Synthesis and properties of a new range of mixed-donor alkynyl ferrocenophanes

Article abstract of DOI:10.1021/om049465e

The acid-catalyzed reaction of [1,1'-Fc{Co₂(CO) ₆(μ:n²-CCMe₂OH)}₂] (Fc = Fe(n⁵-C₅H₄)₂) with a variety of dinucleophiles led to the formation in excellent yields of a novel range of ferrocenophanes containing a variety of donor atoms. The crystal structures of four of these new compounds are reported as well as the results of electrochemical studies of the new complexes.

Full text of DOI:10.1021/om049465e

628
Organometallics 2005, 24, 628-637
Synthesis and Properties of a New Range of
Mixed-Donor Alkynyl Ferrocenophanes
Anthony D. Woods,*,† German Alcalde,† Vladimir B. Golovko,†
Catherine M. Halliwell,‡ Martin J. Mays,† and Jeremy M. Rawson†
Department of Chemistry, University of Cambridge, Lensfield Road,
Cambridge, CB2 1EW, U.K., and National Physical Laboratory, Queens Road,
Teddington, Middlesex, TW11 0LW, U.K.
Received July 15, 2004
The acid-catalyzed reaction of [1,1′-Fc{Co2(CO)6(µ:η2-CtCCMe2OH)}2] (Fc ) Fe(η5-C5H4)2)
with a variety of dinucleophiles led to the formation in excellent yields of a novel range of
ferrocenophanes containing a variety of donor atoms. The crystal structures of four of these
new compounds are reported as well as the results of electrochemical studies of the new
complexes.
Introduction
To be able to observe the binding of guest ions, it is
usual to have either a redox or chromogenic response
on binding.16 Frequently the receptor is a ferrocene-
based system, although cobaltacinium and transition
metal-bipyridyl systems are also well documented.17 To
attain the best communication in the host-guest com-
plexes, it is preferable to have the donor atoms of the
chelating unit directly bonded to the ferrocene.18 It has
previously been demonstrated that Nicholas reactions
of cobalt-coordinated bispropargyl alcohols with dinu-
cleophiles may yield monomeric or dimeric products
depending on both the choice of nucleophile and the
concentration of the reactant.19 Thus, it was hypoth-
esized that the use of a Nicholas reaction of dithiols with
1,1′-bispropargylferrocenes would yield interesting new
ferrocenophanes containing one or two ferrocene units.
There is intense current interest in the synthesis and
behavior of thio-macrocycles.1-3 These compounds may
be suitable for a diverse range of applications, from
molecular sensors to bio-inorganic hosts.4-7 The cyclic
nature of the macrocycle limits the conformational
modes available to any guest metal8 and also makes
possible the stabilization of unusual oxidation states;9
a great deal of attention has been focused on methods
to tailor macrocycles to allow them to bind specific
ions.10 This field has now been extended to include the
synthesis of complexes that contain mixed-donor function-
alities.11-14 Such complexes, especially those containing
both hard and soft donor atoms, are of immense interest
since they can potentially bind two metals of differing
character and oxidation state within the same cavity.15
Results and Discussion
* To whom correspondence should be addressed. E-mail:
anthony_woods@ici.com.
† University of Cambridge.
The synthetic strategy employed requires the use of
1,1′-bispropargylferrocenes, [1,1′-Fc(CtCR2OH)2], as the
key starting materials. There are few examples of 1,1′-
functionalized alkynylferrocenes within the literature
and, to the authors’ knowledge, only one example of a
1,1′-bispropargylferrocene, [Fc(CtCCMe2OH)2], which
was synthesized in low yield by the reaction of [FcLi2]
with ICtCMe2OH and CuBr‚SMe2.20 It was decided to
use a Sonogashira type coupling to synthesize the target
molecules [Fc(CtCCR2OH)2] (R ) H, Me).21 Accordingly,
1,1′-FcI2 was refluxed with excess HCtCCH2OH in Et2-
‡ National Physical Laboratory.
(1) Blake, A. J.; Schro¨der, M. Adv. Inorg. Chem. 1990, 35, 1.
(2) Cooper, S. R. Acc. Chem. Res. 1988, 21, 141.
(3) Blake, A. J.; Li, W.-S.; Lippolis, V.; Taylor, A.; Schro¨der, M. J.
Chem. Soc., Dalton Trans. 1998, 2931.
(4) Izatt, R. M.; Pawlak, K.; Bradshaw J. S.; Breuning, R. L. Chem.
Rev. 1991, 91, 1721.
(5) Smith, R. J.; Adams, G. D.; Richardson, A. P.; Ku¨ppers, H. J.;
Blower, P. J. Chem. Commun. 1991, 475.
(6) Blake, A. J.; Reid, G.; Schro¨der, M. J. Chem. Soc., Dalton Trans.
1990, 3849.
(7) Neve, F.; Ghedini, M.; Francescangeil, M. Liq. Cryst. 1996, 21,
625.
(8) Lindoy, L. F. The Chemistry of Macrocyclic Ligand Complexes;
Cambridge University Press: Cambridge, 1989.
(9) Blake, A. J.; Taylor, A.; Schro¨der, M. Chem. Commun. 1993,
1097.
(16) Beer, P. D.; Gale, P. A.; Chen, G. Z. J. Chem. Soc., Dalton Trans.
1999, 1897.
(10) See for example: Lindoy, L. F. Pure Appl. Chem. 1997, 69, 2179,
and references therein.
(11) Danks, J. P.; Champness, N. R.; Schro¨der, M. Coord. Chem.
Rev. 1998, 174, 417.
(12) Caltagirone, C.; Bencini, A.; Demartin, F.; Devillanova, F. A.;
Garau, A.; Isaia, F.; Lippolis, V.; Mariani, P.; Papke, U.; Tei, L.; Verani,
G. J. Chem. Soc., Dalton Trans. 2003, 901.
(13) Fenton, R. R.; Gauci, R.; Junk, P. C.; Lindoy, L. F.; Luckay, R.
C.; Meehan, G. V.; Price, J. R.; Turner, P.; Wei, G. J. Chem. Soc., Dalton
Trans. 2002, 2185.
(14) van de Water, L. G. A.; Buihs, W.; Driessen, W. L.; Reedijk, J.
New J. Chem. 2001, 25, 243.
(15) Lucas, C. R.; Liang, W.; Miller, D. O.; Brisdon, J. N. Inorg.
Chem. 1997, 36, 4508.
(17) For a recent review see: Beer, P. D.; Hayes, E. J. Coord. Chem.
Rev. 2003, 240, 167.
(18) (a) Plenio, H.; Aberle, C. Organometallics 1997, 16, 5950. (b)
Plenio, H.; Yang, J.; Diodane, R.; Heinze, J. Inorg. Chem. 1994, 33,
4098.
(19) (a) Hope-Weeks, L. J.; Mays, M. J.; Woods, A. D. J. Chem. Soc.,
Dalton Trans. 2002, 1812. (b) Gibe, R.; Green, J. R. Chem. Commun.
2002, 1550.
(20) Buchmeiser, M.; Schottenberger, H. J. Organomet. Chem. 1992,
436, 223.
(21) Long, N. J.; Martin, A. J.; Vilar, R.; White, A. J. P.; Williams,
D. J.; Younus M. Organometallics 1999, 4261, 1. (b) Bunz, U. H. F.
Chem. Rev. 2000, 100, 1605.
10.1021/om049465e CCC: $30.25 © 2005 American Chemical Society
Publication on Web 01/08/2005

Mixed-Donor Alkynyl Ferrocenophanes
Organometallics, Vol. 24, No. 4, 2005 629
Figure 1. Molecular structure of (a) 2 and (b) 4 (ORTEP to 30% probability).
