Iron complexes of facially capping triphosphorus macrocycles

Article abstract of DOI:10.1039/b509627h

Primary and secondary phosphine piano-stool complexes of the type η⁵-CpFeL₃⁺ (L = phenylphosphine, 3, (α-methyl)vinylphosphine, 4, allylphosphine, 5, (2-methylpropenyl) phosphine, 5b, allyl(phenyl)phosphine, 6) are described. The alkenyl phosphine complexes, 5 and 6, react by intramolecular hydrophosphination to give the corresponding η⁵-CpFe⁺ complexes of 1,5,9-triphosphacyclododecane (12-aneP₃R₃, 2, R = H), 9 and 10 respectively. Alkylation of the secondary phosphines in 9 is achieved by hydrophosphinations with ethene to give the 12-aneP₃R₃ (R = Et) derivative 11. These complexes are also obtained by reaction of suitable η⁵-CpFe⁺ containing precursor complexes with the corresponding free 12-aneP₃R₃ macrocycle as is the related η⁵-Cp*Fe⁺ derivative, 8. Direct substitution of acetonitrile in Fe(CH₃CN)₆BF₄₂ by 12-aneP₃Et₃, leads to the macrocycle piano-stool complex, (12-aneP₃Et₃)Fe(CH₃CN)₃BF ₄₂, 7. The crystal structures of selected primary phosphine, η⁵-Cp, η⁵-Cp* complexes and 7, allow a comparison of steric influences upon key macrocycle ring closure reactions and hence an insight into parameters required for the formation of smaller ring sizes by template based methods. The Royal Society of Chemistry 2006.

Full text of DOI:10.1039/b509627h

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www.rsc.org/dalton | Dalton Transactions
Iron complexes of facially capping triphosphorus macrocycles
Peter G. Edwards,* K. M. Abdul Malik, Li-ling Ooi and Andrew J. Price
Received 7th July 2005, Accepted 20th September 2005
First published as an Advance Article on the web 28th October 2005
DOI: 10.1039/b509627h
5
Primary and secondary phosphine piano-stool complexes of the type [g -CpFeL3]+ (L =
phenylphosphine, 3, (a-methyl)vinylphosphine, 4, allylphosphine, 5, (2-methylpropenyl)phosphine, 5b,
allyl(phenyl)phosphine, 6) are described. The alkenyl phosphine complexes, 5 and 6, react by
5
intramolecular hydrophosphination to give the corresponding [g -CpFe]+ complexes of 1,5,9-
triphosphacyclododecane (12-aneP3R3, 2, R = H), 9 and 10 respectively. Alkylation of the secondary
phosphines in 9 is achieved by hydrophosphinations with ethene to give the 12-aneP3R3 (R = Et)
5
derivative 11. These complexes are also obtained by reaction of suitable [g -CpFe]+ containing
5
precursor complexes with the corresponding free 12-aneP3R3 macrocycle as is the related [g -Cp*Fe]+
derivative, 8. Direct substitution of acetonitrile in [Fe(CH3CN)6][BF4]2 by 12-aneP3Et3, leads to the
macrocycle piano-stool complex, [(12-aneP3Et3)Fe(CH3CN)3][BF4]2, 7. The crystal structures of
5
5
selected primary phosphine, g -Cp, g -Cp* complexes and 7, allow a comparison of steric influences
upon key macrocycle ring closure reactions and hence an insight into parameters required for the
formation of smaller ring sizes by template based methods.
Mo, W) template has more recently been used by Gladysz in the
Introduction
formation of large ring triphosphorus macrocycles by ring closing
metathesis of co-ordinated alkenyl phosphines,5 and by Driess in
the synthesis of the 9-membered triphosphacyclononane with –Si–
Si– backbone skeletons.6 The former is not restricted to facially
capping co-ordination modes and would be expected to form less
stable complexes due to large, flexible ring sizes and the latter is not
expected to be stable under a wide range of conditions due to facile
protonolysis of the P–Si bonds. Whereas this template method
leads to 12-aneP3R3 ligands in good yield and stereospecifically,
a major disadvantage is that it has not allowed the synthesis
of smaller ring sizes, which may be expected to enhance the
robustness of the macrocycle–metal interaction.7 In view of this
limitation, we have continued to investigate alternative template
systems that may be amenable to the formation of triphosphorus
macrocycles with smaller cavities. As part of this study we
have investigated iron(II) complexes of primary phosphines in
order to assess their suitability for template assisted phosphine
cyclisation reactions. Fe(II) readily forms ‘piano-stool’ complexes
in which three mutually cis reaction sites are available in a
(distorted) fac-octahedral structure. Of interest in this context are
Triphosphorus macrocycles provide the opportunity to facially
co-ordinate a metal forming a complex where the remaining co-
ordination sites will be mutually cis to each other as well as trans to
the good trans labilising phosphines. The macrocycle–metal unit
may also be expected to be relatively resistant to phosphine disso-
ciation in comparison to analogues with acyclic or monodentate
phosphine ligands. These features are of interest in the stabilisation
of new classes of complexes of phosphorus ligands as well as in
applications such as catalysis. Currently, however, there are only
two triphosphorus macrocyclic ligand systems known as the free
ligands. The first reported is the 11-membered triphosphine (1,
Fig. 1) prepared as a mixture of stereoisomers by a high dilution
(non-template) method.1 We have previously reported the other
example,2 which is based upon the 12-membered symmetrical
1,5,9-triphosphacyclododecane (12-aneP3R3, 2, R = H) structure
originally prepared on a Group 6 metal tricarbonyl template by
Norman.3 As well as developing synthetic routes to a range of
tertiary phosphine derivatives and stereospecific liberations of the
free ligands, we have subsequently studied a range of complexes
of 12-aneP3R3 (R = alkyl, aryl) ligands including functionalised
derivatives (at P, R = pendant amine, ether).4 The M(CO)3 (M =
5
complexes of the form [(g -CpR)FeL3]+ (R = various alkyl/silyl
combinations) for which the syntheses and reactivities have been
extensively studied and there are numerous examples of analogous
complexes containing tertiary mono-phosphines,8 diphosphines,9
triphosphines,10 and phosphite ligands.11 These complexes appear
to offer advantages over previous templates based upon M(CO)3
(M = Cr, Mo, W) units; three features are of particular interest
to us. Firstly, variations in cyclopentadienyl ring substituents are
readily achieved and introduce the opportunity to vary the solu-
bility of template precursors as well as the steric influence over the
trans reaction sites (e.g. compressing P–Fe–P angles to predispose
the phosphines to form smaller ring sizes or alternatively the
introduction of chirality). Selective sequential incorporation of
precursor phosphines is known to be facile in these complexes
Fig. 1 Previously reported 11-membered (1) and 12-membered (2, R =
H) triphosphorus macrocycles.
School of Chemistry, Cardiff University, Cardiff, UK CF10 3AT. E-mail:
Edwardspg@cardiff.ac.uk
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allowing a wide range of precursor complex options including
alternative donors, substituents and ‘backbone’ functions and
˚
lastly, the smaller size of Fe(II) (ionic radius 0.76 A; covalent radius
˚
˚
Cr(0) and Mo(0) is 1.17 A and 1.29 A respectively) should allow
a closer approach of co-ordinated precursor phosphines and a
preference for smaller chelate (and hence macrocycle) ring sizes. In
addition, the kinetically inert d6 [(g -CpR)Fe]+ template should be
5
stable to the conditions of conventional radical or base promoted
hydrophosphinations and thus support a range of P–C bond
forming reactions. In this context, Wild has demonstrated the
deprotonation of co-ordinated phenylphosphine followed by alky-
lation with bromoethane to give the corresponding co-ordinated
5
ethylphenylphosphine in related [(g -CpR)Fe]+ complexes.12
Further to our report of preliminary results of this study,13 in this
paper, we present and discuss the syntheses of Fe(II) 12-aneP3R3
and primary phosphine complexes, their structural properties and
their reactivity in template supported intramolecular ring closure
reactions, and comparisons with (12-aneP3R3)Fe(II) complexes
prepared with ligand derived from our previously reported syn-
thesis.
