Reactions of gold(I) acetylides with l,1'-diisocyanoferrocene: From orthodox to unorthodox behavior

Article abstract of DOI:10.1021/om8005992

1,1'-Diisocyanoferrocene (1) reacts with the gold(I) acetylides [Au(C≡C-p-C₆H4R)]_n (2a R = CF₃, 2b R = H, 2c R = OMe, 2d R = NMe₂) to afford the respective dinuclear gold complexes [{Au(C≡C-p- C₆H₄R)}₂(μ-1)] (3), whose aurophilic aggregation in the solid state depends on the nature of the substituent R. The product of the reaction of 1 with [Au(C≡C-Fc)] _n (2e, Fc = ferrocenyl) is the hexanuclear gold cluster [(Fc-C≡C-Au-C≡N-C₅H₄)Fe{C₅H ₄-N=C(Au)-C≡C-Fc}]₃, which is composed of three subunits 4 and exhibits an unusual arrangement of gold atoms. The formation of (4)₃ is based on a different specific reaction of the two chemically equivalent functional groups of 1 with 2e, viz., coordination and 1,1-insertion. This schizoid behavior apparently is a novel variant of induced reaction asymmetry and constitutes a new phenomenon in chemistry. The reaction of 2e with l,1'-bis(diphenylphosphanyl)ferrocene (5) affords the expected [(Au-C≡C-Fc)₂(μ-5)] (6), which does not exhibit aurophilic interactions.

Full text of DOI:10.1021/om8005992

Organometallics 2008, 27, 6419–6426
6419
Reactions of Gold(I) Acetylides with 1,1′-Diisocyanoferrocene: From
Orthodox to Unorthodox Behavior
Ulrich Siemeling,* Dag Rother, and Clemens Bruhn
Institute of Chemistry, UniVersity of Kassel, Heinrich-Plett-Strasse 40, D-34132 Kassel, Germany
ReceiVed June 27, 2008
1,1′-Diisocyanoferrocene (1) reacts with the gold(I) acetylides [Au(Ct C-p-C6H4R)]n (2a R ) CF3, 2b
R ) H, 2c R ) OMe, 2d R ) NMe2) to afford the respective dinuclear gold complexes [{Au(Ct C-p-
C6H4R)}2(µ-1)] (3), whose aurophilic aggregation in the solid state depends on the nature of the substituent
R. The product of the reaction of 1 with [Au(Ct C-Fc)]n (2e, Fc ) ferrocenyl) is the hexanuclear gold
cluster [(Fc-Ct C-Au-Ct N-C5H4)Fe{C5H4-NdC(Au)-Ct C-Fc}]3, which is composed of three subunits
4 and exhibits an unusual arrangement of gold atoms. The formation of (4)3 is based on a different
specific reaction of the two chemically equivalent functional groups of 1 with 2e, viz., coordination and
1,1-insertion. This “schizoid” behavior apparently is a novel variant of induced reaction asymmetry and
constitutes a new phenomenon in chemistry. The reaction of 2e with 1,1′-bis(diphenylphosphanyl)ferrocene
(5) affords the expected [(Au-Ct C-Fc)2(µ-5)] (6), which does not exhibit aurophilic interactions.
relevant to applications in the field of materials science. For
example, the group of Puddephatt has tested the potential of
such complexes for the chemical vapor deposition of gold.6 They
have also pioneered the study of rigid-rod polymers of the type
[Au(µ-CN-C6R4-Ct C)]n based on bridging (isocyanoaryl)acetyl-
ides.7 The presence of aurophilic interactions8 in these materi-
als is indicated by their solid-state luminescence properties.9
Aurophilic interactions also govern the photophysical behavior
of monomeric complexes of the type [Au(Ct CR)(CNR′)] in
the solid state.10 As another aspect of the optical properties of
such rigid-rod-like species, their cubic hyperpolarizabilities have
been probed.11 Finally, mesogenic behavior has been observed
for such compounds.12 The formation of mesophases has been
attributed in part to aurophilic interactions in these as well as
in closely related complexes.13
Introduction
Gold(I) acetylides are oligomeric or polymeric compounds.
Structural studies have been hampered by their insoluble nature.1
Their reaction with suitable ligands L affords monomeric, and
usually nicely soluble, complexes of the type [Au(Ct CR)L],
especially with L ) PR′3, P(OR′)3, and R′NC.2 Despite the rapid
development of organogold chemistry during the past two
decades,3 gold(I) acetylides have not yet found applications in
organic synthesis. This is in contrast to the closely related
silver(I) acetylides, whose synthetic utility is well documented.4
It has been only very recently that the first examples of C-C
coupling reactions utilizing gold(I) acetylides were described.
Bruce et al. used monomeric complexes of the type [Au-
(Ct CR)(PR3)] in CuI/Pd0-catalyzed reactions with C-X units,
which afforded the structure element C-Ct CR by elimination
of [AuX(PR3)].5
The aurophilic aggregation usually observed in the solid state
for linear dicoordinate gold(I) complexes can give rise to three
principal structural motifs, viz., a parallel, an antiparallel, and
Among the complexes of the type [Au(Ct CR)L], rigid-rod-
like species that contain an isocyanide ligand R′NC have
received particular attention. This is due, inter alia, to a wide
range of interesting properties of this class of compounds,
(6) Puddephatt, R. J.; Treurnicht, I. J. Organomet. Chem. 1987, 319,
129–137.
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N. C. Organometallics 1993, 12, 263–265. (b) Puddephatt, R. J. Coord.
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4412–4456. (b) Gimeno, M. C.; Laguna, A. Gold Bull. 2003, 36, 83–92.
(c) Fackler, J. P., Jr. Inorg. Chem. 2002, 41, 6959–6972. (d) Schmidbaur,
H. Gold Bull. 2000, 33, 3–10. (e) Pyykko¨, P. Chem. ReV. 1997, 97, 597–
636.
* Corresponding author. E-mail: siemeling@uni-kassel.de.
(1) See, for example: Chui, S. S. Y.; Ng, M. F. Y.; Che, C.-M. Chem.-
Eur. J. 2005, 11, 1739–1749.
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3220-3226. Selected recent publications: (b) Vicente, J.; Chicote, M.-T.;
Alvarez-Falco´n, M. M.; Jones, P. G. Organometallics 2005, 24, 5956–5963.
(c) Vicente, J.; Chicote, M.-T.; Alvarez-Falco´n, M. M.; Jones, P. G.
Organometallics 2005, 24, 4666–4675. (d) Chui, S. S. Y.; Ng, M. F. Y.;
Che, C.-M. Chem.-Eur. J. 2005, 11, 1739–1749.
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16, 3541–3547.
