End-on and side-on π-acid ligand adducts of gold(I): Carbonyl, cyanide, isocyanide, and cyclooctyne gold(I) complexes supported by N-heterocyclic carbenes and phosphines

Article abstract of DOI:10.1021/ic301869v

N-Heterocyclic carbene ligand SIDipp (SIDipp = 1,3-bis(2,6- diisopropylphenyl)imidazolin-2-ylidene) and trimesitylphosphine ligand have been used in the synthesis of gold(I) cyanide, t-butylisocyanide, and cyclooctyne complexes (SIDipp)Au(CN) (3), (Mes₃P)Au(CN) (4), [(Mes ₃P)₂Au][Au(CN)₂] (5), [(SIDipp)Au(CN ^tBu)][SbF₆] ([6][SbF₆]), [(SIDipp) Au(cyclooctyne)][SbF₆] ([8][SbF₆]), and [(Mes ₃P)Au(cyclooctyne)][SbF₆] ([9][SbF₆]). A detailed computational study has been carried out on these and the related gold(I) carbonyl adducts [(SIDipp)Au(CO)][SbF₆] ([1][SbF ₆]), [(Mes₃P)Au(CO)][SbF₆] ([2][SbF ₆]), and [(Mes₃P)Au(CN^tBu)]⁺ ([7]⁺). X-ray crystal structures of 3, 5, [6][SbF₆], [8][SbF₆], and [9][SbF₆] revealed that they feature linear gold sites. Experimental and computational data show that the changes in π-acid ligand on (SIDipp)Au⁺ from CO, CN^-, CN ^tBu, cyclooctyne as in [1]⁺, 3, [6]⁺, and [8]⁺ did not lead to large changes in the Au-C_carbene bond distances. A similar phenomenon was also observed in Au-P distance in complexes [2]⁺, 4, [7]⁺, and [9]⁺ bearing trimesitylphosphine. Computational data show that the Au-L bonds of naked [Au-L]⁺ or SIDipp and Mes₃P supported [Au-L]⁺ (L = CO, CN^-, CN^tBu to cyclooctyne) have higher electrostatic character than covalent character. The Au←L σ-donation and Au→L π-back-donation contribute to the orbital term with the former being the dominant component, but the latter is not negligible. In the Au-CO adducts [1]⁺and [2]⁺, the cationic gold center causes the polarization of the C-O σ and π orbitals toward the carbon end making the coefficients at the two atoms more equal which is mainly responsible for the large blue shift in the CO stretching frequency. The SIDipp and Mes₃P supported gold(I) complexes of cyanide and isocyanide also exhibit a significant blue shift in υI..._CN compared to that of the free ligands. Calculated results for Au(CO)Cl and Au(CF ₃)CO suggest that the experimentally observed blue shift in νI..._CO of these compounds may at least partly be caused by intermolecular forces.

Full text of DOI:10.1021/ic301869v

Article
pubs.acs.org/IC
End-On and Side-On π‑Acid Ligand Adducts of Gold(I): Carbonyl,
Cyanide, Isocyanide, and Cyclooctyne Gold(I) Complexes Supported
by N‑Heterocyclic Carbenes and Phosphines
Mehmet Ali Celik,† Chandrakanta Dash,‡ Venkata A. K. Adiraju,‡ Animesh Das,‡
Muhammed Yousufuddin,‡ Gernot Frenking,*,† and H. V. Rasika Dias*,‡
†Fachbereich Chemie, Philipps-Universitat Marburg, D-35039 Marburg, Germany
̈
‡Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019-0065, United States
S
* Supporting Information
ABSTRACT: N-Heterocyclic carbene ligand SIDipp (SIDipp = 1,3-
bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) and trimesitylphos-
phine ligand have been used in the synthesis of gold(I) cyanide, t-
butylisocyanide, and cyclooctyne complexes (SIDipp)Au(CN) (3),
(Mes3P)Au(CN) (4), [(Mes3P)2Au][Au(CN)2] (5), [(SIDipp)Au-
(CNtBu)][SbF6] ([6][SbF6]), [(SIDipp)Au(cyclooctyne)][SbF6]
([8][SbF6]), and [(Mes3P)Au(cyclooctyne)][SbF6] ([9][SbF6]). A
detailed computational study has been carried out on these and the
related gold(I) carbonyl adducts [(SIDipp)Au(CO)][SbF6] ([1]-
[SbF6]), [(Mes3P)Au(CO)][SbF6] ([2][SbF6]), and [(Mes3P)Au-
(CNtBu)]+ ([7]+). X-ray crystal structures of 3, 5, [6][SbF6], [8][SbF6], and [9][SbF6] revealed that they feature linear gold
sites. Experimental and computational data show that the changes in π-acid ligand on (SIDipp)Au+ from CO, CN−, CNtBu,
cyclooctyne as in [1]+, 3, [6]+, and [8]+ did not lead to large changes in the Au−Ccarbene bond distances. A similar phenomenon
was also observed in Au−P distance in complexes [2]+, 4, [7]+, and [9]+ bearing trimesitylphosphine. Computational data show
that the Au−L bonds of “naked” [Au−L]+ or SIDipp and Mes3P supported [Au−L]+ (L = CO, CN−, CNtBu to cyclooctyne)
have higher electrostatic character than covalent character. The Au←L σ-donation and Au→L π-back-donation contribute to the
orbital term with the former being the dominant component, but the latter is not negligible. In the Au−CO adducts [1]+and
[2]+, the cationic gold center causes the polarization of the C−O σ and π orbitals toward the carbon end making the coefficients
at the two atoms more equal which is mainly responsible for the large blue shift in the CO stretching frequency. The SIDipp and
Mes3P supported gold(I) complexes of cyanide and isocyanide also exhibit a significant blue shift in υCN compared to that of the
̅
free ligands. Calculated results for Au(CO)Cl and Au(CF3)CO suggest that the experimentally observed blue shift in νCO of
these compounds may at least partly be caused by intermolecular forces.
̅
1) using N-heterocyclic carbene and phosphine auxiliary
ligands, respectively.20,21 Such species are of significant interest
because they are rare (e.g., structurally characterized species
INTRODUCTION
■
Traditionally, gold is considered as one of the most inert metals
and used widely in jewelry industry and in coins. However,
recent years have seen the emergence of gold as a facilitator of
wide variety of useful reactions especially when used at the
atomic level either in pure metal form or as part of a metal
complex. In fact, novel reactions mediated by gold are reported
in the latest literature in ever-increasing numbers.1−4 Gold is an
excellent choice for various transformations involving carbon
monoxide, alkenes, alkynes, allenes, and arenes.5−8 N-
Heterocyclic carbenes or phosphines are used quite often as
supporting ligands.9−15
An area of research focus in our laboratory concerns the
study of molecules featuring bonds between gold(I) and small
unsaturated molecules like CO, isocyanide, alkenes, and
alkynes.16−19 Recently we communicated the isolation of
gold(I) carbonyl adducts [(SIDipp)Au(CO)][SbF6] ([1]-
[SbF6]) (SIDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-
2-ylidene) and [(Mes3P)Au(CO)][SbF6] ([2][SbF6]) (Figure
Figure 1. Gold(I) carbonyl complexes supported by N-heterocyclic
carbene and phosphine ligands.
Received: August 27, 2012
Published: December 28, 2012
© 2012 American Chemical Society
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Table 1. Comparison of Vibrational (υCO, cm−1), Structural (Bond Distances, Å), and NMR Spectroscopic Data (Chemical
̅
Shifts, ppm) for Gold(I) Carbonyls
compd
υCO, cm−1
Au−CO, Å
C−O, Å
13CO
ref
35
̅
CO
2143
2144
2170
1.12822(7)
1.113(11)
1.11(3)
184 (CD2Cl2)
173 (CDCl3)
172 (CD2Cl2)
174 (CD2Cl2)
171 (CD2Cl2)
162 (HSO3F)
182.7 (CD2Cl2)
182.6 (CD2Cl2)
183.0 (CD2Cl2)
[HB(3,5-(CF3)2Pz)3]AuCO
Au(CO)Cl
1.862(9)
1.93(2)
23
89,22
89
a
Au(CO)Br
2153
b
Au2(CO)Cl4
2180
90
Au(CO)SO3F
2196
2197
2185
2194
2179
2217
2235.5
2235.5
2200
91,92
20
[(SIDipp)Au(CO)][SbF6]
[(Mes3P)Au(CO)][SbF6]
Au(CF3)(CO)
1.971(5)
2.008(6)
1.977(16)
1.110 (6)
1.108(7)
1.08(2)
21
34
[Au(CO)][OTeF5]
[Au(CO)2][Sb2F11]
[Au(CO)2]2[SbF6][Sb2F11]
[Au(CO)2]2[SbF6][Sb2F11]
[Au(CO)2][UF6]
93
174 (HSO3F)
92
1.962(17)
1.972(8)
1.153(17)
1.107(9)
24
24
94
a
b
In 1,2-dibromoethane. In SO2Cl2.
Figure 2. Calculated equilibrium geometries and C−O stretching frequencies of [(SIDipp)Au(CO)]+ ([1]+), [(Mes3P)Au(CO)]+ ([2]+),
[Au(CO)]+, Au(CO)Cl, and Au(CF3)CO at BP86/TZVPP. Bond lengths are given in Å, frequencies in cm−1. Experimental values are given in
parentheses. The calculated frequency for free CO is 2126 cm−1. *See the effects of intermolecular forces of Au(CO)Cl and Au(CF3)CO on υCO
̅
(leading to a blue shift) in the Results and Discussion.
involving terminal Au−CO bonds were limited to Au(CO)Cl,22
[HB(3,5-(CF3)2Pz)3]Au(CO),23 and [Au(CO)2]2[SbF6]-
[Sb2F11]24 until recently), serve as useful models for likely
intermediates in relevant gold catalyzed processes involving
carbon monoxide,7,25−27 and provide valuable spectroscopic
and structural data.