Scheme 1 Reagents and conditions: i) H2PR, CH2Cl2, hm; ii) HPRRꢀ,
CH2Cl2, hm; iii) AIBN, C6H5Cl, 90 ◦C; iv) C2H4 (3 atm), AIBN, C6H5Cl,
90 ◦C; v) Na, NH3(l).
Results and discussion
Primary and secondary phosphine complexes
195, 8%], indicating that the cation sequentially loses phosphine
ligands. Complex 4 is a conductor in CH2Cl2 solution (KM = 14 X
cm2 mol−1) based upon a mono-nuclear cation and consistent with
a 1 : 1 electrolyte.
Crystallisation of 4 from an acetonitrile/diethyl ether mixture
gave X-ray diffraction quality crystals. The (a-methyl)vinylphos-
phine complex 4 is the only structurally characterised complex
containing three co-ordinated primary phosphines on a CpFe+
fragment; its molecular structure is shown in Fig. 2.
5
The photolytic substitution of benzene in (g -cyclopentadienyl)-
6
(g -benzene)iron(II) hexafluorophosphate by phenylphosphine
proceeds smoothly and quantitatively to give the tris-
5
phenylphosphine adduct, [(g -Cp)Fe(PhPH2)3]PF6, 3, which was
isolated as a light-yellow coloured powder. The 31P NMR spectrum
of 3 gives a triplet centred at d − 10 ppm (1JP–H = 344 Hz)
corresponding to the co-ordinated phosphines, and the expected
septet of the hexafluorophosphate anion centred at d − 144 ppm
1
(1JP–F = 711 Hz). In the H NMR spectrum, a quartet assigned
to the cyclopentadienyl protons (3JP–H = 2 Hz) is observed as well
as resonances assigned to phenyl protons and P–H protons (d
5.69 ppm, d, 3JP–H = 344 Hz) in the expected area ratios. A strong
peak (m(P–H)) is observed in the IR spectrum of 3, at 2314 cm−1 and
the mass spectrum shows a strong molecular ion [(M − PF6)+, 451,
100%]. The hexafluorophosphate salt, 3, has a molar conductivity
of 25 X cm2 mol−1 in CH2Cl2 solution, suggesting a 1 : 1 electrolyte.
In a similar fashion, photolysis of a dichloromethane suspen-
5
6
sion of [(g -C5H5)Fe(g -C6H6)][PF6] (Scheme 1) and excess (a-
methyl)vinylphosphine gave a deep-orange homogeneous solution
5
from which the product [(g -C5H5)Fe(H2PC3H5)3][PF6], 4, was
isolated. The tris-phosphine complex 4 gives a singlet and a septet
5
1
in the 31P{ H} NMR spectrum, at d − 4.42 ppm (co-ordinated
Fig. 2 The molecular structure of the cation in (g -cyclopentadienyl)-
phosphines) and d − 144 ppm (PF6−, 1JP–F = 711 Hz) respectively.
tris(a-methylvinylphosphine)iron(II) hexafluorophosphate, 4. Selected
◦
˚
bond lengths (A) and angles ( ): Fe(1)–C(4), 2.077(5); Fe(1)–C(3),
2.079(5); Fe(1)–C(1), 2.079(5); Fe(1)–C(2), 2.083(5); Fe(1)–C(5), 2.079(5);
Fe(1)–P(2), 2.162(1); Fe(1)–P(3), 2.175(1); Fe(1)–P(1), 2.176(1); C(6)–C(7),
1.329(8); C(6)–C(8), 1.496(8); C(9)–C(10), 1.321(8); C(9)–C(11), 1.492(7);
C(12)–C(13), 1.313(8); C(12)–C(14), 1.504(8). P(2)–Fe(1)–P(3), 91.74(5);
P(2)–Fe(1)–P(1), 93.61(6); P(3)–Fe(1)–P(1), 90.35(6); C(6)–P(1)–Fe(1),
121.50(2); C(9)–P(2)–Fe(1), 117.20(2); C(12)–P(3)–Fe(1), 117.82(2).
In the 31P NMR spectrum, the co-ordinated phosphines give
1
rise to a triplet (1JP–H = 336 Hz). In the H NMR spectrum,
cyclopentadienyl and P–H protons give rise to a quartet (d
4.54 ppm, 3JP–H = 2 Hz) and a doublet (d 5.16 ppm, 1JP–H = 336 Hz)
respectively; two further resonances (d 1.95, d 5.45 ppm) are in the
appropriate area ratio and are assigned to the vinyl-methyl and
methylene protons respectively.
5
The IR spectrum of 4 shows a strong, sharp absorption corre-
sponding to m(P–H) at 2319 cm−1, and the mass-spectrum shows a
decomposition pattern relating to [(M − PF6)+, 343, 75%], [(M −
H2PC3H5 − PF6)+, 269, 100%] and [(M − 2{H2PC3H5} − PF6)+,
The photolytic substitution of co-ordinated benzene in [(g -
C5H5)Fe(g -C6H6)][PF6] by three equivalents of allylphosphine
gives (g -cyclopentadienyl)tris(allylphosphine)iron(II) hexafluo-
rophosphate, 5, as an orange/yellow solid in quantitative yield.
6
5
434 | Dalton Trans., 2006, 433–441
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The 31P NMR spectrum shows a triplet (co-ordinated allylphos-
1
−
phine, JP–H = 328 Hz) at d − 9.05 ppm and a septet (PF6
,
1JP–F = 711 Hz) at d − 144 ppm. As with compounds 3 and 4
1
the H NMR spectrum of 5 has a similar quartet, due to the
cyclopentadienyl protons (3JP–H = 2 Hz) and a doublet due to the
P–H protons (1JP–H = 328 Hz); the allyl protons give rise to three
poorly resolved resonances at d 2.54, d 5.20 and d 5.82 ppm in a
ratio of 2 : 1 : 2. The IR spectrum of 5 shows a sharp, strong peak
at 2319 cm−1 corresponding to m(P–H), and the mass-spectrum (ES-
MS) only shows the cation, with no major degradation products,
[(M − PF6)+, 343, 100%]. 5 is a conductor in CH2Cl2 solution
5
with a molar conductivity of 25 X cm2 mol−1. Similarly, [(g -
6
C5H5)Fe(g -C6H6)][PF6] reacts with 2-methylpropenylphosphine
(methallylphosphine) to give yellow/orange 5b for which ana-
lytical, spectroscopic and conductivity data indicate a structure
5
directly analogous to 5. The reaction of allylphosphine with [(g -
5
C5H5)Fe(CH3CN)3][PF6] also gives rise to the tris-allylphosphine
adduct 5, but the substitution was not selective and the product was
obtained as a mixture with partially substituted products. More
forcing conditions result in degradation of allyl phosphines. It has
previously been noted that substitution of the first two acetonitrile
Scheme 2 Reagents and conditions: i) [(g -C5Me5)Fe(CO)2(CH3CN)]-
5
[BF4], THF, hm or Cp2Fe2(CO)4 + [Cp2Fe][BF4], THF, hm; ii) [(g -C5Me5)-
Fe(CO)2(CH3CN)][BF4], THF, hm; iii) [Fe(CH3CN)6][BF4]2, CH3CN/
CH2Cl2.
