Synthesis and thermal behaviour of cyclopentadienylnickel(II) thiolato Schiff base complexes. Molecular structures of Ni(η5-C5H5)(PBu3)(SC 6H4NC(H)C6H4C6H 5)

Article abstract of DOI:10.1016/S0022-328X(01)00859-2

The new complexes Ni(η⁵-C₅H₅)(PR₃)(SC ₆H₄NC(H)C₆H₄OC_nH _2n+1), Ni(η⁵-C₅H₅)(PR₃)(SC ₆H₄NC(H)C₆H₄C₆H ₅) and Ni(η⁵-C₅H₅)(PR₃)(SC ₆H₄NC(H)C₆H₄OCH₂C ₆H₅), (R=Ph or Bu; n=4, 6, 8, 10, 14, 16 and 20), were synthesised from equimolar amounts of Ni(η⁵-C₅H₅)(PR₃)Br (R=Ph or Bu) and the appropriate thiol ligand and were characterised by NMR and elemental analysis. In addition 1a and 3a were characterised by single crystal X-ray diffraction studies. These new complexes were also examined by thermal analytical methods (DSC and TGA) and polarising hot-stage microscopy, but were not found to exhibit any liquid crystalline behaviour. Thermal analysis showed that the complexes were generally stable up to about 180°C and decomposed finally to a species with empirical formula NiSC₆H₅. Two decomposition pathways were established, depending on the phosphine used.

Full text of DOI:10.1016/S0022-328X(01)00859-2

Journal of Organometallic Chemistry 629 (2001) 171–181
www.elsevier.com/locate/jorganchem
Synthesis and thermal behaviour of cyclopentadienylnickel(II)
thiolato Schiff base complexes. Molecular structures of
Ni(h5-C5H5)(PBu3)(SC6H4NC(H)C6H4C6H5) and
Ni(h5-C5H5)(PBu3)(SC6H4NC(H)C6H4OC4H9)
Richard M. Moutloali a, John Bacsa b, Wilfred A. Ddamba c, James Darkwa a,*
a Department of Chemistry, Uni6ersity of the Western Cape, Pri6ate Bag X17, Bell6ille 7535, South Africa
b Department of Chemistry, Uni6ersity of Cape Town, Rondebosch 7701, Cape Town, South Africa
c Department of Chemistry, Uni6ersity of Botswana, Pri6ate Bag 0022, Gaborone, Botswana
Received 13 March 2001; accepted 16 April 2001
Abstract
The new complexes Ni(h5-C5H5)(PR3)(SC6H4NC(H)C6H4OCnH2n+1), Ni(h5-C5H5)(PR3)(SC6H4NC(H)C6H4C6H5) and Ni(h5-
C5H5)(PR3)(SC6H4NC(H)C6H4OCH2C6H5), (R=Ph or Bu; n=4, 6, 8, 10, 14, 16 and 20), were synthesised from equimolar
amounts of Ni(h5-C5H5)(PR3)Br (R=Ph or Bu) and the appropriate thiol ligand and were characterised by NMR and elemental
analysis. In addition 1a and 3a were characterised by single crystal X-ray diffraction studies. These new complexes were also
examined by thermal analytical methods (DSC and TGA) and polarising hot-stage microscopy, but were not found to exhibit any
liquid crystalline behaviour. Thermal analysis showed that the complexes were generally stable up to about 180 °C and
decomposed finally to a species with empirical formula NiSC6H5. Two decomposition pathways were established, depending on
the phosphine used. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Cyclopentadienylnickel(II); Thiolato Schiff base complexes; Thermal behaviour
using what could be described as a non-conventional
approach. The conventional approach involves com-
plexation of an organic liquid crystalline compound
with a metal fragment. However, metal complexes thus
formed by this conventional route do not always show
liquid crystalline properties [4].
In preparing the complexes reported here we have
combined features found in two types of metallomeso-
gens. The first type is a Schiff base metal complexes
that have the Schiff base directly bound to the metal,
with the imine group as part of the ligand backbone,
1. Introduction
The search for metal Schiff base complexes is driven
in part by their potential use in material science. Two
specific applications are liquid crystals [1] and non-lin-
ear optical materials [2]. In most complexes that behave
as liquid crystals or exhibit non-linear optical be-
haviour, the imine group of the Schiff base only forms
part of the ligand backbone and is not coordinated to
the metal centre. The imine group is thus used as a
linker between aromatic rings in both of these
applications.
HgCl(C6H4ꢀ4-NꢁCHꢀC6H4ꢀ4%-OMe),
NꢁCHꢀC6H4ꢀ4%-OMe)2 [5a] and M(CO)2Cl(NC5H5ꢀ4-
NꢁCHꢀC6H4ꢀ4%-CnH2n+1 (M=Rh, Ir; n=5–12)
Hg(C6H4ꢀ4-
We have recently reported the preparation of nickel
complexes that contain Schiff base ligands bound to the
metal through a sulfur atom [3]. This was done in an
attempt to prepare nickel Schiff base metallomesogens,
)
[5a,b]. The second type is metal thiolato complexes that
have either monothiolato ligands, AgSCnH2n+1 (n=4,
6, 8, 10, 12, 16, 18) [6], or dithiolato ligands,
Ni2(S2CꢀCnH2n+1 4
OCnH2n+1 2 (n=4, 8) [8] and Ni(S3CꢀC6H4ꢀ4-
OCnH2n+1)(S2CꢀC6H4ꢀ4-OCnH2n+1) (n=4, 8) [9]. We
)
(n=5–12) [7], Ni(S2CꢀC6H4ꢀ4-
* Corresponding author. Tel.: +27-21-9593053; fax: +27-21-
9593055.