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3211. (b) Fu¨rstner, A.; Davies, P. W. Angew. Chem., Int. Ed. 2007, 46,
3410–3440. (c) Hashmi, A. S. K.; Hutchings, G. J. Angew. Chem., Int. Ed.
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2007, 36, 759–769.
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Humphrey, P. A.; Jevric, M.; Melino, G.; Nicholson, B. K.; Perkins, G. J.;
Skelton, B. W.; Stapleton, B.; White, A. H.; Zaitseva, N. N. Chem. Commun.
2004, 960–961. (b) Bruce, M. I.; Smith, M. E.; Zaitseva, N. N.; Skelton,
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Soc., Dalton Trans. 1996, 3699–3703. Reviews: (b) Yam, V. W.-W.; Wong,
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W.; Wong, K. M.-C. J. Organomet. Chem. 1999, 578, 3–30.
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Takahashi, S. J. Mater. Chem. 1995, 5, 687–692. (b) Alejos, P.; Coco, S.;
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Bruce, D. W. Dalton Trans. 2003, 1914–1931.
10.1021/om8005992 CCC: $40.75
2008 American Chemical Society
Publication on Web 11/11/2008

6420 Organometallics, Vol. 27, No. 24, 2008
Siemeling et al.
a crossed arrangement of neighboring molecules. A recent CSD
analysis14 confirmed the result of an earlier study15 that
Au · · · Au distances are on average shortest for the crossed
arrangement. This is perfectly plausible, since at a given
Au · · · Au distance steric repulsions between the ligands of
neighboring molecules will be least for an essentially staggered
orientation, which corresponds to a crossed arrangement with
a torsion angle of ca. 90°. It is also plausible that for
“asymmetric” (heteroleptic) species [AuX(L)] a preference exists
for the antiparallel over the parallel arrangement on steric as
well as on electrostatic grounds. In the case of gold(I) isocyanide
complexes, only three examples are known that exhibit a parallel
arrangement of neighboring molecules (albeit in combination
with the antiparallel motif), viz., the cyano complexes [Au-
(CN)(CNR′)] (R′ ) Me, i-Pr, n-Bu).16 In view of the isoelec-
tronic nature of cyanide and acetylide ligands, these species are
closely related to the acetylide complexes of the type
[Au(Ct CR)(R′NC)], which are the focus of our present study,
where we have used the bidentate organometallic isocyanide
1,1′-diisocyanoferrocene (1)17 for reactions with a range of gold
acetylides. A selected aspect of the present study has already
been briefly communicated.18 We note that the number of
oligodentate isocyanides has remained small in comparison to
other important ligand families.19 It is also essential to note that
the distance between the two Cp decks of ferrocene is 3.32 Å,
which is at the low end of the range typically observed for
Au · · · Au distances in gold(I) isocyanide complexes.20 In a
preliminary investigation of the coordination chemistry of 1 we
have already prepared the dinuclear gold complex [(AuCl)2(µ-
1)], which exhibits an eclipsed diaura-[6]ferrocenophane-type
structure with an intramolecular Au · · · Au distance of ca. 3.34
Å.21 The molecules form one-dimensional chains in an anti-
parallel zipper-like arrangement through intermolecular auro-
philic interactions with Au · · · Au distances of 3.35 and 3.48 Å.
This structure is related to that of the cyano complexes
[Au(CN)(CNR′)] mentioned above, since a combination of the
parallel with the antiparallel arrangement of the rod-like
[AuX(L)] units occurs.
Figure 1. Molecular structure of [{Au(Ct C-p-C6H4CF3)}2(µ-1)]
(3a) in the crystal.
NMe2) and [Au(Ct C-Fc)]n (2e, Fc ) ferrocenyl18). These
compounds were prepared by an established route from [Au-
Cl(SMe2)] and the respective acetylene derivative in the presence
of triethylamine at room temperature.23 All compounds were
isolated from the reaction mixture as insoluble solids and
characterized by elemental analyses and IR spectra, where their
characteristic ν(Ct C) vibrational band was observed between
ca. 1980 and 2000 cm-1. The reactions worked best for
acetylides bearing electron-donating substituents, while with
HCt C-p-C6H4CF3, which contains the strongly electron-
withdrawing trifluoromethyl group, the reaction was more
sluggish and the yield was only moderate. Furthermore, the
product (2a) proved to be thermally unstable at room temper-
ature and slowly afforded a violet intractable material.
The reactions of 1,1′-diisocyanoferrocene (1) with [Au(Ct C-
p-C6H4R)]n (2, 2/n equiv) were performed in dichloromethane
at room temperature. They proceeded smoothly over the course
of several hours, affording the expected [{Au(Ct C-p-C6H4R)}2(µ-
1)] (3) in the case of 2a-d. The reaction with 2e turned out to
be a special case and will be discussed later. 2a-d were isolated
as yellow, air-stable, microcrystalline solids. Their solubility
in common organic solvents proved to be generally poor.
Dichloromethane turned out to be the best choice. The solubility
in this solvent is highest for the CF3 bearing compound 3a and
1
lowest for the NMe2 bearing analogue 3d. H NMR spectra
could be recorded for all four compounds using CD2Cl2.
However, attempts to recrystallize 3a-d in order to obtain single
crystals suitable for an X-ray diffraction study failed in the case
of the least soluble compound, 3d. The ν(Ct C) and ν(Nt C)
vibrational bands were observed in the IR spectra of 3a-d at
ca. 2115 and 2200 cm-1, respectively. This compares well with
values reported for closely related compounds such as [Au-
Results and Discussion
The gold(I) acetylides used in this study are [Au(Ct C-p-
C6H4R)]n (2a R ) CF3, 2b R ) H, 2c R ) OMe,22 2d R )
2a
(Ct CPh)(CNC6H3Me2-2,6)] [ν(Ct C) 2119 cm-1, ν(Nt C)
(14) Anderson, K. M.; Goeta, A. E.; Steed, J. W. Inorg. Chem. 2007,
46, 6444–6451.
(15) Pathaneni, S. S.; Desiraju, G. R. J. Chem. Soc., Dalton Trans. 1993,
319–322.
(16) (a) Esperas, S. Acta Chem. Scand. A 1976, 30, 527–530. (b) White-
Morris, R. L.; Stender, M.; Tinti, D. S.; Balch, A. L. Inorg. Chem. 2003,
42, 3237–3244.
(17) (a) van Leusen, D.; Hessen, B. Organometallics 2001, 20, 224–
226. For a review concerning symmetrical 1,1′-di(heteroatom)-functionalized
ferrocene derivatives, see: (b) Siemeling, U.; Auch, T.-C. Chem. Soc. ReV.
2005, 34, 584–594.
24
2211 cm-1
]
and corresponds to a ν(Nt C) band shift of ca.
