Structural Investigation of Bis(isonitrile)gold(I) Complexes

Article abstract of DOI:10.1515/znb-1997-0110

The reaction of (MeNC)-, (PhNC)- and (MesNC)AuCl in tetrahydrofuran with an equimolar amount of the corresponding isonitrile ligand and one equivalent of Ag⁺X^- (X^- = BF^-₄ or CF₃SO^-₃) leads to the formation of the bis(isonitrile)gold(I) complexes (MeNC)₂Au⁺ CF₃SO^-₃ (1), (PhNC)₂Au⁺ BF^-₄ (2) and (MesNC)₂Au⁺ BF^-₄ (3). The crystal structures of 1, 2 and 3 have been determined. In compound 1 there are rod-like cations with a parallel packing into meandering puckered layers, in which the gold atoms have alternating Au-Au contacts of 3.611 and 3.624 A. In complex 2 the cations form long double-paddles, with the two paddles at an angle of 77.5°. The individual cations are well separated and have no sub-van-der-Waals Au-Au contacts. The crystal structure of 3 is similar, but with a smaller dihedral angle between the planes of the two mesityl rings (56.0°).

Full text of DOI:10.1515/znb-1997-0110

Structural Investigation of Bis(isonitrile)gold(I) Complexes
Wolfgang Schneider, Alexander Sladek, Andreas Bauer, Klaus Angermaier,
Hubert Schmidbaur*
Anorganisch-chemisches Institut der Technischen Universität München,
Lichtenbergstraße 4, D-85747 Garching, Germany
Dedicated to Professor Walter Siebert on the occasion o f his 60th birthday
Z. Naturforsch. 52 b, 53-56 (1997); received September 18, 1996
Gold(I) Complexes, Isonitrile Complexes, Crystal Structure, Supramolecular Chemistry
The reaction of (MeNC)-, (PhNC)- and (MesNC)AuCl in tetrahydrofuran with an equimolar
amount of the corresponding isonitrile ligand and one equivalent of Ag+X~ (X- = BF^ or
CF3 SO J) leads to the formation of the bis(isonitrile)gold(I) complexes (MeNC)aAu+ CFiSO^
(1), (PhNC)2Au+ BF^ (2) and (MesNC)2Au+ BF^ (3). The crystal structures of 1, 2 and 3
have been determined. In compound 1 there are rod-like cations with a parallel packing into
meandering puckered layers, in which the gold atoms have alternating Au-Au contacts of 3.611
and 3.624 A. In complex 2 the cations form long double-paddles, with the two paddles at an
angle of 11.5°. The individual cations are well separated and have no sub-van-der-Waals Au-Au
contacts. The crystal structure of 3 is similar, but with a smaller dihedral angle between the
planes of the two mesityl rings (56.0°).
Introduction
Results and Discussion
The first bis(isonitrile)gold(I) complexes have
been reported in 1973 [1, 2]. They were important
sources for the preparation of bis(carbene) com -
plexes of gold(I) [3,4], and in 1986 their use as
starting materials and catalysts for the synthesis of
chiral oxazolines was demonstrated [5]. The struc-
ture of the cations [RNCAuCNR]+ in these com -
plexes was assumed to be linear, but no struc-
ture determination has been undertaken. Because
presently there is not only an interest in the molec-
ular structure of such species, but also in their
supramolecular chemistry, we have now investi-
gated three bis(isonitrile)gold(I) complexes con-
taining the small methyl-, the flat phenyl- and the
more extended mesitylisonitrile ligands, where dif-
ferent steric effects are expected to show a growing
influence on the packing of the compounds.
All three complexes were obtained in high yield
(>80%) according to a general synthetic route:
(RNC)AuCl + RNC + AgX -*• (RNC)2AuX + AgCl
(X = CF3SO3“ or BF4 )
The products were identified and characterized
by standard analytical and spectroscopic meth-
ods. The compounds are stable, colourless solids
with melting points at 164°C (1), 159°C (2), and
228°C (3). The FAB mass spectra show the cations
[(RNC)2Au]+as the parent peaks in high abundance,
accompanied by fragment ions generated by the loss
of RNC orR . In the 13C {'H } NMR spectra coupling
of the 14N nucleus to the neighbouring carbon atoms
is observed. The proton NMR spectrum of 1 shows
only a broad singlet for the methyl groups, indicat-
ing poorly resolved second order splitting.
