Synthesis and characterisation of 1-(diphenylphosphino)-1′-(methylsulfanyl)ferrocene and a series of metal (CuI, AgI)-ferrocenylene complexes

Article abstract of DOI:10.1039/a903539g

A novel phosphorus/sulfur-substituted ferrocenylene ligand, 1-(diphenylphosphino)-1′-(methylsulfanyl)ferrocene has been synthesized by two routes and fully characterised. The co-ordination chemistry of this species and analogous phosphorus/phosphorus- and sulfur/sulfur-substituted ferrocenylene ligands, 1,1′-bis(diphenylphosphino)ferrocene, 1,1′-bis(methylsulfanyl)ferrocene and 1,1′-bis(isopropylthio)ferrocene has been demonstrated by reaction with copper and silver tetrakis(acetonitrile) salts to form a series of metal-ferrocenylene complexes where the metal atom acts as a bridging group of two ring systems. Crystal structure determinations have been carried out on [Ag{(C₅H₄P-(C₆H₅)₂) ₂Fe}₂]BF₄ and [Cu{(C₅H₄SCH₃)₂Fe} ₂]PF₆ and illustrate that the former shows a distorted tetrahedral geometry around silver and a significant asymmetry in the geometries of the two pseudo six-membered chelate rings and that the latter possesses S₄ symmetry with a pronounced exo orientation of the four methyl groups.

Full text of DOI:10.1039/a903539g

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Synthesis and characterisation of 1-(diphenylphosphino)-1Ј-
(methylsulfanyl)ferrocene and a series of metal (CuI, AgI)–
ferrocenylene complexes
Nicholas J. Long,*a Jeff Martin,a Giuliana Opromolla,b Andrew J. P. White,a
David J. Williamsa and Piero Zanellob
a Department of Chemistry, Imperial College of Science, Technology and Medicine,
South Kensington, London, UK SW7 2AY
b Dipartimento di Chimica dell’ Universita di Siena, Pian dei Mantellini, I-53100 Siena, Italy
Received 3rd December 1998, Accepted 5th May 1999
A novel phosphorus/sulfur-substituted ferrocenylene ligand, 1-(diphenylphosphino)-1Ј-(methylsulfanyl)ferrocene has
been synthesized by two routes and fully characterised. The co-ordination chemistry of this species and analogous
phosphorus/phosphorus- and sulfur/sulfur-substituted ferrocenylene ligands, 1,1Ј-bis(diphenylphosphino)ferrocene,
1,1Ј-bis(methylsulfanyl)ferrocene and 1,1Ј-bis(isopropylthio)ferrocene has been demonstrated by reaction with
copper and silver tetrakis(acetonitrile) salts to form a series of metal–ferrocenylene complexes where the metal atom
acts as a bridging group of two ring systems. Crystal structure determinations have been carried out on [Ag{(C5H4P-
(C6H5)2)2Fe}2]BF4 and [Cu{(C5H4SCH3)2Fe}2]PF6 and illustrate that the former shows a distorted tetrahedral
geometry around silver and a significant asymmetry in the geometries of the two pseudo six-membered chelate rings
and that the latter possesses S4 symmetry with a pronounced exo orientation of the four methyl groups.
1,1Ј-bis(diphenylphosphino)ferrocene (BPPF) L2, 1,1Ј-bis-
Introduction
(methylsulfanyl)ferrocene (BMSF) L3 and 1,1Ј-bis(isopropyl-
Ferrocene-containing complexes are currently undergoing
sulfanyl)ferrocene (BIPSF) L4 respectively and treated them
something of a renaissance due to their increasing role in the
with labile tetrakis(acetonitrile)-copper() or -silver() centres to
form a series of novel metal–ferrocenylene complexes 1–9.
rapidly growing area of materials science.1 The substitution of
ferrocenes by various donor heteroatoms has led to a series of
chelating ligands that have found wide application, e.g.
Experimental
General
incorporation of phosphines for homogeneous catalysis in
organic synthesis, chiral phosphines for enantiomeric synthesis
and amino alcohols for asymmetric catalysis.1,2 Efforts have
been made to control the 1,1Ј-hetero- or homo-substitution of
ferrocene, normally via lithio intermediates,3–10 to allow the
formation of a number of useful substituted-ferrocenyl syn-
thetic precursors, i.e. halides,11,12 aldehydes,13 phosphines,14–17
amines,18 and stannyl species.19 By linking the heteroatoms, or
by the incorporation of a preformed linkage, metalloceno-
phanes (or ansa-metallocenes) (species that feature linking of
the cyclopentadienyl rings by the introduction of a hetero-
annular bridge or bridges) can be formed. Bridged Group 4
metallocenes have come to the fore as catalysts in stereoselective
olefin polymerisation20 and strained, ring-tilted iron group
metallocenophanes have been found to undergo thermal ring-
opening polymerisation (ROP), leading to rare examples of well
defined, high molecular mass, soluble polymers with transition
metals in the main polymer chain.21
All preparations were carried out using standard Schlenk tech-
niques.30 All solvents were distilled over standard drying agents
under nitrogen directly before use and all reactions were carried
out under an atmosphere of nitrogen. Alumina gel (type UG-1)
was used for chromatographic separations.