In this Article, we report additional details on these
compounds as well as the synthesis of gold(I) complexes
featuring cyanide and isocyanide. The main focus of this study
is to examine the structures, bonding, and properties of closely
related end-on bound π-acceptor ligand (CO, CN−, CNtBu)
adducts of gold(I) having the same supporting ligand. We
picked N-heterocyclic carbene SIDipp (SIDipp = 1,3-bis(2,6-
diisopropylphenyl)imidazolin-2-ylidene) as one of the support-
ing ligands for this purpose as it represents an increasingly
important group of ligands in gold chemistry. We also
synthesized a second series of compounds using Mes3P
(instead of SIDipp), which represents yet another group of
important auxiliary ligands in gold chemistry. The two
categories allow us to investigate the influence of the
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supporting ligand. Furthermore, synthesis and structural data
on two new gold(I) alkyne complexes (an area of high topical
interest)5,17,28−31 are also included in this study. They provide
information on gold(I) adducts involving side-on bound π-acid
ligands.
Table 2. EDA-NOCV Results at BP86/TZ2P+//BP86/
TZVPP for the Au−CO Bonds of [(SIDipp)Au(CO)]+
([1]+), [(Mes3P)Au(CO)]+ ([2]+), [Au(CO)]+, Au(CO)Cl,
and Au(CF3)CO with Energy Values in kcal/mol
(SIDipp)
(Mes3P)
ClAu +
CO
(CF3)Au
+ CO
fragments Au+ + CO Au+ + CO Au+ + CO
RESULTS AND DISCUSSION
■
ΔEint
ΔEpauli
ΔEelstat
−44.3
151.0
−33.4
168.3
−58.9
201.3
−55.6
189.5
−36.5
163.8
In 2011, we communicated that it is possible to use N-
heterocyclic carbenes and phosphines to isolate cationic gold(I)
carbonyl adducts like [(SIDipp)Au(CO)][SbF6] and
[(Mes3P)Au(CO)][SbF6].20,21 Key structural and spectro-
scopic parameters of these and several other isolable or
spectroscopically observed gold(I) adducts are summarized in
Table 1. Interestingly, [(SIDipp)Au(CO)][SbF6] and
[(Mes3P)Au(CO)][SbF6] have rather high CO stretching
frequencies which are higher than in free CO (2143 cm−1).
Since most metal carbonyls have C−O modes which are less
than 2143 cm−1, the former class has been termed by Strauss
“nonclassical carbonyls”.32,33 A quantum chemical investigation
was carried out in order to understand the unusual frequency
shift of the C−O stretching mode toward higher wave numbers.
The Au(CO)Cl and Au(CF3)CO (reported by Fornies and co-
workers)34 were also included in this study for comparison
because they are neutral molecules but display the same feature.
Figure 2 shows the calculated geometries and C−O
stretching frequencies of the cations [(SIDipp)Au(CO)]+
([1]+), [(Mes3P)Au(CO)]+ ([2]+), and [Au(CO)]+ and the
neutral gold carbonyls Au(CO)Cl and Au(CF3)CO. The
agreement between the calculated and experimental bond
lengths in [1]+ and [2]+ is quite good. The theoretical values
for the CO stretching mode are always somewhat smaller than
the experimental data and so is the calculated frequency for free
CO (2126 cm−1) compared with experiment (2143 cm−1).35
Nevertheless, calculations give a blue shift toward higher wave
numbers for [1]+ and [2]+ which agrees with experimental
findings. The largest value for a CO stretching mode is
calculated for [Au(CO)]+ (2205 cm−1) which also agrees with
the experimental observations that “naked” [Au(CO)]+ (2237
cm−1)36 and salt compounds of [Au(CO)]+ with various
counterions exhibit significant blue shifts (Table 1).
a
−122.9
−127.4
−159.7
−153.8
−126.9
(63.0%)
(63.1%)
(61.4%)
(62.8%)
(63.3%)
a
ΔEorb
−72.3
−74.3
(36.9%)
−100.5
(38.6%)
−91.2
(37.2%)
−73.5
(37.1%)
(36.5%)
b
ΔEσ
−41.8
−44.9
(61.4%)
−66.7
(66.4%)
−46.5
(51.0%)
−40.9
(57.8%)
(55.7%)
b
ΔEπ
−29.0
−28.2
(38.0%)
−32.2
(32.0%)
−43.2
(47.4%)
−31.0
(40.2%)
(42.2%)
b
ΔErest
−1.5
−1.2
(0.6%)
−1.1
(1.6%)
−1.5
(1.6%)
−1.6
(2.0%)
(2.2%)
ΔEprep
1.2
1.2
0.1
0.1
3.8
De
43.1
32.2
58.8
55.5
32.7
a
The values in parentheses are the percentage contributions to the
b
total attractive interactions ΔEelsat + ΔEorbital
parentheses are the percentage contributions to the total orbital
interactions ΔEorbital
.
The values in
.
[Au(CO)]+ are only slightly stronger (ΔEint = −58.9 kcal/mol)
than in neutral ClAuCO (ΔEint = −55.6 kcal/mol). Since the
preparation energies of the fragments are very small, the
absolute values of the interaction energies are nearly the same
as the bond dissociation energies (BDEs) which are De = 58.8
kcal/mol for [Au(CO)]+ and De = 55.5 kcal/mol for
Au(CO)Cl. The latter values are probably about 12 kcal/mol
too high. Previous high-level ab initio studies gave De = 45.1
kcal/mol at the QCISD(T) level for [Au(CO)]+ and De = 43.5
kcal/mol at CCSD(T) for ClAuCO.39,40 The trend of the Au−
CO bond strength in the five molecules can be expected to be
correct. Systematic studies of transition metal carbonyls have
shown that standard DFT methods faithfully reproduce trends
of bond dissociation energies which are calculated by highly
accurate ab initio methods such as CCSD(T).41
Table 2 shows that the Au−CO bonds in the five molecules
have a rather uniformly higher electrostatic character than
covalent character. The Coulombic attraction ΔEelstat which
comes mainly from the overlap of the σ lone-pair electrons of
CO with the nucleus of Au42 contributes between 61% and
63% to the total attraction while the orbital interactions ΔEorb
contribute only between 37% and 39%. It is at first sight
surprising that the orbital term comprises a rather larger
contribution from π orbitals. Table 2 shows that ΔEπ
contributes between 32.0% and 47.4% to ΔEorb. Nonclassical
carbonyls which exhibit a blue shift of the CO stretching
frequency are considered to possess only negligible metal→CO
π-backdonation.32,33,43−45 We want to point out that ΔEorb not
only comes from genuine orbital interactions, it also comes
from the polarization of the orbitals within the fragments. The
large contributions of ΔEπ in the gold carbonyl complexes arise
from the significant polarization of the occupied π orbitals in
CO and in the metal fragments. The polarization of the
occupied π and σ orbitals of CO toward the carbon end which
is induced by the positive charge of the metal fragments is the
main reason for the observed blue shift of the CO stretching
frequencies.33
Interestingly, for Au(CO)Cl and Au(CF3)CO, a small red-
shift is calculated which is not what was observed
experimentally. We note however that Au(CO)Cl and
Au(CF3)CO adducts have intermolecular Au···Au interactions
in the solid state.22,34,37,38 It is also known that the CO stretch
value of Au(CO)Cl in solution depends on the solvent.
Therefore, in order to find out whether intermolecular forces
might induce a blue shift for the CO stretching mode of these
molecules, we investigated the υCO values of small aggregates.
̅
The pentamer of Au(CO)Cl having constrained C4v symmetry
was chosen as a model for this study. Indeed, frequency
calculations of [Au(CO)Cl]5 show that the central Au(CO)Cl
species which is surrounded by four neighboring molecules (see
Supporting Information) has a higher CO stretching mode of
2146 cm−1 which gives a blue shift of 20 cm−1 (relative to the
calculated frequency for free CO of 2126 cm−1). In the case of
Au(CF3)CO we found that already a dimer exhibits a higher
CO stretching frequency of 2132 cm−1 yielding a blue shift of 6
cm−1. It means that the experimentally observed blue shifts of
Au(CO)Cl and Au(CF3)CO and perhaps other carbonyls may
at least partly be caused by intermolecular interactions.
Table 2 gives the results of the EDA-NOCV calculations. It is
interesting to note that the Au−CO interactions in the cation
Cyanide ion is isoelectronic to carbon monoxide. It is
however considered as a better σ-donor and a relatively poor π-
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Figure 3. Gold(I) cyanide complexes supported by N-heterocyclic carbene and phosphine ligands and the disproportionated product of
(Mes3P)Au(CN).