Single crystals of compound 1 suitable for X-
Following our recent report on the investigation
of simple (isonitrile)gold(I) halides [6], we present
our results here on the synthesis and structure of
(MeNC)2Au+ CF3SO~ (1), (PhNC)2Au+ B FJ (2)
and (MesNC)2Au+ BF~ (3).
ray diffraction were obtained upon layering
a
dichloromethane solution with pentane. The com-
pound crystallizes in the monoclinic space group
P2i/m with four formula units in the unit cell. The
lattice is built up by independent triflate anions and
rod-like bis(methylisonitrile)gold(I) cations. The
latter are arranged parallel to each other and form
corrugated sheets, the gold atoms in meandering
strings with two nearly equal gold-gold distances
* Reprint requests to Prof. Dr. H. Schmidbaur.
0939-5075/97/0100-0053 $ 06.00
©
1997 Verlag der Zeitschrift für Naturforschung. All rights reserved.
K
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54
W. Schneider et al. ■Structural Investigation of Bis(isonitrile)gold(I) Complexes
C22
N2
C21
Au
C11
N1
C12
Fig. la. Structure of the rod-like cation [(MeNC)2Au]+
in 1 (ORTEP, o50% probability ellipsoids). Selected
bond lengths (Ä) and angles (°): A u-Cll 1.96(1), Au-
C21 1.98(1), N l-C ll 1.13(2), N1-C12 1.46(2), N2-
C21 1.11(2), N2-C22 1.40(2), C21-Au-Cll 175.9(6),
C12-N1-C11 179(2), C22-N2-C21 178(2), N 1-C 11-Au
178(1), N2-C21-Au 179.0(9).
Fig. 1b. Supramolecular aggregation of the
[(MeNC)2Au]+ cations in 1 via weak gold-gold interac-
tions (Au-Au' = 3.611, Au-Au" = 3.624 A). For clarity,
only the C-S cores of the triflate anions are shown. It
should be noted, that the carbon atoms of neighbouring
triflate anions face each other in the middle and the sulfur
atoms are at the outside. The flourine and oxygen atoms
are cylindrically disordered.
(Au-Au' 3.624 and Au-Au" 3.611 A). Disordered
triflate anions are located in the cavities between
the layers. The cations show a C-Au-C angle close
to linearity (175.9(6)°) and Au-C distances Au-Cl 1
1.96( 1) and A u-C 21 1.98( 1) A (Figures 1a,b). These
distances are relatively long as compared to mono
(isonitrile)gold(I) halides (average 1.94 A [6]).
polarizable counterions (BF4 , CF3S O J) have ionic
structures with strictly linear two-coordination of
the gold centers. It is only with the smallest alkyl
substituents (R = Me) that supramolecular aggrega-
tions are observed, which lead to puckered cation
layers. The A u-A u contacts are long indicating
rather weak interactions. With larger groups R no
such aggregates are formed. The cations have the
form of double paddles with the arene rings at in-
terplanar angles of 77.5 and 56.0° for 2 and 3, re-
spectively.
Crystals of compound 2 are monoclinic, space
group P2]/n, with four formula units in the unit
cell (Table I). Unlike in 1 no close Au-Au con-
tacts are observed. The geometry of the core atoms
of the monomeric cation is very similar to that in
the methyl analogue 1 (see the caption of Fig. 2).
There are no sub-van-der-Waals contacts between
the cations and the tetrafluoroborate anions. The
planes defined by the phenyl paddles enclose an an-
gle of 77.5°, and therefore the phenyl groups are
nearly orthogonal to each other.
Experimental
General
All experiments were routinely carried out under dry
and pure nitrogen. Solvents and glassware were dried
and saturated / filled with nitrogen. NMR: Jeol GX 400,
TMS as internal standard. MS: Finnigan MAT 90. Mi-
croanalysis: In-house analyzers (by combustion). Starting
materials were either commercially available or were pre-
pared following literature procedures: MeNC [7], PhNC
[8 ], MesNC [9] (Mes = mesityl), (MeNC)AuCl [10, 11],
(PhNC)AuCl and (MesNC)AuCl [6 , 12],
3
crystallizes in the monoclinic space group Cc
with four formula units in the unit cell. The lattice
features [(MesNC)2Au]+ cations, which show no
aggregation. The individual cations have a quasi-
linear seven-atom rod between the two mesityl
groups, the planes of which form an angle of only
56.0° (Fig. 3).
