Synthesis, structure, and reactions of a binuclear gold(I)-gold(III) complex containing bridging and bidentate (2-diphenylphosphino-6-methyl)phenyl groups

Article abstract of DOI:10.1021/om000672y

Reaction of the organolithium reagents (C₆H₃-2-PPh₂-6-Me)Li or (C₆H₃-2-PPh₂-5-Me)Li with [AuBr(PEt₃)] gives the corresponding cyclometalated digold(I) complexes [Au₂(μ-C₆H₃-2-PPh₂-n-Me)₂] (n = 6, 1a; n = 5, 1b), the metal-metal distance in 1a, 2.861(2) angstrom, being similar to that in the unsubstituted compound [Au₂(μ-2-C₆H₄PPh₂)₂]. Both complexes oxidatively add halogens to give metal-metal bonded digold(II) complexes [Au₂X₂(μ-C₆H₃-2-PPh₂-n-Me)₂] [n = 6, X = Cl (2a), Br (3a), I (4a); n = 5, X = Cl (2b), Br (3b), I (4b)], and 1b also adds dibenzoyl peroxide to give the bis(benzoato)digold(II) complex [Au₂(O₂CPh)₂ (μ-C₆H₃-2-PPh₂-5-Me)₂] (5b), whereas 1a is unreactive. The behavior of the 6- and 5-methyl-substituted digold(II) complexes in solution is very different. Complexes 2a-4a isomerize in solution above -20°C to give gold(I)-gold(III) complexes [XAu^I(μ-2-Ph₂PC₆H₃-6-Me)-Au^III X{η²-(C₆H₃-2-PPh₂-6-Me)}] [X = Cl (6a), Br (7a), I (8a)], whereas complexes 2b-4b isomerize more slowly in solution by C-C coupling to give digold(I) complexes [Au₂X₂{μ-2,2′-Ph₂P(5,5′- Me₂C₆H₃C₆H₃)PPh₂}] [X = Cl (6b), Br (7b), I (8b)] containing (5,5′-dimethyl-2,2′-biphenylyl)bis(diphenylphosphine) (12b); the structures of 8a and 8b have been determined by X-ray crystallography. Complex 8a contains linearly coordinated gold(I) and planar coordinated gold(III) atoms separated by 3.4692(7) angstrom; one arylphosphine group bridges the metal atoms, the other acts as a bidentate chelate ligand to gold(III). Complexes 6a-8a can be oxidized further by halogens to give either gold(I) complexes of (2-halo-3-methylphenyl)diphenylphosphine, [AuX{Ph₂P(C₆H₃-2-X-3-Me)] [X = Br (10a), I (11a)], arising from electrophilic cleavage of the Au-C bonds, or a binuclear digold(III) complex [Cl₃Au(μ-C₆H₃-2-PPh₂-6-Me)AuCl{η²- (C₆H₃-2-PPh₂-6-Me)}] (9a) in which the gold(III)-carbon bonds are retained. The differences in oxidative addition behavior between the 6- and 5-methyl-substituted series of compounds are believed to be caused mainly by the steric effect of the 6-methyl group adjacent to the gold-gold axis.

Full text of DOI:10.1021/om000672y

5628
Organometallics 2000, 19, 5628-5635
Syn th esis, Str u ctu r e, a n d Rea ction s of a Bin u clea r
Gold (I)-Gold (III) Com p lex Con ta in in g Br id gin g a n d
Bid en ta te (2-Dip h en ylp h osp h in o-6-m eth yl)p h en yl Gr ou p s
Suresh K. Bhargava* and Fabian Mohr
Department of Applied Chemistry, RMIT University, GPO Box 2476V,
Melbourne, Victoria 3001, Australia
Martin A. Bennett,* Lee L. Welling, and Anthony C. Willis
Research School of Chemistry, Australian National University, Canberra, ACT 0200, Australia
Received August 4, 2000
Reaction of the organolithium reagents (C6H3-2-PPh2-6-Me)Li or (C6H3-2-PPh2-5-Me)Li
with [AuBr(PEt3)] gives the corresponding cyclometalated digold(I) complexes [Au2(µ-C6H3-
2-PPh2-n-Me)2] (n ) 6, 1a ; n ) 5, 1b), the metal-metal distance in 1a , 2.861(2) Å, being
similar to that in the unsubstituted compound [Au2(µ-2-C6H4PPh2)2]. Both complexes
oxidatively add halogens to give metal-metal bonded digold(II) complexes [Au2X2(µ-C6H3-
2-PPh2-n-Me)2] [n ) 6, X ) Cl (2a ), Br (3a ), I (4a ); n ) 5, X ) Cl (2b), Br (3b), I (4b)], and
1b also adds dibenzoyl peroxide to give the bis(benzoato)digold(II) complex [Au2(O2CPh)2-
(µ-C6H3-2-PPh2-5-Me)2] (5b), whereas 1a is unreactive. The behavior of the 6- and 5-methyl-
substituted digold(II) complexes in solution is very different. Complexes 2a -4a isomerize
in solution above -20 °C to give gold(I)-gold(III) complexes [XAuI(µ-2-Ph2PC6H3-6-Me)-
AuIIIX{η2-(C6H3-2-PPh2-6-Me)}] [X ) Cl (6a ), Br (7a ), I (8a )], whereas complexes 2b-4b
isomerize more slowly in solution by C-C coupling to give digold(I) complexes [Au2X2{µ-
2,2′-Ph2P(5,5′-Me2C6H3C6H3)PPh2}] [X ) Cl (6b), Br (7b), I (8b)] containing (5,5′-dimethyl-
2,2′-biphenylyl)bis(diphenylphosphine) (12b); the structures of 8a and 8b have been
determined by X-ray crystallography. Complex 8a contains linearly coordinated gold(I) and
planar coordinated gold(III) atoms separated by 3.4692(7) Å; one arylphosphine group bridges
the metal atoms, the other acts as a bidentate chelate ligand to gold(III). Complexes 6a -8a
can be oxidized further by halogens to give either gold(I) complexes of (2-halo-3-methylphen-
yl)diphenylphosphine, [AuX{Ph2P(C6H3-2-X-3-Me)] [X ) Br (10a ), I (11a )], arising from
electrophilic cleavage of the Au-C bonds, or a binuclear digold(III) complex [Cl3Au(µ-C6H3-
2-PPh2-6-Me)AuCl{η2-(C6H3-2-PPh2-6-Me)}] (9a ) in which the gold(III)-carbon bonds are
retained. The differences in oxidative addition behavior between the 6- and 5-methyl-
substituted series of compounds are believed to be caused mainly by the steric effect of the
6-methyl group adjacent to the gold-gold axis.
