hz, 1 H), 7.48 (d, full-matrix least-squares techniques with SHELXL-97 based on
J ϭ 5.7 Hz, 1 H), 8.25 (br. s, 2 H), 8.31 (d, J ϭ 5.9 Hz, 1 H), 9.35 F2.[26]
(d, J ϭ 5.7 Hz, 1 H) ppm. C24H28Cl2N3Rh (532.3): C 54.15, H Complex 6: C22H30N4Rh·BF4, orange needles, 0.2 ϫ 0.03 ϫ 0.03
5.31, N 7.89; found C 54.04, H 5.15, N 7.93.
mm3, orthorhombic, Pmc21 (No. 20), a ϭ 6.861(1), b ϭ 16.516(3),
3
˚
˚
c ϭ 21.825(4) A, V ϭ 2473.1(9) A , Z ϭ 4, fw ϭ 540.22, Dc ϭ
1.451 Mg/m3, µ ϭ 0.736 mmϪ1. The final cycle of refinement based
on F2 gave an agreement factor R ϭ 0.0252 for data with I Ͼ 2σ(I)
and R ϭ 0.0294 for all data (2214 reflections) with a goodness-of-
fit of 0.987. Idealized hydrogen atoms were placed and refined in
a riding mode.
Reaction of with Benzyl Chloride. Formation of [RhCl-
5
(CH2C6H5)(dmbpy)(DMSO)2]PF6 (10): Complex (70 mg,
5
0.119 mmol) was dissolved in DMSO (2 mL) and stirred at room
temperature for 30 min giving a deep-red solution. Upon addition
of benzyl chloride (30 mg, 0.238 mmol) the solution turned yellow.
After 12 h at room temperature, the solution was poured into di-
ethyl ether (17 mL) and the resulting yellow precipitate was washed
with additional diethyl ether and dried in vacuo. Yield: 77 mg, 91%.
1H NMR (250 MHz, [D6]DMSO, 298 K): δ ϭ 2.44 (br. d, 6 H),
3.59 (dd, J ϭ 6.8 Hz and 2.9 Hz, 1 H), 4.19 (dd, J ϭ 6.8 Hz and
3.2 Hz, 1 H), 6.28 (d, J ϭ 7.4 Hz, 2 H), 6.50 (dd, J ϭ 7.5 Hz, 2
H), 6.74 (dd, J ϭ 7.3 Hz, 1 H), 8.16 (s, 1 H), 8.26 (s, 1 H), 8.82
(br. s, 2 H), 9.09 (d, J ϭ 5.9 Hz, 1 H), 9.30 (d, J ϭ 5.9 Hz, 1 H)
ppm. C23H31ClF6N2O2PRhS2 (715.0): C 38.64, H 4.37, N 3.92;
found C 38.20, H 4.80, N 4.82.
Complex 8: C15H20Cl3N2OSRh, yellow, thin parallelogram, 0.30 ϫ
0.10 ϫ 0.02 mm3, monoclinic, P21/c (No. 14), a ϭ 7.5840(15), b ϭ
3
˚
˚
10.636(2), c ϭ 23.216(5) A, β ϭ 99.28(3)°, V ϭ 1848.2(6) A , Z ϭ
4, fw ϭ 485.65, Dc ϭ 1.745 Mg/m3, µ ϭ 1.474 mmϪ1. The final
cycle of refinement based on F2 gave an agreement factor R ϭ
0.027 for data with I Ͼ 2σ(I) and R ϭ 0.040 for all data (4219
reflections) with a goodness-of-fit of 1.030. Idealized hydrogen
atoms were placed and refined in a riding mode. Two hydrogen
atoms on C4 were found and refined manually.
Reaction of
5
with Dichloromethane. Formation of [RhCl-
(80 mg,
Complex 9: C24H28N3Cl2Rh·1/2(C3H6O)·H2O, yellow, bipyramidal
prisms, 0.05 ϫ 0.05 ϫ 0.05 mm3, tetragonal, I41/a (No. 88), a ϭ
(CH2Cl)(dmbpy)(DMSO)2]PF6 (11): Complex
5
3
˚
˚
0.136 mmol) was dissolved in DMSO (2 mL) and an excess of
CH2Cl2 (five drops) was added. After two days at room temper-
ature a pale yellow solution was formed. Addition of diethyl ether
and subsequent washing with diethyl ether gave an off-white solid
which was dried in vacuo. Yield: 71 mg, 78%. 1H NMR (250 MHz,
[D6]DMSO, 298 K): δ ϭ 2.59 (s, 6 H), 3.44 (br. d, 2 H), 7.66 (d,
J ϭ 6.0 Hz, 2 H), 7.87 (d, J ϭ 6.0 Hz, 2 H), 8.89 (s, 2 H) ppm.