Scheme 1. Reaction of FcI2 with Propargyl Alcohols
NH (which we have previously found gives the highest
ppm in the 1H NMR spectrum of 1. Coordination of 1 to
Co2(CO)6 leads to a marked downfield shift in the
propargylic CH2 resonance from 4.41 ppm in 1 to 5.04
ppm in 3. This downfield shift is also apparent in the
13C NMR spectra of 1 and 3, with the CtCC resonance
being observed at 51.09 and 63.90 ppm, respectively.
The spectroscopic data for 2 are in accordance with the
literature values.20 Again, coordination of the alkyne
fragment in 2 to Co2(CO)6 leads to a downfield shift in
the propargylic carbon resonance from 65.66 ppm in 2
to 73.19 ppm in 4.
yield for Sonogashira couplings involving HCtCH2OH)
using 1 mol % of both Pd(PPh3)2Cl2 and CuI as catalysts.
Surprisingly, despite prolonged periods of reflux and an
increase in the mol % of catalyst used, no [Fc(CtCCH2-
OH)2] was isolated. Instead, [Fc(CtCCH2OH)I] (1) was
isolated in good (61%) yield (Scheme 1). Attempts to gain
access to the target compound by the isolation of 1
followed by reaction of 1 with fresh HCtCCH2OH under
standard coupling conditions proved unsuccessful. By
contrast, the reaction of FcI2 with HCtCCMe2OH under
Sonogashira conditions did yield the desired [1,1′-Fc-
(CtCCMe2OH)2] (2) in good yield. It was found that best
Additionally, compounds 2 and 4 have been the
subject of single-crystal X-ray diffraction studies (Figure
1); relevant bond lengths and angles are given in Table
1.
i
yields were obtained using Pr2NH as solvent and Cu-
(OAc)2 as the cocatalyst. The yields of 2 proved signifi-
cantly better than those of the previously reported
synthesis, and the current synthetic strategy also
proved markedly simpler, giving access to multigram
quantities of 2 from readily available FcI2.
As is common for bis-substituted ferrocenes, the
cyclopentadienyl rings of 2 are eclipsed (twist ) 3.7°).24
Unusually, however, the rings adopt a 1,1′ conformation
(γ ) 3.8°); the presence of a hydrogen bond between H(1)
and O(2) of the two CtCCMe2OH side chains [H(1)‚‚‚
O(2) 2.076 Å] presumably accounts for the adoption of
this sterically disfavored geometry. The cyclopentadi-
enyl rings are virtually planar (max. deviation 0.0038
Å) and are slightly titlted (3.4°). A further hydrogen-
bonding interaction leads to the formation of a cen-
trosymmetric dimer (Figure 2) [O(1)‚‚‚H(2A) 2.117 Å]
(Figure 2).
The molecular structure of 4 contains a mirror plane
that passes through Fe(1). Complexation of the triple
bond leads to the expected lengthening of the C(2)-C(3)
bond from 1.191(3) Å in 2 to 1.345(6) Å in 4. The
cyclopentadienyl rings of 4 adopt a relative 1,3′ disposi-
tion (γ ) 102.2°) and are in an unusual staggered
configuration (twist ) 29.88°).24 This conformation is
presumably adopted to avoid steric repulsion between
the bulky Co2(CO)6 fragments and allows the formation
of an intramolecular hydrogen bond [O(1)‚‚‚H(1A) 2.282
To activate the propargyl alcohol toward nucleophilic
substitution, it is first necessary to coordinate the
alkyne to Co2(CO)6 (or other dicobalt fragments);22 the
positive charge of the intermediate from SN1 substitu-
tion of the OH group is stabilized by interaction with
the filled Co dx -y orbital.23 Toluene solutions of com-
pounds 1 and 2 were therefore treated with 1.1 and 2.2
equiv of Co2(CO)8, respectively. After stirring for 3 h the
cobalt-complexed alkynes were isolated by flash chro-
matography to yield green oily [1,1′-Fc{Co2(CO)6(µ-η2-
CtCCH2OH)}I] (3) and green crystalline [1,1′-Fc{Co2-
(CO)6(µ-η2-CtCCMe2OH)}2] (4) (Scheme 1). Compounds
2
2
1
1-4 have been fully characterized by IR and H and
1
13C NMR spectroscopy as well as by LSIMS. The H
NMR spectrum of 1 quite clearly indicates that the two
cyclopentadienyl rings are asymmetrically substituted;
four triplets are observed at 4.40, 4.38, 4.20, and 4.19
(22) Nicholas, K. M.; Petit, R. Tetrahedron Lett. 1971, 37, 3475.
(23) Pfletschinger, A.; Koch, W.; Schmalz, H.-G. Chem. Eur. J. 2001,
5325.
(24) Grossel, M. C.; Goldspink, M. R.; Hrihac, J. A.; Weston, S. C.
Organometallics 1991, 10, 851.

630 Organometallics, Vol. 24, No. 4, 2005
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 2 and 4
compound 2 compound 4
Woods et al.
mean Fe-C(5-8)
range Fe-C(5-8)
Fe-C(4)
2.049
mean Fe-C(5-8)
range Fe-C(5-8)
Fe-C(4)
2.046
2.043(2)-2.052(2)
2.063(2)
2.042(2)-2.050(4)
2.066(4)
mean Fe-C(9-12)
range Fe-(C9-12)
Fe-C(13)
2.045
2.039(2)-2.054(2)
2.060(2)
C(1)-C(2)
1.481(2)
C(1)-C(2)
1.500(6)
1.345(6)
1.452(6)
2.4654(9)
1.976(4)
1.967(4)
1.962(4)
1.993(4)
140.5(3)
146.0(4)
C(2)-C(3)
1.191(3)
C(2)-C(3)
C(3)-C(4)
1.431(3)
C(3)-C(4)
C(13)-C(14)
C(14)-C(15)
C(15)-C(16)
1.431(3)
Co(1)-Co(2)
Co(1)-C(2)
Co(1)-C(3)
Co(2)-C(2)
Co(2)-C(3)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
1.191(3)
1.481(3)
C(1)-C(2)-C(3)
174.0(2)
175.4(2)
176.5(2)
172.1(2)
C(2)-C(3)-C(4)
C(13)-C(14)-C(15)
C(14)-C(15)-C(16)
Scheme 2. Reaction of 3 with (HSC2H4)2O
Å]. In this case, however, there are no intermolecular
hydrogen bonds present, presumably because of the
changed geometry of the propargylic fragments leading
to steric hindrance at the O-H groups. The cyclopen-
tadienyl rings are planar (max. deviation 0.0027 Å) and
lie at an angle of 4.1° to each other. Coordination of the
alkyne to Co2(CO)6 leads to the expected decrease in the
alkyne bend-back angle [C(3)-C(2)-C(1) 140.5(3)°],
which has the effect of sterically shielding O(1) by the
C(9) and C(10) Me groups and preventing close approach
of another molecule of 4.25 Notably, the bend-back angle
at the ferrocene-substituted terminus is decreased by a
smaller amount [C(4)-C(3)-C(2) 146.0(4)° in 4, cf.
C(4)-C(3)-C(2) 175.4(2)° in 2] than that at the other
terminus. This is presumably a consequence of competi-
tion for the alkyne’s electron density between the
ferrocene and the dicobalt unit. The hydrogen bond
present in 4 does result in the Co2(CO)6 fragments
adopting a cisoid configuration rather than the usual
transoid geometry. There are no unusual features
within the Co2C2 core of 4.25
Reactions of 3. Despite the fact that 3 was not
substituted by a CtCCH2OH group at both cyclopen-
tadienyl rings (a necessary prerequisite to the formation
of ferrocenophanes), it was decided to explore the
reactivity of 3 toward a variety of dithiols under acid
catalysis conditions. Accordingly, a dichloromethane
solution of 3 was treated with (HSC2H4)2O and a few
drops of HBF4 at -78 °C. Separation by preparative
TLC yielded green [1,1′-Fc{Co2(CO)6(µ:η2-CtCCH2-
SC2H4OC2H4SH)}I] (5) together with several minor
fractions (Scheme 2). Separation of 5 proved somewhat
problematic, with a good deal of decomposition occurring
on the plates. To combat this, it was decided to first
Scheme 3. Reaction of 4 with Dithiols
treat 3 with dppm (bis-diphenylphosphino methane); it
was hoped that the dppm group might add extra
stability to any products formed from the above substi-
tution reactions. Treatment of a toluene solution of 3
with dppm at 70 °C for 2 h yielded, after chromato-
graphic separation, red crystalline [1,1′-Fc{Co2(CO)4-
(dppm)(µ:η2-CtCCH2OH)}I] (6) in good yield. Unfortu-
nately, however, the dppm unit did not help to improve
the stability of any products resulting from acid-
catalyzed substitution reactions.
