Gold(III) complexes with 1,2-disulfanyl-1,2-dicarba-closo-dodecaborane. Synthesis and partial degradation reactions of [Au(S2C2B10H10O)2] - salts

Article abstract of DOI:10.1039/a607329h

The reaction of 1,2-disulfanyl-1,2-dicarba-closo-dodecaborane, under basic conditions, with [N(PPh₃)₂][AuCl₄] or [AuCl₃(tht)]-NBu₄Br (molar ratio 2:1) (tht = tetrahydrothiophene) resulted in the forma

Full text of DOI:10.1039/a607329h

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Gold(III) complexes with 1,2-disulfanyl-1,2-dicarba-closo-
dodecaborane. Synthesis and partial degradation reactions of
[Au(S2C2B10H10)2]Ϫ salts
Olga Crespo,a M. Concepción Gimeno,a Peter G. Jonesb and Antonio Laguna *,a
a
Departamento de Química Inorgánica, Instituto de Ciencia de Materiales de Aragón,
Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain
b Institut für Anorganische und Analytische Chemie, Technische Universität, Postfach 3329,
38023 Braunschweig, Germany
The reaction of 1,2-disulfanyl-1,2-dicarba-closo-dodecaborane, under basic conditions, with [N(PPh3)2][AuCl4] or
[AuCl3(tht)]–NBu4Br (molar ratio 2:1) (tht = tetrahydrothiophene) resulted in the formation of the homoleptic
gold() derivative Q[Au(S2C2B10H10)2] [Q = N(PPh3)2 or NBu4]. Treatment of this complex with hydrazine or
phenylhydrazine partially degraded one or both carborane cages, respectively. The complexes [NBu4]-
[Au(S2C2B10H10)2] and [NBu4]2[Au(S2C2B9H10)(S2C2B10H10)] have been characterized by X-ray diffraction studies.
Table 1 Selected bond lengths (Å) and angles (Њ) for complex 1b
1,2-Dicarba-closo-dodecaborane (o-carborane) forms a great
variety of derivatives as a consequence of the high resistance of
the o-carborane cage to chemical attack.1 Despite their cost,
such properties make them attractive for various specialized
applications. These include the incorporation of high concen-
trations of boron atoms in tumour-seeking drugs for boron
neutron-capture therapy,2–4 the synthesis of high-temperature
polymers,5 the production of ceramics related to boron car-
bide,6 or the synthesis of derivatives with non-linear optical
properties.7 Furthermore, the ability to form nido anionic spe-
cies by treatment with nucleophiles has led to their use in co-
ordination chemistry with potential applications as novel cata-
lysts,8 radiochemical drugs,9 etc.
We are currently studying various o-carborane derivatives as
ligands. Here we focus on 1,2-sulfanyl-1,2-dicarba-closo-
dodecaborane, which has been little studied. Only a few com-
plexes of CoII and NiII have been previously described,10,11 and
we recently reported some gold() derivatives.12,13 We report on
the synthesis of the homoleptic gold()-dithiolate species and
further studies of the partial degradation of one or both carbo-
rane cages. The structural characterization of a complex involv-
ing closo and nido carborane cages allows the comparison of
bond distances and angles in the two different cages.