C17H26Cl2F6N2O2PRhS2 (673.3): C 30.33, H 3.90, N 4.16; found
C 32.70, H 3.73, N 5.15.
b ϭ 20.722(3), c ϭ 26.090(5) A, V ϭ 11203(3) A , Z ϭ 16, fw ϭ
579.36, Dc ϭ 1.374 Mg/m3, µ ϭ 0.824 mmϪ1. The final cycle of
refinement based on F2 gave an agreement factor R ϭ 0.0362 for
data with I Ͼ 2σ(I) and R ϭ 0.0508 for all data (4291 reflections)
with a goodness-of-fit of 1.054. Idealized hydrogen atoms were
placed and refined in riding mode The acetone is disordered with
1/2 a molecule per asymmetric unit.
Complex 12: C29H37N4ClRh·C3H6O·BF4, colorless, prisms, 0.3 ϫ
0.3 ϫ 0.3 mm3, monoclinic, P21/n (No. 14), a ϭ 12.623(3), b ϭ
3
˚
˚
Reaction of
6 with Benzyl Chloride. Formation of [RhCl-
21.262(4), c ϭ 14.011(3) A, β ϭ 105.84(3)°, V ϭ 3617.7(13) A ,
Z ϭ 4, fw ϭ 724.87, Dc ϭ 1.331 Mg/m3, µ ϭ 0.596 mmϪ1. The
final cycle of refinement based on F2 gave an agreement factor R ϭ
0.0491 for data with I Ͼ 2σ(I) and R ϭ 0.0596 for all data (7146
reflections) with a goodness-of-fit of 1.035. Idealized hydrogen
atoms were placed and refined in a riding mode. C32, C33 and C34
(one tert-butyl group) and the BF4 are partially disordered and
modeled with two alternative positions.
(CH2C6H5)(dmbpy){CNC(CH3)3}2]BF4 (12): A deep-red acetone
solution (10 mL) of 6 (60 mg, 0.111 mmol) was treated with benzyl
chloride (28 mg, 0.222 mmol). The color turned to orange within
1 h and leaving the solution overnight led to the precipitation of a
yellow solid. Addition of diethyl ether and subsequent washing
with diethyl ether gave a yellow powder which was dried in vacuo.
1
Yield: 64 mg, 86%. H NMR (250 MHz, [D6]DMSO, 298 K): δ ϭ
1.58 (s, 18 H), 2.57 (s, 6 H), 3.12 (d, J ϭ 2.6 Hz, 2 H), 6.77 (m, 2
H), 7.00 (m, 3 H), 7.63 (d, J ϭ 5.8 Hz, 2 H), 8.54 (d, J ϭ 5.7 Hz,
2 H), 8.59 (s, 2 H) ppm. C29H37BClF4N4Rh (666.8): C 52.24, H
5.60, N 8.40; found C 52.10, H 5.58, N 8.38.
CCDC-176695 (9), -176696 (12), -176697 (6), and -176698 (8)
contain the supplementary crystallographic data for this
paper. These data can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html [or from the Cambridge
Crystallographic Data Centre, 12, Union Road, Cambridge
CB2 1EZ, UK; Fax: (internat.) ϩ44-1223/336-033; E-mail:
deposit@ccdc.cam.ac.uk].
Reaction of
3
with Oxygen. Formation of [RhCl2-
(O2)(dmbpy)(DMSO)] (13): A red DMSO solution (2 mL) of 3
(30 mg, 0.075 mmol) was treated with an equimolar amount of O2
(1.7 mL). The solution turned yellow immediately and after 3 h at
room temperature, it was poured into diethyl ether (17 mL). The
pale-yellow precipitate was filtered, washed with diethyl ether and
Acknowledgments
This work was supported by the Israel Science Foundation, Jerusa-
lem, Israel, and by the Tashtiyot program of the Israeli Ministry of
Science. DM is the Israel Matz professor of organic chemistry.
1
dried in vacuo. Yield: 30 mg, 93%. H NMR (250 MHz, [D6]ace-
tone, 298 K): δ ϭ 2.59 (s, 3 H), 2.62 (s, 3 H), 3.39 (s, 6 H), 7.53 (d,
J ϭ 5.9 Hz, 1 H), 7.58 (d, J ϭ 5.6 Hz, 1 H), 8.38 (s, 1 H), 8.42 (s,
1 H), 8.57 (d, J ϭ 5.6 Hz, 1 H), 9.56 (d, J ϭ 5.5 Hz, 1 H) ppm.
FT-IR (nujol): ν˜ ϭ 870 (OϪO) cmϪ1. C14H18ClN2O3RhS (432.7):
C 38.86, H 4.20, N 6.47; found C 38.30, H 4.26, N 6.55.
[1]
A. Togni, L. M. Venanzi, Angew. Chem. Int. Ed. Engl. 1994,
33, 497Ϫ526.
[2]
X-ray Crystal Structure Determination of 6, 8, 9 and 12: A single
crystal of 6, 8, 9 or 12 were mounted on the nylon loop and flash
C. Kaes, A. Katz, M. W. Hosseini, Chem. Rev. 2000, 100,
3553Ϫ3590.
