Oxidative addition of small molecules to a dinuclear Au(I) amidinate complex, Au2[2,6-Me2Ph2N2CH] 2. Syntheses and characterization of Au(II) amidinate complexes including one which possesses Au(II)-oxygen bonds

Article abstract of DOI:10.1021/ic700929e

The dinuclear Au(I) amidinate complex Au₂(2,6-Me ₂Ph-form)₂ (1) is isolated in quantitative yield by the reaction of (THT)AuCl and the potassium salt of 2,6-Me₂Ph-form in a 1:1 stoichiometric ratio. Various reagents such as Cl₂, Br ₂, I₂, CH₃I, and benzoyl peroxide add to the dinuclear Au(I)amidinate complex Au₂(2,6-Me₂Ph-form) ₂ to form oxidative-addition Au(II) metal-metal-bonded complexes 2, 3, 4, 5, and 6. The Au(II) amidinate complexes are stable as solids at room temperature. The structures of the dinuclear Au₂(2,6-Me ₂Ph-form)₂ and the Au(II) oxidative-addition products Au₂(2,6-Me₂Ph-form)₂X₂, X = Cl, Br, I, are reported. Crystalline products with an equal amount of oxidized and unoxidized complexes in the same unit cell, [Au₂(2,6-Me ₂Ph-form)₂X₂][Au₂(2,6-Me ₂Ph-form)₂], X = Cl, 2m, or Br, 3m, are isolated and their structures are presented. The structure of [Au₂(2,6-Me ₂Ph-form)₂X₂][Au₂(2,6-Me ₂Ph-form)₂], X = Cl has a Au(II)-Au(II) distance slightly longer, 0.05A, than that observed in the fully oxidized product Au ₂(2,6-Me₂-form)₂Cl₂,2. The gold-gold distance in the dinuclear complex decreases upon oxidative addition with halogens from 2.7 to 2.5 A, similar to observations made with the Au(I) dithiolates and ylides. The oxidative addition of benzoyl peroxide leads to the isolation of the first stable dinuclear Au(II) nitrogen complex possessing Au-O bonds, Au₂(2,6-Me₂Ph-form)₂(PhCOO)₂, 6, with the shortest Au-Au distance known for Au(II) amidinate complexes, 2.48 A. The structure consists of unidentate benzoate units linked through oxygen to the Au(II) centers. The replacement of the bromide in 3 by chloride, and the benzoate groups in 6 by chloride or bromide also occurs readily. The unit cell dimensions are, for 1, a = 7.354(6) A, b = 9.661(7) A, c = 11.421(10) A, α = 81.74(5)°, β = 71.23(5)°, and γ = 86.07(9)° (space group P1, Z = 1), for 2·1.5C ₆H₁₂, a = 11.012(2) A, b = 18.464(4) A, c = 19.467(4) A, α = 90°, β = 94.86(3)°, and γ = 90° (space group P2₁/c, Z = 4), for 2m·ClCH ₂CH₂Cl, a = 16.597(3) A b = 10.606(2) A, c = 19.809(3) A, α = 90°, β = 94.155(6)°, and γ = 90° (space group P2₁/n, Z = 2), for 3m, a = 16.967(3) A, b = 10.783(2) A, c = 20.060(4) A, α = 90°, β = 93.77(3)°, and γ = 90° (space group P2₁/n, Z = 2), for 4·THF, a = 8.0611(12) A, b = 10.956(16) A, c = 11.352(17) A, α = 84.815(2)°, β = 78.352(2)°, and γ = 88.577(2)° (space group P1, Z = 1), for 5, a = 16.688 A, b = 10.672(4) A, c = 19.953(7) A, α = 90.00 (6)°, β = 94.565(7)°, and γ = 90.00° (space group P2₁/n, Z = 4), for 6·0.5C₇H₈, a = 11.160(3) A, b = 12.112(3) A c = 12.364(3) A, α = 115.168(4)°, β = 161.112(4)°, and γ = 106.253(5)° (space group P1, Z = 1).

Full text of DOI:10.1021/ic700929e

Inorg. Chem. 2007, 46, 9692−9699
Oxidative Addition of Small Molecules to a Dinuclear Au(I) Amidinate
Complex, Au2[(2,6-Me2Ph)2N2CH]2. Syntheses and Characterization of
Au(II) Amidinate Complexes Including One Which Possesses
Au(II)−Oxygen Bonds
Hanan E. Abdou, Ahmed A. Mohamed, and John P. Fackler, Jr.*
Laboratory for Molecular Structure and Bonding, Department of Chemistry,
Texas A&M UniVersity, College Station, Texas 77843-3255
Received May 14, 2007
The dinuclear Au(I) amidinate complex Au2(2,6-Me2Ph-form)2 (1) is isolated in quantitative yield by the reaction of
(THT)AuCl and the potassium salt of 2,6-Me2Ph-form in a 1:1 stoichiometric ratio. Various reagents such as Cl2,
Br2, I2, CH3I, and benzoyl peroxide add to the dinuclear Au(I)amidinate complex Au2(2,6-Me2Ph-form)2 to form
oxidative-addition Au(II) metal
stable as solids at room temperature. The structures of the dinuclear Au2(2,6-Me2Ph-form)2 and the Au(II) oxidative-
addition products Au2(2,6-Me2Ph-form)2X2, X Cl, Br, I, are reported. Crystalline products with an equal amount
of oxidized and unoxidized complexes in the same unit cell, [Au2(2,6-Me2Ph-form)2X2][Au2(2,6-Me2Ph-form)2], X
Cl, 2m, or Br, 3m, are isolated and their structures are presented. The structure of [Au2(2,6-Me2Ph-form)2X2][Au2(2,6-
Me2Ph-form)2], X Cl has a Au(II) Au(II) distance slightly longer, 0.05Å, than that observed in the fully oxidized
product Au2(2,6-Me2-form)2Cl2, 2. The gold gold distance in the dinuclear complex decreases upon oxidative addition
−metal-bonded complexes 2, 3, 4, 5, and 6. The Au(II) amidinate complexes are
)
)
)
−
−
with halogens from 2.7 to 2.5 Å, similar to observations made with the Au(I) dithiolates and ylides. The oxidative
addition of benzoyl peroxide leads to the isolation of the first stable dinuclear Au(II) nitrogen complex possessing
Au−O bonds, Au2(2,6-Me2Ph-form)2(PhCOO)2, 6, with the shortest Au−Au distance known for Au(II) amidinate
complexes, 2.48 Å. The structure consists of unidentate benzoate units linked through oxygen to the Au(II) centers.
