4-Thiolatobenzoato-bridged rhodium/zirconium complexes: 32-Membered metallamacrocycles and their linear dinuclear counterparts

Article abstract of DOI:10.1002/ejic.200600549

The heterometallic dinuclear complex [Cp*₂Zr(Me){(μ- OOCC₆H₄S)Rh(PEt₃)₃}] (3) is readily obtained by methane elimination in the reaction of [Rh(SC₆H ₄COOH)(PEt₃)₃] with [Cp* ₂ZrMe₂] in a 1:1 ratio. Complex 3 reacts with 1 equiv. of water to give [Cp*₂Zr(OH){(μ-OOCC₆H ₄S)Rh(PEt₃)₃}] (4), a rare example of a terminal hydroxo complex of a zirconocene. Complexes 3 and 4 are isotypic. The influence of the zirconocene group on the properties of the rhodium complex was evaluated with ³¹P NMR spectroscopy, cyclic voltammetry and DFT calculations. [Cp*₂ZrMe₂] reacts with [{Rh(μ-SC₆H₄COOH)(PPh₃)₂} ₂] (even in a 1:1 ratio at room temperature) or with [Rh(SC ₆H₄COOH)(PEt₃)₃] (in a 1:2 ratio at elevated temperature) to give 32-membered metallamacrocycles containing four rhodium and two zirconium atoms, in which each zirconocene group bridges two {Rh(SC₆H₄COO)(PR₃)₂}₂ units [R = Ph (5), Et (6)]. The only significant structural difference in 5 and 6 is the presence of two different isomers, in which the bridging thiolato ligands occupy either the exo or the endo position of the Rh₂S ₂ ring. However, this small difference has a significant influence on the size of the macrocyclic cavity. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejic.200600549

FULL PAPER
DOI: 10.1002/ejic.200600549
4-Thiolatobenzoato-Bridged Rhodium/Zirconium Complexes: 32-Membered
Metallamacrocycles and Their Linear Dinuclear Counterparts
Ulrike Helmstedt,[a] Peter Lönnecke,[a][‡] and Joachim Reinhold,[b][‡‡] and
Evamarie Hey-Hawkins*[a]
Keywords: Heterometallic complexes / Metallacycles / Bridging ligands / Metal–metal interactions / Rhodium / Zircono-
cenes / S,O ligands
The heterometallic dinuclear complex [Cp*2Zr(Me){(µ-
OOCC6H4S)Rh(PEt3)3}] (3) is readily obtained by methane
elimination in the reaction of [Rh(SC6H4COOH)(PEt3)3] with
[Cp*2ZrMe2] in a 1:1 ratio. Complex 3 reacts with 1 equiv. of
water to give [Cp*2Zr(OH){(µ-OOCC6H4S)Rh(PEt3)3}] (4), a
rare example of a terminal hydroxo complex of a zir-
conocene. Complexes 3 and 4 are isotypic. The influence of
at elevated temperature) to give 32-membered metalla-
macrocycles containing four rhodium and two zirconium
atoms, in which each zirconocene group bridges two
{Rh(SC6H4COO)(PR3)2}2 units [R = Ph (5), Et (6)]. The only
significant structural difference in 5 and 6 is the presence of
two different isomers, in which the bridging thiolato ligands
occupy either the exo or the endo position of the Rh2S2 ring.
the zirconocene group on the properties of the rhodium com- However, this small difference has a significant influence on
plex was evaluated with 31P NMR spectroscopy, cyclic vol- the size of the macrocyclic cavity.
tammetry and DFT calculations. [Cp*2ZrMe2] reacts with
[{Rh(µ-SC6H4COOH)(PPh3)2}2] (even in a 1:1 ratio at room
temperature) or with [Rh(SC6H4COOH)(PEt3)3] (in a 1:2 ratio
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
centre to one coordination site of a di- or multifunctional,
potentially bridging ligand, different concepts are known
from the literature, for example exploitation of the chelate
effect[8] or the use of donor atoms with different coordina-
tion behaviour[9] according to the hard and soft acids and
bases concept of Pearson.[10]
We have previously employed S,O ligands, such as mer-
captocarboxylic acids, which show high bonding selectivity
in the synthesis of heterometallic complexes[11] if they can-
not bind in a chelating fashion.[12] By changing the bridging
ligand from saturated mercaptocarboxylic acids to unsatu-
rated ones, we have now extended our studies to the 4-thiol-
atobenzoate dianion and have already prepared several rho-
dium(I) complexes of 4-thiolatobenzoic acid.[13] The special
feature of these complexes is the free carboxyl group, which
allows further coordination to a second metal ion. For this,
we chose zirconocene derivatives, which are known to form
stable carboxylato complexes.[14]
Introduction
Interest in early/late heterobimetallics (ELHBs) has
strongly increased in the last few decades.[1] The reasons for
this are mainly the elucidation of mechanisms of enzymes
whose active centres include more than one metal centre,[2]
the explanation of the strong metal–support interaction
phenomenon in heterogeneous catalysis[3] and the applica-
bility of cooperative effects between different metal centres
for catalysts[4] and magnetic materials.[5] Of special interest
for these applications is the investigation of metal–metal in-
teractions. These can be achieved either by direct contact
of the metal centres within the compounds[6] or with the
help of bridging ligands which allow electronic interactions
through π-conjugated bridges.[7]
To elucidate the influence of the second metal centre, it
is useful to compare the properties of the heterometallic
complexes with those of their mononuclear precursors.
