Synthesis and X-ray crystal structure determination of the first structurally authenticated terphenyl gold complex

Article abstract of DOI:10.1016/S0020-1693(01)00389-9

The synthesis and X-ray crystal structure determination of a novel metal-terphenyl derivative, namely DmpAuPPh₃ (1), is reported (Dmp = 2,6-dimesitylphenyl). Complex 1 is synthesized by the reaction of one equivalent of DmpLi with one equivalent of Ph₃PAuCl in tetrahydrofuran at room temperature in 70% yield. The molecular structure of monomeric 1 features a two-coordinate gold atom with an essentially linear arrangement of the two ligands with an interligand angle of 174.21(8)° as well as a slightly tilted terphenyl moiety.

Full text of DOI:10.1016/S0020-1693(01)00389-9

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Inorganica Chimica Acta 316 (2001) 132–134
Note
Synthesis and X-ray crystal structure determination of the first
structurally authenticated terphenyl gold complex
Gerd W. Rabe *, Norbert W. Mitzel
Technische Uni6ersita¨t Mu¨nchen, Anorganisch-Chemisches Institut, Lichtenbergstrasse 4, 85747 Garching, Germany
Received 8 January 2001; accepted 2 February 2001
Abstract
The synthesis and X-ray crystal structure determination of a novel metal–terphenyl derivative, namely DmpAuPPh3 (1), is
reported (Dmp=2,6-dimesitylphenyl). Complex 1 is synthesized by the reaction of one equivalent of DmpLi with one equivalent
of Ph3PAuCl in tetrahydrofuran at room temperature in 70% yield. The molecular structure of monomeric 1 features a
two-coordinate gold atom with an essentially linear arrangement of the two ligands with an interligand angle of 174.21(8)° as well
as a slightly tilted terphenyl moiety. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Terphenyl complexes; Phosphane complexes; Gold complexes
cantly higher costs of the elements silver and gold,
respectively. In this work the synthesis and structural
characterization of the first terphenyl gold complex is
reported.
1. Introduction
There is much current interest in the chemistry of
terphenyl ligand systems because this type of sterically
demanding ligands was found to be suitable for the
stabilization of main group element complexes in un-
usual coordination geometries and unprecedented
bonding situations [1]. While the vast majority of so far
structurally characterized complexes are based on s and
p block elements, relatively little information is avail-
able on terphenyl complexes of the d block elements.
As a matter of fact, all of the few known examples are
derived from late transition metals [1]. For example,
terphenyl complexes have been reported for the ele-
ments copper [2–6] and silver [7]. However, to the best
of our knowledge, so far there are no reports on
structurally characterized terphenyl gold complexes. In
general, organometallic complexes of the elements gold
and silver have received considerably less attention as
compared with organocopper(I) complexes. An obser-
vation which is most likely partially due to the signifi-
2. Experimental
The compound described below was handled under
nitrogen using Schlenk double manifold, high-vacuum,
and glovebox (M. Braun, Labmaster 130) techniques.
Solvents were dried and physical measurements were
obtained following typical laboratory procedures.
Ph3PAuCl was purchased from Aldrich and used as
received. DmpLi [8] was prepared according to the
literature. NMR spectra were recorded on a JMN-GX
400 instrument. The 13C NMR spectrum, recorded in
C6D6, was referenced to the solvent signal at 128.0
ppm.
2.1. DmpAuPPh3 (1)
Addition of a freshly prepared solution of DmpLi
(320 mg, 1.0 mmol) in 5 ml tetrahydrofuran to a
colorless suspension of Ph3PAuCl (500 mg, 1.0 mmol)
* Corresponding author. Tel.: +49-89-28913085; fax: +49-89-
28913125.
E-mail address: g.rabe@lrz.tum.de (G.W. Rabe).
0020-1693/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00389-9

