Gold(I) carboxylates and fluorocarboxylates

Article abstract of DOI:10.1515/znb-2002-0602

(Triphenylphosphine)gold(I) pivalate (1), and (triphenylphosphine)gold(I), [tri(p-tolyl)-phosphine]gold(I), [(4-dimethylaminophenyl)diphenylphosphine]gold(I), and (cyclohexylisocyanide)gold(I) pentafluoropropionate (2-5) have been prepared from the corresponding gold(I) halide complexes and silver carboxylates in high yields. The products are stable to air and moisture and soluble in most common polar organic solvents. The structures of 1 and 3 have been determined. Owing to the bulk of the carboxylate substituents the molecules are monomers in the crystal. Compounds 1-4 undergo thermal decomposition in a narrow temperature range around 130°C, 5 is less stable and decomposes at 48°C.

Full text of DOI:10.1515/znb-2002-0602

Gold(I) Carboxylates and Fluorocarboxylates
Patric Ro¨mbke, Annette Schier, and Hubert Schmidbaur
Anorganisch-chemisches Institut, Technische Universita¨t Mu¨nchen,
Lichtenbergstrasse 4, D-85747 Garching, Germany
Reprint requests to Prof. Dr. H. Schmidbaur. E-mail: H.Schmidbaur@lrz.tum.de
Z. Naturforsch. 57 b, 605–609 (2002); received March 14, 2002
Gold(I) Complexes, Gold(I) Carboxylates, Pentafluoropropionate Complexes
(Triphenylphosphine)gold(I) pivalate (1), and (triphenylphosphine)gold(I), [tri(p-tolyl)-
phosphine]gold(I), [(4-dimethylaminophenyl)diphenylphosphine]gold(I), and (cyclohexyliso-
cyanide)gold(I) pentafluoropropionate (2- 5) have been prepared from the corresponding gold(I)
halide complexes and silver carboxylates in high yields. The products are stable to air and mois-
ture and soluble in most common polar organic solvents. The structures of 1 and 3 have been
determined. Owing to the bulk of the carboxylate substituents the molecules are monomers in
the crystal. Compounds 1 - 4 undergo thermal decomposition in a narrow temperature range
around 130 C, 5 is less stable and decomposes at 48 C.
Introduction
ence compound with a non-fluorinated carboxylate
group.
Gold(I) complexes of the type L-Au-X with a
neutral and an anionic ligand (L/X) are of current
interest owing to their fascinating structural chem-
istry and their potential for applications in a variety
of technologies and in medicine [1]. Among the lig-
ands L employed for tailoring the properties of the
compounds the large family of tertiary phosphines
and arsines are most prominent [1], but isonitriles
have recently also gained considerable attention [2].
As for the anions X , the heavier halides were most
common counterions in the early fundamental stud-
ies, but most of the contemporary investigations
have focussed on sulfides and selenides. By con-
trast, gold(I) fluorides [3] and gold(I) complexes
with oxygen-bonded anionic components are still
non-existent (F ) or rare (OR ) in gold(I) coordi-
nation chemistry [1].
Preparative Results
Treatment of (triphenylphosphine)gold(I) chlo-
ride with silver pivalate (tbutylcarboxylate) in the
molar ratio 1:1 in dichloromethane at 20 C affords
the expected (triphenylphosphine)gold(I) pivalate
(1) in 95% yield as a colourless crystalline solid,
m. p. 132 C (with decomposition).
(Ph3P)AuCl + AgOCOtBu AgCl + (Ph3P)AuOCOtBu
1
Crystals grown from dichloromethane / pentane
are stable in air and show no sign of decom-
position in solution (tetrahydrofuran, chloroform,
dichloromethane) at 20 C. They are unaffected by
water. The NMR spectra of solutions in chloroform
1
feature the H, 13C and 31P resonances suggested
In a search for compounds with highly elec-
tronegative oxygen-bonded groups X [4] we have
studied a series of perfluorinated carboxylates and
related compounds. Following an initial report pub-
lished in 2000 [5] we now present complementary
results obtained with perfluoropropionic acid. The
by the molecular formula. The elemental analysis
is also in agreement with the calculated data, but
the FAB mass spectrum shows a dinuclear cation
+
[(Ph3P)2Au2]OCOtBu as the parent peak (7%
rel. abundance).
