New thiophene metallacarbaborane compounds of palladium and platinum: X-ray structures of 1-C4H3S-3-(cod)-3,1,2-M-C2B9 H10, 1-C4H3S-3,3-(PMe2Ph)2-3,1,2-Pt-C

Article abstract of DOI:10.1016/S0022-328X(98)00398-2

The icosahedral metallacarboranes [1-C₄H₃S-3,3-(PMe₂Ph)₂-3,1,2-Pt-C₂B₉H₁₀], [1-C₄H₃S-3-(cod)-3,1,2-M-C₂B₉H₁₀] (M=Pt or Pd)

Full text of DOI:10.1016/S0022-328X(98)00398-2

Journal of Organometallic Chemistry 562 (1998) 105–114
New thiophene metallacarbaborane compounds of palladium and
platinum: X-ray structures of 1-C4H3S-3-(cod)-3,1,2-M-C2B9H10,
1-C4H3S-3,3-(PMe2Ph)2-3,1,2-Pt–C2B9H10 and
1-C4H3S-3,3-(PPh2CH2CH2Ph2)-3,1,2-Pd-C2B9H10 (M=Pt or Pd)1
Despo M. Michaelidou, D. Michael P. Mingos *, David J. Williams, Andrew W.J. White
Department of Chemistry, Imperial College of Science, Technology and Medicine, South Kensington, London SW7 2AY, UK
Received 22 December 1997
Abstract
The icosahedral metallacarboranes [1-C4H3S-3,3-(PMe2Ph)2-3,1,2-Pt-C2B9H10], [1-C4H3S-3-(cod)-3,1,2-M-C2B9H10] (M=Pt or
Pd) and [1-C4H3S-3,3-(PPh2CH2CH2Ph2)-3,1,2-Pd-C2B9H10] were synthesised from Tl2[7-(C4H3S)-7,8-nido-C2B9H10],
[PtCl2(PMe2Ph)2], [MCl2(cod)] (M=Pt or Pd) and [PdCl2(PMe2Ph)2], respectively (cod, cyclo-octa-1,5-diene). Their single crystal
X-ray structures have been completed and their molecular structures are described. © 1998 Elsevier Science S.A. All rights
reserved.
Keywords: Icosahedral metallacarboranes; Platinum carboranes; Polyhedral rearrangements; ‘Slip-distortions’
1. Introduction
the metal atom and steric effects associated with sub-
stituents on the ligands and the cage both play an
important role in influencing the barriers for skeletal
rearrangements in these metallacarboranes. The role of
steric effects on the conformational preferences and
rotational barriers for the rotation of the ML2 frag-
ments relative to the pentagonal face of the C2B9 cage
are also of general interest. We recently reported the
products of the reaction of Pd(PMe2Ph)2Cl2 with Tl2[7-
(RC4H2S)-7,8-nido-C2B9H10] (R=Me or H) [4]. This
paper discusses the reactions of Tl2[7-(C4H3S)-7,8-nido-
C2B9H10] with [PtCl2(PMe2Ph)2], [MCl2(cod)] (M=Pt
or Pd) and [PdCl2(PMe2Ph)2] and the rearrangement
properties of the resulting cage compounds.
As part of a study on the effect of substituents on the
conformations and skeletal rearrangements of metal-
lacarboranes, a series of thiophene-substituted metal-
lacarboranes of palladium and platinum have been
synthesised and structurally characterised. The synthe-
ses and rearrangement properties of phenyl-substituted
platinacarbaboranes have been previously reported, for
example [1-Ph-3,3-(PMe2Ph)2-3,1,2,-Pt-C2B9H10] and
the disubstituted compound [1,11-Ph2-3,3-(PMe2Ph)2-
3,1,11-Pt-C2B9H9] [1]. The related palladium com-
pounds
[1-Ph-3(cod)-3,1,2-Pd-C2B9H10]
and
[Pd(cod)-p5-7,8-Me2-7,8-C2B9H9] (cod, cyclo-octa-1,5-
diene) have been reported by other workers [2,3]. These
studies have established that the electronic properties of
2. Experimental details
2.1. Synthesis and characterisation
* Corresponding author. Tel.: +44 171 5945754; fax: +44 171
5945804; e-mail: d.mingos@ic.ac.uk
1 Dedicated to Prof. R. Bruce King on the occasion of his 65th
birthday.
Reactions were generally performed under N2 by
use of standard Schlenk techniques, although some
0022-328X/98/$19.00 © 1998 Elsevier Science S.A. All rights reserved.
