Preparation and properties of heterometallic cube derivatives Mo3M′S4 from [Mo3S4(H2O)9]4+ with M′ = 3 Pt, Rh and Re, and [W3S4(H2O)9]

Article abstract of DOI:10.1039/b104755h

Three heterometallic Mo₃M′S₄ derivatives (M′ = Pt, Rh, Re) of the incomplete single-metal depleted cube [Mo₃S₄(H₂O)₉]⁴⁺ have been prepared by reactions with [PtCl₄]

Full text of DOI:10.1039/b104755h

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Preparation and properties of heterometallic cube derivatives
Mo3MЈS4 from [Mo3S4(H2O)9]4؉ with MЈ ؍ Pt, Rh and Re, and
[W3S4(H2O)9]4؉ analogues
Maxim N. Sokolov, Diego Villagra, Ahmed M. El-Hendawy, Chee-Hun Kwak,
Mark R. J. Elsegood, William Clegg and A. Geoffrey Sykes*
Department of Chemistry, The University of Newcastle, Newcastle upon Tyne, UK NE1 7RU
Received 31st May 2001, Accepted 25th July 2001
First published as an Advance Article on the web 24th August 2001
Three heterometallic Mo3MЈS4 derivatives (MЈ = Pt, Rh, Re) of the incomplete single-metal depleted cube
[Mo3S4(H2O)9]4ϩ have been prepared by reactions with [PtCl4]2Ϫ (ϩ H3PO2 reductant), RhCl3 and [Re(CO)5Br],
respectively. With [PtCl4]2Ϫ, the initial product gives, on standing for 2–3 days, the edge-linked double cube
[{Mo3PtS4(H2O)9}2]8ϩ, which is difficult to elute in Dowex cation-exchange chromatography. In the reaction with
RhCl3, chloro products, e.g. [Mo3RhCl3S4(H2O)9]4ϩ, precede formation of [Mo3RhS4(H2O)12]7ϩ, which is also difficult
to elute, and with [Re(CO)5Br], the product [Mo3Re(CO)3S4(H2O)9]5ϩ is obtained. Analyses are consistent with
oxidation state assignments Pt0, RhIII and ReI, where the reactions proceed by addition of these forms to
[Mo3S4(H2O)9]4ϩ. The analyses and X-ray crystal structure of (Mo2NH2)[Mo3Re(CO)3S4(NCS)4] are consistent
with the formation of an Mo3ReS4 single cube. Yields are high in the first two cases, but much lower in the Re
case. Alternative preparations are described in the case of Rh and Re. All three products decay on heating,
with reformation of trinuclear [Mo3S4 (H2O)9]4ϩ, which can be recovered by Dowex chromatography. As
compared to heterometallic derivatives so far considered, those with MЈ = Pt, Rh, Re are much more
substitution (and redox) inert, and are air stable. Analogues from [W3S4(H2O)9]4ϩ with MЈ = Pt, Rh
have been prepared using similar procedures.
already described. Purification was by Dowex cation-exchange
Introduction
chromatography, where UV-Vis absorbance peaks λ/nm (ε/MϪ1
The trinuclear MoIV incomplete cuboidal cluster [Mo3S4-
cmϪ1 per Mo3) are 370(4995), 616(326) in 2 M HCl, and
3
(H2O)9]4ϩ is able to incorporate a wide range of heteroatoms
366(5550), 603(362) in 2 M Hpts (p-toluenesulfonic acid).
(MЈ) from Groups 6 to 15 in the Periodic Table, with formation
Purple coloured [W3S4(H2O)9]4ϩ was likewise prepared by
of Mo3MЈS4 and/or related double cubes.1,2 In the present work
procedures previously described.11 UV-Vis absorbance peaks
we set out to explore MЈ incorporation of the platinum metals
are λ/nm (ε/MϪ1 cmϪ1 per W3) 317(6100), 570(480) in 2 M HCl;
Pt, Rh, and of Re, using relatively simple reagents, i.e. [PtCl4]2Ϫ
,
and 315(6350), 560(446) in 2 M Hpts.
RhCl3 and [Re(CO)5Br]. An edge-linked cube is formed in the
Pt case, as observed previously with other Group 10 metals Ni
and Pd,3,4 as well as Co and Cu. The reaction is summarised in
eqn. (1),5,6 which shows key atoms only.
Details of the procedures for the preparation of new
heterometal-containing clusters are included in the Results
section.
Other reagents
(1)
The strong acid p-toluenesulfonic acid (Hpts) was obtained as
a white crystalline solid (Aldrich). The reducing agents hypo-
phosphorous acid, H3PO2 (50% w/w H2O solution) and sodium
tetrahydroborate, NaBH4, were from Aldrich. Other reagents
were of analytical grade purity. Multidentate ligands imino-
diacetate (ida), nitrotriacetate (nta), and ethylenediamine-tetra
acetate (Na2H2edta) were used in some procedures described.