G.W. Rabe, N.W. Mitzel / Inorganica Chimica Acta 316 (2001) 132–134
133
by the distribution of the normalized structure factors
and the subsequent results of solution and refinement.
Hydrogen atoms were treated as idealized contribu-
tions. All non-hydrogen atoms were refined anisotropi-
cally. A semi-empirical absorption correction was
performed using c-scans. All software was contained
in the SHELXTL 5.01 library (G. M. Sheldrick, Bruker
XRD, Madison, WI).
in 5 ml tetrahydrofuran caused a color change to pale
pink. The reaction mixture was stirred for 30 min at
ambient temperature, followed by removal of all
volatiles and washing of the residues with hexanes,
which gave the title compound as a colorless powder.
Crystallization of the obtained DmpAuPPh3 from tolu-
ene+hexanes (1:1) at −30°C gave 1 as colorless crys-
tals (544 mg, 70%), which are not light-sensitive and
air-stable. Complex 1 is insoluble in hexanes, but well
soluble in arene solvents and tetrahydrofuran. Anal.
Calc. for C42H40AuP: C, 65.29; H, 5.22. Found: C,
3. Results and discussion
1
65.11; H, 5.07%. H NMR (C6D6, 400.0 MHz, 25°C): l
DmpAuPPh3 (1) is synthesized by reaction of
equimolar amounts of DmpLi and Ph3PAuCl in te-
trahydrofuran at room temperature in 70% yield. Col-
orless crystals of air-stable 1 suitable for an X-ray
diffraction study were grown by slow evaporation of a
toluene solution at ambient temperature.
The molecular structure of complex 1 (Fig. 1) fea-
tures an almost linear C(ipso)–Au–P arrangement. As
was previously observed in the molecular structure of
Ph3PAuPh [9,10], there is no intermolecular Au···Au
interaction in complex 1 (Fig. 2). The Au–C distance of
2.22 (p-Me, 6H), 2.41 (o-Me, 12H) plus several signals
in the aromatic region (from 6.8 to 7.4 ppm). 31P NMR
(C6D6, 161.9 MHz, 25°C): l 43.5. 13C NMR (C6D6,
100.4 MHz, 25°C): l 21.3 (p-Me), 21.8 (o-Me), 127.9,
128.7, 128.8, 130.6 (d, JC–P=3 Hz), 131.4, 132.1, 134.4
(d, JC–P=20 Hz), 134.5, 136.5, 145.6 (d, JC–P=3 Hz),
150.2, 176.7 (ipso-C). IR (Nujol): 1306 w, 1180 m, 1098
s, 1026 m, 997 m, 845 m, 803 m, 782 w, 738 s, 708 m,
691 s, 618 w, 588 w, 574 w, 532 m, 502 s, 444 w, 431 w
cm−1. M.p. (dec.)=233–235. Prior to decomposition
complex 1 turns pink and then decomposes forming a
red oil.
,
,
2.046(3) A, the Au–P distance of 2.2799(8) A, as well
as the C–Au–P angle of 174.21(8)° in complex 1 can
favorably be compared with the corresponding dis-
2.2. X-ray data collection, structure determination, and
refinement for DmpAuPPh3 (1)
,
tances in Ph3PAuPh [Au–C=2.045(6) A; Au–P=
,
2.296(2) A; P–Au–C=175.5(2)°] [9,10]. Besides the
gold–ipso carbon distance in 1, there are weak sec-
Crystallographic data are collected in Table 1. A
sample was mounted on a glass fibre under inert pe-
rfluoropolyether. No symmetry higher than triclinic was
observed and the centrosymmetric option was selected
ondary interactions between the metal atom and the
Table 1
Crystallographic data for DmpAuPPh3 (1) a
1
Formula
Fw
C
772.68
42H40AuP
(
Space group
P1
,
a (A)
8.702(2)
10.668(2)
19.539(1)
85.55(1)
85.85(1)
72.98(1)
1726.8(5)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (g cm−3
)
1.486
Temperature (°C)
−125(2)
0.71073
4.334
Fig. 1. ORTEP diagram and numbering scheme of DmpAuPPh3 (1)
drawn at the 30% probability level. Hydrogen atoms are omitted for
,
Radiation, u(Mo Ka) (A)
v(Mo Ka) (cm−1
R1 (%)
)
clarity. Selected intatomic distances (A) and angles (°): Au(1)–
,
2.33
C(41)=2.046(3), Au(1)···C(51)=3.166(3), Au(1)···C(61)=3.271(3),
wR2 (%)
5.86
Au(1)–P(1)=2.2799(8),
P(1)–C(11)=1.825(3),
P(1)–C(21)=
,
1.816(3), P(1)–C(31)=1.814(3) A; C(41)–Au(1)–P(1)=174.21(8),
a The quantity minimized was wR2=S [w(Fo2−Fc2)2]/S [(wF2o)2]1/2
;
Au(1)–C(41)–C(42)=119.0(2),
Au(1)–P(1)–C(11)=113.64(9),
Au(1)–P(1)–C(31)=111.30(10),
C(41)–C(46)–C(61)=119.3(2)°.
Au(1)–C(41)–C(46)=122.6(2),
Au(1)–P(1)–C(21)=114.77(10),
C(41)–C(42)–C(51)=119.2(2),
R1=S D/S(Fo), D=ꢀ(Fo−Fc)ꢀ, w=1/[|2(Fo2)+(aP)2+bP], P=
[2F2c+max(Fo, 0]/3.