PII S0022-328X(98)00398-2

106
D.M. Michaelidou et al. / Journal of Organometallic Chemistry 562 (1998) 105–114
Table 1
Crystal data, data collection and refinement parametersa
Data
(1)
(3)
(5)
(6)
Formula
Solvent
C22H35B9P2SPt
—
685.9
Deep red blocks
0.43×0.27×0.27
Monoclinic
P21/c
C14H25B9SPt
—
517.8
Orange prisms
0.20×0.17×0.08
Monoclinic
Iab
C14H25B9SPd
—
429.1
Red blocks
0.33×0.33×0.27
Monoclinic
Iac
C32H37B9P2SPd
0.5 Me2CO
748.4
Orange/brown blocks
0.56×0.47×0.17
Triclinic
Formula weight
Colour, habit
Crystal size (mm)
Lattice type
Space group
Cell dimensions
P1
˚
a (A)
14.826(2)
12.662(1)
15.745(2)
—
99.71(1)
—
2913.3(5)
4
1.564
12.458(1)
10.082(1)
15.289(3)
—
98.12(1)
—
1901.0(5)
4
1.809
12.473(1)
10.076(1)
15.335(2)
—
98.76(1)
—
1904.6(3)
4
1.496
10.401(1)
11.076(1)
17.492(3)
88.14(1)
84.96(1)
74.57(1)
1934.8(4)
2
˚
b (A)
˚
c (A)
h (°)
i (°)
k (°)
3
˚
V (A )
Z
Dcalc. (g cm−3
F(000)
)
1.285
764
1344
992
864
Radiation used
Mo–Kh
5.010
2.1–25.0
Cu–Kh
14.733
5.3–63.0
Mo–Kh
1.077
2.4–25.0
Mo–Kh
0.641
1.9–25.0
v (mm−1
)
q Range (°)
No. of unique reflections
Measured
5075
1547
1725
6808
Observed [ꢀFoꢀ\4|(ꢀFoꢀ)]
Absorption correction
Max, min transmission
No. of variables
R1d
3860
1511
1703
—
—
247
0.022
0.058
0.035, 0.000
0.37, −0.24
5875
Semi-empirical
0.1677, 0.1033
305
0.036
0.084
Semi-empirical
0.1899, 0.0504
247
0.027
0.069
Gaussian
0.9079, 0.7483
376
0.044
0.118
wRe2
Weighting factors a, bf
Largest difference peak, hole (e A
0.040, 4.000
0.66, −0.69
0.069, 0.000
0.88, −1.42
0.066, 1.532
0.80, −0.50
−3
˚
)
a Details in common: graphite monochromated radiation, ꢀ-scans, Siemens P4/PC diffractometer, data corrected for Lorentz and polarisation
factors, 293 K, refinement based on F2. b I-face centred cell chosen since C-face centred cell has i=124.2°. c I-face centred cell chosen since
C-face centred cell has i=123.8°. d R1=SꢀꢀFoꢀ−ꢀFcꢀꢀ/SꢀFoꢀ. e wR2=ꢁA{S[w(Fo2−Fc2)2]/S[w(Fo2)2]}. f w−1=|2(Fo2)+(aP)2+bP.
subsequent manipulations were carried out in the open
laboratory. All solvents were dried and distilled under
N2 prior to use. The NMR spectra were recorded on a
(0.526 g, 0.97 mmol), CH2Cl2 (30 ml) was added at
−78°C. The reaction mixture was stirred for 1.5 h at
intermediate temperatures and 1.5 h at room tempera-
ture (r.t.). The resulting orange solution was filtered
and the solvent was removed under reduced pressure.
Preparative TLC (CH2Cl2:hexane, 1:1) gave an inten-
sive orange band (Rf=0.21) as the main product and
two very weak bands (Rf=0.36, 0.34). The main
product was identified as [1-C4H3S-3,3-(PMe2Ph)2-
3,1,2-Pt-C2B9H10] (1) by NMR, MS and a single crystal
X-ray analysis. Crystals suitable for X-ray crystallogra-
phy were grown by layering a CH2Cl2 solution with
Et2O at −20°C.
1
JEOL JNM-EX270 FT spectrometer. H, 13C, 11B{1H}
and 31P{1H} chemical shifts (l) were referenced to
tetramethylsilane (1H, 13C), BF3 ·OEt2 and H3PO4, re-
spectively. Electron impact (EI) mass spectra were
recorded on a VG Micromass 7070B and fast atom
bombardment (FAB) mass spectra were recorded on a
VG AutoSpecQ mass spectrometer using 3-nitrobenzyl
alcohol matrix.
The starting materials [PdCl2(cod)] [5], [PtCl2(cod)]
[6] and Tl2[7-C4H3S-nido-7,8-C2B9H10] [4] were made by
literature methods.
Yield 0.27g, 40%. Anal. Calc. for C22H35B9SP2Pt; C
38.4, H 5.1%. Found: C 38.4, H 5.1%.
1
2.1.1. [1-C4H3S-3,3-(PMe2Ph)2-3,1,2-Pt-C2B9H10],1
To a mixture of solid Tl2[7-C4H3S-nido-7,8-C2B9H10]
(0.605 g, 0.971 mmol) and solid [PtCl2(PMe2Ph)2]
NMR for (1): H (CDCl3): l 7.35 and 7.25 (br s,
obscured under CDCl3, 10 H, 2PMe2Ph), 7.08 [dd, 1 H,
J(H–H) 4.9, J(H–H) 1.3, C4H3S], 7.03 [dd, 1 H, J(H–

D.M. Michaelidou et al. / Journal of Organometallic Chemistry 562 (1998) 105–114
107
Fig. 1. The molecular structures of 1, 3, 5 and 6—the phenyl rings of the phosphine groups have been omitted for clarity.
H) 3.0, J(H–H) 1.3, C4H3S], 6.91 [dd, 1 H, J(H–H)
4.9, J(H–H) 3.6, C4H3S], 3.52 (s, 1 H, cage C–H), 1.67
(m, 12 H, 2PMe2Ph) ppm.
11B{1H} (CD2Cl2): l 11.1 (1 B), −4.5 (2 B), −9.5 (1
B), −15.8 (3 B), −19.5 (1 B), −22.3 (1 B) ppm. 11B:
doublets J=124–149 Hz.
1H (CD2Cl2): l 7.37 and 7.29 (br s, 10 H, 2PMe2Ph),
7.11 [dd, 1 H, J(H–H) 4.9, J(H–H) 1.3, C4H3S], 7.03
[dd, 1 H, J(H–H) 3.6, J(H–H) 1.3, C4H3S], 6.92 [dd, 1
H, J(H–H) 5.2, J(H–H) 3.6, C4H3S], 3.59 (s, 1 H, cage
C–H), 1.66 (m, 12 H, 2PMe2Ph) ppm.
