Trans-Di-μ-bromo-bis[bromo(triethylphosphine-κP)platinum(II)]

Article abstract of DOI:10.1107/S0108270104032731

The title compound, [Pt₂Br₄(C₆H ₁₅P)₂], is a centrosymmetric dinuclear platinum(II) complex consisting of two square-planar platinum centres connected by two bridging Br atoms

Full text of DOI:10.1107/S0108270104032731

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
trans-Di-l-bromo-bis[bromo(triethyl-
phosphine-jP)platinum(II)]
Â
Â
Stephanie M. M. Cornet, Keith. B. Dillon, Andres E. Goeta
and Amber L. Thompson*
Department of Chemistry, University of Durham, South Road, Durham DH1 3LE,
England
Correspondence e-mail: a.l.thompson@durham.ac.uk
Figure 1
A view of (I), with selected atoms labelled. Symmetry equivalents related
by (12 x; 12 y; 1 z) are also shown and are indicated by primes.
Displacement ellipsoids for the non-H atoms are drawn at the 50%
probability level.
Received 1 November 2004
Accepted 9 December 2004
Online 15 January 2005
The title compound, [Pt2Br4(C6H15P)2], is a centrosymmetric
dinuclear platinum(II) complex consisting of two square-
planar platinum centres connected by two bridging Br atoms.
factors also appear to reduce the effect bridging has on the
bond lengths, since the bonds to the bridging Br atoms are
Ê
only 0.023 and 0.122 A longer than those to the terminal Br
Ê
atoms, compared with averages of 0.033 and 0.146 A in
Comment
[PtCl2(PR3)]2 (where R = CH3, C2H5 and C3H7; Boag &
Ravetz, 1996; Blake et al., 1989; Black et al., 1969, respec-
tively).
Bridged chloride complexes of the form [PtCl2(PR3)]2 have
been used extensively as starting materials in the synthesis of
mononuclear platinum±phosphine complexes, which are
formed through cleavage of the bridging PtÐCl bond (Chatt
& Venanzi, 1955; Meidine & Nixon, 1988; Dillon & Goodwin,
1992, 1994). Similar synthetic methodology can also be applied
to bromide analogues (Cornet, 2002). However, while the
crystal structures of the chloro-bridged complexes [PtCl2-
(PMe3)]2, [PtCl2(PEt3)]2 and [PtCl2(PPr3)]2 are known (Boag
& Ravetz, 1996; Blake et al., 1989; Black et al., 1969), struc-
tures of complexes exhibiting the central heavy-atom skeleton
[PtCl2P]2 are surprisingly rare, with only a handful known
(Simms et al., 1987; Cobley et al., 2000).
Experimental
PtBr2 (1.48 g, 4.2 mmol) in PhCN (10 ml) was heated to 373 K to give
a bright-orange solution and a yellow precipitate on cooling {cis-
[PtBr2(PhCN)2], yield 81%}. PEt3 (1.75 g, 2.18 ml, 14.8 mmol) was
then added to a solution of [PtBr2(PhCN)2] (1.77 g, 3.15 mmol) in
CH2Cl2 (15 ml) and the mixture stirred for 3 h. Evaporation of the
solvent produced a white solid {cis-[PtBr2(PEt3)2], yield 83%}, some
of which (1.45 g, 2.45 mmol) was added to a solution of PtBr2 (1.03 g,
2.9 mmol) in (CHCl2)2 and heated to 423 K for 4 h. The yellow
crystals of (I) obtained on cooling were recrystallized from CH2Cl2
(yield 79%). Analysis calculated for C12H30Br4P2Pt2: C 15.23, H
3.20%; found: C 15.27, H 3.23%. 31P NMR (CDCl3): ꢀ 10.9 (singlet
with Pt satellites, 1JPÐPt = 3701 Hz, 3JPÐPt = 24.4 Hz, 4JPÐP = 1.6 Hz).
The AA`XX' part of the spectrum was insuf®ciently resolved for
2JPtÐPt to be evaluated (Kiffen et al., 1975).
The title complex, (I), was prepared by the CHCl2-mediated
reaction of equimolar quantities of PtBr2 and [PtBr2(PEt3)2].
Given the rarity of crystal structures containing the [PtCl2P]2
fragment, it is unsurprising that (I) is the ®rst structure to be
reported containing the [PtBr2P]2 motif.
Crystal data
3
[Pt2Br4(C6H15P)2]
Mr = 946.12
Dx = 2.910 Mg m
Mo Kꢂ radiation
Cell parameters from 7378
re¯ections
Monoclinic, C2=c
Ê
a = 26.522 (6) A
ꢃ = 1.9±30.6ꢀ
ꢄ = 20.48 mm
T = 120 (2) K
Ê
b = 6.8720 (13) A
1
Ê
c = 13.811 (4) A
The chloride complexes [PtCl2(PR3)]2 (where R = CH3,
C2H5 and C3H7) and the title compound are closely related,
and all four complexes possess an inversion centre in the
middle of the dimer, with the PR3 ligands in a trans geometry
(Fig. 1). In addition, all four structures are asymmetric around
the bridging halide ligands, but this asymmetry is reduced in
(I) with respect to the chloride complexes (Table 1). This
degree of asymmetry in (I) is presumably due to the relative
positions of the Cl, Br and P atoms in the trans in¯uence series
and the increased ionic radius of the bromide ligand. These
ꢁ = 120.930 (7)ꢀ
Ê
V = 2159.3 (9) A
Z = 4
3
Block, clear intense orange
0.20 Â 0.10 Â 0.10 mm
Data collection
Bruker SMART CCD 1K area-
detector diffractometer
! scans
Absorption correction: multi-scan
(SADABS; Bruker, 1998)
Tmin = 0.058, Tmax = 0.129
10 540 measured re¯ections
2355 independent re¯ections
2158 re¯ections with I > 2ꢅ(I)
Rint = 0.036
ꢃmax = 27.0ꢀ
h = 32 ! 33
k = 8 ! 8
l = 17 ! 17
m74 # 2005 International Union of Crystallography
DOI: 10.1107/S0108270104032731
Acta Cryst. (2005). C61, m74±m75