134
G.W. Rabe, N.W. Mitzel / Inorganica Chimica Acta 316 (2001) 132–134
parameters for the first terphenyl gold complex are
provided. Our work also allows for a detailed compari-
son of complex 1 with other aryl gold(I) complexes as
well as terphenyl complexes of the late transition
metals. Further investigations in this particular area of
chemistry are clearly warranted. For example, the syn-
thesis and X-ray structural characterization of the silver
analogue of complex 1 is still to be accomplished and
might give further corroboration to the experimentally
evidenced observation of gold(I) being smaller than
silver(I) ions.
Fig. 2. Packing diagram of the molecular structure of complex 1.
5. Supplementary material
ipso carbon atoms of the mesityl rings at a distance of
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 116984. Copies of this infor-
mation may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge, CB2
1EZ, UK (fax: +44-1233-336033; e-mail: deposit@
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
,
,
3.166(3) A [C(51)] and 3.271(3) A [C(61)] in complex 1.
Further comparison of the Au–C(ipso) distance in
complex 1 can be made with the corresponding dis-
tances in two anionic bis(terphenyl) silver complexes,
,
namely [Li(THF)4][Ag(Triph)2]·THF [av. 2.097(9) A]
and [Li(THF)4][Ag(C6H3-2,6-Mes)2]·1/8 OEt2 [av.
,
2.09(3) A] [7]. Both complexes show almost linear coor-
dination of the silver(I) cation. The Dmp ligand in
complex 1 is slightly tilted, as can be seen by inspecting
the Au(1)–C(ipso)–C(ortho) angles [Au(1)–C(41)–
C(42)=119.0(2); Au(1)–C(41)–C(46)=122.6(2)].
Acknowledgements
The authors are grateful to the Deutsche Forschungs-
gemeinschaft, the Fonds der Chemischen Industrie, and
the Leonhard-Lorenz foundation for financial support
for this research. Additionally, generous support from
Professor H. Schmidbaur is gratefully acknowledged.
It is interesting to note that the average Ag–C(ipso)
distances in both diorgano argentates mentioned above
are clearly longer than the Au–C(ipso) distance in the
neutral complex 1, an observation which can most
likely be attributed to increased steric crowding around
the metal center in both silver complexes. Another
possible explanation is based on previously reported
experimental evidence for the ionic radius of gold(I)
being actually smaller than that of silver(I) for a given
coordination number due to relativistic effects [11]. It is
also to be noted that the observed Au–C(ipso) distance
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ver(I) ions are expected to be approximately 0.2 A
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4. Conclusion
The results presented in our work provide more
insight into structural aspects of so far relatively rare
terphenyl complexes of the coinage metals. Bonding
[12] R.D. Shannon, Acta Crystallogr., Sect. A 32 (1976) 752.
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