Mass spectrum (EI): m/z 686 M+, 546 M+
−
PMe2Ph, 471 Pt(PMe2Ph)2, 220 (C4H3S)C2B9H11.
2.1.2. [9-C4H3S-3,3-(PMe2Ph)2-3,1,9-Pt-C2B9H10], 2a
and [1-C4H3S-3,3-(PMe2Ph)2-3,1,11-Pt-C2B9H10], 2b
A sample of compound 1 (30 mg) was dissolved in
CD2Cl2 in a sealed NMR tube and warmed to 50°C for
3 h. Spectroscopic analysis (31P{1H}-, 11B{1H}-NMR)
confirmed the formation of 2a.
11B{1H} (CDCl3): l 11.3 (1 B), −4.2 (2 B), −8.9 (1
B), −16.1 (3 B), −19.3 (1 B), −22.0 (1 B) ppm. 11B:
doublets J=114–127 Hz.
31P{1H} (CDCl3): l −10.4 [s, J1 (31P–195Pt) 3362, J2
(31P–195Pt) 3227].

108
D.M. Michaelidou et al. / Journal of Organometallic Chemistry 562 (1998) 105–114
1
NMR for (2a): H (CD2Cl2): l 7.2–7.6 (multiplets,
10 H, 2PMe2Ph), 6.93 [dd, 1 H, J(H–H) 5.3, J(H–H)
1.3 C4H3S], 7.84 [dd, 1 H, J(H–H) 3.4, J(H–H) 1.5,
C4H3S], 6.73 [dd, 1 H, J(H–H) 5.3, J(H–H) 3.6,
C4H3S], 2.73 (s, 1 H, cage C–H), 1.68 (br s, 12 H,
2PMe2Ph) ppm.
ange crystals from layering a CH2Cl2 solution with
pentane. Three more bands were isolated from TLC
with Rf=0.72, 0.66 and 0.59.
Yield 0.48 g, 78%. Anal. Calc. for C14H25B9SPt; C
32.5, H 4.83%. Found: C 32.49, H 4.6%.
1
NMR for (3): H (CD2Cl2): l 7.05 [dd, 1 H, J(H–H)
11B{1H} (CD2Cl2): l −5.1 (2 B), −10.1 (2 B),
−16.7 (1 B), −20.1 (3 B), −24.4 (1 B) ppm. 11B:
doublets J=138–159 Hz.
5.1, J(H–H) 1.3, C4H3S], 6.97 [dd, 1 H, J(H–H) 3.8,
J(H–H) 1.3, C4H3S], 6.89 [dd, 1 H, J(H–H) 4.9, J(H–
H) 3.6 C4H3S], 5.60 [m, 2 H, J(H–195Pt) 31.3, ꢀCH,
cod], 4.65 (m, 2 H, J(H–195Pt) 32.8, ꢀCH, cod], 4.57 (s,
1 H, cage C–H), 2.66 (m, 4 H, –CH2, cod), 2.26 (m, 4
H, –CH2, cod) ppm.
31P{1H} (CD2Cl2): l −14.5 [s, J(31P–195Pt) 3327]
ppm.
Mass spectrum (EI): m/z 686 M+, 546 M+
−
PMe2Ph, 471 Pt(PMe2Ph)2, 220 (C4H3S)C2B9H11.
11B{1H} (CD2Cl2): l 10.4 [1 B, J(11B–195Pt) 142],
−3.8 (1 B), −7.4 (1 B), −8.8 (2 B), −11.4 (1 B),
−12.9 (1 B), −16.1 (br s, 2 B) ppm. 11B: doublets
J=128–156 Hz.
A sample of compound 1 was dissolved in toluene
and refluxed for 1 h. TLC of the reaction product gave
separation of two yellow bands. The second band gave
compound 2a, identified by its 11B-NMR spectrum. The
first band allowed isolation of a compound identified as
[1-C4H3S-3,3-(PMe2Ph)2-3,1,11-Pt-C2B9H10] (2b) on the
basis of the similarity of its 11B-NMR spectrum with
that of the structurally characterised compound [1-Ph-
3,3-(PMe2Ph)2-3,1,11-Pt-C2B9H10] [1].
13C{1H} (CD2Cl2): l 146.2 (s, C, C4H3S), 126.8 (s,
C–H, C4H3S), 123.4 (s, C–H, C4H3S), 123.0 (s, C–H,
C4H3S), 99.9 [s, ꢀCH, J(13C–195Pt) 68, cod], 91.9 [s,
ꢀCH, J(13C–195Pt) 69, cod], 32.6 (s, –CH2, cod), 30.2
(s, –CH2, cod) ppm.
Mass spectrum (EI): m/z 517 M+, 407 M+ −cod,
303 M+ −(C4H3S)C2B9H10.
NMR for (2b): 11B{1H} (CD2Cl2): l −8.6 (1 B),
−9.7 (2 B), −12.2 (1 B), −13.8 (1 B), −15.6 (1 B),
−19.1(1 B), −21.4 (1 B), −25.5 (1 B) ppm.
2.1.4. [9-C4H3S-3-(cod)-3,1,9-Pt-C2B9H10], 4
A sample of compound 3 (30 mg) was dissolved in
CD2Cl2 in a sealed NMR tube and warmed to 50°C for
15 h. The new NMR spectra were recorded.