Au(1)᎐S(1)
S(1)᎐C(1)
C(1)᎐C(2)
Au(1Ј)᎐S(1Ј)
S(2Ј)᎐C(2Ј)
2.319(2)
1.778(6)
1.641(8)
2.321(2)
1.791(5)
Au(1)᎐S(2)
S(2)᎐C(2)
Au(1Ј)᎐S(2Ј)
S(1Ј)᎐C(1Ј)
C(1Ј)᎐C(2Ј)
2.321(2)
1.784(6)
2.318(2)
1.791(5)
1.640(7)
S(1)᎐Au(1)᎐S(2I )
C(1)᎐S(1)᎐Au(1)
C(2)᎐C(1)᎐S(1)
B(4)᎐C(1)᎐S(1)
B(3)᎐C(1)᎐S(1)
87.37(6)
102.1(2)
119.0(4)
119.8(4)
117.0(4)
120.3(4)
118.1(4)
92.59(6)
101.8(2)
119.3(3)
119.2(4)
116.1(3)
120.8(4)
117.3(3)
S(1)᎐Au(1)᎐S(2)
C(2)᎐S(2)᎐Au(1)
B(5)᎐C(1)᎐S(1)
B(6)᎐C(1)᎐S(1)
C(1)᎐C(2)᎐S(2)
B(9)᎐C(2)᎐S(2)
92.63(6)
102.2(2)
121.4(4)
119.0(4)
118.6(4)
120.6(4)
117.5(4)
87.41(6)
102.7(2)
118.5(4)
120.9(3)
117.9(3)
121.0(4)
116.9(3)
B(8)᎐C(2)᎐S(2)
B(6)᎐C(2)᎐S(2)
B(3)᎐C(2)᎐S(2)
S(2Ј)᎐Au(1Ј)᎐S(1Ј)
C(1Ј)᎐S(1Ј)᎐Au(1Ј)
C(2Ј)᎐C(1Ј)᎐S(1Ј)
B(5Ј)᎐C(1Ј)᎐S(1Ј)
B(6Ј)᎐C(1Ј)᎐S(1Ј)
B(11Ј)᎐C(2Ј)᎐S(2Ј)
B(3Ј)᎐C(2Ј)᎐S(2Ј)
S(2Ј)᎐Au(1Ј)᎐S(1ЈII )
C(2Ј)᎐S(2Ј)᎐Au(1Ј)
B(3Ј)᎐C(1Ј)᎐S(1Ј)
B(4Ј)᎐C(1Ј)᎐S(1Ј)
C(1Ј)᎐C(2Ј)᎐S(2Ј)
B(7Ј)᎐C(2Ј)᎐S(2Ј)
B(6Ј)᎐C(2Ј)᎐S(2Ј)
Symmetry transformations used to generate equivalent atoms: I Ϫx,
Ϫy, Ϫz; II Ϫx + 1, Ϫy + 1, Ϫz + 1.
procedure, consisting of the reaction of 2 equivalents of
(HS)2C2B10H10 with 1 equivalent of [AuCl3(tht)] (tht = tetra-
hydrothiophene) and NBu4Br, affording [NBu4][Au-
(S2C2B10H10)] 1b. Complex 1b possesses similar spectroscopic
data to 1a, but in this case we could grow crystals suitable for an
X-ray diffraction study. The anion of 1b is shown in Fig. 1,
with selected bond lengths and angles in Table 1.
Results and Discussion
The reaction of (HS)2C2B10H10 with [N(PPh3)2][AuCl4] in 2:1
molar ratio in dichloromethane, and in the presence of
Na2CO3, leads to the homoleptic gold() species [N(PPh3)2]-
[Au(S2C2B10H10)2] 1a (Scheme 1). Complex 1a is a red solid
stable to air and moisture and behaves as a 1:1 electrolyte in
acetone solution. The IR spectrum shows the B᎐H stretching
modes of the o-carborane nucleus as a broad band at 2591
cmϪ1, and also the vibration ν(Au᎐S) at 341 cmϪ1. The 11B
NMR spectrum displays resonances between δ Ϫ2.1 and
Ϫ10.9, the pattern and the shift being consistent with two
disubstituted o-carborane cages.
In the negative-ion fast atom bombardment (FAB) spectrum
of complex 1a the anion [Au(S2C2B10H10)2]Ϫ appears at m/z =
609 (100%), and also the fragment due to the loss of one dithio-
late ligand, [Au(S2C2B10H10)]Ϫ, at m/z = 403 (12%).
