Synthesis and coordination chemistry of 1-phenyl-1-phospha-4,7-dithiacyclononane

Article abstract of DOI:10.1016/S0020-1693(99)00206-6

Reaction of PhP(CH₂CH₂SH)₂ with 1,2-dichloroethane and Cs₂CO₃ under high dilution conditions affords 1-phenyl-1-phospha4,7-dithiacyclononane (L) as an oil in 52% yield. The geometry of L has been probed by ¹H NMR spectroscopy, which indicates an equilibrium mixture containing gauche S-C-C-S and S-C-C-P segments, and molecular mechanics calculations which find a lowest energy endodentate conformation minimum and also energetically accessible exodentate minima. Endo- and exodentate conformations are observed in the crystal structure of [Cu(η¹-L)(η³-L)][PF₆] (1) formed by the reaction of L with [Cu(NCMe)₄][PF₆]. Reaction of Hg(ClO₄)₂ with L affords [HgL₂][ClO₄]₂ (2) whose structure has also been established by X-ray diffraction. The mercury ion is in a very distorted octahedral environment with two short Hg-P bonds (average 2.404 A) and four long Hg-S bonds (average 3.092 A). Reaction of L with AgBF₄ or Ni(BF₄)₂ or CoBr₂ or Fe(BF₄)₂ affords [AgL₂][BF₄] (3), [NiL₂][BF₄]₂ (4), [CoL₂]Br₂ (5) and [FeL₂][BF₄]₂ (6), respectively, which were characterised by FAB mass spectroscopy and elemental analysis. Cyclic voltammetry studies were used to compare the redox properties of 4, 5 and 6 with their trithiacy-clononane (9S3) analogues and in compound 4 the ligand L was found to stabilise Ni in the oxidation states 0, I, II and III. UV-Vis spectroscopic measurements show that L is a stronger field ligand than 9S3. EXAFS studies were also performed on 4, 5 and 6, which established that all three complexes are six-coordinate.

Full text of DOI:10.1016/S0020-1693(99)00206-6

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Inorganica Chimica Acta 294 (1999) 170–178
Synthesis and coordination chemistry of
1-phenyl-1-phospha-4,7-dithiacyclononane
Philip J. Blower a, Alan V. Chadwick b, John C. Jeffery c, Gregory E.D. Mullen b,
Anne K. Powell d, Spencer N. Salek a, Raymond J. Smith a, Michael J. Went b,*
a Department of Biosciences, Uni6ersity of Kent, Canterbury, Kent, CT2 7NJ, UK
b School of Physical Sciences, Uni6ersity of Kent, Canterbury, Kent, CT2 7NR, UK
c Department of Inorganic Chemistry, The Uni6ersity, Bristol, BS8 1TS, UK
d School of Chemical Sciences, Uni6ersity of East Anglia, Norwich, NR4 7JT, UK
Received 24 December 1998; accepted 2 March 1999
Abstract
Reaction of PhP(CH2CH2SH)2 with 1,2-dichloroethane and Cs2CO3 under high dilution conditions affords 1-phenyl-1-phospha-
1
4,7-dithiacyclononane (L) as an oil in 52% yield. The geometry of L has been probed by H NMR spectroscopy, which indicates
an equilibrium mixture containing gauche S–C–C–S and S–C–C–P segments, and molecular mechanics calculations which find
a lowest energy endodentate conformation minimum and also energetically accessible exodentate minima. Endo- and exodentate
conformations are observed in the crystal structure of [Cu(h1-L)(h3-L)][PF6] (1) formed by the reaction of L with
[Cu(NCMe)4][PF6]. Reaction of Hg(ClO4)2 with L affords [HgL2][ClO4]2 (2) whose structure has also been established by X-ray
,
diffraction. The mercury ion is in a very distorted octahedral environment with two short Hg–P bonds (average 2.404 A) and four
,
long Hg–S bonds (average 3.092 A). Reaction of L with AgBF4 or Ni(BF4)2 or CoBr2 or Fe(BF4)2 affords [AgL2][BF4] (3),
[NiL2][BF4]2 (4), [CoL2]Br2 (5) and [FeL2][BF4]2 (6), respectively, which were characterised by FAB mass spectroscopy and
elemental analysis. Cyclic voltammetry studies were used to compare the redox properties of 4, 5 and 6 with their trithiacy-
clononane (9S3) analogues and in compound 4 the ligand L was found to stabilise Ni in the oxidation states 0, I, II and III.
UV–Vis spectroscopic measurements show that L is a stronger field ligand than 9S3. EXAFS studies were also performed on 4,
5 and 6, which established that all three complexes are six-coordinate. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Copper complexes; Nickel complexes; Phosphathiamacrocycle complexes; Thioether complexes
1,4,7-trithiacyclononane (9S3) are capable of producing
metal complexes of high thermodynamic and kinetic
stability [4,5]. The unique properties of 9S3 are a result
of the combination of the ‘macrocyclic effect’ with a
conformation which is ideal for facial tridentate coordi-
nation, and consequently many 9S3 complexes exhibit
interesting electronic and electrochemical properties [5].
These observations led to the speculation as to whether
the combination of the nine-membered ring conforma-
tional properties with phosphine donor centres might
offer complexes with extreme chemical robustness and
electronic versatility. Recent reports suggest that syn-
theses of triphosphacyclononane complexes using a
Group 6 metal tricarbonyl template are difficult [6].