Technical grade cylinder carbon monoxide was used.
A sample of [Re(CO)5Br] was prepared by a procedure
modified from that in ref. 12. Rhenium metal powder (0.5 g)
was carefully dissolved in hydrogen peroxide. To do this, four 10
mL portions of 30% H2O2 were used. After the first addition, it
was necessary to allow O2 evolution to subside, before adding a
further portion, etc. Care is required to limit over vigorous
reaction and spillage. To the product HBr (48% by wt; 100 mL)
was added, and the volume reduced on a hotplate to 5 mL.
Formic acid (96% by wt; 5 mL) was added and the mixture
refluxed for 48 h. White crystals of [Re(CO)5Br] collected on the
lower part of the condenser. The crystals were filtered off,
washed with H2O, and dried in air. Elemental analyses and IR
spectra were in good agreement with published data.
At present the only example of Pt incorporation is with
[Mo3(PtCl)S4(dppe)3Cl3], where dppe is 1,2-bis(diphenylphos-
phino)ethane, and the Mo3PtS4 core has a 4ϩ charge.7
Examples of Rh incorporation are with [Mo3(RhCp*)-
8ϩ 8
S4(H2O)9]4ϩ and [Mo3(RhCp*)S4(H2O)7O]2
, where Cp* is
the η5-pentamethylcyclopentadienide ligand, and the core
charge can be assigned as Mo3RhS47ϩ. No Re derivative of
[Mo3S4(H2O)9]4ϩ has so far been reported. The reactivity of
[W3S4(H2O)9]4ϩ with MЈ = Pt, Rh has also been investigated
briefly.
Experimental
Preparation of starting complexes
The green coloured MoIV incomplete cluster [Mo3S4(H2O)9]4ϩ
3
was prepared from the MoV cysteine complex [Mo2O2(µ-S)2
2
(Cys)2]2Ϫ 9
,
or from polymeric {Mo3S7Br4}x,10 by procedures
DOI: 10.1039/b104755h
J. Chem. Soc., Dalton Trans., 2001, 2611–2615
This journal is © The Royal Society of Chemistry 2001
2611

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X-Ray crystallography
Data for (NH2Me2)4[Mo3Re(CO)3S4(NCS)9] were measured on
a Bruker AXS SMART CCD diffractometer with Mo-Kα
radiation (λ = 0.71073 Å) at 160 K. Crystal data: C20H32Mo3-
N13O3ReS13, M = 1393.4, orthorhombic, space group Pbca,
a = 23.1784(11), b = 23.1553(11), c = 43.357(2) Å, U = 23270(2)
Å3, Z = 16 (2 independent anions and 8 cations in the asym-
metric unit), µ = 3.21 mmϪ1, 91979 measured data, 15211
unique (Rint = 0.18); R (F, F 2 > 2σ) = 0.092, wR (F 2, all
data) = 0.301, 910 refined parameters and 1284 restraints.
The structure shows a high degree of disorder, and data were
very weak. The cluster anions are disordered so that each metal
position is statistically occupied by both Mo and Re, and the
carbonyl C and O atoms on Re overlap essentially with the N
and C atoms of the thiocyanate ligands on Mo. Site occupancy
factors were refined for all the metal sites, tied appropriately to
those for the S atoms of thiocyanate and restrained to give a
total ratio of 3 for Mo : Re. The light atoms of the ligands were
assigned as N and C with no attempt to refine mixed N/C and
C/O scattering factors or to resolve overlapping sites. Only four
out of the eight cation positions could be clearly identified
from electron density maps, and even these show high dis-
placement parameters; the remaining cations are presumably
highly disordered, together with any solvent molecules present.
Similarity restraints were applied to the geometry of all ligands
and to the geometry of the refined cations. In view of the
nearly equal values of two cell parameters, twinning models
were investigated, but none was found to give any improve-
ment. Programs used were Bruker SMART,13 SAINT14 and
SHELXTL.15
4ϩ
7ϩ
Fig. 1 UV-Vis spectra of Mo3PtS4
(—), Mo3RhS4
(—ؒؒ—),
alongside [Mo3S4(H2O)9]4ϩ (—ؒ—) in 2 M HCl (ε values per Mo3).
Solutions in HCl are stable in air with only 3–5% decay
to [Mo3S4(H2O)9]4ϩ in a week. Heating 2–4 M HCl solutions
in air on a steam bath (ca. 90 ЊC) for 3–4 h brings about
decomposition to green [Mo3S4(H2O)9]4ϩ and PtII, eqn. (4).