In spite of all our efforts we could not grow crystals of com-
plex 1a of suitable quality for an X-ray diffraction analysis. We
therefore prepared a different salt of the same anion by another
+
The asymmetric unit consists of an NBu4 cation and two
[Au(S2C2B10H10)]Ϫ anions, each with the gold atoms on an
inversion centre. In both anions the gold centre has a square-
planar geometry with similar bond lengths and angles. The lig-
and bite angles, 87.37(6) and 87.41(6)Њ (corresponding S ؒ ؒ ؒ S
distances 3.355 and 3.353 Å), are narrower than the exterior
S᎐Au᎐S angles, in contrast to observations in other gold()
derivatives containing dithiolate ligands, e.g. [N(PPh3)2]-
[Au(C3S5)2] [91.88(5) and 91.76(5)Њ] (C3S5 = 4,5-disulfanyl-1,3-
dithiole-2-thionate)14 or [Au(PPh2Me)2][Au(3,4-S2C6H3Me)2]
[90.02(12)Њ].15 The Au᎐S bond distances are 2.319(2) and
2.321(2) Å in one molecule and 2.318(2) and 2.321(2) Å in the
other; these values, although similar to those in [N(PPh3)2]-
[Au(C3S5)2] [2.321(2)–2.326(2) Å],14 are slightly longer than
J. Chem. Soc., Dalton Trans., 1997, Pages 1099–1102
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Scheme 1 (i) N2H4, NBu4Br; (ii) PhHNNH2, 2NBu4Br
Fig. 2 The anion of complex 2 in the crystal, showing the atom label-
ling scheme. Hydrogen atoms are omitted for clarity; radii are arbitrary
Fig. 1 One of the two independent anions of complex 1b in the crys-
tal, showing the numbering scheme of the independent atoms. Hydro-
gen atoms are omitted for clarity; radii are arbitrary
acetone. In its IR spectrum B᎐H stretching frequencies appear
as a broad band shifted to low frequency, as previously
observed for partially degraded carborane moieties. The 11B
NMR spectrum shows the presence of two different carborane
cages, one closo and one nido. The resonances appear between δ
Ϫ2.5 to Ϫ36.1; some are overlapped. In the 1H NMR spectrum
the signal assigned to the bridging proton B᎐H᎐B at δ Ϫ2.42 is
consistent with the partially degraded nature of one of the
carborane cages.
those in other dithiolate complexes such as [PClPh3][Au-
{S2C2(CF3)2}2] (2.288 Å)16 and [Au(PEt3)2][Au(1,2-S2C6H4)2]
(2.305 Å).17 The S᎐C bond lengths range from 1.778(6) to
1.791(5) Å and the C᎐C distances in the carborane are 1.641(8)
and 1.640(7) Å. The chelate rings display an envelope conform-
ation, with the gold atoms 0.62 and 0.63 Å out of the plane of
the respective C2S2 group.
The electrochemical behaviour of complex 1b has been
studied by cyclic voltammetry at a platinum electrode in
CH2Cl2. The cyclic voltammogram, at a scan rate of 100 mV
In the negative-ion (FAB) mass spectrum of complex 2 the
molecular peak does not appear, but the fragments due to
+
the loss of one or two NBu4 groups are present at m/z = 841
s
Ϫ1, shows a quasi-reversible reduction wave with peak potential
{45, [Au(S2C2B9H10)(S2C2B10H10)(NBu4)]Ϫ} and 599 {47%,
[Au(S2C2B9H10)(S2C2B10H10)]Ϫ}.
Ϫ0.726 V; the peak separation is 78.3 mV and the cathodic to
anodic current ratio 0.993:1. We believe that it is a single-
electron process in which the gold() complex is reduced to the
gold() species.
Crystals of complex 2 were obtained by slow diffusion of
diisopropyl ether into a dichloromethane solution, and the pro-
posed structure was confirmed by X-ray diffraction analysis;
the anion is shown in Fig. 2, with selected bond lengths and
angles in Table 2. The gold centre again has a square-planar
geometry with four sulfur donor atoms; the mean deviation of
these atoms from the best plane is 0.028 Å. The bite angles of
both dithiolate ligands are very dissimilar, 88.40(4) and
93.81(4)Њ (corresponding S ؒ ؒ ؒ S distances 3.227 and 3.400 Å),
the narrower corresponding to the degraded ligand, and the
wider angle is also very different from those in the starting
material (see above). The Au᎐S distances are also distinct for
each type of ligand: 2.3127(13) and 2.3158(11) Å for the nido
and 2.3264(12) and 2.3291(13) Å for the closo ligand. The
reason could be the additional negative charge of the nido lig-
and, which slightly reduces the strength of the sulfur–carbon
We have studied the partial degradation reaction of this
complex. First we refluxed ethanol solutions of the complex, a
method that gives excellent results for 1,2-bis(diphenyl-
phosphine)-o-carborane complexes,18 but only a mixture of the
starting material and degraded products were obtained. Then
we carried out the reaction of 1b with an excess of hydrazine in
dichloromethane and in the presence of NBu4Br, which led to
some decomposition to metallic gold, consistent with the
reducing nature of the hydrazine, and a blue solid that analyses
for [NBu4]2[Au(S2C2B9H10)(S2C2B10H10)] 2; in this derivative
only one of the carborane groups has been degraded. Complex
2 is moderately stable in solution, although it can be stored in
the solid state for a long time; it behaves as a 2:1 electrolyte in
1100
J. Chem. Soc., Dalton Trans., 1997, Pages 1099–1102

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on a VG autospec instrument with the FAB technique, using
3-nitrobenzyl alcohol as matrix, NMR spectra on a Varian
Unity 300 spectrometer in CDCl3. Chemical shifts are cited
relative to SiMe4 (1H, external) and BF3ؒOEt2 (11B, external).