All NMR spectra were recorded on a JEOL 270 MHz
instrument. Chemical shifts are reported in δ using CDCl3 (1H,
δ 7.26) as the reference for 1H spectra, whilst the 31P-{1H} spec-
tra were referenced to 85% H3PO4. Mass spectra were recorded
using positive FAB methods, on a Micromass Autospec Q spec-
trometer. Microanalyses were carried out at the Department of
Chemistry, Imperial College of Science, Technology and
Medicine.
Starting materials
Ferrocenyl dichalcogenide ligands and the Group 4 elements
Si, Ge and Sn are known to form ‘spiro’22 compounds in which
two [3]ferrocenophane rings share the bridge atom in position
2,23–26 e.g. [Z(E2Fc)2] (where Z = Si, Ge or Sn; E = S, Se or Te;
Fc = {(C5H4)2Fe}). Whilst metal complexes with two 1,1Ј-
bis(diphenylphosphino)ferrocene ligands are well known,1,27,28
to date the only transition metal complex with two chelating
ferrocenyl dichalcogenide ligands is the anion of the dia-
magnetic brown rhenate() salt, e.g. [P(C6H5)4][ReO(S2Fc)2].29
To explore the formation of novel ferrocenophanes further,
we have synthesized the first mixed phosphorus/sulfur-substi-
tuted ferrocenylene ligand, 1-(diphenylphosphino)-1Ј-(methyl-
sulfanyl)ferrocene (PSF) L1, along with the more well known
phosphorus/phosphorus- and sulfur/sulfur-substituted species,
The ligands L2,31 L3 10 and L4 10 were synthesized by following
literature procedures, as were [Cu(CH3CN)4]PF6,32 1,1Ј-dilithio-
ferrocene8 and 1,1Ј-phenylphosphinoferrocenophane7 and
were characterised by 1H NMR and mass spectrometry;
[Ag(CH3CN)4]BF4 was purchased from Aldrich Chemical Co.
Ligands
1-(Diphenylphosphino)-1Ј-(methylsulfanyl)ferrocene
L1.
Method 1. 1-Diphenylphosphino-1Ј-lithioferrocene was pre-
pared using the method of Seyferth and Withers16 from 1,1Ј-
phenylphosphinoferrocenophane (6.28 g, 21.50 mmol) and a
10–15 fold excess of C6H5Li (1 M solution in diethyl ether). The
resultant orange-brown precipitate was treated with (CH3)2S2
J. Chem. Soc., Dalton Trans., 1999, 1981–1986
1981

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(1.93 cm3, 21.50 mmol) in diethyl ether (20 cm3) and the mixture
stirred overnight. Water (100 cm3) was added and stirred for 2
h, then the organic layer decanted and the aqueous layer
washed with diethyl ether (2 × 20 cm3). The extracts were com-
bined and dried over MgSO4, filtered and subjected to column
chromatography using an 80% hexane–20% diethyl ether solu-
tion and isolated as an orange solid after evaporation of the
solvents. Overall yield from 1,1Ј-phenylphosphinoferroceno-
phane, 1.64 g (18%).
Method 2. A suspension of 1,1Ј-dilithioferrocene (6.75 g,
21.50 mmol) in hexane (100 cm3) was treated with a premixed
solution of (CH3)2S2 (1.93 cm3, 21.50 mmol) and P(C6H5)2Cl
(3.85 g, 21.50 mmol) in hexane (10 cm3) and the mixture stirred
overnight. Water (20 cm3) was added and stirred for 1 h, then
the organic layer decanted and the aqueous layer washed with
hexane (2 × 10 cm3). The extracts were combined and dried
over MgSO4, filtered, then purified by column chromatography
using first hexane (to remove the starting materials), then an
80% hexane–20% diethyl ether solution, to give the product,
after evaporation of the solvents, as a light orange microcrystal-
line powder. Further purification was achieved by recrystallis-
ation from hexane–diethyl ether (1:1) as orange crystals, 3.44 g
(38%) (Calc. for C23H21FePS: C, 66.35; H, 5.05. Found: C,
66.57; H, 4.87%). 1H NMR (CDCl3): δ 2.23 (s, 3 H, SCH3), 4.06
(t, 2 H, C5H4), 4.11 (q, 2 H, C5H4), 4.20 (t, 2 H, C5H4), 4.38 (t,
2 H, C5H4) and 7.31 (m, 10 H, C6H5). 31P-{1H} NMR (CDCl3):
δ Ϫ16.78.