E-mail address: jdarkwa@uwc.ac.za (J. Darkwa).
)
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00859-2

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R.M. Moutloali et al. / Journal of Organometallic Chemistry 629 (2001) 171–181
Table 1
1H NMR data and elemental analysis for Schiff bases (calculated values in brackets)
Compound
1H-NMR
Elemental analysis
C
H
N
1
2
3
4
5
6
7
8
9
8.48(s), 7.96(d), 7.75(d), 7.64 (m), 7.14(d)
8.37(s), 7.83(d), 7.40(m), 7.08(dd), 5.14(s), 3.47(s)
8.36(s), 7.82(d), 7.30(d), 7.10(d), 6.97(d), 3.47(s)
8.36(s), 7.82(d), 7.52(d), 7.14(d), 6.96(d)
8.35(s), 7.84(d), 7.52(d), 7.16(d), 6.97(d)
8.35(s), 7.82(d), 7.52(d), 7.15(d), 6.96(d)
8.35(s), 7.81(d), 7.51(d), 7.14(d), 6.96(d)
8.36(s), 7.82(d), 7.30(d), 7.10(d), 6.96(d), 3.47(s)
8.35(s), 7.82(d), 7.51(d), 7.14(d), 6.96(d), 3.47(s)
74.68 (75.20)
74.92 (74.74)
71.72 (71.55)
72.86 (72.81)
74.11 (74.08)
73.73 (74.29)
76.55 (76.18)
76.61 (76.77)
77.52 (77.74)
5.56 (5.36)
4.32 (4.38)
4.45 (4.36)
5.04 (4.91)
4.60 (4.47)
4.23 (4.11)
3.67 (4.15)
3.75 (3.29)
2.78 (3.09)
3.33 (2.75)
5.85 (5.33)
6.43 (6.71)
7.51 (7.39)
7.49 (7.70)
10.08 (9.86)
8.95 (9.23)
10.77 (9.99)
9.75 (10.08)
have thus prepared the Schiff base thiols (I) and their
nickel complexes (II) in an effort to obtain metallo-
mesogens. Thermal studies of the ligands and the com-
plexes using differential scanning calorimetry (DSC)
and polarising hot-stage microscopy showed that nei-
ther the ligands nor the complexes have any mesogenic
properties. They, however, show the effect of alkoxy
chain length on the thermal behaviour of both the
ligands and the complexes, which is reported herein.
IR spectra were obtained on
a
Perkin–Elmer
Paragon 1000 PC FT spectrometer as Nujol mulls. The
1H- and 31P-NMR spectra were acquired on a Varian
Gemini 2000 spectrometer at 200 and 80.961 MHz and
referenced to residual CHCl3 (l 7.26) and externally to
PPh3 (l−5.00), respectively. Thermal analyses were
performed on a Universal V2.3H TA instrument. Ele-
mental analysis and GC–MS (in electron impact mode)
were performed in the Department of Chemistry at the
University of the Western Cape.
X-ray diffraction data were collected at a low tem-
perature on a Nonius Kappa CCD with 1.5 kW
graphite monochromated Mo radiation. A selection of
crystal and refinement data is given in Table 3. The
strategy for the data collection was evaluated using the
COLLECT software [12]. The data were scaled and re-
duced using DENZO-SMN [13]. Unit cell dimensions were
refined on all data. The data were treated for absorp-
tion using the program SORTAV [14]. The structures
were solved and refined using SHELX97 [15]. Hydrogen
atoms were placed in calculated positions and refined as
riding atoms. Molecular graphics and additional mate-
rial for publication were obtained using the program
PLATON [16].
(1)
2. Experimental
2.1. Materials and instrumentation
All commercially available chemicals were used as
received. The following specialty chemicals were pur-
chased: 4-aminothiophenol (Fluka), 1-bromooctane
(Saarchem, South Africa), 4-hydroxybenzaldehyde, 4-
biphenylcarboxyaldehyde, 4-benzyloxybenzaldehyde, 4-
butyloxybenzaldehyde, 1-bromodecane, 1-bromohexa-
decane, Et3N (Aldrich). The nickel compounds Ni(h5-
C5H5)(PPh3)Br and Ni(h5-C5H5)(PBu3)Br were pre-
pared by literature methods [10]. The compounds
OHCC6H4OR-4 (R=CnH2n+1, n=2, 6, 8, 10, 14, 16
and 20) were prepared by a modified literature proce-
dure [11]. The Schiff base compounds were synthesised
by the condensation reaction between the aldehydes
and 4-aminothiophenol in ethanol as recently reported
Table 2
Melting points of selected complexes
Complex
Melting point (°C)
3a
3b
6a
6b
7a
7b
8b
9a
9b
99.97
138.83
62.24
120.11
52.26
90.21
89.70
49.70
101.77
1
[3] and characterised by H-NMR, GC–MS and ele-
mental analysis. Reagent grade hexane was distilled and
then stored over molecular sieves, while toluene was
distilled from sodium. All reactions were performed
using standard Schlenk techniques under dinitrogen
atmosphere.