Cyclic voltammetric experiments were performed by employing
an EG&G PARC model 273 potentiostat. A three-electrode
system was used, consisting of a platinum-disc working elec-
trode, a platinum-wire auxiliary electrode, and a saturated
calomel reference electrode. The measurements were carried out
in CH2Cl2 solutions with 0.1 mol dmϪ3 NBu4PF6 as supporting
electrolyte. Under the present experimental conditions, the
ferrocenium–ferrocene couple was located at 0.47 V. The start-
ing materials (HS)2C2B10H10,22 [N(PPh3)2][AuCl4] and [AuCl3-
(tht)]23 were prepared by published procedures.
Table 2 Selected bond lengths (Å) and angles (Њ) for complex 2
Au᎐S(2Ј)
Au᎐S(2)
S(1)᎐C(1)
S(1Ј)᎐C(1Ј)
C(1)᎐C(2)
2.3127(13)
2.3264(12)
1.780(4)
1.799(4)
1.671(5)
Au᎐S(1Ј)
Au᎐S(1)
S(2)᎐C(2)
S(2Ј)᎐C(2Ј)
C(1Ј)᎐C(2Ј)
2.3158(11)
2.3291(13)
1.776(4)
1.795(4)
1.548(5)
S(2Ј)᎐Au᎐S(1Ј)
S(1Ј)᎐Au᎐S(2)
S(1Ј)᎐Au᎐S(1)
C(1)᎐S(1)᎐Au
C(1Ј)᎐S(1Ј)᎐Au
C(2)᎐C(1)᎐S(1)
B(4)᎐C(1)᎐S(1)
B(6)᎐C(1)᎐S(1)
B(8)᎐C(2)᎐S(2)
B(6)᎐C(2)᎐S(2)
C(2Ј)᎐C(1Ј)᎐S(1Ј)
B(6Ј)᎐C(1Ј)᎐S(1Ј)
C(1Ј)᎐C(2Ј)᎐S(2Ј)
88.40(4)
176.97(4)
89.21(4)
102.41(13)
103.01(14)
119.1(3)
120.1(3)
118.6(3)
121.4(3)
118.4(3)
117.7(3)
118.8(3)
117.9(3)
S(2Ј)᎐Au᎐S(2)
S(2Ј)᎐Au᎐S(1)
S(2)᎐Au᎐S(1)
88.59(4)
176.21(5)
93.81(4)
102.64(13)
102.62(13)
121.9(3)
116.6(3)
119.0(3)
119.5(3)
116.9(3)
117.7(3)
C(2)᎐S(2)᎐Au
C(2Ј)᎐S(2Ј)᎐Au
B(5)᎐C(1)᎐S(1)
B(3)᎐C(1)᎐S(1)
C(1)᎐C(2)᎐S(2)
B(9)᎐C(2)᎐S(2)
B(3)᎐C(2)᎐S(2)
B(5Ј)᎐C(1Ј)᎐S(1Ј)
Synthesis
Q[Au(S2C2B10H10)2] [Q = N(PPh3)2 1a or NBu4 1b]. To a solu-
tion of (HS)2C2B10H10 (0.041 g, 0.2 mmol) in dichloromethane
(30 cm3) was added [N(PPh3)2][AuCl4] (0.087 g, 0.1 mmol) and
an excess of Na2CO3 (0.1 g, 1 mmol). The mixture was stirred
for 30 min, the excess of Na2CO3 filtered off and the solution
concentrated to ca. 5 cm3. Addition of diethyl ether (10 cm3)
gave complex 1a as a red solid in 65% yield (Found: C, 41.75; H,
4.55; N, 1.15. Calc. for C40H50AuB20NP2S4: C, 41.85; H, 4.4; N,
B(10Ј)᎐C(1Ј)᎐S(1Ј) 115.7(3)
B(3Ј)᎐C(2Ј)᎐S(2Ј)
B(9Ј)᎐C(2Ј)᎐S(2Ј)
116.6(3)
121.7(3)
B(10Ј)᎐C(2Ј)᎐S(2Ј) 118.0(3)
bonds; in agreement with this the C᎐S bond lengths in the nido
ligand are 1.799(4) and 1.795(4) Å, and those in the closo moi-
ety 1.776(4) and 1.780(4) Å. The chelate rings again display an