Table 3. Comparison of Vibrational (υCN, cm−1), Structural (Bond Distances, Å), and NMR Spectroscopic Data (Chemical
̅
Shifts, ppm) for Gold(I) Cyanides (TPA = 1,3,5-Triaza-7-phosphaadamantane, ItBu = 1,3-Di-t-butylimidazol-2-ylidene, IDipp
=1,3-Bis(2,6-diisopropylphenyl)imidazol-2-ylidene)
compd
υCN cm−1
Au−CN, Å
C−N, Å
Au−P or Au−Ccarb, Å
13CN
ref
̅
Et4N(CN)
2050
2138
95
50
96
49
97
(Et3P)Au(CN)
1.97(2)
1.15(3)
2.288(5)
2.287(3)
2.278(2)
2.284(3)
2.286(3)
2.302(5)
2.314(5)
2.322(5)
158.2(CDCl3)
(Cy3P)Au(CN)
2.006(11)
2.003(7)
2.073(13)
2.087(10)
2.02(3)
1.128(13)
1.136(10)
1.04(2)
(Ph3P)Au(CN)
2147
2143
{Ph2(Cy)P}Au(CN)
{(m-tolyl)3P}Au(CN)
[(TPA)2Au][Au(CN)2]
[{(CNCH2CH2)3P}2Au][Au(CN)2]
[{(CNCH2CH2)3P}2Au][Au(CN)2]
[(Mes3P)2Au][Au(CN)2]
[(Mes3P)2Au][Au(CN)2]
(ItBu)Au(CN)
1.02(2)
96,97
54
1.16(4)
1.77(4)
1.13(5)
98
2.22(3)
0.98(3)
98
a
2142
2142
2148
1.979(10)
2.000(10)
2.009(7)
1.996(17)
2.058(5)
1.124(13)
1.114(12)
1.098(10)
1.117(19)
1.099(7)
2.3275(19)
151.5(CDCl3)
151.5(CDCl3)
150.1(CDCl3)
152.3(CDCl3)
152.4(CDCl3)
this work
this work
46
a
2.3311(19)
2.011(6)
1.985(15)
2.039(5)
(IDipp)Au(CN)
47
(SIDipp)Au(CN)
2151
this work
a
From the two half molecules in unit cell.
acceptor ligand. N-Heterocyclic carbene and phosphine adducts
of gold(I) cyanide, (SIDipp)Au(CN) (3) and (Mes3P)Au(CN)
(4) (see Figure 3), are neutral molecules and are useful systems
for structure and bonding comparisons with corresponding
gold carbonyls. The gold(I) cyanide complex (SIDipp)Au(CN)
was synthesized in good yield by the reaction of (SIDipp)AuCl
with KCN. It is an air stable, colorless compound and has been
characterized by NMR, IR spectroscopy, elemental analysis, and
X-ray crystallography. The corresponding 13C labeled adduct
was also synthesized via a similar route using K13CN (instead of
KCN). The 13C{1H} NMR spectrum of (SIDipp)Au(13CN) in
CDCl3 showed a doublet (2JCC = 41.9 Hz) at δ 206.9 ppm
which can be assigned to the gold bound N-heterocyclic
carbene carbon resonance. The 13C resonance of the cyanide
carbon appeared at δ 152.4 ppm which is in a region
comparable to other reported N-heterocyclic carbene gold(I)
cyanide complexes such as [(1,3-di-t-butylimidazol-2-ylidene)-
Au(CN)] (150.1 ppm)46 and [(1,3-bis(2,6-diisopropylphenyl)-
imidazol-2-ylidene)Au(CN)] (152.3 ppm)47 (Table 3). IR
spectrum of (SIDipp)Au(CN) showed a strong signal
corresponding to the CN stretch at 2151 cm−1.
Figure 4. Molecular structure showing (SIDipp)Au(CN) (3),
ellipsoids are shown at 50% probability level. Selected bond lengths
(Å) and angles (deg): Au−C1 2.039(5), Au−C15 2.058(5), N2−C15
1.099(7), C1−Au−C15 178.62(19), N2−C15−Au 177.6(5), N1−
C1−N1 109.7(4).
The X-ray crystal structure of (SIDipp)Au(CN) (3) is
depicted in Figure 4. It crystallizes in the Pbcm space group and
featured a linear geometry at the gold(I) with C1−Au−C15
angle of 178.62(19)o. The bond lengths of Au−C1 and Au−
CN are 2.039(5) and 2.058(5) Å, respectively. It is possible to
compare the trans influence of CN− ligand to their isoelectronic
CO ligand. Interestingly, the Au−C1 distance in (SIDipp)Au-
(CN) [2.039(5) Å] is not that different from the corresponding
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Au−C distance of the [(SIDipp)Au(CO)][SbF6] [2.020(4) Å].
However, the Au−C1 bond distance in the gold(I) chloride
adduct (SIDipp)AuCl is marginally shorter [1.979(3) Å].48
The synthesis of gold(I) cyanide complex (Mes3P)Au(CN)
(4) was attempted by the reaction of (Mes3P)AuCl with KCN.
The corresponding 13C labeled adduct (134) was also
synthesized via a similar route using K13CN (instead of
KCN). However, unlike (SIDipp)Au(CN), the trimesitylphos-
phine supported AuICN complex was isolated as an ionic
species, [(Mes3P)2Au][Au(CN)2] (5), in the solid state. This is
not always the case for phosphine supported AuICN adducts as
other neutral complexes such as Ph3PAu(CN) and Et3PAu-
(CN) are known in the solid state (Table 3).49,50 The ionic
species presumably formed due to the ligand scrambling in the
solution. The presence of two species, (Mes3P)Au(13CN) (134)
and [(Mes3P)2Au][Au(13CN)2] (135), in CDCl3 solution at
room temperature was confirmed by 31P{1H} NMR and
13C{1H} NMR spectroscopy. The phosphorus signal for 134
was observed as a doublet at δ 5.32 ppm (2JC,P = 121 Hz)
whereas 135 displays a broad singlet at δ 6.33 ppm, which is
very similar to the other reported [(Mes3P)2Au][BF4] complex
(δ 6.3 ppm).51 The 13C{1H} resonance of the anion in 135
appears at δ 151.5 ppm, while in 134 it appeared as a doublet
(2JC,P = 121 Hz) at δ 150.4 ppm. For comparison, the 13C{1H}
NMR of (Et3P)Au(13CN) in CDCl3 solution displays a
resonance at δ 148.6 ppm for [(Et3P)2Au][Au(13CN)2] and a
doublet at δ 158.2 ppm (2JC,P = 122.4 Hz) for (Et3P)Au-
(13CN).50,52
[2.3380(12) Å]21 and [(Mes3P)2Au][BF4] [2.3525(10)].53 The
average Au−C distance of 1.989(10) Å in 5 is similar to the
Au−C bond length found in [(1,3,5-triaza-7-
phosphaadamantane)2Au][Au(CN)2] (2.02(3) Å).54 These
two compounds have the same [Au(CN)2]− anion.
Figure 6 shows the calculated equilibrium geometries of
[(SIDipp)Au(CN)] (3), [(Mes3P)Au(CN)] (4),
[(Mes3P)2Au]+, [Au(CN)2]−, and AuCN. The theoretical and
experimental values for the bond lengths are in reasonable
agreement. The calculated C−N stretching frequencies are very
close to the experimental values. A comparison with the
calculated value for the stretching mode of free CN− (2061
cm−1) shows that all the complexes exhibit a significant blue
shift of ∼100 cm−1. We also calculated the reaction energy for
the disproportionation of 3 and 4:
2[(SIDipp)Au(CN)](3) → [(SIDipp)2Au]+
+ [Au(CN)2]− + 62.9 kcal/mol
(1)
2[(Mes3P)Au(CN)](4) → [(Mes3P)2Au]+
+ [Au(CN)2]−(5) + 50.0 kcal/mol
(2)
The calculations suggest that the disproportionation
reactions of 3 and 4 yielding ionic species are intrinsically
disfavored, which should be expected. However, the charged
compounds which are formed will be stabilized by the solvent.
Assuming that the stabilization of the ions which are formed in
the disproportionation reaction has a similar strength, the
disproportionation of 4 is more likely than that of 3 because
reaction 2 is less endergonic than reaction 1. This is in
agreement with experimental observation that compounds 5
along with 4 are present as a mixture in solution while there is
no sign of the forward reaction 1.
[(Mes3P)2Au][Au(CN)2] (5) (grown from dichloromethane
by slow evaporation at room temperature) crystallizes in the
P21/n space group, and the gold atom of the cationic moiety
[(Mes3P)2Au]+ adopts a linear geometry with a P−Au−P angle
of 180.0° and an inversion center at Au. The cation and the
anion in 5 are well separated (Figure 5), and the shortest
distance between two gold atoms is about 10.96 Å. The average
Au−P distance of 2.3293(19) Å in 5 is similar to the
corresponding distance found in the [(Mes3P)Au(CO)][SbF6]
Table 4 gives the results of the EDA-NOCV calculations for
[(SIDipp)Au(CN)], [(Mes3P)Au(CN)], [Au(CN)2]−, and
Au(CN). The [Au]+/CN− interactions of [(SIDipp)Au(CN)],
[(Mes3P)Au(CN)], and Au(CN) are significantly stronger than
for the carbonyl complexes (Table 2), because the cyanide
complexes feature bonding of charged species. The bonding
comes mainly from the interactions between the carbon σ lone-
pair electrons and Au via electrostatic attraction and through
[Au]←CN− σ-donation which contributes the largest part
(<70%) to the total orbital interactions ΔEorb. The π orbital
interactions in the cyano complexes are much weaker than in
the carbonyl complexes. This is reasonable because CN− is a
much weaker π-acceptor than CO.55−57 The contribution of
ΔEπ to the total binding comes mainly from the polarization of
the π orbital rather than genuine [Au]→CN− π-backdonation.
Isocyanide adducts are also related closely to the
corresponding metal cyanide and carbonyl complexes. Thus,
gold(I) isocyanide complex [(SIDipp)Au(CNtBu)][SbF6]
([6][SbF6]) was also synthesized for a comparison of structure,
bonding, and properties. It was obtained from the reaction
t
between (SIDipp)AuCl and BuNC in the presence of AgSbF6
and characterized by several spectroscopic techniques and X-ray
crystallography. It is a colorless crystalline solid and can be
stored for several weeks in nitrogen atmosphere at room
temperature without any decomposition. IR spectrum of
[6][SbF6] displays a strong band at 2244 cm−1 which can be
Figure 5. Molecular structure showing [(Mes3P)2Au][Au(CN)2] (5),
ellipsoids are shown at 50% probability level. Only one of the two
[(Mes3P)2Au]+ moieties present in the asymmetric unit is shown.