Our studies have so far concentrated on the synthesis of
mixed phosphathiacyclononanes [1,2].
1. Introduction
Our study of mixed phosphathiamacrocycles com-
bines the areas of phosphine coordination chemistry
and the more recent developments in thiamacrocycle
coordination chemistry [1,2]. The chemistry of com-
plexes containing phosphine ligands has been studied
intensively and a vast number of uni- and bidentate
phosphine complexes are known, some of which have
important catalytic properties. In comparison to phos-
phines, thioethers are relatively weakly bound ligands
[3]. However, thioether macrocycles and in particular
* Corresponding author. Tel.: +44-1227-823 540; fax: +44-1227-
827 558.
E-mail address: m.j.went@ukc.ac.uk (M.J. Went)
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00206-6

P.J. Blower et al. / Inorganica Chimica Acta 294 (1999) 170–178
171
We have previously reported the synthesis of 1-
phenyl-phospha-4,7-dithiacyclononane (L) via a tricar-
bonylmolybdenum template cyclisation followed by
treatment with sulfur and then reduction with sodium
naphthalenide [2]. In this paper we give full details of a
high dilution synthesis of L and its coordination chem-
istry with Cu+, Hg2+, Ag+, Co2+, Ni2+ and Fe2+
ions [1]. The aim of this work was to determine to what
extent the conformational preferences of L mimic those
of 9S3, and hence to confirm or refute the suggestion
that nine-membered phosphine containing macrocycles
might form exceptionally robust complexes of soft
metals.
ning potentiostat using Condecon 310 as the data
analysis software. All measurements were carried out
using a glassy carbon electrode (BAS Technicol, Stock-
port, UK) as the working electrode, platinum gauze as
the auxiliary electrode and Ag ꢀ AgCl as the reference
electrode. Elemental analyses were performed by A.J.
Fassam at the University of Kent. Analytical and phys-
ical data for the new compounds are given in Table 1.
2.1. Preparation of PhP(CH2CH2S)2CH2CH2 (L)
A solution of PhP(CH2CH2SH)2 (2.0 g, 8.7 mmol)
and 1,2-dichloroethane (0.860 g, 8.7 mmol) in DMF (50
cm3) was added dropwise to a stirred suspension of
Cs2CO3 (3.114 g, 9.55 mmol) in DMF (100 cm3) at
60°C over 24 h. The solvent was then removed in vacuo
and the residue extracted with dichloromethane (3×50
cm3). The combined extracts were filtered and washed
with 1 M NaOH (2×50 cm3) and water (2×50 cm3).
The solvent was removed in vacuo and the residue flash
chromatographed on a silica column (4×32 cm) elut-
ing with CHCl3–CH2Cl2 (3:2) to afford L (1.16 g, 52%).
1H NMR (CDCl3): l 7.55–7.29 (m, 5H, Ph), 3.181
[dddd, 2H, H1, J(H1H2) 14.52(2), J(H1H3) 3.37(2),
J(H1H4) 7.21(2), J(PH) 22.13], 3.058 [m, 2H, H5H5%, J
8.10(1), J% 2.83(1), Jgem −15.29(1), J(PH) 0.61], 3.041
[dddd, 2H, H2, J(H1H2) 14.52(2), J(H2H3) 10.08(2),
J(H2H4) 3.49(2), J(PH) 10.38], 2.849 [m, 2H, H6H6%, J
8.10(1), J% 2.83(1), Jgem −15.29(1)], 2.682 [dddd, 2H,
H3, J(H1H3) 3.37(2), J(H2H3) 10.08(2), J(H3H4)
14.90(2), J(PH) 3.13], 2.321 [dddd, 2H, H4, J(H1H4)
7.21(2), J(H2H4) 3.49(2), J(H3H4) 14.90(2), J(PH) 3.59].
31P{1H} (CDCl3) −16.9 ppm.
2. Experimental
All reactions were carried out under an atmosphere
of dinitrogen using standard Schlenk tube and vacuum
line techniques, and all solvents were freshly distilled
under a dinitrogen atmosphere and over an appropriate
drying agent. The compound PhP(CH2CH2SH)2 was
prepared by a literature method [7]. Fast atom bom-
bardment spectra were recorded by the EPSRC mass
spectrometry service at the University of Swansea with
a VG ZAB-E instrument from NOBA matrices. Elec-
tronic spectra were recorded in quartz cells on a Philips
PU8730 UV–Vis scanning spectrophotometer. 1H
NMR spectra were recorded by the EPSRC NMR
service with a Varian INOVA 600 MHz spectrometer.
31P NMR spectra were recorded with a JEOL GX 270
instrument referenced to 85% H3PO4 (external). Simula-
1
tion and iterative fitting of the H NMR spectra was
performed using LAOCOON PC [8]. Molecular-me-
chanics calculations were carried out using HYPER-
CHEM (Release 3) [9]. Structures were minimised with
conjugate gradients (Polak–Ribiere algorithm) using
the MM+ force field until the gradients were less than
2.2. Preparation of [CuL2][PF6] (1)
[Cu(NCMe)4][PF6] (0.082 g, 0.22 mmol) was added to
a solution of L (0.12 g, 0.468 mmol) in MeCN (4 cm3).