Therefore, the preferred synthesis of ELHBs starts with the
preparation of a monometallic complex, which is then em-
ployed as a so-called metalloligand to coordinate the sec-
ond metal centre. To selectively coordinate the first metal
Results and Discussion
The reaction of the metalloligands [{Rh(SC6H4COOH)-
(PPh3)2}2] (1)[13] and [Rh(SC6H4COOH)(PEt3)3] (2)[13] with
[Cp*2ZrMe2] (Cp* = C5Me5) yielded the mono- and bis-
(carboxylato) complexes of the zirconocenes, depending on
the stoichiometry and the reactivity of the starting materi-
als. At room temperature, 2 gives only the monosubstitution
product (Scheme 1), while disubstitution is achieved at ele-
[a] Institut für Anorganische Chemie, Universität Leipzig,
Johannisallee 29, 04103 Leipzig, Germany
E-mail: hey@rz.uni-leipzig.de
[b] Institut für Physikalische und Theoretische Chemie, Universität
Leipzig,
Johannisallee 29, 04103 Leipzig, Germany
[‡] Crystal structure determinations
[‡‡] DFT calculations
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4-Thiolatobenzoato-Bridged Rhodium/Zirconium Complexes
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Scheme 1.
Scheme 2.
vated temperatures. In contrast, 1 readily reacts with the Mono(carboxylato)zirconocene Complexes
zirconocene derivative even at room temperature with elimi-
nation of 2 equiv. of methane (Scheme 2). Purification of
As shown previously, 2 dimerises in solution with phos-
the highly air- and moisture-sensitive complexes was facili- phane dissociation (Scheme 3). To stabilise the monomeric
tated by the fact that only methane was produced as bypro- form, an excess of triethylphosphane must be used. Com-
duct.
plex 2 reacts with 1 equiv. of [Cp*2ZrMe2] in the presence
Scheme 3. R = Me (3) or OH (4).
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of an excess of PEt3 to yield [Cp*2Zr(Me){(µ-O2CC6H4S)- usually occurs with elimination of water,[15] as first de-
Rh(PEt3)3}] (3) exclusively. Complex 3 could be isolated as scribed by Hillhouse et al.[16] and Bortolin et al.[17] Complex
orange crystals; the molecular structure in the solid state is 4 is the first heteroleptic carboxylato hydroxo complex
shown in Figure 1.
structurally characterised by X-ray crystallography. Pellny
et al. reported the NMR spectroscopic observation of the
compounds [Cp*2Zr(OH){OOC–C(SiMe3)=CHPh}] and
[Cp*2Zr(OH){OOC–CPh=CH(SiMe3)}], but could not iso-
late them.[18] Yellow needle-like crystals of 4 were structur-
ally characterised by X-ray crystallography. Complex 4
crystallises isotypic to 3 (Figure 1).
The short Zr–O bond length of 207.8 pm corresponds to
those in other structurally characterised compounds of this
kind.[17,19] The O3···O1 distance of 272.1 pm seems to indi-
cate the presence of a hydrogen bond between them. As the
C46···O1 distance in 3 is also only 274.6 pm, it appears that
the two atoms are forced into close proximity due to the
high steric demand of the Cp* rings. The steric crowding is
also apparent from the deviation of the methyl groups from
the C5 ring plane where the two rings are in close proximity.
The OH stretching vibration (3658 cm–1) has very low
intensity but could be observed in the IR spectra of a KBr
pellet and of a single crystal. The intensities of OH vi-
brations reported in the literature also differ.[19a,19b]
Figure 1. View of the molecular structure of [Cp*2Zr(Me){(µ-
O2CC6H4S)Rh(PEt3)3}] (3) (R
= Me) and [Cp*2Zr(OH){(µ-
O2CC6H4S)Rh(PEt3)3}] (4) (R = OH). Hydrogen atoms are omit-
ted for clarity. Thermal ellipsoid level 50%. The atoms not shown
as ellipsoids are the carbon atoms of the coligands. Selected bond
lengths [pm] and bond angles [°] for 3: Zr1–O1 230.3(4), Zr1–O2
227.1(4), Zr1–C46 226.9(8), O1–C25 126.3(8), O2–C25 126.9(7),
Rh1–S1 241.4(2), Rh1–P1 230.5(2), Rh1–P2 224.7(2), Rh1–P3
232.7(2); O1–Zr1–O2 56.6(2), O1–Zr1–C46 73.8(3), O1–C25–O2
117.9(6), S1–Rh1–P1 82.93(6), S1–Rh1–P2 166.98(7), S1–Rh1–P3
83.94(6), P1–Rh1–P2 96.76(6), P2–Rh1–P3 101.05(6), P1–Rh1–P3
153.70(7), Rh1–S1–C19 104.8(2). Selected bond lengths [pm] and
bond angles [°] for 4: Zr1–O1 229.5(5), Zr1–O2 228.6(5), Zr1–O3
207.8(6), O1–C25 128(1), O2–C25 124.8(9), Rh1–S1 241.4(2), Rh1–
P1 231.0(2), Rh1–P2 225.0(3), Rh1–P3 232.6(3); O1–Zr1–O2
56.4(2), O1–Zr1–O3 76.8(2), O1–C25–O2 117.6(8), S1–Rh1–P1
83.06(9), S1–Rh1–P2 167.39(9), S1–Rh1–P3 84.25(9), P1–Rh1–P2
96.39(9), P2–Rh1–P3 100.64(9), P3–Rh1–P1 154.79(9), Rh1–S1–
C19 106.2(3).