Reactions of 4. Treatment of 4 with dithiols under
acid-catalyzed reaction conditions proved appreciably
more successful than the corresponding reactions of 3
or 6. Thus treatment of 4 with the dithiols HS(CH2)n-
SH (n ) 3-6) and (HSC2H4)2S led in each case to the
formation of the desired ferrocenophane [1,1′-Fc{(Co2-
(CO)6)2(µ:η2-µ:η2-CtCCMe2S(CH2)nSCMe2CtC)}] (n )
3, 7; n ) 4, 8; n ) 5, 9; n ) 6, 10) and [1,1′-Fc{(Co2-
(CO)6)2(µ:η2-µ:η2-CtCCMe2SC2H4SC2H4SCMe2CtC)}]
(11) (Scheme 3). On no occasion were any dimeric
compounds containing two ferrocene units isolated.
Complexes 7-11 have been fully characterized by IR,
1H and 13C NMR, and LSIMS. In addition, compounds
7 and 11 have been the subject of single-crystal X-ray
diffraction studies (Figures 3, 4); relevant bond lengths
Figure 2. Hydrogen bonding within the solid-state struc-
ture of 2 (ORTEP to 30% probability).
(25) Went, M. J. Adv. Oragnomet. Chem. 1997, 41, 69.

Mixed-Donor Alkynyl Ferrocenophanes
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 7 and 11
11
2.4481(5)
Organometallics, Vol. 24, No. 4, 2005 631
7
7
11
1.515(4)
Co(1)-Co(2)
Co(3)-Co(4)
2.445(2)
2.472(1)
2.071(6)
2.052
C(1)-C(2)
C(2)-C(3)
1.503(9)
2.4659(5)
2.059(3)
2.051
1.344(9)
2.066(6)
2.041
2.023(7)2.052(7)
1.462(9)
1.461(8)
1.350(8)
1.494(8)
144.5(6)
143.7(6)
1.340(6)
2.065(3)
2.055
2.048(3)-2.064(3)
1.449(4)
1.450(4)
1.342(4)
1.506(4)
144.5(3)
140.3(3)
Fe-C(4)
Fe-C(13)
mean Fe-C(5-8)
range Fe-C(5-8)
mean Calkyne-Co(1)
mean Calkyne-Co(2)
mean Calkyne-Co(3)
mean Calkyne-Co(4)
C(3)-C(2)-C(1)
C(2)-C(3)-C(4)
mean Fe-C(9-12)
range Fe-C(9-12)
C(3)-C(4)
2.041(7)-2.059(7)
1.959
2.045(3)-2.059(3)
1.976
1.978
1.989
C(13)-C(14)
1.974
1.969
1.989
141.0(3)
144.1(3)
C(14)-C(15)
1.980
140.0(6)
142.9(6)
C(15)-C(16)
C(13)-C(14)-C(15)
C(14)-C(15)-C(16)
and angles are given in Table 2. The molecular structure
of 7 contains two crystallographically independent
molecules within its asymmetric unit. The bond lengths
and angles are equivalent within experimental error,
and thus discussion will be based upon the average
values found within the two residues. One of the most
striking features of the solid-state structures of 7 and
11 is that the sulfur atoms are endodentate; normally
sulfur atoms are situated with their lone pairs exo to
the macrocyclic cavity unless coordination to a guest ion
has occurred.26 An inspection of the C-S-C-C torsion
angles confirms that the sulfur-carbon bonds adopt
what is an unusual anti conformation (Table 2). This
results in the S-C-C-S bonds becoming gauche and
creating short sulfur‚‚‚sulfur contacts (3.387 Å in 7 and
3.165, 3.372 Å in 11). Previous work by Wolf and others
suggested that such a contact would be unfavorable due
to electron-electron repulsion between the sulfur lone
pairs exerting a destabilizing effect on the molecule (the
repulsive gauche effect).26,27 The cavity size of 11 may
be estimated from the nonbonding S(1)‚‚‚S(3) separation
of 5.848 Å and the Fe(1)‚‚‚S(2) separation of 5.025 Å.
As might be expected, the long linking chain present
in both 7 and 11 causes little distortion of the cyclo-
pentadienyl rings; the rings are virtually parallel with
a dihedral angle of 1.8° and 2.5° between the mean
planes of the two rings of 7 and 11, respectively. In
contrast to other documented ferrocenophanes,24 how-
ever, the Cp rings are markedly staggered, with a twist
angle of 28.9° and 13.4°, respectively. Compound 7 has
its cyclopentadienyl rings adopting a 1,2′ disposition
with respect to the substituted carbons, with γ being
117°. By contrast, the longer linking chain present in
11 allows the cyclophanes to adopt the more usual 1,3′
disposition (γ ) 157.4°), which is closer to the calculated
ideal value of 144°. The solid-state structure of 11 forms
a loosely associated dimer (Figure 5) by intermolecular
S‚‚‚H hydrogen bonding [S(1)‚‚‚H18(C) 2.857 Å; S(1A)‚
‚‚H(18A) 2.857 Å], representing a weak interaction.28
To create cyclophanes with a variety of donor func-
tionalities, it was decided to investigate the reactivity
of 4 toward 3,6-dithia-1,8-octanediol. Treatment of a
dichloromethane solution of 4 with HOC2H4SC2H4-
SC2H4OH and catalytic amounts of HBF4 yielded, after
separation by preparative TLC, the expected macrocycle
[1,1′-Fc{(Co2(CO)6)2(µ:η2-µ:η2-CtCCMe2OC2H4SC2H4-
SC2H4OCMe2CtC)}] (12) together with [1,1′-Fc{(Co2-
Figure 3. Molecular structure of 7 (ORTEP to 30%
probability).
Figure 4. Molecular structure of 11 (30% probability).
(CO)6}2(µ:η2-µ:η2-CtCC(dCH2)CH2CMe2CtC)}] (13),
which contains a carbon-only cyclic backbone.
The macrocyclic backbone of 12 (Figure 6) contains
both O and S atoms that have adopted an endodentate
conformation. Thus, the average C-S-C-C torsion
angle is 179.8° and the average C-O-C-C torsion
angle is 174.2°. This leads to short O‚‚‚S (3.085 Å) and
S‚‚‚S separations (3.249 Å) and again is in marked
contrast to reports by Wolf that sulfur atoms adopt an
anti conformation with respect to each other,26 although
the oxygen atoms do adopt the expected gauche confor-
mation.29 It should be noted that other structurally
characterized ferrocenophanes that contain both S and
O atoms in their macrocyclic backbone adopt the
expected anti and gauche conformations, respectively.12,30
An estimate of the cavity size is given by the non-
bonding O1‚‚‚O1A separation of 7.561 Å and the Fe(1)-
(26) Wolf, R. E.; Hartman, J. R.; Storey, J. M. E.; Foxman, B. M.;
Cooper, S. R. J. Am. Chem. Soc. 1987, 109, 4328.
(27) (a) Zefirov, N. S. Tetrahedron 1977, 33, 3193. (b) Juaristi, E.