R.M. Moutloali et al. / Journal of Organometallic Chemistry 629 (2001) 171–181
173
Scheme 1. Thermal decomposition patterns of: (a) PPh3 complexes; and (b) PBu3 complexes.
Fig. 1. TGA-DSC curves for 3a.

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R.M. Moutloali et al. / Journal of Organometallic Chemistry 629 (2001) 171–181
2.2. Ni(p5-C5H5)(PBu3)(SC6H4NC(H)C6H4C6H5) (1a)
mixture was filtered to remove the white Et3NHBr
by-product and the filtrate evaporated. The residue was
recrystallised from hexane at −15°C to give green
Preparation of cyclopentadienylnickel thiolato Schiff
base is representative and will only be described in
detail for compound 1a. To a degassed solution of
HSC6H4NC(H)C6H4C6H5 (0.2 g, 0.63 mmol) and
Ni(h5-C5H5)(PBu3)Br (0.28 g, 0.68 mmol) in toluene (50
ml) was added excess Et3N (1.5 ml). The maroon
solution immediately turned to dark green immediately
and was stirred at room temperature (r.t.) for 15 h. The
1
crystalline product in a yield of 0.12 g (38%). H-NMR
(CDCl3, l ppm): 8.52 (s, 1H, NꢁC(H)), 7.94 (d, 2H,
J
HH=8.4 Hz, C(H)C6H4), 7.67 (m, 5H, NC6H4, C6H5),
7.43 (m, 4H, C(H)C6H4, C6H5), 6.99 (d, 2H, JHH=8.6
Hz, SC6H4), 5.28 (s, 5H, h5-C5H5), 1.52–1.35 (m, 18H,
butyl), 0.92 (t, 9H, CH3). 31P{1H}-NMR (CDCl3, l
ppm): 25.36. Anal. Found: C, 68.78; H, 7.89; N, 2.14.
Calc. for C36H46NPSNi: C, 69.17; H, 7.53; N, 2.18%
Fig. 2. TGA-DSC curves for 3b.
Fig. 3. Molecular structure of 1a.

R.M. Moutloali et al. / Journal of Organometallic Chemistry 629 (2001) 171–181
175
Fig. 4. Packing diagram for 1a.
The synthetic route for the remaining complexes is
similar to 1a.
2.5. Ni(p5-C5H5)(PBu3)(SC6H4NC(H)C6H4OC6H13)
(4a)
2.3. Ni(p5-C5H5)(PBu3)(SC6H4NC(H)C6H4OCH2C6H5)
(2a)
A green solid with a yield of 76% (0.58 g) was
obtained. 1H-NMR (CDCl3, l ppm): 8.39 (s, 1H,
C(H)N), 7.80 (d, 2H, JHH=8.2 Hz, C(H)C6H4), 7.60
(d, 2H, JHH=8.2 Hz, NC6H4), 6.94 (d, 2H, JHH=8.4
Hz, OC6H4), 6.93 (d, 2H, JHH=8.6 Hz, SC6H4), 5.26
(s, 5H, h5-C5H5), 4.02 (t, 2H, OCH2), 1.80–1.25 (m,
26H, alkyl), 0.92 (t, 12H, alkoxy, butyl). 31P{1H}-NMR
(CDCl3, l ppm): 25.26. Anal. Found: C, 68.04; H, 8.62;
N, 2.40. Calc. for C36H54NOPSNi: C, 67.93; H, 8.55; N,
2.20%.
A green solid was obtained with a yield of 0.34 g
(33%). 1H-NMR (CDCl3,
l
ppm): 8.40 (s, 1H,
NꢁC(H)), 7.82 (d, 2H, JHH=8.4 Hz, C(H)C6H4), 7.62
(d, 2H, HH=8.0 Hz, NC6H4), 7.40 (m, 5H,
J
OCH2C6H5), 7.04 (d, 2H, JHH=8.4 Hz, OC6H4), 6.93
(d, 2H, JHH=8.4 Hz, SC6H4), 5.27 (s, 5H, h5-C5H5),
5.13 (s, 2H, OCH2), 1.43–1.27 (m, 18H, butyl), 0.92 (t,
9H, CH3). 31P{1H}-NMR (l ppm): 27.33. Anal. Found:
C, 69.22; H, 7.62; N, 2.08. Calc. for C37H48NOPSNi: C,
68.95; H, 7.22, N, 2.18%.
