Phosphine-gold(I) derivatives of 1,1′-bis(alkynyl)metallocenes: Molecular structures of Fc'(CCX)2 [X = Au(PPh3), SiMe 3] and Au4{(CC)2Fc'}2(PPh 3)2 [Fc' = Fe(η-C5H4-) 2]

Article abstract of DOI:10.1016/j.jorganchem.2010.04.026

Desilylation of Fc'(CCSiMe₃)₂ [1; Fc' = Fe(η-C₅H₄^-)₂] with LiMe or KOH/MeOH, followed by addition of AuCl(PR₃), afforded Fc'{CCAu(PR₃)}₂ [R = Ph 2a, tol 2b]; the Ru analogue of 2a was also prepared. The XRD structures of 1 and 2a are reported. In the presence of CuI, a similar reaction over 2 h afforded the Au₄ cluster Au ₄{(CC)₂Fc'}₂(PPh₃)₂ 3. The X-ray determined structure of 3 showed a planar centrosymmetric Au ₄ rhomb, two opposed Au atoms being σ-bonded to the CC group, while the other two Au atoms are each η²-bonded to the CC group and a PPh₃ ligand. The novel cluster complex Au₄{(CC) ₂Fc'}₂(PPh₃)₂ 3 has been obtained by desilylation of Fc'(CCSiMe₃)₂ [Fc' = Fe(η-C ₅H₄-)₂] with LiMe or KOH/MeOH, followed by addition of AuCl(PR₃) in the presence of CuI.

Full text of DOI:10.1016/j.jorganchem.2010.04.026

Journal of Organometallic Chemistry 695 (2010) 1906e1910
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Phosphine-gold(I) derivatives of 1,10-bis(alkynyl)metallocenes: Molecular
structures of Fc’(C^CX)2 [X ¼ Au(PPh3), SiMe3] and Au4{(C^C)2Fc’}2(PPh3)2
[Fc’ ¼ Fe(
h
-C5H4-)2]
Michael I. Bruce a , Martyn Jevric , Brian W. Skelton , Allan H. White , Natasha N. Zaitseva
,
a
b
b
a
*
a Department of Chemistry, University of Adelaide, Adelaide, South Australia 5005, Australia
b Chemistry M313, SBBCS, University of Western Australia, Crawley, Western Australia 6009, Australia
a r t i c l e i n f o
a b s t r a c t
Article history:
Desilylation of Fc’(C^CSiMe3)2 [1; Fc’ ¼ Fe(
h
-C5H4ꢀ)2] with LiMe or KOH/MeOH, followed by addition of
AuCl(PR3), afforded Fc’{C^CAu(PR3)}2 [R ¼ Ph 2a, tol 2b]; the Ru analogue of 2a was also prepared. The
XRD structures of 1 and 2a are reported. In the presence of CuI, a similar reaction over 2 h afforded the
Au4 cluster Au4{(C^C)2Fc’}2(PPh3)2 3. The X-ray determined structure of 3 showed a planar centro-
Received 18 March 2010
Received in revised form
22 April 2010
Accepted 22 April 2010
Available online 29 April 2010
symmetric Au4 rhomb, two opposed Au atoms being
s
-bonded to the C^C group, while the other two Au
2-bonded to the C^C group and a PPh3 ligand.
Ó 2010 Elsevier B.V. All rights reserved.
atoms are each
h
Keywords:
Ferrocene
Gold cluster
Alkynyl
X-ray structure
1. Introduction
afforded the expected aurated products Mc’{C^CAu(PR3)}2
(Mc’ ¼ Fc’, R ¼ Ph 2a 75%, tol 2b 70%; M ¼ Rc’, R ¼ Ph 2c 64%) as
orange or light yellow solids, respectively (Scheme 1). These
compounds were characterised by elemental analyses and from
their mass spectra, which contained [M þ H]þ at m/z 1151, 1235 and
1,10-Bis(ethynyl)ferrocene, Fc’(C^CH)2 [Fc’ ¼ Fe(
h
-C5H4ꢀ)2] is
an unstable molecule, being readily oxidised or converted to cyclic
ferrocenophanes in the presence of air, water or alcohols. However,
the corresponding SiMe3 1 or SnMe3 derivatives are stable [1].