J. Chem. Educ. 1979, 56, 43.
(28) Desiraju, G. R.; Steiner, T. The Weak Hydrogen Bond in
Structural Chemistry and Biology; Oxford University Press, 1999.
(29) Dale, J. Tetrahedron 1974, 30, 1683.

632 Organometallics, Vol. 24, No. 4, 2005
Woods et al.
Figure 7. Sulfur-based HOMO and HOMO-1 of 7 (cal-
culated at AM-1 level).
and result in a gauche placement of the S-C-C-S
bonds.31 This supposition is supported by the work of
Kamigata et al., who reported that all the sulfur atoms
in a series of unsaturated thiacrown ethers adopted an
endodentate conformation.32 They attributed this en-
dodentate conformation to the conformational strain
placed upon the system by the cis-alkenes present
within the backbone. Furthermore, calculations at the
RHF/6-31+G* level have shown that the most stable gas
phase conformation of thiacrown ethers is up to 5 kcal
mol-1 more stable than that found in the solid state,33
thus highlighting the role played by other factors such
as packing forces on the solid-state conformation. It is
also pertinent at this point to note that the S‚‚‚Fe
separation is always greater than 4 Å (range 4.115-
6.432 Å) and that in other documented ferrocene-
containing thiacrowns the sulfur atoms are in the
expected exodentate conformation, thus precluding the
possibility of a stabilizing Fe‚‚‚S interaction.
Figure 5. Weak hydrogen-bonding interactions in 11.
We therefore attribute the unusual gauche conforma-
tion of the sulfur atoms in the cyclophanes reported
herein to the steric demands placed upon the macrocycle
by the cobalt-coordinated alkyne units. The geometry
of these units may be compared with some justification
to the cis-alkenes used in the study by Kamigata and
co-workers.
Compound 13 is most probably a result of a competing
dehydration-cyclization reaction in which one of the
CMe2OH groups eliminates water to yield intermediate
A (Scheme 4); the resulting alkene can then attack a
carbocation formed by loss of H2O from the second
propargylic site to ultimately yield 13. We cannot fully
rule out the possibility that 13 is formed by a radical-
based mechanism similar to that found by Melikyan and
co-workers.34 However, in related studies we have
isolated intermediate ene-ynes that could only be formed
from a stepwise dehydration of the propargyl alcohols.35
It is interesting to note that the related complex [Co2-
(CO)6(µ:η2-HCtCCMe2OH)] reacts with oxygen-based
nucleophiles to only yield the expected substitution
product, whereas [{Co2(CO)6(µ:η2-HOMe2CCtC)-}2]
Figure 6. Molecular structure of 12 (ORTEP to 30%
probability).
midpoint C(9)-C(9A) separation of 5.804 Å. With re-
gards to the ferrocene unit, the cyclopentadienyl rings
are planar (max. deviation 0.002 Å) and are virtually
parallel (tilt angle 6.7°). Despite being distinctly stag-
gered (twist ) 52.5°), the rings adopt the expected 1,3′
disposition (γ ) 163°).
In light of the unexpected conformations of the sulfur
atoms in these complexes it was decided to investigate
whether any stabilizing S‚‚‚S interactions were present
that would account for the endodentate conformation.
Semiempirical (AM-1) calculations revealed that the
HOMO and HOMO-1 (Figure 7) consisted of two
essentially orthogonal sulfur lone pairs and that there
was a negligible S‚‚‚S interaction in complex 7. The
orbitals are essentially degenerate ((0.1 eV) and are
well isolated from the HOMO-2 (-1 eV) and LUMO
(+0.7 eV).
Previous calculations have revealed that the stabili-
zation gained by the sulfur atoms adopting an anti
configuration in thia-crown compounds is in the region
of 1 kcal mol-1, and it should therefore come as little
surprise that other factors may override this preference
(31) (a) Flory, P. J. Statistical Mechanics of Chain Molecules;
Interscience: New York, 1969. (b) Oyanagi, K.; Ohta, M.; Sakakibara,
M.; Matsuura, H.; Harada, I.; Shimanouchi, T. Bull. Chim. Soc. Jpn.
1973, 46, 3685.
(32) Tsuchiya, T.; Shimizu, T.; Kamigata, N. J. Am. Chem. Soc.
2001, 123, 11534.
(33) Hill, S. E.; Feller, D. J. Phys. Chem. A 2000, 104, 652.
(34) Melikyan, G. G.; Villena, F.; Sepanian, S.; Pulido, M.; Sarkis-
sian, H.; Florut, A. Org. Lett. 2003, 5, 3395.
(35) Golovko, V. B.; Hope-Weeks, L. J.; Mays M. J.; McPartlin, M.;
Sloan, A. M.; Woods, A. D. New J. Chem. 2004, 28, 527.
(30) (a) Bernal, I.; Raabe, E.; Reisner, G. M. Organometallics 1988,
7, 247. (b) Beer, P. D.; Nation, J. E.; Harman, M. E.; Hursthouse, M.
B. J. Organomet. Chem. 1992, 441, 465. (c) Sato, M.; Anano, H. J.
Organomet. Chem. 1988, 555, 167.

Mixed-Donor Alkynyl Ferrocenophanes
Organometallics, Vol. 24, No. 4, 2005 633
Scheme 4 . Proposed Pathway Leading to the
Formation of 13
Figure 8. Molecular structure of 13 (ORTEP to 30%
probability).
Table 3. Selected Bond Lengths (Å) and Angles
(deg) for 12
Fe-C(4)
2.063(7)
Co(1)-C(2)
Co(1)-C(3)
1.960(3)
1.961(3)
1.968(3)
2.004(3)
mean Fe-C(5-8) 2.052
range Fe-C(5-8) 2.040(3)-2.070(3) Co(2)-C(2)
Co(1)-Co(2)
C(2)-C(3)
C(3)-C(4)
2.4709(6)
1.339(4)
1.445(4)
Co(2)-C(3)
C(4)-C(3)-C(2) 148.0(3)
C(3)-C(2)-C(1) 140.5(3)
disordered about a pseudo-C2 axis which is located
approximately at the Fe atom and midway between the
C(1) and C(16) atoms.
It is interesting to note that in all of the structurally
characterized complexes presented here except 7 (where
the values are identical within experimental error) the
alkyne bend-back angle is significantly larger at the
terminus bound to the cyclopentadienyl ring (average
145.33° compared to 140.44°) (Table 5). Given that the
Fc-bound bend-back angle is higher in acyclic 4 it seems
unlikely that ring strain is the cause for this difference.
Higher bend-back angles suggest less donation to the
dicobalt unit, and it would therefore make sense that
the alkynic carbon bound directly to the ferrocene has
the greater bend-back angle due to competition for the
alkyne’s electron density between the ferrocene and the
dicobalt unit.
Electrochemical Studies of the New Complexes.
The electrochemical properties of complexes 2, 4, 7, and
11-13 were examined by cyclic voltammetry (Figure 9);
their redox potentials are shown in Table 5. Coordina-
tion of the alkyne to cobalt causes a small cathodic shift
in the Epa from 0.80 to 0.78 V. Such a decrease in
oxidation potential on dicobalt coordination of alkynyl
ferrocenes has also been reported for a series of poly-
ferrocenylalkynes.39 The variation in the redox poten-
tials for the cyclic compounds appears to follow no
discernible pattern (Table 5); certainly it does not
correlate to the ring size or number of heteroatoms
within the macrocycle. There appears to be no com-
munication between the dicobalt fragment and the
ferrocene, as indicated by the two very distinct oxidation
potentials. Robinson and co-workers have previously
investigated the electronic properties of a series of
alkynyl- and dicobaltalkynylferrocenes and have noted
that the two redox centers tend to behave independently
of each other.40
does not react with nucleophiles under any conditions
but instead always yields a cyclic product, [{Co2(CO)6}2-
(µ-η2:µ-η2-C(dCH2)CtC-CtCCMe2CH2)], that contains
a bridging motif similar to that found in 13.35,36 In
further studies it has been shown that only one alkyne
of a bis-propargyl alcohol needs to be coordinated in
order for dehydration to occur at both sites provided that
a direct alkyne-alkyne bond is present.37 It therefore
seems likely that the presence of a second stabilizing
group lowers the activation barrier to elimination. This
favors dehydration and/or cyclization rather than nu-
cleophilic attack in systems where the cobalt-coordi-
nated alkyne is directly bonded to another group capable
of stabilizing a positive charge (e.g., Fc, cobalt-coordi-
nated alkyne).
