Use of phosphine gold acetylides [(R3P)AuC≡CR] to form phosphine gold derivatives of tetra-iron and penta-iron clusters

Article abstract of DOI:10.1016/j.jorganchem.2005.02.045

Five new gold acetylides, [AuCCR], with hydroxyl or amino functions in the organic radical R have been prepared. From these, nine phosphine complexes [(R₃P)AuCCR] with R = Ph or Cy were synthesised. Reactions between the phosphine gold acetylides [(Ph₃P)AuCCC(Me)(OH)Et] or [(Cy ₃P)AuCCC(Me)(OH)Et] and the iron carbonyl cluster [Et ₄N][Fe₄N(CO)₁₂] gave both neutral [(R ₃P)AuFe₄N(CO)₁₂] and ionic compounds [(R ₃P)₂Au][Fe₄N(CO)₁₂]. Reaction with the penta-iron cluster [Et₄N][Fe₅N(CO)₁₄] afforded [(R₃P)₂Au][Fe₅N(CO)₁₄], [(R₃P)₂Au][Fe₄N(CO)₁₂] and [(R ₃P)AuFe₄N(CO)₁₂]. The gold-iron clusters were characterised with spectroscopic methods (IR, NMR and M?ssbauer) and in the case of [(Cy₃P)AuFe₄N(CO)₁₂] a single-crystal X-ray analysis.

Full text of DOI:10.1016/j.jorganchem.2005.02.045

Journal of Organometallic Chemistry 690 (2005) 2888–2894
www.elsevier.com/locate/jorganchem
Use of phosphine gold acetylides [(R3P)AuC„CR] to
form phosphine gold derivatives of tetra-iron and penta-iron clusters
a,b,
c
d
George Ferguson
Trevor R. Spalding *, F. Tony Deeney
*, John F. Gallagher , Ann-Marie Kelleher ,
d,
e
a
School of Chemistry, The University, St. Andrews, Fife KY16 9ST, Scotland
Department of Chemistry, University of Guelph, Guelph, Ont., Canada N1G 2W1
b
c
Department of Chemistry, Dublin City University, Dublin, Ireland
d
Department of Chemistry, University College Cork, National University of Ireland, Cork, Ireland
e
Department of Physics, University College Cork, National University of Ireland, Cork, Ireland
Received 19 January 2005; revised 14 February 2005; accepted 16 February 2005
Available online 4 May 2005
Abstract
Five new gold acetylides, [AuC„CR], with hydroxyl or amino functions in the organic radical R have been prepared. From
these, nine phosphine complexes [(R3P)AuC„CR] with R = Ph or Cy were synthesised. Reactions between the phosphine gold acet-
ylides [(Ph3P)AuC„CC(Me)(OH)Et] or [(Cy3P)AuC„CC(Me)(OH)Et] and the iron carbonyl cluster [Et4N][Fe4N(CO)12] gave
both neutral [(R3P)AuFe4N(CO)12] and ionic compounds [(R3P)2Au][Fe4N(CO)12]. Reaction with the penta-iron cluster [Et4N]-
[Fe5N(CO)14] afforded [(R3P)2Au][Fe5N(CO)14], [(R3P)2Au][Fe4N(CO)12] and [(R3P)AuFe4N(CO)12]. The gold–iron clusters were
characterised with spectroscopic methods (IR, NMR and Mo¨ssbauer) and in the case of [(Cy3P)AuFe4N(CO)12] a single-crystal
X-ray analysis.
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: Gold; Acetylide; Phosphine; Iron; Clusters
1. Introduction
proton by the {Ph3PAu}+ group. In the present work
it was decided to synthesise some phosphine gold acety-
lides as alternative precursors for the formation of
{R3PAu}-containing clusters. The present work initially
describes the synthesis of new gold acetylides,
[AuC„CR], with the R groups containing either a hy-
droxy or amino function. Phosphine derivatives of these
compounds were synthesised and the reactions between
two of the compounds, [(R3P)AuC„CC(Me)(OH)Et]
where R = Ph and Cy, with the tetra- and penta-iron
carbonyl clusters [Et4N][Fe4N(CO)12] and [Et4N][Fe5N-
(CO)14] were investigated. The gold acetylides and their
phosphine derivatives were characterised by elemental
analyses, melting points and IR spectroscopy and the
gold–iron clusters were also characterised with 13C
NMR and Mo¨ssbauer spectroscopies. In the case of
The most common precursor used to form gold-
containing iron carbonyl clusters is [(R3P)AuCl] [1] and
the clusters formed usually incorporate the {Ph3PAu}
group. A notable feature in the structural chemistry of
the gold-containing clusters which has been commented
on by Hoffmann [2] and a number of other authors is the
isolobal nature of the proton and {Ph3PAu}+ species
which often leads to observed structural similarities in
compounds which differ only in the replacement of a
*
Corresponding authors. Tel.: +353 214902602; fax: +353
214274097.
E-mail addresses: crystals@uoguelph.ca (G. Ferguson), t.spalding
@ucc.ie (T.R. Spalding).
0022-328X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.02.045

G. Ferguson et al. / Journal of Organometallic Chemistry 690 (2005) 2888–2894
2889
½ðR3PÞAuCꢁCCðMeÞðOHÞEtꢂ
½ðR3PÞAuFe4NðCOÞ ꢂ
[(Cy3P)AuFe4N(CO)12] a single-crystal X-ray structure
analysis was carried out.
12
þ
!