After stirring for 5 min Et2O (20 cm3) was added and
the mixture left overnight at 4°C to produce off-white
0.01 kcal mol−1
−1. Cyclic voltammetric measure-
,
A
ments were performed on an EG&G Model 362 scan-
Table 1
Analytical a and physical data
Compound
Appearance
Yield (%)
Analysis (%)
m/z
C
H
N
L
colourless oil
white solid
white solid
white solid
green solid
green solid
red solid
52
80
61
72
73
73
88
56.5 (56.2)
40.7 (41.0)
31.5 (31.6)
40.4 (40.8)
39.0 (38.7)
38.9 (39.4)
38.4 (38.9)
6.9 (6.7)
4.6 (4.9)
3.3 (3.7)
4.5 (4.8)
4.6 (5.2)
6.7 (4.7)
4.8 (4.6)
–
b 256 (M+
)
–
–
[CuL2][PF6] (1)·MeCN
[HgL2][ClO4] (2)
[AgL2][BF4] (3)
[NiL2][BF4]2 (4)
[CoL2]Br2 (5)
[FeL2][BF4]2 (6)
1.8 (1.8)
–
–
–
–
–
c 621 (M+−BF4)
c 657 (M+−BF4)
c 652 (M+−Br)
c 655 (M+−BF4)
a Calculated values are given in parentheses.
b Electron impact (EI) mass spectrometry.
c Fast atom bombardment (FAB) mass spectrometry.

172
P.J. Blower et al. / Inorganica Chimica Acta 294 (1999) 170–178
Table 2
crystals which were isolated by filtration and dried
under vacuum to afford [CuL2][PF6] (0.134 g, 80%).
Details of the X-ray structure analyses for compounds [Cu(h1-L)-
(h3-L)][PF6]·(MeCN) (1) and [HgL2][ClO4]2·1/2(MeCN) (2)
2.3. Preparation of [HgL2][ClO4]2 (2)
1
2
Formula
Mf
Space group
Temp. (K)
Cell constants
C26H37CuF6NP3S4 C25H35.5Cl2HgN0.5O8P2S4
Addition of Hg(ClO4)2 (0.08 g, 0.19 mmol) to L (0.10
g, 0.39 mmol) in nitromethane (25 cm3) resulted in
precipitation of [HgL2][ClO4]2 (0.11 g, 61%).
762.3
932.71
P21/n
138
(
P1
294
,
2.4. Preparation of [AgL2][BF4] (3)
a (A)
9.631(3)
12.446(2)
14.404(5)
101.12(2)
94.22(3)
96.26(2)
1676.2(8)
2
10.233(1)
28.756(2)
22.655(2)
,
b (A)
c (A)
h (°)
i (°)
k (°)
,
A solution of AgBF4 (0.114 g, 0.585 mmol) in MeOH
(10 cm3) was added to L (0.300 g, 1.170 mmol) in
MeOH (4 cm3). After 5 h the solid white product was
collected by filtration and washed with Et2O (4×20
cm3) to afford [AgL2][BF4] (0.296 g, 72%).
97.67(1)
3
,
V (A )
6607(1)
8
1.88
5.22
50.8
Z
Dc (g cm−3
v (mm−1
2qmax
)
1.51
1.084
50.0
)
2.5. Preparation of [NiL2][BF4]2 (4)
Tmin, Tmax
No. of reflections
I\n|(I), n
0.33, 0.43
4127, 3
0.23, 0.44
10271, 2
A solution of Ni(BF4)2 (0.136 g, 0.585 mmol) in
CH3NO2 (15 cm3) was added to L (0.300 g, 1.170
mmol) in CH3NO2 (15 cm3) and stirred for 2 h. The
solution was then cooled in the fridge and the dark
green product collected by filtration and washed with
Et2O (4×20 cm3) to afford [NiL2][BF4]2 (0.318 g, 73%).
wR2 a (F2, all reflections)
wR (F, Fo\6|(Fo))
R1 (F, Fo\4|(Fo))
R (F, Fo\6|(Fo))
0.0840
0.0351
0.105
0.075
a wR2=[ꢁ[w(Fo2−Fc2)2]/ꢁw(Fo2)2]1/2 and w−1=[|2(Fo2)+(0.0157P)2+
32.844P] and P=[max(Fo,0)+2Fc2]/3.
2.6. Preparation of [CoL2]Br2 (5)
To a solution of L (0.100 g, 0.39 mmol) in CH3NO2
(25 cm3) was added CoBr2 (0.043 g, 0.195 mmol). After
stirring for 30 min the supernatant was removed by
filtration and the solid dried under vacuum to afford
[CoL2]Br2 (0.104 g, 73%) as a green powder.
factors and a semi-empirical absorption correction was
applied. The structure was solved by Patterson synthe-
sis using Siemens SHELXTL PLUS (VMS) [10] to locate all
the non-hydrogen atoms. Hydrogen atoms were added
in calculated riding positions with fixed isotropic U.
Refinement was by full-matrix least-squares.
2.7. Preparation of [FeL2][BF4]2 (6)
To a solution of L (0.100 g, 0.39 mmol) in CH3CN (4
cm3) was added Fe(BF4)2 (0.046 g, 0.2 mmol) in
CH3CN (5 cm3). The solution turned red immediately
and after stirring for 15 min diethyl ether (10 cm3) was
added to form a bright red precipitate which was
isolated by filtration and washed with diethyl ether
(2×10 cm3) to afford [FeL2][BF4]2 (0.130 g, 88%).