Mo3PtS44ϩ ϩ 21O2 ϩ 2Hϩ → Mo3S44ϩ ϩ PtII ϩ H2O (4)
The [Mo3S4(H2O)9]4ϩ was determined from the visible range
absorbance, and the PtII by addition of a large (ca. 100-fold)
excess of SnCl2ؒ2H2O in 3–5 M HCl after oxidation of the
Mo3S44ϩ with HNO3. Any PtIV formed in eqn. (4) is reduced by
CCDC reference number 165093.
See http://www.rsc.org/suppdata/dt/b1/b104755h/ for crystal-
lographic data in CIF or other electronic format.
SnII. The PtII gives yellow coloured products with as many
as five mol of SnCl3 coordinating to give [Pt(SnCl3)5]3Ϫ
,
Ϫ
Results
which can be determined from the absorbance at 400 nm.18
The procedure was standardised using K2[PtCl4] solutions
of known HCl concentration in the presence of MoVI. A
ratio Mo3S44ϩ : PtII of 1.1 : 1.0 was obtained in support of
the formula Mo3PtS44ϩ. Inductively coupled plasma atomic
emission spectroscopy (ICP-AES) gave Mo : Pt : S ratios of
3.0 : 0.78 : 3.5. Analyses therefore exclude the possibility of the
6 : 1 ratio Mo : Pt corner-shared double cube.
Preparation and properties of Mo3PtS44؉
Solid K2[PtCl4] (0.68 g) was added to [Mo3S4(H2O)9]4ϩ (10 mM;
120 mL) in 2 M HCl. The mixture was flushed with N2 for 30
min (no colour change), and the reductant H3PO2 (0.2 mL; 50%
w/w aqueous solution) added to initiate reaction. At room tem-
perature a dark brown colour begins to develop within 10 min.
To accelerate the process, the mixture was heated to 35–40 ЊC
(more vigorous heating brings about Pt metal formation). The
yield is close to 100% with H3PO2. With NaBH4 (100-fold
excess) high yields of Pt black are observed and only 1–2% of
the cube is obtained. The requirement for a strong reductant
The UV-Vis spectrum of Mo3PtS44ϩ in 2–4 M HCl gives peak
positions λ/nm (ε/MϪ1 cmϪ1 per Mo3) at 361(15600) and
452(9040), with other peaks at 207 and 223 nm, Fig. 1. A 2 M
HCl solution was evaporated to dryness by vacuum line tech-
niques, and dissolved in 0.5 M HClO4 to give a 0.50 × 10Ϫ4
M
4ϩ
suggests that the 4ϩ core Mo3PtS4 is formed (as with
solution with a UV-Vis spectrum showing peaks at λ/nm (ε/MϪ1
cmϪ1 per MO3) 236sh(17100), 297(16240), 346(14240),
443(8820). The latter approach also gives a solution in 4.0 M
Hpts. No suitable crystals were, however, obtained in this or
other procedures involving addition of cyanide, which gave
[Mo3S4(CN)9]5Ϫ, or with the multidentate ligands ida, nta and
edta.
MЈ = Pd3,16 and Ni4,17), eqn. (2).
4ϩ
Mo3S44ϩ ϩ PtII ϩ 2eϪ
Mo3PtS4
(2)
The solution was diluted to 0.5 M in HCl and left to stand for
2–3 days prior to loading on a Dowex 50W-X2 cation-exchange
column. Without this further period, most of the product
passes straight through the column. Only on standing does slow
substitution at the Pt occur to give the 8ϩ edge-linked double
cube. After loading, the column was washed successively with
ca. 100 mL amounts of 0.5 and 1.0 M HCl. With 2.0 M HCl,
unreacted [Mo3S4(H2O)9]4ϩ was eluted before a brown solution
of the Pt product. The latter was obtained as a more concen-
trated solution using 3–4 M HCl. Attempts to elute with 4.0 M
Hpts gave only very dilute solutions, which suggests that an 8ϩ
edge-linked double cube is formed, eqn. (3), which is inert to
Consistent with the low reactivity of Mo3PtS44ϩ with O2, the
one-equivalent oxidants [Co(dipic)2]Ϫ (362 mV), [Fe(H2O)6]3ϩ
(770 mV), [V(O)2(H2O)4]ϩ (1.0 V) give little or no reaction with
the Mo3PtS44ϩ core.
4ϩ
On bubbling CO through solutions of Mo3PtS4 in 3.0 M
HCl or 4.0 M Hpts, no UV-Vis changes were observed within
10 min at ca. 20 ЊC. On heating to 60 ЊC for 20 min, the only
UV-Vis changes observed corresponded to the formation of
[Mo3S4(H2O)9]4ϩ. These experiments suggest that the 8ϩ edge-
linked double cube formed in eqn. (3) is retained in 2 M HCl
solutions, with the Pt unavailable for CO complexation.
4ϩ
8ϩ
2Mo3PtS4
{Mo3PtS4}2
(3)
Finally, the product was reacted with 1,2-bis(diphenyl-
phosphine)ethane (dppe) to give [Mo3(PtCl)4(dppe)3Cl3],7 the
X-ray crystal structure of which has been determined. The
single cube re-formation. The solutions were too dilute to
obtain crystals.