100 cm-1 with respect to uncoordinated 1 and an even slightly
larger ν(Ct C) band shift with respect to the respective gold(I)
acetylide 2, which is in accord with previous observations.2a
These substantial band shifts to higher energy indicate that, in
line with the classic study by Cotton and Zingales,25 the
isocyanide acts as a strongly σ-donating ligand, whose coordi-
nation to Au(Ct C-p-C6H4R) reduces the degree of metal-carbon
π-bonding in this moiety.
(18) Siemeling, U.; Rother, D.; Bruhn, C. Chem. Commun. 2007, 4227–
4229.
(19) Reviews: (a) Harvey, P. D. Coord. Chem. ReV. 2001, 219-221,
17–52. (b) Hahn, F. E. Angew. Chem., Int. Ed. Engl. 1993, 32, 650–665.
(20) See, for example: Liau, R.-Y.; Mathieson, T.; Schier, A.; Berger,
R. J. F.; Runeberg, N.; Schmidbaur, H. Z. Naturforsch. B: Chem. Sci. 2002,
57, 881–889.
(21) (a) Weidner, T.; Ballav, N.; Zharnikov, M.; Priebe, A.; Long, N. J.;
Maurer, J.; Winter, R.; Rothenberger, A.; Fenske, D.; Rother, D.; Bruhn,
C.; Fink, H.; Siemeling, U. Chem.-Eur. J. 2008, 14, 4346–4360. (b)
Siemeling, U.; Rother, D.; Bruhn, C.; Fink, H.; Weidner, T.; Tra¨ger, F.;
Rothenberger, A.; Fenske, D.; Priebe, A.; Maurer, J.; Winter, R. J. Am.
Chem. Soc. 2005, 127, 1102–1103.
The crystal structures of 3a-c were determined by X-ray
diffraction. The molecular structures are shown in Figures 1-3.
In each case the quality of the crystal structure determination
was affected by the small size of the crystal. It was further
compromised by the presence of disordered solvent of crystal-
´
(23) See, for example: Hogarth, G.; Alvarez-Falco´n, M. M. Inorg. Chim.
Acta 2005, 358, 1386–1392.
(24) Xiao, H.; Cheung, K.-K.; Che, C.-M. J. Chem. Soc., Dalton Trans.
1996, 3699–3703.
(22) Yip, S. K.; Lam, W. H.; Zhu, N.; Yam, V. W.-W. Inorg. Chim.
Acta 2006, 359, 3639–3648.
(25) Cotton, F. A.; Zingales, F. J. Am. Chem. Soc. 1961, 83, 351–355.

Reactions of Gold(I) Acetylides
Organometallics, Vol. 27, No. 24, 2008 6421
Figure 2. Molecular structure of [{Au(Ct C-Ph)}2(µ-1)] (3b) in
the crystal.
Figure 3. Molecular structure of [{Au(Ct C-p-C6H4OMe)}2(µ-1)]
(3c) in the crystal.
lization in the case of 3c. Consequently, a meaningful discussion
of bond parameters is possible for the heavy atoms only. The
C-Nt C-Au-Ct C-C chains are nearly linear for all three
compounds with bond angles between ca. 171° and 178°, as
expected for such rigid-rod-type molecular units. A prominent
feature of all three molecular structures is the fact that the
molecules adopt an eclipsed conformation with an intramolecular
aurophilic contact. This Au · · · Au distance apparently depends
on the electronic properties of the acetylide ligand Ct C-p-
C6H4R. It is 3.3011(11) Å for 3a (R ) CF3), 3.3617(5) Å for
3b (R ) H), and 3.6219(12) Å for 3c (R ) OMe). Correlations
between Au · · · Au distances and the “hard” or “soft” character
of anionic ligands X in linear dicoordinate gold(I) complexes
[AuX(L)] have been found in previous theoretical and experi-
mental studies. For example, Pyykko¨ et al. predicted an increase
in the strength of the aurophilic interaction for staggered dimers
of the phosphane complexes [AuX(PH3)] in the series of
halogeno ligands with F < Cl < Br < I.26 This trend was
verified by X-ray crystallography for [AuX(PPhMe2)] (X ) Cl,
Br, I) by Balch and co-workers.27 In the case of isocyanide
Figure 4. Stereographic representation of the crystal packing of
[{Au(Ct C-p-C6H4CF3)}2(µ-1)] (3a). Au · · · Au distances < 4 Å
are indicated by dotted lines.
N)(CNR′)] (R′ ) Me, i-Pr, n-Bu) (vide supra). In the case of
3c, a one-dimensional chain of antiparallel molecules is formed,
whose intermolecular Au · · · Au distances of 3.5576(15) and
3.5921(16) Å are very similar to the intramolecular distance of
3.6219(12) Å. We have previously observed a similarly nice
balance between intra- and intermolecular aurophilicity in the
case of [(AuCl)2(µ-1)], which is aggregated as one-dimensional
chains, too.21 The insoluble nature of [(AuCl)2(µ-1)] is remi-
niscent of the very low solubility of 3c and the even poorer
solubility of the NMe2-substituted analogue 3d. We therefore
assume that 3d probably also forms such one-dimensional chains
in the crystal. In the case of 3b, the molecules are aggregated
as antiparallel dimers with intermolecular Au · · · Au distances
of 3.9509(5) Å. In the case of 3a, which exhibits the shortest
intramolecular Au · · · Au contact in this series, no such inter-
molecular contacts are present. In addition to the short intramo-
lecular Au · · · Au contact, an intramolecular C-F · · · H-C
interaction is observed for this compound (indicated by a dotted
line in Figure 1). The FHC angle of ca. 168.8° and the F · · · C
and F · · · H distances of ca. 3.47 and 2.54 Å, respectively, are
compatible with a weak hydrogen bond.29 Although their
existence, nature, and supramolecular relevance still is a
contentious issue, weak intramolecular C-F · · · H-C hydrogen
bonds have recently been probed and authenticated by NMR
spectroscopic methods in solution and by neutron diffraction
in the solid state.30
complexes [AuX(CNR)], an opposite trend was found.28
A
theoretical study performed for dimers of [AuX(CNMe)] (X )
Cl, I) revealed that in this case the antiparallel, instead of the
staggered, arrangement of monomeric units is preferred.20 The
major attractive contribution between monomeric units was
found to originate from the dipole-dipole interaction. Conse-
quently, the Au · · · Au distance is indicative of the presence,
but not commensurate with the strength, of aurophilic interac-
tions. In view of these results, the eclipsed molecular structures
of 3a-c, which correspond to the parallel arrangement of
[AuX(CNR)] units, might appear extraordinary. However, closer
inspection of the crystal packing reveals an antiparallel orienta-
tion of neighboring molecules (Figures 4-6).