The replacement of the bromide in 3 by chloride, and the benzoate groups in 6 by chloride or bromide also occurs
readily. The unit cell dimensions are, for 1, a
â ) 71.23(5) , and γ ) 86.07(9) (space group P1
19.467(4) Å, R ) 90 â ) 94.86(3) , and γ ) 90
19.809(3) Å, R ) 90
10.783(2) Å, c 20.060(4) Å, R ) 90
8.0611(12) Å, b 10.956(16) Å, c
(space group P1, Z 1), for 5, a 16.688 Å, b
â ) 94.565(7) , and γ ) 90.00 (space group P21/n, Z 4), for 6
12.112(3) Å, c 12.364(3) Å, R ) 115.168(4) â ) 161.112(4) , and γ ) 106.253(5)
1).
)
7.354(6) Å, b
)
9.661(7) Å, c
)
)
)
11.421(10) Å, R ) 81.74(5)
11.012(2) Å, b 18.464(4) Å,
4), for 2m ClCH2CH2Cl, a
, and γ ) 90 (space group P21/n, Z
â ) 93.77(3) , and γ ) 90 (space
11.352(17) Å, R ) 84.815(2)
°,
°
°
h
, Z 1), for 2
)
‚
1.5C6H12, a
)
c
)
°
,
°
°
(space group P21/c, Z
‚
)
16.597(3) Å, b
2), for 3m, a
group P21/n, Z
78.352(2) , and γ ) 88.577(2)
Å, R ) 90.00 (6)
Å, b
)
)
)
10.606(2) Å, c
16.967(3) Å, b
)
)
THF, a
°
,
â ) 94.155(6)
°
°
)
)
°
,
°
°
2), for 4
‚
)
)
)
°, â )
°
°
h
)
)
)
10.672(4) Å, c
)
)
19.953(7)
11.160(3)
°
,
°
°
)
‚
0.5C7H8, a
)
)
°
,
°
° (space group P1h,
Z
)
Introduction
compounds occur with gold in the oxidation states +I and
+III, which have electronic configurations [Xe]4f145d10 and
[Xe]4f145d8, respectively.1 It has been known that there is a
strong tendency for Au(II) products to disproportionate to
form Au(I) and Au(III) materials.2 However, oxidative
addition results in the formation of a Au(II)-Au(II) bond.
Gold-nitrogen compounds with Au(II)-to-nitrogen bonds
are very scarce.1 The great majority of gold-nitrogen
* To whom correspondence should be addressed. E-mail: fackler@
mail.chem.tamu.edu. Fax: (979) 845-2373. Tel: (979) 845-0548.
(1) Gold Progress in Chemistry, Biochemistry, and Technology; Schmid-
baur, H., Ed.; Wiley: West Sussex, England, 1999.
4+
The Au2 core derivatives are the most stable and most
9692 Inorganic Chemistry, Vol. 46, No. 23, 2007
10.1021/ic700929e CCC: $37.00
© 2007 American Chemical Society
Published on Web 10/03/2007

OxidatiWe Addition to a Dinuclear Au(I) Amidinate Complex
Chart 1
Table 1. X-ray Data Collection and Structure Refinement for
Complexes 1, 2‚1.5C6H12, and 2m•ClCH2CH2Cl
compound
1
2•1.5C6H12
2m•ClCH2CH2Cl
empirical
formula
fw
cryst syst
space group
a(Å)
C34H38Au2N4
C43H56Au2Cl2N4
C70H80Au4N8Cl4
896.62
tricinic
P1h
1093.76
monoclinic
P21/c
11.012(2)
18.464(4)
19.467(4)
90.00
94.86(3)
90.00
3943.7(14)
4
1962.1
monoclinic
P21/n
16.597(3)
10.606(2)
19.809(3)
90.00
94.155(6)
90.00
7.354(6)
9.661(7)
11.421(10)
81.74(5)
71.23(5)
86.07(9)
760.1(11)
1
b(Å)
c(Å)
R(°)
commonly found Au(II) complexes.2 The formation of
metal-metal-bonded Au(II) products is strongly dependent
on the type of the ligands bonded to the Au(I) centers. The
charge on the metal centers and the metal-metal distance,
which result from the ligand type bonded to the Au(I) atoms,
both influence the oxidation process. Anionic ligands such
as the ylides are known to support this process and even
allow further oxidation to stable dinuclear Au(III) products.
It has been suggested3 that the strong σ-donor capability of
carbon atoms in the ylide ligands, promoted by the presence
of the four-coordinate onium phosphorus ylide centers, is
responsible for the ease of the reactions and stability of the
products.3a,b Mixed sulfur-carbon methylene thiophospho-
nate ligands also produce Au(II) products, but these are
somewhat less stable.3
With other sulfur ligand complexes such as the dithiocar-
bamates, 1,1-dithiolates, and the mixed-ligand dithiophos-
phinate-ylide species, formation of metal-metal-bonded
Au(II) products has been observed.2 However, these sulfur
ligand products are considerably less stable than the Au(II)
ylides. Electron delocalization associated with the π system
of these ligands appears to play a role in stabilizing the Au-
(II) products. The structurally similar dinuclear Au(I) xan-
thate4 shows no evidence of formation of stable Au(II)
products, presumably because charge delocalization onto the
ligand oxygen atoms is greatly diminished relative to the
charge on the P atoms of the ylides and other phosphorus
compounds or the N atoms of the dithiocarbamates. Di-
nuclear cationic diphosphine Au(I) complexes such as
[Au2(diphos)2)]2+, diphos ) CH2(PPh2)2, show no tendency
at all to form Au(II) products.2
â(°)
γ(°)
V(Å3)
Z
3477.9(11)
2
R1, wR2
GOF
0.047, 0.124
1.044
0.0689, 0.1707
1.015
0.1104, 0.2956
1.334
of the transition metals has produced complexes with
extraordinarily short M-M distances.6 Preliminary work with
oxidative addition to Au-N has been reported recently by
our group.7,8
Our work with Au(I) amidinates has been found to be
successful in producing products of various nuclearity
such as dinuclear, trinuclear, and tetranuclear species.7,9-11
The tetranuclear Au(I) clusters Au4(ArNC(H)NAr)4, Ar )
C6H4-4-OMe,9 C6H3-3,5-Cl2,9 C6H4-4-Me,9 C6H4-2-CF3,10
C6F5,10 C10H7,10 and ArNC(Me)NAr, Ar ) C6H511, and
ArNC(Ph)NAr, Ar ) C6H5,10 have been synthesized and
described structurally. The dinuclear and trinuclear Au(I)
amidinates can be isolated when the amidinate has sterically
bulky groups in the ortho positions of the aryl groups.7 The
trinuclear species Au3(2,6-Me2Ph-form)2(THT)Cl and Au3(2,6-
ipr2Ph-form)2(THT)Cl were isolated by the reaction of the
potassium salt of the formamidinate ligand with (THT)AuCl
in a 1:1.5 stoichiometric ratio.7 Tetranuclear Au(I) complexes
with mixed pyrazolate-amidinate nitrogen ligands, Au4(3,5-
Ph2pz)2(2,6-Me2Ph-form)2 and Au4(3,5-Ph2pz)3(2,6-Me2Ph-
form), also have been prepared.12
Preliminary studies of the oxidative addition of several
small molecules to the dinuclear Au(I) amidinate, Au2(2,6-
Me2Ph-form)2, have been communicated.7,8 Here we report
details of the syntheses of dinuclear Au(II) amidinate
complexes formed by addition of Cl2, Br2, I2, and CH3I, and
the first example involving a Au(II)-oxygen bond formed
Recently there has been a growing interest in another class
of anionic bridging ligands, the amidinates [ArNHC(H)NAr]-1.