2.7.2. Crystal structure determination of 2
Crystals of [HgL2][ClO4]2 (2) were obtained from
MeCN solution as poorly formed white plates. A crys-
tal (0.41×0.30×0.20 mm) was mounted on a glass
fibre and low temperature data were collected on a
Siemens SMART CCD area-detector 3-circle diffrac-
tometer (Mo Ka X-radiation, graphite monochroma-
,
tor, u=0.710 73 A). For three settings of 8, narrow
2.7.1. Crystal structure determination of 1
data ‘frames’ were collected for 0.3° increments in ꢀ. A
total of 1271 frames of data were collected affording
rather more than a hemisphere of data for the complex.
At the end of data collection the first 50 frames of data
were recollected to establish that crystal decay had not
taken place during the course of data collection. The
substantial redundancy in data allowed empirical ab-
sorption corrections to be applied using multiple mea-
surements of equivalent reflections. Data frames were
collected for 20 s per frame giving an overall time for
data collection of ca. 12 h. The data frames were
integrated using SAINT [10].
Details of the X-ray structure analyses are sum-
marised in Table 2. A crystal of [CuL2][PF6] (1) (0.30×
0.35×0.58) was obtained from acetonitrile solution.
Intensity data were collected on a Siemens R3m/V
diffractometer with graphite monochromated Mo Ka
,
X-radiation (u=0.710 73 A). Cell constants were ob-
tained from least-squares refinement of the setting an-
gles of 25 centred reflections in the range 22°BqB25°.
The data were collected in the ꢀ scan mode and two
standard reflections were measured every 50 reflections.
The data were corrected for Lorentz and polarisation

P.J. Blower et al. / Inorganica Chimica Acta 294 (1999) 170–178
173
The structure was solved by conventional direct
methods procedures and was refined by full-matrix
least-squares on all F2 data using Siemens SHELXTL
5.03 [10]. All non-hydrogen atoms were refined with
anisotropic thermal parameters. Hydrogen atoms were
included in calculated positions with isotropic thermal
parameters ca. 1.2× the equivalent isotropic thermal
parameters of their parent carbon atoms. The asymmet-
ric unit contains two crystallographically independent
molecules of the cation, four ClO−4 anions and one
molecule of MeCN. One of the ClO−4 anions is disor-
dered. All calculations were carried out on Silicon
Graphics Indy or Indigo computers.
compares with yields of typically 35–40% for the
analogous 9S3 preparation using S(CH2CH2SH)2 with
1,2-dibromoethane and Cs2CO3. The macrocycle was
characterised by elemental analysis, observation of a
molecular ion in the mass spectrum (see Table 1) and
by NMR spectroscopy. The 1H and 1H{31P} NMR
spectra recorded at 600 MHz were sufficiently well
resolved to allow simulation and iterative fitting using
LAOCOON PC8 (see Section 2 and Fig. 1). The vicinal
coupling constants (J 8.10, J% 2.83) for the S–C–C–S
fragment are close to those calculated (J 8.18, J% 3.79)
for a gauche equilibrium mixture as would be expected
for a nine-membered ring [11]. Using the equations
derived empirically by Abraham and Gatti [12], and
applied by Lockhart and Tomkinson [11] to a range of
thiamacrocycles, the expected values for the vicinal
couplings in the P–C–C–S segments in a gauche equi-
librium mixture are 8.64 and 4.28 Hz, close to the
average of those observed (8.65 and 3.43 Hz). The
observation of gauche placements does not, however,
distinguish between exo- and endodentate conforma-
tions of L and therefore we undertook a molecular
mechanics study to assess the likely geometry of L.
Initially we modelled the phosphine sulfide c-PhPS-
(CH2CH2S)2CH2CH2, whose structure has been deter-
mined by X-ray crystallography [2], by starting from
analogous conformations known for 9S3 [13]. Using the
MM+ force field in the HYPERCHEM package [9] (see
Section 2) a minimum was found corresponding very
closely to the crystallographically observed solid-state
geometry, which is an exodentate conformation corre-
sponding to the C2 conformation of 9S3 [13]. A similar
procedure for L produced an endodentate conforma-
tion corresponding to that observed in [Mo(CO)3L]
2.7.3. EXAFS studies
Extended X-ray absorption fine structure (EXAFS)
spectroscopic measurements were performed at the
Daresbury Synchroton Radiation Source (Daresbury
Laboratory, Warrington, UK). Iron, cobalt, nickel and
copper K-edge data were obtained on Station 8.1 using
an order-sorting double crystal monochromator with
focusing optics. Harmonic rejection was achieved by
stepping off the peak of the rocking curve by 70% of
the full height level. The monochromator was fitted
with a Si(220) crystal which produced X-rays varying in
energy from 5.5 to 11 KeV. Samples were prepared by
pressing 13 mm pellets containing a mixture of complex
(30–45 mg) and boron nitride (90–100 mg) and
mounted in a cryogenically cooled aluminium holder.
EXAFS were recorded at 293 and 77 K. Typically four
or five data sets were collected for each complex and
the analyses were carried out on the average spectra.
Data analyses were performed using the program EX-
CURV92 [24]. The programme performs least squares
fitting of the EXAFS spectrum to a structural model
with coordination numbers, radial distances (d) and
Debye Waller factors as floating parameters. The errors
(Fig. 2(a)) as the lowest energy (16.61 kcal mol−1
)
conformation. Exodentate conformations were found
(Fig. 2(b)–(d)) at energies of 16.80, 17.28 and 17.91
kcal mol−1, respectively. The results suggest that
the endodentate conformation is preferred over exoden-
tate conformations, which are however still ener-
,
in d are approximately 90.02 A and in the coordina-
tion number 920%.