As already mentioned above, the reaction of [Au(Ct C-Fc)]n
(2e) deserves special attention.18 In view of the results just
described, we anticipated the formation of [Fe{C5H4(NC-Au-
Ct C-Fc)}2] (3e) in the reaction of 1 with [Au(Ct C-Fc)]n (2/n
This combination of parallel and antiparallel alignments is
reminiscent of the structural motifs observed for the chloro
complex [(AuCl)2(µ-1)] and the cyano complexes [Au(C-
(26) Pyykko¨, P.; Li, J.; Runeberg, N. Chem. Phys. Lett. 1994, 218, 133–
138.
(27) Toronto, D. V.; Weissbart, B.; Tinti, D. S.; Balch, A. L. Inorg.
Chem. 1996, 35, 2484–2489.
(29) Selected recent reviews: (a) Reichenba¨cher, K.; Su¨ss, H. I.; Hulliger,
J. Chem. Soc. ReV. 2005, 34, 22–30. (b) Desiraju, G. R. Acc. Chem. Res.
2002, 35, 565–573.
(28) Schneider, W.; Angermaier, K.; Sladek, A.; Schmidbaur, H. Z.
Naturforsch. B: Chem. Sci. 1996, 51, 790–800.
(30) Chan, M. W. C.; Kui, S. C. F.; Cole, J. M.; McIntyre, G. J.; Matsui,
S.; Zhu, N.; Tam, K.-H. Chem.-Eur. J. 2006, 12, 2607–2619.

6422 Organometallics, Vol. 27, No. 24, 2008
Siemeling et al.
Figure 6. Stereographic representation of the crystal packing of
[{Au(Ct C-p-C6H4OMe)}2(µ-1)] (3c). Au · · · Au distances < 4 Å
are indicated by dotted lines.
occurs at 1530 cm-1 in the case of the mononuclear iminoacyl
complex [Pd{C(Ct C-Ph)(dNPh)}Cl(PEt3)2].32 It is well docu-
mented for binuclear complexes that a σ,µ2-iminoacyl coordina-
tion leads to a notable energy decrease of this band of ca. 60
cm-1 with respect to the parent imine.33 Due to the poor quality
of the crystal, the data/parameter ratio of the X-ray structure
analysis is rather low. Consequently, a detailed discussion of
bond parameters is meaningful only for the heavy atoms.
The gold cluster exhibits Au · · · Au distances that are typical
for aurophilic interactions, ranging from 3.165(2) to 3.391(2)
Å. The cluster core is a triangle of gold atoms whose three sides
are each bridged by the NdC unit of a single iminoacyl ligand.
Such σ,µ2-bridging iminoacyl ligands RNdCR′ are quite
common. In fact, even several clusters are known with a side
of an M3 triangle bridged by a σ,µ2-iminoacyl ligand, especially
in the chemistry of osmium.34 In contrast, clusters with two
bridged triangular sides of this type are rare.35 (4)3 is unique
since bridging of all three sides of an M3 triangle with σ,µ2-
RNdCR′ ligands has not been described to date. We note,
however, that the general structural motif is not unfamiliar in
the chemistry of gold. Several triply bridged triangular clusters
of the type [Au3{σ,µ2-RNdC(OR′)}3] have been reported that
contain carbeniate ligands RNdC(OR′), which are akin to
iminoacyl ligands RNdCR′. These gold clusters were obtained
from the reaction of [AuCl(L)] (L ) SMe2, PPh3) with
isocyanides RNC in a suitable alcohol R′OH in the presence of
KOH.36 They usually aggregate in the solid state due to
aurophilic interactions.37 For example, [Au3{σ,µ2-p-TolNdC-
(OEt)}3] forms dimeric units in the crystal through two
intermolecular Au · · · Au contacts.38 A similar motif is observed
for (4)3, where two atoms of the Au3 triangle are each connected
with a further gold atom, in this case, however, intramolecularly.
This is caused by the Au-Au contact present within two of the
three subunits of (4)3. These Au-Au interactions altogether
result in an unprecedented chain of five gold atoms with two
neighboring atoms being bridged by a sixth one.
Figure 5. Stereographic representation of the crystal packing of
[{Au(Ct C-Ph)}2(µ-1)] (3b). Au · · · Au distances < 4 Å are
indicated by dotted lines.
Scheme 1
equiv). Furthermore, we expected that the product would exhibit
an eclipsed molecular conformation similar to that found for
3a-c, so that an efficient communication between the two
redox-active terminal ferrocenyl units seemed feasible and might
have been probed by cyclic voltammetry. Microanalytical data
of the product that we obtained in good yield from this reaction
agreed well with the composition of 3e. However, its 1H NMR
spectrum was incompatible with 3e, since it exhibited too many
signals for a species of such symmetry. Characterization of the
product was hampered by its poor solubility in common organic
solvents. Again, dichloromethane proved to be the best solvent.
We eventually succeeded in obtaining single crystals suitable
for an X-ray structure analysis, which proved that the product
is not 3e, but rather the hexanuclear gold cluster [(Fc-Ct C-
Au-Ct N-C5H4)Fe{C5H4-NdC(Au)-Ct C-Fc}]3, which is com-
posed of three subunits 4 (Figure 7, Scheme 1).
(32) Onitsuka, K.; Ogawa, H.; Joh, T.; Takahashi, S.; Yamamoto, Y.;
Yamazaki, H. J. Chem. Soc., Dalton Trans. 1991, 1531–1536.
(33) Seyferth, D.; Hoke, J. B. Organometallics 1988, 7, 524–528.
(34) Review: Deeming, A. J. AdV. Organomet. Chem. 1986, 26, 1–96.
(35) (a) Hardcastle, K. I.; Minassian, H.; Arce, A. J.; De Sanctis, Y.;
Deeming, A. J. J. Organomet. Chem. 1989, 368, 119–130. (b) Choo Yin,
C.; Deeming, A. J. J. Organomet. Chem. 1977, 133, 123–138.
(36) (a) Balch, A. L.; Olmstead, M. M.; Vickery, J. C. Inorg. Chem.
1999, 38, 3494–3499. (b) Minghetti, G.; Bonati, F. Inorg. Chem. 1974, 13,
1600–1602. (c) Parks, J. E.; Balch, A. L. J. Organomet. Chem. 1974, 71,
453–463. (d) Minghetti, G.; Bonati, F. Gazz. Chim. Ital. 1972, 102, 205–
213. (e) Minghetti, G.; Bonati, F. Angew. Chem., Int. Ed. Engl. 1972, 11,
429.