The amidinate ligands have the ability to bridge the metal
ions and bring the metal ions close together, facilitating the
formation of short metal-metal distances and Au(II)-Au-
(II) bond formation.5 In addition, these ligands can delocalize
electron density through their B-bonding network and
strongly donate π electron density to the metal atoms.5 The
use of these amidinate ligands in the coordination chemistry
(6) (a) Clerac, R.; Cotton, F. A.; Dunbar, R. A.; Murillo, C. A.; Wang,
X. Inorg. Chem. 2001, 40, 420-426. (b) Cotton, F. A.; Lin, C.;
Murillo, C. A. Inorg. Chem. 2000, 39, 4574-4578. (c) Cotton, F. A.;
Daniels, L. M.; Murillo, C. A.; Schooler, P. J. Chem. Soc. Dalton
Trans. 2000, 2007-2012. (d) Cotton, F. A.; Daniels, L. M.; Murillo,
C. A.; Schooler, P. J. Chem. Soc. Dalton Trans. 2000, 2001-2005.
(e) Cotton, F. A.; Daniels, L. M.; Matonic, J. H.; Murillo, C. A. Inorg.
Chim. Acta 1997, 256, 277-282.
(7) Abdou, H. E.; Mohamed, A. A.; Fackler, J. P., Jr. Inorg. Chem. 2005,
44, 166-168.
(8) Abdou, H. E.; Mohamed, A. A.; Fackler, Jr., J. P. Z. Naturforsch. B
2004, 59, 1480-1482.
(9) Mohamed, A. A.; Abdou, H. E.; Irwin, M. D.; Lo´pez-de-Luzuriaga,
J. M.; Fackler, Jr., J. P. J. Cluster Sci. 2003, 14, 253-266.
(10) Abdou, H. E.; Mohamed, A. A.; Lo´pez-de-Luzuriaga, J. M.; Fackler,
Jr., J. P. J. Cluster Sci. 2004, 15, 397-411.
(11) Abdou, H. E.; Mohamed, A. A.; Fackler, Jr, J. P. J. Cluster Sci. 2007,
in press.
(2) Laguna, A.; Laguna, M. Coord. Chem. ReV. 1999, 193-195, 837-
856.
(3) (a) Fackler, J. P. Polyhedron 1997, 16, 1. (b) Fackler, J. P. Inorg.
Chem. 2002, 41, 6959. (c) Grohmann, A.; Schmidbaur, H. In
ComprehensiVe Organometallic Chemistry II; Abel, E. W., Stone, F.
G., Wilkinson G., Eds.; Pergamon, Oxford, 1995; Vol. 3, pp 1-56.
(4) Mohamed, A. A.; Kani, I.; Ramirez, A. O.; Fackler, Jr., J. P. Inorg.
Chem. 2004, 43, 3833-3839.
(5) Barker, J.; Kilner, M. Coord. Chem. ReV. 1994, 133, 219-300 and
references cited therein. (b) Patai, S. The Chemistry of Amidines and
Imidates; Wiley: New York, 1975; Vol. 1.
(12) Abdou, H. E.; Mohamed, A. A.; Fackler, Jr, J. P. Inorg. Chem. 2007,
46, 141-146.
Inorganic Chemistry, Vol. 46, No. 23, 2007 9693

Abdou et al.
Table 2. Details of X-ray Data Collection and Structure Refinement for Complexes 3m, 4‚THF, 5, and 6‚0.5C7H8
compound
3m
4•THF
5
6•0.5C7H8
empirical formula
fw
cryst syst
space group
a(Å)
C68H76Au4Br2N8
1951.03
monoclinic
P21/n
16.967(3)
10.783(2)
20.060(4)
90.00
93.77 (3)
90.00
3662.1(13)
2
C38H46Au2I2N4O
1150.43
triclinic
C35H41Au2N4I
1038.62
monoclinic
P21/n
16.688(6)
10.672(4)
19.953(7)
90.00
94.565(7)
90.00
3542(2)
4
C48H48Au2N4O4
1210.90
triclinic
P1h
P1h
8.0611(12)
10.956(16)
11.352(17)
84.815(2)
78.352(2)
88.577(2)
977.9(3)
1
11.160(3)
12.112(3)
12.364(3)
115.168(4)
161.112(4)
106.253(5)
1355.4(6)
1
b(Å)
c(Å)
R(°)
â(°)
γ(°)
V(Å3)
Z
R1, wR2
GOF
0.100, 0.2429
0.966
0.0422, 0.1204
1.062
0.0581, 0.1329
1.133
0.0691, 0.1964
1.193
Table 3. Selected Bond Distances (Å) and Angles (deg) for Complexes
1, 2, and 2m
Table 4. Selected Bond Distances (Å) and Angles (deg) for Complexes
3m, 4, 5, and 6
[Au2(2,6-Me2Ph-form)2][Au2(2,6-Me2Ph-form)2Br2], 3m
Au2(2,6-Me2Ph-form)2, 1
Au(1)-N(1)
Au(1)-N(2)
Au(1)-Br(1)
Au(1)-Au(1A)
N(1)-C(1)
2.004(17)
2.023(18)
2.470(2)
2.5251(15) Br(1)-Au(1)-Au1A
1.32(3)
1.28(2)
N(1)-Au(1)-N(2)
N(1)-Au(1)-Br(1)
N(1)-Au(1)-Au(1A)
173.4(6)
93.1(4)
86.9(4)
179.62(10)
121.2(14)
N(2)-Au(1)-N(1)
Au(1)-N(2)
N(1)-C(1)
171.1(6)
2.026(13)
1.36(2)
N(2)-C(1)-N(1)
127.8(15)
2.018(13)
2.712(2)
Au(1)-N(1)
Au(1)‚‚‚Au(1)
N(2)-C(1)
1.31(2)
C(1)-N(1)-Au(1)
Au2(2,6-Me2Ph-form)2Cl2, 2
C(1)-N(2A)
N(1)-Au(1)-N(3)
N(1)-C(1)-N(2)
Au(2)-Cl(2)
Au(2)-Au(1)
Au(1)-N(1)
175.0(4)
124.3(10)
2.366(3)
2.5176(7)
2.022(8)
N(2)-Au(2)-N(4)
174.4(4)
Au2(2,6-Me2Ph-form)2I2, 4
N(2)-C(1A)-N(1A)
Au(1)-Au(1A)
Au(1)-I(1)
126.1(5)
2.5794(4)
2.6828(4)