Elimination reactions at activated propargylic centers
are well documented in the case where no nucleophile
is present.38 Thus, compound 13 was synthesized in
greater yield by treatment of 4 with an excess of HBF4
1
in the absence of nucleophiles. The H NMR spectrum
of 13 quite clearly indicates that dehydration has
occurred; two broad singlets are observed at 5.67 and
5.41 ppm that are assigned as the inequivalent CdCH2
protons.
The molecular structure of 13 is shown in Figure 8,
and relevant bond angles and lengths are shown in
Table 4. Regarding the ferrocene unit, the cyclopenta-
dienyl rings are virtually planar (maximum deviation
of 0.005 Å) and lie at an angle of 7.1° to each other. The
rings are essentially eclipsed (R ) 7.62°) and adopt a
relative 1,2′ disposition (γ ) 65.1°). The complex is
(36) Lockwood, F.; Nicholas, K. M. Tettrahedron Lett. 1977, 4163.
(37) Golovko, V. B.; Mays, M. J.; Woods, A. D. New J. Chem. 2002,
26, 1706.
(39) Hore, L.-A.; McAdam, C. J.; Kerr, J. L.; Duffy, N. W.; Robinson,
B. H.; Simpson, J. Organometallics 2000, 19, 5039.
(38) Nicholas, K. M. Acc. Chem. Res. 1987, 20, 207.

634 Organometallics, Vol. 24, No. 4, 2005
Table 4. Selected Bond Lengths (Å) and Angles (deg) for 13
Woods et al.
Fe-C(4)
2.091(6)
2.055
2.045(7)-2.076(6)
2.079(6)
2.052
C(1)-C(17)
1.562(1)
mean Fe-C(5-8)
range Fe-C(5-8)
Fe-C(13)
C(17)-C(16)
1.48(2)
1.347(9)
1.34(1)
120(1)
C(15)-C(14)
C(2)-C(3)
mean Fe-C(9-12)
range Fe-C(9-12)
Co(1)-Co(2)
C(1)-C(2)-C(18)
C(15)-C(16)-C(19)
C(15)-C(16)-C(17)
C(15)-C(16)-C(20)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(13)-C(14)-C(15)
C(14)-C(15)-C(16)
2.047(7)-2.058(6)
2.464(1)
2.464(1)
1.985
106.8(9)
106(1)
115.3(1)
142.4(7)
147.2(6)
145.5(6)
137.5(8)
Co(3)-Co(4)
mean Co(1)-Calkyne
mean Co(2)-Calkyne
mean Co(3)-Calkyne
mean Co(4)-Calkyne
C(1)-C(18)
1.961
1.982
1.977
1.35(2)
Table 5. Comparison of Geometric Features for
the New Complexes
bend-back
twist
angle
ring atoms
tilt in
angle (deg)
γ
Epa Epc E1/2
Fc
NA
146.0(4) 140.0(5) 30
non-Fc (deg) (deg) (deg) link (V) (V) (V)
2
4
7
NA
3.7
3.8 4.1
102.2 1.3
NA 0.80 0.71 0.76
NA 0.78 0.67 0.73
11
142.9(6) 141.0(6) 28.9 117.0 2.5
144.5(6) 143.7
0.77 0.72 0.75
11 144.1(3) 141.0(3) 13.4 157.4 6.7
13
0.85 0.67 0.76
144.5(3) 140.3(3)
12 148.0(3) 140.5(3) 52.5 163
7.1
65.1 4.1
16
7
0.79 0.63 0.71
0.85 0.73 0.79
13 147.2(6) 138.8(8)
145.4(6) 138.2(7)
7.6
av 145.33 140.44
At standard scan rates (ca. 100 mV s-1) all the
complexes exhibit quasi-reversible electrochemical be-
havior. The voltammogram displays a catalytic current
profile at scan rates less than 3 mV s-1 for 2 and 20
mV s-1 for 4, indicative of an ECE′ mechanism (Figure
10). The rate of this chemical reaction is only competi-
tive with the electrochemical process at slower scan
rates, but it is interesting to note that the rate appears
to increase upon complexation with Co2(CO)6, suggest-
ing that the chemical reaction may be centered at the
propargyl unit, which is further activated by complex-
ation with Co2(CO)6. To the best of the authors’ knowl-
edge there has been no research into the electrochemical
behavior of cobalt-coordinated propargyl alcohols, al-
though it is known that propargyl cations can undergo
a one-electron reduction on treatment with zinc to form
radical species.41 Furthermore, Melikyan has observed
that electron transfer between a Co2(CO)6 center and a
propargyl cation can occur prior to a radical coupling
reaction, and it seems likely that a similar transfer
between ferrocene and the propargyl center is occurring
in the present case.34
Figure 9. Cyclic voltammograms of the new complexes
(ν ) 100 ms-1).
Figure 10. Cyclic voltammograms of 2 at varying scan
rates.
Conclusions
To explore this reaction more, it was decided to carry
out the bulk oxidation of a sample of 2. Treatment of
an acetone solution of 2 with 0.5 equiv of ammonical
cerium(IV) nitrate resulted in an immediate color
change from orange to green. However, after stirring
for several minutes a second color change from green
to deep orange occurred, suggesting a chemical reduc-
tion of 2. Unfortunately, despite repeated efforts we
have not been able to separate the products of this
reaction.
A facile one-pot synthesis of a new range of alkynyl-
ferrocene-containing macrocycles is reported; in all cases
only monomeric products were formed. The presence of
the dicobalt-coordinated alkyne results in both the
oxygen and sulfur heteroatoms being located with their
lone pairs endodentate. The electrochemical properties
of the new complexes have been investigated; these
show quasi-reversible behavior at high scan rates, but
oxidation of 2 and 4 becomes irreversible at slow (<20
mV s-1) scan rates, presumably due to a chemical
reaction involving the propargyl centers.
(40) (a) McAdam, C. J.; Kerr, J. L.; Duffy, N. W.; Robinson, B. H.;
Simpson, J. Organometallics 1996, 15, 3935. (b) McAdam, C. J.;
Brunton, J. L.; Robinson, B. H.; Simpson, J. J. Chem. Soc., Dalton
Trans. 1999, 2487.
(41) Melikyan, G. G.; Khan, M. A.; Nicholas, K. M. Organometallics
1995, 14, 2170.