composition is also confirmed by analytical data. The 31P{ H}
1
5
ligands in [(g -C5H5)Fe(CH3CN)3]+ proceeds more readily than the
NMR spectrum of 7 shows a singlet at d 36 ppm corresponding
to the co-ordinated phosphines. The 1H NMR spectrum of 7
gives rise to broad and complex resonances due to coincident and
overlapping multiplets but is consistent with other 12-aneP3Et3
last and that ‘mixed’ complexes are readily formed.14
In a similar manner to the synthesis of 5, the reaction of
5
6
[(g -C5H5)Fe(g -C6H6)][PF6] with rac-allyl(phenyl)phosphine also
proceeds to give the corresponding tris-phosphine complex 6,
quantitatively. Since racemic secondary phosphine was used, there
are a number of possible diasteromers of 6 and NMR spectra were
complexes. The 13C{ H} NMR spectrum shows resonances due
1
to co-ordinated macrocycle and ethyl groups. 7 is poorly soluble
in most solvents with which it does not react, except acetonitrile
and nitromethane. The m(C–N) absorptions in the IR spectrum
of 7 are observed at 2290 cm−1 and 2330 cm−1, as expected for a
complex of this nature with approximate C3v symmetry and in close
agreement with an analogous tripodal phosphine complex, [4-
MeOC6H4CH2C(CH2PPh2)3Fe(NCMe)3](BF4)2, which has m(C–
N) stretching frequencies at 2288 cm−1 and 2324 cm−1.16 Crystals
suitable for X-ray diffraction studies were readily obtained and the
molecular structure of 7 is shown in Fig. 3 together with selected
bond lengths and angles.
1
correspondingly complex. In the 31P{ H} NMR spectrum, four
broad resonances were observed in the region expected for co-
ordinated secondary phosphines and each gave rise to a doublet
(1JP–H = 346 Hz) in the 31P NMR spectrum. The IR spectrum
of 6 showed a single, strong, but broad absorption for m(P–H) at
2303 cm−1. The salt is a 1 : 1 electrolyte in dichloromethane and
an intense molecular ion was observed in the mass-spectrum.
Direct formation of iron(II) 12-aneP3R3 complexes
5
Reaction of the pentamethylcyclopentadienyl precursor [(g -
Since the steric properties of the cyclopentadienyliron cationic
complexes (and substituted cyclopentadienyl derivatives) may be
anticipated to influence subsequent intermolecular cyclisations of
primary alkenyl phosphines, it is of interest to compare relevant
iron complexes with sterically non-demanding ligands with those
bearing more sterically demanding cyclopentadienyl ligands. For
this purpose, halogeno and acetonitrile complexes should be
readily accessible by reaction of suitable iron precursors with the
free macrocycle.
The reaction of 12-aneP3Et3 with hexa(acetonitrile)iron(II)
bis(tetrafluoroborate) is more straightforward and proceeds
rapidly and in high yield at room temperature to give
the half-sandwich (piano-stool) compound [fac-(12-aneP3Et3)-
Fe(CH3CN)3][BF4]2, 7 (Scheme 2). In the presence of excess
macrocycle, there is no evidence of alternative species such as
the bis-macrocycle complex in contrast to the behaviour noted
for the related trithiacyclononane.15 7 may be isolated as a
yellow powder, which on crystallisation from acetonitrile/diethyl
ether forms deep-orange crystals. 7 has a molar conductivity
of 275 X cm2 mol−1 in CH3CN solution, consistent with it
being a 2 : 1 electrolyte (based on a mono-nuclear cation); its
C5Me5)Fe(CO)2(CH3CN)][BF4] with 12-aneP3Et3 under UV irra-
diation gave the mixed sandwich compound [(g -C5Me5)Fe(12-
5
aneP3Et3)][BF4], 8 as expected, in high yield (80%). Complex 8
is a conductor in CH2Cl2 solution with a molar conductivity of
50 X cm2 mol−1, based upon a mono-nuclear cation, confirming
that the complex is a 1 : 1 electrolyte. 8 gives a single resonance at
d 32.9 ppm in the 31P NMR spectrum, and has a mass spectrum
showing the molecular ion [(M − BF4)+, 497, 100%]. Crystalli-
sation of 8 from an acetonitrile/diethyl ether mixture afforded
crystals suitable for X-ray diffraction studies. The structure of 8
with selected bond angles and lengths is shown in Fig. 4.
Template assisted formation of iron(II) macrocycle complexes
A number of ring-closing methods for the template assisted
5
formation of macrocycles were investigated. Reaction of [(g -
t
C5H5)Fe(PhPH2)3][PF6], 3 with six equivalents of BuOK and
three equivalents of 1,3-dibromopropane, either sequentially or
simultaneously leads to a large array of products which could
not be separated and a complex of the target macrocycle,
triphenyltriphosphacyclododecane, could not be identified.
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to be similar to those expected for a co-ordinated triphosphacy-
clononane macrocycle, the tri-primary phosphine complex failed
to cyclise in a range of different solvents, radical initiators or
photolysis, reaction times and temperatures (e.g. 120 ◦C for 7 days);
these attempts led to recovery of 4 or decomposition.
Intramolecular hydrophosphinations of the tris-allylphosphine
derivative 5 proceed differently however. Heating 5 in a suitable
solvent in the presence of a radical initiator gives rise to the
cyclised tri-secondary phosphine macrocycle complex 9, which
was isolated as a yellow powder. A sharp singlet is observed in the
1
31P{ H} NMR spectrum at d 12.7 ppm; the 31P NMR spectrum
is a doublet (1JP–H = 336 Hz) confirming this peak to be due to
secondary phosphines. There is also the expected septet attributed
to the hexafluorophosphate anion. The 1H NMR spectrum shows
two resonances for the backbone methylene protons as complex
and broadened multiplets at d 1.60 and 1.90 ppm in a ratio of 2 :
1 respectively and a doublet assigned to the P–H proton at d 4.80
(1JP–H = 336 Hz); as before, the cyclopentadienyl protons give rise
3
Fig. 3 The molecular structure of the cation in tris(acetonitrile)(g -1,5,9-
3
to a quartet (d 4.64 ppm, JP–H = 2 Hz). The m(P–H) absorption
triethyl-1,5,9-triphosphacyclododecane)iron(II) bis(tetrafluoroborate), 7.
in the IR spectrum is readily identified (2303 cm−1). The mass
spectrum of 9 also shows the cation, with no major degradation
products, [(M − PF6)+, 343, 100%]. The molar conductivity of 9
is 32 X cm2 mol−1, consistent with a 1 : 1 electrolyte.