1.325(7)
N(2)-Au(1)-N(1)
Au(1)-N(1)
N(2)-C(1)
173.36(16)
2.027(4)
1.310(7)
N(2)-C(1)
N(1)-C(1)
1.328(14)
1.318(14)
N(1)-C(1)
[Au2(2,6-Me2Ph-form)2][Au2(2,6-Me2Ph-form)2Cl2], 2m
[Au2(o-Me2-form)2CH3I], 5
N(2A)-Au(1A)-N(1A) 174.8(4) N(2AA)-Au(1B)-I(1) 92.5(3)
I(1)-Au(1B)-Au(1A) 178.72(7)
Au(1)-(N1)
1.99(3)
Au(2)-N(4)
2.03(3)
2.7098(15)
1.36(3)
Au(1)-Au(1A)
N(2)-C(1A)
2.5671(19) Au(2)-Au(2A)
1.30(4)
174.6(10)
N(1A)-Au(1A)-C(1)
Au(1A)-Au(1B)
N(2AA)-C(10A)
Au(1A)-N(2A)
92.3(3)
2.5293(11) Au(1A)-C(1)
1.318(16)
2.011(10)
C(1)-N(1)
2.120(10)
2.499(3)
N(1)-Au(1)-N(2)
N(3)-Au(2)-N(4)
169.1(7)
Au(1B)-I(1)
N(3)-Au(2)-Au(2A) 83.5(5)
N(2)-C(1A)-N(1A) 127(3)
N(2)-Au(1)-Au(1A) 87.4(7)
Au2(2,6-Me2Ph-form)2(PhCOO)2, 6
O(2)-C(18)-O(1)
O(1)-C(18)
130.4(11)
1.284(14)
1.323(16)
1.264(15)
N(2)-Au(1)-N(1)
Au(1)-Au(1A)
Au(1)-N(1)
175.5(4)
by the reaction with benzoyl peroxide, Chart 1. These
materials are relatively stable as solids and in solution.
Attempts to oxidatively add thiolate ligands with tetraeth-
ylthiuram disulfide failed to give the expected oxidative-
addition product [Au2(2,6-Me2-form)2][S2CNEt2]2,13 as in the
case of the dinuclear Au(I) ylide, [Au(CH2)2PPhMe]2[S2-
CNEt2]2,14 and resulted in the formation of the dinuclear
complex Au2[S2CN(C2H5)2]2, which was reported previously
by the reaction of Au(THT)Cl with KS2CN(C2H5)2 in THF.15
The diethyldithiocarbmate ligand replaced the bulky amidi-
nate ligand, (2,6-Me2-form), in the dinuclear Au(I) amidinate
1, but the oxidation product was not identified.13 The reaction
with Hg(CN)2 results in the formation of the 2D mercury-
(II) cyanide coordination polymer, [Au2(o-Me2-form)2]‚2Hg-
(CN)2.2THF,16 not the oxidative addition product expected
as had been observed with the ylide complex.16
2.4899(10)
2.010(10)
2.045(8)
N(1)-C(1)
O(2)-C(18)
Au(1)-O(1)
ligand was purchased from TCI, Tokyo. The solvents THF, CH2-
Cl2, cyclohexane, toluene, and ether were purchased from Aldrich
and used as received. Br2, I2, CH3I, CCl4 CBr4, CI4, CH2Br2, CH2I2,
ClCH2CH2Cl, BrCH2CH2Br, ICH2CH2I, PhICl2, Bu4NBr, (Ph-
COO)2, and KOH were purchased from Aldrich. Elemental analyses
were performed by Guelph Chemical Laboratories, Ltd. and
Chemisar Laboratories Inc, Guelph, Ontario, Canada. UV-vis
spectra were recorded on a Shimadzu UV-2501 PC spectrometer.
1H spectra were recorded on a Unity Plus 300 NMR spectrometer
using solvent peaks to reference the chemical shifts (δ).
Synthesis of Au2(2,6-Me2Ph-form)2, 1. N,N′-Bis(2,6-dimethyl)-
phenylformamidine (126 mg, 0.5 mmol) was stirred with (28 mg,
0.5 mmol) of KOH in 20 mL of THF for 24 h. The solution was
colorless. Au(THT)Cl (160 mg, 0.5 mmol) was added and stirring
continued for an additional 4-5 h. The solution was filtered and
cyclohexane was added to form an off-white precipitate. The
product was filtered and recrystallized from THF/cyclohexane to
give colorless crystals. Yield: 75%. Anal. Calcd for C34H38-
Experimental
General Procedures. All glassware was oven-dried prior to use.
Triethylorthoformamate (orthoester) and 2,6-dimethylaniline were
purchased from Aldrich and used as received. Tetrahydrothiophene
1
Au2N4: C, 45.53; H, 4.24. Found: C, 45.67; H, 4.45. H NMR
(CDCl3, ppm): 2.48 (3H, 8(CH3)), 6.91-6.99 (m, 12H (CH,
phenyl)), 7.44 (1H, 2(CH) amidine). UV-vis (CH2Cl2): λmax (nm),
ꢀ (L/M-1 cm-1): 259, 60 800.
(13) Abdou, H. E.; Ph.D. thesis, 2006, Texas A&M University, College
Station, TX.
(14) Heinrich, D. D.; Staples, R. J.; Fackler, J. P., Jr. Inorg. Chim. Acta
1995, 229, 61-75.
Au2(2,6-Me2Ph-form)2Cl2, 2‚1.5C6H12, and [Au2(2,6-Me2-
form)2Cl2][Au2(2,6-Me2-form)2], 2m‚ClCH2CH2Cl. Compound 2‚
1.5C6H12 is prepared by using any of several oxidizing agents, PhI‚
Cl2, CCl4, CH2Cl2, ClCH2CH2Cl, and aqua regia. For example,
(15) Heinrich, D. D.; Wang, J.; Fackler, J. P., Jr. Acta Crystallogr. 1990,
46, 1444-1447.