In tr od u ction
ditions with halogens, pseudohalogens, and, in the case
of the bis(ylides), alkyl halides to give either metal-
metal bonded digold(II) compounds or heterovalent gold-
(I)-gold(III) compounds; sometimes both can be isolated
depending on the conditions.4-13 Reaction with an
additional equivalent of halogen can give binuclear
digold(III) compounds.7,14,15
A wide variety of binuclear compounds containing two
gold(I) atoms held in close proximity by a pair of
bifunctional ligands is known. Examples of such ligands
include dithiocarbamate,1 bis(diphenylphosphino)meth-
ane,2 (2-pyridyl)dimethylphosphine,3 methylenethio-
phosphinate,4 and phosphorus bis(ylides).5,6 The digold-
(I) complexes characteristically undergo oxidative ad-
(7) Schmidbaur, H.; Wohlleben, A.; Wagner, F. E.; Van de Vondel,
D. F.; Van der Kelen, G. P. Chem. Ber. 1977, 110, 2758.
(8) Fackler, J . P., J r. Polyhedron 1997, 16, 1, and references therein.
(9) Calabro, D. C.; Harrison, B. A.; Palmer, G. T.; Moguel, M. K.;
Rebbert, R. L.; Burmeister, J . L. Inorg. Chem. 1981, 20, 4311.
(10) Fackler, J . P., J r.; Trczinska-Bancroft, B. Organometallics 1985,
4, 1891.
(11) Raptis, R. G.; Porter, L. C.; Emrich, R. J .; Murray, H. H.;
Fackler, J . P., J r. Inorg. Chem. 1990, 29, 4408.
(12) Laguna, A.; Laguna, M. Coord. Chem. Rev. 1999, 193-195, 837,
and references therein.
(13) Laguna, M.; Cerrada E. In Metal Clusters in Chemistry;
Braunstein, P., Oro, L. A., Raithby, P. R., Eds.; Wiley-VCH: Weinheim,
1999; Vol 1, p 459, and references therein.
(14) Schmidbaur, H.; Franke, Inorg. Chim. Acta 1975, 13, 85.
(15) Dudis, D. S.; Fackler, J . P., J r. Inorg. Chem. 1985, 24, 3758.
(1) A° kerstro¨m, S. Ark. Kemi. 1959, 14, 387.
(2) Schmidbaur, H.; Wohlleben, A.; Schubert, U.; Frank, A.; Huttner,
G. Chem. Ber. 1977, 110, 2751.
(3) Inoguchi, Y.; Milewski-Mahrla, B.; Schmidbaur, H. Chem. Ber.
1982, 115, 3085.
(4) Mazany, A. M.; Fackler, J . P., J r. J . Am. Chem. Soc. 1984, 106,
801.
(5) Grohmann, A.; Schmidbaur, H. In Comprehensive Organome-
tallic Chemistry II; Wardell, J ., Abel, E. W., Stone, F. G. A., Wilkinson,
G., Eds.; Pergamon: Oxford, 1995; Vol. 3, p 1, and references therein.
(6) Schmidbaur, H.; Grohmann, A.; Olmos, M. E. In Gold, Progress
in Chemistry, Biochemistry and Technology; Schmidbaur, H., Ed.;
Wiley: Chichester, 1999; p 747, and references therein.
10.1021/om000672y CCC: $19.00 © 2000 American Chemical Society
Publication on Web 11/17/2000

Binuclear Gold(I)-Gold(III) Complex
Organometallics, Vol. 19, No. 26, 2000 5629
Sch em e 1
We have been interested in binuclear cycloaurated
complexes [Au2(µ-2-C6H4PPh2)2] containing a pair of (2-
diphenylphosphino)phenyl ligands, which undergo oxi-
dative addition of halogens or dibenzoyl peroxide to give
symmetrical digold(II) compounds [Au2X2(µ-2-C6H4-
PPh2)2] (X ) Cl, Br, I, O2CPh).16-18 In the cases of X )
Cl, Br, or I, the compounds rearrange spontaneously
by coupling of the C6H4PPh2 units to give digold(I)
complexes of 2,2′-(biphenylyl)bis(diphenylphosphine),
[Au2X2(2,2′-Ph2PC6H4C6H4PPh2)] (Scheme 1;Y ) H).17,18
Although the rearrangements (for X ) Br, I) are cleanly
first-order in digold(II) complex, we suggested18 that
they are multistep processes involving a preliminary
isomerization to a heterovalent gold(I)-gold(III) isomer
(I). In the second step, the metal-carbon bond of one of
the 2-C6H4PPh2 groups migrates from gold(I) to gold-
(III) to give species such as II or III (Figure 1). The 2,2′-
Ph2PC6H4C6H4PPh2 ligand is then generated in the
coordination sphere by reductive elimination of the two
σ-bonded aryl groups at the gold(III) center.
We wondered whether the course of these reactions
could be modified by steric effects, e.g., by strategic
placement of a substituent adjacent to the gold-gold
axis of the starting material, or by electronic effects, e.g.,
by substitution at the position of the aromatic ring para
to phosphorus. We have, therefore, studied digold
compounds containing as bridging groups (2-diphen-
ylphosphino-6-methyl)phenyl and (2-diphenylphosphino-
5-methyl)phenyl, µ-C6H3-2-PPh2-6-Me and µ-C6H3-2-
PPh2-5-Me, respectively.
F igu r e 1. Suggested intermediates in the C-C coupling
shown in Scheme 1.
Sch em e 2
their 31P{1H} NMR spectra contain the singlet expected
for equivalent phosphorus atoms. Compound 1a has also
been characterized by single-crystal X-ray diffraction.
The molecular structure, shown in Figure 2, is very
similar to that of [Au2(µ-2-C6H4PPh2)2], and the Au-
Au distance, 2.861(2) Å, is equal, within experimental
error, to that in the parent compound [2.8594(3) Å].16
Other important bond lengths and angles in 1a are
listed in Table 2.
Treatment of 1a or 1b with 1 equiv of PhICl2, Br2, or
I2 in dichloromethane at ca. -70 °C gives yellow, orange,
or red solutions containing the dihalodigold(II) com-
plexes [Au2X2(µ-C6H3-2-PPh2-n-Me)2] [n ) 6, X ) Cl
(2a ), Br (3a ), I (4a ); n ) 5, X ) Cl (2b), Br (3b), I (4b)],
which can be isolated by precipitation with hexane at
low temperature. Complex 1b also reacts with an excess
of dibenzoyl peroxide over a period of days at room
temperature to give the corresponding pale yellow bis-
(benzoato)digold(II) complex [Au2(O2CPh)2{µ-(C6H3-2-
PPh2-5-Me}2] (5b). The IR spectrum of 5b shows typical
carboxylate bands at 1632 and 1577 cm-1 due to ν(Cd
O) and at 1320 and 1298 cm-1 due to ν(C-O). In
contrast, 1a does not react with dibenzoyl peroxide even
on heating; long reaction times cause decomposition to
elemental gold. All these compounds show singlet 31P-
{1H} NMR resonances, the chemical shifts (Table 1)
being very similar to those of their C6H4PPh2 counter-
parts;18 as found in the latter, the shielding decreases
in the order I > Br > Cl > O2CPh. The mass spectra do
not show a parent ion, the highest mass peak corre-
sponding to the loss of one halide ion. The formulation
of the compounds as metal-metal bonded, digold(II)
complexes (5d9-5d9) has been confirmed by X-ray-
photoelectron and Mo¨ssbauer spectroscopies.19,20
Resu lts
The chemistry of the gold complexes containing C6H3-
2-PPh2-n-Me is summarized in Scheme 1 (Y ) Me) for
n ) 5 and Scheme 2 for n ) 6. Analytical and 31P{1H}
NMR spectroscopic data for the new compounds are
collected in Table 1.