IR and NMR spectroscopic data are fully in accord with this
result. In particular, due to the presence of the σ,µ2-iminoacyl
group a ν(NdC) vibrational band is observed at 1491 cm-1 in
addition to the expected ν(Nt C) and ν(Ct C) bands at 2201
and 2155 cm-1, respectively. For comparison, the ν(CdN) band
31
of Ph-Ct C-C(dNPh)Ph is located at 1560 cm-1
,
while it
(37) Review: Burini, A.; Mohamed, A. A.; Fackler, J. P., Jr. Comments
Inorg. Chem. 2003, 24, 253–280.
(31) Wu¨rthwein, E.-U.; Weigmann, R. Angew. Chem., Int. Ed. Engl.
1987, 26, 923–924.
(38) Tiripicchio, A.; Tiripicchio Camellini, M.; Minghetti, G. J. Orga-
nomet. Chem. 1979, 171, 399–406.

Reactions of Gold(I) Acetylides
Organometallics, Vol. 27, No. 24, 2008 6423
Table 1. Crystal Data and Structure Refinement for 3a, 3b, 3c, and 6
3a
3b
3c
6
emp. formula
fw
C30H16Au2F6FeN2
968.23
C28H18Au2FeN2
832.23
C30.50H23Au2ClFeN2O2
934.74
C58H46Au2Fe3P2
1366.37
temp/K
143(2)
173(2)
173(2)
143(2)
cryst syst
space group
lattice param
monoclinic
P21/m
a ) 11.4667(13)
b ) 8.5646(8)
c ) 14.1478(16)
ꢀ ) 98.271(9)
monoclinic
P21/c
a ) 9.0781(7)
b ) 24.9236(18)
c ) 13.4933(11)
ꢀ ) 128.191(5)
triclinic
P1
orthorhombic
Pbca
a ) 14.6431(8)
b ) 11.7790(5)
c ) 27.4725(15)
j
a ) 8.4412(12)
b ) 11.8387(18)
c ) 14.197(2)
R ) 87.290(12)
ꢀ ) 81.080(11)
γ ) 84.569(12)
1394.6(4)
length/Å
angle/deg
cell volume/Å3
Z
1375.0(3)
2
2.339
11.228
896
2399.5(4)
4
2.304
12.813
4738.5(4)
4
1.915
7.174
2640
2
dcalc/g cm-3
2.226
11.134
874
µ/mm-1
F(000)
1536
θ range/deg
1.45 to 25.00
-13 f h f 13
-10 f k f 10
-16 f l f 16
8971
1.63 to 25.00
-10 f h f 10
-29 f k f 29
-15 f l f 16
14 072
1.45 to 25.23
-9 f h f 10
-14 f k f 14
-17 f l f 16
9181
1.48 to 25.00
-9 f h f 17
-14 f k f 12
-32 f l f 32
15 824
index ranges
reflns collected
indep reflns
reflns obsd
2601 [Rint ) 0.1376]
1652
4226 [Rint ) 0.1336]
3584
4698 [Rint ) 0.0995]
2523
3995 [Rint ) 0.1162]
2466
Tmin/Tmax
0.08/0.23
0.02/0.75
0.07/0.73
0.28/0.82
data/restraints/params
2601/0/223
0.878
4226/0/298
1.004
4698/1/349
0.820
3995/0/295
0.879
GOF on F2
final R indices
[I > 2σ(I)]
R1 ) 0.0455
wR2 ) 0.0819
R1 ) 0.0829
wR2 ) 0.0910
1.758/-1.639
R1 ) 0.0457
wR2 ) 0.1044
R1 ) 0.0539
wR2 ) 0.1073
1.853/-2.167
R1 ) 0.0614
wR2 ) 0.1363
R1 ) 0.1034
wR2 ) 0.1478
1.679/-2.375
R1 ) 0.0430
wR2 ) 0.0808
R1 ) 0.0862
wR2 ) 0.0900
1.579/-0.702
R indices
(all data)
largest diff peak/hole/e Å-3
Finally, we focus our attention on the component of 4 that is
based on 1,1′-diisocyanoferrocene (1). This unit was formed in
a peculiar way. One of the two isocyano groups shows the usual,
and expected, coordination of the gold acetylide unit Au(Ct C-
Fc). In contrast, the other one has undergone a 1,1-insertion
reaction with the Au-C bond of the gold acetylide, thus forming
an iminoacyl group. 1,1-Insertion or R-addition reactions are
common in the chemistry of isocyanides and can occur with a
wide range of metal-carbon bonds. For example, metalated
aldimines are formed in their reaction with organolithium
compounds and Grignard reagents, respectively.39 Analogous
reactions are observed with M-C bonds of transition metal
complexes, which often lead to the formation of η2-iminoacyl
complexes, especially in the case of early transition metals.40
We note that insertion reactions of isocyanides with transition
metal acetylide complexes are currently attracting particular
attention. This is primarily due to two reasons. First, multiple
and successive insertions have been observed with heterodi-
nuclear complexes of the type [Cl(PR3)2Pd-Ct C-Pt(PR3)2Cl],
and even the living polymerization of aryl isocyanides has been
described with this system.41 Second, examples have been
reported for the catalytic coupling of isocyanides with terminal
alkynes.42 These reactions afford 1-aza-1,3-enines, which are
useful synthons in organic chemistry.43 Surprisingly, despite the
recent dynamic progress in the chemistry of gold,3 insertion
reactions of isocyanides with Au-C bonds are practically
unknown. Only two examples have been described to date,44
and only one of these involves a gold(I) species,44b viz., the
1,1-insertion of 2,6-dimethylphenylisocyanide into the Au-C
bond of the gold(I) enolate [Au{CH2C(O)Ph}(PPh3)].
The 1,1-insertion of an isocyanide into an Au-C bond is
very unusual as such. It is even more unusual that in the
present case this reaction occurs in conjunction with a second,
different, reaction. This observation requires some reflection.
It is common knowledge that two equivalent groups in a
molecule often do not react independently from one another.
The fact that the reaction of the first group influences that of
an equivalent second group is known as induced reactivity
asymmetry.45 This effect can be thermodynamic (different
equilibrium constants) and/or kinetic (different reaction rates)
in origin. Simple examples reflecting a thermodynamic
influence are polyprotic acids such as H3PO4, where the
consecutive decrease in acidity (pKa1 ) 2.16, pKa2 ) 7.21,
pKa3 ) 12.32) is mainly due to electrostatic reasons.46
Essentially the same holds true for the different redox
potentials observed for the two formally identical subunits
of 1,1′-biferrocene (Fc-Fc) (E0′1 ) +0.31 V, E0′2 ) +0.64
V vs SCE).47 With respect to kinetic effects, a common
observation is that the reaction rate slows down in consecutive
(39) Smith, M. B.; March, J. March’s AdVanced Organic Chemistry,
6th ed.; Wiley: New York, 2007; pp 1466-1470.