þ
½Fe4NðCOÞ ꢂꢀ
½ðR3PÞ Auꢂ½Fe4NðCOÞ ꢂ
12
2
12
ð1Þ
2. Results and discussion
The neutral products were isolated by TLC in 100%
hexane. Following this, elution with 80:20 CH2Cl2:hex-
ane afforded the cationic complexes. Both gold acetylide
complexes (8) and (15) appeared to react in the same
way with the major difference being that [(Cy3-
P)AuC„CC(Me)(OH)Et] (15) afforded 72% the neutral
product (22) with only 9% of the cationic species (24)
whereas the reaction of [(Ph3P)AuC„CC(Me)(OH)Et]
(8) afforded approximately 62% of the neutral species
(21) and 11% of the cationic product (23).
When a solution of the penta-iron cluster [Et4N]-
[Fe5N(CO)14] (20) in dichloromethane was reacted with
[(Ph3P)AuC„CC(Me)(OH)Et] (8) at room temperature
for 23 h, the cationic penta-iron complex [(Ph3P)2Au]-
[Fe5N(CO)14] (25, 32%) and the tetra-iron complexes
[(Ph3P)AuFe4N(CO)12] (21, 46%) and [(Ph3P)2Au]-
[Fe4N(CO)12] (23, 10%) were isolated and characterised,
Eq. (2), R = Ph.
2.1. Synthesis of gold acetylides and their phosphine
derivatives
Two gold acetylides had been previously prepared,
i.e. [AuC„CC(Me)(OH)Et] (1) and [AuC„CC-
(Me)(OH)Ph] (2) and their Ph3P derivatives synthesised
[3]. The synthetic method used to prepare five new
compounds, i.e. [AuC„CC(Me)2NH2] (7, 63%),
[AuC„C–C(Me)(OH)CH2CH(Me)2] (5, 75%), [AuC„
CC(H)(OH)Et] (3, 92%), AuC„CC(H)(OH)(CH2)4Me]
(4, 80%) and [AuC„CCH2Optm] (ptm = phthalimide,
6, 26%) was based on a literature procedure [4].
Generally, phosphine derivatives of the parent gold
acetylides were prepared from the reaction between a
suspension of the gold acetylide in toluene and a solu-
tion of the ligand in toluene. After stirring the reaction
mixture at room temperature for 5 min, it was filtered
and the solvent removed under reduced pressure to af-
ford samples of the product, [LAuC„CR].
½ðR3PÞAuC ꢁ CCðMeÞðOHÞEtꢂ
½ðR3PÞAuFe4NðCOÞ ꢂ
12
þ
þ
½Fe5NðCOÞ ꢂꢀ
! ½ðR3PÞ Auꢂ½Fe5NðCOÞ ꢂ
14
2
14
2.2. Reactions between phosphine gold acetylides
[(Ph3P)AuCCC(Me)(OH)Et] (8) or
[(Cy3P)AuCCC(Me)(OH)Et] (15) and the iron
carbonyl clusters [Et4N][Fe4N(CO)12] (19) and
[Et4N][Fe5N(CO)14] (20)
þ
½ðR3PÞ Auꢂ½Fe4NðCOÞ ꢂ
2
12
ð2Þ
Another product was isolated by TLC but it was too
unstable to characterise fully. The CH2Cl2 solution IR
spectrum of the unstable compound showed strong or
very strong absorptions due to carbonyl groups at
2038 vs, 2024 s, 2012 vs and 2002 vs, while a 13C
NMR spectrum confirmed the presence of CO groups
at 220.59, 218.28, 213.26 and 210.12 ppm. It may be
postulated that the unstable product was [(Ph3P)Au-
Fe5N(CO)14] (27), which spontaneously decomposed to
give an Fe4 species. The loss of an iron atom from an
Fe5-system has previously been observed for a gold–iron
cluster system with a Fe5C framework, Eq. (3), [6]. This
reaction occurred when a solution of [(Et3PAu)2Fe5C
(CO)14] was stirred at 4 °C for 100 h in air.
It was decided to investigate the use of two typical
phosphine gold acetylides as reagents for the introduc-
tion of {(R3P)Au}-units into transition element-based
clusters. The clusters chosen were [Fe4N(CO)12]ꢀ
and [Fe5N(CO)14]ꢀ [5]. The reactions were carried
out at room temperature in dichloromethane solu-
tion. Six compounds were successfully characterised,
namely [(R3P)AuFe4N(CO)12], R = Ph (21), Cy (22),
[(R3P)2Au][Fe4N(CO)12], R = Ph (23), Cy = (24) and
[(R3P)2Au][Fe5N(CO)14], R = Ph (25), Cy (26). In all
cases the products were separated by preparative thin
layer chromatography. They were characterised by C/
H/N elemental analyses, infrared spectroscopy for com-
pounds (21)–(26), 13C NMR spectroscopy for com-
pounds (21)–(24) and Mo¨ssbauer spectroscopy for
(21)–(23), (25), (26). The structure of (22) was deter-
mined by a single crystal X-ray analysis.
Reaction of [(R3P)AuC„CC(Me)(OH)Et], R = Ph
(8) or Cy (15) with [Et4N] [Fe4N(CO)12] (19) in dichloro-
methane at room temperature for between 30 min and
1 h resulted in the formation of the neutral complexes
[(Ph3P)AuFe4N(CO)12] (21) or [(Cy3P)AuFe4N(CO)12]
(22) and the cationic species [(Ph3P)2Au][Fe4N(CO)12]
(23) or [(Cy3P)2Au][Fe4N(CO)12] (24), Eq. (1).
½ðEt3PAuÞ Fe5CðCOÞ ꢂ ! ½ðEt3PAuÞ Fe4CðCOÞ ꢂ
2
14
2
12
þ Fe2þ þ 2CO
ð3Þ
Some evidence for the loss of an iron atom from an
Fe5-system in the present work is the observation that
when [Et4N][Fe5N(CO)14] (20) and [(Ph3P)AuC„CC
(Me)(OH)Et] (8) were stirred in CH2Cl2 at room temper-
ature, gas evolution was observed over 5–6 h as expected
from Eq. (3).