[Cu(L3)2]PF6 5. From [Cu(CH3CN)4]PF6 (0.19 g, 0.52 mmol)
and ligand L3 (0.29 g, 1.04 mmol) in CH2Cl2 (20 cm3). The
resulting dark brown solution was reduced under vacuum,
washed with hexane (10 cm3) and dried to yield a brown crystal-
line solid, 0.38 g (96%) (Calc. for C24H28CuF6Fe2PS4: C, 37.65;
H, 3.66. Found: C, 37.48; H, 3.14%). 1H NMR (CDCl3): δ 2.68
(br s, 3 H, SCH3) and 4.43 (br s, 4 H, C5H4). m/z 620 [(L3)2Cu],
341 [(L3)Cu], 326 [(C5H4SMe)Fe(C5H4S)Cu] and 278 (L3).
Suitable crystals for X-ray analysis were grown as transparent
brown pyramids by cooling a saturated CH2Cl2 solution.
[Ag(L3)2]BF4 6. From [Ag(CH3CN)4]BF4 (0.30 g, 0.85 mmol)
and ligand L3 (0.47 g, 1.69 mmol). Dark brown solution
reduced under vacuum to a brown solid, 0.42 g (67%) (Calc. for
C24H28AgBF4Fe2S4: C, 38.35; H, 3.73. Found: C, 38.10; H,
3.74%). 1H NMR (CDCl3): δ 2–3 (br s, 3 H, SCH3) and 4–5 (m,
4 H, C5H4). m/z 664 [(L3)2Ag], 385 [(L3)Ag] and 278 (L3).
[Cu(L4)2]PF6 7. From ligand L4 (0.52 g, 1.56 mmol) and
[Cu(CH3CN)4]PF6 (0.29 g, 0.78 mmol). Dark brown oily solid
formed on evaporation of solvent, brown solid formed on cool-
ing, 0.53 g (78%) (Calc. for C32H44CuF6Fe2PS4: C, 43.79; H,
5.02. Found: C, 43.82; H, 5.06%). 1H NMR (CDCl3): δ 1.39 [d,
6 H, SCH(CH3)2], 3.30 [septet, 1 H, SCH(CH3)2], 4.40 (br, 2 H,
C5H4) and 4.51 (br, 2 H, C5H4). m/z 732 [(L4)2Cu], 471
[(L4)CuC5H4SCH(CH3)2Fe(C5H4)], 397 [(L4)Cu] and 334 (L4).
[Ag(L4)2]BF4 8. From ligand L4 (0.41 g, 1.2 mmol) and
[Ag(CH3CN)4]BF4 (0.22 g, 0.61 mmol). Light orange solid, 0.38
g (72%) (Calc. for C32H44AgBF4Fe2S4: C, 44.50; H, 5.10. Found:
C, 44.41; H, 4.84%). 1H NMR (CDCl3): δ 1.38 [d, 6 H,
SCH(CH3)2], 3.22 [septet, 1 H, SCH(CH3)2], 4.34 (t, 2 H, C5H4)
and 4.52 (t, 2 H, C5H4). m/z 776 [(L4)2Ag], 472 [(L4)AgS], 442
[(L4)Ag], 398 [AgC5H4SCH(CH3)2)Fe(C5H4)S] and 334 (L4).
Complexes
Formation of the complexes followed the same general pro-
cedure as for the formation of 5 using either [Cu(CH3CN)4]PF6
or [Ag(CH3CN)4]BF4 and the appropriate bidentate ligand.
[Cu(L1)2]PF6 1. The salt [Cu(CH3CN)4]PF6 (0.09 g, 2.33
mmol) was added to a solution of ligand L1 (0.19 g, 4.66 mmol)
in CH2Cl2 (20 cm3) and stirred for 1 h. The resulting dark brown
solution was reduced under vacuum, washed with diethyl ether
(10 cm3) and dried (MgSO4) to yield a brown microcrystalline
solid, 0.16 g (66%) (Calc. for C46H42CuF6Fe2P3S2: C, 53.03; H,
[Cu(L3){P(C6H5)3}2]PF6 9. A solution of [Cu(L3)2]PF6 (0.35 g,
4.58 mmol) was treated with P(C6H5)3 (0.24 g, 9.15 mmol) and
stirred for 1 h. The solution was reduced under vacuum and
washed with diethyl ether (2 × 10 cm3) to leave an orange solid,
0.31 g (67%) (Calc. for C48H44CuF6FeP3S2: C, 56.97; H, 4.35.