Selected bond lengths (Å) and angles (deg): Au1−P1 2.3275(19),
Au2−P2 2.3311(19), Au3−C55 1.979(10), Au3−C56 2.000(10), N1−
C55 1.124(13), N2−C56 1.114(12); P1−Au1−P1 180.0, P2−Au2−
P2 180.0, C55−Au3−C56 178.5(4), N1−C55−Au3 177.0(9), N2−
C56−Au3 177.7(9).
assigned to the CN stretch. The increase in υCN upon
̅
coordination to gold(I) is normal as evident from CN stretch
of the Au(CNtBu) adducts like [HB(3,5-(CF3)2Pz)3]Au-
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Figure 6. Calculated equilibrium geometries and C−N stretching frequencies of [(SIDipp)Au(CN)] (3), [(Mes3P)Au(CN)] (4), [(Mes3P)2Au]+,
[Au(CN)2]−, and Au(CN) at BP86/TZVPP. Bond lengths are given in Å, frequencies in cm−1. Experimental values are given in parentheses. The
calculated frequency for free CN− is 2061 cm−1.
(CNtBu) [2248 cm−1] and (p-TolSO2S)Au(CNtBu) [2238
cm−1] (Table 5). For comparison, the free t-butylisocyanide
ligand shows νCN stretch at 2135 cm−1. The protons of t-Bu
group in [6][SbF6] appeared as a singlet at 1.47 ppm in the 1H
NMR spectrum which is not much different from the chemical
shift value observed for the corresponding protons of the free
ligand at 1.42 ppm.
pursue the isolation of [(Mes3P)Au(CNtBu)][SbF6] any
further.
Figure 8 shows the calculated geometries of [(SIDipp)Au-
(CNtBu)]+ ([6]+), [(Mes3P)Au(CNtBu)]+ ([7]+), [Au-
(CNtBu)]+, and Au(CNtBu)Cl. The EDA results are given in
Table 6. The agreement between the calculated and
experimental bond lengths in [6]+ is quite good. The calculated
frequency for the CN stretching mode in the [(SIDipp)Au-
(CNtBu)]+ ([6]+) (2227 cm−1) shows a significant blue shift
compared to the calculated value for the free ligand CNtBu
(2127 cm−1). This is in excellent agreement with the
experimental observations. [(Mes3P)Au(CNtBu)]+ ([7]+)
adducts also predicted a blue shift (although bit smaller
compared to the related (SIDipp) supported system). As with
the Au−CO systems, “naked” [Au(CNtBu)]+ shows the highest
calculated CN frequency. It is also interesting to note that the
The gold(I) isocyanide complex [(SIDipp)Au(CNtBu)]-
[SbF ] ([6][SbF ]) crystallizes in the P1 space group with
̅
6
6
two chemically similar molecules in the asymmetric unit
(Figure 7). The geometry at the gold is essentially linear with
C−Au−C angle of about 178°. The average Au−Ccarbene
distance in [6][SbF6] is 2.018(4) Å which is similar to the
corresponding distance in gold(I) cyanide complex [(SIDipp)-
Au(CN)] (3) [2.039(5) Å].
The synthesis of phosphine supported gold(I) isocyanide
complex, [(Mes3P)Au(CNtBu)][SbF6], was attempted by the
reaction of ClAu(CNtBu) with Mes3P in the presence of
AgSbF6. The analysis of the resulting crystalline product using
X-ray crystallography indicated the formation of [(Mes3P)2Au]-
[SbF6] as one of the products, pointing to a likely ligand
redistribution in solution during the synthesis. We did not
Au(CNtBu)Cl has a calculated νCN value of 2194 cm−1, which is
̅
a blue shift relative to that of the free CNtBu even without
considering any intermolecular interactions.
It is also interesting to compare the experimental and
calculated νCN values of ClAu(CNtBu) and [(SIDipp)Au-
̅
(CNtBu)][SbF6]. Experimentally, neutral ClAu(CNtBu) shows
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Table 4. EDA-NOCV Results at BP86/TZ2P+//BP86/
TZVPP for the Au−CN Bonds of [(SIDipp)Au(CN)] (3),
[(Mes3P)Au(CN)] (4), [Au(CN)2]−, and AuCN with Energy
Values in kcal/mol
(SIDipp)Au+
CN−
+
(Mes3P)Au+ +
CN−
(NC)Au +
CN−
Au+
+
fragments
CN−
ΔEint
−164.0
−155.1
−106.1
−230.4
ΔEpauli
ΔEelstat
187.3
202.9
182.4
261.4
a
−266.5
−262.4
−214.9
−371.33
(75.9%)
(73.3%)
(74.5%)
(75.5%)
a
ΔEorb
−84.8
−95.6
−73.5
−120.5
(24.1%)
(26.7%)
(25.5%)
(24.5%)
b
ΔEσ
−59.4
−71.5
−54.5
−90.1
(70.0%)
(74.8%)
(74.1%)
(74.8%)
b
ΔEπ
−13.7
−13.4
−16.5
−23.8
(16.2%)
(14.0%)
(22.4%)
(19.8%)
b
ΔErest
−11.7
−10.7
−2.5
−6.6
(13.8%)
(11.2%)
(3.5%)
(5.4%)
Figure 7. Molecular structure showing [(SIDipp)Au(CNtBu)][SbF6]
([6][SbF6]) ellipsoids shown at 50% probability level. Only one of the
molecules (out of two) present in the asymmetric unit is shown.
Selected bond lengths (Å) and angles (deg): Au1−C13 2.022(4),
Au2−C45 2.015(4), Au1−C28 1.988(4), Au2−C60 1.983(4), C28−
N3 1.142(5), C60−N6 1.146(5), C29−N3 1.473(5), C61−N6
1.463(5), C14−C15 1.528(5), C46−C47 1.530(6), C28−Au1−C13
177.62(15), C60−Au2−C45 177.65(16), N1−C13−N2 109.9(3),
N4−C45−N5 108.8(3), C28−N3−C29 179.3(5), C60−N6−C61
177.2(4), N3−C28−Au1 176.3(4), N6−C60−Au2 177.5(4).
ΔEprep
De
2.3
1.7
0.2
0.2
161.7
153.4
105.9
230.2
a
The values in parentheses are the percentage contributions to the
b
total attractive interactions ΔEelsat + ΔEorbital
parentheses are the percentage contributions to the total orbital
interactions ΔEorbital
.
The values in
.
a much larger shift in the υCN compared to the cationic
̅
[(SIDipp)Au(CNtBu)][SbF6] upon CNtBu coordination (for
example, the υCN of [(SIDipp)Au(CNtBu)][SbF6] (2244 cm−1)
̅
is more closer to the free CNtBu (2135 cm−1) than
and Au via electrostatic attraction and through [Au]←CNtBu
σ-donation which is similar to that noted above for the
corresponding CO adducts. Both these contributions however
are slightly larger in the CNtBu adducts. The π orbital
interaction in the CNtBu complexes is somewhat weaker than
in the carbonyl complexes but stronger compared to the
cyanide analogues (Table 4).
We have also examined the chemistry of gold cyclooctyne
adducts supported by phosphines and N-heterocyclic carbenes.
Isolable gold(I) alkyne complexes are still fewer in number and
are of interest as models for intermediates in gold mediated
processes involving alkynes.17,18,58−63 Keep in mind however
that in contrast to the π-acid ligands like CO, CN−, and CNtBu
which use a lone pair of electrons on carbon to coordinate to
metals in end-on fashion, alkynes use π-electrons and bind to
metals in side-on fashion.
ClAu(CNtBu) (2260 cm−1)). However, calculations indicate a
much larger shift in the νCN for the cationic [(SIDipp)Au-
̅
(CNtBu)]+ ([6]+) compared to the neutral Au(CNtBu)Cl upon
CNtBu coordination (for comparison, computed values for the
three species are 2227, 2194, and 2127 cm−1, respectively). We
think that the difference between the calculated and
experimental frequency shift trends may come from inter-
molecular interactions which we did not include in calculations
and should be particularly large (and also experimentally
observed) for the Au(CNtBu)Cl.38 As we computed for
Au(CO)Cl and Au(CF3)CO, such interactions could induce
an additional blue shift in υCN for Au(CNtBu)Cl.
̅
Table 6 gives the results of the EDA-NOCV calculations for
the isocyanide adducts. A comparison to the analogous
carbonyl adducts (Table 2) indicates that the [Au]−CNtBu
interactions are stronger (Table 2) perhaps because CNtBu is a
much better σ-donor than the CO. The bonding comes mainly
from the interactions between the carbon σ lone-pair electrons
Cationic gold(I) π-alkyne complexes, [(SIDipp)Au-
(cyclooctyne)][SbF6] ([8][SbF6]) and [(Mes3P)Au-
(cyclooctyne)][SbF6] ([9][SbF6]), were synthesized and
Table 5. Comparison of Vibrational (υCN, cm−1), Structural (bond distances, Å), and NMR Spectroscopic Data (chemical shifts,
̅
ppm) for Gold(I) Isocyanides
compound
υCN cm−1
Au−CN, Å
C−N, Å
Au−Ccarb, Å
ref
̅
CNtBu
ClAu(CNtBu)
BrAu(CNtBu)
NCAu(CNtBu)
(NO3)Au(CNtBu)
(p-TolSO2S)Au(CNtBu)
[Au(CCSiMe3)(CNtBu)]
[HB(3,5-(CF3)2Pz)3]Au(CNtBu)
[(IMes)Au{CN(2,6-Me2C6H3)}][BF4]
[(SIDipp)Au(CNtBu)][SbF6]
2135
2260
2235.8
2224
2258
2238
2230
2248
2218.8
2244
99
1.92(1)
1.939(8)
1.93(3)
1.92(1)
1.972(4)
1.98(5)
1.939(8)
1.954(6)
1.13(2)
1.13(1)
1.21(3)
1.13(2)
1.135(6)
1.17(5)
1.131(10)
1.171(7)
100,101
102
103
104
105
106
23
1.998(5)
107
a
a
a
1.986(4)
1.144(5)
2.018(4)
this work
a
Average distances.