2.6. Ni(p5-C5H5)(PBu3)(SC6H4NC(H)C6H4OC8H17)
(5a)
2.4. Ni(p5-C5H5)(PBu3)(SC6H4NC(H)C6H4OC4H9) (3a)
Green crystals with a yield of 0.94 g (88%) were
obtained. 1H-NMR (CDCl3, l ppm): 8.39 (s, 1H,
NꢁC(H)), 7.80 (d, 2H, JHH=8.8 Hz, C(H)C6H4), 7.61
(d, 2H, JHH=8.4 Hz, NC6H4), 6.94 (d, 2H, JHH=8.8
Hz, OC6H4), 6.93 (d, 2H, JHH=8.6 Hz, SC6H4), 5.26
(s, 5H, h5-C5H5), 4.02 (t, 2H, OCH2), 1.80 (q, 2H,
OCH2CH2), 1.41 (m, 20H, alkoxy, butyl), 0.98 (t, 12H,
alkoxy, butyl). 31P{1H}-NMR (CDCl3, l ppm): 25.29.
Anal. Found: C, 66.82; H, 8.33; N, 2.77. Calc. for
C34H50NOPSNi: C, 66.89; H, 8.25; N, 2.29%.
A green solid with a yield of 0.43 g (75%) was
obtained. 1H-NMR (CDCl3, l ppm): 8.39 (s, 1H,
NꢁC(H)), 7.80 (d, 2H, JHH=8.4 Hz, C(H)C6H4), 7.60
(d, 2H, JHH=8.4 Hz, NC6H4), 6.94 (d, 2H, JHH=8.8
Hz, OC6H4), 6.93 (d, 2H, JHH=8.6 Hz, SC6H4), 5.26
(s, 5H, h5-C5H5), 4.01 (t, 2H, OCH2), 1.80–1.23 (m,
30H, alkoxy, butyl), 0.92 (t, 12H, alkoxy, butyl).
31P{1H}-NMR (CDCl3, l ppm): 25.26. Anal. Found: C,
69.65; H, 8.52; N, 1.69.Calc. for C38H58NOPSNi: C,
69.71; H, 8.93; N, 2.14%.

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R.M. Moutloali et al. / Journal of Organometallic Chemistry 629 (2001) 171–181
2.7. Ni(p5-C5H5)(PBu3)(SC6H4NC(H)C6H4OC10H21
(6a)
Table 5
,
Selected bond lengths (A) and bond angles (°) for 3a
Bond lengths
A green solid with a yield of 0.26 g (46%) was
obtained. 1H NMR (CDCl3, l ppm): 8.39 (s, 1H,
NꢁC(H)), 7.80 (d, 2H, JHH=8.8 Hz, C(H)C6H4), 7.61
(d, 2H, JHH=8.4 Hz, NC6H4), 6.95 (d, 2H, JHH=8.8
NiꢀS
2.184(1)
1.752(3)
1.271(3)
1.822(2)
NiꢀP
2.145(1)
1.761(3)
1.820(2)
1.834(2)
NiꢀCp a
C(24)ꢀN
C(6)ꢀP
C(18)ꢀS
C(14)ꢀP
C(10)ꢀP
Bond angles
SꢀNiꢀCp
C(18)ꢀSꢀNi
C(6)ꢀPꢀNi
PꢀNiꢀS
131.6(1)
109.7(1)
113.4(1)
91.2(1)
CpꢀNiꢀP
C(10)ꢀPꢀNi
C(14)ꢀPꢀNi
136.3 (1)
113.7(1)
115.2(1)
Table 3
Crystal data and structure refinement parameters for compounds 1a
and 3a
a Cp is the cyclopentadienyl ring centroid.
1a
3a
Hz, OC6H4), 6.92 (d, 2H, JHH=8.6 Hz, SC6H4), 5.26
(s, 5H, h5-C5H5), 4.01 (t, 2H, OCH2), 1.78 (q, 2H,
OCH2CH2), 1.57–1.27 (m, 28H, alkoxy, butyl), 0.92
(m, 12H, butyl, alkoxy). 31P{1H}-NMR (CDCl3, l
ppm): 25.29. Anal. Found: C, 70.15; H, 9.04; N, 2.11.
Calc. for C40H62NOPSNi: C, 69.16; H, 9.95; N, 2.02%.
Empirical formula
Formula weight
Temperature (K)
C34H50NOPSNi C36H46NPSNi
610.49
614.48
150(2)
173(2)
,
Wavelength (A)
0.71073
Triclinic
0.71073
Monoclinic
P21/c
Crystal system
Space group
(
P1
Unit cell dimensions
,
a (A)
10.455(1)
12.375(1)
13.567(1)
104.25(1)
99.31(1)
92.47(1)
1672.6(2)
2
13.164(2)
20.277(2)
12.740(2)
90.0
106.46(1)
90.0
2.8. Ni(p5-C5H5)(PBu3)(SC6H4NC(H)C6H4OC14H29)
(7a)
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
A green solid with a yield of 0.48 g (49%) was
obtained. 1H-NMR (CDCl3, l ppm): 8.40 (s, 1H,
NꢁC(H)), 7.81 (d, 2H, JHH=8.8 Hz, C(H)C6H4), 7.62
(d, 2H, JHH=8.4 Hz, NC6H5), 6.95 (d, 2H, JHH=8.4
Hz, OC6H4,), 6.94 (d, 2H, JHH=8.4 Hz, SC6H4) 5.27
(s, 5H, h5-C5H5), 4.02 (t, 2H, OCH2), 1.81 (q, 2H,
OCH2CH2), 1.59–1.27 (m, 22H, alkoxy, butyl), 0.93
(t, 12H, alkoxy, butyl). Anal. Found: C, 70.87; H, 9.33;
N, 1.62. Calc. for C44H70NOPSNi: C, 70.40; H, 9.40; N,
1.85%.