(40) (a) Kayaki, Y.; Yamamoto, A. In Current Methods in Inorganic
Chemistry; Kurosawa, H.; Yamamoto, A., Eds.; Elsevier: Amsterdam, 2003;
Vol. 3, pp 373-409. (b) Durfee, L. D.; Rothwell, I. P. Chem. ReV. 1988,
88, 1059–1079.
(41) (a) Onitsuka, K.; Yanai, K.; Takei, F.; Joh, T.; Takahashi, S.
Organometallics 1994, 13, 3862–3867. (b) Onitsuka, K.; Joh, T.; Takahashi,
S. Angew. Chem., Int. Ed. Engl. 1992, 31, 851–852.
(43) Review: Stadnichuk, M. D.; Khramchikhin, A. V.; Piterskaya, Y. L.;
Suvorova, I. V. Russ. J. Gen. Chem. 1999, 69, 593–609.
(44) (a) Henderson, W.; Nicholson, B. K.; Wilkins, A. L. J. Organomet.
Chem. 2005, 690, 4971–4977. (b) Murakami, M.; Inouye, M.; Suginome,
M.; Ito, Y. Bull. Chem. Soc. Jpn. 1988, 61, 3649–3652.
(45) Levi, M.; Biondi, R.; Danusso, F. Eur. Polym. J. 1998, 34, 1689–
1696.
(42) (a) Komeyama, K.; Sasayama, D.; Kawabata, T.; Takehira, K.;
Takaki, K. J. Org. Chem. 2005, 70, 10679–10687. (b) Komeyama, K.;
Sasayama, D.; Kawabata, T.; Takehira, K.; Takaki, K. Chem. Commun.
2005, 634–635. (c) Barnea, E.; Andrea, T.; Kapon, M.; Berthet, J.-C.;
Ephritikhine, M.; Eisen, M. S. J. Am. Chem. Soc. 2004, 126, 10860–10861.
(46) See, for example: Anslyn, E. V.; Dougherty, D. A. Modern Physical
Organic Chemistry; University Science Books: Sausalito, CA, 2006, p 283.
(47) (a) Morrison, W. H., Jr.; Krogsrud, S.; Hendrickson, D. N. Inorg.
Chem. 1973, 12, 1998–2004. Review: (b) Barlow, S.; O’Hare, D. Chem.
ReV. 1997, 97, 637–670.

6424 Organometallics, Vol. 27, No. 24, 2008
Siemeling et al.
Figure 7. (a) Molecular structure of (4)3 in the crystal (stereographic representation with subunits marked in different colors). Interatomic
distances < 4.0 Å in the Au6 cluster: Au1A-Au1B 3.356(2), Au1A-Au1C 3.278(2), Au1A--Au2A 3.352(2), Au2A-Au2B 3.165(2),
Au1B-Au1C 3.284(2), Au1C-Au2C 3.391(2) Å. (b) Molecular structure of the subunit colored blue in (a). Selected bond lengths (Å):
C1A-N1A 1.31(3), C1A-C2A 1.40(4), C1A-Au1A 1.98(3), C2A-C3A 1.22(4), C24A-N2A 1.15(3), C24A-Au2A 1.90(3), C25A-C26A
1.25(5), C25A-Au2A 1.95(3), N1A-Au1C 1.99(2).
reactions of equivalent groups. Due to their relevance to
polymer chemistry, the kinetics of consecutive reactions of
difunctional substrates has been treated theoretically, for both
interacting and noninteracting functional groups already half
a century ago.48 A simple and particularly well-studied
example in this context is the reaction of aromatic diisocy-
anates with alcohols.49
Although the induced reactivity asymmetry is a commonly
known and widely studied phenomenon in chemistry, the
variant we have observed in our work is extraordinary, since
the consecutive reactions are not the same. To the best of
our knowledge, it has never been observed before that two
chemically equivalent groups in a molecule undergo a
different specific reaction with the same reagent. This
“schizoid” reactivity observed for 1 in its reaction with 2e
apparently constitutes a novel phenomenon in chemistry50
Figure 8. Molecular structure of [(Au-Ct C-Fc)2(µ-5)] (6) in the
and will demand further systematic investigations in the near
future. Unfortunately, attempts to study the course of the
crystal.
1
The molecule exhibits crystallographically imposed inver-
reaction by H NMR spectroscopy have not been successful
sion symmetry. The P-Au-Ct C-C chain is essentially
linear, with bond angles between ca. 173° and 178°. The
Au-P bond length of 2.293(2) Å is similar to the values
found for closely related compounds such as [{Au-Ct C-
C(CH2)Me}2(µ-5)] [2.279(2) Å],51 [{(AuCt CCH2O)2-p-
C6H4}{µ-Ph2P(CH2)3PPh2}] [2.261(7) and 2.278(7) Å],54 and
[{(Ph3P)2Au}2{µ-1,12-(Ct C)2-1,12-C2B10H10}] [2.2743(14)
Å].55 We note that these Au-P bond length are marginally
longer than those of the chloro complex [(AuCl)2(µ-5)]
[2.239(3) Å],53 which reflects the comparatively higher trans
influence of an alkynyl ligand as opposed to a chloro ligand.
The Au-C bond length of 1.998(10) Å found for [(Au-Ct C-
Fc)2(µ-5)] compares well with values observed for similar
compounds such as the three dinuclear gold(I) acetylide
complexes just mentioned; the corresponding values are
2.005(10) Å for [{Au-Ct C-C(CH2)Me}2(µ-5)], 2.03(2) and
2.05(3) Å for [{(AuCt CCH2O)2-p-C6H4}{µ-Ph2P(CH2)3-
PPh2}], and 2.007(5) Å for [{(Ph3P)2Au}2{µ-1,12-(Ct C)2-
so far because of the essentially insoluble nature of both the
gold acetylide starting material and the gold cluster product.
While the reaction of 2e with 1,1′-diisocyanoferrocene (1)
proved to be rather peculiar, its reaction with 1,1′-bis(diphe-
nylphosphanyl)ferrocene (5, dppf) gave the expected result, viz.,
the complex [(Au-Ct C-Fc)2(µ-5)] (6), which was isolated in
high yield as a yellow, microcrystalline solid. The ∆(Ct C)
vibrational band is observed at 2110 cm-1 in the IR spectrum,
which is very similar to the values of 2105 and 2115 cm-1
reported for the closely related [{Au-Ct C-C(CH2)Me}2(µ-5)]51
and [(Au-Ct C-Ph)2(µ-5)],52 respectively. It is also in line with
the value of ca. 2115 cm-1 found in the case of 3a-d. The
31P{1H} NMR signal is observed as a singlet at 24.8 ppm, which
is very similar to the value of 27.4 ppm reported for the chloro
analogue [(AuCl)2(µ-5)].53 A single-crystal X-ray structure
determination was performed for [(Au-Ct C-Fc)2(µ-5)] (Fig-
ure 8).