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Figure 9. Gold(I) cyclooctyne complexes supported by N-heterocyclic
carbene and phosphine ligands.
The [(SIDipp)Au(cyclooctyne)][SbF6] ([8][SbF6]) is stable
in CD2Cl2 solution even at room temperature, whereas
[(Mes3P)Au(cyclooctyne)][SbF6] ([9][SbF6]) decomposes
slowly in CD2Cl2 solution forming black deposits. In this
regard it is worth noting that the gold(I) alkyne complex
[{(3,5-(CF3)2C6H3)3P)}Au(2-hexyne)][BF4] also quickly de-
composes at higher temperature (>223 K) yielding [{(3,5-
(CF3)2C6H3)3P)}2Au][BF4] and colloidal gold.62 The cyclo-
octyne coordination to the gold(I) in solution was confirmed
from the 13C NMR spectrum. In the 13C{1H} NMR spectrum
of the gold(I) π-alkyne complex [8][SbF6] displayed a
resonance at δ 97.4 ppm corresponding to the CC carbon
signal of cyclooctyne, which shows downfield field shift relative
to that of the free cyclooctyne CC carbon chemical shift
value (δ 94.9 ppm).58 It is interesting to note that the strong σ-
donor properties of carbene ligand resulted in the upfield shift
of CC carbon signal in [8][SbF6] complex (δ 97.4 ppm)
compared to the related phosphine adducts [9][SbF6] (δ 101.9
ppm). The protons on the α-carbons of the alkyne moiety in
[8][SbF6] also exhibit a larger upfield shift (δ 2.02 ppm) in
comparison to the corresponding phosphine analogue (δ 2.66
ppm). The corresponding 1H NMR resonance signal in the free
cyclooctyne appears at δ 2.13 ppm. The 31P{1H} NMR
spectrum of [(Mes3P)Au(cyclooctyne)][SbF6] exhibited a
resonance at δ 6.39 ppm which is a downfield shift compared
to that of the [(Mes3P)Au(CO)][SbF6] (δ −4.7) and free
Mes3P signal (δ −35.9).
Figure 8. Calculated equilibrium geometries of [(SIDipp)Au-
(CNtBu)]+ ([6]+), [(Mes3P)Au(CNtBu)]+ ([7]+), [ClAu(CNtBu)],
and [Au(CNtBu)]+ at BP86/TZVPP. Bond lengths are given in Å.
Experimental values are given in parentheses. The calculated CN
stretching frequency for free CNtBu is 2127 cm−1.
Table 6. EDA-NOCV Results at BP86/TZ2P+//BP86/
TZVPP for the Au-CNtBu Bonds [(SIDipp)Au(CNtBu)]+
([6]+), [(Mes3P)Au(CNtBu)]+ ([7]+), [ClAu(CNtBu)], and
[Au(CNtBu)]+ with Energy Values in kcal/mol
(SIDipp)Au+
CNtBu
+
(Mes3P)Au+
CNtBu
+
ClAu +
CNtBu
Au+ +
fragments
CNtBu
ΔEint
−66.0
−54.7
−65.2
−101.1
ΔEpauli
ΔEelstat
159.4
176.2
197.7
223.2
a
−156.7
−158.2
−182.9
−216.8
(69.5%)
(68.5%)
(69.6%)
(66.9%)
The X-ray quality crystals of the complex [(SIDipp)Au-
(cyclooctyne)][SbF6] ([8][SbF6]) were grown from the slow
diffusion of hexanes into a CH2Cl2 solution at −5 °C. The
molecular structure of [8][SbF6] is depicted in Figure 10. As
expected, the gold center adopts a linear geometry with the
C(carbene)−Au−cyclooctyne(centroid) angle of 178.13°. The
Au−C3 and Au−(CC centroid) distances are 2.022(3) and
2.115 Å, respectively. Interestingly, the imidazole plane is nearly
perpendicular to the C29−Au−C28 plane with a dihedral angle
of ca. 88.15°. The Au−(CC centroid) distance of [8][SbF6]
[2.115 Å] is marginally shorter than the corresponding
parameter of N-heterocyclic carbene analogue [(IDipp)Au-
a
ΔEorbital
−68.7
−72.7
−80.0
−107.5
(30.5%)
(31.5%)
(30.4%)
(33.2%)
b
ΔEσ
−44.5
−50.2
−47.8
−72.9
(64.7%)
(69.1%)
(59.7%)
(67.8%)
b
ΔEπ
−21.3
−20.4
−30.6
−30.8
(31.0%)
(28.1%)
(38.2%)
(28.6%)
b
ΔErest
−2.9
−2.1
−1.6
−3.8
(4.2%)
(2.9%)
(2.0%)
(3.5%)
ΔEprep
1.7
1.8
0.1
0.8
De
64.3
52.9
65.1
100.3
a
The values in parentheses are the percentage contributions to the
b
total attractive interactions ΔEelsat + ΔEorbital
parentheses are the percentage contributions to the total orbital
interactions ΔEorbital
.
The values in
(cyclododecyne)][SbF ] [2.142(5) Å] reported by Furstner.63
̈
6
.
The CC bond distance in complex [8][SbF6] [1.213(5) Å]
is similar to that reported cationic gold complex,
[(cyclooctyne)3Au][SbF6] [1.213(7)−1.217(7) Å].58 There
are no close Au···Au or Au···F contacts in the [8][SbF6]
complex.
isolated from the reaction of the corresponding LAuCl (L =
SIDipp and Mes3P) salts, cyclooctyne, and AgSbF6 in
dichloromethane at 0 °C in good yield (Figure 9). These
gold(I) π-alkyne complexes are thermally stable white solids
and have been characterized by NMR, elemental analysis, and
X-ray crystallography.
The molecular structure of [(Mes3P)Au(cyclooctyne)]-
[SbF6] ([9][SbF6]) is shown in Figure 11. It crystallizes in
the P1 space group. There are two molecules of [(Mes P)Au-
̅
3
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Figure 12 shows the calculated geometries of [(SIDipp)Au-
(cyclooctyne)]+ ([8]+), [(Mes3P)Au(cyclooctyne)]+ ([9]+),
Figure 10. Molecular structure showing [(SIDipp)Au(cyclooctyne)]-
[SbF6] ([8][SbF6]), ellipsoids are shown at 50% probability level.
Selected bond lengths (Å) and angles (deg): Au−C3 2.022(3), Au−
C28 2.199(3), Au−C29 2.201(4), C28−C29, 1.213(5), C1−C2
1.512(5), C3−Au−C28 163.05(13), C3−Au−C29, 164.78(13),
C28−C29−C30 157.0(4), C29−C28−C35 157.5(4), C28−Au−C29
32.00(13), N1−C3−N2 108.8(3).
Figure 12. Calculated equilibrium geometries of [(SIDipp)Au-
(cyclooctyne)]+ ([8]+), [(Mes3P)Au(cyclooctyne)]+ ([9]+), [ClAu-
(cyclooctyne)] (10), and [Au(cyclooctyne)]+ at BP86/TZVPP. Bond
lengths are given in Å. Experimental values are given in parentheses.
The calculated CC stretching frequency for free cyclooctyne is 2259
cm−1.
[Au(cyclooctyne)]+, and Au(cyclooctyne)Cl (10). The EDA
results are given in Table 7. The calculated bond lengths of [8]+
and [9]+ show a very good agreement with the experimental
data (Figure 12). The intrinsic interaction energy between the
gold fragment and cyclooctyne is significantly higher in
[Au(cyclooctyne)]+ (ΔEint = −100.7 kcal/mol) compared to
[8]+, [9]+, and 10, pointing to notable supporting ligand effect.
The electrostatic interaction (ΔEelstat) predominates over the
orbital interactions (ΔEorb) in [8]+, [9]+, [Au(cyclooctyne)]+,
and 10. The breakdown of ΔEorb into contributions of orbitals
that have different symmetry shows that the ([CC]→Au) σ-
donation is the larger component in these adducts and it is the
significantly larger component based on percentage contribu-
tions to the total orbital interactions ΔEorbital in the cationic
adducts [8]+, [9]+, and [Au(cyclooctyne)]+, while in the neutral
adduct 10, the σ-contribution is relatively lower and the −C
C−→Au backbonding is much higher.
Overall, SIDipp and Mes3P supported gold(I) complexes of
carbonyl, cyanide, isocyanide, and cyclooctyne reported in this
paper are monomeric, two-coordinate species and display linear
geometry at gold(I). The gold(I) carbonyl adducts [(SIDipp)-
Au(CO)][SbF6] ([1][SbF6]) and [(Mes3P)Au(CO)][SbF6]
([2][SbF6]) are air sensitive and thermally less stable compared
to the related gold(I) cyanide, isocyanide, and cyclooctyne
complexes. The gold(I) cyanides are air stable, whereas the
solid samples of gold(I) isocyanide and cyclooctyne adducts are
moderately air stable but best stored under an inert atmosphere
at −10 °C refrigerator. The stability of gold(I) cyanides is also
supported from the computational data. The SIDipp and Mes3P
supported Au−CN bond strength is much stronger (De =
Figure 11. Molecular structure showing [(Mes3P)Au(cyclooctyne)]-
[SbF6] ([9][SbF6]), ellipsoids are shown at 50% probability level.