(16) Mohamed, A. A.; Abdou, H. E.; Fackler, Jr., J. P. Inorg. Chem. 2006,
45, 11-12.
9694 Inorganic Chemistry, Vol. 46, No. 23, 2007

OxidatiWe Addition to a Dinuclear Au(I) Amidinate Complex
CH2Cl, (0.31 g, 0.03 × 10-2 mol) of Au2(2,6-Me2-form)2 was mixed
with 5-10 mL (excess) of the solvent and the mixture stirred for
2-3 days (7 days in the case of CH2Cl2), then filtered. The solvent
was removed under vacuum, and the product was collected. Yield:
80%. Anal. Calcd For 2‚1.5C6H12, C43H56Au2Cl2N4: C, 42.20; H,
3.95. Found: C, 41.77; H, 3.88. 1H NMR (CDCl3, ppm): 2.51 (s,
24H (CH3)), 6.99 (br, 12H (CH, phenyl)), 7.97 (s, 2H (CH
amidinate)). UV-vis (CH2Cl2): λmax (nm), ꢀ (L/M-1 cm-1): 346,
29 400; 456, 5535. The crystalline product [Au2(2,6-Me2-form)2-
Cl2][Au2(2,6-Me2-form)2], 2m‚ClCH2CH2Cl, which contains an
equal amount of oxidized and unoxidized complexes in the same
unit cell, was isolated when the reaction of the dinuclear with the
halogenated solvents ClCH2CH2Cl was stopped after 3-4 h of
stirring (before oxidizing all the Au(I) material).
Au2(2,6-Me2Ph-form)2Br2, 3, and [Au2(2,6-Me2-form)2Br2]-
[Au2(2,6-Me2-form)2], 3m. Several oxidizing agents, Br2, CBr4,
BrCH2CH2Br, and CH2Br2, can be used to prepare compound 3.
An example is given here. Au2(2,6-Me2Ph-form)2 (0.22 g, 2.5 ×
10-4 mol) was dissolved in 10 mL of THF, and CBr4 (0.08 g, 2.5
× 10-4 mol) was added. After 20 min of stirring, the color of the
reaction mixture changed to light brown. The reaction mixture was
stirred for 2-3 days, then filtered. The THF solvent was removed
under vacuum, and the product was collected. Brown crystals of 3
were formed by slow evaporation of a THF/cyclohexane solution
at room temperature. Yield: 85%. Anal. Calcd for 3, C68H76Au4N8-
Br2: C, 41.81; H, 3.92. Found: C, 42.22; H, 3.54. 1H NMR (CDCl3,
ppm): 2.54 (s, 24H, (CH3)), 6.99 (br, 12H (CH, phenyl)), 8.13 (s,
2H (CH amidinate)). UV-vis (CH2Cl2): λmax (nm), ꢀ (L/M-1 cm-1):
379, 27 200. The crystalline product 3m, which contains an equal
amount of oxidized and unoxidized dinuclear complexes in the same
unit cell, was isolated when the reaction of the dinuclear with the
halogenated solvents was stopped after 3-4 h of stirring before all
the Au(I) material was oxidized.
Figure 1. Thermal ellipsoid plot of 1 is drawn at the 50% probability
level. Hydrogen atoms are removed for clarity. Selected distances (Å): Au-
(1)‚‚‚Au(1A) 2.712 (2); Au-N(av) 2.022.
Au2(2,6-Me2Ph-form)2I2, 4‚THF. Several oxidizing agents, I2,
CI4, CH2I2, and ICH2CH2I, can be used to prepare compound 4‚
THF. An example is given here. Au2(2,6-Me2Ph-form)2 (0.22 g,
2.5 × 10-4 mol) was dissolved in 10 mL of THF and stirred for 15
min. I2 (0.07 g, 2.5 × 10-4 mol) was added. The color of the
reaction mixture changed to dark green after 5 min. The stirring
was continued for 2 h, and the reaction mixture was filtered. The
solvent was removed under vacuum, and the product was collected.
Brown crystals of 4‚THF were formed by slow evaporation at room
temperature of a THF solution. The oxidation also was achieved
with halogenated solvents CI4, CH2I2, and ICH2CH2I. Au2(2,6-Me2-
Ph-form)2 (0.22 g, 2.5 × 10-4 mol) was mixed with 5-10 mL
(excess) of the solvent, and the mixture was stirred for 2 h then
Figure 2. Thermal ellipsoid plot of 2 is drawn at the 50% probability
level. Hydrogen atoms are removed for clarity. Selected distances (Å): Au-
(1)‚‚‚Au(2) 2.517(2); Au(2)-Cl(2) 2.366(3); Au(1)-N(1) 2.022 (8).
Au2(2,6-Me2Ph-form)2, (0.31 g, 0.03 × 10-2 mol) was dissolved
in 5 mL THF and stirred for 15 min. PhI‚Cl2 (0.095 g, 0.03 ×
10-2 mol) was added, and the color of the solution changes to dark
green immediately. The reaction mixture was stirred for 3 h, then
filtered. The solvent was removed under vacuum and the product
was collected. Brown crystals of 2‚1.5C6H12 formed at room
temperature by slow evaporation of a THF/cyclohexane solution.
The oxidation by halogenated solvents CCl4, CH2Cl2, and ClCH2-
Chart 2
Inorganic Chemistry, Vol. 46, No. 23, 2007 9695

Abdou et al.
Figure 3. Thermal ellipsoid plot of 2m. Ellipsoids are drawn at the 50% probability level. Hydrogen atoms are removed for clarity.
Figure 4. Thermal ellipsoid plot of 3m drawn at the 50% probability
level. Hydrogen atoms are removed for clarity.
Figure 6. Thermal ellipsoid plot of 5 is drawn at the 50% probability
level. Hydrogen atoms are removed for clarity. The structure has a disorder
in the positions of the CH3 and iodide atoms. Selected distances (Å): Au-
(1A)‚‚‚Au(1B) 2.529(11).