Found: C, 57.71; H, 4.36%). 1H NMR (CDCl3): δ 2.29 (s, 6 H,
SCH3), 4.31 (t, 4 H, C5H4), 4.95 (t, 4 H, C5H4), 7.11 (m, 15 H,
C6H5) and 7.41 (m, 15H, C6H5). m/z 603 [(L3)Cu(PPh3)], 587
[Cu(PPh3)2], 341 [(L3)Cu] and 278 (L3).
1
4.04. Found: C, 53.02, H, 4.31%). H NMR (CDCl3): δ 2.61
(br, 3 H, SCH3), 4.29 (br, 4 H, C5H4), 4.50 (br, 2 H, C5H4), 4.65
(br, 2 H, C5H4), 7.41 (br, 5 H, C6H5) and 7.58 (br, 5 H, C6H5).
m/z 896 [(L1)2Cu], 480 [(L1)Cu], 416 (L1).
[Ag(L1)2]BF4 2. From the salt [Ag(CH3CN)4]BF4 (0.14 g, 3.80
mmol) and ligand L1 (0.32 g, 7.64 mmol). Orange microcrystal-
line solid, 0.30 g (77%) (Calc. for C46H42AgBF4Fe2P2S2: C,
53.75; H, 4.09. Found: C, 54.09; H, 4.07%). 1H NMR (CDCl3):
δ 2.22 (s, 3 H, SCH3), 4.14 (t, 2 H, C5H4), 4.19 (t, 2 H, C5H4),
4.29 (t, 2 H, C5H4), 4.61 (t, 2 H, C5H4) and 7.45 (m, 10 H,
C6H5). m/z 941 [(L1)2Ag], 523 [(L1)Ag], 416 (L1) and 401
[(C5H4PPh2)Fe(C5H4S)].
X-Ray crystallography
Table 2 provides a summary of the crystal data, data collection
and refinement parameters for complexes 4 and 5. The struc-
tures were solved by direct methods and the heavy atom method
for 5 and 4 respectively, and refined by full matrix least squares
based on F 2. In 5 the complex and the PF6 anion were found to
be disordered over independent crystallographic S4 positions. In
the case of the complex two discrete half-occupancy orien-
tations were identified, with only their copper and iron centres
in common, and refined anisotropically, with the cyclopentadi-
enyl rings treated as optimised rigid bodies. The disorder in the
anion was modelled by the assignment of sufficient electron
density around the central phosphorus atom to match a single
quarter-occupancy (due to site symmetry) molecule, all atoms
being refined anisotropically. In 4 the complex was ordered
and refined anisotropically with the phenyl rings treated as
optimised rigid bodies (the cyclopentadienyl rings were not opti-
mised). The BF4 anion was found to be distributed over three
partial occupancy sites (two of which were located proximal to
crystallographic special positions); only the major occupancy
atoms were refined anisotropically. In both structures the
hydrogen atoms were placed in calculated positions, assigned
isotropic thermal parameters, U(H) = 1.2Ueq(C), and allowed to
[Cu(L2)2]PF6 3. From the salt [Cu(CH3CN)4]PF6 (0.07 g, 1.81
mmol) and ligand L2 (0.20 g, 3.61 mmol). The complex was
allowed to recrystallise from the CH2Cl2 solution, producing
light orange crystals, 0.17 g (71%) (Calc. for C68H56CuF6Fe2P5:
C, 61.96: H, 4.25. Found: C, 61.64; H, 4.60%). 1H NMR
(CDCl3): δ 4.10 (br, 4 H, C5H4), 4.31 (br, 4 H, C5H4), 7.25 (m, 10
H, C6H5) and 7.40 (m, 10 H, C6H5). m/z 1172 [(L2)2Cu], 617
[(L2)Cu] and 554 (L2).
[Ag(L2)2]BF4 4. From ligand L2 (0.10 g, 0.18 mmol) and
[Ag(CH3CN)4]BF4 (0.03 g, 0.09 mmol). Light orange solid,
0.076 g (65%) (Calc. for C68H56AgBF4Fe2P4: C, 62.62; H, 4.30.
Found: C, 62.66; H, 3.95%). 1H NMR (CDCl3): δ 4.10 (br, 4 H,
C5H4), 4.40 (br, 4 H, C5H4), 7.10 (m, 10 H, C6H5) and 7.30 (m,
10 H, C6H5). m/z 1216 [(L2)2Ag], 1139 [(L2)Ag(C5H4PPh2)-
Fe(C5H4PPh)], 661 [(L2)Ag] and 554 (L2).