2.7.4. Electrochemistry
Cyclic voltammograms were performed under a dry
dinitrogen atmosphere on 1 mM solutions of the com-
plexes in dry deoxygenated acetonitrile containing 0.1
mol dm−3 NBu4BF4 as a supporting electrolyte, at scan
rates of 50 to 500 mV s−1. Then an equimolar amount
of ferrocene was added as an internal standard.
3. Results and discussion
3.1. Synthesis and characterisation of L
Reaction of PhP(CH2CH2SH)2 with 1,2-dichloro-
ethane and Cs2CO3 under high dilution conditions af-
fords L as an oil in reasonable yield (52%). This
Fig. 1. 1-phenyl-1-phospha-4,7-dithiacyclononane (L) showing the
NMR labelling system.

174
P.J. Blower et al. / Inorganica Chimica Acta 294 (1999) 170–178
Fig. 3. The molecular structure of [Cu(h1-L)(h3-L)]+ (1) showing the
atom labelling system. Atoms are represented as 50% probability
ellipsoids.
[Cu(9S3)(EPh3)][ClO4] (E=P, As) prepared by reaction
of 9S3 with [Cu(NCMe)4][ClO4] in the presence of EPh3
[16]. The h3-L has an endodentate conformation similar
to that already established by X-ray crystallography in
the structure of [Mo(CO)3L]2 and by molecular me-
chanics for the free ligand (Fig. 2(a)). The conforma-
tion of h1-L is similar to Fig. 2(d) found for the free
Fig. 2. Local energy minima of L established using HYPERCHEM. (a)
Endodentate 16.61 kcal mol−1; (b) exodentate 16.80 kcal mol−1; (c)
Table 3
exodentate 17.28 kcal mol−1; (d) exodentate 17.91 kcal mol−1
.
1
3
,
Selected bond lengths (A) and angles (°) for [Cu(h -L)(h -L)][PF6] (1)
,
getically accessible, and that complexes of L would be
expected to show high thermodynamic stability because
there would be no enthalpy lost in conformationally
adapting the ligand for facial coordination. Conforma-
tion Fig. 2(c) is similar to that observed in c-
PhPS(CH2CH2S)2CH2CH2 and Fig. 2(d) has been
observed in [Cu(h1-L)(h3-L)][PF6] (see above). Similar
calculations with 9S3 suggest that the energy difference
between endo- and exodentate conformations are even
smaller (ca. 0.03 kcal mol−1) [14].
Bond lengths (A)
Cu(1)–P(1)
Cu(1)–S(2)
P(1)–C(1)
P(1)–C(7)
S(1)–C(3)
S(2)–C(5)
C(3)–C(4)
P(2)–C(13)
P(2)–C(19)
S(3)–C(15)
S(4)–C(17)
C(15)–C(16)
2.246(3)
2.366(4)
Cu(1)–S(1)
Cu(1)–P(2)
P(1)–C(6)
S(1)–C(2)
2.354(3)
2.215(3)
1.842(12)
1.818(15)
1.828(15)
1.836(13)
1.509(20)
1.853(10)
1.832(12)
1.820(17)
1.817(15)
1.495(21)
1.850(14)
1.815(13)
1.825(13)
1.512(15)
1.495(23)
1.839(12)
1.791(13)
1.798(15)
1.533(16)
1.535(21)
S(2)–C(4)
C(1)–C(2)
C(5)–C(6)
P(2)–C(18)
S(3)–C(14)
S(4)–C(16)
C(13)–C(14)
C(17)–C(18)
Bond angles (°)
P(1)–Cu(1)–S(1)
S(1)–Cu(1)–S(2)
S(1)–Cu(1)–P(2)
Cu(1)–P(1)–C(1)
C(1)–P(1)–C(6)
C(1)–P(1)–C(7)
Cu(1)–S(1)–C(2)
C(2)–S(1)–C(3)
Cu(1)–S(2)–C(5)
3.2. Synthesis and structure of [Cu(p1-L)(p3-L)][PF6]
91.5(1)
91.2(1)
P(1)–Cu(1)–S(2)
P(1)–Cu(1)–P(2)
S(2)–Cu(1)–P(2)
Cu(1)–P(1)–C(6)
Cu(1)–P(1)–C(7)
C(6)–P(1)–C(7)
Cu(1)–S(1)–C(3)
Cu(1)–S(2)–C(4)
C(4)–S(2)–C(5)
Cu(1)–P(2)–C(18)
Cu(1)–P(2)–C(19)
C(18)–P(2)–C(19)
C(16)–S(4)–C(17)
90.1(1)
130.5(1)
116.7(1)
102.4(4)
131.5(4)
106.6(6)
101.7(4)
97.8(5)
102.9(7)
112.1(4)
113.0(4)
103.7(6)
104.9(7)
125.9(1)
104.9(4)
103.4(6)
105.1(6)
99.1(4)
Reaction of
L with [Cu(NCMe)4][PF6] affords
[Cu(h1-L)(h3-L)][PF6] (1). The compound was charac-
terised by X-ray crystallography (see Fig. 3 and Table
3). One equiv. of acetonitrile is incorporated in the
crystal lattice. The complex is a distorted tetrahedron
with one ligand facially tridentate and the other uniden-
tate and coordinated via the phosphorus. A similar
tetrahedral geometry has been observed for [Cu(h1-
9S3)(h3-9S3)][PF6] in which one of the 9S3 ligands is
unidentate [15,17]. The structure is also similar to
103.1(6)
102.3(5)
Cu(1)–P(2)–C(13) 118.1(4)
C(13)–P(2)–C(18) 106.9(6)
C(13)–P(2)–C(19) 101.5(5)
C(14)–S(3)–C(15) 104.3(7)

P.J. Blower et al. / Inorganica Chimica Acta 294 (1999) 170–178
175
tially the same geometry, but are pseudo enantiomeric.