(48) Case, L. C. J. Polym. Sci. 1960, 48, 27–35.
(49) See, for example: Brock, F. H. J. Org. Chem. 1959, 24, 1802–
1804.
(53) Hill, D. T.; Girard, G. R.; McCabe, F. L.; Johnson, R. K.; Stupik,
P. D.; Zhang, J. H.; Reiff, W. R.; Eggleston, D. S. Inorg. Chem. 1989, 28,
3529–3533.
(50) Chem. Eng. News 2007, 85 (44), 29.
(51) Yam, V. W.-W.; Cheung, K.-L.; Cheng, E. C.-C.; Zhu, N.; Cheung,
K.-K. Dalton Trans. 2003, 1830–1835.
(52) Yam, V. W.-W.; Choi, S. W.-K.; Cheung, K.-K. J. Chem. Soc.,
Dalton Trans. 1996, 3411–3415.
(54) Hunks, W. J.; MacDonald, M.-A.; Jennings, M. C.; Puddephatt,
R. J. Organometallics 2000, 19, 5063–5070.
(55) Vicente, J.; Chicote, M.-T.; Alvarez-Falco´n, M. M.; Fox, M. A.;
Bautista, D. Organometallics 2003, 22, 4792–4797.

Reactions of Gold(I) Acetylides
Organometallics, Vol. 27, No. 24, 2008 6425
spectrometer operating at 500.13 MHz for 1H. IR: BIO-RAD FTS-
40A. Elemental analyses: microanalytical laboratory of the Uni-
versity of Kassel.
1,12-C2B10H10}]. The structure of [{Au-Ct C-C(CH2)Me}2(µ-
5)], which seems to be the closest structurally characterized
relative of [(Au-Ct C-Fc)2(µ-5)], also exhibits centrosym-
metric molecules. Aurophilic interactions are absent in both
cases, which is probably due to the steric bulk of the acetylide
ligands. In the structure of [(AuCl)2(µ-5)], which contains
the much less bulky chloro ligand, two crystallographically
independent molecules are present. One of them exhibits
crystallographically imposed inversion symmetry with exactly
staggered cyclopentadienyl rings, too. In contrast to the two
acetylide complexes [(Au-Ct C-Fc)2(µ-5)] and [{Au-Ct C-
C(CH2)Me}2(µ-5)], particularly short intermolecular Au · · · Au
distances of 3.083(1) Å are observed in this case.53 With the
di(acetylide) ligand (Ct C-CH2O-p-C6H4)2SO2, which is
unbranched at the R-carbon atom and therefore “leaner” than
Ct C-C(CH2)Me and Ct C-Fc, aurophilic aggregation to
dimeric units has been observed.56 However, the Au · · · Au
distance of 3.1488(7) Å is still longer than that of the chloro
complex [(AuCl)2(µ-5)].
[Au(Ct C-p-C6H4CF3)]n (2a). HCt C-p-C6H4CF3 (255 mg, 1.5
mmol) and NEt3 (730 mg, 7.3 mmol) were added sequentially to a
stirred solution of [AuCl(SMe2)] (442 mg, 1.5 mmol) in dichlo-
romethane (20 mL) at 0 °C. The solution was stirred for 1 h. Cold
methanol (20 mL) was added and the mixture was stirred at 0 °C
for a further 2 h. The pale yellow precipitate was isolated by
centrifugation and dried in vacuo at 0 °C. Yield: 210 mg (38%).
Anal. Calcd for C9H4AuF3 (366.1): C, 29.53; H, 1.10. Found: C,
29.31; H, 1.06. IR (cm-1): ν(Ct C) 2003 (w).
[Au(Ct C-p-C6H4NMe2)]n (2d). HCt C-p-C6H4NMe2 (218 mg,
1.5 mmol) and NEt3 (300 mg, 3.0 mmol) were added sequentially
to a stirred solution of [AuCl(SMe2)] (442 mg, 1.5 mmol) in
dichloromethane (20 mL). After 30 min the yellow precipitate was
filtered off, washed with methanol (5 mL) and diethyl ether (5 mL),
and dried in vacuo. Yield: 470 mg (92%). Anal. Calcd for
C10H10AuN (341.2): C, 35.21; H, 2.95; N, 4.11. Found: C, 35.28;
H, 2.98; N, 3.92. IR (cm-1): ν(Ct C) 1999 (w).
[{Au(Ct C-p-C6H4R)}2(µ-1)] (3). General procedure: A solution
of 1 (50 mg, 0.21 mmol) in dichloromethane (10 mL) was added
to a stirred suspension of the respective gold(I) acetylide (2) (0.42
mmol; a 155 mg, b 126 mg, c 140 mg, d 145 mg) in dichlo-
romethane (50 mL). The mixture was stirred for 14 h. The product
was isolated by cannula filtration, washed with methanol (10 mL)
and diethyl ether (10 mL), and dried in vacuo.
Conclusion
The reaction of the gold(I) acetylides [Au(Ct C-p-C6H4R)]n
(2a R ) CF3, 2b R ) H, 2c R ) OMe, 2d R ) NMe2) with
1,1′-diisocyanoferrocene (1) proceeds in an “orthodox” way,
affording the respective dinuclear gold complexes [{Au(Ct C-
p-C6H4R)}2(µ-1)] (3). The molecules exhibit an eclipsed con-
formation with an intramolecular aurophilic contact in conjunc-
tion with an antiparallel orientation of neighboring molecules
in the crystal. The intramolecular Au · · · Au distance correlates
with the electron-donating properties of the substituent R (CF3
< H < OMe), while the corresponding intermolecular
distances show the opposite trend. Curiously, the product of
the reaction of 1 with [Au(Ct C-Fc)]n (2e, Fc ) ferrocenyl)
is the hexanuclear gold cluster [(Fc-Ct C-Au-Ct N-
C5H4)Fe{C5H4-NdC(Au)-Ct C-Fc}]3, whose formation is
based on a different specific reaction of the two chemically
equivalent functional groups of 1 with 2e, viz., coordination
and 1,1-insertion. This “unorthodox” behavior appears schiz-
oid and constitutes a novel variant of induced reaction
asymmetry. Systematic investigations, including quantum-
chemical calculations, are currently underway to shed more
light on this phenomenon.