An analogous reaction of (Ph3P)AuCl with silver
complexes are expected to undergo "clean" decom- pentafluoropropionate carried out at –70 C gives
position to leave pure gold on a variety of sub- (triphenylphosphine)gold(I) pentafluoropropionate
strates that find applications in microelectronics or (2) in 85% yield, m. p. 134 C (with decomposi-
in catalysis [6]. The synthesis and structure of a tion). The corresponding tri(p-tolyl)phosphine (3)
gold(I) pivalate complex is also reported as a refer- and diphenyl-(p-dimethylamino-phenyl)phosphine
c
¨
¨
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2002 Verlag der Zeitschrift fur Naturforschung, Tubingen www.znaturforsch.com
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P. Ro¨mbke et al. · Gold(I) Carboxylates and Fluorocarboxylates
Table 1. Crystal data, data collec-
1
3
tion, and structure refinement of
compounds 1 and 3.
Crystal data
Formula
Mr
[a]
2
2
wR2 = [Σ w(Fo – Fc )2] /
C23H24AuO2P
560.36
C24H21AuF5O2P
664.34
monoclinic
P21/n
13.0318(3)
11.6964(2)
15.6841(4)
90
100.601(1)
90
2
1
2
Σ [w(Fo )2] 2; w = 1/[ 2(Fo ) +
Crystal system
Space group
triclinic
(ap)2 + bp]; p = (Fo2 + 2Fc )/3; a =
2
¯
P1
0.0368 (1), 0.0373 (3); b = 4.66 (1),
7.09 (3).
˚
a (A)
12.5777(2)
13.4590(2)
14.4535(3)
68.179(1)
71.106(1)
70.588(1)
2085.51(6)
1.785
˚
b (A)
˚
c (A)
( )
( )
( )
3
˚
V (A )
2349.85(9)
1.878
3
calc (gcm
Z
F(000)
)
4
4
1088
1280
1
(Mo-K ) (cm
Data collection
T (K)
Measured reflections
Unique reflections
Absorption correction
Tmin/Tmax
)
71.85
63.87
143
47991
143
76807
12617 [Rint = 0.046] 4951 [Rint = 0.059]
DELABS
0.511/0.845
DELABS
0.188/0.658
Refinement
Refined parameters
487
298
Final R values [I 2 (I)]
R1
0.0359
0.0374
wR2[a]
0.0879
0.0836
(shift/error)max
< 0.001
< 0.001
3
˚
fin (max/min) (eA
)
1.502/–1.419
1.370/–1.059
complex (4) are obtained similarly in 95% and 98% ature to avoid decomposition both as a solid and in
yield, m. p. 138 C / 132 C (with decomposition), solution.
respectively.
(cHexNC)AuCl + AgOCOC2F5
AgCl + (cHexNC)AuOCOC2F5 (5)
(R3P)AuCl + AgOCOC2F5 AgCl + (R3P)AuOCOC2F5
2: R = Ph, 3: R = p-Tol,
4: R3 = Ph2(4-Me2N-C6H4)
While compounds 1 - 4 are not sensitive to light,
complex 5 requires careful protection of the reac-
tion and storage vessels by aluminium foil. The
compound has an infrared absorption (KBr) at
All three products are stable to air and water at
room temperature. Elemental analyses and solu-
tion NMR spectra confirm the expected compo-
sition and structure. In the mass spectra (FAB)
the dinuclear cations [(R3P)Au]2OCOC2F5 + rep-
resent the peaks of highest mass. Attempts
to grow single crystals were only successful
for complex 3.
1
2253 cm assigned to the isocyanide stretching
frequency. The parent ion in the FAB mass spec-
+
trum is [(cHexNC)Au]2OCOC2F5 in 100% rel.
abundance.
Thermal decomposition of compounds 1 - 5 on
solidsubstratesyieldselementalgold withlittlecon-
tamination because of the excellent leaving group
(Cyclohexylisocyanide)gold(I) chloride was also properties of the phosphines and isocyanide, and –
found to give an analogous pentafluoropropionate in particular – of the perfluoropropionate groups.
complex (5, 90% yield, m. p. 48 C with decompo- The resulting gold particles or thin films are under
sition), but this product is of very limited stability investigation for application in surface technology
and needs to be handled and stored at low temper- [1] and in heterogeneous catalysis [5].