1
In the H NMR spectrum, the signals of the protons of
the aromatic ring of the 4-thiolatobenzoate ligand (AAЈBBЈ
spin system) are broader than the other signals. This indi-
cates hindered rotation of the SC6H4COOZr(R)Cp*2 group
(R = Me, OH) and prevents simulation of the spectra to
determine the coupling constants. As can be observed with
the help of 31P NMR spectroscopy, 3 and 4 dimerise in
solution with dissociation of 1 equiv. of PEt3 per rhodium
atom, as already described for 2 (Scheme 3). The equilib-
rium can be shifted towards the monomer by adding an
excess of triethylphosphane.
Complex 3 crystallises in the monoclinic space group
P21/c with four molecules per unit cell. The rhodium atom
is coordinated by three triethylphosphane and one thiolato
ligand in a tetrahedrally distorted square-planar fashion
Bis(carboxylato)zirconocene Complexes
Treatment of 1 with [Cp*2ZrMe2] in a 1:1 ratio as well
[S1–Rh1–P2 166.98(7)°, P1–Rh1–P3 153.70(7)°]. The car- as of 2 with [Cp*2ZrMe2] in a 2:1 ratio results in the forma-
boxylato group coordinates in a bidentate mode, resulting tion of compounds of the type [(Cp*2Zr{(µ-O2CC6H4S)-
in the zirconium atom being an 18-valence-electron species. Rh(PR3)2}2)2] [R = Ph (5), R = Et (6)]. In the solid state
The two oxygen atoms, the carbon atom of the methyl both compounds reveal a nearly identical molecular struc-
group and the zirconium atom are coplanar. The plane de- ture, that is, a 32-membered macrocycle containing two di-
fined by Zr1, O1 and O2 forms an angle of 9.12° with the meric Rh2(SR)2 units, as observed in metalloligand 1, which
plane of the aromatic ring. The bond lengths C25–O1 are deprotonated and bridged by two zirconocene groups
[126.3(8) pm] and C25–O2 [126.9(7) pm] as well as Zr1–O1 (Scheme 2).
[230.3(4) pm] and Zr1–O2 [227.1(4) pm] are similar, and
Both compounds crystallise in the triclinic space group
¯
this indicates delocalisation of the lone pair of electrons. P1, and one molecule in the unit cell is located on a crystal-
This is supported by the IR spectrum (KBr), which shows lographic centre of inversion (Figures 2 and 3). Co-crystalli-
symmetric and asymmetric COO vibrations at 1561 and at sation of 12 molecules of thf (two of them disordered) for
1420 cm–1 instead of discrete C=O and C–O vibrations.
By treating a solution of 3 with 1 equiv. of water, the unit cell.
5 and one molecule of diethyl ether for 6 is observed per
methyl group can be exchanged selectively with an OH
The typical bonding mode for zirconocene bis(carboxyl-
group to form [Cp*2Zr(OH){(µ-OOCC6H4S)Rh(PEt3)3}] ato) complexes[20,24–26] is also observed in 5 and 6: one car-
(4), a rare example of a terminal hydroxo complex of a zir- boxylato ligand coordinates in a bidentate fashion and the
conocene. Stabilisation by the sterically bulky Cp* ligands other in a monodentate one. All coordinating oxygen atoms
prevents dimerisation with formation of oxo bridges, which are coplanar with the zirconium atom. In contrast to 3 and
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4-Thiolatobenzoato-Bridged Rhodium/Zirconium Complexes
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Figure 2. View of the molecular structure of [(Cp*2Zr{(µ-O2CC6H4S)Rh(PPh3)2}2)2] (5). Thermal ellipsoid level 50%. Hydrogen atoms
and the carbon atoms of the coligands and thf molecules are omitted for clarity. Selected bond lengths [pm] and bond angles [°]: Zr1–
O1 207.1(2), Zr1–O3 232.2(2), Zr1–O4 223.9(2), Rh1–S1 244.12(9), Rh1–S2 237.73(9), Rh1–P1 228.0(1), Rh1–P2 224.3(1), Rh2–S1
236.72(9), Rh2–S2 239.41(9), Rh2–P3 224.8(1), Rh2–P4 226.6(1), C79–O1 129.9(4), C79–O2 122.4(4), C86–O3 126.9(4), C86–O4 127.5(4);
O3–Zr1–O4 56.94(8), S1–Rh1–S2 78.76(3), P1–Rh1–S1 96.64(3), P1–Rh1–P2 94.36(4), S1–Rh2–S2 79.91(3), P3–Rh2–S1 99.75(3), P3–
Rh2–P4 98.13(4), (S1–Rh1–S2)/(S1–Rh2–S2) 146.46(5).