Only one of the molecules (out of two) present in the asymmetric unit
is shown. Selected bond lengths (Å) and angles (deg): Au1−P1
2.3220(15), Au2−P2 2.3087(14), Au1−C28 2.223(6), Au2−C63
2.191(5), Au1−C29 2.197(6), Au2−C64 2.188(6), P1−C1 1.843(6),
P1−C10 1.850(6), P1−C19 1.841(6), P2−C36 1.835(6), P2−C45
1.836(6), P2−C54 1.831(6), C28−C29 1.223(9), C63−C64 1.203(9),
P1−Au1−C28 160.20(17), P1−Au1−C29 166.73(17), P2−Au2−C63
168.43(18), P2−Au2−C64 159.51(19), C28−C29−C30 154.3(7),
C29−C28−C35 158.8(7), C63−C64−C65 157.0(6), C64−C63−C70
156.7(6), C29−Au1−C28 32.1(2), C64−Au2−C63 31.9(2).
(cyclooctyne)][SbF6] in the asymmetric unit. The structure
showed a slightly distorted linear conformation with (CC
centroid)−Au−P angles of 174.75° and 175.25° for the two
molecules. The average Mes3P−Au bond length in [9][SbF6] is
2.3153(15) Å, and it is longer than the Au−P distance of
(Mes3P)AuCl (2.2634(15) Å).64 The average CC bond
distance of [9][SbF6] [1.213(9) Å] is identical to the
corresponding distances in N-heterocyclic carbene analogue
[8][SbF6] [1.213(5) Å] and [(cyclooctyne)3Au][SbF6]
[1.213(7)−1.217(7) Å].
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Table 7. EDA-NOCV results at BP86/TZ2P+//BP86/TZVPP for the Au-cyclooctyne bonds [(SIDipp)Au(cyclooctyne)]+
([8]+), [(Mes3P)Au(cyclooctyne)]+ ([9]+), [ClAu(cyclooctyne)] and [Au(cyclooctyne)]+ with Energy values in kcal/mol
fragments
(SIDipp)Au+ + cyclooctyne
(Mes3P)Au+ + cyclooctyne
ClAu + cyclooctyne
Au+ + cyclooctyne
ΔEint
−54.2
−44.8
−57.0
−100.7
ΔEpauli
ΔEelstat
133.2
148.2
169.6
178.8
a
−117.51 (62.7%)
−69.9 (37.3%)
−34.2 (48.9%)
−20.7 (29.6%)
−3.7 (5.2%)
−11.3 (16.2%)
3.2
−121.4 (62.9%)
−71.5 (37.1%)
−36.8 (51.5%)
−20.0 (28.0%)
−3.9 (5.5%)
−10.8 (15.1%)
3.4
−144.6 (63.8%)
−82.0 (36.2%)
−38.4 (46.8%)
−33.8 (41.2%)
−3.0 (3.7%)
−6.8 (8.3%)
3.2
−162.7 (58.2%)
−116.8 (41.8%)
−68.8 (58.9%)
−28.0 (24.0%)
−11.4 (9.8%)
−8.6 (7.4%)
4.6
a
ΔEorbital
b
ΔEσ (−CC−→Au)
b
ΔEπ∥ (Au→−CC−)
b
ΔEπ⊥ (−CC−→Au)
ΔErest
ΔEprep
De
51.0
41.4
53.8
96.1
υCC [cm−1
]
2099.6
2093.7
2040.9
1982.3
̅
r(CC) [Å]
1.244
1.245
1.256
1.270
a
b
The values in parentheses are the percentage contributions to the total attractive interactions ΔEelsat + ΔEorbital. The values in parentheses are the
percentage contributions to the total orbital interactions ΔEorbital
.
161.7, 153.4 kcal/mol) than the gold(I) interaction with CO
(De = 43.1, 32.2 kcal/mol), CNtBu (De = 64.3, 52.9 kcal/mol),
and cyclooctyne (De = 51.0, 41.4 kcal/mol) supported by the
same auxiliary ligands. The Au−L (CO, CN−, CNtBu,
cyclooctyne) bonds are relatively stronger in the SIDipp
systems compared to the corresponding Mes3P adducts.
Interestingly, De values of cationic Au(I)CO, CNtBu, and
cyclooctyne systems show that end-on bound Au−CO bonds
are the weakest while the corresponding Au−isocyanide
contacts are the strongest. The side-on bound Au−cyclooctynes
show intermediate bond strengths among the three types. The
“naked” [Au(CO)]+, [Au(CNtBu)]+, and [Au(cyclooctyne)]+
systems have much stronger Au−ligand bonds compared to the
corresponding SIDipp and Mes3P supported systems.
Experimental and computational data show that the changes
in unsaturated ligand on (SIDipp)Au+ from CO, CN−, CNtBu
to cyclooctyne as in [1]+, 3, [6]+, and [8]+ did not lead to
notable changes in the Au−Ccarbene bond distances. A similar
phenomenon was also observed in Au−P distance in complexes
[2]+, 4, [7]+, and [9]+ bearing trimesitylphosphine ligands. In
solution 13C{1H} NMR spectra, the gold(I) bonded carbene
carbon resonance of the complexes [1][SbF6] (195.4 ppm), 3
(206.9 ppm), [6][SbF6] (199.9 ppm), and [9][SbF6] (202.5
ppm) was observed in somewhat narrow region of 195−207
ppm. This shows that different types of ligands like CN−,
CNtBu, and cyclooctyne did not have much effect on gold-
bound carbene carbon shift.
Calculated frequencies for the CO and CN stretching modes
of SIDipp and Mes3P supported gold(I) adducts of carbonyl,
cyanide, and isocyanide reported here show a blue shift
compared to the corresponding stretch of the free ligands.
These data agree with the experimental results. In the case of
neutral gold(I) carbonyls Au(CO)Cl and Au(CF3)CO, small
red shifts were predicted for CO stretching modes of
monomers but they changed to blue shifts upon inclusion of
intermolecular interactions.
We did not analyze the gold(I)−carbene and Au(I)−
phosphine bond strengths of the present complexes. However,
relative stabilities suggest that the SIDipp ligand binds to
gold(I) much stronger than the Mes3P. There are computa-
tional studies on other molecules supporting this trend.65
In summary, we present here structures, properties, and
computational data on closely related end-on bound π-acceptor
ligand (CO, CN−, CNtBu) adducts of gold(I) and side-on
bound cyclooctyne on gold(I) having the same supporting
ligand. We are presently investigating the related chemistry of
lighter members of coinage metal family.
EXPERIMENTAL SECTIONS
■
General Procedures. All manipulations were carried out under an
atmosphere of dry nitrogen, using standard Schlenk techniques or in a
glovebox. Solvents were purchased from commercial sources, purified
using an Innovative Technology SPS-400 PureSolv solvent drying
system degassed by the freeze−pump−thaw method twice prior to
use. Glassware was oven-dried at 150 °C overnight. NMR spectra were
recorded at 298 K on JEOL Eclipse 500 and 300 spectrometer. Proton
and carbon chemical shifts are reported in ppm, and referenced using
the residual proton and carbon signals of the deuterated solvent. 31P
NMR chemical shifts were referenced to a 85% H3PO4 standard. The
31P NMR spectroscopic data were accumulated with H decoupling.
1
NMR annotations used are as follows: br = broad, d = doublet, m =
multiplet, s = singlet, t = triplet, sept = septet. Infrared spectra were
recorded on a JASCO FT-IR 410 spectrometer operating at 2 cm−1
spectral resolution. IR spectroscopic data were collected using KBr
pellets or mulls between NaCl plates prepared using solid material and
Nujol. Herein we use abbreviations based on IUPAC guidelines, that
is, υ for frequency and υ for wavenumber. Elemental analyses were
̅
performed using a Perkin-Elmer Series II CHNS/O analyzer.
Cyclooctyne,66 and (SIDipp)AuCl48 and (Mes3P)AuCl67 were
t
synthesized using literature procedure. Mes3P, BuNC, KCN, K13CN,
AuCl, and AgSbF6 were purchased from Sigma-Aldrich and used
without further purification.
[(SIDipp)Au(CN)] (3). A mixture of (SIDipp)AuCl (0.073 g, 0.117
mmol) and KCN (0.008 g, 0.117 mmol) in ethanol (ca. 30 mL) was
stirred overnight at room temperature (for (SIDipp)Au(13CN) the
K13CN was used). The solvent was removed under reduced pressure.
The residue was dissolved in dichloromethane (ca. 20 mL) and
filtered, and the filtrate was concentrated to ∼2 mL under reduced
pressure. The solution was kept in a refrigerator at 0 °C to obtain
colorless prism shaped crystals of (SIDipp)Au(CN) (0.056 g, 78%
yield). 1H NMR (CDCl3,3500.16 MHz, 298 K): δ 7.42 (t, 2H, 3JHH = 8
Hz, C6H3), 7.23 (d, 4H, JHH = 8 Hz, C6H3), 4.05 (s, 4H, CH2), 3.00
3
3
(sept, 4H, JHH = 6.9 Hz, CH(CH3)2), 1.37 (d, 12H, JHH = 6.9 Hz,
CH(CH3)2), 1.33 (d, 12H, 3JHH = 6.9 Hz, CH(CH3)2). 13C{1H} NMR
2
(CDCl3, 125.77 MHz, 298 K): δ 206.9 (d, JCC = 41.9 Hz, Au−
N13CN), 152.4 (13CN), 146.6, 133.6, 130.3, 124.8, 53.9, 29.1, 25.3,
24.2. IR (KBr, selected bands) cm−1: 2151 (CN). IR (Nujol mull,
selected bands) cm− 1
: 2151 (CN). Anal. Calcd for
C28H38N3Au·CH2Cl2: C, 49.86; H, 5.77; N, 6.02. Found: C, 49.70;
H, 5.50; N, 5.82%.