The digold(I) precursors [Au2(µ-C6H3-2-PPh2-n-Me)2]
(n ) 6, 1a ; n ) 5, 1b) are obtained similarly to [Au2(µ-
2-C6H4PPh2)2] in ca. 40-50% yield by reaction of the
appropriate aryllithium reagents with [AuBr(PEt3)] in
ether at -70 °C. The compounds are white solids that
are stable to air and moisture. Their EI-mass spectra
each show a parent-ion molecular peak at m/z 944, and
(16) Bennett, M. A.; Bhargava, S. K.; Griffiths, K. D.; Robertson,
G. B.; Wickramasinghe, W. A.; Willis, A. C. Angew. Chem., Int. Ed.
Engl. 1987, 26, 258.
(17) Bennett, M. A.; Bhargava, S. K.; Griffiths, K. D.; Robertson,
G. B. Angew. Chem., Int. Ed. Engl. 1987, 26, 260.
(18) Bennett, M. A.; Bhargava, S. K.; Hockless, D. C. R.; Welling,
L. L.; Willis, A. C. J . Am. Chem. Soc. 1996, 118, 10469.

5630 Organometallics, Vol. 19, No. 26, 2000
Bhargava et al.
Ta ble 1. Elem en ta l An a lyses a n d 31P NMR Da ta for Gold Com p lexes Der ived fr om C6H3-2-P P h 2-6-Me a n d
C6H3-2-P P h 2-5-Mea
Anal. [calcd (found)]
b
color
white
white
yellow
% C
% H
% other
δP(J PP)
[AuI2{(C6H3-6-Me)PPh2}2] (1a )
48.32 (47.99)
48.32 (48.43)
nm
3.41 (3.13)
3.41 (3.48)
nm
6.56 (6.32) (P)
6.56 (6.16) (P)
nm
36.2c
[AuI2{(C6H3-5-Me)PPh2}2] (1b)
35.9c
-0.5d
1.3
[AuII2Cl2{(C6H3-6-Me)PPh2}2] (2a )
[AuII2Cl2{(C6H3-5-Me)PPh2}2] (2b)
[AuII2Br2{(C6H3-6-Me)PPh2}2] (3a )
[AuII2Br2{(C6H3-5-Me)PPh2}2] (3b)
[AuII2I2{(C6H3-6-Me)PPh2}2] (4a )
[AuII2I2{(C6H3-5-Me)PPh2}2] (4b)
[AuII2(O2CPh)2{(C6H3-5-Me)PPh2}2] (5b)
[AuI,III2Cl2{(C6H3-6-Me)PPh2}2] (6a )
[AuI,III2Br2{(C6H3-6-Me)PPh2}2] (7a )
[AuI,III2I2{(C6H3-6-Me)PPh2}2] (8a )
[AuI2I2{2,2′-PPh2(5,5′-Me2C6H3C6H3)PPh2}] (8b)
[AuIII2Cl4{(C6H3-6-Me)PPh2}2]0.2CH2Cl2 (9a )
yellow
44.95 (44.72)
41.33 (41.57)
41.33 (40.89)
38.09 (37.53)
38.09 (37.74)
52.63 (51.48)
44.95 (45.14)
41.33 (41.41)
38.09 (37.47)
38.09 (37.87)
38.24 (37.93)
3.18 (3.10)
2.92 (3.08)
2.92 (3.08)
2.69 (3.18)
2.69 (2.87)
3.57 (3.75)
3.18 (2.86)
2.92 (3.12)
2.69 (3.12)
2.69 (2.84)
2.89 (2.97)
6.10 (6.24) (P)
14.47 (14.38) (Br)
5.61 (5.61) (P)
5.17 (4.93) (P)
5.17 (4.62) (P)
5.22 (4.91) (P)
6.10 (6.32) (P)
14.47 (14.31) (Br)
5.17 (4.86) (P)
21.18 (21.54) (I)
4.93 (4.59) (P)
22.58 (22.14) (Cl)
4.90 (5.13) (P)
4.27 (4.01) (P)
orange
orange
rust-red
rust-red
pale yellow
white
cream
pale pink
white
-5.3d
-3.9
-13.1d
-12.5
4.3
34.3, -58.4 (13)
33.9, -65.2 (13)
37.5, -78.2 (13)
31.6e
yellow
49.8, -65.3 (19)c
[AuBr{Ph2P(C6H3-2-Br-3-Me)}] (10a )
[AuI{Ph2P(C6H3-2-I-3-Me)}] (11a )
white
white
36.10 (36.24)
31.43 (31.37)
2.55 (2.20)
2.22 (2.42)
35.9
48.2
a
b
d
Abbreviation: nm ) not measured. In CD2Cl2 at 23 °C, except where stated. c In CDCl3 at 23 °C. In CDCl3 at -40 °C. e δP values
for corresponding dichloro and dibromo compounds, 6b and 7b, are 27.3 and 29.0, respectively.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) in [Au 2(µ-C6H3-2-P P h 2-6-Me)2] (1a )
Au(1)‚‚‚Au(2)
Au(1)-P(1)
Au(1)-C(21)
2.861(2)
2.302(2)
2.061(7)
P-C
Au(2)-P(2)
Au(2)-C(2)
1.819(8)-1.829(8)
2.295(2)
2.042(7)
Au(2)-Au(1)-P(1)
78.87(5) Au(2)-Au(1)-C(21)
95.6(2)
77.18(6)
171.8(2)
114.3(3)
P(1)-Au(1)-C(21) 174.3(2)
Au(1)-Au(2)-P(2)
P(2)-Au(2)-C(2)
Au(2)-P(2)-C(20)
Au(1)-Au(2)-C(2)
Au(1)-P(1)-C(1)
Au(2)-C(2)-C(1)
96.3(2)
116.0(3)
119.2(6)
Au(1)-C(21)-C(20) 118.6(6)
membered metallacycle;21 the 1H NMR spectra show two
singlets arising from inequivalent methyl groups. These
data are consistent with the formulation of compounds
6a -8a as heterovalent gold(I)-gold(III) complexes con-
taining one bidentate C6H3-2-PPh2-6-Me group bound
to gold(III) and one C6H3-2-PPh2-6-Me group bridging
gold(I) and gold(III), i.e., [XAuI{µ-2-Ph2P(C6H3-6-Me)}-
AuIIIX{η2-(C6H3-2-PPh2-6-Me)}] (Scheme 2). This con-
clusion has been confirmed by a single-crystal X-ray
diffraction study of 8a (X ) I) (see below).
The far IR spectrum of 6a shows a strong band due
F igu r e 2. Molecular structure of [Au2(µ-C6H3-2-PPh2-6-
Me)2] (1a ) with atom labeling; ellipsoids show 30% prob-
ability levels, and hydrogen atoms are drawn as circles with
small radii.
to ν(AuCl) at 328 cm-1, which is replaced in the
spectrum of 7a by a band due to ν(AuBr) at 233 cm-1
.
