Novel mixed coordination of N and C donors to gold-gold centers

Article abstract of DOI:10.1021/om200556x

Mixed-ligand gold(I) compounds featuring N and C connectivity from two dissimilar ligands, a formamidinate and a phosphorus ylide, are obtained by the reaction of a dinuclear gold(I) formamidinate with a phosphorus ylide in toluene solution under Schlenk conditions. When the reaction conditions such as polarity, basicity, and gold to ylide ratio are varied, a series of structures are produced, where the formamidinate (f = N,N′-bis(2,6-dimethylphenyl) methanimidamide) invariably bridges gold(I) centers. The aurophilic distances of Au(I)???Au(I) range around 3.00 A, whereas the ylide (dimethyldiphenylphosphonium, [H₂y]⁺) is monocoordinated as [Hy]. This produces open dinuclear species, with two terminal Hy's as the cation [Au₂f(Hy)₂]⁺ (1), with the nitrate anion or terminal Hy and chloride anion in [Cl-Au₂f(Hy)] (2), or Hy and phenyl in [Ph-Au₂f(Hy)] (3). The activation of the ylide ligand by base liberates the phenyl group which produces 3. A related cationic mononuclear moiety [Au(Hf)(Hy)] (4), with neutral amidinate and ylide, is produced from the neutral amidine upon reaction with [Au(THT)Cl] in a THF solution of ylide. These new compounds have been characterized by X-ray crystal structures, ¹H NMR, IR, and elemental analysis.

Full text of DOI:10.1021/om200556x

ARTICLE
pubs.acs.org/Organometallics
Novel Mixed Coordination of N and C Donors to GoldꢀGold Centers
Doris Y. Melgarejo, Gina M. Chiarella, and John P. Fackler, Jr.*
Department of Chemistry, P.O. Box 3012, Texas A&M University, College Station, Texas 77843-3255, United States
S Supporting Information
b
ABSTRACT: Mixed-ligand gold(I) compounds featuring N and C connec-
tivity from two dissimilar ligands, a formamidinate and a phosphorus ylide, are
obtained by the reaction of a dinuclear gold(I) formamidinate with a
phosphorus ylide in toluene solution under Schlenk conditions. When the
reaction conditions such as polarity, basicity, and gold to ylide ratio are varied,
a series of structures are produced, where the formamidinate (f = N,N0-
bis(2,6-dimethylphenyl)methanimidamide) invariably bridges gold(I) cen-
ters. The aurophilic distances of Au(I)
Au(I) range around 3.00 Å, whereas
3 3 3
the ylide (dimethyldiphenylphosphonium, [H2y]+) is monocoordinated as
[Hy]. This produces open dinuclear species, with two terminal Hy's as the
cation [Au2f(Hy)2]+ (1), with the nitrate anion or terminal Hy and chloride
anion in [Cl-Au2f(Hy)] (2), or Hy and phenyl in [Ph-Au2f(Hy)] (3). The
activation of the ylide ligand by base liberates the phenyl group which
produces 3. A related cationic mononuclear moiety [Au(Hf)(Hy)] (4), with neutral amidinate and ylide, is produced from
the neutral amidine upon reaction with [Au(THT)Cl] in a THF solution of ylide. These new compounds have been
characterized by X-ray crystal structures, 1H NMR, IR, and elemental analysis.
’ INTRODUCTION
connecting two gold(I) atoms at aurophilic distances (less than
3 Å). Trinuclear gold(I) complexes with AuꢀN and AuꢀC
bonds result from using ligands (pyridine, imidazoles, isocya-
nides, imidoyls) with adjacent N,C donors that require goldꢀ
gold separations to be larger than 3 Å. Tetranucleation with
gold16 can be obtained by a ligand designed with two C donors
(NHC) tagged to a N,N donor (imidazole).
The nearly identical Pauling electronegativities of gold (2.54)
and carbon (2.55) led to the early dinuclear gold chemistry with
goldꢀcarbon complexes of ylides, pioneered by Schmidbaur.17
In contrast with nitrogen ligands, dinuclear and polynuclear
gold(I,II) chemistry is a more recent research topic, dominated
by amidinate ligands.18 A mixed-ligand system involving both
amidinate N-donor and ylide C-donor ligands offered an evalua-
tion of the combined influence of a strong σ-donor (ylidic
carbon, y) with a strong π-withdrawing ligand (formamidinate, f).
Of special interest is the possible luminescent behavior known
for the homoligand dinuclear complexes Au2y2 and Au2f2. These
materials luminesce only faintly at room temperature, in con-
trast with the strongly luminescent Au4f4. While our focus was
on the synthesis of the first mixed-ligand [Au2fy] complexes,
the early stages of research produced the series of compounds
reported here.
Heterobridged dinuclear gold(I) complexes provide addi-
tional information about the role of the bridging ligand in
comparison with related homobridged complexes (Chart 1).