While these properties have limited the application of this diyne as
a ligand, the literature contains accounts of complexes derived from
Co2(CO)8 [1], Ru3(CO)12 [2], Os3(CO)12 [3], PtCl2Ph(PR3)2 and related
oligomeric materials [4]. The rutheniumevinylidene complex {Fc’[C
(SiMe3)¼C¼]}2RuCl2(PPri3)2 is also known [5]. In seeking to extend
this chemistry, we have made phosphine-gold(I) derivatives of 1,10-
bis(ethynyl)-ferrocene and -ruthenocene and have found that
formation of a related derivative containing an Au4 cluster bridging
two bis(ethynyl)ferrocene moieties may also occur. This work is
described below.
1197, respectively. Their IR spectra contain very weak n(C^C) bands
between 2102 and 2125 cmꢀ1, while the 1H and 13C NMR spectra
contain resonances characteristic of the C5H4 and R groups
respectively. We found only resonances for the C(sp) attached to
the C5 ring at
PPh3 resonances occurred at
d
101.05 (2a) and 99.85 (2c). In the 31P spectrum, the
d
43.3, 41.6 and 42.85, respectively.
The molecular structures of Fc’(C^CX)2 [X ¼ SiMe3 1, Au(PPh3)
2a,] have been determined from single-crystal XRD studies. Fig. 1
contains plots of molecule 1 of the silane 1 (upper) and one
centrosymmetric molecule of 2a (lower), with significant bond
parameters being presented in the caption. The central ferrocene-
1,10-diyl fragment of 2a carries a C^CAu(PPh3) substituent on each
ring, disposed in a trans arrangement. The bond lengths fall in the
expected ranges for AueP, AueC(sp) single and C^C triple bonds;
average CeC bonds within the C5 rings [1.42(1) Å] and FeeC bonds
to these rings [2.04(2) Å] do not deserve comment, with the
exception of FeeC(3) (bearing the alkynyl substituent) which is the
longest separation at 2.065(11) Å. The P(1)eAueC(1)eC(2)eC(3)
sequence shows the usual small deviations from linearity [2.6, 7.4,
6.3ꢁ] probably induced by “crystal packing forces”. The common
2. Results and discussion
Desilylation of Mc’(C^CSiMe3)2 [Mc’ ¼ M(
h
-C5H4ꢀ)2, M ¼ Fe 1,
Ru] with LiMe followed by addition of two equivalents of AuCl(PR3)
* Corresponding author. Fax: þ61 8 8303 4358.
E-mail address: michael.bruce@adelaide.edu.au (M.I. Bruce).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.04.026

M.I. Bruce et al. / Journal of Organometallic Chemistry 695 (2010) 1906e1910
1907
Au(PR3)
Au(PR3)
SiMe3
(i) LiMe
M
M
(ii) Au(PR3)
SiMe3
M = Fe, R = Ph 2a, tol 2b
M = Ru, R = Ph 2c
M = Fe 1, Ru
(i) LiMe
(ii) AuCl(PPh3) / CuI
Fe
C
C
C
C
PPh3
Au
Au
Au
Au
C
C
Ph3P
C
C
Fe
3
Scheme 1.
geometries of 1 and 2a are closely similar, the former containing
two molecules in the unit cell, each of which has independent
C5H4C^CSiMe3 ligands on the central Fe atom.
with that in Ru3(m-H)(m3-CCFc)(CO)9 4 [8]. Of note in 4 is the
considerably longer coordinated C^C triple bond [1.30(1) Å in 4,
vs 1.236(14) Å in 3] and the larger departure from linearity of the C
(Fc)eC(2)eC(1)eRu fragment, which has angles at C(1) and C(2) of
152.5(7) and 143.6(8)ꢁ [cf. 172.6(9) and 170.5(10)ꢁ in 3]. These
differences demonstrate the much greater back-bonding from the
Ru3 cluster to the alkynyl unit compared with that from the gold
centres.