Figure 3. View of the molecular structure of [(Cp*2Zr{(µ-O2CC6H4S)Rh(PEt3)2}2)2] (6). Thermal ellipsoid level 50%. Diethyl ether,
hydrogen atoms and the carbon atoms of the coligands are omitted for clarity. Selected bond lengths [pm] and bond angles [°]: Zr1–O1
206.9(3), Zr1–O3 236.1(3), Zr1–O4 222.2(3), Rh1–S1 239.8(1), Rh1–S2 241.3(1), Rh1–P1 224.3(1), Rh1–P2 226.5(1), Rh2–S1 240.6(1),
Rh2–S2 242.2(1), Rh2–P3 224.5(1), Rh2–P4 224.5(1), C31–O1 131.2(5), C31–O2 121.9(5), C38–O3 126.3(5), C38–O4 127.6(5); O3–Zr1–
O4 56.6(2), S1–Rh1–S2 81.47(4), P1–Rh1–S1 85.33(4), P1–Rh1–P2 102.08(5), S1–Rh2–S2 81.47(4), P3–Rh2–S1 93.40(4), P3–Rh2–P4
97.69(5), (S1–Rh1–S2)/(S1–Rh2–S2) 145.50(5).
4, the Zr–O bond lengths of the bidentate ligand differ by OH] and a symmetric vibration of the COO group as ex-
8 pm (5) and 14 pm (6) and are thus indicative of the strain pected for unstrained molecules {e.g. 1561 cm–1 for
imposed by the macrocycle. This is also supported by the [Cp*2Zr(Me){(µ-O2CC6H4S)Rh(PEt3)3}] (3) and [Cp*2Zr-
IR spectrum (KBr), in which the COO vibration is observed (OH){(µ-O2CC6H4S)Rh(PEt3)3}] (4)}. The position of the
at 1633 cm–1 (5) and 1635 cm–1 (6), which are in between asymmetric COO vibration could not be identified because
the values for a C=O bond [1678 cm–1 for HSC6H4(C=O)- of overlap with other bands.
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U. Helmstedt, P. Lönnecke, J. Reinhold, E. Hey-Hawkins
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In both compounds, the Rh2S2 ring is puckered and of the different conformation of the Rh2S2 ring and the
shows an anti conformation. The angle between the S–Rh– different orientation of the arylene bridges, the cavity is di-
S planes is 147° for 5 and 146° for 6. The only considerable vided into two smaller cavities with dimensions of
difference is that in 5 the thiolato ligands occupy the exo 87×380 pm.
position of the Rh2S2 ring, and the endo position in 6. This
The cavity is shielded by coligands, as shown exemplarily
has a crucial influence on the size and shape of the macro- for 6 in Figure 5. Thus, the solvent molecules are not lo-
cyclic cavity (Figure 4). For 5 the cavity is rhombohedral cated inside the cavity. Figure 5 also shows that the 32-
with internal edges of 470 and 331 pm, while in 6, because membered rings are almost planar, with the exception of
Figure 4. Space-filling model of the macrocycles 5 (left) and 6 (right). The carbon atoms of the coligands and those hydrogen atoms that
do not influence the size of the cavities are omitted for clarity. The metal atoms are black, the heteroatoms (oxygen, sulfur and phospho-
rus) grey, the carbon atoms light grey and the hydrogen atoms white.
Figure 5. View of the molecular structure of [(Cp*2Zr{(µ-O2CC6H4S)Rh(PEt3)2}2)2] (6). Thermal ellipsoid level 50%. Hydrogen atoms
and Et2O have been omitted for clarity. The atoms not shown as ellipsoids are the carbon atoms of the coligands. Top: View along the
axis through the Rh2S2 rings. Bottom: View along the axis through the zirconocene groups.
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4-Thiolatobenzoato-Bridged Rhodium/Zirconium Complexes
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the aromatic rings of two of the bridging thiolatobenzoato
ligands.
The solubility of 5 and 6 in common organic solvents (n-
hexane, toluene, thf, Et2O, CH3CN, dmf and dmso) is very
low. A sufficient concentration for 31P{1H} NMR studies
was achieved solely for 5 in thf. At room temperature, a
very broad signal is observed at δ = 38 ppm, which splits
1
into two broad doublets (δ =37.7 ppm, JP-Rh = 153 Hz,
1
PPh3 of isomer 1, and 38.4 ppm, JP-Rh = 149 Hz, PPh3 of
isomer 2) on cooling the sample to –100 °C. Considering
that fluxional behaviour of zirconocene bis(carboxylato)
complexes in solution is known from the literature[12b] (one
of the ligands coordinates alternatingly in a mono- or bi-
dentate fashion) and that dynamic behaviour, that is ex-
change between different conformers of the Rh2S2 ring,
could be observed for 1,[13] one could consider different iso-
mers in solution. However, because of solvent restrictions,
the sample could not be cooled down sufficiently to achieve
fine splitting and to gain deeper insights into the species
present in solution.