Bands at similar positions are observed in the spectra
of tertiary phosphine-gold(I) complexes [AuX(PR3)] (X
) Cl, Br, respectively).22-24 A band at 291 cm-1 in the
spectrum of 6a is assigned tentatively to ν(AuCl) for Cl
trans to aryl carbon on gold(III); the corresponding band
due to ν(AuBr) appears at 207 cm-1 in the spectrum of
6b.
The molecular structure of 8a is shown in Figure 3,
together with atom numbering. Selected bond lengths
and angles are listed in Table 3. The trivalent gold atom,
Au(1), is coordinated in a planar array by the four-
membered chelate C6H3-2-PPh2-6-Me group, the carbon
atom of the bridging C6H3-2-PPh2-6-Me group, and
iodide; the iodide is trans to the carbon atom of the four-
membered ring. The univalent gold atom, Au(2), is
The solutions of the digold(II) complexes 2a -4a
containing C6H3-2-PPh2-6-Me decolorize within minutes
above -20 °C, and almost colorless solids of the same
empirical formula [X ) Cl (6a ), Br (7a ), I (8a )] can be
isolated in good yield by adding hexane to the resulting
solutions. Qualitatively, the rate of isomerization de-
creases in the order I > Br > Cl. The half-life for the
disappearance of 2a was estimated as ca. 70 s at 308 K
by UV-visible spectroscopy. The highest mass peak in
the FAB-mass spectra of the isolated solids corresponds
to the loss of one halide ion. The 31P{1H} NMR spectra
contain a pair of doublets (2J PP ) 13 Hz) in the regions
of δ 35 and -60 to -80, the highly shielded resonance
being characteristic of a phosphorus atom in a four-
(21) Garrou, P. E. Chem. Rev. 1981, 81, 229.
(22) Coates, G. E.; Parkin, C. J . Chem. Soc. 1963, 421.
(23) Williamson, D. R.; Baird, M. C. J . Inorg. Nucl. Chem. 1972,
34, 3393.
(19) Bhargava, S. K.; Mohr, F.; Gorman, J . D. J . Organomet. Chem.
2000, 607, 93.
(20) Bhargava, S. K.; Mohr, F.; Takahashi, M.; Takeda, M. Unpub-
lished work.
(24) J ones, A. G.; Powell, D. B. Spectrochim. Acta, Part A 1974, 30,
563.

Binuclear Gold(I)-Gold(III) Complex
Organometallics, Vol. 19, No. 26, 2000 5631
F igu r e 4. Molecular structure of [Au2I2{µ-2,2′-Ph2P(5,5′-
Me2C6H3C6H3)PPh2}] (8b) with selected atom labeling
viewed along the C-C axis of the biphenyl backbone.
Asterisks indicate atoms generated by crystallographic
symmetry. Ellipsoids show 50% probability levels, and
hydrogen atoms have been omitted. Distances: Au(1)‚‚‚Au-
(1)* 2.9789(3) Å, Au(1)-P(1) 2.256(1) Å, Au(1)-I(1) 2.5498-
(4) Å; angle I(1)-Au(1)-P(1) 170.58(3)°.
F igu r e 3. Molecular structure of [IAuI(µ-2-Ph2PC6H3-6-
Me)AuIIII{η2-C6H3-2-PPh2-6-Me)}] (8a ) with atom labeling;
ellipsoids show 30% probability levels, and hydrogen atoms
are drawn as circles with small radii.
by 3.47 Å, indicative of little or no interaction. Other
bond lengths are unexceptional.
Solutions of the digold(II) complexes 2b-4b having
the 5-methyl substituent also decolorize at room tem-
perature over a period of hours. The 31P{1H} NMR
spectra of these solutions show singlets in the region of
δ 30, similar to those reported for the (2,2′-biphenylyl)-
bis(diphenylphosphine) complexes [Au2X2(µ-2,2′-Ph2-
PC6H4C6H4PPh2)];17,18 no intermediates could be de-
tected. From the solutions, the colorless digold(I)
complexes [Au2X2{µ-2,2′-Ph2P(5,5′-Me2C6H3C6H3)PPh2}]
[X ) Cl (6b), Br (7b), I (8b)] can be isolated as colorless
solids in good yield (Scheme 1; Y ) Me). As in the case
of the parent series, the bis(benzoato)digold(II) complex
5b does not rearrange, even on heating. The structural
formulation of 8b has been established by single-crystal
X-ray diffraction. The molecular structure is shown in
Figure 4, together with atom numbering. As in the cases
of [Au2Br2(µ-2,2′-Ph2PC6H4C6H4PPh2)] and [Au2I2(µ-
2,2′-Et2PC6H4C6H4PEt2)], the aromatic rings of the
biphenyl backbone are approximately perpendicular to
each other, the dihedral angle being 101°; the Au‚‚‚Au
separation of 2.98 Å is suggestive of a weak aurophilic
interaction.35 The ligand 2,2′-Ph2P(5,5′-Me2C6H3C6H3)-
PPh2 (12b) is liberated from 8b by treatment with
NaCN.
Ta ble 3. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) in [IAu I(µ-2-P h 2P C6H3-6-Me)Au III
I{η2-(C6H3-2-P P h 2-6-Me)}] (8a )
-
Au(1)‚‚‚Au(2)
3.4692(7)
2.645(1)
2.092(11)
2.545(1)
Au(1)-I(1)
Au(1)-C(2)
Au(2)-I(2)
Au(1)-P(1)
Au(1)-C(21)
Au(2)-P(2)
2.347(3)
2.079(11)
2.252(3)
I(1)-Au(1)-P(1)
I(1)-Au(1)-C(21)
99.02(8) I(1)-Au(1)-C(2)
90.4(3)
163.7(3)
68.6(3)
P(1)-Au(1)-C(2)
P(1)-Au(1)-C(21) 170.4(3)
C(2)-Au(1)-C(21) 102.4(4)
I(2)-Au(2)-P(2)
172.50(8) Au(1)-P(1)-C(1)
84.4(4)
101.9(9)
104.7(8)
Au(2)-P(2)-C(20) 116.1(3)
P(1)-C(1)-C(2)
Au(1)-C(2)-C(1)
P(1)-C(1)-C(6)
Au(1)-C(2)-C(3)
136(1)
134.1(9)
linearly coordinated by iodide and the phosphorus atom
of the bridging C6H3-2-PPh2-6-Me group. The angle
subtended at Au(1) by the chelate four-membered ring
is only 69°, typical of that observed in η2-C6H4PPh2, or
substituted derivatives thereof, in planar platinum(II)
complexes25-27 and in complexes of iridium(III),28,29
rhodium(III),29 platinum(IV),30 osmium(II),31 and man-
ganese(I).32 The gold(III)-carbon bond lengths [Au(1)-
C(2) ) 2.092(11) Å; Au(1)-C(21) ) 2.079(11) Å] are
significantly greater than those in gold(III) complexes
containing cyclometalated N-donors such as C6H4(CH2-
NMe2)-2 or C6H4(NdNPh)-2, which generally fall in the
range 2.01-2.03 Å.33,34 The gold atoms are separated
The 5-methyl-substituted gold complexes thus behave
very similarly to their unsubstituted analogues (Scheme
1). The only difference that we have observed is that,
qualitatively, the rate of isomerization is in the order
X ) Cl (2b) > I (4b) > Br (3b), the position for X ) Cl
being the reverse of that found in the parent series. The
half-lives t1/2 for these rearrangements determined by
31P NMR spectroscopy at 310 K were 3.8 min (2b), 22.5
(25) Bennett, M. A.; Berry, D. E.; Bhargava, S. K.; Ditzel, E. J .;
Robertson, G. B.; Willis, A. C. J . Chem. Soc., Chem. Commun. 1987,
1613.