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P. Ro¨mbke et al. · Gold(I) Carboxylates and Fluorocarboxylates
607
Fig. 1. The two independent molecules of the complex
(Ph3P)AuOCOtBu (1) in the crystal with atomic number-
Fig. 2. The molecular structure of the complex
[(pTol)3P]AuOCOC2F5 (3) with atomic numbering (OR-
TEP, 50% probability ellipsoids). Selected bond lengths
ing (ORTEP, 50% probability ellipsoids). Selected bond
˚
lengths [A] and angles [ ]: Au1-O1 2.052(3), Au1-P1
2.217(1), Au2-O3 2.050(3), Au2-P2 2.214(1), O1-C11
1.280(5), O2-C11 1.188(6), O3-C21 1.276(5), O4-C21
1.212(6); O1-Au1-P1 173.03(9), O3-Au2-P2 171.82(9),
Au1-O1-C11 117.7(3), Au2-O3-C21 117.4(3), O1-C11-
O2 123.8(5), O3-C21-O4 125.0(4).
˚
[A] and angles [ ]: Au1-O1 2.069(4), Au1-P1 2.204(1),
O1-C1 1.261(7), O2-C2 1.213(7); O1-Au1-P1 178.7(1),
Au1-O1-C1 115.2(3), O1-C1-O2 129.8(5), O2-C1-C2
109.9(5), O2-C1-C2 120.2(5).
The asymmetric unit contains one molecule which
has no unusually short contacts with neighbouring
units (Fig. 2). The P-Au-O axis in this molecule is
very close to linear [178.7(1) ] with Au-P and Au-O
bond lengths similar to those in 1 and other refer-
ence compounds. The Au-O-C angle is 115.2(3) ,
only a little smaller than in 1. The C-O distances
Structures
The crystal and molecular structures of com-
pounds 1 and 3 have been determined by single
crystal X-ray methods (Table 1).
Crystals of complex 1 (from dichloromethane /
pentane at –30 C) are triclinic, space group P1, with
¯
˚
C1-O1 1.261(7) and C1-O2 1.213(7) A differ by
Z = 4 formula units in the unit cell. The asymmetric
unit contains two independent monomers with very
similar structures (Fig. 1). The bulk of the phosphine
and pivalate ligands rules out any close approach of
the monomers to allow aurophilic contacts between
the metal atoms. The Au-O and Au-P distances are
close to standard values available in the literature.
The deviations of the P-Au-O angles from linearity
by about 7 (Au1) and 8 (Au2) are probably also
caused by packing forces between the large organic
groups. The carbon-oxygen distances are different
in each carboxylate group with the shorter values for
the carbonyl part and the longer values for the gold-
bound oxygen atoms Au-O-C. The angles Au-O-C
in the two molecules are equal within the standard
deviations (average 117.5 ).
˚
0.048 A, with the shorter bond again found for the
carbonyl group. This difference is significantly less
than for complex 1 with C11-O1 1.280(5), C11-O2
˚
1.188(6), C21-O3 1.276(5), and C21-O4 1.212(6) A
˚
anddifferencesof0.092 and 0.064A, respectively. It
appears that the highly electronegative substituents
in 3 lead to an equilibration of the C-O distances in
the carboxylate group. The pentafluoropropionate
groups have their fluorine and oxygen atoms in
staggered conformations. The remainder parts of
the compound (3) and the packing of the molecules
show no irregularities. Selected data are given in the
caption to Fig. 2.