3a. Yield: 115 mg (56%). IR (cm-1): ν(Nt C) 2192 (s), ν(Ct C)
1
2115 (m). H NMR (CD2Cl2): δ 7.32 (d, J ) 8.0 Hz, 4 H, C6H4),
7.28 (d, J ) 8.0 Hz, 4 H, C6H4), 4.93 (s, 4 H, C5H4), 4.49 (s, 4 H,
C5H4). Anal. Calcd for C30H16Au2F6FeN2 · 0.5CH2Cl2 (1010.7): C,
36.25; H, 1.70; N 2.77. Found: C, 35.78; H, 1.54; N 2.48.
3b. Yield: 71 mg (40%). IR (cm-1): ν(Nt C) 2203 (s), ν(Ct C)
1
2121 (m). H NMR (CD2Cl2): δ 7.30 (s, 2 H, Ph), 7.13 (s, 8 H,
Ph), 4.94 (s, 4 H, C5H4), 4. 47 (s, 4 H, C5H4). Anal. Calcd for for
C28H18Au2FeN2 · 0.5CH2Cl2 (874.7): C, 39.13; H, 2.19; N, 3.20.
Found: C, 39.27; H, 2.81; N, 3.08.
3c. Yield: 117 mg (61%). IR (cm-1): ν(Nt C) 2204 (s), ν(Ct C)
1
2123 (w). H NMR (CD2Cl2): δ 7.24 (d, J ) 9.0 Hz, 4 H, C6H4),
6.65 (d, J ) 9.0 Hz, 4 H, C6H4), 4.93 (s, 4 H, C5H4), 4. 47 (s, 4 H,
C5H4), 3.72 (s,
6 H, Me). Anal. Calcd for C30H22Au2-
FeN2O2 · 0.5CH2Cl2 (934.8): C, 39.19; H, 2.48; N, 3.00. Found: C,
39.26; H, 2.37; N, 2.92.
3d. Yield: 129 mg (66%). IR (cm-1): ν(Nt C) 2192 (s), ν(Ct C)
1
2115 (m). H NMR (CD2Cl2): δ 7.19 (d, J ) 9.0 Hz, 4 H, C6H4),
6.47 (d, J ) 9.0 Hz, 4 H, C6H4), 4.92 (s, 4H, C5H4), 4.47 (s, 4 H,
C5H4), 2.89 (s, 12 H, Me). Anal. Calcd for C32H28Au2-
FeN4 · 0.5CH2Cl2 (960.9): C, 40.62; H, 3.04; N, 5.83. Found: C,
40.58; H, 3.03; N, 5.89.
Experimental Section
General Procedures. All reactions were performed in an inert
atmosphere (dinitrogen) by using standard Schlenk techniques
or a conventional glovebox. 1,1′-Diisocyanoferrocene (1)17a and
[AuCl(SMe2)]57 were prepared according to published procedures.
The gold(I) acetylides [Au(Ct C-Ph)]n (2b)2a and [Au(Ct C-p-
C6H4OMe)]n (2c)22 were prepared by slight variation of a published
method,23 which is detailed below for the new compounds 2a and
2d. Preparative details for [Au(Ct C-Fc)]n (2e) and (4)3 have already
been communicated.18 Solvents and reagents were procured from
standard commercial sources. NMR: Varian Unity INOVA 500
[(Au-Ct C-Fc)2(µ-5)] (6). Dppf (5) (110 mg, 0.2 mmol) was
added to a stirred suspension of 2e (160 mg, 0.4 mmol) in
dichloromethane (50 mL). The mixture was stirred for 3 h. The
slightly turbid solution was filtered to remove traces of insoluble
material. The volume of the filtrate was reduced in vacuo to ca.
10 mL. The product was precipitated by slow addition of diethyl
ether (10 mL). Yield: 242 mg (89%). IR (cm-1): ν(Ct C) 2110
1
(w). H NMR (CDCl3): δ 7.36-7.28 (m, 20 H, Ph), 4.44 (s, 4
H, C5H4), 4. 36 (s, 4 H, C5H4), 4.21 (s, 10 H, Cp), 4.11 (s, 4 H,
C5H4), 4.05 (s, 4 H, C5H4). 13C{1H} NMR (CDCl3): δ 133.6 (d,
J ) 15.5 Hz), 131.6, 131.2 (d, J ) 10.0 Hz), 130.4, 128.6, (d,
J ) 9.5 Hz), 128.2 (d, J ) 12.1 Hz), 102.2, 98.7, 82.0, 81.6,
74.5 (d, J ) 12.7 Hz), 73.4 (d, J ) 12.3 Hz), 71.8, 69.9, 67.8.
31P{1H} NMR (CDCl3): δ 24.8. Anal. Calcd for C58H46Au2Fe3P2
(1366.4): C, 50.98; H, 3.39. Found: C, 51.56; H, 3.92.
(56) Mohr, F.; Jennings, M. C.; Puddephatt, R. J. Eur. J. Inorg. Chem.
2003, 217–223.
(57) (a) Ahmad, S.; Isab, A. A.; Perzenowski, H. P.; Hussain, M. S.;
Akhtar, M. N. Transition Met. Chem. 2002, 27, 177–183. (b) Dash, K. C.;
Schmidbaur, H. Chem. Ber. 1973, 106, 1221–1225.
(58) X-red Ver. 1.06, Program for numerical absorption correction; Stoe
& Cie: Darmstadt, 2004.
(59) Sheldrick, G. M. SHELXS 97 and SHELXL 97, Programs for crystal
structure solution and refinement; University of Go¨ttingen: Germany, 1997.
(60) Farrugia, L. J. J. Appl. Crystallogr. 1999, 32, 837–838.
X-ray Crystallography. For each data collection a single
crystal was mounted on a glass fiber and all geometric and
intensity data were taken from this sample. Data collection using

6426 Organometallics, Vol. 27, No. 24, 2008
Siemeling et al.
Mo KR radiation (λ ) 0.71073 Å) was made on a Stoe IPDS2
diffractometer equipped with a two-circle goniometer and an
area detector. Absorption correction was done by integration
using X-red.58 The data sets were corrected for Lorentz and
polarization effects. The structures were solved by direct methods
(SHELXS97) and refined using alternating cycles of least-squares
refinements against F2 (SHELXL97).59 All non H atoms were
found in difference Fourier maps and were refined with
anisotropic displacement parameters. H atoms were placed in
constrained positions according to the riding model with the 1.2-
fold isotropic displacement parameters. Pertinent crystallographic
data are collected in Table 1. The crystal structure of (4)3 has
already been published elsewhere.18 Graphical representations
were made using ORTEP-3 win.60
Acknowledgment. We are grateful to Umicore AG&Co.
KG (Hanau, Germany) for a generous gift of precious metal
compounds. D.R. thanks the Otto Braun Fonds for a doctoral
fellowship.
Supporting Information Available: Crystallographic data of
compounds 3a, 3b, 3c, and 6 (CIF file). This material is available
free of charge via the Internet at http://pubs.acs.org.
OM8005992