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J. Chem. Soc., Dalton Trans., 2001, 2611–2615

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only detectable Mo product, and since the UV-Vis peak
positions are well known, such a procedure provides the means
of determining absorption coefficients. Hence, in 2 M HCl,
peak positions λ/nm (ε/MϪ1 cmϪ1 per Mo3) are 260(sh), 291(sh),
370 (1.17 × 104), 422(9700), 533(2730), 670(sh) (ca. 1250),
Fig. 1.
4ϩ
The Mo3(RhCl3)S4 cluster equilibrated in 0.5 M HCl was
loaded onto a Dowex column. The dark band which formed
could not be eluted with 4 M Hpts and the aqua form [Mo3-
RhS4(H2O)12]7ϩ is believed to be present under these conditions.
A solution of Mo3(RhCl3)S44ϩ in 0.5 M HCl was evaporated to
dryness (vacuum line), and then dissolved in 4 M Hpts. No
crystals formed on leaving the solution to stand at 4 ЊC. With
excess NCSϪ, formation of [Mo3S4(NCS)9]5Ϫ (or related) is
observed, and the multidentate ligands ida, nta and edta
gave green Mo3S44ϩproducts. No satisfactory crystallisation
procedure was identified.
The Mo3(RhCl3)S4 cube gave no reaction with a 10-fold
excess of [Co(dipic)2]Ϫ in 2 M HCl. Over ca. 30 min the [Co-
(dipic)2]Ϫ absorbance decayed, but that of Mo3RhS4 remained
unchanged. No reaction was observed on bubbling CO through
a 2 M HCl solution for 40 min, with and without heating to
50 ЊC.
Fig. 2 UV-Vis spectra of W3PtS44ϩ (—) and W3RhS47ϩ (—ؒؒ—) in 2 M
HCl (ε values per W3).
product was identified by elemental analyses and 31P NMR
spectra.
Preparation of W3PtS44؉
The same procedure was used with H3PO2 as reductant. Elution
of a brown product from a Dowex 50W-X2 resin was again
with 3–4 M HCl. The UV-Vis spectrum in 3 M HCl gave peak
positions λ/nm (ε/MϪ1 cmϪ1 per Mo3) at 306(17600), 396(6990),
Fig. 2. ICP-AES analyses gave a W : Pt ratio of 3.0 : 0.8 consist-
ent with the core structure W3PtS44ϩ. Dowex cation-exchange
behaviour was similar to that of Mo3PtS44ϩ, indicating form-
ation of an edge-linked dimer [{W3PtS4(H2O)9}2]8ϩ, which is
7؉
Preparation of W3RhS4
A brown coloured derivative was prepared in the same way as
7ϩ
for the Mo3RhS4 core from [W3S4(H2O)9]4ϩ. The UV-Vis
spectrum in 3 M HCl gave peak positions λ/nm (ε/MϪ1 cmϪ1 per
W3) at 359(8600) and 497(2080), Fig. 2. ICP-AES analyses gave
a W : Rh ratio of W : Rh or 3.0 : 0.93, consistent with
7ϩ
4ϩ
4
W3RhS4
.
also known to form in the case of W3NiS4
.
Preparation and properties of the Mo3RhS47؉
5؉
Preparation and properties of Mo3ReS4
A solution of RhCl3 (five-fold excess) and [Mo3S4(H2O)9]4ϩ in
4.0 M HCl (1 mM; 15 mL) was heated in air on a hotplate
for 3 h. Within 20 min, a colour change to brown com-
menced. The final solution was diluted to 0.5 M HCl and
loaded onto a Dowex 50W-X2 cation-exchange column,
washed with ca. 100 mL amounts of 0.5 M HCl (to remove any
[RhCl6]3Ϫ as a pink solution), and then 1.0 M HCl (to remove
unreacted [Mo3S4(H2O)9]4ϩ). No reductant was used and
A 10 : 1 solution of [Re(CO)5Br] and [Mo3S4(H2O)9]4ϩ (20 mL;
5 mM) was taken to dryness, and concentrated HCO2H and
HCl (50 : 1 by volume) added. The mixture was refluxed for 48h
(oil bath). The resulting brown solution was cooled down,
evaporated to dryness (vacuum line), and re-dissolved in 4 M
HCl. After diluting to 0.2–0.3 M HCl, this was loaded onto
Dowex 50W-X2 cation-exchange resin. Washing was with
100 mL amounts of 0.5 M and 1 M HCl, the latter eluting any
unreacted [Mo3S4(H2O)9]4ϩ. A brown solution eluted with 2 M
HCl, and was purified using the same column procedure. Yields
5–8%. A higher 5ϩ charge was ascribed to this product from its
Dowex cation-exchange column behaviour. ICP-AES gave a
ratio Mo : Re : S of 3.00 : 0.94 : 4.11. A Dowex columned sol-
ution of the Re cube was taken to dryness (vacuum line), and
the IR spectrum of the solid recorded. This gave absorption
bands at 1904, 1947 and 2016 cmϪ1 consistent with three CO
ligands attached to the Re, and a formula of [Mo3Re-
(CO)3S4(H2O)9]5ϩ. No change in the UV-Vis spectrum was
observed after passing N2 through a 2 M HCl solution for 3
days at ca. 20 ЊC, indicating that the CO remains strongly
bonded to the Re. No corresponding derivative was obtained on
treating [W3S4(H2O)9]4ϩ with [Re(CO)5Br].