Comparison of the Spectroscopic and Electrochemical
Properties of 2 and 3
Information about the change in electron density at the
rhodium atom after introduction of the second metal centre
can be obtained by comparing the spectroscopic and elec-
trochemical properties of the monometallic complex
[Rh(SC6H4COOH)(PEt3)3] (2)[13] and the corresponding
heterometallic
complex
[Cp*2Zr(Me){(µ-O2CC6H4S)-
Rh(PEt3)3}] (3). For this purpose, the 31P NMR chemical
shifts of the phosphorus nuclei of the phosphane ligands,
the oxidation potentials (Table 1) and the wavelengths of
the S–Rh charge-transfer bands of 2 and 3 (Figure 6) were
compared.
Figure 6. Comparison of the observed UV/Vis spectra of 2 (top)
and 3 (bottom) in thf with the calculated transitions (line spectra).
Table 1. Anodic peak potentials vs. SCE, 31P NMR shifts of the
phosphorus nucleus trans (δtrans) and cis (δcis) to the thiolato ligand
and the lowest energy UV/Vis absorption bands.
[Cp2ZrCH3{(µ-OOCC6H4S)Rh(PMe3)3}] (for 3; Cp
=
Compound
Epa [V]
δtrans [ppm]
δcis [ppm]
λmax [nm]
C5H5). According to these calculations for both model
compounds, the highest occupied molecular orbitals
(HOMO) have both sulfur lone pair and rhodium d charac-
ter. The HOMO itself is mainly sulfur-centred with some
2
3
1.28
1.32
26.7
28.4
12.1
13.5
337
358
After introduction of the zirconium atom as the second rhodium contribution. The lowest unoccupied molecular
metal centre, the 31P chemical shifts of the phosphorus nu- orbitals (LUMO) correspond to the σ* orbitals of the al-
clei cis and trans to the thiolato ligand are shifted to lower most square-planar coordination sphere of the rhodium(I)
field by 1.4 and 1.7 ppm, respectively. This indicates a weak centre.
electron-withdrawing character of the Lewis-acidic zirco-
The UV/Vis spectra of 2 and 3 are dominated by one
nium atom. This is also shown by a 40-mV shift of the broad band at 337 nm for 2 and 358 nm for 3. TD-DFT
oxidation potential of 3 compared to 2. The oxidation is studies show that for both model compounds this band can
irreversible, as known for other rhodium(I) complexes.[21] be assigned to several HOMO-to-LUMO excitations (Fig-
The observation of a small cathodic peak at –0.72 V in both ure 6). CpǞZr charge transfer processes, usually reported
cases proposes a following chemical reaction and the re- for the UV/Vis spectra of zirconocene complexes,[22] seem
duction of its reaction product.
to play no role for 3. They are calculated to be of too high
The DFT calculations were carried out for the model energy and too low oscillator strength to be observable in
compounds [Rh(SC6H4COOH)(PMe3)3] (for 2) and the spectrum.
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U. Helmstedt, P. Lönnecke, J. Reinhold, E. Hey-Hawkins
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0 °C. The suspension was warmed to room temperature over 1 h
and was then stirred for 16 h. The red solution was filtered and
added to a solution of [Cp*2ZrMe2] (194 mg, 0.5 mmol) in thf
(5 mL). After stirring at room temperature overnight, the solvent
was removed in vacuo and the resulting red solid was washed with
cold diethyl ether (2 mL) and cold n-hexane (2 mL). Recrystalli-
sation from n-hexane/PEt3 gave 380 mg (77%) of orange needles.
M.p. 175–180 °C (dec.). C46H82O2P3RhSZr (986.26): calcd. C
56.02, H 8.38; found C 55.75, H 8.45. 1H NMR ([D8]thf): δ =
–0.26 (s, 3 H, ZrCH3), 1.20, 1.38, 1.94 [each m, 45 H, P(C2H5)3],
1.94 [s, 30 H, C5(CH3)5], 7.59 [m, 2 H, A part of the AAЈBBЈ spin
system, H1 in O2CC6H4S (for numbering, see Scheme 1)], 8.04 (m,
2 H, B part of the AAЈBBЈ spin system, H2 in O2CC6H4S) ppm.
13C{1H} NMR ([D8]thf): δ = 1.7 (ZrCH3), 9.5 [2×P(CH2CH3)3]†,
10.0 [P(CH2CH3)3], 11.6 [C5(CH3)5], 18.8 [2×P(CH2CH3)3]†, 22.7
Conclusions
While [Cp*2ZrMe2] reacts with [Rh(SC6H4COOH)-
(PEt3)3] to give selectively either the 1:1 or the 2:4 product,
[Cp*2Zr(Me){(µ-OOCC6H4S)Rh(PEt3)3}] (3) or [(Cp*2Zr-
{(µ-O2CC6H4S)Rh(PEt3)2}2)2] (6), the reaction with
[{Rh(µ-SC6H4COO)(PPh3)2}2] (more labile phosphane
ligands) gives exclusively the 2:4 product, [(Cp*2Zr{(µ-
O2CC6H4S)Rh(PPh3)2}2)2] (5).