(26) Rice, N. C.; Oliver, J . D. J . Organomet. Chem. 1978, 145, 121.
(27) Bennett, M. A.; Dirnberger, T.; Hockless, D. C. R.; Wenger, E.;
Willis, A. C. J . Chem. Soc., Dalton Trans. 1998, 271.
(28) del Piero, G.; Perego, G.; Zazzetta, A.; Cesari, M. Cryst. Struct.
Commun. 1974, 3, 725.
(32) McKinney, R. J .; Knobler, C. B.; Huie, B. T.; Kaesz, H. D. J .
Am. Chem. Soc. 1977, 99, 2988.
(29) von Deuten, K.; Dahlenburg, L. Cryst. Struct. Commun. 1980,
9, 421.
(30) Bennett, M. A.; Bhargava, S. K.; Ke, M.; Willis, A. C. J . Chem.
Soc., Dalton Trans., submitted for publication.
(31) Bennett, M. A.; Clark, A. M.; Contel, M.; Rickard, C. E. F.;
Roper, W. R.; Wright, L. J . J . Organomet. Chem. 2000, 601, 299.
(33) Vicente, J .; Chicote, M.-T.; Bermu´dez, M. D.; J ones, P. G.;
Fittschen, C.; Sheldrick, G. M. J . Organomet. Chem. 1986, 310, 401.
(34) Vicente, J .; Bermu´dez, M. D.; Escribano, J .; Carrillo, M. P.;
J ones, P. G. J . Chem. Soc., Dalton Trans. 1990, 3083.
(35) Schmidbaur, H. Gold Bull. 1990, 23, 11; Chem. Soc. Rev. 1995,
24, 391.

5632 Organometallics, Vol. 19, No. 26, 2000
Bhargava et al.
Sch em e 3
min (3b), and 17.0 min (4b). The half-life for 4b is very
similar to that for the iodo compound in the parent
series (18 min, 311 K), whereas the half-life for the
bromo compound 3b is much less than for its analogue
in the parent series (165 min, 311 K).18
Although complexes 6a -8a are structurally analo-
gous to one of the intermediates, III, suggested to be a
precursor to the C-C coupled product in the unsubsti-
tuted series (Scheme 1), attempts to induce C-C
coupling in complex 8a have failed. The main product
identified by 31P NMR spectroscopy after heating 8a in
toluene for 6 days was the digold(I) complex formed by
loss of iodine. There was also a small amount of the
product of iodine oxidation of 8a (see below) and other
unidentified species. Heating 6a in toluene for the same
period of time led to decomposition to elemental gold
and several other unidentified species.
F igu r e 5. Molecular structure of [AuI{Ph2P(C6H3-2-I-3-
Me)}] (11a ) with atom labeling; ellipsoids show 30%
probability levels, and hydrogen atoms have been omitted.
Distances: Au(1)-P(1) 2.251(4) Å, Au(1)-I(1) 2.550(1) Å;
angle I(1)-Au-P(1) 174.0(1)°.
Sch em e 4
Complexes 6a -8a react with an additional equivalent
of halogen, but the products depend on the halogen used.
Treatment of 7a with bromine or of 8a with iodine gives
colorless halogold(I) complexes of the appropriate (2-
halogeno-3-methylphenyl)diphenylphosphine, [AuX-
{Ph2P(C6H3-2-X-3-Me)}] [X ) Br (10a ), I (11a )], arising
from electrophilic cleavage of the gold(III)-carbon bonds
(Scheme 3). The same compounds are obtained by
treatment of 1a with 2 equiv of bromine or iodine. They
show singlets in their 31P{1H} NMR spectra whose
chemical shifts are close to those of [AuBr(2-BrC6H4-
PPh2)] and [AuI(2-IC6H4PPh2)], respectively.18 The iden-
tity of 11a has been confirmed by single-crystal X-ray
diffraction, and 10a has been synthesized independently
from K[AuBr4] and (2-bromo-3-methylphenyl)diphen-
ylphosphine. The structure of 11a (Figure 5) shows the
expected linear coordination about gold(I).
bauer spectra20 have also confirmed that 9a contains a
pair of inequivalent gold(III) centers.
Discu ssion
The marked differences in the behavior of the digold
complexes containing the C6H3-2-PPh2-6-Me group com-
pared with that of the corresponding complexes contain-
ing C6H3-2-PPh2-5-Me or 2-C6H4PPh2 can be attributed
to steric repulsion between the 6-methyl substituents
and ligands in the axial positions. This must be suf-
ficient to prevent the addition of dibenzoyl peroxide to
the digold(I) complex 1a and to destabilize the sym-
metrical dihalodigold(II) complexes 2a -4a in favor of
their unsymmetrical gold(I)-gold(III) isomers 6a -8a .
The fact that complexes 2a -4a can be isolated and
characterized at low temperature clearly shows that
they are the kinetic products of oxidative addition. This
process must, therefore, involve both metal centers, in
agreement with conclusions drawn about the oxidative
addition of alkyl halides to the corresponding bis(ylide)
complexes.8
Although the digold(II) complexes of C6H3-2-PPh2-5-
Me and 2-C6H4PPh2 undergo similar C-C coupling
reactions, the introduction of the methyl group para to
phosphorus has the surprising effect of causing the
chloro complex to become the most prone to isomeriza-
tion rather than the least. There can be no doubt that
the C-C coupling reaction is a multistep process involv-
Treatment of 6a with 1 equiv of PhICl2 or of 1a with
2 equiv of PhICl2 gives a yellow solution, which, on
standing, deposits a yellow solid, 9a , that is insoluble
in common organic solvents. However, the 31P{1H} NMR
spectrum could be measured in situ as a suspension in
CDCl3. It shows a pair of doublets at δ 49.8 and -65.3
(J PP ) 19 Hz), similar in pattern to those of 6a but
differing in chemical shift. The matrix-assisted laser
desorption ionization (MALDI) mass spectrum shows
peaks at m/z 979 and 943 corresponding to the loss of
three and four chlorine atoms, respectively. The IR
spectrum shows strong bands at 366, 340, and 312 cm-1
,
which are almost identical with the ν(AuCl) frequencies
reported for [AuCl3(PPh3)].36 These observations suggest
that 9a is derived from 6a by addition of Cl2 to the gold-
(I) atom (Scheme 4), and, in agreement, treatment of a
suspension of 9a in CH2Cl2 with zinc powder re-forms
6a quantitatively, as shown by 31P{1H} NMR spectros-
copy. Measurements of X-ray photoelectron19 and Mo¨ss-
(36) Boschi, T.; Crociani, B.; Cattalini, L.; Marangoni, G. J . Chem.
Soc. A 1970, 2408.