4ϩ
the Mo3(RhCl3)S4 core was formed in an addition process
[eqn. (5)].
4ϩ
Mo3S44ϩ ϩ RhCl3
Mo3(RhCl3)S4
(5)
Elution with 2 M HCl gave a brown solution and behaviour
characteristic of the 4ϩ ion [Mo3(RhCl3)S4(H2O)9]4ϩ. Increas-
ing the time of the reaction or addition of ethanol (which
catalyses reactions of RhIII) did not affect the yield, which was
up to 80%.
A second procedure requires air-free (N2) conditions. A
sample of blue–green [Rh2(O2CCH3)4] was first prepared as
previously described.19 A sample of [Rh2(O2CCH3)4] (5.4 mg)
was dissolved in 2 M HCl with heating, and [Mo3S4(H2O)9]4ϩ in
2 M Hpts (2.75 mM; 10 mL) added. The resultant mixture was
kept on a hotplate for 6 h, whereupon the colour gradually
became brown. After dilution to 0.5 M in Hpts, the solution
was loaded onto a Dowex 50W-X2 cation-exchange column.
Any black precipitate was removed by filtration prior to
loading on the column. After washing and removal of
unwanted fractions with 0.5–1 M HCl, a brown product was
eluted with 2 M HCl. Yields of 20–40% were obtained from five
repeat experiments. The product has the same UV-Vis spectrum
as in the first procedure, and complexing by ClϪ gives
[Mo3(RhCl3)S4(H2O)9]4ϩ as the dominant product.
In 2 M HCl, the UV-Vis spectrum gives peak positions λ/nm
(ε/MϪ1 cmϪ1 per Mo3) at 248 (1.56 × 104), 287 (1.13 × 104),
380(3500), 452(1345), Fig. 3. Solutions of the [Mo3Re-
(CO)3S4(H2O)9]5ϩ in 2 M HCl can be kept in air for several
weeks without decomposition. When air is passed through a
solution of the cube at 90 ЊC, the UV-Vis spectrum begins to
change after 2 h, and after >8 h quantitative formation of green
[Mo3S4(H2O)9]4ϩ was observed, and could be separated by
column chromatography.
5ϩ
A sample of the Mo3ReS4 cube in 2 M HCl was taken to
dryness (vacuum line) giving ca. 0.3 g of brown solid. This was
re-dissolved in 2 M HCl (5 mL), to which solid KϩNCSϪ (0.5 g)
and Me2NH2Cl (0.2 g) were added. The solution turned grad-
Elemental analysis by ICP-AES gave an Mo : Rh ratio of
3.0 : 1.0. On heating, [Mo3S4(H2O)9]4ϩ reforms slowly as the
J. Chem. Soc., Dalton Trans., 2001, 2611–2615
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Fig. 3 UV-Vis spectrum of [Mo3Re(CO)3S4(H2O)9]5ϩ in 2 M HCl
(ε values per Mo3).
ually to a purple–brown colour. After one day at 4 ЊC dark
crystals of (Me2NH2)4[Mo3Re(CO)3(NCS)9] were obtained.
Analyses: Calc. for C20H32N13S13O3Mo3Re: C, 29.7; H, 2.8; N,
13.0; S, 29.7%. Found: C, 29.3; H, 2.6; N, 13.9; S, 29.3%. The
structure from X-ray crystallography is given below.
Fig.
4
One of the two independent anions of (NH2Me2)4-
[Mo3Re(CO)3S4(NCS)9] with 20% displacement ellipsoids. All atoms
within each ligand have the same number, which is shown only for the
S atoms of NCSϪ and O atoms of CO.