◦
˚
Selected bond lengths (A) and angles ( ): Fe(1)–N(2), 1.956(4); Fe(1)–N(3),
1.960(4); Fe(1)–N(1), 1.971(5); Fe(1)–P(1), 2.215(2); Fe(1)–P(3), 2.220(2);
Fe(1)–P(2), 2.225(2); N(1)–C(16), 1.117(6); N(2)–C(18), 1.131(6);
N(3)–C(20), 1.120(6). N(2)–Fe(1)–N(3), 86.22(18); N(2)–Fe(1)–N(1),
88.33(18); N(3)–Fe(1)–N(1), 86.09(18); N(2)–Fe(1)–P(1), 90.14(14); N(3)–
Fe(1)–P(1), 175.43(14); N(1)–Fe(1)–P(1), 91.05(14); N(2)–Fe(1)–P(3),
89.72(14); N(3)–Fe(1)–P(3), 91.33(14); N(1)–Fe(1)–P(3), 176.86(14);
P(1)–Fe(1)–P(3), 91.41(7); N(2)–Fe(1)–P(2), 175.82(13); N(3)–Fe(1)–P(2),
91.23(13); N(1)–Fe(1)–P(2), 88.19(13); P(1)–Fe(1)–P(2), 92.24(6); P(3)–
Fe(1)–P(2), 93.65(7); C(16)–N(1)–Fe(1), 176.0(5); N(1)–C(16)–C(17),
178.5(7); C(18)–N(2)–Fe(1), 175.4(5); N(2)–C(18)–C(19), 179.0(7);
C(20)–N(3)–Fe(1), 171.3(5); N(3)–C(20)–C(21), 177.4(6).
Cyclisation reactions of 5 were shown to be solvent dependent.
In THF, the intermediates and final product have low solubilities
and precipitated during the reaction giving rise to correspondingly
poor yields. In anisole, reasonable yields were obtained, although
the reaction was relatively slow and intermediates predominated
after extended reaction times. Chlorobenzene was found to be
the most successful, and yields of 40% for the final macrocyclic
product were recorded.
1
The cyclisation was monitored by 31P and 31P{ H} NMR
spectroscopy, and if stopped prior to completion, the starting
material, intermediates, and final product were all observed. These
NMR spectra are remarkably similar to those obtained from
the analogous partially completed Cr(0) and Mo(0) template
cyclisations. For Mo and Cr, this behaviour has been explained
by stepwise P–C bond formation as the reaction proceeds, giving
rise to acyclic phosphine intermediate complexes bearing both sec-
ondary and primary phosphine ligands (clearly two intermediates
are feasible).3,4d The spectra obtained from the reaction of 5 (under
similar conditions to that of Mo or Cr) also indicate that the iron
template behaves similarly.
In a similar fashion and despite the mixture of diastereomers,
the radical (AIBN) promoted intramolecular hydrophosphination
of the allyl functions in 6, gave rise to a number of products from
which the desired 1,5,9-triphenyl-1,5,9-triphosphacyclododecane
5
macrocycle complex, [(g -C5H5)Fe(12-aneP3Ph3)][PF6] 10, can be
5
Fig. 4 The molecular structure of the cation in (g -pentamethylcyclo-
isolated in moderate (30%) yield as a yellow/orange powder. The
identity of 10 is also confirmed by its alternative preparation
directly from the free triphenyl macrocycle;17 reaction of syn,syn-
3
pentadienyl )(g - 1,5,9 - triethyl - 1,5,9 - triphosphacyclododecane )iron(II )
tetrafluoroborate, 8. Selected bond lengths (A) and angles (◦):
˚
Fe(1)–C(2), 2.135(10); Fe(1)–C(1), 2.150(10); Fe(1)–C(5), 2.121(11);
Fe(1)–C(4), 2.147(11); Fe(1)–C(3), 2.165(10); Fe(1)–P(2), 2.204(3);
Fe(1)–P(3), 2.213(3); Fe(1)–P(1), 2.214(3). P(2)–Fe(1)–P(3), 89.67(12);
P(2)–Fe(1)–P(1), 89.78(12); P(3)–Fe(1)–P(1), 91.78(11).
5
1,5,9-triphenyl-1,5,9-triphosphacyclododecane with [(g -C5H5)-
6
Fe(g -C6H6)][PF6] under photolytic conditions allowed the iso-
lation of 10 in high yield. The 31 P NMR spectrum of 10 shows a
singlet at d 35 ppm assigned to the tertiary phosphines of the co-
ordinated triphenyl-macrocycle and the expected resonance due
In an attempt to cyclotrimerise the co-ordinated a-methyl-
(vinyl)phosphine ligands in 4, to give the respective triphos-
phacyclononane complex, several experimental methods were
attempted. Although the non-bonded P–P distances in 4 appear
−
1
to the PF6 counter-ion (d − 144 ppm, septet, JP–F = 711 Hz).
Again, there is a characteristic quartet (3JP–H = 2 Hz) due to
the cyclopentadienyl protons in the 1H NMR spectrum of 10
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1
1
and there are two broad resonances in both the H and 13C{ H}
NMR spectra attributable to the backbone methylenes indicating
the equivalence of the P-bonded carbons and their protons. The
IR spectrum of the material obtained by either method shows
the absence of m(P–H) absorptions, as expected. The macrocycle
complex 10 is a 1 : 1 electrolyte in CH2Cl2 and shows an intense
molecular ion in the mass-spectrum (ES-MS) with no identifiable
degradation products, [(M − PF6)+, 571, 100%].
For complex 4, the average P–P non-bonded distance
(3.120(2) A) is significantly shorter than in the Cr(0) and Mo(0)
˚
˚
˚
analogues (3.30 A and 3.49 A respectively). The metal–phosphorus
˚
distances in 4 are shorter (average 2.171(1) A) than those in the
˚
Cr(0) and Mo(0) analogues (averages: 2.326(2) and 2.501(1) A
respectively), although, the average P–M–P bond angle in the Fe
complex (91.90(6)◦) is slightly larger than for Cr(0) (91.09(5)◦) and
significantly larger than that for Mo(0) (88.47(4)◦).7 The structure
confirms that the CpFe+ fragment does indeed enable closer P–P
approaches than in the Cr/Mo(CO)3 analogues. The non-bonded
P · · · P distances in 4 are also very close to the observed S · · · S
In a manner similar to the synthesis of the tritertiary phosphine
macrocycle on either the Cr or Mo templates,2 the reaction
of 9 with excess ethene, in the presence of a radical initiator
(AIBN), proceeds smoothly to give the co-ordinated 1,5,9-triethyl-
5
non-bonded distances in the related (g -cyclopentadienyl)(1,4,7-
18
5
˚
trithiacyclononane)iron(II) cation (average 3.14 A). Other pa-
1,5,9-triphosphacyclododecane ligand complex, [(g -C5H5)Fe(12-
rameters in the structure of 4 are unremarkable and a relatively
regular piano-stool arrangement is observed in which the planes
containing the three phosphines and the five carbons of the
cyclopentadienyl ligand are close to parallel with a dihedral angle
of 1.7◦ (1.6◦ for Fe(1) and 1.8◦ for Fe(2)).
The two cyclopentadienyl macrocycle complexes 8 and 11
clearly have closely related ‘sandwich’ structures. Comparisons
of structural parameters are of interest however since these two
examples allow an analysis of the significance of steric influences
of substituted cyclopentadienyl ligands. In the ‘parent’ cyclopen-
aneP3Et3)][BF4], 11. Alternatively, 11 may be prepared by reaction
of the free tritertiary phosphine macrocycle ligand with a number
of mono-cyclopentadienyl precursor complexes in yields up to
80%. In either case, 11 is isolated as an orange crystalline solid with
identical spectroscopic and analytical properties. The 31P NMR
spectrum consists of a temperature-invariant singlet at d 38 ppm
indicating magnetically equivalent phosphines and the absence of
secondary phosphines. The cyclopentadienyl protons appear as a
quartet in the 1H NMR spectrum, centred at d 4.26 ppm (3JP–H
=
2 Hz). The molar conductivity of 11 in CH2Cl2 was 40 X cm2 mol−1,
again consistent with a 1 : 1 electrolyte and the mass spectrum of
11 shows the molecular cation as the main peak, i.e. [(M − BF4)+,
427, 100%]. 11 is soluble in most polar solvents, and is readily
crystallised from such solvents. The molecular structure of 11 is
shown in Fig. 5.