1982
J. Chem. Soc., Dalton Trans., 1999, 1981–1986

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ride on their parent atoms. The polarity of 5 was determined by
R-factor tests [R1ϩ = 0.031, R1Ϫ = 0.039] and by use of the Flack
parameter [xϩ = Ϫ0.03(4), xϪ = ϩ1.03(4)]. Computations were
carried out using the SHELXTL PC program system.33
CCDC reference number 186/1452.
See http://www.rsc.org/suppdata/dt/1999/1981/ for crystallo-
graphic files in .cif format.
Results and discussion
Synthesis
The new hetero-donor ligand, PSF (L1), may be prepared by
two methods (Scheme 1) which involve the initial formation of
Li
PCl2C6H5
n-BuLi
PC6H5
TMEDA
Fe
Fe
Fe
Method 1
TMEDA
Li
PCl(C6H5)2,
(CH3)2S2
C6H5Li
Method 2
Scheme 2 The syntheses of complexes 1–8.
P(C6H5)2
P(C6H5)2
metal complex with two ferrocenylene ligands (Scheme 2). Each
complex 1–8 appears to possess the same structure where the
metal atom acts as a bridging group of two ring systems. The
air- and moisture-stable orange solids were formed in excellent
yields and could be recrystallised from saturated chlorocarbon
solutions.
(CH3)2S2
Fe
Fe
Li
SCH3
Scheme 1 Two methods for the synthesis of ligand L1.
the well known intermediate 1,1Ј-dilithioferrocene. Addition of
dichlorophenylphosphine produces 1,1Ј-phenylphosphinoferro-
cenophane (Method 1),7 which was isolated and characterised
spectroscopically. This [1]ferrocenophane was then treated with
a 10–15 fold excess of phenyllithium (1 M solution in diethyl
ether) to cleave one of the P–C bonds and yield the air- and
Spectroscopy
Each complex 1–8 displays broadened signals in the cyclo-
pentadienyl ring region of its room temperature 1H NMR
spectrum which was initially thought to be due to fluxional
processes, such as pyramidal sulfur inversion or bridge
reversal,35 being observed in solution. However, dynamic NMR
experiments and, in particular, cooling solutions to low temper-
atures (ca. Ϫ80 ЊC) failed to elucidate any fine structure on the
cyclopentadienyl proton signals. This could be due to a lack of
slowing of the fluxional processes but is thought more likely to
be a dissociative process in solution (breaking of the metal–
heteroatom bonds) giving rise to an averaged set of peaks. To
elucidate this phenomenon, a solution of 5 was treated with two
equivalents of P(C6H5)3 and substitution of a labile ligand
indeed occurred to form a [3]ferrocenophane 9 (Scheme 3). (NB
9 was also formed by the addition of [Cu(CH3CN)2{(P-
(C6H5)3)}2]PF6 to a stirred solution of the ligand L3). The lack
of sulfur inversion is perhaps surprising but there is clearly
something of a ‘potential well’ in the thermodynamics of the
structure especially when considering the crystal structure
determination (see later). The methyl groups are ‘locked’ into a
very stable exo orientation and this seems to preclude any
movement and therefore fluxional behaviour of these units.
moisture-sensitive
1-diphenylphosphino-1Ј-lithioferrocene.16
The orange-brown precipitate was treated in situ with dimethyl
disulfide to give a crude dark orange oil (L1). Purification
was effected by column chromatography on neutral grade II
alumina (hexane–diethyl ether (80:20)) to give an orange solid
in an overall yield from ferrocene of 11%, or 18% from 1,1Ј-
phenylphosphinoferrocenophane.
Method 2 was more direct and involved treating a hexane
suspension of the 1,1Ј-dilithioferrocene intermediate with a
mixture (1:1) of dimethyl disulfide and dichlorophenylphos-
phine, also in hexane. Perhaps surprisingly, a reasonable yield
of the desired product was obtained (along with mainly BMSF
and monosubstituted ferrocenes as by-products) which was
again purified by column chromatography using first hexane
as eluent (to remove the starting materials) and then hexane–
diethyl ether (80:20) to give the orange solid (yield 38% from
ferrocene).