[(Mes3P)2Au][Au(CN)2] (5). A mixture of Mes3P (0.167 g, 0.430
mmol) and AuCl (0.099 g, 0.430 mmol) in dichloromethane (ca. 10
738
dx.doi.org/10.1021/ic301869v | Inorg. Chem. 2013, 52, 729−742

Inorganic Chemistry
Article
Table 8. Crystallographic Data
[(SIDipp)Au(CNtBu)]
[SbF6]
[(SIDipp)
Au(cyclooctyne)][SbF6]
[(Mes3P)Au(cyclooctyne)]
[SbF6]
[(SIDipp)Au(CN)]
[(Mes3P)2Au][Au(CN)2]
formula
C28H38N3Au·CH2Cl2
698.51
C56H66N2P2Au2·2CH2Cl2
1392.83
C32H47F6N3SbAu·2CH2Cl2
C35H50F6N2SbAu·CH2Cl2
1016.41
C35H45F6PSbAu·0.5CH2Cl2
fw
1076.32
100(2)
triclinic
971.86
100(2)
triclinic
T (K)
100(2)
100(2)
100(2)
cryst syst
space group
cell dimensions
orthorhombic
Pbcm
monoclinic
P21/n
monoclinic
P21/c
P1
̅
P1
̅
a = 8.150(8) Å
b = 16.321(17) Å
c = 23.29(2) Å
α = 90°
β = 90°
γ = 90°
a = 12.1018(9) Å
b = 28.890(2) Å
c = 16.0447(12) Å
α = 90°
β = 90.694(1)°
γ = 90°
a = 12.410(4) Å
b = 14.622(4) Å
c = 23.418(7) Å
α = 82.180(4)°
β = 82.853(3)°
γ = 85.706(4)°
4170(2)
a = 14.1827(9) Å
b = 14.4496(9) Å
c = 22.4045(11) Å
α = 90°
β = 120.917(3)°
γ = 90°
a = 11.8942(13) Å
b = 15.9993(18) Å
c = 19.680(2) Å
α = 79.001(1)°
β = 86.028(1)°
γ = 77.996(1)°
3594.1(7)
3
́
V (Å)
3098(6)
5609.2(7)
4
3939.1(4)
Z
4
4
4
4
dcalcd (g cm−3
)
1.498
1.649
1.714
1.714
1.796
abs coeff
4.942
5.511
4.472
4.597
5.003
(mm−1
)
F (000)
1392
2752
2112
2000
1900
θ range (deg)
reflns collected
1.75−28.19
22 602
1.41−28.34
54 830
1.41−28.47
41 541
1.67−28.30
38 446
1.32−28.34
35 171
Rint (indep
reflns)
0.0521 (3860)
0.0574 (13986)
0.0230 (20698)
0.0369 (9780)
0.0392 (17638)
data/restr/
params
GOF on F2
3860/0/183
1.103
13 986/6/634
20 698/6/905
9780/0/460
17 638/60/894
1.222
1.052
1.062
1.036
R1 [I > 2σ(I)]/ 0.0306/0.0365
all data
0.0596/0.0757
0.0353/0.0423
0.0333/0.0424
0.0506/0.0705
wR2 [I >
2σ(I)]/all
data
0.0735/0.0761
0.1300/0.1351
0.0919/0.0965
0.0808/0.0849
0.1283/0.1393
mL) stirred for 2 h at room temperature. The solution was filtered
through a pad of Celite via canula, and the filtrate was evaporated to
dryness. The residue was dissolved in ethanol (ca. 15 mL), and KCN
(0.028 g, 0.430 mmol) was added (for the preparation of
[(Mes3P)2Au][Au(13CN)2] the K13CN was used). The reaction
mixture was stirred for overnight at room temperature. The solvent
was removed under reduced pressure, the residue was dissolved
dichloromethane (ca. 10 mL) and filtered, and the solvent was
removed under reduced pressure to give the product as a white solid.
Single crystals for X-ray analysis were obtained by slow evaporation
from dichloromethane solution. 31P NMR (CDCl3, 121.66 MHz, 298
K) [(Mes3P)2Au][Au(CN)2]: δ 6.35 (br s). [(Mes3P)Au(CN)]: δ
5.32 (s). IR (KBr, selected bands) cm−1: 2142 (CN). Anal. Calcd for
C56H66N2P2Au2: C, 55.00; H, 5.44; N, 2.29. Found: C, 56.00; H, 5.41;
N, 2.00%.
3JHH = 6.9 Hz, CH(CH3)2), 1.33 (d, 12H, 3JHH = 6.9 Hz, CH(CH3)2).
13C{1H} NMR (CDCl3, 125.77 MHz, 298 K): δ 199.9 (Au−NCN),
147.0, 133.1, 130.6, 125.0, 54.5, 29.8, 29.0, 25.6, 24.1; CN and CtBu
not detected. IR (KBr, selected bands) cm−1: 2244 (CN). IR (Nujol
mull, selected bands) cm−1: 2243 (CN). Anal. Calcd for
C32H47N3F6AuSb·CH2Cl2: C, 39.98; H, 4.98; N, 4.24. Found: C,
40.32; H, 5.02; N, 4.99%.
[(SIDipp)Au(cyclooctyne)][SbF6] ([8][SbF6]). Cyclooctyne (0.029 g,
0.271 mmol) in dichloromethane (8 mL) was placed in Schlenk flask
together with several pieces of 4 Å molecular sieve and degassed by the
freeze−pump−thaw method. The degassed cyclooctyne−dichloro-
methane solution was added to the mixture of AgSbF6 (0.062 g, 0.181
mmol) and (SIDipp)AuCl (0.113 g, 0.181 mmol) as solid at 0 °C. The
reaction mixture was stirred for 1 h 0 °C. The resulting mixture was
filtered through a pad of Celite via canula, and the filtrate was
concentrated to ∼4 mL under reduced pressure. The concentrated
solution was layered with hexane and kept in refrigerator at −5 °C to
obtain colorless prism shaped crystals of [(SIDipp)Au(cyclooctyne)]-
[SbF6] (0.089 g, 53% yield). 1H NMR (CD2Cl2, 500.16 MHz, 298 K):
[(Mes3P)2Au][Au(13CN)2] (0.107 g, 41% Yield). 13C{1H} NMR
(CDCl3, 125.77 MHz, 298 K, selected peaks) [(Mes3P)2Au][Au-
(13CN)2]: δ 151.5 (Au−13CN). [(Mes3P)Au(13CN)]: δ 150.4 (d, 2JC,P
= 121 Hz, Au−13CN). 31P{1H} NMR (CDCl3, 121.66 MHz, 298 K)
[(Mes3P)2Au][Au(13CN)2]: δ 6.33 (br). [(Mes3P)Au(13CN)]: δ 5.32
3
3
δ 7.47 (t, 2H, JHH = 8 Hz, C6H3), 7.29 (d, 4H, JHH = 8 Hz, C6H3),
2
3
(d, JC,P = 121 Hz).
4.25 (s, 4H, CH2), 3.06 (sept, 4H, JHH = 6.9 Hz, CH(CH3)2), 2.02
[(SIDipp)Au(CNtBu)][SbF6] ([6][SbF6]). A mixture of (SIDipp)AuCl
(0.113 g, 0.181 mmol) and AgSbF6 (0.062 g, 0.181 mmol) in
dichloromethane (ca. 8 mL) was stirred for 30 min at room
temperature to obtain an off-white precipitate. The resulting mixture
was filtered through a pad of Celite via canula, and the filtrate was
concentrated to ∼3 mL under reduced pressure. The mixture was
(m, 4H, C8H12), 1.76 (m, 4H, C8H12), 1.51 (m, 4H, C8H12), 1.37 (d,
3
3
12H, JHH = 6.9 Hz, CH(CH3)2), 1.32 (d, 12H, JHH = 6.9 Hz,
CH(CH3)2). 13C{1H} NMR (CD2Cl2, 125.77 MHz, 298 K): δ 202.5
(Au−NCN), 147.3, 133.0, 131.1, 125.3, 97.4 (cyclooctyne), 54.3, 34.1
(cyclooctyne), 29.4, 28.7 (cyclooctyne), 25.5, 24.2, 22.1 (cyclooctyne).
Anal. Calcd for C35H50N2F6AuSb·0.5CH2Cl2: C, 43.78; H, 5.28; N,
2.88. Found: C, 43.59; H, 5.01; N, 2.77%.
t
cooled to −18 °C (using ice/acetone bath), and BuNC (0.018 g,
0.217 mmol) was added. The reaction mixture was stirred for 1 h, and
the solution was kept in a refrigerator at 0 °C to obtain colorless prism
shaped crystals of [(SIDipp)Au(CNtBu)][SbF6] (0.093 g, 57% yield).
[(Mes3P)Au(cyclooctyne)][SbF6] ([9][SbF6]). Cyclooctyne (0.028 g,
0.262 mmol) in dichloromethane (6 mL) was placed in a Schlenk flask
together with several pieces of 4 Å molecular sieve and degassed by the
freeze−pump−thaw method. The degassed cyclooctyne−dichloro-
methane solution was added to the mixture of (Mes3P)AuCl (0.109 g,
0.175 mmol) and AgSbF6 (0.060 g, 0.175 mmol) as solid at 0 °C. The
3
1H NMR (CDCl3, 500.16 MHz, 298 K): δ 7.48 (t, 2H, JHH = 8 Hz,
C6H3), 7.28 (d, 4H, 3JHH = 8 Hz, C6H3), 4.24 (s, 4H, CH2), 3.03 (sept,
4H, 3JHH = 6.9 Hz, CH(CH3)2), 1.47 (s, 9H, C(CH3)3), 1.37 (d, 12H,
739
dx.doi.org/10.1021/ic301869v | Inorg. Chem. 2013, 52, 729−742

Inorganic Chemistry
Article
reaction mixture was stirred for 3 h and filtered through a pad of Celite
via canula. The filtrate was concentrated to ∼2 mL, diluted with
hexane (2 mL), and cooled at −5 °C for 24 h in a refrigerator to form
[(Mes3P)Au(cyclooctyne)][SbF6] as a colorless solid (0.105 g, 64%
yield). X-ray quality crystals were obtained from dichloromethane
solution layered with hexane at −5 °C. [(Mes3P)Au(cyclooctyne)]-
[SbF6] slowly decomposes in CD2Cl2 solution at room temperature
presumably forming [(Mes3P)2Au][SbF6] as one of the products (based on
comparison of spectroscopic data to previously reported [(Mes3P)2Au]-
[BF4]).51 1H NMR (CD2Cl2, 500.16 MHz, 298 K): δ 7.01 (br. s, 3H,
C6H2), 6.88 (s, 3H, C6H2), 2.66 (m, 4H, C8H12), 2.33 (br, 9H, o-CH3),
2.27 (br, 9H, p-CH3), 2.01 (m, 4H, C8H12), 1.81 (br s, 9H, o-CH3),
1.72 (m, 4H, C8H12). 13C{1H} NMR (CD2Cl2, 125.77 MHz, 298 K):
(selected peaks, cyclooctyne) δ 101.9 (br), 33.9, 29.1, 23.1. 31P{1H}
NMR (CD2Cl2, 202.47 MHz, 298 K): δ 6.39 (s). Anal. Calcd for
C35H45F6PAuSb: C, 45.23; H, 4.88. Found: C, 46.04; H, 4.24%.