It is interesting to compare the structure with that of
[Hg(9S3)2][PF6]2 which is approximately octahedral
with two of the Hg–S bonds significantly shorter than
the other four indicating a small tetragonal compres-
sion [18]. This structural feature was interpreted as a
compromise between the third-row d10 metal ion’s ten-
dency to adopt linear coordination and the preference
of 9S3 for facial binding. In [Hg(9S3)2]2+ the latter
preference appears to dominate. The structure of 2
shows a much finer balance. The Hg–P bonds are short
,
(average 2.404 A) as is expected for a pseudo two-
Table 4
,
Selected bond lengths (A) and angles (°) for [HgL2][ClO4]2·1/2-
(MeCN) (2)
Fig. 4. The molecular structure of [HgL2]2+ (2) (molecule 1) showing
the atom labelling system. Atoms are represented as 40% probability
ellipsoids.
Molecule 1
(n=1)
Molecule 2
(n=2)
,
Bond lengths (A)
ligand by molecular mechanics. The bite angles from
the h3-L (average 90.9°) are substantially reduced from
the values expected for a tetrahedral metal centre and
are a consequence of the strained restricted conforma-
tion of L. The remaining angles at the copper centre are
correspondingly larger (average 124.3°) and range from
130.5(1)° for P(1)–Cu(1)–P(2) to 116.7° for S(2)–
Cu(1)–P(2) reflecting the steric interaction of the
phenyl groups and the non-chelating part of h1-L. The
steric crowding is also manifest in the large angle
Cu(1)–P(1)–C(7) [131.5(4)°] and the orientation of the
phenyl group attached to P(1) which is approximately
co-planar with S(1), S(2) and P(1). When L is h3-
coordinated to a Mo(CO)3 fragment the phenyl group
is orientated perpendicular to the plane of the macrocy-
cle; however, when in the more sterically congested
seven-coordinate complex [Mo(CO)2Br2(h3-L)] the
phenyl group adopts a co-planar orientation [2]. The
Hg(n)–P(n11)
Hg(n)–P(n31)
Hg(n)–S(n37)
Hg(n)–S(n34)
Hg(n)–S(n17)
Hg(n)–S(n14)
P(n11)–C(n12)
P(n11)–C(n21)
P(n11)–C(n19)
C(n12)–C(n13)
C(n13)–S(n14)
S(n14)–C(n15)
C(n15)–C(n16)
C(n16)–S(n17)
S(n17)–C(n18)
C(n18)–C(n19)
P(n31)–C(n41)
P(n31)–C(n32)
P(n31)–C(n39)
C(n32)–C(n33)
C(n33)–S(n34)
S(n34)–C(n35)
C(n35)–C(n36)
C(n36)–S(n37)
S(n37)–C(n38)
C(n38)–C(n39)
2.391(2)
2.3940(14)
3.055(2)
3.082(2)
3.109(2)
3.265(2)
1.804(7)
1.805(7)
1.888(9)
1.430(12)
1.8269(8)
1.797(9)
1.404(13)
1.839(10)
1.765(10)
1.419(14)
1.796(6)
1.822(6)
1.832(6)
1.534(8)
1.825(6)
1.814(7)
1.536(9)
1.821(6)
1.815(7)
1.539(9)
2.4157(14)
2.4151(14)
3.0587(14)
3.0590(14)
2.975(2)
3.131(2)
1.816(6)
1.806(6)
1.822(6)
1.530(8)
1.829(6)
1.812(7)
1.522(9)
1.821(6)
1.813(6)
1.533(8)
1.814(6)
1.826(6)
1.831(6)
1.549(8)
1.823(6)
1.822(6)
1.530(8)
1.823(6)
1.817(6)
1.525(9)
,
Cu–S distances [average 2.360(4) A] are longer than
those observed in [Cu(9S3)(AsPh3)]+ [2.303(6) A]
,
[16], [Cu(h1-9S3)(h3-9S3)]+ [2.316(7) A] [15] and
,
[Cu2(9S3)3]2+ [2.300 A] [17]. Both the Cu–P distances
,
,
are as expected with Cu(1)–P(1) being 0.032(3) A
Bond angles (°)
longer than Cu(1)–P(2). The Cu–P distances are
shorter than the Cu–S distances in accord with the
greater s-donor and p-acceptor abilities of phosphines
compared with thioethers. The distance between Cu(1)
P(n11)–Hg(n)–P(n31)
P(n11)–Hg(n)–S(n37)
P(n31)–Hg(n)–S(n37)
P(n11)–Hg(n)–S(n34)
P(n31)–Hg(n)–S(n34)
S(n37)–Hg(n)–S(n34)
P(n11)–Hg(n)–S(n17)
P(n31)–Hg(n)–S(n17)
S(n37)–Hg(n)–S(n17)
S(n34)–Hg(n)–S(n17)
P(n11)–Hg(n)–S(n14)
P(n31)–Hg(n)–S(n14)
S(n37)–Hg(n)–S(n14)
S(n34)–Hg(n)–S(n14)
S(n17)–Hg(n)–S(n14)
175.86(5)
98.83(5)
79.32(5)
100.55(5)
75.35(4)
69.92(4)
75.26(6)
104.29(5)
147.80(5)
79.96(4)
73.42(5)
110.29(5)
143.06(4)
146.48(4)
66.56(5)
164.84(5)
113.59(4)
78.57(4)
99.94(4)
75.08(4)
69.94(6)
79.12(5)
115.16(5)
65.74(4)
130.49(4)
74.42(4)
105.14(5)
130.52(4)
159.50(5)
68.61(4)
,
and S(3) (3.546 A) is too long to represent a significant
interaction.