Experimental Section
Unless otherwise stated all experiments were carried out
under an atmosphere of dry, oxygen-free nitrogen, using

Mixed-Donor Alkynyl Ferrocenophanes
Organometallics, Vol. 24, No. 4, 2005 635
Table 6. X-ray Crystallographic Data for the New Complexesa
2
4
7
11
12
13
empirical formula
weight
C
20H22FeO2
C
32H22Co4O14
C
35H26Co4O12S2
C
36H28Co4O12S3
C
38H32Co4FeO14S2
C
32H18Co4FeO12
350.23
922.07
994.25
1040.33
monoclinic
0.28 × 0.23 ×
0.12
1068.33
monoclinic
0.35 × 0.32 ×
0.12
886.03
cryst syst
monoclinic
0.32 × 0.10 ×
0.10
orthorhombic
0.16 × 0.14 ×
0.12
monoclinic
0.23 × 0.18 ×
0.02
monoclinic
0.46 × 0.28 ×
0.05
P2(1)/n
8.4267(1)
30.2975(4)
13.4300(2)
90
cryst size
space group
a (Å)
b (Å)
c (Å)
P2(1)/c
P1
P2(1)/c
P(2)1/c
P2/c
14.2647(4)
10.9838(3)
10.6930(2)
90
12.3936(3)
10.4536(2)
26.6811(5)
90
12.4781(2)
22.3700(3)
27.1757(4)
90
8.1828(1)
34.1578(3)
14.6109(1)
90
14.4980(5)
10.8391(3)
14.0975(4)
90
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
90.252(1)
90
90
90
90.0790
90
102.049(1)
90
108.514(1)
90
106.568(1)
90
1675.37(7)
4
3456.7(1)
4
7585.68(19)
8
3993.87(7)
4
2100.7(11)
2
3286.43(8)
4
Dc (Mg/m3)
1.389
1.772
1.741
1.730
1.689
1.791
abs coeff (mm-1
F(000)
)
0.907
2.357
2.257
2.198
2.048
2.471
736
1840
3984
2088
1076
1760
θ range (deg)
index ranges
3.71 to 27.42
-12 e h e 18
-14 e k e 14
-13 e l e 13
10 581
3.63 ro 20.62
-12 e h e 12
-7 e k e 10
-26 e l e 26
13 109
3.52 to 27.16
-15 e h e 15
-28 e k e 28
-34 e l e 34
53 199
1.19 to 27.49
-10 e h e 10
-44 e k e 44
-15 e l e 18
30 802
3.58 to 27.50
-18 e h e 18
-14 e k e 13
-18 e l e 18
12 057
3.60 to 27.49
-10 e h e 10
-39 e k e 39
-17 e l e 17
22 450
reflns no. of measd
no. of indep reflns
Rint
3809
1753
15 988
8847
4785
7212
0.0477
0.0974
0.0701
0.0387
0.0333
0.1202
goodness of fit on F2
final R indices R1
wR2
1.031
1.202
1.091
1.257
1.064
1.037
0.0371
0.0327
0.0659
0.0297
0.0413
0.0626
0.0812
0.0900
0.1444
0.0963
0.1088
0.1599
R indices (all data)
R1
0.0524
0.0384
0.0950
0.0452
0.0494
0.0973
wR2
0.0882
0.416 and
-0.478
0.1067
0.496 and
-0.603
0.1610
2.192 and
-1.231
0.1330
0.827 and
-1.505
0.1150
1.697 and
-1.084
0.2038
0.904 and
-1.179
largest diff peak
and hole (e/Å3)
a Data collected at 180(2) K.
conventional Schlenk line techniques, and solvents freshly
distilled from the appropriate drying agent. Except where
otherwise indicated NMR spectra were recorded in CDCl3
using a Bruker DRX 400 spectrometer, with TMS as an
external standard for 1H and 13C spectra and H3PO4 as an
external standard for 31P NMR spectra. Infrared spectra were,
unless otherwise stated, recorded in dichloromethane solution
in 0.5 mm NaCl solution cells, using a Perkin-Elmer 1710
Fourier transform spectrometer. FAB mass spectra were
obtained using a Kratos MS 890 instrument, using 3-nitroben-
zyl alcohol as a matrix. Preparative TLC was carried out on 1
mm silica plates prepared at the University of Cambridge.
Column chromatography was performed on Kieselgel 60
(70-230 mesh ASTM). All products are listed in order of
decreasing Rf. Unless otherwise stated, all reagents were
obtained from commercial suppliers and used without further
purification. Diiodoferrocene was prepared by the literature
method.42
Crystal Structure Determinations. Single-crystal X-ray
diffraction data were collected using a Nonius-Kappa CCD
diffractometer, equipped with an Oxford Cryosystems cryo-
stream and employing Mo KR (0.71069 Å) irradiation from a
sealed tube X-ray source. Cell refinement, data collection, and
data reduction were performed with the programs DENZO and
COLLECT, and multiscan absorption corrections were applied
to all intensity data with the program SORTAV. All structures
were solved and refined with the programs SHELXS97 and
SHELXL97, respectively.43-46 The structure of complex 13
shows disorder about a pseudo-C2 axis located approximately
between the Fe(1) atom and the midpoint of the C(16)-C(1)
atoms of the carbacyclic ring. This leads to two positions of
the C(1), and C(16) to C(20) atoms being observed in an
approximately 2:1 ratio. The two positions were refined with
the total occupancy of the site summing to unity. A summary
of data collection and data refinement details is given in Table
6.
Electrochemical Studies. Cyclic voltammetric studies
were carried out using tetra(tert-butyl)ammonium tetrafluo-
roborate as the electrolyte (0.1 M) and dichloromethane as the
solvent. A standard Ag/AgCl electrode was used as the
reference electrode, along with platinum working and auxiliary
electrodes. The scan rate was 100 mV s-1. Each voltammogram
shows linear plots of Iap versus v1/2
.
Theoretical Calculations. Semiempirical RHF calcula-
tions were made using MOPAC, implemented through Quan-
tum Cache (Fujitsu Co.) utilizing the crystallographic geom-
etry.47 Semiempirical calculations on transition metal complexes
at this level are hindered by a shortage of appropriate basis
sets. However, the Austin Model 1 (AM1) is parameterized for
Fe,48 but not Co, and so the bonding in 7 was probed using
the isoelectronic Fe complex in which Co atoms were replaced
by Fe- ions.
Synthesis of [1,1′-Fc(CtCCH2OH)I] (1) and [1,1′-Fc(Ct
CCMe2OH)2] (2). To a solution of 1,1′-FcI2 (5.2 g, 12 mmol)
i
in Pr2NH (200 mL) were added Cu(OAc)2 (0.09 g, 4 mol %)
and Pd(PPh3)2Cl2 (0.34 g, 4 mol %), and the resulting mixture
was stirred for 30 min. The relevant propargyl alcohol (3 equiv)
was added, and the solution was heated under reflux over-
night. The solvent was removed in vacuo, and the residue was
dissolved in the minimum dichloromethane, absorbed on silica,
and applied to the top of a silica column.
(42) Kovar, R. F.; Raush, M. D.; Rosenberg, H. Organomet. Chem.
Synth. 1970/1971, 1, 173.
(43) Otwinowski, Z.; Minor, W. Methods Enzymol. 1997, 276, 307.
(44) Hooft, R. COLLECT; Nonius BV: Delft, The Netherlands, 1998.
(45) Blessing, R. H. Acta Crystallogr. 1995, A51, 33.
(46) Sheldrick, G. M. SHELXS97 and SHELXL97; University of
Go¨ttingen: Germany.
(47) Quantum Cache vers. 5.0; Fujitsu Co.: Japan, 2001.
(48) Parameters for C, H, and O are published in: Dewar, M. J. S.;
Zoebisch, E. G.; Healy, E. F.; Stewart J. J. P. J. Am. Chem. Soc. 1985,
107, 3902. For S, see: Dewar, M. J. S.; Yuan, Y.-C. Inorg. Chem. 1990,
29, 3881. Parametrization of Fe, see: Voityuk, A. A. Unpublished,
MOPAC implemented in ref 47.

636 Organometallics, Vol. 24, No. 4, 2005
Woods et al.