On a few occasions, similar reactions between 1, LiMe and AuCl
(PPh3), carried out in thf in the presence of CuI, afforded a different
orange product, formulated as Au4{Fc’(C^C)2}2(PPh3)2 3 from
a single-crystal X-ray structure determination. A molecule of 3 is
shown in Fig. 2, selected bond parameters being collected in the
caption. The molecule contains two Fc’(C^C)2 moieties linked by
an Au4(PPh3)2 cluster. The central Au4 cluster forms a centrosym-
metric planar rhombus [Au(1)eAu(2, 20) 3.0029(6), 3.2956(6) Å], of
which Au(1) is two-coordinate, being
groups [Au(1)eC(1,30) 1.984(10), 1.975(12) Å], while Au(2) is
-bonded to the two C^C triple bonds [Au(2)eC(1,2) 2.208(9),
s-bonded to two alkynyl
p
2.376(10) Å] and also carries a PPh3 ligand [Au(2)eP 2.238(2) Å].
The ferrocene-1,10-diyl nucleus serves to hold the C2 groups apart,
controlling the interaction with Au(2) [Au(2)/C(3,4) 2.986(10),
3.360(12) Å]. Au(1) is coplanar with C(1e4) [c2 891;
d(Au) 0.003
(1) Å].
The C(1)eC(2), C(3)eC(4) separations are 1.236(14), 1.212(15) Å,
slightly elongated from the normal C(sp)eC(sp) bond length and
consistent with a small lowering of bond order as a result of
p
-bonding to the Au atoms. There is only a slight deviation from
linearity along the C(201)eC(2)eC(1)eAu(1)eC(30) and C(401)eC
(4)eC(3)eAu(1)eC(10) arrays [angles at individual atoms range
between 170.3(1) and 176.2(4)ꢁ. These parameters are similar to
those found in the gold(I) alkynylcalix[4]crown-6 complex
described by Yam and coworkers [6] [cf. values for Au(1)/Au(2)
3.1344(8), 3.2048(8) Å]. The central structure is also related to that
found in Ag2Au2(C^CPh)4(PPh3)2, obtained from the reaction
between Au(C^CPh)(PPh3) and {Ag(C^CPh)}n [7]. As is evident
from the Figure, one of the phenyl rings projects over the central
plane, with H/Au(1,10,2) distances 3.02, 3.23, 2.87 Å]. It is also of
interest to compare the coordination of the alkynyl groups of 3
In conclusion, while the ferrocene-1,10-bis(alkynyl) derivatives
with SiMe3 (1) or Au(PR3) (2) substituents are stable [in contrast to
Fc’(C^CH)2], loss of PPh3 may occur during the preparation of 2a in
the presence of CuI (which acts as a PPh3-abstractor) followed by
dimerisation to give the Au4 cluster 3.

1908
M.I. Bruce et al. / Journal of Organometallic Chemistry 695 (2010) 1906e1910
Fig. 1. Plots of (a) molecule 1 of Fc’(C^CSiMe3)2 1. Selected bond parameters: distances (Å), mean values: C(cp)eC(alkyne) 1.434(4), C^CeSi 1.204(2), C(alkyne)eSi 1.844(4); angles
(ꢁ) (ranges): C(cp)eC^C 177.20(4), C^CeSi 168.63(3)-177.37(3); (b) a molecule of Fc’{C^CAu(PPh3)}2 2a. Selected bond parameters: AueP(1) 2.269(3), AueC(1) 1.994(10), C(1)eC
(2) 1.20(1), C(2)eC(3) 1.44(2) Å, P(1)eAueC(1) 177.4(3), AueC(1)eC(2) 172.9(10), C(1)eC(2)eC(3) 173.7(13)ꢁ.