2.1.3. [1-C4H3S-3-(cod)-3,1,2-Pt-C2B9H10], 3
To a mixture of solid Tl2[7-C4H3S-nido-7,8-C2B9H10]
(0.326 g, 0.52 mmol) and solid [PtCl2(cod)] (0.196 g,
0.52 mmol), CH2Cl2 (30 ml) was added at −180°C.
The reaction mixture was allowed to warm to r.t. and
was stirred for a further 1.5 h. The resulting brown
solution was filtered and the solvent removed under
reduced pressure. Preparative TLC (CH2Cl2: hexane,
1:1) gave a brown band (Rf=0.41) from which [1-
C4H3S-3-(cod)-3,1,2-Pt-C2B9H10] (3) was isolated as or-
1
NMR: H (CD2Cl2): l 7.03 [dd, 1 H, J(H–H) 5.1,
J(H–H) 1.3, C4H3S], 6.91 [dd, 1 H, J(H–H) 3.7, J(H–
H) 1.3, C4H3S], 6.77 [dd, 1 H, J(H–H) 5.1, J(H–H) 3.7
C4H3S], 5.20–5.45 [m, 4 H, ꢀCH, cod], 3.27 (s, 1 H,
cage C–H), 2.55–3.10 (m, 8 H, –CH2, cod) ppm.
11B{1H} (CD2Cl2): l −4.8 (1 B), −6.6 (2 B), −9.9
(1 B), −14.1 (1 B), −18.9 (1 B), −20.5 (3 B) ppm.
2.1.5. [1-C4H3S-3-(cod)-3,1,2-Pd-C2B9H10], 5
To
a
mixture of solid Tl2[7-(C4H3S)-nido-7,8-
Table 2
C2B9H10] (0.433 g, 0.7 mmol) and solid [PdCl2(cod)]
(0.196 g, 0.7 mmol), CH2Cl2 (30 ml) was added at
−180°C. The reaction mixture was allowed to warm to
r.t. and was stirred for a further 2 h. The deep red–
black solution formed was filtered from the grey precip-
itate and the solvent removed under reduced pressure.
Preparative TLC (CH2Cl2:hexane, 1:1) gave an intense
brown band (Rf=0.45) from which [1-C4H3S-3-(cod)-
3,1,2-Pd-C2B9H10] was isolated as dark crystals by lay-
ering a CH2Cl2 solution with Et2O. Three more bands
were isolated from TLC with Rf=0.72, 0.71 and 0.64.
Yield 0.045 g, 15%. Anal. Calc. for C14H25B9SPd; C
39.2, H 5.8%. Found: C 38.5, H 5.7%.
Slip and fold parameters for the metal–carboborane cages in 1, 3, 5
and 6
1
3
5
6
a
˚
D (A)
+0.45
3.0
4.1
+0.34
3.6
4.6
+0.36
5.1
6.4
+0.35
4.2
5.1
q (°)b
ƒ (°)c
 (°)d
17.8
17.4
16.6
17.9
a Calculated as the square root of the difference of the squares of the
distance of the metal from the centroid of the lower pentagonal belt
and the perpendicular distance of the metal from the plane of this
belt. A positive value indicates movement towards B(8) when viewed
perpendicular to the plane of the lower pentagonal belt. b Calculated
as the angle between the plane of the lower pentagonal belt and the
C(1)/C(2)/B(4)/B(7) plane. c Calculated as the angle between the plane
of the lower pentagonal belt and the B(4)/B(7)/B(8) plane.
d Calculated for the B(8)–H bond with respect to the plane of the
lower pentagonal belt, with the hydrogen atoms placed in calculated
positions (see Section 2.2).
1
NMR for (5): H (CD2Cl2): l 7.19 [dd, 1 H, J(H–H)
3.3, J(H–H) 1.3, C4H3S], 7.17 [dd, 1 H, J(H–H) 2.1,
J(H–H) 1.3, C4H3S], 6.96 (dd, 1 H, J(H–H) 4.9,
J(H–H) 4.0, C4H3S], 5.96 (m, 2 H, ꢀCH, cod), 4.97 (m,
2 H, ꢀCH, cod), 4.73 (s, 1 H, cage C–H), 2.65 (m, 4 H,

D.M. Michaelidou et al. / Journal of Organometallic Chemistry 562 (1998) 105–114
109
Table 3
Selected bond lengths (A), angles (°) and derived parameters for 1, 3, 5 and 6
˚
(1) M=Pt
(3) M=Pt
(5) M=Pd
(6) M=Pd
˚
Bond lengths (A)
M–C(1)
M–C(2)
M–B(4)
M–B(7)
M–B(8)
M–C(18)
M–C(19)
M–C(22)
M–C(23)
M–P
2.620(6)
2.445(7)
2.295(7)
2.262(8)
2.227(8)
—
—
—
2.468(8)
2.466(8)
2.259(10)
2.211(12)
2.257(15)
2.257(9)
2.228(14)
2.218(10)
2.170(11)
—
2.521(4)
2.519(5)
2.218(5)
2.186(5)
2.266(7)
2.282(5)
2.247(6)
2.263(5)
2.228(5)
—
2.542(4)
2.516(4)
2.264(4)
2.247(4)
2.273(4)
—
—
—
—
—
2.250(2) [P(18)], 2.277(2) [P(27)]
2.261(1) [P(18)], 2.287(1) [P(33)]
C(1)–C(2)
C(1)–B(4)
C(2)–B(7)
B(4)–B(8)
B(7)–B(8)
1.533(8)
1.711(9)
1.754(10)
1.860(12)
1.782(13)
1.527(10)
1.822(14)
