Halogenation of (phosphine chalcogenide)gold(i) halides; Some unexpected products

Article abstract of DOI:10.1039/c1dt11476j

The monoselenide of 1,8-bis(diphenylphosphino)naphthalene reacts with (tht)AuCl to give the gold(iii) system [(dppnAuSe)₂]²⁺ 2Cl^- (1); bromination of the bromogold(i) complex of the 1,2-bis(diphenylphosphino)methane monosulfide ligand furnishes the tribromide salt (2a) of a gold(iii) cation [LAuBr₂]⁺; bromination of the bromogold(i) complex of the 1,2-bis(diphenylphosphino)benzene monosulfide ligand leads to a mixed bromide/tetrabromoaurate salt (3) of a heterocyclic dication involving a [-PPh₂-S-PPh₂-]²⁺ moiety; analogous reactions of triphenylphosphine sulfide and selenide complexes lead to tetrabromoaurate salts (4a and 4b) of the (bromochalcogeno)phosphonium cations Ph₃PEBr⁺. The Royal Society of Chemistry 2011.

Full text of DOI:10.1039/c1dt11476j

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COMMUNICATION
Halogenation of (phosphine chalcogenide)gold(I) halides; some unexpected
products†
Christina Taouss and Peter G. Jones*
Received 1st August 2011, Accepted 15th September 2011
DOI: 10.1039/c1dt11476j
The monoselenide of 1,8-bis(diphenylphosphino)naphtha-
lene reacts with (tht)AuCl to give the gold(III) system
[(dppnAuSe)2]2+ 2Cl- (1); bromination of the bromogold(I)
complex of the 1,2-bis(diphenylphosphino)methane mono-
sulfide ligand furnishes the tribromide salt (2a) of a gold(III)
cation [LAuBr2]+; bromination of the bromogold(I) complex
of the 1,2-bis(diphenylphosphino)benzene monosulfide lig-
and leads to a mixed bromide/tetrabromoaurate salt (3) of
a heterocyclic dication involving a [-PPh2-S-PPh2-]2+ moiety;
analogous reactions of triphenylphosphine sulfide and se-
lenide complexes lead to tetrabromoaurate salts (4a and 4b)
of the (bromochalcogeno)phosphonium cations Ph3PEBr+.
oxidation occurs, the gold(I) complexes may crystallise as adducts
with elemental iodine.7
As regards the halogenation of phosphine chalcogenides them-
selves, du Mont showed that the iodination of phosphine selenides
leads to [R3PSeI]+ cations.8 Reaction of phosphine selenides with
elemental bromine, in contrast, leads to hypervalent compounds
R3PSeBr2 with a T-shaped structure at selenium in the solid state.
The addition of bromine to such a dibromide was assumed to give
R3PSeBr+ derivatives, but these were never isolated.9,10
We wished to combine these various fields of investigation
by synthesizing new gold(I) halide derivatives with diphosphine
monochalcogenide ligands (E = S, Se) and oxidizing both these
and the known monophosphine chalcogenide complexes with
halogens. Here we present some unexpected and novel products of
these reactions.