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G. Ferguson et al. / Journal of Organometallic Chemistry 690 (2005) 2888–2894
When a solution of the penta-iron cluster, [Et4N]-
[Fe5N(CO)14] (20) in dichloromethane was reacted with
[(Cy3P)AuC„CC(Me)(OH)Et] (9) at room temperature
for 23 h, the cationic penta-iron complex [(Cy3P)2Au]-
[Fe5N(CO)14] (26, 20%) and the tetra-iron complexes
[(Cy3P)AuFe4N(CO)12] (22, 50%) and [(Cy3P)2Au]-
[Fe4N(CO)12] (24, 5%) were isolated and characterised,
Eq. (2), R = Cy.
The carbonyl infrared frequencies for the [(R3P)Au-
Fe4N(CO)12] clusters (21) and (22) are almost identical
to those previously reported by Gladfelter et al. for
[(Ph3P)AuFe4N(CO)12] (21), [7]. They prepared (21) in
53% yield from [PPN][Fe4N(CO)12] and [(Ph3P)AuCl]
in the presence of Tl[PF6] in CH2Cl2 solution. The fre-
quencies are similar to those reported for [HFe4N-
(CO)12] (28) [8] and there is no evidence of bridging
carbonyl ligands in the infrared spectra of the neutral
Fe4N systems (21) and (22). The data obtained for the
[(R3P)2Au][Fe4N(CO)12] compounds (23) and (24) are
very similar to those for the starting material [Et4N]-
[Fe4N(CO)12] (19) [9]. This can be taken as an indication
that the overall structure of the anion has not been
perturbed by the presence of the bis(phosphine)gold cat-
ions. In the solid state (KBr) spectra of the [(R3P)2Au]-
[Fe5N(CO)14] clusters (25) and (26), carbonyl absorptions
at 1802 and 1800 cmꢀ1, respectively are due to the
presence of bridging ligands. These are absent from
the CH2Cl2 solution spectra. Other [X][Fe5N(CO)14] sys-
tems have bridging carbonyl absorptions in their solid
state spectra at 1796, 1806 and 1808 cmꢀ1 where
[X] = [PPN], [Et4N] and [Me4N], respectively and solid
state isomers of the [Fe5N(CO)14]ꢀ anion have been re-
ported [10].
Fig. 1. ORTEP plot of the molecular structure of [(Cy3P)Au-
Fe4N(CO)12] (22) showing the numbering scheme; ellipsoids are shown
˚
at the 30% probability level. Selected bond distances (A) and angles (°):
Au(1)–Fe(3) 2.7108(11), Au(1)–Fe(4) 2.6876(13), Fe(1)–N(1) 1.778(7),
Fe(2)–N(1) 1.773(7), Fe(3)–N(1) 1.915(7), Fe(4)–N(1) 1.918(6), Fe(1)–
Fe(3) 2.5886(16), Fe(1)–Fe(4) 2.5835(17), Fe(2)–Fe(3) 2.5969(17),
Fe(2)–Fe(4) 2.6137(16), Fe(3)–Fe(4) 2.6242(15), Au–P(1) 2.297(2);
Fe(1)–N(1)–Fe(2) 178.0(4), Fe(3)–Au(1)–Fe(4) 58.17(3), Fe(3)–Au(1)–
P(1) 146.63(6), Fe(4)–Au(1)–P(1) 154.95(6), Fe(3)–N(1)–Fe(4) 86.4(3).
˚
Fe–C distances range from 1.773(11) to 1.830(10) (mean 1.795 A) and
˚
˚
P–C distances from 1.838(9) to 1.873(10) A (mean 1.851 A). Dimen-
sions in CO and Cy groups are normal. Within the Fe4N framework:
mean Fewing-tip–N–Fehinge 89.3°, mean Fewing-tip–Fehinge–N 43.2°, mean
Fehinge–Fewing-tip–N 47.6°, mean Fe–C–O 176.8° and mean Au–P–C
111.7°.
2.3. Crystal and molecular structure of
[(Cy3P)AuFe4N(CO)12] (22)
The Fe(3)–Au(1)–Fe(4) angle in (22) is 58.17(3)° sim-
ilar to the Fe–Au–Fe angles in [Et4N][(Ph3PAu)Fe2-
(CO)8] (31) at 58.6(1)° and in [(Et3P)AuFe4(CO)13]ꢀ
(29) at 59.57(4)° [11]. The Fe–Au–Fe angle reported
for (30) was much larger at 80.5(1)° but this is a result
of the gold phosphine unit spanning the ‘‘wing-tip’’ iron
atoms rather than the hinge position. The Fe–H–Fe an-
gle in (29) was 87(3)° [12].
An X-ray analysis of compound (22) was undertaken
in order to determine details of its crystal and molecular
structure. Dark green crystals of [(Cy3P)AuFe4N(CO)12]
(22) were grown by slow diffusion of a layer of hexane
into a CH2Cl2 solution of (22). The Fe4 unit has the but-
terfly arrangement with the nitrogen atom co-ordinated
to all four iron atoms and the gold atom bridging the
hinge positions in the Fe4 butterfly, Fig. 1. All carbonyl
groups in (22) are terminal and each iron atom is
bonded to three carbonyl ligands. Selected bond dis-
tances and angles are given in the figure legend. The gold
phosphine unit in (22), bridges the Fe(3)–Fe(4) interac-
tion but is tipped slightly towards the Fe(1) ‘‘wing-tip’’
site. This aspect of (22) is very similar to
[(Et3P)AuFe4(CO)13]ꢀ (29) [11] but in [(Ph3PAu)(l-
H)Fe4C(CO)12] (30) it is the hydride ligand which
bridges the hinge Fe–Fe bond while the gold atom inter-
acts with both wing-tip iron sites and the carbide C atom
[12].