Eur. J. Inorg. Chem. 2002, 1827Ϫ1834
1833

R. Dorta, L. J. W. Shimon, H. Rozenberg, D. Milstein
FULL PAPER
[3]
[15]
[16]
[17]
[18]
[19]
G. Zassinovich, G. Mestroni, S. Gladiali, Chem. Rev. 1992,
T. Yoshida, T. Ueda, T. Adachi, K. Yamamoto, T. Higuchi, J.
Chem. Soc., Chem. Commun. 1985, 1137Ϫ1138.
E. G. Burns, S. S. C. Chu, P. de Meester, M. Lattman, Organo-
metallics 1986, 5, 2383Ϫ2384.
K. Kashiwabara, A. Morikawa, T. Suzuki, K. Isobe, K. Tats-
umi, J. Chem. Soc., Dalton Trans. 1997, 1075Ϫ1081.
R. Ziessel, L. Toupet, S. Chardon-Noblat, A. Deronzier, D.
Matt, J. Chem. Soc., Dalton Trans. 1997, 3777Ϫ3784.
We chose this ligand over the parent 2,2Ј-bipyridine for reasons
of solubility and easier characterization by NMR of the com-
plexes.
92, 1051Ϫ1069.
G. Mestroni, R. Spogliarich, A. Camus, F. Martinelli, G. Zassi-
[4]
novich, J. Organomet. Chem. 1978, 157, 345Ϫ352.
[5]
R. D. Gillard, K. Harrison, I. H. Mather, J. Chem. Soc. 1975,
133Ϫ140, and references therein.
For 1,5-cyclooctadiene, see ref.[4] and references therein; for
[6]
cyclooctatetraene, see: C. Cocevar, G. Mestroni, A. Camus, J.
Organomet. Chem. 1972, 35, 389Ϫ395, and references therein.
For norbornadiene, see: J. J. Robertson, A. Kadziola, R. A.
Krause, S. Larsen, Inorg. Chem. 1989, 28, 2097Ϫ2102, and ref-
erences therein. For 1,5-hexadiene, see: G. Mestroni, G. Zassi-
novich, A. Camus, J. Organomet. Chem. 1977, 140, 63Ϫ72.
[20]
[21]
[22]
M. Aresta, E. Quaranta, J. Organomet. Chem. 1993, 463,
215Ϫ221.
[7]
S. Morton, J. F. Nixon, J. Organomet. Chem. 1985, 282,
R. Dorta, H. Rozenberg, D. Milstein, Chem. Commun. 2002,
710Ϫ711.
Surprisingly, besides these two complexes, two new species were
detected which were the only ones remaining after prolonged
heating (2 weeks at 80 °C). Although these complexes were not
isolated, we believe that water present in the [D6]DMSO led
123Ϫ126.
[8]
G. Mestroni, A. Camus, G. Zassinovich, J. Organomet. Chem.
1974, 65, 119Ϫ129. For oxidative addition of hydrogen to
[Rh(bpy)2]X, see: S. G. Yan, B. S. Brunschwig, C. Creutz, E.
Fujita, N. Sutin, J. Am. Chem. Soc. 1998, 120, 10553Ϫ10554.
[9]
H. Werner, L. Hofmann, R. Feser, W. Paul, J. Organomet.
to
the
formation
of
the
trichloro
compound
1
Chem. 1985, 281, 317Ϫ347.
T. B. Marder, W. C. Fultz, J. C. Calabrese, R. L. Harlow, D.
[RhCl3(dmbpy)(DMSO)]. The H NMR signals of the dmbpy
ligand indicate a ca. 1:1 ratio of the two possible isomers.
For a similar peroxo complex, see: H. F. Haarman, F. R. Breg-
man, P. W. N. M. van Leeuwen, K. Vrieze, Organometallics
1997, 16, 979Ϫ985.
[10]
[23]
[24]
Milstein, J. Chem. Soc., Chem. Commun. 1987, 1543Ϫ1545.
P. J. Fennis, P. H. M. Budzelaar, J. H. G. Frijns, A. G. Orpen,
[11]
J. Organomet. Chem. 1990, 393, 287Ϫ298.
H. Nishiyama, M. Horihata, T. Hirai, S. Wakamatsu, K. Itoh,
[12]
P. Hofmann, C. Meier, U. Englert, U. Schmidt, Chem. Ber.
1992, 125, 353Ϫ365.
R. Cramer, Inorg. Chem. 1962, 1, 722Ϫ723.
SHELX-97, Program for Crystal Structure Refinement, G. M.
Sheldrick, University of Goettingen, 1997.
Received January 11, 2002
Organometallics 1991, 10, 2706Ϫ2708.
H. F. Haarman, J. M. Ernsting, M. Kranenburg, H. Kooijman,
[13]
[25]
[26]
N. Veldman, A. L. Spek, P. W. N. M. van Leeuwen, K. Vrieze,
Organometallics 1997, 16, 887Ϫ900.
K. J. Bradd, B. T. Heaton, C. Jacob, J. T. Sampanthar, A.
[14]
Steiner, J. Chem. Soc., Dalton Trans. 1999, 1109Ϫ1112.
[I02016]
1834
Eur. J. Inorg. Chem. 2002, 1827Ϫ1834