3. Experimental
Electrospray mass spectra (ES MS): Fisons Platform II spec-
trometer. Solutions in MeOH were injected via a 10 ml injection
loop. Nitrogen was used as the drying and nebulising gas.
Chemical aids to ionisation were used as required [9]. Elemental
analyses were by CMAS, Belmont, Victoria, Australia, and
Campbell Microanalytical Laboratory, University of Otago, Dun-
edin, New Zealand.
3.1. General
All reactions were carried out under dry nitrogen, although
normally no special precautions to exclude air were taken during
subsequent work-up. Common solvents were dried, distilled under
argon and degassed before use. Separations were carried out by
preparative thin-layer chromatography on glass plates
(20 ꢂ 20 cm2) coated with silica gel (Merck, 0.5 mm thick).
3.3. Reagents
AuCl(PR3) (R ¼ Ph, tol) [10], Fc’-1,10-(C^CSiMe3)2 1 [1] and Rc’-
1,10-(C^CSiMe3)2 [11] were made by the cited procedures.
3.2. Instruments
IR spectra: Bruker IFS28 FT-IR spectrometer. Nujol mull
spectra were obtained from samples mounted between NaCl
discs. NMR spectra: Varian 2000 instrument (1H at 300.13 MHz,
13C at 75.47 MHz, 31P at 121.503 MHz). Samples were dissolved
in C6D6 contained in 5 mm sample tubes. Chemical shifts are
3.3.1. Fc0-1,10-{C^CAu(PPh3)}2 2a
LiMe (0.30 ml, 1.5 M in Et2O, 0.45 mmol) was added to a solution
of Fc’-1,10-(C^CSiMe3)2 (40 mg, 0.11 mmol) in dry thf (25 ml) and
the mixture was stirred for 20 h at r.t. Solid AuCl(PPh3) (155 mg,
0.313 mmol) was then added and the mixture stirred for a further
10 min. After removal of solvent under vacuum, the residue was
washed several times with Et2O and then extracted into benzene.
given in ppm relative to internal tetramethylsilane for 1H and 13
C
NMR spectra and external H3PO4 for 31P NMR spectra.

M.I. Bruce et al. / Journal of Organometallic Chemistry 695 (2010) 1906e1910
1909
Fig. 2. Plot of a molecule of {Fc’(C^C)2}2Au4(PPh3)2 3. Selected distances: Au(1)/Au(2,20) 3.0029(6), 3.2956(6), Au(2)eP(1) 2.238(2), Au(1)eC(1,30) 1.984(10), 1.975(12), Au(2)eC(1)
2.208(9), Au(2)eC(2) 2.376(10), C(1)eC(2) 1.236(14), C(3)eC(4) 1.212(15), C(2)eC(201) 1.419(14), C(4)eC(401) 1.419(15) Å. Au(2)eAu(1)eAu(20) 107.31(1), Au(1)eAu(2)eAu(10)
72.69(1), Au(10)eAu(2)eP(1) 91.32(6), Au(1)eAu(2)eP(1) 127.48(7), C(1)eAu(1)eC(30) 176.2(4), Au(1)eC(1)eC(2) 173.0(8), C(1)eC(2)eC(201) 170.3(10)ꢁ.