3
,
V (A )
Z
3261.2(11)
4
Dcalc (Mg m−3
)
1.212
1.252
Absorption coefficient
(mm−1
F(000)
0.716
0.733
)
656
1312
Crystal size (mm)
Reflections collected
Unique reflections
Completeness to q=25° (%) 99.8
Rint
0.35×0.35×0.25 0.41×0.37×0.25
13 454
7614
12 387
6623
97.9
0.0191
0.0326
Data/restraints/parameters
Final R indices [I\2|(I)]
7614/0/357
6623/0/463
R1=0.0409,
wR2=0.0845
R1=0.0693,
wR2=0.0950
0.445 and
−0.418
2.9. Ni(p5-C5H5)(PBu3)(SC6H4NC(H)C6H4OC16H33)
(8a)
R1=0.0338,
wR2=0.0717
R1=0.0495,
wR2=0.0774
R indices (all data)
Green crystals with a yield of 0.14 g (87%)b were
isolated. 1H-NMR (CDCl3, l ppm): 8.39 (s, 1H,
NꢁC(H)), 7.80 (d, 2H, JHH=8.6 Hz, C(H)C6H4), 7.60
(d, 2H, JHH=8.4 Hz, NC6H4), 6.94 (d, 2H, JHH=8.6
Hz, OC6H4), 6.93 (d, 2H, JHH=8.4 Hz, SC6H4), 5.26
(s, 5H, h5-C5H5), 4.01 (t, 2H, OCH2), 1.80–1.30
(m, 46H, alkoxy, butyl), 0.92 (t, 12H, alkoxy, butyl).
31P{1H}-NMR (CDCl3, l ppm): 22.31 (s). Anal. Found:
C, 70.22; H, 10.52; N, 1.67. Calc. for C46H74NOPSNi:
C, 69.96; H, 9.74; N, 1.73%.
Largest difference peak and 0.332 and
−3
,
hole (e A
)
−0.353
Table 4
,
Selected bond lengths (A) and bond angles (°) for 1a
Bond lengths
NiꢀS
2.193(1)
1.750(3)
1.277(3)
1.834(2)
NiꢀP
2.145(1)
1.764(2)
1.828(2)
1.824(2)
NiꢀCp a
C(24)ꢀN
C(10)ꢀP
C(18)ꢀS
C(6)ꢀP
C(14)ꢀP
2.10. Ni(p5-C5H5)(PBu3)(SC6H4NC(H)C6H4OC20H41)
(9a)
Bond angles
SꢀNiꢀCp
C(18)ꢀSꢀNi
PꢀNiꢀS
132.43(1)
107.5(1)
91.7(1)
PꢀNiꢀCp
C(14)ꢀPꢀNi
C(6)ꢀPꢀNi
136.28(1)
115.1(1)
113.6(1)
A green solid with a yield of 0.21 g (19.5%) was
isolated. 1H-NMR (CDCl3, l ppm): 8.40 (s, 1H,
NꢁC(H)), 7.81 (d, 2H, JHH=8.8 Hz, C(H)C6H4), 7.62
(d, 2H, JHH=8.4 Hz, NC6H4), 6.95 (d, 2H, JHH=8.8
C(10)ꢀPꢀNi
114.6(1)
a Cp is the cyclopentadienyl ring centroid.

R.M. Moutloali et al. / Journal of Organometallic Chemistry 629 (2001) 171–181
177
Hz, OC6H4), 6.94 (d, 2H, JHH=8.4 Hz, SC6H4), 5.27
(s, 5H, h5-C5H5), 4.01 (t, 2H, OCH2), 1.81 (q, 2H,
OCH2CH2), 1.52–1.27 (m, 34H, alkoxy, butyl), 0.93 (t,
3H, alkoxy, butyl). 31P{1H}-NMR (l ppm): 22.45.
Anal. Found: C, 71.21; H, 10.26; N, 1.92. Calc. for
C50H82NOPSNi: C, 71.93; H, 9.90; N, 1.68%.
Found: C, 74.14; H, 5.42; N, 3.27. Calc. for
C42H34NPSNi: C, 74.80; H, 5.08; N, 2.08%.
2.12. Ni(p5-C5H5)(PPh3)(SC6H4NC(H)-
C6H4OCH2C6H5) (2b)
A green solid with a yield of 0.34 g (54%) was
obtained. 1H-NMR (CDCl3, l ppm): 8.51 (s, 1H,
NꢁC(H)), 7.97 (d, 2H, JHH=8.4 Hz, C(H)C6H4), 7.71
(m, 6H, PPh3), 7.44 (m, 15H, PPh3, OCH2C6H5,
NC6H4), 7.19 (d, 2H, JHH=8.4 Hz, OC6H4), 6.90 (d,
2H, JHH=8.4 Hz, SC6H4), 5.30 (s, 2H, OCH2), 5.15 (s,
5H, h5-C5H5). 31P{1H}-NMR (l ppm): 35.77. Anal.