metal-organic compounds
Re®nement
graphics: SHELXTL (Sheldrick, 1997b); software used to prepare
material for publication: SHELXTL.
Re®nement on F2
R[F2 > 2ꢅ(F2)] = 0.020
wR(F2) = 0.046
S = 1.11
2355 re¯ections
w = 1/[ꢅ2(Fo2) + (0.0168P)2
+ 10.3265P]
where P = (Fo2 + 2Fc2)/3
(Á/ꢅ)max = 0.001
The authors thank the EPSRC for postgraduate student-
ships (SMMC and ALT) and Johnson±Matthey plc for the
loan of platinum compounds.
3
Ê
Áꢆmax = 0.85 e A
3
Ê
1.75 e A
94 parameters
H-atom parameters constrained
Áꢆmin
=
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: HJ1034). Services for accessing these data are
described at the back of the journal.
Table 1
Selected geometric parameters (A, ꢀ) for (I) and the related chloro
Ê
complexes [PtCl2(PMe3)]2, [PtCl2(PEt3)]2 and [PtCl2(PPr3)]2 (Hal = Cl or
Br).
References
[PtCl2(PMe3)]2 [PtCl2(PEt3)]2 [PtCl2(PPr3)]2 (I)
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È
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(1989). Acta Cryst. C45, 1218±1219.
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PtÐP
2.205 (3)
2.212 (3)
2.282 (3)
2.318 (3)
2.431 (3)
2.230 (9)
2.279 (9)
2.315 (8)
2.425 (8)
2.2266 (11)
2.4229 (7)
2.4455 (7)
2.5451 (6)
PtÐHalterminal 2.281 (3)
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2.423 (3)
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PtÐHalÐPt 96.19 (10)
HalÐPtÐHal 83.81 (10)
96.48 (10)
83.52 (9)
96.4 (3)
83.6 (2)
96.17 (2)
83.83 (2)
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All H atoms were placed geometrically and re®ned using a riding
Ê
model (CÐH = 0.98 and 0.99 A), with their Uiso(H) values ®xed at 1.2
or 1.5 times Ueq of the parent C atom. Although there are difference
Meidine, M. F. & Nixon, J. F. (1988). Private communication to K. B. Dillon.
Sheldrick, G. M. (1997a). SHELXL97 and SHELXS97. University of
3
Ê
Ê
density holes larger than 1 e A , they are within 1 A of the Pt atom.
Data collection: SMART-NT (Bruker, 1998); cell re®nement:
SMART-NT; data reduction: SAINT-NT (Bruker, 1998); program(s)
used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s)
used to re®ne structure: SHELXS97 (Sheldrick, 1997a); molecular
È
Gottingen, Germany.
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USA.
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metallics, 6, 1118±1126.
ꢁ
Â
Acta Cryst. (2005). C61, m74±m75
Stephanie M. M. Cornet et al.
[Pt2Br4(C6H15P)2] m75