The filtered solution was reduced in volume and crystallisation was
induced by addition of a small amount of hexane to give Fc’-1,10-
{C^CAu(PPh3)}2 2a as an orange solid (95 mg, 75%). Anal. Found: C,
52.28; H, 3.35. Calcd (C50H38Au2FeP2): C, 52.20; H, 3.33; M, 1150. IR
residue was washed several times with Et2O and then dissolved in
benzene. The filtered solution was evaporated to give Rc’-1,10-
{C^CAu(PPh3)}2 2c as a light yellow solid (82 mg, 64%). Anal. Calcd
(C50H38Au2P2Ru.C6H6): C, 52.80; H, 3.48; M, 1196. Found: C, 52.40;
(nujol, cmꢀ1): 2101w, 2052w, 1914w [
n
(C^C)], 1603w, 1584w. 1H
H, 3.54. IR (nujol, cmꢀ1): 2125w [ (C^C)], 1584w. 1H NMR (C6D6):
n
NMR (C6D6):
d
4.28e4.29, 4.76e4.77 (2 ꢂ m, 2 ꢂ 4H, C5H4),
d
4.58e4.59, 5.20e5.21 (2ꢂ m, 2ꢂ 4H, C5H4), 6.88e6.94, 7.00e7.04,
6.88e6.93, 6.99e7.04, 7.19e7.25 (3 ꢂ m, 13 þ 6 þ 11H, Ph). 13C NMR
7.17e7.24 (3ꢂ m, 13 þ 6 þ 11H, Ph). 13C NMR (C6D6):
d 73.27, 75.96
(C6D6):
d
70.57 (Cipso of Fc), 72.19, 73.72 (C5H4),101.05 (br, FceC^C),
(C5H4), 73.98 (Cipso), 99.85 (br, RceC^C), 128.92, 129.44e129.59,
128.92, 129.50, 129.65, 130.54, 131.27, 131.66e131.67 (m), 134.73,
130.53, 131.25, 131.60, 134.72e134.90 (Ph). 31P NMR (C6D6):
d 42.9.
134.91 (Ph). 31P NMR (C6D6):
d
43.3. HR-MS [found (calcd)]:
HR-MS [found (calcd)]: [M þ Au]þ 1393.050 (1393.050); [M þ H]þ
[M þ Na]þ 1173.111 (1173.102); [M þ H]þ 1151.128 (1151.120).
1197.090 (1197.090); [Au(PPh3)2]þ 721.154 (721.148).
3.3.2. Fc0-1,10-{C^CAu[P(tol)3]}2 2b
3.3.4. Au4{(C^C)2Fc0}2(PPh3)2
3
A solution of KOH (100 mg in 5 ml MeOH, 2.78 mmol) was added
to a stirred suspension of AuCl{P(tol)3} (217 mg, 0.40 mmol) and
Fc’(C^CSiMe3)2 (70 mg, 0.19 mmol) in dry MeOH (20 ml) and the
mixture was stirred for 1 h in an ice-bath. The resulting orange
precipitate was collected and washed with cold MeOH to give
Fc’-1,10-{C^CAu[P(tol)3]}2 2b (163 mg, 70%) as an orange powder.
Anal. Calcd (C56H50Au2FeP2): C, 54.47; H, 4.08; M, 1234. Found: C,
LiMe (0.30 ml, 1.5 M in Et2O, 0.45 mmol) was added to
a solution of Fc’-1,10-(C^CSiMe3)2 (40 mg, 0.11 mmol) in dry thf
(10 ml) and the mixture was stirred for 20 h at r.t. A solution of
AuCl(PPh3) (153 mg, 0.309 mmol) and CuI (7 mg, 0.037 mmol) in
thf (20 ml) was added and the mixture was stirred for 2 h. After
removal of solvent, the residue was extracted into C6H6 and
purified by chromatography (neutral alumina, benzene). The
orange band was collected and crystallised (Et2O/hexane) to give
Au4{(C^C)2Fc’}2(PPh3)2 3 as an orange solid (55 mg, 56%). Calcd
(C64H46Au4Fe2P2): C, 43.27; H, 2.61; M, 1776. Found: C, 46.19; H,
3.00 [satisfactory analyses could not be obtained]. IR (nujol,
52.52; H, 3.97. IR (Nujol, cmꢀ1):
1597s, 1563w. 1H NMR (C6D6):
1.93 (s, 18H, Me), 4.31e4.33 (m, 4H,
C5H4), 4.79e4.81 (m, 4H, C5H4), 6.78e6.82 (m, 12H, C6H4),
n(C^C) 2101w, 2025w, 1914w;
d
7.27e7.38 (m, 12H, C6H4). 31P NMR:
d 41.6. ES-MS/m/z: 1235,
[M þ H]þ. HR-MS [found (calcd)]: [M þ Na]þ 1257.196 (1257.196);
cmꢀ1): 2125w [ (C^C)], 1653w (br), 1100s. 1H NMR (C6D6):
n
[M þ H]þ 1235.215 (1235.214).