Data for 1. Elution with hexane/ethyl acetate (3:2) yielded
[1,1′-Fc(CtCCH2OH)I] (1) as a yellow oil (2.66 g, 61%). 1H
NMR δ: 4.41 (s, 2H, CH2OH), 4.40 (t, 2H, Cp, JH-H ) 1.9
CH2SH)}I] (5) (0.03 mmol, 14%). IR νCO (cm-1): 2079.5(s),
2048.0(vs), 2018.6(vs). 1H NMR δ: 4.45 (t, 2H, Cp, JH-H ) 1.5
3
Hz), 4.42 (t, 2H, Cp, JH-H ) 1.5 Hz), 4.35 (t, 2H, Cp, JH-H
1.6 Hz), 4.29 (s, 2H, C2CH2S), 4.25 (t, 2H, Cp, JH-H ) 1.5 Hz),
3.80 (t, 2H, CH2O, JH-H ) 6.4 Hz), 3.78 (t, 2H, CH2O, JH-H
)
Hz), 4.38 (t, 2H, Cp, JH-H ) 1.9 Hz), 4.20 (t, 2H, Cp, JH-H
)
1.9 Hz), 4.19 (t, 2H, Cp, JH-H ) 2.0 Hz). 13C NMR δ: 86.1 (Cp,
C-C) 84.9, 83.3 (CtC), 76.2, 74.1, 71.9, 70.9 (Cp, CH), 66.7
(Cp, C-C), 53.09 (CH2OH), 41.0 (Cp, C). FABm/s: 366 (MH+).
Anal. Calcd for C13FeH11IO: C 42.66, H 3.03. Found: C 43.28,
H 3.05.
)
6.4 Hz), 2.97 (t, 2H, CH2S, JH-H ) 6.4 Hz), 2.91 (t, 2H, CH2S,
JH-H ) 6.4 Hz). 13C NMR δ: 89.9, 86.4 (CtC), 75.8, 73.3, 72.5
(Cp, CH), 71.5 (Cp, C-C), 70.9 (Cp, CH), 69.4 (Cp, C-C), 53.4
(C2CH2S), 38.6, 37.8, 33.3, 29.7 (CH2).
Data for 2. Elution with hexane/ethyl acetate (1:1) yielded
orange crystalline 2 (2.48, 70%). Spectra were in accordance
with the literature values.
Data for [1,1′-Fc{(Co2(CO)6)2(µ:η2-µ:η2-CtCCMe2S-
(CH2)3SCMe2CtC)}], 7. IR νCO (cm-1): 2082.4(s), 2049.0-
1
(vs), 2019.0(s). H NMR δ: 4.59 (s, 4H, Cp), 4.17 (s, 4H, Cp),
Synthesis of [1,1′-Fc{Co2(CO)6(µ-η2-CtCCH2OH)}I] (3)
and [1,1′-Fc{Co2(CO)6(µ-η2-CtCCMe2OH)}2] (4). To a solu-
tion of 1 or 2 (5 mmol) in toluene (250 mL) was added Co2-
(CO)8 (2.05 g, 6 mmol for 1; 4.1 g, 12 mmol for 2), and the
mixture was stirred at room temperature for 3 h. The solvent
was removed on a rotary evaporator, and the residue was
dissolved in the minimum volume of dichloromethane and
applied to the top of a silica chromatography column. Elution
with hexane/ethyl acetate (1:1) followed by removal of solvent
yielded green crystalline 3 (1.43 g, 44%) or 4 (2.76 g, 60%).
Data for 3. IR νCO (cm-1): 2076.1(s), 2052.4(vs), 2022.6-
(vs). 1H NMR δ: 5.04 (d, 2H, CH2OH, 3JH-H ) 6.1 Hz), 4.40 (t,
2H, Cp, 3JH-H ) 1.8 Hz), 4.37 (t, 2H, Cp, 3JH-H ) 1.9 Hz), 4.30
2.93 (m, 4H, Me2CSCH2), 2.19 (m, 2H, SCH2CH2), 1.76 (s, 12H,
CH3). 13C NMR δ: 199.78 (s, CO), 106.5 (CtC), 91.12 (s, Ct
C), 86.85 (s, CpCC), 74.77, 73.57 (s, CpCH), 48.57 (s, CMe2),
31.57 (CH3), 29.51 (s, SCH2), 29.18 (s, SCH2CH2). FABm/s:
993.7 (MH+), M+ - nCO (n ) 2,4, 6-10). Anal. Calcd for
C35H26Co4FeO12S2: C 42.28, H 2.64. Found: C 43.06, H 2.12.
Data for [1,1′-Fc{(Co2(CO)6)2(µ:η2-µ:η2-CtCCMe2S-
(CH2)4SCMe2CtC)}], 8. IR νCO (cm-1): 2083.3(m), 2054.2-
3
(s), 2022.6(s). 1H NMR δ: 4.61 (t, JH-H ) 1.8 Hz, 4H, Cp),
3
4.22 (t, JH-H ) 1.8 Hz, 4H, Cp), 2.20 (m, 4H, CH2S), 1.75 (s,
12H, Me), 1.15 (m, 4H, CH2). 13C NMR δ: 199.5 (br, CO), 105.8
(CtC), 90.89 (CtC), 85.89 (s, Cp, C-C), 74.12, 72.78 (s, Cp,
CH), 48.71 (CMe2), 33.10 (SCH2CH2), 32.80 (CH3) 30.6 (CH2).
FABm/s: 1008 (MH+), M+ - nCO (n ) 1-4). Anal. Calcd for
C36H28Co4FeO12S2: C 42.88, H 2.80. Found: C 42.96, H 3.10.
Data for [1,1′-Fc{(Co2(CO)6)2(µ:η2-µ:η2-CtCCMe2S-
(CH2)5SCMe2CtC)}], 9. IR νCO (cm-1): 2085.3(m), 2050.2-
3
3
(t, 2H, Cp, JH-H ) 1.8 Hz), 4.20 (t, 2H, Cp, JH-H ) 1.9 Hz).
13C NMR δ: 199.3 (CO), 97.1, 89.7, (CtC), 86.2 (Cp, C-C),
75.9, 72.9, 72.8, 70.6 (Cp, CH), 66.75 (Cp CC), 63.90 (CH2OH).
FABm/s: 652 (MH+), MH+ - nCO (n ) 2-5). Anal. Calcd for
C19Co2FeH11IO7: C 35.00, H 1.70. Found: C 33.29, H 1.92.
Data for 4. IR νCO (cm-1): 2079.6(s), 2050.2(vs), 2023.0-
(vs). 1H NMR δ: 4.47 (s, 2H, CpH), 4.44 (s, 2H, CpH), 1.74 (s,
6H, Me). 13C NMR δ: 199.6 (s, CO), 107.2 (s, CtC), 89.96 (s,
CtC), 86.28 (s, Cp, C-C), 73.19 (s, CMe2), 72.30, 70.63 (s,
CpH), 32.66 (s, CH3). FABm/s: 922.6 (MH+), 921.6 (M+), M+
- nCO (n ) 3-8). Anal. Calcd for C32H22Co4FeO14: C 41.68, H
2.40. Found: C 41.54, H 2.36.
3
(s), 2020.6(s). 1H NMR δ: 4.58 (t, JH-H ) 1.8 Hz, 4H, Cp),
3
4.26 (t, JH-H ) 1.8 Hz, 4H, Cp), 2.26 (m, 4H, CH2S), 1.81 (s,
12H, CH3), 1.18 (m, 4H, CH2), 1.16 (m, 2H, CH2). 13C NMR δ:
199.5 (br, CO), 108.8, 94.5 (CtC), 86.12 (s, Cp, C-C), 74.12,
71.26 (s, Cp, CH), 48.7 (CMe2), 33.14 (SCH2CH2), 32.62 (CH3),
30.6 (CH2), 28.0 (CH2). FABm/s: 1022 (MH+), M+ - nCO (n )