Such complexes may integrate disparate ligand properties, which
has produced new chemistry with mixed donors such as a C,C-
donor phosphorus ylide with S,S (dithiocarbamate, phosphonio-
dithioformate, xanthate)1 and P,P (diphosphinomethanide)2 ligands,
a sulfur ylide with P,P (dppm),3 and others, including P,P donor
diphosphines with S,S (dithiophosphonate, dithiolates, and
dangling thiolates)4 and an S,S donor dithiolate with a P,C
donor (C6H3-2-PPh2-n-Me).5
Prior to this work, no digold(I) systems with combined C,C
and N,N donors have been produced, with the exception of
[Au3(C6F5)3(η3-Fcterpy)],6 which contains an N,N,N-terpyri-
dine and three C-C6F5 ligands, and mononuclear complexes with
NꢀAuΙꢀC linkages.7,8 However, there are a large number of
gold(III) complexes with AuꢀN and AuꢀC connectivities. One
of the earliest reported is the heterocycle [(CH3)2AuN(CH3)2]2,
with two symmetrical amido bridges and methyl ligands.9
One approach to the study of dinuclear gold(I) complexes
with NꢀAuꢀC connectivities has been to use pincerlike
ligands with simultaneous C,N donation. Such ligands result
from attaching pendant N moieties (pyridine, amine) to an
imidazolium-based N-heterocyclic carbene (NHC),10,11 to a
phenyl ring,12 or to ferrocene.13 Conversely, a C-donor moiety
appended to pyridine14 produces such complexes. The most
apparent N,C donor, however, is an azaallyl (RNC(R)CR)
ligand.15 Usually these ligands arrange in a head-to-tail fashion
Prior to this report, only one cluster was known to connect
dissimilar N donors (amidinate) and C donors(phosphorus ylide)
in a neutral cubic assembly.19 It turned out to be a special cluster
Received: June 27, 2011
Published: September 26, 2011
r
2011 American Chemical Society
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Chart 1. Dinuclear Gold(I) Complexes
Further reactions were performed at ꢀ20 °C, not only because of
the instability of the ylide but because there is a tendency of
gold(I) formamidinate solutions in toluene to oxidize in the
presence of nitrate anions, yielding [Au2f2(NO3)2].20
For compound 1, [Au2f(Hy)2]NO3, the gold to ylide ratio is
1:1 in toluene; the nitrate comes from the [Au(THT)NO3].
With this ratio the mixed ligand complex being sought, [Au2fy],
would be produced by proton exchange between two ylide
molecules, giving the negatively charged ylide anion ligand.
However, the high yield achieved for 1 indicates that goldꢀ
carbon bond formation is the favored process. Addition of 2
equiv of ylide to further promote ylide deprotonation leads to
formation of the bridging ylide complex [Au2y2] and 1. A
procedure which leads to the desired [Au2fy] required a process
starting with the Au(II) amidinate.21
Chart 2. Cubic Gold(I) Cluster with Mixed Coordination of
Bridging Formamidinates and Hypercoordinating Carbons
from a Phosphorus Ylide
Compound 2, [Cl-Au2f(Hy)], is obtained in a straightforward
manner in a CH3CNꢀtoluene solution when [Au(THT)Cl] is
the starting material and the ratio gold to ylide is 2:1. The
formation of the strong AuꢀCl bond appears to dominate this
chemistry.
The mononuclear complex 4, with the PF6ꢀ anion, is obtained
by first reacting [Au(THT)Cl] and formamidine in a 1:2 ratio in
CH3CN, followed by addition of the ylide prepared from
[(CH3)2(Ph)2P]PF6. The large anion is used to inhibit the
tendency of gold(I) complexes to associate.
Compound 3, [Ph-Au2f(Hy)], is obtained with a ratio of gold
to ylide of 1:1, using KOH in a mixture of ethanol and toluene
solvents. The KOH purportedly would remove the ylide methyl
proton, but base reaction on the ylide releases a phenyl anion
which ends up coordinating to gold and in smaller amounts as
benzene in the solution. The modified ylide is found as crystalline
[Ph(CH3)2PdO].
Phosphine oxides R3PO are widely used as complexing agents
of oxophilic metals such as lanthanides,22,23 actinides,24 and
transition metals;25ꢀ28 the methyl phosphine oxide is known29
to be lithiated by nBuLi, tBuLi, and iPrLi at ꢀ78 °C as the first
step in the HornerꢀWittig reaction.30 Usual syntheses involve
oxidation of the phosphine PR3 with hydrogen peroxide.31 The
basic path that converts ylides [Ph3P+(R)]Xꢀ into oxopho-
sphanes has been studied in terms of solvent effects.32 A low-
polarity solvent is needed to speed up the hydrolysis, but a high-
polarity solvent actually slows the reaction. This is coincident
with the experimental observations here with a toluene to
ethanol ratio of 10ꢀ20% v/v. The solvent polarity may be related
to the polarity of the products. In the process the nucleophile
OHꢀ attacks the onium center and the proton is transferred to a
CH2-Ph group, producing free Me-Ph and the PdO bond. In our
synthesis a phenyl anion, Phꢀ, is released from the neutral
ylide [Ph2P(CH2)CH3] rather than the less stable Meꢀ anion
(Scheme 2).
Structural Characteristics. The thermal ellipsoid structures
of 1ꢀ4 are shown in Figures 1 and 2. The formamidinate is a
methanimidamide (NCHN) moiety N,N-substituted with 2,5-
dimethylphenyl rings with two N donors; the ylide is an onium
phosphine with two phenyls and two methyls, which upon losing
a methyl proton monocoordinates through CH2. Compounds
1ꢀ3 are open dinuclear structures (Scheme 1) exhibiting a
formamidinate NꢀCHꢀN bridge (f) opposite to the two dan-
gling neutral ylide ligands (Hy) coordinating through CH2 in 1. In
2, instead of an ylide, there is a chloride, and in 3 there is a phenyl
group. The NꢀAuꢀC (C-phenyl or C-ylide) and NꢀAuꢀCl
angles are close to linear (Table 1). In these compounds a
with eight gold(I) atoms at the corners of a distorted cube,
bridged along the sides by four amidinates and capped above and
below the cube by two hypercoordinating carbon atoms from the
phosphorus ylide (Chart 2). This cluster showed green lumines-
cence under UV light. The group of gold(I) complexes reported
here is related to that cubic assembly in that they exhibit the same
amidinate and ylide ligands in their structures.