Unsymmetrical diphosphine monochalcogenides were prepared
from bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenyl-
phosphino)benzene (dppbz) and 1,8-bis(diphenylphosphino)-
naphthalene (dppn) according to literature methods.11,12 For the
dppm and dppbz chalcogenides, the corresponding gold(I) halides
were obtained for X = Cl, Br by reaction of the ligand with
(tht)AuX; as expected, the gold centres are coordinated by the
phosphine donors. Reaction of the chlorides with an excess
of potassium iodide in dichloromethane/water gave the gold(I)
iodides.2,4,7,13
Phosphine chalcogenides R3P E (E = O, S, Se; the R groups
may be different or form part of ring systems) are well-known
compounds that can act as ligands. In particular, gold(I) complexes
of the type R3PEAuX (X = halogen) have been reported by several
groups; they are synthesized by direct reaction of the phosphine
chalcogenide with L¢AuX, where L¢ is an easily displaced ligand
such as tetrahydrothiophene (tht) or Me2S.1 Similarly, diphosphine
dichalcogenides have been shown to form gold(I) complexes
such as XAuEP(CH2)nPEAuX,2 although no X-ray structures
of these halogen derivatives were reported. To the best of
our knowledge, however, few gold(I) complexes of diphosphine
monochalcogenides are known; this may in part be associated
with the difficulties of obtaining some of the ligands in a pure
state.3 The compound ClAuPh2PCH2P( Se)Ph2 (dppmSeAuCl)
was synthesized by Schmidbaur and used to prepare the cyclic
dication [(dppmSe)2Au2]2+;4 we determined the X-ray structure of
dppmSeAuCl,5 and of two salts of the tetrahedral Au(I) cation
[(dppmSe)2Au]+.6
For dppnSe, however, the reaction with (tht)AuCl does not lead
to the expected gold(I) complex (dppnSe)AuCl. Instead, a dark
brown gold(III) complex of the same stoichiometry (1) is obtained
(Scheme 1); the selenium has dissociated from the dppn but still
forms part of the product. In its 31P-NMR spectrum 1 displays
a singlet at 13.7 ppm. X-ray structure analysis‡ showed that 1
¯
crystallises in the space group P1 with half a cation (Fig. 1), one
Many gold(I) complexes of the type LAuX (L = phosphine,
X = Cl, Br) undergo oxidative addition with elemental chlorine
or bromine to give the gold(III) complexes LAuX3.7 With iodine,
the halogenation depends strongly on electronic and steric effects
of the ligand; complexes with small trialkylphosphines are readily
oxidised, whereas those with more bulky ligands are not. Where no
chloride and three chloroform molecules in the asymmetric unit.
The gold centre has an approximately square planar geometry and
is coordinated to both phosphorus atoms of the dppn ligand and
to two selenium atoms. Inversion symmetry completes the central
Institut fu¨r Anorganische und Analytische Chemie, Technische Univer-
sita¨t Carolo-Wilhelmina, Hagenring 30, D-38106 Braunschweig, Germany.
E-mail: p.jones@tu-bs.de; Fax: +49 531-391-5387; Tel: +49 531-391-5382
† Electronic supplementary information (ESI) available. CCDC reference
numbers 837547–837553. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c1dt11476j
Scheme 1 Reaction of dppnSe with (tht)AuCl.
Dalton Trans., 2011, 40, 11687–11689 | 11687
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Fig. 2 Crystal structure of 2a (H atoms omitted). Selected bond lengths
◦
˚
[A] and angles [ ]: P1–S 2.048(2), P2–Au 2.307(2), S–Au 2.330(2),
Au–Br1 2.458(1), Au–Br2 2.429(1); P1–S–Au 103.86(6), P2–Au–S 94.19(5),
P2–Au–Br2 88.53(4), Br2–Au–Br1 92.18(2), Br1–Au–S 85.07(4).
Fig. 1 Crystal structure of the cation [(dppnAuSe)2]2+ in 1 (H atoms
The 31P-NMR spectrum of the gold(I) complex shows two
doublets at 44.5 and 26.8 ppm with a coupling of 17 Hz, whereas
for 3 a singlet at 50.2 ppm is observed.
◦
˚
omitted). Selected bond lengths [A] and angles [ ]: P1–Au 2.323(3),
P2–Au 2.341(3), Au–Se 2.443(2), Au–Se¢ 2.451(2); P1–Au–P2 87.64(10),
P1–Au–Se¢ 92.29(8), P2–Au–Se 98.91(8), Se–Au–Se¢ 81.08(5), Au–Se–Au¢
98.92(5).
The structure of 3 was determined by X-ray analysis (Fig. 3).
¯
It crystallizes in the triclinic space group P1; within the asym-
Au2Se2 four-membered ring,14 in which the gold has an oxidation
state of +III while the selenium can be formally regarded as -II
(selenide).
metric unit are two independent dications, two bromide anions,
each coordinating to one of the dications, together with two
tetrabromoaurate(III) anions and one dichloromethane molecule.