Discussion
Crystals of complex 3 (from dichloromethane /
pentane at –30 C) are monoclinic, space group
In the present study five compounds have
P21/n, with Z = 4 formula units in the unit cell. been prepared with pivalate or perfluoropropionate
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P. Ro¨mbke et al. · Gold(I) Carboxylates and Fluorocarboxylates
groups attached to two-coordinate gold(I) centers (Triphenylphosphine)- , [tri(p-tolyl)phosphine]-, and
[(4-dimethylaminophenyl)diphenylphosphine]-gold
pentafluoropropionate (2 - 4)
bearing either a tertiary phosphine or an isocyanide
auxiliary ligand. These bulky carboxylate groups
rule out any significant intermolecular interactions
both in solution and in the solid state [1b]. The phos-
phine complexes are readily soluble in common or-
ganic solvents and decompose in the narrow range
of 130 - 140 C (1 - 4). The isocyanide complex
is less stable and must be kept at low temperature
in order to avoid decomposition. Owing to the low
affinity of oxygen and fluorine for gold, the car-
boxylates have excellent leaving group properties
which provide minimum contamination in the metal
residue. For this reason compounds 1 - 4 are promis-
ing candidates for the controlled decomposition on
surfaces to give gold thin films for heterogeneous
catalysis [6] or other applications.
The three compounds were obtained from the fol-
lowing reagents: 2: F5C2COOAg (200 mg, 0.74 mmol),
(Ph3P)AuCl (300 mg, 0.60 mmol); 3: F5C2COOAg
(180 mg, 0.67 mmol), [(pTol)3P]AuCl (300 mg,
0.56 mmol); 4: F5C2COOAg (110 mg, 0.41 mmol),
[(4-Me2N-C6H4)Ph2P]AuCl (200 mg, 0.37 mmol), with
20 ml of CH2Cl2 used for each component. The prepara-
tions followed generally the procedure described for the
synthesis of compound 1, but the reactions were carried
out at –78 C. Yields, melting points and microanalyses:
2, 320 mg, 85%, m. p. 134 C (decomp.); C21H15AuO2PF5
(619.27): calcd. C 40.5, H 2.4; found C 40.8, H 2.5. 3,
350 mg, 94 %, m.p. 138 C (decomp.); C24H21AuO2PF5
(661.35) calcd. C 43.4, H 3.2, P 4.7; found C 43.1, H
3.3, P 4.6 %. 4, 240 mg, 97.5%, m.p. 132 C (decomp.);
C23H20AuO2PF5 (665.30): calcd. C 41.5, H 3.0, N 2.1;
found C 40.9, H 2.8, N 1.9.
Experimental Section
MS (FAB), 2: m/z 1081, 10% [(Ph3PAu)2OCOC2F5]+;
721, 18% [(Ph3P)2Au]+; 459, 100% [Ph3PAu]+. 3: 1168,
6% [(pTol)3PAu]2OCOC2F5 +, 805, 56% [(pTol)3P]2-
Au +; 501, 100% [(pTol)3PAu]+. 4: 807, 53% [(Me2-
NC6H4)Ph2P]2AuH +; 304, 100% [(Me2NC6H4)Ph2P]+.
Conventional equipment was used throughout. All ex-
periments were carried out under an atmosphere of dry
and pure nitrogen. Solvents were dried and distilled un-
der nitrogen prior to use. Glassware was oven-dried and
filled with nitrogen. The silver carboxylates were pre-
pared from the corresponding carboxylic acids follow-
ing literature procedures. The (phosphine)gold chlorides
were generated from tetrachloroauric acid and the phos-
phines in a conventional redox reaction [7]. (cHexyl-
isocyanide)gold chloride was obtained by reaction
NMR (CD2Cl2, 20 C), 2, 1H: 6.68 - 7.12, m, Ph. 13
C
1H :
128.4, d, J = 67.7, C(ipso); 129.8, d, J = 12.3, C(meta);
132.7, d, J = 2.3, C(para); 134.6, d, J = 13.1, C(ortho).
3
3
19F 1H : –6.3, tr, JFF = 112 Hz, CF3; –42.7, q, JFF
=
112 Hz, CF2. 31
P
1H : 27.5, s. 3, 1H: 2.4, s, 3H, Me; 7.1
- 7.7, m, 4H, C6H4. 13C 1H : 21.6, s, Me; 125.4, d, J =
70.0, C(ipso); 130.4, d, J = 12.3, C(meta); 134.4, d, J =
c
of (tetrahydrothiophene) gold chloride with hexyliso-
cyanide [8].