As mentioned in the Introduction, hetero-donor substituted
ferrocenes are known but to date most have featured pnictinide
substituents. The different co-ordinating abilities of the phos-
phorus and sulfur substituents in L1, along with the possibility
for further donor atom substitution around the same ferrocene
unit,34 opens up diverse co-ordination chemistry of these sys-
tems which is the subject of ongoing studies. As a starting point
for the co-ordination chemistry and as a comparison to the
more well known analogues 1,1Ј-bis(diphenylphosphino)ferro-
cene (BPPF) (L2), 1,1Ј-bis(methylsulfanyl)ferrocene (BMSF)
(L3) and 1,1Ј-bis(isopropylsulfanyl)ferrocene (BPSF) (L4), each
ligand was treated with simple copper and silver tetrakis-
(acetonitrile) complexes. Using a 2:1 ratio of ligand to metal,
the acetonitrile moieties could be displaced within a few min-
utes by stirring at room temperature, to yield a tetrasubstituted
Electrochemistry
A preliminary investigation on dichloromethane solutions of
the reported complexes using platinum electrodes illustrated the
occurrence of interfering adsorption phenomena, whereas the
use of glassy-carbon electrodes overcame these problems. Figs.
1 and 2, which compare the cyclic voltammetric responses of
the ligands L1 and L2 with those of their copper() and silver()
complexes, show the subtle electronic effects that govern the
redox behaviour of these species.
With respect to the ligand L1, the bis(ferrocenediyl) copper()
and silver() complexes 1 and 2 undergo anodic oxidations at
potentials shifted toward more positive potential values by
about 0.25 V (Fig. 1). In particular, the copper complex 1
J. Chem. Soc., Dalton Trans., 1999, 1981–1986
1983

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Fig. 1 Cyclic voltammetric responses recorded at a glassy-carbon elec-
trode on CH2Cl2 solutions containing [NBu4][PF6] (0.2 mol dmϪ3) and
(a) L1 (1.0 × 10Ϫ3 mol dmϪ3), (b) complex 1 (0.4 × 10Ϫ3 mol dmϪ3), (c)
Fig. 2 Cyclic voltammetric responses recorded at a glassy-carbon elec-
trode on CH2Cl2 solutions containing [NBu4][PF6] (0.2 mol dmϪ3) and
(a) L2 (0.8 × 10Ϫ3 mol dmϪ3), (b) complex 3 (1.0 × 10Ϫ3 mol dmϪ3), (c)
complex 2 (0.8 × 10Ϫ3 mol dmϪ3). Scan rate 0.05 V sϪ1
.
complex 4 (0.9 × 10Ϫ3 mol dmϪ3). Scan rates: (a, c) 0.05; (b) 0.1 V sϪ1
.
CH3
S
PF6
Fe
Cu
+
2 P(C6H5)3
S
CH3
2
Fig. 3 The molecular structure of one of the two 50% orientations
of the S4-symmetric cation present in the structure of complex 5. The
Cu–S and S–C5 bond lengths are 2.331(2) [2.327(2)] and 1.746(5)
[1.755(6) Å] respectively. The associated bite and interligand S–Cu–S
angles are 112.28(10) [112.33(10)] and 108.08(5) [108.06(5)Њ] respect-
ively; the Cu–S–C5 angles are 109.2(3) [109.6(3)Њ], the number in
[ ] referring to the alternative orientation present in the crystal.
PF6
CH3
S
CH3
S
Cu (P(C6H5)3)2
Fe
+
Fe
S
CH3
S
CH3
complexes suggest slight communication between the two
ferrocene units, but it can be deduced that the communication is
probably attributable to the nature of the ferrocene ligands
rather than to that of the metals.
Scheme 3 The synthesis of complex 9.
exhibits two substantially overlapping one-electron oxidations,
which could not be resolved with additional use of differential
pulse voltammetry, and simply afforded a rounded peak. On the
other hand, the silver complex 2 displays a single two-electron
oxidation. In spite of the apparent chemical reversibility of
these anodic processes on the cyclic voltammetric timescale,
cyclic voltammetric tests on solutions from exhaustive two-
electron oxidation of both complexes showed partial decom-
position of the corresponding trications.
X-Ray crystallography
The X-ray analysis of complex 5 reveals a structure that has 50/
50 reflection disorder about a non-crystallographic mirror
plane perpendicular to the a direction, the two orientations
having essentially identical geometries. The complex has crys-
tallographic S4 symmetry, the copper lying at the S4 position
and the two iron atoms on the C2 axis (Fig. 3). The geometry at
copper is slightly distorted tetrahedral, the bite angles of the
two chelating ligands being 112.3(1)Њ. The Cu–S distance of
2.33(1) Å is unexceptional. There is a marked departure from
tetrahedral geometry at sulfur with the C5–S–Me angles con-
tracted to 101(1)Њ, the other two angles being 109(1) [Cu–S–C5]
and 110(1)Њ [Cu–S–Me]. The ferrocenyl C5H4 rings are
staggered (48Њ), the two S–C5 vectors being skewed by ca. 24Њ,
with an essentially parallel orientation of the two rings. The
Cu ؒ ؒ ؒ Fe distance of 4.02 Å is too long for any significant
metal–metal interaction.