’ RESULTS AND DISCUSSION
Synthetic Procedures. Due to the special affinity between
gold and carbon, it was expected that AuꢀC bonds would form
preferentially to AuꢀN bonds. Thermodynamically, the interac-
tion of the carbon donor ylide (y) with the gold formamidinate
[Au2f2] would seem to favor the formation of mixed species
[Auxfyyz] prior to forming [Au2y2]. The product would depend
on the ratio of the ylide to Au2f2. Initially aiming to produce a
dinuclear [Au2fy], the synthetic protocol was to react the di-
nuclear amidinate [Au2f2] with the diphenylmethylmethylene-
substituted phosphorus ylide, [Hy], in toluene at ꢀ20 °C, under
nitrogen (Scheme 1).
The [Au2f2] was synthesized by stirring [Au(THT)Cl] or
[Au(THT)NO3] with potassium formamidinate in ethanol; a
white solid formed, and the solvent was removed. The product
was kept at 0 °C. The ylide [CH3CH2(Ph)2P] was produced by
deprotonation of [(CH3)2(Ph)2P]NO3 or [(CH3)2(Ph)2P]PF6
with KH in THF at ꢀ20 °C; the THF was removed, and toluene
was added to form a yellow solution, which was kept at ꢀ20 °C.
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Scheme 1. Synthetic Conditions Originating Mixed-Ligand Compounds of Gold(I)
Scheme 2
Figure 2. Structures of the mixed formamidinateꢀylide ligand com-
pounds 2 and 3 with displacement ellipsoids drawn at the 30%
probability level. Hydrogen atoms are omitted for clarity.
of nitrate anions parallel to the bc plane and to the AuꢀAu bond,
with short CH3 ONO2ꢀ contacts of 2.299(5) and 2.579(7) Å
3 3 3
to the two nitrate anions on the same side of the molecule
(Figure 3). On the opposite side another nitrate in the unit cell
establishes contacts to an ylide CH2 and a phenyl proton at
2.711(3) and 2.504(2) Å. This causes phenyls on both ylide
ligands to point toward the formamidinate phenyls, though not
Figure 1. Structures of the mixed formamidinateꢀylide ligand compounds
1 and 4 with displacement ellipsoids drawn at the 30% probability level.
establishing any short contact to them. The Au Au distance
3 3 3
stretches to 2.997(2) Å compared to 2.96[12] Å in 2 and 3 and
cannot possibly be longer due to the angular constraints on the
trigonal N donors. In 2 and 3 one ylide phenyl is pointing
opposite the formamidinate bridge; in 3 this is because there is a
short CꢀPh contact between this ylide phenyl and the lone
phenyl ligand on the vicinal molecule of 2.822(3) and 2.74(4) Å;
in 2 it is the ylide methyl that comes closer to the coordinating
chlorine at 2.96(4) Å.
formamidinate bridge connects Au(I) atoms, at distances greater
than in [Au2f2] (2.711(3) Å) but still in the aurophilic range of
<3.00 Å. The orientations of the formamidinate phenyl groups are
the sameasthatfound inthe dinucleargold(I) formamidinate: e.g.,
face to face.
In the cationic structure 1, the methyl groups on the ylide are
oriented away from the amidinate bridge. Close to them is a layer
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Table 1. Selected Bond Distances (Å) and Angles (deg) for Mixed-Ligand Compounds of Gold(I)
compd
AuꢀAu
AuꢀN
AuꢀC
CꢀAuꢀN
AuꢀX
[Au2F(HY)2]NO3(1)
[Au2F(HY)Cl] (2)
[Au2F(HY)Ph] (3)
[Au(HF)(HY)]PF6 (4)
2.997(2)
2.100[2]
2.038[2]
2.062[2]
2.069(8)
2.059[2]
2.044(7)
2.068 (10)
2.020(11)
175.9[2]
176.9(3)
178.6(4)
172.3(4)
2.9644(12)
2.9599(5)
2.269(2) (X = Cl)
1.973(12) (X = Ph)
Scheme 3. Base Hydrolysis of Ylide To Produce a Phenyl
Anion and the Dimethyl Phenyl Phosphite
constraint on the NꢀAuꢀC bond ,which is more bent (172.52°)
than in 1ꢀ3.
The AuꢀN distances are large compared to AuꢀN bonds in
[Au2f2] (2.035(4) Å),17 revealing the strong σ-donor character
of the ylide carbon atom. In 1 the elongation increases to
2.095(4) and 2.105(3) Å. In 2 the AuꢀN bond opposite to
the ylide C is 2.051(3) Å, whereas that opposite to chlorine is
2.025(3) Å. In 3, both AuꢀN bonds are elongated (2.047(4),
2.084(3) Å) but the effect is more pronounced on the bond
opposite to the phenyl ligand. In 4, the AuꢀN distance is
2.072(3) Å. Conversely, AuꢀC bonds to the ylide show a slight
contraction in comparison to those in [Au2y2] (2.075(5) Å), with
distances of 2.052(4) Å in 1, 2.051(4) Å in 2, 2.047(3) Å in 3,
and 2.016(2) Å in 4.
The constraint on the NꢀCꢀN angle imposed by an oppos-
ing bridge is no longer present in 1 and is reflected in the NꢀN
distance of 2.278(5) Å, which is shorter than the 2.363(5) Å
distance in [Au2f2]. This shortened distance in 1 compared with
the eight membered ring compound18 appears to occur because
of the strain to maintain the linear NꢀAuꢀN angles in the bowed
ring, a strain which is absent in 1. This lack of strain in 1 shows even
more distinctively in the separation between ylidic CH2 CH2
3 3 3
units of 3.982(17) Å.