Binuclear Gold(I)-Gold(III) Complex
Organometallics, Vol. 19, No. 26, 2000 5633
prepared in a three-step sequence from 2-methyl-6-nitroaniline
(Aldrich)40-42 and 3-bromo-4-iodotoluene in a two-step se-
quence from p-toluidine (BDH).42,43 These compounds were
converted into (2-bromo-3-methylphenyl)diphenylphosphine
and (2-bromo-4-methylphenyl)diphenylphosphine by PdCl2-
(NCMe)2-catalyzed reaction with diphenyl(trimethylsilyl)phos-
phine, Ph2PSiMe3, in yields of 76% and 80%, respectively.42
31P{1H} NMR (CD2Cl2): δ -4.1 (s) and -5.5 (s), respectively.
Sch em e 5
Digold (I) Com p lexes, [Au 2(µ-(C6H3-2-P P h 2-n -Me)2] (n )
6, 1a ; n ) 5, 1b). A solution of (C6H3-2-Br-3-Me)PPh2 or (C6H3-
2-Br-4-Me)PPh2 (1.0 g, 2.8 mmol) in a mixture of ether (20
mL) and hexane (20 mL) treated with a 1.6 M solution of
n-BuLi (2 mL) gave a white precipitate of the appropriate
organolithium compound, (C6H3-2-PPh2-6-Me)Li or (C6H3-2-
PPh2-5-Me)Li, which was washed with hexane and dried in
vacuo. The yield in both cases was ca. 70%. A suspension of
the solid in ether was added to a solution of [AuBr(PEt3)] (1.27
g, 3.2 mmol) in ether at -70 °C. The mixture was stirred
overnight at room temperature, and the resulting off-white
solid was washed successively with ether (3 × 10 mL),
methanol (15 mL), and hexane (2 × 20 mL). It was then
extracted with hot dichloromethane (1b being particularly
poorly soluble), and the solution was filtered through Celite.
Evaporation and addition of hexane gave 1a or 1b as white,
air-stable solids in yields of 0.83 g (50%) and 0.62 g (43%),
respectively, which melted with decomposition at 280 °C (1a )
and 260 °C (1b). 1a : 1H NMR (CDCl3) δ 2.6 (s, CH3), 6.8-7.7
(m, arom); EI-MS m/z 944 (M+), 754, 471, 276, 197. 1b: EI-
MS m/z 745 (M+), 471, 276, 197.
ing several undetected intermediates; hence, the net
effect of changing axial halide and aromatic ring sub-
stituents on the rates of the intervening steps is not easy
to predict. Clearly, the kinetics of the process require
more detailed study.
Complexes 6a -8a represent the first fully character-
ized examples of complexes that contain a four-mem-
bered ring derived from a cyclometalated triarylphos-
phine attached to gold(III). In earlier work,18 it was
shown that bromination or iodination of [AuII2X2(µ-2-
C6H4PPh2)2] to give as the final products [AuIX(Ph2-
PC6H4-2-X)] (X ) Br, I) proceeds through a number of
cycloaurated intermediates, some of which were formu-
lated as monomers, [AuX2(2-C6H4PPh2)], on the basis
of their highly shielded 31P resonances.
The formation of 6a -8a from 2a -4a requires migra-
tion of one of the metal-carbon σ-bonds from a gold
atom to its neighbor; a similar process may occur also
in the closely related isomerization in the bis(ylide)
series shown in Scheme 5.10 As noted above, the
structure of 6a -8a is very similar to that of one of the
proposed intermediates, III, in the C-C coupling reac-
tion (Scheme 1), and, in agreement, we have recently
detected, though not isolated, intermediates in the
corresponding rearrangements of [Au2X2(µ-2-C6H4-
PPh2)2] (X ) SCN, C6F5), whose 31P{1H} NMR spectra
closely resemble those of 6a -8a .37 It may be that
reductive elimination of the two metal-carbon σ-bonds
from the gold(III) centers of 6a -8a is sterically hindered
by the ortho-methyl groups.
Dih a lod igold (II) Com p lexes, [Au 2X2(µ-C6H3-2-P P h 2-n -
Me)2] [n ) 6, X ) Cl (2a ), Br (3a ), I (4a ); n ) 5, X ) Cl (2b),
Br (3b), I (4b)]. A stirred solution or suspension of 1a or 1b
(100 mg, 0.106 mmol) in dichloromethane (10 mL) at -70 °C
was treated dropwise with an equimolar amount of PhICl2,
bromine, or iodine in dichloromethane (5 mL), the temperature
being kept below -65 °C. The mixture was stirred for 30 min,
and an approximately equal volume of hexane was added. The
solution was evaporated under reduced pressure at or below
-20 °C until the product began to precipitate. The solid was
separated by filtration, washed with hexane, and dried in
vacuo. The complexes were obtained in yields of 60-70%.
Complexes 2b-4b could also be prepared by treatment of
the bis(benzoato) complex 5b (see below) with a solution or
suspension of the appropriate lithium halide in acetone. The
suspension was filtered through Celite, and the product was
precipitated by addition of hexane to the filtrate. Yields were
>85%. 2a : 1H NMR (CD2Cl2, -40 °C) δ 2.5 (s, 2CH3), 6.7-7.6
(m, arom). 2b: 1H NMR (CD2Cl2) δ 2.3 (s, 2CH3), 6.6 (q, J )
7 Hz, 1 H), 7.0 (d, J ) 7 Hz, 2 H), 7.2-7.8 (m, 19 H), 8.1 (d, J
) 7 Hz, 4 H) (arom); FAB-MS m/z 1014 (M+), 979, 943, 747,
471, 365. 3b: 1H NMR (CD2Cl2) δ 2.3 (s, 2CH3), 6.5 (q, J ) 7
Hz, 2 H), 7.0 (d, J ) 7 Hz, 2 H), 7.2-7.6 (m, 20 H), 7.9 (t, J )
5 Hz, 2 H) (arom); FAB-MS m/z 1025 (M+ - Br), 747, 473. 4b:
(CD2Cl2) δ 2.3 (s, 2CH3), 6.3 (q, J ) 7 Hz, 2 H), 6.9 (d, J ) 7
Hz, 2 H), 7.1-7.6 (m, 20 H), 8.0 (m, 2 H) (arom); FAB-MS m/z
1071 (M+ - I), 747, 589, 473, 365.
Bis(b en zoa t o)d igold (II) Com p lex [Au 2(O2CP h )2{(µ-
C6H3-2-P P h 2-5-Me)2}] (5b). A stirred suspension of 1b (0.581
g, 0.615 mmol) in dichloromethane (25 mL) was treated with
an excess of solid dibenzoyl peroxide (0.29 g, 1.20 mmol). The
mixture was stirred at room temperature for 3 days and
evaporated to dryness in vacuo. The yellow solid was stirred
with ether for 2 h to remove the excess of peroxide, the ether
was removed by decantation, and the solid was dried in vacuo.