Two equivalent dications are bridged by two bromide anions
coordinating weakly to the sulphur atoms to complete a four-
In order to investigate the halogenation products, the gold(I)
complexes were treated with the corresponding halogen in
dichloromethane. Various types of products were observed, which
seem to depend on the steric requirements of the ligand.
For dppmSeAuBr, the halogenation product could not be
identified. The other dppmS and dppmSe complexes react with
two mole equivalents of halogen X2, whereby gold(I) is oxidised to
gold(III) with concomitant ring closure involving the formation of
˚
membered S2Br2 ring with S ◊ ◊ ◊ Br 3.108(4) A.
+
-
an Au–E bond, leading to the products dppmEAuX2 X3 (2a–c;
Scheme 2, Fig. 2), which are not isostructural. Such five-membered
auracycles are known for Au(I) (see above) but not for Au(III).
Scheme 2 Halogenation of (dppmE)AuX with E = S, X = Br (a); E = S,
X = I (b) and E = Se, X = I (c).
Fig. 3 Crystal structure of one inversion-symmetric [(dppbzS)2Br2]2+
Halogenation of the (dppbzSe)gold(I) complexes caused sep-
aration of elemental selenium and led to the gold(III) com-
pounds dppbzAuI2 I3
derivative of dppbzS, in contrast, is oxidized by two mole
equivalents of bromine to the mixed bromide/tetrabromoaurate
salt of an unusual heterocyclic dication, formally (1,1,3,3)-
tetraphenylbenzo[d]-(2,1,3)thiadiphosphol-1,3-diium, analogous
to the as yet unknown acyclic species [Ph3P-S-PPh3]2+ (Scheme 3).
◦
˚
unit in 3 (H atoms omitted). Selected bond lengths [A] and angles [ ]:
P1–S1 2.121(4), P2–S1 2.114(4), S1 ◊ ◊ ◊ Br1 3.108(4), S1 ◊ ◊ ◊ Br1¢ 3.108(4);
P1–S1–P2 95.90(17), Br1 ◊ ◊ ◊ S1 ◊ ◊ ◊ Br1¢ 101.95(9), P1–S1 ◊ ◊ ◊ Br1¢ 84.73(14),
P2–S1 ◊ ◊ ◊ Br1 77.35(13), S1 ◊ ◊ ◊ Br1 ◊ ◊ ◊ S1¢ 78.05(9).
+
- 7
and dppbzAuBr3.15 The bromogold(I)
Bromination
of
the
known
gold(I)
complexes
Ph3PEAuBr1 led to tetrabromoaurate salts 4a and 4b of
(bromochalcogeno)phosphonium cations (Scheme 4), which
show a downfield shift in the 31P-NMR spectrum in comparison
to the gold(I) complexes; 4a shows a singlet at 49.4 ppm and 4b a
Scheme 3 Bromination of (dppbzS)AuBr.
Scheme 4 Halogenation of Ph3PEAuBr with E = S (a) and E = Se (b).
11688 | Dalton Trans., 2011, 40, 11687–11689
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singlet at 52.3 ppm. The values for the gold(I) complexes are 49.4
and 30.0, respectively.
Crystal data for 2b: C25H22AuI5P2S, M = 1247.89, orthorhombic, a =
3
˚
˚
˚
˚
10.4495(5) A, b = 14.0201(3) A, c = 21.6335(5) A, V = 3169.37(18) A ,
T = 100(2)K, space group P212121, Z = 4, 80673 reflections measured,
7552 independent reflections (Rint = 0.056). The final wR2 value was 0.0425
(all data), with R1 0.0238 (I > 2s(I)).
The structures of 4a and 4b, which are not isostructural, were
determined by X-ray analysis. Ph3PSeBr+ AuBr4 (4b) crystallizes
-
¯
Crystal data for 2c: C25H22AuI5P2Se, M = 1294.79, orthorhombic, a =
in the triclinic space group P1 with one cation and two half anions
3
˚
˚
˚
˚
21.931(2) A, b = 10.4353(10) A, c = 13.7270(8) A, V = 3141.5(5) A ,
T = 100 K, space group Pna21, Z = 4, 42845 reflections measured, 5548
independent reflections (Rint = 0.157). The final wR2 value was 0.0490 (all
data), with R1 0.0391 (I > 2s(I)).