X-ray Crystallographic Data. A suitable crystal covered with a
layer of paratone-N oil was selected and mounted within a cryo-loop
and immediately placed in the low-temperature nitrogen stream.
Diffraction data were collected at T = 100(2) K. The data sets were
collected on a Bruker SMART APEX CCD diffractometer with
graphite monochromated Mo Kα radiation (λ = 0.710 73 Å). The cell
parameters were obtained from a least-squares refinement of the spots
(from 60 collected frames) using the SMART program. Intensity data
were processed using the Saint Plus program. All the calculations for
the structure determination were carried out using the SHELXTL
package (version 6.14).68 Initial atomic positions were located by
direct methods using XS, and the structures of the compounds were
refined by the least-squares method using XL. Absorption corrections
were applied by using SADABS. Hydrogen positions were input and
refined in a riding manner along with the attached carbons.
Crystallographic data are summarized in Table 8.
treated with a combination of FVAR and ISOR restraints. ISOR was
used for atoms Cl2, F8, F9, F10, F11, and F12.
COMPUTATIONAL METHODS
■
Geometry optimizations of the molecules have been carried out
without symmetry constraints using Turbomole 6.3.169 at the
BP86,69,70/def2-TZVPP72 level of theory (denoted BP86/TZVPP).
The nature of the stationary points on the potential energy surface has
been confirmed as energy minima by frequency calculations. Partial
charges (NBO)73 were calculated at the same level of theory using the
Gaussian09 program.74
The energy decomposition analysis (EDA) has been carried out
with the program package ADF 2009.0175 at BP86 in conjunction with
a triple-ζ-quality basis set using uncontracted Slater-type orbitals
(STOs) augmented by two sets of polarization function with a frozen-
core approximation for the core electrons using the BP86/TZVPP
optimized geometries.76 This level of theory is denoted as BP86/TZ2P
+//BP86/TZVPP. An auxiliary set of s, p, d, f, and g STOs were used
to fit the molecular densities and to represent the Coulomb and
exchange potentials accurately in each SCF cycle.77 Scalar relativistic
effects were incorporated by applying the zeroth-order regular
approximation (ZORA).78−80
The energy decomposition analysis (EDA) gives a quantitative
description of the chemical bonds in molecules.81−83 In the EDA
developed independently by Morokuma,84 and Zieglar and Rauk,85
and the recently introduced EDA-NOCV,86,87 the bond dissociation
energy, De, of a molecule AB is divided into the instantaneous
interaction energy ΔEint and the preparation energy ΔEprep
:
ΔE ( = −D) = ΔEint + ΔEprep
e
(1)
The preparation energy ΔEprep is the energy which is required to
promote the fragments A and B from their equilibrium geometries in
the electronic ground state to the geometries and electronic reference
state which they have in the molecule. The interaction energy ΔEint
can be further divided into three main components
[(SIDipp)Au(CN)]. This compound crystallized in space group Pbcm.
All the non-hydrogen atoms were refined with anisotropic displace-
ment parameters. All the hydrogen atoms were placed in ideal
positions and refined as riding atoms with relative isotropic
displacement parameters. FVAR commands were used to treat
occupancy disorder for dichloromethane.
ΔEint = ΔEelstat + ΔEPauli + ΔEorb
(2)
where ΔEelstat is the quasiclassical electrostatic interaction energy
between the fragments, calculated by means of the frozen electron
density distribution of the fragments in the geometry of the molecules.
ΔEPauli refers to the repulsive interactions between the fragments,
which are caused by the fact that two electrons with the same spin
cannot occupy the same region in space, and can be calculated by
enforcing the Kohn−Sham determinant on the superimposed
fragments to obey the Pauli principle by antisymmetrization and
renormalization. The stabilizing orbital interaction term ΔEorb is
calculated in the final step of the energy partitioning analysis when the
Kohn−Sham orbitals relax to their optimal form.
[(Mes3P)2Au][Au(CN)2]. This compound crystallized in space group
P21/n with two half complexes appearing in the asymmetric unit.
There is a center of inversion at the gold center of [(Mes3P)2Au]
moieties. All the non-hydrogen atoms were refined with anisotropic
displacement parameters. All the hydrogen atoms were placed in ideal
positions and refined as riding atoms with relative isotropic
displacement parameters. ISOR restraints were required to treat
Non-Positive Definite messages for Cl atoms from dichloromethane
solvent.
[(SIDipp)Au(CNtBu)][SbF6]. This compound crystallized in space
The EDA-NOCV87 method combines charge (NOCV) and energy
(EDA) partitioning schemes to decompose the deformation density
which is associated with the bond formation, Δρ, into different
components of the chemical bond. The EDA-NOCV calculations
provide pair wise energy contributions for each pair or interacting
orbitals to the total bond energy. NOCV (natural orbital for chemical
group P1 with two independent [(SIDipp)Au(CNtBu)][SbF ]
̅
6
moieties in the asymmetric unit. All the non-hydrogen atoms were
refined with anisotropic displacement parameters. All the hydrogen
atoms were placed in ideal positions and refined as riding atoms with
relative isotropic displacement parameters. ISOR restraints were
required to treat Non-Positive Definite messages for Cl atoms from
dichloromethane solvent.
valence)86,88 is defined as the eigenvector of the valence operator,V,
̂
given by eq 3:
[(SIDipp)Au(cyclooctyne)][SbF6]. This compound crystallized in
space group P21/c. All the non-hydrogen atoms were refined with
anisotropic displacement parameters. All the hydrogen atoms were
placed in ideal positions and refined as riding atoms with relative
isotropic displacement parameters. FVAR commands were used to
treat occupancy disorder for the cyclooctyne ligand (atoms C32 and
C33).
̂
Vψ = υψ
(3)
i
i
i
In the EDA-NOCV scheme the orbital interaction term, ΔEorb, is given
by eq 4
N/2
N/2
ΔEorb
=
ΔEorb
=
υ [−F TS + FTS
]
−k,−k k,k
∑
∑
k
k
[(Mes3P)Au(cyclooctyne)][SbF6]. This compound crystallized in
(4)
k=1
k=1
space group P1 with two independent [(Mes P)Au(cyclooctyne)]-
̅
3
TS
−k,−k
TS
k,k
[SbF6] moieties in the asymmetric unit. All the non-hydrogen atoms
were refined with anisotropic displacement parameters. All the
hydrogen atoms were placed in ideal positions and refined as riding
atoms with relative isotropic displacement parameters. The [SbF6]−
counterion and dichloromethane solvent were disordered and were
in which F
and F are diagonal transition-state Kohn−Sham
matrix elements corresponding to NOCVs with the eigenvalues −υk
and υk, respectively. The ΔEokrb terms of a particular type of bond are
assigned by visual inspection of the shape of the deformation density,
Δρk. The EDA-NOCV scheme thus provides information about the
740
dx.doi.org/10.1021/ic301869v | Inorg. Chem. 2013, 52, 729−742

Inorganic Chemistry
Article
strength of orbital interactions in terms of both charge (Δρorb) and
energy contributions (ΔEorb) in chemical bonds, even in molecules
with C1 symmetry.
(25) Xu, Q.; Imamura, Y.; Fujiwara, M.; Souma, Y. J. Org. Chem.
1997, 62, 1594−1598.
(26) Davis, R. J. Science 2003, 301, 926−927.
(27) Zhu, B.; Angelici, R. J. J. Am. Chem. Soc. 2006, 128, 14460−
14461.
ASSOCIATED CONTENT
* Supporting Information
■
(28) Ye, L.; Wang, Y.; Aue, D. H.; Zhang, L. J. Am. Chem. Soc. 2012,
S
134, 31−34.
X-ray crystallographic data (CIF) for (SIDipp)Au(CN),
[(Mes3P)2Au][Au(CN)2], [(SIDipp)Au(CNtBu)][SbF6],
[(SIDipp)Au(cyclooctyne)][SbF6], and [(Mes3P)Au-
(cyclooctyne)][SbF6], and additional computational study
data. This material is available free of charge via the Internet
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AUTHOR INFORMATION
Corresponding Author
*E-mail: frenking@chemie.uni-marburg.de (G.F.), dias@uta.
edu (H.V.R.D.).
■
Notes
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The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the National Science Foundation
(CHE-0845321) and the Robert A. Welch Foundation (Grant
Y-1289). The NSF (CHE-0840509) is thanked for providing
funds to upgrade the NMR spectrometer used in this work. The
X-ray crystallography was performed in the Center for
Nanostructured Materials (CNM) at the University of Texas
at Arlington.
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