1.79(2)
1.83(2)
1.86(2)
1.520(5)
1.834(7)
1.777(7)
1.785(8)
1.805(8)
1.524(6)
1.783(6)
1.753(7)
1.785(7)
1.778(7)
Bond angles (°)
C(1)–C(2)–B(7) 116.8(6)
111.9(7)
107.5(7)
101.1(8)
107.5(7)
111.2(7)
110.8(3)
109.7(3)
99.9(4)
109.2(3)
108.9(3)
112.1(3)
108.0(4)
101.7(3)
108.4(3)
108.9(3)
C(2)–B(7)–B(8)
B(4)–B(8)–B(7)
C(1)–B(4)–B(8)
104.4(5)
101.9(5)
109.1(5)
C(2)–C(1)–B(4) 106.9(5)
Derived parameters
A
B
C
D
E
F
+0.065 [B(4)]a
−0.061 [B(8)]
0.042
−0.088 [B(8)]
0.059
−0.069 [B(8)]
0.046
0.043
−0.044 [B(6)]
0.028
−0.066 [B(6)]
0.043
−0.084 [B(6)]
0.054
−0.061 [B(6)]
0.039
1.83
3.33
1.76
1.79
1.84
3.25
3.29
3.33
G
89
87
87
89
˚
A and C are the maximum deviations from planarity (A) for the upper and lower pentagonal belts, respectively, with a negative value indicating
˚
a displacement away from the metal atom. B and D are the mean deviations from planarity (A) for the upper and lower pentagonal belts,
˚
respectively. E and F are the perpendicular distances (A) of the metal atom from the plane of the upper and lower pentagonal belts, respectively.
G is the angle (°) between the metal coordination plane and the plane of the lower pentagonal belt.
a −0.051 for B(8).
–CH2, cod), 2.39 (m, 2 H –CH2, cod), 2.23 (m, 2 H,
–CH2, cod) ppm.
was stirred for a further 3 h. The resulting deep red
solution was filtered. The product was extracted in
acetone. TLC in acetone gave a single red band from
which the compound [1-C4H3S-3,3-(PPh2CH2CH2
PPh2)-3,1,2-Pd-C2B9 H10] (6) was isolated.
11B{1H} (CD2Cl2): l 19.4 (1 B), −1.7 (1 B), −3.6 (1
B), −7.4 (2 B), −8.4 (2 B), −15.0 (1 B), −16.8 (1 B)
ppm. 11B: doublets J=104–175 Hz.
13C{1H} (CD2Cl2): l 127.3 (s, C–H, C4H3S), 124.5 (s,
C–H, C4H3S), 124.0 (s, C–H, C4H3S), 116.1 (s, ꢀCH,
cod), 108.4 (s, ꢀCH, cod), 30.9 (s, –CH2, cod), 29.0 (s,
–CH2, cod) ppm.
Yield
0.074
g,
60%.
Anal.
Calc.
for
C32H37B9P2SPd·0.5(CH3COCH3); C 53.4, H 4.5%.
Found: C 53.5%, H 5.2%.
1
NMR for (6): H (CD3COCD3): l 7.92 [m, 4 H, Ph],
Mass spectrum (FAB): m/z 428 M+.
7.58 [m, 6 H, Ph], 7.34–7.49 [m, 10 H, Ph], 6.77 [d, 1 H,
J(H–H) 5.3, C4H3S], 6.37 [dd, 1 H, J(H–H) 4.9, J(H–
H) 3.6, C4H3S], 6.19 [d, 1 H, J(H–H) 3.6, C4H3S], 3.13
[s, 1 H, cage C–H], 2.77–2.80 [m, 4 H, CH2CH2] ppm.
11B{1H} (CD3COCD3): l 16.3 s, −5.4 s, −8.1 s,
−11.8 s, −13.6 s, −15.8 s, −19.7 s ppm.
2.1.6. [1-C4H3S-3,3-(PPh2CH2CH2PPh2)-3,1,2-Pd-
C2B9H10], 6
To a mixture of dry Tl2[7-(C4H3S)-nido-7,8-C2B9H10]
(0.11 g, 0.17 mmol) and dry [PdCl2(PPh2CH2CH2PPh2)]
(0.1 g, 0.17 mmol), THF (30 ml) was added at −78°C.
The reaction mixture was allowed to warm to r.t and
31P{1H} (CD3COCD3): l 55.5 s (ppm).
Mass spectrum (FAB): m/z 719 M+.

110
D.M. Michaelidou et al. / Journal of Organometallic Chemistry 562 (1998) 105–114
Fig. 2. The structures of 1, 3, 5 and 6 viewed in parallel projection in the plane of the coordinated phosphine/cod ligand atoms and down their
bisector.
2.1.7. Thermolysis of [1-C4H3S-3,3-(PMe2Ph)2-3,1,2-
Pd-C2B9H10], 7 [4]
cated partial decomposition.
A sample of compound 7 (30 mg) was dissolved in
CD2Cl2 in a sealed NMR tube and warmed to 50°C for
3 h. Spectroscopic analysis (31P{1H}-, 11B{1H}-NMR)
showed no change in the original spectra. Some black
material was deposited in the NMR tube which indi-
2.2. Crystallographic studies
A summary of the crystal data, data collection and
refinement parameters for 1, 3, 5 and 6 is given in Table
1. The platinum structures were solved by the heavy

D.M. Michaelidou et al. / Journal of Organometallic Chemistry 562 (1998) 105–114
111
ried out using the SHELXTL PC program system [7].