1
Figure 3. Space-filling picture of 1, [Au2f(Hy)2]NO3, showing an
oxygen from the nitrate in short contact with the ylide methyl carbon
(C33). This oxygen is disordered, and the short contact becomes the
ylide methyl carbon of another cation.
H NMR Spectra. H NMR spectra were taken in d-benzene
from crystals. Signals in the aromatic region (6ꢀ8 ppm) are due
to phenyl protons from both ligands, the formamidinate and the
ylide. They usually overlap. Also in this region, characteristically
at ∼7.4 ppm, the N(CH)N signals appear. Signals in the aliphatic
region (1ꢀ3 ppm) derive from methyls on the formamidinate
and the methyl/methylene on the ylide. The latter are split due to
The cationic mononuclear complex 4, with neutral amidine
ꢀ
and neutral ylide ligands, has a large PF6 anion presumably
assisting in the prevention of an aurophilic goldꢀgold associa-
tion. Here the formamidine NH proton is directed away from the
NꢀAuꢀC bond, allowing the adjacent phenyl to be closer to
thisꢀbond. The NH proton is H-bonded to two fluorides of a
PF6 anion at 2.3927(10) and 2.433(9) Å. The anion shows
additional short contacts through fluorines to the ylide methyl
(2.283(7) Å), to ylide phenyls (2.403(12), 2.638(13) Å) to
phenyls (2.382(13), 2.644(12), 2.638(13) Å), to a methyl phenyl
(2.597(12) Å), and to the NCHN (2.582(14), 2.519(13) Å) on
the surrounding formamidinates. This extensive net of short
contacts governs the orientation of the ylide phenyls, so that
one sits close to a formamidinate phenyl and the ylide methyl is
pointing opposite to the AuꢀCH2 bond. It also produces a spatial
1
31Pꢀ H coupling.
In [Au2fy2]NO3 (1) the aromatic region shows phenyl signals
spread from 7.7 to 6.90 ppm. There is a marked shift of the
methyl/methylene signal to lower field arising from the positive
charge on the molecule, an effect also observed in the 1H NMR of
the ylide precursor [H2y]NO3 with a CH3 signal at 2.9 ppm and
in the cationic mononuclear complex 4. Additionally the proxi-
mity of the nitrate anion to the ylide methyl group, described in
Structural Characteristics, causes this doublet to appear at
2.40ꢀ2.45 ppm (integrating to 6). It appears at a higher field
than the coordinating ylide CH2 at 2.17ꢀ2.13 ppm (integrating
to 4). The formamidinate methyl signal is at 2.32 ppm. Phenyl
signals from 4 in the aromatic region span from 7.8 to 6.7 ppm.
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Table 2. Crystallographic Data
1
2
3
4
chem formula
fw
Au2C45H49N3O3P2
1135.75
P2/c
Au2C31H34N2PCl
894.96
Au2C37H39N2P
936.0
C31H35N2P2F6Au
808.52
space group
a (Å)
P21/c
Fdd2
P1
20.034(16)
16.208(13)
13.630(11)
90
10.580(6)
16.133(9)
18.634(10)
90
22.1144(16)
56.875(4)
10.8177(7)
90
8.594(8)
12.966(12)
14.062(14)
92.895(17)
95.603(17)
92.166(17)
1556(3)
2
b (Å)
c (Å)
α (deg)
β (deg)
γ (deg)
V (Å3)
Z
100.972(9)
90
104.024(8)
90
90
90
4345(6)
4
3086(3)
4
13606.2(16)
16
dcalcd (g cmꢀ3
)
1.736
1.926
1.829
1.726
μ (mmꢀ1
)
6.861
9.658
8.690
4.890
T (K)
213
213
110
213
R1a (wR2b)
0.0682 (0.1370)
0.0371 (0.0991)
0.0502 (0.1161)
0.0613 (0.1280)
a R1 = [∑w(Fo ꢀ Fc)2/∑wFo2]1/2. b wR2 = [∑[w(Fo ꢀ Fc2)2]/∑w(Fo2)2]1/2; w = 1/[σ2(Fo ) + (aP)2 + bP], where P = [max(Fo ,0) + 2(Fc2)]/3.
2
2
2
There are formamidinate methyl signals at 2.34 and 2.28 ppm in
4; the ylide methyl group which is in short contact with the anion
shows up at a low field, 2.46ꢀ2.42 ppm, similar to the case for the
cation 1. The ylide methylene, with no short contacts to the
anion, has its signal at 1.71ꢀ1.75 ppm, which compares well to
signals found for 2 and 3.
coordination on the dinuclear gold formamidinate is displaced
by CH2 donation from the strongly σ-donating ylide which
produces the monocoordinate ylide ligand. Additional ylide
favors further deprotonation, but the reaction produces the
resulting dinuclear gold(I) ylide complex. Base activation of
the ylide is observed upon addition of KOH, releasing a phenyl
anion which ends up attached to a gold(I) center. It also
produces benzene, as observed in the 1H NMR.
For [Au2f(Hy)Cl] (2) the two formamidinate methyl signals
are at 2.40 and 2.32 ppm. The ylide methylene signal is at
1.76ꢀ1.72 ppm and the methyl at 1.46ꢀ1.50 ppm. For [Au2f-
(Hy)Ph] (3) the aromatic region shows the phenyl proton signal
centered at 8.1 ppm. Since there are two different C-donor
groups, there are two formamidinate methyl signals: 2.54 and
2.29 ppm. The ylide methylene doublet is at 1.79ꢀ1.75 ppm and
the methyl at 1.45ꢀ1.49 ppm.