envelope conformation, which is more pronounced in the nido
ligand; the gold atoms lie 0.46 and 0.83 Å out of the plane of
the respective C2S2 group. The C᎐C bond distances are 1.671(5)
Å for the closo and 1.548(5) Å for the nido ligand. The appre-
ciable C᎐C shortening from the parent carborane complex to
the partially degraded species is expected since a filled orbital
derived from 6a1 [B11H11]4Ϫ (orbital labelling as by Mingos)19
is formed upon partial degradation.20 The ‘additional’H atom of
the open B3H4C2 face (see Experimental section) bridges the
B(3Ј)᎐B(4Ј) bond, which is the longest B᎐B bond at 1.858(7) Å.
We have observed a similar open-face structure in a related
light-atom derivative, where the H atom position is more
reliable.21
.
1.2%). ΛM 129 ΩϪ1 cm2 molϪ1 11B NMR: δ Ϫ2.7 (2B), Ϫ6.1
(2B), Ϫ7.5 (4B) and Ϫ10.1 (12B).
To a solution of (HS)2C2B10H10 (0.041 g, 0.2 mmol) in dichlo-
romethane (30 cm3) was added [AuCl3(tht)] (0.1 mmol, 0.039 g),
NBu4Br (0.1 mmol, 0.032 g) and an excess of Na2CO3. The
suspension was stirred for 30 min and then filtered, concen-
trated to ca. 5 cm3 and addition of hexane (10 cm3) gave com-
plex 1b as a red solid in 60% yield (Found: C, 28.55; H, 6.55; N,
1.7. Calc. for C20H56AuB20NS4: C, 28.2; H, 6.6; N, 1.7%). ΛM
132 ΩϪ1 cm2 molϪ1
.
[NBu4]2[Au(S2C2B9H10)(S2C2B10H10)] 2. To
a
dichloro-
methane solution (20 cm3) of [NBu4][Au(S2C2B10H10)2] (0.1
mmol, 0.85 g) was added an excess of N2H4.H2O (50 µl, 1.6
mmol). The solution was stirred for 2 h, filtered over Celite to
eliminate metallic gold and then the solvent was removed in
vacuo; after addition of diethyl ether (10 cm3) complex 2 was
isolated as a blue solid in 63% yield (Found: C, 39.5; H, 8.75;
N, 3.0. Calc. for C36H92AuB19N2S4: C, 39.9; H, 8.55; N, 2.6%).
ΛM 190 ΩϪ1 cm2 molϪ1. NMR: 1H, δ Ϫ2.4 (br, ∆ = 186 Hz); 11B,
δ Ϫ2.5 (1B), Ϫ8.1 (2B), Ϫ9.6 (5B), Ϫ12.6 (4B), Ϫ19.2 (3B),
Ϫ22.5 (2B), Ϫ33.0 (1B) and Ϫ36.1 (1B).
Treatment of complex 1b with further hydrazine and/or for
longer periods of time did not lead to the doubly degraded
species. We then tried the reaction with other bases such as
phenylhydrazine, which gives the desired complex [NBu4]3-
[Au(S2C2B9H10)2] 3 as a green solid. Complex 3 is not very stable
in solution, but behaves in acetone solution as a 3:1 electrolyte.