Additional material available from the Cambridge
Crystallographic Data Centre include fractional atomic
coordinates, H-atom coordinates, thermal parameters
and additional bond lengths and angles.
3. Results
3.1. Synthesis and characterisation
Fig. 3. The possible slip distortions observed in icosahedral metal-
lacarboranes.
Reaction of Tl2[7-(C4H3S)-nido-7,8-C2B9H10] and cis-
[PtCl2(PMe2Ph)2] gave the expected icosahedral closo-
product [1-C4H3S-3,3-(PMe2Ph)2-3,1,2-Pt-C2B9H10], 1,
in 40% yield after purification by TLC. Compound 1
was characterised using NMR, MS and a single crystal
X-ray analysis. The 31P{1H}-NMR spectrum of 1 in
CDCl3 at r.t. showed a single resonance at l −10.4
with a double set of satellites [J1(P–Pt) 3362, J2(P–Pt)
3227 Hz] which is consistent with essentially free rota-
tion of the {Pt(PMe2Ph)2} fragment about the metal–
cage axis.
In order to study the skeletal rearrangement be-
haviour of 1 it was dissolved in CD2Cl2 in a sealed
NMR tube and the sample was heated to 50°C for 3 h.
This caused the original orange colour of the solution
to become paler. The 31P{1H}-NMR spectrum showed
the presence of only a single new resonance at l −14.5
with a single set of Pt satellites J(P–Pt) 3327 Hz. This
suggested that 1 was undergoing a specific rearrange-
ment process to quantitatively yield the rearranged
product. The rearranged product also formed when a
solution of 1 was allowed to stand at r.t. for 10 days.
The rearranged product was identified as [9-C4H3S-3,3-
(PMe2Ph)2-3,1,9-Pt-C2B9H10], 2a, by comparing its
11B{1H}-NMR spectrum with that reported for the
atom method and the palladium structures by direct
methods. In all four structures, the major occupancy
non-hydrogen atoms were refined anisotropically, with
the phenyl rings being treated as optimised rigid bodies.
In 1, there is a 75/25 slewing disorder of the phenyl ring
in one of the dimethylphenylphosphine ligands. In the
isomorphous compounds 3 and 5 there is 65/35 disor-
der in the orientation of the thiophene ligand, taking, in
each case, the form of a ca. 180° rotation about the
C(1)–C(13) bond. In 6, a DF map revealed the presence
of a 50% occupancy included acetone molecule; this
molecule was refined isotropically. In all four struc-
tures, the hydrogen atoms were placed in calculated
positions, (the B–H hydrogen atoms were placed on
the vector representing the negative sum of the five
other bonds to the boron atom), assigned isotropic
thermal parameters, U(H)=1.2U(eq) C–B [U(H)=
1.5U(eq ) C–Me], and allowed to ride on their parent
atoms. The polarities of structures 3 and 5 were deter-
mined unambiguously by use of the Flack parameter,
which refined to values of −0.02(2) and 0.03(4),
respectively.
For all four structures, the computations were car-
Fig. 4. The rearrangement of icosahedral metallacarboranes via a triangular face rotation. (a) This illustrates the effect of an anticlockwise rotation
of the C(1)B(5)B(4) face and (b) illustrates a clockwise rotation of the C(2)B(4)B(7) face.

112
D.M. Michaelidou et al. / Journal of Organometallic Chemistry 562 (1998) 105–114
analogous Ph-substituted compound, which has been
structurally characterised [1]. Thus 2a is an isomer of 1
where the {C–C4H3S} fragment is located in the lower
pentagonal belt with the {CH} fragment in the upper
belt. The 11B{1H}-NMR spectrum of 2a in CD2Cl2
shows five single resonances at l −5.1 (2 B), −10.1 (2
B), −16.6 (1 B), −20.1 (1 B) and −24.4 (1 B) which
reform as doublets in the 11B-NMR spectrum with
coupling constants between 138 and 159 Hz. The char-
acteristic and well-separated low field resonance, which
is diagnostic of the 3,1,2-Pt–C2B9 cage isomer, is ab-
sent. Compound 2a was isolated from the solution and
a mass spectrometric analysis showed a molecular ion
at 686 and a similar fragmentation pattern to 1. Heat-
ing a toluene solution of 1 gave, after separation by
TLC, two yellow bands. The second band corresponded
to compound 2a, whereas the first band gave com-
pound 2b which was characterised as the rearranged
product [1-C4H3S-3,3-(PMe2Ph)2-3,1,11-Pt-C2B9H10] by
comparison of its 11B-NMR spectrum with that of the
previously structurally characterised phenyl-substituted
analogue [1]. Reaction of [PtCl2(cod)] with the thallium
salt Tl2[7-C4H3S-nido-7,8-C2B9H10] gave the expected
product 3 as the only isolable product. This reaction
resulted in the formation of more complex mixtures of
products than that discussed above for the Pt(PMe2Ph)2
compound. A stationary black band was noted during
TLC purification and it was assigned to a decomposi-
tion product.