The mixed coordination is reflected in the 1H NMR as a shift
of formamidinate methyl substituents to higher field and of ylide
methyl/methylene signals to lower field in comparison with the
signals for the homoligand dinuclear complexes. The effect is
especially marked on the ylide methylene group. A screening of
the luminescence of 3 and 2 under UV light at room temperature
shows only a dull red emission. Additional studies of the emission
spectra of these mixed-ligand species will be reported elsewhere.
Two distinct factors influence the shifts of methylene and
methyls on both the ylide and the formamidinate ligands: (a)
short contacts with anions produce a deshielding effect on ylide
methyl protons, moving the signal up to ∼2.4 ppm to a lower
field in both cationic 1 and 4; (b) the strong σ-donor character of
the trans ligand across the gold(I) exerts a shielding effect on the
coordinating methylene and on the formamidine methyl groups,
moving these signals to a higher field. This is noted when
’ EXPERIMENTAL SECTION
Syntheses were carried out under an inert atmosphere using standard
Schlenk techniques, unless otherwise noted. Solvents (THF, toluene,
ether, and hexane) were dried using a Glass Contour solvent system.
Ethanol was used freshly distilled with Mg/I2 under nitrogen. The
phosphorus ylide [PPh2CH3CH2] was prepared by stirring a 1/1
(mmol/mmol) mixture of [PPh2(CH3)2]NO3 and KH (25% slurry in
mineral oil) in 10 mL of THF (ꢀ20 °C, dark, N2) over 6 h. The THF
was removed by vacuum pumping, keeping the flask at ꢀ20 °C. Then
toluene (10ꢀ20 mL) was added and the yellow solution was stored at
ꢀ20 °C. The potassium formamidinate was prepared by refluxing at
60 °C the formamidine [(2,6-Me2Ph)2NCHN] with KOH in a 1/1 ratio
in ethanol; the solvent was slowly evaporated in air, which produced
crystals that were rinsed with hexanes. Elemental analyses were per-
formed by Robertson Microlit Laboratories, Inc., Madison, NJ. 1H NMR
spectra were recorded on a Mercury-300 NMR spectrometer.
1
comparing H NMR data to data for Au2f2 and Au2y2. In the
mixed-ligand compounds the NꢀAuꢀC linkage has a strong σ
donor (ylide C) trans to a weaker σ donor (formamidinate N);
therefore, the ylide methylene signals shift to lower field (1.71ꢀ
1.79 ppm) in comparison with those for Au2y2 (1.42ꢀ1.38 ppm),
while the formamidinate methyl signals (2.32ꢀ2.29 ppm) shift
to a slightly higher field compared with Au2f2 (2.34 ppm). The
shift of the formamidinate methyls is less marked, since these are
more remote from the coordination.
’ CONCLUSIONS
Two dissimilar ligands, a N-donor formamidinate and a
C-donor phosphorus ylide, are used to produce four gold(I)
compounds with novel mixed NꢀAuꢀC coordination. Com-
pounds 1ꢀ3 are open binuclear structures with bridging for-
mamidinate and monocoordinating ylide and/or chloride and
phenyl ligands. Compound 4 is a mononuclear complex with
monocoordinating formamidine and ylide ligands. The N
X-ray Structure Determinations. Data for 1 and 3 were
collected (Table 2) on a Bruker APEX-II 100033 CCD area detector
system using ω scans of 0.3°/frame and 30 s per frame (2000 frames,
18 h 21 min) for 1 and 0.5°/frame and 10 s per frame (1208 frames, 4 h
33 min) for 3, while data for 2 and 4 were collected on a Bruker SMART
1000 CCD area detector system using ω scans of 0.3°/frame and 40 s
per frame (2000 frames, 28 h 41 min) for 2 and 0.3°/frame and 90 s per
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frame (2400 frames, 65 h 2 min) for 4. For 1 and 3 cell parameters were
determined using the program APEX. For 2 and 4 cell parameters were
determined using the SMART software suite.34 Data reduction and
integration were performed with the software package SAINT,35 which
corrects for Lorentz and polarization effects, while absorption correc-
tions were applied by using the program SADABS.36
The positions of the Au atoms were found via direct methods using
the program SHELXTL.37 Subsequent cycles of least-squares refine-
ment followed by difference Fourier syntheses revealed the positions of
the remaining non-hydrogen atoms. Hydrogen atoms were added in
idealized positions. All hydrogen atoms were included in the calculation
of the structure factors. All non-hydrogen atoms were refined with
anisotropic displacement parameters.
Compound 1 crystallized in the monoclinic centrosymmetric space
group P2/c; one of the NO3ꢀ anions in the structure was disordered in a
special position. Compound 2 was refined in the monoclinic centrosym-
metric space group P21/c. Compound 3 crystallized in the orthorhombic
noncentrosymmetric space group Fdd2. Compound 4 was initially
solved in the triclinic noncentrosymmetric space group P1 suggested
by the XPREP program; however, following the recommendation of
choosing the higher symmetry group advised by Marsh,38 the final
refinement was done in the centrosymmetric P1. This structure has four
fluorine atoms of the PF6ꢀ anion disordered; the positional disorder was
treated by defining a second free variable,and the final refinement gave
SOF = 0.56139 and 0.43861 for the major and minor components,
respectively.