˚
tadienyl derivative 11, the average Fe–P distances (2.194(2) A) are
only marginally shorter than in the pentamethylcyclopentadienyl
˚
analogue 8 (2.210(3) A). The average Fe–C distances are a little
˚
˚
longer in 8 (2.144(11) A) than they are in 11 (2.100(5) A). This
slight expansion of Fe–ligand distances in 8 with respect to 11
is consistent with a higher steric demand in the former Cp*
complex. Perhaps of more significance however are the P–Fe–
P angles which in 8 are significantly compressed with respect to
those in 11 (averages: 90.41(12)◦ and 92.61(6)◦ respectively). These
differences lead to a small but significant decrease in the average
˚
˚
non-bonded P · · · P distances (3.171(3) A in 11 and 3.137(4) A in 8)
as the steric bulk of the ancillary cyclopentadienyl ligand increases.
In addition, the non-bonded P · · · P distances in 11 are similar
to those in 4 indicating that the constraints of the macrocycle
backbone do not have a major influence in restricting the freedom
of the phosphorus atoms to adopt a favourable bonding position.
This relative trend in steric influence upon the phosphines ap-
pears to be further supported by comparisons with the structure of
the tris-acetonitrile compound 7. In 7, the trans acetonitrile ligands
will have about as little a steric influence upon the phosphines
as is possible, however the average Fe–P distance (2.220(2)
˚
A) is slightly longer than in 11 although the average P–Fe–P
angle (92.43(7)◦) is similar. A steric origin of this relative bond
lengthening in 7 appears unsupportable and is more likely due
to electronic factors; acetonitrile is probably a better r-donor in
these systems than is cyclopentadienyl which might be expected
to lead to a higher trans influence as observed. This leads to an
increase in the average non-bonded P · · · P distance in 7 (3.206(3)
5
Fig. 5 The molecular structure of the cation in (g -cyclopentadienyl)-
3
(g -1,5,9-triethyl-1,5,9-triphosphacyclododecane)iron(II) hexafluorophos-
phate, 11. Selected bond lengths (A) and angles (◦): Fe(1)–C(3),
˚
2.088(5); Fe(1)–C(2), 2.098(5); Fe(1)–C(1), 2.102(5); Fe(1)–C(5),
2.109(5); Fe(1)–C(4), 2.103(5); Fe(1)–P(3), 2.183(2); Fe(1)–P(1), 2.188(2);
Fe(1)–P(2), 2.211(2). P(3)–Fe(1)–P(1), 92.06(6); P(3)–Fe(1)–P(2), 95.43(6);
P(1)–Fe(1)–P(2), 90.34(6).
˚
A) in comparison to 11. In other respects, the structure of 7
is unremarkable. The trends in structural data discussed above
do indicate that not only does reducing the size of the metal
ion/atom decrease the non-bonded P · · · P distances, but so does
the steric influence of the ancillary ‘spectator’ ligands. The ability
to manipulate steric properties to useful effect is absent in the
metal–tricarbonyl templates previously reported and the use of
cyclopentadienyl–metal templates introduces another potentially
Structural studies
The crystal structures of complexes (4), (7), (8) and (11) confirm
the distorted fac-octahedral co-ordination environment around
the iron centre in each case.
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Dalton Trans., 2006, 433–441 | 437
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very useful control over template supported ring closure reactions
of these types.
NMR, d (ppm): 81.1 (s, cyclopentadienyl C’s); 126.5, 129.9, 131.4,
132.8 (all s, phenyl C’s).
(g5-Cyclopentadienyl)tris(a-methylvinylphosphine)iron(II) hexa-
fluorophosphate, 4. Analysis found (calculated): C, 34.6 (34.45);
H, 5.5 (5.37%). MS(ES), m/z: [(M − PF6)+, 343, 75%], [(M −
PF6 − H2PC3H5)+, 269, 100%], and [(M − PF6 − 2H2PC3H5)+, 195,
8%]. IR: m(P–H) = 2319 cm−1 (KBr disc). KM = 14 X cm2 mol−1.
Experimental
Techniques and instruments
All reactions were carried out in an atmosphere of dry ni-
trogen. All solvents were dried by refluxing over conventional
1
31P NMR, d (ppm): −4.42 (t, JP–H = 336 Hz, cation); −144.44
(septet, 1JP–F = 711 Hz, anion). 1H NMR, d (ppm): 1.95 (d, 2JH–H
=
drying agents. The compounds [(g -C5H5)Fe(g -C6H6)][PF6],19
a-methyl(vinyl)phosphine,20 (2-methylpropenyl)phosphine and
allylphosphine,21 phenylphosphine,22 allyl(phenyl)phosphine,23
syn,syn-1,5,9-triethyl-1,5,9-triphosphacyclododecane,2 syn,syn-
1,5,9-triphenyl-1,5,9-triphosphacyclododecane,17 were prepared
5
6
40 Hz, H2PC(CH3)CH2); 4.54 (q, 3JP–H = 2 Hz, Cp–H); 5.16 (d br
1
1
m, JP–H = 336 Hz, P–H); 5.45 (c m, H2PC(CH3)CH2). 13C{ H}
NMR, d (ppm): 22.8 (s, H2PC(CH3)CH2); 79.1 (s, cyclopenta-
dienyl C); 124.9 (s, H2PC(CH3)CH2); 128.0 (d, JP–C ≈ 56 Hz,
1
H2PC(CH3)CH2).
5
6
by literature methods. [(g -C5H5)Fe(g -C6H6)][PF6] was purified by
extraction into acetone, filtration through Celiteꢀ and evaporation
R
(g5-Cyclopentadienyl)tris(allylphosphine)iron(II) hexafluorophos-
phate, 5. Analysis found (calculated): C, 34.5 (34.45); H, 5.3
(5.37%). MS(ES), m/z: [(M − PF6)+, 343, 100%]. IR: m(P–H) =
2319 cm−1/KBr disc. KM = 25 X cm2 mol−1. 31P NMR, d (ppm):
in vacuo followed by recrystallisation from an acetone/diethyl
ether mixture in order to remove aluminium containing impurities.
All other reagents were obtained from the Aldrich Chemical
Company and, where appropriate, were degassed before use.
NMR spectra were recorded on a Bruker WM360 instrument
operating at 360.13 (1H), 90.53 (13C) MHz or a JEOL FX-90
instrument operating at 36.23 (31P) MHz. All NMR spectra were
recorded in CDCl3 solution except where noted, with the 1H
and 13C NMR chemical shifts quoted in ppm relative to solvent
and 31P NMR chemical shifts quoted in ppm relative to 85%
external H3PO4. The infrared spectra were recorded in Nujol,
or as KBr discs on a Perkin-Elmer 783-IR spectrometer. Mass
spectra and microanalyses were obta◦ined within this department.
Conductivities were measured at 25 C using 5 × 10−5 mol dm−3
solutions. UV photolyses were performed with a Hanovia 125 W
mercury discharge lamp at room temperature under a N2 stream.