In an alternative procedure for the preparation of
Mo3ReS45ϩ, a sample of (NH4)2[Mo2S4Br8] was first prepared
from (NH4)2[Mo2S12] using an excess of liquid Br2 in an inert
organic solvent (CH3CN).20 The mixture was stirred at room
temperature until all the black (NH4)2[Mo2S12] had changed
into orange (NH4)2[Mo2S4Br8]. On completion of the reaction,
the solid was filtered off and dried in vacuo. The solid obtained
is air stable over several months. A sample of K2[ReCl6] was
prepared from NH4[ReO4].21 Amounts of (NH4)2[Mo2S4Br8]
(0.46 g) and K2[ReCl6] (0.18 g) were mixed with conc. HCl
(20 mL). The mixture was brought to boiling and zinc granules
(ca. 1 g) were added. After all the zinc had been consumed, the
resultant solution was diluted 1 : 2 with H2O and filtered from a
copious brown precipitate. The solution was further evaporated
to dryness on a rotavap, dissolved in 0.5 M HCl and then
loaded onto a Dowex 50W-X2 cation-exchange column. A blue
solution of [Re2Cl8]2Ϫ (identified by its UV-Vis spectrum),22
formed by Zn reduction of [ReCl6]2Ϫ was not retained. After
washing with 0.5 M HCl, unreacted [Mo3S4(H2O)9]4ϩ was
eluted with 1 M HCl. Finally, a brown product was eluted
with 2 M HCl. This was collected, diluted to 0.5 M HCl, and
recolumned using Dowex chromatography as a single brown
band. Yield 3%.
Discussion
Heterometal Pt, Rh, Re-containing cube derivatives of
[Mo3S4(H2O)9]4ϩ have been prepared in this work. The reaction
of the strong reductant H3PO2 with [PtCl4]2Ϫ results in incipient
formation of Pt0, which reacts with [Mo3S4(H2O)9]4ϩ to give the
Mo3PtS44ϩ core. The reaction is similar to that of Pd0 (Pd black)
with [Mo3S4(H2O)9]4ϩ 3,16
No reaction is observed however with
.
Pt black.24 Attempts to load the product obtained after ca. 30
min onto Dowex cation-exchange resin were unsuccessful,
suggesting that a lower charged ClϪ complexed single cube is
present in 2 M HCl. On leaving to stand for 2–3 days in 0.5 M
HCl, aquation of the ClϪ occurs, and all observations point to
the formation of the edge-linked double cube [{Mo3PtS4-
(H2O)9}2 ]8ϩ. No reductant was used with RhCl3, which gives
4ϩ
the Mo3(RhCl3)S4 adduct, and subsequently (in 0.5 M HCl)
aquates to give [Mo3RhS4(H2O)12]7ϩ or a related product. The
inability to elute the Pt and Rh products from a Dowex column
using 4 M Hpts is consistent with the presence of highly-
charged species, one the 8ϩ edge-linked Pt-containing double
cube, and the other the single cube [Mo3RhS4(H2O)12]7ϩ
.
Both products are however eluted with ≥ 3 M HCl. In the Pt
case ClϪ complexing to the Mo’s occurs. In the Rh case, ClϪ
complexation at the Mo and Rh atoms is likely. Both the single
core components have been identified previously in the X-ray
Elemental analysis by ICP gave Mo : Re of 3.0 : 1.15. The
UV-Vis spectrum gave peak positions λ/nm at 207(7.1),
269(4.8), 370sh(1.5), 467(1.0), relative absorbance values in
brackets. The product appears to be related to [Mo3Re-
crystal structures of [Mo3(PtCl)S4(dppe)3]Cl3,7 and [Mo3(Rh-
Cp*)S4(H2O)9]4ϩ.8 The Pt single cube can be written as Mo3S4
,
4ϩ
(CO)3S4(H2O)9]5ϩ
, and a possible formula is [Mo3ReS4-
Pt0 consistent with tetrahedral Pt0. The ability to form an
edge-linked double cube is similar to that observed for the d10
(H2O)12]5ϩ. Some chloro complexation of the Re (ClϪ for H2O)
is possible.
heterometals (Pd, Ni) in Mo3PdS44ϩ and W3NiS44ϩ 4,5 From the
.
properties observed, the Pt0 is more inert than Pd0,25 and the Pt
double cube appears to persist in 2 M HCl. The Rh-containing
single cube can be written as Mo3S44ϩ, RhIII with d6 RhIII
expected to be substitution inert.26,27 The three µ3-sulfido core
ligands do not give an obvious labilisation of the Pt0 or RhIII,
see also the discussion in ref. 28. No reaction of CO with the Pt0
Crystal structure
The crystal structure for (NH2Me2)4[Mo3Re(CO)3S4(NCS)9]
shows the expected M4S4 single cube core structure, Fig. 4.
There are two independent cations in the structure.