3.3. Synthesis and structure of [HgL2][ClO4]2
Reaction of Hg(ClO4)2 with L affords [HgL2][ClO4]2
(2) whose structure has been established by X-ray dif-
fraction (Fig. 4 and Table 4). The asymmetric unit
contains two independent cations which have essen-

176
P.J. Blower et al. / Inorganica Chimica Acta 294 (1999) 170–178
Table 5
the EXAFS the coordination numbers were allowed to
EXAFS data a
float. The values obtained were within 20% of the
crystallographic coordination numbers and therefore
further analyses were undertaken with these latter val-
ues. A similar approach was taken for the EXAFS of 4,
5 and 6. The best fit (R=20%) for 1 was obtained for
a model analogous to the X-ray structure with a first
c
Complex
Shell
d
(A)
2|2 b
R
2
,
,
(A )
(%)
[Cu(h1–L)(h3–L)][PF6] (1) 2P
2.216(4) 0.002(03) 20.0
2.339(5) 0.004(06)
2S
6C
3.230(9) 0.018(2)
,
shell comprising of two phosphorus atoms (2.216 A)
[NiL2][BF4]2 (4)
[CoL2]Br2 (5)
2P
4S
12C
2.212(2) 0.007(03) 31.7
2.356(3) 0.015(05)
,
and two sulfur atoms (2.339 A) and a second shell of
,
six carbon atoms (3.230 A).
3.308(6) 0.021(1)
Three distinct shells are observed for 4 corresponding
2P
4S
12C
2Br
2.220(2) 0.006(03) 31.0
2.351(3) 0.017(06)
3.298(6) 0.021(2)
to phosphorus, sulfur and carbon as shown in Fig. 5(a).
,
The phosphorus shell at 2.212 A compares well with the
,
average Ni–P distance of 2.201 A obtained for nickel
4.187(13) 0.021(3)
phosphine complexes in the Cambridge Crystallo-
[FeL2][BF4]2 (6)
2P
4S
12C
2.266(5) 0.004(05) 23.8
2.217(5) 0.011(09)
,
graphic Database [21]. The sulfur shell at 2.356 A is in
accord with the average Ni–S distance in [Ni(9S3)2]2+
3.288(9) 0.023(3)
,
(2.386 A) [22]. The complex is therefore six-coordinate
and probably a distorted octahedron of more regular
a Standard deviations in parentheses. Note that the systematic
errors in bond distances arising from the data collection and analysis
symmetry than 2.
,
procedures are ca. 0.02–0.03 A for well-defined coordination shells.
b Debye–Waller factor.
Four distinct shells are observed for 5 corresponding
to phosphorus, sulfur, carbon and bromine as illus-
trated in Fig. 5(b). Again the complex is six-coordinate
c R factor defined as [ (T−E)k3 dk/ Ek3 dk]×100.
,
with the phosphorus shell at 2.220 A being close to that
coordinate complex and can be compared with a length
of 2.389(5)
tris(2,4,6-trimethoxyphenyl)phosphine) [19]. The four
,
expected from the average Co–P distance of 2.223 A
found in [Hg(tmpp)2]2+ (tmpp=
,
A
for cobalt phosphine complexes in the Cambridge Crys-
,
Hg–S bond lengths (average 3.092 A) are considerably
,
longer than those in [Hg(9S3)2][PF6]2 (average 2.693 A).
Similar weak interactions have been observed in 9S3
complexes of palladium(II) where the metal has a pref-
erence for square planar coordination [20]. For exam-
ple, [Pd(9S3)Br2] has a long Pd–S distance of 3.125(1)
,
A. The structure suggests that L readily adopts an
endodentate conformation even in the absence of a
strong metal preference for facial coordination, consis-
tent with the molecular mechanics results.
3.4. Synthesis of Ag, Ni, Co and Fe complexes
Reaction of L with AgBF4, Ni(BF4)2, CoBr2 and
Fe(BF4)2 affords [AgL2][BF4] (3), [NiL2][BF4]2 (4),
[CoL2]Br2 (5), [FeL2][BF4]2 (6), respectively, which were
characterised by FAB mass spectroscopy and elemental
analysis (Table 1), but unfortunately we were not able
to obtain single crystals suitable for X-ray diffraction.
3.4.1. EXAFS
Further structure information for complexes 4, 5 and
6 was obtained by EXAFS. Data were recorded at 293
and 77 K, but in all cases the low temperature data was
superior and is summarised in Table 5. This was partic-
ularly noticeable for 4 and 5 where the phosphorus and
sulfur shells were resolved at 77 K, but not at 293 K.