1
1
−9.05 (t, JP–H = 328 Hz, cation); −144 (septet, JP–F = 711 Hz,
anion). 1H NMR, d (ppm): 2.54 (m, H2PCH2CHCH2); 4.56 (br d,
1JP–H = 328 Hz, H2PCH2CHCH2); 4.55 (q, 3JP–H = 2 Hz, Cp–H);
1
5.20 (m, H2PCH2CHCH2); 5.82 (m, H2PCH2CHCH2). 13C{ H}
1
NMR, d (ppm): 28.2 (d, JP–C = 40 Hz, H2PCH2CHCH2); 80.1
(s, cyclopentadienyl C’s); 119.7 (s, H2PCH2CHCH2); 133.9 (s,
H2PCH2CHCH2).
(g5 -Cyclopentadienyl)tris(2-methylpropenylphosphine)iron(II )
hexafluorophosphate, 5b. Analysis found (calculated): C, 38.4
(38.51); H, 6.2 (6.08%). MS(ES), m/z: [(M − PF6)+, 385, 40%].
IR: m(P–H) = 2306 cm−1/KBr disc. KM = 25 X cm2 mol−1. 31P
1
NMR, d (ppm): −13.35 (t, JP–H = 332 Hz, cation); −143.80
1
1
(septet, JP–F = 711 Hz, anion). H NMR, d (ppm): 1.80 (br s,
H2PCH2C(CH3)CH2); 2.52 (br s, H2PCH2C(CH3)CH2); 4.63 (br
Preparation of complexes 3, 4, 5, 5b and 6
3
1
q, JP–H = 2 Hz, Cp–H); 4.74 (d br m, JP–H = 332 Hz, P–H);
4.93 (d m, 2JH–H = 11 Hz, H2PCH2C(CH3)CH2). 13C{ H} NMR,
1
The syntheses of these complexes were very similar and so a
general method is described. To a frozen solution of phosphine
[1.20 × 10−3 mol, phenylphosphine (3), (a-methyl)vinylphosphine
(4), allylphosphine (5), (2-methyl)propenylphosphine (5b),
and (allyl)phenylphosphine (6)] in CH2Cl2 (50 ml) was
1
d (ppm): 22.2 (s, H2PCH2C(CH3)CH2); 31.7 (d, JP–C ≈ 50 Hz,
H2PCH2C(CH3)CH2); 79.3 (s, cyclopentadienyl C); 114.7 (s,
H2PCH2C(CH3)CH2); 141.3 (s, H2PCH2C(CH3)CH2).
rac-(g5-Cyclopentadienyl)tris(allylphenylphosphine)iron(II) hexa-
fluorophosphate, 6. Analysis found (calculated): C, 53.9 (53.67);
5
6
added (g -cyclopentadienyl)(g -benzene)iron(II) hexafluorophos-
phate (2.91 × 10−4 mol, 0.10 g). The mixture was allowed to
warm to room temperature and was photolysed, with stirring for
8 hours at ambient temperature using an incandescent tungsten
lamp (white light, 150 W). Following removal of solvent and
unreacted phosphine in vacuo, the product remained as a powder
(varying from light-yellow to deep-orange depending upon the
phosphine) in almost quantitative yields (>90% yield in all cases).
Purification was by recrystallisation from acetonitrile/diethyl
ether mixtures, except 6, where the crude product was purified
by column chromatography (silica gel, 2% MeOH in CH2Cl2).
+
H, 5.4 (5.31%). MS(ES), m/z: [{(g5-C5H5)Fe(PhPHC3H5)3} , 571,
100%]. IR: m(P–H) = 2303 cm−1 (KBr disc). KM = 39 X cm2 mol−1.
1
31P{ H} NMR, d (ppm): 55.79, 57.19, 61.28, 63.11 (all br d, all
1
1
1JP–H = 346 Hz, P–H); −144 (septet, JP–F = 711 Hz, anion). H
3
NMR, d (ppm): 2.5 (br m, PhHPCH2CHCH2); 4.42 (q, JP–H
=
1
2 Hz, Cp–H’s); 4.64 (br d, JP–H = 346 Hz, P–H); 5.25 (br
m, PhHPCH2CHCH2); 5.6 (br m, PhHPCH2CHCH2); 7.3 (m,
phenyl H’s). 13C{ H} NMR, d (ppm): 27.9 (br d, 1JP–C ≈ 40 Hz),
1
PhHPCH2CHCH2); 79.7 (br s, cyclopentadienyl C’s); 120.5 (br s,
PhHPCH2CHCH2); 135.2 (br s, PhHPCH2CHCH2) [127.4 (s),
130.4 (d), 131.7 (s), 132.8 (s), phenyl C’s, doublet is the ipso C.]
(g5 -Cyclopentadienyl)tris(phenylphosphine)iron(II) hexafluoro-
phosphate, 3. Analysis found (calculated): C, 46.2 (46.34); H, 4.6
(4.40%). MS(ES), m/z: [(M − PF6)+, 451, 100%]. IR: m(P–H) =
2314 cm−1/KBr disc. KM = 24.90 X cm2 mol−1. 31P NMR, d (ppm):
−9.91 (t, 1JP–H = 344 Hz, cation); −144.00 (septet, 1JP–F = 711 Hz,
Preparation of tris(acetonitrile)(g3-1,5,9-triethyl-1,5,9-
triphosphacyclododecane)iron(II) bis(tetrafluoroborate), 7
[Fe(CH3CN)6][BF4]2 (0.233 g, 4.90 × 10−4 mol) was dissolved in
a mixture of acetonitrile (20 ml) and dichloromethane (20 ml).
To this was added 1,5,9-triethyl-1,5,9-triphosphacyclododecane
1
3
anion). H NMR, d (ppm): 4.48 (q, JP–H = 2 Hz, Cp–H); 5.69
1
1
(d br m, JP–H = 344 Hz, P–H); 7.35 (c m, phenyl H’s). 13C{ H}
438 | Dalton Trans., 2006, 433–441
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(0.150 g, 4.90 × 10−4mol) as a solution in CH2Cl2 (10 ml), the
colour of the solution immediately became orange. The solution
was stirred for 1 hour, and the solvent removed in vacuo leaving
an oily residue of 7, which was washed with diethyl ether (2 ×
20 ml). The resultant powder was recrystallised from a mixture
of acetonitrile with diethyl ether to give X-ray quality crystals
(0.134 g, 63% yield). Analysis found (calculated): C, 38.3 (38.49);
H, 6.4 (6.27%). MS(ES), m/z: no assignable peaks. IR: m(C–N) =
The crude product was isolated as an orange powder following
removal of solvent and washing with diethyl ether (2 × 20 ml).
Column chromatography using basic alumina with CH2Cl2 and
methanol (0.2% by volume) as eluant yielded the desired product
(0.030 g, 30% yield). The cyclo-trimerisation may also be carried
out in other polar solvents including chlorobenzene or anisole but
the reaction is less efficient. Analysis found (calculated): C, 53.7
(53.60); H, 5.4 (5.31%). MS(ES), m/z: [(M − PF6)+, 571, 100%].