The Fe–Fe distances in [(Cy3P)AuFe4N(CO)12] range
˚
from 2.5835(17)–2.6242(15) A, with the gold phosphine
bridged Fe(3)–Fe(4) hinge distance being the longest.
In [(Ph3PAu)(l-H)Fe4C(CO)12] (30) the hydride bridged
˚
Fe–Fe hinge distance is 2.618(1) A, while the other Fe–
˚
Fe distances range from 2.626(1) to 2.644(1) A (29). In
(29) the Fe–Fe distances range from 2.623(1) to
˚
2.654(1) A with the gold phosphine bridged distance
˚
being 2.649(2) A [11]. The Fe–Au distances in (22)
˚
are not unusual at 2.7108(11) and 2.6876(13) A and
˚
compare with analogous distances of 2.666(1) A in
[(Et3P)AuFe4(CO)13]ꢀ (29) [11]. The Fe–N distances in

G. Ferguson et al. / Journal of Organometallic Chemistry 690 (2005) 2888–2894
2891
(22) are Fe(1)–N(1) 1.778(7), Fe(2)–N(1) 1.773(7) for
bonds to the ‘‘wing-tip’’ iron atoms and Fe(3)–N(1)
˚
1.915(7) and Fe(4)–N(1) 1.918(6) A for the hinge iron
atoms. The stronger interaction with the ‘‘wing-tip’’ sites
is typical of the M4N butterfly structures, e.g. in
˚
[HFe4N(CO)12] (28) the Fehinge–N distance is 1.92(2) A
velocity are slightly better resolved. The quadrupole
splitting, q, and isomer shift d, values assigned to
the Fehinge site are 0.85 and 0.09 mm sꢀ1, and for the
Fewing-tip site the values are 0.62 and 0.43 mm sꢀ1. The
quadrupole splitting values reported for [HFe4N(CO)12]
(28) are 1.01 and 0.87 mm sꢀ1, with corresponding
isomer shift values of 0.15 and 0.42 mm sꢀ1, these are
˚
and the Fewing-tip–N distance is 1.77(1) A [9].
t
t
assigned as FeðCOÞ Hbr and FeðCOÞ , respectively
3
3
2.4. Mo¨ssbauer spectra
[10,13]. Hence for (21) the signal at 0.90 mm sꢀ1 is as-
signed to the Fehinge {Fe(CO)3(Ph3PAu)br} site and the
signal at 0.65 mm sꢀ1 is assigned to the Fewing-tip site.
2.4.1. [(Ph3P)AuFe4N(CO)12] (21) and
[(Cy3P)AuFe4N(CO)12] (22)
In the solid state structure of [(Cy3P)AuFe4N(CO)12],
Fig. 1, there appear to be three independent iron sites.
The Au to Fe(1) distance was shorter than the Au to
Fe(2) distance due to the displacement of the {Au
(Cy3P)} group towards the Fe(1) atom, [i.e.
Fe(1) ¼ Fe(2) ¼ Fe(3) = Fe(4)]. All Fe sites have only
terminal carbonyl ligands. Thus, the Mo¨ssbauer spec-
trum could consist of three doublets if there are three
independent sites, or, if the difference between Fe(1)
and Fe(2) sites is not significant, two doublets. More-
over, if it is correct that the {(R3P)Au}+ group and
the proton are isolobal species, it may be expected that
compounds (21), (22) and [HFe4N(CO)12] (28) will have
similar Mo¨ssbauer spectra [10,13]. The spectra of (21)
and (22), Fig. 2, and (28) all show closely similar spectra
with two doublets due to two independent iron sites.
This indicates that the difference between the Fe(1)
and Fe(2) environment observed in the X-ray diffraction
study of (22) was not detected by Mo¨ssbauer spectros-
copy. For [(Ph3P)AuFe4N(CO)12] (21) the spectrum
consists of four signals with only partial resolution of
the two signals at positive velocity. The quadrupole
splitting values (q) for the two iron sites are 0.90 and
0.65 mm sꢀ1, the associated isomer shift values (d) are
0.09 and 0.46 mm sꢀ1. The spectrum shown by [(Cy3-
P)AuFe4N(CO)12] (22) is almost identical to that of
(21), the only difference is that the signals at positive
2.4.2. [(Ph3P)2Au][Fe4N(CO)12] (23)
The core structure of the [Fe4N(CO)12]ꢀ anion most
probably contains four iron atoms in a butterfly
arrangement with two independent sites, Fehinge and
Fewing-tip similar to the neutral compounds (21) and
(22). The Mo¨ssbauer spectrum of (23) shows three sig-
nals with the one signal at positive velocity approxi-
mately twice the intensity of the others. Based on
previously published Mo¨ssbauer data of [Fe4N(CO)12]ꢀ
compounds [10,13] the pair of signals in the spectrum of
(23) with quadrupole splitting of 0.80 mm sꢀ1 and iso-
mer shift of 0.18 mm sꢀ1 may be assigned to the Fehinge
sites and those with quadrupole splitting of 0.58 mm sꢀ1
and isomer shift 0.33 mm sꢀ1 assigned to the wing-tip
iron atoms. The values reported for [Et4N][Fe4N(CO)12]
(19) are q = 0.88 and d = 0.21 mm sꢀ1 and q = 0.63,
d = 0.34 mm sꢀ1, respectively, while the values reported
for the isoelectronic species, [Fe4C(CO)12]2ꢀ are q =
0.88, d = 0.22 mm sꢀ1 and q = 0.62, d = 0.35 mm sꢀ1
for hinge and wing-tip iron sites, respectively.