Bis(methylisonitrile)gold(I) triflate, (I)
To a solution of (MeNC)AuCl (100 mg, 0.367 mmol)
in 60 ml of dichloromethane a solution of MeNC (15 mg,
0.367 mmol) and AgCF^SCb (94 mg. 0.367 mmol) in 10
The present study has shown that bis(iso-
nitrile)gold(I) salts with non-coordinating, non-
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W. Schneider et al. ■Structural Investigation of Bis(isonitrile)gold(I) Complexes
55
Table I. Crystallographic Data for [(CH,NC)tAu]+CF,SO,
(1), [(PhNC)2Au]+BF4_ (2)
and [(MesNC)2Au]+BF4_ (3).
1
2
3
Compound
Empirical formula
Formula weight
Crystal system
Space group (No.)
a [A]
b [A]
c [A]
a [° ]
C5 H6AuF3N ,0 3S
428.14
monoclinic
P2,/m (N o.ll)
7.649(1)
12.057(2)
12.425(1)
90
C |4HiqAuBF4N->
490.02
O o H ^A u B F ^ ,
574.18
monoclinic
P2,/n (No.14)
8.435(1)
12.922(1)
13.594(1)
90
monoclinic
Cc (No.9)
12.538(1)
11.095(1)
14.864(2)
90
107.89(1)
90
1090.5(6)
2.61
104.01(1)
90
2005.7(4)
1.90
94.79(1)
90
1476.5(3)
2 . 2 1
ß[°]
7 [°J
V [A3]
Pcalc [gem ' ]
Z
4
4
4
784
137.1
1104
73.8
F(000) [e]
/L/(Mo-Ka ) [cm-1]
T[°C]
912
1 0 0 . 0
- 6 8
- 6 8
- 6 8
Enraf Nonius CAD4
6-6
Diffractometer
scan
Enraf Nonius CAD4
0
Enraf Nonius CAD4
CJ
hkl Range
- 9 < h < 9 , -15 < k < 15,
0 < / < 15
3360/2076
1616
0 < h < 1 0 , 0 < k < 16,
-17 < / < 17
3568/2942
2505
0 < h < 14,0 < k < 14
-23 < / < 23
3816/3704
3464
Measured/unique refl.
Observed reflections
4<j (F0)
143
- 16
4ct(F0)
199
- / 1 0
4<j (F0)
251
-122
F0 >
Refined parameters
H-Atoms (found/calc.)
Absorption corr.:
Tmin / Tmax
R ~
empirical
0.5720 / 0.9969
0.0443
empirical
0.3925 / 0.9978
0.0383
empirical
0.8062/0.9989
0.0185
0.0492
0.0498
0.0230
Rw
Weighting scheme ***
/ = 1 .0 0 0 0 /
k = 0.00018
+ 0.63 / - 0.70
/= 1 .0 0 0 0 /
k = 0.000354
+ 1.40 / - 1.02
/= 1 .0 0 0 0 /
k = 0.000563
+ 1.25/- 1.14
pfin(max/min) [eA-3]
'2 i 1/ 2
R = £H F0 I-IFcII/£IF0L- - R w = [^vv(IF0 I-IFcI)2/^w F ^]
w = 1/(<t (F0)+£F0).
(75.7 mg, 0.387 mmol) in 15 ml of CH2C12 / 5 ml of thf.
Yield 155 mg (82%), m. p. 159°C.
ml of tetrahydrofuran is added during a period of 30 min
at room temperature. After stirring for 1 h the solvents are
removed in a vacuum. The off-white residue is taken up
in dichloromethane and crystallized by adding pentane.
128 mg of colourless crystals of 1 are obtained (81%),
m.p. 164°C.
'H NMR (CDCI3): 6 = 3.6, br. s, CH3. 13 C{'H} NMR
(CDCI3): 6 = 139.5, t, '7(C,N) = 27.6 Hz, NCAu; 121.4,
q, '7(C,F) = 321 Hz, CF3; 30.5, br., CH3 N. MS (FAB):
m/z = 278.9, [(MeNC)2Au]+, 100%.