Table 5. Au(II)-Au(II), Au(I)‚‚‚Au(I), and Au-Cl Bond Distances
(Å) in [Au2(2,6-Me2Ph-form)2X2][Au2(2,6-Me2Ph-form)2], X ) Cl, 2m,
and Au2(2,6-Me2Ph-form)2, 1
oxidizing
reagent
Au(II)-Au(II) Au(I)‚‚‚Au(I)
Au-Cl
CH2Cl2
aqua regia
PhICl2
ClCH2CH2Cl
CCl4
2.527(3)
-
-
-
2.360(18), 2.345(16)
2.368(3), 2.355(3)
2.365(2), 2.356(2)
2.321(8)
2.5242(7)
2.5176(6)
2.5671(19)
2.5502(13)
2.7098(15)
2.7132(14)
2.342(6)
Au2(2,6-Me2Ph-form)2(PhCOO)2, 6‚0.5C7H8. Au2(2,6-Me2Ph-
form)2 (0.11 g, 1.2 × 10-4 mol) was dissolved in 10 mL of toluene
and stirred for 15 min. [Ph(CO)O]2 (0.03 g, 1.2 × 10-4 mol) was
added, and the color of the reaction mixture gradually changed to
dark brown. The reaction mixture was stirred for 3 h, then filtered.
The solvent was removed under vacuum and the product was
collected. Dark brown crystals of 6 were formed by slow evapora-
tion of a toluene solution. Yield: 85%. Anal. Calcd for 6‚0.5C7H8,
Figure 5. Thermal ellipsoid plot of 4 is drawn at the 50% probability
level. Hydrogen atoms are removed for clarity. Selected distances (Å): Au-
(1)‚‚‚Au(1A) 2.579(4); Au(1)-I(1) 2.682(4)
filtered. The solvent was removed under vacuum and the product
was collected. Yield: 80%. Anal. Calcd For 4‚THF, C38H46-
Au2I2N4O: C, 35.49; H, 3.32. Found: C, 34.73; H, 3.66. 1H NMR
(CDCl3, ppm): 2.55 (s, 24H (CH3)), 6.99 (br, 12H (CH, phenyl)),
8.19 (s, 2H, (CH amidinate)). UV-vis (CH2Cl2): λmax (nm), ꢀ (L/
M-1 cm-1): 379, 17 300.
1
C55H56Au2N4O4: C, 52.20; H 4.42. Found: C, 52.40; H, 4.67. H
NMR (CDCl3, ppm): 2.54 (s, 24H (CH3)), 6.71-6.79 (m, 10H
(CH, benzoyl phenyl)), 6.92-7.00 (m, 12H (CH, phenyl)), 7.97
(s, 2H (CH amidinate)). UV-vis (CH2Cl2) : λmax (nm), ꢀ (L/M-1
cm-1): 345, 30 600.
Au2(2,6-Me2Ph-form)2CH3I, 5. To 0.23 g (2.5 × 10-4 mol) of
the dinuclear gold amidinate Au2(2,6-Me2Ph-form)2 in 20 mL of
freshly distilled ether in round-bottom flask, 0.5 mL (excess) of
CH3I was added. After stirring for 2 h under a N2 stream in an ice
bath, in the absence of light, a brown product was formed and then
Crystallographic Studies. Cell parameters and refinement results
of the gold amidinate complexes 1, 2, 2m, 3m, 4, 5, and 6 are
summarized in Tables 1 and 2. Tables 3 and 4 present important
interatomic distances and angles. X-ray data were collected using
a Siemens (Bruker) SMART CCD (charge-coupled device)-based
diffractometer equipped with a LT-2 low-temperature apparatus
operating at 110 K. A suitable crystal was chosen and mounted on
a glass fiber using cryogenic grease. Data were measured using ω
scans of 0.3°/frame for 60 s. The first 50 frames were recollected
1
filtered, 85% yield. H NMR (CDCl3, ppm): 1.37 (s, 3H (Au-
CH3)), 2.39 (s, 24H (CH3)), 6.78 (br, 12H (CH, phenyl)), 8.10 (s,
2H, (CH amidinate)). Anal. Calcd for 5, C35H41Au2IN4: C, 40.47;
H, 3.97. Found: C, 39.91; H, 4.05.
9696 Inorganic Chemistry, Vol. 46, No. 23, 2007

OxidatiWe Addition to a Dinuclear Au(I) Amidinate Complex
Table 6. Dinuclear Au(II) Ylide and Amidinate Complexes Characterized by X-ray Studies
complex
d(AuII‚‚‚AuII)
d(Au-X)
d(Au-R)
ref
[ClAu(CH2PPh2CH2)2AuCl]
[BrAu(CH2PPh2CH2)2AuBr]
[IAu(CH2PPh2CH2)2AuI]
2.600(1)
2.614(1)
2.650
2.388(8)
2.516(1)
2.693(8)
2
2
2
2
2
[(CH3)Au(CH2PPh2CH2)2AuI]
[(CH3)Au(CH2PMe2CH2)2AuI]
[PhCO2Au(CH2PPh2CH2)2AuO2CPh]
[ClAu(2,6-Me2Ph-form)2AuCl], 2
[BrAu(2,6-Me2Ph-form)2AuBr], 3m
[IAu(2,6-Me2Ph-form)2AuI], 4
[(CH3)Au2(2,6-Me2Ph-form)2AuI], 5
[PhCO2Au(2,6-Me2Ph-form)2AuO2CPh], 6
2.695(4)
2.695(4)
2.561(2)
2.517(7)
2.525(15)
2.579(4)
2.529(11)
2.489(10)
2.894(5)
2.117(13)
2.356(2)
2.470(2)
2.682(4)
2.50
2.13(5)
2.12
2
a
a
a
a
a
2.045(8)
a This work
at the end of data collection as a monitor for decay. No decay was
detected. Cell parameters were retrieved using SMART software
and refined using SAINT on all observed reflections.17 Data
reductions were performed using SAINT software.18 The structures
were solved by direct methods using SHELXS-97 and refined by
least-squares on F2, with SHELXL-97 incorporated in SHELXTL-
PC V 5.03.19,20 The structures were determined in the space groups
reported in Tables 1 and 2 by analysis of systematic absences.
Hydrogen atom positions were calculated by geometrical methods
and refined as a riding model.
for several days produced the completely oxidized products,
Au2(2,6-Me2Ph-form)2X2, X ) Cl, 2; X ) Br, 3, as was
confirmed by the UV-vis spectroscopy. In the reaction of
the halo-alkyls CHnXm to produce the dihalides, the qualita-
tive order of reactivity with the gold complexes (I > Br >
Cl) follows inversely the order of carbon-halogen bond
dissociation energy, C-Cl > C-Br > C-I.21
The replacement of the bromide from Au2(2,6-Me2Ph-
form)2Br2, 3, by chloride is achieved by adding 1 mol of
PhICl2 to 1 mol of 3 in polar solvent, CH3CN. After 30 min
of mixing the UV-vis peak of the bromide derivative, 3 at
379 nm in CH2Cl2 was shifted to 346 and 456 nm (shoulder),
indicating the formation of the dichloride product, 2. This
product also was obtained by metathesis (see below and
Chart 2).