13.0, C(ortho); 143.5, d, J = 4.6, C(para). 31
P
1H : 24.9,
s. 4, 1H: 3.0, s, 6H, Me; 6.74 and 7.36, d, 4H, C6H4; 7.38
- 7.42, m, 10H, Ph. 31 1H : 24.8, s.
(Triphenylphosphine)gold pivalate (1)
P
(cHexylisocyanide)gold pentafluoropropionate (5)
A solution of Ph3PAuCl (350 mg, 0.71 mmol) in
dichloromethane (20 ml) is added to a suspension of
tBuCOOAg (180 mg, 0.86 mmol) in the same volume of
the same solvent at 20 C with stirring and under protec-
tion against incandescent light. The mixture is stirred for
12 h and subsequently filtered, and the product precipi-
tated from the filtrate by addition of pentane, collected
by filtration and recrystallized from dichloromethane
(376 mg, 95% yield), m. p. 132 C (decomp.). NMR
As described for 2, C2F5COOAg (200 mg, 0.74 mmol)
and (cHexNC)AuCl (230 mg, 0.67 mmol) were reacted in
a total of 25 ml of CH2Cl2 at –78 C; yield 280 mg (89.2
%), m. p. 48 C (decomp.). IR (KBr): 2253 cm 1. MS
(FAB): m/z 775, 100% [(cHexNCAu)2OCOC2F5]+; 470,
7.5% [MH]+. 1H NMR (CD2Cl2, 20 C): 1.52, 1.73, 1.97,
and 3.80, m, C6H11 (2:4:4:1). C10H11NAuO2F5 (469.2)
calcd. C 25.6, H 2.3, N 3.0; found C 25.0, H 2.2, N 2.8.
1
(CDCl3, 20 C), H: 1.23, s, 9H, Me; 7.57 - 7.39, m,
15H, Ph. 13
C
1H : 27.9, s, Me; 39.8, s, Me3C; 128.3, d,
X-ray Crystallography. Specimens of suitable qual-
J = 62.8 Hz, C(ipso); 128.6, d, J = 12.3 Hz, C(meta); ity and size of compounds 1 and 3 were mounted on
131.2, s, C(para); 133.7, d, J = 13.1 Hz, C(ortho); COO the ends of quartz fibers in F06206R oil and used for
not detected. 31
P
1H : 28.2, s. MS (FAB): m/z 1021, 7% intensity data collection on a Nonius DIP2020 diffrac-
[[(Ph3P)Au]2OCOCMe3]+; 721, 32% [(Ph3P)2Au]+; 561, tometer, employing graphite-monochromated Mo-K ra-
3% [M]+; 459, 100% [Ph3PAu]+. C23H24AuO2P (560.36): diation. The structures were solved by a combination
calcd. C 49.3, H 4.3; found C 49.4, H 4.4.
of direct methods (SHELXS-97) and difference-Fourier
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P. Ro¨mbke et al. · Gold(I) Carboxylates and Fluorocarboxylates
609
syntheses and refined by full matrix least-squares calcu- graphic Data Centre, CCDC-181633/4. Copies of the
lations on F2 (SHELXL-97). The atomic displacements data can be obtained free of charge on application to
are treated anisotropically for all non-hydrogen atoms. the Director, 12 Union Road, Cambridge CB2 1EZ,
All hydrogen atoms were calculated and allowed to ride UK (Fax: int.code+(1223)336-033; e-mail for inquiry:
on their parent atoms with fixed isotropic contributions. fileserv@ccdc.cam.ac.uk)
Further information on crystal data, data collection and
structure refinement are summarized in Table 1. Impor-
tant interatomic distances and angles are given in the
corresponding Figure Captions. Displacement parame-
Acknowledgements
This work was generously supported by Deutsche
ters and complete tables of interatomic distances and an- Forschungsgemeinschaft, Fonds der Chemischen Indus-
gles have been deposited with the Cambridge Crystallo- trie, Volkswagenstiftung, and Degussa AG.
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[5] P. Ro¨mbke, A. Schier, H. Schmidbaur, J. Chem.
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[6] G. C. Bond, D. T. Thompson, Gold Bulletin 33, 41
(2000).
[7] N. C. Baenziger, W. E. Bennet, D. M. Soboroff,
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