1-4, 6, 8-10). Anal. Calcd for C37H30Co4FeO12S2: C 43.47, H
2.96. Found: C 43.48, H 3.10.
Data for [1,1′-Fc{(Co2(CO)6)2(µ:η2-µ:η2-CtCCMe2S-
(CH2)6SCMe2CtC)}], 10. IR νCO (cm-1): 2086.4(m), 2051.4-
Preparation
of
[1,1′-Fc{Co2(CO)4(dppm)(µ-η2-Ct
CCH2OH)}I], 6. To a solution of 3 (2.0 g, 3.07 mmol) in toluene
(200 mL) was added dppm (1.84 g, 4.80 mmol) and the mixture
heated to 70 °C and stirred for 2 h. The solvent was removed
on a rotary evaporator, and the residue was dissolved in the
minimum volume of dichloromethane and applied to the top
of a silica chromatography column. Elution with 4:1 hexane/
ethyl acetate yielded [1,1′-Fc{Co2(CO)4(dppm)(µ-η2-CtCCH2-
OH)}I] (6) as a red solid (2.58 g, 86%). IR νCO (cm-1):
2020.1(s), 1992.0(vs), 1964.7(s). 1H NMR δ: 7.36-7.18 (m, 20H,
Ph), 5.10 (br s, 2H, CH2OH), 4.42 (t, 2H, Cp, JH-H ) 1.8 Hz),
4.28 (t, 2H, Cp, JH-H ) 1.8 Hz), 4.26 (t, 2H, Cp, JH-H ) 1.8
Hz), 4.21 (t, 2H, Cp, JH-H ) 1.8 Hz), 3.74 (m, PCHHP, 1H),
3.50 (m, PCHHP). 13C NMR δ: 204.8 (s, CO), 131.6 (m, Ph),
129.5 (d, Ph, JC-P ) 30 Hz), 128.2 (d, Ph, JC-P ) 15 Hz), 91.4
(CtC), 88.61 (CtC), 84.80 (Cp, C-C), 75.2, 72.5, 71.8, 70.5
(Cp, H), 69.01 (s, Cp, C-C), 65.9 (CH2OH), 40.2 (t, PCH2P,
3
(s), 2021.4(s). 1H NMR δ: 4.55 (t, JH-H ) 1.8 Hz, 4H, Cp),
3
4.21 (t, JH-H ) 1.8 Hz, 4H, Cp), 2.7 (m, 8H, CH2S), 2.25 (m
4H, CH2S), 1.8 (s, 12H, CH3). 13C NMR δ: 200.0 (s, CO), 106.6
(CtC), 94.0 (CtC), 86.12 (s, Cp, C-C), 74.12, 71.26 (s, CpC-
H), 49.2 (CtCCMe2S), 38.9 (SCH2), 31.0 (CCH3), 28 (br, CH2).
FABm/s: 1037 (MH+), M+ - nCO (n ) 1, 3-10, 12). Anal.
Calcd for C38H32Co4FeO12S2: C 44.04 H 3.11. Found: C 45.18,
H 4.02.
[1,1′-Fc{(Co2(CO)6)2(µ:η2-µ:η2-CtCCMe2SC2H4SC2-
H4SCMe2CtC)}], 11. IR νCO (cm-1): 2084(s), 2049(vs), 2021-
1
3
(vs). H NMR δ: 4.29 (s, v br, 8H, Cp); 3.09 (d, JH-H 6.1 Hz,
3
4H, SCH2), 3.04 (d, JH-H ) 6.1 Hz, 4H, SCH2CH2S), 1.80(s,
12H, Me). 13C NMR δ: 199.80 (s, CO), 96.12 (s, CtC), 84.16
(s, CtC), 82.32 (s, Cp, C-C), 74.38 (s, Cp, CH), 70.14 (s, CMe2),
69.65 (s, Cp, CH), 32.80 (s, CH2), 31.98 (s, CH2), 31.55 (s, CH3).
FABm/s: 1040.2 (M+), M+ - nCO (n ) 2-10). Anal. Calcd for
C36H28Co4FeO12S3: C 41.56, H 2.71. Found: C 41.44, H 2.98.
[1,1′-Fc{(Co2(CO)6)2(µ:η2-µ:η2-CtCCMe2OC2H4SC2H4-
SC2H4OCMe2CtC)}], 12. IR νCO (cm-1): 2085(s), 2050(vs),
2020(vs). 1H NMR δ: 4.58 (t, 3JH-H 1.8 Hz, 4H, CpH), 4.46 (t,
3JH-H 1.8 Hz, 4H, CpH), 3.68 (t, 3JH-H 7.2 Hz, 4H, OCH2), 2.77
JC-P ) 76 Hz). 31P NMR δ: 38.5 (s). FABm/s: 981 (M+), M+
-
nCO (n ) 1-4). Anal. Calcd for C42H22Co2FeIO5P2: C 51.5, H
3.4, P 6.3. Found: C 52.1, H 3.67, P 4.76.
General Methodology for Reaction with Thiols. To a
solution of 3 or 4 (0.20 mmol) in DCM (50 cm3) were added 54
wt % HBF4‚OEt2 (0.05 mL, 0.0034 mmol) at -78 °C and the
appropriate dithiol HSZSH (0.24 mmol, 1.2 equiv). The result-
ant mixture was stirred for 10 min at -78 °C, then allowed to
warm to RT and stirred for a further 2 h. The reaction was
quenched with an excess of NaHCO3 and dried with MgSO4.
The mixture was filtered through a silica plug, the solvent
removed in vacuo, and the residue redissolved in the minimum
DCM and applied to the base of TLC plates. The reaction
products were separated as follows.
3
(s, 4H, SCH2), 2.75 (t, JH-H 7.2 Hz, 4H, OCH2CH2), 1.67 (s,
12H, CH3). 13C NMR δ: 199.78 (s, CO), 106.131 (s, CtC), 91.57
(s, CtC), 86.28 (s, Cp, C-C), 72.27 (s, Cp, CH), 71.46 (s, Cp,
CH), 63.09 (s, OCH2), 33.04 (s, CH2S), 32.52 (s, SCH2), 27.53
(s, CH3). FABm/s: 1068.3 (M+), M+ - nCO (n ) 3, 6-10). Anal.
Calcd for C38H32Co4FeO14S2: C 42.72, H 3.02. Found: C 43.07,
H 2.12.
Data for [1,1′-Fc{(Co2(CO)6}2(µ:η2-µ:η2-CtCC(dCH2)-
CH2CMe2CtC)}], 13. IR νCO (cm-1): 2083(s), 2050(vs), 2023-
(vs). 1H NMR δ: 5.67 (s, br, 1H, CdCHH), 5.41 (s, br, 1H, Cd
Data for 5. Elution with 4:1 hexane/ethyl acetate yielded
two major fractions, but decomposition led to isolation of only
the green solid [1,1′-Fc{Co2(CO)6(µ:η2-CtCCH2SCH2CH2OCH2-
3
3
CHH), 4.43 (t, JH-H 1.9 Hz, 4H, CpH), 4.41 (t, JH-H 1.9 Hz,

Mixed-Donor Alkynyl Ferrocenophanes
Organometallics, Vol. 24, No. 4, 2005 637
4H, CpH), 2.27 (s, 6H, Me), 1.66 (s, 2H, CH2). 13C NMR δ:
199.48, 145.22 (s, CdCH2), 121.78 (s, CdCH2), 106.31 (s, Ct
C), 90.46 (s, CtC), 87.68 (s, Cp, C-C), 72.41 (s, Cp, CH), 69.46
(s, Cp, CH), 47.33 (s, CMe2), 40.06 (s, CH2), 31.38 (s, Me).
FABm/s: 887 (MH+), 886 (M+), M+ - nCO (n ) 1-11). Anal.
Calcd for C32H18Co4FeO12: C 43.38, H 2.05. Found: C 43.05,
H 2.05.
to St. Catharine’s College, Cambridge, for the award of
a Research Fellowship. We thank the Cambridge Over-
seas Trust for financial support to V.B.G. C.M.H. would
like to acknowledge support from NPL’s Strategic
Research Programme. Dr. John E. Davies is thanked
for help with data collection and crystal structure
determination.
Acknowledgment. We acknowledge the financial
support of the EPSRC for the purchase of the Nonius
Kappa CCD diffractometer and the help of the EPSRC
mass spectrometry service, Swansea. A.D.W. is grateful
Supporting Information Available: This material is
available free of charge via the Internet at http://pubs.acs.org.
OM049465E