Found: C, 72.19; H, 5.20; N, 1.83. Calc. for
C43H36NOPSNi: C, 72.79; H, 5.82; N, 1.97%.
2.11. Ni(p5-C5H5)(PPh3)(SC6H4NC(H)C6H4C6H5) (1b)
A brown solid with a yield of 0.55 g (64%) was
obtained. 1H-NMR (CDCl3, l ppm): 8.36 (s, 1H,
NꢁC(H)), 7.83 (d, 2H, JHH=8.8 Hz, C(H)C6H4), 7.68
(t, 6H, PPh3), 7.49 (m, 15H, PPh3, NC6H4, C6H5), 7.13
(d, 2H, JHH=8.4 Hz, C(H)C6H4C6H5), 7.05 (d, 2H,
J
HH=8.8 Hz, SC6H4), 5.14 (s, 5H, h5-C5H5). Anal.
Fig. 5. Molecular structure of 3a.
Fig. 6. Packing diagram for 3a.

178
R.M. Moutloali et al. / Journal of Organometallic Chemistry 629 (2001) 171–181
2.13. Ni(p5-C5H5)(PPh3)(SC6H4NC(H)C6H4OC4H9
(3b)
SC6H4), 5.13 (s, 5H, h5-C5H5), 4.01 (t, 2H, OCH2), 1.80
(q, 2H, OCH2CH2), 1.26 (br s, 22H, alkoxy), 0.88 (t,
3H, CH3). 31P{1H}-NMR (l ppm): 35.41. Anal. Found:
C, 73.82; H, 7.22; N, 1.32. Calc. for C50H58NOPSNi: C,
74.08; H, 7.21; N, 1.73%.
A brown solid with a yield of 0.38 g (74%) was
obtained 1H-NMR (CDCl3, l ppm): 8.38 (s, 1H,
NꢁC(H)), 7.80 (d, 2H, JHH=8.8 Hz, C(H)C6H4), 7.70
(t, 6H, PPh3), 7.38 (s, 11H, PPh3, NC6H4), 6.95 (d, 2H,
2.17. Ni(p5-C5H5)(PPh3)(SC6H4NC(H)C6H4OC16H33)
(8b)
J
HH=8.4 Hz, OC6H4), 6.85 (d, 2H, JHH=6.4 Hz,
SC6H4), 5.13 (s, 5H, h5-C5H5), 4.02 (t, 2H, OCH2), 1.78
(q, 2H, OCH2H2), 1.49 (q, 2H, OCH2CH2CH2), 0.99 (t,
3H, CH3). 31P{1H}-NMR (l ppm): 35.40. Anal. Found:
C, 71.89; H, 6.39; N, 2.11. Calc. for C40H38NOPSNi: C,
71.66; H, 5.71; N, 2.09%.
A brick-red solid with a yield of 0.49 g (77%) was
obtained. 1H-NMR (CDCl3, l ppm): 8.38 (s, 1H,
NꢁC(H)), 7.80 (d, 2H, JHH=8.4 Hz, C(H)C6H4), 7.70
(m, 6H, PPh3), 7.38 (m, 11H, PPh3, NC6H4), 6.95 (d,
2H, JHH=8.40 Hz, OC6H4), 6.85 (d, 2H, JHH=8.6 Hz,
SC6H4), 5.13 (s, 5H, h5-C5H5), 4.01 (t, 2H, OCH2),
1.80–1.25 (m, 28H, alkoxy), 0.88 (t, 3H, CH3). Anal.
Found: C, 74.22; H, 7.79; N, 1.53. Calc. for
C52H62NOPSNi: C, 74.46; H, 7.45; N, 1.67%.
2.14. Ni(p5-C5H5)(PPh3)(SC6H4NC(H)C6H4OC8H17
(5b)
A brown solid with a yield of 0.33 g (87%) was
obtained. 1H-NMR (CDCl3, l ppm): 8.38 (s, 1H,
NꢁC(H)), 7.80 (d, JHH=8.8 Hz, C(H)C6H4), 7.71 (t,
8H, PPh3, NC6H4), 7.39 (m, 9H, PPh3), 6.95 (d, 2H,
2.18. Ni(p5-C5H5)(PPh3)(SC6H4NC(H)C6H4OC20H41)
(9b)
J
HH=8.80 Hz, OC6H4), 6.85 (d, 2H, JHH=8.6 Hz,
SC6H4), 5.13 (s, 5H, h5-C5H5), 4.02 (t, 2H, OCH2),1.78
(q, 2H, OCH2CH2), 1.6–1.16 (m, 10H, alkoxy), 0.88 (t,
3H, CH3) 31P-NMR (CDCl3, l ppm): 35.40. Anal.
Found: C, 72.54; H, 6.44; N, 2.17. Calc. for
C44H46NOPSNi: C, 72.41; H, 6.38; N, 1.93%.
A brick-red solid with a yield of 0.75 g (65.0%) was
isolated. 1H-NMR (CDCl3, l ppm): 8.31 (s, 1H,
NꢁC(H)), 7.80 (d, 2H, JHH=8.8 Hz, C(H)C6H4), 7.70
(t, 6H, PPh3), 7.38 (s, 11H, PPh3, NC6H4), 6.95 (d, 2H,
J
HH=8.8 Hz, OC6H4), 6.85 (d, 2H, JHH=Hz, SC6H4),
5.13 (s, 5H, h5-C5H5), 4.01 (t, 2H, OCH2), 1.78 (q, 2H,
OCH2CH2), 1.27 (s, 34H, alkoxy), 0.88 (t, 3H, CH3).