Unfortunately, there is a high degree of disorder, with Re
4ϩ
distributed unequally over all four metal sites of each cation.
of Mo3PtS4 in 3.0 M HCl is observed. From studies on car-
5ϩ/6ϩ
Similar disorder has been observed in the W3MoS4
clus-
bonyl and phosphine binary complexes it has been noted that
in transition metal triads (e.g. Ni0, Pd0, Pt0), the second-row
element reacts the faster.29 This appears to be the case here also
with an order Pd > Ni > Pt applying. Thus the reaction of
ters.23 This means the carbonyl and thiocyanate ligands are also
scrambled in the average structure observed, precluding a free
refinement and meaningful analysis of the ligand geometry. The
results, requiring many restraints on geometry and atomic dis-
placement parameters, are consistent with the proposed cation
formulation, but do not provide an independent proof of the
composition. However, analytical data and relatively straight-
forward synthesis leave little doubt as to the identity of the
product. Extensive disorder is also observed in the cations.
4ϩ
4ϩ
Mo3PdS4
k = 1.1 × 105 MϪ1 sϪ1 16
k = 0.66 MϪ1 s
with CO is fast to give Mo3(PdCO)S4 ,
4ϩ
,
while that of Mo3NiS4 is slower,
4ϩ
, .
Ϫ1 17 and no reaction is detected with Mo3PtS4
Neither is any reaction of CO with RhIII observed. As a result,
the potential of Pt and Rh to bind organic moieties (as with Pd
and Ni), and serve as centres for catalytic changes is much less.
2614
J. Chem. Soc., Dalton Trans., 2001, 2611–2615

View Article Online
A. G. Sykes, in Sulfur Coordinated Transition Metal Complexes,
The Re-containing cube Mo3ReS45ϩ has been synthesised for
the first time, and likewise exhibits substitution and redox inert
properties. On treating the parent compound [Mo3Re-
(CO)3S4(H2O)9]5ϩ with 1 M NCSϪ, the latter coordinates to the
Mo’s, but whether it displaces the 3CO’s was at first uncertain.
However, elemental analyses on the product indicate a formula
(Me2NH2)4[Mo3Re(CO)3(NCS)9] with the CO’s retained. The
X-ray structure is shown in Fig. 4.
ACS Symp. Ser. No. 653, ed. K. Matsumoto and E. I. Stiefel,
American Chemical Society, Washington D.C., 1996, pp. 216–224.
2 T. Shibahara, Adv. Inorg. Chem., 1991, 37, 143.
3 T. Murata, Y. Mizobe, H. Gao, Y. Ishii, T. Wakabayashi, F. Nakano,
T. Tanase, S. Yano, M. Hidai, I. Echizen, H. Namikawa and
S. Motomura, J. Am. Chem. Soc., 1994, 116, 3389.
4 T. Shibahara, G. Sakane, M. Maeyama, H. Kobashi, T. Yamamoto
and T. Watase, Inorg. Chim. Acta, 1996, 251, 207.
5 T. Shibahara, H. Akashi, M. Yamasaki and K. Hashimoto, Chem.
Lett., 1991, 689.
The stability of Group 10 (Ni, Pd, Pt) cubes with tetrahedral
MЈ sites, and of Group 9 octahedral RhIII can be explained by
the electron counts of 60 which are exactly as required to fill all
the bonding orbitals. In the case of the odd electron clusters
6 T. Shibahara, H. Akashi and H. Kuroya, J. Am. Chem. Soc., 1988,
110, 3313.
7 D. Masai, Y. Ishii and M. Hidai, 48th Japanese Conference on
Coordination Chemistry, Kochi, Japan, 1998, abstract 3A306.
8 (a) H. Akashi and T. Shibahara, Abstracts to the 30th ICCC, Kyoto,
Japan, 1994, p. 175; (b) H. Akashi, A. Nakano and T. Shibahara,
XVIIth IUCr Congress, Glasgow, UK, 1999, abstract P07.07.041.
9 M. Martinez, B.-L. Ooi and A. G. Sykes, J. Am. Chem. Soc., 1987,
109, 4615.
10 M. N. Sokolov, N. Coichev, H. D. Moya, R. Hernandez-Molina,
C. D. Borman and A. G. Sykes, J. Chem. Soc., Dalton Trans., 1997,
1863.
4ϩ
4ϩ
Mo3CuS4
(61e) and Mo3CoS4
(59e), both are highly
reactive, and dimerisation with formation of MЈ–MЈ bonds
occurs.5,6 The Cuϩ adduct Mo3CuS4 (60e) has also been pre-
5ϩ
pared,30,31 but here the Cuϩ is less likely to form MЈ–MЈ bonds.
5ϩ
A stable cube structure Mo3ReS4 (60e) incorporating an
octahedral ReI is therefore perfectly reasonable.
In spite of the reluctance of [W3S4(H2O)9]4ϩ to form hetero-
metallic derivatives, it is possible with Pt and Rh to prepare
analogues of those from [Mo3S4(H2O)9]4ϩ using the same
procedures. From studies carried out similar structures are
indicated. With the inclusion of Pt and Rh eight derivatives of
[W3S4(H2O)9]4ϩ are now known to form (Mo, Rh, Ni, Pt, Cu,
In, Ge, Sn). The greater reluctance of [W3S4(H2O)9]4ϩ to form
heterometal adducts has already been discussed.32
11 V. P. Fedin, M. N. Sokolov and A. G. Sykes, J. Chem. Soc., Dalton
Trans., 1996, 44089.