(m), 982 (m), 943 (ylide, m), 915 (m), 819 (ylide, w), 755 (s), 725
(m), 691 (m), 663 (ylide, m), 618 (w), 475 (m), 425 (m). H NMR
1
(C6D6): δ 7.4 (NCHN), 2.40ꢀ2.32 (CH3 form), 1.76ꢀ1.72 (CH2
ylide), 1.46ꢀ1.50 (CH3 ylide).
Synthesis of [Ph-Au2f(Hy)] (3). The gold(I) formamidinate was
prepared as for 1 (with Au(THT)Cl 0.0800 g, 0.25 mmol), and the
solvent (ethanol) was reduced to 1ꢀ2 mL under vacuum, and then the
flask under N2 was cooled in a dry ice bath. In this flask the ylide solution
(0.25 mmol) in 10 mL of toluene (at ꢀ20 °C, in the dark) was transferred
using a cannula. KOH (0.12 mmol) was added to the mixture, which was
stirred for 4 h at ꢀ20 °C. The solvents were removed by vacuum, and the
residue iswas extracted with 10 mL of ether. The ether solution layered
with hexane produced large prismatic, colorless crystals of [Ph-Au2f(Hy)]
after 2 weeks. Yield: 40%. Anal. Calcd for C37H39N2PAu2: C, 47.44; N,
2.99; H, 4.17. Found: C, 47.64; N, 2.96; H, 4.09. IR: 3167 (ylide, m), 2964
(s), 2892 (ylide, s), 1605 (s), 1650 (phenyl, s), 1571 (s), 1470 (s), 1440
(s), 1373(m), 1345(m), 1290(m), 1310(phenyl, m), 1255(m), 1199(m),
1179 (phenyl, m), 1160 (w), 1150 (ylide, m), 1090 (m), 1117 (ylide, m),
1031 (m), 982 (m), 943 (ylide, m), 915 (m), 848 (phenyl, m), 819
(ylide, w), 755 (s), 725 (m), 691 (m), 663 (ylide, m), 618 (w), 475 (m),
425 (m). 1H NMR (C6D6): δ 8.1 (Ph), 7.4 (NCHN), 2.54, 2.29 (CH3
form), 1.79ꢀ1.75 (CH2 ylide), 1.49ꢀ1.45 (CH3 ylide).
Synthesis of [Au(Hf)(Hy)]PF6 (4). A solution of [Au(THT)Cl]
(0.0800 g, 0.25 mmol) and the neutral formamidine (0.0730 g, 0.50
mmol) in 20 mL of CH3CN was stirred for 2 h until a white suspension
formed. The solvent was partially reduced to 10 mL by vacuum, and the
flask under N2 was cooled in a dry ice bath. The ylide solution prepared
from [PPh2(CH3)2]PF6 (0.25 mmol) in 10 mL of THF (at ꢀ20 °C, in
the dark) was transferred into this flask using a cannula. The yellow
suspension was stirred for 4 h until the cloudiness cleared up. The
solvents were removed under vacuum, and the residue was rinsed with
ether. The solid was dissolved in THF and layered with hexane; after 1
week small prismatic crystals grew. Yield: 60%. Anal. Calcd for
C31H35N2P2F6Au: C, 46.03; N, 3.46; H, 4.331. Found: C, 45.72; N,
3.18; H, 4.20. IR (KBr): 3166 (ylide, m), 2966 (s), 2892 (ylide, s), 1604
(s), 1571 (s), 1470 (s), 1440 (s), 1373 (m), 1345 (m), 1290 (m), 1255
(m), 1199 (m), 1160 (w), 1150 (ylide, m), 1090 (m), 1117 (ylide, m),
1031 (m), 982 (m), 943 (ylide, m), 915 (m), 819 (ylide, w), 755 (s), 725
Additional crystallographic information for 1ꢀ4 are given in Table 2,
and selected bond lengths are provided in Table 1.
Synthesis of [Au2f(Hy)2]NO3 (1). To a suspension of [Au-
(THT)Cl] (0.0800 g, 0.25 mmol) and THT (0.25 mmol) in 20 mL
of ethanol, at 0 °C, was added 0.25 mmol of AgNO3, and the contents
were stirred for 4 h. The white suspension was allowed to settle, and the
liquid was canullated to a flask containing the potassium salt (0.0730 g,
0.25 mmol). The mixture was stirred for 3 h until a white solid formed.
After the solvent was removed under vacuum, the flask with the gold(I)
formamidinate was put in a dry ice bath and the ylide solution (0.25
mmol) in 20 mL of toluene (at ꢀ20 °C, in the dark) was transferred using
a cannula. The mixture was stirred for 3 h at ꢀ20 °C. The toluene was
removed under vacuum, and the residue was first extracted with 5 mL of
ether and then with 5 mL of toluene. From the toluene solution layered
with hexane colorless crystals of [Au2fy2] NO3 grew in 1 week. Yield:
63%. Anal. Calcd for C45H49N3O3P2Au2: C, 47.57; N, 3.70, H, 4.32.
Found: C, 47.85; N, 4.05; H, 4.37. IR (KBr): 3166 (ylide, m), 2966 (s),
2892 (ylide, s), 1604 (s), 1571 (s), 1470 (s), 1440 (s), 1373 (m), 1345
(m), 1300 (m), 1290 (m), 1255 (m), 1199 (m), 1160 (w), 1150 (ylide, m),
1090 (m), 1118 (ylide, m), 1031 (m), 982 (m), 943 (ylide, m), 915 (m),
819 (ylide, w), 755 (s), 725 (m), 691 (m), 663 (ylide, m), 618 (w), 475
1
(m), 691 (m), 663 (ylide, m), 618 (w), 475 (m), 425 (m). H NMR
(C6D6): δ 7.4 (NCHN), 2.40ꢀ2.32 (CH3 form), 1.76ꢀ1.72 (CH2
ylide), 1.46ꢀ1.50 (CH3 ylide).