Complex 3 reacts with 1 equiv. of water to yield
[Cp*2Zr(OH){(µ-OOCC6H4S)Rh(PEt3)3}] (4), a rare exam-
ple of a terminal hydroxo complex of a zirconocene. Com-
plexes 3 and 4 are isotypic in the solid state. The introduc-
tion of the Lewis-acidic zirconium atom in 3 has a weak
electron-withdrawing effect on the rhodium centre.
The hexanuclear complexes 5 and 6 consist of 32-mem-
bered metallacycles in which two zirconocene groups bridge
two {Rh(SC6H4COO)(PR3)2}2 units [R = Ph (5), Et (6)].
The main structural difference in 5 and 6 is the presence of
two different isomers, in which the bridging thiolato ligands
occupy either the exo or the endo position of the Rh2S2
ring, which has, however, a significant influence on the size
of the macrocyclic cavity.
1
[d, JC,P = 34.6 Hz, P(CH2CH3)3], 118.1 [C5(CH3)5], 123.8 (SC),
127.9 (C1 in O2CC6H4S), 132.7 (C2 in O2CC6H4S), 164.6 (CCO2),
181.6 (CCO2) ppm (†coupling constants JA-X, JAЈ-X and JM-X of
the AAЈMX spin system could not be simulated because of low
1
resolution). 31P{1H} NMR ([D8]thf): δ = 13.5 [dd, JP-Rh
=
2
1
137.4 Hz, JP-P = 38.6 Hz, 2 P, P(C2H5)3], 28.4 [dt, JP-Rh = 160.4,
2JP-P = 38.6 Hz, 1 P, P(C H ) ] ppm. IR (KBr): ν = 2960 s, 2908 s,
˜
2
5 3
2890 m, 1583 s, 1561 w, 1494 m, 1420 s (sh), 1377 m, 1290 w, 1262
w (sh), 1168 w, 1078 m (sh), 1030 s (sh), 869 m, 847 w, 806 w (br),
775 m, 763 m, 732 w, 703 m, 677 w, 617 w, 552 m, 481 w cm–1.
(Hydroxo-1κO)bis(pentamethylcyclopentadienyl-1κ5C)-(µ-4-thio-
latobenzoato-1κ2O:2κS)tris(triethylphosphane-2κP)zirconium-
rhodium (4): Complex 3 was prepared as described above from
[RhCl(PEt3)3] (162 mg, 0.33 mmol), PEt3 (1 mL), K(Hmba)
(67 mg, 0.35 mmol) and [Cp*2ZrMe2] (129 mg, 0.33 mmol). The re-
sulting red solid was dissolved in n-hexane (5 mL) which contained
H2O (6 µL, 0.33 mmol) and PEt3 (1 mL). The solution was refluxed
for 15 min and the solvent evaporated in vacuo until the solution
became slightly cloudy. Light orange crystals (209 mg, 64 %)
were obtained at room temperature from this mixture.
C45H80O3P3RhSZr (988.19): calcd. C 54.69, H 8.16; found C 54.39,
H 8.32. 1H NMR (C6D6): δ = 1.20, 1.39, 1.88 [each m, 45 H,
P(C2H5)3], 1.91 [s, 30 H, C5(CH3)5], 3.47 [s (br), 1 H, ZrOH], 7.45
(m, 2 H, A part of the AAЈBBЈ spin system, H1 in O2CC6H4S),
8.10 (m, 2 H, B part of the AAЈBBЈ spin system, H2 in O2CC6H4S)
ppm. 13C{1H} NMR (C6D6): δ = 9.0 [2 × P(CH2CH3)3]†, 10.8
[P(CH2CH3)3], 11.9 [C5(CH3)5], 17.6 [2×P(CH2CH3)3]†, 21.4 [d,
1JC-P = 34.5 Hz, P(CH2CH3)3], 118.7 [C5(CH3)5], 123.8 (SC, over-
lapped by solvent signal), 124.5 (C1 in O2CC6H4S), 131.8 (C2 in
O2CC6H4S), 163.3 (CCO2), 180.5 (CCO2) ppm (†coupling con-
stants JA-X, JAЈ-X and JM-X of the AAЈMX spin system could not
be simulated because of low resolution). 31P{1H} NMR (C6D6): δ
= 14.2 [dd, 1JP-Rh = 136.6 Hz, 2JP-P = 38.6 Hz, 2 P, P(C2H5)3], 28.4
Experimental Section
General Remarks: All reactions were performed under nitrogen
using standard Schlenk techniques. Solvents were dried with the
appropriate drying agents and distilled under nitrogen. K(Hmba)
(H2mba
=
4-mercaptobenzoic acid),[13] [RhCl(PPh3)3],[23]
[RhCl(PEt3)3][24] and [Cp*2ZrMe2][25] were prepared according to
literature procedures. Complexes 1 and 2 were prepared in situ;
their synthesis and spectroscopic data are given in ref.[13] NMR
spectra were recorded with a Bruker AVANCE DRX 400 (1H
NMR 400.13 MHz, 13C NMR 100.3 MHz, 31P NMR
161.97 MHz); Si(CH3)4 was used as internal standard in the 1H
NMR spectra. All heteronuclei spectra were referenced to Si-
(CH3)4 with the Ξ scale.[26] NMR spectra of 3 and 4 were measured
in the presence of excess PEt3. IR spectra were recorded with an
FTIR spectrometer Perkin–Elmer Spektrum 2000 (KBr) in the
range of 350–4000 cm–1; a single crystal of 4 was measured with a
Perkin–Elmer AutoImage microscope system with a diamond cell.