12 R. Colton and J. Knapp, Aust. J. Chem., 1971, 9.
13 SMART, Program for X-Ray Diffraction Data Collection, Siemens
Analytical X-Ray Instruments Inc., Madison, WI, 1998.
14 SAINT, Program for Area Detector Absorption Correction,
Siemens Analytical X-Ray Instruments Inc., Madison, WI, 1994.
15 G. M. Sheldrick, SHELXTL, Program for Crystal Structure
Determination, Siemens Analytical X-Ray Instruments Inc.,
Madison, WI, 1994.
16 D. M. Saysell, G. J. Lamprecht, J. Darkwa and A. G. Sykes, Inorg.
Chem., 1996, 35, 5531.
17 D. M. Saysell, C. D. Borman, C.-H. Kwak and A. G. Sykes, Inorg.
Chem., 1996, 35, 173.
18 See e.g.: Analytical Chemistry of the Elements – Platinum Metals,
J. Wiley & Sons, New York, 1975, p. 339.
19 G. A. Rempel, P. Legzdins, H. Smith and G. Wilkinson, Inorg.
Synth., 1972, 13, 90.
20 V. P. Fedin, Y. Mironov and V. Fedorov, Zh. Neorg. Khim, 1989, 34,
2984.
21 G. W. Watt and R. J. Thompson, Inorg. Synth., 1963, 7, 189.
22 F. A. Cotton, N. F. Curtis, B. F. G. Johnson and W. R. Robinson,
Inorg. Chem., 1965, 4, 326.
23 I. J. McLean, R. Hernandez-Molina, M. N. Sokolov, M.-S. Seo,
A. V. Virovets, M. R. J. Elsegood, W. Clegg and A. G. Sykes,
J. Chem. Soc., Dalton Trans., 1998, 2557.
24 V. P. Fedin, M.-S. Seo, D. M. Saysell, D. N. Dybtsev, M. R. J.
Elsegood, W. Clegg and A. G. Sykes, to be published.
25 R. Hernandez-Molina and A. G. Sykes, Coord. Chem. Rev., 1999,
187, 291.
26 S. F. Lincoln and A. E. Merbach, Adv. Inorg. Chem., 1995, 42, 3.
27 G. Laurenczy, I. Rapaport, D. Zbinden and A. E. Merbach, Magn.
Reson. Chem., 1991, 29, 545.
28 C. A. Routledge, M. Humanes, Y.-J. Li and A. G. Sykes, J. Chem.
Soc., Dalton Trans., 1994, 1275.
In conclusion, derivatives of [Mo3S4(H2O)9]4ϩ have been
prepared by addition of Pt0 (d10), RhIII (d6) and ReI (d6) to give
the edge-linked double cube [{Mo3PtS4(H2O)9}2]8ϩ, and double
cubes [Mo3RhS4(H2O)12]7ϩ and [Mo3(Re(CO)3)S4(H2O)9]5ϩ. In
the case of the Pt and Rh derivatives the formulae are consist-
ent with previous studies, with the important difference that
aqua ligands are present. The tendency of the Pt double cube to
reform the single cube with different ligands, e.g. CO, is much
less than in the case of the Pd analogue. The studies described
indicate substitution and redox inert properties in all three
cases. Whereas the Pt0 assignment is consistent with existing
Group 10 Ni0 and Pd0 studies, the RhIII (d6) oxidation state with
7ϩ
high overall charge of Mo3RhS4 is a novel feature. In the Re
5ϩ
case, an Mo3ReS4 structure, and ReI (d6) state provide the
most reasonable assignment. In all three cases, it is possible to
recover [Mo3S4(H2O)9]4ϩ by heating, which is consistent with
representations Mo3S44ϩ,Pt0; Mo3S44ϩ,RhIII and Mo3S44ϩ,ReI.10
Acknowledgements
We are grateful for financial support from the British Council
(A. M. El-H.), the European Union Alpha Programme (D. V.),
and the University of Newcastle (M. N. S.). Thanks are also
due to the EPSRC for equipment funding (W. C.).
29 F. Basolo, Polyhedron, 1990, 9, 1503.
30 M. Nasreldin, Y.-J. Li, F. E. Mabbs and A. G. Sykes, Inorg. Chem.,
1994, 33, 4283.
31 H. Akashi and T. Shibahara, Inorg. Chim. Acta, 2000, 572, 300.
32 R. Hernandez-Molina, M. R. J. Elsegood, W. Clegg and A. G. Sykes,
J. Chem. Soc., Dalton Trans., 2001, 2173.
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2615