■H NMR (CDCI3): b = 7.6 - 7.7, m, Ph-H; l3C{'H}
NMR (CDCI3 ): 6 = 147.0, t, *7(C,N) = 28 Hz, NCAu;
133.3, 130.6 and 128.0, all s, ortho-, meta-, para-C;
123.3, t, '/(C,N ) = 14 Hz, ipso-C. MS (FAB): m/z =
403, [(PhNC)2Au]+, 100%.
C,4H,oAuBF4N2 (490.02)
Calcd C 34.29, H 2.04, N5.71%,
Found C 35.45, H2.14, N5.81%.
C5H6AuF3N20 3S (428.14)
Calcd C 14.03, H 1.41, N 6.54%,
Found C 14.03, H 1.50, N 6.43%.
Bis(mesitylisonitrile)gold(I) tetrafluoroborate (3)
Bis(phenylisonitrile)gold(I) tetrafluoroborate, (2)
As described for compound 1, from (MesNC)AuCl
(125 mg, 0.331 mmol), MesNC (48 mg, 0.331 mmol)
and AgBF4 (64.5 mg, 0.331 mmol) in 15 ml of CH2C12
As described for compound 1, from (PhNC)AuCl (130
mg, 0.387 mmol), PhNC (40 mg, 0.387 mmol) and AgBF4
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56
W. Schneider et eil. • Structural Investigation of Bis(isonitrile)gold(I) Complexes
Fig. 2. Structure of the double-
paddle-like [(PhNC)2Au]+ cation in
2 (ORTEP, 50% probability ellip-
soids). Selected bond lengths (A)
and angles (°): Au-Cl 1.987(9), Au-
C8 1.992(9), N l-C l 1.13(1), N l-
C2 1.39(1), N2-C8 1.11(1), N2-
C9 1.38(1), C8 -Au-Cl 177.5(3),
N l-C l-A u 178.4(7), C2-N1-C1
175.2(9), N2-C8-Au 179.0(7), C9-
N2-C8 179.7(7).
Fig. 3. Structure of the cation
[(MesNC)2Au]+ in
3
(ORTEP,
50% probability ellipsoids). Se-
lected bond lenghts (A) and angles
(°). Au-Cl 1.96(1). Au-C2 1.99(1),
N l-C l 1.16(1), N l-C l 1 1.41(1),
N2-C2 1.13(2), N2-C21 1.40(1),
C2-Au-Cl 173.6(4), C11-N1-C1
176(1),C21-N2-C2 174(1), N l-C l-
Au 174.1(8), N2-C2-Au 173.6(9).
data in the captions of Fig. la, 2 and 3. Further infor-
mation on the structure determinations may be obtained
from Fachinformationszentrum Karlsruhe, Gesellschaft
für wissenschaftlich-technische Information GmbH, D-
76344 Eggenstein-Leopoldshafen, Germany, on quoting
the names of the authors, the journal citation and the CSD
number 59368.
/ 5 ml of thf. Yield 162 mg (85%), m.p. 228°C with
decomposition.
'H NMR (CDCI3 ): 6 = 2.3, s, para-CHy 2.4, s, ortho-
CH3; 7.2, s, meta-H. 13C{'H} NMR (CDCI3 ): 6 = 151.0,
t, '/(C ,N ) = 23 Hz, NCAu; 143.0. 137.0 and 129.3,
all s, ortho-, meta-, para-C; 120.2, br., ipso-C; 21.5, s,
para-CHy, 18.5, s, ortho-CH3. MS (FAB): m/z = 487.3,
[(MesNC)2Au]+, 100%.
C70H22AuBF4N2 (574.18)
Calcd C 41.84, H 3.86, N 4.88%,
Found C 42.01, H 3.70, N 4.87%.
Acknowledgement
J. Riede is thanked for establishing the X-ray data sets
and F. R. Kreissl for mass spectrometric measurements.
Support by Deutsche Forschungsgemeinschaft and Fonds
der Chemischen Industrie is gratefully acknowledged.
Crystal structure determination:
Crystallographic and structure solution data of com-
pounds 1, 2 and 3 are summarized in Table I, structural
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