1
2290 cm−1 and 2330 cm−1 (KBr disc). KM = 275 X cm2 mol−1. 31
P
KM, 36 X cm2 mol−1. 31P{ H} NMR, d (ppm): 35.00 (s). 1H NMR, d
1
NMR, d (ppm): 36.21 (s, cation). H NMR, d (ppm): 1.06 (m,
PCH2CH3); 1.65 (br m, PCH2CH3 and PCH2CH3CH2P); 1.83 (br
(ppm): 1.85 (br m, PCH2CH3CH2P); 2.05 (br m, PCH2CH2CH2P);
3
1
4.20 (q, JP–H = 2 Hz, Cp–H’s); 7.34 (c m, phenyl H’s). 13C{ H}
NMR, d (ppm): 24.0 (br s, PCH2CH2CH2P); 29.1 (d, 1JP–C ≈ 40 Hz,
PCH2CH2CH2P); 79.7 (s, cyclopentadienyl C’s) [127.1 (s), 130.2
(d), 131.4 (s), 132.9 (s); phenyl C’s, doublet is the substituted C.]
1
m, PCH2CH2CH2P); 1.93 (s, CH3CN). 13C{ H} NMR, d (ppm):
3.8 (s, CH3CN) 16.2 (s, PCH2CH3); 22.8 (br s, PCH2CH2CH2P);
23.4 (d, 1JP–C ≈ 50 Hz); 26.4 (d, 1JP–C ≈ 50 Hz, PCH2CH2CH2P);
129.8 (s, CH3CN).
Alternative preparation of (g5-cyclopentadienyl)(g3-1,5,9-
triphenyl-1,5,9-triphosphacyclododecane)iron(II)
hexafluorophosphate, 10
Preparation of (g5-pentamethylcyclopentadienyl)(g3-1,5,9-triethyl-
1,5,9-triphosphacyclododecane)iron(II) tetrafluoroborate, 8
[(g -C5Me5)Fe(CO)2(CH3CN)][BF4] (0.123 g, 3.27 × 10−4 mol)
5
A
solution of 1,5,9-triphenyl-1,5,9-triphosphacyclododecane
and 1,5,9-triethyl-1,5,9-triphosphacyclododecane (0.110 g, 3.59 ×
10−4 mol, in 10 ml of THF) were dissolved in THF (100 ml), and the
solution irradiated (UV, 3 hours). The orange solution was filtered
(0.100 g, 2.2 × 10−4 mol, in 10 ml of THF) was added to a solution
of [(g -C5H5)(g -C6H6)Fe][PF6] (0.076 g, 2.2 × 10−4 mol), and the
mixture irradiated (UV, 8 hours). Removal of solvent in vacuo and
recrystallisation from an acetonitrile/diethyl ether mixture gave 10
as an orange powder (0.158 g, 80% yield). Analytical data matched
that found for the product obtained from 6 described above.
5
5
R
through Celiteꢀ and the solvent removed in vacuo to leave 9 as a
dark orangepowder. Recrystallisation froman acetonitrile/diethyl
ether mixture yielded crystals of X-ray diffraction quality (0.150 g,
80% yield). Analysis found (calculated): C, 51.2 (51.40); H, 8.1
(8.28%). MS(ES), m/z: [(M − BF4)+, 497, 100%]. KM = 50 X
Preparation of (g5-cyclopentadienyl)(g3-1,5,9-triethyl-1,5,9-
triphosphacyclododecane)-iron(II) hexafluorophosphate, 11
1
cm2 mol−1. 31P{ H} NMR, d (ppm): 32.86 (s). 1H NMR, d (ppm):
1.15 (br m, PCH2CH3), 1.50 (br m, PCH2CH3), 1.65 (s, Cp–CH3),
1.68 (br m, PCH2CH2CH2P), and 1.92 (br m, PCH2CH2CH2P).
Complex 9 (0.100 g, 2.05 × 10−4 mol) was dissolved in chloroben-
zene (∼50 ml) and transferred to a 500 ml steel autoclave,
containing AIBN (∼1–2% molar equivalent). The vessel was
pressurised with ethene (3 atm), and the sealed autoclave was
heated at 90 ◦C for 8 hours. Following cooling and venting the
solvent was removed in vacuo and the residue crystallised from ace-
tonitrile/diethyl ether to give 11 as a deep-orange microcrystalline
solid (0.111 g, 95% yield). Analysis found (calculated): C, 47.0
1
13C{ H} NMR, d (ppm): 9.0 (s, Cp–CH3); 14.8 (s, PCH2CH3); 22.9
(br s, PCH2CH2CH2P); 27.8 (d, 1JP–C ≈ 40 Hz, PCH2CH2CH2P);
78.4 (br s, cyclopentadienyl C’s).
Preparation of (g5-cyclopentadienyl)(g3-1,5,9-
triphosphacyclododecane)iron(II) hexafluorophosphate, 9
5 (0.100 g, 2.05 × 10−4 mol) and AIBN (∼1–2% molar equivalent)
were dissolved in chlorobenzene (∼70 ml), giving a yellow
homogeneous solution which was stirred at 90 ◦C for 8 hours. After
cooling to ambient temperature and removal of the solvent under
reduced pressure. the residue was extracted into CH2Cl2, filtered
and the solvent again removed to yield 9 as a light yellow powder
(0.040 g, 40% yield). Analysis found (calculated): C, 34.1 (34.45);
H, 5.1 (5.37%). MS(ES), m/z: [(M − PF6)+, 343, 100%]. IR: m(P–
H) = 2303 cm−1 (KBr disc). KM = 32 X cm2 mol−1. 31P NMR, d
(46.74); H, 7.6 (7.45%). MS(ES), m/z: [(M − PF6)+, 427, 100%].
KM, 40 X cm2 mol−1. 31P: 38.09 (s, cation); −145 (septet, JP–F
=
1
711 Hz, anion). 1H NMR, d (ppm): 1.28 (br m, PCH2CH3); 1.61 (br
m, PCH2CH3 and PCH2CH3CH2P); 1.87 (br m, PCH2CH2CH2P);
4.26 (q, JP–H = 2 Hz, Cp–H). 13C{ H} NMR, d (ppm): 14.6 (s,
3
1
1
PCH2CH3); 23.1 (br s, PCH2CH2CH2P); 28.2 (d, JP–C ≈ 40 Hz,
PCH2CH2CH2P); 78.9 (br s, cyclopentadienyl C’s).
1
1
Alternative preparations of (g5-cyclopentadienyl)(g3-1,5,9-triethyl-
1,5,9-triphosphacyclododecane)iron(II) hexafluorophosphate, 11
(ppm): 12.71 (d, JP–H = 336 Hz, cation); −145 (septet, JP–F
=
1
711 Hz, anion). H NMR, d (ppm): 1.60 (m, PCH2CH2CH2P);
3
1.90 (m, PCH2CH2CH2P); 4.40 (q, JP–H = 2 Hz, Cp–H’s); 4.80
Route 1. Cp2Fe2(CO)4 (0.058 g, 1.64 × 10−4 mol) and
[Cp2Fe][BF4] (0.089 g, 3.27 × 10−4 mol) were suspended in
THF (50 ml). A solution of 1,5,9-triethyl-1,5,9-triphosphacyclo-
dodecane (0.100 g, 3.27 × 10−4 mol) in THF (10 ml), was added
dropwise, and the mixture allowed to stir for 2 hours, during
which time the colour changed from brown/blue to a dark
brown. The mixture was then irradiated (UV, 3 hours), during
which time the colour changed to give a homogeneous yellow
solution. The solvent was removed under reduced pressure, and
the residue washed with diethyl ether (2 × 20 ml). Recrystallisation
(br d, 1JP–H = 336 Hz, P–H). 13C{ H} NMR, d (ppm): 22.0 (br s,
1
1
PCH2CH2CH2P); 25.2 (d, JP–C ≈ 40 Hz, PCH2CH2CH2P); 79.5
(br s, cyclopentadienyl C’s).