The dropwise addition of methyl iodide, CH3I, to a solution
of Au2(2,6-Me2-form)2 in ether generates CH3Au(2,6-Me2-
Ph-form)2AuI, 5, in quantitative yield under nitrogen at
0 °C and in the absence of light.8 Crystal growth from ether
was successful at 0 °C after one week. The dark orange
brown crystals, which form as large blocks, are stable at room
temperature. A gold metal mirror forms around the wall of
the reaction vessel if the reaction is carried out in open air
at room temperature.
The benzoate addition product 6 was obtained by adding
an equivalent amount of benzoyl peroxide to a toluene
solution of the dinuclear amidinate complex. The reaction
was stirred for a few hours before the solvent was slowly
evaporated to form crystals. A brown product was isolated
in a good yield. The Au(II) product is stable at room
temperature. Infrared spectroscopic studies of the Au(II)
benzoate complex showed two intense bands at 1628 and
1578 cm-1 due to ν(CdO) and at 1320-1295 cm-1 for the
ν(C-O) frequencies. The separation between the two bands,
∼300 cm-1, is typical of unidentate benzoate bonding, a
“pseudo ester” character.22 The bonding of the benzoates to
the dinuclear Au(I) amidinate is similar to the unidentate
bonding observed in the ylide complexes which also adopt
a anti geometry.23 A facile metathesis replacement of the
benzoate groups in 6 by chloride or bromide was achieved
Results
Syntheses. The dinuclear complex Au2(2,6-Me2Ph-form)2,
1, is isolated in a nearly quantitative yield by the reaction of
(THT)AuCl with the potassium salt of 2,6-Me2Ph-form in a
1:1 stoichiometric ratio. The addition of 1 molar equiv of
Cl2, Br2, or I2 to the dinuclear amidinate, 1, in a THF solution
at room temperature produces an immediate color change
from colorless or light yellow to a very deep, dark green or
brown. Recrystallization produces dark orange or brown
crystals from which the X-ray crystallography established
Au(II) products 2-4, containing solvents such as THF or
cyclohexane in the lattice. Thermal gravimetric analysis and
differential thermal analysis showed the release of the solvent
followed by the loss of the halogen. The reactions of the
dinuclear complex with the halogenated solvents, CH2X2,
XCH2CH2X, and CX4 (X ) Cl, Br, I) also formed Au(II)
products. With the iodide derivative the reaction occurs in
the time of mixing. The analogous reactions with chloride
and bromide derivatives takes ∼2-3 days and 7 days with
CH2Cl2 in order to oxidize all of the Au(I) material. No
bridged CH2 product was observed as had been formed when
CH2Cl2 reacts with the dinuclear Au(I) ylides.3 Crystalline
products in which there are equal amounts of oxidized and
unoxidized complexes in the same unit cell, [Au2(2,6-Me2-
Ph-form)2X2][Au2(2,6-Me2Ph-form)2], X ) Cl, 2m; X ) Br,
3m, are isolated when the reaction is stopped after 3-4 h of
stirring (Chart 2). Continuous stirring of the reaction mixture
(17) SMART V 4.043 Software for the CCD Detector System; Bruker
Analytical X-Ray Systems: Madison, WI, 1995.
(18) SAINT V 4.035 Software for the CCD Detector System; Bruker
Analytical X-Ray Systems: Madison, WI, 1995.
(19) Scheldrick, G. M. SHELXS-97, Program for the Solution of Crystal
Structure; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(20) SHELXTL 5.03 (PC-Version), Program Library for Structure Solution
and Molecular Graphics; Bruker Analytical X-ray Systems, Madison,
WI, 1995.
(21) Atkins, P. W.; Jones, L. L. Chemical Principles; W. H. Freeman and
Company: New York, 2007; p 254.
(22) Handbook of Chemistry and Physics; Lide, D. R., Ed.; CRC Press:
Boca Raton, FL, 1992-93.
(23) Porter, L. C.; Fackler, Jr., J. P. Acta Crystallogr. 1986, 42, 1128-
1131.
Inorganic Chemistry, Vol. 46, No. 23, 2007 9697

Abdou et al.
disorder to be reported here. However, the X-ray structure
of 3 can be seen clearly in the X-ray structure of the oxidized
and unoxidized complexes 3 and 3m in the same unit cell
shown in Figure 4. The Au-X distances, Au-Cl ) 2.36 Å,
Au-Br ) 2.47 Å, Au-I ) 2.68 Å, are typical for these
Au(I) halide distances.2 The N-Au-N angles of 173.9° (av)
show a deviation from linearity. The Au-N distances
decreased from 2.035(7) Å in the dinuclear complex to
2.000-2.004 Å in the oxidative-addition products. The Au-
(II) atoms have nearly square planer coordination geometries
with formation of bonds to a second Au center, two N atoms,
and one halide atom.
A crystalline product in which there is an equal amount
of oxidized and unoxidized complexes in the same unit cell,
2m or 3m, was isolated when the reaction of dinuclear
complex with the halogenated solvents, CH2X2, XCH2CH2X,
and CX4 (X ) Cl, Br), was stopped after 3-4 h of stirring
before oxidizing all the Au(I) material. The X-ray structures
of 2m and 3m are shown in Figures 3 and 4, respectively.
The Au-Au and the Au-Cl distances in 2m changed from
2.52 (av) and 2.35 Å (av) in the fully oxidized complex, 2,
to 2.55 (av) and 2.34 Å (av), respectively, Table 5. The
reasons for these differences are small and presumably relate
to crystallographic difficulties.
Growing crystals of the methyl iodide addition product,
5, was successful at 0 °C over 1 week. Although well-shaped,
brown-black crystals were grown from ether, which dif-
fracted well, the spatial volume occupied by CH3 and I is
approximately identical. This leads to a disorder in the
positions of the CH3 and iodide atoms. While the Au(II)
atoms and the amidinate ligand atoms refine well, the CH3
and I atom positions remain uncertain regarding their exact
distances from the Au(II) atoms. The X-ray structure of 5
shows oxidized and unoxidized molecules in the same unit
cell of 1 and 5, respectively. Figure 6 shows the structure of
the oxidized product, 5, only. The Au-CH3 and Au-I
distances in 5 appear to be 2.12 and 2.50 Å, respectively,
while in the dinuclear Au(I) ylide, [(CH3)Au(CH2PMe2CH2)2-
AuI], the Au-CH3 and Au-I distances are 2.13(5) and
2.894(5) Å, respectively, Table 6.2 This apparent lack of a
amplified structural trans effect in the amidinate complex
may be related to the fact that the HOMO in this system
involves little M-M σ bonding as it is in the ylide complex3
but contains substantial M-L π* character. Unfortunately,
the crystallography is not sufficiently good due to the
disorder to dwell further on this point with this interesting
observation. The Au(II)-Au(II) distance increased consis-
tently for the addition products of the dinuclear Au(I) ylide
with chloride, bromide, iodide, and methyl iodide having
values of 2.600, 2.614, 2.650, and 2.69 Å, respectively, Table
6. With the dinuclear Au(I) amidinate, 1, the Au(II)-Au(II)
distances of the addition products with chloride, bromide,
and iodide increased to values of 2.517, 2.525, and 2.579
Å, respectively but decreased for methyl iodide product to
2.529 Å, Table 6. Since this latter distance is relatively
unaffected by disorder, we suspect that the M-L π*
character of the HOMO plays an important role structurally,
just as the LUMO of the Au(I) amidinate, which has largely
Figure 7. Thermal ellipsoid plot of 6 is drawn at the 50% probability
level. Hydrogen atoms are removed for clarity. Selected distances (Å): Au-
(1)‚‚‚Au(1A) 2.489(10); Au(1)-O(1) 2.045(8).