Compound 3 was isolated as orange crystals by
layering a CH2Cl2 solution with pentane and character-
ised by NMR spectroscopy and a single crystal X-ray
analysis. The 11B{1H}-NMR spectrum in CD2Cl2
showed seven resonances which all showed the expected
doublet coupling [J(B–H)=128–156 Hz] in the 11B-
NMR spectrum. The low field signal in the 11B{1H}
spectrum showed an additional set of Pt satellites with
J(11B–195Pt)=142 Hz. The 13C{1H}-NMR spectrum of
3 in CD2Cl2 showed three signals at l 126.8, 123.4 and
123.0 assignable to the CH carbon of the thiophene
ring and a singlet at 146.2 assignable to the quaternary
C atom. Two singlets at l 99.9 and 91.9 were observed,
assignable to the ꢀCH groups of the cod ligand, both
revealing 195Pt satellites with J(13C–195Pt) 68 and 69
Hz, respectively. The two observed singlets at l 32.6
and 30.2 were finally assigned to the two –CH2 groups
of the cod ligand. The observation of only two reso-
nances which may be assigned to cod CH carbons and
two to cod CH2 protons in the 13C-NMR spectrum
implies that the cod ligand is free to rotate about the
metal axis at ambient temperatures. Compound 1 ex-
hibits similar characteristics. The analogous Pd com-
pound 5 was isolated as the major product from
[PdCl2(cod)] with the thallium salt Tl2[7-C4H3S-nido-
7,8-C2B9H10], and characterised using NMR, MS and a
single crystal X-ray analysis.
Compound 3 was found to rearrange after 15 h
heating in a sealed NMR tube. During this time the
original spectrum showed the following changes: The
thiophene protons moved to 7.03, 6.91 and 6.77 ppm.
The peaks at 4.65 (m) and 4.57 (s) disappeared whereas
a new broad singlet appeared at 3.27 ppm which was
assignable to the new C–H resonance. In the 11B{1H}-
NMR spectrum the peak at 10.4 ppm which is charac-
teristic for a C2B3 structure almost disappeared. New
resonances appeared at −4.8, −6.6, −9.9,−14.1,
−18.9 and −20.5 ppm with an intensity ratio of
1:2:1:1:1:3. This is consistent with a rearrangement
process leading to [9-C4H3S-3-(cod)-3,1,9-Pt-C2B9H10]
which is analogous to [9-C4H3S-3,3-(PMe2Ph)2-3,1,9-Pt-
C2B9H10] 1.
Compound 5 was found not to rearrange after pro-
longed heating in a sealed NMR tube at 55°C. This is
consistent with the observation that the Ph analogue
does not rearrange [8] but in contrast to the observation
by Stone that heating of [Pd(cod)[p5-7,8-Me2-C2B9H9]
results in the formation of the polytopal isomer [Pd(-
cod)[p5-2,7-Me2-C2B9H9] [3]. Finally, the reaction of
the thallium salt with [PdCl2(PPh2CH2CH2Ph2)] gave
the compound [1-C4H3S-3,3-(PPh2CH2CH2PPh2)-3,1,2-
Pd-C2B9H10], 6, as the only product after TLC purifica-
tion with acetone as eluent. Crystals of 6 were obtained
by slow evaporation of an acetone solution and the
crystal structure was obtained.
The compound was very sparingly soluble in
dichloromethane but soluble enough in acetone for a
11B-NMR spectrum to be obtained.
3.2. Single crystal X-ray analysis discussion
The crystal structures of compounds 1, 3, 5 and 6
(shown in Fig. 1a–d) have been determined and a
comparative analysis of the ‘slip’ and ‘fold’ parameters
for the icosahedral carboborane cages in these com-
pounds is presented in Table 2. All of the compounds
are based on an icosahedral cage geometry with the two
carbons occupying the open pentagonal face. Table 3
gives selected bond lengths and angles for the four
structures, together with calculations of the planes for
the upper and lower pentagonal belts. The perpendicu-
lar distances of the metal atoms from the planes associ-
ated with these belts and the inclination of the metal
coordination plane to the plane of the lower pentagonal
belt are also given. The metal coordination plane is
defined as the plane containing the metal and the two
phosphorus atoms in the case of 1 and 6, and the metal
atom and the centres of the two double bonds of the
cyclooctadiene ligands for the two isomorphous com-
pounds 3 and 5. The upper and lower pentagonal belts
are defined by the atoms C(1)–C(2)–B(7)–B(8)–B(4)
and B(5)–B(6)–B(11)–B(12)–B(9), respectively.

D.M. Michaelidou et al. / Journal of Organometallic Chemistry 562 (1998) 105–114
113
4. Discussion
In all four structures the plane associated with the
lower pentagonal belt of the carbaborane cage is virtu-
ally orthogonal to the metal coordination plane. The
distance of the metal from the coordinated face of the
cage appears to be virtually independent of the nature
of the metal atom, but dependent upon the other
coordinating ligand(s), with the metal lying closer to
this face in the case of the cyclo-octadiene compounds
than for those with phosphine based ligands. The
metal–phosphine distances are unexceptional and ap-
pear to be unaffected by their orientation with respect
to the carbaborane cage. The metal–C(carbaborane)
distances are fairly similar for all four compounds,
though in 1 the Pt–C(1) bond is significantly longer
than the corresponding bond in any of the other three
structures (vide infra).
The most noticeable differences between the four
structures can be appreciated by the views given in Fig.
2a–d. These show each complex viewed from the L2M
direction. In the two cyclooctadiene complexes 3 and 5,
the apical atom of the carboborane cage, B(10), lies
only slightly below the horizon of the metal coordina-
tion plane, the metal atom in both cases being slipped
in the direction of B(9). In the two phosphine com-
plexes 1 and 6 the displacement of B(10) is more
marked, the distance below the horizon being in each
case very similar, though with the direction of slippage
of the metal atom being towards B(12) in 1 but towards
B(9) in 6. The magnitude and variation of these dis-
placements is, however, not apparent from a consider-
ation of the slippage parameter (D) in Table 2.