The elemental composition was determined with a Hereaus CHN-
O-S Analyzer. The melting points were determined in sealed capil-
laries (under nitrogen) using a Gallenkamp apparatus and are un-
corrected. Cyclovoltammetry experiments were performed in an
airtight three-electrode cell attached to a Schlenk line. The working
electrode was a platinum disc electrode (diameter 2 mm), the
counter electrode a platinum sheet and a silver wire was used as
pseudoreference electrode. The working electrode was polished on
alumina according to standard procedures. The measurements were
performed in 5×10–3  solutions of the substances in thf contain-
ing 0.1 mol of [nBu4N]BF4 per L. The potentials were referenced to
the ferrocene/ferrocenium redox couple (E1/2 = 0.54 V vs. saturated
calomel electrode). UV/Vis spectra were recorded with a Perkin–
Elmer UV/Vis/NIR spectrometer Lambda 900.
1
2
[dt, JP-Rh = 162.5 Hz, JP-P = 38.4 Hz, 1 P, P(C2H5)3] ppm. IR
(KBr): ν = 3658 w, 2960 m, 2924 m, 2908 m, 2874 m, 1583 m, 1561
˜
m, 1494 m, 1420 s (sh), 1377 w, 1306 w (br), 1260 w (br), 1169 w,
1078 m (sh), 1030 m (sh), 869 m, 848 w, 805 w (br), 775 m, 763 m,
733 w, 702 w, 616 w, 552 w (sh) cm–1.
Bis[bis(pentamethylcyclopentadienyl-1κ5C)(µ-4-thiolatobenzoato-
1κ2O:2κS)bis(triphenylphosphane-2κP)zirconiumdirhodium] (5): A
solution of [RhCl(PPh3)3] (167 mg, 0.18 mmol) in thf (50 mL) was
added to a suspension of K(Hmba) (27 mg, 0.18 mmol) in thf
(50 mL). The mixture was heated to 50 °C for 4 h. The resulting
orange solution was filtered and added to a solution of
[Cp*2ZrMe2] (35.2 mg, 0.09 mmol) in thf (5 mL). After standing at
room temperature for 3 d (stirring resulted in the precipitation of
(Methyl-1κC)bis(pentamethylcyclopentadienyl-1κ5C)(µ-4-thiolato-
benzoato-1κ2O:2κS)tris(triethylphosphane-2κP)zirconiumrhodium
(3): Complex 2 was prepared in situ by adding a solution of
[RhCl(PEt3)3] (243 mg, 0.5 mmol) and PEt3 (1 mL) in thf (15 mL) impure product), the solvent was removed in vacuo and the brown
to a suspension of K(Hmba) (100 mg, 0.5 mmol) in thf (10 mL) at residue was washed with cold thf (0.5 mL) and n-hexane (2 mL).
4928
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2006, 4922–4930

4-Thiolatobenzoato-Bridged Rhodium/Zirconium Complexes
FULL PAPER
Table 2. Crystallographic data for 3, 4, 5·12thf and 6·Et2O.
3
4
5·12thf
6·Et2O
Empirical formula
Mr
T [K]
C46H82O2P3RhSZr
986.22
213(2)
C45H80O3P3RhSZr
988.19
213(2)
C260H292O20P8Rh4S4Zr2 C120H206O9P8Rh4S4Zr2
4707.02
243(2)
2762.93
213(2)
λ [pm]
71.073
monoclinic
P21/c
931.91(8)
3155.1(3)
1706.3(1)
90
90.833(1)
90
5.0163(7)
4
1.306
0.707
2080
71.073
monoclinic
P21/c
932.52(6)
3160.6(2)
1695.1(2)
90
90.083(9)
90
4.9961(7)
4
1.314
0.712
2080
71.073
triclinic
P1
71.073
triclinic
P1
Crystal system
Space group
a [pm]
b [pm]
c [pm]
α [°]
β [°]
¯
¯
1732.7(1)
1854.2(1)
2044.1(1)
86.354(1)
76.425(1)
67.987(1)
5.9161(7)
1
1418.35(9)
1564.7(1)
1822.6(1)
66.950(1)
86.797(1)
67.515(1)
3.4180(4)
1
γ [°]
V [nm3]
Z
ρcalcd. [gcm–3]
µ [mm–1]
F(000)
1.321
0.509
2456
1.342
0.822
1442
Crystal size [mm]
θ range [°]
h, k, l collected
0.60×0.10×0.08
1.76–26.39
–11 Յ h Յ 11
–38 Յ k Յ 39
–21 Յ l Յ 21
36561
10148
0/518
1.582
0.20×0.10×0.05
1.76–24.10
–10 Յ h Յ 9
–36 Յ k Յ 36
–16 Յ l Յ 19
19408
7733
0/507
0.597
0.60×0.30×0.30
1.83–28.40
–21 Յ h Յ 22
–24 Յ k Յ 16
–26 Յ l Յ 24
37232
27376
352/1347
0.935
0.30×0.30×0.05
1.54–28.32
–18 Յ h Յ 18
–20 Յ k Յ 20
–22 Յ l Յ 24
24670
12941
7/682
1.093
Measured reflections
Unique reflections
Restraints/parameters
Gof (all data)
Final R indices
[I Ͼ 2σ(I)]
R indices
R1 = 0.0931
wR2 = 0.1391
R1 = 0.1010
wR2 = 0.1410
0.795/–1.229
R1 = 0.0470
wR2 = 0.1004
R1 = 0.1237
wR2 = 0.1126
1.044/–0.576
R1 = 0.0479
wR2 = 0.1065
R1 = 0.1011
wR2 = 0.1248
1.184/–0.664
R1 = 0.0499
wR2 = 0.0978
R1 = 0.0716
wR2 = 0.1046
0.853/–0.379
(all data)
∆ρ(max/min) [eÅ–3]
Recrystallisation from thf gave 146 mg (42%) of red crystals. M.p.