Initial studies were performed on 1 where single crystal
data is available for comparison. In the initial fitting of
Fig. 5. (a) Fourier transformed nickel K-edge EXAFS spectrum of
[NiL2][BF4]2 (4) (full line: experimental, broken line: theory). (b)
Fourier transformed cobalt K-edge EXAFS spectrum of [CoL2]Br2
(5) (full line: experimental, broken line: theory).

P.J. Blower et al. / Inorganica Chimica Acta 294 (1999) 170–178
177
Table 6
Electronic spectroscopy data for complexes of L and 9S3 [23]
Table 7
Cyclic voltammetry data for complexes of L and 9S3 [23]
Complex
l (nm) (o (dm3 mol−1 cm−1))
Solvent
Complex
Couple
E1/2 (V)
Rev/Irrev
[NiL2]2+ (4)
[Ni(9S3)2]2+
[CoL2]2+ (5)
[Co(9S3)2]2+
675 (98), 317 (16434), 200 (42155)
784 (27), 527 (26), 325 (14000)
327 (14147), 264 (11750), 200 (43603) H2O
730 (11), 560 (sh), 480 (92), 338
(6600), 264 (6500)
480 (308), 375 (259), 275 (17470),
211 (26272)
H2O
H2O
[NiL2]2+ (4)
Ni2+/Ni3+
Ni2+/Ni+
Ni+/Ni0
+0.22
−0.99
−1.43
Rev
Rev
Rev
MeCN
[Ni(9S3)2]2+
Ni2+/Ni3+
Ni2+/Ni+
+0.97
−1.07
Rev
Irrev
[FeL2]2+ (6)
MeCN
H2O
[CoL2]2+ (5)
Co2+/Co3+
−0.17
Rev
[Fe(9S3)2]2+
523 (53), 395 (52)
[Co(9S3)2]2+
Co2+/Co3+
Co2+/Co+
−0.013
−0.86
Rev
Rev
[FeL2]2+ (6)
Fe2+/Fe3+
Fe2+/Fe3+
+0.96
+0.98
Rev
Rev
[Fe(9S3)2]2+
tallographic Database. The sulfur shell distance of
,
2.351 A is similar to the average Co–S distance (2.321
2+
,
A) in [Co(9S3)2]
[22].
Even at low temperature distinct phosphorus and
sulfur shells were not resolved for 6. This is not surpris-
ing since average Fe–S and Fe–P distances for iron
thioether and iron phosphine complexes obtained for
the Cambridge Crystallographic Database are very sim-
,
ilar (2.273 and 2.247 A). Again EXAFS confirms the
presence of a six-coordinate complex.
3.5. Electronic spectroscopy
The electronic spectra of 4, 5 and 6 were recorded
(see Table 6) and all have intense absorptions below
250 nm due to the phenyl rings. The spectrum of 4
contains a band at 675 nm (m=98) assigned to the d–d
Fig. 6. Cyclic voltammogram of [NiL2][BF4]2 (4).
3.6. Electrochemistry
3
transition A2g“3T2g, characteristic of a Ni2+ ion in a
Electrochemical data for the complexes and of
analogous 9S3 complexes are shown in Table 7. These
studies were undertaken to determine whether or not
substitution of a thioether donor by a phosphine donor
would render the complexes easier to oxidise (as a
result of the greater s-donor capacity of the phos-
phine), or easier to reduce (as a consequence of the
greater p-acceptor capacity of the phosphine). In the
case of the Ni(II) complex 4 (Fig. 6) both effects seem
to operate with the complex being both easier to oxidise
to Ni(III) and reduce to Ni(I) than its 9S3 analogue.
Additionally in the case of 4 the Ni(0) state is reversibly
accessible, thus L has the ability to stabilise Ni in four
oxidation states. The differences for the Fe and Co
complexes are less pronounced.
pseudo-octahedral environment, and a higher energy
3
transition at 317 nm (m=16434) assigned to the A2g“
3T1g(F) transition overlapping with a charge-transfer
band. The increase in transition energies and extinction
coefficients compared with the analogous 9S3 derivative
(Table 6) indicates that L is a stronger field ligand
(Zo=14810 versus 12760 cm−1) and that, as expected,
the L complex is of lower symmetry.
Complex 6 has two d–d absorption maxima typical
of low spin Fe(II) in a pseudo-octahedral field corre-
1
1
sponding to A1g“1T1g and A1g“1T2g which are not
obscured by intense charge-transfer bands. From the
energy difference of these two maxima, which is ap-
proximately 16B, and assuming C=4B, Zo is calcu-
lated to be 22290 cm−1 and B=364 cm−1 [23].
1A1g“1T1g=Zo−C
1A1g“1T2g=Zo+16B−C
4. Conclusions
For [Fe(9S3)2]2+ Zo is 20670 cm−1 and B=387 cm−1
.
We can conclude that the structural studies confirm
that the conformational preferences of L can be pre-
dicted by reference to the known behaviour of 9S3. L
can coordinate in a facial, tridentate manner, and
where this is precluded by the stereochemical prefer-
In the spectrum of the Co2+ complex 5 no d–d bands
were observed, presumably due to the high intensity
charge-transfer bands tailing off into the low energy
region of the spectrum.

178
P.J. Blower et al. / Inorganica Chimica Acta 294 (1999) 170–178
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We thank the EPSRC and the Cancer Research
Campaign for studentships (S.N.S., G.E.D.M. and
R.J.S.) and the EPSRC for access to the mass spec-
trometry, NMR and Chemical Database (D.A.
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We thank Dr R.E. Benfield for assistance in collecting
the EXAFS data.
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