Interestingly, L2, which is known to undergo a one-electron
oxidation coupled to chemical complications,36 when part of
the metal complexes 3 and 4 gives rise to oxidation processes
with features of chemical reversibility (also in these cases it is
limited to the cyclic voltammetric timescale), Fig. 2. In addi-
tion, a slight wave splitting occurs for the silver complex 4.
As Table 1 summarises, analogous behaviour is seen for the
remaining complexes. The oxidations of the metal complexes
occur at potentials which range from 0.25 to 0.42 V higher than
those of the corresponding ligands. It has to be taken into
account that these shifts must be attributed either to the electro-
static effect of removing electrons from monocations, or to the
metals themselves. The minor wave splittings observed for some
When viewed down the metal–metal–metal axis the exo
orientation of the four methyl groups is particularly pro-
nounced (Fig. 4), a geometry that is dominant in solution as
1984
J. Chem. Soc., Dalton Trans., 1999, 1981–1986

View Article Online
Table 1 Formal electrode potentials (in V, vs. SCE) and peak-to-peak separations (in mV) for the anodic oxidation of the ferrocenediyl ligands
L1–L4 and their metal derivatives 1–8 in CH2Cl2 solutions
a
a
Compound
EЊ (0/ϩ)
∆Ep
EЊ (ϩ/2ϩ)
EЊ (2ϩ/3ϩ)
EЊ (ϩ/3ϩ)
∆Ep
L1
L2
L3
L4
1
ϩ0.48
85
69
94
ϩ0.56b
ϩ0.37c
ϩ0.43
180
ϩ0.68d
ϩ0.78d
2
ϩ0.75
ϩ0.84
115
140
3
4
ϩ0.89d
ϩ0.74d
ϩ0.84d
ϩ0.64d
5
7
ϩ0.85e
ϩ0.85f
8
90
a Measured at 0.1 V sϪ1 b Coupled to chemical complications. c See ref. 37. d Measured according to ref. 38. e Irreversible two electron step. f Coupled
.
to slight adsorption of the reagent.
Table 2 Selected bond lengths (Å) and angles (Њ) for complex 4
Ag–P(1)
Ag–P(3)
P(1)–C(17)
P(3)–C(51)
2.662(3)
2.622(3)
1.790(12)
1.811(14)
Ag–P(2)
Ag–P(4)
P(2)–C(22)
P(4)–C(56)
2.558(3)
2.553(3)
1.775(12)
1.832(13)
P(1)–Ag–P(2)
P(1)–Ag–P(4)
P(2)–Ag–P(4)
Ag–P(1)–C(17)
Ag–P(3)–C(51)
105.51(10)
109.34(11)
118.92(11)
106.4(4)
P(1)–Ag–P(3)
P(3)–Ag–P(3)
P(3)–Ag–P(4)
Ag–P(2)–C(22)
Ag–P(4)–C(56)
114.65(11)
110.98(11)
97.76(10)
113.5(4)
106.4(4)
110.0(4)
Fig. 5 The molecular structure of the cation in complex 4.
being one “short” and one “long” bond in each ring, 2.662(3)
[P(1)] and 2.558(3) Å [P(2)] in the skewed ring and 2.622(3)
[P(3)] and 2.553(3) Å [P(4)] in the envelope ring. The trans-
annular Ag ؒ ؒ ؒ Fe(1) and Ag ؒ ؒ ؒ Fe(2) distances are 4.25 and
4.15 Å respectively. The analogous complex [Ag(L2)2]ClO4ؒ
27
2CHCl3 has also been studied and shows a more regular
tetrahedral geometry around Ag with the bite angles of
the diphosphine P(1)–Ag–P(2) and P(3)–Ag–P(4) being
105.71(4) and 98.39(4)Њ respectively. However, no mention is
made of any asymmetry in the pseudo six-membered chelate
rings.
Both ferrocenyl ring systems have slightly staggered geom-
etries [ca. 15Њ for Fe(1) and ca. 11Њ for Fe(2)], though whereas
the C5 rings are essentially parallel in the Fe(1) ferrocenyl unit
[2Њ] they are significantly inclined in the Fe(2) unit [8Њ].
Accompanying the aforementioned staggering of the rings are
very different relative orientations of the P–C5 bonds which are
skewed by 53Њ for the Fe(1) chelate but by only 10Њ in the Fe(2)
chelate which has the “envelope” conformation. There are no
noteworthy intermolecular interactions.