31P{1H}-NMR (l ppm): 35.40. Anal. Found: C, 74.74;
H, 7.15; N, 1.45. Calc. for C56H70NOPSNi: C, 75.08; H,
7.87; N, 1.56%.
2.15. Ni(p5-C5H5)(PPh3)(SC6H4NC(H)C6H4OC10H21)
(6b)
A brown solid with a yield of 0.36 g (82%) was
obtained. 1H-NMR (CDCl3, l ppm): 8.38 (s, 1H,
NꢁC(H)), 7.80 (d, 2H, JHH=8.8 Hz, C(H)C6H4), 7.72
(t, 8H, PPh3, NC6H4), 7.39 (m, 9H, PPh3), 6.95 (d, 2H,
J
HH=8.8 Hz, OC6H4), 6.85 (d, 2H, JHH=8.8 Hz,
3. Results and discussion
SC6H4), 5.13 (s, 5H, h5-C5H5), 4.01 (t, 2H, OCH2), 1.78
(q, 2H, OCH2CH2), 1.58–1.28 (m, 14H, alkoxy), 0.89
(t, 3H, CH3). 31P-NMR (CDCl3, l ppm): 35.38. Anal.
Found: C, 73.19; H, 6.79; N, 1.45. Calc. for
C46H50NOPSNi: C, 73.22; H, 6.68; N, 1.86%.
3.1. Synthesis of ligands
The Schiff base ligands, HSC6H4NC(H)C6H4O-
CnH2n+1 (n=4 (3), 6 (4), 8 (5), 10 (6), 14 (7), 16 (8), 20
(9)) and HSC6H4NC(H)C6H4R¦ (R¦=C6H5 (1), OCH2-
C6H5 (2)), were prepared by condensation of equimolar
amounts of 4-aminothiophenol and the appropriate
aldehydes in ethanol Eq. (1). The products precipitated
as yellow solids or thick oils within 30 min and were
recrystallised from CH2Cl2–hexane solution at −15
°C. The yields ranged from 60 to 100%. The analytical
data of these ligands are presented in Table 1.
2.16. Ni(p5-C5H5)(PPh3)(SC6H4NC(H)C6H4OC14H29)
(7b)
A brick-red solid with a yield of 0.72 g (68.0%) was
obtained. 1H-NMR (CDCl3, l ppm): 8.38 (s, 1H,
NꢁC(H)), 7.80 (d, 2H, JHH=8.4 Hz, C(H)C6H4), 7.70
(t, 6H, PPh3), 7.38 (br s, 11H, PPh3, NC6H4), 6.95 (d,
2H, JHH=8.8 Hz, OC6H4), 6.85 (d, 2H, JHH=8.4 Hz

R.M. Moutloali et al. / Journal of Organometallic Chemistry 629 (2001) 171–181
179
3.2. Synthesis and characterisation of complexes
uid crystals. In the known mesogenic metal phosphine
complex Pt(PMe3)2(CꢂCC6H4ꢀ4-OCnH2n+1 2 [20], the
)
The above ligands were treated with either Ni(h5-
C5H5)(PBu3)Br or Ni(h5-C5H5)(PPh3)Br to form the
new complexes according to previously reported proce-
dures [3]. The complexes were recrystallised from
CH2Cl2–hexane at −15 °C to give analytically pure
phosphine is less bulky. The lack of mesogenic be-
haviour for the PBu3 and PPh3 complexes might be due
to their steric bulk, which prevents regular ordering on
melting. This steric prevention to regular packing is
also compounded by the presence of the cyclopentadi-
enyl ring, which is out-of-plane of the phenyl rings of
the thiolato ligand, as well as the geometry around the
nickel centre. These are some of the issues that need to
be addressed for these complexes to be mesogenic. One
of the ways of concealing these features is to increase
the number of rings in the ligand backbone [21].
Generally, the melting point of both the ligands and
the complexes is dependent on the substituent in the 4%
position of the ligand (Table 2). The PBu3 complexes
also melted at considerably lower temperatures than
their PPh3 analogues, some even 60 °C lower. When the
substituent was an alkoxy group, the longer the alkoxy
chain length the lower the melting point; though some
leveling off effect seem to set in when the alkoxy
carbons exceeded 10. Similar levelling off of the melting
points has previously been observed [22]. For phenyl
and benzyloxy substituted ligands the melting points
were higher than their alkoxy analogues.
From the TGA data two thermal decomposition
pathways could be established which were dependent
on the phosphine substituent. Complexes that have
PPh3 initially lost the cyclopentadienyl ligand followed
by the loss of the phosphine and rapture of the Schiff
base ligand (Scheme 1a). Fig. 1 shows representative
TGA-DSC curves for the PPh3 complex series, reveal-
ing three steps of the decomposition in the TGA and
four peaks in the DTA. The first step in the decomposi-
tion sequence occurred at 180 °C and corresponds to
the loss of the cyclopentadienyl ligand accompanied by
a large exothermic effect in the DSC curve. The second
step is the gradual endothermic process in the tempera-
ture range 190–320 °C centred at 248.5 °C, correspond-
ing to the loss of PPh3 ligand. In comparison to the
PBu3 complexes, the PPh3 ligand is lost at a relatively
higher temperature suggesting a stronger NiꢀP bond.