1
The 11B and H NMR spectra are consistent with the presence
of two partially degraded carborane cages. In the negative-ion
mass spectrum the molecular peak does not appear, and neither
does the species arising from the loss of one or two NBu4
+
[NBu4]3[Au(S2C2B9H10)2] 3. To a dichloromethane solution
(20 cm3) of [NBu4][Au(S2C2B10H10)2] (0.1 mmol, 0.85 g) was
added an excess of PhNHNH2 (0.16 cm3, 1.6 mmol). The solu-
tion was stirred for 2 h. The solution was filtered over Celite to
eliminate metallic gold and then the solvent was removed in
vacuo; after addition of diethyl ether (10 cm3) complex 3 was
isolated as a green solid in 57% yield (Found: C, 47.55; H, 10.0;
N, 3.2. Calc. for C52H128AuB18N3S4: C, 47.5; H, 9.8; N, 3.2%).
ΛM 274 ΩϪ1 cm2 molϪ1. NMR: 1H, δ Ϫ2.1 (br, ∆ = 150 Hz); 11B,
δ Ϫ9.5 (4B), Ϫ13.7 (6B), Ϫ16.5 (4B), Ϫ31.2 (2B) and Ϫ36.0
(2B).
groups, but the anion containing the two partially degraded
species [Au(S2C2B9H10)2]Ϫ is present at m/z = 587 (38%). Other
fragments correspond to the addition of one or two boron
atoms and appear at m/z = 599 (45) and 610 (100%), respec-
tively.
We could not grow crystals of sufficient quality to confirm
the structure of complex 3, although in all the cases the same
unit cell could be determined; a = 10.991, b = 12.015, c = 21.688
Å, α = 78.91, β = 78.51 and γ = 72.32Њ, U = 2892 Å3. For a tri-
clinic cell with Z = 2 this indicates approximately 80 non-
hydrogen atoms, agreeing well with the calculated 78 for
[NBu4]3[Au(S2C2B9H10)2].
Crystallography
The crystals were mounted in inert oil on glass fibres and trans-
ferred to the cold gas stream of a Siemens R3 diffractometer
with an LT-2 low-temperature attachment. Data were collected
using monochromated Mo-Kα radiation (λ = 0.710 73 Å). Scan
type ω. Cell constants were refined from setting angles of ca. 50
reflections in the range 2θ 20–23Њ. Absorption corrections were
applied on the basis of ψ scans. Structures were solved by the
heavy-atom method and refined on F2 using the program
SHELXL 93.24 All non-hydrogen atoms were refined aniso-
tropically for complex 2; for 1b the boron atoms were refined
Experimental
Instrumentation
Infrared spectra were recorded in the range 4000–200 cmϪ1 on a
Perkin-Elmer 883 spectrophotometer using Nujol mulls
between polyethylene sheets. Conductivities were measured in
ca. 5 × 10Ϫ4 mol dmϪ3 solutions with a Philips 9509 conducti-
meter. Carbon and hydrogen analyses were carried out with a
Perkin-Elmer 2400 microanalyser. Mass spectra were recorded
J. Chem. Soc., Dalton Trans., 1997, Pages 1099–1102
1101

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References
Table 3 Data collection and structure refinement details for complexes
1b and 2*
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S. A. Westcott, T. B. Marder, N. J. Taylor and D. R. Kanio, J. Mater.
Chem., 1993, 3, 139.
8 M. F. Hawthorne, J. F. Liebman, A. Greenberg and R. E. Willians
(Editors), Advances in Boron and the Boranes, VCH, New York,
1988, ch. 10, p. 225.
9 R. J. Paxton, B. G. Beatty, M. F. Hawthorne, A. Varadarajan,
L. E. Willians, F. L. Curtis, C. B. Knobler, J. D. Beatty and
J. E. Shively, Proc. Natl. Acad. Sci. USA, 1991, 88, 3387.
10 H. D. Smith, jun., J. Am. Chem. Soc., 1965, 87, 1817.
11 H. D. Smith, jun., M. A. Robinson and S. Papetti, Inorg. Chem.,
1967, 6, 1014.