2.4.3. [(Ph3P)2Au][Fe5N(CO)14] (25) and
[(Cy3P)2Au][Fe5N(CO)14] (26)
If one assumes that the Fe5N-compounds (25) and
(26) both have core structures and the disposition of car-
bonyl ligands similar to [Et4N][Fe5N(CO)14] (20), then
there should be three distinct iron sites. However, the
Mo¨ssbauer spectra of (26) and (25), like that of (20),
consist of one unresolved doublet and it is impossible
to discern different sites and make detailed assignments,
e.g. averaged values of d = 0.59 and q = 0.30 mm sꢀ1
cover all sites in (25). Solid state isomers of
[Fe5N(CO)14]ꢀ existing with different carbonyl ligand
dispositions depending on the cation present {[PPN]+,
[Et4N]+ or Cs+} have been reported and their Mo¨ss-
bauer spectra studied [10,13].
3. Conclusions
Five new gold acetylides, [AuC„CR], with hydroxyl
or amino functions in the organic radical R and nine
phosphine complexes of these gold acetylides
[(R3P)AuC„CR] where R = Ph or Cy were synthesised
Fig. 2. Mo¨ssbauer spectra of (a) [(Cy3P)AuFe4N(CO)12] (22, above)
and (b) [(Ph3P)AuFe4N(CO)12] (21, below).

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G. Ferguson et al. / Journal of Organometallic Chemistry 690 (2005) 2888–2894
and characterised. The phosphine gold acetylides were
soluble in dichloromethane and proved to be effective
reagents for the formation of {(R3P)nAu}-containing
clusters (n = 1 or 2). Reactions between two of the phos-
phine gold acetylides, [(Ph3P)AuC„CC(Me)(OH)Et]
and [(Cy3P)AuC„CC(Me)(OH)Et], and the tetra-iron
carbonyl cluster [Et4N][Fe4N(CO)12] afforded two com-
pounds, namely [(R3P)AuFe4N(CO)12] and [(R3P)2Au]-
[Fe4N(CO)12]. Reactions between the phosphine gold
acetylides and [Et4N][Fe5N(CO)14] gave [(R3P)2Au]-
[Fe5N(CO)14] and both the tetra-iron complexes
[(R3P)AuFe4N(CO)12] and [(R3P)2Au][Fe4N(CO)12].
The gold–iron clusters were characterised with spectro-
scopic methods (IR, NMR and Mo¨ssbauer) and in the
case of [(Cy3P)AuFe4N(CO)12] a single-crystal X-ray
analysis.
On the basis of both FT-IR and Mo¨ssbauer spectra
the solid state structures of [(R3P)AuFe4N(CO)12] and
[(R3P)2Au][Fe4N(CO)12] appeared to contain terminally
bonded CO groups only as is also the case for the species
[HFe4N(CO)12]. The single-crystal X-ray analysis of
[(Cy3P)AuFe4N(CO)12] confirmed this but also showed
an asymmetry in the bonding of the {(Cy3P)Au}-group
to the Fe4-skeleton. This was not reflected in the Mo¨ss-
bauer spectrum. The reason for the asymmetric bonding
is unclear. It seems unlikely that the H atom in [HFe4N-
(CO)12] would adopt a similar arrangement. The asym-
metric bonding of the {(Cy3P)Au}-group may be due
to some weak solid-state interactions in the crystal
rather than any difference in ‘‘isolobal’’ character of
the gold atom compared to hydrogen.
diffractometer. Accurate cell dimensions and crystal ori-
entation matrix were determined by a least squares pro-
cedure from reflections obtained in the range 2 < h < 25°
using graphite monochromatised (Mo-Ka) radiation
˚
(k = 0.71073 A). The structure was solved via standard
heavy-atom procedures using the NRCVAX suite of
programs [14] and refined with full-matrix least-squares
calculations using SHELXL-97-2 [15] in WinGX [16]. Plots
and data validation checks were made with PLATON
[17]. Full structural details in CIF format of [(Cy3P)Au-
Fe4N(CO)12] (22) are available from the CCDC (refer-
ence number 263356).
Mo¨ssbauer spectra of the iron clusters were re-
corded at liquid nitrogen temperatures (80 K) using
a commercial constant acceleration drive unit and
transducer (Marwell Instruments) in conjunction with
a Canberra System 40 multichannel analyser. The
source was 57Co in Rh and was of 20 mCi nominal
strength. Data were referred to the spectrum of so-
dium nitroprusside as standard. Sampling times varied
from 2–4 days.
The compounds [Et4N][Fe4N(CO)12] (19), [Et4N]-
[Fe5N(CO)14] (20) were prepared according to literature
methods [5]. The preparations of [AuC„CC(Me)-
(OH)Et] (1) and [AuC„CC(Me)(OH)Ph] (2) were as
reported previously. The acetylenes and phosphine li-
gands were used as supplied by the Aldrich Chemical
Co. Ltd. The gold reagent H[AuCl4] Æ 2H2O was sup-
plied by Johnson Matthey.
4.2. Preparation of gold acetylides – general method
The complex [(R3P)2Au][Fe5N(CO)14] contained
bridging and terminal CO groups as observed in previ-
ous [Fe5N(CO)14]ꢀ compounds. Neutral [(R3P)Au-
Fe5N(CO)14] complexes could not be isolated during
the present work.
A solution of KBr (12.8 mmol) in water (40 ml) was
a stirred solution of H[AuCl4] Æ 2H2O
added to
(1.68 mmol) in water (60 ml). After stirring for 2–
3 min the resulting red solution of gold(III) was reduced
to a colourless gold(I) solution by the dropwise addition
of a freshly prepared aqueous solution of SO2. A solu-
tion of excess of the acetylene in acetone (2 mmol in
10 ml) was quickly added to the colourless solution
and the mixture stirred for approximately 1 min. After
this time the product was precipitated by the addition
of a saturated aqueous solution of K2[CO3]. The solid
product was isolated by filtration, washed with water
and air-dried.