˚
in the asymmetric unit. The Se–Br bond length is 2.3121(4) A
and the Br ◊ ◊ ◊ Br contact between cation and anion is 3.4009(5)
˚
A. Compound 4b represents the first successful isolation and
structure determination of an R3PSeBr+ cation.
Crystal data for 3: C30.5H25AuBr5ClP2S, M = 1117.47, triclinic, a =
◦
˚
˚
˚
˚
14.948(2) A, b = 16.397(3) ◦A, c = 16.986(3) A, a = 117.927(15) , b =
For phosphane sulfides, which are weaker donors than the
selenides towards dihalogen molecules, no such adducts are known
so far. The crystal structure of the Ph3PSBr+ AuBr4- salt 4a, shown
in Fig. 4, is the first crystal structure of any species with a P–S–
Br unit, according to the Cambridge Structural Database (2010
version). It crystallizes in the monoclinic space group P21/n with
one formula unit in the asymmetric unit. The Br ◊ ◊ ◊ Br contact
◦
3
94.835(12) , g = 108.542(15) , V = 3349.6(10) A , T = 100 K, space group
¯
P1, Z = 4, 94741 reflections measured, 11848 independent reflections (Rint
=
0.204). The final wR2 value was 0.0726 (all data), with R1 0.0467 (I >
2s(I)).
Crystal data for 4a: C18H15AuBr5PS, M = 890.85, monoclinic, a =
◦
˚
˚
˚
13.7340(4) A, b = 12.2533(2) A, c = 14.9748(4) A, b = 114.913(5) , V =
3
˚
2285.56(10) A , T = 100 K, space group P21/n, Z = 4, 58880 reflections
measured, 4661 independent reflections (Rint = 0.045). The final wR2 value
was 0.0462 (all data), with R1 0.0221 (I > 2s(I)).
˚
of 3.151(1) A is very short and is comparable with the value of
Crystal data for 4b: C18H15AuBr5PSe, M = 937.75, t◦riclinic, a = 8.7461(4)
16
˚
◦
3.123(2) A in the adduct Ph3PBr2.
˚
˚
˚
A, b = 9.4386(5) A, c = 16.4508(7) A, a = 84.594(4) , b = 76.871(4) , g =
◦
3
¯
˚
62.835(5) , V = 1176.58(10) A , T = 100 K, space group P1, Z = 2, 86646
reflections measured, 6278 independent reflections (Rint = 0.039). The final
wR2 value was 0.0348 (all data), with R1 0.0170 (I > 2s(I)).
1 See for instance M. S. Hussain, Acta Crystallogr., Sect. C: Cryst. Struct.
Commun., 1987, C43, 450–453; M. S. Hussain, J. Chem. Cryst., 1986,
16, 91–99; P. G. Jones and E. Bembenek, J. Crystallogr. Spectrosc. Res.,
1992, 22, 397–401.
2 M. Preisenberger, A. Bauer and H. Schmidbaur, Chem. Ber., 1997, 130,
955–958.
3 D. H. Brown, R. J. Cross and R. Keat, J. Chem. Soc., Dalton Trans.,
1980, 871–874; S. W. Carr and R. Colton, Aust. J. Chem., 1981, 34,
35–44.
4 H. Schmidbaur, J. Ebner von Eschenbach, O. Krumberger and G.
Mu¨ller, Chem. Ber., 1990, 123, 2261–2265.
5 P. G. Jones and C. Tho¨ne, Acta Crystallogr., Sect. C: Cryst. Struct.
Commun., 1992, 48, 2114–2116.
6 P. G. Jones and B. Ahrens, Chem. Commun., 1998, 2307–2308; P. G.
Jones and B. Ahrens, Z. Naturforsch., 1999, B54, 1474–1477.
7 D. Schneider, A. Schier and H. Schmidbaur, Dalton Trans., 2004, 1995–
2005.