It was dissolved in a small volume of dichloromethane, and
hexane was added. The solution was evaporated until the
Exp er im en ta l Section
Gen er a l P r oced u r es. Most syntheses were performed
under dry argon with use of standard Schlenk techniques,
although the solid gold complexes, once isolated, were air-
stable. Solvents were dried by standard procedures, distilled,
and stored under nitrogen. The following instruments were
used for spectroscopic measurements: Varian XL-200E (1H at
200 MHz, 31P at 80.96 MHz), Varian Gemini 300 (1H at 300
MHz), Bruker Aspect 2000 (31P at 80.96 MHz), VG ZAB-2SEQ
(high-resolution EI and FAB mass spectra), Perkin-Elmer PE
683 (infrared spectra as KBr disks in the range 4000-400
cm-1), Perkin-Elmer FT 1800 (infrared spectra as polyethylene
disks in the range 400-150 cm-1). The NMR chemical shifts
(δ) are given in ppm relative to TMS (1H) and 85% H3PO4 (31P),
referenced either to residual solvent signals (1H) or externally
(31P). Coupling constants (J ) are given in hertz. The UV-vis
kinetic experiments were performed with use of a Perkin-
Elmer Lambda 12 spectrometer. Elemental analyses were
carried out in the Microanalytical Laboratory of the Research
School of Chemistry, Canberra.
38
Sta r tin g Ma ter ia ls. The compounds PhICl2 and [AuBr-
(PEt3)]39 were prepared as described in the literature. By use
of modified literature procedures, 2-bromo-3-iodotoluene was
(37) Bennett, M. A.; Welling, L. L. Unpublished work.
(38) Lucas, H. J .; Kennedy, E. R. Organic Syntheses; Wiley: New
York, 1955; Collect. Vol. III, p 482.
(39) Coates, G. E.; Kowala, C.; Swan, J . M. Aust. J . Chem. 1966,
19, 539.
(40) Gibson, C. S.; J ohnson, J . D. A. J . Chem. Soc. 1929, 1229.
(41) Wibaut, J . P. J . R. Neth. Chem. Soc. 1913, 32, 245.
(42) Tunney, S. E.; Stille, J . K. J . Org. Chem. 1987, 52, 748.
(43) Kosolapoff, G. M. J . Am. Chem. Soc. 1953, 75, 3396.

5634 Organometallics, Vol. 19, No. 26, 2000
Ta ble 4. Cr ysta l a n d Refin em en t Da ta for Com p ou n d s 1a , 8a , 8b, a n d 11a
Bhargava et al.
1a
8a
8b
11a
(a) Crystal Data
C38H32Au2I2P2
1198.36
chem formula
fw
C
38H32Au2P2
C38H32Au2I2P2
1198.36
C19H16AuI2P
726.08
944.55
cryst syst
unit cell dimens
a (Å)
b (Å)
c (Å)
triclinic
monoclinic
monoclinic
orthorhombic
10.808(6)
12.795(5)
13.191(6)
98.63(4)
112.59(4)
97.66(5)
1628(2)
14.749(2)
11.559(3)
21.691(2)
19.2078(3)
10.7202(2)
19.0440(3)
15.717(2)
15.217(3)
17.026(2)
R (deg)
â (deg)
101.631(9)
112.823(1)
γ (deg)
V (Å3)
3622(1)
3614.4(1)
4072(2)
space group
P
P21/c (# 14)
2.197
4
C2/c (# 15)
2.202
4
Pbca (# 61)
2.369
8
Dc (g cm-3
Z
)
1.926
2
F(000)
896.00
2216.00
2216.00
2640.00
color, habit
colorless, needle
0.40 × 0.15 × 0.08
90.93 (Mo KR)
pale yellow, blade
0.27 × 0.13 × 0.06
98.66 (Mo KR)
colorless, cuboid
0.20 × 0.15 × 0.13
99.60 (Mo KR)
colorless, block
0.23 × 0.12 × 0.09
385.99 (Cu KR)
cryst dimens (mm)
µ (cm-1
)
(b) Data Collection and Processing
diffractometer
X-radiation
T (°C)
scan mode
ω-scan width
2θmax (deg)
no. of reflens
unique
Rigaku AFC6S
Mo KR
Rigaku AFC6S
Mo KR
Nonius Kappa CCD
Mo KR
Rigaku AFC6R
Cu KR
23(1)
23(1)
-73(1)
23(1)
ω-2θ
1.20 + 0.34 tan θ
55.1
ω-2θ
1.00 + 0.34 tan θ
55.1
ω-2θ
1.10 + 0.30 tan θ
120.0
7504
8768
4141a
3417
obsd
4807
4016
3456
2009
[I > 2.0σ(I)]
analytical
(0.26-0.53)
[I > 2.0σ(I)]
numericalb
(0.34-0.63)
[I > 2.0σ(I)
analytical
(0.25-0.45)
[I > 2.0σ(I)]
analytical
(0.02-0.14)
abs corr
(transm factors)
(c) Structure Analysis and Refinement
structure soln
refinement
Patterson methods
direct methods
direct methods
direct methods
208
full matrix least squares
no. of params
weighting scheme w
R (obsd data) %
Rw (obsd data) %
GOF
379
397
199
[σ2(F) + (0.0001)F2]-1
3.3
3.1
1.52
1.90, -1.51
3.5
2.9
2.9
1.11
0.96, -1.49
4.1
5.0
1.61
1.44, -1.11
3.3
1.13
0.84, -0.83
F
max, Fmin (e Å-3
)
a
b
Total reflections 33 991. Correction for 1.7% decay also applied.
product began to separate and then set aside at 0 °C. The solid
was separated by filtration, washed with hexane, and dried
in vacuo. The yield was 0.40 g, 0.337 mmol, 55%: 1H NMR
(CD2Cl2) δ 2.3 (s, 2CH3), 6.7 (q, J ) 7 Hz, 2 H), 6.9-7.1 (m, 2
H), 7.2-7.6 (m, 30 H), 7.7 (t, J ) 7 Hz, 2 H) (arom); FAB-MS
m/z 945 (M+ - 2 OBz), 747, 473, 365.
tion of 6a (250 mg, 0.265 mmol) in dichloromethane (20 mL)
was added dropwise an equimolar solution of PhICl2 in
dichloromethane (10 mL) at room temperature. The mixture
was set aside overnight. The resulting bright yellow solid was
separated by filtration and washed with dichloromethane and
hexane. The yield was 200 mg (70%). The compound was also
obtained by treatment of 1a with an excess of PhICl2 under
similar conditions. FAB-MS: m/z 979 (M+ - 3 Cl), 943, 747,
471, 313, 289, 252.
Under the same conditions, complex 1a did not react with
dibenzoyl peroxide.
Gold (I)-Gold (III) Com p lexes, [XAu (µ-2-P h 2P C6H3-6-
Me)Au X{η2-(C6H3-2-P P h 2-6-Me)}] [X ) Cl (6a ), Br (7a ), I
(8a )]. These were prepared from 1a as described for 2a -4a
(see above), except that the solutions were kept at room
temperature. Immediately after addition of the halogenating
agent, the solutions were strongly colored, but they became
colorless within a few minutes. Hexane was added, and the
solutions were evaporated until the products began to pre-
cipitate; the solutions were then set aside at 0 °C. The yields
of 6a -8a were >60%. The compounds were also obtained
quantitatively by allowing solutions of 2a -4a to stand at room
temperature for 20 min and then adding hexane to precipitate
colorless solids. 6a : 1H NMR (CD2Cl2) δ 1.2 (s, CH3), 2.6 (s,
CH3), 6.8-8.1 (m, arom); FAB-MS m/z 979 (M+ - Cl), 747, 472,
306. 7a : 1H NMR (CD2Cl2) δ 1.8 (s, CH3) 2.5 (s, CH3), 6.6-8.0
(m, arom); FAB-MS m/z 1025 (M+ - Br), 747, 471, 384. 8a :
1H NMR (CD2Cl2) δ 1.8 (s, CH3), 2.4 (s, CH3), 6.5-8.2 (m,
arom); FAB-MS m/z 1198 (M+), 1071, 943, 747, 471, 275.