by adding equivalent amounts of PhICl2 or Bu4NBr to 6 in
polar solvents such as CH3CN, Chart 2.
After 5 min of mixing of PhICl2 with 6 in CH3CN/THF,
the color of the reaction mixture changed from yellow to
bright green, indicating the formation of the dichloride
product, 2, as confirmed by the UV-vis spectrum. The
reaction of 6 with Bu4NBr formed the dibromide derivative,
3, after 7 days of mixing (Chart 2).
Structure Results and Discussion. The dinuclear complex
1 is crystallized in the space group P1h, Figure 1. The
Au‚‚‚Au distance is 2.711(3) Å, and the N-Au-N angle is
170.2(3)°. To our knowledge, there is only one other example
of a symmetrically bridged dinuclear Au(I) nitrogen complex,
Au2[(Me3SiN)2C(Ph)]2; it has a Au‚‚‚Au distance of 2.646
Å.24 In complex 1, the Au‚‚‚Au distance, 2.711 Å, is shorter
than in the xanthate, Au2(nBu-xanthate)2 (2.849 Å),25 the
dithiophosphinate (AuS2PPh2)2 (3.085 Å),26 ylide [Au(CH2)2-
PPh2]2 (2.977 Å),27 and dithiophosphonate [AuS2PPh(OEt)]2
(3.042 Å);28 however, closer to the bond distance in the
dithiolates [PPN]2[Au2(µ2-η2-CS3)2](2.799 Å),29 [n-Bu4N]-
[Au(S2CdC(CN)2]2 (2.796 Å),30 and [Au(S2C-N(C5H11)2)]2
(2.769 Å).31
The Au(II) amidinate complexes 2, 3, and 4 readily form
crystals suitable for X-ray diffraction. X-ray crystallography
established the formation of Au(II) products containing
solvent such as THF or cyclohexane. The Au‚‚‚Au distance
decreases from 2.71 Å in the starting dinuclear complex to
2.51-2.57 Å in the oxidized species. The X-ray structures
of 2 and 4 are shown in Figures 2 and 5. The X-ray structure
of 3, even at 77 K, is not sufficiently well resolved due to a
(24) Fenske, D.; Baum, G.; Zinn, A.; Dehnicke, K. Z. Naturforsch., B:
Chem. Sci. 1990, 45, 1273-1278.
(25) Mohamed, A. A.; Kani, I.; Ramirez, A. O.; Fackler, Jr., J. P. Inorg.
Chem. 2004, 43, 3833-3839.
(26) Van Zyl, W. E.; Lo´pez-de-Luzuriga, J. M.; Fackler, Jr., J. P.; Staples,
R. J. Can. J. Chem. 2001, 79, 896-903.
(27) King, C.; Wang, J. -C.; Khan, M. N. I.; Fackler, Jr., J. P. Inorg. Chem.
1989, 28, 2145-2149.
(28) Van Zyl, W. E.; Staples, R. J.; Fackler, Jr., J. P. Inorg. Chem. Commun.
1998, 1, 51-54. (b) Van Zyl, W. E.; Lopez-de-Luzuriaga, J. M.;
Fackler, Jr., J. P. J. Mol. Struct. 2000, 516, 99-106.
(29) Vicente, J.; Chicote, M.-T.; Herrero, G. P.; Jones, P. G. J. Chem. Soc.,
Chem. Comun. 1995, 745-746.
(30) Nazrul, Md.; Khan, I.; Wang, S.; Fackler, Jr., J. P. Inorg. Chem. 1989,
28, 3579-3588.
(31) Mansour, M. A.; Connick, W. B.; Lachicotte, R. J.; Gysling, H. J.;
Eisenberg, R. J. Am. Chem. Soc. 1998, 120, 1329-1330.
9698 Inorganic Chemistry, Vol. 46, No. 23, 2007

OxidatiWe Addition to a Dinuclear Au(I) Amidinate Complex
amidinate carbon character, not M-M antibonding character
as in the ylides, influences the emission spectrum of the
complexes.
Au‚‚‚Au distance observed, 2.56-2.58 Å,2 in the dinuclear
Au(II) ylide complexes, Table 6. Similarly, the Au‚‚‚Au
distance in the oxidized product, 6, 2.48 Å, is the shortest
Au‚‚‚Au distance in the Au(II) amidinate complexes. The
short Au‚‚‚Au distance in these complexes is due to the weak
trans influencing ability of the carboxylate ligand.23
The structure of 6, Figure 7, consists of unidentate
benzoate units linked through oxygen to the Au(II) centers;
the two benzoate units are anti to each other. The carbon-
to-oxygen atom distances in the carbonyls are longer by 0.02
Å compared with free carbonyl O atoms (1.28 vs 1.264 Å).22
The Au-N distances decrease from 2.035(7) Å in the
dinuclear complex to 2.01 and 2.008 Å in the oxidative-
addition product. The Au-O distance is 2.045 Å. The Au
atoms have nearly square planar coordination geometries
considering formation of bonds to a second Au center, two
N atoms, and one O atom. The oxidative addition of benzoyl
peroxide to the dinuclear Au(I) ylide complex, Au2(CH2-
PPh2CH2)2 formed a Au(II) product with the shortest
Acknowledgment. The Robert A. Welch Foundation of
Houston, Texas is acknowledged for financial support of this
work. The DFT calculations were performed by Dr. Lisa
Perez who it thanked.
Supporting Information Available: X-ray crystallographic
files, in cif format, for complexes 2, 3, 4, 5, and 6. This material
is available free of charge via the Internet at http://pubs.acs.org.
IC700929E
Inorganic Chemistry, Vol. 46, No. 23, 2007 9699