’ ASSOCIATED CONTENT
S
Supporting Information. CIF files giving X-ray crystal-
b
lographic data for 1ꢀ4. This material is available free of charge
via the Internet at http://pubs.acs.org.
1
(m), 425 (m). H NMR (C6D6): δ 7.4 (NCHN), 2.32 (CH3 form),
2.45ꢀ2.40 (CH3 ylide), 2.17ꢀ2.13 (CH2 ylide).
’ ACKNOWLEDGMENT
Synthesis of [Cl-Au2f(Hy)] (2). A solution of [Au(THT)Cl]
(0.0800 g, 0.25 mmol) and the potassium formamidinate salt (0.0730 g,
0.25 mmol) in 20 mL of CH3CN was stirred for 2 h until a white
suspension formed. The solvent was partially reduced to 10 mL by
vacuum, and the flask under N2 was cooled in a dry ice bath. In this flask
the ylide solution (0.25 mmol) in 10 mL of toluene (at ꢀ20 °C, in the
dark) was transferred using a cannula. The yellow suspension was stirred
for 4 h until it cleared up. The solvents were removed under vacuum, and
the residue was extracted first with 5 mL of CH3CN and then with 10 mL
of toluene. From the toluene solution layered with hexane bulky
colorless crystals of [Cl-Au2fy] grew in 1 week. Yield: 63%. Anal. Calcd
for C31H34N2PClAu2: C, 41.61; N, 3.13; H, 3.80. Found: C, 41.10; N,
2.97; H, 4.20. IR: 3157 (ylide, m), 2965 (s), 2892 (ylide, s), 1607 (s),
1571 (s), 1473 (s), 1440 (s), 1374 (m), 1345 (m), 1290 (m), 1255 (m),
1199 (m), 1161 (w), 1150 (ylide, m), 1089 (m), 1117 (ylide, m), 1031
This work was supported by the Robert A. Welch Foundation,
Houston, TX, Grant No. A-0960.
’ REFERENCES
(1) (a) Bardaji, M.; Connelly, N. G.; Gimeno, M. C.; Jimenez, J.;
Jones, P. G.; Laguna, A.; Laguna, M. J. Chem. Soc., Dalton Trans.
1994, 1163–1164. (b) Bardaji, M.; Laguna, A.; Laguna, M. J. Organomet.
Chem. 1995, 496, 245–248. (c) Bardaji, M.; Jones, P. G.; Laguna, A.;
Laguna, M. Organometallics 1996, 14, 1310–1315.
(2) Scmidbaur, H.; Mandl, J. R. Angew. Chem., Int. Ed. Engl. 1977, 16
(9), 640–641.Grohmann, A.; Schmidbaur, H. Comprehensive Organome-
tallic Chemistry II; Pergamon: London, 1995; Vol. 3, pp 1ꢀ56.
(3) Lin, I. J. B.; Liu, C. W.; Liu, L. K.; Wen, Y. S. Organometallics
1992, 11, 1447–1449.
5379
dx.doi.org/10.1021/om200556x |Organometallics 2011, 30, 5374–5380

Organometallics
ARTICLE
(4) (a) van Zyl, W. E.; Staples, R. J.; Fackler, J. P., Jr. Inorg. Chem.
Commun. 1998, 1, 51–54. (b) Tang, S. S.; Chang, Ch. P.; Lin, I. J. B.; Liou,
L. S.; Wang, J. Ch. Inorg. Chem. 1997, 36, 2294–2300. (c) Davila, R. M.;
Elduque, A.; Staples, R. J.; Harlass, M.; Fackler, J. P., Jr. Inorg. Chim. Acta
1994, 217, 45–49. (d) Davila, R. M.; Elduque, A.; Grant, T.; Staples, R. J.;
Fackler, J. P., Jr. Inorg. Chem. 1993, 32, 1749–1755. (e) Narayanaswamy, R.;
Young, M. A.; Parkhurst, E.; Ouellette, M.; Kerr, M. E.; Ho, D. M.; Elder,
R. C.; Bruce, A. E.; Bruce, M. R. M. Inorg. Chem. 1993, 32, 2506–2517.
(5) Mohr, F.; Bhargava, S. K. Inorg. Chem. 2001, 40 (17), 4271–4275.
(6) Aguado, J. E.; Calhorda, M. J.; Gimeno, M. C.; Laguna, A. Chem.
Commun. 2005, 3355–3356.
(7) (a) Vicente, J.; Arcas, A.; Jones, P. G.; Lautner, J. J. Chem. Soc.,
Dalton Trans. 1990, 451–456. (b) Wang, H. M. J.; Vasam, Ch. S.; Tsai,
T. Y. R.; Chen, S. H.; Chang, A. H. H.; Lin, I. J. B. Organometallics 2005,
24, 486–493. (c) Ricard, L.; Gagosz, F. Organometallics 2007, 26, 4704–4707.
(d) Bordoni, S.; Busetto, L.; Cassani, M. C. Inorg. Chim. Acta 1994,
222, 267–273. (e) Codina, A.; Fernandez, E. J.; Jones, P. G.; Laguna, A.;
Lopez-de-Luzuriaga, J. M.; Monge, M.; Olmos, M. E.; Perez, J.; Rodriguez,
M. A. J. Am. Chem. Soc. 2002, 124, 6781–6786. (f) Corfield, P.W. R.; Shearer,
H. M. M. Acta Crystallogr. 1967,23, 156–162. (g) Dias, H. V. R.; Wu, J. Angew.
Chem., Int. Ed. 2007, 46, 7814–7816. (h)Zharkova, G. I.; Baidina, I. A.Russian
J. Coord. Chem. 2009, 35, 36–41. (i) Contel, M.; Nobel, D.; Spek, A. L.;
van Koten, G. Organometallics 2000, 19, 3288–3295.