Gold (III)-Gold (III) Com p lex [Cl3Au (µ-2-P h 2P C6H3-6-
Me)Au Cl{η2-(C6H3-2-P P h 2-6-Me)}][ (9a ). To a stirred solu-
Rea ction s of 7a or 8a w ith Ha logen . A stirred solution
of 7a or 8a (100 mg, 0.106 mmol) in dichloromethane (10 mL)
was treated dropwise with a solution of bromine (for 7a ) or
iodine (for 8a ) (0.11 mmol) in dichloromethane (5 mL) at room
temperature. After 20 min, hexane was added to precipitate
the colorless solids [AuX{Ph2P(C6H3-2-X-3-Me)}] [X ) Br (10a ),
I (11a )] in yields of 60-70%.
An authentic sample of 10a was prepared by adding an
ethanolic solution of (C6H3-2-Br-3-Me)PPh2 (1.8 g, 5.1 mmol)
to an ethanolic solution of K[AuBr4] (1.39 g, 2.5 mmol). The
resulting colorless solid was separated by filtration and washed
with ethanol. Recrystallization from ethanol gave white needles
of 10a (0.7 g, 44%). 10a : 1H NMR (CD2Cl2) δ 2.5 (s, CH3), 6.6
(t, J ) 7 Hz, 1 H), 7.2 (dt, J ) 7, 1 Hz, 1 H), 7.4 (d, J ) 7 Hz,
1 H), 7.5-7.7 (m, 10 H) (arom); FAB-MS m/z 632 (M+), 551,
471, 355, 275. 11a : 1H NMR (CD2Cl2) δ 2.5 (s, CH3), 6.6 (t, J
) 7 Hz, 1 H), 7.2 (dt, J ) 7, 1 Hz. 1 H), 7.4 (d, J ) 7 Hz, 1 H),
7.5-7.7 (m, 10 H) (arom); EI-MS m/z 726 (M+), 599, 471, 401,
275, 197.

Binuclear Gold(I)-Gold(III) Complex
Organometallics, Vol. 19, No. 26, 2000 5635
Digold(I) Com plex [Au 2I2{µ-2,2′-P h 2P (5,5′-Me2C6H3C6H3)-
P P h 2}] (8b). When heated at 50 °C for 2 h a solution of
complex 4b (45 mg, 0.038 mmol) in toluene (5 mL) became
colorless. The solution was evaporated under reduced pressure,
and the colorless compound 8b was precipitated almost
quantitatively by addition of hexane. Crystals suitable for
X-ray crystallography were obtained from dichloromethane/
hexane: 1H NMR (CD2Cl2) δ 1.8 (s, 2CH3), 6.1 (d, J ) 4 Hz, 2
H), 7.0-7.2 (m, 4 H), 7.4-7.7 (m, 20 H), 7.8-8.0 (m, 4 H)
(arom); FAB-MS m/z 1071 (M+ - I), 747, 365.
5,5′-D i m e t h y l-2,2′-b i p h e n y ly l)b i s (d i p h e n y lp h o s -
p h in e) (12b). A suspension of 8b (30 mg, 0.025 mmol) in
degassed ethanol (10 mL) was stirred for 24 h with an aqueous
solution of NaCN. The white solid that had formed was filtered
and washed with water. Recrystallization from hexane af-
forded 13 mg (0.024 mmol, 93%) of 12b as colorless needles,
mp 182-183 °C: 1H NMR (CD2Cl2) δ 2.1 (s, 2CH3), 6.6 (d, J )
4 Hz, 2 H), 6.9-7.1 (m, 4 H), 7.1-7.5 (m, 20 H) (arom); 31P-
{1H} NMR (CD2Cl2) δ -14.9 (s); EI-MS m/z 549 (M+), 473, 365.
Anal. Calcd for C38H32P2: C, 82.89; H, 5.86; P, 11.25. Found:
C, 82.52; H, 5.92; P, 10.93.
4. The structure of 1a was solved by Patterson methods;44 the
others by direct methods (SIR 92).45 They were expanded by
use of Fourier techniques.46 Hydrogen atoms were included
at geometrically determined positions, which were periodically
recalculated but not refined. Methyl hydrogen atoms were
oriented to best-fit peaks in difference electron density maps.
The neutral atom scattering factors were taken from ref 47;
∆f′ and ∆f′′ values and mass attenuation coefficients were
taken from ref 48. Anomalous dispersion effects were included
49
in Fcalc
.
All calculations were performed with the teXsan
crystallographic software package.50
Su p p or t in g In for m a t ion Ava ila b le: Full crystallo-
graphic data for 1a , 8a , 8b, and 11a including tables of atomic
coordinates, anisotropic displacement parameters and bond
lengths and angles is available free of charge via the Internet
at http://pubs.acs.org.
OM000672Y
(44) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C.
PATTY: The DIRDIF Program System; Technical Report of the
Crystallography Laboratory; University of Nijmegen: The Nether-
lands, 1992.
(45) Altomare, A.; Cascarano, M.; Giacovazzo, C.; Guagliardi, A.;
Burla, M. C.; Polidori, G.; Camalli, M. J . Appl. Crystallogr. 1994, 27,
435.
(46) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
de Gelder, R.; Israel, R.; Smits, J . M. M. The DIRDIF-94 Program
System; Technical Report of the Crystallography Laboratory; Univer-
sity of Nijmegen: The Netherlands, 1994.
(47) Cromer, D. T.; Waber, J . T. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, England, 1974; Vol IV.
(48) International Tables for Crystallography; Wilson, A. J . C., Ed.;
Kluwer Academic: Dordrecht, The Netherlands, 1992; Vol. C.
(49) Ibers, J . A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
(50) teXsan: Single-Crystal Structure Analysis Software, Version
1.8; Molecular Structure Corp.: 3200 Research Forest Dr., The
Woodlands, TX 77381, 1997.
Kin etic Exp er im en ts. (1) A sample of the digold(II)
complex was dissolved in CDCl3 in an NMR tube and placed
in the NMR spectrometer set to 310 K. The half-lives of the
digold(II) compounds were determined from the increase in
peak height of the product or from the decrease in peak height
of the starting compound. (2) A small amount of 2a was placed
in a quartz cell of path length 1 cm. Toluene was added and
the cell heated with a Peltier heating system. The half-life was
determined from the decrease in absorbance at 354 nm. Half-
lives for 3a and 4a could not be determined because of the
very fast isomerization of these compounds.
X-r a y Cr ysta llogr a p h y. The crystal and refinement data
for compounds 1a , 8a , 8b, and 11a are summarized in Table