d
4.31e4.33, 4.79e4.81 (2ꢂ m, 2ꢂ 8H, C5H4), 6.78e6.82,
7.27e7.38 (2ꢂ m, 15 þ 15H, Ph). 31P NMR (C6D6):
d 48.1. EI-MS
3.3.3. Rc0-1,10-{C^CAu(PPh3)}2 2c
(MeCN, m/z): 857, [M e 2Au(PPh3)]þ; 721, [Au(PPh3)2]þ; 575,
[M ꢀ 2Au]2þ. X-ray quality crystals were obtained from benzene/
MeOH.
Similarly, LiMe (0.30 ml, 1.5 M in Et2O, 0.45 mmol) was added to
a solution of Rc’-1,10-(C^CSiMe3)2 (46 mg, 0.11 mmol) in dry thf
(20 ml) and the mixture was stirred for 20 h at r.t. Solid AuCl(PPh3)
(157 mg, 0.317 mmol) was then added and the mixture stirred for
a further 10 min. After removal of solvent under vacuum, the
This compound was not formed in the reaction of Fc’{C^CAu
(PPh3)}2 with CuI in Et2O as a potential PPh3-abstraction agent.
Further attempts to obtain the Au4 cluster resulted in the formation

1910
M.I. Bruce et al. / Journal of Organometallic Chemistry 695 (2010) 1906e1910
Table 1
SHELXL 97 program [12]. Pertinent results are given in Table 1 and
Crystal data and refinement details.
the Figures (which show non-hydrogen atoms with 50% probability
amplitude displacement ellipsoids and hydrogen atoms with arbi-
trary radii of 0.1 Å) and in the captions thereto.
1
2a
3
Formula
MW
Crystal
Space group
a/Å
C20H26FeSi2
378.44
Triclinic
P1
9.192(2)
14.196(3)
16.845(3)
70.92(2)
89.49(1)
82.87(2)
2060.1
1.220
C50H38Au2FeP2
1150.5
Monoclinic
P21/c
6.960(5)
20.895(5)
14.365(5)
90
94.731(5)
90
2082.0
1.835
C64H46Au4Fe2P2
1776.5
Monoclinic
P21/n
14.242(2)
12.156(1)
15.550(2)
90
Acknowledgements
We thank Professor Brian Nicholson (University of Waikato,
Hamilton, New Zealand) for providing the mass spectra and the
ARC for support of this work.
b/Å
c/Å
ꢁ
ꢁ
a
/
b
/
109.436(3)
90
2539
ꢁ
/
g
V/Å3
Appendix. Supplementary material
rc/g cm-3
2.324
Z
2
m
4
69
0.85
0.81
2
62
7.5
0.84
2
60
12.2
0.47
Full details of the structure determinations (except structure
factors) have been deposited with the Cambridge Crystallographic
Data Centre as CCDC 769762 (1), 765 979 (2a), 735 019 (3). Copies of
this information may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: þ 44
1223 336 033; e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
ꢁ
qmax
/
/mmꢀ1
Tmin/max
Crystal/mm3
Ntot
N (Rint
No
0.31 ꢂ 0.30 ꢂ 0.08 0.16 ꢂ 0.15 ꢂ 0.02 0.11 ꢂ 0.09 ꢂ 0.04
40 612
21 453
6105 (0.110)
4248
39 203
7366 (0.084)
4974
)
16 459 (0.032)
9795
0.038
R1 (I > 2
s(I))
0.063
0.052
wR2 (all data) 0.098
T/K 100
0.17
100
0.15
150
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Diffraction data were measured using a CCD area-detector
instrument using monochromatic Mo-K
Ntot reflections were merged to N unique (Rint cited) after multi-
a
radiation,
l
¼ 0.71073 Å.
scan absorption correction (proprietary software), No with I > 2
s
(I);
all data were used in the full matrix least squares refinements on F2.
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