(30) (a) Buss, D. A.; Warren, S. J. Chem. Soc., Perkin Trans.
1985, 2307–232. (b) Clayden, J.; Warren, S. Angew. Chem. 1996,
108, 261–291.
(31) Marr, G.; White, T. M. J. Chem. Soc., Perkin Trans. 1 1973, 155–158.
(32) Schnell, A.; Tebby, J. J. Chem. Soc., Chem. Commun. 1975, 134–133.
(33) APEX2, Version 2008.4-0; BrukerꢀNonius, Madison, WI, 2008.
(34) SMART for Windows NT, Version 5.618; Bruker Advanced X-ray
Solutions, Madison, WI, 2001.
(35) SAINT, Data Reduction Software, Version 6.36A; Bruker Ad-
vanced X-ray Solutions, Madison, WI, 2001.
(36) SADABS: Area Detector Absorption and other Corrections Soft-
ware, Version 2.05; Bruker Advanced X-ray Solutions, Madison, WI,
2001.
(37) Sheldrick, G. M. SHELXTL, Version 6.12; Bruker Advanced
X-ray Solutions, Madison, WI, 2002.
(38) Marsh, R. E. Acta Crystallogr. 2009, B65, 782.
(8) Uson, R.; Laguna, A.; Laguna, M.; Manzano, B.; Jones, P. G.;
Sheldrick, G. M. J. Chem. Soc., Dalton Trans. 1985, 2417–2420.
(9) Adams, Von H. N.; Gr€assle, U.; Hiller, W.; Str€ahle, J. Z. Anorg.
Allg. Chem. 1983, 504, 7–12.
(10) Paꢀzick^y, M.; Loos, A.; Ferreira, M. J.; Serra, D.; Vinokurov, N.;
Rominger, F.; J€akel, Ch.; Hashmi, A. S. K.; Limbach, M. Organometallics
2010, 29, 4448–4458.
(11) Catalano, V. J.; Moore, A. L. Inorg. Chem. 2005, 44, 6558–6566.
(12) Schuster, O.; Schier, A.; Schmidbaur, H. Organometallics 2003,
22, 4079–4083.
(13) Jacob, K.; Voigt, F.; Merzweiler, K.; Pietzsch, C. J. Org. Chem.
1997, 545, 421–433.
(14) Papasergio, R. I.; Raston, C. L.; White, A. H. J. Chem. Soc.,
Dalton Trans. 1987, 3085–3091.
(15) Hitchcock, P. B.; Lappert, M. F.; Layha, M.; Klein, A. J. Chem.
Soc., Dalton Trans. 1999, 1455–1459.
(16) Zhou, Y.; Chen, W. Organometallics 2007, 26, 2742–2746.
(17) Basil, J. D.; Murray, H. H.; Fackler, J. P., Jr.; Tocher, J.; Mazany,
A. M.; Trzcinska-Bancroft, B.; Knachel, H.; Dudis, D.; Delord, T. J.;
Marler, D. O. J. Am. Chem. Soc. 1985, 107, 6908–6915.
(18) Abdou, H. E.; Mohamed, A. A.; Fackler, J. P., Jr. Inorg. Chem.
2005, 44, 166–168.Abdou, H. E.; Mohamed, A. A.; Fackler, Jr., J. P.
Gold Chemistry; Mohr, F. Ed.; Wiley-VCH: Weinheim, Germany, 2009;
pp 1ꢀ46.
(19) Melgarejo, D. Y.; Chiarella, G. M.; Mohamed, A. A.; Fackler,
J. P., Jr. Z. Naturforsch., B 2009, 64, 1487–1490.
(20) Melgarejo, D. Y.; Chiarella, G. M.; Fackler, J. P., Jr. Inorg. Chem.
2011, 50 (10), 4238–4240.
(21) Fackler, J. P., Jr. Comments Inorg. Chem. 2010, 31, 104–110.
(22) Bosson, M.; Levasson, W.; Patel, T.; Popham, M. C.; Webster,
M. Polyhedron 2001, 20, 2055–2062.
(23) Sen, A.; Chebolu, V. Inorg. Chim. Acta 1986, 118, 87–90.
(24) Kannan, S.; Moody, M. A.; Barnes, Ch. L.; Duval, P. B. Inorg.
Chem. 2006, 45, 9206–9212.
(25) Godfrey, S. M.; McAuliffe, Ch. A.; Ndifon, P. T.; Pritchard,
R. G. J. Chem. Soc., Dalton Trans. 1993, 3373–3377.
(26) Cotton, F. A.; Kohli, M.; Luck, R. L.; Silverton, J. V. Inorg. Chem.
1993, 32, 1868–1870.
(27) Fronczek, F. R.; Luck, R. L.; Wang, G. Inorg. Chem. Commun.
2002, 5, 384–387.
(28) Jimtaisong, A.; Luck, R. L. Inorg. Chem. 2006, 45, 10391–10402.
(29) Armstrong, D. R.; Davidson, M. G.; Davies, R. P.; Mitchell,
H. J.; Oakley, R. M.; Raithby, P. R.; Snaith, R.; Warren, S. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 1942–1944.
5380
dx.doi.org/10.1021/om200556x |Organometallics 2011, 30, 5374–5380