The structure of compound 1 may be discussed in
terms of the bonding between Pt and the C2B3 face of
the carborane ligand, and whether this bonding predis-
poses it towards a polyhedral rearrangement process.
Kennedy et al. [9] have distinguished two types of
bonding in Pt–C2B3 compounds: a simple ring slippage
whereby Pt moves towards the three borons and rela-
tively equally away from the two carbon atoms (their
structure type 3B), and an p4-CB3 structure, whereby
the Pt is located farther from one of the carbons (their
structure type 3A) (See Fig. 3).
Kennedy was able to observe both these structures in
the unsubstituted compound [3,3-(PMe2Ph)2-3,1,2-
PtC2B9H11], and points out that therefore steric factors
cannot be the underlying cause of the p4 distorted
structures. This had earlier been suggested by Mingos
et al. [1], based on structural data on Ph-substituted
C(1) carboranes, including an p4 type structure with
˚
Pt–C(1)=2.596 and Pt–C(2)=2.362 A bond lengths.
In 1, the Pt–C2B3 atom distances also show the
molecule to be of the p4 type, with Pt–C(1)=2.620 and
˚
Pt–C(2)=2.445 A.
The rearrangement processes noted for 1 to 2a and
2b may be related to rearrangements of similar com-
pounds described previously by ourselves and by
Kennedy et al. [9]. The former used microwave dielec-
tric heating to induce the transformation, compared to
the thermal or r.t. methods described in this paper.
Compounds monosubstituted on C(1) give rearranged
products as two isomers. As a result of the rearrang-
ment process the bulky substituent at C(1) or unsubsti-
tuted C(2) move out of the C2B3 ring to give either a
less crowded or more crowded product. In the case of
[1-Ph-3,3-(PMe2Ph)2-3,1,2-PtC2B9H10], equal amounts
of the two isomers were obtained under the vigorous
conditions of the microwave experiment [1]. However,
in the thermal reaction described here, 1 rearranged to
give ca. 80% of the more sterically-favoured (C(1)
rearranged) 2a product and only 20% of the less steri-
cally favoured (C(2) rearranged) 2b product. Moreover,
the r.t. reaction gave 2a as the only isolated product,
thus suggesting that steric interactions do indeed con-
tribute significantly to the activation energies for the
rearrangement process in these systems.
In general, the rearrangement of icosahedral carbo-
ranes and metallacarboranes (Fig. 4) where the C(1)–
C(2) connectivity is broken has been discussed in terms
of a diamond–square–diamond (DSD) mechanism.
However, as Bruce King elegantly demonstrated [10] it
is not possible to isomerise icosahedral boranes, carbo-
ranes or metallacorborane via a single DSD process—
multiple DSD’s are required. The products of the
rearrangement of 1 to form 2a and 2b may be ac-
counted for in terms of a triangular face rotation. Thus
The only other feature of note is the respective
orientations of the pendant thiophene ligands with re-
spect to the coordination plane. In 3, 5 and 6 it is
oriented at ca. 5 o’clock whereas in 1 it is positioned at
6 o’clock, a factor that may contribute to the noticeable
longer M–C(1) bond in this complex mentioned earlier.
The reason for the difference in orientation in the
thiophene ligand is not immediately apparent as the
steric constraints of the phosphine ligands in 1 and 6
are not that dissimilar. However, the 5 o’clock orienta-
tion in 6 is favoured by an intramolecular y-stacking
interaction between the thiophene ring and one of the
phosphine phenyl rings. The two rings are inclined by
only 4° to each other and have a mean interplanar
˚
separation of 3.62 A. An equivalent interaction in 1 is
not possible. A discussion of the relative positioning of
the sulphur atoms is not pertinent as in two of the
structures 180° rotational disorder is observed for these
rings.
An inspection of the packing of the molecules in all
four structures does not reveal any noteworthy inter-
molecular packing interactions which could not be con-
sidered as resulting from normal van der Waals
interactions.

114
D.M. Michaelidou et al. / Journal of Organometallic Chemistry 562 (1998) 105–114
for the formation of 2a, the triangular face C(1)–B(5)–
B(6) of 1 rotates by 60° clockwise so that C(1) moves to
the position of B(5), B(5) to that of B(6) and B(6) to that
of C(1) (Fig. 4). Similarly, for the formation of 2b the
triangular face C(2)–B(11)–B(6) in 1 rotates by 60°
anticlockwise so that C(2) moves to the position of B(11),
B(11) to B(6), and B(6) to C(2). However, this does not
mean that the mechanism actually involves a triangular
face rotation. A recent paper by Welch and Weller [11]
has shown that for a sterically crowded molybdenum
carborane it is possible to isolate an intermediate for the
rearrangement process, which results from multiple DSD
processes and has two four and two six connected
vertices. This molecule rearranges on heating to give an
icosahedral isomer analogous to that described above.
Thus isomerisation of a 3,1,2-MC2B9 architecture is a
complex process which probably involves several DSD
processes and may also require the formation of an
alternative poyhedral entity as an intermediate.
The experiments we have described have shown that
the platinum compounds rearrange more readily than the
palladium compounds. This illustrates how the nature of
the metal atom can greatly influence the ease with which
carbametalloboranes undergo polyhedral rearrange-
ment. This observation is in agreement with Stone et al.
who have previously demonstrated the greater tendency
of the third row transition metal (W) carbametallobo-
ranes to undergo rearrangement compared to their
second row (Mo) analogues in chemical reactions [12,13].
Acknowledgements
We would like to thank BP for endowing D.M.P.
Mingos’s Chair and the EPSRC for financial support to
D.M. Michaelidou.
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