Fig. 4 The view down the Fe ؒ ؒ ؒ Cu ؒ ؒ ؒ Fe direction in the structure of
complex 5 showing the radial orientation of the SMe groups.
shown by the NMR experiments. There are no intermolecular
interactions of note, the packing being normal van der Waals.
In the solid state structure of complex 4 (Fig. 5) the geometry
at silver is distorted tetrahedral with angles ranging between
97.8(1) and 118.9(1)Њ. There is a pronounced asymmetry in the
geometries of the two pseudo six-membered chelate rings (Fig.
6), an asymmetry that includes both the bond lengths and
angles (Table 2) and their conformations. The Ag/Fe(1) ring has
a skewed “l” conformation, the C2Fe plane being “rotated” by
23Њ out of the P2Ag plane about the Fe ؒ ؒ ؒ Ag axis. In contrast
the Ag/Fe(2) ring has a slightly twisted envelope conformation,
the Ag atom being 1.38 Å out of the plane of the other five
atoms which are coplanar to within 0.09 Å, corresponding to a
fold about the P(3) ؒ ؒ ؒ P(4) vector of ca. 54Њ. The angle at silver
within the skewed ring is 105.5(1)Њ whereas that in the ring with
the envelope conformation is 97.8(1)Њ. Possibly most surprising
is the disparity in the Ag–P distances within each pseudo chel-
ate ring, though the asymmetry is remarkably consistent there
Conclusion
A new 1,1Ј-heterodisubstituted ferrocenediyl ligand featuring P
and S substituents has been synthesized by two routes. Its co-
ordination chemistry with labile copper() and silver() centres
gives metal-bridged bis(ferrocenylene) species in analogy
to other more well known P/P- and S/S-substituted ligands,
J. Chem. Soc., Dalton Trans., 1999, 1981–1986
1985

View Article Online
Table 3 Crystal data, data collection and refinement parameters for
complexes 4 and 5a
Dr Keith Orrell (University of Exeter) for helpful NMR
discussions.
5
4
References
Formula
M
Colour, habit
Crystal size/mm
Lattice type
Space group symbol,
number
a/Å
b/Å
c/Å
C24H28CuF6Fe2PS4 C68H56AgBF4Fe2P4
764.9 1303.4
Orange tetrahedra Orange-yellow prisms
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0.33 × 0.33 × 0.27
Tetragonal
I4, 82
0.18 × 0.16 × 0.09
Monoclinic
I2/a, 15
¯
10.493(1)
—
13.340(1)
—
22.627(5)
23.575(6)
22.970(6)
100.92(1)
12031(5)
8
β/Њ
V/Å3
1468.8(2)
Z
2b
Dc/g cmϪ3
F (000)
1.730
772
Mo-Kα
2.08
1.439
5312
Cu-Kα
7.84
Radiation used
µ/mmϪ1
θ Range/Њ
No. unique reflections
measured
No. observed reflections, 1060
|Fo| > 4σ(|Fo|)
Absorption correction
Maximum, minimum
transmission
No. variables
R1
2.5–30.0
1209
2.7–60.0
7891
4658
Semi-empirical
0.50, 0.38
Semi-empirical
0.99, 0.45
164
0.031
651
0.085
wR2
0.078
0.21, Ϫ0.41
0.197
1.08, Ϫ1.81
Largest difference
peak, hole/e ÅϪ3
a Details in common: graphite monochromated radiation, ω scans,
Siemens P4 diffractometer, 293 K. b The molecule has crystallographic
S4 symmetry.
21 I. Manners, Angew. Chem., 1996, 108, 1712; Angew. Chem., Int. Ed.
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22 Dictionary of Chemical Terminology, Elsevier, Oxford, 1980.
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29 J. R. Dilworth and S. K. Ibrahim, Transition Met. Chem., 1991, 16,
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30 D. F. Shriver, in Manipulation of Air-Sensitive Compounds,
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32 G. J. Kubas, Inorg. Synth., 1990, 28, 68.
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Fig. 6 The two “pseudo six-membered chelate” rings in complex 4,
showing their skewed [Fe(1)] and envelope [Fe(2)] conformations
respectively.
though structural determinations illustrate some significant dis-
tortion and asymmetry within the structures. Electrochemical
investigations show some subtle electronic effects and there
are significant shifts to more positive potentials of the cyclic
voltammetric responses of the complexes with respect to those
of the ligands.
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28, 2347.
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Acknowledgements
We wish to thank the EPSRC for a studentship (to J. M.) and
Paper 9/03539G
1986
J. Chem. Soc., Dalton Trans., 1999, 1981–1986