Compounds prepared by this method were
[AuC„CC(Me)(OH)Et] (1), [AuC„CC(Me)(OH)Ph]
(2), [AuC„CC(H)(OH)Et] (3), [AuC„CC(H)(OH)-
(CH2)4Me] (4), [AuC„CC(Me)(OH)CH2CHMe2] (5),
[AuC„CCH2Optm] (6, ptm = phthalimide) and
[AuC„CC(Me)2NH2] (7). Analytical (%) and infrared
spectral data {mmax(C„C) cmꢀ1} for (3)–(7): (3) requires
C, 21.4, H, 2.5; found C, 21.1, H, 2.5: 1982; (4)
requires C, 29.8, H, 4.0; found C, 31.0, H, 4.3: 1978;
(5) requires C, 29.8, H, 4.1; found C, 29.8, H, 4.15:
1972; (6) requires C, 32.3, H, 1.5, N, 3.5; found C,
4. Experimental
4.1. General methodology
All reactions and crystallisations were carried out un-
der an inert nitrogen atmosphere but products were ini-
tially isolated and then manipulated in air. Preparative
thin layer chromatography was carried out with Merck
silica gel PF254 on glass plates prepared in UCC. Ele-
mental analyses, (C/H/N), were performed at the Micro-
analytical Laboratory, University College, Cork.
Infrared spectra were recorded either as KBr discs or
in CH2Cl2 solution on a Perkin–Elmer Paragon FTIR
spectrometer. 13C NMR spectra were recorded at 6.3
Tesla using a JEOL FT GSX-270 series spectrometer.
Chemical shifts (d) are expressed relative to internal
SiMe4 {(1H) and (13C)} standard. Single crystal X-ray
analysis was performed using an Enraf-Nonius CAD-4

G. Ferguson et al. / Journal of Organometallic Chemistry 690 (2005) 2888–2894
2893
31.6, H, 1.5, N, 2.9%: 2003; (7) requires C, 21.6, H, 2.9,
N, 5.0; found C, 20.8, H, 2.45, N, 4.7%: 2119.
in CH2Cl2:hexane, (80:20), to yield [(Ph3P)2Au][Fe4N
(CO)12] (23) (0.018 g, 11.0%). C30H15PAuFe4NO12 (21)
requires C, 36.0, H,1.5, N,1.4; found C, 35.4, H, 1.8,
N, 1.00%. C48H30P2AuFe4NO12 (23) requires C, 44.5,
H, 2.3, N, 1.1; found C, 44.6, H, 2.4, N, 1.1%. IR data
cmꢀ1 (CH2Cl2 solution) [(Ph3P)AuFe4N(CO)12] (21)
2078 m, 2039 vs, 2025 vs, 2003 s, 1991 w, 1959 w,
1942 vw; [(Ph3P)2Au][Fe4N(CO)12] (23) 2015 s, 1987
vs, 1966 m, 1929 w. 13C NMR data [(Ph3P)AuFe4N-
(CO)12] (21), 213.2, 210.1 ppm (carbonyl groups),
135.0–130.2 ppm (phenyl groups); [(Ph3P)2Au][Fe4N-
(CO)12] (23), 216.5, 213.6 ppm (carbonyl groups),
134.6–130.4 ppm (phenyl groups).
4.3. Preparation of phosphine derivatives of gold
acetylides – general method
To a suspension of gold acetylide (0.28 mmol) in tol-
uene (25 ml) was added an equimolar solution of the re-
quired phosphine (0.28 mmol) in toluene (5 ml). After
stirring for 5–10 min, all of the acetylide had dissolved
to yield a colourless solution. The solution was filtered
and the solvent removed under reduced pressure
(50 °C) to yield a colourless solid. The product was puri-
fied by recrystallisation from toluene/heptane solution.
Analytical (%), melting point, yield and infrared spectral
data {mmax(C„C) cmꢀ1} for (8)–(18): are as follows:
[(Ph3P)AuC„CC(Me)(OH)Et] (8) requires C, 51.8, H,
4.3; found C, 51.0, H, 4.7: 162–164, 79, 2134(w);
(Ph3P)AuC„C–C(Me)(OH)Ph] (9), requires C, 55.6,
H, 4.0; found C, 55.9, H, 4.0: 168–170, 80, 2110(w);
[(Ph3P)AuC„CC(H)(OH)Et] (10), requires C, 51.15,
H, 4.2; found C, 50.9, H, 4.1: 99–101, 81, 2128(w);
[(Ph3P)Au-C„CC(H)(OH)(CH2)4Me] (11), requires C,
53.4, H, 4.8; found C, 53.3, H, 4.8: 150–152, 75,
4.4.2. Reaction of [Et4N][Fe5N(CO)14] (20) with
[(Ph3P)AuC„CC(Me)(OH)Et] (8)
To a brown–green solution of [Et4N][Fe5N(CO)14]
(20) (0.095 g, 0.12 mmol) in CH2Cl2 (50 ml) was
added [(Ph3P)AuC„CC(Me)(OH)Et] (8) (0.064 g,
0.115 mmol). The reaction mixture was stirred for 23 h
and the solvent removed under reduced pressure
(25 °C). The residue was purified using p.l.c. with ini-
tially 100% hexane to yield a dark green compound
identified as [(Ph3P)AuFe4N(CO)12] (21) (0.054 g,
45.5%). Two further brown–green products were iso-
lated by elution in CH2Cl2/cyclohexane (70:30). These
two compounds were identified as [(Ph3P)2Au][Fe5N-
(CO)14] (25), (0.052 g, 32.1%) and [(Ph3P)2Au][Fe4N-
(CO)12] (23), (0.015 g, 10.1%). C30H15PAuFe4NO12
(21) requires C, 36.0, H, 1.5, N, 1.4; found C, 35.2, H,
1.4, N, 1.5%. C50H30P2AuFe5NO14 requires (25) C,
42.7, H, 2.15, N, 1.0; found C, 42.7, H, 2.2, N, 1.0%.