The third step centred at about 400 °C was the exother-
mic rapture and subsequent loss of the Schiff base
moiety, leaving a residual mass that corresponded to
the Ni(SC6H5) moiety. The PBu3 analogue, on the other
hand, decomposed first by simultaneous loss of cy-
clopentadienyl and phosphine ligand followed by the
rupturing the Schiff base ligand (Scheme 1b). Fig. 2
shows representative TGA-DSC curves for PBu3 com-
plex series. The residual mass in all the cases corre-
spond to a Ni(SC6H5) moiety. The above thermal
decomposition pathways demonstrate the relative
strengths of the three Ni–ligand interactions. The
strongest of these bonds appear to be the NiꢀS bond in
both types of complexes, which stays intact even at
1
products in yields ranging from 30 to 88%. H-NMR
spectral data showed that thiolato resonance of the
complexes and that of free ligands were very similar.
Changes in the substituents of the thiolato ligands also
had no significant influence on the electronic environ-
ment of either the cyclopentadienyl or the phosphine
ligands. The 1H-NMR spectra gave cyclopentadienyl
resonance at 5.26–5.28 ppm (1a–9a) and 5.13–5.15
ppm (1b–9b) and 31P-NMR spectra at ca. 22.4 ppm
(1a–9a) and 35.5 ppm (1b–9b). These differences in
peak values between the PBu3 and PPh3 complexes
appear to be independent of the nature of the thiolato
ligands. Similar chemical shifts have been reported for
Ni(h5-C5H5)(PR3)(SC6H4X-4) (X=Cl, Br, NH2) {R=
Bu (5.25, 22.4 ppm), R=Ph (5.13, 35.4 ppm)} [17] and
Ni(h5-C5H5)(PR3)(SC6H4NꢁCHC6H4X-4%) {X=F, Cl,
Br, H, OH, Me; R=Bu (5.27, 22.4 ppm), R=Ph (5.14,
35.4 ppm)} [3]. The basicity of the phosphine thus
determines the cyclopentadienyl resonance, with the
more basic PBu3 deshielding the cyclopentadienyl
ligand.
3.3. Thermal studies
Thermal behaviour of the Schiff base ligands and
their cyclopentadienylnickelphosphino complexes were
investigated by TGA and DSC as well as polarising
hot-stage microscope. They were generally stable up to
180 °C before decomposing, however none of the lig-
ands or the complexes showed any birefringence on
heating and therefore are not liquid crystalline. The
absence of liquid crystalline behaviour by the Schiff
base compounds may be due to the terminal SH group.
Most of organic compounds that are mesogenic feature
nitro, cyano, halo, alkoxy or alkyl groups [18]. It is also
known that when there is a potential for hydrogen
bonding between molecules of a compound, mesogenic
behaviour may be precluded [4a]. In the Schiff base
ligands reported here the possibility of hydrogen bond-
ing exists; which would involve the interaction of the
thiol hydrogens with the alkoxy oxygens. Hydrogen
bonding in the ligands is supported by the presence of
S···H and N···H distances in the packing of 3a (vide
infra) that are in the range for hydrogen bonding [19].
Hence this could account for the lack of mesogenic
properties when compounds 1–9 were heated.
The absence of mesogenic behaviour for the nickel
complexes is also not surprising since there are no
known bulky metal phosphine complexes that are liq-

180
R.M. Moutloali et al. / Journal of Organometallic Chemistry 629 (2001) 171–181
temperatures above 800 °C. It is interesting to note that
the NiꢀP bonds of the more basic phosphine (PBu3)
only breaks around 200 °C, whilst those of the less basic
phosphine (PPh3) are only stable up to about 300 °C.
Their thermal stability is independent of the nature of
the phosphine but their decomposition pathways differ.
Complexes containing PPh3 have stronger NiꢀP bonds
compared to their PBu3 analogues. Melting points of
complexes were lower for all PBu3 complexes compared
to their PPh3 analogues and were also progressively
lower as the alkoxy chain length increased up to C10
after which the melting point levelled off.
3.4. Molecular structures of 1a and 3a
The molecular structures of 1a and 3a determined by
X-ray crystallography are shown in Figs. 3 and 5 and
confirm that the proposed structures derived from the
analytical data are correct. A selection of crystal data
and structure refinement parameters for 1a and 3a is
given in Table 3. Selected bond angles and distances for
1a and 3a are shown in Tables 4 and 5, respectively. The
structures are typical of monocyclopentadienylnickel
complexes that have a monophosphine ligand. The
cyclopentadienyl centroidꢀnickel bond distances in 1a
Acknowledgements
Financial support from the National Research Foun-
dation (South Africa) (J.D. and R.M.M.) and ESKOM
(South Africa) is gratefully acknowledged.
,
and 3a are 1.750(3) and 1.752(3) A, respectively and lie
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