Preparation of (g5-cyclopentadienyl)(g3-1,5,9-triphenyl-1,5,9-
triphosphacyclododecane)iron(II) hexafluorophosphate, 10
6 (0.100 g, 1.39 × 10−4 mol) was dissolved in chlorobenzene
(∼50 ml), and AIBN (∼1–2% molar equivalent) was added.
The mixture was heated at 90 ◦C for 48 hours giving crude 10.
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from acetonitrile/diethyl ether gave orange crystals of X-ray
crystallographic quality (0.138 g, 82% yield).
diethyl ether (3 × 40 ml) gave rise to a yellow organic phase
which was washed with water (2 × 40 ml) to remove residual
salts. The organic phase was dried (MgSO4) and the solvent
removed in vacuo to give the crude macrocycle as a mixture with
cyclopentadiene. The triphosphine ligand was obtained as white
crystals by recrystallisation from a saturated solution in diethyl
ether (0.014 g, 30% yield). Spectroscopic and analytical data were
identical to those previously reported.4
Route 2. CpFe(CO)2I (0.099 g, 3.27 × 10−4 mol) and AgBF4
(64 mg, 3.27 × 10−4 mol) were dissolved in CH2Cl2 (50 ml),
and 1,5,9-triethyl-1,5,9-triphosphacyclododecane (0.100 g, 3.27 ×
10−4 mol, in CH2Cl2 (10 ml) was added by syringe. The mixture was
refluxed for 8 hours, and after cooling, the solution was filtered to
remove AgI leaving a homogeneous yellow solution. The solvent
was then removed in vacuo, and the residue recrystallised from
acetonitrile/diethyl ether (0.146 g, 87% yield).
Crystallography
Route 3. A solution of 1,5,9-triethyl-1,5,9-triphosphacyclo-
dodecane (0.100 g, 3.27 × 10−4 mol, in 10 ml of THF) was added to
[(g5 -C5H5 )Fe(H2PC3H5 )3 ][PF6 ] (4), [fac-(12-aneP3Et3 )Fe-
(CH3CN)3][BF4]2 (7), [(g5-C5Me5)Fe(12-aneP3Et3)][BF4] (8) and
[(g5-C5Me5)Fe(12-aneP3Et3)][BF4] (11). Crystallographic data
for compounds 4, 7, 8 and 11 were recorded on a fast area
detector diffractometer using monochromatic Mo-Ka radiation
in a manner described previously.24 The unit-cell parameters for
each compound were determined by least-squares refinement of
the setting angles for 250 reflections. The structures of all four
compounds were solved by direct methods (SHELXS-96)25 and
refined on F2 by full-matrix least-squares methods (SHELXL-
97)26 using all unique data (following absorption correction using
DIFABS27). The F atoms of the PF6 (2) and BF4 (7, 8 and
11) anions are extensively disordered, and these were refined with
partial site occupancies. The C(3), C(4) and C(12) atoms in 4, the O
atom of the diethyl ether solvate in 11, and C(12)–C(15) and C(25)
atoms in 8 were also disordered, and similarly treated. All non-
hydrogen atoms were refined anisotropically, with ISOR restraints
being used for some of the atoms belonging to the disordered
groups in compounds 7, 8 and 11. The hydrogen atoms in all
structures were included in calculated positions (riding model),
except those on the disordered carbon atoms in 8. Diagrams
were drawn with ORTEP3 for Windows.28 The crystal data and
refinement results are summarised in Table 1.
5
5
a solution of [(g -C5H5)(g -C6H6)Fe][BF4] (3.27 × 10−4 mol), and
the mixture irradiated (UV, 8 hours). After removal of solvent
in vacuo and recrystallisation, 6 was obtained as an orange,
microcrystalline solid (84% yield).
Routes 1, 2, and 3 gave analytical and spectroscopic data
identical to that found for the product prepared via the new
template, as described above.
Liberation of syn,syn-1,5,9-triethyl-1,5,9-triphosphacyclododecane
and syn,syn-1,5,9-triphenyl-1,5,9-triphosphacyclododecane from
the ‘(g5-C5H5)Fe’ and ‘(g5-C5Me5)Feꢀ based templates
−
−
The liberation reactions where complexes 9, 10, and 11 were
degraded to their constituent ligands were very similar, and so
a general method is described. The cyclopentadienyl macrocycle
complex 9 (0.100 g, 1.75 × 10−4 mol) along with sodium metal
(1 g, large excess, Li can also be used) were dissolved in liquid
ammonia (approximately 50 ml) and the mixture stirred at
−78 ◦C for 8 hours following which the ammonia was allowed
to evaporate of its own accord. Methanolic digestion of the excess
sodium, followed by removal of solvent in vacuo yielded a grey
powder. Addition of water (50 ml), followed by extraction into
Table 1 Data collection and refinement parameters for compounds 4, 7, 8 and 11
Compound 4
Compound 7
Compound 8
Compound 11
Empirical formula
Formula weight
Temperature/K
C28H52F12Fe2P8
976.16
293(2)
0.71069
Monoclinic
P21/n
17.011(3)
10.913(2)
22.793(5)
90
90.65(3)
90
4231.0(14)
4
1.532
1.062
C21H42B2F8 FeN3P3
658.96
293(2)
0.71069
Monoclinic
P21/n
10.296(2)
15.901(3)
18.784(4)
90
92.23(3)
90
3072.9(11)
4
1.424
0.712
C25H48BF4FeP3
584.20
150(2)
0.71069
Orthorhombic
Pbca
15.3920(10)
13.1650(10)
27.211(3)
90
90
90
5513.9(8)
8
1.407
0.762
C24H48BF4FeOP3
588.19
150(2)
0.71069
Monoclinic
P2(1)/c
8.0750(10)
19.277(2)
17.8520(10)
90
92.190(10)
90
2776.8(5)
4
1.407
˚
Wavelength/A
Crystal system
Space group
˚
a/A
˚
b/A
˚
c/A
a/◦
b/◦
c /◦
3
˚
V/A
Z
qcalc/Mg m−3
l/mm−1
0.759
F(000)
2000
1368
2480
1248
Crystal size/mm
Reflections collected
Independent reflections
Goodness-of-fit on F2
Final R indices [I > 2r(I)]
R indices (all data)
0.35 × 0.20 × 0.20
0.35 × 0.20 × 0.20
0.40 × 0.15 × 0.05
0.35 × 0.20 × 0.20
68181
9317
17175
9165
7394 [R(int) = 0.1094]
1.057
4358 [R(int) = 0.0649]
0.955
4244 [R(int) = 0.1618]
1.270
3964 [R(int) = 0.0978]
0.898
R1 = 0.0642, wR2 = 0.1697 R1 = 0.0521, wR2 = 0.1032 R1 = 0.0756, wR2 = 0.1539 R1 = 0.0534, wR2 = 0.1247
R1 = 0.0755, wR2 = 0.1792 R1 = 0.0909, wR2 = 0.1089 R1 = 0.2197, wR2 = 0.1805 R1 = 0.0842, wR2 = 0.1309
−3
˚
Largest diff. peak and hole/e A
1.625 and −1.120
0.517 and −0.297
0.756 and −0.503
This journal is
0.580 and −0.507
440 | Dalton Trans., 2006, 433–441
The Royal Society of Chemistry 2006
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View Article Online
CCDC reference numbers 277603–277606.
For crystallographic data in CIF or other electronic format see
DOI: 10.1039/b509627h
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This journal is
The Royal Society of Chemistry 2006
Dalton Trans., 2006, 433–441 | 441
©