C48H30P2AuFe4NO12 (23) requires C, 44.5, H, 2.3, N,
1.1; found C, 44.6, H, 2.5, N, 1.2%. A fourth product
was also isolated but was very unstable and was only
characterised by IR spectroscopy. IR data cmꢀ1
(CH2Cl2 solution) [(Ph3P)2Au][Fe5N(CO)14] (25), 2059
w, 2011 s, 2000 vs, 1989 s, 1965 w, 1941 w.
2127(m);
[(Ph3P)AuC„CC(Me)(OH)CH2-CH(Me)2]
(12), requires C, 53.4, H, 4.8; found C, 53.8, H, 5.0:
129–131, 92, 2124(w); [(Ph3P)AuC„CCH2Optm] (13),
requires C, 52.8, H, 3.2, N, 2.2; found C, 53.6, H, 3.5,
N, 2.2: 170–172, 74, 2142(m); [(Ph3P)AuC„CC-
(Me)2NH2] (14), requires C, 51.0, H, 4.3, N, 2.6; found
C, 51.6, H, 4.3, N, 2.8: 114–116, 57, 2100(w); (Cy3-
P)AuC„C-C(Me)(OH)Et] (15), requires C, 50.1, H,
7.4; found C, 50.4, H, 7.4: 196–198, 75, 2120(m); [(Cy3-
P)AuC„C-C(H)(OH)Et] (16), requires C, 49.3, H, 7.2;
found C, 49.75, H, 7.6: 125–128, 80, 2116(w); [(Cy3-
P)AuC„CC(H)(OH)(CH2)4Me] (17), requires C, 51.8,
H, 7.7; found C, 52.5, H, 8.0: 113–116, 65, 2122(w); [(Cy3-
P)AuC„CC(Me)(OH)CH2-CH(Me)2] (18), requires C,
51.8, H, 7.7; found C, 52.3, H, 7.9: 112–114, 78, 1998(w).
4.4.3. Reaction of [Et4N][Fe4N(CO)12] (19) with
[(Cy3P)AuC„CC(Me)(OH)Et] (15)
4.4. Reactions between phosphine gold acetylides
[(Ph3P)AuCCC(Me)(OH)Et] (8) or
[(Cy3P)AuCCC(Me)(OH)Et] (15) and the iron
carbonyl clusters [Et4N][Fe4N(CO)12] (19) and
[Et4N][Fe5N(CO)14] (20)
To a brown–green solution of [Et4N][Fe4N(CO)12] (19)
(0.023 g, 0.03 mmol) in CH2Cl2 (15 ml) was added a solu-
tion of [(Cy3P)AuC„CC(Me)(OH)Et] (15) (0.019 g,
0.033 mmol) in CH2Cl2 (10 ml). The reaction mixture
was stirred for 60 min at room temperature, whereupon
it was concentrated under reduced pressure (25 °C) and
subjected to p.l.c initially in hexane 100% and then in
CH2Cl2/cyclohexane (40:60) to yield two products,
[(Cy3P)AuFe4N(CO)12] (22), (0.025 g, 72.0%), and [(Cy3-
P)2Au][Fe4N(CO)12] (24), (0.004 g, 9.1%). C30H33PAu-
Fe4NO12(22) requires C, 34.3, H, 3.2, N, 1.3; found C,
35.5, H, 3.5, N, 1.8. C48H66P2AuFe4NO12 (24) requires
C, 43.3, H, 5.0, N, 1.1; found C, 43.7, H, 4.9, N, 0.85%.
IR data cmꢀ1 (CH2Cl2 solution) [(Cy3P)AuFe4N(CO)12]
(22) 2077 m, 2060 w, 2038 vs, 2023 vs, 2002 s, 1990 m,
4.4.1. Reaction of [Et4N][Fe4N(CO)12] (19) with
[(Ph3P)AuC„CC(Me)(OH)Et] (8)
To a brown–green solution of [Et4N][Fe4N(CO)12]
(19) (0.055 g, 0.078 mmol) in CH2Cl2 (30 ml) was
added a solution of [(Ph3P)AuC„CC(Me)(OH)Et] (8)
(0.039 g, 0.070 mmol) in CH2Cl2 (10 ml) and the reac-
tion mixture was stirred for 30 min. The mixture
was concentrated under reduced pressure (25 °C) and
subjected to p.l.c. initially in cyclohexane to yield
[(Ph3P)AuFe4N(CO)12] (21) (0.045 g, 62.2%) and then

2894
G. Ferguson et al. / Journal of Organometallic Chemistry 690 (2005) 2888–2894
1956 w, 1936 w; [(Cy3P)2Au][Fe4N(CO)12] (24) 2035 w,
2014 w, 2000 s, 1989 s, 1966 w. 13C NMR data [(Cy3P)Au-
Fe4N(CO)12] (22), 214.3, 210.9 ppm (carbonyl groups),
26.0–35.3 ppm (aliphatic groups); [(Cy3P)2Au][Fe4N-
(CO)12] (24), 216.7, 213.5 ppm (carbonyl groups), 26.3–
36.0 ppm (aliphatic groups).
References
[1] See for example G.E. Coffey, J. Lewis, R.S. Nyholm, J. Chem.