1b
2
Chemical formula
M
Crystal habit
Crystal size/mm
a/Å
b/Å
c/Å
α/Њ
C20H56AuB20NS4
852.06
C36H92AuB19N2S4
1083.71
Blue tablet
0.60 × 0.40 × 0.20
13.947(2)
15.087(3)
15.572(3)
100.89(2)
95.18(2)
116.67(2)
2817.5(9)
1.277
Red tablet
0.50 × 0.40 × 0.25
11.428(3)
11.489(4)
16.272(5)
97.06(3)
93.84(3)
111.95(3)
1951.7(10)
1.450
β/Њ
γ/Њ
U/Å3
Dc/Mg mϪ3
F(000)
852
1120
T/ЊC
Ϫ95
4.0
0.53–0.97
6901
6874
Ϫ100
2.79
0.624–0.953
12 491
9885
µ(Mo-Kα)/mmϪ1
Transmission
No. reflections measured
No. unique reflections
Rint
0.028
0.031
R[F, F > 4σ(F)]
wR ( F2, all reflections)
No. parameters
No. restraints
S
0.035
0.101
318
34
1.099
1.53
0.033
0.067
571
404
0.929
0.906
12 O. Crespo, M. C. Gimeno, P. G. Jones and A. Laguna, J. Chem. Soc.,
Chem. Commun., 1993, 1697.
13 O. Crespo, M. C. Gimeno, P. G. Jones, B. Ahrens and A. Laguna,
Inorg. Chem., in the press.
14 P. G. Jones, E. Cerrada, M. C. Gimeno and M. Laguna,
Z. Kristallogr., 1994, 209, 827.
15 M. C. Gimeno, P. G. Jones, A. Laguna, M. Laguna and R. Terroba,
Inorg. Chem., 1994, 33, 3932.
Maximum ∆ρ/e ÅϪ3
¯
* Details in common: space group P1; Z = 2; 2θmax = 50Њ; R (F) =
¹
2 2

Σ |Fo| Ϫ |Fc| /Σ|Fo|; wR (F2) = [Σw(Fo2 Ϫ Fc )2/Σw(Fo ) ]²; wϪ1 = σ2(Fo2) +
2
(aP)2 + bP, where P = (Fo2 + 2Fc )/3 and a and b are constants adjusted
2
¹
16 J. H. Enemark and J. A. Ibers, Inorg. Chem., 1968, 7, 2636.
17 M. Nakamoto, H. Koijman, M. Paul, W. Hiller and H. Schmidbaur,
Z. Anorg. Allg. Chem., 1993, 619, 1341.
2
2 2

bytheprogram;S = [Σw(Fo Ϫ Fc ) /(nϪp)]² wherenisthenumber of data
and p the number of parameters.
18 O. Crespo, M. C. Gimeno, P. G. Jones and A. Laguna, Inorg. Chem.,
1996, 35, 1361.
19 D. M. P. Mingos, J. Chem. Soc., Dalton Trans., 1977, 602.
20 F. Teixidor, J. Rius, A. M. Romerosa, C. Miravitlles, L. Escriche,
E. Sanchez, C. Viñas and J. Casabó, Inorg. Chim. Acta, 1990, 176,
287.
isotropically. Hydrogen atoms were included using a riding
model where possible; the open face hydrogens of 2 were refined
‘freely’ but with terminal and bridging BH separately con-
strained equal. Further details are given in Table 3.
Atomic coordinates, thermal parameters, and bond lengths
and angles have been deposited at the Cambridge Crystallo-
graphic Data Centre (CCDC). See Instructions for Authors,
J. Chem. Soc., Dalton Trans., 1997, Issue 1. Any request to the
CCDC for this material should quote the full literature citation
and the reference number 186/392.
21 P. G. Jones, O. Crespo, M. C. Gimeno and A. Laguna,
Acta Crystallogr., Sect. C, in the press.
22 H. D. Smith, jun., C. O. Obenland and S. Papetti, Inorg. Chem.,
1967, 5, 1013.
23 E. A. Allen and W. Wilkinson, Spectrochim. Acta, Part A, 1972, 28,
2257.
24 G. M. Sheldrick, SHELXL 93, A Program for Crystal Structure
Refinement, University of Göttingen, 1993.
Acknowledgements
We thank the Dirección General de Investigación Científica y
Técnica (No. PB94-0079) and the Fonds der Chemischen
Industrie for financial support.
Received 28th October 1996; Paper 6/07329H
1102
J. Chem. Soc., Dalton Trans., 1997, Pages 1099–1102