198–202 °C (dec.). C212H196O8P8Rh4S4Zr2 (3842.04): calcd. C
gram SADABS[27] for 3, 5 and 6, and numerically for 4. Structure
solution and refinement were performed with WinGX,[28]
66.27, H 5.14; found C 65.85, H 5.32. 1H NMR ([D8]thf, T = SHELXS-97 and SHELXL-97.[29] All non-hydrogen atoms were re-
300 K): δ = 1.73–1.78 (br., 60 H, C5Me5), 7.00–8.00 [br., 136 H, fined anisotropically; most hydrogen atoms were refined in calcu-
P(C6H5)3 + O2CC6H4S] ppm. 31P{1H} NMR ([D8]thf): T = 300 K:
δ Ϸ 38 (br. d, PPh3); T = 173 K: 37.7 (br. d, 1JP-Rh = 153 Hz, PPh3
lated positions. Visualisation was carried out with the program
DIAMOND. The crystallographic data are summarised in
Table 2. CCDC-609917 (for 3), -609918 (for 4), -609915 (for 5)
1
of isomer 1), 38.4 (br. d, JP-Rh = 149 Hz, PPh3 of isomer 2) ppm.
IR (KBr): ν = 3050 m, 3000 w, 1633 m, 1585 m, 1495 m, 1481 m, and -609916 (for 6) contain the supplementary crystallographic
˜
1432 s, 1380 w, 1306 s, 1262 m, 1170 w, 1135 w, 1091 m (sh), 1027
m, 1016 m, 872 w, 848 w, 805 w, 775 w, 740 m, 694 s, 619 w, 534
m, 522 s, 492 w, 458 w, 437 w cm–1.
data for this paper. These data can be obtained free of
charge from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Bis[bis(pentamethylcyclopentadienyl-1κ5C)(µ-4-thiolatobenzoato-
1κ2O:2κS)bis(triethylphosphane-2κP)zirconiumdirhodium] (6):
[RhCl(PEt3)3] (162 mg, 0.33 mmol) was dissolved in thf (7 mL) and
added to a suspension of K(Hmba) (67 mg, 0.35 mmol) in thf
(7 mL) at 0 °C. The suspension was warmed to room temperature
over 1 h and then stirred for 16 h. The red solution was filtered,
treated with a solution of [Cp*2ZrMe2] (65 mg, 0.17 mmol) in thf
(5 mL) and heated to reflux for 3 h. After cooling, the solvent was
reduced to half its volume. Vapour diffusion with diethyl ether
yielded dark red crystals (170 mg, 37 %), which were washed
with n-hexane and dried in vacuo. M.p. 239–242 °C (dec.).
C116H196O8P8Rh4S4Zr2 (2688.97): calcd. C 51.81, H 7.35; found C
DFT Calculations: The calculations were carried out with the
Gaussian03 program package[30] using B3LYP[31] hybrid function-
als. For the metal atoms, effective core potentials were used;[32] the
outer core electrons were considered explicitly. For the coordinating
atoms, the standard 6-31g(d) basis set was used.[33] The calculations
of the ultraviolet spectra were performed with time-dependent den-
sity functional theory based on the optimised ground-state struc-
ture for 2 and on the experimental structure for 3.
Acknowledgments
U. H. thanks the Studienstiftung des Deutschen Volkes for a PhD
grant. Support from the Graduiertenkolleg 378 (DFG) and a gen-
erous donation of RhCl3 from Umicore AG & Co KG are grate-
fully acknowledged.
51.28, H 7.69. IR (KBr): ν = 2958, 2908, 2873, 1635, 1585, 1494,
˜
1429, 1392, 1379, 1301, 1261, 1169, 1136, 1094, 1032, 873, 848,
807, 766, 730, 702, 658, 622, 549, 515, 480, 413 cm–1.
X-ray Crystallography: X-ray data were collected with a Siemens
CCD Smart diffractometer for 3, 5 and 6, and with a Stoe IPDS1
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Eur. J. Inorg. Chem. 2006, 4922–4930
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
4929

U. Helmstedt, P. Lönnecke, J. Reinhold, E. Hey-Hawkins
FULL PAPER
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Received: June 14, 2006
Published Online: October 12, 2006
4930
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Eur. J. Inorg. Chem. 2006, 4922–4930