Soc. (1964) 1741;
O. Rossell, M. Seco, P.G. Jones, Inorg. Chem. 29 (1990)
348;
R. Reina, O. Rossell, M. Seco, J. Ros, R. Yanez, A.
Perales, Inorg. Chem. 30 (1991) 3973;
M.I. Bruce, B.K. Nicholson, J. Organomet. Chem. 250 (1983)
627;
4.4.4. X-ray analysis of [(Cy3P)AuFe4N(CO)12] (22)
Crystals of (22) suitable for X-ray diffraction were
grown from dichloromethane/hexane solution. Crystal
L.A. Poliakova, S.P. Gubin, O.A. Belyakova, Y.V. Zubavi-
chus, Y.L. Slovokhotov, Organometal 16 (1997) 4527;
C.P. Horwitz, E.M. Holt, C.P. Brock, D.F. Shriver, J. Am.
Chem. Soc. 107 (1985) 8136;
ꢀ
data: C30H33AuFe4NO12P, M = 1050.91, triclinic, P1,
˚
a = 8.8806(19) A, b = 12.5470(19) A, c = 17.048(3) A,
˚
˚
B.F.G. Johnson, D.A. Kaner, J. Lewis, P.R. Raithby, M.J.
Rosales, J. Organomet. Chem. 238 (1982) C73;
S.M. Draper, C.E. Housecroft, J.E. Rees, M.S. Shongwe,
B.S. Haggerty, A.L. Rheingold, Organometal 11 (1992)
2356;
a = 103.249(13), b = 97.860(16), c = 92.601(18)°, Z = 2,
Dx = 1.911 mg mꢀ3, F(0 0 0) = 1028, l = 5.657 mmꢀ1
,
˚
k = (Mo–Ka) = 0.71073 A, Total number of reflec-
tions = 7924, RF = 0.0604 based on 5914 data with
[F2 > 2r(F2)], Rw = R[wR(F2)] = 0.1644 for 7924 data.
C.E. Housecroft, A.L. Rheingold, J. Am. Chem. Soc. 108
(1986) 6420.
[2] R. Hoffmann, Ang. Chem. Int. Ed. Engl. 21 (1982)
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4.4.5. Reaction of [Et4N][Fe5N(CO)14] (20) with
[(Cy3P)AuC„CC(Me)(OH)Et] (15)
[3] M.I. Bruce, E. Horn, J.G. Matisons, M.R. Snow, Aust. J. Chem.
37 (1984) 1163.
To a brown–green solution of [Et4N][Fe5N(CO)14] (20)
(0.032 g, 0.04 mmol) in CH2Cl2 (20 ml) was added a solu-
tion of [(Cy3P)AuC„CC(Me)(OH)Et] (15) (0.024 g,
0.042 mmol) in CH2Cl2 (10 ml). The reaction mixture
was stirred at room temperature for 23 h after which time
it was concentrated under reduced pressure (25 °C) and
subjectedtop.l.cinhexanetoyield[(Cy3P)AuFe4N(CO)12]
(22), (0.022 g, 49.8%). Re-elution in (CH2Cl2:cyclohexane,
70:30), yielded two further products identified as
[(Cy3P)2Au][Fe5N(CO)14] (26), (0.012 g, 19.8%) and [(Cy3-
P)2Au][Fe4N(CO)12] (24), (0.003 g, 5.4%). C30H33PAu-
Fe4NO12 (22) requires C, 36.0, H, 1.5, N, 1.4; found C,
36.1, H, 1.45, N, 1.05%. C50H66P2AuFe5NO14 (26) re-
quires C, 41.6, H, 4.6, N, 1.0; found C, 41.9, H, 4.45, N,
1.0%. C48H66P2AuFe4NO12 (24) requires C, 43.3, H, 5.0,
N, 1.0; found C, 44.1, H, 4.95, N, 1.0%. IR data cmꢀ1
(CH2Cl2 solution) [(Cy3P)2Au][Fe5N(CO)14] (26) 2035 w,
2014 w, 2000 s, 1989 s, 1966 w.
[4] A.-M. Kelleher, M.Sc. Thesis, National University of Ireland,
1991.
[5] M. Tachikawa, J. Stein, E.L. Muetterties, R.G. Teller, M.A.
Beno, E. Gebert, J.M. Williams, J. Am. Chem. Soc. 102 (1980)
6648.
[6] K.S. Harpp, C.E. Housecroft, A.L. Rheingold, M.S. Shongwe, J.
Chem. Soc., Chem. Commun. (1988) 965.
[7] M.L. Blohm, W.L. Gladfelter, Inorg. Chem. 26 (1987) 459.
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4799.
[9] M. Tachikawa, J. Stein, E.L. Muetterties, R.G. Teller, M.A.
Beno, E. Gebert, J.M. Williams, J. Am. Chem. Soc. 102 (1980)
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[10] R.P. Brint, K. OꢀCuill, T.R. Spalding, F.A. Deeney, J. Organo-
met. Chem. 247 (1983) 61.
[11] E.M. Holt, K.H. Whitmire, D.F. Shriver, J. Organomet. Chem.
213 (1981) 125.
[12] B.F.G. Johnson, D.A. Kaner, J. Lewis, P.R. Raithby, M.J.
Rosales, J. Organomet. Chem. 231 (1982) C59.
[13] R.P. Brint, M.P. Collins, T.R. Spalding, F.A. Deeney, J.
Organomet. Chem. 258 (1983) C57.
[14] E.J. Gabe, Y. Le Page, J.-P. Charland, F.L. Lee, P.S. White, J.
Appl. Cryst. 22 (1989) 876.
Acknowledgement
[15] G.M. Sheldrick, SHELXL-97-2, University of Gottingen, Germany,
1997.
GF thanks the NSERC (Canada) for Research Grants,
TRS acknowledges the generosity of Johnson-Matthey plc.
[16] L.J. Farrugia, J. Appl. Cryst. 30 (1997) 565.
[17] A.L. Spek, J. Appl. Cryst. 36 (2003) 7.