Fig. 4 Crystal structure of Ph3PSBr+AuBr4- (H atoms omitted). Selected
bond lengths [A] and angles [ ]: P–S 2.085(2), Br1–S 2.202(2), Br1 ◊ ◊ ◊ Br2
3.151(1); P–S–Br1 101.31(6), S–Br1 ◊ ◊ ◊ Br2 174.79(4), Br1 ◊ ◊ ◊ Br2–Au
99.41(2).
◦
˚
8 W.-W. du Mont, M. Ba¨tcher, C. Daniliuc, F. A. Devillanova, C.
Druckenbrodt, J. Jeske, P. G. Jones, V. Lippolis, F. Ruthe and E. Seppa¨la¨,
Eur. J. Inorg. Chem., 2008, 4562–4577.
9 S. M. Godfrey, S. L. Jackson, C. A. McAuliffe and R. G. Pritchard, J.
Chem. Soc., Dalton Trans., 1998, 4201–4204.
10 C. G. Hrib, F. Ruthe, E. Seppa¨la¨, M. Ba¨tcher, C. Druckenbrodt, C.
Wismach, P. G. Jones, W.-W. du Mont, V. Lippolis, F. A. Devillanova
and M. Bu¨hl, Eur. J. Inorg. Chem., 2006, 88–100.
More gold(I) complexes with various mono- and diphosphine
chalcogenide ligands are currently being synthesised with a
view to investigating their halogenation products; studies on
gold complexes with diphosphane dichalcogenide ligands are in
progress.
11 S. O. Grim and E. D. Walton, Inorg. Chem., 1980, 19, 1982–1987.
12 A. Karac¸ar, M. Freytag, H. Tho¨nnessen, J. Omelanczuk, P. G. Jones,
R. Bartsch and R. Schmutzler, Z. Anorg. Allg. Chem., 2000, 626, 2361–
2372.
13 H. Schmidbaur, A. Wohlleben, F. Wagner, O. Orama and G. Huttner,
Chem. Ber., 1977, 110, 1748–1754.
14 Only two previous examples of Au2Se2 rings are known, in a gold(III)
polyselenide complex [M. G. Katzanidis and S.-P. Huang, Inorg.
Chem., 1989, 28, 4667–4669] and in the mixed-valence compound
{Ph3PAuSe}2{m-Au(C6F5)3}2; S. Canales, O. Crespo, M. C. Gimeno,
P. G. Jones, A. Laguna and F. Mendizabal, Organometallics, 2001, 20,
4812–4848].
15 Confirmed by X-ray structure determination; details to be published
elsewhere.
16 N. Bricklebank, S. M. Godfrey, A. G. Mackie, C. A. McAuliffe
and R. G. Pritchard, J. Chem. Soc., Chem. Commun., 1992, 355–
356.
Notes and references
‡ X-Ray structure determinations: Data were collected at 100 K on an
Oxford Diffraction Xcalibur E diffractometer using monochromated Mo-
Ka radiation. Structures were refined using the program SHELXL-97 (G.
M. Sheldrick, University of Go¨ttingen, Germany).
Crystal data for 1: C74H58Au2Cl20P4Se2, M = 2331.94, triclinic, a = 9.974(2)
◦
◦
˚
˚
˚
A, b = 13.760(3) A, c = 15.679(3) A, a = 95.70(3) , b = 97.32(3) , g =
◦
3
¯
˚
95.08(3) , V = 2112.5(7) A , T = 100 K, space group P1, Z = 1, 68021
reflections measured, 7450 independent reflections (Rint = 0.186). The final
wR2 value was 0.1695 (all data), with R1 0.0687 (I > 2s(I)).
Crystal data for 2a: C25H22AuBr5P2S, M = 1012.94, monoclini◦c, a =
˚
˚
˚
10.3072(6) A, b = 13.378(2) A, c = 21.0032(16) A, b = 91.302(7) , V =
3
˚
2895.4(5) A , T = 100 K, space group P21/c, Z = 4, 44975 reflections
measured, 5293 independent reflections (Rint = 0.089). The final wR2 value
was 0.0300 (all data), with R1 0.0256 (I > 2s(I)).
This journal is
The Royal Society of Chemistry 2011
Dalton Trans., 2011, 40, 11687–11689 | 11689
©